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Results for “Spatial Distribution”

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At least 433 records · Page 24Linked to original sources

PubMed2006

New evaluation of reconstructed spatial distribution function from radial distribution functions.

Although three dimensional (3D) solvation structure is much more informative than one dimensional structure, its evaluation is difficult experimentally and theoretically. In our previous Communication [Yokogawa et al., J. Chem. Phys. 123, 211102 (2005)], we proposed a new method to present reconstructed spatial distribution function (RC-SDF) from a set of radial distribution functions (RDFs). In this article, we successfully extended the method more accurately with new basis sets. This new method was applied to two liquid solvation structures, methanol and dimethyl sulfoxide, as examples. Their RC-SDFs evaluated here clearly show that the former solvation structure is well defined while the latter one is broad, which agrees well with the SDFs calculated directly from molecular dynamics simulations. These results indicate that the method can reproduce well these 3D solvation structures in reasonable computational cost.

Journal Article↗

PubMed1994

Platelet-derived growth factor and angiotensin II induce different spatial distribution of protein kinase C-alpha and -beta in vascular smooth muscle cells.

Protein kinase C is an important second-messenger system that is translocated from the cytosol to the cell membrane on cell stimulation. We used confocal microscopy to study the spatial distribution of protein kinase C isoforms after stimulation of cultured vascular smooth muscle cells with platelet-derived growth factor and angiotensin II (Ang II). Monoclonal antibodies for the isoforms alpha and beta were used. Translocation was also assessed by Western blot. Isoform alpha was evenly distributed in the cytosol, whereas the beta isoform formed coarse granules in the perinuclear region. Both isoforms shifted from the cytosolic to the membrane fraction after exposure to Ang II (10(-7) mol/L) and platelet-derived growth factor (100 ng/mL at 6, 12, and 20 minutes). Confocal microscopy showed a rapid assembly of isoform alpha along cytosolic fibers at 6 minutes followed by a translocation toward the nucleus at 12 minutes with Ang II. Platelet-derived growth factor engendered a similar response; however, a cytoskeletal distribution was not observed. The beta isoform was rapidly translocated by both inducers to the perinuclear region and the nucleus. Our results show that inducers cause a translocation of protein kinase C isoforms not only into the cell membrane but also into the cell nucleus. We suggest that protein kinase C may also be important for nuclear signaling.

Angiotensin II↗

PubMed1990

Spatial distribution of Aedes triseriatus eggs in a site endemic for La Crosse encephalitis virus.

Egg laying behavior in Aedes triseriatus was studied in an oak woodlot endemic for La Crosse encephalitis virus in southwestern Wisconsin. Daily counts from oviposition traps allowed the calculation of spatial distribution parameters for eggs during 1988. Egg distribution along an ellipsoidal transect of 25 traps was clumped with some traps being more attractive to ovipositing female Ae. triseriatus than others. Females were estimated to deposit a mean of 31 +/- 9.8 eggs per oviposition.

Aedes↗

PubMed1983

The spatial distribution of fixed mutations within genes coding for proteins.

We have examined the extensive amino acid sequence data now available for five protein families - the alpha crystallin A chain, myoglobin, alpha and beta hemoglobin, and the cytochromes c - with the goal of estimating the true spatial distribution of base substitutions within genes that code for proteins. In every case the commonly used Poisson density failed to even approximate the experimental pattern of base substitution. For the 87 species of beta hemoglobin examined, for example, the probability that the observed results were from a Poisson process was the minuscule 10(-44). Analogous results were obtained for the other functional families. All the data were reasonably, but not perfectly, described by the negative binomial density. In particular, most of the data were described by one of the very simple limiting forms of this density, the geometric density. The implications of this for evolutionary inference are discussed. It is evident that most estimates of total base substitutions between genes are badly in need of revision.

Amino Acid Sequence↗

PubMed2002

A dynamical model of saccade generation in reading based on spatially distributed lexical processing.

The understanding of the control of eye movements has greatly benefited from the analysis of mathematical models. Currently most comprehensive models include sequential shifts of visual attention. Here we propose an alternative model of eye movement control, which includes three new principles: spatially distributed lexical processing, a separation of saccade timing from saccade target selection, and autonomous (random) generation of saccades with foveal inhibition. These three features provide a common control mechanism for fixations, refixations, and regressions. Consequently, the model is called SWIFT (Saccade-generation with inhibition by foveal targets). Results from numerical simulations are in good agreement with effects of word frequency on single-fixation, first-fixation, and gaze durations as well as fixation and word skipping probabilities in first-pass analysis. The model inherently produces complex eye movement patterns including refixations and regressions due to its underlying dynamical principles.

Computer Simulation↗

PubMed2002

Spatial distribution of ion channel activity in biological membranes: the role of noise.

