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At least 1,459 records · Page 81Linked to original sources
PubMed2001

Assessment of the position of the distal portion of the ulna in lateral projection radiographs of the wrist: analysis of the influence of pronation-supination and flexion-extension on the pisoscaphoid and the ulnotriquetral distances: a cadaver study.

RATIONALE AND OBJECTIVES: Accurate assessment of the distal radioulnar joint is of paramount importance for the detection of possible dislocation or subluxation. Using a cadaveric model, the authors attempted to establish a quantitative method that would allow identification of normal and abnormal distal radioulnar joint anatomy on well-positioned and rotated conventional radiographs. METHODS: Four cadaveric wrists, in which subsequent sectioning confirmed the absence of disease, and one cadaveric wrist with a circumscribed lesion of the triangular fibrocartilaginous complex were studied. Defined movements in flexion and extension (+/- 10 degrees, 20 degrees, 30 degrees ) and in pronation and supination (+/- 10 degrees, 20 degrees, 30 degrees ) as well as combined flexion/extension and pronation/supination were performed. The ulnotriquetral and the pisoscaphoid distances were assessed in each position. Correlation with cryosections was achieved. RESULTS: A strong linear correlation between the degree of pronation or supination and the pisoscaphoid and ulnotriquetral distances was noted. Flexion and extension produced no significant effect on the pisoscaphoid distance, but a defined shift of the ulnotriquetral distance occurred with increasing flexion and extension. CONCLUSIONS: If all parameters are taken into account, this correlation aids in estimating the degree of possible malpositioning of the wrist during radiography and the degree of subluxation of the distal radioulnar joint. Tabular data with parameters to correct for instances of malrotated images and to estimate the extent of dislocation or malrotation of the distal radioulnar joint are provided.

Cadaver↗
PubMed2002

Measurement of the distance between the minor foramen and the anatomic apex by digital and conventional radiography.

The purpose of this study was to determine the distance between the minor foramen and the anatomic apex from digital and conventional radiographs. Thirty permanent single-canal teeth with mature root apex were used. After access preparation, a K-file was inserted into the canal until the tip of the file was just seen at the minor foramen under a x40 stereomicroscope. The file was fixed in the canal by filling the access with composite resin. The teeth with files in the canals were radiographed using a Schick CDR digital system and conventional radiography with E-speed film. For digital radiographs, the distance between the file tip and the center of radiographic apex was directly measured from the computer screen by using Schick CDR measurement software. For conventional radiographs, the distance was measured under a stereomicroscope at a magnification of x10 with a calibrated millimeter ruler. The mean distance was 0.494 mm measured from conventional radiographs and 0.594 mm from digital radiographs. These results agree with the current conception that endodontic working length should terminate 1 mm from the radiographic apex. There was a significant difference between the measurements on digital radiographs and those on conventional radiographs (p < 0.05, paired t test). However, the 0.1-mm difference has no clinical significance, because clinically, the working length is generally measured to the nearest 0.5 mm.

Dental Pulp Cavity↗
PubMed2002

Distance from acoustic neuroma to fundus and a postoperative facial palsy.

OBJECTIVE/HYPOTHESIS: Generally, patients with small acoustic neuroma have less facial palsy after its removal. The middle cranial fossa approach is mainly applied to the small acoustic neuroma and tumor size does not influence the prognosis of facial palsy. The internal auditory canal cannot be fully opened in the middle cranial fossa approach, and the facial nerve is tightly attached in the fundus. According to these anatomical factors, we hypothesized that acoustic neuromas located away from the fundus might be removed with less facial nerve damage. We investigated the distance between the acoustic neuroma and fundus and its clinical relationship. STUDY DESIGN: Retrospective study of 45 patients with acoustic neuroma who underwent a middle cranial fossa approach. METHODS: The distance between the acoustic neuroma and fundus and the tumor diameter were measured on T2-weighted and contrast-enhanced magnetic resonance images, respectively. These data were compared with the postoperative facial nerve function. RESULTS: The mean distance was 3.0 +/- 1.8 mm (range, 0-10 mm), and the mean diameter was 11.3 +/- 3.7 mm (means +/- standard deviation; range, 4-20 mm). Neither the distance nor the diameter had any correlation to the degrees of postoperative facial palsy either immediately or at 3 months after surgery. CONCLUSIONS: As far as the nerve was anatomically preserved, postoperative facial nerve function seemed to be influenced by factors other than surgical manipulation among small acoustic neuromas. Although the tumor fills in the fundus, it may not influence postoperative facial nerve function and also may not interfere with indication of the middle cranial fossa approach for removal of the acoustic neuroma.

