多相异步电机谐波电流与谐波磁势的对应关系

为了分析定子绕组流过非正弦电流时多相异步电机的运行性能,必须了解谐波电流与谐波磁势的对应关系。通过Fourier级数把非正弦电流分解为基波电流和一系列谐波电流,分别计算各次时间谐波电流所产生的不同次空间谐波磁势,得到谐波电流次数与产生的合成谐波磁势次数间关系且给出通用表达式。结果表明:多相异步电机谐波电流与谐波磁势间的对应关系不同于三相异步电机。分析了某十二相异步发电机未能建立基波电压却建立了谐波电压的原因,并提出了解决方法。     

美洲商陆营养器官的解剖结构与其耐锰的关系

美洲商陆（Phytolacca acinosa Roxb）属于商陆科多年生草本植物,是一种适应性强的锰超积累植物．石蜡切片观察表明．美洲商陆经0．125、0．250、0．500和1．000g·kg^-1Mn^2＋处理7d后,根中柱的导管均变得发达．其中锰处理量为1．000g·kg^-1时,根表层细胞变得松散,茎内细胞内含物增加,叶片细胞内容物增加;当锰处理量大于0．250g·kg^-1时,海绵组织和栅栏组织变得松散,出现空隙．经0．125、0．250、0．500和1．000g·kg^-1Mn^2＋处理14d后．美洲商陆茎中的维管束数量迅速增加;根和叶片与处理7d的根和叶片比较结构变化不大．     

How some T cells escape tolerance induction

A feature common to many animal models of autoimmune disease, for example, experimental allergic encephalomyelitis, experimental autoimmune myasthenia gravis and collagen-induced arthritis, is the presence of self-reactive T cells in healthy animals, which are activated to produce disease by immunization with exogenous antigen. It is unclear why these T cells are not deleted during ontogeny in the thymus and, having escaped tolerance induction, why they are not spontaneously activated by self-antigen. To investigate these questions, we have examined an experimental model in which mice are tolerant to an antigen despite the presence of antigen-reactive T cells. We find that the T cells that escape tolerance induction are specific for minor determinants on the antigen. We propose that these T cells evade tolerance induction because some minor determinants are only available in relatively low amounts after in vivo processing of the whole antigen. For the same reason, these T cells are not normally activated but can be stimulated under special circumstances to circumvent tolerance.     

Essential requirement for major histocompatibility complex recognition in T-cell tolerance induction

The induction of T-cell responses involves the recognition of extrinsic antigen in association with antigens of the major histocompatibility complex (MHC), in mice and man, with different T cells recognizing antigen in association with either class I (H-2K/D, HLA-A, B, C) or class II (Ia, HLA-D/DR) MHC antigens. However, the requirement of MHC recognition in the induction of immunological tolerance remains ill defined. With human T helper clones recognizing synthetic peptides of influenza haemagglutinin (HA-1), we have investigated the nature of antigen-induced stimulation, and antigen-induced antigen-specific unresponsiveness, immunological tolerance. Tolerance is not due to cell death, as the cells remain responsive to interleukin-2 and is associated with the loss of T3 antigen from the cell surface. Using monoclonal antibodies to the non-polymorphic regions of human class II antigens to inhibit the induction of T-cell tolerance we report here that induction of tolerance requires the recognition of MHC antigens.     

符号与语境的关系

一切被赋予了人的意识的事物都是符号,而语境是符号意义相互＂溶解＂而形成的一种多维度的意向性场所。那么,符号和语境的关系怎样,它们以怎样的态势相依相存,本文尝试从现代语言学的角度分析符号与语境的关系,进而解释社会生活中的一些语言现象的产生。     

比喻与夸张的关系

人们对比喻和夸张的理解一般都囿于传统的认识，认为二者毫不相干。比喻跟夸张之间事实上存在着联系：喻体是相对于本体更为典型的事物，实质上起着放大本体相似点的作用，这就形成了事实上的夸张；间接夸张要通过比喻、比拟等修辞方式来实现，部分夸张中兼含有比喻。但作为修辞学上的两种辞格，比喻跟夸张又存在着一些不同。     

Relationship between science and technology

Do economic advances spring directly from fundamental scientific discoveries? The early history of the transistor suggests that the situation is not nearly so simple as this.     