A new approach is proposed to model a collective ion channel dynamics. We have assumed that ion channels create a two-component spatio-temporal interaction field. Every channel at its current spatial location in membrane contributes permanently to this field with its state (open or closed) and coupling strength to other channels. This field is described by a reaction-diffusion equation, the transition of ion channel from closed to open state (and vice versa) is described by a master equation, and migration of channels in membrane is described by a set of Langevin equations coupled by the interaction field. Within this model, we have investigated critical conditions for spatial distribution of ion channel activity.

Cell Membrane↗

PubMedDate not supplied

[Trends and spatial distribution of mortality from external causes in Salvador, Bahia State, Brazil].

Since 1980, external causes (ICD-9 E800-E999) have been ranked as the second leading causal group for mortality in Brazil, thus becoming a major public health problem. This study aimed to describe spatial distribution trends for violent deaths in the urban setting of Salvador, a city in Northeast Brazil, for the years 1988, 1991, and 1994. An ecological study was conducted, and mortality data were obtained from death certificates and the archives of the Institute for Forensic Medicine. There was an increase of 34.6% in the number of deaths from external causes between 1988 and 1994. The highest mortality rates were among men from 20 to 29 years of age (from 192.0 to 262.0/100,000) and those 65 years and over (from 188.7 to 258.1/100,000). Homicides were the leading cause of violent deaths in about 75.0% of neighborhoods. The authors discuss the need for comprehensive public policies and an interdisciplinary approach to elucidate the causes and deal with the problem of violence.

Adolescent↗

PubMed2004

[Spatial distribution of seawater dimethylsulfide in winter of Jiulong Jiang Estuary].

Cruise investigation of dimethylsulfide (DMS) emission in estuarine areas, heavily disturbed by human activities, was carried out in the winter of 2001 in Jiulong Jiang Estuary. The concentrations of chlorophyll, salinity and nutrients showed evidently spatial distribution in Jiulong Jiang Estuary, so did DMS concentrations in surface water. The average of seawater DMS was 101.0 and 242.1 ng x L(-1) in river mouth area and gulf area, respectively. DMS concentrations decreased first with the increase of seawater salinity and then increased. The highest DMS concentration occurred at river plume front of maximum turbidity zone of the estuary.

Air Pollutants↗

PubMed2004

Complex spatial distribution and dynamics of an abundant Escherichia coli outer membrane protein, LamB.

Advanced techniques for observing protein localization in live bacteria show that the distributions are dynamic. For technical reasons, most such techniques have not been applied to outer membrane proteins in Gram-negative bacteria. We have developed two novel live-cell imaging techniques to observe the surface distribution of LamB, an abundant integral outer membrane protein in Escherichia coli responsible for maltose uptake and for attachment of bacteriophage lambda. Using fluorescently labelled bacteriophage lambda tails, we quantitatively described the spatial distribution and dynamic movement of LamB in the outer membrane. LamB accumulated in spiral patterns. The distribution depended on cell length and changed rapidly. The majority of the protein diffused along spirals extending across the cell body. Tracking single particles, we found that there are two populations of LamB--one shows very restricted diffusion and the other shows greater mobility. The presence of two populations recalls the partitioning of eukaryotic membrane proteins between 'mobile' and 'immobile' populations. In this study, we have demonstrated that LamB moves along the bacterial surface and that these movements are restricted by an underlying dynamic spiral pattern.

Bacterial Outer Membrane Proteins↗

PubMed2006

Spatial distribution of repolarization and depolarization abnormalities evaluated by body surface potential mapping in patients with Brugada syndrome.

BACKGROUND: Mutations in sodium channel gene, SCN5A, have been identified in Brugada syndrome, but it is still unclear as to how sodium channel dysfunction relates to arrhythmogenesis. We examined spatial distribution of both repolarization and depolarization abnormalities in patients with Brugada syndrome by using 87-leads body surface potential mapping (BSPM). METHODS: BSPM was recorded under baseline condition and after pharmacological interventions in 28 patients with Brugada syndrome (27 males, 49 +/- 14 years). The ST-segment amplitude 20 ms after the end of QRS (ST20), QRS duration, and corrected recovery time (RTc) were measured in all 87-leads, and averaged among 6-leads (D-F, 5-6) reflecting right ventricular outflow tract (RVOT) potentials and the other 81-leads. RESULTS: The ST20 was elevated at baseline, normalized by isoproterenol, and augmented by pilsicainide in only the RVOT. The RTc was longer at baseline and increased by pilsicainide in only the RVOT. On the other hand, the QRS duration was slightly widened at baseline, further increased by pilsicainide, but not changed by isoproterenol in both leads. CONCLUSIONS: The ST-segment elevation and the RTc prolongation were localized and modulated by agents only in the RVOT region, while the slight QRS widening at baseline and further increase by pilsicainide were observed homogeneously. Our data suggest that depolarization abnormalities are distributed homogeneously, whereas repolarization abnormalities are localized in the RVOT.

