Reaction of molecular hydrogen with the 100 face of MoO3: II. Kinetics initiated by atomic hydrogen and characterization of the surface electronic state

In order to provide a physical background to the model proposed in Part I, the kinetics of the reaction between the 100 face of a MoO₃ single crystal and, first a mixture of 4% atomic hydrogen in H₂, and later molecular hydrogen only, has been studied. The rate processes of the activation step and of the stationary step are entirely comparable with those observed for one single crystal surface loaded with platinum particles. Thus atomic hydrogen in the gas phase as well as atomic hydrogen produced by the dissociation of molecular hydrogen on a Pt particle may prepare the favourable surface state able to dissociatively chemisorb molecular hydrogen, ruling out — once again — the classical model of the hydrogen spillover process. This “favourable” state has a Fermi level which is 0.25 eV lower than that of initial MoO₃, as shown by measuring the work function with a Kelvin probe. This lowering is in good agreement with the variation of the free energy between MoO₃ and H_1.6MoO₃, measured electrochemically by others. This suggests that the protons inserted into the surface layers transform the initial MoO₃ layers into layers with composition H_1.6MoO₃. The starting material is thus transformed into a biphasic system, the diffusion of the reaction boundary between the two types of layers being the overall rate limiting process. The Fermi energy of H_1.6MoO₃ being known, it is possible to show that in transformed surface layers the conduction and the valence bands overlap, in agreement with the approximate profile of this band observed by XPS for a reacted single crystal surface. The d character of this band would explain why molecular hydrogen can be dissociatively chemisorbed when this favourable surface state is obtained. The fast electron delocalization within the Mo-O-Mo bonds yields fast oscillations in the oxidation states of the molybdenum atom in the surface layer, accounting for the presence of “oxidized” and “reduced” sites. The formal equation observed in Part I for the rate of stationary step is therefore explained, the impinging H₂ molecules reducing temporarily the oxidized fraction of the surface.     

Unscrambling the Quantum Omelette

Based on recent theorems about quantum value-indefiniteness it is conjectured that many issues of “Born’s quantum mechanics” can be overcome by supposing that only a single pure state exists; and that the quantum evolution permutes this state.     

Water-mediated correlations in DNA-enzyme interactions

In this letter we consider dipole-mediated correlations between DNA and enzymes in the context of their water environment. Such correlations emerge from electric dipole-dipole interactions between aromatic ring structures in DNA and in enzymes. We show that there are matching collective modes between DNA and enzyme dipole fields, and that a dynamic time-averaged polarization vanishes in the water dipole field only if either DNA, enzyme, or both are absent from the sample. This persistent field may serve as the electromagnetic image that, in popular colloquialisms about DNA biochemistry, allows enzymes to “scan” or “read” the double helix. Topologically nontrivial configurations in the coherent ground state requiring clamplike enzyme behavior on the DNA may stem, ultimately, from spontaneously broken gauge symmetries.     

Thermoluminescence of pure and doped ThO2

Thermoluminescence (TL) measurements in the temperature range 295–675 K indicate the existence of at least five trapping centres for single crystals of nominally pure “reduced” ThO₂ and three trapping centres for “oxidized” ThO₂. Deliberate doping with Ca²⁺, Y³⁺ and Ta⁵⁺ impurities decreases TL emission. For reduced ThO₂, accidentally incorporated rare-earth impurities, Pr³⁺, Tb³⁺, Er³⁺ act as the electron-hole recombination sites. In oxidized crystals the impurity Fe³⁺ is thought to be involved in the recombination process. In the temperature range 80–295 K an additional eight trapping centres exist for both oxidized and reduced ThO₂. For the reduced crystals the emission is probably associated with Fe in the +2 state, and in the +3 state for oxidized crystals. The differences in the TL glow curve intensities are partially explained by differences in the temperature dependence of the luminescence efficiency of the different recombination centres.     

Allmagnetische boolesche Schaltungen mit Transfluxoren

All-magnetic Boolean (logic) circuits are described which can perform the logical operations “AND”, “AND-NOT” and “NOT”. They use a special-shaped “AND”-transfluxor. It is demonstrated that the guidance of the switching flux into particular paths by a special form of wiring leads to better efficiency and reliability of these logic devices. As a measure of efficiency and optimated operating conditions a graph is used which shows the output of the transfluxor plotted as a function of the driving current for the set and blocked state. The transfluxors can be combined to more complicated logical circuits like half adders and others.     

Modeling pressure-ionization of hydrogen in the context of astrophysics

Abstract

The recent development of techniques for laser-driven shock compression of hydrogen has opened the door to the experimental determination of its behavior under conditions characteristic of stellar and planetary interiors. The new data probe the equation of state (EOS) of dense hydrogen in the complex regime of pressure ionization. The structure and evolution of dense astrophysical bodies depend on whether the pressure ionization of hydrogen occurs continuously or through a “plasma phase transition” (PPT) between a molecular state and a plasma state. For the first time, the new experiments constrain predictions for the PPT. We show here that the EOS model developed by Saumon and Chabrier can successfully account for the data, and we propose an experiment that should provide a definitive test of the predicted PPT of hydrogen. The usefulness of the chemical picture for computing astrophysical EOS and in modeling pressure ionization is discussed.     

