An electron paramagnetic resonance study of the tetragonally distorted [Formula: see text] ion in [Formula: see text] and [Formula: see text

Chromium-doped [Formula: see text] and [Formula: see text] have been studied by both EPR and ENDOR spectroscopy. [Formula: see text] ions enter the fluorite structure in distorted substitution cation sites. In both matrices the distortion observed is tetragonal. X- and Q-band EPR measurements at temperatures between 4 and 300 K allowed us to determine the ion symmetry and the following spin-Hamiltonian parameters: [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] for [Formula: see text]; and [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] for [Formula: see text]. For [Formula: see text], the weak superhyperfine interaction of [Formula: see text] with the surrounding [Formula: see text] ions has been studied by both EPR and ENDOR techniques for [Formula: see text]. No ENDOR signals were detected for [Formula: see text]. The results are tentatively explained in terms of a Jahn - Teller effect corresponding to [Formula: see text] coupling strongly stabilized by lattice stresses, although other possible origins for the distortion cannot be completely ruled out.     

An adaptive VQ method used on interferential multi-spectral image lossless compression

In this paper, a high efficient adaptive LBG VQ (vector quantization) method is proposed, which is an improved version of the expansion LBG VQ method [1] (proposed in 2009)and exploits the shortest distance from a point to line segment. Moreover, the proposed method is used on the lossless compression of LASIS (Large Aperture Static Imaging Spectrometer) interferential multi-spectral images. Compared with the expansion LBG VQ method proposed in 2009, the experimental results showed that the adaptive LBG VQ method improved the compression performance obviously. And the experiment also showed that when using these LBG VQ methods above without Dual-Direction Prediction [2], the entropy generated by expansion LBG VQ method [1] sometimes will be larger than that generated by traditional LBG VQ method [3], and when using these LBG VQ methods above after Dual-Direction Prediction [2], CR (compression ratio) generated by expansion LBG VQ method [1] sometimes will be less than that generated by traditional LBG VQ method [3], while the entropy generated by the method proposed in this paper will be much less than that generated by either traditional LBG VQ method [3] or the expansion LBG VQ method [1], and CR generated by the method proposed in this paper will be much larger than that generated by either traditional LBG VQ method [3] or the expansion LBG VQ method [1].     

Influence of structural parameters on electroluminescent emittance

On the basis of the measurements made in [1], [2], [3], [4], [5], [6] and [7], and from the relation derived by Goldberg [8] and empirically improved in [6] and [7], a new relation is derived for the dependence of the electroluminescent emittance on the structural parameters of electroluminescent material. The relation, which is in qualitative agreement with the experimentally obtained dependence of electroluminescent emittance, leads to conclusions for improving the preparation of electroluminescent powders and layers.     

Automatic detection and branch switching methods for steady bifurcation in fluid mechanics

This paper deals with the computation of steady bifurcations in the framework of 2D incompressible Navier–Stokes flow. We first propose a numerical method to accurately detect the critical Reynolds number where this kind of bifurcation appears. From this singular value, we introduce a numerical tool to compute all the steady bifurcated branches. All these algorithms are based on the Asymptotic Numerical Method [1], [2]. The critical values are determined by using a bifurcation indicator [3], [4], [5] and the bifurcated branches are computed by using an augmented system which was first introduced in solid mechanics [4], [6]. Several numerical examples from 2D Navier–Stokes show the reliability and the efficiency of the proposed methods.     

Template analysis of a Faraday disk dynamo

In a recent paper Moroz [1] returned to a nonlinear three-dimensional model of dynamo action for a self-exciting Faraday disk dynamo introduced by Hide et al. [2]. Since only two examples of chaotic behaviour were shown in [2], Moroz [1] performed a more extensive analysis of the dynamo model, producing a selection of bifurcation transition diagrams, including those encompassing the two examples of chaotic behaviour in [2]. Unstable periodic orbits were extracted and presented in [1], but no attempt was made to identify the underlying chaotic attractor. We rectify that here. Illustrating the procedure with one of the cases considered in [1], we use some of the unstable periodic orbits to identify a possible template for the chaotic attractor, using ideas from topology [3]. In particular, we investigate how the template is affected by changes in bifurcation parameter.     

Static and time-dependent solutions of Einstein-Maxwell-Yukawa fields

An exact solution of Einstein-Maxwell-Yukawa field equations has been obtained in a space-time with a static metric. A critical analysis reveals that the results previously obtained by Patel [9], Singh [10], and Taub [11] are particular cases of our solution. The singular behavior of the solutions has also been discussed in this paper. Further, extending the technique developed by Janis et al. [12], for static fields, to the case of nonstatic fields, an exact time-dependent axially symmetric solution of EMY fields has been obtained. Our solution in the nonstatic case is nonsingular in the sense of Bonnor [15] and presents a generalization of the results obtained by Misra [7] to the case when a zero-mass scalar field coexists with a source free electromagnetic field.     

