Asymptotic magnetic behavior of gas transport properties

The nonvanishing elements of the viscosity and thermal conductivity tensors of polyatomic gases fall into two classes: those that change sign with a rotation about the magnetic field line and those that do not. It is shown that the boundedness of the linearized Waldmann-Snider collision operator and its properties under symmetry transformations imply that for linear Zeeman splitting the first class vanishes at zero and infinite field as ¦B ¦ and ¦B ¦^–1 and that the second class approaches its asymptotes as ¦B ¦² and ¦B ¦^–2.Supported by the Department of Naval Ordnance Systems Command N-00017-62-C-0604.     

Entanglement and nonlocality of one- and two-mode combination squeezed state

We investigate the entanglement and nonlocality properties of one- and two-mode combination squeezed vacuum state (OTCSS, with two-parameter λ and γ) by analyzing the logarithmic negativity and the Bell's inequality. It is found that this state exhibits larger entanglement than that of the usual two-mode squeezed vacuum state (TSVS), and that in a certain regime of λ, the violation of Bell's inequality becomes more obvious, which indicates that the nonlocality of OTCSS can be stronger than that of TSVS. As an application of OTCSS, the quantum teleportation is examined, which shows that there is a region spanned by λ and γin which the fidelity of OTCSS channel is larger than that of TSVS.     

Temporal behavior of dark spatial solitons in closed-circuit photovoltaic media

We show that the time-dependent nonlinear wave equation in closed-circuit photovoltaic media can exhibit quasi-steady-state and steady-state spatial solitons. We demonstrate that the formation time of open-circuit quasi-steady-state and open-circuit steady-state dark solitons decreases with an increase in the intensity ratio of the soliton, which is the ratio between the soliton peak intensity and the dark irradiance. We find that for the time-dependent nonlinear wave equation that exhibits only an open-circuit steady-state dark soliton, changing the electric current density J₀ does not generate quasi-steady-state dark solitons and affects the formation time of steady-state dark solitons and that for the time-dependent nonlinear wave equation that exhibits an open-circuit quasi-steady-state dark soliton, changing J₀ gives rise to three different time evolution regimes of the full width half maximum of the soliton’s intensity. The first regime shows that the formation time of steady-state dark solitons increases with J₀ whereas the formation time of quasi-steady-state dark solitons is independent of J₀. The second regime shows that the formation time of steady-state dark solitons decreases with an increases in J₀ and the formation time of quasi-steady-state dark solitons increases with J₀. The third regime shows that changing J₀ enables only steady-state dark solitons in the time-dependent nonlinear wave equation, of which the formation time increases with J₀.     

Structural and electronic properties of type-I and type-VIII Ba8Ga16Sn30 clathrates under compression

The total energy and electronic structures for type-I (β phase) and type-VIII (α phase) Ba₈Ga₁₆Sn₃₀ clathrates under hydrostatic pressure have been investigated using density functional theory (DFT) calculations. It was found that the type-VIII phase is more stable than the type-I one at ambient conditions and that β→α phase transition can not occur under hydrostatic pressure. The band structures show that the type-I and type-VIII Ba₈Ga₁₆Sn₃₀ are indirect semiconductors with band gaps of 0.24 eV and 0.19 eV, respectively. The results suggested that type-I clathrate Ba₈Ga₁₆Sn₃₀ has a larger value of the thermoelectric (TE) power than that of type-VIII clathrate. We found that pressure tuning changes the k-point of conduction band minimum (CBM) in the Brillouin zone for β-phase, but it is not the case for α-phase. Furthermore, the results show that the pressure can change the interaction between guest atoms and the host lattice, and consequently results in the decrease of the band gap of β-phase and the increase of the band gap of α-phase, indicating that the pressure effect can play an important role in the magnitude of the TE power.     

An evolutionary framework for cultural change: Selectionism versus communal exchange

Dawkins? replicator-based conception of evolution has led to widespread mis-application of selectionism across the social sciences because it does not address the paradox that necessitated the theory of natural selection in the first place: how do organisms accumulate change when traits acquired over their lifetime are obliterated? This is addressed by von Neumann?s concept of a self-replicating automaton (SRA). A SRA consists of a self-assembly code that is used in two distinct ways: (1) actively deciphered during development to construct a self-similar replicant, and (2) passively copied to the replicant to ensure that it can reproduce. Information that is acquired over a lifetime is not transmitted to offspring, whereas information that is inherited during copying is transmitted. In cultural evolution there is no mechanism for discarding acquired change. Acquired change can accumulate orders of magnitude faster than, and quickly overwhelm, inherited change due to differential replication of variants in response to selection. This prohibits a selectionist but not an evolutionary framework for culture and the creative processes that fuel it. The importance non-Darwinian processes in biological evolution is increasingly recognized. Recent work on the origin of life suggests that early life evolved through a non-Darwinian process referred to as communal exchange that does not involve a self-assembly code, and that natural selection emerged from this more haphazard, ancestral evolutionary process. It is proposed that communal exchange provides an evolutionary framework for culture that enables specification of cognitive features necessary for a (real or artificial) societies to evolve culture. This is supported by a computational model of cultural evolution and a conceptual network based program for documenting material cultural history, and it is consistent with high levels of human cooperation.     

