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At least 1,369 records · Page 76Linked to original sources
PubMed1994

Axon regeneration after decompression of the conus medullaris.

STUDY DESIGN: The effect of acute spinal stenosis (simulating fracture) and decompression of stenosis on axon regeneration was evaluated in an animal model. OBJECTIVES: Clinical function and quantitative histomorphometry were used to gain insight into the clinicopathologic effects of acute spinal stenosis and decompression. SUMMARY OF BACKGROUND DATA: Decompression of extrinsic compression after thoracolumbar fractures has been suggested to maximize recovery of neurologic function. Clinical studies seem to support this, but the histologic results of decompression are poorly understood. METHODS: Experimental spinal stenosis was created in 5 female beagle dogs, followed by decompression in three of the beagles at 6 weeks. Clinical function and histologic appearance were analyzed using a monoclonal antibody to neurofilaments. RESULTS: Stenosis consistently produced significant neurologic deficit and axon degeneration within motor roots distal to the stenosis. Decompression resulted in improved neurologic function and a tendency for the axons to return to normal number and volume based on quantitative histomorphometry. CONCLUSION: This study provides an animal model and functional and histologic data that support the use of decompression of acute spinal stenosis of 50% or more canal compromise at the level of the conus medullaris and a neurologic deficit. This may be seen clinically in thoracolumbar fractures.

Animals↗
PubMed2006

Compression of EMG signals with wavelet transform and artificial neural networks.

This paper presents a hybrid adaptive algorithm for the compression of surface electromyographic (S-EMG) signals recorded during isometric and/or isotonic contractions. This technique is useful for minimizing data storage and transmission requirements for applications where multiple channels with high bandwidth data are digitized, such as telemedicine applications. The compression algorithm proposed in this work uses a discrete wavelet transform for spectral decomposition and an intelligent dynamic bit allocation scheme implemented by an approach using the Kohonen layer, which improves the bit allocation for sections of the S-EMG with different characteristics. Finally, data and overhead information are packed by entropy coding. The results for the compression of isometric EMG signals showed that this algorithm has a better performance than standard wavelet compression algorithms presented in the literature (presenting a decrease of at least 5% in per cent residual difference (PRD) for the same compression ratio), and a performance that is comparable with the performance of algorithms based on an embedded zero-tree wavelet. For isotonic EMG signals, its performance is better than the performance of the algorithms based on embedded zero-tree wavelets (presenting a decrease in PRD of about 3.6% for the same compression ratios, in the useful compression range).

Algorithms↗
PubMed1994

MOUSE-III: learning rules of conformational analysis from X-ray data.

MOUSE-III is learning program that finds rules of conformational analysis from raw crystallographic data. The program perceives molecular features, finds conformational classes in the data and then learns rules that link features to classes. The rules that MOUSE learns are capable of correctly assigning conformations to ring systems that were not used for training with greater than 95% accuracy, when MOUSE was presented with sufficient data. The rules also show a compression of as much as 99% when compared to the raw data. This is accomplished through abstraction and generalization. The algorithm is presented along with a carefully worked example. An example of a learned rule is also presented and analyzed. Some conclusions about the scope and limitations of the learning process are presented.

Algorithms↗
PubMed1987

EEG data acquisition.

This paper is a compressed version of a tutorial which was presented during the 1986 training course of the International Pharmaco-EEG Group, in Santa Margherita Ligure, Italy. The paper starts with a discussion of some basic features of the encephalograph, sketches the frequency modulation recording technique and presents some fundamental rules and concepts concerning digital data acquisition. Patient safety is a further aspect of the tutorial. Finally, two calibration procedures are outlined.

Analog-Digital Conversion↗
PubMed2006

Lossless compression of color mosaic images.

Lossless compression of color mosaic images poses a unique and interesting problem of spectral decorrelation of spatially interleaved R, G, B samples. We investigate reversible lossless spectral-spatial transforms that can remove statistical redundancies in both spectral and spatial domains and discover that a particular wavelet decomposition scheme, called Mallat wavelet packet transform, is ideally suited to the task of decorrelating color mosaic data. We also propose a low-complexity adaptive context-based Golomb-Rice coding technique to compress the coefficients of Mallat wavelet packet transform. The lossless compression performance of the proposed method on color mosaic images is apparently the best so far among the existing lossless image codecs.

