Cost Saving by Heat Recovery. 1 – Stenters

From Mr T A Weaver Sir, I read with interest the above publication [J. S. D. C., 96 (June 1980) 305], and feel that observations arising from our own experience in supplying stenters over a number of years may be appropriate.     

Early diagnosis of rheumatoid arthritis

On the basis of own observations of courses the author adopts a definite attitude to the early symptomatology of the rheumatoid arthritis. During the first weeks of the rheumatoid arthritis the following symptoms are found: articular syndromes, more frequently in form of obstinate polyarthralgias, mono-oligoarthritis, accompanied by morning rigidity and accelerated BSR as well as impairment of the general condition. In the majority of the patients only the tentative diagnosis rheumatoid arthritis may be made. After a one to three months' course of the disease the diagnosis becomes more probable. It is above all based on constancy and symmetry, characteristic localisation of the articular process, morning rigidity, radiologically paraarticular loosening of the structure and morphological symptoms of an acute and subacute synovialitis. 6 to 12 months after the beginning of the disease a clinical picture forms which allows to make the diagnosis of a certain or classical rheumatoid arthritis in accordance with the criteria of the ARA. The occurrence of a high activity of multiple affection of the joints (permanent symmetrical polyarthritis including the small joints of the hands and feet), distinctive morning rigidity, high fever and much accelerated BSR, beginning with the first weeks of the disease, speaks for the possibility of the development of an arthrovisceral form of the course of rheumatoid arthritis.     

时域有限差分法研究骨传导超声特性

自发现通过骨传导人可以感知超声以来,骨传导超声技术已被应用于助听中。为进一步了解骨传导超声特性,采用时域有限差分(FDTD)法,在单耳激励和双耳激励的情况下,计算超声经骨传导在头内形成的声场。仿真实验结果表明:双耳超声激励没有普通双耳听觉的定位能力,而单耳超声激励可同时激励双耳耳蜗。因此,单耳骨传导超声助听的效果可能比双耳骨传导超声助听的效果好。     

评价松质骨状况的一种背散射频谱方法

采用超声背散射信号的质心偏移量来评价松质骨,并对牛胫骨和人体跟骨中背散射信号的质心偏移量与松质骨表观密度的关系,以及人体跟骨松质骨中背散射信号频谱质心位置与年龄的关系进行了分析讨论。分析结果表明,随松质骨表观密度的增大,背散射信号频谱的质心向低频方向移动;随年龄的增大,质心位置越接近于发射超声的中心频率。根据超声背散射信号质心偏移量的大小,可用于评价松质骨健康状况。     

水热法合成羟基磷灰石晶须的工艺研究

纳米羟基磷灰石（HAP）增强聚合物基复合材料是替换硬组织的最理想材料，是植入材料的研究重点之一。为了制备与天然骨结构非常相似的复合材料，必须首先制备出性能优良的的纳米HAP粉体。对水热法制备HAP纳米晶须的工艺进行了研究，研究了反应时间、温度、起始反应物的浓度、钙磷比以及反应体系的pH值对合成HAP纳米晶须形貌的影响。用X射线衍射（XRD）、扫描电镜（SEM）和红外光谱（FT-IR）法，对制备的羟基磷灰石进行了表征和分析。结果表明：生成的HAP晶须的长度及长径比随反应时间的延长而增大。温度〈150℃时，得到HAP晶须；温度〉180℃，则得到细小HAP晶体的聚集产物。当反应物的pH=9时，得到的是缺钙型的HAP；当反应物的pH〈4时，产物中出现新相磷酸氢钙；当pH=2时，得到纯的磷酸氢钙。     

An automatic braking system that stabilizes leukocyte rolling by an increase in selectin bond number with shear

Wall shear stress in postcapillary venules varies widely within and between tissues and in response to inflammation and exercise. However, the speed at which leukocytes roll in vivo has been shown to be almost constant within a wide range of wall shear stress, i.e., force on the cell. Similarly, rolling velocities on purified selectins and their ligands in vitro tend to plateau. This may be important to enable rolling leukocytes to be exposed uniformly to activating stimuli on endothelium, independent of local hemodynamic conditions. Wall shear stress increases the rate of dissociation of individual selectin-ligand tether bonds exponentially (, ) thereby destabilizing rolling. We find that this is compensated by a shear-dependent increase in the number of bonds per rolling step. We also find an increase in the number of microvillous tethers to the substrate. This explains (a) the lack of firm adhesion through selectins at low shear stress or high ligand density, and (b) the stability of rolling on selectins to wide variation in wall shear stress and ligand density, in contrast to rolling on antibodies (). Furthermore, our data successfully predict the threshold wall shear stress below which rolling does not occur. This is a special case of the more general regulation by shear of the number of bonds, in which the number of bonds falls below one.     

低频波动条件下流体平面渗流模型研究

低频振动采油技术已成为一项重要的物理增产、增注措施,但其理论研究水平目前还相对滞后于现场应用.针对这一问题,运用渗流力学、波场传播的基本原理,建立了低频波动条件下地层流体的渗流模型,定量描述了地层、流体参数与振动采油压力波动之间的关系,并利用解析方法分析计算,认为低频波场主要受储层渗透率和振动频率两大因素影响.振动采油现场施工可以通过适当调整振动频率改善施工效果.