Residual stress relaxation in the core of optical fiber by CO(2) laser irradiation

We observed residual stress relaxation by CO(2) laser irradiation in the cores of optical fibers by direct stress measurement. It was demonstrated that the mechanical stress was fully relaxed by CO(2) laser irradiation and that the remaining stress in the core was thermal stress that was due to a mismatch of the thermal expansion coefficients of the fiber core and cladding. The net core stresses after relaxation were 17, 68, and 203 MPa in Ge-B-codoped fibers drawn at 0.53, 1.38, and 3.48 N, respectively. Changes in the refractive indices of the cores as a result of residual stress relaxation were also estimated.     

卵磷脂中PE及不同种类PC的高效液相色谱分析

卵磷脂具有重要的生理功能,是人体正常新陈代谢和健康生存不可少的物质,能改善治疗神经系统疾病,增强记忆力,防止心血管疾病等。在临床上卵磷脂的主要的用途是用于治疗动脉粥样硬化、脂肪肝、神经衰弱、营养不良及静脉注射脂肪乳的乳化剂、胆固醇结石的防治药物,引。美国、欧洲、日本等已将磷脂在临床上用于防治脑、心、肝、肿瘤等疾病。     

Enhanced reversible capacity of Li-S battery cathode based on graphene oxide

Lithium sulfur battery (LSB) offers several advantages such as very high energy density, low-cost, and environmental-friendliness. However, it suffers from serious degradation of its reversible capacity because of the dissolution of reaction intermediates, lithium polysulfides, into the electrolyte. To solve this limitation, there are many studies using graphene-based materials due to their excellent mechanical strength and high conductivity. Compared with graphene, graphene oxide (GO) contains various oxygen functional groups, which enhance the reaction with lithium polysulfides. Here, we investigated the positive effect of using GO mixed with carbon black on the performance of cathode in LSB. We have observed a smaller drop of capacity in GO mixed sulfur cathode. We further demonstrate that the mechanistic origin of reversibility improvement, as confirmed through CV and Raman spectra, can be explained by the stabilization of sulfur in lithium polysulfide intermediates by oxygen functional groups of GO to prevent dissolution. Our findings suggest that the use of graphene oxide-based cathode is a promising route to significantly improve the reversibility of current LSB.     

Double-Gyroid Network Morphology in Tapered Diblock Copolymers

We report the formation of a double-gyroid network morphology in normal-tapered poly(isoprene-b-isoprene/styrene-b-styrene) [P(I-IS-S)] and inverse-tapered poly(isoprene-b- styrene/isoprene-b-styrene) [P(I-SI-S)] diblock copolymers. Our tapered diblock copolymers with overall poly(styrene) volume fractions of 0.65 (normal-tapered) and 0.67 (inverse-tapered), and tapered regions comprising 30 volume percent of the total polymer, were shown to self-assemble into the double-gyroid network morphology through a combination of small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The block copolymers were synthesized by anionic polymerization, where the tapered region between the pure poly(isoprene) and poly(styrene) blocks was generated using a semi-batch feed with programmed syringe pumps. The overall composition of these tapered copolymers lies within the expected network-forming region for conventional poly(isoprene-b-styrene) [P(I-S)] diblock copolymers. Dynamic mechanical analysis (DMA) clearly demonstrated that the order-disorder transition temperatures (T(ODT)'s) of the network-forming tapered block copolymers were depressed when compared to the T(ODT) of their non-tapered counterpart, with the P(I-SI-S) showing the greater drop in T(ODT). These results indicate that it is possible to manipulate the copolymer composition profile between blocks in a diblock copolymer, allowing significant control over the T(ODT), while maintaining the ability to form complex network structures.     

Plasma-enhanced atomic layer deposition of Co using Co（MeCp）2 precursor

Cobalt（Co） thermal or plasma enhanced atomic layer deposition（PE-ALD） was investigated using a novel metal organic precursor,Co（MeCp）₂, and NH₃ or H₂ or their plasma as a reactant.The growth characteristics,electrical and microstructural properties were investigated.Especially, PE-ALD produced Co thin films at low growth temperature down to 100℃.Interestingly,the low temperature growth of Co films showed the formation of columnar structure at substrate temperature below 300℃.The growth characteristics and films properties of PE-ALD Co using bis（η-methylcyclopentadienyl） Co（Ⅱ）（Co（MeCp）₂） was compared with those of PE-ALD Co using other Cp based metal organic precursors, bis-cyclopentadienyl cobalt（II）（CoCP₂） and cyclopentadienyl isopropyl acetarrudinato-cobalt（Co（CpAMD））.     