Adult↗
PubMed1997

Wet bulb globe temperature index and performance in competitive distance runners.

In 1974 two sets of heat stress guidelines, each based on the wet bulb globe temperature (WBGT) index, were designed for men's National Collegiate Athletic Association (NCAA) Championship Division I distance running competitions. One set of guidelines was established to minimize the chance of heat injury during distance running events. A second set was designed to predict heat stress related performance decrements. During the time the heat injury guidelines were used (1974-1993), no heat injuries were reported. The purpose of this study was to assess the accuracy of the performance decrement guidelines and determine whether the WBGT indices were linearly related to men's championship distance running performance. WBGT index data were collected during the 1500-, 3000-steeplechase (SC), 5000-, and 10,000-m events at men's NCAA Division I Track and Field Championships held from 1974 to 1981 (excluding 1975). These data were compared to the average running performance of the top six finishers in each event. Analysis of the accuracy of the NCAA performance decrement guidelines revealed four unexpected performances out of 28 predictions. Pearson product-moment correlation and linear regression analyses between the WBGT indices and performance revealed statistically significant linear relationships for the 3000-SC and 10,000-m events (P < 0.05). A significant linear relationship was also found when the 1500-, 3000-SC, 5000-, and 10,000-m results were pooled (P < 0.05). In conclusion, the NCAA guidelines were effective in preventing heat injury and fairly successful in predicting performance. However, a linear relationship between WBGT indices and distance running performance did not exist in all running events.

Adolescent↗
PubMed2000

Cardiac fatigue following prolonged endurance exercise of differing distances.

PURPOSE: Recent echocardiographic studies have reported cardiac dysfunction following ultra-endurance exercise in trained individuals. The duration of exercise required to elicit cardiac dysfunction and the mechanisms underlying this phenomenon have not been fully elucidated. The aim of the present study was to examine the presence of cardiac dysfunction following a half-Ironman and Ironman triathlon in trained individuals. METHODS: 14 male triathletes (age: 32 +/- 5 yr; height: 180 +/- 8 cm; body mass: 75 +/- 9 kg) completed a half-Ironman triathlon. Following a 4-wk period, 10 of the original 14 triathletes completed an Ironman triathlon. All triathletes were assessed using ECG, echocardiography, and blood analysis pre-, immediately post-, and 48 h postrace for both distances. RESULTS: Echocardiographic results indicated diastolic and systolic left ventricular dysfunction, for both race distances, which were associated with altered relaxation characteristics and a reduced inotropic contractility, respectively. Following 48-h recovery, all echocardiographic measures were similar to resting values. Creatine kinase MB (CKMB) was significantly elevated immediately postrace for both distances; however, it accounted for less than 5% of the total CK value and in the presence of an elevated total CK and CKMM implied that the elevated CKMB was noncardiac in origin. Troponin-T, however, was significantly elevated immediately postrace for both distances and returned to normal following 48-h recovery indicating myocardial damage. CONCLUSIONS: Ironman and half-Ironman competition resulted in reversible abnormalities in resting left ventricular diastolic and systolic function. Results suggest that myocardial damage may be, in part, responsible for cardiac dysfunction, although the mechanisms responsible for this cardiac damage remain to be fully elucidated.

Adult↗
PubMed1994

Magnitude, distance, and orthogonality for thin spherocylindrical lenses.

