Carbon nanobud

In nanotechnology, a carbon nanobud is a material that combines carbon nanotubes and spheroidal fullerenes, both allotropes of carbon, in the same structure, forming "buds" attached to the tubes. Carbon nanobuds were discovered and synthesized in 2006.
In this material, fullerenes are covalently bonded to the outer sidewalls of the underlying nanotube. Consequently, nanobuds exhibit properties of both carbon nanotubes and fullerenes. For instance, the mechanical properties and the electrical conductivity of the nanobuds are similar to those of corresponding carbon nanotubes. However, because of the higher reactivity of the attached fullerene molecules, the hybrid material can be further functionalized through known fullerene chemistry. Additionally, the attached fullerene molecules can be used as molecular anchors to prevent slipping of the nanotubes in various composite materials, thus modifying the composite’s mechanical properties.
Owing to the large number of highly curved fullerene surfaces acting as electron emission sites on conductive carbon nanotubes, nanobuds possess advantageous field electron emission characteristics. Randomly oriented nanobuds have already been demonstrated to have an extremely low work function for field electron emission. Reported test measurements show (macroscopic) field thresholds of about 0.65 V/μm, (non-functionalized single-walled carbon nanotubes have a macroscopic field threshold for field electron emission ~2 V/μm) and a much higher current density as compared with that of the corresponding pure single-walled carbon nanotubes. The electron transport properties of certain nanobud classes have been treated theoretically. The study shows that electrons indeed pass to the neck and bud region of the nanobud system.
Canatu Oy, a Finnish company, claims the intellectual property rights for nanobud material, its synthesis processes, and several applications.
Properties.
Carbon nanobuds (CNBs) have some properties of carbon nanotubes such as one-dimensional electrical conductivity, flexibility and adaptability to manufacture while also having some chemical properties of fullerenes. Examples of these properties include engaging in cycloaddition reactions and can easily form the chemical bonds capable of attaching to other molecules with complex structures. CNBs have a much higher chemical activity than single walled carbon nanotubes (SWCNTs).
Electrical Properties.
This new structure has been shown to have electronic properties that differ from those of fullerenes and carbon nanotubes (CNTs). CNBs exhibit lower field thresholds and higher current densities and electric field emission than SWCNTs. The chemical bonds between the nanotube's wall and the fullerenes on the surface can lead to charge transfer between the surfaces. The presence of fullerenes in CNBs lead to smaller bundle formation and larger chemical reactivity. CNBs can engage in cycloaddiiton reactions and easily form the chemical bonds capable of attaching molecules with complex structures. this can be explained by a greater availability of CNB surface to the reactants the presence of "π-"conjugated structures, and having 5-atom rings with excess pirimidization energy. Formation energy indicated that preparation of CNBs is endothermic, meaning that it is not favorable to create.
All CNBs are conducting, regardless of whether the single walled CNT is a metallic or semiconducting base. The band gap of carbon nanobuds is not constant, it can change through the size of the fullerene group. The attachment of C60 added to the armchair orientation of the SWCNT opens up the band gap. On the other hand, adding it to a semiconducting SWCNT could introduce impurity states to the band gap, which would reduce the band gap. The band gap of CNBs can also be modified by changing the density of the carbons of the C60 attached to the sidewall of the SWCNT.
Magnetic Properties.
Geometrical factors are integral to study the magnetic properties of nanobuds. There are two structures of CNBs that are ferromagnetic in their ground state, and two that are nonmagnetic. The attached C60 molecule on the surface of the CNTs gives more space between the nanotubes and adhesion between the single walled CNTS can be weakened to prevent the formation of tight bundles of CNTs. Carbon nanobuds can be used as molecular support to prevent slipping of the matrix in composite materials and to increase the mechanical strength of them.
Structural Properties.
The stability of CNBs is dependent on the type of carbon-carbon bond that is dissociated in the cycloaddition reaction. It has been shown that carbon atoms of the SWCNT near the fullerene C60 molecule were pulled outward from the original wall surface due to the covalent bonding with cycloaddition reaction between the fullerene and nanotube; in addition, their bonding was transformed from sp2 to sp3 hybridization. An analysis using Raman scattering spectroscopy shows that the CNB sample had stronger chemical modification compared to CNTs. This indicates that there is a carbon sp3 hybridization that occurs after the chemical addition creation of CNBs.
Synthesis.
The single wall carbon nanotubes, SWCNTs, are capable of being covered with covalently bonded fullerenes (a specific type of spheroidal carbon). This was able to occur when water vapor or carbon dioxide concentrations were instituted into the reactor. This occurrence produces a material that looks similar to buds that are on a tree branch. Therefore, this is the reasoning behind the term, nanobud, being chosen for the material.
The vapor concentrations for the water and the density of the fullerenes were looked into with a lot more detail. At 45 ppm and higher, the nanobuds began to be formed in abundance. However, when the concentration for the water that was added was about 365 ppm, something different happened. Rather than being a significant amount of nanobuds, it contained a large amount of inactive catalyst particles.
Characterization.
There are multiple methods that were used in order to discover the fullerenes on the single wall carbon nanotube surfaces, each giving its own contribution to what is currently known about nanobuds. A few of these methods are ultraviolet-visible spectroscopy (UV-Vis), transmission electron microscopy (TEM), and scanning tunneling microscopy (STM).
To look even further into the functionality of CNBs and how the single wall carbon nanotubes interact with the fullerenes to produce the nanobuds, calculations were done. The calculations that were done came from the atomistic density functional theory (quantum mechanical modelling method) and gave quite a bit of information about the bonding that is taking place. They told the scientists that there seem to be two possibilities for the interaction. One of the possibilities is that the fullerenes can be covalently bonded to the single wall carbon nanotubes directly. The other possibility is that the fullerenes are forming hybrid structures.
Regardless of how they are bonding to the single wall nanotubes, studies have shown that the fullerenes are stationary and do not seem to want to move from the interaction with the nanotubes, concluding that the bond they have is very strong. This study was done using transmission electron microscopy.
Another study was done to see how washing the nanobuds in different solvents, such as toluene, decaline, and hexane, would affect the fullerenes and their interaction with the nanotubes. Of the solvents that were tested, none of them resulted in fullerenes being dissolved in the solvent. This continues to defend the discovery that the bond between the two is significantly strong. In one more additional study that was done, it was discovered that each of the nanobud samples contained oxygen.
Applications.
The research, development, and manufacture of flexible and transparent electronics relies on novel materials, or materials which are mechanically flexible, lightweight and relatively low cost. These materials must also be conductive and optically transparent. Due to their close relation to the carbon nanotube family, carbon NanoBuds offer all of those traits, as well as more due to their inclusion of fullerene.
Esko Kauppinen, a professor and researcher at the Helsinki University of Technology and the technology development organization VTT Biotechnology, and his team found that carbon NanoBuds have properties that are often associated with cold electron field emitters. Such materials emit electrons at room temperature under a high applied electric field, a property that is very important with regard to technologies such as flat-panel displays and electron microscopes. Carbon NanoBuds can be much more effective than flat surfaces with respect to how efficiently they can emit electrons. This is due to the many curved surfaces of both the fullerene and the carbon nanotube that make up the carbon NanoBud.
As a result of the curvature of the fullerenes and the nanotubes, almost any surface could potentially be transformed into a surface with touch sensing ability. Canatu, a company which specializes in electronic carbon NanoBud products, claims that the films that result from the synthesis of the NanoBuds are very rugged and flexible. They also claim that the NanoBuds allow for easy application to flexible and curved surfaces. NanoBuds are able to maintain their electronic capabilities while being bent up to 200 percent. This property is a result of the rounded surfaces, which allow the NanoBuds to slide past each other without damaging the electronic structure of the material. Typically, touch screen surfaces are made by placing a sheet of indium tin oxide, also a transparent film, over a display screen. However, indium tin oxide sheets are very brittle like glass and can only be applied to relatively flat surfaces in order to maintain the integrity of the structure.
As a result of their close lineage with carbon nanotubes, NanoBuds have a tunable electrical conductivity. Since the electrical properties of the NanoBuds can be individually tuned (provided that single wall nanotubes with distinct regions of different electrical properties are a part of the NanoBud), according to Esko Kauppinen and his team, it is entirely possible that NanoBuds may at some point be used in applications such as memory storage devices and quantum dots. The Kauppinen team argues that the conductivity of the crystalline carbon structure allow for this application. In fact, the small size of carbon nanotubes and carbon NanoBuds, in theory, allow for a very high density of energy storage. The most common memory technology that is associated with carbon NanoBuds is Nano random-access memory (NRAM), or Nano-RAM. This technology is a type of nonvolatile random access memory, but it is based on the position of carbon nanotubes, or in this case, carbon NanoBuds on a chip like substrate. Its developing company Nantero give it its common name, NRAM. When compared to other forms of nonvolatile random access memory, NanoRAM has several advantages, but one really stands out. NRAM is believed to be within a variety of new memory systems, a variety which many people believe to be universal. Nantero claims that Nano-RAM (NRAM) could eventually replace almost all memory systems from flash to DRAM to SRAM.


Triphenylstibine

Triphenylstibine is the chemical compound with the formula Sb(C6H5)3. Abbreviated SbPh3, this colourless solid is often considered the prototypical organoantimony compound. It is used as a ligand in coordination chemistry and as a reagent in organic synthesis.
Like the related molecules triphenylphosphine and triphenylarsine, SbPh3 is pyramidal with a propeller-like arrangement of the phenyl groups. The Sb-C distances average 2.14-2.17 Å and the C-Sb-C angle are 95°.
SbPh3 was first reported in 1886, being prepared from antimony trichloride by the reaction:
An alternative method treats phenylmagnesium bromide with SbCl3.


Sodium tetrathionate

Sodium tetrathionate is a salt of sodium and tetrathionate with the formula Na2S4O6.H2O. The salt normally is obtained as the dihydrate ( = 2). It is a colorless, water-soluble solid. It is one member of the polythionates, which have the formula [S(SO3)2]2-. Other members include trithionite ( = 1), pentathionate ( = 3), hexathionate ( = 4).
Sodium tetrathionate is formed by the oxidation of sodium thiosulfate (Na2S2O3), e.g. by the action of iodine:.
The reaction is signaled by the decoloration of iodine. This reaction is the basis of iodometric titrations.
Other methods include the coupling of sodium bisulfite with disulfur dichloride:
The ion has idealizes C2 symmetry, like H2S2. The S-S-S dihedral angle is nearly 90 °. The central S-S distance is 2.115 Å, 0.01 Å longer than the two other S-S distances as well as those distances in most polysulfanes.