What Laboratory-Produced Plasma Structures Can Contribute to the Understanding of Cosmic Structures Both Large and Small

The tradition of the classical 1901 work by Birkeland [1] on aurora phenomena by laboratory terrella experiments was resumed by Alfvén [2], Cowling [3], Ferraro et al. [4], and by Bennett [5] in his terrella experiments. In 1954 [6] when experimenters accidentally produced in the laboratory structures later identified as diamagnetic vortex filaments, and in 1961 [7] when filaments, later identified as current-carrying paramagnetic plasma vortex structures (which are both electric motors and dynamos), were observed in the Z and theta-pinch experiments, this tradition was being further reestablished. It has been successfully argued [6], [8], [11], [20] that both of these types of vortices are force-free minimum-free-energy structures that spontaneously spring to life as readily as do thousands of spherical bubbles and water droplets during the splash of a breaking water wave. The Birkeland aurora filaments are a hybrid combination of these two basic types (paramagnetic and diamagnetic) of plasma vortices. It is to be expected that such structures on a cosmic scale play an important role in the cosmos, and indeed they do in the formation of galaxies, stars, binary stars, solar systems, solar prominences, solar flares, solar wind, comet tails, cosmic "strings" in the Crab nebula, string-like galactic clusters, expansion of the Universe, giant galactic jets, cosmic rays, sunspots, vortex rolls in sunspot penumbra, twinkling of radio stars by the density fluctuations in the ionosphere, turbulence at the interface between the solar wind and the earth's magnetosphere, etc.     

Deformable gyroscope in a non-euclidean space classical,non-relativistic theory

The classical mechanics of structured test particles in a manifold with affine connection is studied. Gyroscopic rotations and homogeneous deformations are taken into account as internal degrees of freedom. Hence, in addition to the orbital motion of the centre of mass, the body undergoes affine rotations about the centre (“affinely-rigid body”). Configurations of particles are described mathematically by linear frames in an underlying manifold (physical space).Symmetries of the theory are discussed and in some special cases the equations of motion are derived. The orbital motion is found to be influenced by internal degrees of freedom which are dynamically coupled to the geometry of the manifold. For example, in a Riemann-Cartan space ([4], [8], [9], [25]), internal degrees of freedom interact with curvature and torsion tensors. Imposing then some holonomic constraints (orthonormal frames only), one gets the theory of test rigid bodies in a curved space with torsion. In a Riemannian case (no torsion) such a theory seems to coincide with non-relativistic (although spatially non-Euclidean) limit of theories studied by Dixon, Künzle, Tulczyjew and Papapetrou [5], [13], [26], [15].As for all standard techniques and notations of differential geometry, we follow mainly Kobayashi-Nomizu [12] and Sternberg [23].     

Zeeman studies of the 0.839eV emission in SI GaAs:Cr

The multi-structured zero phonon transitions of the 0.839eV emission observed in SI GaAs:Cr have been investigated by Zeeman measurements. Magnetic splittings for the directions [111], [110] and [100] as well as angular dependence studies in the (110) plane show that the centre has a symmetry axis along [111] with a small orthorhombic distortion. The emissions cannot be due to the isolated [100] Jahn-Teller distorted Cr²⁺ ions observed in magnetic resonance but to [111] centres such as the (Cr²⁺-donor) pairs as suggested by White.     

Site connectivities in sodium aluminoborate glasses: multinuclear and multiple quantum NMR results

In a series of sodium aluminoborate glasses, we have applied triple-quantum magic-angle spinning (3QMAS) 17O NMR to obtain high-resolution information about the connections among various network structural units, to explore the mixing of aluminum and boron species. Oxygen-17 3QMAS spectra reveal changes in connectivities between AlO4 ([4]Al), AlO5 and AlO6 ([5,6]Al), BO3 ([3]B) and BO4 ([4]B) units, by quantifying populations of bridging oxygens such as Al-O-Al, Al-O-B and B-O-B and of non-bridging oxygens. Several linkages such as [4]Al-O-[4]Al and three-coordinated oxygen associated with [5,6]Al in Al-O-Al, [4]Al-O-[4]B, [4]Al-O-[3]B and [5,6]Al-O-[3]B in Al-O-B as well as [4]B-O-[3]B and [3]B-O-[3]B in B-O-B can be distinguished for the first time. The fractions of these linkages were calculated from models of random mixing and of mixing with maximum avoidance of tetrahedral-tetrahedral linkages. The results suggest that the structure of all of glasses in this study is well approximated by the latter model. However, the energetic "penalty" for formation of [4]Al-O-[4]B may be somewhat less than for [4]Al-O-[4]Al and [4]B-O-[4]B. In general, the new results presented here are similar to those obtained on glasses in this system by 27Al{11B} REDOR NMR (J. Phys. Chem. B 104 (2000) 6541), but provide considerably more detail on network connectivity and ordering schemes.     