Algorithms↗
PubMed2004

Estimation of the minimum number of test specimens for fatigue testing of acrylic bone cement.

In the literature on fatigue testing of acrylic bone cements, data sets of various sizes have been used in different test series for the same cement formulation. There are two important consequences of this situation. First, it means that some test series last much longer than others, with all the implications for the cost of testing. Second, it makes drawing conclusions about the fatigue performance of a cement, based on the results of different literature series, a problematic issue. Clearly then, a recommendation as to what should be the minimum number of test specimens to use that would allow for confidence in the results of the statistical treatment of the test results (Gmin) would be desirable. In the present work, a method that could be used to culminate in such a recommendation is described. This method involves (i) obtaining experimental fatigue test results and (ii) analyzing those results using the Weibull probability distribution function and other statistical methods. This methodology is illustrated using fatigue life results obtained from uniaxial tension-compression fatigue tests on specimens fabricated from the polymerizing dough of one commercially available acrylic bone cement. For a tolerable error of 5%, we estimated Gmin to be either 7 (if the fatigue life results are treated using the two-parameter Weibull distribution function) or 11 (if the fatigue life results are treated using the three-parameter Weibull distribution function). To be on the conservative side, we therefore recommend that Gmin be 11. Three key limitations of the methodology presented here are discussed.

Cementation↗
PubMed1998

The spinal lax zone and neutral zone: measurement techniques and parameter comparisons.

The neutral zone (NZ) is a well-established parameter that describes the loose region of the spinal range of motion (ROM) where the spine moves easily with minimal applied force. The loose region is of interest clinically because in vitro studies show that with the onset of instability, this region increases before the ROM increases. The upper boundary of the NZ has been described as the displacement at which ligamentous resistance just begins. However, we hypothesized that a different parameter that we have named the lax zone (LZ) more accurately describes the region of ligamentous laxity. We hypothesized that the NZ is a smaller subset of the LZ that is governed by frictional properties at the joint. Methods for determining the spinal LZ experimentally are introduced. To demonstrate that the LZ is distinct from the NZ, both parameters were quantified in six normal cadaveric human C5-C6 specimens for three different preload magnitudes and three different preload directions. LZ variations with changing preload closely matched variations in the location of the load-deformation curve elbow, whereas NZ values followed specimen resting position instead, verifying parameter independence. Reproducibility and interspecimen variability values were approximately equivalent for both parameters. Compared in a separate data set, NZ and LZ were both more sensitive than ROM in response to cervical discectomy. With discectomy, the absolute change in LZ was larger and the percentage change in LZ was smaller than in NZ. The NZ may be a more appropriate measure when investigating the biomechanical effect of alterations to joint articulations and when the loading environment is well controlled. The LZ may be a more appropriate measure when investigating the effect of ligament/disc alterations and when the loading environment cannot be controlled. Future work is needed to compare the sensitivities of the LZ and NZ in detecting spinal instability onset for various injuries.

Cadaver↗
PubMed2006

Simultaneous quantification of carbamazepine crystal forms in ternary mixtures (I, III, and IV) by diffuse reflectance FTIR spectroscopy (DRIFTS) and multivariate calibration.

Diffuse reflectance FTIR spectroscopy (DRIFTS) coupled with modern multivariate calibration methods, namely artificial neural networks (ANNs) in two versions (ANN-raw and ANN-pca), support vector machines (SVMs), lazy learning (LL) and partial least squares (PLS) regression, is used in this study for the quantification of carbamazepine crystal forms in ternary powder mixtures (I, III, and IV). Two spectral regions (675-1180 and 3400-3600/cm) were selected and the data were partitioned into training and test subsets applying the Kennard-Stone design. It was found that all the selected algorithms perform better than the PLS regression (root mean squared error of prediction (RMSEP) from 3.0% to 8.2%). ANN-raw, trained on uncompressed spectral data, shows best predictive performance (RMSEP < 2.25%) but longest computation (up to 10 min). Principal component analysis (PCA) compression of the input spectral data accelerates significantly the computation (<16 s) at a relatively low cost in precision (RMSEP < 3.24%). The LL algorithm shows excellent performance in the 3400-3600/cm range (RMSEP < 1.6%), but in the 675-1180/cm range it shows strong dependence on data set structure (RMSEP between 1.6% and 8.9%). SVMs perform comparably well with ANNs (RMSEP < 3.1%), not showing the long computation time of ANNs (<1 s) and therefore may provide an attractive alternative to ANNs.

