Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Distance”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55Linked to original sources
PubMed2003

Minimum distance probability discriminant analysis for mixed variables.

Minimum distance probability (MDP) is a robust discriminant algorithm based on a distance function. In this article, we generalize the use of MDP to the case of mixed (continuous and categorical) variables by means of the individual-score (IS) distance. This distance assumes an underlying parametric model and is based on the score transformation of the data. We have adapted it to the usual case of ignoring the distribution of the whole set of observed variables, but assuming that some knowledge about the marginal distributions is available. Finally, MDP with IS distance (IS-MDP) is compared with other discriminant methods (including those designed for mixed data) in several examples and simulations. IS-MDP is shown to be the most efficient method according the leave-one-out criterion.

Breast Neoplasms↗
PubMed1995

Relations between genetic distance of parental pig breeds and heterozygosity of their F1 crosses measured by genetic markers.

The aim of this paper is to examine the extent to which increment of heterozygosity in F1 crosses can be predicted from genetic distance of parental breeds. For this purpose, 38 polymorphic marker loci (blood groups, allotypes, polymorphic proteins and enzymes) were tested in 1115 purebred animals (Duroc, Hampshire and Czech Meat Pig as sire breeds; Landrace, Large White and Black Pied Prestice as dam breeds) and in 1428 crossbred animals of the resulting nine crossbred groups. The number of animals in each genetic group ranged from 75 to 230. On the basis of the allele frequencies of the scored loci, three measures of genetic diversity (heterozygosity, standardized heterozygosity, effective number of alleles) were calculated in all 15 genetic groups. Furthermore, two measures of genetic distance (Nei's standard genetic distance and Gregorius' absolute genetic distance) were calculated between the parental populations. High correlations (Pearson product-moment correlation 0.62 to 0.73; Spearman rank correlation 0.58 to 0.85) were found between the increment of heterozygosity in the crosses (in relation to the mean of the heterozygosities of parental populations) and the genetic distance between the parental populations.

Animals↗
PubMed1992

Women and distance education: a nursing perspective.

It is only very recently that studies of distance learners have begun to consider gender as a variable. Given the rapid growth of distance education programmes for nurses, it is appropriate to consider at this time how educators can best meet the needs of these (mostly) women students. Distance education tends to mean different things in different institutions, ranging from the 'industrial model' self-study course package with limited teacher student interaction to the fully interactive audio and video conferencing of the 'virtual classroom'. Each of these teaching/learning situations poses a different set of challenges, and each requires different solutions. Using illustrations drawn from experiences with a BN programme for registered nurses in Atlantic Canada, and from the limited literature, this paper explores both women's participation in distance education and the barriers that sometimes prevent this, as well as the kind of support women distance learners need most in order to learn effectively.

Attitude↗
PubMed2004

Psychological size and distance: emphasising the interpersonal relationship as a pathway to optimal teaching and learning conditions.

BACKGROUND: Positive interpersonal relationships between teachers and learners increase the quality of learning. The purpose of this study was to investigate psychological size (perceived status) and psychological distance (perceived emotional connectedness) in medical teaching interactions and their impact on the teaching and learning process. METHOD: A total of 45 paediatric preceptor/resident pairs engaged in longitudinal continuity training experiences at different sites were surveyed about teaching effectiveness, satisfaction with teaching, and the psychological size and distance in the relationship between each pair. RESULTS: Both residents and preceptors perceived the resident as having a smaller psychological size compared to the preceptor. Residents perceived greater psychological distance in the relationship than did preceptors, and this distance was significantly related to both residents' satisfaction with particular preceptors and their perception of the preceptors' effectiveness. CONCLUSIONS: Psychological size and distance contribute to effective and satisfactory teaching. Investigating additional aspects of the teaching-learning relationship should help identify optimal educational conditions.

Communication↗
PubMed2006

Decomposed pairwise regression analysis of genetic and geographic distances reveals a metapopulation structure of stream-dwelling Dolly Varden charr.

Isolation by distance is usually tested by the correlation of genetic and geographic distances separating all pairwise populations' combinations. However, this method can be significantly biased by only a few highly diverged populations and lose the information of individual population. To detect outlier populations and investigate the relative strengths of gene flow and genetic drift for each population, we propose a decomposed pairwise regression analysis. This analysis was applied to the well-described one-dimensional stepping-stone system of stream-dwelling Dolly Varden charr (Salvelinus malma). When genetic and geographic distances were plotted for all pairs of 17 tributary populations, the correlation was significant but weak (r(2) = 0.184). Seven outlier populations were determined based on the systematic bias of the regression residuals, followed by Akaike's information criteria. The best model, 10 populations included, showed a strong pattern of isolation by distance (r(2) = 0.758), suggesting equilibrium between gene flow and genetic drift in these populations. Each outlier population was also analysed by plotting pairwise genetic and geographic distances against the 10 nonoutlier populations, and categorized into one of the three patterns: strong genetic drift, genetic drift with a limited gene flow and a high level of gene flow. These classifications were generally consistent with a priori predictions for each population (physical barrier, population size, anthropogenic impacts). Combined the genetic analysis with field observations, Dolly Varden in this river appeared to form a mainland-island or source-sink metapopulation structure. The generality of the method will merit many types of spatial genetic analyses.