Diphenyl diselenide

Diphenyl diselenide is the chemical compound with the formula (C6H5)2Se2, abbreviated Ph2Se2. This orange-coloured solid is the oxidized derivative of benzeneselenol. It is used as a source of the PhSe unit in organic synthesis.
Preparation and properties.
Ph2Se2 is prepared by the oxidation of benzeneselenoate, the conjugate base of benzeneselenol which is generated via the Grignard reagent:
The molecule has idealized C2-symmetry, like hydrogen peroxide and related molecules. The Se-Se bond length of 2.29 Å the C-Se-Se-C dihedral angle is 82° and the C-Se-Se angles are near 110°.
Antioxidant action.
"Dietary supplementation with Ph2Se2 prevented CH3HgCl-induced locomotor impairment. This effect appeared to be mediated by antioxidant action. Ph2Se2 may be a viable approach to prevention or reduction CH3HgCl-mediated neurotoxic effects."
Reactions.
A reaction characteristic of Ph2Se2 is its reduction:
PhSeNa is a useful nucleophile used to introduce the phenylselenyl group by nucleophilic substitution of alkyl halides, alkyl sulfonates (mesylates or tosylates) and epoxides. The example below was taken from a synthesis of morphine.
Another characteristic reaction is chlorination:
PhSeCl is a powerful electrophile, used to introduce PhSe groups by reaction with a variety of nucleophiles, including enolates, enol silyl ethers, Grignard reagents, organolithium reagents, alkenes and amines. In the sequence below (early steps in the synthesis of Strychnofoline), a PhSe group is introduced by reaction of a lactam enolate with PhSeCl. This sequence is a powerful method for the conversion of carbonyl compounds to their α,β-unsaturated analogs.
Diphenyl diselenide itself is also a source of a weakly electrophilic PhSe group in reactions with relatively powerful nucleophiles like Grignard reagents, lithium reagents and ester enolates (but not ketone enolates or weaker nucleophiles). PhSeCl is both more reactive, and more efficient, since with Ph2Se2 half of the selenium is wasted.
"N"-Phenylselenophthalimide (N-PSP) can be used if PhSeCl is too strong and diphenyl diselenide is too weak or wasteful.


Weapons-grade plutonium


Dmitryivanovite

Dmitryivanovite is a natural mineral composed of calcium, aluminium and oxygen, with the molecular formula CaAl2O4. It was reported in 2009 in a calcium-aluminium-rich inclusion in the carbonaceous chondrite meteorite 470 (NWA470) CH3, which landed in North Africa. The mineral name was chosen to honor Dmitriy A. Ivanov (1962–1986), a geologist, mineralogist, and petrologist who died on a field expedition.
It is the high-pressure CaAl2O4 dimorph of krotite.


Potassium propanoate

Potassium propanoate or potassium propionate has formula K(C2H5COO). Its melting point is 410 °C. It is the potassium salt of propanoic acid.
Use.
It is used as a food preservative and is represented by the food labeling E number E283 in Europe and by the INS number 283 in Australia and New Zealand.


Methyltriphenylphosphonium bromide

Methyltriphenylphosphonium bromide is the organophosphorus compound with the formula [(C6H5)3PCH3]Br. It is the bromide salt of a phosphonium cation. It is a white salt that is soluble in polar organic solvents.
Synthesis and reactions.
Methyltriphenylphosphonium bromide is produced by treating triphenylphosphine with methyl bromide:
Methyltriphenylphosphonium bromide is the principal precursor to methylenetriphenylphosphorane, a useful methylenating reagent. This conversion is achieved by treating methyltriphenylphosphonium bromide with strong base.


Diethylmercury

Diethylmercury is a flammable, colorless liquid, and one of the strongest known neurotoxins. This organomercury compound is described as having a slightly sweet smell, though inhaling enough fumes to notice this would be hazardous.
This chemical can cross the blood–brain barrier, causing permanent brain damage. It is, however, considerably less toxic than dimethylmercury.
Synthesis.
Diethylmercury can be obtained from the reaction between ethylmagnesium bromide and mercury(II) chloride.
Other methods are also known.


Strontium perchlorate

Strontium perchlorate is a white powder or colorless crystals with the formula Sr(ClO4)2.
It is a strong oxidizer which gives red flames. It can be used in pyrotechnics; however, usually the more common strontium nitrate is used. It is also used in Liquid Injection Thrust Vector Control (LITVC) in solid-propellant rockets to enable steering control with a simple fixed nozzle.
It can be prepared by oxidizing strontium chlorate with hypochlorites.


Tashkooh

Tashkooh () or Firing Mount, is a mountain near the Ramhormoz, Iran.
Tashkooh which also named "Atashkooh" (in Persian means "Fire Mount"), is known for its permanent flames. This mount is always firing, because of the sulfur vapors rising from the porous layer of mountain surface and firing affected by the sublimation and nebulization.
Tashkooh is near the pair of villages called Mamatin, between Ramhormoz and Izeh.


Alicyclic compound

An alicyclic compound contains one or more all-carbon rings which may be either saturated or unsaturated, but do not have aromatic character. Alicyclic compounds may have one or more aliphatic side chains attached.
The simplest alicyclic compounds are the monocyclic cycloalkanes: cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, and so on. Bicyclic alkanes include bicycloundecane, decalin, and housane. Polycyclic alkanes include cubane, basketane, and tetrahedrane.
Spiro compounds have two or more rings that are connected through only one carbon atom.
The mode of ring-closing in the formation of many alicyclic compounds can be predicted by Baldwin's rules.
Otto Wallach, a German chemist, received the 1910 Nobel Prize in Chemistry for his work on alicyclic compounds.
Cycloalkenes.
Monocyclic cycloalkenes are cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, and so on. Bicyclic alkenes include norbornene and norbornadiene.
Two more examples are shown below, on the left methylenecyclohexane and on the right 1-methylcyclohexene:
An exocyclic group is always shown outside the ring structure, take for instance the exocyclic double bond of the former molecule. Isotoluenes are a prominent class of compounds with exocyclic double bonds.
The placement of double bonds in many alicyclic compounds can be predicted with Bredt's rule.


Vanadium(V) chloride

Vanadium(V) chloride is the inorganic compound with the formula VCl5. It is a black diamagnetic solid. The molecules adopt a bioctahedral structure similar to that of niobium(V) chloride.
Preparation and reactions.
Vanadium(V) chloride is prepared from the vanadium pentafluoride with excess boron trichloride:
It is unstable at room temperature with respect to vanadium(IV) chloride:


Diphenylmercury

Diphenylmercury is the organomercury compound with the formula Hg(C6H5)2. It is a white solid. The compound is of historic interest as a particularly stable organometallic compound but it finds few uses because of its high toxicity.
Preparation.
Commercially available, this compound can be prepared by several routes. It results from treating phenylmercury acetate with sodium stannite, by the reaction of mercuric halides with phenylmagnesium bromide, and the reaction of bromobenzene with sodium amalgam.
Safety.
Diphenylmercury is highly toxic.


Chloroiodomethane

Chloroiodomethane is the halomethane with the formula is . It is a colorless liquid of use in organic synthesis. Together with other iodomethanes, chloroiodomethane is produced by some microorganisms.
Applications.
Chloroiodomethane is used in cyclopropanation ("Simmon-Smith reaction"), where it often replaces diiodomethane because of higher yields and selectivity. It is also used in Mannich reaction, aminomethylation, epoxidation, ring opening and addition to terminal alkenes. It is a precursor to chloromethylenating agent Ph3P=CHCl. It reacts with organolithium compounds to give chloromethyllithium (ClCH2Li).
Crystallography.
It crystallizes orthorhombic crystal system with space group "Pnma" with lattice constants: "a" = 6.383, "b" = 6.706, "c" = 8.867 (.10−1 nm).


Potassium pyrosulfate

Potassium pyrosulfate, or potassium disulfate, is an inorganic compound with the chemical formula K2S2O7.
Production.
Potassium pyrosulfate is obtained by the thermal decomposition of other salts, most directly from potassium bisulfate:
Temperatures above 600°C further decompose potassium pyrosulfate to potassium sulfate and sulfur trioxide however:
Other salts, such as potassium trisulfate, can also decompose into potassium pyrosulfate.
Chemical structure.
Potassium pyrosulfate contains the pyrosulfate anion which has a dichromate like structure. The geometry can be visualized as a tetrahedron with two corners sharing the SO4 anion's configuration and a centrally bridged oxygen atom. A semi-structural formula for the pyrosulfate anion is O3SOSO32−. The oxidation state of sulfur in this compound is +6.
Uses.
Potassium pyrosulfate is used in analytical chemistry; samples are fused with potassium pyrosulfate, (or a mixture of potassium pyrosulfate and potassium fluoride) to ensure complete dissolution prior to a quantitative analysis.
The compound is also present in a catalyst in conjunction with vanadium(V) oxide in the industrial production of sulfur trioxide.


