The formation of α at triple junctions of parent β phase in titanium alloys

We have examined the formation of α phase at grain boundary triple junctions of parent β in a metastable β titanium alloy with orientation imaging microscopy based on electron backscattered diffraction (EBSD). As in the case of α formed at grain boundaries of parent β grains, α at a triple junction also forms with the Burgers orientation relationship with one of the three neighbouring β grains. The experimental results are analyzed in terms of the deviation of the 36 possible α variants that can form at a triple junction from the Burgers orientation relationship with neighbouring grains.     

Probing the role of metal cations on the aggregation behavior of amyloid β-peptide at a single molecule level by AFM

With the development of nanotechnology, understanding of intermolecular interactions on a single molecule level by atomic force spectroscopy (AFM) has played an important role in molecular biology and biomedical science. In recent years, some research suggested that the presence of metal cations is an important regulator in the processes of misfolding and aggregation of the amyloid β-protein (Aβ), which may be an important etiological factor of Alzheimer’s disease. However, the knowledge on the principle of interactions between Aβ and metal cations at the single molecule level is still poor understood. In this paper, the amyloid β-protein (Aβ) was fabricated on substrate of mixed thiol-modified gold nanoparticles using self-assembled monolayer method and the adhesion force in the longitudinal direction between metal cations and Aβ42 were investigated by AFM. The role of metal ions on Aβ aggregation is discussed from the perspective of single molecular force. The force results showed that the specific adhesion force F _i and the nonspecific force F ₀ between a single Aβ–Aβ pair in control experiment were calculated as 42 ± 3 and 80 pN, respectively. However, F _i between a single Aβ–Aβ pair in the presence of Cu²⁺, Zn²⁺, Ca²⁺ and Al³⁺ increased dramatically to 84 ± 6, 89 ± 3, 73 ± 5, 95 ± 5 pN successively, which indicated that unbinding between Aβ proteins is accelerated in the presence of metal cations. What is more, the imaging results showed that substoichiometric copper cations accelerate the formation of fibrils within 3 days. The combined atomic force spectroscopy and imaging analysis indicate that metal cations play a role in promoting the aggregating behavior of Aβ42.     

The role of potassium ions in the degradation of sodium β/β″-alumina

Fracture mechanics and radiographic experiments were undertaken to determine the role of K⁺ impurity in electrolyte degradation during Na⁺ electrolysis through Na β/β″ -Al₂O₃. The results indicate that potassium ions enhance the degradation. Radiographic results indicate that for current densities of ∽ 1 A cm⁻², K⁺ is reduced and precipitates in the ceramic microstructure. Spontaneous fracture of samples during electrolysis at high current densities was observed.     

The role of diffusion in broadband infrared absorption in chalcogen-doped silicon

Sulfur doping of silicon beyond the solubility limit by femtosecond laser irradiation leads to near-unity broadband absorption of visible and infrared light and the realization of silicon-based infrared photodetectors. The nature of the infrared absorption is not yet well understood. Here we present a study on the reduction of infrared absorptance after various anneals of different temperatures and durations for three chalcogens (sulfur, selenium, and tellurium) dissolved into silicon by femtosecond laser irradiation. For sulfur doping, we irradiate silicon in SF₆ gas; for selenium and tellurium, we evaporate a film onto the silicon and irradiate in N₂ gas; lastly, as a control, we irradiated untreated silicon in N₂ gas. Our analysis shows that the deactivation of infrared absorption after thermal annealing is likely caused by dopant diffusion. We observe that a characteristic diffusion length—common to all three dopants—leads to the reduction of infrared absorption. Using diffusion theory, we suggest a model in which grain size of the resolidified surface layer can account for this characteristic diffusion length, indicating that deactivation of infrared absorptance may be caused by precipitation of the dopant at the grain boundaries.     

The mechanism and rate of dtμ formation in solid hydrogen

The partial spectral distribution function for muonic molecule formation turns out to play an important role in understanding the effect of interactions with surrounding spectator molecules. We formulate and numerically calculate it for a solid hydrogen. First of all, in addition to a conventional Lorentzian peak centered at a resonance energy , there appears another very broad peak in the spectral distribution, which extends from the resonance energy to energies higher by the Debye energy _D of the solid. It is shown that the latter corresponds to the spectral distribution of phonon excitations caused by a sudden dt formation. Secondly, a strong intensity borrowing from the Lorentzian peak to the broad one occurs. Thanks to this fact, a large formation rate is yielded for subthreshold transitions. The comparison with Vesman's spectral distribution function, namely, of a dt formation for an isolated D₂, is made.     

