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PubMed1984

The distance between S1, S21, and the 3' end of 16S RNA in 30S ribosomal subunits. The effect of poly(uridylic acid) and 50S subunits on these distances.

The apparent distances between probes covalently attached to the cysteine thiols of S1 or S21 and the 3' end of 16S RNA in Escherichia coli 30S ribosomal subunits were determined by non-radiative energy transfer to be: S21-16S RNA, 5.1 nm; S21-S1, 6.9 nm; S1-16S RNA, 6.8 nm. Binding of poly(uridylic acid) to 30S subunits causes the apparent distances between S1 and 16S RNA or S21 and 16S RNA to increase by more than 1.2 nm and 0.5 nm, respectively, but has little or no effect on the S1-S21 distance. Binding of 50S subunits causes an apparent increase in the S21-16S RNA and S21-S1 distances by 1.0 nm and 0.8 nm, respectively, but has little or no effect on the S1-16S-RNA distance.

Coumarins↗
PubMed1978

Genetical distance and dermatoglyphic characters. II. Intrapopulation distance coefficients.

This paper attempts to evaluate the dermatoglyphic (genetical) distance between two Polish population samples in relation to the intrapopulation distance coefficients estimated within each sample. All the coefficients have been based, in turn, on frequencies of fingertip, palmar and sole pattern elements, separately and for all characters combined. The results of a comparison of various combinations of dermatoglyphic characters with one another in respect of all successive values of a distance coefficient indicate that, if populations of mostly related individuals were compared, sole patterns have been the most efficient ones in differentiating between the two normal population samples. The values of inter- and intrapopulation distance coefficients obtained from samples consisting mostly of family units have been compared with those estimated in samples of non-related individuals. The limitations and difficulties in the interpretation of the values of a distance coefficient related both to the material used and statistical procedures are discussed.

Dermatoglyphics↗
PubMed2001

Anthropometric and demographic factors affecting distance hopped and limb symmetry index for the crossover hop-for-distance test in high school athletes.

STUDY DESIGN: Prospective cohort study using a random selection from an accessible population. OBJECTIVES: We examined anthropometric and demographic characteristics affecting distance hopped (DH) and limb symmetry index (LSI) in the crossover hop-for-distance test in uninjured high school athletes. BACKGROUND: Between-subject comparisons of hop test results described by DH and LSI are common in the literature and clinical practice. The effect that anthropometric traits and demographic characteristics have on these measures is uncertain but must be known to correctly interpret hop-for-distance test results in research or to determine suitability of return to sports. METHODS AND MEASURES: For 201 high school athletes (age = 15.15+/-1.45 years, mean weight = 63.67+/-14.02 kg, mean height = 167.92+/-9.58 cm) completing the crossover hop-for-distance test, we recorded maximum DH for each leg and calculated the LSI of each subject. We performed 2 separate step-wise regression analysis models to develop predictive equations for DH and LSI. RESULTS: Age (r = 0.36), weight r = 0.41), and body fat percentage (r = 0.58) were significant predictors of DH, with the regression model explaining 59% of the variability. None of the measured variables were significant predictors of LSI (r = 0.03). The regression model explained only 3% of the variability of LSI. CONCLUSIONS: The LSI for the crossover hop-for-distance test can be compared among all individuals without subdividing into groups. Subject characteristics should be as homogeneous as possible when comparing DH among subjects or groups.

Adipose Tissue↗
PubMed1990

Isolation by distance and correlation analysis of distance measures in the study of population structure: example from the Island of Hvar.

Assessment of the population structure on the island of Hvar is based on the analysis of Malécot's isolation by distance model. We have tested the fit of the model by regression analysis of different measures of similarity (genetic kinship) and distance [Hamming's HSM distance for linguistic data; Mahalanobis's D2 distances for anthropometric head and body dimensions, radiogrammetric dimensions of metacarpal bones, physiological (cardiorespiratory) traits, and quantitative dermatoglyphic properties of the digitopalmar complex; and Edwards's E2 for frequencies of erythrocyte antigens]. Good fit of the model for linguistic and anthropometric data, which was demonstrated in previous studies on other eastern Adriatic populations, is confirmed. We compared parameters of the model with those already published for various populations in the eastern Adriatic and other parts of the world. We also evaluated the pattern of correlations between different measures of geographic, biological, and sociocultural distances through principal components analysis and interpreted the results within the context of microevolutionary theory and the population's ethnohistorical background.

Adult↗
PubMed1998

The necessity of a perception-action approach to definite distance perception: monocular distance perception to guide reaching.

