Folk experiments

Folk experiments in agriculture are often inspired by new ideas blended with old ones, motivated by economic and environmental change. They tend to save labor or capital. These notions are illustrated with nine short case studies from Nicaragua and El Salvador. The new ideas that catalyze folk experiments may be provided by development agencies, but paradoxically, the folk experiments are so common that the agencies that inspire them usually pay little attention to them. Some folk experiments are original, but others simply copy innovations that farmers have seen somewhere else. Unlike formal scientific research, in which results are consistently written, folk experiments are rarely “inscribed,” because the results are for use by individual farmers and need not be shared with an audience.     

Embryonic and neoplastic cell surfaces: availability of receptors for concanavalin A and wheat germ agglutinin

Embryonic tissue cells dissociated with ethylenediaminetetraacetate are readily agglutinated by the carbohydrate-binding protein concanavalin A. In this property, they resemble transformed, neoplastic cells; and they differ from untransformed adult cells, which are agglutinated by concanavalin A only after their receptors are unmasked by proteolytic treatment. Receptor sites for wheat germ agglutinin are also present on the surface of embryonic cells, but in a masked form, as on untransformed adult culture cells; they can be unmasked by treatment of the cells with trypsin. Concanavalin A binding sites on embryonic cells may function in cell contact and cell organization during embryonic morphogenesis and differentiation and later become masked in adult cells. The unmasking of these sites in neoplastic cells may represent a return, in this respect, to a condition resembling that of embryonic cells and may be related to cell mobility associated with infiltration and metastasis.     

Light scattering by irregular randomly oriented particles

A method for calculating light scattering by irregular randomly oriented particles yields results that are in good agreement with experimental data. The method is based on the assumption that surface waves are present in scattering by spherical particles, but they are absent in scattering by irregular particles.     

Doctorates Granted to Women and Minority Group Members: What changes have there been in recent years in numbers and in distribution among fields of study?

The AAU universities, a prime recruiting ground for new faculty members in selective colleges and research-oriented universities, are significantly increasing the number of doctorates awarded to women and minority members and are decreasing the numbers awarded to majority males. Between 1969-72 and 1972-75, doctorates awarded by AAU universities to majority men declined by 9 percent; to majority women increased by 34 percent; to minority men increased by 61 percent; and to minority women increased by 133 percent. The field distribution is very uneven. In some fields women with doctorates are fairly numerous, but most of these fields are ones in which women have for long constituted a significant portion of the total. In other fields, notably engineering and some of the physical sciences, it is still difficult to find women with doctorates from the universities in which large numbers of new faculty members receive their graduate education. Increasing numbers of minority students are earning doctorates in some fields, but in many fields the number is still very low. The several minority groups show quite different patterns of distribution among fields of specialization. The two smaller groups-American Indian and Spanish-origin-are most like the white majority in distribution by fields. Black doctorates are concentrated in education, with relatively few in the sciences. Students of Asian ancestry are heavily concentrated in engineering and the natural sciences.     

基于云的过渡区提取与图像分割算法

提出了一种基于云的图像过渡区提取算法.该方法利用区域生长算法提取目标内部灰度同质性及相似性最高的区域作为云核,结合云发生器,对图像进行云化处理.通过相邻云之间的逻辑运算生成边界云,提取边界云的数字特征,利用边界云的熵来确定过渡区的两端极值.在此基础上,采用过渡区象素的直方图峰值对应灰度作为分割阈值并进行图像划分.试验结果表明,该算法在能取得较好分割效果.     

侧耳杀线虫特性研究现状和应用于防治松材线虫病的前景

综述了侧耳的生物学特性和侧耳对线虫的毒杀特性 ,简述了松树材线虫病在中国的发生危害与处理松材线虫病木的方法 ,指出了现有处理方法的缺陷、原因。依据作者的初步试验 ,首次提出了将侧耳引入松材线虫病死木的设想 ,认为侧耳的生态习性、强烈的杀线虫活性、对病木中细菌的融解能力、以及线虫对侧耳的营养性和侧耳对松树立木的安全性 ,将有助于应用侧耳有效处理松材线虫病死木的成功     

Population genetics in forensic DNA typing.

Variable number of tandem repeat (VNTR) sequences are used to link defendants with crimes by matching DNA patterns. The probative value of a match is often calculated by multiplying together the estimated frequencies with which each particular VNTR pattern occurs in a reference database. However, this method is liable to potentially serious errors because ethnic subgroups within major racial categories exhibit genetic differences that are maintained by endogamy. The multiplication procedure currently in use can be made scientifically valid only by extensive sampling of VNTR frequency distributions in a variety of ethnic groups, similar to the ethnic studies of various blood groups done in the past. Alternative approaches for dealing with subpopulation heterogeneity are discussed.     