Algorithms↗
PubMed1998

An investigation of the influence of the core material properties on the compression and properties of dry-coated tablets.

The effect of core material properties on the process of compression and physical properties of compression-coated tablets were investigated using microcrystalline cellulose as the coating material (mantle). Three model core materials: borosilicate glass, silicone rubber, and steel, each of different Young's modulus, were selected to give a range of core mechanical properties. Coated tablets were prepared using a single-punch press, with facilities for monitoring the compression cycle and analysis of data using the Heckel (1) equation. This analysis showed a considerable effect of different core materials on the compression process, (i) as an unanchored core, and (ii) due to core material type with differing Young's modulus.

Cellulose↗
PubMed1979

Intonation and intelligibility of time-compressed speech. Supplementary report: English vs. French.

Comparative data are reported for the intelligibility of English and of French time-compressed speech when heard spoken either in normal intonation or in intonation patterns conflicting with underlying syntactic structure. Within an overall decrement in intelligibility with increasing compression, both French and English show similar superiority functions for sentences heard in normal intonation. Results suggest a role of prosodic features in perceptual processing of French comparable to that previously reported for English.

Adult↗
PubMed1998

Central nervous system metastases.

OBJECTIVES: To provide an overview and up-to-date information on the presentation and treatment of central nervous system (CNS) metastases, including brain metastases, spinal cord compression, and leptomeningeal metastases. DATA SOURCES: Published articles, research reports, and book chapters pertaining to CNS metastases. CONCLUSIONS: Most patients with CNS metastases have a limited life expectancy. Therapies are palliative, except in select patients who have improved chances for long-term control or occasional cures. In general, early detection and treatment of CNS metastases prevents devastating neurological disabilities. IMPLICATIONS FOR NURSING PRACTICE: Nurses across all health care settings can play an important role in early recognition of signs and symptoms of CNS metastases, and assist patients and families in preventing devastating neurological disabilities. Nurses are also frontline care providers for patients requiring various treatments and rehabilitation for metastatic CNS disease.

Brain Neoplasms↗
PubMed1997

Compression of nucleotide databases for fast searching.

MOTIVATION: International sequencing efforts are creating huge nucleotide databases, which are used in searching applications to locate sequences homologous to a query sequence. In such applications, it is desirable that databases are stored compactly, that sequences can be accessed independently of the order in which they were stored, and that data can be rapidly retrieved from secondary storage, since disk costs are often the bottleneck in searching. RESULTS: We present a purpose-built direct coding scheme for fast retrieval and compression of genomic nucleotide data. The scheme is lossless, readily integrated with sequence search tools, and does not require a model. Direct coding gives good compression and allows faster retrieval than with either uncompressed data or data compressed by other methods, thus yielding significant improvements in search times for high-speed homology search tools.

Algorithms↗
PubMed2000

Infection as a cause of spinal cord compression: a review of 36 spinal epidural abscess cases.

A retrospective survey of 36 cases treated in the Department of Neurosurgery, Hacettepe University Hospitals since 1970 was performed. Clinical presentation, aetiology and outcome of this rare disease compared to recently published series. All cases were admitted with signs of neural compression. Clinical and laboratory data suggesting an infectious origin were present only in 4 cases. Radiological investigation including magnetic resonance imaging in 10 patients, were not confirmative for an epidural abscess except for two cases. All cases underwent urgent surgical decompression and tuberculous abscess either in granulation or pus form was found in the majority. Overall mortality rate was 5.8%. Outcome was closely related to the neurological condition on admission rather than the underlying infectious origin. When compared with recently reported series, our cases demonstrated a significant divergence in terms of clinical presentation, pathogenesis and outcome. The most probable reason for this discrepancy is that risk factors for compromised immunity or systemic infection were much less than the other series and mycobacterium tuberculosis is the responsible agent in the majority which has a much more favourable outcome than non-spesific infections.

