**7. Conclusion**

*Mineralogy - Significance and Applications*

sis routes, are shown in **Figure 9(a)** and **(b)**.

nano-hematite particles, TEM micrographs of the chosen nanocomposite samples annealed at 1050°C, obtained by auto-catalyzed and base-catalyzed sol-gel synthe-

Detailed TEM analysis is given in Ref. [59, 63]. Quantitative description of morphological properties of the investigated particles is performed by measuring ellipticity. The results of the analysis showed that the shape of observed Fe2O3 nanoparticles (ε-Fe2O3 and α-Fe2O3) varies from ellipticity to circularity. In other words, **Figure 9** confirms the presence of nonideally spherical particles, whose shape deviates from circularity in a different measure [59]. Fe2O3 particle sizes, presented in **Figure 9(a)**, are ranging between 10 and 20 nm, while the sample presented in **Figure 9(b)** showed a wider particle size distribution, from 4 to 50 nm, and the same variations from ellipticity to circularity. Wide size distribution leads to the presence of different particle shapes during the annealing treatment, elliptic/spherical (**Figure 9(a)**). This feature appeared as a consequence of the fact that sol-gel method consisted of coprecipitation of the particles within the SiO2 pores (coprecipitated samples are characterized by wide particle size distribution) [53]. The best way to overcome the mentioned problem is the coating of the nanoparticles within the SiO2 pores [69]. Notwithstanding, a significant difference between micrographs is the presence of nanorod particles within the sample synthesized by base-catalyzed sol-gel synthesis (**Figure 9(b)**). Rod-like morphology appeared as a consequence of the participation of group II element, Sr2+, in the synthesis procedure (**Figure 9(b)**). The addition of Sr2+ ions accelerated the growth of the ε-Fe2O3 particles in one crystallographic axis [63], inducing more pronounced shape variations and formation of rod-like nanoparticles. If we recall the fact that TEM image shown in **Figure 9(b)** revealed the presence of the only γ-Fe2O3 and ε-Fe2O3 nanoparticles in the investigated sample (discussed in more detail in the Ref. [63]), as well as having in mind that α-Fe2O3 formation occurs as a consequence of phase transformations ε-Fe2O3 → α-Fe2O3, it can be assumed that

the sample presented in **Figure 8** contained rod-like α-Fe2O3 nanoparticles.

It is important to note that the origin of dependence of Hmeas behavior on the synthesis conditions of the samples investigated in this chapter is found in quantum

Briefly, the quantity that strongly affects the shape of hysteresis loop is magnetic anisotropy [parameter ι, in Eq. (3)]. For the most simplest case, in crystal systems whose symmetry is determined by a single axis of high symmetry (uniaxial sym-

Ea~KVsin2 θ (4)

where K is the anisotropy constant, V is the volume, and θ is the angle between two spins with respect to each other [17]. The overall magnetic anisotropy energy is dependent on the symmetry of the investigated systems and defined by various contributions, such as magnetocrystalline anisotropy, shape anisotropy, surface

Anisotropy energy appeared as a consequence of spin-orbit interaction and the partial quenching of the angular momentum [17]. From the aspect of nanomaterial preparation and dependence of samples of magnetic properties on synthesis conditions (annealing temperature and time), it is important to emphasize that the anisotropy constant is strongly temperature dependent [17]. Independent of the presence of the same or different iron oxide polymorph phases within the sample, differences in the structure and morphology characteristics of each individual

Noteworthy, alteration of the SiO2 matrix during the annealing treatment impacts magnetic properties of the samples [59]. Gas diffusion in the SiO2 matrix,

**118**

mechanics.

metry), anisotropy energy is defined as:

anisotropy, strain anisotropy and stress anisotropy.

nanoparticle resulted in the changes in a magnetic anisotropy.

The main message of this chapter was to emphasize the importance of the investigation of the influence of the synthesis parameter variations onto the magnetic properties of the composite materials containing nano-hematite particles that could be used as a starting material for preparation of multifunctional nanoparticles, used in different areas of biomedicine. Since coercivity field presents a parameter of importance for application of this type of materials, alterations of measured measured Hcrit value, initiated by changing the synthesis parameters, are discussed. To get a better insight into relation between synthesis conditions and magnetic properties of composites containing α-Fe2O3 nanoparticles, sol-gel synthesis is recognized as a suitable preparation method. Alterations of measured Hcrit value of the samples are driven by the variation of the pH of the performed sol-gel synthesis (auto-, acid-, or base-catalyzed), initial Fe**3**+ and Si4+ precursor ratio, amount of the iron precursor, and annealing conditions (T and t) and by performing postannealing treatment. The author expected that this chapter will facilitate a current and objective evaluation of the knowledge regarding the search for the exact mathematical expression of the measured intrinsic coercivity field value of the composite nanomaterials containing nano-hematite phase, which is of significance for improvement of the preparation of a high-quality nano-α-Fe2O3 particles for biomedical application.


