Magnetic penetration depth in V3Si and LiTi2O4 measured by μSR

Muon spin relaxation (SR) studies have been performed in the normal spinel LiTi₂O₄ and the A-15 superconductor V₃Si to measure the magnetic penetration depth . The relaxation rate(T) 1/² in field-cooled measurements shows a sharp increase belowT _c followed by saturation at low temperatures in both systems. This feature implies an isotropic energy gap without anomalous zeros, and most likelys-wave pairing. The low temperature penetration depth (T 0) is determined to be 2100Å for LiTi₂O₄ and 1300Å for V₃Si respectively. Assuming a clean limit relation ^–2 n _s /m ^*, we derive the Fermi temperatureT _F n _s/ ^2/3 m ^* from the relaxation rate and the Sommerfeld constant asT _F ^3/4–1/4. Unlike conventional superconductors, both LiTi₂O₄ and V₃Si have a large ratio ofT _c /T _F 0.01, only slightly smaller than those ratios in more exotic superconductors.We thank C. Ballard and K. Hoyle for technical assistance. Work at Columbia University is supported by NSF Grant No. DMR-89-13784 and Packard Foundation (YJU). Ames Laboratory is operated for the U. S. Department of Energy by Iowa State University under Contract No. W-7405-Eng-82. Work at Ames was supported by the Director for Energy Research, Office of Basic Energy Sciences.     

Synthesis and characterization of TiO2/Ag/polymer ternary nanoparticles via surface-initiated atom transfer radical polymerization

We report on the novel ternary hybrid materials consisting of semiconductor (TiO₂), metal (Ag) and polymer (poly(oxyethylene methacrylate) (POEM)). First, a hydrophilic polymer, i.e. POEM, was grafted from TiO₂ nanoparticles via the surface-initiated atom transfer radical polymerization (ATRP) technique. These TiO₂-POEM brush nanoparticles were used to template the formation of Ag nanoparticles by introduction of a AgCF₃SO₃ precursor and a NaBH₄ aqueous solution for reduction process. Successful grafting of polymeric chains from the surface of TiO₂ nanoparticles and the in situ formation of Ag nanoparticles within the polymeric chains were confirmed using transmission electron microscopy (TEM), UV-vis spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). FT-IR spectroscopy also revealed the specific interaction of Ag nanoparticles with the CO groups of POEM brushes. This study presents a simple route for the in situ synthesis of both metal and polymer confined within the semiconductor, producing ternary hybrid inorganic-organic nanomaterials.     

Three-dimensional photon counting integral imaging using moving array lens technique

In this Letter, we present three-dimensional (3D) photon counting integral imaging using the moving array-lens technique (MALT) to improve the visualization of a reconstructed 3D scene. In 3D scene reconstruction of photon counting integral imaging, various techniques such as maximum likelihood estimation may be used. However, the visual quality depends on the number of scene photons or detector pixels activated by photons. We show that MALT may improve the viewing resolution of integral imaging for reconstructed 3D scene under photon-starved conditions.     

First observation of B(s)(0) → J/ψη and B(s)(0) → J/ψη'

We report first observations of B(s)(0) → J/ψη and B(s)(0) → J/ψη'. The results are obtained from 121.4 fb(-1) of data collected at the Υ(5S) resonance with the Belle detector at the KEKB e+ e- collider. We obtain the branching fractions B(B(s)(0) → J/ψη)=[5.10±0.50(stat)±0.25(syst)(-0.79)(+1.14)(N(B(s)(*) B(s)(*))]×10(-4), and B(B(s)(0) → J/ψη')=[3.71±0.61(stat)±0.18(syst)(-0.57)(+0.83)(N(B(s)(*) B(s)(*))]×10(-4). The ratio of the two branching fractions is measured to be (B(B(s) → J/ψη'))/(B(B(s) → J/ψη))=0.73±0.14(stat)±0.02(syst).     

Differences in Self-Rated, Perceived, and Acoustic Voice Qualities Between High- and Low-Fatigue Groups

Objectives

The present study was performed to examine which factors among self-rated scales, perceptual evaluations, and acoustic parameters, calculated from sustained vowels, are reliable indicators of physical and mental fatigues.

