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PubMed1979

Spatial distribution of pulmonary blood flow in the dog with PEEP ventilation.

The effects of mechanical ventilation without and with a positive end-expiratory pressure (PEEP) of 20 cmH2O and, after hemorrhage, on the spatial distribution of lobar lung blood flow were studied by means of iv injections of radioactive microspheres in supine dogs. The lungs were excised and dried at an inflation pressure of 30 cmH2O. Each lobe was cut into slices. In five slices from each lobe, 30--60 samples were punched out. The activity was measured in a gamma counter. By this means distribution of lobar blood flow could be described three-dimensionally. In dogs awake and spontaneously breathing or anesthetized and mechanically ventilated, blood flow distribution was rather even, except for a vertical gradient. PEEP caused a) a two- to threefold reduction in total lung blood flow, b) a redistribution from the right to the left lung, and c) a redistribution from the core to the periphery of the lung. This pattern of redistribution could not be reproduced by reducing cardiac output by hemorrhage during mechanical ventilation without PEEP.

Animals↗

PubMed2000

Spatial distribution and population composition of the brown mouse lemur (Microcebus rufus) in Ranomafana National Park, Madagascar, and its implications for social organization.

Through a 16-mo mark-recapture trap study, I examined aspects of spatial distribution and population composition in the brown mouse lemur, Microcebus rufus, a 42 g nocturnal strepsirhine. The study took place in the rainforest of Ranomafana National Park in southeastern Madagascar. Sherman live traps were set monthly for a variable number of nights in a quasi-grid 50 m apart. Captured individuals were marked for future identification and released at site of capture. More males than females were captured overall (102 versus 72) and at 83% of trap sites. Trap sex ratio fluctuated significantly over the course of the study. It was particularly male-biased between June and August (3.9:1), when more previously uncaptured males than females (14 versus 6) entered the trap population. Some of these males remained in the trap population. Although the average number of individuals captured was not significantly different between the first four and last four months of the study, the composition of the population changed. The female population, however, changed less: 28.9% of all females captured in the first four months of the study were recaptured in the last four months, compared to 9.7% of males. It is suggested that the pattern of appearance of new individuals and disappearance of others, both predominantly male, may indicate migratory activity. Furthermore, an average of eight individuals were captured at each trap site (approximately 70% of traps captured more than five), suggesting a high degree of spatial overlap. The average number of male and female individuals captured in each trap (5.5 males versus 2.5 females), the average number of trap sites at which males and females were captured (3.6 versus 2.4), and the average number of captures for males and females (9.8 versus 5.7) all differed significantly between the sexes.

Animals↗

PubMed1975

The number, size and spatial distribution of neurons in lamina IV of the mouse SmI neocortex.

We located the corresponding barrel in Layer IV of the mouse SmI cortex in eleven cerebral hemispheres sectioned in a plane tangential to the pia overlying SmI and in one sectioned and prepared by a combined Golgi-Nissl method. In the section in which barrel C-1 could be optimally visualized each neuronal soma was outlined with a camera lucida and the cross-sectional area measured with the aid of a small computer. In all, nearly 7,000 neurons were measured. We estimate that on average barrel C-1 contains about 2,000 neurons. The mean cross-sectional area of the perikarya is 62.51 mu2 (S.D. plus or minus 14.51 mu2) and the size distribution of the neurons is unimodal and positively skewed. There is no segregation of cells within the barrel on the basis of size. The spatial distribution of cells in the barrel is fairly constant, from specimen to specimen, and the charactieristic cytoarchitectonic appearance of the barrel can be related to regional neuronal packing density since there are at least 1.6 as many neurons in the sides of the barrel as the hollow. The constancy of the cellular composition of the barrels indicates that the mechanisms responsible for the development of the mouse SmI cortex are fairly rigidly determined, and that the barrel field should lend itself well to further quantitative, developmental and physiological analysis.