BE-3

The BE-3 ("Blue Engine 3") is a LH2/LOX rocket engine developed by Blue Origin.
The engine began development in the early 2010s, and completed acceptance testing in early 2015. The engine is being used on the New Shepard suborbital rocket, for which test flights began in 2015.
The engine was under consideration by United Launch Alliance (ULA) for use in a new second stage, the Advanced Cryogenic Evolved Stage, in ULA's Vulcan orbital launch vehicle with first flight in the 2020s.
History.
The BE-3 follows the earliest rocket engine development efforts at Blue Origin in the 2000s. Blue Origin's first engine was a "simple, single-propellant engine" called the Blue Engine-1 (BE-1) which used peroxide propellant and generated only of thrust, and their second, the Blue Engine-2 (BE-2) which was a bipropellant engine using kerosene and peroxide, producing thrust.
In January 2013, the company announced the development of the Blue Engine-3 BE-3, a new liquid hydrogen/liquid oxygen (LH2/LOX) cryogenic engine. The engine was originally announced to produce thrust, with initial thrust chamber tests planned for mid-February 2013 at NASA Stennis. The thrust chamber tests were run sometime in 2013.
The BE-3 was successfully tested in late 2013 on a full-duration simulated suborbital burn, with coast phases and engine relights, "demonstrating deep throttle, full power, long-duration and reliable restart all in a single-test sequence." NASA has released a video of the test.
By December 2013, Blue Origin updated engine specifications following engine tests conducted on test stands at ground level, near sea level. This demonstrated that the engine could produce of thrust at full power, and could successfully throttle down to as low as for use in controlled vertical landings if needed for that purpose on particular launch vehicles. The final engine specifications, released in April 2015 following the full test phase, included a minimum thrust of , an even wider throttling capability by 20 percent than the preliminary numbers, while maintaining the previously released full power thrust spec.
, the engine had "demonstrated more than 160 starts and of operation at Blue Origin's test facility near Van Horn, Texas." Additional testing of the BE-3 was completed in 2014, with the engine "simulating a sub-scale booster suborbital mission duty cycle."
Test stand testing of the engine was completed by April 2015, with over 450 engine firings and a cumulative engine test time of over 500 minutes. Blue Origin stated it would make the first test flight of its "New Shepard" vehicle later in 2015.
In the event, Blue Origin made the first flight test of the engine on the "New Shepard" suborbital vehicle before the month was out, flying a boost profile to altitude on 29 April 2015.
, United Launch Alliance (ULA) is considering the BE-3 for use in a new second stage, the Advanced Cryogenic Evolved Stage (ACES), which is, , planned to become the primary upper stage for ULA's Vulcan orbital launch vehicle in the 2020s. The Vulcan is planned to begin orbital flights in 2019 with an existing Centaur upper stage, and is considering three engines from various manufacturers for the ACES stage which would putatively begin flight in 2023, with selection expected before 2019.
While development of a sea-level version of the engine was completed and fully qualified by early 2015, Blue Origin said then that they intend to develop a vacuum version of the engine to operate in space.
In January 2016, the US Air Force provided partial development funding to Orbital ATK to develop an extendable nozzle for the Blue Origin BE-3U.
Engine design.
The BE-3 uses a pump-fed engine design, with a combustion tap-off cycle to take a small amount of combustion gases from the main combustion chamber in order to power the engine turbopumps.
BE-3U.
For Blue Origin's orbital launch vehicle—New Glenn—Blue has developed an open expander cycle variant of the BE-3, the BE-3U, for use in upper stages. Two of these engines will be used to power New Glenn second stage.
In November 2015, the engine was projected to have a vacuum thrust of .
Development had begun on the extendable nozzle for BE-3U by early 2016.
By August 2018, BE-3U engine development had proceeded, test engines built, and had accumulated over 700 seconds of test time, confirming performance assumptions in the design. In February 2019, Blue Origin updated the thrust of BE-3U as used on New Glenn to .
Technical specifications.
The performance of the sea-level version of the BE-3 include:


Aegirine

Aegirine is a member of the clinopyroxene group of inosilicate minerals. Aegirine is the sodium endmember of the aegirine-augite series. Aegirine has the chemical formula NaFeSi2O6 in which the iron is present as Fe3+. In the aegirine-augite series the sodium is variably replaced by calcium with iron(II) and magnesium replacing the iron(III) to balance the charge. Aluminium also substitutes for the iron(III). Acmite is a fibrous, green-colored variety.
Aegirine occurs as dark green monoclinic prismatic crystals. It has a glassy luster and perfect cleavage. Its Mohs hardness varies from 5 to 6, and its specific gravity is between 3.2 and 3.4.
This mineral commonly occurs in alkalic igneous rocks, nepheline syenites, carbonatites and pegmatites. It also appears in regionally
metamorphosed schists, gneisses, and iron formations; in blueschist facies rocks, and from sodium metasomatism in granulites. It may occur as an authigenic mineral in shales and marls. It occurs in association with potassic feldspar, nepheline, riebeckite, arfvedsonite, aenigmatite, astrophyllite, catapleiite, eudialyte, serandite and apophyllite.
Localities include Mont Saint-Hilaire, Quebec, Canada; Kongsberg, Norway; Narsarssuk, Greenland; Kola Peninsula, Russia; Magnet Cove, Arkansas, US; Kenya; Scotland and Nigeria.
The acmite variety was first described in 1821, at Kongsberg, Norway, and the aegirine variety in 1835 for an occurrence in Rundemyr, Øvre Eiker, Buskerud, Norway. Aegirine was named after Ægir, the Norse god of the sea. A synonym for the mineral is "acmite" (from Greek ἀκμή "point, edge") in reference to the typical pointed crystals.
It is sometimes used as a gemstone.


Pentakis(dimethylamido)tantalum

Pentakis(dimethylamido)tantalum is an organometallic compound of tantalum. It is a colorless solid that is soluble in organic solvents. It hydrolyzes readily to release dimethylamine.
Synthesis and structure.
Ta(NMe2)5 is prepared by treating TaCl5 with lithium dimethylamide. The preparation is similar to that for tetrakis(dimethylamido)titanium.
The compound has idealized D3h symmetry (ignoring the organic substituents).
Applications to organic synthesis.
The complex effects C-alkylation of secondary amines with 1-alkenes and hydroaminoalkylation of olefins to form alkylamines.


Mercury(II) acetate

Mercury(II) acetate is the chemical compound with the formula Hg(O2CCH3)2. Commonly abbreviated Hg(OAc)2, this compound is employed as a reagent to generate organomercury compounds from unsaturated organic precursors.
Structure.
Mercury(II) acetate is a crystalline solid consisting of isolated Hg(OAc)2 molecules with Hg-O distances of 2.07 Å. Three long, weak intermolecular Hg···O bonds of about 2.75 Å are also present, resulting in a slightly distorted square pyramidal coordination geometry at Hg.
Reactions.
Arenes undergo "mercuration" upon treatment with Hg(OAc)2. The one acetate group (OAc) that remains on mercury can be displaced by chloride:
The Hg2+ center binds to alkenes, inducing the addition of hydroxide and alkoxide. For example, treatment of methylacrylate with mercuric acetate in methanol gives an α-mercuri ester:
Exploitting the high affinity of mercury(II) for sulfur ligands, Hg(OAc)2 can be used as a reagent to deprotect thiol groups in organic synthesis. Similarly Hg(OAc)2 has been used to convert thiocarbonate esters into dithiocarbonates:
Mercury(II) acetate is used for oxymercuration reactions.


Kalinite

Kalinite is a mineral composed of hydrated potassium aluminium sulfate (a type of alum). It is a fibrous monoclinic alum, distinct from isometric potassium alum, named in 1868. Its name comes from "kalium" (derived from Arabic: القَلْيَه al-qalyah “plant ashes”) which is the Latin name for potassium, hence its chemical symbol, "K".
A proposal to remove recognition of kalinite as a mineral species was submitted to the International Mineralogical Association, however, kalinite is still on the list of approved minerals. Many older samples, however, have been found to be potassium alum.
Environment.
Kalinite is a rare secondary mineral observed in the oxidized zone of mineral deposits, as efflorescence on alum slates, in caves, and as a volcanic sublimate. It is associated with jarosite, KFe3+3(SO4)2(OH)6, and cuprian melanterite (pisanite), (Fe2+,Cu2+)SO4·7H2O, at Quetena, Chile.


Plutonium hydride

Plutonium hydride is a non-stoichiometric chemical compound with the formula PuH2+x. It is one of two characterised hydrides of plutonium, the other is PuH3. PuH2 is non-stoichiometric with a composition range of PuH2 – PuH2.7. Additionally metastable stoichiometries with an excess of hydrogen (PuH2.7 – PuH3) can be formed. PuH2 has a cubic structure. It is readily formed from the elements at 1 atmosphere at 100–200 °C: When the stoichiometry is close to PuH2 it has a silver appearance, but gets blacker as the hydrogen content increases, additionally the color change is associated with a reduction in conductivity.
Studies of the reaction of plutonium metal with moist air at 200–350 °C showed the presence of cubic plutonium hydride on the surface along with Pu2O3, PuO2 and a higher oxide identified by X-ray diffraction and X-ray photoelectron spectroscopy as the mixed-valence phase PuIV3−xPuVIxO6+x. Investigation of the reaction performed without heating suggests that the reaction of Pu metal and moist air the production of PuO2 and a higher oxide along with adsorbed hydrogen, which catalytically combines with O2 to form water.
Plutonium dihydride on the surface of hydrided plutonium acts as a catalyst for the oxidation of the metal with consumption of both O2 and N2 from air.