Unraveling the radical chain mechanism in the pyrolysis of β-O-4 linked lignin: The role of aliphatic substituents

Lignin pyrolysis involves complex radical reactions, whereas the radical chain process, especially the influence of aliphatic substituents, has been rarely studied. Herein, the typical β-O-4 lignin dimer, phenethyl phenyl ether (PPE), and three aliphatic substituted derivatives of PPE, namely α-OH substituted, β-CH₂OH substituted, and α,β-disubstituted PPE (αPPE, βPPE, and αβPPE) were employed as model compounds. DFT calculations, electronic analyses, and fast pyrolysis experiments were combined to investigate three core steps of the radical chain mechanism in lignin pyrolysis, i.e., homolysis, hydrogen abstraction, and radical decomposition. The pathway involving successive C_β-O homolysis → α-hydrogen abstraction → C_β-O breakage of α-dehydrogenated radical is dominated for the pyrolysis of aliphatic substituted β-O-4 linked lignin, with the formation of phenolics. The hydrogen abstraction reactions at the C_α site are obviously superior to those at other sites for PPE derivatives, due to the p-π conjugate stability. Notably, α-hydrogen abstraction can be significantly promoted by the π-electron-dispersing α-OH substitution. The decomposition step of dehydrogenated radicals can be facilitated by the electron-donating β-CH₂OH substitution, where the C_β-O breakage of the α-dehydrogenated radical is dominant. Totally, aliphatic substituents can improve the radical growth stage and change the competitiveness of the hydrogen abstraction and radical decomposition reactions. The fast pyrolysis experiments of PPE and αPPE gave direct proof that the generation of characteristic products from the radical chain process, i.e., benzaldehyde and phenylacetaldehyde, was enhanced by the α-OH substitution. The present work offers the potential to give a comprehensive image of the radical chain mechanism in lignin pyrolysis.     

The role of surface hydroxils of Al2O3·xH2O in the luminescence of adsorbed fluorescein molecules

Acta physica Academiae Scientiarum Hungaricae - Producing various surface hydroxil concentrations on Al2O3 films by surface reactions it was found that there is a distinct relation between the...     

Mechanisms of structure formation in particulate gels of β-lactoglobulin formed near the isoelectric point

Particulate gels are known to be formed by bovine β-lactoglobulin near the isoelectric point when partial unfolding is allowed to occur under heating. The aggregation process of the protein has been investigated within the context of a nucleation and growth process by preparing gels under precisely controlled thermal histories. This was achieved using a Differential Scanning Calorimeter (DSC) to provide controlled heating rates, and known final temperatures and incubation times. The resulting particulate gels were characterized by their particle size and polydispersity using Environmental Scanning Electron Microscopy (ESEM), which permits hydrated samples to be observed. Particle size was found to decrease with increasing final temperature, with the aggregation taking longer to reach completion for lower temperatures. Particle size was also found to decrease with increasing heating rate. This system could be modelled as evolving via nucleation and growth by taking into account the fact that the concentration of the aggregating species was varying as a function of temperature as well as time. The intrinsic tryptophan fluorescence as a function of temperature was used as a guide to the fraction of unfolded protein in solution, thereby permitting successful comparisons between the model predictions and the particle sizes to be made.-1     

The effects of pitch and duration on the perception of the neutral tone in standard Chinese

The research aim is to investigate that how pitch and duration affect the perception of the neutral tone in standard Chinese and that which one of the two factors is more important. A psycho-acoustic experiment was conducted, in which the listening stimuli consisted of 15 groups of disyllabic words, and the pitches and durations of the two syllables in each of the words were artificially controlled. Thirty-three standard Chinese native speakers participated in a forced-choice task to judge if the second syllables of the words they heard carried the neutral tone or the normal tones. The results of the experiment indicated that, (1) the effects of both pitch and duration on the perception of the neutral tone are significant; (2) the effect of pitch is larger than that of duration; (3) both the F0 values of the high point in the pitch contour and the pitch contour pattern have influence on the perception. The results of the experiment were correspondent to some extent to those of the previous acoustic analyses on the neutral tone. The diversity between the results of the presented perceptual study and those of the acoustical studies implies that the acoustic features of the neutral tone that exist in natural speech while do not affect the perception may be phonologically redundant.     

The role of conformal symmetry in the Jackiw–Pi model

The Jackiw–Pi model in 2+1$2+1$ dimensions is a non-relativistic conformal field theory of charged particles with point-like self-interaction. For specific values of the interaction strengths the classical theory possesses vortex and multi-vortex solutions, which are all degenerate in energy. We compute the full set of first-order perturbative quantum corrections. Only the coupling constant g²$g^2$ requires renormalization; the fields and electric charge e are not renormalized. It is shown that in general the conformal symmetries are broken by an anomalous contribution to the conservation law, proportional to the β-function. However, the β  -function vanishes upon restricting the coupling constants to values g²=±e²$g^2=\pm e^2$, which includes the case in which vortex solutions exist. Therefore the existence of vortices also guarantees the preservation of the conformal symmetries.     

