Magneto-optical imaging of polycrystalline FeTe1−xSex prepared at various conditions

We have prepared high-quality polycrystalline FeTe_1?xSe_x by sintering at different temperatures and characterized their structural and magnetic properties with X-ray diffraction, magnetization measurements, and magneto-optical imaging. The intragranular J_c was estimated to be 5 × 10⁴ A/cm², which is smaller than the single crystal, but still in the range for practical applications.     

All-optical cascaded laser wakefield accelerator using ionization-induced injection

We report on near-GeV electron beam generation from an all-optical cascaded laser wakefield accelerator (LWFA). Electron injection and acceleration are successfully separated and controlled in different LWFA stages by employing two gas cells filled with a He/O2 mixture and pure He gas, respectively. Electrons with a Maxwellian spectrum, generated from the first LWFA assisted by ionization-induced injection, were seeded into the second LWFA with a 3-mm-thick gas cell and accelerated to be a 0.8-GeV quasimonoenergetic electron beam, corresponding to an acceleration gradient of 187 GV/m. The demonstrated scheme paves the way towards the multi-GeV laser accelerators.     

Intense terahertz emission from undoped GaAs/n-type GaAs and?InAs/AlSb structures grown on Si substrates in the transmission-geometry excitation

Intense terahertz radiation was generated from femtosecond laser-irradiated InAs and GaAs layers on Si substrates. Results show that InAs/Si and GaAs/Si films can be excited in reflection and transmission geometries. The InAs/Si film exhibited weaker emission for both excitation cases but it will be more feasible as a spectroscopic THz source due to the absence of complex spectral features in its emission spectrum. The GaAs/Si emission is characterized by Fabry?CPerot oscillations but it is 90% of that of p-InAs bulk crystal emission intensity in the reflection geometry. Excitation fluence measurements showed that the InAs/Si film saturates easily due to the laser??s shallow penetration depth in InAs.     

Abilities of Antioxidants to Eliminate the Peroxyl Radical Derived from 2,2′-Azobis(2-Amidinopropane) Dihydrochloride (AAPH)

Electron spin resonance (ESR) of 5-(2,2-dimethyl-1,3-propoxy cyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO) spin adducts of free radicals derived from the UV irradiation of 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) under rapid scanning condition was examined. The ESR signal obtained was the superposition of two spectra, the spin adduct of the alkoxyl radical [CYPMPO-ORa, Ra = C(CH₃)₂-C(⁺NH₂Cl^?)NH₂] and the peroxyl radical (CYPMPO-OORa). The decay rate of CYPMPO-OORa was 8,400 times that of CYPMPO-ORa. The order of the k _SB/k _ST values (the slope of the Stern–Volmer’s plot) for the peroxyl radical (RaOO·) was l-ascorbic acid > caffeic acid > rutin ~ Trolox ~ (+)-catechin ~ glutathione (reduced), which was almost the same order as that for the alkoxyl radical (RaO·). Though the k _SB/k _ST value of each antioxidant for the peroxyl radical was about half of that for the alkoxyl radical, the ratios of the values of antioxidants to that of trolox (the relative ORAC values) were almost the same between the peroxyl and alkoxyl radicals. The relative oxygen radical absorbance capacity (ORAC) values of polyphenols estimated by the ORAC-ESR assay using both peroxyl and alkoxyl radicals were smaller than those by the ORAC-FL assay.     

Superheated water chromatography of low molecular weight polyethylene glycols with ultraviolet detection.

Superheated water chromatography (SWC) with ultraviolet detection was applied to the separation of low molecular weight polyethylene glycols (PEGs). PEG oligomers could be detected sensitively when the detection wavelength was set at 190 nm. The effect of column temperature on the separation of PEG oligomers was investigated. The elution time of all PEG oligomers decreased with increase in the column temperature; linear relationships were obtained between ln k and 1/T. A temperature-programmed SWC separation enabled the baseline separation of a PEG 200 sample within 50 min.     

Negative ion photoelectron spectroscopy of 2,2’-bithiophene cluster anions, (2T)n - (n = 1–100)

Cluster anions of 2,2’-bithiophene, (2T)_n^-, were produced up to n ∼500 in the gas-phase. The energetics of the excess electron in the (2T)_n^- clusters with n =1-100 were explored by negative ion photoelectron spectroscopy. When the vertical detachment energies (VDEs) obtained from the photoelectron spectra were analyzed by a plot against n^-1/3, it has been revealed that the excess electron trapping level thus extrapolated is located at ∼0.8 eV below the conduction band minimum (i.e. LUMO) of the 2T thin film. The large slope of the VDEs vs. n^-1/3 plot suggests that the neutral 2T molecules surrounding the anion core take non-planar twisted conformations with permanent dipole moments, resulting in the exceedingly deep trapping of the excess electron in the 2T cluster anions.     

UV-Laser Ablation Spectroscopy in Element Analysis of Solid Surface

Laser ablation for the atomic emission spectroscopy of a glass sample is studied using pulsed UV laser systems and the effect of the laser wavelength is investigated. The threshold fluence for ablation is decreased and the detection sensitivity is improved for shorter wavelengths. Furthermore, very thin (less than 1 nm/shot) surface slicing is possible at a wavelength as short as 193 nm. Polymers also show good ablation characteristics. Improvement of sensitivity and spatial resolution by using shorter wavelength laser ablation is discussed for Na detection in a glass sample.     

Preparation and Water Droplet Sliding Properties of Transparent Hydrophobic Polymer Coating by Molecular Design for Self-Organization

Transparent hydrophobic polymer coating was prepared from methacrylate copolymer with molecular modeling in order to improve hydrophobicity and durability. Organic-inorganic hybridization improved the durability of the thin films. Furthermore the control of hydrophobicity and water droplet sliding properties of the flat coating was successfully performed. Water droplet sliding angle depended on the chemical structure of the materials, not on the hydrophobicity, while sliding motion simply depended on the hydrophobicity.