Radium paint


Amorphous calcium carbonate

Amorphous calcium carbonate (ACC) is the amorphous and least stable polymorph of calcium carbonate. ACC is extremely unstable under normal conditions and is found naturally in taxa as wide-ranging as sea urchins, corals, mollusks, and foraminifera. It is usually found as a monohydrate, holding the chemical formula CaCO3·H2O; however, it can also exist in a dehydrated state, CaCO3. ACC has been known to science for over 100 years when a non-diffraction pattern of calcium carbonate was discovered by Sturcke Herman, exhibiting its poorly-ordered nature.
ACC is an example of crystallization by particle attachment (CPA), where crystals form via the addition of particles ranging from multi-ion complexes to fully formed nanocrystals. Research of such systems have diverse application; however, the current lack of unambiguous answers to fundamental questions (i.e. solubility product, interfacial forces, structure, etc.) causes them to be topics of study in fields ranging from chemistry, geology, biology, physics, and materials science engineering.
Stability.
ACC is the sixth and least stable polymorph of calcium carbonate. The remaining five polymorphs (in decreasing stability) are: calcite, aragonite, vaterite, monohydrocalcite and ikaite. When mixing two supersaturated solutions of calcium chloride and sodium carbonate (or sodium bicarbonates) these polymorphs will precipitate from solution following Ostwald's step rule, which states that the least stable polymorph will precipitate first. But while ACC is the first product to precipitate, it rapidly transforms into one of the more stable polymorphs within seconds. When in pure CaCO3, ACC transforms within seconds into one of the crystalline calcium carbonate polymorphs. This transformation from amorphous to crystalline is proposed to be a dissolution-reprecipitation mechanism. Despite ACC's highly unstable nature, some organisms are able to produce stable ACC. For example, the American Lobster "Homarus americanus", maintains stable ACC throughout its yearly molt cycle. Studies of biogenic ACC have also shown that these stable forms of ACC are hydrated whereas the transient forms are not. From observations of spicule growth in sea urchins, it seems that ACC is deposited at the location of new mineral growth where it then dehydrates and transforms into calcite.
In biology.
Several organisms have developed methods to stabilize ACC by using specialized proteins for various purposes. The function of ACC in these species is inferred to be for the storage/transport of materials for biomineralization or enhancement of physical properties, but the validity of such inferences has yet to be determined. Earthworms, some bivalves species, and some gastropods species are known to produce very stable ACC. ACC is widely used by crustaceans to stiffen the exoskeleton as well as to store calcium in gastroliths during the molt cycle. Here, the benefit of utilizing ACC may not be for physical strength, but for its periodic need of the exoskeleton to be dissolved for molting. Sea urchins and their larvae utilize the transient form of ACC when forming spicules. The new material, a hydrated form of ACC, for the spicule is transported and deposited at the outer edges of the spicule. Then the deposited material, ACC·H2O, rapidly dehydrates to ACC. Following the dehydration, within 24 hours, all of the ACC will have transformed into calcite.
Synthetic ACC.
Many methods, have been devised for synthetically producing ACC since its discovery at 1989, however, only few syntheses successfully stabilized ACC for more than several weeks. The best effective method to stabilize ACC lifetime is by forming it in the presence of magnesium and/or phosphorus. Also, ACC crystallisation pathways have been observed to depend on its Mg/Ca ratio, transforming to aragonite, Mg-calcite, monohydrocalcite or dolomite with increasing Mg content. Huang "et al." managed to stabilize ACC using polyacrylic acid for several months, while Loste "et al." showed that magnesium ions can increase ACC stability as well. But only the discovery that aspartic acid, glycine, citrate, and phosphorylated amino acids can produce long term stable ACC have opened the door for production commercialization.
Highly porous ACC.
Highly porous ACC has been synthesized using a surfactant-free method. In this method CaO is dispersed in methanol under a pressure of carbon dioxide in a sealed reaction vessel. ACC with surface area over 350 m2/g was synthesized using this method. Highly porous ACC appeared to be made up aggregated nanoparticles with dimensions less than 10 nm in size. Highly porous ACC was also found to be stable in ambient conditions for up to 3 weeks with most of its porosity retained.
Applications and uses.
Bioavailability: Since 2013 a company named Amorphical Ltd. sells an ACC dietary supplement. Calcium carbonate is used as a calcium supplement worldwide, however, it is known that its bioavailability is very low, only around 20–30%. ACC is roughly 40% more bioavailable than crystalline calcium carbonate.
Drug delivery: Due to the ability to tune the size and morphology of the amorphous calcium carbonate particles (as well as other calcium carbonate particles), they have huge applications in drug delivery systems. Highly porous ACC showed the ability to stabilize poorly soluble drug molecules in its extensive pore system and could also enhance the drug release rates of these drugs.
Paleoclimate reconstruction: A better understanding of the transformation process from amorphous to crystalline calcium carbonate will improve reconstructions of past climates that use chemical and biological proxies. For example, the calibrations of the clumped 13C-18O carbonate paleothermometer and understanding the origins and evolution of skeletal structures.
Environmental remediation: Improving environmental remediation efforts through gaining insight into the roles of earth materials in biogeochemical cycling of nutrients and metals through better understandings of the properties of environmental mineral phases involved in elemental uptake and release.
Material science: Improving nanomaterials design and synthesis such as improving photovoltaic, photocatalytic, and thermoelectric materials for energy applications or improving biomedical cementations. Also improving framework material development for CO2 capture, H2 storage, emissions control, biomass conversion, molecular separations, and biofuel purification.


Tugtupite

Tugtupite is a beryllium aluminium tectosilicate. It also contains sodium and chlorine and has the formula Na4AlBeSi4O12Cl. Tugtupite is a member of the silica-deficient feldspathoid mineral group. It occurs in high alkali intrusive igneous rocks.
Tugtupite is tenebrescent, sharing much of its crystal structure with sodalite, and the two minerals are occasionally found together in the same sample.
Tugtupite occurs as vitreous, transparent to translucent masses of tetragonal crystals and is commonly found in white, pink, to crimson, and even blue and green. It has a Mohs hardness of 4 and a specific gravity of 2.36. It fluoresces crimson under ultraviolet radiation.
It was first found in 1962 at Tugtup agtakôrfia Ilimaussaq intrusive complex of southwest Greenland. It has also been found at Mont-Saint-Hilaire in Quebec and in the Lovozero Massif of the Kola Peninsula in Russia
The name is derived from the Greenlandic Inuit word for reindeer ("tuttu"), and means "reindeer blood."
The U.S. Geological Survey reports that in Nepal, tugtupite (as well as jasper and nephrite) were found extensively in most of the rivers from the Bardia to the Dang.
It is used as a gemstone.
References.


Sodium arsenate

Sodium arsenate is the inorganic compound with the formula Na3AsO4. Related salts are also called sodium arsenate, including Na2HAsO4 (disodium hydrogen arsenate) and NaH2AsO4 (sodium dihydrogen arsenate). The trisodium salt is a white or colourless solid that is highly toxic. It is usually handled as the dodecahydrate Na3AsO4.12H2O.
The compound can be obtained by neutralizing arsenic acid:
The salt (as its dodecahydrate) is isomorphous with trisodium phosphate. The anion AsO43- exists at high pH, but below pH 11.5, it converts to HAsO42- (also written HOAsO32-).


Magnesium (medical use)

Magnesium salts are available as a medication in a number of formulations. They are used to treat magnesium deficiency, low blood magnesium, eclampsia, and several other conditions. Magnesium is important to health.
Usually in lower dosages, magnesium is commonly included in dietary mineral preparations, including many multivitamin preparations. Chelated magnesium is sometimes used to aid in absorption.
In 2017, it was the 171st most commonly prescribed medication in the United States, with more than three million prescriptions.
Side effects.
More common side effects from magnesium include upset stomach and diarrhea, and calcium deficiency if calcium levels are already low.
Overdose.
Overdose of magnesium (hypermagnesemia) is only possible in special circumstances. It can cause diarrhea, nausea, vomiting, severely lowered blood pressure, confusion, slowed heart rate, respiratory paralysis. In very severe cases, it can cause coma, cardiac arrhythmia, cardiac arrest and death.
Magnesium overdose can be counteracted by administering calcium gluconate.
Types of preparations.
In practice, magnesium is given in a salt form together with any of several anionic compounds serving as counter-ions, such as chloride or sulfate. Nevertheless, magnesium is generally presumed to be the active component. An exception is the administration of magnesium sulfate in barium chloride poisoning, where sulfate binds to barium to form insoluble barium sulfate.
Magnesium is absorbed orally at about 30% bioavailability from any "water soluble salt," such as magnesium chloride or magnesium citrate. The citrate is the least expensive soluble (high bioavailability) oral magnesium salt available in supplements, with 100 mg and 200 mg magnesium typically contained per capsule or tablet.
Magnesium aspartate, chloride, lactate, citrate and glycinate each have bioavailability 4 times greater than the oxide form and are equivalent to each other per amount of magnesium, though not in price.
The ligand of choice for large-scale manufacturers of multivitamins and minerals containing magnesium is the magnesium oxide due to its compactness, high magnesium content by weight, low cost, and ease-of-use in manufacturing. However it is insoluble in water. Insoluble magnesium salts such as magnesium oxide or magnesium hydroxide (milk of magnesia) depend on stomach acid for neutralization before they can be absorbed, and thus are relatively poor oral magnesium sources, on average.
Magnesium sulfate (Epsom salts) is soluble in water. It is commonly used as a laxative, owing to the poor absorption of the sulfate component. In lower doses, they may be used as an oral magnesium source, however.
Intravenous or intramuscular magnesium is generally in the form of magnesium sulfate solution. Intravenous or intramuscular magnesium is completely bioavailable, and effective. It is used in severe hypomagnesemia and eclampsia.


Cangrelor

Cangrelor, sold under the brand name Kengreal in the United States and Kengrexal in the European Union) is a P2Y12 inhibitor FDA approved as of June 2015 as an antiplatelet drug for intravenous application. Some P2Y12 inhibitors are used clinically as effective inhibitors of adenosine diphosphate-mediated platelet activation and aggregation. Unlike clopidogrel (Plavix), which is a prodrug, cangrelor is an active drug not requiring metabolic conversion.
Poor interim results led to the abandonment of the two CHAMPION clinical trials in mid-2009. The BRIDGE study, for short term use prior to surgery, continues. The CHAMPION PHOENIX trial was a randomized study of over 11,000 patients published in 2013. It found usefulness of cangrelor in patients getting cardiac stents. Compared with clopidogrel given around the time of stenting, intravenous ADP-receptor blockade with cangrelor significantly reduced the rate of stent thrombosis and myocardial infarction. Reviewers have questioned the methodology of the trial.
Medical use.
According to recent phase 3 randomized trials, a cangrelor–clopidogrel combination is safe and has been found to be more effective than standard clopidogrel treatment at reducing ischemic events in the heart, without increasing major bleeding in the treatment of stenotic coronary arteries. The advantages of this drug combination are most prominent in patients with myocardial infarction.
Available antiplatelet drugs have delayed onset and offset of action. Since cangrelor’s effects are immediate and quickly reversed, it is a more desirable drug for elective treatment of stenotic coronary arteries, high risk acute coronary syndromes treated with immediate coronary stenting, and for bridging those surgery patients who require P2Y12 inhibition.
Current evidence regarding cangrelor therapy is limited by the lack studies assessing cangrelor administration in conjunction with either prasugrel or ticagrelor.
Recently, it's been approved for adult patients undergoing percutaneous coronary intervention (PCI).
Pharmacology.
Cangrelor is a high-affinity, reversible inhibitor of P2Y12 receptors that causes almost complete inhibition of ADP-induced platelet aggregate. It is a modified ATP derivative stable to enzymatic degradation. It does not require metabolic conversion to an active metabolite. This allows cangrelor’s immediate effect after infusion, and the therapeutic effects can be maintained with continuous infusion. The pharmacokinetics of cangrelor has allow it to rapidly achieve steady-state concentrations with a clearance of 50 L/h and a half-life of 2.6 to 3.3 minutes. Cessation of its administration is associated with rapid removal, and normal platelet function is restored within 1 hour.
Adverse effects.
Despite fewer bleeding events during cardiac surgery, cangrelor carries the risk of potential autoimmune reactions manifesting as breathlessness. Potential mechanisms for dyspnea following cangrelor treatment include: repeated binding and unbinding cycles, impaired platelet turnover, and lung sequestration or apoptosis of overloaded destructive platelets. The dyspnea risks following cangrelor treatment, suggest a common mechanism linking transfusion-related acute lung injury, dyspnea, and reversible platelet inhibition.
The risk of breathlessness after intravenous cangrelor is smaller when compared with other reversible platelet P2Y12 receptor inhibitors, however, it is still significantly higher when compared to irreversible oral antiplatelet drugs or intravenous glycoprotein IIb/IIIa inhibitors; which do not increase the incidence of breathlessness at all.


