12.4: What have we learned about virtual learning?
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Deborah Rosenthal starts her virtual kindergarten class on Zoom every morning with a song — today, it's the Spanish version of "If You're Happy and You Know It." Her students clap along. There's a greeting from the class mascot (a dragon), yoga, meditation and then some practice with letter sounds: "Oso, oso, O, O, O."
Rosenthal teaches Spanish immersion in a public school in San Francisco's Mission District. Most of the families are low-income, and many are now affected by job losses related to COVID-19. She has taught kindergarten for 15 years, and she loves how "hands-on," "tactile" and "cozy" it is to work with 5-year-olds.
But this year, she's spending 10 or 12 hours a day on, basically, her own home production of Mister Rogers' Neighborhood en Español. "It's a very two-dimensional experience," she says.
Few people would tell you that online kindergarten was a good idea, or frankly even possible. That was before 2020. The number has fluctuated as cases rise across the country, but throughout this fall pandemic semester, between 40% and 60% of students have been enrolled in districts that offer only remote learning, according to a tracker maintained by Burbio.
And even in hybrid districts, some students have been learning remotely, either part or full time. In short, online learning is the reality for a majority of students this fall.
We are still starved for data on what this all means. The earliest standardized test scores coming out show modest learning loss for students in math, but there are worries that the most at-risk students are not being tested at all.
For this story I talked to educators in six states, from California to South Carolina. For the most part they say things have improved since the spring. But they are close to burnout, with only a patchwork of support. They say the heart of the job right now is getting students connected with school and keeping them that way — both technologically and even more importantly, emotionally. Here are five lessons learned so far:
1. The digital divide is still big and complex.
Eight months after schools first shut down, how many students still can't sign on? We don't really know, and that's a problem, says Nicol Turner Lee, director of the Center for Technology Innovation at the Brookings Institution. "We've not done a really great job in aggregating the data as to how many kids are still disconnected," she adds. "It's very disappointing as well as concerning."
The National Education Association recently reported, based on pre-pandemic census data, that one quarter of households with children ages 5 to 17 lacked either high-speed Wi-Fi, a computer or both. For households near the poverty line, the number was closer to half.
That figure may have gotten better. Many districts have scrambled to distribute their classroom laptops to families, to buy portable hot spots, and call on private and corporate donations. But there are still gaps.
Partly, that's because there hasn't been any pandemic federal stimulus aid to public schools since April. State revenue is down, too. For example, Richard Carranza, chancellor of New York City public schools, said last month that 60,000 of the district's 1.1 million students are still missing devices — about 5.5%.
Lee at Brookings is working on a book about the digital divide, and she says it's multidimensional.  There are backlogs of items such as Chromebooks.
Then there's infrastructure.
"That rural Internet divide is real. I mean it's a real problem right now in America," says Caroline Weathers, who teaches in a small town in South Carolina. Her district gave out hot spots, but in some places they didn't work because there wasn't cell service from the major carriers.
And the digital divide is about more than equipment. Rosenthal's school in San Francisco, Buena Vista Horace Mann, is a community school, meaning there are wraparound services, including lots of help with technology.
Despite all that, she didn't make contact with one of her students until 2 1/2 months into the school year. That's so even though her mother had come to school to pick up a laptop and hot spot. "The little girl was going to a babysitter that was not literate," Rosenthal says. "And so nobody could help this child get onto a computer."
Another of her students has a single mother who works cleaning hotel rooms; the girl goes along and often joins the class from her mother's smartphone.
2. Relationships are everything when it comes to keeping kids engaged remotely.
Successful schools are using every adult on the team and every form of communication possible. Theresa Rouse is the superintendent of Joliet Public Schools District 86 in Illinois, where a majority of the students are low-income and either Latino or Black. She says their focus has been on relationships.
The district spent the first three weeks of the school year focusing just on social and emotional learning. Educators communicate expectations to parents and teachers by email, calls, texts, over social media, YouTube videos and podcasts.
And, Rouse says, any adult at a school — from teachers, to the assistant principal, to a school counselor or social worker — might drop in during video class to show they care: "If they're seeing a student that looks distressed, they pull them aside into a breakout room, have a conversation."
In South Carolina, Weathers usually teaches science at St. George Middle School. This year she created a new role for herself, helping families — sometimes with an app that parents can download to track kids' grades, or with strategies to build kids' executive function skills so they can succeed in remote learning. She says she'd like to continue the role going forward, making parents more active partners in their kids' education and taking learning out into the community as well.
"We could take this as a learning moment," Weathers says. "Now we have the parents' attention. So maybe now is the time to really reach out and say, 'This is what we need you to do on your end, and we'll take care of this on our end.' And in 10 years, we might see something entirely different in education in the country if we did that."
3. Digital teaching can be good, even great with the right support for teachers. But that's far from the norm.
Districts such as Weathers' and Rouse's are working with the Digital Learning Collaborative, a nonprofit that is dedicated to best practices in digital learning.
Rouse, in Joliet, calls its training "pretty fabulous" and essential to her district's transition from teaching mainly through paper packets in the spring to full-on remote using Google Classroom this fall. The training "was more intense than [teachers] expected it would be, but that's OK because teaching online is more intense than people anticipate as well."
Another organization, Cadence, is also trying to improve digital teaching at scale. It pairs "mentor teachers" with "partner teachers" to deliver a standardized curriculum in reading, math and science. The teaching is a high-intensity blend of video lessons, active classroom instruction with breakout sessions, and software-based practice.
Olyvia Kozicki teaches fifth grade at Augustine Prep, a nondenominational private school in Milwaukee, and is a Cadence partner teacher for English language arts. She says she's overjoyed at the quality and quantity of work her students are producing. It's not only more than she expected from online teaching, "it's more just in general."
Twice a week, she meets with other Cadence teachers from around the country who are also teaching the exact same material on the same timetable. She says that makes it the most practical and actionable professional education she's ever had.
"When we switched to virtual, it was very overwhelming, and it seemed like such a daunting task," she says. And now "I am so happy with what the kids have been able to do."
Justin Reich says Kozicki's experience is unusual for teachers this year. Reich is an expert on educational technology at Massachusetts Institute of Technology and the author of the new book Failure to Disrupt: Why Technology Alone Can't Transform Education.
He says that across the country this fall, "I've heard very little evidence of innovation." Even moves that might seem relatively simple, such as adopting a free, online university-level course for use by high school students, aren't happening often. Mostly, he adds, districts are trying to re-create classroom teaching routines online with varying levels of success.
"I don't think it's getting better because there are major approaches that people have figured out or there's a model that's sort of spreading around," he says. Nor is there a lot of leadership or direction on improving online learning coming from the federal Department of Education or anyone else.
Instead, Reich says, what improvement there has been since spring comes mainly from teachers such as Rosenthal — putting in long hours and learning as they go. "It's just kind of folks sanding down one little rough edge at a time."
4. Hybrid models are extremely challenging.
At last count, according to Burbio, 17.5% of districts were offering school in person just a few days a week, with students learning from home the rest of the time. The purpose was to maintain social distancing by reducing class sizes, but the model has created confusion and constant interruptions. Many students are struggling to adjust to classroom routines when they may attend only five days out of three weeks.
Depending on available staffing, teachers, meanwhile, may be yelling through a mask and face shield to be heard by students over Zoom. Jennifer Echols is the director of online and personalized learning for Mesa Public Schools, the largest school district in Arizona. She calls this model "one of the biggest challenges" in remote learning right now. Randi Weingarten, president of the American Federation of Teachers, has called for this "hybrid" model to be phased out. "Hybrid doesn't work," Weingarten says flatly. "You can't livestream and teach in person at the same time."
5. Some kids are not learning much online. They'll be playing catch-up in years to come.
There are some anecdotes of children who are thriving with remote learning. "There's [approximately] 10% of people for whom it works better," Reich says. And for these students, "this is actually a better version of school."
Maybe they had school anxiety, he explains, or were victims of bullying or discrimination, or have sensory issues and enjoy having more control over their learning environment.
But districts including Houston, St. Paul, Minn., and Fairfax County, Va., have reported historically high failure rates this fall.
Echols, in Arizona, says both attendance and engagement in online learning is suffering. "Some kids have had difficulty just paying attention and keeping themselves focused." In other cases, she adds, "we have families where parents are working, and there's not the appropriate supervision for young learners, or children that need to be babysitting siblings during the school day."
What keeps Rosenthal up at night are the kids she just can't reach. Every year, she says, out of a class of 20 or 21, there are five or six students who show up unprepared for kindergarten.
"They're struggling, but at least they're with me all day long. And so I can support them six or seven hours a day."
This year, she sees most of her students learning and growing despite all the obstacles. But those five or six who started out behind aren't getting much of anywhere.
References
https://www.npr.org/2020/12/04/93805...school-in-2020
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4.8: EPR Spectroscopy
Basic Principles for EPR Spectroscopy
Electron paramagnetic resonance spectroscopy (EPR) is a powerful tool for investigating paramagnetic species, including organic radicals, inorganic radicals, and triplet states. The basic principles behind EPR are very similar to the more ubiquitous nuclear magnetic resonance spectroscopy (NMR), except that EPR focuses on the interaction of an external magnetic field with the unpaired electron(s) in a molecule, rather than the nuclei of individual atoms. EPR has been used to investigate kinetics, mechanisms, and structures of paramagnetic species and along with general chemistry and physics, has applications in biochemistry, polymer science, and geosciences.
The degeneracy of the electron spin states is lifted when an unpaired electron is placed in a magnetic field, creating two spin states, m s = ± ½, where m s = - ½, the lower energy state, is aligned with the magnetic field. The spin state on the electron can flip when electromagnetic radiation is applied. In the case of electron spin transitions, this corresponds to radiation in the microwave range.