Methods

A total of 73 volunteers (male:female, 52:21), aged 19–24 years, were enrolled in this study. We defined the high- and low-fatigue groups using the Chalder Fatigue Scale score. For assessment of self-rated symptoms, each subject was asked to complete Voice Handicap Index (VHI) and Voice Rating Scale (VRS). For perceptual evaluations, three clinicians assessed each subject’s vocal quality on the Grade, Roughness, Breathiness, Asthenia, Strain Scale. For acoustic analysis, each subject was asked to produce sustained vowels /a/, /e/, /i/, /o/, and /u/ for 3 seconds. Then, the habitual fundamental frequency (F₀), jitter, shimmer, F₀ tremor, mean F₀, standard deviation of F₀, maximum F₀, minimum F₀, normalized noise energy, harmonic-to-noise ratio (HNR), signal-to-noise ratio (SNR), amplitude tremor, and ratio within 2–4 kHz were calculated using Dr. Speech software.

Results

In men, VHI, VRS, F₀ tremor, shimmer, HNR, SNR, and amplitude tremor were related to mental fatigue. In women, only VHI was related to physical fatigue, and none of the acoustic parameters was related to the fatigue score. Perceptual evaluations were not related to fatigue in men or women.

Conclusions

These findings suggest that self-rated symptoms and acoustic parameters related to voice quality are indicative of mental fatigue, and these features are prominent in men.     

Forming the graded-refractive-index antireflection layers on light-emitting diodes to enhance the light extraction

Distributed antireflection (AR) layers with different composition ratios of ITO and SiO(2) formed on an ITO electrode of GaN-based LEDs provide substantial enhancement in light-extraction efficiency. By using the coradio frequency magnetron sputtering deposition, four 50 nm thick AR layers with graduated refractive indices were fabricated. The effect of the AR layers on enhancing the efficiency of the LED device was analyzed by electroluminescence (EL) and I-V measurements. As a result, the EL intensity of the LED device grown on the patterned sapphire substrate with AR layers was increased by up to 13% compared to the conventional patterned sapphire substrate-applied LED device without AR layers at a drive current of 20 mA. The AR layers on top of the LED device gradually changed the refractive indices between ITO (n=2.1) and air (n=1.0), which minimized the total internal reflection of generated light. And no degradation in the electrical characteristic of the LEDs was observed according to the I-V measurements.     

Spin gapless semiconductor like Ti2MnAl film as a new candidate for spintronics application

A novel Heusler ferrimagnet Ti₂MnAl film has been grown on Si(001) substrate using magnetron sputtering. Characteristics of its magnetic and transport properties reveal the spin‐gapless‐semiconductor (SGS) nature of the stoichiometric Ti₂MnAl, in agreement with theoretical prediction. The as‐grown SGS‐like Ti₂MnAl film demonstrated high Curie temperature, nearly compensated ferrimagnetic properties with small coercivity and low magnetization. It also showed semiconductor‐like behavior at room temperature allowing good compatibility with commercial Si‐based semiconductor. In this regards, Ti₂MnAl film is a potential candidate material for spintronics application, especially for the minimization of energy consumption of device. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Memory characteristics of platinum nanoparticle-embedded MOS capacitors

The capacitance characteristics of platinum nanoparticle (NP)-embedded metal–oxide–semiconductor (MOS) capacitors with gate Al₂O₃ layers are studied in this work. The capacitance versus voltage (C–V) curves obtained for a representative MOS capacitor exhibit flat-band voltage shifts, demonstrating the presence of charge storages in the platinum NPs. The counterclockwise hysteresis and flat-band voltage shift, observed from the C–V curves imply that electrons are stored in a floating gate layer consisting of the platinum NPs present between the tunneling and control oxide layers in the MOS capacitor and that these stored electrons originate from the Si substrate. Moreover, the charge remains versus time curve for the platinum NP-embedded MOS capacitor is investigated in this work.