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PubMed2005

High-precision absolute distance and vibration measurement with frequency scanned interferometry.

We report high-precision absolute distance and vibration measurements performed with frequency scanned interferometry using a pair of single-mode optical fibers. Absolute distance was determined by counting the interference fringes produced while scanning the laser frequency. A high-finesse Fabry-Perot interferometer was used to determine frequency changes during scanning. Two multiple-distance-measurement analysis techniques were developed to improve distance precision and to extract the amplitude and frequency of vibrations. Under laboratory conditions, measurement precision of approximately 50 nm was achieved for absolute distances ranging from 0.1 to 0.7 m by use of the first multiple-distance-measurement technique. The second analysis technique has the capability to measure vibration frequencies ranging from 0.1 to 100 Hz with an amplitude as small as a few nanometers without a priori knowledge.

Journal Article↗

PubMed2004

Distance-restrained docking of rifampicin and rifamycin SV to RNA polymerase using systematic FRET measurements: developing benchmarks of model quality and reliability.

We are developing distance-restrained docking strategies for modeling macromolecular complexes that combine available high-resolution structures of the components and intercomponent distance restraints derived from systematic fluorescence resonance energy transfer (FRET) measurements. In this article, we consider the problem of docking small-molecule ligands within macromolecular complexes. Using simulated FRET data, we have generated a series of benchmarks that permit estimation of model accuracy based on the quantity and quality of FRET-derived distance restraints, including the number, random error, systematic error, distance distribution, and radial distribution of FRET-derived distance restraints. We find that expected model accuracy is 10 A or better for models based on: i), > or =20 restraints with up to 15% random error and no systematic error, or ii), > or =20 restraints with up to 15% random error, up to 10% systematic error, and a symmetric radial distribution of restraints. Model accuracies can be improved to 5 A or better by increasing the number of restraints to > or =40 and/or by optimizing the distance distribution of restraints. Using experimental FRET data, we have defined the positions of the binding sites within bacterial RNA polymerase of the small-molecule inhibitors rifampicin (Rif) and rifamycin SV (Rif SV). The inferred binding sites for Rif and Rif SV were located with accuracies of, respectively, 7 and 10 A relative to the crystallographically defined binding site for Rif. These accuracies agree with expectations from the benchmark simulations and suffice to indicate that the binding sites for Rif and Rif SV are located within the RNA polymerase active-center cleft, overlapping the binding site for the RNA-DNA hybrid.

Binding Sites↗

PubMedDate not supplied

[Environmental PM2.5 levels and distance from a heavy traffic road in Ciudad Juarez, Chihuahua, Mexico].

OBJECTIVE: To assess PM2.5 levels at different distances from a heavy traffic road. MATERIAL AND METHODS: Daily measurements of PM2.5 were taken between August 26 and 30, 2002, at different distances from Tecnológico Avenue in Ciudad Juarez, Chihuahua, Mexico. Data analysis consisted of descriptive statistics for each distance and KruskalWallis and cross trend for ranks. RESULTS: We found a significantly decreasing trend of PM2.5 median levels with increasing distance from Tecnológico Avenue (p<0.001). At 100 m distance from the avenue, PM2.5 levels decreased by 9.5 microg/m3 (40.6%) when compared to median levels registered on the avenue. The results showed a highly significant negative correlation between PM2.5 measurements and the distance from the avenue (r=-0.70, n=20 and p=0.0005). CONCLUSIONS: PM2.5 median levels decreased significantly after 100 meters from heavy traffic roads. These results are of great relevance when assessing exposure to PM2.5 in epidemiological studies.

Air Pollutants↗

PubMed2006

Modeling seed dispersal distances: implications for transgenic Pinus taeda.

