Gamma ray energy-absorption buildup factors were computed, using the five-parameter Geometric Progression fitting formula and the ANSI/ANS-6.4.3 report, for some fluorides and sulfates in the energy range 0.015−15 MeV, and for penetration depths up to 40 mfp. The generated energy-absorption buildup factors are studied as functions of penetration depth and incident photon energy. At a given penetration depth, the buildup factor first increases, reaching a maximum value, and then decreases with increasing energy. The maximum value of the buildup factor occurs in the energy range 0.15–0.3 MeV. At these energies, Compton scattering is the major photon interaction process, and photoelectric absorption is of relatively little importance, leading to large buildup factors. The results of the present work should be useful in radiation dosimetry, diagnostics and therapy. The tissue equivalence of these materials is also discussed. It is found that lithium fluoride can be effectively used as a tissue equivalent material for cortical bone in the energy region 0.2−2 MeV.

The high-pressure structural behaviour of a series of binary thorium compounds ThX (X = C, N, P, As, Sb, Bi, S, Se, Te) is studied using the all-electron full potential linear muffin-tin orbital (FP-LMTO) method within the generalized gradient approximation (GGA) for the exchange and correlation potential. The calculated equlibrium lattice parameters and bulk moduli, as well as the equations of state agree well with experimental results. New experiments are reported for ThBi and ThN. Calculations are performed for the ThX compounds in the NaCl- and CsCl-type crystal structures, and structural phase transitions from NaCl to CsCl are found in ThP, ThAs, ThSb and ThSe at pressures of 26.1, 22.1, 8.1 and 23.2 GPa, respectively, in excellent agreement with experimental results. ThC, ThN and ThS are found to be stable in the NaCl structure, and ThBi and ThTe in the CsCl structure, for pressures below 50 GPa. The electronic structures of the ThX compounds are studied using the quasiparticle self-consistent GW method (G: Green function, W: dynamically screened interaction).

The chapter includes a history of the discovery and characterization of radioactivity. It follows with a description of the properties of atomic constituents, and the relation between mass and energy. This is followed with a treatment on the properties of the nucleus, nuclear forces, binding energy, nuclear models, and the relativistic properties of nuclear radiation. Natural and artificially produced radionuclides are discussed including radionuclides of cosmogenic origin and natural radionuclide decay chains. Nuclear reactions are discussed including reaction types, energy of reactions (Q value), and reaction cross section. A treatment of alpha decay, beta decay including negatron emission, positron emission, electron capture (EC), double beta (ββ) decay, and the interactions of alpha and beta radiation with matter. Also discussed are internal conversion and Auger electron emissions and a detailed treatment of neutron sources, interaction of neutrons with matter, neutron attenuation and cross section, and neutron decay. The wave-particle dual nature of matter is discussed and a treatment of electromagnetic radiation or photons including the mechanisms of photon interaction with matter. Cherenkov radiation, its origin, and properties are discussed. The origins, properties and applications of synchrotron radiation are also discussed. The chapter continues with a treatment of nuclear recoil and the calculations of recoil energy following alpha, beta, gamma, X-ray, and neutrino emission in radionuclide decay. Cosmic radiation is discussed including the origins, properties, classification, and showers of the cosmic radiation. A treatment of radiation dose, stopping power, and linear energy transfer is included. The principles of radionuclide decay, ingrowth, and equilibrium are included. There is also a discussion of radioactivity units and the correlation of radioactivity and radionuclide mass.

The ground-state \( (\mu_{\text{g}} ) \) and excited-state \( (\mu_{\text{e}} ) \) dipole moments of three 1, 2-diazine nanomaterials (pyrrolo-pyridazine derivatives) were determined using the solvatochromic shift methods, i.e. Lippert-Mataga, Bakhshiev, Kawski-Chamma-Viallet and Reichardt equations. All these equations are based on the variation of Stokes shift with solvent’s dielectric constant and refractive index. Theoretical \( \mu_{\text{g}} \) values were also evaluated by quantum chemical calculations using the DFT method by adopting B3LYP/6-31G* level of theory (Gaussian 03). It was observed that all the three 1, 2-diazine nanomaterials possess higher dipole moment values in the excited singlet-state than in the ground-state. This confirms that the excited state of these nanomaterials is more polar than the ground state. Therefore, the solvent–solute interactions should be stronger in the excited singlet-state than in the ground-state, demonstrating an important redistribution of charge densities between both electronic states.

