The vDVZ Discontinuity,DGP Gravity,and Cosmology

We discuss some properties of the van Dam–Veltman–Zakharov (vDVZ) discontinuity in the Dvali–Gabadadze–Porrati (DGP also called brane-induced) gravity. This model exhibits a vDVZ discontinuity when linearized over a Minkowski background. However, one can show that this discontinuity disappears on general Friedmann–Lemaître–Robertson–Walker space-times, when the radius of transition between 4D and 5D gravity is sent to infinity with respect to the background Hubble radius. This radius of transition plays for the brane-induced gravity model a rôle equivalent to the Compton wavelength of the graviton in a Pauli–Fierz theory, as far as the vDVZ discontinuity is concerned. These results were obtained considering the Cauchy problem associated with linearized DGP model over a cosmological background and provide a novel way to address the issue of the vDVZ discontinuity, as well as to look at some properties of the DGP model. Some parts of the discussion have not been presented before and comments are also made on the issue of the growth of cosmological perturbations in the DGP model.     

Determination of Tourmaline Composition in Pegmatite From Buldan,Denizli (Western Anatolia,Turkey) Using XRD,XRF, and Confocal Raman Spectroscopy

ABSTRACT

Tourmaline minerals observed in different geologic environments show significant variations in terms of chemical compositions. Determination of tourmaline species gives useful petrogenetic information about both igneous and metamorphic environments. Microscopic, XRD, XRF, and confocal Raman spectroscopic features of tourmaline segregations that are 2–4 cm thick, dark-blue to black in color, and mostly fractured occurring in the Buldan pegmatite are reported. Under the microscope, tourmaline samples show indigo blue, light blue, and olive-brown pleochroism with a thin long columnar, bladed shape. They exhibit distinctive enrichments in Fe₂O₃ (7.83–10.16 wt%), V (245.0–591.0 ppm), Sn (70.1–147.3 ppm), W (1076.0–1887.0 ppm), U (1.2–18.2 ppm), and Th (9.6–28.0 ppm). In terms of geochemistry, the tourmaline samples are schorl with Fe/(Fe + Mg) ratios of 0.65–0.74 and Na/(Na + Ca) ratios of 0.88–0.93. Five characteristic bands of tourmaline samples are observed at 1050, 710, 370, 220–245, and 185 cm^?1. Tourmaline segregations in the Buldan pegmatite are schorl in composition and are probably generated from Li-poor granitoids and their associated pegmatites.     

Raman spectroscopic investigations of natural jennite from Maroldsweisach,Bavaria, Germany

A full‐range pattern (100–3700 cm⁻¹) analysis of natural jennite was performed for the first time by Raman spectroscopy, applying a polarized laser at a wavelength of 532 nm. A prominent structural feature of jennite is the preferred orientation of Si‐tetrahedron and Ca‐octahedron chains parallel [010]. The latter ones are additionally coupled to H₂O molecules and OH groups. This arrangement leads to a strong dependence on orientation for the intensity ratios of mainly three different regions in the Raman spectra: 180–210, 950–1050 and 3100–3650 cm⁻¹. These sections can be assigned to Ca–O lattice vibrations, Q² Si–tetrahedron stretching and O–H vibrations of H₂O molecules and Ca–OH structures, respectively. Copyright © 2015 John Wiley & Sons, Ltd.     

Atomic collapse,Lorentz boosts,Klein scattering,and other quantum-relativistic phenomena in graphene

Electrons in graphene, which behave as massless relativistic Dirac particles, provide a new perspective on the relation between condensed matter and high-energy physics. We discuss atomic collapse, a phenomenon in which discrete energy levels of superheavy atoms are transformed into resonant states. Charge impurities in graphene provide a convenient condensed matter system in which this effect can be explored. Relativistic dynamics also manifests itself in graphene p–n junctions. We show how the transport problem in the presence of a magnetic field can be solved with the help of a Lorentz transformation, and use it to investigate magnetotransport in p–n junctions. Finally, we review a recent proposal to use Fabry–Pérot resonances in p–n–p structures as a vehicle to investigate Klein scattering, another hallmark phenomenon of relativistic dynamics.     