Incorporation of iodine into the channels of AlPO4-5 crystals

Iodine molecules have been incorporated into the channels of calcined AlPO₄-5 crystals by using vapor-phase diffusion method. XRD results indicate that the iodine-loaded AlPO₄-5 crystals are of similar structure as that of as-synthesized AlPO₄-5 crystals. TG and XRF analyses reveal that the iodine molecules have not compactly filled the channels of AlPO₄-5 crystals, and the desorbing process of adsorbed iodine is quite different from that of adsorbed water. Polarized Raman spectra imply that the iodine exists in the channels of AlPO₄-5 crystals as vapor-like I₂ molecules, and the I₂ molecules orientate randomly.     

On Classical and Quantum Objectivity

We propose a conceptual framework for understanding the relationship between observables and operators in mechanics. To do so, we introduce a postulate that establishes a correspondence between the objective properties permitting to identify physical states and the symmetry transformations that modify their gauge dependant properties. We show that the uncertainty principle results from a faithful—or equivariant—realization of this correspondence. It is a consequence of the proposed postulate that the quantum notion of objective physical states is not incomplete, but rather that the classical notion is overdetermined.     

Projective Invariance in Cosmological Models and Dark Energy

We study theories of gravitation that are based on the Einstein – Hilbert action that are not projectively invariant and can therefore completely determine their connections. We are thus lead to the conclusion that the geometry is necessarily Riemann – Cartan and at least the trace part of a torsion field must be present. We examine the consequence of including these torsion fields in cosmological models. Our results differ from those obtained earlier in the Einstein – Cartan – Sciama – Kibble theory. We also consider a model that includes a series of quadratic torsion terms. This series leads to a potential function that has the effect of “turning on” the cosmological constant. This potential function then acts like dark energy. This model also shows that the torsion field can produce an inflationary period. PACS: 04.02 Cv, 95.30 Sf, 98.80-k     

On the problem of the relation between phason elasticity and phason dynamics in quasicrystals

It has recently been claimed that the dynamics of long-wavelength phason fluctuations has been observed in i-AlPdMn quasicrystals [S. Francoual et al. Phys. Rev. Lett. 91, 225501 (2003); A. Létoublon et al. 54, 753 (2001)]. We will show that the data reported call for a more detailed development of the elasticity theory of Jarić and Nelsson [M.V. Jarić and D.R. Nelsson, Phys. Rev. B 37, 4458 (1988)] in order to determine the nature of small phonon-like atomic displacements with a symmetry that follows the phason elastic constants. We also show that a simple model with a single diffusing tile is sufficient to produce a signal that (1) is situated at a “satellite position” at a distance q from each Bragg peak; that (2) has an intensity that scales with the intensity of the corresponding Bragg peak; (3) falls off as 1/q²; and (4) has a time decay constant that is proportional to 1/Dq². It is thus superfluous to call for a picture of “phason waves” in order to explain such data, especially as such “waves” violate many physical principles.     

Pattern Theorems,Ratio Limit Theorems and Gumbel Maximal Clusters for Random Fields

We study occurrences of patterns on clusters of size n in random fields on ℤ ^d . We prove that for a given pattern, there is a constant a>0 such that the probability that this pattern occurs at most na times on a cluster of size n is exponentially small. Moreover, for random fields obeying a certain Markov property, we show that the ratio between the numbers of occurrences of two distinct patterns on a cluster is concentrated around a constant value. This leads to an elegant and simple proof of the ratio limit theorem for these random fields, which states that the ratio of the probabilities that the cluster of the origin has sizes n+1 and n converges as n→∞. Implications for the maximal cluster in a finite box are discussed.     