The energy difference between the two spin states is given by the equation
\[ \Delta E \ =\ E_{+} - E_{-} = h \nu = g \beta B \label{1} \]
where h is Planck’s constant (6.626 x 10 -34 J s -1 ), v is the frequency of radiation, ß is the Bohr magneton (9.274 x 10 -24 J T -1 ), B is the strength of the magnetic field in Tesla, and g is known as the g-factor. The g-factor is a unitless measurement of the intrinsic magnetic moment of the electron, and its value for a free electron is 2.0023. The value of g can vary, however, and can be calculated by rearrangement of the above equation, i.e.,
\[ g = \dfrac{h \nu}{\beta B }\label{2} \]
using the magnetic field and the frequency of the spectrometer. Since h, v , and ß should not change during an experiment, g values decrease as B increases. The concept of g can be roughly equated to that of chemical shift in NMR.
Instrumentation
EPR spectroscopy can be carried out by either 1) varying the magnetic field and holding the frequency constant or 2) varying the frequency and holding the magnetic field constant (as is the case for NMR spectroscopy). Commercial EPR spectrometers typically vary the magnetic field and holding the frequency constant, opposite of NMR spectrometers. The majority of EPR spectrometers are in the range of 8-10 GHz (X-band), though there are spectrometers which work at lower and higher fields: 1-2 GHz (L-band) and 2-4 GHz (S-band), 35 GHz (Q-band) and 95 GHz (W-band).
EPR spectrometers work by generating microwaves from a source (typically a klystron), sending them through an attenuator, and passing them on to the sample, which is located in a microwave cavity (Figure \(\PageIndex{1}\)).
Microwaves reflected back from the cavity are routed to the detector diode, and the signal comes out as a decrease in current at the detector analogous to absorption of microwaves by the sample.
Samples for EPR can be gases, single crystals, solutions, powders, and frozen solutions. For solutions, solvents with high dielectric constants are not advisable, as they will absorb microwaves. For frozen solutions, solvents that will form a glass when frozen are preferable. Good glasses are formed from solvents with low symmetry and solvents that do not hydrogen bond. Drago provides an extensive list of solvents that form good glasses.
EPR spectra are generally presented as the first derivative of the absorption spectra for ease of interpretation. An example is given in Figure \(\PageIndex{2}\).
Magnetic field strength is generally reported in units of Gauss or mTesla. Often EPR spectra are very complicated, and analysis of spectra through the use of computer programs is usual. There are computer programs that will predict the EPR spectra of compounds with the input of a few parameters.
Factors that Affect EPR Spectra
Hyperfine Coupling
Hyperfine coupling in EPR is analogous to spin-spin coupling in NMR. There are two kinds of hyperfine coupling: 1) coupling of the electron magnetic moment to the magnetic moment of its own nucleus; and 2) coupling of the electron to a nucleus of a different atom, called super hyperfine splitting . Both types of hyperfine coupling cause a splitting of the spectral lines with intensities following Pascal’s triangle for I = 1/2 nuclei, similar to J-coupling in NMR. A simulated spectrum of the methyl radical is shown in Figure \(\PageIndex{3}\). The line is split equally by the three hydrogens giving rise to four lines of intensity 1:3:3:1 with hyperfine coupling constant a.
The hyperfine splitting constant, known as a , can be determined by measuring the distance between each of the hyperfine lines. This value can be converted into Hz (A) using the g value in the equation:
\[ hA\ =\ g \beta a \label{3} \]
In the specific case of Cu(II), the nuclear spin of Cu is I = 3/2, so the hyperfine splitting would result in four lines of intensity 1:1:1:1. Similarly, super hyperfine splitting of Cu(II) ligated to four symmetric I = 1 nuclei, such as 14 N, would yield nine lines with intensities would be 1:8:28:56:70:56:28:8:1.
Anisotropy
The g factor of many paramagnetic species, including Cu(II), is anisotropic, meaning that it depends on its orientation in the magnetic field. The g factor for anisotropic species breaks down generally into three values of g following a Cartesian coordinate system which is symmetric along the diagonal: g x , g y , and g z . There are four limits to this system:
- When g x = g y = g z the spectrum is considered to be isotropic, and is not dependent on orientation in the magnetic field.
- When g x = g y > g z the spectrum is said to be axial, and is elongated along the z-axis. The two equivalent g values are known as g ⊥ while the singular value is known as g ‖ . It exhibits a small peak at low field and a large peak at high field.
- When g x = g y < g z the spectrum is also said to be axial, but is shortened in the xy plane. It exhibits a large peak at low field and a small peak at high field.
- When g x ≠ g y ≠ g z the spectrum is said to be rhombic, and shows three large peaks corresponding to the different components of g .
Condition ii corresponds to Cu(II) in a square planar geometry with the unpaired electron in the d x 2 -y 2 orbital. Where there is also hyperfine splitting involved, g is defined as being the weighted average of the lines.
Electron Paramagnetic Resonance Spectroscopy of Copper(II) Compounds
Copper(II) Compounds
Copper compounds play a valuable role in both synthetic and biological chemistry. Copper catalyzes a vast array of reactions, primarily oxidation-reduction reactions which make use of the Cu(I)/Cu(II) redox cycle. Copper is found in the active site of many enzymes and proteins, including the oxygen carrying proteins called hemocyanins.
Common oxidation states of copper include the less stable copper(I) state, Cu + ; and the more stable copper(II) state, Cu 2 + . Copper (I) has a d 10 electronic configuration with no unpaired electrons, making it undetectable by EPR. The d 9 configuration of Cu 2 + means that its compounds are paramagnetic making EPR of Cu(II) containing species a useful tool for both structural and mechanistic studies. Two literature examples of how EPR can provide insight into the mechanisms of reactivity of Cu(II) are discussed herein.
Copper (II) centers typically have tetrahedral, or axially elongated octahedral geometry. Their spectra are anisotropic and generally give signals of the axial or orthorhombic type. From EPR spectra of copper (II) compounds, the coordination geometry can be determined. An example of a typical powder Cu(II) spectrum is shown in Figure \(\PageIndex{4}\).
The spectrum above shows four absorption-like peaks corresponding to g ‖ indicating coordination to four identical atoms, most likely nitrogen. There is also an asymmetric derivative peak corresponding to g ⊥ at higher field indicating elongation along the z axis.
Determination of an Intermediate
The reactivity and mechanism of Cu(II)-peroxy systems was investigated by studying the decomposition of the Cu(II) complex 1 with EPR as well as UV-Vis and Raman spectroscopy. The structure (Figure \(\PageIndex{5}\)) and EPR spectrum Figure \(\PageIndex{6}\) of 1 are given. It was postulated that decomposition of 1 may go through intermediates LCu(II)OOH, LCu(II)OO•, or LCu(II)O• where L = ligand.
To determine the intermediate, a common radical trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) was added. A 1:1 complex of intermediate and DMPO was isolated, and given the possible structure 2 (Figure \(\PageIndex{7}\), which is shown along with its EPR specturm (Figure \(\PageIndex{8}\)).
The EPR data show similar though different spectra for Cu(II) in each compound, indicating a similar coordination environment – elongated axial, and most likely a LCu(II)O• intermediate.
Determination of a Catalytic Cycle
The mechanism of oxidizing alcohols to aldehydes using a Cu(II) catalyst, TEMPO, and O 2 was investigated using EPR. A proposed mechanism is given in Figure \(\PageIndex{9}\).
EPR studies were conducted during the reaction by taking aliquots at various time points and immediately freezing the samples for EPR analysis. The resulting spectra are shown in Figure \(\PageIndex{10}\).
The EPR spectrum (a) in Figure 6, after 1.2 hours shows a signal for TEMPO at g = 2.006 as well as a signal for Cu(II) with g ‖ = 2.26, g ⊥ = 2.06, A ‖ = 520 MHz, and A ⊥ < 50 MHz. After 4 hours, the signal for Cu(II) is no longer in the reaction mixture, and the TEMPO signal has decreased significantly. Suggesting that all the Cu(II) has been reduced to Cu(I) and the majority of TEMPO has been oxidized. After 8 hours, the signals for both Cu(II) and TEMPO have returned indicating regeneration of both species. In this way, EPR evidence supports the proposed mechanism.
Electron-Nuclear Double Resonance Spectroscopy
Electron nuclear double resonance (ENDOR) uses magnetic resonance to simplify the electron paramagnetic resonance (EPR) spectra of paramagnetic species (one which contains an unpaired electron). It is very powerful and advanced and it works by probing the environment of these species. ENDOR was invented in 1956 by George Feher (Figure \(\PageIndex{11}\)).
ENDOR: NMR Spectroscopy on an EPR Spectrometer
A transition’s metal electron spin can interact with the nuclear spins of ligands through dipolar contact interactions. This causes shifts in the nuclear magnetic resonance (NMR) Spectrum lines caused by the ligand nuclei. The NMR technique uses these dipolar interactions, as they correspond to the nuclear spin’s relative position to the metal atom, to give information about the nuclear coordinates. However, a paramagnetic species (one that contains unpaired electrons) complicates the NMR spectrum by broadening the lines considerably.
EPR is a technique used to study paramagnetic compounds. However, EPR has its limitations as it offers low resolution that result in line broadening and line splitting. This is partly due to the electron spins coupling to surrounding nuclear spins. However, this coupling are important to understand a paramagnetic compound and determine the coordinates of its ligands. While neither NMR or EPR can be used to study these coupling interaction, one can use both techniques simultaneously, which is the concept behind ENDOR. An ENDOR experiment is a double resonance experiment in which NMR resonances are detected using intensity changes of an EPR line that is irradiated simultaneously. An important difference is that the NRM portion of an ENDOR experiment uses microwaves rather than radiofrequencies, which results in an enhancement of the sensitivity by several orders of magnitude.
Theory
The ENDOR technique involves monitoring the effects of EPR transitions of a simultaneously driven NMR transition, which allows for the detection of the NMR absorption with much greater sensitivity than EPR. In order to illustrate the ENDOR system, a two-spin system is used. This involves a magnetic field (B o ) interacting with one electron (S = 1/2) and one proton (I = 1/2).