This paper shows that for thin spherocylindrical lenses there is only one reasonable way to define the magnitude of a lens, the distance between two lenses, and orthogonality of lenses. Although any selection of a real inner product on the vector space of thin spherocylindrical lenses extends the space to be a Euclidean space and automatically defines these concepts, requiring the inner product to be rotation invariant makes selecting a Euclidean space equivalent to fixing only the magnitudes of two particular lenses. It is shown that among Euclidean spaces having rotation-invariant inner products there is one that is much preferred to the others. For this space, and for all other rotation-invariant spaces, equations are provided to determine magnitude, distance, inner product, and orthogonality, both in terms of the coordinates of lenses and in terms of the parameters of the prescriptions of the lenses. Also introduced are spherical magnitude and distance, Jackson magnitude and distance, and the six-dimensional Euclidean space of pairs of lenses, which is necessary to describe fully the right and left lenses needed by a patient.

Eyeglasses↗
PubMed1997

Optical performance of aspheric concave ophthalmic lenses: the effect of vertex distance.

Variations of power errors in the periphery of concave aspheric lenses were assessed as a function of vertex distance. Comparisons were made between the performance of different types of spherical lenses and that of aspheric lenses (-6.00 and -8.00 D lenses were used). Off-axis measurements were made by means of a modified focimeter, which enabled rotation of the lens around the center of the vertex sphere. Reduction of the vertex sphere's radius from 27 to 23 mm simulated a 4-mm decrease in vertex distance. Results of the measurements are compared with a computed model. These results indicate that off-axis performance is more affected by a reduction of vertex distance in the case of aspheric lenses compared to spherical lenses. Resulting increases in oblique astigmatism (OA) and mean oblique error (MOE) are at the limit of clinical acceptance. The importance, for the practitioner, of respecting the vertex distance selected for a specific aspheric design when fitting this type of lens is emphasized.

Computer Graphics↗
PubMed2001

Estimating sound source distance with and without vision.

BACKGROUND: Visual capture is an important perceptual phenomenon in which the spatial location of a visual target influences the perceived location of a related auditory target. Little is known about visual capture in a distance dimension. METHODS: Two groups of listeners judged the apparent distances of five loudspeaker sound sources, extending from 1 to 5 m. In one group, each listener was allowed to view the loudspeaker array. In the second group, listeners were blindfolded for the duration of the experiment. RESULTS: No visual capture effects were observed. Instead, the addition of vision was found to both improve distance judgment accuracy and lower judgment variability compared with the auditory-only stimulus. Auditory-only accuracy was found to substantially improve over the course of the experiment, however. CONCLUSIONS: Visual capture in distance is perhaps less general than suggested by past research, a result that has important implications for the display of spatial layout under conditions where vision is either missing or degraded.

Adolescent↗
PubMed2000

Impact of longitudinal distance of the cervical spine on the results of expansive open-door laminoplasty.

STUDY DESIGN: A retrospective study in patients who underwent expansive open-door laminoplasty (ELAP) for cervical myelopathy and in whom the cervical alignment was nonlordotic at the final follow-up to analyze the correlation between the longitudinal distance of the cervical spine and surgical results. OBJECTIVES: To determine the impact of longitudinal distance of the cervical spine on surgical results of ELAP and to propose a new concept, the redundant spinal cord, that may influence patient selection for ELAP. SUMMARY OF BACKGROUND DATA: Results in many studies have demonstrated that postoperative cervical alignment has significant effect on surgical results, and spines that are malaligned are thought to deteriorate. The current surgical data showed that not all patients with postoperative malalignment had poor surgical results. Patients with cervical spondylotic myelopathy (CSM) tended to have better clinical results than those with ossification of the posterior longitudinal ligament (OPLL). METHODS: Results in 70 patients who underwent ELAP for cervical myelopathy with postoperative cervical malalignment were investigated. The longitudinal distance index (LDI) was defined as the length of a vertical line between the posteroinferior edges of C2 and C7 divided by the anteroposterior diameter of C4 and was measured on lateral neutral radiographs at final follow-up. Correlation between LDI and surgical results represented by Japanese Orthopedic Association scores and percentage of recovery were analyzed statistically in each patient. RESULTS: Patients with CSM had smaller LDI and better surgical results than those with OPLL. Weak but significant negative correlation was detected between LDI and percentage of recovery, indicating that longitudinal distance of the cervical spine may have some degree of impact on the surgical results of ELAP. CONCLUSION: A decrease in LDI represents shortening of the cervical spine caused by multiple disc degeneration and may influence surgical results of ELAP by inducing redundancy of the spinal cord in patients with postoperative malalignment.

