Masses Of Various Sizes Research Articles

Electronically controlled etch-mask for silicon bulk micromachining

Wafers that are to be submitted to anisotropic etching in aqueous KOH are conventionally passivated with a silicon dioxide or nitride layer in which backside windows are etched to define the microstructures. A different method to mask the backside of a silicon wafer for this purpose is presented. The method makes use of the phenomenon that silicon is not etched in KOH when biased above the passivation potential. The mask is defined by applying a set of bias voltages to the front of the wafer instead of patterning a deposited passivation layer at the backside, for which an accurate double-sided alignment is required. The feasibility of the method was demonstrated with the fabrication of membranes and suspended masses of various sizes. >

Asymptomatic cerebral calcification—a previously unrecognized feature

While investigating the radiological appearances of globus pallidus calcification in an autopsy case, cortical-pia mater calcification was detected. There was no documentation of its existence in the literature of radiology, neurology and neuropathology. To establish its incidence and clinical significance, 20 consecutive autopsy brains (15 males, 5 females, age 32-73 years, mean age 56.7) were studied with high resolution radiography and histology. Clinical records, autopsy findings, in-life plain skull films and computed tomography of the brain (if available) were reviewed. Radiologically, the calcifications appeared as 1-2 mm irregular spots or tiny pin-point opacities in the pia mater and subcortical regions, either unilaterally or bilaterally in the frontal (15 cases), temporal (15), parietal (3) and occipital lobes (1). Similar calcification was detected in 1 of the 3 in-life computed tomographic scans available. Histologically, these cortical-pia mater calcifications were extracellular amorphous calcified masses of various sizes in necrotic neural tissue, frequently associated with microscopic haemorrhage and hypoxic neuronal changes in the adjacent brain tissue. Blood vessels in the region were not hyalinized or calcified. The occurrence was not related to age. Hospital stay was less than 7 days in 14 and less than 30 days in 2; 50% of patients died within 48 hours after admission. None of the patients had records of long term cytotoxic chemotherapy, radiotherapy or central nervous system infection. Two had stroke, one had cerebellar atrophy and one mild hypercalcaemia. The high incidence of calcifications in the temporal lobes, while asymptomatic, suggests that cortical calcification may be a pointer to the aetiology of idiopathic epilepsies in the elderly.

An Ultrastructural Study of Inclusions and Disease Development in Plant Cells Infected by Cowpea Chlorotic Mottle Virus

SUMMARY Subcellular responses of leaf cells to infection by bean yellow stipple virus, a strain of cowpea chlorotic mottle virus (CCMV), in two varieties of bean, Phaseolus vulgaris L., and three varieties of cowpea, Vigna sinensis (Torner) Savi, were investigated by electron microscopy. Amorphous inclusions (AI), filamentous inclusions (FI), which appeared to be characteristic of CCMV infection, and membranous vesicles (30 to 100 nm in diam.), containing fibrils and virus particles, were consistently found in cells in all infected hosts. The AI occurred in cytoplasm as granular masses sandwiched between the rough endoplasmic reticulum (RER) and the nuclear envelope (NE) at an early stage of infection. In later samples AI were scattered randomly in masses of various sizes, numbers and shapes. Electron lucent areas containing virus particles were present in large masses of AI. The FI were long, unbranched, flexuous, rod-like structures of 17 nm in diam. They appeared after AI were formed in the cytoplasm and also occurred in the nucleus. Cytoplasmic FI were usually associated with AI, and nuclear FI with the nucleolus. Intranuclear virus particles were observed only when FI were located in the nuclei. Both FI and AI were similarly degraded by treatment with subtilisin or pronase, but virus particles were not. Fibril-containing vesicles arising from the membranes of NE and RER were concurrently present in the perinuclear space and the lumen of ER associated with AI and FI.