Hamiltonian Equation
The Hamiltonian equation for a two-spin system is described by \ref{4}. The equation lists four terms: the electron Zeeman interaction (EZ), the nuclear Zeeman interaction (NZ), the hyperfine interaction (HFS), respectively. The EZ relates to the interaction the spin of the electron and the magnetic field applied. The NZ describes the interaction of the proton’s magnetic moment and the magnetic field. The HSF is the interaction of the coupling that occurs between spin of the electron and the nuclear spin of the proton. ENDOR spectra contain information on all three terms of the Hamiltonian.
\[ H_{0} \ =\ H_{EZ}\ +\ H_{NZ}\ +\ H_{HFS} \label{4} \]
Selection Rules
\ref{4} can be further expanded to \ref{5}. g n is the nuclear g-factor, which characterizes the magnetic moment of the nucleus. S and I are the vector operators for the spins of the electron and nucleus, respectively. μ B is the Bohr magneton (9.274 x 10 -24 JT -1 ). μ n is the nuclear magneton (5.05 x 10 -27 JT -1 ). h is the Plank constant (6.626 x 10 -34 J s). g and A are the g and hyperfine tensors. \ref{5} becomes \ref{6} by assuming only isotropic interactions and the magnetic filed aligned along the Z-axis. In \ref{6}, g is the isotropic g-factor and a is the isotropic hyperfine constant.
\[ H\ =\ \mu_{B}B_{0}gS\ -\ g_{n}\mu _{n}B_{0}I \ +\ hSAI \label{5} \]
\[ H\ =\ g\mu_{B}B_{0}S_{Z} - g_{n}\mu _{n} B_{0} I_{Z} \ +\ haSI \label{6} \]
The energy levels for the two spin systems can be calculated by ignoring second order terms in the high filed approximation by \ref{7}. This equation can be used to express the four possible energy levels of the two-spin system (S = 1/2, I = 1/2) in \ref{8} - \ref{11}
\[E(M_{S},M_{I}) = g \mu _{B} B_{0} M_{S} - g_{n} \mu _{n} B_{0} M_{I} \ +\ haM_{S}M_{I} \label{7} \]
\[E_{a}\ =\ -1/2g\mu _{B} B_{0} - 1/2g_{n} \mu _{n} B_{0} - 1/4ha \label{8} \]
\[E_{b}\ =\ +1/2g\mu _{B} B_{0} - 1/2g_{n} \mu _{n} B_{0} + 1/4ha \label{9} \]
\[E_{c}\ =\ +1/2g\mu _{B} B_{0} + 1/2g_{n} \mu _{n} B_{0} - 1/4ha \label{10} \]
\[E_{d}\ =\ -1/2g\mu _{B} B_{0} + 1/2g_{n} \mu _{n} B_{0} + 1/4ha \label{11} \]
We can apply the EPR selection rules to these energy levels ( ΔM I = 0 and ΔM S = ±1 ) to find the two possible resonance transitions that can occur, shown in \ref{12} and \ref{13}. These equations can be further simplified by expressing them in frequency units, where ν e = gμ n B 0 /h to derive \ref{14}, which defines the EPR transitions (Figure \(\PageIndex{12}\)). In the spectrum this would give two absorption peaks that are separated by the isotropic hyperfine splitting, a ( Figure \(\PageIndex{12}\)).
\[ \Delta E_{cd}\ =\ E_{c}\ -\ E_{d} \ =\ g \mu_{B} B - 1/2ha \label{12} \]
\[ \Delta E_{ab}\ =\ E_{b}\ -\ E_{a} \ =\ g \mu_{B} B + 1/2ha \label{13} \]
\[V_{EPR} \ =\ v_{e} \pm a/2 \label{14} \]
Applications
ENDOR has advantages in both organic and inorganic paramagnetic species as it is helpful in characterizing their structure in both solution and in the solid state. First, it enhances the resolution gained in organic radicals in solution. In ENDOR, each group of equivalent nuclei contributes only 2 lines to the spectrum, and nonequivalent nuclei cause only an additive increase as opposed to a multiplicative increase like in EPR. For example, the radical cation 9,10-dimethilanthracene (Figure \(\PageIndex{14}\)) would produce 175 lines in an EPR spectrum because the spectra would include 3 sets of inequivalent protons. However ENDOR produces only three pairs of lines (1 for each set of equivalent nuclei), which can be used to find the hyperfine couplings. This is also shown in Figure \(\PageIndex{14}\).
ENDOR can also be used to obtain structural information from the powder EPR spectra of metal complexes. ENDOR spectroscopy can be used to obtain the electron nuclear hyperfine interaction tensor, which is the most sensitive probe for structure determination. A magnetic filed that assumes all possible orientations with respect to the molecular frame is applied to the randomly oriented molecules. The resonances from this are superimposed on each other and make up the powder EPR spectrum. ENDOR measurements are made at a selected field position in the EPR spectrum, which only contain that subset of molecules that have orientations that contribute to the EPR intensity at the chosen value of the observing field. By selected EPR turning points at magnetic filed values that correspond to defined molecular orientations, a “single crystal like” ENDOR spectra is obtained. This is also called a “orientation selective” ENDOR experiment which can use simulation of the data to obtain the principal components of the magnetic tensors for each interacting nucleus. This information can then be used to provide structural information about the distance and spatial orientation of the remote nucleus. This can be especially interesting since a three dimensional structure for a paramagnetic system where a single crystal cannot be prepared can be obtained.


11.2: How are individual schools governed?
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Students will identify the tiers of the hierarchy of public school governing.
Students will identify the responsibilities of each tier.
Who is the boss in the school systems? The public school governing system is actually a hierarchy (March, 1978). There are several tiers to this hierarchy beginning with the federal level and ending with the individual teachers. It is a pyramid of administrators doing everything they can to educate today's students.
While some may believe that administration of schools starts with the federal government, the truth is that on the federal level there is very little involvement in education, even in funding (Federal Role, n.d.). The federal government sets some guidelines for education, such as the No Child Left Behind Act, but not specific ones such as curriculum taught. In actuality, the states have most of the power over their own schools and what they teach (Education Commission of the States [ECS], 1999). The states set what the students will learn and what standards they have to meet. This means that if a child is meeting their grade level standard in Tennessee they may or may not be meeting the Virginia standards for that grade level. States try to decide what knowledge is imperative for students to learn before they move on to the next grade or even college (ECS, 1999).
States also choose the standards that the teachers must meet (ECS, 1999). The state wants the teacher to be able to educate the students to achieve the set standards. There are things that every state requires, but each of them has their own variation. Every state requires the teacher to have a college degree and some form of standardized testing to be able to teach in their public school system. There are national tests available, but each state requires different ones. Teachers moving to a different state may be required to complete a new test or even a new course before gaining licensure in that state.
States have the largest financial role in the schools. Very little funding comes from the federal government. Most of the federal funding is applied for by the individual school in the form of a grant for a special purpose (Federal Role, n.d.). The states provide teacher salaries and the money required to run each individual school. Each individual school has a PTA that can help the school gain funds for things like technology (ECS, 1999).
Hierarchy Tiers on a District Level
School Board
Superintendent
Principal
Teacher
Each state is broken up into districts (ECS, 1999). Most administration deals on a small level, either within the district, or in the individual school (March, 1978). The districts each have their own school board made of elected members (Office of the Education Ombudsman, n.d.). Those boards decide how their schools will achieve the standards set by the state. They will also decide anything else they believe the schools should be doing to service their district's children. Some of these things include overseeing the curriculum and helping to promote better teaching techniques (Education Administrators, n.d.). The board has to have all schools achieving at a level set by the state, so they use their resources to push the schools to achieve the standards they have set (ECS, 1999).
A superintendent is chosen to oversee the schools in the district (ECS, 1999). Much like a politician, this office is often given to those who have worked their way up from the bottom of the hierarchy (March, 1978). They are in charge of making sure the schools are doing what is required by the school board. They make routine visits to schools to check on how they are doing. They work with the principals and teachers to see that children are getting the most out of each school day.
The district hires principals to oversee each individual school. These principals are there to see that the teachers are doing their job and the children are getting the education they deserve (Office of the Education Ombudsman, n.d.). They are responsible for scheduling, planning the daily activities, and managing the overall activities of the school (Office of the Education Ombudsman, n.d.). Principals make routine visits to classrooms to make sure they are running smoothly and that teachers are making the most of their instructional time. Another difficult duty of the principal is the budget for the school. The principal must decide how to best spend the school's money (Education Administrators, n.d.).
The schools also have assistant principals. These administrators help the principal in the daily activities of the school. They also handle most of the discipline problems leaving the principal available to focus on other duties (Education Administrators, n.d.).
Each school is responsible for the hire of their teachers. The principal can decide who to hire as long as they are qualified by the state (ECS, 1999). Teachers apply for a job through the district and might interview at several schools before being hired by one. Each school is different so principals often look for a teacher who will fit into the school.
The teacher is the one with the most direct affect on students. They ultimately decide what happens in the classrooms (ECS, 1999). When the door closes every morning it is up to the teacher to make an effective use of time and get children to those standards set by the state. If children in their classrooms are not performing well, the teacher is held responsible.
In summary, the federal government makes general regulations for education and contributes very little funding for the schools (Federal Role, n.d.).
The states have most of the power because they are able to set the standards for teachers and students, and they fund the public school system almost completely (ECS, 1999).
The district has the power in the area entrusted to them by the state. Each district has an elected school board that determines how state standards are achieved and anything else they see fit to better the students' education (Office of the Education Ombudsman, n.d.).
The superintendent oversees the schools in the district and makes sure they are following what is set by the states and the district (ECS, 1999).
The principals manage their individual school with assistance from the assistant principal (Office of the Education Ombudsman, n.d.).
The teachers instruct the students in accordance with the standards set before them by all levels of the hierarchy.
Education Administrators . (n.d.). Retrieved February 8, 2009, from http://www.bls.gov .
Education Commission of the States. (1999). Governing America's Schools: Changing the Rules . Denver, CO: Education Commission of the States.