沧临管道大浪淀跨越段管壁皱折原因分析

按结构分析方法建立了斜拉钢索支承跨越段力学模型,提出了钢索非线性结构性能的线性化处理方法及数值实施方案。在此基础上,编制了大浪淀跨越段整体结构分析程序,对不同输送工艺对应的载荷条件下跨越管道的拉移及应力进行了分析,并根据计算结果按相应设计规范进行了结构安全性校核评估。结果表明,该处管壁局部皱折的出现与工艺条件变化,温度变化,输量减少后内压变化以及固定墩可能产生的轴向位移等因素有关。     

Like attracts like: getting RNA processing together in the nucleus

Structures visible within the eukaryotic nucleus have fascinated generations of biologists. Recent data show that these structures form in response to gene expression and are highly dynamic in living cells. RNA processing and assembly require many factors but the nucleus apparently lacks any active transport system to deliver these to the RNAs. Instead, processing factors move by diffusion but are concentrated by transient association with functionally related components. At sites of high activity this gives rise to visible structures, with components in dynamic equilibrium with the surrounding nucleoplasm. Processing factors are recruited from this pool by cooperative binding to RNA substrates.     

T and Tn, general carcinoma autoantigens

Primary and metastatic carcinomas are epithelial in origin and comprise by far the largest group of malignant tumors in humans. In most of these tumors, T and Tn antigens, whose epitopes have been synthesized, are uncovered and immunoreactive. In all other tissues T and Tn antigens are masked and not accessible to the immune system; they are generally precursors in normal complex carbohydrate chains. Thus, carcinomas have antigens recognized as foreign by the patients' immune system. The expression of T and Tn antigens has pathogenic and clinical consequences, and the antigens themselves are powerful histological markers in carcinoma diagnosis and frequently in prognosis. Most patients distinguish their carcinoma from all other cells, as shown by strong autoimmune responses to T antigen. These responses are readily measured by assays, and they allow detection of carcinomas with greater sensitivity and specificity frequently earlier than previously possible. Moreover, the extent of T and Tn expression often correlates with carcinoma differentiation; on a molecular level, clustered T- and Tn-active structures on carcinoma cell surfaces may be involved in invasion.     

汽车发电机抛负载电压的分析与估算

分析了汽车发电机抛负载电压的形成过程及其与发电机的相电动势、激磁电流和转速之间的关系，汽车发电机抛负载电压包含两个部分，且均由定子绕组本身产生．其一为定子绕组中负载电流突变产生的自感电动势，其特点是持续时间短，危害较小；其二为在激磁磁场作用下定子绕组产生的感应电动势经整流后得到的电压，其特点是电压持续时间长，危害较大，最后推导了发电机磁路在未饱和及饱和时抛负载电压的计算公式，并给出了相应的实例分析。     

水稻异交性状的质核互作分析

利用三套同核异质系分析了影响水稻异交性能的九项性状质、核、互作关系．结果表明，柱头总外露率、双外露率主要受核背景控制，也受质的影响；总外露率还有质该互作效应．包粒率、株高、穗颈节长和倒一节长主要受质背景控制；其中包粒率还受质核互作和核的影响；株高和穗颈节长也有核的作用．住头单外露率以核质工作效应为主，同时也有质的作用．闭颖率和倒二节长则主要受环境或其他因素影响．与正常胞质相比，不育胞质具有提高柱头外露率和包粒率，降低株高、穗颈节长和倒一节长的作用．K型胞质和D型胞质对提高柱头外露率的作用明显优于W型胞质．讨论了细胞质雄性不育系的改良策略。     

Wolbachia and virus protection in insects

Wolbachia pipientis bacteria are common endosymbionts of insects that are best known for their ability to increase their prevalence in populations by manipulating host reproductive systems. However, there are examples of Wolbachia that exist in nature that seem to induce no reproductive parasitism trait and yet are able to invade populations. We demonstrate a fitness benefit for Wolbachia-infected insects that may explain this paradox. Drosophila melanogaster flies infected with Wolbachia are less susceptible to mortality induced by a range of RNA viruses. The antiviral protection associated with Wolbachia infection might be exploited in future strategies to reduce transmission of pathogens by insects.     

苏扬园林风格差异及其成因初探

扬州园林色彩艳,建筑大,有市民化的倾向;苏州园林色彩雅,建筑巧,有文人化的倾向.扬州园林具有开放性和多样性的特点;苏州园林具有传统性和纯正性的特点.究其原因,苏、扬两地园林风格的差异性,是因为两地不同的园主、画风和学风造成的.扬州多盐商巨贾造园,苏州多官宦文人构园.扬州园林受扬州画派和扬学的影响;苏州园林受吴门画派和吴学的影响.参15     

Land-grant university governance: an analysis of board composition and corporate interlocks

This paper was inspired by the intersection of Tom Lyson’s interest in how power is concentrated in society’s institutions and his concern for the role of the land-grant system in revealing and addressing inequities that occur as a result of such concentration. This study examines the power structure that governs land-grant universities by presenting social and demographic information on 635 trustees at the 50 US land-grant universities established by the Morrill Act of 1862. Along with these data, Fortune 1000 companies with which land-grant universities are connected through board member interlocks are listed and charted out. The research found that land-grant governing boards are characterized by some degree of demographic homogeneity, but they are less corporately interconnected than their private university counterparts.     