4. Calibration of the inverter I

To calibrate the inverter, the VV measures three signals of the calibration circuit R1–R2:

Complex of these signals is described by proper system of equations. Solution of this system (formula 38) gets the accurate deviation δi of the inverter transfer coefficient from its nominal value "1."

$$\delta\_i = \delta\_{\text{it}} (1 + \delta\_{\text{kin}}) \tag{28}$$

After the calibration procedure, we know the real value of the phase shifter transfer coefficient with an uncertainty better than 1–3 ppm. μC makes this calibration procedure automatically at

Variational Calibration

45

http://dx.doi.org/10.5772/intechopen.74220

least every hour.

Figure 10. Some results of experimental investigations.

where.

δia ≈ δiv 2 Ui3þUi1 Ui2�Ui1 ; δkia ≈ δiv 2 Ui3�Ui1 Ui2�Ui1 ; δia and δkia are the approximate values of the transfer coefficients of the inverter I and calibration circuit R1-R2.


**3. Pathways of cellular uptake**

In drug delivery applications, the nanocarriers should go inside the cells to efficiently deliver drugs to target organelles or cells. Thus, the uptake route or mechanism of NP into cell should be considered in designing a nanocarrier system. Cell membrane is the protective coating of a cell and is not permeable to all particles as it maintains homeostasis. The lipid molecules of the cell membrane have hydrophilic heads and hydrophobic tails. Lot of small molecules enter the cell by passive diffusion. The cell uptake of molecules with the help of energy from ATP (Adenosine triphosphate) is called active diffusion [19].

There are a lot of factors which influence the internalization of the NP and their interaction with intracellular components such as size, surface modifications, net charge, hydrodynamic volume and stiffness. The persistence of nanoparticles in the cell and their release of free radicals to induce oxidative stress bring toxicity and cell death. Endocytosis, an active transport, is the most important pathway by which molecules enter the cell and trigger responses. The main types of endocytosis are phagocytosis (cell eating) and pinocytosis. In the process of endocytosis, the particle

#### **Figure 3.**

*Schematic diagram showing the types of nanomaterials and their impact on various organ systems. Created with the help of Biorender.com [18].*

*Toxicity Evaluation and Biocompatibility of Nanostructured Biomaterials DOI: http://dx.doi.org/10.5772/intechopen.109078*

to be internalized with be covered by a part of cell membrane which the buds off inside the cell to form vesicle containing the particle [20].

Phagocytes are immune cells that protect from infections and pollution by engulfing foreign bodies. The 3 main phagocytes are macrophages, neutrophils and monocytes. In phagocytosis opsonins (group of proteins found in serum) play a major role by adsorbing onto NP surface and form protein corona. Phagocytes recognize these and a signaling cascade is triggered which internalizes the particles forming phagosome [18] (**Figures 3** and **4**).

Different cell types use different uptake mechanisms for the same NP. It can occur through phagocytosis, macropinocytosis, clathrin and caveolin mediated endocytosis, non-clathrin and non-caveolin mediated endocytosis are some among them. Nanoparticles less than 100 nm in size can enter the cells and size less than 40 nm can enter the nucleus. The surface charge of the NP are a crucial factor for cell internalization where the negatively charged cell membrane is attracted towards positively charged NP. Small NPs are engulfed by F-actin mechanism, dynamin and lipid rafts which are energy-dependent. NP of size more than 500 nm are engulfed by phagocytosis and macropinocytosis. Aggregated NPs, TiO2 or carbon black undergo opsonization in the biological fluid and undergo phagocytosis or macropinocytosis [19].

#### **3.1 Adverse effects of the cellular uptake**

The bio resistance of certain nanomaterials to degradation is the root cause of toxicity. These nanoparticles retain in the endosomal compartment of cell. Certain other nanoparticles like ZnO, when taken into the acidic part of lysosome will get dissolved into Zn2+ ions which in excess amounts will cause cytokine production leading to cytotoxicity. Non-soluble nanoparticles like TiO2 and carbon black NP were found to be free in cytoplasm and even in the D.N.A. The reasons for this toxicity could be that these NP diffuse through the cell membrane through transient holes or they may

#### **Figure 4.**

*Schematic representation showing the mechanisms of nanoparticle cellular internalization such as clathrinmediated; caveolin-mediated; clathrin- and caveolin-independent; phagocytosis and macropinocytosis pathways. Reproduced with creative commons attribution 4.0 (CC-BY-4.0) license from Augustine et al. [19].*

be accumulated in the lysosome where later on lead to membrane rupture and release in the cytoplasm. These cytoplasmic NP during mitosis can enter the nucleus through microtubules and are found in the DNA [21].

