Ab initio study on nonmetal and nonmagnetic metal atoms doped arsenene

The structural, electronic, and magnetic properties of arsenene doped with a series of nonmetals (B, C, F, N, and O) and nonmagnetic metals (Al, Ga, Li, Mg, and Na) are investigated using density functional theory. Magnetism is observed in the case of C. Among all the cases, the C-doped system is the most stable formed system. Hence, we study the ferromagnetic interaction in two-C-doped arsenene. Interestingly, both nonmagnetic (NM) and antiferromagnetic (AFM) states have been observed. As the increasing C?C distance, the magnetic coupling between the moments induced by two C is found to be AFM and the origin of the coupling can be attributed to the p?p hybridization interaction involving polarized electrons.     

Brillouin zone effects on the critical temperature of superconductors and some related normal metal properties

A Fermi surface passing through a set of Bragg planes gives rise to variations of several normal metal properties, e.g. the electronic density of states N(0), the magnetic susceptibility, the Seebeck coefficient, the Debye temperature and the electron-phonon interaction strength V_ph, and consequently also to variation of the critical temperature for superconductivity, T_c.This behaviour is analysed on the basis of a nearly free electron model and a comparison is made with experimental results in various alloy systems. These systems include alloys of non-transition metals and pseudo-binary alloyed compounds with Cu₃Au- and CuAl₂-type structure.The observed variations of normal metal properties are in reasonable agreement with the theoretical estimates. The variations in T_c indicate that enhancements not only of N(0) but probably also of V_ph occur near Bragg planes.     

On some thermodynamic effects in small molecular systems

The behavior of a gas-liquid system in a small volume has been studied. In the absence of the thermodynamic limit, the problem has been examined by methods of statistical physics. This allows the use of new mathematical methods previously applied in nuclear physics. Within the modified droplet model of a real gas sandwiched between two extended plates, an additional component of the pressure, which was previously discussed and exhibits characteristic oscillations at change in the volume, has been found. Qualitative coincidence with the previously reported molecular dynamics simulations has been found.     

金属和非金属原子间协同效应调控气体小分子的吸附特性研究

采用基于密度泛函理论方法系统地研究了单个NO和CO小分子在非金属(B和N)与金属Ni原子共掺杂石墨烯(Bx-Ny-gra-Ni,x+y=0,1,2,3)表面的吸附特性,分析了吸附气体小分子的几何结构,吸附能,电荷转移量以及引起体系磁性变化等情况.研究结果表明：NO和CO倾向于吸附在Ni原子的顶位,B和N掺杂原子的数量和比例能够有效地调制小分子的吸附强度;与吸附的CO分子相比,Bx-Ny-gra-Ni表面吸附的NO分子能获得较多的电荷,进而表现出高的稳定性.此外,利用吸附的气体小分子与衬底间相互作用强度和灵敏性的差异、以及引起反应衬底的磁性变化将为设计石墨烯基气敏、催化和电子器件提供重要参考.     

A strategy of enhancing the photoactivity of TiO2 containing nonmetal and transition metal dopants

An effective structural codoping approach is proposed to modify the photoelectrochemical （PEC） properties of anatase TiO2 by being doped with nonmetal （N or/and C） and transition metal （Re） elements. The electronic structures and for- mation energies of different doped systems are investigated using spin-polarized density functional theory. We find that （C, Re） doped TiO2, with a low formation energy and a large binding energy, reduces the band gap to a large extent, thus it could contribute to the significant enhancement of the photocatalytic activity in the visible-light region. It should be pointed out that, to be successful, the proper proportion of the dopants C and Re should be controlled, so that reasonable PEC properties can be achieved.     

Effect of ultrasound on heterogeneous systems

Examples of sonochemical reactions occuring under heterogeneous conditions are discussed with respect to their mechanism. The activation of a metal surface involves complex phenomena, in which parameters of importance seem to be the hardness and the adhesion of the passivating layer. Some considerations are given on the probable link between sonochemistry and tribochemistry.     

Action of high intensity ultrasound on solidifying metal

The mechanism of metal solidification in an ultrasonic field and associated structure changes in ingots is described. Development of cavitation and acoustic flow in melts, and the nucleation and dispersion of growing crystals are discussed. The effects of material properties and solidification conditions on the effectiveness of structure refinement during ultrasonic treatment are evaluated. As an example, the structure changes in steels treated by ultrasound are examined.     