Mineralogical and geochemical investigation of some pegmatites from the Mashad area, northeastern Iran

Pegmatitic dikes and masses of various sizes occur in a granite intrusion in the Mashad area, northeastern Iran. Their geochemistry, as well as that of the parent granite was investigated using some 40 specimens. Major constituents and trace elements were determined by means of X-ray fluorescence and spectrographic methods. Anomalously high concentrations of Be and Nb and indications of their minerals beryl and columbite were observed. Therefore, the pegmatites of this area may prove to be a potential source for Be, Nb, Ta and possibly Li.

Monofactorial ?multiploid sporocytes? condition induced by EMS in Pearl Millet

“Multiploid sporocytes” condition was observed in the M2 generation of Pennisetum typhoides raised from seeds treated with 0.3 percent EMS at pH 7. The pollen mother cells in the anther locules were devoid of individual boundaries and aggregated into plasmodium-like masses of various sizes in which the chromosomes were lying in groups. The number of chromosome pairs in these groups varied from 7 to 42 and in a few cases much larger groups were observed. At diakinesis and metaphase I, trivalents and quadrivalents were observed, which suggested that the chromosomes from different cells were in proximity at an early stage. Apparently cytokinesis was suppressed at the premeiotic divisions. Sometimes groups of chromosomes from several nuclei were together at metaphase I, the bivalents and multivalents co-orienting on a single spindle. Then the spindle was many times wider than normal, but the length was not greatly changed. Anaphase I segregation and second division were irregular. The microspores formed were of variable size. Sterility was high. This condition behaved as one controlled by a single recessive gene.

Design of a single electrode capacitor for use with moisture meters and similar apparatus

Measurements of the capacitance of a single cylindrical electrode in air have been made for each of the three variables, length, radius and height above earth. The effect of surrounding it by dielectric masses of various sizes was also investigated, and the change of capacitance with increase in dielectric volume determined. The influence of these factors when designing a capacitor of this type is discussed. This electrode has been successfully used for measuring the moisture content of textile packages, and could be used for similar applications involving measurement of dielectric properties.

CYTOGENETICS OF A FACTOR FOR MULTIPLOID SPOROCYTES IN BARLEY

A CONSIDERABLE number of genetic factors have been found in various organisms which disturb the process of meiosis and thus contribute to the analysis of its mechanism and complexities. Descriptions of the irregularities wrought by a number of these factors and reviews of and citations to literature dealing with many others may be found in Darlington (1937), Smith (1936, 1939), and Clark (1940). The present paper deals with the cytology and genetics of a recessive factor in barley (Hordeum vulgare, n=7) which affects meiosis in such a manner as to result in meiotic metaphases with 14, 21, 28, 56, 112, or various other numbers of pairs of chromosomes instead of the normal seven. This is apparently accomplished by the assembling of chromosomes from different cells rather than by the repeated division of chromosomes within individual cells. MATERIALS AND METHODS.-Seed of the multiploid sporocytes (symbol mu) line was supplied in 1939 by G. A. Wiebe of the Bureau of Plant Industry from a selection out of C. 1.2 No. 3845, a sixrowed variety. (The mutant was formerly referred to as contabescent anther.) Cytological observations were made on aceto-carmine smear preparations. Whole heads were fixed in Carnoy's fluid for a day or more; root tips for a week or longer. Some smears were made permanent by a tertiary butyl alcohol method described by Sears (1941). Most of the photomicrographs are from slides made permanent by this method. CYTOLOGICAL OBSERVATIONs.-Typically at diakinesis the pollen mother cells (hereafter referred to as PMC's) have seven pairs of chromosomes as in normal barley though frequently the boundaries of individual cells are not clear. That is, the PMC's in an anther sac tend to form plasmodium-like masses of various sizes in which the chromosomes lie in groups (fig. 1). The numbers in the groups are not large and usually the seven bivalents belonging with a particular nucleolus can be identified. At first meiotic metaphase the chromosomes form a plate in the PMC material. In some instances this material consists of only one PMC and in others consists of the aggregated cvtoplasm of several microsporocytes. In some groups there are 7 pairs, in others 14, 21, 28, 35, 42, etc. As many as approxi-