XANES and EXAFS in Cu-Ti and Ni-Zr glasses

X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements have been done at the K-edge of Cu in Cu-Ti glasses and on the K-edges of Ni and Zr in Ni-Zr glasses using a synchrotron radiation source. The results are discussed in terms of the shape shift and intensity of the absorption edge as well as the principal absorption maximum. The values of bondlength calculated by the one-electron multiple scattering XANES theory as well as the graphical analysis EXAFS technique show good agreement.     

Electromagnetic and magnetoacoustic waves in magnetized and polarized fluids

Electromagnetic and magnetoacoustic adiabatic waves propagating in magnetized and polarized fluids are studied in terms of linearized equations. The dispersion equations obtained as a result of calculations describe two electromagnetic waves, transverse and longitudinal, as well as sound waves.     

Structural and optical properties of single and bilayer silver and gold films

Physics of the Solid State - An experimental study of structural and optical properties of silver and gold thin films, as well as bilayer films based on these metals, has been carried out. To study...     

Membranes and films of zeolite and zeolite-like materials

An ideal structure of zeolite membrane should be a slice of a perfect zeolite crystal attached on a porous metal or ceramic support. To maximize the throughput, the zeolite layer must be very thin, limited only by the cell dimension of zeolite. Separation of a mixture may then be achieved based on the molecular sieving ability of zeolite, which allows only molecules smaller than a critical size to pass through. A variety of methods have been reported for the preparation of zeolite membranes, but so far a perfect epitaxial zeolite layer is still out of reach and only a polycrystalline zeolite membrane can be obtained. The first part of this review focuses on the permeation of gases and vapors through a polycrystalline zeolite membrane as a separation means. The effect of microstructure on permeance will also be discussed, as well as the preparation methods leading to different microstructures. In addition to the usage as a shape-selective membrane, thin films of zeolite and zeolite-like molecular sieves can also serve as hosts for the encapsulation and orientation of guest atoms and molecules and their clusters. In the second part of this review, the production of layers of aligned microporous molecular sieve crystals on supports and the fabrication of supported thin zeolite-like nanoporous silica films as well as their potential applications on the preparation of advanced materials are discussed.     

Plasticity and strength of micro- and nanocrystalline materials

This review is devoted to the effect of grain boundaries on the deformational and strength properties of poly-, micro-, and nanocrystalline materials (predominantly metals). The main experimental facts and mechanisms concerning the dislocation structure and mechanical behavior of these materials over wide ranges of temperatures and grain sizes are presented. The experimentally established regularities are analyzed theoretically in terms of equations of dislocation kinetics taking into account the properties of grain boundaries as barriers, sources, and sinks for dislocations and as places where dislocations annihilate. The origin of the Hall-Petch relations for the yield stress and the flow stress as functions of the grain size, as well as the deviations from these relations observed in nano- and microcrystalline materials, is discussed in detail in terms of the dislocation-kinetics approach. Embrittlement of micro- and nanocrystalline materials at low temperatures and superplasticity of these materials at elevated temperatures are also analyzed in terms of the dislocation-kinetics approach.     

Physical and chemical phenomena occurring between solid ceramics and liquid metals and alloys at laser and plasma composite coatings formation: A review

The review describes the physical and chemical phenomena occurring between solid ceramics used as reinforcement and liquid metals and alloys used as matrix in the composite coatings. Initially, the properties of typical matrix metals as Ni, Co, Fe and alloys as Ni-based (NiCr, NiAl, NiCrAlY,…) and Co-based (Stellites) alloys in liquid state are described. Then, the phenomena related to the diffusion of some atoms such as nitrogen or carbon in liquid metals and alloys solidification are described. Subsequently, the phenomena at the interface between liquid metals and alloys and solid ceramics such as oxides or carbides during the coatings' formation are reviewed. Finally, the methods of composite coatings deposition using laser cladding and plasma transferred arc are described and the properties of the composite coatings related to their microstructure are discussed by taking into account the phenomena in melt-pool.     

Hot and cold,nuclear and neutron matter

We report variational calculations of the equation of state of hot and cold, nuclear and neutron matter. The calculations cover a wide density range of interest in heavy-ion collisions and astrophysics. The “hot” calculations are limited to temperatures less than 20 MeV. A realistic nuclear hamiltonian that contains two- and three-nucleon interactions and fits the nucléon-nucléon scattering, as well as nuclear matter data, is used. Neutron star structure calculations are reported and their sensitivity to the three-neutron interactipn is examined. The liquid-vapor phase equilibrium, as well as the behavior of the effective mass in nuclear matter is discussed.     

