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At least 973 records · Page 54Linked to original sources
PubMedDate not supplied

Effects of long-term exercise rehabilitation on claudication distances in patients with peripheral arterial disease: a randomized controlled trial.

PURPOSE: To determine if improvements in physical function and peripheral circulation after 6 months of exercise rehabilitation could be sustained over a subsequent 12-month maintenance exercise program in older patients with intermittent claudication. METHODS: Seventeen patients randomized to exercise rehabilitation and 14 patients randomized to usual care control completed this 18-month study. Patients exercised three times per week during the first 6 months of a progressive exercise program, followed by two times per week during the final 12 months of a maintenance program. Patients were studied at baseline, 6 months, and 18 months during the study. RESULTS: Eighteen months of exercise rehabilitation increased the initial claudication distance by 373 meters (189%) (P <.001), the absolute claudication distance by 358 meters (80%) (P <.001), walking economy by 11% (P <.001), 6-minute walk distance by 10% (P <.001), daily physical activity by 31%, and maximal calf blood flow by 18% (P <.001). These changes were similar to those found after 6 months of exercise rehabilitation (P = NS), and were significantly greater than the changes in the control group throughout the study (P <.05). CONCLUSION: Improvements in claudication distances, walking economy, 6-minute walk distance, physical activity level, and peripheral circulation after 6 months of exercise rehabilitation are sustained for an additional 12 months in older patients with intermittent claudication using a less frequent exercise maintenance program.

Aged↗
PubMed2001

The role of gastrointestinal endoscopy in long-distance runners with gastrointestinal symptoms.

BACKGROUND: Exercise-related gastrointestinal symptoms are not uncommon among athletes. The occurrence of gastrointestinal bleeding has been reported, especially in long-distance runners. We studied gastrointestinal mucosal damage, using gastrointestinal endoscopy, in competitive long-distance runners. Gastrointestinal blood loss and anaemia before and after running were also assessed. METHODS: Sixteen competitive long-distance runners (all men; age range 16-19 years) participated in the study. All runners completed a symptom questionnaire prior to a 20 km race. Stool occult blood and haematological studies (haemoglobin, haematocrit, serum iron, total iron-binding capacity [TIBC] and ferritin) were performed before and immediately after the race. Gastrointestinal endoscopy was performed to assess macroscopic changes. Colonoscopy was also performed on the patients who had positive stool occult blood before or after the race. RESULTS: Gastrointestinal symptoms were frequently experienced by the runners. Gastritis (n = 16), oesophagitis (n = 6) and gastric ulcer (n = 1) were found at gastroscopy. Colonoscopy was performed on four patients who had positive stool occult blood. One had multiple erosions at the splenic flexure and one had a rectal polyp. Five runners had anaemia, and all of these had at least one endoscopic lesion (three gastritis, two oesophagitis and one multiple erosion at the splenic flexure). There were significant changes in the following haematological parameters after the race: iron (decreased, P = 0.02), ferritin (decreased, P = 0.001) and TIBC (increased, P = 0.00005). CONCLUSIONS: Gastrointestinal symptoms and gastrointestinal mucosal damage are prevalent among long-distance runners. Prior to treatment, gastrointestinal endoscopy should be considered in long-distance runners with gastrointestinal symptoms and/or anaemia.

Adolescent↗
PubMedDate not supplied

Predictors of extracapsular extension and its radial distance in prostate cancer: implications for prostate IMRT, brachytherapy, and surgery.