The influence of aliovalent impurities on the oxidation kinetics of nickel at high temperatures

The influence of chromium and sodium on the nickel oxidation kinetics has been studied as a function of temperature (1373-1673 K) and oxygen activity (10−10⁵ Pa O₂), using microthermogravimetric techniques. It has been shown that the oxidation of Ni-Cr and Ni-Na alloys, like that of pure nickel, follows strictly the parabolic rate law being thus diffusion controlled. In agreement with the defect model of Ni_1−yO, it has been found that the oxidation rate of the Ni-Cr alloy is higher than that of pure nickel, the reaction rate is pressure independent and the activation energy of this process is lower. This implies that the concentration of double ionized cation vacancies in a Ni_1−yO-Cr₂O₃ solid solution is fixed on a constant level by trivalent chromium ions, substitutionally incorporated into the cation sublattice of this oxide. In the case of the Ni-Na alloy, on the other hand, the oxidation rate is lower than that of pure nickel, the activation energy is higher and the oxidation rate increases more rapidly with oxygen pressure. These results can again be explained in terms of the doping effect, by assuming that univalent sodium ions dissolve substitutionally in the cation sublattice of nickel oxide.     

Overcoming apparent susceptibility-induced anisotropy (aSIA) by bipolar double-pulsed-field-gradient NMR

Double-Pulsed-Field-Gradient (d-PFG) MR is emerging as a powerful new means for obtaining unique microstructural information in opaque porous systems that cannot be obtained by conventional single-PFG (s-PFG) methods. The angular d-PFG MR methodology is particularly important since it can utilize the effects of microscopic anisotropy (μA) and compartment shape anisotropy (csA) in the E(ψ) profile at the different t_m regimes to provide detailed information on compartment size and eccentricity. An underlying assumption is that the PFGs that are imparted to weigh diffusion are the only gradients present; however, in realistic systems and especially where there are randomly oriented anisotropic pores, susceptibility effects may induce strong internal gradients. In this study, the effects of such internal gradients on E(ψ) plots obtained from angular d-PFG MR and on microstructural information that can be obtained from s-PFG and d-PFG MR were investigated. First, it was found that internal gradients induce a bias in the s-PFG MR results, thus creating an anisotropy that is not related to microstructure, termed apparent-Susceptibility-Induced-Anisotropy (aSIA). We then show that aSIA effects are also manifest in different ways in the angular d-PFG MR experiment in controlled phantoms and in realistic systems such as quartz sand, emulsions, and biological systems. The effects of aSIA in some cases completely masked the effects of μA and csA; however, we subsequently show that by introducing bipolar gradients to the d-PFG MR (bp-d-PFG), the effects of aSIA can be largely suppressed, restoring the E(ψ) plots that are expected from the theory along with the microstructural information that it conveys. We conclude that when specimens are characterized by strong internal gradients, the novel information on μA and csA that is manifest in the E(ψ) plots can indeed be inferred when bp-d-PFG MR is used, i.e. when bipolar gradients are applied.     

On the (Non)Existence of States on Orthogonally Closed Subspaces in an Inner Product Space

Suppose that S is an incomplete inner product space. In (Dvurečenskij, 1992, Gleason's Theorem and Its Applications, Ister Science Press, Bratislava, Kluwer Academic Publishers, Dordrecht), A. Dvurečenskij shows that there are no finitely additive states on orthogonally closed subspaces, F(S), of S that are regular with respect to finitely dimensional spaces. In this note we show that the most important special case of the former result—the case of the evaluations given by vectors in the “Gleason manner”—allows for a relatively simple proof. This result further reinforces the conjecture that there are no finitely additive states on F(S) at all.     

Temperature dependence and the effect of hydrogen peroxide on ITO/poly-ZnO Schottky diodes fabricated by laser evaporation

Transparent and efficient poly-ZnO ultraviolet Schottky diodes grown at different temperatures with indium-tin-oxide (ITO) as the metallic contact layer were fabricated with hydrogen peroxide (H₂O₂) applied as a surface treatment at 70 °C for 20 min. Analysis via field-emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) demonstrated that the ZnO films underwent gradual oxidation and that H₂O₂ treatment resulted in an interfacial ZnO₂ layer that covered the ZnO surface. I–V measurements indicated that the ideality factor and the Schottky barrier height improved with increasing shunt resistance, and the trade-off between film quality and the degree of oxidation revealed that films grown at 400 °C exhibited the best diode characteristics.     

Effect of annealing atmosphere on ferromagnetism in Mn doped ZnO films

This paper reports that Zn_0.97Mn_0.03O thin films have been prepared by radio-frequency sputtering technology followed by rapid thermal processing in nitrogen and oxygen ambient respectively. Magnetic property investigation indicates that the films are ferromagnetic and that the Curie temperature (T_c) is over room temperature. It is observed that the saturation magnetization of the films increases after annealing in nitrogen ambience but decreases after annealing in oxygen. Room temperature photoluminescence spectra indicate that the amount of defects in the films differs after annealing in the different ambiences. This suggests that the ferromagnetism in Zn_0.97Mn_0.03O films is strongly related to the defects in the films.     