Study of Pulsed Cathodoluminescence of Calcium,Barium, Lithium,and Magnesium Fluorides

Russian Physics Journal - Studies of the spectral and kinetic characteristics of CaF2, BaF2–Ce, LiF, LiF–W and MgF2 crystal glow irradiated by the electron beam with energy of 350 keV...     

Synthesis,spectral characterization,docking studies and biological activity of urea,thiourea, sulfonamide and carbamate derivatives of imatinib intermediate

Molecular Diversity - A series of new urea/thiourea derivatives 3a–j were synthesized by simple addition reaction of functionalized phenyl isocyanates/isothiocyanates 2a–j with...     

Local structure and local conduction paths in amorphous (In,Ga,Hf)–ZnO semiconductor thin films

The local structure and local conduction paths of Ga–In–Zn–O (GIZO) and Hf–In–Zn–O (HIZO) amorphous thin films were investigated by the extended X-ray absorption fine structure (EXAFS). We found that the local hindrance paths of In–Ga and In–Hf exist in the conduction paths of amorphous GIZO and HIZO semiconductor thin films, respectively.     

Equations of state of MgO,Au, Pt,NaCl-B1, and NaCl-B2: Internally consistent high-temperature pressure scales

Semiempirical equations of state (EoS) of Au, Pt, MgO, NaCl-B1, and NaCl-B2 based on expanded Mie–Grüneisen–Debye approach, which are consistent both with the Mie–Grüneisen–Bose–Einstein approach and the thermochemical, X-ray, ultrasonic and shock-wave data in a wide pressure-temperature range, have been constructed. It is shown that to determine the volume dependence of the Grüneisen parameter, not only shock-wave and static compression data, but also experimental information on heat capacity, bulk moduli, volume, and thermal expansion coefficient at zero pressure need to be taken into account. Intrinsic anharmonicity is of great importance at construction of EoS at high temperatures and x=V/V ₀>1. Cross-comparison of the current equations of state with independent measurements shows that these EoS may be used as the internally consistent and independent pressure scales in a wide range of temperatures and pressures.     

Energy Levels,Lifetimes, and Radiative Data of Xe XXIV

Journal of Applied Spectroscopy - The multi-configuration Dirac–Hartree–Fock method is employed to calculate the energy levels, wavelengths, transition probabilities, and line strengths...     

Spectrometric-based techniques for metal-binding protein assessment in clinical,environmental, and food samples

Metalloproteins and metal–protein complexes play key roles in all organisms. For example, certain metalloproteins are involved in metal homeostasis and detoxification, or oxidative stress protection; whereas, metals serve as essential cofactors in a large number of metal–protein complexes. Advances in analytical instrumentation as well as informatics have allowed a complete characterization/assessment of both metalloproteins and metal–protein complexes. In some cases, the identification of the protein is a key factor for understanding its physiological function, such as when assessing protein corona in nanoparticles–protein assemblies. On other occasions, the identification of the binding sites in the peptide chain and conformational changes as a consequence of the metal–protein interaction, as well as the lability of this interaction, can explain the role of these metal-based biomolecules in living organisms. This article attempts to critically review the current state-of-the-art of the available analytical techniques for characterizing metalloproteins and metal–protein complexes. Methods for assessing the structure, characterization of the metal-binding sites, as well as the class of proteins involved in some metal (metallic nanoparticle)-binding proteins are discussed. Recent developments when assessing metalloproteins and metal–protein complexes in the clinical, environmental, and food fields, and pioneering research regarding nanoparticle–protein characterization, are also reviewed.     