The engineered NP persisting in the cell result in oxidative stress leading to apoptosis and inflammation. Oxidative stress is a result of imbalance between reactive oxygen species [ROS] and antioxidant capacity of cell. NP trigger the ROS production and thus leads to the imbalance and oxidative stress. ROS has various cellular roles by acting as secondary messengers. If the stress caused by ROS is at a higher level, it can result in cell membrane and organelle injury leading to necrosis or apoptosis. The smaller the size of the nanoparticles, the higher the surface area and thus produce more ROS. Thus, the oxidative stress caused by the small NP affect lipid membrane and cause their disorganization in structure and function. Inactivation of certain sensitive proteins which have methionine or cysteine in their active site are also the toxic effects of the NP which entered the cells. Genotoxicity is also a serious effect of NP which damages DNA because of intrachain adducts and strand breakage [22].


**6. Atmospheric gravity waves in the troposphere**

evaporation of the cloud liquid water and settled down. The pressure jump was generated in the dry sector of the vapour front in the mid-troposphere. The back trajectory analysis of the air particle [39] depicted in **Figure 9** showed that the air particle in the East China Sea during the meteotsunami event came from mainly two or three regions. The warm moist air mainly came from South China Sea, Indochina Peninsula and Bengal Bay. Those air particles moved northeast along with the high-pressure system located in the Philippines, and lifted orographically over the inland area of the South China (region 'SW' and 'S'). Other particles came from upper dry air of northwest Eurasian continent or along with the subtropical jets via Tibetan Plateau (region 'NE' and 'E'). Further analysis in **Figure 10** showed that the anomalous mass of the moist air in the lower troposphere was transported from the tropical regions within 3 days before the meteotsunami event on March 31, 1979. The peak value of the moisture transport in the end of March (~200 kgm/s) was much greater than the peak value in the summer monsoon season (~150 kgm/s). The massive transport of the lower moist air into inland China can be seen especially in the late winter and early spring (February–April) for nearly every year. In the same period, the secondary oscillations larger than 1.0 m in amplitude were

**Figure 10.** The northward component of water vapour flux across the line of South China coasts (22.5N, 105–120E) after the vertical integration between 850- and 1000-hPa isobar surface. Red line indicates the 3-day average from 6-h data in

the year 1979. Blue line indicates the 10-day average of climatic value for 55 years (1958–2012) [26].

**Figure 9.** Air particle distribution into East China Sea. The left panel indicates the analysis area with initial particles located in region X. The middle panel shows the distribution of the individual particles 72 h before the meteorological tsunami over the East China Sea. The colour markers indicate the altitude of each air particles. The right panel indi-

cates the particle proportion in each sector shown in the left panel [26].

24 Tsunami

The atmospheric gravity waves are also one of the typical processes to generate pressure disturbance in the sea level, travelling with a long disturbances. There are two mechanisms supporting such characteristics of the atmospheric gravity wave: wave duct [40] and wave CISK [41]. The stable lower troposphere with an increasing wind in a vertical direction is overtopped with an unstable layer in the mid-troposphere as illustrated in **Figure 11** [10]. The Richardson number Ri

$$Ri = \frac{N^2}{\left(dU \wedge dz\right)^2} \tag{9}$$

is generally used to see the atmospheric stability, where *N* = the Brunt-Väisälä frequency and *U* = horizontal velocity. Such vertical structure reflects the wave energy and traps the gravity waves towards the long distance [40, 42, 43]. The potential for downward or upward propagation of mid-tropospheric internal gravity waves may be assessed from the inequality of the linear gravity wave theory [43, 44].

$$N > \frac{2\pi U}{\lambda} \tag{10}$$

where *λ* = the horizontal wavelength of internal gravity wave. The depth of the wave duct D is described as

$$D = \mathcal{A}\_{\varepsilon} \left( \frac{1}{4} + \frac{1}{2}n \right) \qquad \qquad (n = 0, 1, 2, \dots), \tag{11}$$

where *λz* denotes the vertical wave length. Using the wind speed at critical level *Uc*, the *λz* can be approximated as

$$
\lambda\_{\pm} \approx 2\pi \frac{U\_c - U}{N} \tag{12}
$$

The wave CISK denotes the coupling between the gravity wave and convection. The convergences associated with the gravity wave force the moist convection while convection heating provides the energy for the wave [26, 41, 45].