Low-dimensional systems: Quantum size effects and electronic properties of semiconductor microcrystallites (zero-dimensional systems) and some quasi-two-dimensional systems

This review is concerned with quantum confinement effects in low-dimensional semiconductor systems. The emphasis is on the optical properties, including luminescence, of nanometre-sized microcrystallites, also referred to as zerodimensional systems. There is some discussion on certain of the two-dimensional systems, such as thin films and layer structures. The increase in energy of excitation peaks (blue shift) as the radius R of a microcrystallite is reduced is treated theoretically, and experimental data when they are available are used to assess the reliability of the different models that have been used. These experiments normally make use of microcrystallites dispersed in a large-bandgap matrix such as glass, rocksalt, polymers, zeolites or liquids. Exciton binding energies E b are larger than for bulk semiconductors, and oscillator strengths are higher for the microcrystallites. The regimes of direct interest are as follows. Firstly there is the so-called weak-confinement regime where R is greater than the bulk exciton Bohr radius a B . Experimentally, semiconductors such as CuCl with a B , 7 Å, are suitable for study in this case. Secondly there is the moderate-confinement regime, where R , a B , and a h < R < a e , a h and a e being the hole and electron Bohr radii, respectively. Finally there is the strong-confinement regime, with R < a B , and R < a h , a e . For this case we are concerned with a ladder of discrete energy levels, as in molecular systems, rather than energy bands. The electrons and holes are treated as independent particles, and for excited states we refer to electron-hole pairs rather than excitons. Suitable materials for investigation in this regime are the II-VI semiconductors, and also GaAs and Ge, for which a B is relatively large. Although a number of different theoretical models have been used, none can be described as completely first-principles calculations, and there is room for improvement on this aspect. However, useful expressions have been developed by Brus and by Lippens and Lannoo, giving the energy of excited states as a function of R , in terms of the bulk energy gap, kinetic energy, Coulomb energy and correlation energy. Other phenomena discussed are firstly biexciton formation by the use of high intensity laser beams and secondly nonlinear optical effects. Strong nonlinearities and short decay times for excited states have been predicted, and the models developed cover both the resonant and the non-resonant cases. The possibility of using microcrystallites embedded at reasonable concentrations in a glass matrix in the field of optical communications and optical switching is also considered.     

Annealing effects on the plasmonic excitations of metal/metal interfaces

The effects of the annealing procedure at 400-450 K on the electronic properties of nanoscale thin films of Ca, Au and Ag grown on Cu(1 1 1) at room temperature were probed by high-resolution electron energy loss spectroscopy measurements. Ca surface plasmon underwent to a significant red-shift upon annealing, due to the oxidation of the topmost Ca layer. Water strongly interacted with the CaO interface at room temperature. Au surface plasmon disappeared upon annealing the gold film, as a consequence of the formation of an Au-Cu alloy. Ag surface plasmon red-shifted both in the annealed adlayer and with increasing temperature compared with the frequency recorded for the as-deposited silver film.     

Impact of ultrasound processing on alternative protein systems: Protein extraction,nutritional effects and associated challenges

Proteins from alternative sources including terrestrial and aquatic plants, microbes and insects are being increasingly explored to combat the dietary, environmental and ethical challenges linked primarily to conventional sources of protein, mainly meat and dairy proteins. Ultrasound (US) technologies have emerged as a clean, green and efficient methods for the extraction of proteins from alternative sources compared to conventional methods. However, the application of US can also lead to modifications of the proteins extracted from alternative sources, including changes in their nutritional quality (protein content, amino acid composition, protein digestibility, anti-nutritional factors) and allergenicity, as well as damage of the compounds associated with an increased degradation resulting from extreme US processing conditions. This work aims to summarise the main advances in US equipment currently available to date, including the main US parameters and their effects on the extraction of protein from alternative sources, as well as the studies available on the effects of US processing on the nutritional value, allergenicity and degradation damage of these alternative protein ingredients. The main research gaps identified in this work and future challenges associated to the widespread application of US and their scale-up to industry operations are also covered in detail.     

Investigations of fission characteristics and correlation effects

We review the experimental results on the P-even and P-odd angular correlations of fission fragments in the fission of the ²³⁵U and ²³⁹Pu nuclei induced by unpolarized and polarized resonance neutrons, and on the TRI and ROT effects in the ternary and binary fission of actinides induced by polarized thermal neutrons. Also reported are the measured yields of prompt and delayed neutrons per fission event. The experimental data are analyzed within a novel theoretical framework developed by the JINR—RNC KI Collaboration, whereby the reduction of the multidimensional phase space of fission fragments to the JπK-channel space is consistently validated and the role of resonance interference in the observed correlation effects is revealed.     

Effect of metal and substituents on the quasi-line spectra of some metalloporphyrins

Absorption spectra are reported for a number of metalloporphyrins in n-octane. For ZnP and PdP, sharp quasi-lines with linewidths ≈4 cm^?1 are observed at 15 and 35 K, respectively. The narrowest linewidths for PtP are ≈12 cm at 15 K, while NiP and CuP show no quasi-linear structure. In these latter cases, quasi-linewidth is attributed to electronic radiationless decay of the visible excited state. The various vibronic bands within Q(1, 0) are tabulated. The quasi-line structures for several zinc porphyrins at 77 K are also reported. Generally, these are not as sharp as those found in ZnP; in particular, Zn tetraphenyl porphin shows no quasi-linear structure. In these cases, the quasi-line structure is attributed to inhomogeneous broadening.     