3,3-Bis(chloromethyl)oxetane

3,3-Bis(chloromethyl)oxetane (BCMO) is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities. It can cause kidney damage, lacrimation, and somnolence if consumed.
BCMO is a useful pre-polymer in the field of energetic materials for synthesis of Poly-BAMO which is under extensive research in numerous military departments around the world. Poly-BAMO is an energetic polymer that have potential to replace the current propellant binder formulations.


Zirconium lactate

Zirconium lactate is the zirconium salt of lactic acid. It is used in some deodorants. It is a colourless solid. Zirconium carboxylates adopt highly complex structures and are heterogeneous compositions with the approximate formula Zr(OH)4-n(O2CCHOHCH3)n(H2O)x where 1 < n < 3.
It is also used in the petroleum industry as a cross-linking agent to prepare gels for fracturing fluids, fluids which
are pumped into an oil-bearing rock formation to cause cracks in the rock and so to allow the oil to be extracted. It may be prepared by treating zirconium oxide with lactic acid.
Safety.
Its  >10 g/kg). It is suspected of causing zirconium granulomas (a form of skin irritation) in a small number of users.


Scandium-44

Scandium-44 (44Sc) is a radioactive isotope of scandium that decays by positron emission to stable 44Ca with a half-life of 4.042 hours.
44Sc can be obtained as a daughter radionuclide of long-lived 44Ti (t1/2 60.4 a) from 44Ti /44Sc generator or can be produced by nuclear reaction 44Ca ( p, n)44Sc in small cyclotrons. This isotope is of potential interest for clinical PET imaging.
Applications.
Titanium-44 generation.
44Ti with its long half-life of ca. 60 years provides a cyclotron-independent source of 44Sc for several decades.
44Ti is obtained in the nuclear reaction 45Sc(p,2n)44Ti and it transforms directly into the ground state of 44Sc via electron capture, emitting low energetic photons at 67.9 keV and 78.3 keV.
The 44Ti /44Sc generator represents a secular equilibrium system with a half-life ratio between parent and daughter of ca. 130 000. Consequently, 50% of saturation activity is generated every 3.97 hours, and identical 44Sc batch activities very close to saturation may be eluted each day. >97% elution efficacy for 44Sc and very low breakthrough of < 5*10−5 % of 44Ti.
44Ti is adsorbed onto column filled with anion-exchange resin. 44Sc is eluted with 20 mL
of 0.005M H2C2O4/0.07M HCl solution. The eluate is directly post-processed on miniaturized column filled with cation-exchange resin where 44Sc is quantitatively adsorbed online and successively eluted using 2–3 mL of 0.25 M ammonium acetate buffer (pH 4.0). This 44Sc solution of small volume and free of competing oxalates can be used for further labelling studies.
small cyclotrons.
Scandium-44 as a PET tracer.
44Sc complexates with DOTA, a well-established bifunctional chelators conjugated to peptides or other molecular targeting vectors, its half-life of 4 h, a high positron branching, stable and non-toxic decay product and being generator-produced makes it an appropriate candidate in PET/CT diagnosis.
44Sc has an almost 4-times longer half-life and higher β+ branching than commonly used 68Ga, therefore it can be used for more accurate planning and dosimetric calculations being able to cover imaging periods of more than one day.
A specific field might be application of diagnostic 44Sc tracers for matching therapeutic analog compounds labelled with e. g. 90Y, 177Lu or with the β− emitter 47Sc.
Recent studies with 44Sc-DOTA-conjugated tumor targeting vectors such as octreotides, showed in vitro and in vivo stability and revealed pharmacological parameters adequate to long-term (up to one day) molecular imaging. Initial human studies with 44Sc-DOTATOC PET/CT imaging of somatostatin receptor positive liver metastases in a patient at early time-points (40 min p.i.) showed comparable results to 68Ga-DOTATATE(90 min. p.i.) in the same patient.


Meridianiite

Meridianiite is the mineral consisting of magnesium sulfate undecahydrate, . It is colorless transparent crystalline salt that precipitates from solutions saturated in Mg2+ and SO42− ions at temperatures less than 2 °C. The synthetic compound was formerly known as Fritzsche's salt.
Meridianiite is a naturally occurring mineral species found on Earth in a variety of environments including sea ice, crusts and efflorescences in coal/metal mines, cave systems, oxidized zones of sulfide deposits, salt lakes/playas and Antarctic ice-cores. It is commonly associated with other evaporite minerals such as epsomite, mirabilite, halides, and other sodium-magnesium-sulfates. There is some evidence that it was once present on the surface of Mars, and may occur in several bodies of the Solar system. As of 2012, it was the only undecahydrate sulfate known.
Properties.
Meridianiite belongs to the triclinic crystal system, having cell parameters a = 6.7459 Å, b = 6.8173 Å, c = 17.299 Å, a density = 1.512 g/cm3, x-ray diffraction peaks at d-spacings = 5.73, 5.62, 5.41, 4.91, 4.85, 2.988, 2.958 (highest intensity), and 2.940, and is IR active. It produces needle-shaped to broad flat crystals that are clear to colorless-white.
Meridianiite decomposes incongruently above 2 °C to produce epsomite (MgSO4·7H2O) and water. Meridaniite and water have an eutectic point at −3.9 °C and 17.3% (mass) of MgSO4.
Meridianiite can incorporate large proportions of other divalent cations (whose sulfates themselves do not seem to form an undecahydrate) as solid solution, without changes to its structure. These include nickel (up to about 27% of the cations replaced), zinc (up to about 27%), cobalt (up to about 67%), manganese(II) (about 62%), copper (about 8%), and iron(II) (about 8%).
At pressures of about 0.9 GPa and at 240 K, meridianiite decomposes into a mixture of ice VI and the enneahydrate ,
Discovery.
In 1837 by C. J. Fritzsche described what he interpreted as magnesium sulfate dodecahydrate, based on the weight loss during dehydration to the anhydrous salt. The substance was referred to as "Frizsche's salt" and not formally given a mineral name or designation.
The crystal structure was later resolved by Peterson and Wang in 2006, revealing that it belonged to the triclinic crystal system, and each formula unit included 11 molecules of water, not 12.
The name "meridianite" is derived from Meridiani Planum, the locality on Mars where it is believed to have existed in the past. The mineral species and the name were approved by the Commission on New Mineral Names and Mineral Nomenclature of the International Mineralogical Association in November 2007.
Occurrence on Earth.
Meridianiite has been found to occur on the surface of the ice layer formed in winter over the ponds known as Basque Lakes, in Canada. The water in those ponds has a high concentration of magnesium sulfate and other salts. Water seeping through the ice layer evaporates at the surface leaving a deposit of crystalline meridianiite.
Meridianiite has also been detected in sea-ice collected in winter from the saline Lake Saroma in Japan, as well as in ice cores from Dome Fuji station, Antarctica, near the summit of the east Dronning Maud Land plateau.
Extraterrestrial occurrence.
Imagery of the massive sulfate deposits sent back by the NASA Opportunity Rover in Meridiani Planum show numerous needle-shaped void spaces throughout the deposit. The now empty angular holes are interpreted as being cavities once filled by a highly soluble mineral species, most likely a magnesium sulfate. These cavities are observed to closely match the crystal habit of meridianiite, and have been proposed as sites where crystals of meridianiite were located, having subsequently dissolved when environmental conditions rendered the crystal unstable. Due to the decomposition of meridianiite to 70% epsomite and 30% water, it has been proposed that meridianiite may represent a periodic reservoir of water near the Martian surface. During warmer periods in Mars’ history it is possible that triggered melting of this mineral may help explain the occurrence of some of the chaotic, and short lived, surface-water episodes throughout Martian history.
Remote sensing of other planetary bodies has also indicated the presence of numerous hydrated mineral species, including sulfates, near various planetary surfaces, a prominent example of which is Jupiter’s moon Europa. The relatively smooth, and very young surface of Europa has been interpreted as evidence for a putative ocean beneath the moons icy surface, and is therefore suggestive of liquid brine at depth. Due to the cryospheric conditions present on Europa it is likely that any magnesium sulfate minerals present, and in contact with liquid water, would inherently occur as meridianiite, and thus, it may make up an important mineral phase, and liquid water reservoir at depth.


Perovskite

Perovskite (pronunciation: ) is a calcium titanium oxide mineral composed of calcium titanate (CaTiO3). Its name is also applied to the class of compounds which have the same type of crystal structure as CaTiO3 (XIIA2+VIB4+X2−3), known as the perovskite structure. Many different cations can be embedded in this structure, allowing the development of diverse engineered materials.
History.
The mineral was discovered in the Ural Mountains of Russia by Gustav Rose in 1839 and is named after Russian mineralogist Lev Perovski (1792–1856). Perovskite's notable crystal structure was first described by Victor Goldschmidt in 1926 in his work on tolerance factors. The crystal structure was later published in 1945 from X-ray diffraction data on barium titanate by Helen Dick Megaw.
Occurrence.
Found in the Earth's mantle, perovskite's occurrence at Khibina Massif is restricted to the silica under-saturated ultramafic rocks and foidolites, due to the instability in a paragenesis with feldspar. Perovskite occurs as small anhedral to subhedral crystals filling interstices between the rock-forming silicates.
Perovskite is found in contact carbonate skarns at Magnet Cove, Arkansas, in altered blocks of limestone ejected from Mount Vesuvius, in chlorite and talc schist in the Urals and Switzerland, and as an accessory mineral in alkaline and mafic igneous rocks, nepheline syenite, melilitite, kimberlites and rare carbonatites. Perovskite is a common mineral in the Ca-Al-rich inclusions found in some chondritic meteorites.
A rare-earth-bearing variety "knopite" ((Ca,Ce,Na)(Ti,Fe)O3) is found in alkali intrusive rocks in the Kola Peninsula and near Alnö, Sweden. A niobium-bearing variety "dysanalyte" occurs in carbonatite near Schelingen, Kaiserstuhl, Germany.
In stars and brown dwarfs.
In stars and brown dwarfs the formation of perovskite grains is responsible for the depletion of titanium oxide in the photosphere. Stars with a low temperature have dominant bands of TiO in their spectrum; as the temperature gets lower for stars and brown dwarfs with an even lower mass, CaTiO3 forms and at temperatures below 2000 K TiO is undetectable. The presence of TiO is used to define the transition between cool M-dwarf stars and the colder L-dwarfs.
Special characteristics.
The stability of perovskite in igneous rocks is limited by its reaction relation with sphene. In volcanic rocks perovskite and sphene are not found together, the only exception being an etindite from Cameroon.
Physical properties.
Perovskites have a nearly cubic structure with the general formula . In this structure the A-site ion, in the center of the lattice, is usually an alkaline earth or rare-earth element. B-site ions, on the corners of the lattice, are 3d, 4d, and 5d transition metal elements. A large number of metallic elements are stable in the perovskite structure if the Goldschmidt tolerance factor formula_1 is in the range of 0.75–1.0
where "R""A", "R""B" and "R"O are the ionic radii of "A" and "B" site elements and oxygen, respectively.
Perovskites have sub-metallic to metallic luster, colorless streak, and cube-like structure along with imperfect cleavage and brittle tenacity. Colors include black, brown, gray, orange to yellow. Perovskite crystals may appear to have the cubic crystal form, but are often "pseudocubic" and actually crystallize in the orthorhombic system, as is the case for (Strontium titanate, with the larger strontium cation in the A-site, is cubic). Perovskite crystals have been mistaken for galena; however, galena has a better metallic luster, greater density, perfect cleavage and true cubic symmetry.
Applications.
A perovskite solar cell (PSC) is a type of solar cell which includes a perovskite-structured compound, most commonly a hybrid organic-inorganic lead or tin halide-based material, as the light-harvesting active layer. Perovskite materials, such as methylammonium lead halides and all-inorganic caesium lead halide, are cheap to produce and simple to manufacture.