Federal Role in Education . (n.d.). Retrieved February 8, 2009, from http://www.ed.gov .
March, James G. (1978). The School Review, Vol. 86, No. 2. In American Public School Administration: A Short Analysis . Retrieved February 8, 2009, from http://www.jstor.org .
Office of the Education Ombudsman. (n.d.). How Does a School District Work? . [Brochure]. Olympia, WA: Office of the Education Ombudsman.


12.5: Biotechnology (Exercises)
12.1: Cloning and Genetic Engineering
Multiple Choice
In gel electrophoresis of DNA, the different bands in the final gel form because the DNA molecules ________.
- are from different organisms
- have different lengths
- have different nucleotide compositions
- have different genes
- Answer
-
B
In the reproductive cloning of an animal, the genome of the cloned individual comes from ________.
A. a sperm cell
B. an egg cell
C. any gamete cell
D. a body cell
- Answer
-
D
What carries a gene from one organism into a bacteria cell?
A. a plasmid
B. an electrophoresis gel
C. a restriction enzyme
D. polymerase chain reaction
- Answer
-
A
Free Response
What is the purpose and benefit of the polymerase chain reaction?
- Answer
-
The polymerase chain reaction is used to quickly produce many copies of a specific segment of DNA when only one or a very few copies are originally present. The benefit of PCR is that there are many instances in which we would like to know something about a sample of DNA when only very small amounts are available. PCR allows us to increase the number of DNA molecules so that other tests, such as sequencing, can be performed with it.
12.2: Biotechnology in Medicine and Agriculture
Multiple Choice
What is a genetically modified organism (GMO)?
A. a plant with certain genes removed
B. an organism with an artificially altered genome
C. a hybrid organism
D. any agricultural organism produced by breeding or biotechnology
- Answer
-
B
What is the role of Agrobacterium tumefaciens in the production of transgenic plants?
A. Genes from
A. tumefaciens
are inserted into plant DNA to give the plant different traits.
B. Transgenic plants have been given resistance to the pest
A. tumefaciens
.
C. A. tumefaciens
is used as a vector to move genes into plant cells.
D. Plant genes are incorporated into the genome of
Agrobacterium tumefaciens
.
- Answer
-
C
Free Response
Today, it is possible for a diabetic patient to purchase human insulin from a pharmacist. What technology makes this possible and why is it a benefit over how things used to be?
- Answer
-
The human insulin comes from the gene that produces insulin in humans, which has been spliced into a bacterial genome using recombinant DNA technology. The bacterium produces the insulin, which is then purified for human use. Before there was genetically engineered human insulin, diabetics were given insulin extracted from pig pancreases, which was similar to, but not exactly like, human insulin. Because it was not exactly like human insulin, the pig insulin caused complications in some diabetic patients.
12.3: Genomics and Proteomics
Multiple Choice
What is the most challenging issue facing genome sequencing?
A. the inability to develop fast and accurate sequencing techniques
B. the ethics of using information from genomes at the individual level
C. the availability and stability of DNA
D. all of the above
- Answer
-
B
Genomics can be used in agriculture to:
A. generate new hybrid strains
B. improve disease resistance
C. improve yield
D. all of the above
- Answer
-
D
What kind of diseases are studied using genome-wide association studies?
A. viral diseases
B. single-gene inherited diseases
C. diseases caused by multiple genes
D. diseases caused by environmental factors
- Answer
-
C
Free Response
Describe two of the applications for genome mapping.
- Answer
-
Genome mapping helps researchers to study disease-causing genes in humans. It also helps to identify traits of organisms that can be used in applications such as cleaning up pollution.
Identify a possible advantage and a possible disadvantage of a genetic test that would identify genes in individuals that increase their probability of having Alzheimer's disease later in life.
- Answer
-
The benefit of such a test is that the individual can make preparations for having the disease including taking treatments that slow the disease. The disadvantage of the test is that it might be used by insurance companies to deny coverage to the person.
Contributors and Attributions
Remixed and/or curated from the following works:
Fowler, S., Roush, R., & Wise, J. (2013). 10.E Biotechnology (Exercises) . In Concepts of Biology . OpenStax (CC BY 4.0; Access for free at https://openstax.org/books/concepts-biology/pages/1-introduction ).


44.5D: Past and Present Effects of Climate Change
- Describe the effects of current and geological climate change
Documented results of climate change: past and present
Scientists have geological evidence of the consequences of long-ago climate change. Modern-day phenomena, such as retreating glaciers and melting polar ice, cause a continual rise in sea level. Changes in climate can negatively affect organisms.
Geological climate change effects
Global warming has been associated with at least one planet-wide extinction event during the geological past. The Permian extinction event occurred about 251 million years ago toward the end of the roughly 50-million-year-long geological time span known as the Permian period. This geologic time period was one of the three warmest periods in earth’s geologic history. Scientists estimate that approximately 70 percent of the terrestrial plant and animal species and 84 percent of marine species became extinct, vanishing forever near the end of the Permian period. Organisms that had adapted to wet and warm climatic conditions, such as annual rainfall of 300–400 cm (118–157 in) and 20 °C–30 °C (68 °F–86 °F) in the tropical wet forest, may not have been able to survive the Permian climate change.
Present climate change effects
A number of global events have occurred that may be attributed to recent climate change during our lifetimes. Glacier National Park in Montana, among others, is undergoing the retreat of many of its glaciers, a phenomenon known as glacier recession. In 1850, the area contained approximately 150 glaciers. By 2010, however, the park contained only about 24 glaciers greater than 25 acres in size. One of these glaciers is the Grinnell Glacier at Mount Gould. Between 1966 and 2005, the size of Grinnell Glacier shrank by 40 percent. Similarly, the mass of the ice sheets in Greenland and the Antarctic is decreasing: Greenland lost 150–250 km 3 of ice per year between 2002 and 2006. In addition, the size and thickness of the Arctic sea ice is decreasing.
This loss of ice is leading to rises in the global sea level. On average, the sea is rising at a rate of 1.8 mm per year. However, between 1993 and 2010, the rate of sea-level increase ranged between 2.9 and 3.4 mm per year. A variety of factors affect the volume of water in the ocean, including the temperature of the water (the density of water is related to its temperature) and the amount of water found in rivers, lakes, glaciers, polar ice caps, and sea ice. As glaciers and polar ice caps melt, there is a significant contribution of liquid water that was previously frozen.
In addition to some abiotic conditions changing in response to climate change, many organisms are also being affected by the changes in temperature. Temperature and precipitation play key roles in determining the geographic distribution and phenology of plants and animals. Phenology is the study of the effects of climatic conditions on the timing of periodic lifecycle events, such as flowering in plants or migration in birds. Researchers have shown that 385 plant species in Great Britain are flowering 4.5 days sooner than was recorded during the previous 40 years. In addition, insect-pollinated species were more likely to flower earlier than wind-pollinated species. The impact of changes in flowering date would be mitigated if the insect pollinators emerged earlier. This mismatched timing of plants and pollinators could result in injurious ecosystem effects because, for continued survival, insect-pollinated plants must flower when their pollinators are present.
Contributions and Attributions
- OpenStax College, Biology. October 17, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44861/latest...ol11448/latest . License : CC BY: Attribution
- biome. Provided by : Wiktionary. Located at : http://en.wiktionary.org/wiki/biome . License : CC BY-SA: Attribution-ShareAlike
- climate. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/climate . License : CC BY-SA: Attribution-ShareAlike
- weather. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/weather . License : CC BY-SA: Attribution-ShareAlike
- Provided by : Daily Galaxy. Located at : www.dailygalaxy.com/photos/un...es_zones_2.gif . License : CC BY: Attribution
- greenhouse gas. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/greenhouse_gas . License : CC BY-SA: Attribution-ShareAlike
- OpenStax College, Biology. October 17, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44861/latest...ol11448/latest . License : CC BY: Attribution
- Milankovitch cycle. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/Milankovitch_cycle . License : CC BY-SA: Attribution-ShareAlike
- greenhouse effect. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/greenhouse_effect . License : CC BY-SA: Attribution-ShareAlike
- Provided by : Daily Galaxy. Located at : www.dailygalaxy.com/photos/un...es_zones_2.gif . License : CC BY: Attribution
- OpenStax College, Climate and the Effects of Global Climate Change. October 17, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44861/latest...e_44_05_03.jpg . License : CC BY: Attribution
- OpenStax College, Biology. October 17, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44861/latest/?collection=col11448/latest . License : CC BY: Attribution
- fossil fuel. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/fossil_fuel . License : CC BY-SA: Attribution-ShareAlike
- Provided by : Daily Galaxy. Located at : www.dailygalaxy.com/photos/un...es_zones_2.gif . License : CC BY: Attribution
- OpenStax College, Climate and the Effects of Global Climate Change. October 17, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44861/latest/Figure_44_05_03.jpg . License : CC BY: Attribution
- OpenStax College, Climate and the Effects of Global Climate Change. October 17, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44861/latest...e_44_05_01.jpg . License : CC BY: Attribution
- OpenStax College, Climate and the Effects of Global Climate Change. October 17, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44861/latest...e_44_05_02.jpg . License : CC BY: Attribution
- OpenStax College, Biology. October 17, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44861/latest/?collection=col11448/latest . License : CC BY: Attribution
- Permian. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/Permian . License : CC BY-SA: Attribution-ShareAlike
- phenology. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/phenology . License : CC BY-SA: Attribution-ShareAlike
- Provided by : Daily Galaxy. Located at : www.dailygalaxy.com/photos/un...es_zones_2.gif . License : CC BY: Attribution
- OpenStax College, Climate and the Effects of Global Climate Change. October 17, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44861/latest/Figure_44_05_03.jpg . License : CC BY: Attribution
- OpenStax College, Climate and the Effects of Global Climate Change. October 17, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44861/latest/Figure_44_05_01.jpg . License : CC BY: Attribution
- OpenStax College, Climate and the Effects of Global Climate Change. October 17, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44861/latest/Figure_44_05_02.jpg . License : CC BY: Attribution
- OpenStax College, Climate and the Effects of Global Climate Change. October 17, 2013. Provided by : OpenStax CNX. Located at : http://cnx.org/content/m44861/latest...e_44_05_04.jpg . License : CC BY: Attribution
Key Points
- Global warming has been associated with at least one planet-wide extinction event during the geological past; scientists estimate that during the Permian period, approximately 70 percent of the terrestrial plant and animal species along with 84 percent of marine species became extinct.
