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 1,279 records · Page 71Linked to original sources
PubMed1985

An investigation of the SH1-SH2 and SH1-ATPase distances in myosin subfragment-1 by resonance energy transfer using nanosecond fluorimetry.

The separation between the two reactive thiols SH1 (Cys-704) and SH2 (Cys-694) and that between SH1 and the active site of myosin subfragment-1 were further investigated by Förster energy transfer techniques. The SH1-SH2 distance was determined with the probe 5-[[2-[(iodoacetyl)amino]ethyl] amino]naphthalene-1-sulfonic acid (AEDANS) attached to SH1 as the energy donor and 5-(iodoacetamido)fluorescein (IAF) attached to SH2 as energy acceptor. The results derived from measurements of donor lifetimes yielded a donor-acceptor separation in the range 26-52 A, with the distance R(2/3) based on rapid and isotropic probe motions being 40 A. These parameters were not sensitive to added MgADP, in agreement with previous results obtained by using the steady-state method. The SH1-SH2 distance was also determined with AEDANS attached to SH1 and N-(4-dimethylamino-3,5-dinitrophenyl)maleimide (DDPM) attached to SH2. The range in R for the AEDANS/DDPM pair was 12-36 A, with R(2/3) equal to 27 A. The transfer efficiency between these two probes increased by an average of 38% upon addition of MgADP. These results are in agreement with those previously reported (Dalbey, R.E., Weiel, J. and Yount, R.G. (1983) Biochemistry 22, 4696-4706), but the uncertainty in choosing an appropriate value of the orientation factor to describe the AEDANS-DDPM separation does not allow a unique interpretation of the observed increase in energy transfer because it could reflect either an increase in the average orientation factor or a decrease in the donor-acceptor separation. Nevertheless, the results are consistent with the notion that nucleotide binding induces structural perturbations that can be sensed by SH1 and SH2. The distance between SH1 and the ATPase site was determined with AEDANS linked to SH1 and the nucleotide analogue 2'(3')-O-(2,4,6-trinitrophenyl)adenosine 5'-diphosphate (TNP-ADP) noncovalently bound to the active site as energy acceptor. The bound TNP-ADP was highly immobilized, with a depolarization factor approaching unity. The separation between AEDANS at SH1 and TNP-ADP at the active site was in the range 15-44 A. The actual minimal separation between SH1 and the active site is probably less than 15 A, which suggests that direct interaction between the two sites cannot be ruled out from energy transfer results.

Adenosine Diphosphate↗
PubMed1995

Is measuring postnatal symphysis-fundal distance worthwhile?

OBJECTIVE: to assess levels of intra-observer and inter-observer variability in the measurement of postnatal symphysis-fundal distance and establish whether the measurement is sufficiently precise for it to be of use in clinical practice. SETTING: a consultant obstetric maternity unit in the south of England which caters for approximately 6000 deliveries per annum. METHODS: in the intra-observer study 15 midwives took repeated readings of symphysis-fundal distance on 30 postnatal women. In the inter-observer study 13 midwives took readings of symphysis-fundal distances on 24 postnatal women. Repeatability coefficients (the variability to be expected in the change between two measurements) were calculated. FINDINGS: the repeatability coefficient, that is the maximum difference that is likely to occur, 95% of the time, for the difference between two measurements obtained by the same midwife on the same woman is 2.94 cm (intra-observer study). Where measurements are obtained by different midwives on the same mother the repeatability coefficient is 5.01 cm (inter-observer study). In everyday clinical practice variability is likely to be greater than that found in this study. IMPLICATIONS FOR PRACTICE: the daily measurement of the postnatal symphysis-fundal distance with a tape measure cannot be obtained with enough precision to be useful in making clinical judgements and therefore should be discontinued. Further research is required to assess the value of routine palpation of the uterine fundus to assess involution during the postnatal period.

Anthropometry↗
PubMed1983

The distance behavior of hospital patients: a disaggregated analysis.

Regional health systems planning implicitly incorporates information about the distance behavior of hospital patients, in specifying hospital catchment areas, service-specific catchment areas and levels of centralization. Distance behavior of patients varies depending on their diagnoses and on the treatment and diagnostic procedure(s). In this study, a variety of procedures, ranging from those which are routine to those which are highly specialized, are analyzed within the framework of distance behavior. Regionalization of selected services will, by definition, affect distance behavior.

Catchment Area, Health↗
PubMed1994

The effect of distance to VA facilities on the choice and level of utilization of VA outpatient services.