PURPOSE: Tightly constricted isodose lines are generated using brachytherapy or intensity-modulated radiation therapy (IMRT) treatment planning systems for prostate cancer. Definition of margins that encompass subclinical disease extension is important to maximize dose escalation while attemptingto adhere to normal tissue dose tolerances. In this study, we attempted to find predictors of extracapsular extension (ECE) and its radial distance. MATERIALS AND METHODS: Pathological assessment of ECE and its radial distance was performed on 712 radical prostatectomy specimens. Preoperative data (initial prostate-specific antigen, clinical stage, ultrasound volume, and biopsy Gleason score) were evaluated for their ability to predict the presence of ECE and its radial distance. RESULTS: Measurable disease was noted outside the prostatic capsule in 185 of 712 (26.0%) specimens. All preoperative parameters except ultrasound volume were able to predict the presence of ECE. However, none of them was predictive of the radial ECE distance. In this group, the median and the range of the maximum depth of invasion (radial extension from the capsule) were 2.00 and 0.5-12.00 mm, respectively. The mean radial distance from the capsule was 2.93 mm, SD +/- 2.286 mm. All subgroups had some patients with radial extension ranging from 0-2 mm, 2-5 mm, to > 5 mm. Only patients with a prostate-specific antigen of 0-4 ng/mL had no extension > 5 mm. CONCLUSIONS: This is the largest series in the literature thus far that quantitatively assesses radial extracapsular extension. Coverage of subclinical disease must be addressed carefully before successful implementation of intensity-modulated radiation therapy, brachytherapy, or prostatectomy in order to avoid geographical miss.

Adult↗
PubMed2006

The repeatability of MNREAD acuity charts and variability at different test distances.

PURPOSE: The purposes of this study are to establish the repeatability of the MNREAD acuity charts in a normal adult population and to determine the coefficient of repeatability for reading acuity, reading speed, and critical print size. The study also investigates how changing the working distance affects these parameters. METHODS: Thirty normal young adults (mean age, 23.3 years) participated. Test-retest repeatability was assessed at 40 cm over two sessions by the same examiner using MNREAD charts 1 and 2. Additional measurements were also carried out at 24 cm and 52 cm working distances. The distance and the version of the chart used were randomized. RESULTS: The coefficient of repeatability was found to be +/- 0.05 logarithm of the minimum angle of resolution (logMAR) for reading acuity, +/- 0.12 logMAR for critical print size, and +/- 8.6 words per minute for reading speed. Reading acuity and critical print size changed significantly with testing distance (p = 0.001). No changes were found in the reading speed at the different test distances (p = 0.27). CONCLUSIONS: The MNREAD acuity charts can be used reliably to measure reading acuity, reading speed, and critical print size in a normal adult population.

Adolescent↗
PubMed2005

Closest distance between tumor and resection margin in radical prostatectomy specimens: lack of prognostic significance.

Complete removal of the tumor by surgery offers the best chance for cancer cure; however, many prostate cancer patients who have negative surgical margins at radical prostatectomy will still experience local and distant tumor recurrence. In other organs, the closest distance between tumor and resection margin has prognostic significance. This has not been adequately studied in prostatectomy specimens. We undertook a prospective study of 278 consecutive margin-negative whole-mount prostatectomy cases. The anatomic location and closest distance between tumor and resection margin, measured with an ocular micrometer, were analyzed. All the slides were reviewed by a single pathologist, and data were collected prospectively. The closest distance between tumor and resection margin ranged from 0.02 to 5.0 mm (mean, 0.7 mm; median, 0.5 mm) and correlated with patient age (P = 0.03), prostate weight (P = 0.002), Gleason score (P = 0.001), pathologic stage (P = 0.01), tumor volume (P < 0.001), and perineural invasion (P < 0.001). The closest distance between tumor and resection margin was not a significant predictor of PSA recurrence in univariate or multivariate logistic regression; and we do not, therefore, advocate reporting the closest distance between tumor and resection margin as a standard part of the surgical pathology report on prostatectomy specimens.

Adult↗
PubMed2004

Amorphous silicon, flat-panel, x-ray detector: reliability of digital image fusion regarding angle and distance measurements in long-leg radiography.

