Alternating,all-trans polyenynes: Model compounds for poly(diacetylene)s with defined conjugation length

The syntheses of polyenynes as model compounds for poly(diacetylene)s (PDAs) are described. Variation of properties (UV–VIS, Raman, NMR and bond geometries) as a function of the chain length was investigated. After extrapolation to infinite chain length these data were compared to those for PDAs. From UV–VIS spectra a value of λ = 551 nm (2.25 eV) was calculated corresponding to the electronic transition of a single polyenyne chain. This energy is located at the low energy end of a yellow PDA solution spectrum. From Raman scattering v_(C?C) = 2108–2128 cm^?1 and v_(C?C) = 1505–1532 cm^?1 were calculated after extrapolation. Similarly sp-C¹³C NMR data yielded a shift of δ = 100 ppm. These data are almost identical to data known for yellow PDA solutions. Bond geometries are almost identical to those of poly(diacetylene)s and theoretical data.     

Rhizobium trifolii capsular polysaccharide: a novel biopolymer with striking physical properties

The physical properties of the capsular polysaccharide of Rhizobium Trifolii (CPS) were investigated. Viscosity measurements provided information about the hydrodynamic volume of single coils, the perturbation of solvent flow and the shear-thinning behaviour of concentrated solutions. Changes in chain geometry and the development of an intermolecular network as a function of temperature were monitored using the techniques of optical rotation and dynamic oscillation. Finally, analysis of calorimetric thermograms elucidated the type of interactions between CPS and the bacterial levan. Overall, the Rhizobium polysaccharide was found to form thermally-reversible gels at an extremely low 'minimum critical gelling concentration' (c_o∼ 0.35gl^-1). At temperatures above the gel melting point (∼ 48°C), however, the compact polymer coils entangled at comparatively high concentrations (about 60 times higher than c_o). In the presence of a highly branched levan, the thermal stability of ordered CPS structures increased as a consequence of thermodynamic incompatibility between the two polymers.     

Calculations of the Elastic Scattering Properties of Ultra-cold Francium Isotopes

The calculations of the elastic scattering properties of ultra-cold francium isotopes are reported in detail. A parametric model potential for the triplet molecular states of the Fr₂ is represented, and the scattering lengths a_t and the effective range r_e are calculated using WKB and Numerov methods for Fr--Fr in the triplet state. The convergence of these scattering properties depending on a K⁰ parameter and core radius is also investigated using two methods: Quantum Defect Theory and analytical formula of Symskoviski.     

Two Modified Semicircle Control Charts for Detecting Process Improvement

A semicircle control chart can be used in detecting both increases and decreases in the mean and/or variance. In this paper, we propose two modified semicircle charts for detecting a reduction in the process variance, a.k.a. process improvement. Each of these modified semicircle charts, namely, SC1 and SC2 has two limits, defined by the inner and outer semicircles. A process improvement is detected by the SC1 scheme if a point is plotted inside the smallest semicircle, or if two successive points are plotted between the inner and outer semicircles and by the SC2 scheme if a point plots inside the smallest semicircle or if two of three successive points plot between the inner and outer semicircles. It will be shown that the two modified semicircle charts have superior average run length (ARL) performances to the basic semicircle chart in the detection of process improvement. The ARL study is conducted by means of a simulation.     

Error Analysis for High-precision 7m Laser Measuring Machine

This paper introduces a high precision 7m laser measuring instrument developedby the anthors and its operating principle,and systematically analyses the errors havinginfluence on the performance of the measuring instrument.Error analysis and actualverification indicate that all the characteristics reached or exceeded the original designspecifications.     

有一个紧固件的半无限板孔周应力有限元分析

用有限元法计算了有一个紧固件孔的半无限平板在紧固件力作用下的孔周应力．在紧固件与孔之间的接触区域的结点间加无长刚杆元．用反复计算的方法确定接触范围；计算出孔周应力等，并与文献［１］的实验结果进行了比较．     

检定S型短型热电偶的4种不同冷端补偿方法之比较

检定长度在200～700 mm范围内的S型热电偶时,由于参考端温度大都处于室温或者波动的温场之中,需要将参考端温度恒定在0℃或采取修正、补偿等措施进行修正。现采取检定中最常用的4种不同的冷端补偿方法检定同一支S型短型热电偶,对结果进行比较分析,得到这4种不同的冷端补偿方法的优劣性及其准确度排序。结果表明,将参考端应用达到一等标准热电偶准确度水平的同极性热电偶丝延伸至参考端恒温器方法能获得较为理想的补偿效果。     

One-dimensional V-Scope analysis of habituation to simulated cross-country skiing

Abstract

Responses to simulated cross-country skiing were measured using the V-Scope, a new telemetric ultrasound motion monitor. Ten young male adults performed a total of 45 minutes of distributed practice on a Nordic-Track^R ski simulator. Over a period of three 15-minute sessions cadence and velocity were unchanged. Step and stride lengths decreased significantly (p < 0-05) after the first 15-minute session and then remained unchanged. There were no left-right limb differences across all sessions indicating a normal gait. Response variability in velocity, step lengths and stride length was dramatically reduced after the first exposure period. This study demonstrates that the V-Scope system is a useful motion analysing device and, on the basis of the data presented in this preliminary investigation, at least two 15-minute habituation sessions are required for initial habituation to simulated cross-country skiing.     

Chemistry of electron doped Ln2−xCexCuO4 superconductors

The electron doped Ln_2−xCe_xCuO₄ (Ln=lanthanide) oxides have intergrowth structures consisting of superconductively active CuO₂ sheets alternating with inactive (Ln, Ce)₂O₂ fluorite layers along the c-axis. Stabilization of such intergrowth structures requires bond length matching across the intergrowth interface. The bond length matching criterion causes a monotonic decrease in the Ce solubility limit from x=0.24 to x=0.15 as the size of Ln³⁺ decreased from Ln=La_0.5Nd_0.5 to Ln=Gd. Annealing in N₂ atm of Ln_2−xCe_xCuO₄ at temperatures above 900°C creates oxygen vacancies and the number of vacancies decreases with increasing Ce content. The value of x at which a semiconductor to superconductor transition occurs in Ln_2−xCe_xCuO₄ increases with decreasing size of Ln³⁺ due to an increasing Madelung energy caused by a decreasing Cu−O bond length.