In this investigation of monocular perception of egocentric distance, the authors advocate the necessity of a perception-action approach because calibration is intrinsic to definite distance perception. A helmet-mounted camera and display were used to isolate optic flow generated by participants' head movements toward a target, and participants' reaches to place a stylus either in a target hole (Experiments 1, 2, and 4) or aligned under a target surface (Experiment 3) were analyzed. Conclusions are that binocular distance perception is accurate, monocular distance perception yields compression that is not eliminated by feedback, but feedback is used to eliminate underestimation generated by restriction of the size of the visual field.

Adult↗
PubMed1988

Determination of three-dimensional structures of proteins from interproton distance data by hybrid distance geometry-dynamical simulated annealing calculations.

A new hybrid distance space-real space method for determining three-dimensional structures of proteins on the basis of interproton distance restraints is presented. It involves the following steps: (i) the approximate polypeptide fold is obtained by generating a set of substructures comprising only a small subset of atoms by projection from multi-dimensional distance space into three-dimensional cartesian coordinate space using a procedure known as 'embedding'; (ii) all remaining atoms are then added by best fitting extended amino acids one residue at a time to the substructures; (iii) the resulting structures are used as the starting point for real space dynamical simulated annealing calculations. The latter involve heating the system to a high temperature followed by slow cooling in order to overcome potential barriers along the pathway towards the global minimum region. This is carried out by solving Newton's equations of motion. Unlike conventional restrained molecular dynamics, however, the non-bonded interactions are represented by a simple van der Waals repulsion term. The method is illustrated by calculations on crambin (46 residues) and the globular domain of histone H5 (79 residues). It is shown that the hybrid method is more efficient computationally and samples a larger region of conformational space consistent with the experimental data than full metric matrix distance geometry calculations alone, particularly for large systems.

Histones↗
PubMed2001

Geographical and genetic distances among zooplankton populations in a set of interconnected ponds: a plea for using GIS modelling of the effective geographical distance.

In systems of interconnected ponds or lakes, the dispersal of zooplankton may be mediated by the active population component, with rivulets and overflows functioning as dispersal pathways. Using a landscape-based approach, we modelled the effective geographical distance among a set of interconnected ponds (De Maten, Genk, Belgium) in a Geographic Information System (GIS) environment. The first model (the Landscape Model; LM) corrects for the presence of direct connections among ponds and was based on the existing landscape structure (i.e. network of connecting elements among ponds, travelling distance and direction of the current). A second model (the Flow Rate Model; FRM) also incorporated field data on flow rates in the connecting elements as the driving force for the passive dispersal of the active zooplankton population component. Finally, the third model (the Dispersal Rate Model; DRM) incorporated field data on zooplankton dispersal rates. An analysis of the pattern of genetic differentiation among Daphnia ambigua populations inhabiting 10 ponds in the pond complex reveals that the effective geographical distance as modelled by the flow rate and the dispersal rate model provide a better approximation of the true rates of genetic exchange among populations than mere Euclidean geographical distances or the landscape model that takes into account solely the presence of physical connections.

Alleles↗
PubMed1998

Comparison of frequency-distance relationship and Gaussian-diffusion-based methods of compensation for distance-dependent spatial resolution in SPECT imaging.

The goal of this investigation was to compare resolution recovery versus noise level of two methods for compensation of distance-dependent resolution (DDR) in SPECT imaging. The two methods of compensation were restoration filtering based on the frequency-distance relationship (FDR) prior to iterative reconstruction, and modelling DDR in the projector/backprojector pair employed in iterative reconstruction. FDR restoration filtering was computationally faster than modelling the detector response in iterative reconstruction. Using Gaussian diffusion to model the detector response in iterative reconstruction sped up the process by a factor of 2.5 over frequency domain filtering in the projector/backprojector pair. Gaussian diffusion modelling resulted in a better resolution versus noise tradeoff than either FDR restoration filtering or solely modelling attenuation in the projector/backprojector pair of iterative reconstruction. For the pixel size investigated herein (0.317 cm), accounting for DDR in the projector/backprojector pair by Gaussian diffusion, or by applying a blurring function based on the distance from the face of the collimator at each distance, resulted in very similar resolution recovery and slice noise level.

Computer Simulation↗
PubMed1976

Genetical distance and dermatoglyphic characters. I. Interpopulation distance coefficients.

The distance coefficients between two relatively isolated population groups in Poland, based on various combinations of dermatoglyphic non-measurable characters were estimated. These were compared with the overall dermatoglyphic distance coefficients estimated separately for left and right, as well as with the serologic distance coefficient, based on ABO, Rh and Duffy blood groups. Dermatoglyphic distance coefficients, estimated from quantitative variables (pattern intensities) using Penrose's C2H analysis of variance method, were also introduced for a comparison. The differences in frequencies between two populations, separately for each character, were also compared with its heritability values.