Predicting forest-tree seed dispersal across a landscape is useful for estimating gene flow from genetically engineered (GE) or transgenic trees. The question of biocontainment has yet to be resolved, although field-trial permits for transgenic forest trees are on the rise. Most current field trials in the United States occur in the Southeast where Pinus taeda L., an indigenous species, is the major timber commodity. Seed dispersal distances were simulated using a model where the major determinants were: (1) forest canopy height at seed release, (2) terminal velocity of the seeds, (3) absolute seed release, and (4) turbulent-flow statistics, all of which were measured or determined within a P. taeda plantation established from seeds collected from wild forest-tree stands at the Duke Forest near Durham, North Carolina, USA. In plantations aged 16 and 25 years our model results showed that most of the seeds fell within local-neighborhood dispersal distances, with estimates ranging from 0.05 to 0.14 km from the source. A fraction of seeds was uplifted above the forest canopy and moved via the long-distance dispersal (LDD) process as far as 11.9-33.7 km. Out of 10(5) seeds produced per hectare per year, roughly 440 seeds were predicted to be uplifted by vertical eddies above the forest canopy and transported via LDD. Of these, 70 seeds/ha traveled distances in excess of 1 km from the source, a distance too great to serve as a biocontainment zone. The probability of LDD occurrence of transgenic conifer seeds at distances exceeding 1 km approached 100%.

Ecology↗

PubMed1995

Maintained nodal-distance effects in equivalence classes.

Twelve subjects were trained to select one of two stimuli from a pair (the B pair) when presented with one of two stimuli from another pair (the A pair), thus establishing two AB relations, A1-B1 and A2-B2. In a similar fashion, additional stimuli were used to establish BC, CD, and DE relations. Trials used to train all relations occurred in each session. Once performances were established, probe trials were introduced that tested for the emergence of untrained relations (e.g., B1-D1 or A1-E1). These emergent relations were categorized according to nodal distance (i.e., the number of stimuli across which transitivity would have to hold in order for the relation to emerge). For example, a test for A2-C2 crosses one node (B2), whereas a test for A1-E1 crosses three nodes (B1, C1, and D1). Only 2 of the subjects formed equivalence classes. The evocation of class-appropriate responding by each emergent-relation probe was an inverse function of nodal distance for all 12 subjects. In addition, performance on the originally trained relations was disrupted by the introduction of probes. The 2 subjects who exhibited equivalence classes were then trained to make different numbers of key presses in the presence of each of the four A and E stimuli. In a response-transfer test, the B, C, and D stimuli evoked the responses trained to the A and E stimuli in the same equivalence class. Likelihood of class-appropriate responses was an inverse function of nodal distance, and this pattern persisted across testing. Reaction times in the transfer test were an inverted U-shaped function of nodal distance. Because training of the baseline relations occurred concurrently and the B, C, and D stimuli were presented an equal number of times before the transfer test, the test performances illustrate effects of nodal distance that were not confounded by order or amount of experience with the stimuli. The results imply that ordered, sequential exposure to individual stimulus relations may facilitate the development of equivalence classes and that the relatedness of stimuli within an equivalence class is a relatively permanent inverse function of nodal distance.

Journal Article↗

PubMed1995

The value of the tip-apex distance in predicting failure of fixation of peritrochanteric fractures of the hip.

Failure of fixation of peritrochanteric fractures that have been treated with a fixed-angle sliding hip-screw device is frequently related to the position of the lag screw in the femoral head. A simple measurement has been developed to describe the position of the screw. This measurement, the tip-apex distance, is the sum of the distance from the tip of the lag screw to the apex of the femoral head on an anteroposterior radiograph and this distance on a lateral radiograph, after controlling for magnification. To determine the value of this measurement in the prediction of so-called cutout of the lag screw, 198 peritrochanteric fractures (193 patients) were studied. The minimum duration of follow-up was three months (average, thirteen months), during which period all of the fractures either healed or had failure of the fixation. Of the nineteen failures that were identified, sixteen were due to the device cutting out of the femoral head. The average tip-apex distance was twenty-four millimeters (range, nine to sixty-three millimeters) for the successfully treated fractures compared with thirty-eight millimeters (range, twenty-eight to forty-eight millimeters) for those in which the screw cut out (p = 0.0001). None of the 120 screws with a tip-apex distance of twenty-five millimeters or less cut out, but there was a very strong statistical relationship between an increasing tip-apex distance and the rate of cutout, regardless of all other variables related to the fracture.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

[Comparison of methods for estimating percent body fat in distance-runners].

