Composition dependent phase transformation of Pt0.5−x Mn0.5+x from A1 to L10 phase

Pt_0.5−x Mn_0.5+x films were prepared by sputtering deposition of Pt foil and Mn target to study the order-disorder transition from a thermodynamic metastable fcc (A1) phase to L1₀ phase. Both Differential Scanning Calorimetry and High Temperature X-Ray Diffraction studies showed the phase transformation from fcc to the L1₀ structure for the Pt_0.50Mn_0.50 and Pt_0.40Mn_0.60 samples but along completely different kinetic paths. A composition dependent phase transformation was observed by comprehensive Differential Scanning Calorimetry studies on a series of Pt_0.5−x Mn_0.5+x samples. The changes of the lattice parameter and the cell volume of L1₀ Pt_0.5−x Mn_0.5+x as a function of composition suggest that the anti-site is not the dominant point defect for L1₀ Pt_0.5−x Mn_0.5+x .     

Physical characteristics of polyimide films for flexible sensors

Physical characteristics of polyimide films, including optical, micro/nano mechanical, and thermophysical characteristics were investigated using a photometric, a nanoindentation, and a thermomechanical analyzer for applications in flexible sensors. Experimental results show that UV light cannot transmit into the polyimide films. The transmittances, with a maximum of about 86%, at VIS and near IR lights decrease with increasing PI film thicknesses. The mechanical characteristics were determined using tensile, bending moment, and nanoindentation testing. The stress–strain curve approximated bilinear characteristics, the load–unload bending moment exhibited hysteresis, and nanoindentation generated elastic energy dissipation in the loading–unloading region. Nanoindentation showed an almost uniform hardness and a reduced Young’s modulus of about 0.181±0.03 and 3.21±0.06 GPa, respectively, when the penetrating depth was more than about 2 μm. Thermophysical characteristics were greatly influenced on 8.3 and 25 μm specimens due to the higher relaxation of thin PI films. The thermal expansion remained steady when the thickness was over 50 μm. The results show that PI films have potential in flexible sensing and higher temperature fabrication.     

Green approaches via nanocatalysis with nanoporous materials: Functionalization of mesoporous materials for single site catalysis

Among the various green keys, catalysis, especially using heterogeneous catalysts, has been powerfully applied to achieve greener chemical processes. Here are presented nanoporous materials which have mesoporosity with the functional groups on the inner pore walls. The materials were synthesized via a rather greener process, such as microwave synthesis, and over these nanocatalysts some of the green chemical reactions were carried out with high activities and selectivities. Cobalt species has been successfully functionalized and stabilized as a Co(III) complex onto SBA-15 support and proven to be an active catalyst in alkylaromatic oxidation with molecular oxygen, styrene epoxidation with tert-butyl hydroperoxide (TBHP), and allylic oxidation of cycloolefins with H₂O₂. Short-channeled amino-functionalized SBA-15 catalyst with hexagonal plate morphology was synthesized directly by using microwave synthesis from the co-condensation of aminopropyl triethoxysilane (APTES) and sodium metasilicate under a strong acidic condition. The catalyst showed high catalytic activity in liquid-phase Knoevenagel condensation reactions, due to easy diffusion and mass transfer of substrates into the short mesopore channel. The HO₃S–SBA-15 was prepared by grafting of mercaptopropyl trimethoxysilane onto the calcined mesoporous silica surface and subsequently oxidized with H₂O₂. The resulting catalyst was applied as a Bronsted solid-acid catalyst for the esterification of oleic acid with methanol.     

Formation of pancakelike Ising domains and giant magnetic coercivity in ferrimagnetic LuFe2O4

We have studied quasi-two-dimensional multiferroic LuFe2O4 with strong charge-spin-lattice coupling, in which low-temperature coercivity approaches an extraordinary value of 9 T in single crystals. The enhancement of the coercivity is connected to the collective freezing of nanoscale pancakelike ferrimagnetic domains with large uniaxial magnetic anisotropy ("Ising pancakes"). Our results suggest that collective freezing in low-dimensional magnets with large uniaxial anisotropy provides an effective mechanism to achieve enhanced coercivity. This observation may help identify novel approaches for synthesis of magnets with enhanced properties.     

Spectral-domain optical coherence phase microscopy for quantitative phase-contrast imaging

We describe a novel microscopy technique for quantitative phase-contrast imaging of a transparent specimen. The technique is based on depth-resolved phase information provided by common path spectral-domain optical coherence tomography and can measure minute phase variations caused by changes in refractive index and thickness inside the specimen. We demonstrate subnanometer level path-length sensitivity and present images obtained on reflection from a known phase object and human epithelial cheek cells.     

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.     

Neutral Bremsstrahlung radiation of Ne,Ar and O

The neutral Bremsstrahlung cross-sections of Ne, Ar and atomic oxygen around the 3 and 10μ wavelength regions were measured in a high temperature plasma generated in a shock tube. The results were generally a factor of three higher than the theoretical values calculated by Geltman. Agreement with the experimental results of Taylor and Caledonia around 3μ was good except for the case of Ne. The cross-sections around 10μ are the first measurements in this wavelength region. Enhanced radiation due to atomic line emission on top of the Bremsstrahlung continuum, as predicted by Hyman was observed around 7.44μ.     

Optical and acoustic study of nucleation and growth of bubbles at a liquid-solid interface induced by nanosecond-pulsed-laser heating

The dynamics of liquid-vapor phase-change in the nanosecond time-scale induced by pulsed-laser heating of a liquid on a solid sample is studied by means of optical reflectance and scattering measurements, and the piezoelectric detection technique. The liquids studied include water, ethanol, methanol, IsoproPropyl Alcohol (IPA), and mixtures of water and IPA. The threshold fluence for nucleation is determined with high accuracy using the optical and acoustic signals. Heat diffusion calculations performed for the threshold fluences indicate that the liquids are sufficiently superheated before nucleation sets on. The transient optical reflectance signal is analyzed by an effective-medium theory to provide bubble-growth kinetics, so that the bubble-growth velocity for the test liquids could be estimated. In addition, it is observed that, following the thermally induced nucleation, repetitive acoustic cavitation at the surface of the solid sample occurs, with a time interval related to the speed of sound in the liquid.