Electron relaxation and transport in nanostructured and bulk silica

Processes of ballistic and hot electron relaxation in extended bulk as well as nanostructured silica have been analyzed by means of a phonon-based scattering model and respective Monte-Carlo computer simulation. Optical as well as acoustic phonons are taken into account. Trajectories of electrons and their energy attenuation in nanostructured silica are additionally affected by scattering processes at the grain boundaries between the nanoparticles, i.e. by surface phonon as well as potential scattering. Moreover, a flatter conduction band and a higher effective electron mass have been taken into account too. According to these calculations, electrons with an initial energy of several eV, but still below the valence band ionization threshold, were thermalized in 50–300 fs increasing with the silica grain size from 1 nm up to bulk material. The electron emission probabilities over the surface barrier into vacuum are extended up to depths of 60–100 nm, respectively, increasing with enhancement by an electric field.     

Read and write processes, and head technology for perpendicular recording

In this paper, we present a review of the write and read processes in perpendicular magnetic recording. We also discuss their impact, based on recording physics aspects, on design considerations for writers and readers. For the write process, we discuss fundamental write-ability limitations as well as possible paths to ultra-high areal density perpendicular recording. The impacts of different medium designs, geometrical scaling, and the breakdown of scaling, both in terms of write-ability and transition curvature, are shown based on different modeling techniques, including analytical formulas, finite element modeling (FEM), and micromagnetic simulations. Basic design rules as well as alternative designs that enable high areal density are briefly explained. For the read-back process, the relation between reader signal to noise ratio (SNR) and resistance, as well as reader resistance shunt and spacing loss, are discussed. Finally, we use a simple example to illustrate, both from a write as well as a read-back perspective, the complicated nature of perpendicular recording systems, and how different medium designs impact recording head technology for ultra high density perpendicular recording.     

Organic- and molecule-based magnets

The discovery of organic- and molecule-based magnets has led to design and synthesis of several families with magnetic ordering temperatures as high as ∼125°C. Examples of soft and hard magnets with coercivities as high as 27 kOe have also been reported. Examples from our laboratory of organic-based magnets using the tetracyanoethylene radical anion, [TCNE]^•−, are discussed. In addition, several molecule-based magnets based on Prussian Blue structured materials as well as dicyanamide are discussed.     

Saddles and trajectories,and poles and surface waves in heavy-ion elastic scattering

The terms I_m^±(θ) of the Poisson summation formula are used to describe and classify the oscillatory structures of the heavy-ion elastic cross sections coming from a strong-absorption model. The method of stationary phase, which relates these terms to branches of a deflection function, is shown to be inadequate and is replaced by the saddle-point method in the plane of complex angular momenta. The positions of the saddle points are found to be fairly independent of the parametrisation and define certain “active” regions which contribute to the scattering amplitude. The complex saddle points may be thought of as corresponding to complex trajectories in the nuclear potential. If the strong-absorption parametrisation possesses poles many saddle-point contributions can be simply expressed as the residues of the poles nearest the real axis. One of these leading parametric poles has an energy dependence similar to that of the dominant Regge pole generated by a complex optical potential. Poles lying above the real axis give rise to terms which may be thought of as surface waves, i.e. they are damped as they progress around the nuclear surface. These terms possess classically equivalent paths in the sense that they correspond to deflections less than π. Terms coming from poles below the real axis have no classical equivalent, increase as they progress and can, then, only be thought of as being diffractive. Some useful formulae for the cross section are given and the limiting case of a sharp cut-off is discussed.     

钨钼杂多化合物及其用途

简要介绍了钨、钼的性质和用途,主要综述了钨钼杂多化合物的合成方法、结构、性质,及其在催化、水质缓蚀剂、分析检测、生物医学、无机离子交换剂等方面的应用。     

Smooth conjugacy and S-R-B measures for uniformly and non-uniformly hyperbolic systems

We give a new proof of the fact that the eigenvalues at corresponding periodic orbits forms a complete set of invariants for the smooth conjugacy of low dimensional Anosov systems. We also show that, if a homeomorphism conjugating two smooth low dimensional Anosov systems is absolutely continuous, then it is as smooth as the maps. We furthermore prove generalizations of these facts for non-uniformly hyperbolic systems as well as extensions and counterexamples in higher dimensions.     