The effects of ultrasound on micromixing

The Villermaux–Dushman reaction is a widely used technique to study micromixing efficiencies with and without sonication. This paper shows that ultrasound can interfere with this reaction by sonolysis of potassium iodide, which is excessively available in the Villermaux–Dushman solution, into triiodide ions. Some corrective actions, to minimize this interference, are proposed. Furthermore, the effect of ultrasonic frequency, power dissipation, probe tip surface area and stirring speed on micromixing were investigated. The power and frequency seem to have a significant impact on micromixing in contrast to the stirring speed and probe tip surface area. Best micromixing was observed with a 24 kHz probe and high power intensities. Experiments with different frequencies but a constant power intensity, emitter surface, stirring speed, cavitation bubble type and reactor design showed best micromixing for the highest frequency of 1135 kHz. Finally, these results were used to test the power law model of Rahimi et al. This model was not able to predict micromixing accurately and the addition of the frequency, as an additional parameter, was needed to improve the simulations.     

Investigations on the generation of oil-in-water (O/W) nanoemulsions through the combination of ultrasound and microchannel

O/W nanoemulsions are isotropic colloidal systems constituted of oil droplets dispersed in continuous aqueous media and stabilised by surfactant molecules. Nanoemulsions hold applications in more widespread technological domains, more crucially in the pharmaceutical industry. Innovative nanoemulsion-based drug delivery system has been suggested as a powerful alternative strategy through the useful means of encapsulating, protecting, and delivering the poorly water-soluble bioactive components. Consequently, there is a need to generate an emulsion with small and consistent droplets. Diverse studies acknowledged that ultrasonic cavitation is a feasible and energy-efficient method in making pharmaceutical-grade nanoemulsions. This method offers more notable improvements in terms of stability with a lower Ostwald ripening rate. Meanwhile, a microstructured reactor, for instance, microchannel, has further been realised as an innovative technology that facilitates combinatorial approaches with the acceleration of reaction, analysis, and measurement. The recent breakthrough that has been achieved is the controlled generation of fine and monodispersed multiple emulsions through microstructured reactors. The small inner dimensions of microchannel display properties such as short diffusion paths and high specific interfacial areas, which increase the mass and heat transfer rates. Hence, the combination of ultrasonic cavitation with microstructures (microchannel) provides process intensification of creating a smaller monodispersed nanoemulsion system. This investigation is vital as it will then facilitate the creation of new nanoemulsion based drug delivery system continuously. Following this, the fabrication of microchannel and setup of its combination with ultrasound was conducted in the generation of O/W nanoemulsion, as well as optimisation to analyse the effect of varied operating parameters on the mean droplet diameter and dispersity of the nanoemulsion generated, besides monitoring the stability of the nanoemulsion. Scanning transmission electron microscopy (STEM) images were also carried out for the droplet size measurements. In short, the outcomes of this study are encouraging, which necessitates further investigations to be carried out to advance a better understanding of coupling microchannel with ultrasound to produce pharmaceutical-grade nanoemulsions.     

Investigations of the excitation energy transport mechanism in donor-acceptor systems

Measurements of fluorescence quantum yield _D/_oD of Na-fluorescein (donor; D) versus concentration of rhodamine B (acceptor; A) in viscous solutions have been carried out. The donor concentration in these solutions was as follows:C _D=2·10^–2 M (system I), 1.5·10^–2 M (II), 10^–2 M (III), 3·10^–3 M (IV), and 5·10^–5 M (V). The experimental results have been compared with current theories of nonradiative electronic energy transfer (NEET). In the case of very strong migration (systems I, II, and III), a significant influence of correlations (between configurations of D and A molecules in the surroundings of successively excited donors) on quantum yield _D/_oD has been determined. Experimental values have been found to be clearly higher in comparison with those predicted theoretically. The influence of possible factors on the decrease in the effectiveness of excitation energy transport to traps-acceptors in systems of very strong migration has been discussed.Dedicated to Professor A. Kawski on the occasion of his 65th birthday.     

The effects of ultrasound on starch grains

Ultrasound has been applied to an aqueous starch suspension and the erosion of starch grains that are free to move and whose dimensions approximate those of cavitational bubbles has been examined. The examination was carried out with a scanning electron microscope. The type of erosion (state of the surface and position and form of the pits) is analysed as a function of the experimental conditions — chiefly the type of surrounding gas: air, hydrogen, oxygen and carbon dioxide.     

功率超声对溶液性质的影响

本文研究了在功率超声作用下，电解质溶液，小分子溶液和大分子溶液的粘度，表面张力和电导率等物理化学性质的变化规律。实验结果表明，在超声波作用下，溶液的粘度和表面张力暂时下降，而电导率长期升高。     

Tissue-damaging effects of ultrasound

Professor Wittenzellners' hitherto unpublished work was completed in January 1951 and is now presented as an item of historical and current interest. It contains some of the first studies on the effects of ultrasonic irradiation applied to body tissues, a subject now of popular interest in medical ultrasonics.