Unoctunium


Minrecordite

Minrecordite, CaZn(CO3)2 , is a very rare mineral belonging to the dolomite group, the member with Ca and Zn. It was discovered, associated with dioptase, in a specimen from the Tsumeb mine (Namibia), which is consequently its type locality. Its name is a tribute to The Mineralogical Record magazine, representing the collaboration between professional and amateur mineralogists. In this locality it is associated primarily with dioptase, and less frequently with duftite, calcite and malachite. It is a rare mineral, which has been found only in a few deposits in the world. In addition to the type locality, it appears in the Preguiça mine, in Moura, district of Beja (Portugal) .


Tetramethyl orthosilicate

Tetramethyl orthosilicate is the chemical compound with the formula Si(OCH3)4. This molecule consists of four methoxy groups bonded to a silicon atom. The basic properties are similar to the more popular tetraethyl orthosilicate, which is usually preferred because the product of hydrolysis, ethanol, is less toxic than methanol.
Tetramethyl orthosilicate hydrolyzes to SiO2:
In organic synthesis, Si(OCH3)4 has been used to convert ketones and aldehydes to the corresponding ketals and acetals, respectively.
Safety.
The hydrolysis of Si(OCH3)4 produces insoluble SiO2 and CH3OH (methanol). Even at low concentrations inhalation causes lung lesions, and at slightly higher concentrations eye contact with the vapor causes blindness. Worse, at low concentrations (200 ppm/15 min) the damage is often insidious, with onset of symptoms hours after exposure. The mode of action is the precipitation of silica in the eyes and/or lungs. Contrary to common information, including several erroneous MSDS sheets, the methanol produced is only a risk through chronic exposure and is a comparatively small concern. The mechanisms of methanol toxicity are well established, methanol causes blindness via conversion to formaldehyde, then to toxic formic acid in the liver; methanol splashes to the eye cause only moderate and reversible eye irritation.


Silver proteinate

Silver proteinate (brand name: Protargol) is used in electron microscopy with periodic acid and thiocarbohydrazide or thiosemicarbohydrazide as a positive stain for carbohydrates such as glycogen. It can also be used for light microscopy to stain nerve tissue. It is normally available as 8% silver in combination with albumin.
Because of its bactericidal properties it was used to treat gonorrhea before the discovery of antibiotics. The inventor of the first silver protein formulation was Arthur Eichengrün, a German chemist working for Bayer. It was introduced for therapeutic use in 1897.


4-Fluorobutanol

4-Fluorobutanol is a chemical compound, a flammable colorless liquid which is a fluorinated alcohol. Like 2-fluoroethanol, it is highly toxic due to its ready metabolism to fluoroacetate.


Zinc titanate

Zinc titanate, also known as zinc titanium oxide, is an inorganic compound existing in three major forms: ZnTiO3 (ZnO-TiO2), Zn2TiO4 (2ZnO-TiO2) and Zn2Ti3O8 (2ZnO-3TiO2). It is used as a regenerable catalyst, a pigment and a sorbent of sulfur compounds at elevated temperatures. It is a white powder that is insoluble in water.
Synthesis and properties.
The ZnTiO3, Zn2TiO4 and Zn2Ti3O8 forms crystallize in hexagonal, cubic (inverse spinel) and cubic structures, respectively. They can be produced by heating a mixture of ZnO and TiO2 powders or processing it with a ball mill. Zn2Ti3O8 forms at lowest temperatures, followed by ZnTiO3 and then Zn2TiO4; the last phase dominates at temperatures above 1000 °C.
Toxicity.
Zinc titanate irritates the skin, mucous membranes and eyes. Zinc fumes can cause metal fume fever.


Diethylaluminium chloride

Diethylaluminium chloride, abbreviated DEAC, is an organoaluminium compound. Although usually given the chemical formula (C2H5)2AlCl, it exists as a dimer, [(C2H5)2AlCl]2 It is a precursor to Ziegler-Natta catalysts employed for the production of polyolefins. The compound is also a Lewis acid, useful in organic synthesis. The compound is a colorless waxy solid, but is usually handled as a solution in hydrocarbon solvents. It is highly reactive, even pyrophoric.
Structure.
Compounds of the empirical formula AlR2Cl (R = alkyl, aryl) exist as dimers with the formula (R2Al)2(μ-Cl)2. The aluminium adopts a tetrahedral geometry.
Production.
Diethylaluminium chloride can be produced from ethylaluminium sesquichloride, (C2H5)3Al2Cl3, by reduction with sodium:
It is also obtained from the reaction of triethylaluminium with hydrochloric acid:
Reproportionation reactions can also be used:
Uses.
Diethylaluminium chloride and other organoaluminium compounds are used in combination with transition metal compounds as Ziegler–Natta catalysts for the polymerization of various alkenes.
As a Lewis acid, diethylaluminium chloride also has uses in organic synthesis. For example, it is used to catalyze the Diels–Alder and ene reactions. Alternatively, it can react as a nucleophile or a proton scavenger.
Safety.
Diethylaluminium chloride is not only flammable but pyrophoric.


Organoruthenium chemistry

Organoruthenium chemistry is the chemistry of organometallic compounds containing a carbon to ruthenium chemical bond. Several organoruthenium catalysts are of commercial interest and organoruthenium compounds have been considered for cancer therapy.
The chemistry has some stoichiometric similarities with organoiron chemistry, as iron is directly above ruthenium in group 8 of the periodic table. The most important reagents for the introduction of ruthenium are ruthenium(III) chloride and triruthenium dodecacarbonyl.
In its organometallic compounds, ruthenium is known to adopt oxidation states from -2 ([Ru(CO)4]2−) to +6 ([RuN(Me)4]−). Most common are those in the 2+ oxidation state, as illustrated below.
Ligands.
As with other late transition metals, ruthenium binds more favorably with soft ligands. The most important ligands for ruthenium are:
Phosphine ligands.
While monodentate phosphine ligands such as triphenylphosphine and tricyclohexylphosphine are most common, bidentate phosphine ligands can also be useful in organoruthenium compounds. BINAP, in particular, is a useful asymmetric ligand for many asymmetric ruthenium catalysts.
N-Heterocyclic carbene ligands.
NHC ligands have become very common in organoruthenium complexes. NHC ligands can be prepared with precise steric and electronic parameters, and can be chiral for use in asymmetric catalysis. NHCs, as strongly donating L-type ligands, are often used to replace phosphine ligands. A notable example is 2nd generation Grubbs catalyst, in which a phosphine of the 1st generation catalyst is replaced by an NHC.
Cyclopentadienyl ligands.
The parent compound ruthenocene is unreactive because it is coordinatively saturated and contains no reactive groups. Shvo's catalyst ([Ph4(η5-C4CO)]2H]}Ru2(CO)4(μ-H)) is also coordinatively saturated, but features reactive OH and RuH groups that enable it to function in transfer hydrogenation. It is used in hydrogenation of aldehydes, ketones, via transfer hydrogenation, in disproportionation of aldehydes to esters and in the isomerization of allylic alcohols.
Chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium features a reactive chloro group, which is readily substituted by organic substrates.
Arene and alkene ligands.
One example of an Ru-arene complex is (cymene)ruthenium dichloride dimer, which is the precursor to a versatile catalyst for transfer hydrogenation. Acenaphthylene forms a useful catalyst derived from triruthenium dodecacarbonyl. The hapticity of the hexamethylbenzene ligand in Ru(C6Me6)2 depends on the oxidation state of the metal centre: The compound Ru(COD)(COT) is capable of dimerizing norbornadiene:
Multinuclear organo-ruthenium complexes have been investigated for anti-cancer properties. The compounds studied include di-, tri-, and tetra-nuclear complexes and tetrara-, hexa-, and octa- metalla-cages.
Carbonyls.
The main ruthenium carbonyl is triruthenium dodecacarbonyl, Ru3(CO)12. The analogues of the popular reagents Fe(CO)5 and Fe2(CO)9 are not very useful. Ruthenium pentacarbonyl decarbonylates readily:
Carbonylation of ruthenium trichloride gives a series of Ru(II) chlorocarbonyls. These are the precursors to Ru3(CO)12.
Organoosmium compounds.
In the same group 8 elements osmium resembles ruthenium in its complexes. Because Os is more expensive than Ru, the chemistry is less developed and has fewer applications. Of course the cost of the catalyst is offset if turnover numbers are high. Thus, Osmium tetroxide is an important oxidizing agent in organic chemistry especially in the conversion of alkenes to 1,2-diols.
The 5d-orbitals in Os are higher in energy that the 4d-orbitals in Ru. Thus, π backbonding to alkenes and CO is stronger for Os compounds, which leads to more stable organic derivatives. This effect is illustrated by the stability of the alkene derivatives of the type or as in the example below.
Important compounds, at least for academic studies, are the carbonyls such as triosmium dodecacarbonyl and decacarbonyldihydridotriosmium. The phosphine complexes are analogous to those or ruthenium, but hydride derivatives, e.g. OsHCl(CO)(PPh3)3, tend to be more stable.