边界层中TS波及其高阶谐波的演化

基于抛物化稳定性方程，研究了边界层中TS波及其高阶谐波的线性和非线性演化问题。由局部法和Landau展开式导出初始条件，并计算了扰动幅值和速度型等的演化过程和特征，特别是非线性的重要作用。探讨了初始幅值、压力梯度、扰动频率对扰动演化的影响及其规律，这与边界层的稳定性和转捩研究紧密相关。算例结果与全Navier—Stokes方程的直接数值模拟结果一致。     

Helical filaments produced by a Mycoplasma-like organism associated with corn stunt disease

Mycoplasma-like bodies with helical filaments were seen by phase contrast microscopy in juice expressed from tissues of plants infected with corn stunt agent. Each filament is bounded by a "unit membrane" and no cell wall, sheath, envelope, or second membrane has yet been discerned by electron microscopy. The association of these filaments with development of disease, their occurrence in phloem cells as seen by both freeze-etching and thin-section electron microscopy, the diagnosis of infection based on their presence in plants without symptoms, and their absence in noninfected corn are consistent with the hypothesis that these unusual filaments are formed by the mycoplasma-like organism presumed to be the corn stunt agent.     

Dissolution of pyroxenes and amphiboles during weathering

Augite, hypersthene, diopside, and hornblende all undergo dissolution during weathering by means of the formation, growth, and coalescence of distinctive, parallel, lens-shaped etch pits. Similar etch features can be produced if these minerals are treated in the laboratory with concentrated hydrofluoric acid plus hydrochloric acid. These pits most likely form at dislocation outcrops, and their shape and orientation are controlled primarily by the crystallography of the underlying mineral. The results are similar to those found for soil feldspars and suggest that silicate weathering, in general, takes place by selective etching and not by general attack of the surface with consequent rounding as necessiated by bulk diffusion-type weathering theories.     

Selenium accumulation by cereals in Russia

Data of monitoring selenium accumulation by wheat, barley, oats, and rye in 53 regions of the country are given. The intervals of its concentrations and average intake by the Russian population with cereal products are shown. It is noted that reduction of the import of wheat with a high selenium content will lead to a decrease in providing inhabitants of certain regions of the country with this trace element.     

黔西南州乡镇雨量站的暴雨基本特征分析

本文利用2013～2017年共五年乡镇自动站雨量,分析了暴雨、大暴雨、特大暴雨的逐月变化及空间分布特征,并就分布的空间差异性进行了探讨。结果显示：(1)黔西南州近五年特大暴雨点数累积集中出现在5-9月,其中6月最多,其次为8月;大暴雨主要出现在5-10月,6月最多;暴雨集中出现在5-9月,其中6月最多,其次为7月、9月;(2)暴雨及以上量级的雨日呈现明显的单峰结构,6月最多,达到88日,7、8月相当,11月至来年的3月暴雨日很少,大暴雨分布在4-12月,集中分布在6-9月,其中6月最多,达到27个大暴雨日,平均每年4.5日;特大暴雨分布在5-9月,其中8月最多,有4个特大暴雨日,平均每年0.8日;(3)暴雨以上量级日数夏季出现最多,其次为秋季、春季,冬季最少。暴雨、大暴雨季节变化特征相同,均为夏季最多,秋季次之,再次为春季,冬季最少;特大暴雨夏季最多,春秋季相同,均为2日;(4)近五年黔西南州暴雨及以上量级日数空间分布不均匀,总体呈现南北多中间少的特征：兴义市大部、中西部,册亨县大部,望谟县西南部,晴隆县大部,普安县北部暴雨及以上量级日数近五年合计超过20d,兴义市敬南镇、册亨县秧坝镇最多达37d,望谟县昂武乡、兴仁市新龙场镇、贞丰县沙坪镇最少,五年合计仅有6d。大暴雨日数空间总体呈现南北多中间少的特征：兴义市东南部、册亨县大部、望谟县中西部、晴隆县东部近五年合计超过5d,其中兴义市敬南镇、册亨县城、晴隆县光照镇、大田乡最多,达到8d,贞丰县、望谟县交界处近五年未出现大暴雨;特大暴雨主要出现在兴义市的东南部、兴义、兴仁交界以及兴仁的中部以北。