Mechanical properties of CRETE,a polyurethane foam

The room-temperature mechanical properties of a closed-cell, polyurethane encapsulant foam were measured as a function of foam density. Over the range of densities examined, the modulus could be described by a power-law relationship with respect to density. This power-law relationship was the same for both tension and compression testing. The basis for this power-law relationship is explained in terms of the elastic compliance of the cellular structure of the foam using a simple geometric model put forth by Gibson and Ashby. The elastic collapse stress, a property relevant to compression testing, also is found to exhibit a power-law relationship with respect to density. The density dependence of this property is also found in the work of Gibson and Ashby and is explained in terms of the Euler buckling of the struts that comprise the cellular structure. Energy absorption during deformation is also reported for both tension and compression testing. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1045–1055, 1998     

Functional conservation of cytosolic proteins required for endosomal vesicle fusion

Recent studies suggest that intracellular membrane traffic relies upon families of related proteins which confer specificity to individual transport reactions but which operate in tandem with a ubiquitous fusogenic complex containing the N-ethylmaleimide-sensitive fusion protein (NSF). The extent to which components of this process are functionally conserved is apparent from the finding that yeast Sec18 protein (Sec18p) can substitute for mammalian NSF in intra-Golgi transport reactions. Here we report that yeast cytosol can support mammalian endosomal vesicle fusion, demonstrating conservation of cytosolic components required for this reaction. Furthermore, under conditions in which the fusion reaction is NSF-dependent we show that yeast Sec18p can functionally substitute for NSF, showing that the yeast protein is capable of catalysing at least two distinct mammalian membrane fusion events. In addition we exploit the complex pattern of sensitivity of the mammalian reaction to N-ethylmaleimide (NEM), coupled with the use of yeast cytosol, to dissect a number of factors required for fusion. We reveal at least three novel NEM-sensitive activities. One of these can be restored by yeast cytosol suggesting that it is functionally conserved.     

Micro-ESR：微型电子自旋共振光谱仪

电子自旋共振光谱（ESR）,又称顺磁共振光谱（EPR）,是直接检测自由基、引起石油氧化降解含有未成对电子的活性分子以及食物的唯一方法,也在生物化学研究疾病方面起着一定的作用。本文所描述的微型、高灵敏度的ESR光谱仪通过显著降低光谱技术的成本,能够为工业和科学研究者扩大ESR光谱学的实用范围。     

Mapping granular structure in the biological adhesive of Phragmatopoma californica using phase diverse coherent diffractive imaging

This paper demonstrates the application of the high sensitivity, low radiation dose imaging method recently presented as phase diverse coherent diffraction imaging, to the study of biological and other weakly scattering samples. The method is applied, using X-ray illumination, to quantitative imaging of the granular precursors of underwater adhesive produced by the marine sandcastle worm, Phragmatopoma californica. We are able to observe the internal structure of the adhesive precursors in a number of states.     

MOSFET effective channel width determination by nonlinear optimization

Accurate determination of MOSFET effective channel width W_eff is important for process control and device design. Existing methods to determine W_eff are sensitive to measurement noise, and to nonlinearities in the data. In this paper we present a new method to determine W_eff that overcomes these problems. The method uses nonlinear optimization, and is based on a drain current model that accounts for the variations of W_eff, of series resistance, and of threshold voltage, with masked channel width and gate bias. We also show that our new method is more accurate and less sensitive to measurement procedure than other methods.     

On the dynamics of a slender rod

The moment equation for the space rotation of a slender rod about a fixed point on its axis is developed with the aid of a visual vector approach and is shown to have the same form as the moment equation for the plane rotation of a slender rod. Also, an analogy between the general rotation of the rod and the plane motion of a point expressed in polar coordinates is presented as an aid to the more complete physical understanding of the motion.     

Creep properties of Sn-8Mass%Zn-3Mass%Bi lead-free alloy

The creep properties of Sn-8mass%Zn-3mass%Bi were investigated and compared with those of other lead-free solders and a Sn-Pb eutectic solder. The creep rupture time decreases with increasing the initial stress and the temperature. For high stresses, the linear relationships between the minimum strain rate and the applied stress were observed. The stress exponents were examined to be 9.3, 7, and 4 at 298 K, 348 K, and 398 K, respectively. For low stresses, the minimum creep rate becomes relatively fast, and the creep resistance diminishes. In this range, secondary creep reduces, and the tertiary creep predominates. The creep properties of Sn-8Zn-3Bi are similar to those of Sn-Ag alloys at high stresses and those of Sn-0.5Cu at low stresses.     

Misfit relaxation behavior in CdHgTe layers grown by molecular beam epitaxy on CdZnTe substrates

Uniform layers of cadmium mercury telluride have been grown on inhomogeneous cadmium zinc telluride substrates by molecular beam epitaxy so that a single epitaxial layer experiences a laterally varying lattice mismatch. The lateral variations of layer and substrate lattice parameters, layer lattice tilt, diffraction peak width, etch pit density (EPD) and surface crosshatch have been characterized, and all measured quantities are reported as functions of the substrate lattice parameter. At small mismatch, the layer appears to be elastically deformed. Beyond a certain critical mismatch, the onset of relaxation is clearly observed in the layer lattice parameter. Relaxation leads to appearance of surface crosshatch and an increased diffraction peak width, but a reduction in EPD, suggesting a reduction in the density of threading dislocations within the layer.     

AlGaAs/GaAs pnp heterojunction bipolar transistor with carbon-doped collector and emitter grown by atomic layer epitaxy

The first AlGaAs/GaAs pnp heterojunction bipolar transistor (HBT) grown entirely by atomic layer epitaxy (ALE) is reported. Carbon was used as the p-type dopant in the emitter and collector. The use of carbon, with its low diffusivity and the potential for very heavy doping, will lead to reduced emitter and collector resistances in a pnp structure. For the devices reported here, a common emitter current gain over 100 was obtained, with good I/V characteristics.<>     

The composition and concentration of n-alkanes in retail samples of edible oils

Abstract : A range of edible oils were purchased from a variety of retail outlets and analysed for their n-alkane (Σ33/15) content. The concentrations ranged from 7 to 166 mg kg^?1, the lowest being walnut oil and the highest sunflower oil. n-Alkanes with chain lengths of C₂₇, C₂₉ and C₃₁ predominated in all of the plant oils except olive oil where C₂₃, C₂₅ and C₂₇ were the most significant. The results of this pilot survey suggest that the n-alkanes are indigenous and that their composition may be useful in characterising a specific plant seed oil. Two of the 42 samples analysed showed markedly different alkane patterns in which profiles similar to petroleum-based sources dominated the contribution from odd carbon n-alkanes typical of seed oils.