Adolescent↗

PubMed1998

Spatial distribution patterns of Echinococcus multilocularis (Leuckart 1863) (Cestoda: Cyclophyllidea: Taeniidae) among red foxes in an endemic focus in Brandenburg, Germany.

Over a period of 40 months, 4374 foxes were randomly sampled from an area located in northwestern Brandenburg, Germany, and examined parasitologically for infections with Echinococcus multilocularis. Spatial analysis of the origin of infected animals identified two (one central and one southeastern) high-endemic foci with an estimated prevalence of 23.8%. By contrast, a prevalence of 4.9% was found in the remaining (low-endemic) area. The prevalences among juvenile and adult foxes were compared in the high-endemic and the low-endemic areas. To analyse the central high-endemic focus further, the random sample was stratified by zones representing concentric circles with a radius of 13 km (zone 1) or x(n-1) + 7 km for the remaining three zones from the apparent centre of this focus (anchor point). Prevalences calculated for each zone showed a decrease from zone 1 (18.8%) to zone 4 (2.4%) with significant differences for all zones but zones 3 and 4. The relative risk of an infection decreased rapidly in a distance range of 26 km around the high-endemic focus, whereas the relative risk remained unchanged within a distance of 5 km around the anchor point. The importance of heterogeneous spatial distribution patterns for the diagnosis and epidemiology of the infection is discussed.

Age Distribution↗

PubMed2002

Spatial distribution of indoor aerosol deposition under accidental release conditions.

Indoor aerosol dispersion and particle deposition was investigated using a series of puff releases of nonspecific activatable tracers simulating an accidental source. Initial particle size distribution included the respirable range, with most of the particles between 0.5 to 5.0 microm. Tracers were released in a nuclear laboratory/work environment and were collected via passive collector foils to obtain the spatial distribution of deposition. The observed distribution characteristics did not always correspond to the measured air flow patterns, and they showed a non-negligible dependence on aerosol dynamics such as thermophoretic effects. The collected data represent integrated deposition flux, which can serve for validation of aerosol dynamics models that aim to predict the deposition fluence of particles and may also be used for planning surface contamination surveys following accidental releases.

Accidents, Occupational↗

PubMed2004

Impact of finer grid resolution on the spatial distribution of vehicle emissions inventories.

The ability to model air quality dispersion at increasingly smaller resolutions requires a concomitant improvement in the resolution of the gridded mobile source emissions used as input to these models. Two methods are currently used to allocate mobile emissions to grids; because of the limitations associated with these methods, their application is usually restricted to coarser grid resolutions. This paper uses a new mobile emissions inventory model (UCDrive) to explore the spatial distribution of mobile source emissions using finer grid cell resolutions. Our results indicate that the new model improves the precision of the spatial allocation of mobile source emissions, which in turn improves our ability to identify and implement pollutant control strategies.

Air Pollutants↗

PubMed1988

Growth of the maize primary root at low water potentials : I. Spatial distribution of expansive growth.

Seedlings of maize (Zea mays L. cv WF9 x Mo 17) were grown in vermiculite at various water potentials. The primary root continued slow rates of elongation at water potentials which completely inhibited shoot growth. To gain an increased understanding of the root growth response, we examined the spatial distribution of growth at various water potentials. Time lapse photography of the growth of marked roots revealed that inhibition of root elongation at low water potentials was not explained by a proportional decrease in growth along the length of the growing zone. Instead, longitudinal growth was insensitive to water potentials as low as - 1.6 megapascal close to the root apex, but was inhibited increasingly in more basal locations such that the length of the growing zone decreased progressively as the water potential decreased. Cessation of longitudinal growth occurred in tissue of approximately the same age regardless of spatial location or water status, however. Roots growing at low water potentials were also thinner, and analysis revealed that radial growth rates were decreased throughout the elongation zone, resulting in greatly decreased rates of volume expansion.

Journal Article↗

PubMedDate not supplied

[Spatial distribution of Lutzomyia longipalpis (Lutz & Neiva, 1912) and Lutzomyia cruzi (Mangabeira, 1938) in the State of Mato Grosso].