**Figure 11.** Schematic of the generation and the propagation of the atmospheric gravity wave in the presence of the wave-ducting layer, and the enhancement of the ocean long wave. A case study for widespread meteorological tsunami on Mediterranean and Black Sea, in June 2014 (Šepić et al., 2015) [10].

The large-scale motions with meso-α scale, synoptic scale or monsoon scale provide the structure of wave-ducting layer or wave CISK. In June 2014 event, the expansion of the waveducting layer generates and propagates the atmospheric gravity waves. The synoptic weather pattern and the sea level oscillation in that event are shown in **Figure 12** [10]. According to the Šepić et al. (2015) [10], the synoptic structure can be summarized as follows: first, inflows of warm and dry air from Africa in the low troposphere (~850 hPa); second, a strong south-west jet stream in the middle troposphere (~500 hPa) and the presence of the unstable layer between 600 and 400 hPa isobar [10]. The first pattern appeared at Menorca Island, Spain, in the west of the Mediterranean Sea, and the area of the wave propagation moved eastward [10]. The area of the high wind speed in the middle troposphere was located east of the trough.

The cold or dry sector of the cold or stationary front can satisfy the wave-CISK or wave-duct structure very well. In February 2009 event in the west Kyushu in **Figure 13**, Japan, a train of the pressure wave was generated in the north sector of the stationary front under both mechanisms of wave duct and wave CISK. The warm moist air lifted by the mountain effect in South China mixed with the dry air of the mid-troposphere from the south of the Himalaya mountain range. The mixed air generated the unstable layer in the mid-troposphere and covered above the East China Sea. The trough extended from the Siberia and the subtropical high-pressure system generated the latitudinal convergence over the area of the unstable midtroposphere [26]. The wave length of the pressure waves ranged 30–100 km with the period of 20–60 min including the eigen oscillation mode in various bays in that area.

Multiscale Meteorological Systems Resulted in Meteorological Tsunamis http://dx.doi.org/10.5772/63762 27

The wave CISK denotes the coupling between the gravity wave and convection. The convergences associated with the gravity wave force the moist convection while convection

**Figure 11.** Schematic of the generation and the propagation of the atmospheric gravity wave in the presence of the wave-ducting layer, and the enhancement of the ocean long wave. A case study for widespread meteorological tsuna-

The large-scale motions with meso-α scale, synoptic scale or monsoon scale provide the structure of wave-ducting layer or wave CISK. In June 2014 event, the expansion of the waveducting layer generates and propagates the atmospheric gravity waves. The synoptic weather pattern and the sea level oscillation in that event are shown in **Figure 12** [10]. According to the Šepić et al. (2015) [10], the synoptic structure can be summarized as follows: first, inflows of warm and dry air from Africa in the low troposphere (~850 hPa); second, a strong south-west jet stream in the middle troposphere (~500 hPa) and the presence of the unstable layer between 600 and 400 hPa isobar [10]. The first pattern appeared at Menorca Island, Spain, in the west of the Mediterranean Sea, and the area of the wave propagation moved eastward [10]. The area

The cold or dry sector of the cold or stationary front can satisfy the wave-CISK or wave-duct structure very well. In February 2009 event in the west Kyushu in **Figure 13**, Japan, a train of the pressure wave was generated in the north sector of the stationary front under both mechanisms of wave duct and wave CISK. The warm moist air lifted by the mountain effect in South China mixed with the dry air of the mid-troposphere from the south of the Himalaya mountain range. The mixed air generated the unstable layer in the mid-troposphere and covered above the East China Sea. The trough extended from the Siberia and the subtropical high-pressure system generated the latitudinal convergence over the area of the unstable midtroposphere [26]. The wave length of the pressure waves ranged 30–100 km with the period of

of the high wind speed in the middle troposphere was located east of the trough.

20–60 min including the eigen oscillation mode in various bays in that area.

heating provides the energy for the wave [26, 41, 45].

26 Tsunami

mi on Mediterranean and Black Sea, in June 2014 (Šepić et al., 2015) [10].

**Figure 12.** Propagation of the meteotsunamigenic synoptic pattern of 2014 together with the maximum heights of corresponding sea level oscillations at the times of the meteotsunami events. Left panels are 850 hPa air temperature, middle panels are 500 hPa wind and right panels are distribution of the unstable layer (Ri <0.25) in the mid-troposphere. (Šepić et al., 2015) [10].

**Figure 13.** Weather condition of meteorological tsunami around the cold front on February 25, 2009. The surface weather chart (left), wavy clouds by satellite IR image (middle) and unstable layer covered with the East China Sea (right) [26].