Synthesis of Furoxans (1,2,5‐oxadiazole 2‐oxides) from Styrenes and Nitrosonium Tetrafluoroborate in Non‐Acidic Media and Mechanistic Study

Diverse furoxans (1,2,5‐oxadiazole 2‐oxides) were synthesized from the corresponding styrenes using nitrosonium tetrafluoroborate as the nitrosation reagent in pyridine (basic media) or dichloromethane (neutral media). Acid‐sensitive functional groups were tolerated under these conditions. The probable reaction mechanism was elucidated. The experimental results support an ionic reaction pathway in contrast to the conventional acidic conditions with a radical mechanism.     

Reaction of calcium and phosphate ions with titanium,zirconium, niobium,and tantalum

To understand the bone formation ability of constituent metal elements of new titanium alloys, titanium, zirconium, niobium, and tantalum, these metals were immersed in various electrolytes containing calcium and/or phosphate ions and characterized using X‐ray photoelectron spectroscopy. In addition, cathodic polarization of the metals in the electrolytes was performed to evaluate the stability of the surface oxide films on the metals in the electrolyte. The calcium phosphate layer formed on Ti in electrolytes containing calcium and phosphate ions is relatively protective against mass transfer throughout the layer. However, the zirconium phosphate layer formed on Zr is much more protective and stable than that on Ti. Therefore, calcium ions were not incorporated. Nb and Ta formed calcium phosphate, but the amount was smaller than that in Ti, because phosphates formed on Nb and Ta are somewhat protective and the incorporation of the calcium ion is inhibited. Titanium played the most important role in forming calcium phosphate, while zirconium inhibited the formation of calcium phosphate on titanium alloys. The control of bone formation is feasible by the design of titanium alloys. Copyright © 2015 John Wiley & Sons, Ltd.     

Total synthesis of (-)-brevisin: a concise synthesis of a new marine polycyclic ether

The first and highly efficient total synthesis of (-)-brevisin has been achieved. The title compound was synthesized in only 29 steps (longest linear sequence) from commercially available starting materials. The synthesis provided over 70 mg of a marine polycyclic ether compound.     

All organic DFB laser enhanced by intermediate high refractive index polymer layer

Performances of a distributed feedback (DFB) organic dye laser were enhanced by introducing an intermediate high refractive index layer of poly(N-vinylcarbazole) (PVCz) laminated between a glass substrate and a laser dye doped active polymer layer. The active layer is consisted of rhodamine 6G and cellulose acetate (CA). Introduction of an intermediate layer allows a single mode lasing. Slope efficiencies of 2.2 and 4.7% and thresholds of 0.3 and 0.14 mJ/cm²/pulse were measured for the waveguides with 1.7 and 3.4 μm active layers, respectively. Furthermore, permanent relief grating on an intermediate layer gave rise to the reduction of the threshold. With increasing in amplitude of the relief grating from 20 to 45 nm, lasing threshold was reduced from 0.18 to 0.04 mJ/cm²/pulse for the waveguide with 1.7 μm active layer. The slope efficiency increased from 3.5 to 4.2%.     

Optical band gap of semiconductive type II Si clathrate purified by centrifugation

The optical properties of Si clathrate, which is believed to have potential as a new Si-based material for optical devices, were investigated in this study. Si clathrates with type II structure (Na_xSi₁₃₆) with low Na content (x = 1.3, 2.0) were synthesized by thermal decomposition of NaSi. The synthesized samples were purified by centrifugation using a solution of CH₂Br₂–C₂Cl₄ to remove impurities. Using the obtained high purity samples (Na_1.3Si₁₃₆, 93 wt.%; Na_2.0Si₁₃₆, 90 wt.%), the optical absorption spectra of Na_xSi₁₃₆ were clarified, for the first time, from diffuse reflection measurements. The inclusion of Na in Si₁₃₆ was found to cause free carrier absorption in the infrared region but had little effect on the fundamental absorption edge found in the visible region.     

Twofold spontaneous symmetry breaking in the heavy-fermion superconductor UPt3

The field-orientation dependent thermal conductivity of the heavy-fermion superconductor UPt3 was measured down to very low temperatures and under magnetic fields throughout the distinct superconducting phases: B and C phases. In the C phase, a striking twofold oscillation of the thermal conductivity within the basal plane is resolved reflecting the superconducting gap structure with a line of node along the a axis. Moreover, we find an abrupt vanishing of the oscillation across a transition to the B phase, as a clear indication of a change of gap symmetries. We also identify extra two line nodes below and above the equator in both B and C phases. From these results together with the symmetry consideration, the gap function of UPt3 is determined as a E(1u) representation characterized by a combination of two line nodes at the tropics and point nodes at the poles.     

Evaluation of target photon dose mixed in mono-energetic neutron fields using 7Li(p,n)7Be reaction

Target photons mixed in the 144, 250 and 565 keV mono-energetic neutron calibration fields were measured using a cylindrical NaI(Tl) detector with 7.62 cm both in diameter and in length. The ambient dose equivalent H*(10) of the photons was evaluated by applying the “G(E) function” to the measured pulse height spectrum. Neutrons induce photons by nuclear reactions in the NaI(Tl) detector and affect the pulse height spectrum. In order to eliminate the influence of these neutron events, the time-of-flight technique was applied with operating the accelerator in the pulse mode. The ratios by the ambient dose equivalent H*(10) of the photons to the 144, 250 and 565 keV neutrons were evaluated to be 3.3%, 4.7% and 0.9%, respectively. Although high energy photons ranging from 6 to 7 MeV are emitted by the ¹⁹F(p,αγ)¹⁶O reactions, the dose of the target photons is low enough to calibrate neutron dosemeters except for ones with high sensitivity to the photons.     

Photorefractive performance of poly(triarylamine)‐Based polymer composites: An approach from the photoconductive properties

Photorefractive (PR) and photoconductive properties of methyl‐substituted poly(triarylamine) (PTAA) based PR composite is presented. PR composite consisted of PTAA, piperidinodicyanostyrene, (2,4,6‐trimethylphenyl)diphenylamine, and [6,6]‐phenyl‐C61‐butyric acid methyl ester. Photocurrent is simultaneously measured when a transient degenerate four wave mixing is recorded. Diffraction efficiency of 16.6%, response time of 5 ms, and sensitivity of 43 cm² J^?1 are measured under an applied field of 45 V μm^?1 and 632.8 nm illumination with the intensity of 1.5 W cm^?2. Response time of 10.2 ms with diffraction efficiency of 47.0% is obtained under a same field and 532 nm illumination with the intensity of 0.427 W cm^?2. Higher diffraction and faster response is due to the large photocurrent in the order of hundreds μA measured. The resultant trap density is in the order of 10¹⁴ cm^?3. Thus, space–charge field less than 1 V μm^?1 is evaluated, which limits the PR response. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 502–508     

Oberflächeneigenschaften von energiereichen festen Körpern. I. Bestimmung der Dispersionskomponenten der freien Oberflächenenergie von Glimmer und die Adhäsionsenergie an Wasser und n-Alkane

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