Cofactor F430

F430 is the cofactor (sometimes called the coenzyme) of the enzyme methyl coenzyme M reductase (MCR).
MCR catalyzes the reaction that releases methane in the final step of methanogenesis:
It is found only in methanogenic Archaea and anaerobic methanotrophic Archaea. It occurs in relatively high concentrations in archaea that are involved in reverse methanogenesis: these can contain up to 7% by weight of the nickel protein.
Structure.
The trivial name cofactor F430 was assigned in 1978 based on the properties of a yellow sample extracted from "Methanobacterium thermoautotrophicum", which had a spectroscopic maximum at 430 nm. It was identified as the MCR cofactor in 1982 and the complete structure was deduced by X-ray crystallography and NMR spectroscopy. Coenzyme F430 features a reduced porphyrin in a macrocyclic ring system called a corphin. In addition, it possesses two additional rings in comparison to the standard tetrapyrrole (rings A-D), having a γ-lactam ring E and a keto-containing carbocyclic ring F. It is the only natural tetrapyrrole containing nickel, an element rarely found in biological systems.
Biosynthesis.
The biosynthesis builds from uroporphyrinogen III, the progenitor of all natural tetrapyrroles, including chlorophyll, vitamin B12, phycobilins, siroheme, heme, and heme "d"1. It is converted to sirohydrochlorin via dihydrosirohydrochlorin. Insertion of nickel into this tetrapyrrole is catalysed in reaction by the same chelatase, CbiX, which inserts cobalt in the biosynthesis of cobalamin, here giving nickel(II)-sirohydrochlorin.
The ATP-dependent Ni-sirohydrochlorin a,c-diamide synthase (CfbE) then converts the "a" and "c" acetate side chains to acetamide in reactions , generating nickel(II)-sirohydrochlorin "a","c"-diamide. The sequence of the two amidations is random. A two-component complex Ni-sirohydrochlorin a,c-diamide reductive cyclase (CfbCD) carries out a 6-electron and 7-proton reduction of the ring system in a reaction generating the 15,173-"seco"-F430-173-acid ("seco"-F430) intermediate. Reduction involves ATP hydrolysis and electrons are relayed through two 4Fe-4S centres. In the final step, the keto-containing carbocylic ring F is formed by an ATP-dependent enzyme Coenzyme F(430) synthetase (CfbB) in reaction , generating coenzyme F430. This enzyme is a MurF-like ligase, as found in peptidoglycan biosynthesis.


Uranium(IV) hydride

Uranium(IV) hydride is a chemical compound with the chemical formula UH4, a metal hydride composed of uranium and hydrogen.
In 1997, Souter "et al." reported the production of UH4 reacting laser ablated uranium atoms with dihydrogen and capturing the product on solid argon. The assignment of the structure was made using infrared spectroscopic evidence supported by DFT calculations. Uranium(IV) hydride has a quasi-tetrahedral ("C""s") structure. UH4 is formed by the successive insertion of uranium into two hydrogen molecules:
Further reaction with hydrogen, only produces dihydrogen complexes: UH4(H2)"n" (1 ≤ "n" ≤ 6).


Tribromofluoromethane

Tribromofluoromethane or Halon 1103 or R 11B3 is a fully halogenated mixed halomethane or more exactly a bromofluorocarbon (BFC). It is a colorless liquid.
Tribromofluoromethane can be used in fire extinguishers. However, because it contains bromine, it has high ozone depletion potential (ODP) and most of the halons are banned by Montreal Protocol.


Tetrabromoethylene

Tetrabromoethylene is a brominated derivative of ethylene. It can be produced by oxybrominating butane with free oxygen and bromine.


Trineutron


Titanium disilicide

Titanium disilicide (TiSi2) is an inorganic chemical compound of titanium and silicon.
Preparation.
Titanium disilicide can be obtained from the reaction between titanium or titanium hydride with silicon.
It is also possible to prepare it aluminothermically by the ignition of aluminium powder, sulfur, silicon dioxide, and titanium dioxide or potassium hexafluorotitanate, K2TiF6, by electrolysis of a melt of potassium hexafluorotitanate and titanium dioxide, or by reaction of titanium with silicon tetrachloride.
Another method is the reaction of titanium tetrachloride with silane, dichlorosilane or silicon.
Uses.
Titanium silicide is used in the semiconductor industry. It is typically grown by means of salicide technology over silicon and polysilicon lines to reduce the sheet resistance of local transistors connections.
In the microelectronic industry it is typically used in the C54 phase.


Zirconium phosphate

Zirconium phosphates (zirconium hydrogen phosphate) are acidic, inorganic cation exchange materials that have a layered structure with formula Zr(HPO4)2∙nH2O. These salts have high thermal and chemical stability, solid state ion conductivity, resistance to ionizing radiation, and the capacity to incorporate different types of molecules with different sizes between their layers. There are various phases of zirconium phosphate which vary in their interlaminar spaces and their crystalline structure. Among all the Zirconium phosphate phases the most widely used are the alpha (Zr(HPO4)2∙H2O) and the gamma (Zr(PO4)(H2PO4)∙2H2O) phase. The salts have been widely used in several applications such as: drug delivery, catalysis, nanocomposite, nuclear waste management, clinical dialyzer, among others.
Crystal structure.
Zirconium phosphate crystal structure was elucidated by Clearfield and coworkers in 1968 by the single-crystal method. The layered structure of α-Zirconium phosphate consists of Zr(IV) ions situated alternately slightly above and below the ab plane, forming an octahedron with the oxygen atoms of the tetrahedral phosphate groups. Of the four oxygen atoms in the phosphate groups, three are bonded to three different Zr atoms, forming a cross-linked covalent network. The fourth oxygen atom of the phosphate is perpendicular to the layer pointed toward the interlayer region. In the interlayer region is localized a zeolitic cavity where a basal water molecule resides, forming a hydrogen bond with the OH group of the phosphate that is perpendicular to the layer. The alpha phase of zirconium phosphate is under the P21/n space group, with cell dimensions of a = 9.060 Å, b = 5.297 Å, c = 15.414 Å, α = γ = 90°, β = 101.71° and Z = 4.21 The basal interlayer distance for the α-Zirconium phosphate is 7.6 Å, where 6.6 Å is the layer thickness and the remaining 1 Å space is occupied by the interstitial water molecules in the interlayer gallery. The distance between adjacent orthophosphates on one side of the layer is 5.3 Å. There are two phosphates in each ab plane in the surface layer forming a “free area” of 24 Å2 associated to each phosphate group.
For the gamma phase (γ-Zirconium phosphate), unfortunately, an appropriate single crystal for single-crystal structure determination has been futile to obtain. In 1995 Clearfield and coworkers elucidated its structure using X-ray powder diffractometry (XRPD) and the Rietveld refinement method. The structure of γ-Zirconium phosphate consists of Zr(IV) atoms octahedrally coordinated to four different oxygen atoms of an orthophosphate. The other two resting octahedral position of the Zr(IV) atoms are occupied by two different dihydrogen phosphate groups. The orthophosphate molecules are located alternatively above and below the ab main plane and the dihydrogen phosphates are in the layer edges crosslinked by two of their oxygen atoms to two different zirconium atoms. The remaining two hydroxyl groups of the dihydrogen phosphate are pointing toward the interlayer gallery forming a pocket where a hydrogen bond is formed with the interlayer water molecules. The basal interlayer distance for γ-Zirconium phosphate is 12.2 Å, and the area surrounding the dihydrogen phosphate on the surface of the layers is 35 Å2.


Lead citrate

Lead citrate is a compound of lead and citrate that is primarily used as an enhancer for heavy metal staining in electron microscopy. It binds to osmium and uranyl acetate and enhances contrast in many cellular structures. Lead citrate is highly reactive with carbon dioxide.


Siloxide

Siloxides are chemical compounds with the formula R3SiOM, where R is usually an organic group and M is usually a metal cation. Also called silanoates, they are derived by deprotonation of silanols. They also arise by the degradation of siloxanes by base:
Cleavage of cyclic siloxanes affords siloxides:
These anions function as ligands for metal ions, forming complexes similar to metal alkoxides. Sodium trimethylsiloxide is useful for generating metal complexes by salt metathesis reactions. A very bulky siloxide is tert-butyl3SiO−, sometimes called silox.


BCN nanotube

BCN nanotubes are tubular structures with a sub-micrometer diameter and a length much longer than diameter. They are composed of comparable amounts of boron, carbon and nitrogen atoms.
First made in 1994, synthesis methods have included: arc-discharge, laser ablation, chemical vapor deposition (CVD), template route, and pyrolysis techniques. Single-walled B–C–N nanotubes have been made with a hot-filament method.
Solvothermal synthesis.
Vertically aligned arrays of ~BC2N nanotubes can be produced by solvothermal synthesis in a stainless steel autoclave from a mixture of sodium azide (NaN3), ammonium fluoroborate (NH4BF4) and methyl cyanide (CH3CN). The mixture, together with the solvent and other additives is heated to 400 °C for ~14 h. The final composition was approx B19C55N26.
Potential applications.
The vertically-aligned BCN nanotubes (made as above) exhibit a high and stable specific capacitance (>500 F/g), which exceeds that of alternative carbon nanomaterials, and therefore have potential applications in supercapacitors.
Facile synthesis.
Another method produced nanotubes of composition : B45%,C31%,N24%
The method was grow them on stainless steel by reacting boron, zinc oxide (ZnO), and ethanol in nitrogen and hydrogen at 1150 °C. The resulting nanotubes had an average diameter of about 90 nm.