Adolescent↗
PubMed2000

Effects of backward bending on lumbar intervertebral discs. Relevance to physical therapy treatments for low back pain.

STUDY DESIGN: Mechanical testing of cadaveric motion segments. OBJECTIVES: To test the hypothesis that backward bending of the lumbar spine can reduce compressive stresses within lumbar intervertebral discs. SUMMARY OF BACKGROUND DATA: Lumbar extension affects the distribution of compressive stress inside normal cadaveric discs, but little is known about its effect on mechanically disrupted and degenerated discs. METHODS: Nineteen lumbar motion segments (mean donor age, 48 years) were subjected to complex mechanical loading to simulate the following postures: moderate lumbar flexion, 2 degrees of extension, 4 degrees of extension, and the neutral position (no bending). The distribution of compressive stress within the disc matrix was measured in each posture by pulling a miniature pressure transducer along the midsagittal diameter of the disc. Stress profiles were repeated after a mechanical treatment that was intended to simulate severe disc degeneration in vivo. RESULTS: The "degeneration" treatment reduced pressure in the nucleus pulposus and generated stress concentrations within the anulus, in a manner similar to that found in severely degenerated discs in vivo. When all discs were considered together, 2 degrees of extension increased the maximum compressive stress within the posterior anulus by an average of 16%, compared with the neutral posture. The size of localized stress peaks within the posterior anulus was increased by 43% (P = 0.02). In 4 degrees of extension, changes observed between 0 degree and 2 degrees were usually exaggerated. In contrast, moderate flexion tended to equalize the distribution of compressive stress. In 7 of the 19 discs, 2 degrees of lumbar extension decreased maximum compressive stress in the posterior anulus relative to the neutral posture by up to 40%. Linear regression showed that lumbar extension tended to reduce stresses in the posterior anulus in those discs that exhibited the lowest compressive stresses in the neutral posture (P = 0.003; R2 = 41%). CONCLUSIONS: The posterior anulus can be stress shielded by the neural arch in extended postures, but the effect is variable. This may explain why extension exercises can relieve low back pain in some patients.

Adult↗
PubMed2005

Method for determination of the mean fraction of glandular tissue in individual female breasts using mammography.

The nationwide breast cancer screening programme using mammography has been in full operation in the Netherlands since 1997. Quality control of the screening programme has been assigned to the National Expert and Training Centre for Breast Cancer Screening. Limits are set to the mean glandular dose and the centre monitors these for all facilities engaged in the screening programme. This procedure is restricted to the determination of the entrance dose on a 5 cm thick polymethylmethacrylate (PMMA) phantom. The mean glandular dose for a compressed breast is estimated from these data. Individual breasts may deviate largely from this 5 cm PMMA breast model. Not only may the compressed breast size vary from 2 to 10 cm, but breast composition varies also. The mean glandular dose is dependent on the fraction of glandular tissue (glandularity) of the breast. To estimate the risk related to individual mammograms requires the development of a method for determination of the glandularity of individual breasts. A method has been developed to derive the glandularity using the attenuation of mammography x-rays in the breast. The method was applied to a series of mammograms at a screening unit. The results, i.e., a glandularity of 93% within the range of 0 to 1, were comparable with data in the literature. The glandularity as a function of compressed breast thickness is similar to results from other investigators using differing methods.

Breast↗
PubMed1997

[Contractility of the striated urethral sphincter in dogs--an analysis with pressure-time curve and ATPase stain method].