Associated production of a neutral top-Higgs with a heavy-quark pair in the γγ collisions at ILC

We have studied the associated production processes of a neutral top-Higgs in the topcolor assisted technicolor model with a pair of heavy quarks in γγ collisions at the International Linear Collider (ILC). We find that the cross section for ttht in γγ collisions is at the level of a few fb with the c.m. energy √s=1000 GeV, which is consistent with the results of the cross section of ttH in the standard model and the cross section of tth in the minimal supersymmetric standard model. It should be clear that hundreds of to thousands of ht per year can be produced at the ILC. This process of γγ→ttht is really interesting in testing the standard model and searching the signs of technicolor.     

Associated production of a neutral top-Higgs with a heavy-quark pair in the γγ collisions at ILC

We have studied the associated production processes of a neutral top-Higgs in the topcolor assisted technicolor model with a pair of heavy quarks in γγ collisions at the International Linear Collider （ILC）. We find that the cross section for ttht in γγ collisions is at the level of a few fb with the c.m. energy √s=1000 GeV, which is consistent with the results of the cross section of ttH in the standard model and the cross section of tth in the minimal supersymmetric standard model. It should be clear that hundreds of to thousands of ht per year can be produced at the ILC. This process of γγ→ttht is really interesting in testing the standard model and searching the signs of technicolor.     

The Oxidation Behavior of Vanadium Alloys in Air at Elevated Temperature

Vanadium alloy is one of the most important candidate structural materials for a fusion reactor. Its main advantages over other candidates are its low activity feature and feasible properties at high temperature. However, vanadium is easily oxidized at high temperature to form a non-protective surface film of V2O5. Oxygen concentration would thus get high and the properties get worse in not only the loss of the ductility but also the enhanced hydrogen embrittlement by the oxidation.     

The role of radical-radical chain-propagating pathways in the phenyl + propargyl reaction

Well-skipping radical-radical reactions can provide a chain-propagating pathway for formation of polycyclic radicals implicated in soot inception. Here we use controlled pyrolysis in a microreactor to isolate and examine the role of well-skipping channels in the phenyl (C₆H₅) + propargyl (C₃H₃) radical-radical reaction at temperatures of 800–1600 K and pressures near 25 Torr. The temperature and concentration dependence of the closed-shell (C₉H₈) and radical (C₉H₇) products are observed using electron-ionization mass spectrometry. The flow in the reactor is simulated using a boundary layer model employing a chemical mechanism based on recent rate coefficient calculations. Comparison between simulation and experiment shows reasonable agreement, within a factor of 3, while suggesting possible improvements to the model. In contrast, eliminating the well-skipping reactions from the chemistry mechanism causes a much larger discrepancy between simulation and experiment in the temperature dependence of the radical concentration, revealing that the well-skipping pathways, especially to form indenyl radical, are significant at temperatures of 1200 K and higher. While most C₉H₇ forms by well-skipping at 25 Torr, an additional simulation indicates that the well-skipping channels only contribute around 3% of the C₉H_x yield at atmospheric pressure, thus indicating a negligible role of the well-skipping pathways at atmospheric and higher pressures.     

The role of cosmic rays in the Earth’s atmospheric processes

In this paper, we have provided an overview of cosmic ray effects on terrestrial processes such as electrical properties, global electric circuit, lightning, cloud formation, cloud coverage, atmospheric temperature, space weather phenomena, climate, etc. It is suggested that cosmic rays control short-term and long-term variations in climate. There are many basic phenomena which need further study and require new and long-term data set. Some of these have been pointed out.     

The spectroscopy of 22Al: a βp, β2p and βα emitter

In an experiment at the LISE3 facility of GANIL, we produced the proton-rich isotope ²²Al by the fragmentation of a ³⁶Ar primary beam at 95 MeV/nucleon. After implantation in a detector telescope, the decay of ²²Al via β-delayed proton emission, β-delayed two-proton emission as well as, for the first time, via β-delayed α emission has been studied. An α peak has been observed at (3.27 ± 0.04) MeV with a branching ratio of (0.31 ± 0.09) %. The comparison of the different decay channels to those of the mirror nucleus ²²F and to shell-model calculations favor a 3⁺ state as being the ground state of ²²Al. A half life of T_1/2 = (59 ± 3) ms has been measured.     

The Measurements of Photostimulated Luminescence in Alkali Doped BaFBr:Eu2☎ at Liquid Nitrogen Temperature

Considerable increase of the photostimulated luminescence (PSL) intensity and red shift of the excitation spectrum was obtained by alkali doping of BaFBr:Eu^2? crystals [1]. The band of the F_A(Br^?) centers about 0.1 eV shifted to low energy side against the “normal” F(Br^?) centers. The F_A(Br^?) centers are destroyed after heating to 330 K.