Synthesis,structure, and electrochemistry of Ag-modified LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> cathode materials for lithium-ion batteries

The composite of silver-modified lithium manganese oxide were prepared using thermal decomposition method of different mole ratio. Structural characterization was carried out by X-ray diffraction (XRD). XRD analysis revealed different patterns as the content of the dopant in the spinel increases. Phase analysis shows that Ag particles were dispersed on the LiMn₂O₄ surface instead of entering the spinel structure. On the other hand, the electrochemical behavior of cathode powder was examined by using two-electrode test cells consisting of a cathode, metallic lithium as anode, and a solid polymer electrolyte of 0.87PEO-0.13LiCF₃SO₃-0.10DBP. According to the electrochemical tests results, the influence of the Ag additive content on the electrochemical properties of Ag/LiMn₂O₄ composites is clearly shown.     

Interpretation of transport measurements in ZnO-thin films

In order to interpret results of temperature dependent Hall measurements in heteroepitaxial ZnO-thin films, we adopted a multilayer conductivity model considering carrier-transport through the interfacial layer with degenerate electron gas as well as the upper part of ZnO layers with lower conductivity. This model was applied to the temperature dependence of the carrier concentration and mobility measured by Hall effect in a ZnO-layer grown on c-sapphire with conventional high-temperature MgO and low-temperature ZnO buffer. We also compared our results with the results of maximum entropy mobility-spectrum analysis (MEMSA). The formation of the highly conductive interfacial layer was explained by analysis of transmission electron microscopy (TEM) images taken from similar layers.     

High-energy femtosecond photonic crystal fiber laser

We report the generation of high-energy high-peak power pulses in an all-normal dispersion fiber laser featuring large-mode-area photonic crystal fibers. The self-starting chirped-pulse fiber oscillator delivers 11 W of average power at 15.5 MHz repetition rate, resulting in 710 nJ of pulse energy. The output pulses are dechirped outside the cavity from 7 ps to nearly transform-limited duration of 300 fs, leading to pulse peak powers as high as 1.9 MW. Numerical simulations reveal that pulse shaping is dominated by the amplitude modulation and spectral filtering provided by a resonant semiconductor saturable absorber.     

Action Spectroscopy on Dense Samples of Photosynthetic Reaction Centers of Rhodobacter sphaeroides WT Based on Nanosecond Laser-Flash 13C Photo-CIDNP MAS NMR

Photochemically induced dynamic nuclear polarization magic-angle spinning nuclear magnetic resonance (photo-CIDNP MAS NMR) allows for the investigation of the electronic structure of the photochemical machinery of photosynthetic reaction centers (RCs) at atomic resolution. For such experiments, either continuous radiation from white xenon lamps or green laser pulses are applied to optically dense samples. In order to explore their optical properties, optically thick samples of isolated and quinone-removed RCs of the purple bacteria of Rhodobacter sphaeroides wild type are studied by nanosecond laser-flash ¹³C photo-CIDNP MAS NMR using excitation wavelengths between 720 and 940 nm. Action spectra of both the transient nuclear polarization as well as the nuclear hyperpolarization, remaining in the electronic ground state at the end of the photocycle, are obtained. It is shown that the signal intensity is limited by the amount of accessible RCs and that the different mechanisms of the photo-CIDNP production rely on the same photophysical origin, which is the photocycle induced by one single photon.     

Vocal Fold Vibration and Phonation Start in Aspirated, Unaspirated, and Staccato Onset

Objectives/Hypotheses

Singers learn to produce well-controlled tone onsets by accurate synchronization of glottal adduction and buildup of subglottal pressure. Spectrographic analyses have shown that the higher spectrum partials are present also at the vowel onset in classically trained singers’ performances. Such partials are produced by a sharp discontinuity in the waveform of the transglottal airflow, presumably produced by vocal fold collision.

Study Design

After hearing a prompt series of a triad pattern, six singer subjects sang the same triad pattern on the vowel /i/ (1) preceded by an aspirated /p/, (2) preceded by an unaspirated /p/, and (3) without any preceding consonant in staccato.

Methods

Using high-speed imaging we examined the initiation of vocal fold vibration in aspirated and unaspirated productions of the consonant /p/ as well as in the staccato tones.

Results

The number vibrations failing to produce vocal fold collision were significantly higher in the aspirated /p/ than in the unaspirated /p/ and in the staccato tones. High frequency ripple in the audio waveform was significantly delayed in the aspirated /p/.

Conclusions

Initiation of vocal fold collision and the appearance of high-frequency ripple in the vowel /i/ are slightly delayed in aspirated productions of a preceding consonant /p/.     

Photocatalytic properties of Ta-doped TiO2

Ionics - This work reports the effect of tantalum (0.1–1&nbsp;at.% Ta) on the photocatalytic performance of TiO2 annealed at 1373 and 1673&nbsp;K in air. It was shown that addition of...     

Mössbauer study of the magnetocaloric compound AlFe<Subscript>2</Subscript><Emphasis Type="Bold">B</Emphasis><Subscript>2</Subscript>

Mössbauer spectroscopy in the ferromagnetic AlFe₂ B ₂ reveals T_c=299 K and shows good agreement with magnetic measurements. The crystals are plate-shaped. The flakes are found from X-ray diffraction to be in the crystallographic ac-plane in the orthorhombic system. The axes of the principle electric field gradient tensor are, by symmetry, colinear with the crystal a-, b- and c-axes. By using information about the quadrupole splitting and line asymmetry in the paramagnetic regime together with the quadrupole shift of the resonance lines in the ferromagnetic regime the magnetic hyperfine field direction is found to be in the ab-plane having an angle =40^° to the b-axis.     

Molecular dynamic studies of the solubility of sodium chloride: fast calculations using seed crystalline cluster probe

Theoretical predictions of solubility, typically accomplished by comparing the chemical potential of pure solid and solution, currently suffer from a lack of accuracy. We suggest an alternative method for predicting solubility based on molecular dynamics simulations of the behaviour of a small seed crystalline cluster probe in solutions of varying concentrations. The size dynamics of a properly chosen seed cluster that dissolves in unsaturated solutions and grows in size in supersaturated solutions is indicative of the saturation point. This approach is illustrated by its application to NaCl in water.