Zinc-finger motif noncovalent interactions with double-stranded DNA characterized by negative-ion electrospray ionization mass spectrometry

A zinc-finger motif recognizes specific sequences on the double helical structure of DNA. This sequence recognition property offers great promise for various biotechnology applications. Accordingly, it is crucially important to characterize zinc-finger binding characteristics for further developments. Although the gel shift assay or phage display is traditionally used for determining the binding characteristics of zinc-fingers for double stranded DNA, in the present study we utilize electrospray ionization mass spectrometry as an advanced and convenient characterization tool because of the rich information it provides, and its quantitative sensitivity, operational simplicity, and no need for radioactive labeling. Here we demonstrate the use of negative-ion electrospray ionization mass spectrometry for competition-based quantitative comparison of the zinc-finger motif sequence specificity, stoichiometry, and metal ion dependence.     

Sensitive fluorescence assay of anthrax protective antigen with two new DNA aptamers and their binding properties

A homogeneous assay of the protective antigen in anthrax toxin is reported using two new PA-specific aptamers for selective and sensitive detection, based on reduction in the fluorescence emission according to the formation of the aptamer-PA ternary complex. PA at 1 nM was readily detected using OliGreen as a fluorophore in HEPES buffer. We also demonstrated that the PA detection could be performed in blood serum. The binding interaction between the aptamer and PA was strong enough to dehybridize double-stranded DNA paired completely with 12 bases at room temperature. Moreover, this fluorescence study revealed that the binding sites of the two aptamers were located differently on the PA protein. We believe our approach may lay the groundwork for the real-time detection of PA.     

Investigation of the signaling mechanism and verification of the performance of an electrochemical real-time PCR system based on the interaction of methylene blue with DNA

The operation of an electrochemical real-time PCR system, based on intercalative binding of methylene blue (MB) with dsDNA, has been demonstrated. PCR was performed on a fabricated electrode-patterned glass chip containing MB while recording the cathodic current peak by measuring the square wave voltammogram (SWV). The current peak signal was found to decrease with an increase in the PCR cycle number. This phenomenon was found to be mainly a consequence of the lower apparent diffusion rate of the MB-DNA complex (D(b) = 6.82 × 10(-6) cm(2) s(-1) with 612 bp dsDNA) as compared to that of free MB (D(f) = 5.06 × 10(-5) cm(2) s(-1)). Utilizing this signal changing mechanism, we successfully demonstrated the feasibility of an electrochemical real-time PCR system by accurately quantifying initial copy numbers of Chlamydia trachomatis DNA templates on a direct electrode chip. A standard calibration plot of the threshold cycle (C(t)) value versus the log of the input template quantity demonstrated reliable linearity and a good PCR efficiency (106%) that is comparable to that of a conventional TaqMan probe-based real time PCR. Finally, the system developed in this effort can be employed as a key technology for the achievement of point-of-care genetic diagnosis based on the electrochemical real-time PCR.     

Segregation of hydroxide ions to an ice surface

Hydroxide ions that are initially buried within an ice film segregate to the ice film surface at elevated temperatures. This process was observed by conducting experiments with an ice film constructed with a bottom H(2)O layer and an upper D(2)O layer, with an excess of hydroxide ions trapped at the H(2)O/D(2)O interface as they were generated by Na hydrolysis. The transport of hydroxide ions from the interfacial layer to the surface was examined as a function of time using a low energy sputtering method. The progress of the H/D exchange reaction in surface water molecules was also monitored with the Cs(+) reactive ion scattering technique. At 90 K, only a small portion of buried hydroxide ions moved to the surface in the form of OD(-) species. This was due to hydroxide transport via proton hopping through a D(2)O layer, 3 BL thick, in the surface region. At 135 K, at which point water self-diffusion is active in the ice film, the majority of the buried hydroxide ions segregated to the surface after ～1 h. Both OH(-) and OD(-) species were produced at the surface, at an OH(-)/OD(-) population ratio ≥1. Based on kinetic measurements for the transport of OH(-) and OD(-) species and the H/D exchange of surface water molecules, we concluded that the major transport channel for hydroxide ions in this regime is the migration of molecular hydroxide species. H/D exchange reactions also occur between surface hydroxide ions and water molecules. No evidence was observed for the occurrence of the hop-and-turn process at 135 K, although it is known as an important mechanism of proton transport in ice.     

Coupled magnetic cycloids in multiferroic TbMnO3 and Eu3/4Y1/4MnO3

Based on the detailed Mn L(2,3)-edge x-ray resonant scattering results, we report a new complexity in the magnetic order of multiferroic orthomangnites, which has been considered as the simple A-type cycloid order inducing ferroelectricity. The Dzyaloshinskii-Moriya interaction involved in the orthorhombic distortion brings on F-type canting from the A type, and the ordering type becomes the off-phase synchronized bc cycloid in TbMnO(3) or the tilted antiphase ab cycloid in Eu(3/4)Y(1/4)MnO(3). The F-type canting is responsible for the magnetic field-driven multiferroicity to weak ferromagnetism transition.