RATIONALE AND OBJECTIVES: To evaluate composed long-leg images acquired with a large-area, flat-panel x-ray detector with regard to angle and distance measurements. METHODS: Radiographs of a long-leg phantom were acquired at 13 different angle settings with a 43-cm x 43-cm digital x-ray detector based on cesium iodide (CsI) and amorphous silicon (a-Si) technology. Three overlapping single images of the phantom were reconstructed at a workstation using a generalized correlation method. Four blinded observers were instructed to determine the angle of the axis of the long-legs as well as the length of "femur" and "tibia" on soft-copy displays. For that, the angle and distance measurement software integrated in the workstation was used. The images were analyzed with and without prior manual fine tuning of the primary composition result according to a mapped scale. Standard of reference was angle and distance determination at the phantom. RESULTS: On average, the difference between the observers' angle measurements and the standard of reference was 0.4 degrees for both images with and without prior manual correction. Regarding distance measurements, the average discrepancies to the standard were 0.2 cm (femur) and 0.1 cm (tibia) when analyzing images that had undergone manual fine tuning and 0.5 cm and 0.7 cm, respectively, for images without manual correction. CONCLUSIONS: The evaluated image fusion algorithm in conjunction with a 43-cm x 43-cm flat-panel detector is feasible regarding angle and distance measurements on long-leg images. In the case of inaccurate primary composition, results can be corrected easily by manual fine tuning.

Algorithms↗
PubMed1990

The efficiency of RNA 3'-end formation is determined by the distance between the cap site and the poly(A) site in spleen necrosis virus.

The efficiency of RNA 3'-end formation of spleen necrosis virus (SNV) is determined by the distance between the cap site and the poly(A) site. When the distance between the cap site and the poly(A) site was shorter than 500 bases, only 3-9% of the RNA was polyadenylated at the SNV poly(A) site. However, when the distance between the cap site and the poly(A) site was 1400 bases or more, 70% of the total RNA was polyadenylated at the SNV poly(A) site. In contrast, the poly(A) signal sequences of the thymidine kinase (tk) and SV40 late genes functioned at high efficiency, even with a distance between the cap site and the poly(A) site that was short enough to inactivate the SNV poly(A) signal. Therefore, this distance-dependent inactivation of RNA 3'-end formation is specific for SNV sequences and perhaps for related retroviruses. This finding explains the difference between the 5' and 3' poly(A) sites in many retrovirus RNAs.

Animals↗
PubMed2002

Evolving networks with distance preferences.

We study evolving networks where new nodes when attached to the network form links with other nodes of preferred distances. A particular case is where always the shortest distances are selected ("make friends with the friends of your present friends"). We present simulation results for network parameters like the first eigenvalue of the graph Laplacian (synchronizability), clustering coefficients, average distances, and degree distributions for different distance preferences and compare them with the parameter values for random and scale-free networks. We find that for the shortest distance rule we obtain a power-law degree distribution as in scale-free networks, while the other parameters are significantly different, especially the clustering coefficient.

Journal Article↗
PubMed2003

Compressions of electrorheological fluids under different initial gap distances.

Compressions of electrorheological (ER) fluids have been carried out under different initial gap distances and different applied voltages. The nominal yield stresses of the compressed ER fluid under different conditions, according to the mechanics of compressing continuous fluids considering the yield stress of the plastic fluid, have been calculated. Curves of nominal yield stress under different applied voltages at an initial gap distance of 4 mm overlapped well and were shown to be proportional to the square of the external electric field and agree well with the traditional description. With the decrease of the initial gap distance, the difference between the nominal yield stress curves increased. The gap distance effect on the compression of ER fluids could not be explained by the traditional description based on the Bingham model and the continuous media theory. An explanation based on the mechanics of particle chain is proposed to describe the gap distance effect on the compression of ER fluids.

Journal Article↗
PubMed1996

Molecular replacement with NMR models using distance-derived pseudo B factors.

The statistical significance of molecular-replacement solutions with models derived from NMR data is strongly enhanced if pseudo B factors that reflect expected atomic coordinate errors are introduced. These B factors are derived from atomic distances of an ensemble of NMR models and an averaged model. A recently determined X-ray structure of a Pleckstrin homology domain:ligand complex has been used as a test case for molecular replacement with NMR templates. The feasibility of the models for molecular replacement has been studied in two steps: (i) correctness of solutions, verified by correct rotational angles and translations; (ii) statistical significance (detection) of solutions, measured by R factors and correlation coefficients in the translation function. None of the models with uniform B factors were detectable in the translation function whereas two models with distance-derived B factors gave statistically significant R factors and correlation coefficients. The potential impact of distance-derived B factors on the detectability of molecular-replacement solutions was further tested by using B factors that were derived from spatial distances between each NMR model and the X-ray structure. It is concluded that the introduction of distance-derived B factors can be an essential component of many future molecular-replacement problems that use NMR models as templates.