PURPOSE: A comparative study about the contractility of the external urethral sphincter in the pelvic floor muscle (PFM) and about that of the periurethral striated sphincter (PUS), which is independent of PFM, was made by employing adult male mongrels. METHODS: This study was done by using the compression-time curve. Moreover, the study about the formation of muscle fibers was carried out by the aid of ATPase staining. RESULTS: Stimulus to one side of pudendal nerve increased each sphincter M-wave amplitudes and its compressive differences in contraction. Easy repetitions of the experiment made it possible to use the compression-time curve. The compressive differences in the urethral contraction was significantly greater in the urethra of PUS than in that of PFM. Data obtained from the compressive-time curve showed PUS premotor time was significantly longer than PFM in electromyograms, PUS motor time and time to peak force was significantly shorter, and PUS rate of force development was significantly faster. The histochemical study showed that fast muscles account for 70% in PUS, while they account for approximate 50% in PFM, which supported the results of the compression-time curve. CONCLUSION: The above suggested the contractility of PUS apparently differed from that of PFM; PUS contracts quickly, while PFM contracts slowly. Also, it seemed that forming conjectures with the compression-time curve on the formation of muscle fibers in the striated urethral sphincters were possible to some degree.

Adenosine Triphosphatases↗
PubMed2001

Local structure and local compressibilities around Co2+ impurity in ZnSiF6.6H2O crystal determined from electron paramagnetic resonance data.

The perturbation formulas of g-factors gparallel, gperpendicular and hyperfine structure constants Aparallel, Aperpendicular for 3d7 ion in trigonal octahedral crystal field are established on the basis of a cluster approach. These formulas consist of the contributions from configuration interaction and covalency effect and the parameters related to both effects can be estimated from the optical spectra and the structural data of the system under study. According to these formulas, the local trigonal distortion angle beta at pressure P = 0 and the local compressibilities d ln beta/dP in two pressure regions around Co2+ impurity in ZnSiF6.6H2O crystal are estimated by fitting the calculated electron paramagnetic resonance parameters gi, Ai and their pressure coefficients to the observed values. The results show that these local values are different from those of the host crystal because of the influence of impurity.

Cations, Divalent↗
PubMed2002

Ambulatory oxygen for chronic obstructive pulmonary disease.

BACKGROUND: Little is known about the effectiveness of ambulatory domicilary oxygen therapy. At present ambulatory oxygen in the UK is provided with small oxygen cylinders but in other countries such as the USA and Italy, liquid oxygen systems with higher oxygen carrying capacity are widely used. Both these systems are used without adequate evidence of their effectiveness. OBJECTIVES: To determine the effectiveness of long-term ambulatory domicilary oxygen therapy in patients with chronic obstructive pulmonary disease. SEARCH STRATEGY: The Cochrane Airways Group specialised trials register was searched. In addition, bibliographies of each trial retrieved were also searched for additional papers that may contain further studies. Authors of identified trials were contacted for other published and unpublished studies. SELECTION CRITERIA: Only randomised controlled trials in patients with chronic obstructive pulmonary disease were considered for inclusion. Trials must have randomised patients into long-term ambulatory oxygen therapy or placebo while at home. Ambulatory oxygen can be provided either through portable oxygen cylinders or with liquid oxygen canisters and the placebo group using compressed or liquid air. DATA COLLECTION AND ANALYSIS: Two reviewers assessed all potential trials independently. Data abstraction was completed by one reviewer and re-checked by the second reviewer. MAIN RESULTS: Only two studies met the inclusion criteria. These provided data on 70 patients. Statistically significant effects of oxygen were found in only one of the studies, a crossover trial involving 9 patients with severe hypoxia at rest. This study reported a reduction in minute ventilation at maximal exercise (WMD -11.00 L/min; 95%CI -17.53, -4.47L/min) and an increase in PaO2 at rest (WMD 17.00 mmHg; 95%CI 9.13,24.87 L/min) with oxygen therapy when compared to placebo. The other study recruited patients who did not have resting hypoxaemia. REVIEWER'S CONCLUSIONS: Evidence available to date does not allow any firm conclusions to be drawn concerning the effectiveness of ambulatory domicilary oxygen therapy in patients with COPD. Further studies are required in order to understand the role of ambulatory oxygen in the management of patients with COPD on long-term oxygen therapy. These studies should separate patients who desaturate from those who do not desaturate.

Ambulatory Care↗