Stability and entropy production in electrical circuits

A number of the theorems expounded by Prigogine, Glansdorff and their collaborators are translated into electrical circuit terminology and their validity and significance discussed. The simultaneous occurrence of inductors and capacitors represents a situation not envisioned in the chemically oriented discussions and imposes some limitations. The electrical terminology also leads to “dual” theorems, in which voltage sources are replaced by current sources. The validity of the theorems in situations in which fluctuations are critical to the relaxation behavior is analyzed. The “excess entropy production” theorem is only valid if the circuit relaxation can be described by single-valued macroscopic variables, but not if it must be described by distribution functions. We stress that no purely local characterization, which examines a multistable system only in the neighborhoods where it occurs with high probability, can predict or characterize the steady state.     

Dissipative control in thermal ensembles using tunneling ionization

It has been observed that non-resonant tunneling ionization of diatomic molecules by strong laser fields can lead to readily observable coherent vibrations in the molecular ground state of both hydrogen and iodine. Moreover, we have shown that this process, called “Lochfrass” or “R-selective ionization,” produces larger amplitude coherent motion in hotter systems than cold. In contrast, reversible interactions, like bond-softening, become less effective as the temperature increases. In this paper, we present a density matrix analysis to demonstrate this unusual temperature dependence and suggest that dissipative interactions, like tunneling ionization, can provide strong-field control in hot systems.     

Stability of the so-called “Co−Mo−S” phase in a carbonsupported Co−Mo sulfide catalyst at very low Co/Mo ratio

Several aspects of the stability of the so-called “Co?Mo?S” phase in a fully sulfided Co(0.04)Mo(6.84)/C (wt%) catalyst have been examined by Mössbauer emission spectroscopy. The “Co?Mo?S” parameters turned out to be unchanged when the catalyst is exposed for 23 days to ambient air at room temperature. However, if this exposure to air is extended for over 100 days, the so-called “Co?Mo?S” phase was found to be oxidized to a high-spin Fe²⁺ phase which has no strong interaction with the “MoS₂” particles. After resulfidation of the catalyst the so-called “Co?Mo?S” phase is formed again.     

非各态历经噪声的产生及其应用

用n阶时间导数噪声作为内部热噪声驱动自由粒子运动时,若该噪声所对应的非各态历经强度b?=0,且系统初始处于热平衡,则此时系统的长时稳态速度可以作为非各态历经噪声使用.非各态历经噪声具有谱密度在零频处发散的特点,一维半无界耦合简谐振子链对与之相连的气体分子的作用具有非各态历经噪声的特点,是非各态历经噪声的实例.最后将非各态历经噪声作为外噪声驱动倾斜周期势中的粒子运动,系统出现扩散指数α2的超弹道扩散现象.同时发现系统的速度分布将呈现出迁移态和锁定态两种不同状态,并且处于迁移态的粒子的速度分布为双峰.迁移态中双峰的出现是一种比较新奇的现象.     

Astrophysical Black Holes as Natural Laboratories for Fundamental Physics and Strong-Field Gravity

Astrophysical tests of general relativity belong to two categories: 1) “internal”, i.e. consistency tests within the theory (for example, tests that astrophysical black holes are indeed described by the Kerr solution and its perturbations), or 2) “external”, i.e. tests of the many proposed extensions of the theory. I review some ways in which astrophysical black holes can be used as natural laboratories for both “internal” and “external” tests of general relativity. The examples provided here (ringdown tests of the black hole “no-hair” theorem, bosonic superradiant instabilities in rotating black holes and gravitational-wave tests of massive scalar-tensor theories) are shamelessly biased towards recent research by myself and my collaborators. Hopefully this colloquial introduction aimed mainly at astrophysicists will convince skeptics (if there are any) that space-based detectors will be crucial to study fundamental physics through gravitational-wave observations.     

Uninformed sacrifice: Evidence against long-range alarm transmission in foraging ants exposed to localized abduction

It is well established that danger information can be transmitted by ants through relatively small distances, provoking either a state of alarm when they move away from potentially dangerous stimulus, or charge toward it aggressively. There is almost no knowledge if danger information can be transmitted along large distances. In this paper, we abduct leaf cutting ants of the species Atta insularis while they forage in their natural environment at a certain point of the foraging line, so ants make a “U” turn to escape from the danger zone and go back to the nest. Our results strongly suggest that those ants do not transmit “danger information” to other nestmates marching towards the abduction area. The individualistic behavior of the ants returning from the danger zone results in a depression of the foraging activity due to the systematic sacrifice of non-informed individuals.     