- Glacier recession and melting ice caps are direct effects of current global climate change, ultimately leading to higher global sea levels; as glaciers and polar ice caps melt, there is a significant contribution of liquid water that was previously frozen.
- Changes in temperature and precipitation are causing plants to flower earlier, before their insect pollinators have emerged; mismatched timing of plants and pollinators could result in injurious ecosystem effects.
- This mismatched timing of plants and pollinators could result in injurious ecosystem effects because, for continued survival, insect-pollinated plants must flower when their pollinators are present.
Key Terms
- phenology : the study of the effect of climate on periodic biological phenomena
- Permian : of a geologic period within the Paleozoic era; comprises the Cisuralian, Guadalupian, and Lopingian epochs from about 280 to 248 million years ago


6.7: Product vs. Period Costs
Learning Outcomes
- Differentiate between product costs and period costs
When preparing financial statements, companies need to classify costs as either product costs or period costs. We need to first revisit the concept of the matching principle from financial accounting.
As a general rule, costs are recognized as expenses on the income statement in the period that the benefit was derived from the cost. So if you pay for two years of liability insurance, it wouldn’t be good to claim all of that expense in the period the bill was paid. Since the expense covers a two year period, it should be recognized over both years. This is an example of the accrual basis of recording costs.
The matching principle operates on the accrual basis of accounting and states: Costs incurred to generate a particular revenue, should be recognized as expense in the same period that the revenue is recognized. If a cost is incurred to acquire or produce a product that will ultimately be sold, then the cost should be recorded as an expense when the sale takes place because that is when the benefit occurs. These costs are called product costs.
Product Costs
Product Costs include any cost of acquiring or producing a product. If you manufacture a product, these costs would include direct materials and labor along with manufacturing overhead. Most of the components of a manufactured item will be raw materials that, when received, are recorded as inventory on the balance sheet. Only when they are used to produce and sell goods are they moved to cost of goods sold, which is located on the income statement. When the raw materials are brought in they will sit on the balance sheet. When the product is manufactured and then sold a corresponding amount from the inventory account will be moved to the income statement. So if you sell a widget for $20 that had $10 worth of raw materials, you would record the sale as a credit (increasing) to sales and a debit (increasing) either cash or accounts receivable. The $10 direct materials would be a debit to cost of goods sold (increasing) and a credit to inventory (decreasing).
Period Costs
Period costs include any costs not related to the manufacture or acquisition of your product. Sales commissions, administrative costs, advertising and rent of office space are all period costs. These costs are not included as part of the cost of either purchased or manufactured goods, but are recorded as expenses on the income statement in the period they are incurred. Remember, when expenses incurred may not be when cash changes hands. If advertising happens in June, you will receive an invoice, and record the expense in June, even if you have terms that allow you to actually pay the expense in July. Remember back to our insurance situation in the first paragraph. The cash may actually be spent on an item that will be incurred later, like insurance. It is important to understand through the accrual method of accounting, that expenses and income should be recognized when incurred, not necessarily when they are paid or cash received.
Practice Questions


E.2: Reliability of a Measurement & Significant Figures
- Compare and contrast exact and uncertain numbers.
- Correctly represent uncertainty in quantities using significant figures.
- Identify the number of significant figures in value.
- Solve problems that involve various calculations and report the results with the appropriate number of significant figures.
- Apply proper rounding rules to computed quantities
- Define accuracy and precision, and use accuracy and precision to describe data sets.
Counting is the only type of measurement that is free from uncertainty, provided the number of objects being counted does not change while the counting process is underway. The result of such a counting measurement is an example of an exact number . If we count eggs in a carton, we know exactly how many eggs the carton contains. The numbers of defined quantities are also exact. By definition, 1 foot is exactly 12 inches, 1 inch is exactly 2.54 centimeters, and 1 gram is exactly 0.001 kilogram. Quantities derived from measurements other than counting, however, are uncertain to varying extents due to practical limitations of the measurement process used.
Significant Figures in Measurement
The numbers of measured quantities, unlike defined or directly counted quantities, are not exact. To measure the volume of liquid in a graduated cylinder, you should make a reading at the bottom of the meniscus, the lowest point on the curved surface of the liquid.
Refer to the illustration in Figure \(\PageIndex{1}\). The bottom of the meniscus in this case clearly lies between the 21 and 22 markings, meaning the liquid volume is certainly greater than 21 mL but less than 22 mL. The meniscus appears to be a bit closer to the 22-mL mark than to the 21-mL mark, and so a reasonable estimate of the liquid’s volume would be 21.6 mL. In the number 21.6, then, the digits 2 and 1 are certain, but the 6 is an estimate. Some people might estimate the meniscus position to be equally distant from each of the markings and estimate the tenth-place digit as 5, while others may think it to be even closer to the 22-mL mark and estimate this digit to be 7. Note that it would be pointless to attempt to estimate a digit for the hundredths place, given that the tenths-place digit is uncertain. In general, numerical scales such as the one on this graduated cylinder will permit measurements to one-tenth of the smallest scale division. The scale in this case has 1-mL divisions, and so volumes may be measured to the nearest 0.1 mL.
This concept holds true for all measurements, even if you do not actively make an estimate. If you place a quarter on a standard electronic balance, you may obtain a reading of 6.72 g. The digits 6 and 7 are certain, and the 2 indicates that the mass of the quarter is likely between 6.71 and 6.73 grams. The quarter weighs about 6.72 grams, with a nominal uncertainty in the measurement of ± 0.01 gram. If we weigh the quarter on a more sensitive balance, we may find that its mass is 6.723 g. This means its mass lies between 6.722 and 6.724 grams, an uncertainty of 0.001 gram. Every measurement has some uncertainty , which depends on the device used (and the user’s ability). All of the digits in a measurement, including the uncertain last digit, are called significant figures or significant digits . Note that zero may be a measured value; for example, if you stand on a scale that shows weight to the nearest pound and it shows “120,” then the 1 (hundreds), 2 (tens) and 0 (ones) are all significant (measured) values.
Whenever you make a measurement properly, all the digits in the result are significant. But what if you were analyzing a reported value and trying to determine what is significant and what is not? Well, for starters, all nonzero digits are significant, and it is only zeros that require some thought. We will use the terms “leading,” “trailing,” and “captive” for the zeros and will consider how to deal with them.
Starting with the first nonzero digit on the left, count this digit and all remaining digits to the right. This is the number of significant figures in the measurement unless the last digit is a trailing zero lying to the left of the decimal point.
Captive zeros result from measurement and are therefore always significant. Leading zeros, however, are never significant—they merely tell us where the decimal point is located.
The leading zeros in this example are not significant. We could use exponential notation (as described in Appendix B) and express the number as 8.32407 \(\times\) 10 −3 ; then the number 8.32407 contains all of the significant figures, and 10 −3 locates the decimal point.
The number of significant figures is uncertain in a number that ends with a zero to the left of the decimal point location. The zeros in the measurement 1,300 grams could be significant or they could simply indicate where the decimal point is located. The ambiguity can be resolved with the use of exponential notation: 1.3 \(\times\) 10 3 (two significant figures), 1.30 \(\times\) 10 3 (three significant figures, if the tens place was measured), or 1.300 \(\times\) 10 3 (four significant figures, if the ones place was also measured). In cases where only the decimal-formatted number is available, it is prudent to assume that all trailing zeros are not significant.
When determining significant figures, be sure to pay attention to reported values and think about the measurement and significant figures in terms of what is reasonable or likely—that is, whether the value makes sense. For example, the official January 2014 census reported the resident population of the US as 317,297,725. Do you think the US population was correctly determined to the reported nine significant figures, that is, to the exact number of people? People are constantly being born, dying, or moving into or out of the country, and assumptions are made to account for the large number of people who are not actually counted. Because of these uncertainties, it might be more reasonable to expect that we know the population to within perhaps a million or so, in which case the population should be reported as 317 million, or \(3.17 \times 10^8 \) people.
Significant Figures in Calculations
A second important principle of uncertainty is that results calculated from a measurement are at least as uncertain as the measurement itself. We must take the uncertainty in our measurements into account to avoid misrepresenting the uncertainty in calculated results. One way to do this is to report the result of a calculation with the correct number of significant figures, which is determined by the following three rules for rounding numbers:
- When we add or subtract numbers, we should round the result to the same number of decimal places as the number with the least number of decimal places (the least precise value in terms of addition and subtraction).
- When we multiply or divide numbers, we should round the result to the same number of digits as the number with the least number of significant figures (the least precise value in terms of multiplication and division).
- If the digit to be dropped (the one immediately to the right of the digit to be retained) is less than 5, we “round down” and leave the retained digit unchanged; if it is more than 5, we “round up” and increase the retained digit by 1; if the dropped digit is 5, we round up or down, whichever yields an even value for the retained digit. (The last part of this rule may strike you as a bit odd, but it’s based on reliable statistics and is aimed at avoiding any bias when dropping the digit “5,” since it is equally close to both possible values of the retained digit.)
The following examples illustrate the application of this rule in rounding a few different numbers to three significant figures:
- 0.028675 rounds “up” to 0.0287 (the dropped digit, 7, is greater than 5)
- 18.3384 rounds “down” to 18.3 (the dropped digit, 3, is less than 5)
- 6.8752 rounds “up” to 6.88 (the dropped digit is 5, and the retained digit is even)
- 92.85 rounds “down” to 92.8 (the dropped digit is 5, and the retained digit is even)
Let’s work through these rules with a few examples.
