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At least 217 records · Page 12Linked to original sources
PubMed1992

The geographic structure of measles epidemics in the northeastern United States.

The incidence of disease across geographic space often produces distinctive regional patterns. In this paper, a modeling approach to the identification of the factors that shape the patterns is presented, and a procedure for fitting the model to observed data is given. The methodology is illustrated by an application to the geographic structure of measles epidemics among 22 states of the northeastern United States, New York City, and Washington, D.C., from 1962 to 1988. The patterns identified are interpreted in terms of the spatial behavior of measles epidemics in the region, and the implications of the methodology for surveillance and control are considered.

Humans↗
PubMed2002

Modelling transfer characteristics of vestibular neurons in the fastigial nucleus of the behaving monkey on the basis of canal-otolith interaction.

The interaction of vestibular inputs with different dynamic and spatial behavior, i.e., canal-otolith interaction, leads to spatio-temporal convergence. Vestibular neurons in the fastigial nucleus often exhibit spatio-temporal convergence. The present report demonstrates that the discharge rates of most vestibular neurons in the primate fastigial nucleus can be simulated at different stimulus frequencies and orientations by a simple linear summation of the signals of the semicircular canals and the otoliths. In this way, a number of complex characteristics that depend on frequency, i.e. changing response-vector orientations, large phase changes, absence and presence of spatio-temporal convergence, can be easily explained.

Action Potentials↗
PubMedDate not supplied

Automatic analysis of left ventricular ejection fraction using stroke volume images.

The purpose of this study was to analyze, validate, and report on an automatic computer algorithm for analyzing left ventricular ejection fraction and to indicate future applications of the technique to other chambers and more advanced measurements. Thirty-eight patients were studied in the cardiac catheterization laboratory by equilibrium radionuclide ventriculography and concurrent contrast ventriculography. The temporal and spatial behavior of each picture element in a filtered stroke volume image series was monitored throughout the cardiac cycle. Pixels that met specific phase, amplitude, and derivative criteria were assigned to the appropriate chamber. Volume curves were generated from regions of interest for each chamber to enable calculation of the left ventricular ejection fraction. Left ventricular ejection fractions showed a good correlation (r = 0.89) between the two techniques. Ejection fractions ranged between 0.12 and 0.88, showing a wide range of application. It is concluded that automatic analysis of left ventricular ejection fraction is possible using the present algorithm and will be useful in improving the reproducibility and providing more accurate information during exercise protocols, pharmaceutical interventions, and routine clinical studies.

Cardiac Output↗
PubMed1992

Neural stimulation with magnetic fields: analysis of induced electric fields.

Spatial distributions of the derivative of the electric field induced in a planar semi-infinite tissue model by various current-carrying coils and their utility in neural stimulation are evaluated. Analytical expressions are obtained for the electric field and its spatial derivatives produced by an infinitely short current element. Fields and their derivatives for an arbitrarily shaped coil are then obtained by numerical summation of contributions from all the elements forming the coil. The simplicity of the solution and a very short computation time make this method particularly attractive for gaining a physical insight into the spatial behavior of the stimulating parameter and for the optimization of coils. Such analysis is useful as the first step before undertaking a more complex numerical analysis of a model more closely representing the tissue geometry and heterogeneity.

Computer Simulation↗
PubMed1995

Patient suffering: a taxonomy from the nurse's perspective.

Using the ethnoscientific method, a taxonomy depicting types of suffering experienced by patients was developed. Nurses were asked to describe patients' suffering and, from this data, the differing types were identified. The four major domains identified were 'to bear it', 'to stay in control', 'to protect', and 'to strengthen'. Under these broad domains, nurses identified 24 different types of suffering, such as peaceful, meaningful, self-absorbed, silent, stoic, flaunted, martyr-like, 'in limbo', and hopeless. Implications for nurses are that: (a) patients expend much energy in their suffering and this should be considered when giving care, (b) nurses' personal evaluation of patient suffering should not preclude individualized care, (c) patients need personal space periodically, (d) some patients do not want their suffering alleviated, and (e) hidden reasons for patient behaviour are likely to exist.

Adaptation, Psychological↗
PubMed1976

Social behavior of the conilurine rodents (Muridae) of Australia.

This paper describes in detail the elements of social behaviour and social organizations of four closely related rodents (Notomys alexis, Pseudomys albocinereus, P. shortridgei and P. desertor) from diverse habitats, and the social organizations of seven other conilurine rodents are described briefly. Most of the data were determined from quantitative observations of animals caged in twos or in larger groups for at least ten days. Breeding pairs were observed daily throughout pregnancy and parenthood. A dispersed organization and three types of communal organization are described, and evolutionary trends in dispersion and territoriality, cohesion, communication and co-operation are discussed.

Agonistic Behavior↗
PubMed1976

Field studies on the African fruit bat Epomophorus wahlbergi (Sundevall), with special reference to male calling.

Social interactions, site attachment and group cohesion were studied in a free-living colony of Epomophorus fruit bats. Daily activites in an undisturbed colony were recorded. Special attention was paid to the peculiar calling behavior of courting male during the night. Structure and repetition rate of their sounds were analyzed in the laboratory. A special mode of acoustic interaction was found and related to the observed spacing out of calling males. By following feeding animals in the field and by analysis of their faeces we found that besides fruits they eat special leaves which afford steroidal sapogenins.

Animals↗
PubMed1976

Visual behaviour in social interaction: the validity of eye contact assessments under different conditions of observation.