Journal Article↗
PubMedDate not supplied

New bounds and tractable instances for the transposition distance.

The problem of sorting by transpositions asks for a sequence of adjacent interval exchanges that sorts a permutation and is of the shortest possible length. The distance of the permutation is defined as the length of such a sequence. Despite the apparently intuitive nature of this problem, introduced in 1995 by Bafna and Pevzner, the complexity of both finding an optimal sequence and computing the distance remains open today. In this paper, we establish connections between two different graph representations of permutations, which allows us to compute the distance of a few non-trivial classes of permutations in linear time and space, bypassing the use of any graph structure. By showing that every permutation can be obtained from one of these classes, we prove a new tight upper bound on the transposition distance. Finally, we give improved bounds on some other families of permutations and prove formulas for computing the exact distance of other classes of permutations, again in polynomial time.

Algorithms↗
PubMed2005

On the Euclidean distance of images.

We present a new Euclidean distance for images, which we call IMage Euclidean Distance (IMED). Unlike the traditional Euclidean distance, IMED takes into account the spatial relationships of pixels. Therefore, it is robust to small perturbation of images. We argue that IMED is the only intuitively reasonable Euclidean distance for images. IMED is then applied to image recognition. The key advantage of this distance measure is that it can be embedded in most image classification techniques such as SVM, LDA, and PCA. The embedding is rather efficient by involving a transformation referred to as Standardizing Transform (ST). We show that ST is a transform domain smoothing. Using the Face Recognition Technology (FERET) database and two state-of-the-art face identification algorithms, we demonstrate a consistent performance improvement of the algorithms embedded with the new metric over their original versions.

Algorithms↗
PubMed2005

Graph edit distance from spectral seriation.

This paper is concerned with computing graph edit distance. One of the criticisms that can be leveled at existing methods for computing graph edit distance is that they lack some of the formality and rigor of the computation of string edit distance. Hence, our aim is to convert graphs to string sequences so that string matching techniques can be used. To do this, we use a graph spectral seriation method to convert the adjacency matrix into a string or sequence order. We show how the serial ordering can be established using the leading eigenvector of the graph adjacency matrix. We pose the problem of graph-matching as a maximum a posteriori probability (MAP) alignment of the seriation sequences for pairs of graphs. This treatment leads to an expression in which the edit cost is the negative logarithm of the a posteriori sequence alignment probability. We compute the edit distance by finding the sequence of string edit operations which minimizes the cost of the path traversing the edit lattice. The edit costs are determined by the components of the leading eigenvectors of the adjacency matrix and by the edge densities of the graphs being matched. We demonstrate the utility of the edit distance on a number of graph clustering problems.

Algorithms↗
PubMed2006

From sample similarity to ensemble similarity: probabilistic distance measures in reproducing kernel Hilbert space.

This paper addresses the problem of characterizing ensemble similarity from sample similarity in a principled manner. Using reproducing kernel as a characterization of sample similarity, we suggest a probabilistic distance measure in the reproducing kernel Hilbert space (RKHS) as the ensemble similarity. Assuming normality in the RKHS, we derive analytic expressions for probabilistic distance measures that are commonly used in many applications, such as Chernoff distance (or the Bhattacharyya distance as its special case), Kullback-Leibler divergence, etc. Since the reproducing kernel implicitly embeds a nonlinear mapping, our approach presents a new way to study these distances whose feasibility and efficiency is demonstrated using experiments with synthetic and real examples. Further, we extend the ensemble similarity to the reproducing kernel for ensemble and study the ensemble similarity for more general data representations.

Algorithms↗
PubMed2005

MetricMap: an embedding technique for processing distance-based queries in metric spaces.