On the cutoff parameter in the translation-invariant theory of the strong coupling polaron (response to comments [8] on the paper V.D. Lakhno,SSC 152 (2012) 621)

The paper is a reply to the arguments adduced by the authors of [8] against the results obtained by the author in [6], [7]. It is shown that these arguments are based on the erroneous approach made in [8] to the strong coupling limit when the cutoff parameter is introduced in the theory.     

Neighboring spectral content influences vowel identification

Four experiments explored the relative contributions of spectral content and phonetic labeling in effects of context on vowel perception. Two 10-step series of CVC syllables ([bVb] and [dVd]) varying acoustically in F2 midpoint frequency and varying perceptually in vowel height from [delta] to [epsilon] were synthesized. In a forced-choice identification task, listeners more often labeled vowels as [delta] in [dVd] context than in [bVb] context. To examine whether spectral content predicts this effect, nonspeech-speech hybrid series were created by appending 70-ms sine-wave glides following the trajectory of CVC F2's to 60-ms members of a steady-state vowel series varying in F2 frequency. In addition, a second hybrid series was created by appending constant-frequency sine-wave tones equivalent in frequency to CVC F2 onset/offset frequencies. Vowels flanked by frequency-modulated glides or steady-state tones modeling [dVd] were more often labeled as [delta] than were the same vowels surrounded by nonspeech modeling [bVb]. These results suggest that spectral content is important in understanding vowel context effects. A final experiment tested whether spectral content can modulate vowel perception when phonetic labeling remains intact. Voiceless consonants, with lower-amplitude more-diffuse spectra, were found to exert less of an influence on vowel perception than do their voiced counterparts. The data are discussed in terms of a general perceptual account of context effects in speech perception.     

Some observations on the development of anticipatory coarticulation

The influence of vocalic context on various temporal and spectral properties of preceding acoustic segments was investigated in utterances containing [schwa No. CV] sequences produced by two girls aged 4;8 and 9;5 years and by their father. The younger (but not the older) child's speech showed a systematic lowering of [s] noise and [th] release burst spectra before [u] as compared to [i] and [ae]. The older child's speech, on the other hand, showed an orderly relationship of the second-formant frequency in [] to the transconsonantal vowel. Both children tended to produce longer [s] noises and voice onset times as well as higher second-formant peaks at constriction noise offset before [i] than before [u] and [ae]. All effects except the first were shown by the adult who, in addition, produced first-formant frequencies in [] that anticipated the transconsonantal vowel. These observations suggest that different forms of anticipatory coarticulation may have different causes and may follow different developmental patterns. A strategy for future research is suggested.     

Stochastic processes associated with quantum systems

Stochastic processes have been useful in constructing and studying states in Quantum Field Theory (e.g., the Erice Lectures [3], Simon [2], Glimm and Jaffle [6] and in Quantum Statistical Mechanics (e.g., Ginibre [5], Høegh-Khron [7], Fröhlich [4], Driessler, Landau and Perez [2]). By analytically continuing into imaginary time, we may in certain cases replace the non-commulative algebra of observables of the quantum system by a commulative algebra consisting of functions of a stochastic process.In this article we are going to discuss an appropriate mathematical framework for this connection between quantum systems and stochastic processes.     

Biomedical Applications of Selected Ion Monitoring

In 1961 Henneberg [1] employed selected ion monitoring (SIM) to study hydrocarbons eluting from a gas chromatographic column, and in 1966 the first biological application was reported by Sweeley, Elliott, Fries, and Ryhage [2]. Since these efforts and the early impetus given by Hammar, Holmstedt, and co-workers [3–6], SIM has found widespread application in biological, medicinal, and environmental research. Recent review articles have described ion monitoring work with magnetic sector instruments [7,8,8a,8b], quadrupole instruments [9], and time-of-flight instruments [19]. These articles provide comprehensive coverage of applications through 1972. This review emphasizes medicinal and biological applications through 1973 and attempts to evaluate current methods and recent developments.     