On each session of the experiment, each of five subjects was assigned to act as either gaze-sender (GS), gaze-receiver (GR), direct-sight observer (DSO) TV observer (TVO) or one-way mirror observer (OWO). The GS had to look into the GR's eyes each time he received prerecorded signal through earphones. The GR and the three observers recorded GS's eye-gaze behaviour. Two conditions of distance between GR and GS were included. Results showed that (1) the GR, DSO and TVO presented an equivalent accuracy in their EC recordings as compared with the programmed signals, while the OWO's accuracy appeared significantly lesser; (2) as a concealed observer, OWO was also less efficient than TVO since the agreement of the former with GR's records was significantly lower than that of the DSO, which was not the case for the latter; (3) with increment of distance, OWOs recorded longer EC periods, a tendency which was not found significant among the other observers.

Eye Movements↗
PubMedDate not supplied

Neutron fluxes in radiotherapy rooms.

The spatial distribution of the neutron flux, originated in an electron accelerator therapy room when energies above the threshold of (y,n) and (e,e'n) reactions are employed, is physically due to a direct flux, coming from the accelerator head, and to a flux diffused from the walls. In this work, the flux is described to a high degree of approximation by a set of functions whose spatial behavior is univocally determined by the angular distributions of the neutrons emitted from the shield of the accelerator head and diffused from the walls. The analytical results are verified with an extended series of Monte Carlo simulations obtained with the MCNP code.

Monte Carlo Method↗
PubMed2002

Tactic responses to oxygen in the phototrophic bacterium Rhodobacter sphaeroides WS8N.

The temporal and spatial behavior of a number of mutants of the photosynthetic, facultative anaerobe Rhodobacter sphaeroides to both step changes and to gradients of oxygen was analyzed. Wild-type cells, grown under a range of conditions, showed microaerophilic behavior, accumulating in a 1.3-mm band about 1.3 mm from the meniscus of capillaries. Evidence suggests this is the result of two signaling pathways. The strength of any response depended on the growth and incubation conditions. Deletion of either the complete chemosensory operons 1 and 2 plus the response regulator genes cheY(4) and cheY(5) or cheA(2) alone led to the loss of all aerotactic responses, although the cells still swam normally. The Prr system of R. sphaeroides responds to electron flow through the alternative high-affinity cytochrome oxidase, cbb(3), controlling expression of a wide range of metabolic pathways. Mutants with deletions of either the complete Prr operon or the histidine kinase, PrrB, accumulated up to the meniscus but still formed a thick band 1.3 mm from the aerobic interface. This indicates that the negative aerotactic response to high oxygen levels depends on PrrB, but the mutant cells still retain the positive response. Tethered PrrB(-) cells also showed no response to a step-down in oxygen concentration, although those with deletions of the whole operon showed some response. In gradients of oxygen where the concentration was reduced at 0.4 micro M/s, tethered wild-type cells showed two different phases of response, with an increase in stopping frequency when the oxygen concentration fell from 80 to 50% dissolved oxygen and a decrease in stopping at 50 to 20% dissolved oxygen, with cells returning to their normal stopping frequency in 0% oxygen. PrrB and CheA(2) mutants showed no response, while PrrCBA mutants still showed some response.

Bacterial Proteins↗
PubMed2002

GIS and health care.

GIS and related spatial analysis methods provide a set of tools for describing and understanding the changing spatial organization of health care, for examining its relationship to health outcomes and access, and for exploring how the delivery of health care can be improved. This review discusses recent literature on GIS and health care. It considers the use of GIS in analyzing health care need, access, and utilization; in planning and evaluating service locations; and in spatial decision support for health care delivery. The adoption of GIS by health care researchers and policy-makers will depend on access to integrated spatial data on health services utilization and outcomes and data that cut across human service systems. We also need to understand better the spatial behaviors of health care providers and consumers in the rapidly changing health care landscape and how geographic information affects these dynamic relationships.

Bioterrorism↗
PubMed2000

Age-related decrease in the Schaffer collateral-evoked EPSP in awake, freely behaving rats.

Synaptic response size in the CA1 region of the hippocampus in aged rats is reduced for a given stimulus intensity, compared with that elicited in young rats. Consistent with the in vitro findings of reduced Schaffer collateral-evoked CA1 EPSPs in old rats, the population currents evoked to iontophoretically applied AMPA are also smaller relative to the presynaptic fiber potential amplitude. On the other hand, the size of the presynaptic fiber potential and amplitude of unitary intra-cellularly recorded EPSP responses do not change across age in the CA1 region. These electrophysiological findings are consistent with the hypothesis that old rats have fewer functional synaptic contacts per Schaffer collateral axon than do young rats. The possibility that this age change arises as a result of a differential tissue recovery response to in vitro preparation was examined in the present study. CA1 presynaptic fiber potential and EPSP amplitudes evoked by the stimulation of Schaffer collateral afferents were studied in intact, freely behaving young and old rats. We confirmed in vivo the pattern of electrophysiophysiological results previously reported in vitro and found significant correlations between the synaptic response amplitudes and the accuracy of spatial behavior in the Morris swim task. The data suggest that changes in functional connectivity of old rats may be a significant contributor to cognitive changes during aging.

Afferent Pathways↗
PubMed1976

Ranging patterns of a troop of baboons (Papio anubis) in Kenya.

A troop of olive baboons, Papio anubis, was studied for 11 months in an open-country habitat near Gilgil, Kenya. Detailed mapping of troop movements was undertaken and provided a precise picture of range usage, showing that a small part of the range was used intensively. Gradations of home range use are described quantitatively. Tendencies to spread out and coalesce in different parts of the range are investigated. Shifting ranging patterns are examined together with meteorological factors, seasonal food supplies and water availability.

Age Factors↗