Pressure effects on the quadrupole coupling constant of 7Li in first stage lithium graphite

The pressure dependence of the experimental ⁷Li NMR spectra is reported for first stage lithium graphite (LiC₆) intercalation compound at temperatures T = 232 and 293 K. This experiment together with the presented point charge model calculation of the ⁷Li quadrupole coupling constant $\text{(}\text{e}{}^2\text{qQ}\text{h}\text{)}$ allows an unambiguous determination of the sign of e²qQ/h which is negative: $\text{e}{}^2\text{qQ}\text{h=-52 kHz}$ at p = 1 bar and T = 232 K. The averaged location of the electrons transferred from the Li intercalant to the graphite layers, as estimated in this study, is in excellent agreement with earlier theoretical energy-band calculations. The compressibility of LiC₆ in the c-direction is predicted to be k_c = 1.7 × 10^-12cm²dyn^-1, it agrees with estimates derived from the available phonon dispersion relations.     

Mode-locking dynamics of a laser coupled to an empty external cavity

The effect of incorporating an empty external cavity into the feedback loop of a mode-locked laser is investigated. Particular attention is paid to the response of the mode-locking as the external cavity is detuned by a fraction of a wavelength from the round trip transit time associated with the laser. The results for two regimes of operation are presented. In the first case a series of short lived transients develop whereas the other case leads to a persistent intermittent Q-switching scenario, where mode-locking fails. The role of coupling between the cavities and the laser's memory time in relation to the results is discussed. A mechanism for the improved mode-locking observed with non-linear external cavities is suggested.     

Two-mass models of the vocal cords for natural sounding voice synthesis

Three new two-mass models of the vocal cords are treated. First, the features, structure, and differential equations of motion are described for each of the new models and compared with those of previous models. Second, performances of the models are discussed in terms of glottal volume flow, glottal area, radiated sound pressure, trajectories of mass movement, running spectra of the output sound pressure, and perceptual naturalness of the output sound. Finally, the major effects of glottal source-vocal tract interaction including skewing, truncation, and superposition are investigated, using one of the simplest types of two-mass models and two types of load representing the vocal tract.     

An equation for the characteristic function of a stable distribution on the Heisenberg group

Translated fromProblemy Ustoichivosti Stokhasticheskikh Modelei. Trudy Seminara, 1988, pp. 137–140.     

Interaction of metals with an organic semiconductor: Ag and In on PTCDA

The interaction of Ag and In with a thin film of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) was studied by near-edge X-ray absorption fine structure (NEXAFS). Upon Ag deposition on a PTCDA film of 20 nm thickness the relative intensities and lineshapes, as well as the angular dependence of the spectra remains unchanged, illustrating the formation of a chemically unreactive Ag/PTCDA interface. On the other hand, the adsorption of 0.3 nm In strongly decreases the intensity of the π^* resonances in C and O K-edge NEXAFS spectra. This is attributed to a strong charge transfer between In and PTCDA, leading to a redistribution of the charge in the molecule. However, the absence of a strong shift or new features and negligible dependence of peak intensities corresponding to π^* resonances on the In thickness indicate that the interaction between In and PTCDA is not accompanied by a covalent bond formation.     

Specific Features of the Quasilocal State Densities in the Presence of Defects in Media with Spatial Dispersion

The density of stationary quasilocal states of the continuous spectrum arising due to the presence of defects in a medium with spatial dispersion is analyzed. The influence of plane and point defects on the specific features of the spectral quasilocal state density is studied. It is demonstrated that the spectral density has a strict maximum caused by the quasilocal energy level arising in the system. For a plane defect, the energy of the quasilocal level is displaced from the resonance energy of total quasi-particle reflection from the defect. The influence of the quasilocal state on the electronic heat capacity in the presence of the point defect is analyzed.     

Two-stream-like mechanism of zonal-flow generation by Rossby waves in a shallow rotating fluid

It is shown that the small-scale Rossby waves in a shallow rotating fluid placed in a gravitational field can generate large-scale zonal flows by means of a two-stream-like mechanism. This mechanism is revealed under the conditions when the Lighthill instability criterion is not satisfied. The text was submitted by the authors in English.