A comparative study was conducted between two independent methods to estimate body fat in 13 college male distance-runners (20.2 +/- 1.1 yrs) and 11 male college students (19.6 +/- 0.7 yrs) as control group. The methods dealt with different body component parameters. Body fat was estimated (1) in terms of total body water based on the analysis of dilution of orally ingested deuterium oxide (D2O) in urine, and (2) in terms of body density based on underwater weighing. The results were as follows: 1) The skinfold thickness at 14 sites in distance-runners were thinner than those in control group. The mean values for subcutaneous fat in distance-runners were 4.3 +/- 0.7 kg (7.2 +/- 1.1%), which were lower than those (8.3 +/- 2.7 kg & 13.3 +/- 3.4%) in control group significantly. Oh the other hand, the mean values for internal fat in distance-runners were 8.7 +/- 1.4 kg (14.4 +/- 1.6%), which were larger than those (6.5 +/- 3.1 kg & 10.2 +/- 4.3%) in control group. 2) The mean values for percent body fat in control group were 16.1 +/- 1.6% by skinfolds method, 20.2 +/- 5.1% by body density method and 23.5 +/- 4.6% by total body water method. The estimated values of percent body fat by the methods of body density and total body water were approximately the same. 3) The mean values for percent body fat in distance-runners were 11.9 +/- 1.4% by skinfolds method, 11.8 +/- 1.7% by body density method and 21.5 +/- 1.9% by total body water method. The estimated values of percent body fat in distance-runners were lower than those in control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed2002

Relationship between distance from major roads and adolescent health in Japan.

A relationship between distance from major roads and the prevalence of allergic disorders and general symptoms among junior high school students was assessed, separating the effects of distance of residence and school from the roads. Study subjects were 5,652 students aged 12 to 15 years. This study used diagnostic criteria from the International Study of Asthma and Allergies in Childhood. The questionnaire also asked about symptoms of headache, stomachache, tiredness, and cough and the shortest distance from residence to major roads. Distance from school to the nearest major road was measured on a map. Adjustment was made for gender, grade, the number of older siblings, smoking in the household, and maternal history of allergy. A shorter distance between residence and major roads was associated with an increased prevalence of headache, stomachache, tiredness, and cough. There was a marginally significant positive association between residence facing major roads and the prevalence of allergic rhinoconjunctivitis. Residence within 100 m of major roads showed a tendency for a positive relationship with the prevalence of wheeze and atopic dermatitis. There was no apparent relationship between distance of school from major roads and allergic disorders or the general symptoms. The findings suggest that proximity of residence, not school, to major roads may be associated with an increased prevalence of allergic disorders, headache, stomachache, and tiredness among Japanese adolescents. Further investigations with more precise and detailed exposure and health outcome measurements are needed to corroborate the relationship between traffic related factors and allergic disorders and general symptoms.

Adolescent↗

PubMed2006

Effects of endurance training on blood lipid profiles in adolescent female distance runners.