Unquadseptium


Indium wire

Indium is a soft, malleable, silver, shiny metal with atomic weight of 114.82 and resides as number 49 on the Chemical Periodic Table. Below 3.4Kelvin indium is a superconductor and at 20 C it has a resistance of 8.8 micro-ohms with a melting point of 156.598 C, a boiling point of 2080C and a density of 7.3 g/cc. Indium can be alloyed with a wide range of other metals to lower their melting point.
Indium is an ideal thermal interface material for heat dissipation in many of today's very hot integrated circuits. Of all the common materials, copper and aluminum have the highest thermal conductivity. But on the micro level most materials are very rough and a two piece sandwich of copper may not have a good conductive path between them. To overcome this limitation, indium is the ideal material due to its high bulk thermal conductivity (86W/mK) and its soft compressibility allowing it to fill voids in rough surfaces. In addition, as a seal indium will not pump out or dry out. In fact, indium has the unique ability to cold weld two dissimilar materials if the materials have a thin coating of .002”-.003” of indium they will ‘cold-weld’ together if the clamping pressure is more than 40 psi.
When indium is compressed its bulk thermal conductivity of 86 W/mK pushes down the resistance at the interface to be much lower than greases, fluids, or adhesives. For high power applications there is no better thermal interface material than indium due to its high conductivity, low tensile strength, and ability to alter melting point of alloys, in addition to indium's ability to dissipate great amounts of heat away from sensitive devices.
Technical Information.
 PRODUCTION RATE FOR (5 OZ.) 140 GRAM INGOT
 SIZE LGTH FT./OZ. GR./FT. AREA GROOVE 'D'
 'W' (sq. in.) 80% 90%
 .020"(0.5mm) 300' 60' (20'/$100) .46 .000314
 .030" 135' 27' 1.04 .000706 .020" .021"
 .040" (1.0mm) 75' 15' 1.88 .001256 .025" .028"
 .050" 50' 10' 2.80 .001962 .031" .035"
 .060"(1.5mm) 35' 7' 4.00 .002826 .038" .042"
 .0625" 32' 6.4' 4.37
 .070" 26' 5.2' 5.38 .003846 .044" .049"
 .080"(2.0mm) 20' 4' 7.00 .005024 .050" .056"
 .090" 15' 3' 9.33 .006358 .056" .064"
 .100" 12.5' 2.5' 11.2 .007850 .063" .070"
 .125" 8' 1.6' 17.50 .012265 .078" .088"
 .1875" 44" 8.76" 38.35 .027597
 D=Half dia. +.005>.015 min.
 Rectangular groove dimensions: [Depth x Width = .80min. x cross section]


Calcium signaling in cell division

Calcium plays a crucial role in regulating the events of cellular division. Calcium acts both to modulate intracellular signaling as a secondary messenger and to facilitate structural changes as cells progress through division. Exquisite control of intracellular calcium dynamics are required, as calcium appears to play a role at multiple cell cycle checkpoints.
The major downstream calcium effectors are the calcium-binding calmodulin protein and downstream calmodulin-dependent protein kinases I / II. Evidence points to this signaling cascade as a major mediator of calcium signaling in cell division.
Meiosis.
Historically, one of the most well characterized roles of intracellular calcium is activation of the ovum after sperm fertilization. In deuterosome eggs (mammals, fish, amphibians, ascidians, sea urchins, etc.), successful sperm entry leads to a distinct rise in intracellular calcium ions (Ca2+), with mammals and ascidians displaying a series of intracellular calcium spikes required for completion of meiosis... Unfertilized vertebrate eggs arrest development after meiosis I. This developmental pause is attributed to the vaguely defined cytostatic factor (CSF). Current research suggest “CSF” is actually multiple pathways working together to halt division at metaphase of meiosis II. Upon sperm entry into the egg, Ca2+ is released from intracellular stores, leading to inhibition of the CSF-arrest mechanism. Calmodulin dependent kinase II was shown to be the protein responsible for converting the Ca2+ influx signal into inhibition of CSF and activation of cyclin degradation machinery to degrade cyclin B, resulting in progression through meiosis II.
In mammals, this rise in Ca2+ was shown to be driven by IP3 stimulation induced by PLCζ provided by the sperm. In general, PLC enzymes stimulate calcium release by internal stores through the breakdown of PIP2 into IP3 and DAG.
Mitosis.
Signaling.
Beyond the events of meiosis, changes in Ca2+ levels are observed in a variety of organisms at different stages of division, such as nuclear membrane breakdown and the metaphase-anaphase transition. Further, recent work has shown mechanically induced rapid entry into mitosis of cells paused in G2. Further, progression through division requires the presence of calcium (G1/S, G2/M, and metaphase/anaphase), suggesting checkpoints require a calcium-dependent signaling mechanism
G1/S.
Entry into S-phase is calcium dependent. Depleting internal calcium stores inhibits initiation of DNA synthesis. One possible mechanism is that cyclin A synthesis is inhibited, preventing cdk2 activity which is required for initiation of DNA synthesis.
G2/M.
Cell cycle progression is regulated by multiple pathways. It was shown using human cancer cell lines, that the G2/M checkpoint is regulated by CaMKII and MAPK crosstalk. Here, CaMKII activates MEK/ERK, which degrades the cell cycle arresting p27 protein
Disease.
In general, transformed cells proliferate in a calcium-independent manner, whereas non-transformed cells show high sensitivity to extra-cellular calcium concentration, suggesting oncogenic growth may include disruption of calcium signaling.
Chromatin Structure.
Condensation of chromatin is a vital step in cell division, allowing cells to equally distribute chromosomes to the daughter cells. Recent work has suggested that Ca2+ is required for enabling chromatin condensation in prometaphase. Calcium was found to concentrate on condensed DNA to much higher levels compared to normal cytosolic calcium concentration. The role of calcium in condensation was independent of CAMK function, suggesting a purely structural role of Ca2+ in chromatin compaction. Further, this result was demonstrated "in vitro" with extracted chromatin, emphasizing that the mere presence of Ca2+ can influence the structure of chromatin


Oxotrichlorobis(triphenylphosphine)rhenium(V)

Oxotrichlorobis(triphenylphosphine)rhenium(V) is the chemical compound with the formula ReOCl3(PPh3)2. This yellow, air-stable solid is a precursor to a variety of other rhenium complexes. In this diamagnetic compound, Re has an octahedral coordination environment with one oxo, three chloro and two mutually trans triphenylphosphine ligands. The oxidation state of rhenium is +5 and its configuration is d2.
Synthesis.
ReOCl3(PPh3)2 is commercially available, but it is readily synthesized by reaction of perrhenic acid with triphenylphosphine in a mixture of hydrochloric acid and acetic acid. In this reaction, Re(VII) is reduced to Re(V), and triphenylphosphine is oxidized to its oxide.
The required perrhenic acid solution can be prepared in situ from rhenium(VII) oxide.
Uses.
ReOCl3(PPh3)2 is a precursor to a variety of other oxo-, nitridio, and hydrido complexes. It converts to ReH7(PPh3)2 by a treatment with LiAlH4.
ReOCl3(PPh3)2 catalyzes the selective oxidation of secondary alcohols by DMSO, producing the corresponding ketals.


FL3 (flavagline)

FL3 is a synthetic flavagline that displays potent anticancer and cardioprotectant activities. This compound induces the death of cancer cells by an original mechanism that involves the apoptosis-inducing factor and caspase 12, suggesting that it may improve the efficacy of cancer chemotherapies. It was also shown that FL3 may enhance the efficacy of one of the most widely used anticancer agents, doxorubicin, and alleviate its main adverse effect, cardiac damage.


Lithium Triangle

The Lithium Triangle () is a region of the Andes rich in lithium reserves around the borders of Argentina, Bolivia and Chile. The lithium in the triangle is concentrated in various salt pans that exist along the Atacama Desert and neighboring arid areas.
The area is thought to hold around 54% of the world's lithium reserves. The Indian Navy has shown interest in the Lithium Triangle as lithium will be required on Li-ION batteries that are planned to be fitted in future submarines.


Chalcostibite

Chalcostibite is a copper antimony sulfide mineral.
Příbramite is related, having selenium instead of sulfur. Emplectite contains bismuth instead of antimony.


Pearceite

Pearceite is one of the four so-called "ruby silvers", pearceite Cu(Ag,Cu)6Ag9As2S11, pyrargyrite Ag3SbS3, proustite Ag3AsS3 and miargyrite AgSbS2. It was discovered in 1896 and named after Dr Richard Pearce (1837–1927), a Cornish–American chemist and metallurgist from Denver, Colorado.
Nomenclature.
Pearceite and polybasite are closely related minerals that form the pearceite-polybasite series. Originally pearceite was thought to be an arsenic analogue of polybasite Cu(Ag,Cu)6Ag9Sb2S11, and was called arsenpolybasite, and one polytype of polybasite was called antimonpearceite. Arsenpolybasite was found to represent two different polytypes, arsenpolybasite-221 and arsenpolybasite-222. In modern usage the old name pearceite is replaced by the polytype name pearceite-Tac, arsenpolybasite-221 by pearceite-T2ac, arsenpolybasite-222 by pearceite-M2a2b2c and antimonpearcite by polybasite-Tac. Pearceite-Tac forms a series with polybasite-Tac.
Crystallography and Structure.
Two structural varieties, trigonal and monoclinic, are known. The trigonal variety crystallizes in the hexagonal scalenohedral class m ( 2/m), space group Pm1 (P 2/m 1). The monoclinic variety crystallises in the prismatic 2/m class, space group C2/m.
Unit cell parameters
The crystal structure consists of sheets stacked along the c axis. The arsenic atoms form isolated (As,Sb)S3 pyramids, copper cations link two sulfur atoms and the silver cations are found in various sites with low coordination numbers, 2,3 and 4, as is usually the case with silver.
Properties.
Pearceite is often granular and massive; crystals are short, tabular pseudohexagonal prisms with bevelled edges, showing triangular striations on faces parallel to the plane containing the a and b axes, and rosettes of such crystals, to 3 cm across.
The mineral is black, and in polished section it is white with very dark red internal reflections. It has a black to reddish black streak and a metallic luster, generally opaque, but translucent in very thin fragments.
It is biaxial with a very high refractive index of 2.7 and maximum birefringence δ also 2.7. Dispersion of the optic axes is relatively strong.
Reflected light anisotropism is the property of appearing to change color when viewed under crossed polarised light in a reflected light microscope. Pearceite exhibits moderate anisotropism, often dark violet. The color in reflected plane polarised light is white, with very dark red internal reflections and very weak pleochroism in air, fair in oil. Reflectivity in air at 540 nm is about 30%. It is not fluorescent.
Pearceite is a brittle mineral that breaks with a conchoidal to irregular fracture. It is soft, with hardness only 3, the same as calcite. The silver content gives it a high specific gravity of 6.15, the highest of the ruby silvers. Cleavage is either absent or poor. The mineral is neither magnetic nor radioactive.
Occurrence and associations.
The type locality is the Mollie Gibson Mine, Aspen, Aspen District (Roaring Fork District), Pitkin County, Colorado, where the mineral occurs in hydrothermal deposits formed at low to medium temperatures, associated with acanthite, tetrahedrite, native silver, proustite, quartz, baryte and calcite. Type material is lodged at Yale University, New Haven, Connecticut, references 3.4270, 3.4292, 3.4293, and at The Natural History Museum, London, England, reference 84843.