Using the theory of solvatochromism, the difference in the excited-state (μe) and ground-state (μg) dipole moments was determined from Lippert–Mataga, Bakhshiev, Kawski–Chamma–Viallet, and McRae equations for three 1,2-diazines (pyrrolo-pyridazine derivatives). All of these equations are based on the variation of Stokes shift with solvent's relative permittivity and refractive index. Further, the change in dipole moment value (Δμ) was also calculated using the variation of Stokes shift with the molecular-microscopic empirical solvent polarity parameter. Theoretical μg values were evaluated by quantum chemical calculations using the DFT method by adopting B3LYP/6-31G* level of theory (Gaussian 03) and using the AM1 method (Chem3D Ultra 8.0). It was observed that, dipole moments of diazines in the excited-state (μe) were greater than the corresponding ground-state values (μg), indicating a substantial redistribution of the π-electron densities in a more polar excited-state. Also, with the increase in the polarity of the solvent, the fluorescence emission peak undergoes a red-shift, confirming a π→π* transition.

This paper describes a few episodes from the early days of X-ray spectroscopy. It relies on contemporary publications, especially those by Barkla, Moseley, Siegbahn, and Compton. The paper addresses the subject from the vantage point of physics and should be of interest to the X-ray spectroscopist, who wants to obtain a glimpse of the history of his chosen field. Copyright (c) 2013 John Wiley & Sons, Ltd.

In this work, multilayered perceptron neural networks (MLPNNs) were presented for the computation of the gamma-ray energy absorption buildup factors (BA) of seven thermoluminescent dosimetric (TLD) materials [LiF, BeO, Na2B4O7, CaSO4, Li2B4O7, KMgF3, Ca3(PO4)2] in the energy region 0.015–15MeV, and for penetration depths up to 10 mfp (mean-free-path). The MLPNNs have been trained by a Levenberg–Marquardt learning algorithm. The developed model is in 99% agreement with the ANSI/ANS-6.4.3 standard data set. Furthermore, the model is fast and does not require tremendous computational efforts. The estimated BA data for TLD materials have been given with penetration depth and incident photon energy as comparative to the results of the interpolation method using the Geometrical Progression (G-P) fitting formula.

The structural behaviour of Cu0.5Fe0.5Cr2S4 has been studied experimentally and theoretically at pressures up to 44 GPa. The experiments are supported by density functional calculations using the full-potential linear muffin-tin orbital method for investigating ground state properties and high-pressure behaviour. We report here the first experimental and theoretical determinations of the bulk modulus: B-0 = 106(2) GPa and B-0' = 4.0 (experimental), and B-0 = 96 GPa and B-0' = 3.9 (calculated). Moreover, a pressure-induced structural and electronic phase transformation occurs at 14.5 GPa accompanied by a volume collapse of about 6%. Tentatively, the high-pressure phase is assigned the defect NiAs structure of Cr3S4 type with space group I2/m (12). The mechanism of the phase transition is explained by a Jahn-Teller type distortion, associated with geometrical frustration and magnetic spin changes. (c) 2013 Elsevier B.V. All rights reserved.

The high-pressure structural stability of CeN is investigated by experiment and theory. Experiments are carried out by energy-dispersive X-ray diffraction and synchrotron radiation, using a diamond anvil cell, to a maximum pressure of 77 GPa. The experimental results are in remarkably good agreement with ab initio calculations using the full-potential linear muffin-tin orbital method within the generalized gradient approximation (GGA). The experimental zero pressure bulk modulus is B-0 = 156(3) GPa, the pressure derivative being constrained to B-0' = 4.00. The corresponding calculated data are B-0 = 158.1 GPa and B-0' = 3.3. We report here the first experimental observation of the transformation of CeN from the ambient B1 type crystal structure to the B2 type. The onset of the transition is in the range 65-70 GPa, and the relative volume change at the transition is Delta V/V = -10.9(3)%. These data compare well with the calculated transition pressure P-tr = 68 GPa and Delta V/V= -10.8%. Experimentally, the transition is found to be rather sluggish. (C) 2012 Elsevier B.V. All rights reserved.