The 1987 survey of Veterans is used to explain the effects of distance to VA facilities on the choice and level of utilization of VA outpatient services by U.S. veterans. A two part discrete/continuous model is used to separate two elements of the decision to seek outpatient services from federally operated VA facilities. First, a discrete choice is made to seek care from the VA. Second, a continuous choice is made to seek a particular level of utilization. Distance is found to affect the initial discrete choice significantly for measured distances up to 60 miles at a decreasing rate. Once some VA outpatient contact is made, distance is a major factor only for the elderly in determining the amount of utilization. Disturbingly, elderly veteran users living more than 30-40 miles from the nearest VA are expected to make fewer visits in a year than younger veterans.

Aged↗
PubMed1987

Capillary growth and diffusion distances in muscle.

1. Tissue capillarity in muscle was modelled as square-ordered arrays with capillary-to-fiber ratios (C/F) from 0.5 to 'infinity'. 2. C/F up to two had marked effects on diffusion distances, but C/F above had only slight effects on average distances and almost no effect on maximal distances. 3. Capillary growth during normal maturation results in C/F around two. Thus, capillary growth in adult muscle may not be an adaptive mechanism for reducing diffusion distances.

Aging↗
PubMed1996

The midbrain creates and the thalamus sharpens echo-delay tuning for the cortical representation of target-distance information in the mustached bat.

Mustached bats emit complex biosonar 'pulses' for echolocation. A delay of an echo from the emitted pulse carries target-distance information. At the auditory periphery, distance information is expressed by a time interval between the responses of neurons to the emitted pulse and its echo. In the auditory cortex (AC), however, it is mapped by 'FM-FM' neurons which are tuned to particular echo delays. FM-FM neurons have been found not only in the AC but also in the inferior colliculus (IC) of the midbrain and the medial geniculate body (MGB) of the thalamus. In the present study, we found that the IC has a precursor of the cortical echo-delay axis for the systematic representation of target-distance information and that the MGB shows the improved neural representation of target-distance information.

Animals↗
PubMed1987

Relative wire stiffness due to lingual versus labial interbracket distance.

Orthodontic treatment of patients with lingual appliances necessitates modifications of the conventional mechanotherapy used with labial appliances. When the brackets are placed on the lingual instead of the labial surface, the interbracket distances in the anterior region of the arches are decreased significantly. The purpose of this study was to determine by how much these interbracket distances are decreased, and to quantitate what effect this has on relative wire stiffness. Lingual and labial brackets were placed on models of 30 orthodontically treated patients and a ratio comparing the lingual to labial interbracket distances was calculated to be 1:1.47. Twenty-five orthodontic wires at lengths of 1 inch and 1.47 inches were then evaluated for their stiffness in first-, second-, and third-order bending. The results showed that the decreased interbracket distance associated with lingual appliances makes a wire seem approximately 3 times as stiff as when used with labial appliances for first- and second-order bends, and approximately 1 1/2 times as stiff for third-order bends. Wire equivalence charts were developed to help orthodontists make direct comparisons between labial and lingual arch wires in regard to stiffness. These charts should prove useful to the clinician during initial alignment and final detailing when adequate arch wire flexibility is essential.

Cuspid↗
PubMed1991

Verification of optical distance indicator accuracy.

The purpose of the optical distance indicator, or rangefinder, is to set the patient at a certain distance from the radiotherapy source when using either fixed SSD or an isocentric technique. If the distance that is set is not accurate, then the tumor dose calculated using this distance is also incorrect. Unfortunately, an ODI that is not properly aligned may show an accurate reading on a flat surface and may give an inaccurate reading on a sloped surface.

Humans↗
PubMed2005

Radiographic left ventricular-right ventricular interlead distance predicts the acute hemodynamic response to cardiac resynchronization therapy.

Placement of left ventricular (LV) and right ventricular (RV) leads with maximal interlead separation is frequently sought during cardiac resynchronization therapy (CRT), but few published data are available to support this. This study examined the relation between LV and RV lead separation and the acute effects of CRT on cardiac contractility. A total of 51 consecutive patients who underwent CRT for standard indications with sufficient mitral regurgitation for echocardiographic assessment of contractility (using Doppler profiles of mitral regurgitation as a percentage of change in dP/dt [DeltadP/dt] with CRT on and off), successful transvenous LV lead placement, and postprocedural chest radiography were evaluated. The separation of the LV and RV lead tips (direct interlead distance and horizontal and vertical components) was determined on postprocedural posteroanterior and lateral radiographs. The corrected direct LV-RV interlead distance on the lateral radiograph was correlated with the DeltadP/dt (n = 51, r = 0.43, p = 0.002). The lateral interlead distance in the horizontal plane (r = 0.58, p <0.0001), but not the vertical plane (r = -0.28, p = NS), correlated with the DeltadP/dt. The corrected horizontal interlead distance on the lateral film was greater in acute hemodynamic responders to CRT (DeltadP/dt >25%) compared with nonresponders (14.4 +/- 5.4 vs 9.2 +/- 5.8 cm, p = 0.002). Other LV-RV measures on the posteroanterior and lateral radiographs did not correlate with the DeltadP/dt. Use of these findings may help to guide the sites of LV and RV lead placement to maximize the benefit derived from CRT.