Round the following to the indicated number of significant figures:
- 31.57 (to two significant figures)
- 8.1649 (to three significant figures)
- 0.051065 (to four significant figures)
- 0.90275 (to four significant figures)
Solution
- 31.57 rounds “up” to 32 (the dropped digit is 5, and the retained digit is even)
- 8.1649 rounds “down” to 8.16 (the dropped digit, 4, is less than 5)
- 0.051065 rounds “down” to 0.05106 (the dropped digit is 5, and the retained digit is even)
- 0.90275 rounds “up” to 0.9028 (the dropped digit is 5, and the retained digit is even)
Round the following to the indicated number of significant figures:
- 0.424 (to two significant figures)
- 0.0038661 (to three significant figures)
- 421.25 (to four significant figures)
- 28,683.5 (to five significant figures)
- Answer a
-
0.42
- Answer b
-
0.00387
- Answer c
-
421.2
- Answer d
-
28,684
When we add or subtract numbers, we should round the result to the same number of decimal places as the number with the least number of decimal places (i.e., the least precise value in terms of addition and subtraction).
- Add 1.0023 g and 4.383 g.
- Subtract 421.23 g from 486 g.
Solution
(a)
\[\begin{align*}
&\mathrm{1.0023\: g}\\ +\: &\underline{\mathrm{4.383\: g}\:\:}\\ &\mathrm{5.3853\: g}
\end{align*} \nonumber \]
Answer is 5.385 g (round to the thousandths place; three decimal places)
(b)
\[\begin{align*}
&\mathrm{486\: g}\\ -\: &\underline{\mathrm{421.23\: g}}\\ &\mathrm{\:\:64.77\: g}
\end{align*} \nonumber \]
Answer is 65 g (round to the ones place; no decimal places)
- Add 2.334 mL and 0.31 mL.
- Subtract 55.8752 m from 56.533 m.
- Answer a
-
2.64 mL
- Answer b
-
0.658 m
Rule: When we multiply or divide numbers, we should round the result to the same number of digits as the number with the least number of significant figures (the least precise value in terms of multiplication and division).
- Multiply 0.6238 cm by 6.6 cm.
- Divide 421.23 g by 486 mL.
Solution
(a)
\[\mathrm{0.6238\: cm\times6.6\:cm=4.11708\:cm^2\rightarrow result\: is\:4.1\:cm^2}\:\textrm{(round to two significant figures)} \nonumber \]
\[\textrm{four significant figures}\times \textrm{two significant figures}\rightarrow \textrm{two significant figures answer} \nonumber \]
(b)
\[\mathrm{\dfrac{421.23\: g}{486\: mL}=0.86728...\: g/mL\rightarrow result\: is\: 0.867\: g/mL} \: \textrm{(round to three significant figures)} \nonumber \]
\[\mathrm{\dfrac{five\: significant\: figures}{three\: significant\: figures}\rightarrow three\: significant\: figures\: answer} \nonumber \]
- Multiply 2.334 cm and 0.320 cm.
- Divide 55.8752 m by 56.53 s.
- Answer a
-
0.747 cm 2
- Answer b
-
0.9884 m/s
In the midst of all these technicalities, it is important to keep in mind the reason why we use significant figures and rounding rules—to correctly represent the certainty of the values we report and to ensure that a calculated result is not represented as being more certain than the least certain value used in the calculation.
One common bathtub is 13.44 dm long, 5.920 dm wide, and 2.54 dm deep. Assume that the tub is rectangular and calculate its approximate volume in liters.
Solution
\[\begin{align*}
V&=l\times w\times d\\ &=\mathrm{13.44\: dm\times 5.920\: dm\times 2.54\: dm}\\ &=\mathrm{202.09459...dm^3}\:\textrm{(value from calculator)}\\ &=\mathrm{202\: dm^3,}\textrm{ or 202 L (answer rounded to three significant figures)}
\end{align*} \nonumber \]
What is the density of a liquid with a mass of 31.1415 g and a volume of 30.13 cm 3 ?
- Answer
-
1.034 g/mL
A piece of rebar is weighed and then submerged in a graduated cylinder partially filled with water, with results as shown.
- Use these values to determine the density of this piece of rebar.
- Rebar is mostly iron. Does your result in (a) support this statement? How?
Solution
The volume of the piece of rebar is equal to the volume of the water displaced:
\[\mathrm{volume=22.4\: mL-13.5\: mL=8.9\: mL=8.9\: cm^3}\nonumber \]
(rounded to the nearest 0.1 mL, per the rule for addition and subtraction)
The density is the mass-to-volume ratio:
\[\mathrm{density=\dfrac{mass}{volume}=\dfrac{69.658\: g}{8.9\: cm^3}=7.8\: g/cm^3}\nonumber \]
(rounded to two significant figures, per the rule for multiplication and division)
The density of iron is 7.9 g/cm 3 , very close to that of rebar, which lends some support to the fact that rebar is mostly iron.
An irregularly shaped piece of a shiny yellowish material is weighed and then submerged in a graduated cylinder, with results as shown.
- Use these values to determine the density of this material.
- Do you have any reasonable guesses as to the identity of this material? Explain your reasoning.
- Answer a
-
19 g/cm 3
- Answer b
-
It is likely gold; it has the right appearance for gold and very close to the density given for gold.
Accuracy and Precision
Scientists typically make repeated measurements of a quantity to ensure the quality of their findings and to know both the precision and the accuracy of their results. Measurements are said to be precise if they yield very similar results when repeated in the same manner. A measurement is considered accurate if it yields a result that is very close to the true or accepted value. Precise values agree with each other; accurate values agree with a true value. These characterizations can be extended to other contexts, such as the results of an archery competition (Figure \(\PageIndex{2}\)).
Suppose a quality control chemist at a pharmaceutical company is tasked with checking the accuracy and precision of three different machines that are meant to dispense 10 ounces (296 mL) of cough syrup into storage bottles. She proceeds to use each machine to fill five bottles and then carefully determines the actual volume dispensed, obtaining the results tabulated in Table \(\PageIndex{2}\).
| Dispenser #1 | Dispenser #2 | Dispenser #3 |
|---|---|---|
| 283.3 | 298.3 | 296.1 |
| 284.1 | 294.2 | 295.9 |
| 283.9 | 296.0 | 296.1 |
| 284.0 | 297.8 | 296.0 |
| 284.1 | 293.9 | 296.1 |
Considering these results, she will report that dispenser #1 is precise (values all close to one another, within a few tenths of a milliliter) but not accurate (none of the values are close to the target value of 296 mL, each being more than 10 mL too low). Results for dispenser #2 represent improved accuracy (each volume is less than 3 mL away from 296 mL) but worse precision (volumes vary by more than 4 mL). Finally, she can report that dispenser #3 is working well, dispensing cough syrup both accurately (all volumes within 0.1 mL of the target volume) and precisely (volumes differing from each other by no more than 0.2 mL).
Summary
Quantities can be exact or measured. Measured quantities have an associated uncertainty that is represented by the number of significant figures in the measurement. The uncertainty of a calculated value depends on the uncertainties in the values used in the calculation and is reflected in how the value is rounded. Measured values can be accurate (close to the true value) and/or precise (showing little variation when measured repeatedly).
Glossary
- uncertainty
- estimate of amount by which measurement differs from true value
- significant figures
- (also, significant digits) all of the measured digits in a determination, including the uncertain last digit
- rounding
- procedure used to ensure that calculated results properly reflect the uncertainty in the measurements used in the calculation
- precision
- how closely a measurement matches the same measurement when repeated
- exact number
- number derived by counting or by definition
- accuracy
- how closely a measurement aligns with a correct value


21: Nuclear Chemistry
The chemical reactions that we have considered in previous chapters involve changes in the electronic structure of the species involved, that is, the arrangement of the electrons around atoms, ions, or molecules. Nuclear structure, the numbers of protons and neutrons within the nuclei of the atoms involved, remains unchanged during chemical reactions. This chapter will introduce the topic of nuclear chemistry, which began with the discovery of radioactivity in 1896 by French physicist Antoine Becquerel and has become increasingly important during the twentieth and twenty-first centuries, providing the basis for various technologies related to energy, medicine, geology, and many other areas.
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- 21.1: Nuclear Structure and Stability
- An atomic nucleus consists of protons and neutrons, collectively called nucleons. Although protons repel each other, the nucleus is held tightly together by a short-range, but very strong, force called the strong nuclear force. A nucleus has less mass than the total mass of its constituent nucleons. This “missing” mass is the mass defect, which has been converted into the binding energy that holds the nucleus together according to Einstein’s mass-energy equivalence equation, E = mc2.
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- 21.2: Nuclear Equations
- Nuclei can undergo reactions that change their number of protons, number of neutrons, or energy state. Many different particles can be involved in nuclear reactions. The most common are protons, neutrons, positrons (which are positively charged electrons), alpha (α) particles (which are high-energy helium nuclei), beta (β) particles (which are high-energy electrons), and gamma (γ) rays (which compose high-energy electromagnetic radiation).
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- 21.3: Radioactive Decay
- Unstable nuclei undergo spontaneous radioactive decay. The most common types of radioactivity are α decay, β decay, γ emission, positron emission, and electron capture. Nuclear reactions also often involve γ rays, and some nuclei decay by electron capture. Each of these modes of decay leads to the formation of a new stable nuclei sometimes via multiple decays before ending in a stable isotope. All nuclear decay processes follow first-order kinetics and each radioisotope has its own half-life.
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- 21.4: Transmutation and Nuclear Energy
- It is possible to produce new atoms by bombarding other atoms with nuclei or high-speed particles. The products of these transmutation reactions can be stable or radioactive. A number of artificial elements, including technetium, astatine, and the transuranium elements, have been produced in this way. Nuclear power as well as nuclear weapon detonations can be generated through fission (reactions in which a heavy nucleus is split into two or more lighter nuclei and several neutrons).