High-loading polyglycerol supported reagents for Mitsunobu- and acylation-reactions and other useful polyglycerol derivatives

Summary In this paper we present soluble dendritic polyglycerol (PG) supported reagents PG-DEAD, PG-PPh₃, and PG-DCC as well as scavengers PG-carbonate, PG-carbazate, and PG-amine, which all have been synthesized in high overall conversions and yields using simple purification techniques. The supported reagents have been used simultaneously in Mitsunobu and acylation reactions. All polymeric reagents and scavengers can be removed by simple precipitation/filtration protocols to give chromatography-free products of high purity. In the course of the syntheses of the polymeric reagents three intermediates turned out to be precious polyglycerol derivatives: a mixed carbonate as an electrophilic derivative, polyglyceryl carbazate as a scavenger for carbonyl compounds, as well as polyglycerylamines as amino analogues of polyglycerol.     

Visualization and interferometry for cylindrical and spherical sample tomography and profilometry

A technique combining image processing and laser interferometry for visualizing and detecting the deformation of transparent cylindrical and spherical sample is proposed. This deformation includes geometric deformation such as volume transition in profilometry and physical deformation such as refractive index change in tomography. Phase contour lines are used for quantitative analysis and graphical representation of the deformation. This method allows us to visually detect the spatial variation of the deformation field and to evaluate the test quality such as misalignment of optical system. A theoretical analysis using phase contour map to characterize the deformation field is described in detail. A method using phase contour map to qualify the interferometric test is proposed. Analysis of test examples is carried out. Suggestions on using phase contour line method to ameliorate test system design are finally discussed.     

Cooperation between scientists and the government in the US: benefits and problems

This paper discusses the importance of maintaining close working relations between scientists and their government. Several examples of this cooperation in the U.S. are presented to illustrate the benefits, as well as problems, that result from such cooperation, or lack thereof. These examples include government support of scientific research, as well as contributions by science to help governments understand both the possibilities and the limitations of science as they formulate national policy.     

Nuclear physics with simple and multi-element detectors and with stable and radioactive beams

The phenomenon of fusion barrier distributions is discussed in the context of a problem already investigated in some detail with simple detection systems, but possessing avenues to studies with multi-detector arrays. The complementarity of research with simple and complex detectors, as well as with stable and radioactive beams, will be highlighted.     

从“福岛第一核电站事故”看我国核能利用的核安全

文章简要说明了福岛第一核电站事故的起因、发展和后果,并对核电站全厂断电、反应堆压力容器及安全壳超压、氢爆等导致事故恶化的原因作了分析.文章还就导致福岛核事故的相关因素与我国核电站的安全设计及防范对策进行了分析比较.在吸取福岛核事故的经验教训方面,文章提出了若干值得引发关注的启示,作为我国在建和在役核电站的改进,以及新设计核电站的参考.文章还就我国能源的状况,核能发展的必要性,以及核能发展的方针进行了探讨.     

Virasoro and KdV

We investigate the structure of representations of the (positive half of the) Virasoro algebra and situations in which they decompose as a tensor product of Lie algebra representations. As an illustration, we apply these results to the differential operators defined by the Virasoro conjecture and obtain some factorization properties of the solutions as well as a link to the multicomponent KP hierarchy.     

Estimating and adjusting abnormal networks with unknown parameters and topology

The changes of parameters and topology in a complex network often lead to unexpected accidents in complex systems, such as diseases in neural systems and unexpected current in circuit system, so the methods of adjusting the abnormal network back to its normal conditions are necessary to avoid these problems. However, it is not easy to detect the structures and information of each network, even if we can find a network which has the same function as the abnormal network, it is still hard to use it as a reference to adjust the abnormal network because a lot of network information is unknown. In this paper, we design a "bridging network" as an information bridge between a normal network and an abnormal network to estimate and control the abnormal network. Through the "bridging network" and some adaptive laws, the abnormal parameters and connections in abnormal network can be adjusted to the same conditions as those of the normal network which is chosen as a reference model. Finally, the "bridging network" and the abnormal network achieve synchronization with the normal network. Besides, the detailed inner information in normal network and abnormal network can be accurately estimated by this "bridging network." Finally, the nodes in the abnormal network will behave normally after the correction. In this paper, we use Hindmarsh-Rose model as an example to describe our method.