Aged↗
PubMed2006

The use of a heel-mounted accelerometer as an adjunct measure of slip distance.

A human-centered measure of floor slipperiness could be useful as an adjunct to conventional tribologic measures. This paper reports on the development and evaluation of a measure of slip distance based on variables derived from the signal of a heel-mounted accelerometer. Twenty-one participants walked on a laboratory runway under several surface slipperiness conditions at three walking speeds during a protocol designed to produce a wide range of slip distances at heel strike. Analysis of variance showed significant effects of slip distance (no-slip, micro-slip and slide), walking speed (1.52, 1.78 and 2.13 m/s) and their interactions on peak forward acceleration, peak vertical acceleration and deceleration time of the heel following heel strike in 704 trials. Regression analysis of slip distance and deceleration time showed the strongest relationship with R2=0.511. Large individual variation in the strength of this relationship was observed. The heel-mounted accelerometer may have utility as an adjunct measure in the evaluation of floor slipperiness, particularly for field applications where direct measurement may not be feasible.

Acceleration↗
PubMedDate not supplied

A neural mechanism for detecting the distance of a selected target by modulating the FM sweep rate of biosonar in echolocation of bat.

Most species of bats making echolocation use frequency modulated (FM) ultrasonic pulses to measure the distance to targets. These bats detect with a high accuracy the arrival time differences between emitted pulses and their echoes generated by targets. In order to clarify the neural mechanism for echolocation, we present neural model of inferior colliculus (IC), medial geniculate body (MGB) and auditory cortex (AC) along which information of echo delay times is processed. The bats increase the downward frequency sweep rate of emitted FM pulse as they approach the target. The functional role of this modulation of sweep rate is not yet clear. In order to investigate the role, we calculated the response properties of our models of IC, MGB, and AC changing the target distance and the sweep rate. We found based on the simulations that the distance of a target in various ranges may be encoded the most clearly into the activity pattern of delay time map network in AC, when the sweep rate of FM pulse used is coincided with the observed value which the bats adopt for each range of target distance.

Animals↗
PubMed2005

Correlation coefficients between the dioxin levels in mother's milk and the distances to the nearest waste incinerator which was the largest source of dioxins from each mother's place of residence in Tokyo, Japan.

BACKGROUND: To observe the relationship between the PCDD/F and Co-PCB levels in samples of human breast milk and nearby waste incinerators in Tokyo, Japan. METHODS: Breast milk was taken from 240 mothers residing in Tokyo, Japan to measure and analyze the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs; 14 congeners), polychlorinated dibenzofurans (PCDFs; 15 congeners), and coplanar polychlorinated biphenyls (Co-PCBs; 12 congeners) contained in the fat. Individual milk samples (about 50 ml) were obtained from the mothers 30 days after delivery, between the months of June and September in 1999 and 2000. A map of Tokyo was used to measure the distances between each mother's place of residence and the closest public and industrial waste incinerators. RESULTS: The distances to the nearest waste incinerators bore no apparent correlations with the congeners of PCDD/Fs and Co-PCBs. The distances were also uncorrelated with the mean toxic equivalent quantities (TEQs) of PCDD/Fs (the sum of PCDDs and PCDFs), Co-PCBs, and the total PCDD/Fs and Co-PCBs. CONCLUSIONS: Although waste incinerators were the largest source of dioxins in Japan at the time of the study, the dioxins levels of mother's milk bore no apparent relationships with the distances between the mothers' domiciles and the nearest waste incinerators. In this study, several meaningful factors were not taken into account, namely, the wind direction, the level of dioxin emitted from each incinerator, the level of environmental pollution of dioxins, and the average time the mothers stayed at home each day. A full understanding of these points awaits future studies.

Activities of Daily Living↗
PubMed2005

The effect of numerical distance and stimulus probability on ERP components elicited by numerical incongruencies in mental addition.