The purpose of this study was to investigate the cross-sectional and longitudinal effects of endurance training on the relationships of body composition, blood lipid profiles and sex hormones in adolescent female distance-runners. We cross-sectionally compared body composition, blood lipid profiles and blood sex hormones of non-athletes (n=7) and distance-runners (n=8), with the similar lower level of BMI (17.1 kg/m(2) vs. 18.7 kg/m(2), respectively). After the cross sectional comparison on the influence of endurance training, body composition, blood lipid profiles and blood sex hormones were examined at pre- and post-one year endurance training in the distance-runners (n=6) to determine longitudinal effects. %Fat in distance-runners revealed a tendency to be lower than that in non-athletes (23.8+/-3.5 vs 27.3+/-2.5%). Both groups showed good blood lipid profiles, such as high levels of high density lipoprotein-cholesterol (HDL-c), HDL-2c, and apolipoprotein A-I (ApoA-I). However, the estrogen (E(2)) level of distance-runners was less than one third of that in non-athletes (30.5+/-11.3 vs 112.9+/-66.2 pg/ml, p<0.01). In addition, the blood E(2) levels (pg/ml) were significantly associated with the internal fat mass (IF, kg) in all subjects (r=-0.613, p<0.05, n=15). On the other hand, the overall body composition and good blood lipid profiles in the longitudinal comparison were maintained to a constant level for one year endurance training, except for significant elevations in the two enzyme activities and E(2) level (LPL activity: from 145.3+/-40.8 to 362.2+/-65.8 ng/ml, HTGL activity: from 0.054+/-0.020 to 0.173+/-0.080 micromole/ml/min, E(2): from 30.7+/-13.2 to 65.6+/-24.2 pg/ml, p<0.05). These results suggest that the lipid profiles such as HDL-c and Apo A-I in adolescent female distance-runners could be rather affected by endurance training, despite the low level of E(2) for a long term.

Body Composition↗

PubMed1991

Predicting the shape of distance functions in curve tracing: evidence for a zoom lens operator.

Jolicoeur, Ullman, and MacKay (1986) showed that the time to confirm that two dots are on the same curve increases monotonically, but nonlinearly, as the curve distance between the two dots increases. These displays contained two curves and two dots. On same trials, the two dots were on the same curve (target curve), while the other curve served as a foil (distractor curve). The monotonically increasing effects of curve distance on response times for same trials suggested that the intervening curve segment was traced. In the present investigation of the source of the nonlinearity in these distance functions, it was hypothesized that differences in the distractor curves may have allowed a curve tracing operator with zoom lens properties to widen its receptive field while tracing parts of certain target curves. The wider receptive field may have allowed faster tracing over certain segments, owing to a reduced number of shifts required by the operator to scan the curve. The consequence of training certain segments of the curve more quickly than other segments of the curve would be a nonlinear effect of distance. A new set of stimuli was created for testing this hypothesis directly. Fairly linear distance effects were found for stimuli that contained a distractor curve that constrained the breadth of the postulated curve tracing operator, whereas stimuli that contained a distractor curve that could allow for a larger receptive field yielded nonlinear distance functions. The results are compared with the predictions of three quantitative models: pixel-by-pixel tracing; Jolicoeur, Ullman, and MacKay's (1991) bipartite operator; and a new zoom lens model, analogous to the zoom lens model of visual attention. The results were fit best by the latter model, in which tracing is accomplished by tracking the curve with a variably sized local operator.

Adult↗

PubMed1991

Professional resocialization of post-RN baccalaureate students by distance education.

Distance education is being used to increase access to post-RN baccalaureate education. One of the objectives of degree programs is the professional resocialization of post-RN students. Because of the limited contacts with the institution, faculty, and student peers, the effectiveness of professional resocialization by distance education may be questioned. In this qualitative study, the responses of 24 students who had taken distance courses in Nursing Issues from four universities were analyzed for evidence of professional resocialization. Two of the universities used a group-oriented approach to distance education; two used an individual approach. Responses of students from the four schools and the two approaches were similar. All reported more awareness of issues in nursing and most reported attitude changes reflecting a more professional orientation. Among the changes were attitudes toward baccalaureate entry to practice, nursing theory and research, and the place of nurses and nursing in society. Despite the limitations of distance education, distance courses can be influential in the professional resocialization of post-RN students.

Adult↗

PubMedDate not supplied

A new method for evaluating distance stereo acuity.

A new standardized method for evaluating distance stereo acuity has been developed, using the graphic capacity of a high-frequency microprocessor and liquid crystal binocular glasses. Images are alternately presented at a frequency of 60 cycles per second to each eye, using synchronized liquid crystal shutter glasses. The amount of disparity in the stereo patterns can be altered to allow a measurement as refined as 15 seconds of arc ("). This instrument is now commercially available as part of the Mentor B-Vat system. We evaluated distance Random Dot and Contour circle stereo acuity of 50 normal subjects using this new method and compared these results to conventional Titmus and Randot circles at near. The distance stereo acuity mean results were 139" for the Random Dot test and 41.1" for the Contour circles. The near stereo acuity results were 41.8" for the Titmus circles and 27" for the Randot circles. Statistically, the Titmus results at near can be compared to the Contour circles at distance. The distance Random Dot test results demonstrate much less stereoability than the other test. The application of these new distance stereotests will be discussed.