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- 21.5: Uses of Radioisotopes
- Compounds known as radioactive tracers can be used to follow reactions, track the distribution of a substance, diagnose and treat medical conditions, and much more. Other radioactive substances are helpful for controlling pests, visualizing structures, providing fire warnings, and for many other applications. Hundreds of millions of nuclear medicine tests and procedures, using a wide variety of radioisotopes with relatively short half-lives, are performed every year in the US.
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- 21.6: Biological Effects of Radiation
- We are constantly exposed to radiation from naturally occurring and human-produced sources. This radiation can affect living organisms. Ionizing radiation is particularly harmful because it can ionize molecules or break chemical bonds, which damages the molecules & causes malfunctions in cell processes. Types of radiation differ in their ability to penetrate material and damage tissue, with alpha particles the least penetrating, but potentially most damaging, and gamma rays the most penetrating.


19.7: Nucleophilic Addition of HCN- Cyanohydrin Formation
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Objectives
After completing this section, you should be able to
- write an equation to describe the formation of a cyanohydrin from an aldehyde or ketone.
- identify the cyanohydrin formed from the reaction of a given aldehyde or ketone with hydrogen cyanide.
- identify the aldehyde or ketone, the reagents, or both, needed to prepare a given cyanohydrin.
- write the detailed mechanism for the addition of hydrogen cyanide to an aldehyde or ketone.
Key Terms
Make certain that you can define, and use in context, the key term below.
- cyanohydrin
Study Notes
For successful cyanohydrin formation it is important to have free cyanide ions available to react with the ketone or aldehyde. This can be achieved by using a salt (e.g. KCN or NaCN) or a silylated (e.g. Me 3 SiCN) form of cyanide under acidic conditions or by using HCN with some base added to produce the needed CN − nucleophile.
Hydrogen cyanide (HC≡N), adds reversibly to aldehydes and many ketones forming hydroxyalkanenitrile adducts commonly known and as cyanohydrins . Cyanohydrins have the structural formula of R 2 C(OH)CN. The “R” on the formula represents an alkyl group, aryl group, or hydrogen.
An important feature of cyanohydrin formation is that it requires a basic catalyst. Since hydrogen cyanide itself is a weak acid (pK a = 9.25), the best results occur when a small amount of a strong base activates hydrogen cyanide by converting it to cyanide ion ( - C≡N) , which can function as a carbon nucleophile. In the absence of base, the reaction does not proceed, or is at best very slow. Cyanohydrin formation is weakly exothermic, and is favored for aldehydes, and unhindered cyclic and methyl ketones.
Hydrogen cyanide (HCN) is hazardous to handle because it is highly toxic. Therefore in many syntheses of cyanohydrins, HCN is created in situ by adding a strong acid to a mixture of sodium cyanide and the carbonyl compound, so that hydrogen cyanide is generated in situ . The amount of acid added should be insufficient to consume all the cyanide ion, therefore sufficiently alkaline conditions are maintained for rapid addition.
Mechanism of Cyanohydrin Formation
In the first step of the mechanism, the cyanide ion acts as a nucleophile and forms a C-C bond with the electrophillic carbonyl carbon. The two electrons in the carbonyl pi bond are pushed on to the electronegative oxygen forming a tetrahedral alkoxide ion intermediate. In the second step, the alkoxide ion is protonated by HCN which regenerates the cyanide ion.
Step 1: Nucleophilic attack
Step 2: Protonation
Further Chemistry of Cyanohydrins
Cyanohydrin functional groups often prove useful because of the further chemistry that can be carried out due to the presence of a hydroxyl and a nitrile functionality. In particular, dehydration can convert the hydroxyl group into an alkene ( Section 17.6 ). The nitrile can be converted into a carboxylic acid function group through reaction with a hot acidic aqueous solution ( Section 20.7 ). Also, the nitrile can be reduced by the addition of LiAlH 4 to form a primary amine.
Other Cyanohydrins
Other interesting cyanohydrins are: acetone cyanohydrin , and glycolonitrile .
Acetone cyanohydrin has the structure, (CH 3 ) 2 C(OH)CN, and is used in the production of methyl methacrylate (also known as acrylic). Glycolonitrile is an organic compound with the structural formula of HOCH 2 CN, which is the simplest cyanohydrin that is derived by formaldehydes.
Exercise \(\PageIndex{1}\)
Complete the following reaction for cyanohydrins.
- Answer
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Exercise \(\PageIndex{2}\)
Complete the following reaction for cyanohydrins.
- Answer
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Exercise \(\PageIndex{3}\)
True or False: For a cyanohydrin to form, a fast addition of strong acid to cyanide salt is carried out to convert the salt into HCN.
- Answer
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False, slow addition
Exercise \(\PageIndex{4}\)
True or False: Cyanohydrin reactions are irreversible .
- Answer
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False, reversible
Exercise \(\PageIndex{5}\)
What is the product for the overall reaction?
- Answer
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5.7: Red-Black trees
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A red-black tree is a self-balancing tree structure that applies a color to each of its nodes. The structure of a red-black tree must adhere to a set of rules which dictate how nodes of a certain color can be arranged. The application of these rules is performed when the tree is modified in some way, causing the rotation and recolouring of certain nodes when a new node is inserted or an old node is deleted. This keeps the red-black tree balanced, guaranteeing a search complexity of O(log n ).
The rules that a red-black tree must adhere to are as follows:
- Each node must be either red or black.
- The root is always black.
- All leaves within the tree are black (leaves do not contain data and can be modelled as null or nil references in most programming languages).
- Every red node must have two black child nodes.
- Every path from a given node to any of its descendant leaves must contain the same number of black nodes.
A red-black tree can be modelled as 2-3-4 tree, which is a sub-class of B tree (below). A black node with one red node can be seen as linked together as a 3-node, and a black node with 2 red child nodes can be seen as a 4-node.
4-nodes are split , producing a two node, and the middle node made red, which turns a parent of the middle node which has no red child from a 2-node to a 3-node, and turns a parent with one red child into a 4-node (but this doesn't occur with always left red nodes).
A in-line arrangement of two red nodes, is rotated into a parent with two red children, a 4-node, which is later split , as described before.
A right rotate 'split 4-node' |red red / \ --> B ---> B B red/ \red / \ red / \ C A C A C D / / D D
An optimization mentioned by Sedgewick is that all right inserted red nodes are left rotated to become left red nodes, so that only inline left red nodes ever have to be rotated right before splitting. AA-trees (above) by Arne Anderson , described in a paper in 1993 , seem an earlier exposition of the simplification, however he suggested right-leaning 'red marking' instead of left leaning , as suggested by Sedgewick, but AA trees seem to have precedence over left leaning red black trees. It would be quite a shock if the Linux CFS scheduler was described in the future as 'AA based'.
In summary, red-black trees are a way of detecting two insertions into the same side, and levelling out the tree before things get worse . Two left sided insertions will be rotated, and the two right sided insertions, would look like two left sided insertions after left rotation to remove right leaning red nodes. Two balanced insertions for the same parent could result in a 4-node split without rotation, so the question arises as to whether a red black tree could be attacked with serial insertions of one sided triads of a < P < b, and then the next triad's P' < a.
Python illustrative code follows
RED = 1 BLACK = 0 class Node: def __init__(self, k, v): # all newly inserted node's are RED self.color = RED self.k = k self.v = v self.left = None self.right = None class RBTree: def __init__(self): self.root = None def insert(self, k, v) : self.root = self._insert(self.root, k,v) def _insert(self, n , k, v): if n is None: return Node(k,v) if k < n.k : n.left = self._insert(n.left, k , v) elif k > n.k : n.right = self._insert(n.right, k, v) if n.right.color is RED: #always on the left red's #left rotate tmp = n.right n.right = tmp.left tmp.left = n n = tmp #color rotation is actually a swap tmpcolor = n.color n.color = n.left.color n.left.color = tmpcolor if n.left <> None and n.left.left <> None and n.left.left.color == RED and n.left.color == RED: # right rotate in-line reds print "right rotate" tmp = n.left n.left = tmp.right tmp.right = n n = tmp #color rotation is actually a swap tmpcolor = n.color n.color = n.right.color n.right.color = tmpcolor if n.left <> None: print n.left.color, n.color, n.right.color #no need to test, because after right rotation, will need to split 3-node , as right rotation has #brought red left grandchild to become left red child, and left red child is now red right child #so there are two red children. #if n.left <> None and n.right <> None and n.left.color == RED and n.right.color == RED: print "split" n.color = RED n.left.color = BLACK n.right.color = BLACK return n def find(self, k): return self._find_rb(k, self.root) def _find_rb(self, k, n): if n is None: return None if k < n.k: return self._find_rb( k, n.left) if k > n. k: return self._find_rb( k, n.right) return n.v def inorder(self): self.inorder_visit(self.root, "O") def inorder_visit(self, node,label=""): if node is None: return self.inorder_visit(node.left, label+"/L") print label, "val=", node.v self.inorder_visit(node.right, label+"/R") def test1(N): t = RBTree() for i in xrange(0,N): t.insert(i,i) l = [] t.inorder() for i in xrange(0,N): x =t.find(i) if x <> None: l.append((x, i) ) print "found", len(l) if __name__ == "__main__": import random test1(100000) test1(1000) test1(100) test1(10)


8.5: Summary
8.1 Wound Classification
Wounds are classified in several ways and include intentional or un intentional wound s (i.e., from treatment/therapy or accidental), open or closed wound s (i.e., break in the skin or under the skin layers), acute or chronic wound s (i.e., follows normal healing process or is delayed and does not follow normal healing process), pressure injuries, and friction and shear. Pressure injuries are localized ischemic lesions of the skin and underlying tissue caused by external pressure that impair blood and lymph flow. Friction and shear are mechanical forces that tear and injure blood vessels and can contribute to the development of pressure injuries.
Risk factors for development of pressure injuries include exposure to excessive moisture, malnutrition and dehydration, and decreased mobility and cognition . Moisture weakens the skin integrity and makes it more susceptible to breakdown and infection. Malnourishment leads to cell damage, inadequate perfusion, and lack of padding for bony prominences. People who have mobility issues or are bedridden are unable to adjust themselves in response to pressure and are often in one position for a prolonged period of time. Those with altered mental status and who have decreased awareness (e.g., unconsciousness, sedation, or dementia) are at risk because they are less likely to recognize and respond to the discomfort from pressure.