In two experiments, we investigated the effect of the numerical distance of incongruous results from correct results and stimulus probability on the N270/N400 event-related brain potential components. In Experiment 1, 12 subjects saw two one-digit addends and a possible solution and signaled if the proposed result (falling in the range of 3-17) was true or false. Incorrect results could deviate by +/-2 or by +/-9 from the correct answer. The probability of correct results was 50%. Twelve subjects carried out a similar task in Experiment 2 without giving behavioral responses. The probability of incorrect results was 20%, 50% or 80% in different conditions. Both raw potentials and incorrect minus correct difference potentials were analyzed. A fronto-central N3 and a centro-parietal dN3 (incorrect-correct difference) were present for incongruous results in both experiments. The amplitude of the dN3 was not sensitive to numerical distance, but the latency of the dN3 was longer when numerical distance was larger. The overall amplitude of the N3 and of the dN3 was not sensitive to the probability manipulation. However, there was a parietally localized effect of probability on N3 amplitude. The dN3 in mental addition is most probably identical to the arithmetic N400 effect reported earlier in mental multiplication. The distance effect in latency may be a correlate of the discrimination of correct vs. incorrect results. A parietally localized probability effect (right greater than left) was found in the N3 amplitude. The dN3 was insensitive to the probability manipulation. In accord with its insensitivity to stimulus probability, the dN3 seems to be more related to the N400 than to the N2b. Posterior attentional processes sensitive to the allocation of attentional resources may have contributed to the topography of the dN3. The N3 is more related to the detection of expectation violation, while the P3 reflects the ease of identifying stimulus categories.

Adolescent↗
PubMed2005

An ultrasonic device for source to skin surface distance measurement in patient setup.

PURPOSE: To develop an ultrasound-based source to skin surface distance (SSD) measurement technique and device for patient setup and test its feasibility and accuracy. METHODS AND MATERIALS: The ultrasonic SSD measurement device (USD) prototype consists of two main parts: a probe plate with an ultrasonic transducer in the center and a control unit that displays the SSD in millimeters. The probe plate can be slid into the block tray accessory slot of any treatment machine at the time of the SSD measurement. The probe plate contains an ultrasonic transducer as both the source and the detector for measuring the distance between the transducer and the target surfaces on the basis of an echo-detecting technique. The device was calibrated by a mechanical ruler with an accuracy of 0.01 mm and corrected by an offset of 601.7 mm, which is the distance from the radiation source to the ultrasonic transducer surface for the Siemens Primus linear accelerator (Linac). The ultrasound device provided digital readout with an accuracy of +/-0.1 mm for a flat surface after calibration. The SSD measurement experiments were done with the USD, an optical distance indicator (ODI), and an AKTINA 53-104 Mechanical Front Pointer (FP) on a Siemens Primus Linac with a full-sized female phantom. Ten measurements were carried out at each gantry angle of 0 degrees , 52 degrees , 85 degrees , 90 degrees , and 227 degrees for anatomic locations of head, thorax, breast, and pelvis, to obtain the average values and standard deviations. RESULTS: The comparison study with the ODI and FP showed that the USD had an accuracy of less than +/-1.0 mm and that USD measurements had the minimum standard deviations among the three methods; therefore, USD gave more consistent and accurate readouts for SSD measurement. When considering the FP as a reference, the USD yields smaller deviations than the ODI for all measured locations (less than +/-2 mm). The variation of USD digital readout with a room temperature change of +/-2 degrees C is +/-0.1 mm, which is sufficiently accurate for SSD measurement. CONCLUSIONS: The USD method has the following advantages. First, it decreases patient setup time by avoiding problems related to the blocking of the device by the patient or by the immobilization device. Second, it is more accurate than the other two methods currently used, as the test data show. Last, the digital readout eliminates the possibility of human reading error associated with the visual scales.

Calibration↗
PubMed2006

Age-related distance esotropia.

PURPOSE: To describe a form of acquired esotropia occurring in older adults, which here is termed age-related distance esotropia. METHODS: A retrospective consecutive case series of 26 patients with this condition was reviewed. RESULTS: The patients ranged in age from 62 to 91 years old with a median age of 77 years. The distance deviation varied from 4 prism diopters (PD) ET (esotropia) to 20 PD ET, with a median angle of 9 PD ET. At near fixation, the measurements ranged from 9 PD ET' to 10 PD X' (exophoria), with a median deviation of 3 PD ET'. Ductions and versions were full, with no evidence of lateral rectus paresis. None of these patients had an obvious underlying neurologic disorder, such as tumor or stroke. Treatment consisted of prescribing the minimum prismatic correction that eliminated distance diplopia, which was then incorporated into the patients' current spectacles. This treatment successfully eliminated the symptoms in all patients. No patient in this study required surgery. CONCLUSION: A distinctive form of strabismus occurs in older adults that is characterized by esotropia greater at distance than near fixation. The etiology of this disorder is unknown, but it is likely secondary to anatomical changes in the orbit and/or muscles associated with aging. Most patients are readily corrected by prisms but, surgical correction might be required in some cases.