Inelastic cross-sections and natural lifetimes for the 62D3/2, 5/2 and 82S1/2 states of Rb

The results of an experimental study of population dynamics following excitation of [0pt] and [0pt] states of rubidium are reported. Excitation transfer and quenching cross-sections in collisions with ground state rubidium atoms, and natural lifetimes have been measured. The experiment was performed in a vapour cell, using pulsed two-photon excitation and photon counting detection. The analysis of time dependent signals was based on a rate equation model in which transitions induced by thermal radiation have been accounted for. The measurements yielded following results: (1) [0pt] state J-mixing cross-section: [0pt] ; (2) cross-sections for [0pt] excitation transfer process: [0pt] ; (3) quenching cross-sections: [0pt] , [0pt] , [0pt] ; [0pt](4) radiative lifetimes: [0pt] ns, [0pt] ns, [0pt] ns. Received 1st December 1998 and Received in final form 17 May 1999     

气相外延ZnSe单晶薄膜的蓝色电致发光

本文在300℃—700℃温度范围内,在GaAs衬底上气相外延生长了ZnSe单晶薄膜。讨论了衬底温度对外延层电学性质及光学特性的影响。ZnSe外延层经Zn气氛热处理后,发光特性大为改善。用处理后的ZnSe外延膜做成MIS发光二极管,首次得到了室温下气相外延ZnSe单晶薄膜的蓝色电致发光。     

Chemical Far Infrared Spectroscopy

Abstract

A number of books, symposia, proceedings, special publications [1–9], and review papers in English covering catalytic surfaces [10, 11], solid surface characterization [12–191, thin film analysis [20–22], surface structure and bonding [23, 24], angular distribution of photoelectrons [25, 26], use of synchrotron radiation [27, 281, ion beam effects [29], different methods of surface study [30, 31], experimental and theoretical aspects of ultraviolet photoelectron spectroscopy (UPS) [32], and angle resolved UPS [33, 34] are available in literature. Reviews in other languages, namely Japanese [35–41], German [42–46], French [47–50], Italian [51], Russian [52], and Polish [53], are also available. But the present situation demands a thorough and up-to-date literature survey of the surface study by photoelectron spectroscopy in order to assess what has been done and what is left to be done. This paper is aimed at that goal.     

The first in vivo observation of (13)C-(15)N coupling in mammalian brain.

[5-(13)C,(15)N]Glutamine, with (1)J((13)C-(15)N) of 16 Hz, was observed in vivo in the brain of spontaneously breathing rats by (13)C MRS at 4.7 T. The brain [5-(13)C]glutamine peak consisted of the doublet from [5-(13)C,(15)N]glutamine and the center [5-(13)C,(14)N]glutamine peak, resulting in an apparent triplet with a separation of 8 Hz. The time course of formation of brain [5-(13)C,(15)N]glutamine was monitored in vivo with a time resolution of 20-35 min. This [5-(13)C,(15)N]glutamine was formed by glial uptake of released neurotransmitter [5-(13)C]glutamate and its reaction with (15)NH(3) catalyzed by the glia-specific glutamine synthetase. The neurotransmitter glutamate C5 was selectively (13)C-enriched by intravenous [2,5-(13)C]glucose infusion to (13)C-label whole-brain glutamate C5, followed by [(12)C]glucose infusion to chase (13)C from the small and rapidly turning-over glial glutamate pool, leaving (13)C mainly in the neurotransmitter [5-(13)C]glutamate pool, which is sequestered in vesicles until release. Hence, the observed [5-(13)C,(15)N]glutamine arises from a coupling between (13)C of neuronal origin and (15)N of glial origin. Measurement of the rate of brain [5-(13)C,(15)N]glutamine formation provides a novel noninvasive method of studying the kinetics of neurotransmitter uptake into glia in vivo, a process that is crucial for protecting the brain from glutamate excitotoxicity.     

光谱法研究1-萘酚、2-萘酚与瓜环的包结作用

用荧光光谱、紫外吸收光谱法研究了瓜环与1-萘酚、2-萘酚的相互作用,考察了pH对体系的影响。结果表明,1-萘酚、2-萘酚与六元、七元瓜环都不发生作用,而与八元瓜环发生相互作用,形成物质的量比为1∶1的稳定包结配合物。用荧光法测定1-萘酚、2-萘酚与八元瓜环包结配合物的稳定常数为4.2×104 L·mol-1和1.6×104 L·mol-1,紫外光谱法测定的稳定常数为4.2×104 L·mol-1和5.4×104 L·mol-1;在酸性和中性条件下1-萘酚、2-萘酚与八元瓜环发生包结作用,形成稳定包结物,而在强碱性条件下不发生包结作用。