Animals↗

PubMed1999

Does the spatial distribution of the parasitic mite varroa jacobsoni oud. (Mesostigmata: varroidae) in worker brood of honey bee apis mellifera L. (Hymenoptera: apidae) rely on an aggregative process?

Varroa jacobsoni is an ectoparasite of honey bees which reproduces in capped brood cells. Multi-infestation is frequently observed in worker brood and can be interpreted as an aggregative phenomenon. The aim of this study was to determine whether the distribution of V. jacobsoni in worker brood cells relies on a random or an aggregative process. We studied the distribution of Varroa females in capped worker brood at similar age by comparing, by a Monte Carlo test, the observed frequency distribution of mites per cell to simulated distributions based on a random process. A complementary approach, using the "nearest neighbor distances" (NND) with Monte Carlo tests, was investigated to study the spatial distribution (a) between mites in different cells and (b) between infested cells in brood. The observed distributions did not differ significantly from that expected by a random process, and we conclude that there is no aggregation during invasion of V. jacobsoni in worker brood.

Journal Article↗

PubMed1994

Spatial distribution of sound pressure and energy flow in the ear canals of cats.

Spatial pressure distributions have been measured in the ear canals of ten cats and analyzed to obtain the energy reflection properties of the middle ear over a 10- to 25-kHz range of frequencies. Considerable intersubject variability is observed, much of which can be correlated with the condition of the tympanic membrane. For ears judged to be in good condition, reflection coefficients typically take values of about 0.2 between 15 and 25 kHz, indicating good matching of the dynamical properties of the auditory system to the ear canal sound field. At lower frequencies, the reflection coefficients tend to be somewhat higher and at higher frequencies the reflection coefficients increase quite rapidly with frequency. For ears judged to be in poorer condition, energy reflection coefficients of 0.5 and 0.9 were determined for the 15- to 25-kHz range. The variations of sound pressure along the canal (about 10 dB, even in well-coupled systems) confirm that single point pressure measurements may be inappropriate for defining the acoustical input at higher frequencies and new measures for specifying the input should be investigated. The net flow of acoustic energy into the auditory system, the sound power, is one possibility. Some initial measurements of sound power, obtained from analysis of the spatial pressure distributions, are presented.

Acoustic Stimulation↗

PubMed1993

Quantitative Determination of the Spatial Distribution of Nitrosomonas europaea and Nitrobacter agilis Cells Immobilized in kappa-Carrageenan Gel Beads by a Specific Fluorescent-Antibody Labelling Technique.

A novel technique, combining labelling and stereological methods, for the determination of spatial distribution of two microorganisms in a biofilm is presented. Cells of Nitrosomonas europaea (ATCC 19718) and Nitrobacter agilis (ATCC 14123) were homogeneously distributed in a kappa-carrageenan gel during immobilization and allowed to grow out to colonies. The gel beads were sliced in thin cross sections after fixation and embedding. A two-step labelling method resulted in green fluorescent colonies of either N. europaea or N. agilis in the respective cross sections. The positions and surface areas of the colonies of each species were determined, and from that a biomass volume distribution for N. europaea and N. agilis in kappa-carrageenan gel beads was estimated. This technique will be useful for the validation of biofilm models, which predict such biomass distributions.

Journal Article↗

PubMed1996

Performance differences as a function of stimulus-response compatibility with rapid serial visual presentation and spatially distributed presentation styles.

A means of presenting information temporally has been developed from the basic research on reading. Temporal displays allowed for faster processing speeds by reducing the number of saccades normally required to process spatially distributed information; however, a potential disadvantage to using temporal displays was an increased rate of error. Payne and Lang reported that a tradeoff between speed and accuracy is sometimes the result of using temporally distributed displays. As they used an alphabetic coding scheme which may not have facilitated the most optimal stimulus-response mapping, the current experiment tested the effects of a directional coding scheme on a temporally distributed display with 24 subjects. Analysis indicated the coding scheme did improve processing speed on the temporal display, but the error rate for the temporal display was higher than with the alphabetic coding scheme. Therefore, the limitation of temporal displays in a tradeoff between speed and accuracy persisted using the directional coding scheme.