Silica-coated Y2O3:Eu nanoparticles and their luminescence properties

Crystalline Y₂O₃:Eu is of paramount significance in rare earth materials and research on luminescence spectra. In this work, the nanocrystalline Y₂O₃:Eu was coated with silica by a facile solid state reaction method at room temperature. The transmission electron microscope (TEM) photographs showed that the prepared Y₂O₃:Eu particle is polycrystalline with the size of 20 nm, the size of silica-coated particle is about 25 nm. The XPS spectra indicated that the silica layer is likely to interact with Y₂O₃:Eu by a Si-O-Y chemical bond. The luminescence spectra showed that the intensity of ground samples is lower than that of unground ones, the intensity of silica-coated phosphors is higher than that of the ground samples, while almost the same as that of the unground ones. Therefore, the silica coating decreases the surface defects of nanoparticles of the nanocrystalline Y₂O₃:Eu, thus increasing their luminescent intensity.     

Relationship between chemical bond parameters and superconducting temperature in HgBa2Can−1CunO2n+2+δ (n=1, 2, 3, 4)

Bond covalency and valence of elements in HgBa₂Ca_n−1Cu_nO_2n+2+δ (n=1, 2, 3, 4) were calculated and their relationship with T_c was discussed. For both oxygen and argon annealed samples, the results indicated that with the increase of n, the trend of bond covalency of Hg-O and Cu-O was the same or opposite compared with that of superconducting temperature. This may suggest that the magnitudes of Cu-O and Hg-O bond covalency are important in governing the superconducting temperature. For the highest T_c sample, Hg had the lowest valence, implying that lower valence of Hg was preferred in order to produce higher T_c. For fixed n, the valence of Cu in oxygen annealed samples was larger than that in argon annealed samples, indicating that oxygen annealed samples produced more carriers than argon annealed samples.     

First‐principles study of CrB4 as a high shear modulus compound

First‐principles calculations were carried out to investigate the synthesized orthorhombic CrB₄. Our calculations show that the shear modulus of orthorhombic CrB₄ is much higher than that of superhard WB₄. Moreover, its shear modulus is larger than its bulk modulus. Boron atoms in CrB₄ form a strong covalent cage which dramatically increases its mechanical strength. The calculated elastic constants imply that CrB₄ is elastically stable. The calculated density of states shows that CrB₄ is metallic. The appearance of pesudogap near the Fermi level means that CrB₄ is a stable compound. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Proton activity and spontaneous strain of Cs3H(SeO4)2 in the phase transition at 369 K

We have investigated the origin of the change in proton activity in the phase transition at T_II-III (=369 K) in Cs₃H(SeO₄)₂ from the viewpoint of its ferroelasticity by using ¹H NMR and X-ray measurements. It is found that the second moment of the ¹H NMR absorption line rapidly decreases at T_II-III with increasing temperature. From this result, we conclude that the hopping motion of a proton, which is the precursor motion in the superprotonic phase, becomes more active above T_II-III. This result is consistent with the fact that the electrical conductivity in phase II is larger than that in phase III. Furthermore, it is also found that the spontaneous strain decreases abruptly at T_II-III. From these results, it is deduced that the decrease in the spontaneous strain at T_II-III causes the increase in the proton activity at T_II-III. In addition, it is deduced that the increase in proton activity and the decrease in the spontaneous strain at T_II-III are closely related with the appearance of the superprotonic phase transition at T_I-II (=456 K).     

Photoconductivity of Se85−xTe15Hgx thin films

The photoconductive properties such as dark conductivity, steady state and transient characteristics of a-Se_85−xTe₁₅Hg_x thin films, prepared by thermal vacuum evaporation technique have been studied in the temperature range 312–380 K. Analysis of data shows that the activation energy of dark current is greater as compared to the activation energy of photocurrent. The activation energy increases at higher concentration of Hg which shows that the defect density of states decreases. Analysis of intensity dependent photoconductivity shows that the bimolecular recombination is predominant. The transient photoconductivity shows that the carrier lifetime decreases with the increase in Hg concentration and increases at higher concentration of Hg. This decrease is due to the transition trapping process. Further the photosensitivity and carrier lifetime increases at higher concentration of Hg which also confirms that the density of defect states decreases.