水杨酸在诱导番茄抗冷性中的作用

以番茄为试验材料,探讨了叶面喷施水杨酸对于番茄幼苗抗低温能力的影响.实验结果表明番茄叶片中的SA在常温下主要以结合态形式存在.低温下SA质量分数大幅上升,而造成其上升的主要原因是游离态SA的大量积累.对番茄叶面喷施不同浓度SA,24 h后番茄叶片中游离态SA和结合态SA均大量积累,并且积累程度与喷施浓度呈显著正相关.低温下番茄叶片的抗氧化防御系统被明显激发,但并不足以减缓低温胁迫对植物所造成的氧化损伤.对番茄幼苗进行不同浓度的SA预处理,发现0.5 mmol/LSA能够显著提高其抗冷性.0.5 mmol/LSA预处理24 h后,低温下番茄叶片的相对电导率、MDA浓度较对照明显降低,而H2O2质量分数以及CAT,POD,APX,GR的活性则显著上升,叶片内c(AsA)/c(DHA)与c(GSH)/c(GSSG)维持在相对稳定的水平.因此,我们推测对番茄幼苗进行适宜浓度的SA预处理能够使其叶片中的SA质量分数上升至一定程度,从而诱导H2O2的适量积累,上调植物的抗氧化能力,使植物细胞在低温下维持相对稳定的氧化还原状态,从而缓解了低温对植物所造成的氧化损伤,提高了其抗冷性.     

皮质醇与运动训练关系研究

应用文献综述法，论述了不同运动负荷、不同运动项目中皮质醇的变化及影响皮质醇变化的非训练因素．用皮质醇监控运动训练，可以快速、准确地反映训练的强度和训练量以及运动员的机能状态，进而指导教练员和运动员调整运动负荷，合理安排训练内容．     

β-统计收敛与收敛的关系

利用β-统计收敛说明统计收敛、A-统计收敛、缺项统计收敛、λ-统计收敛及强统计收敛分别是β-统计收敛的特殊形式,并分别给予测度刻画.考察β-统计收敛与一般序列收敛之间的关系,得到统计收敛、λ-统计收敛及强统计收敛与收敛之间的等价描述.     

R-收敛因子和σ-收敛因子之间的关系

收敛速度是衡量一个最优化算法好坏的重要指标．1970年Ortega和Rheinboldt给出了两种度量一个迭代过程收敛快慢的精确标志．笔者证明了当收敛阶p＝1时，R—收敛因子和σ—收敛因子是相等的，从而可以用两种度量标志中的任何一种进行度量．     

细胞自噬与肝病

细胞自噬是真核细胞在长期进化过程中形成的一种自我保护机制,它在清除细胞内蛋白质聚集体、维持细胞内稳态中发挥着重要的作用.近年来研究表明,细胞自噬与各种肝病的病理发生密切相关,本文简要综述该方面的研究进展.     

包装工程与流体力学的一些关系(上)

从学术视角研究包装工程与流体力学的一些关系 .阐述了包装工程中的流体力学现象与包装阻隔模型 ;根据流体力学的相关原理、公式 ,分别论述了液体包装容器底部受力、气体包装中的溢散规律、物品包装中介质扩散的机理与包装防潮原理 .已有的研究提示 ,流体力学是包装防护理论与技术的基础学科之一     

Relationship between cholecystolithiasis and polypoid gallbladder

OBJECTIVE: To study the relationship between cholecystolithiasis and polypoid gallbladder (PLG), 260 patients with polypoid gallbladder were investigated. The patients were divided into 2 groups: group A (PLG combined with cholecystolithiasis) and group B (without cholecystolithiasis). The clinical pathological characteristics were analyzed. The intestinal epithelium metaplasia and atypical hyperplasia of the gallbladder mucosa were observed under light microscope. RESULTS: Intestinal epithelium metaplasia and atypical hyperplasia of gallbladder mucosa were found in 47 of the 260 cases. The pathological lesions included 16 gallbladder carcinoma, 11 adenomatosis polyp, 5 myoadenoma, 7 cholesterol polyp, 4 inflammatory polyp and 4 adenomatosis hyperplasia, which occurred in 26 and 21 patients in group A and group B, i.e. 44.0% and 10.3% respectively. The difference between group A and group B was statistically significant (P<0.01). CONCLUSION: Cholecystolithiasis and the succeeding inflammatory reaction is a risk-factor for the polypoid gallbladder to develop tumour.     

降雪现象与能见度关系的探讨

针对降雪现象器测困难这一问题,通过分析降雪粒子的大小、速度、密度、谱分布和光学特性等特征来讨论降雪现象与大气消光系数和能见度的关系.通过数值模拟分析与实测数据对比发现,当降雪强度一定时,能见度随雪花密度增大而增大;能见度随降雪强度的增大呈指数降低,不同类型雪花对应的能见度随降雪强度的变化曲线也各不相同;实测数据与理论分...