Stopping of crosslinking reaction in a PDMS polymer at the gel point

Summary A method has been developed to stop the crosslinking reaction of a polydimethylsiloxane system without disturbing the state of the sample. Oscillatory shear experiments on samples just before and just beyond the gelation point demonstrated the transition of the material from a viscoelastic liquid to a viscoelastic solid. At the gel point the loss modulus and the storage modulus were found to be identical over several decades of frequency and for temperatures ranging between -50°C and +180°C. Both moduli were proportional to the square root of the frequency.     

The complete sequence of a 6794 bp segment located on the right arm of chromosome II of Saccharomyces cerevisiae. Finding of a putative dUTPase in a yeast

The DNA sequence of a 6794 bp fragment located at about 100 kb from the right telomere of chromosome II from Saccharomyces cerevisiae has been determined. Sequence analysis reveals five open reading frames. One is the ARO4 gene encoding the 3-deoxy-D -arabinoheptulosonate 7-phosphate synthase. Another presents strong homology with the S5 ribosomal protein from bacteria. The open reading frame YBR1705 shows significant homology with dUTPase, suggesting for the first time the existence of such an enzyme in S. cerevisiae.     

Self-Supervised Monocular Depth and Motion Learning in Dynamic Scenes: Semantic Prior to Rescue

International Journal of Computer Vision - We introduce an end-to-end joint training framework that explicitly models 6-DoF motion of multiple dynamic objects, ego-motion, and depth in a monocular...     

An Energy‐Conserving Hair Reflectance Model

We present a reflectance model for dielectric cylinders with rough surfaces such as human hair fibers. Our model is energy conserving and can evaluate arbitrarily many orders of internal reflection. Accounting for compression and contraction of specular cones produces a new longitudinal scattering function which is non‐Gaussian and includes an off‐specular peak. Accounting for roughness in the azimuthal direction leads to an integral across the hair fiber which is efficiently evaluated using a Gaussian quadrature. Solving cubic equations is avoided, caustics are included in the model in a consistent fashion, and more accurate colors are predicted by considering many internal pathways.     

QJRN-114膨润土气垫式泥水平衡盾构机

法国NFM技术公司 Francois Janneau膨润土气垫式泥水加压平衡盾构机是目前世界上公认的最先进的穿越江河的地下隧道工程施工设备,适用于开挖不稳定或静水压比较高的含水地层.武汉长江隧道工程就选用两台QJRN-114膨润土气垫式泥水平衡盾构机.该设备采用法国NFM技术公司的技术,由沈阳重型机械集团有限责任公司与法国NFM技术公司联合设计并合作制造.下面就该设备的构成、工作原理、性能参数和结构特点做简要介绍.……     

Subchronic and Reproductive/Developmental (Screening Level) Toxicity of Complexation Products of Iron Trichloride and Sodium Tartrate (FemTA)

A complexation/reaction product, termed FemTA, of sodium tartrate [D(–)‐ and L(+)‐tartaric acid and mesotartaric acid], sodium hydroxide, and iron trichloride may have use as an anticaking agent in salt preparations. FemTA is composed of about 4% sodium tartrate, approximately 10% mesotartaric acid, approximately 7% chloride, approximately 4% iron, approximately 7% sodium, approximately 0.3% sodium oxalate, and approximately 65% water. FemTA was tested in a 90‐d oral toxicity study, which included a screening level reproductive/developmental toxicity phase, in Harlan Wistar rats. FemTA was administered by oral gavage at 500, 1000, and 2000 mg/kg body weight/d prior to and during mating, or about 20, 40, or 80 mg of iron/kg body weight/d, such that males received 90/91 d of treatment and females 104 to 109 d. Treatment was associated with inflammatory lesions of the lower GI tract at the mid‐ and high‐dose levels, increased liver and kidney weights, increased serum bile acids and blood urea nitrogen, decreased chloride, and changes to hematological parameters consistent with inflammation. The effects were considered the result of iron overload. There were no effects on reproductive/developmental toxicity parameters. The no‐observed‐adverse‐effect level (NOAEL), based on gastrointestinal tract effects was 500 mg/kg body weight/d. The NOAEL for reproductive/developmental toxicity was 2000 mg/kg body weight/d, the highest dose tested.     

