Demographic intermediation between development and population redistribution in Sudan.
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Africa↗
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Results for “Spatial Distribution--determinants”
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The internal migration patterns of the foreign-born and native-born populations in the United States: 1975-80 and 1985-90.
"The focus of this article is on an examination of the influence of birthplace on the internal migration and spatial redistribution patterns of the foreign-born and native-born populations in the United States during the 1975-80 and 1985-90 periods. The analyses presented here consider the following principal questions: (1) What are the internal migration patterns of the foreign-born population in the United States, and how do they differ from those of the native-born population? (2) How do the relocation choices of various birthplace-specific foreign-born and native-born subpopulations differ from each other? (3) Are the internal migration patterns generating an increased or a decreased geographical concentration of such birthplace-specific subgroups?"
Americas↗
[Trend analysis for interprefectural migration in Japan, 1954-1993].
"In this paper, our main aim is to examine long-term trends of Japanese interprefectural migration after the War by using a Markov migration model.... We observed dependence of in- and out-migration on the size of populations by prefecture.... Major findings based on the time-series observation of stationary distributions by year are as follows: First from [the 1950s] to 1970 migrants tended to concentrate [on] densely populated industrialized prefectures (Tokyo, Osaka and Aichi), but after that during [the 1970s] populations have redistributed to provincial prefectures. Reconcentration of population to [the] Tokyo area again occurred around [the mid-1980s, but] it ceased at the beginning of the [1990s] in accordance with economic recession.... It can be concluded that [the] recent Japanese interprefectural migration system has lost its potential power to redistribute populations." (SUMMARY IN ENG)
Asia↗
[Preliminary analysis of population distribution in Beijing, Tianjin, and Tangshan].
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Asia↗
[Changing distribution of university graduates in Japan--from a cohort-by-cohort perspective].
"This paper aims at describing and explaining the changing distribution of university graduates [UGs] in Japan in order to clarify the effects of interregional migration on changes in the social class composition of the Tokyo metropolitan area (TMA) and the rest of Japan (Non-TMA).... The analysis thereby begins with the distribution of the UGs by 5-year cohort in 1970, 1980 and 1990 measured by location quotients (LQs) of UGs in the TMA.... The paper then proceeds to an analysis of the determining process of the distribution pattern of the UGs by 5-year cohort." (SUMMARY IN ENG)
Asia↗
Population dynamics in Ciskei.
"Population density is one of the most widely-used statistics in human geography. Maps showing areas of high and low density illustrate stark contrasts which result from the interplay of numerous forces. In South Africa political developments during the apartheid era have left a long-lasting impression upon population distribution and density. Conditions in one former homeland, Ciskei, are examined."
Africa↗
DNA double-strand breaks in mammalian cells exposed to gamma-rays and very heavy ions. Fragment-size distributions determined by pulsed-field gel electrophoresis.
The spatial distribution of DNA double-strand breaks (DSB) was assessed after treatment of mammalian cells (V79) with densely ionizing radiation. Cells were exposed to beams of heavy charged particles (calcium ions: 6.9 MeV/u, 2.1.10(3) keV/microm; uranium ions: 9.0 MeV/u, 1.4.10(4) keV/microm) at the linear accelerator UNILAC of GSI, Darmstadt. DNA was isolated in agarose plugs and subjected to pulsed-field gel electrophoresis under conditions that separated DNA fragments of size 50 kbp to 5 Mbp. The measured fragment distributions were compared to those obtained after gamma-irradiation and were analyzed by means of a convolution and a deconvolution technique. In contrast to the finding for gamma-radiation, the distributions produced by heavy ions do not correspond to the random breakage model. Their marked overdispersion and the observed excess of short fragments reflect spatial clustering of DSB that extends over large regions of the DNA, up to several mega base pairs (Mbp). At fluences of 0.75 and 1.5/microm2, calcium ions produce nearly the same shape of fragment spectrum, merely with a difference in the amount of DNA entering the gel; this suggests that the DNA is fragmented by individual calcium ions. At a fluence of 0.8/microm2 uranium ions produce a profile that is shifted to smaller fragment sizes in comparison to the profile obtained at a fluence of 0.4/microm2; this suggests cumulative action of two separate ions in the formation of fragments. These observations are not consistent with the expectation that the uranium ions, with their much larger LET, should be more likely to produce single particle action than the calcium ions. However, a consideration of the greater lateral extension of the tracks of the faster uranium ions explains the observed differences; it suggests that the DNA is closely coiled so that even DNA locations several Mbp apart are usually not separated by less than 0. 1 or 0.2 microm.