High-pressure powder x-ray diffraction experiments using synchrotron radiation are performed on the yttrium monochalcogenides YS, YSe, and YTe up to a maximum pressure of 23 GPa. The ambient NaCl structure is stable throughout the pressure range covered. The bulk moduli are determined to be 93, 82, and 67 GPa for YS, YSe, and YTe, respectively. First-principles total energy calculations are carried out using the full-potential linear muffin-tin orbital method. The calculated and measured lattice constants and bulk moduli are in good agrement. Under applied pressure, the yttrium monochalcogenides are predicted to undergo a structural transition. Assuming that the high-pressure phase corresponds to the CsCl crystal structure, transition pressures of 53, 36, and 14 GPa are found for YS, YSe, and YTe, respectively.

Single crystals of HoB4 have been grown and used for synchrotron X-ray diffraction studies at pressures up to 23 GPa and temperatures down to 100 K. The experimental bulk modulus 195±6 GPa is in good agreement with 188.4 and 198.2 GPa values calculated in the LSDA and LSDA+U approximations, indicating that mainly the boron sublattice determines the bulk modulus. The experimental c/a ratio decreases slightly with pressure, but the effect is small. An orthorhombic distortion begins at T c≈ 295 K, i.e. at a temperature much higher than the Néel temperature T N1=7.1 K. The behavior is interpreted in terms of built-in strains and crystal mosaicity.

High-pressure X-ray diffraction in ScB2, TiB2, YB4 and HoB4 powders and single crystals has been studied using synchrotron radiation as well as conventional X-rays. The experimental results are supported by calculations using density functional theory. ScB2, YB4 and HoB4 are hard materials (bulk modulus 180–200GPa), while TiB2 may be classified as superhard (bulk modulus about 260GPa). We report here first experimental and theoretical determinations of the bulk modulus for HoB4 (195(5) and 198.2GPa, respectively), and first experimental values of the bulk modulus for ScB2 (196(2)GPa) and YB4 (185(4)GPa). No pressure-induced phase transformations are observed in any of the above borides up to about 20GPa. A continuous temperature-driven orthorhombic distortion is observed for HoB4 below 285K. Values of the thermal expansion coefficient are reported for ScB2 and HoB4 at 293, 200 and 100K. The thermoelastic behavior is explained in terms of bonding characteristics.

Energy absorption geometric progression (GP) fitting parameters and the corresponding buildup factors have been computed for human organs and tissues, such as adipose tissue, blood (whole), cortical bone, brain (grey/white matter), breast tissue, eye lens, lung tissue, skeletal muscle, ovary, testis, soft tissue, and soft tissue (4-component), for the photon energy range 0.015-15 MeV and for penetration depths up to 40 mfp (mean free path). The chemical composition of human organs and tissues is seen to influence the energy absorption buildup factors. It is also found that the buildup factor of human organs and tissues changes significantly with the change of incident photon energy and effective atomic number, Z(eff). These changes are due to the dominance of different photon interaction processes in different energy regions and different chemical compositions of human organs and tissues.With the proper knowledge of buildup factors of human organs and tissues, energy absorption in the human body can be carefully controlled. The present results will help in estimating safe dose levels for radiotherapy patients and also useful in diagnostics and dosimetry. The tissue-equivalent materials for skeletal muscle, adipose tissue, cortical bone, and lung tissue are also discussed. It is observed that water and MS20 are good tissue equivalent materials for skeletal muscle in the extended energy range.

Fe1.087Te exhibits three phases in the pressure range from ambient to 16.6 GPa and becomes amorphous at higher pressures. All three phases have tetragonal symmetry. The low pressure T-phase is stable in the pressure range 0 <= P < 4.1 GPa and is found to be relatively soft having zero pressure bulk modulus B-0 = 36(1) GPa. The intermediate cT-phase is less compressible with B-0 = 88(5) GPa and stable in the pressure range 4.1 <= P < 10 GPa while a more compressible phase was observed between 10 and 16.6 GPa.