In this paper, we present an embedding technique, called MetricMap, which is capable of estimating distances in a pseudometric space. Given a database of objects and a distance function for the objects, which is a pseudometric, we map the objects to vectors in a pseudo-Euclidean space with a reasonably low dimension while preserving the distance between two objects approximately. Such an embedding technique can be used as an approximate oracle to process a broad class of distance-based queries. It is also adaptable to data mining applications such as data clustering and classification. We present the theory underlying MetricMap and conduct experiments to compare MetricMap with other methods including MVP-tree and M-tree in processing the distance-based queries. Experimental results on both protein and RNA data show the good performance and the superiority of MetricMap over the other methods.

Algorithms↗
PubMed2005

Solving minimum distance problems with convex or concave bodies using combinatorial global optimization algorithms.

Determining the minimum distance between convex objects is a problem that has been solved using many different approaches. On the other hand, computing the minimum distance between combinations of convex and concave objects is known to be a more complicated problem. Most methods propose to partition the concave object into convex subobjects and then solve the convex problem between all possible subobject combinations. This can add a large computational expense to the solution of the minimum distance problem. In this paper, an optimization-based approach is used to solve the concave problem without the need for partitioning concave objects into convex pieces. Since the optimization problem is no longer unimodal (i.e., has more than one local minimum point), global optimization techniques are used. Simulated Annealing (SA) and Genetic Algorithms (GAs) are used to solve the concave minimum distance problem. In order to reduce the computational expense, it is proposed to replace the objects' geometry by a set of points on the surface of each body. This reduces the problem to an unconstrained combinatorial optimization problem, where the combination of points (one on the surface of each body) that minimizes the distance will be the solution. Additionally, if the surface points are set as the nodes of a surface mesh, it is possible to accelerate the convergence of the global optimization algorithm by using a hill-climbing local optimization algorithm. Some examples using these novel approaches are presented.

Algorithms↗
PubMedDate not supplied

Distance preserving flattening of surface sections.

Curved cross-sections extracted from medical volume images are useful for analyzing nonplanar anatomic structures such as the aorta arch or the pelvis. For visualization and for performing distance measurements, extracted surface sections need to be adequately flattened. We present two different distance preserving surface flattening methods which preserve distances according to a user-specified center of interest and according to user-specified orientations. The first method flattens surface sections by preserving distances along surface curves located within planes having a user specified constant orientation. The second method flattens surfaces along curves located within radial planes crossing the center of interest. We study and compare the properties of the two flattening methods by analyzing their distortion maps. Thanks to a multiresolution approach, we provide surface flattening at interactive rates, allowing users to displace their focus point while visualizing the resulting flattened surface. These distance preserving flattening methods provide new means of inspecting curved cross-sections extracted from medical images.

Algorithms↗
PubMed2000

An interdomain distance in cardiac troponin C determined by fluorescence spectroscopy.

The distance between Ca2+-binding site III in the C-terminal domain and Cys35 in the N-terminal domain in cardiac muscle troponin C (cTnC) was determined with a single-tryptophan mutant using bound Tb3+ as the energy donor and iodoacetamidotetramethylrhodamine linked to the cysteine residue as energy acceptor. The luminescence of bound Tb3+ was generated through sensitization by the tryptophan located in the 12-residue binding loop of site III upon irradiation at 295 nm, and this sensitized luminescence was the donor signal transferred to the acceptor. In the absence of bound cation at site II, the mean interdomain distance was found to be 48-49 A regardless of whether the cTnC was unbound or bound to cardiac troponin I, or reconstituted into cardiac troponin. These results suggest that cTnC retains its overall length in the presence of bound target proteins. The distribution of the distances was wide (half-width >9 A) and suggests considerable interdomain flexibility in isolated cTnC, but the distributions became narrower for cTnC in the complexes with the other subunits. In the presence of bound cation at the regulatory site II, the interdomain distance was shortened by 6 A for cTnC, but without an effect on the half-width. The decrease in the mean distance was much smaller or negligible when cTnC was complexed with cTnI or cTnI and cTnT under the same conditions. Although free cTnC has considerable interdomain flexibility, this dynamics is slightly reduced in troponin. These results indicate that the transition from the relaxed state to an activated state in cardiac muscle is not accompanied by a gross alteration of the cTnC conformation in cardiac troponin.

Amino Acid Substitution↗