Adult↗

PubMed1987

[Spatial distribution of hippocampal responses to dental pulp stimulation and acoustic clicks].

Evoked potentials and unitary discharges in responses to tooth pulp and acoustic click stimuli were recorded from the hippocampus of freely moving rats. The spatial distribution of evoked field responses to tooth pulp stimulation and acoustic clicks were identical. Averaged evoked potentials consisted of a large negative deflection (N1) preceded by a small positive potential (P1). The shortest latency N1 was recorded from the middle third of the dentate molecular layer and the outer portion of apical dendrites of Ca3 (27 ms). The peak latency of N1 was significantly longer (34 ms) in the stratum radiatum of CA1. Laminar profiles of N1 in the dentate gyrus and CA3 were similar to that evoked by electrical stimulation of the perforant path and in CA1 similar to the response profile evoked by the Schaffer collaterals. The largest amplitude P1 was observed above the pyramidal layer of CA1 and the hilus. Both sensory modalities were able to modify the discharge rate of neurons in all hippocampal regions. A conclusion is made that information about sensory stimuli can reach the hippocampus by two distinctive pathways: a short-latency inhibitory input via the fimbrial fornix and a longer-latency path via the entorhinal cortex.

Afferent Pathways↗

PubMed2003

The use of trans-vinylene formation in quantifying the spatial distribution of electron beam penetration in polyethylene. Single-sided, double-sided and shielded irradiation.

The use of the quantification of trans-vinylene unsaturations in irradiated ultrahigh molecular weight polyethylene (UHMWPE) in determining the spatial distribution of electron beam penetration was investigated. UHMWPE was irradiated with a 10MeV linear electron beam accelerator to 100kGy at both room temperature and 125 degrees C in air. The irradiation was carried out in shielded and unshielded single-sided and unshielded double-sided irradiation modes. Dose-depth profiles were measured by quantifying the yields of trans-vinylene unsaturations as a function of depth away from the e-beam incidence surfaces using infrared spectroscopy. The extent of beam penetration increased with increasing irradiation temperature as was manifested by the increase in the iso-dose penetration with the unshielded single-sided irradiation and increased dose overlap with the unshielded double-sided irradiation. The optimum thickness with maximum uniformity in dose-depth distribution for double-sided irradiation was 85 and 90mm for 25 degrees C and 125 degrees C irradiation temperatures, respectively.

Biocompatible Materials↗

PubMed2005

Structure and thermodynamics of protein-polymer solutions: effects of spatially distributed hydrophobic surface residues.

Protein-polymer association in solution driven by a short-range attraction has been investigated using a simple coarse-grain model solved by Monte Carlo simulations. The effect of the spatial distribution of the hydrophobic surface residues of the protein on the adsorption of weakly hydrophobic polymers at variable polymer concentration, polymer length, and polymer stiffness has been considered. Structural data on the adsorbed polymer layer and thermodynamic properties, such as the free energy, energy, and entropy, related to the protein-polymer interaction were calculated. It was found that a more heterogeneous distribution of the surface residues promotes adsorption and that this also applies for different polymer concentrations, polymer chain lengths, and polymer flexibilities. Furthermore, the polymer adsorption onto proteins with more homogeneous surface distributions displayed larger sensitivity to polymer properties such as chain length and flexibility. Finally, a simple relation between the adsorption probability and the change in the free energy was found and rationalized by a simple two-state adsorption model.

Adsorption↗

PubMed1984

Temporal sequence and spatial distribution of early events of fertilization in single sea urchin eggs.