Structure of Polyethylene from X-Ray Powder Diffraction: Influence of the Amorphous Fraction on Data Analysis

It is now well established that the relaxation of volume of frozen-in liquids cannot be interpreted by single relaxation mechanisms. However, it remains obscure whether the decomposition of the volume relaxation curves into a sum of exponential terms has a physical sense or is merely a mathematical curve-fitting model. The fact that experimental data can be represented by a spectrum of relaxation times does not imply that there is physically such a spectrum. In particular, the experimental curves can also be fitted by nonlinear mathematical expressions. Kovacs has suggested that if a distribution of relaxation times exists, it should depend not only on the equilibrium temperature but also on the actual state of the glass [1]. This statement suggests that both the nonlinearity of the relaxation mechanism and the presence of relaxation times have to be expected. According to Kovacs et al. [2], the reason for the dependence of the relaxation times on the state of the glass is particularly demonstrated in the experiment of the “paradox of nonsymmetry”: Two specimens held at the same temperature are brought to the same final volume from a higher and a lower initial volume but with the same initial departure from the equilibrium value. Their contraction and dilatation are then observed to be asymmetrical, which cannot, according to Kovacs, be explained by only a distribution of relaxation times. Contrasting with Kovacs's approach, we resolve the “paradox” mathematically starting from the classical assumption of a distribution of relaxation times independent of the actual state of the glass. In other words, in our interpretation, the relaxation times vary with temperature only. The preexponential volume terms V_ij vary with the thermal past and can even assume negative values. The implications of our new analysis in regard to the concept of a “spectrum of relaxation times” for a glass are also discussed.     

Direct transference applied to the study of room acoustics

In a recent article Kruzins and Fricke [1] applied the method of Markov chains to represent the “random walk” of phonons inside an enclosed space and to predict stationary state acoustic pressure levels, at sufficiently high frequencies, in geometrically complex spaces. In this paper it is demonstrated that with the same initial hypothesis the exact solution can be obtained directly by using the method of direct transference. Explicit expressions for the coefficients of the solution matrix are found, their physical significance is made evident, and a simple method for calculating the solution is presented.     

Specific features of interference of photons and other quantum particles

Specific features of the behavior of quantum particles in different experimental situations are considered. The variants of two-beam interference of single photon and other quantum particles, as well as their ability to form “standing” and “progressive” waves with the interference minima, i.e., “dead” zones in the propagation path, are studied. We also consider some type of quantum particle teleportation in an unconventional understanding of this word, where elementary particles overcome regions of the space where they cannot be, or rather the borders where the probability of finding them is zero. At these boundaries there is no pulse impact of particles on anything, it is as if they are unobservable. When observing three-beam interference, it turns out that all three modes should be present simultaneously in the light field prior to photodetection. If each mode involves a photon, it contradicts the energy conservation law, it is indicative of the fact that the observed quantity (number of photons in the field) has no any particular value prior to the measurement (a priori) unless the quantum system is in the eigen state of a measured value (Fock state).     

All optical logic gates based on cavity solitons with nonlinear gain

In this work we present a scheme based on the complementary behavior of the two effective parameters in Cavity Soliton switching process by which it is possible to design logic gates, namely “OR” and “AND”. By considering two independent writing beams, it is shown that by properly adjusting the amplitude and duration of switching pulses, “AND” and “OR” logical operations can be carried out. Specifically, the output of the system, which is the on or off state of the Cavity Soliton, is determined according to the inputs of the system which depend on the type of desired operation. The simulations show that these processes take place in a time scale of less than a nanosecond. The cascadibility of these gates is also studied.     

About a “Nonlocal” Local Model Considered by L. Vervoort,and the Necessity to Distinguish Locality from Einstein Locality

L. Vervoort claims to have found a model which “can violate the Bell inequality and reproduce the quantum statistics, even if it is based on local dynamics only”. This claim is false. The proposed model contains global elements. The physics behind the model is local, but would not allow the explanation of violations of Bell inequalities for space-like separated events, if superluminal causal influences are forbidden. To use it for this purpose, one has to introduce a preferred frame where information can be send faster than light. As a cause of the misunderstanding we identify the unfortunate convention to use “local” as a synonym for Einstein-local, so that theories which are local in every physically relevant sense have to be named “non-local”, and argue that this convention should be abandoned.     

Ferroelasticity in non-group-subgroup transitions

Aizu's definition of ferroelasticity can be extended to transitions between two crystals whose point groups are not group-subgroup related. In general, two different variant structures then appear on both sides of the transition, each variant structure being determined by the operators “lost” at the transition. If a minimal common supergroup exists, then it is the prototype group. For each variant structure, a spontaneous strain tensor can be defined. Ferroelasticity occurs for both structures, and is termed “double ferroelasticity”, if none of the groups belong to the same symmetry system as the common minimal supergroup. Examples are discussed.