Age Factors↗
PubMed2004

Mapping high-dimensional data onto a relative distance plane--an exact method for visualizing and characterizing high-dimensional patterns.

We introduce a distance (similarity)-based mapping for the visualization of high-dimensional patterns and their relative relationships. The mapping preserves exactly the original distances between points with respect to any two reference patterns in a special two-dimensional coordinate system, the relative distance plane (RDP). As only a single calculation of a distance matrix is required, this method is computationally efficient, an essential requirement for any exploratory data analysis. The data visualization afforded by this representation permits a rapid assessment of class pattern distributions. In particular, we can determine with a simple statistical test whether both training and validation sets of a 2-class, high-dimensional dataset derive from the same class distributions. We can explore any dataset in detail by identifying the subset of reference pairs whose members belong to different classes, cycling through this subset, and for each pair, mapping the remaining patterns. These multiple viewpoints facilitate the identification and confirmation of outliers. We demonstrate the effectiveness of this method on several complex biomedical datasets. Because of its efficiency, effectiveness, and versatility, one may use the RDP representation as an initial, data mining exploration that precedes classification by some classifier. Once final enhancements to the RDP mapping software are completed, we plan to make it freely available to researchers.

Algorithms↗
PubMed2005

Influence of Er:YAG laser irradiation distance on the bond strength of a restorative system to enamel.

OBJECTIVES: The aim of the present study was to investigate in vitro the effect of Er:YAG laser on bonding to enamel, varying the irradiation distance. METHOD: Tensile bond strength of an adhesive restorative system to non-irradiated and irradiated enamel surfaces was evaluated. Thirty caries-free human third molars were sectioned in mesio-distal direction and embedded in acrylic resin. Enamel was flattened, and a 3-mm-diameter bonding area was demarcated. Specimens were randomly assigned into six groups: groups I-V were treated with the Er:YAG laser (80 mJ/2 Hz), varying the irradiation distance (11, 12 mm-focused, 14, 16 and 17 mm, respectively), followed by 35% phosphoric acid etching. Control group (VI) received treatment with phosphoric acid alone. Single Bond adhesive system was applied on the conditioned enamel, and composite resin cones, bonded to enamel, were fabricated with Z250. After storage, samples were tested in tensile to failure (50 kgf and 0.5 mm/min). RESULTS: Means in MPa were: I-9.67 (+/-3.44); II-13.29 (+/-2.65); III-13.33 (+/-2.22); IV-14.87 (+/-3.58); V-16.43 (+/-4.52); VI-22.90 (+/-3.03). ANOVA and Tukey test revealed statistically significant decrease of bond strength in group I (P < 0.05). Groups II-IV presented similar results, as did groups IV and V. Control group (VI) yielded the best overall performance (P < 0.05). CONCLUSION: Er:YAG laser irradiation adversely affected adhesion to enamel. However, bond strength was influenced by the irradiation distance, thus being stronger with the increase of distance to the target tissue.

Acid Etching, Dental↗
PubMed2004

Conclusions on plutonium separation from atmospheric krypton-85 measured at various distances from the Karlsruhe reprocessing plant.

For wide-area atmospheric monitoring, krypton-85 is the best indicator for clandestine plutonium separations. The detection and false alarm rates were determined from weekly samples at five different distances from the Karlsruhe reprocessing plant between 1985 and 1988. The detection rate for the separation of 4 kg of plutonium per week was found to be as high as 80-90% at a distance of less than 1 km, 70% at 5 km, 40% at 39 km, and 15% at 130 km. At distances up to 40 km, the false alarm rate is less than 3.5%. On average, the fuel released 28 TBq krypton-85 per kg plutonium. For weapons-grade plutonium, the krypton signal would be lower by a factor of 2. Hence, the given percentages correspond to the detection probabilities for the separation of a significant quantity (8 kg) of plutonium per weekly sample under the specific meteorological conditions of the WAK. The minimum separation rates that could have been detected are 2 gram of weapons-grade plutonium per week at a distance of less than 1 km, 40 g/week at 5 km, 200 g/week at 39 km, and 1000 g/week at 130 km.

Air Pollutants, Radioactive↗