Depending on the extent of damage, pressure injuries are assessed and classified as stages I through IV and as deep tissue or unstageable. A stage I pressure injury is characterized by localized, nonblanchable erythema of intact skin. Stage II pressure injuries are characterized by Partial-thickness (second-degree) skin loss involving the epidermis or dermis. Stage III pressure injuries are characterized by full-thickness skin loss in which the adipose, granulation, and deeper tissues are visible and may have a presence of slough or eschar . Stage IV pressure injuries are characterized by full-thickness skin loss with extensive destruction, necrosis, and exposed or palpable fascia, tendon, ligament, muscle, cartilage, and bone. Slough and eschar are often visible along with epibole , undermining , and/or tunneling . Deep-tissue pressure injuries are characterized by persistent, nonblanchable areas of intact skin that have maroon, deep red, or purple discoloration. Pressure injuries are classified as unstageable if they have full-thickness skin or tissue loss with excessive slough or eschar that obscures the extent of the damage.
8.2 Wound Assessment
Whether in physician’s offices, emergency rooms, or inpatient facilities, the nurse will encounter patients with wounds. Understanding wound assessment and description, such as appearance and types of wounds, is a critical skill for any registered nurse. There are many tools available to help nurses and other healthcare professionals assess and document wounds. Tools such as the Braden Scale and Wagner Ulcer Classification System assist healthcare providers in establishing a patient’s risk for developing wounds or experiencing complications from them. These tools and effective, knowledgeable assessment allow nurses to provide appropriate documentation, which can be used by other providers to effectively manage patient care and ensure accurate and timely treatment.
8.3 Wound Management
Wound management encompasses many nursing interventions that are essential for promoting healing and tissue regeneration. To effectively manage wounds, nurses must understand the phases of wound healing, factors affecting wound healing, psychological effects of wounds, complications affecting wound healing, and the nurse’s role in wound care management. Wounds are healed by primary, secondary, or tertiary intention. Wound healing can be broken down into the following phases: hemostasis , inflammatory phase, proliferation phase, and maturation. Several factors may influence the speed of wound healing and may be localized or systemic. Localized factors are those factors that occur directly in the wound (i.e., desiccation , maceration , trauma , edema, and infection). Systemic factors are not related to the wound itself. These factors take place throughout the body (i.e., age, venous insufficiency , poor oxygenation, obesity, diabetes, medications, and smoking and alcohol use). Wounds and pressure injuries causes stress and emotional challenges caused by pain, fear, disruption to activities of daily living, and an altered body image that can have a significant effect on an affected person’s self-identity and mental well-being. There are several events that can interfere with wound healing and cause complications. Infection, hemorrhage, dehiscence and evisceration , and fistulas can increase the risk of death or generalized illness, increase healthcare costs, and prolong the need for healthcare interventions. The nursing role includes assessment and documentation, positioning, dressing care, drain care, suture and staple care, cleaning, debridement , administration of growth factors and heat and cold therapy, wound care education and health promotion, and education of the patient to perform self-care at home. Other therapies that the nurse may be required to assist with include hyperbaric oxygen therapy and surgery. It is essential that nurses understand their role in wound care management to effectively implement interventions within their scope of practice.
8.4 Burn Injuries and Management
Burn injuries are both preventable and different from other wounds. Their assessment requires evaluation of the type of burn, its depth, and the amount of body surface area it covers. Management of burns is based on the type and degree of burn, and ranges from basic first aid to long-term inpatient care and surgeries requiring extensive support from a large interdisciplinary healthcare team. Due to the complexity of burns, there are a variety of complications related to them, including psychological trauma, respiratory dysfunction, sepsis, and potentially death. The healing process includes the rehabilitation phase, which can be extensive, lasting from weeks to years depending upon functional impairment and loss of ability. Nurses must prepare patients for realistic expectations in the healing process.


7: Western Europe and Byzantium (Middle Ages)
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- 7.2: Expansion of Christendom
- In the Middle Ages, the people of Western Europe did not think of Europe as a geographic and cultural area. Rather, they thought of Christendom, those peoples and nations of the world that embraced the Christian religion. We might compare it to the Muslim notion of Dar al-Islam. In eleventh century, Christendom expanded into the north and east. In Spain, Christian kingdoms practiced what would be known as the Reconquista at the expense of Muslim al-Andalus.
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- 7.3: Church Reform in the Eleventh Century
- By the eleventh century, Europe suffered from frequent violence and the Church itself was in a sorry state. For example, Pope John XII was so infamous for his immorality. From the mid-eleventh century, both popes and other clergymen would seek to reform both the institutional structures of the Church and Christian society as a whole.
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- 7.10: Later Crusades and Crusading's Ultimate Failure
- After the Third Crusade, the re-established Crusader States managed to survive and even expand in power for the next several decades. Syria and Egypt were split between Saladin’s heirs, and the crusader kingdoms often enjoyed good relations with Ayyubid Egypt. Indeed, in 1229, a truce worked out between Holy Roman Emperor Frederick II and the Egyptian sultan al-Kamil resulted in the city of Jerusalem returning to Christian rule.
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- 7.5: The Twelfth-Century Renaissance
- The Twelfth-Century Renaissance was a time of renewed vibrancy in intellectual activity, as well as witness an immense growth of interest in philosophy on the part of men (and a few women) who had a formal education. Events in Southwestern Europe would spur this renewal.
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- 7.6: The Crusades
- On the surface, the Byzantine Empire of the eleventh century looked like one of the world’s great powers. It dominated the Eastern Mediterranean, with its emperors reigning from Constantinople, a city full of magnificent churches, splendid palaces, and centuries-old monuments of an ancient empire.
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- 7.7: Empires- Recovery and Collapse
- In the early part of the twelfth century, power in the Holy Roman Empire decentralized, while the cities of northern Italy were increasingly governing themselves. The Holy Roman Emperor Frederick Barbarossa (r. 1152 – 1190) sought to arrest this decline and make his subjects adhere to his authority.
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- 7.8: The Third Crusade
- The Crusader States had endured from 1099 to 1187 because the Muslim Middle East was politically fragmented. Once Saladin had overthrown Egypt’s Fatimid Caliphate and united Egypt to Muslim-controlled Syria and northern Iraq, he was able to turn his resources to destroying the Crusader States. Eventually, at the 1187 Battle of Hattin, his forces met the combined forces of the Kingdom of Jerusalem. The result was a complete victory for Saladin. With the manpower of most of the Kingdom of Jerusale
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- 7.9: The Fourth Crusade
- While Jerusalem remained under Muslim control, the papacy’s goal was to retake it. In 1198, one of the most ambitious popes of the Middle Ages was elected:Pope Innocent III (r. 1198 – 1216). His goals were to morally reform society and to launch a crusade for retaking the holy city of Jerusalem. In the year of his election, he issued a call to a crusade that ended up as a disaster.
Thumbnail: Baldwin of Boulogne entering Edessa in 1098 (history painting, Joseph-Nicolas Robert-Fleury 1840). (Public Domain).


28.8: Review Questions
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1.
The nurse is assessing a family that includes an adult and a school-aged child named Jackson. Which of the following questions should the nurse prioritize to ask the adult?
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Do you have any concerns about your son’s health?
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What is your relationship to Jackson?
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Is Jackson’s other parent a source of support for you?
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How many other children do you have?
2.
The nurse observes the interaction between a father and his school-age child during which the father tells the child that he needs to “shut up and leave him alone.” According to Maslow’s hierarchy, which of the following needs are most likely threatened in this interaction?
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Self-actualization
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Esteem
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Social
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Security
3.
According to general systems theory, which of the following events represents a change in a family’s subsystem?
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Two parents divorce.
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One parent loses their job.
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The family moves to another home.
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The children start school.
4.
A nurse is teaching family members how to read food labels. According to the Calgary Family Intervention Model, which of the following actions by the family incorporates all three functional domains?
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The family groups the low-sodium foods together in the cabinets.
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The family explains back to the nurse how to read a nutrition label.
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The family practices reading labels at home to reinforce what they learned.
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The family reads nutrition labels when shopping and selects low-sodium foods for their meals.
5.
The nurse is working with a group of older adult couples to help them learn more about fall prevention and how to make modifications in their home to decrease their risk of falls. This is an example of which level of health promotion?
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Primary
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Secondary
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Tertiary
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Primordial
6.
Which of the following actions by a home health nurse can decrease the risk of experiencing unsafe conditions while in a family’s home?
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Research and learn more about the surrounding neighborhood before the visit.
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Maintain situational awareness of other people and pets in the home.
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Make the visit as brief as possible to minimize time spent in the home.
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Maintain an updated visit schedule with the main office.
7.
The community nurse is working with a family and determines one of the family members is repeatedly telling another family member who has a disability that “he needs to stop being lazy and get a job.” This is an example of what type of abuse?

Which of the following would be included on a genogram?
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Occupations
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Religious affiliations
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Sources of health care
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Health conditions
9.
A community nurse is making a home visit to a client who has recently had a baby and has a history of experiencing IPV. During the visit, the nurse observes an interaction between the client and the baby’s father. The father seems very loving and attentive to the client. Which of the following is the most appropriate conclusion by the nurse?
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The client’s history must be inaccurately documented.
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The IPV has been resolved and is no longer an issue for the couple.
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The couple appears to be in the honeymoon phase of the IPV cycle.
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The couple appears to be in the tension-building phase of the IPV cycle.
10.
A community nurse is making a visit to an older adult client. The nurse identifies which of the following strategies that can be used in prevention of abuse in this client population?
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Take the time to listen to the client and the family to offer resources and support.
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Talk to the caregiver or family member only since older adults are often confused.
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Talk to the older client alone without involving family members.
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Because it is likely that older adult clients are abused, provide resources to other housing options.