Cervical Vertebrae↗
PubMed2004

Temperatures within the lumbar disc and endplates during intradiscal electrothermal therapy: formulation of a predictive temperature map in relation to distance from the catheter.

STUDY DESIGN: Temperatures were measured in human cadaveric lumbar discs during intradiscal electrothermal therapy. OBJECTIVES: To determine if sufficient temperatures for collagen denaturation and nociceptive ablation can be achieved at clinically significant distances from the intradiscal electrothermal therapy heating catheter. SUMMARY OF BACKGROUND DATA: Previous cadaveric studies have contested the ability of the intradiscal electrothermal therapy catheter to produce sufficient temperatures to denature collagen and cause neural ablation within the posterior anulus of the disc. However, these experiments used clinically unrepresentative device placements along the anterolateral anulus. METHODS: Intradiscal electrothermal therapy was performed in 14 human cadaveric discs. Devices were inserted using a standard posterolateral approach to orient the heating catheter along the posterior anulus. Temperature recordings were collected using multiple sensors placed along the posterior anulus, anterior anulus, and endplates. RESULTS: Temperatures greater than 60 C and 65 C were achieved in 14 and 5 specimens, respectively, at distances up to 2 mm from the catheter. Between 2 and 4 mm, more than 60 C was achieved in all specimens. More than 45 C was achieved in all specimens at distances of 9 to 14 mm from the device. CONCLUSIONS: Temperatures sufficient for collagen denaturation and nociceptive ablation were detected at distances greater than previously documented. These data suggest that intradiscal electrothermal therapy's proposed heat-dependent mechanisms of action are achievable in most discs. Among other factors, interspecimen variability of maximum temperatures may help explain the somewhat inconsistent clinical results following intradiscal electrothermal therapy.

Adult↗
PubMed2000

Changes in muscle power and neuromuscular efficiency after a 40-minute downhill run in veteran long distance runners.

OBJECTIVE: To establish whether there was a relationship between the total accumulated distances of racing in veteran runners and the neuromuscular efficiency of the quadriceps muscles before and after a downhill run. SETTING: University of Cape Town, Sports Science Institute of South Africa. PARTICIPANTS: Twenty male veteran long distance runners (45-50 years of age) with a range of training (1,300 km to 111,280 km) and racing (0 km to 9,737 km) experience. INTERVENTION: A 40-minute downhill run (-10% decline) on a treadmill, at a speed corresponding to 70% of the subject's peak treadmill running speed. MAIN OUTCOME MEASURES: The difference between integrated electromyography (IEMG)/mean force over a 5 s maximal voluntary isometric contraction before and after the downhill run was calculated as the delta (delta) neuromuscular efficiency. This was related to the total kilometers trained, current training distance, total kilometers raced, and number of races > 56 km. The difference in drop jump height before and after the downhill run was measured as well as changes in heart rate throughout the run. RESULTS: There was a significant curvilinear relationship between the delta neuromuscular efficiency and total kilometers raced (R2 = 0.53, p < 0.05), and a significant inverse relationship between delta neuromuscular efficiency and the number of races > 56 km (r = -0.50, p < 0.05). Drop jump height decreased after the downhill run, and heart rate increased during the run. CONCLUSIONS: Runners who have raced an accumulated distance of > 5,000 km show a significant dissociation in the delta neuromuscular efficiency after a downhill run, compared with less experienced runners. Although possible causes for the dissociation are discussed, further research is needed.