ABO Blood-Group System↗
PubMed1978

Genetical distance and dermatoglyphic characters. III. Dermatoglyphic distances within twin pairs, between left and right sides and between normals and 21-trisomics.

The dermatoglyphic (genetical) distance coefficients have been estimated within monozygotic and dizygotic twin pairs, between left and right sides of the same individual and between normal subjects and 21-trisomics. All the coefficients have been based, in turn, on frequencies of fingertip, palmar and sole pattern elements, separately and for all characters combined. Quantitative variables (pattern intensities) have also been used for independent evaluation of the C2H distance coefficient in monozygotic and dizygotic twins, and in 21-trisomics as compared with normal individuals. The values of a distance have then been considered in relation to the degree of genetical likeness between the compared items as well as to the relative contribution of each pattern combination to the overall value of a distance. Some limitations in the interpretation of the results, connected mainly with statistical procedures, are also discussed.

Chromosomes, Human, 21-22 and Y↗
PubMed1987

A comparison of the restrained molecular dynamics and distance geometry methods for determining three-dimensional structures of proteins on the basis of interproton distances.

A direct comparison of the metric matrix distance geometry and restrained molecular dynamics methods for determining three-dimensional structures of proteins on the basis of interproton distances is presented using crambin as a model system. It is shown that both methods reproduce the overall features of the secondary and tertiary structure (shape and polypeptide fold). The region of conformational space sampled by the converged structures generated by the two methods is similar in size, and in both cases the converged structures are distributed about mean structures which are closer to the X-ray structure than any of the individual structures. The restrained molecular dynamics structures are superior to those obtained from distance geometry as regards local backbone conformation, side chain positions and non-bonding energies.

Chemical Phenomena↗
PubMed2003

Long-distance colonization, isolation by distance, and historical demography in a relictual Mexican pinyon pine (Pinus nelsonii Shaw) as revealed by paternally inherited genetic markers (cpSSRs).

Pinus nelsonii is a relictual pinyon pine distributed across a wide altitudinal range in semiarid zones in Mexico near the border between the States of Nuevo León and Tamaulipas. It also occurs in small patches in the State of San Luis Potosí. Pinus nelsonii is classified in the monotypic subsection Nelsoniae, separated from other pinyon pines (subsection Cembroides), because it possesses several distinctive characters including persistent fascicle sheaths, connate needles, and a distinctive wood anatomy. In the present study, chloroplast simple sequence repeats (cpSSRs) were used to estimate genetic variation in most known populations (nine) of P. nelsonii. The genetic variation (HT = 0.73; 27 haplotypes in 256 individuals) is moderate when compared to other pine species. Population differentiation ranged between low and moderate (FST = 0.13 and RST = 0.05), as did the Nei and Goldstein genetic distances between populations. However, this pattern varied depending on whether the infinite alleles or stepwise mutation model was used. In the former case a significant isolation by distance was found, but not in the latter. A significant association between geographical and genetic structure in one clade, through a nested clade analysis, was found, which suggested long-distance colonization between 125000 and 309000 years ago. We found weak evidence for a population expansion. A mismatch distribution suggests that P. nelsonii populations underwent an expansion 4.25 times their size between 59000 and 146000 years ago. On the other hand, the populations' star-like phylogeny and a slight parabolic relationship between coalescence times and lineage number also suggest weak population expansion. Overall, this species appears to have been in demographic stasis for a large proportion of the time detected by the markers used.

Cluster Analysis↗
PubMed2000

[The measurement of normal values of exophthalmos, interpupillary distance and interorbital distance of children and adolescence in Xiamen and the rule of their development].

OBJECTIVE: To investigate the developing rhythm of children and adolescent exophthalmos, interorbital distance (IOD) and interpupillary distance (IPD) and their mutual relationships. The study will provide biometry data for formulating juvenile criteria of correcting spectacles. METHODS: Random sampling was performed among children and adolescence aged 5 - 17 years in Xiamen. Adopting epidemic survey, we measured the biometry values of IOD, IPD and exophthalmos with a sliding gauge and exophthalmometer. RESULTS: The average value of exophthalmos was (14.48 +/- 1.71) mm. For the 5 - 8 years old children, the value of exophthalmos trended to increase with the increase of age, meanwhile the value of exophthalmos of adolescence aged 9 - 17 years old tended to be stabilized. The average value of IOD was (95.55 +/- 5.32) mm and the average value of IPD was (56.99 +/- 3.93) mm. Both the values of the IOD and IPD of the male were higher than that of the female. The results of the IOD and IDP distance increased with the increase of age and it trended to be periodic. There was positive correlation between the development of IOD and that of IPD, and it could be described by a linear equation. CONCLUSIONS: There is only one rush-increase stage of ocular development which is before the 8 years old in children. The rule of its development is in accordance with the growing and developing mode of neurological system.