Selective Ring-Opening of Methylcyclopentane Over Titania-Supported Monometallic (Pt, Ir) and Bimetallic (Pt–Ir) Catalysts

An investigation of the selective ring-opening of methylcyclopentane (MCP) was conducted for the first time on Pt/TiO₂, Ir/TiO₂ and Pt?CIr/TiO₂ catalysts with low amounts of noble metals (0.5?wt%) over a temperature range of 180?C400?°C under hydrogen at atmospheric pressure. The catalysts were prepared by impregnation or co-impregnation and characterized by different physico-chemical techniques, including SEM, XRD, H₂-TPR, N₂-sorption, TEM and elemental analysis. The metallic particles were highly dispersed on the TiO₂ support at isodispersion of ~1?nm. The particles exhibited icosahedral Mackay structures limited by (111) planes. The catalytic results show that the activity in the MCP was strongly influenced by the intrinsic nature of the metal and by the temperature. The most active catalyst was Ir/TiO₂. The order of the reactivity as a function of the temperature and total conversion was Ir/TiO₂ 180?°C (???=?2?%)?>?Pt?CIr/TiO₂ 220?°C (???=?27.8?%)?>?Pt/TiO₂ 260?°C (???=?9.9?%). Under these conditions, all of the catalysts exhibited the ability to open the ring of MCP with an atom economy, without unwanted products of cracking and ring-enlargement reactions. The synergy between Pt?CIr bimetallic particles was assessed by the total conversion of MCP, whereas the ring-opening results indicated that the reaction took place on Ir sites. These results suggest that the bimetallic catalyst contained separate entities of two metals. Increased reaction temperatures led to reduced reaction selectivity with respect to ring-opening of MCP versus the cracking side reaction.     

Vertical Transport in GaN/AlGaN Resonant Tunneling Diodes and Superlattices

Using the transfer matrix formalism, we have theoretically studied the vertical ballistic transport in GaN/AlGaN resonant tunneling diodes (RTDs) and superlattices with a small number of periods. We have calculated the transmission probability versus the longitudinal electron energy (T–E) and the current density–voltage (J–V) characteristics. Calculations of both T–E and J–V characteristics have been performed for different Al contents in the barriers. The asymmetry effects due to the internal electric field in the barriers are discussed. Applied to the RTD structure, our calculations demonstrate: (i) the increase of the peak-to-valley ratio of the negative differential resistance (NDR) with increasing Al content in the barriers, (ii) the dependence of the J–V resonance values on the current direction, and (iii) the asymmetry of the NDR with respect to the current direction due to the huge internal electric field in the structure. In the case of multiple quantum well structure (MQWS), the calculation results confirm the same trends as in the RTD case when the Al content is varied. In spite of the fact that it is more difficult to analyze the results in the case of MQWS, the obtained calculations demonstrate the applicability of the used model and of the numerical method to study GaN/AlGaN devices based on quantum well (QW) heterostructures. Furthermore, a design of an optimized 7QW structure operating symmetrically whatever the direction of the applied voltage is presented.     

The role of gradation on the improvement of effective properties of highly heterogeneous multilayered thermoviscoplastic materials under simple shearing

In this paper we study the role of the gradation on the effective properties of heterogeneous multilayered thermoviscoplastic materials with discontinuous properties under simple shearing. Starting from the bimetallic multilayered material, we produce a new multicomponent material with discontinuous gradation having improved effective properties. We also present the effective properties of the continuously graded material functionally graded material (FGM). The main results are illustrated with some numerical examples.