Adolescent↗

PubMedDate not supplied

Clinical importance of accurate refractor vertex distance measurements prior to refractive surgery.

PURPOSE: To determine directly measured vertex distances in a consecutive series of patients refracted at a refractor and to examine the clinical importance of such a measurements for improving refractive surgical results. METHODS: Vertex distance measurements were obtained in 189 consecutive patients by using a new device capable of taking direct and accurate measurements behind a refractor. Eyelid thickness was measured with an industrial caliper in five patients. RESULTS: The average true vertex distance was 20.4 mm with a range of 10 to 34 mm. Eyelid thickness was 3 mm in all five patients. CONCLUSIONS: Precise measurement of true refractor vertex distance is important for accuracy of refractive surgical procedures. The practice of assuming an average vertex distance of 12 to 14 mm for all refractive patients underestimates the vertex distance in many patients refracted at the refractor, resulting in overcorrecting minus and undercorrecting plus refractions.

Eyeglasses↗

PubMed2001

[The effects of spatial information for cognitive distance in an architectural space].

The present study investigated the effects of the spatial information for cognitive distance in an architectural space. One hundred undergraduate students participated in the experiment, and they were divided into two groups. The control group (CG) was given the pictures of both ends of the routes, and the experimental group (EG) was given some scenes of the routes in addition to the ends. The subjects have used the building used for the experiment for more than 2 years, and they estimated each walk of the 10 routes in the building. Each of those routes (50 m-144 m) is longer than the standard route (34 m). Before estimating the distance, the pictures were given on display through World Wide Web with questionnaires. The ratio method was used to obtain the cognitive distance data. As a result, the cognitive distance data of both groups showed similar distribution, and the cognitive distance data of EG were longer than those of CG in all routes. However, the effects of the number of the pictures were varied. These results suggested that not only the amount of the spatial information (i.e., chair, pillar, garbage box) but also the subjects' cognitive processing of the information affected the cognitive distance.

Cognition↗

PubMed1999

Isonymy and isolation by distance in Italy.

The isonymy structure of Italy was studied using the surname distribution of 5,043,580 private telephone users selected from a 1996 commercial CD-ROM that contains all 24 million users in the country. The users were distributed in 123 towns selected on a geographic basis. The 123 towns were either on the main communication roads of the country or at the ends of such roads. The shortest distance between nearest neighbor towns was 5.3 km (Carrara and Massa), and the largest distance was 1,136 km (Aosta and Castrignano del Capo). The number of different surnames found in the whole analysis was 215,623. Lasker's distance, the negative value of the logarithm of random isonymy between localities, was linearly and significantly correlated with the logarithm of geographic distance, with r = 0.63 +/- 0.008. A dendrogram was built from the matrix of isonymy distances, using UPGMA. It separates the Italian towns into 5 main clusters: 1 in the southern portion of the country, a second cluster toward the center, and 3 in the northern area of Italy. Within each cluster small subclusters with specific geographic distributions could be related to regional borders. Comparisons with the results of a previous analysis of Switzerland and Germany's structures are given. From the present analysis isolation by distance emerges clearly, although it is less strong than in Switzerland and stronger than in Germany. The random component of inbreeding estimated from isonymy indicates that the southern area of Italy is on average more inbred than the northern area. In fact, the heterogeneity is greater in the northern area, particularly in the plain of the Po River, than anywhere else in Italy.

Cluster Analysis↗

PubMed2000

Influence of curing tip distance on composite Knoop hardness values.