Adolescent↗
PubMed1990

[Determining gunshot distance without bullet entry--a new source of error in determining gunshot distance from point of entry].

A court case lead to a quantitative determination of lead and antimony by atomic-absorption at distances 10 to 20 cm from the bullet hole. As a surprising result at first the area-concentrations of lead and antimony increased with rising distance from the muzzle and reached a maximum, after that maximum like expected a decrease was found. The phenomena is of general interest because otherwise misinterpretations in chemical determination of gunshot firing distances would be possible.

Antimony↗
PubMedDate not supplied

Distance learning and distance education: a personal perspective.

During 50 years of service, the Centers for Disease Control and Prevention has made important contributions to U.S. public health, particularly in the area of training, an essential CDC activity. I summarize some of CDC's experiences with distance learning and distance education, describe the need for public health education and training, and consider how distance education can fill that need.

Centers for Disease Control and Prevention, U.S.↗
PubMed1998

Effect of distance traveled and speed of racing on body weight and serum enzyme activity of sled dogs competing in a long-distance race.

OBJECTIVE: To determine the relationship of serum biochemical values and change in body weight with finishing status (retired from or finished the race), finishing order of a team, and distance traveled for dogs participating in a long-distance sled dog race. ANIMALS: 262 of 848 dogs that participated in the 1995 Iditarod Trail sled dog race. DESIGN: Prospective study. PROCEDURE: Body weight was recorded for 261 dogs before the race and again when these dogs retired from or completed the race. Using a nonrandom convenience sample of participating dogs, blood samples were obtained from 151 dogs that retired from the race and 111 dogs that completed the race. RESULTS: Serum biochemical indices of skeletal muscle damage were significantly higher in dogs retiring during the first 500 miles of the race than in dogs retiring in the last 638 miles or finishing the race. Serum sodium concentration was less than the reference range in a significantly greater proportion of dogs that retired from the race than of dogs that completed the race. There was little relationship between finishing order and serum biochemical values. Dogs completing the race lost a mean of 8.9% of body weight, and amount of weight lost was not related to finishing order. CLINICAL IMPLICATIONS: Results indicated that exertional rhabdomyolysis develops more often in dogs that retire during the initial 500 miles of a long-distance race, compared with dogs that complete the race. There is no detectable relationship between the speed with which the race is run (finishing order) and body weight loss or serum biochemical values.

Animals↗
PubMed2000

Distance education. Part 4. Supervision of family medicine research at a distance. A formative evaluation.

INTRODUCTION: A survey on supervision of research projects was undertaken among current general practitioner students, recent graduates and supervisors of a Masters of Family Medicine degree. The aim was to describe and compare the experience of the three groups and, in particular, to identify the problems associated with distance supervision. METHODS: A self-administered questionnaire survey was distributed to current students (n = 21), graduates (n = 16) and current supervisors (n = 7). RESULTS: Forty out of 44 doctors returned completed questionnaires. Distance was a relatively minor barrier to successful supervision, provided that the student and supervisor established good communication patterns and were able to respond to each other with minimal delay. The commencement of the study and its final write-up were critical phases in the supervision process. DISCUSSION: Communication, including emotional and psychological support, was at least as important as expert opinion in helping Masters students to successfully complete their research projects. Attention must be paid to establishing good understanding and regular means of communication at the beginning of the supervisory process.

Data Collection↗
PubMed2000

Distance education. Part 5. Family medicine research at a distance. Guidelines for supervisors.

INTRODUCTION: This paper recommends guidelines for the supervision of Masters degrees or similar postgraduate courses, in which research projects are supervised at a distance. METHODS: The guidelines are based on the experiences of the authors with a five year old Masters of Family Medicine degree and a formative evaluation conducted by questionnaire survey among its students, graduates and supervisors. RESULTS: It is important to establish ground rules for communication at an early point in the supervisory process. Supervisors need to take into account psychosocial, pedagogical and organisational aspects of their mentorship of students. DISCUSSION: These guidelines are relevant to courses where there remains a strong one-to-one relationship between supervisors and students. In these cases, 'distance' need not be a barrier provided that both sides are aware of and committed to maintaining good patterns of communications with each other.

Communication↗