Animals↗
An analysis of neural spike-train distributions: determinants of the response of visual cortex neurons to changes in orientation and spatial frequency.
A previously unexploited method of examining neural spike-trains was applied to data obtained from cells in the visual cortex. Distributions of interspike intervals recorded extracellularly from cat visual cortex under four conditions were analyzed. Stimuli were gratings differing in orientation and spatial frequency. The probability density function of first passage time for a random walk with drift process, which is defined by its barrier height and drift coefficient, was used to characterize the generating process of axonal discharge under resting and stimulus conditions. Drift coefficient and barrier height were derived from the sample mean and standard deviation of the measured inter-spike intervals. For cells with simple receptive fields, variations in the drift coefficient were produced by changes in orientation and spatial frequency. Variations in barrier height were produced only by changes in orientation of the stimulus.
Animals↗
On nature of Y chromosome fragments induced in Drosophila melanogaster females. III. C(1)RA vs C(1)RM females.
The distribution of breakpoints in the Y chromosome has been determined for samples of Y chromosome fragments recovered from irradiated immature and mature oocytes of females carrying a reversed acrocentric compound X chromosome. Both distributions differ from the distributions determined from Y chromosome fragments recovered from irradiated females carrying a reversed metacentric compound X chromosome. Differential spatial associations of chromosomes in the oocyte nuclei of the two types of females is discussed as a possible cause of the observed differences.
Animals↗
Spatial variability of in situ microbial activity: biotracer tests.
Biotracer tests have been proposed as a means by which to characterize the in situ biodegradation potential for field-scale systems. In this study, field experiments were conducted at two sites to evaluate the utility of the biotracer method for characterizing the spatial variability of microbial activity. The first site is a mixed waste-contaminated surficial aquifer in Utah, and the second site is a chlorinated solvent-contaminated regional aquifer in Tucson, Arizona. Mass recovery of the biotracer decreased approximately linearly with increasing residence time for the Tucson site. Similar behavior was observed at the Utah site, except in the region adjacent to the injection zone, where percent recoveries were much lower than those predicted using a correlation determined using data collected downgradient of the injection zone. First-order biodegradation rate coefficients obtained from model calibration of the tracer data varied between 0.2 and 0.5/day for the Tucson site. For the Utah site, the values varied between 0.1 and 0.6/day downgradient of the injection wells, and between 0.7 and 2.6/day near the injection wells. Considering the large range over which biodegradation rate coefficients can vary, the rate coefficient exhibited relatively minimal spatial variability (factor of 2.5) for the Tucson site. Conversely, the spatial variability of the rate coefficient was an order of magnitude greater for the Utah site. These differences in variability are consistent with conditions associated with the respective sites. For example, the greater microbial activity observed in the vicinity of the injection wells for the Utah site is consistent with the biomass distribution determined from analysis of core samples, which shows larger bacterial cell densities for the region near the injection wells. These results illustrate the utility of biotracer tests for in situ characterization of microbial activity (e.g., biodegradation potential), including evaluation of potential spatial variability.
Biodegradation, Environmental↗
Preparation, characterization and utility of a novel antibody for resolving the spatial and temporal dynamics of the calcium chelator BAPTA.
In spite of its importance as a tool to manipulate cell calcium, the versatility of the octadentate chelator BAPTA in cell physiological and diverse other applications is limited by the difficulty with which it can be quantified and its cell and tissue distributions determined. Conventional approaches, such as HPLC analysis or autoradiography, are of limited sensitivity and resolution and have attendant biohazard risks. We now describe a versatile, facile and inexpensive means for quantifying and determining the distribution of BAPTA which exploits an immunological approach based on our generation of novel antibodies to BAPTA. Antibodies to BAPTA were prepared by immunizing rabbits with BAPTA conjugated to keyhole limpet hemocyanin via a zero-order cross-linking reagent-EDC. The ability of anti-BAPTA IgGs to recognize free or conjugated BAPTA was confirmed using enzyme-linked and immunoblotting assays made possible by our introduction of a BAPTA-BSA adduct. Using such assays, we show that the anti-BAPTA antibodies possess marked selectivity for BAPTA compared to several structurally-related BAPTA analogs. The utility of the anti-BAPTA antibodies in cell calcium research has been confirmed in two ways. First, by determining the spatial distribution of BAPTA through immunocytochemistry and confocal microscopy of cortical neurons loaded with BAPTA/AM and, second, by determination of the kinetics of loading and efflux of BAPTA through enzyme-linked cell immunoassays (ELISA) and immunocytochemistry. Together, these data demonstrate that anti-BAPTA antibodies are a powerful new tool with which to quantify BAPTA and to define the spatial and temporal distribution of this important calcium chelator in live cells. Such information should greatly aid the design of cell physiological experiments, the development of new chelators and the identification of sources of chelator selectivity in emerging therapeutic applications.