Animals↗
PubMed1989

Calculating three-dimensional molecular structure from atom-atom distance information: cyclosporin A.

In recent years methods for deriving spatial molecular structure from atom-atom distance information have gained in importance due to the emergence of two-dimensional nuclear magnetic resonance (n.m.r) techniques, which make it possible to obtain such distance information for polypeptides, small proteins, sugars, and DNA fragments in solution. Distance geometry (DG) and restrained molecular dynamics (MD) refinement are applied to a cyclic polypeptide, the immunosuppressive drug cyclosporin A, and the results are compared. Two different procedures, DG followed by restrained MD, and straightforward restrained MD starting from the X-ray structure, both lead to a unique conformation that satisfies the 58 experimentally determined distance constraints. The results nicely show the relative merits of DG and restrained MD techniques for determining spatial molecular structure from distance information.

Cyclosporins↗
PubMed1994

Coupling constants and hydrogen bonds as experimental restraints in a distance geometry refinement protocol.

A refinement procedure commonly used after distance geometry calculations has been modified to include the use of experimental restraints from coupling constants and hydrogen bonds. Fewer experimental distance constrains (NOEs) are available for peptides as compared to proteins; therefore it is important to incorporate other conformational restraints into refinement methods. The procedure was applied to a cyclic hexapeptide containing two thioamide substitutions, cyclo(-Gly1-Pro2-Phe3 psi [CS-NH]Val4-D-Phe5-Phe6 psi [CS-NH]-). Distance geometry was used to study this peptide, since no potential energy parameters, required in molecular mechanics or dynamics calculations, are available for the thioamide. This is a general problem in the study of peptidomimetics; physiochemical properties of heteroatoms are required within a self-consistent force field. Here, we illustrate the use of metric matrix distance geometry followed by refinement with distance and angle driven dynamics (DADD). We also introduce a new way to handle intramolecular hydrogen bonds by an additional very small and flexible restraint. This method is a viable alternative for the conformational examination of peptides and peptidomimetics. The modifications described here should also find use in the conformational determination of flexible regions of proteins, where the number of NOEs are limited.

Amino Acid Sequence↗
PubMed1988

Distances between functional sites in cardiac sarcoplasmic reticulum (Ca2+ +Mg2+)-ATPase. Inter-lanthanide energy transfer.

The high-affinity Ca2+-binding sites of cardiac sarcoplasmic reticulum (Ca2+ +Mg2+)-ATPase have been probed using trivalent lanthanide ions. Non-radiative energy-transfer studies, using luminescent probe Eu3+ as a donor and Nd3+ or Pr3+ as acceptor, were carried out to estimate the distance between two high-affinity Ca2+-binding/transport sites. Eu3+ was excited directly with pulsed laser light and the energy-transfer efficiency to Nd3+ or Pr3+ was measured, under the conditions in which most donor-acceptor pairs occupied the high-affinity Ca2+ sites. The distance between two high-affinity Ca2+ sites is about 0.89 nm. In the presence of ATP the distance between the high-affinity sites is about 0.855 nm, whereas in the presence of adenosine 5'-[beta, gamma-methylene]triphosphate or adenosine 5'-[beta, gamma-imino]triphosphate the distance is about 0.895 nm. To estimate the distance between the high-affinity Ca2+ sites and ATP-binding/hydrolytic site, we have measured the energy-transfer efficiency between Eu3+ and Cr3+-ATP with Eu3+ at the high-affinity Ca2+ sites and Cr3+-ATP at the ATP-binding/hydrolytic site. Our results show that ATP-binding/hydrolytic site is separated by about 2.2 nm from each high-affinity Ca2+ site.

Animals↗
PubMed1993

Intramolecular distances within the Ca(2+)-ATPase from sarcoplasmic reticulum as estimated through fluorescence energy transfer between probes.