Transmittance of CsI,AgCl, KRS-5, and KRS-6 Crystals in the Terahertz Range

Optics and Spectroscopy - Spectral dependences of the transmittance of CsI, AgCl, KRS-5 (TlBr–TlI), and KRS-6 (TlCl–TlBr) single crystals in the infrared (IR) and terahertz (THz)...     

Laser Induced I.R. Fluorescence Spectra of Ethylene,Propylene, 1-Butene,Ethyl Acetate,Acetaldehyde, Ethyl Ether,Methyl Alcohol and Ethyl Alcohol

Infrared laser have been widely used as an excitation source to stimulate infrared fluorescence for various molecules (1–8). The process of stimulation is not clearly understood but is felt to depend on the high power density and the coherent nature of the radiation from the laser amongst other parameters. In recent years, the laser has been used increasingly for air pollution monitoring (9–11).     

Insight into the structural,electronic and elastic properties of AInQ2 (A: K,Rb and Q: S,Se, Te) layered structures from first-principles calculations

First-principles calculations were performed to explore the structural, elastic and electronic properties of the ternary indium chalcogenides AInQ₂ (A: K, Rb and Q: S, Se, Te) in both monoclinic and triclinic phases. This study is carried out by using the first-principles pseudopotential plane-wave (PP–PW) method as implemented in CASTEP code. Both the generalized gradient approximation of Perdew–Burke–Ernzerhof scheme (GGA–PBE) and the Heyd–Scuseria–Ernzerhof (HSE06) hybrid functional were used to treat the exchange-correlation interactions. In order to confirm the previous reports and to understand the effect of symmetry in determining the physical properties of these layered materials we have calculated the structural and the electronic properties at the equilibrium lattice constant for both the systems. The single-crystal elastic constants C_{i j} are calculated using the stress-strain approach. The elastic moduli of the polycrystalline aggregates and their related properties are obtained in the framework of Voigt–Reuss–Hill approximations. Electronic band structure indicates the semiconducting behaviour with a direct band gap at Γ–Γ. The results obtained from the (HSE06) hybrid functional are in excellent agreement with the available experimental data and computed results for the monoclinic and triclinic structures.     

Graphene oxide–gellan gum–sodium alginate nanocomposites: synthesis,characterization, and mechanical behavior

This paper reports the preparation and characterization of graphene oxide–gellan gum–sodium alginate nanocomposites (GO–GG–Alg). The nanocomposites were prepared by a simple solution mixing-evaporation method. Fourier transform infrared spectroscopy, X-ray diffractions, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, thermal gravimetric analysis, and mechanical testing were conducted to study the structure and properties of the nanocomposites. The obtained findings reveal that gellan gum, sodium alginate, and graphene oxide are able to form a homogeneous mixture. Small amount of GO loading on GO–GG–Alg drastically improves its tensile strength and Young’s modulus. Detailed material characteristics of the nanocomposites are addressed.     

Transformation of Phenol,Resorcinol, Pyrocatechol,and Hydroquinone in Water Under Exposure to Low Doses of UV Radiation

Journal of Applied Spectroscopy - The transformation of phenol, resorcinol, pyrocatechol, and hydroquinone in water at concentrations of 10–4 to 10–6 M under short-term exposure to UV...     

Pressure-induced variation of structural,elastic, vibrational,electronic, thermodynamic properties and hardness of Ruthenium Carbides

Three of the five structures obtained from the evolutionary algorithm based structure search of Ruthenium Carbide systems in the stoichiometries RuC, Ru₂C and Ru₃C are relaxed at different pressures in the range 0–200 GPa and the pressure-induced variation of their structural, elastic, dynamical, electronic and thermodynamic properties as well as hardness is investigated in detail. No structural transition is present for these systems in this pressure range. RuC–Zinc blende is mechanically and dynamically unstable close to 100 GPa. RuC-Rhombohedral and Ru₃C-Hexagonal retain mechanical and dynamical stability up to 200 GPa. For all three systems the electronic bands and density of states spread out with pressure and the band gap increases with pressure for the semiconducting RuC–Zinc blende. From the computed IR spectrum of RuC–Zinc blende at 50 GPa it is noted that the IR frequency increases with pressure. Using a semi-empirical model for hardness it is estimated that hardness of all three systems consistently increases with pressure. The hardness of RuC–Zinc blende increases towards the superhard regime up to the limiting pressure of its mechanical stability while that of RuC-Rhombohedral becomes 30 GPa at the pressure of 150 GPa.     