Anthropometry↗
PubMed2007

Radiographic assessment of lumbar facet distance spacing and spondylolysis.

STUDY DESIGN: Spondylolytic defects at L5 are influenced by insufficient differential spacing between the inferior articular facets of L4 and superior facets of S1. These structures then impinge on the intervening L5 pars interarticularis during hyperlordosis, contributing to fracture and resorption of the pars. OBJECTIVES: Articular facet spacing was evaluated on clinical radiographs of normal and spondylolytic patients. SUMMARY OF BACKGROUND DATA: Spondylolysis ranges from a hairline fracture through the pars to a complete pseudarthrotic defect. Insufficient increase in the distance between articular facets from L4-L5 to L5-S1 has been associated with chronic lytic defects in a skeletal sample. METHODS: Anteroposterior radiographs of 39 patients with L5-S1 spondylolysis were compared with radiographs from 42 normal individuals. Differences in transverse distances between lumbar articular facets and pedicles were compared using 2-tailed t tests. RESULTS: Patients with spondylolysis exhibited a smaller increase in interfacet distance from the L3-L4 facet joints to the L5-S1 joints than do normal patients, even relative to vertebral size. CONCLUSIONS: Spondylolytic fractures at L5 are influenced by an inadequate increase in interfacet distances between adjacent vertebrae. Individuals lacking sufficient increase in lower lumbar transverse interfacet dimensions are at greater risk of developing and maintaining spondylolytic defects.

Adolescent↗
PubMed2004

Tolerating vertex distance changes for spherocylindrical corrections.

Prescriptions depend on the vertex distance. Although weak prescriptions are insensitive to a vertex distance change, stronger ones must be adjusted if the vertex distance is modified by an appreciable amount. The tolerable amount can be specified for pure spherical powers. For spherocylindrical corrections, the concept of dioptric distance is invoked in this article and applied to the propagation of an astigmatic wavefront. This leads to a simple rule that is well suited to decide on the necessity of modifying a prescription.

Astigmatism↗
PubMed1998

Spatially induced speciation prevents extinction: the evolution of dispersal distance in oscillatory predator-prey models.

In a discrete-generation, individual-oriented model of predator-prey interactions that exhibits oscillations, we show that the self-structuring of the populations into spiral waves induces a selection pressure for ever-increasing dispersal distances in both populations. As the dispersal distances increase, the sizes of the spatial patterns increase, until they are too large to fit into the limited space. The patterns are then lost and the predators go extinct. This scenario, is, however, not the only outcome. A second selection pressure induced by the spatial boundary can cause reduction of the dispersal distances. Depending on the relative strengths of the two selection pressures, the predators and prey may speciate to give coexistence between short-dispersing boundary quasi-species and far-dispersing spiral quasi-species. Now, when pattern loss occurs, the predators switch to predating on the boundary prey quasi-species and do not go extinct. Also, if the populations reproduce sexually, local gene flow can inhibit the evolution of increasing dispersal distances, and hence the spatial patterns are not lost. Speciation and coexistence can also occur in the sexually reproducing species.

Biological Evolution↗
PubMed2002

Distance between inherent structures and the influence of saddles on approaching the mode coupling transition in a simple glass former.

We analyze through molecular dynamics simulations of a Lennard-Jones (LJ) binary mixture the statistics of the distances between inherent structures sampled at temperatures above the mode coupling transition temperature T(MCT). After equilibrating at T>T(MCT) we take equilibrated configurations and randomly perturb the coordinates of a given number of particles. After that we find the nearby inherent structures (IS) of both the original and perturbed configurations and evaluate the distance between them. This distance presents an inflection point at T(li) approximately 1 with a strong decrease below this temperature which goes to a small but nonzero value on approaching T(MCT). In the low-temperature region we study the statistics of events which give zero distance, i.e., dominated by minima, and find evidence that the number of saddles decreases exponentially near T(MCT). This implies that saddles continue to exist even at T<or=T(MCT). As at T(MCT) the diffusivity goes to zero, our results imply that there are saddles associated with nondiffusive events at T<T(MCT).