Fluorescence energy transfer measurements have been carried out to estimate intramolecular distances between probes bound to Ca(2+)-transporting ATPase (Ca(2+)-ATPase) as well as distances between these probes and the phospholipid headgroup. The nucleotide binding site was monitored by using 1,N6-ethenoadenosine 5'-triphosphate, a fluorescent analogue of ATP, and also by labelling Lys515 with fluorescein 5'-isothiocyanate. Three different cysteine residues were individually labelled using the following probes: 5-[(2-iodoacetyl)aminoethyl]amino-naphthalene-1-sulfonic acid (I-AEDANS), 7-chloro-4-nitro-2,1,3-benzoxadiazole (NBD-Cl) and fluorescent maleimides. The surface of the membrane was labelled by reconstitution with fluorescent phospholipids (fluorescein and rhodamine derivatives). We found a distance of 4.1 nm from the nucleotide binding site to NBD (at Cys344), and the same distance to fluorescent maleimides (at Cys364). The AEDANS label (at Cys670,672) was found separated 3.5 nm from NBD, 4.4 nm from fluorescent maleimides, and 3.9 nm from the lipid matrix. The NBD label was 3.2 nm apart from fluorescent maleimides and 2.2 nm from the lipid matrix. Finally, fluorescent maleimides were found to be located 4.2 nm above the membrane surface. All these distances agree with a molecular model in which NBD is located in the stalk portion of the Ca(2+)-ATPase, near the surface of the membrane, and the rest of the probes are above it, in the globular domain of the protein.

4-Chloro-7-nitrobenzofurazan↗
PubMed2006

Effect of the oral hypoglycaemic sulphonylurea glibenclamide, a blocker of ATP-sensitive potassium channels, on walking distance in patients with intermittent claudication.

AIMS: The oral hypoglycaemic sulphonylurea glibenclamide stimulates endogenous insulin secretion through blockade of ATP-sensitive potassium (KATP) channels on pancreatic beta cells, but also blocks cardiovascular KATP channels, leading to increased peripheral vascular resistance and reduced peripheral blood flow in non-diabetic subjects. Therefore, this study examined whether a single oral dose of glibenclamide adversely affected the pain-free or maximal walking distance in patients with intermittent claudication. METHODS: In a double-blind, randomized crossover study, 12 non-diabetic patients with intermittent claudication were given a single oral dose of glibenclamide (5.25 mg) or placebo separated by a washout period of 1 week. A treadmill test was carried out 180 min after glibenclamide/placebo intake for determination of pain-free and maximal walking distance. Plasma glucose concentrations were kept constant by an euglycemic clamp. Changes in ankle/brachial blood pressure index (ABI), serum insulin, and serum glibenclamide were also assessed. RESULTS: The pain-free walking distance was 62.8 +/- 9.8 metres (mean +/- sem) after glibenclamide and 52.6 +/- 5.9 metres after placebo (P = 0.52). The maximal walking distance was 142.7 +/- 18.7 metres after glibenclamide and 132.6 +/- 16.6 metres after placebo (P = 0.23). The ABI was not significantly changed by glibenclamide compared with placebo. Serum glibenclamide was 0.51 +/- 0.08 microm 180 min after administration of the drug. Glibenclamide produced an 8-fold increase in circulating insulin compared with placebo (P < 0.001). CONCLUSIONS: Glibenclamide given as a single oral dose commonly used in glucose-lowering drug therapy does not reduce pain-free or maximal walking distance in non-diabetic patients with intermittent claudication.

Adenosine Triphosphate↗
PubMed1977

A new model for measuring breeding genetic distance.

A model is proposed for measuring the genetic 'distance' between two populations having gene frequencies p and p. The measure of distance is based on a hypothetical selection process as follows: From population P a subpopulation P can be selected having gene frequency p. Let Po be the largest subpopulation yielding gene frequency p, then the relative size of Po to p--denoted by thetao (p,p)--is a measure of the 'closeness' of populations having gene frequencies p and p, and 1-thetao (p,p) whould be a reasonable measure of genetic distance. We show that the calculation of thetao (p,p) is a special case of the linear programming problem and derive algebraic expressions for thetao (p,p) in the two-allele case. We discuse some of the implications of the use of this measure of distance and compare it to others which have been proposed. We use linear programming methods to calculate genetic distance for three alleles.

Alleles↗
PubMed1993

Fixation disparity at different viewing distances of a visual display unit.