Measurements and observations of five early events of fertilization, singly and in pairs, from single sea urchin eggs have revealed the precise temporal sequence and spatial distribution of these events. In the Arbacia punctulata egg, a wave of surface contraction occurs coincident with membrane depolarization (t = 0). These two earliest events are followed by the onset of a rapid, propagated increase in cytoplasmic-free calcium at approximately 23 s as measured by calcium-aequorin luminescence. The luminescence reaches its peak value by 40 s after the membrane depolarization. The luminescence remains uniformly elevated for some time before its decay over several minutes. The onset of an increase in the pyridine nucleotide (NAD(P)H) fluorescence follows the membrane depolarization at approximately 51 s. The fertilization membrane begins its elevation in a wave-like fashion coincidentally with the increase in NAD(P)H fluorescence. Similar results are observed in the Lytechinus variegatus egg. The results suggest that while the increase in cytoplasmic-free calcium may be important for many changes occurring in the egg, the elevated-free calcium is not directly responsible for the propagated wave of cortical granule exocytosis.

Animals↗

PubMedDate not supplied

Spatial distribution of DDT in sediments from estuarine rivers of central Florida.

Sediments may act as both a carrier for and a potential source of contaminants such as toxic organics in aquatic environments. This study investigated the spatial distribution of the pesticide DDT [1,1, 1-trichloro-2,2-bis(p-chlorophenyl)ethane] in sediments from the Cedar and Ortega Rivers located in the lower St. Johns River basin, Florida, USA, using field measurements and three-dimensional kriging analysis. High DDT concentrations were found near the junction of the Cedar and Ortega Rivers and at the north end of the Ortega River in the upper 0.5 m of the sediments, indicating that the sediment was enriched with DDT in the top layer although use of this chlorinated compound was banned in 1972. Further study revealed that the influence of sediment grain size or texture on DDT contamination was negligible in this river system and no linear correlations existed among DDT and its metabolites such as DDD [1,1-dichloro-2,2-bis(p-chlorophenyl)ethane] and DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene]. Comparison of three-dimensional distribution of DDT content to the Florida sediment quality assessment guideline or probable effect level (PEL) showed several "hot spots" in the Ortega River sediments, where DDT contents exceeded the PEL value of 4.78 microg kg(-1). Such contamination may pose a significant hazard to aquatic life.

DDT↗

PubMed1975

The spatial distribution of urban pharmacies.

Pharmacists are thought to play a central role in providing information and advice on health to lower income and other socially disadvantaged groups. However, recent evidence suggests that social biases exist in the spatial distribution of urban pharmacies. Such biases would severely limit the accessibility of the poor and the nonwhite to pharmacy services. To test the general nature of this evidence, we used multiple regression techniques to assess the simultaneous influence of several ecological and socioeconomic variables on the location of pharmacies in Pittsburgh and Omaha. After controlling for the influence of physicians, hospitals, commercial activity, population, and other variables thought to affect pharmacy location, we were unable to detect any evidence of a direct association between pharmacy location and the socioeconomic or demographic (other than total population) characteristics of areas in either city.

Delivery of Health Care↗

PubMed2004

[Spatial distribution and landscape ecological impact degree assessment of quarry in Zhuhai City].

Artificial erosion is one of the typical artificial landscape degradation. Based on the support of GIS and RS and combined with field investigation data, the spatial distribution characteristics and landscape ecological impact degree of quarry were analyzed. There were 235 quarries in Zhuhai city, which concentrated on Sanzao town and Jingan town. According to buffer analysis, the quarries distribution had a obviously logarithm relationship with its distances from roads. 152 quarries with the area of more than 5000 m2 were assessed by landscape ecological impact degree (LEI) index. The results indicated that 9 quarries belonged to great influence level and 19 quarries belonged to strong influence on ecological environment.

Ecology↗

PubMed2006

[Temporal and spatial distribution characteristics and indicator effects of Corbicula fluminea in coastal flat of Changjiang estuary].