Animals↗
Determining the size distribution of core-shell spheres and other complex particles by laser diffraction.
The goal of this work is to determine the size distribution of hollow glass spheres by laser diffraction, an experiment which involves measuring angle-dependent scattering of light from particles dispersed in a liquid. The proprietary software supplied with commercial instruments is not strictly applicable to our two-layer, glass-shell, hollow-core spheres because it requires that the particles have spatially homogeneous properties. We therefore developed Fortran code to compute the scattering from core-shell spherical particles. The results show that the scattering from representative hollow glass particles diverges from homogeneous sphere scattering when the radius decreases from 10 to 3 microm. Additionally, scattering measurements on two core-shell hollow glass powders were analyzed using the exact core-shell optical model and homogeneous sphere approximations. In both cases, the size distribution determined using the exact core-shell model differs from that determined using the homogeneous-sphere approximation when the distribution covers radii smaller than about 10 microm, as expected. The size distribution based on the exact core-shell optical model was determined using a new algorithm. Although the basic equations used in the algorithm have been published previously, they are developed here in a different form, which can be implemented using Fortran and MatLab routines available commercially and in the public domain. This algorithm could be used to determine the size distribution of other kinds of particles, such as cylindrical rods, as long as their angle-dependent scattering could be computed.
Journal Article↗
On the arrangement of chromosomes in the elongated sperm nuclei of Anura (Amphibia).
The position of specific constitutive heterochromatic chromosome regions within the elongated sperm nuclei of eight species of Anura was examined with Q- and C-banding. These species differ widely with regard to the number, size and position of the brightly fluorescing heterochromatic regions. The empirical frequency distributions determined for the heterochromatic regions relative to the longitudinal axis of the sperm nuclei were compared with random frequency distributions calculated on the basis of two spatial models. None of the specifically stained heterochromatic regions occupy any definite preferential position within the sperm nuclei. In two instances, a specific sequence of the heterochromatic regions within the sperm nuclei could be excluded. The type of chromosomal arrangement within the elongated sperm nuclei of Anura is discussed on the basis of the distribution patterns obtained.
Amphibians↗
2D and 3D dose distribution determination in proton beam radiotherapy with GafChromic film detectors.
This paper presents the results obtained using radiochromic (MD-55 GafChromic) film for the 2D and 3D dosimetric reconstruction of the dose delivered by a proton beam under the real conditions of a programme of radiotherapy treatment for ocular tumours. Standard microdensitometric measurements were used to determine the variation in film optical density (O.D.) vs dose. Calibration curves were obtained by least-square fitting of the experimental OD values using a second order polynomial. This allows conversion of O.D. to dose. With this procedure it was possible to determine the distribution of the dose delivered by the proton beam in a phantom composed of layers of GafChromic film, with high surface spatial resolution and, through sections, the complete mapping of the dose delivered to a volume subjected to irradiation, as in a course of radiotherapy treatment.
Eye Neoplasms↗
Coronary angiogenesis: detection in vivo with MR imaging sensitive to collateral neocirculation--preliminary study in pigs.
PURPOSE: To assess the ability to track neovascularization over time with a magnetic resonance (MR) imaging technique sensitized to new intramyocardial collateral development as a means of evaluating therapeutic angiogenesis. MATERIALS AND METHODS: Magnetization preparation plus spatial frequency reordering was applied to distinguish new intramyocardial collateral vessels from normal circulation on the basis of geometric differences. A vascular occluder was inserted in 34 pigs, and they were assigned randomly to treatment groups with either placebo or angiogenic growth factor. Collateral extent determined with collateral-sensitive MR imaging was correlated with direct measurements by means of three-dimensional (3D) computed tomography (CT), coronary blood flow distribution determined with microspheres, and findings at histologic examination. Changes in the signal at collateral-sensitive MR imaging before and after treatment were assessed by two observers blinded to treatment. RESULTS: The collateral extent determined with collateral-sensitive MR imaging correlated well with findings at 3D CT (r = 0.95) and with microspheres (r = 0.86). Furthermore, the collateral extent determined with collateral-sensitive MR imaging increased significantly (P < .001) in response to the administration of an angiogenic growth factor but not to placebo. The correspondence of findings at collateral-sensitive MR imaging to collateral neovascularization was confirmed at histologic examination. CONCLUSION: The presence of intramyocardial collateral microvessels was accurately determined with collateral-sensitive MR imaging. The technique may be useful in clinical studies of therapeutic angiogenesis.
Animals↗