Fixation disparity was measured while subjects observed a realistic alphanumeric pattern on the cathode ray tube (CRT) of a visual display unit at viewing distances of 25-85 cm. The psychometric function of fixation disparity was determined by analysing the observers' responses to a series of short (100 ms) flashes of nonius targets that were superimposed on the CRT-image by means of a half-silvered mirror. Test-retest correlation of fixation disparity was high (r = 0.8) at viewing distances of 40 and 82 cm and lower (r = 0.55) at the shorter distance of 26.5 cm. Mean fixation disparity increased to a more exophoric condition as the display approached the eyes. However, this effect was observed only in some of the subjects, so the susceptibility of fixation disparity to viewing distance appears to be an individual characteristic. When subjects observed the VDU screen continuously for 30 min at viewing distances of 85, 47, 31 and 25 cm in different sessions, fixation disparity and accommodation remained unchanged over time.

Accommodation, Ocular↗
PubMed2006

Driving distance as a barrier to glycemic control in diabetes.

BACKGROUND: Despite advances in treatment of diabetes, many barriers to good glycemic control remain. OBJECTIVE: To determine the relationship between glycemic control and the driving distance from home to the site of primary care. DESIGN: Cross-sectional analysis of data from the Vermont Diabetes Information System. PARTICIPANTS: Nine-hundred and seventy-three adults with diabetes in primary care. The mean age was 64.9 years, 57% were female, and 18.4% used insulin. MEASUREMENTS: Hemoglobin A1c, shortest driving distance from a patient's home to the site of primary care calculated by geographic software, self-reported gender, age, education, income, marital status, race, insurance coverage, diabetic complications, and use of insulin and oral hypoglycemic agents. RESULTS: Controlling for social, demographic, seasonal, and treatment variables, there was a positive, significant relationship between glycemic control and driving distance (beta=+0.07%/10 km, P<.001, 95% confidence interval [CI]=+0.03, +0.11). Driving distance had a stronger association with glycemic control among insulin users (beta=+0.22%/10 km, P=.016, 95% CI=+0.04, +0.40) than among noninsulin users (beta=+0.06%/10 km, P=.006, 95% CI=+0.02, +0.10). CONCLUSION: Longer driving distances from home to the site of primary care were associated with poorer glycemic control in this population of older, rural subjects. While the mechanism for this effect is not known, providers should be aware of this potential barrier to good glycemic control.

Adult↗
PubMed1996

Dimension and related anatomical distance of Koch's triangle in patients with atrioventricular nodal reentrant tachycardia.

INTRODUCTION: The dimension of Koch's triangle in patients with AV nodal reentrant tachycardia has not been well described. Understanding the dimension and anatomical distance related to Koch's triangle might be useful in avoiding accidental AV block during ablation of the slow pathway. The purposes of this study were to define the dimension of Koch's triangle and its related anatomical distance and correlate these parameters with the successful ablation sites in patients with AV nodal reentrant tachycardia. METHODS AND RESULTS: We studied 218 patients with AV nodal reentrant tachycardia. The distance between the presumed proximal His-bundle area and the base of the coronary sinus orifice (DHis-OS) measured in the right anterior oblique view was used to define the dimension of Koch's triangle. The distance of the proximal His-bundle recording site from the successful ablation site (DHis-Ab) and the distance as a fraction of the entire length of Koch's triangle (DHis-Ab/DHis-Os) were determined. The mean DHis-Os and DHis-Ab were 25.9 +/- 7.9 and 13.4 +/- 3.8 mm, respectively. DHis-Os negatively correlated with patient age (r = -0.41, P < 0.0001) and body mass index (r = -0.18, P = 0.004). Among the patients with successful ablation sites in the medial area, DHis-Os was longer (27.2 +/- 6.6 vs 24.6 +/- 8.4 mm, P < 0.005), DHis-Ab was similar (12.9 +/- 3.1 vs 13.9 +/- 4.0, P > 0.05) and DHis-Ab/DHis-Os was smaller (0.48 +/- 0.04 vs 0.74 +/- 0.11, P < 0.05). Furthermore, the patients with successful ablation sites in the medial location needed more radiofrequency pulse numbers than those in the posterior location (6 +/- 4 vs 4 +/- 3, P < 0.05). CONCLUSION: The site of successful slow pathway ablation was consistently about 13 mm from the site recording the proximal His-bundle deflection in patients with AV nodal reentrant tachycardia despite marked variability in the dimensions of Koch's triangle; therefore, patients with large triangles required ablation in the medial region rather than the posterior region. Care should be taken when delivering radiofrequency energy to the posteroseptal area in patients with shorter DHis-Os to avoid injury to AV node.

Adolescent↗
PubMed2007

Child abduction murder: an analysis of the effect of time and distance separation between murder incident sites on solvability.