Visceral leishmaniasis is currently considered an emergent and reemergent disease, in agricultural and urban zones, both in domestic and peridomestic areas. The objective of this work was to verify the spatial distribution of Lutzomyia longipalpis and Lutzomyia cruzi in Mato Grosso State. Data from 1996 to 2004 was collected by the Entomology Laboratory, whose captures were carried with a CDC light trap. Sixty-eight of the 139 cities in the state have been studied. Lutzomyia longipalpis and Lutzomyia cruzi occurred in 23 and 22 cities, respectively. The results demonstrate the extensive occurrence of Lutzomyia longipalpis in areas with different vegetation types: savanna, transition and Amazon forest. Lutzomyia cruzi occurred mainly in cities with areas of marshland and savanna. Verification of the distribution of the vector populations in the state and their preferential vegetation type, provides an indication of vulnerable and/or receptive areas for disease transmission.

Animals↗

PubMed2003

[Temporal-spatial distribution characteristics of microclimate in tropical secondary forest canopy gap in Xishuangbanna].

Based on the data obtained from vertical gradient measurements of microclimatic elements of canopy gap in tropical secondary forest of Xishuangbanna in fog-cool and dry-hot season, the daytime characteristics of temporal-spatial distribution and variation of trunk surface temperature, air temperature, water vapor pressure and relative humidity in canopy gap were discussed. The data showed that gap edge had not only a remarkable thermal effect, but also a significant water vapor effect. These effects resulted in environmental heterogeneity in canopy gap. The results provided a basis for further studying heat and water vapor transport, microclimatic formation, biodiversity, and forest succession in canopy gap.

Climate↗

PubMed2006

Pbx1/Pbx2 requirement for distal limb patterning is mediated by the hierarchical control of Hox gene spatial distribution and Shh expression.

Vertebrate limb development occurs along three cardinal axes-proximodistal, anteroposterior and dorsoventral-that are established via the organization of signaling centers, such as the zone of polarizing activity (ZPA). Distal limb development, in turn, requires a molecular feedback loop between the ZPA expression of sonic hedgehog (Shh) and the apical ectodermal ridge. The TALE homeoprotein Pbx1 has been shown to be essential for proximal limb development. In this study, we first uncover that Pbx1 and Pbx2 are co-expressed in the lateral plate and early limb field mesoderm. Later, Pbx2 is expressed throughout the limb, unlike Pbx1, which is expressed only in the proximal bud. By exploiting a Pbx1/Pbx2 loss-of-function mouse model, we demonstrate that, despite the lack of limb abnormalities in Pbx2-deficient (Pbx2(-/-)) embryos, compound Pbx1(-/-); Pbx2(+/-) mutants, in addition to their exacerbated proximal limb defects, exhibit novel and severe distal abnormalities. Additionally, we reveal that Pbx1(-/-); Pbx2(-/-) embryos lack limbs altogether. Furthermore, we establish that, unlike in flies, where the leg develops independently of Hox and where the Pbx ortholog Exd is required for specification of proximal (but not distal) limbs, in vertebrates, distal limb patterning is Pbx1/Pbx2 dependent. Indeed, we demonstrate that Pbx genetic requirement is mediated, at least in part, through their hierarchical control of Hox spatial distribution and Shh expression. Overall, we establish that, by controlling the spatial expression of Hox genes in the posterior limb and regulating ZPA function, Pbx1/Pbx2 exert a primary hierarchical function on Hox genes, rather than behaving merely as Hox ancillary factors.

Animals↗

PubMed2001

Comparison of two micro-analytical methods for detecting the spatial distribution of sorbed Pu on geologic materials.

Subsurface transport of groundwater contaminants is greatly influenced by chemical speciation, precipitation and sorption processes at the mineral-water interface. The retardation of contaminants is often greatest at boundaries between minerals and in fractures and pore spaces. The investigation of the spatial distribution of sorbed contaminants along these boundaries requires micro-analytical techniques. The sorption of dissolved Pu(V) on a natural zeolitic tuff from Yucca Mountain (NV, USA) was examined using microautoradiography (MAR), X-ray diffraction (XRD), electron microprobe (EM) techniques, and synchrotron-based micro-X-ray fluorescence (micro-SXRF). The tuff contained a heterogeneous distribution of zeolites and trace quantities of smectites, Fe oxides (hematite), and Mn oxides (rancieite), which are present as fracture fill and pore space materials. Micro-SXRF studies showed that Pu is mostly associated with bodies of smectite plus Mn oxides, which were typically elevated in Ce, Ga, Nb, Pb, Y, Ca, Ti, and Zn. Sorbed Pu was not associated with Fe-rich bodies, which were enriched in Cl and Rb. Results of the MAR studies were complementary to that of the micro-SXRF studies in that Pu was associated with similar elements in the tuff. Indirect detection of Pu by EM or micro-SXRF (by analyzing Ag developed on the MAR photoemulsion) was a more sensitive method for detecting lower levels of sorbed Pu than the direct detection of sorbed Pu via micro-SXRF in the absence of the photoemulsion.

Adsorption↗