Journal Article↗
PubMed2003

Operationally invariant measure of the distance between quantum states by complementary measurements.

We propose an operational measure of distance of two quantum states, which conversely tells us their closeness. This is defined as a sum of differences in partial knowledge over a complete set of mutually complementary measurements for the two states. It is shown that the measure is operationally invariant and it is equivalent to the Hilbert-Schmidt distance. The operational measure of distance provides a remarkable interpretation of the information distance between quantum states.

Journal Article↗
PubMed2006

An improved grafting technique for mature Arabidopsis plants demonstrates long-distance shoot-to-root transport of phytochelatins in Arabidopsis.

Phytochelatins (PCs) are peptides that function in heavy-metal chelation and detoxification in plants and fungi. A recent study showed that PCs have the ability to undergo long-distance transport in a root-to-shoot direction in transgenic Arabidopsis (Arabidopsis thaliana). To determine whether long-distance transport of PCs can occur in the opposite direction, from shoots to roots, the wheat (Triticum aestivum) PC synthase (TaPCS1) gene was expressed under the control of a shoot-specific promoter (CAB2) in an Arabidopsis PC-deficient mutant, cad1-3 (CAB2TaPCS1/cad1-3). Analyses demonstrated that TaPCS1 is expressed only in shoots and that CAB2TaPCS1/cad1-3 lines complement the cadmium (Cd) and arsenic metal sensitivity of cad1-3 shoots. CAB2TaPCS1/cad1-3 plants exhibited higher Cd accumulation in roots and lower Cd accumulation in shoots compared to wild type. Fluorescence HPLC coupled to mass spectrometry analyses directly detected PC2 in the roots of CAB2:TaPCS1/cad1-3 but not in cad1-3 controls, suggesting that PC2 is transported over long distances in the shoot-to-root direction. In addition, wild-type shoot tissues were grafted onto PC synthase cad1-3 atpcs2-1 double loss-of-function mutant root tissues. An Arabidopsis grafting technique for mature plants was modified to obtain an 84% success rate, significantly greater than a previous rate of approximately 11%. Fluorescence HPLC-mass spectrometry showed the presence of PC2, PC3, and PC4 in the root tissue of grafts between wild-type shoots and cad1-3 atpcs2-1 double-mutant roots, demonstrating that PCs are transported over long distances from shoots to roots in Arabidopsis.

Arabidopsis↗
PubMed2005

Destination-selective long-distance movement of phloem proteins.

The phloem macromolecular transport system plays a pivotal role in plant growth and development. However, little information is available regarding whether the long-distance trafficking of macromolecules is a controlled process or passive movement. Here, we demonstrate the destination-selective long-distance trafficking of phloem proteins. Direct introduction, into rice (Oryza sativa), of phloem proteins from pumpkin (Cucurbita maxima) was used to screen for the capacity of specific proteins to move long distance in rice sieve tubes. In our system, shoot-ward translocation appeared to be passively carried by bulk flow. By contrast, root-ward movement of the phloem RNA binding proteins 16-kD C. maxima phloem protein 1 (CmPP16-1) and CmPP16-2 was selectively controlled. When CmPP16 proteins were purified, the root-ward movement of CmPP16-1 became inefficient, suggesting the presence of pumpkin phloem factors that are responsible for determining protein destination. Gel-filtration chromatography and immunoprecipitation showed that CmPP16-1 formed a complex with other phloem sap proteins. These interacting proteins positively regulated the root-ward movement of CmPP16-1. The same proteins interacted with CmPP16-2 as well and did not positively regulate its root-ward movement. Our data demonstrate that, in addition to passive bulk flow transport, a destination-selective process is involved in long-distance movement control, and the selective movement is regulated by protein-protein interaction in the phloem sap.

Cucurbita↗