Corbicula fluminea is a kind of macrobenthos commonly seen in the coastal wetland ecosystem of Changjiang estuary. This paper studied the temporal and spatial distribution characteristics of its population density and biomass, and analyzed the heavy metals concentrations in its body and in suspended particles and sediments. The results showed that the distribution of C. fluminea was discrepant in different seasons, sampling sites, and even, sampling sections of same sampling site. The population density and biomass of C. fluminea were higher in spring and autumn but lower in summer, and higher in mid-tidal flat than in low and high flats of Chongming. Its annual average population density and biomass was the maximal in Xupu. C. fluminea had definite accumulation ability to copper and zinc, but not to lead and chromium. There was a significant negative correlation between the lead concentrations in C. fluminea and sediments.

Animals↗

PubMed1990

Spatial distribution of protein in interstitial matrix of rat mesenteric tissue.

Interstitial matrix protein has been measured by collecting fluid from implanted capsules and wicks. If the interstitial matrix is well mixed, then these measurements provide an accurate indication of perivascular protein concentration. However, there is increasing evidence suggesting that interstitial protein distribution is nonuniform. To test this hypothesis, a combined light-scattering and protein absorbance image of mesenteric tissue in a pentobarbital-anesthetized rat was obtained by using an ultraviolet-sensitive television camera to perform videomicrospectrophotometry. In avascular tissue regions protein was organized into periodic nonuniform ridges and valleys. On a smaller scale, the protein along a ridge was organized into clusters. Similar clusters were seen along the wall of small tortuous microvessels and were accompanied by radial gradients in protein distribution. High protein concentration tunnels were occasionally seen extending from a microvessel into the interstitial matrix. A two-way analysis of variance shows that macromolecular spatial distribution is nonuniform (P less than 0.001). Thus the hypothesis that the extracellular matrix is well mixed fails for macromolecules in rat mesenteric loose connective tissue.

Animals↗

PubMed1997

Spatial distribution of collagen type I mRNA in Paracentrotus lividus eggs and embryos.

We have identified the presence of type I collagen (COLL1alpha) mRNA in Paracentrotus lividus unfertilized egg, indicating a maternal origin of this mRNA. By in situ whole mount hybridization the spatial distribution of COLL1alpha mRNA in egg and embryo at different developmental stages was established. Moreover, the presence of COLL1alpha gene in Paracentrotus lividus genome was analyzed by Southern blot experiments. The localization pattern indicates that the maternal mRNA is placed in the fertilized egg in a fixed position, relative to the embryonic axes. Furthermore, the embryonic expression is spatially restricted during development, suggesting involvement in sea urchin embryo cell specification events. The presence of two bands in Southern blot hybridization may indicate that two genes specific for COLL1alpha are present in the sea urchin genome.

Animals↗

PubMed1997

Host-habitat relations as an important determinant of spatial distribution of flea assemblages (Siphonaptera) on rodents in the Negev Desert.

We studied flea assemblages on rodents in different habitats of the Ramon erosion cirque in the Negev Desert to examine whether host-habitat relations influence flea spatial distribution. Eleven flea species parasitizing 12 rodent species were recorded. There was significant positive relationship between flea species richness and body mass of the host species; no relationships were found between relative richness of flea assemblage and either the number of habitats occupied by the host species or the size of host geographical range. The differences in pattern of flea parasitism among habitat types within host species were determined by both environmental features of a habitat and the specific pattern of habitat use by rodents. There was replacement of Xenopsylla conformis by Xenopsylla ramesis on Meriones crassus and Gerbillus dasyurus among different habitats. The results of ordination of the flea collections from each individual host demonstrated that the flea assemblages were segregated mainly along 4 axes, which explained 86% of total variance. Each of the ordination axes corresponded with a change in flea species composition. The directions of these changes were (1) among-hosts within a habitat and (2) among-habitats within a host.

Animals↗