Empirical studies of child abduction murder investigations are lacking. Accordingly, an empirical analysis of the effect of time and distance relationships on case solvability in child abduction murders (N=735) was conducted. The murders occurred across the United States from 1968 to 2002. Murder incident components examined were: victim last seen site, initial contact site, murder site, and body recovery site. Time and distance intervals between component pairings were also examined. Descriptive, bivariate, and multivariate analyses were performed to determine if information relating to time and distance intervals between components were critical solvability factors. Results show that information about time and distance increases case solvability. Results also demonstrate that time and distance relationships contribute uniquely to case solvability in murders of abducted children. Findings also indicate that additional factors such as type of forensic evidence, investigative resources, or actions by first responders, may be critical to case solvability.

Child↗
PubMedDate not supplied

Mortalities in bobby calves associated with long distance transport.

OBJECTIVE: To investigate how distance of transportation and time of year affects mortality of bobby calves. METHOD: The overall mortality of bobby calves transported by road to an abattoir in Northern Victoria was investigated by the analysis of mortality data from 1998 to 2000 from the abattoir records. RESULTS: Mortality of bobby calves increased exponentially with distance of transportation to the abattoir. The association between distance travelled and mortality was greatest in August. The increased mortality associated with greater distance travelled occurred during transportation rather than after arrival at the abattoir. The highest mortality of bobby calves was seen in October, followed by September, and the lowest was observed in August. CONCLUSION: Limits on the distance of transportation of bobby calves should be incorporated into future codes of practice to reduce the mortality of bobby calves.

Abattoirs↗
PubMed2001

Spatially modulated illumination microscopy: online visualization of intensity distribution and prediction of nanometer precision of axial distance measurements by computer simulations.

During the last years, measurements considerably beyond the conventional "Abbe-Limit" of optical resolution in far field light microscopy were realized by several light microscopical approaches. Point spread function (PSF) engineering, spectral precision distance microscopy (SPDM), and related methods were used to demonstrate the feasibility of such measurements. SPDM allows the measurement of position and multiple distances between point-like fluorescent objects of different spectral signatures far below the optical resolution criterion as defined by the full width at half maximum of the PSF. Here, we report a software method to obtain online visualization of light distribution in the lateral and axial direction of any object detected in a spatially modulated illumination (SMI) microscope. This strongly facilitates routine application of SMI microscopy. The software was developed using Microsoft Visual C++ running on Windows NT. Furthermore, some aspects of the theoretical limits of the SPDM method were studied by virtual microscopy. For the case of SMI microscopy the precision of axial distance measurements was studied, taking into account photon statistics and image analysis procedures. The results indicate that even under low fluorescence intensity conditions typical for biological structure research, precise distance measurements in the nanometer range can be determined, and that axial distances in the order of 40 nm are detectable with such precision.

Computer Simulation↗
PubMed2004

Dosimetric characteristics of the Novoste Beta-Cath 90Sr/Y source trains at submillimeter distances.

Measurements were performed on the 30, 40, and 60 mm 90Sr/Y beta-emitter source trains used in the Novoste Beta-Cath system to determine their dosimetric characteristics at submillimeter distances and provide the necessary TG-60 parameters for mapping their dose distributions. These measurements were carried out in a Solid Water phantom where MD55-2 Gafchromic films were placed in direct contact with a 5 French (F) catheter used for the 30 and 60 mm source trains and a 3.5F catheter used for thinner 30 and 40 mm source trains. A data set consisted of three pieces of Gafchromic film irradiated for periods of 1.5, 5, and 10 minutes, respectively. This 3-film irradiation technique provided reliable dose data at short, intermediate and long distances from a source train. Three data sets per source train were collected in this study. For the 30 mm source train with a 5F catheter, data were collected with the source axis at proximal (0.41 mm) and distal (1.19 mm) positions to the film surface in order to investigate dosimetric effects due to the off centering of the source train lumen within the catheter. Absolute doses were determined by calibrating the Gafchromic film in a high-energy electron beam from a radiotherapy accelerator. The absolute dose rates at a distance of 2 mm along the source trains transverse axis were found to be within 13.7% of the values provided by Novoste. Radial dose functions were within 13% compared to 90Sr/Y source train data constructed from Soares' 90Sr/Y single seed data and within 17% and 25% compared to Monte Carlo data by Ye et al., and Wang et al., respectively. Discrepancies of 33% and 19% were observed at short radial distances (< or = 1 mm) between the Novoste Monte Carlo and the 3.5F and 5F catheter measured data, respectively. The source off centering data showed higher dose contribution from the source train at its distal rather than proximal position. Radial dose function comparisons between the Novoste Monte Carlo and the measured data, calculated as a function of radial distance from the catheter's center showed good agreement (< or = 10%).

Brachytherapy↗