The purpose of this paper was to study the influence of curing tip distance on Knoop hardness values, at different depths, of two composites, Z100 and Silux Plus. Specimens (5 mm in diameter and 2.5 mm in height) were prepared in a copper mold, covered with mylar strip and polymerized for 40 s, at 3 tip-to-composite surface distances: 0 mm (surface contact), 6 and 12 mm, utilizing an XL 3000 curing unit, with 750 mW/cm2 power. The specimens were then stored at 37 degrees C for 24 h. Knoop hardness values were measured using a microhardness tester, with a load of 50 g for 30 s for each indentation. Four specimens were made for each distance and composite and eighteen indentations were made of each specimen. The results were submitted to analysis of variance and Tukey test at 5% significance level. The results indicated that 1) composite Z100: the larger the curing tip distance in relation to the composite, the lower the Knoop hardness values; 2) Silux Plus: increasing the curing tip distance did not produce a statistically significant difference in the Knoop hardness values; however, at 6 and 12 mm, the deeper layers showed lower Knoop hardness values in relation to the surface; 3) Z100: statistically superior in relation to Silux Plus at all three curing tip distances and at all depths (P < 0.05).

Analysis of Variance↗

PubMed2002

Decrease in power output of new light-emitting diode (LED) curing devices with increasing distance to filling surface.

PURPOSE: This study compares the percentage decrease in power output of light-emitting diode (LED) and quartz-tungsten-halogen (QTH) curing devices at different distances between the light guide tip and a radiometer. MATERIALS AND METHODS: Three LED curing devices (Elipar FreeLight/3M ESPE, Luxomax/Akeda, e-Light/GC) were compared to two QTH curing devices (Elipar TriLight/3M ESPE, Optilux 501 conventional and Turbo light guides/Kerr-Demetron). Power density was measured with a Fieldmaster GS/Coherent unit (Sensor LM-3 HTD) at increasing distances from the light guide tip (0 to 20 mm at 1-mm increments, n=6). RESULTS: The mean decrease in power density available for curing at a distance of 10 mm between the light guide tip and the radiometer was 68% for the FreeLight, 83% for the e-Light, 42% for the Luxomax, 38% for the TriLight, 33% for the Optilux with the standard light guide, and 44% for the Optilux with the turbo light guide. The power density of the Luxomax was only 40% of that of the other LED curing devices at 0 mm distance. CONCLUSION: The blue LED curing devices Elipar FreeLight and GC e-Light showed a significantly higher percentage decrease in power output at a distance of 10 mm from the light guide tip to the radiometer compared to the QTH curing devices. Therefore, although blue LED curing devices might have the same curing potential compared to a QTH device when placed in direct contact to a resin composite, blue LED curing devices may not provide a sufficient cure when placed at a clinically relevant distance of 10 mm to the resin composite surface.

Composite Resins↗

PubMed2003

The influence of the distance from the contact point to the crest of bone on the presence of the interproximal dental papilla.

BACKGROUND: Loss of the interproximal dental papilla may cause functional and, especially in the maxillary anterior region, phonetic and severe esthetic problems. The purpose of this study was to investigate whether the distance from the contact point to the bone crest on standardized periapical radiographs of the maxillary anterior teeth could be correlated with the presence of the interproximal papilla in Taiwanese patients. METHODS: In total, 200 interproximal sites of maxillary anterior teeth in 45 randomly selected patients were examined. Selected subjects were adult Taiwanese with fully erupted permanent dentition. The presence of the interproximal papilla was determined visually. If there was no visible space apical to the contact area, the papilla was recorded as being present. The distance from the contact point to the crest of bone was measured on standardized periapical radiographs using a paralleling technique with a RinnXCP holder. RESULTS: Data revealed that when the distance from the contact point to the bone crest on standardized periapical radiographs was 5 mm or less, the papillae were almost 100% present. When the distance was 6 mm, 51% of the papillae were present, and when the distance was 7 mm or greater, only 23% of the papillae were present. CONCLUSION: The distance from the contact point to the bone crest on standardized periapical radiographs of the maxillary anterior teeth is highly associated with the presence or absence of the interproximal papilla in Taiwanese patients, and is a useful guide for clinical evaluation.

Adult↗