Gamma ray exposure buildup factors for three Heavy Metal Oxide (HMO) glass systems, viz. PbO-Bi(2)O(3)-B(2)O(3), PbO-B(2)O(3), and Bi(2)O(3)-B(2)O(3) glasses are presented. The computations were done by interpolation method using the Geometric Progression fitting formula and ANSI/ANS-6.4.3 library for the energy range from 0.015 to 15 MeV, up to penetration depths of 40 mfp (mean free path). The buildup factors have been studied as functions of incident photon energy and penetration depth. The variations in the buildup factor, for all the glass systems, in different energy regions; have been presented in the form of graphs. Buildup factors of these HMO glasses cannot be found in any standard database, but they are useful for practical calculations in gamma ray shield designs, and they also, help to determine and control the thickness of the shielding material used.

The effective atomic number, Z(eff), has been calculated for fatty acids and cysteine. It is shown that Z(eff) is a useful parameter for low-Z materials at any energy above 1 keV. Absorption edges of medium-Z elements may complicate the energy dependence of Z(eff) below 10 keV. The notion of Z(eff) is perhaps most useful at energies where Compton scattering is dominating, and where Z(eff) is equal to the mean atomic number, Z, over a wide energy range around 1 MeV.

Trigonal RbFe(MoO4)2 is a quasi-two-dimensional antiferromagnet on a triangular lattice below TN = 3.8 K, The crystal exhibits also a structural phase transition at Tc = 190 K related to symmetry change from to . We present the temperature- and pressure-dependent characteristics of this material in the context of ambiguous opinions on the symmetry and crystal properties below Tc. A single-crystal x-ray diffraction shows that the temperature-dependent evolution of the unit cell in the range 100–300 K is strongly anisotropic with markedly discontinuous changes at Tc. The transition is connected with a spontaneous strain developing in effect of the volume decrease. The structure releases the strain by rotation of corner-sharing rigid MoO4 and FeO6 polyhedra in the (a,b) basal plane. The temperature dependence of the IR vibrational wavenumbers exhibits weak changes near Tc, which are consistent with the symmetry transformation from to . High-pressure x-ray powder diffraction indicates that the material is extremely soft but with some stiffening at high pressure. The zero-pressure bulk modulus is B0 = 7.9(6) GPa and the pressure derivative is B0′ = 10(1). The compression curve can be described by a single equation of state, corresponding to the trigonal cell, up to 5 GPa. An amorphization appearing above 5 GPa and increasing gradually on further pressure increase suggests the thermodynamic instability of the high-pressure structure.

The effective atomic number, Z(eff), and the effective electron density, N-el,N-eff, have been calculated at photon energies from 1 keV to 100 GeV for CaO-SrO-B2O3, ZnO-PbO-B2O3, and CdO-PbO-B2O3 glasses with potential applications as gamma ray shielding materials. Appreciable variations are noted for all parameters by changing the chemical composition and the photon energy. The calculated parameters are compared with experimental data wherever possible. Comparisons are also made with the single-valued effective atomic number given by the program XMuDat. Finally, it is concluded that lead oxide glasses have gamma ray shielding properties comparable with standard shielding materials, such as concrete.

The VF3-type compounds MF3 with M = Fe and Ga have been studied by high-pressure energy-dispersive X-ray diffraction. The compression mechanism was found to be highly anisotropic for both compounds, with the c-axis showing little pressure dependence. The volume reduction is mainly achieved through coupled rotations of the MF6 octahedra around the c-axis, which reduces the length of the a-axis. The compression mechanism of both compounds is reasonably well described in terms of deformation of an 8/3/c2 sphere-packing model up to the pressures where the fluorine atoms become hexagonally close-packed. It is proposed that both compounds enter a phase with the fluorine atom arranged in a osuper-denseo sphere packing at higher pressures. The zero pressure bulk modulus of FeF3 and GaF3 was determined as 12(2) and 37(3)GPa, respectively, and a scaling relation between the zero pressure bulk modulus and unit cell volumes was found for TiF3, CrF3, FeF3 and GaF3.