Optimization of Composition,Synthesis, and Study of Broadband Multilayer Mirrors for the EUV Spectral Range

Technical Physics - Broadband Mo/Si and Mo/Be multilayer stack-type mirrors for wavelength intervals of 11.1–13.8, 17–21, and 28–33 nm have been developed and fabricated. Uniform...     

Thermal stability of alkylbiphenyls in the subcritical,critical, and supercritical states

The kinetics of gas-phase thermal transformations of 4-methyl-, 4,4′-dimethyl-, 4-tert-butyl-, and 4,4′-di-tert-butylbiphenyls was studied over the temperature ranges 813–848, 733–793, 703–763, and 703–763 K, respectively. Competition between cracking and alkyl substituent isomerization at aromatic nuclei of the initial substance and products formed was observed for tert-butylbiphenyls. The kinetic parameters of the overall transformation of alkylbiphenyls (ABPs) were determined. Recommendations for the determination of the critical temperatures of ABPs, their synthesis, processing, and use of articles with structural fragments in molecules identical to those studied in this work were given. It was found experimentally that 2-, 3-, and 4-methylbiphenyls and their mixtures with toluene were thermally unstable over the whole composition range at critical temperatures (600–780 K).     

Comparison of polystyrene IR spectra obtained by the T,R, ATR,and DR methods

The results of measuring the spectra of polystyrene samples in the IR range (4000–400 cm^–1) obtained by transmission, specular reflection, frustrated total internal reflection, and diffuse reflection have been compared. Polystyrene samples in the form of a thin film, a bulk sample, and foamed polystyrene have been investigated. The frequencies of the strongest bands in the spectra obtained by the methods under comparison are shown to depend on the anomalous dispersion in the vicinity of these bands and the specific features of structural chemical composition of the polystyrene–air interfaces. The presence of these interfaces is most pronounced in the reflection methods.     

Analysis of the Auger-photoelectron coincidence spectroscopy (APECS) spectra of metallic Pd,Ag, and Sn

The M45-level photoelectron spectrum of Ag metal measured in coincidence with the M45–VV(¹G) Auger-electron line is analyzed by taking into account the possibility of the M4–M5–VV Coster–Kronig (CK)-transition preceded Auger transition. We denote the atomic shells Mx(Mxy) and Nxy (x, y = 4,5) by MX(MXY) and V, respectively. The M4–M5 CK-transition rate is very small. The M45–VV Auger-electron spectra of metallic Pd and Sn measured in coincidence with the M4 (or M5)-level photoelectron line are analyzed. The M4–M5 CK-transition rates are also very small in metallic Pd and Sn. The coincidence Auger-electron line previously interpreted as the M4–M5–VV (or M4–M5V–VVV) Auger-electron line is largely due to the inelastically scattered M5-level photoelectron background beneath the M4-level photoelectron line. The APECS spectrum of Pd metal shows the first evidence of the M5V–VVV transition of the localized M5V shakeup two-hole state. The intensity ratio of the inelastically scattered Auger-electron background to the M5–VV Auger-electron main line of Ag metal measured in coincidence with the inelastically scattered M5-level photoelectron background beneath the M4-level photoemission line increases, as compared to that measured in coincidence with the M5-level photoelectron main line. This is because when the probability of the photoelectron being inelastically scattered increases, that of the Auger electron emitted by the same ionized atom, being inelastically scattered increases. In other words the photoelectrons and the Auger electrons are originated from the deeper atomic sites (longer pathlength).