Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Data Compression”

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 1,657 records · Page 92Linked to original sources
PubMedDate not supplied

Ultrasonography in the diagnosis of appendicitis: evaluation by meta-analysis.

OBJECTIVE: We wanted to review the usefulness of ultrasonography (US) for the diagnosis of appendicitis and to evaluate the diagnostic accuracy of US according to patients' and researchers' characteristics. MATERIALS AND METHODS: The relevant Korean articles published between 1985 and 2003 were included in this study if the patients had clinical symptoms of acute appendicitis. The histopathologic findings were the reference standard and the data were presented for 2 x 2 tables. Articles were excluded if patients had no sonographic signs of appendicitis according to graded-compression US. Two reviewers independently extracted the data on study characteristics. The Hasselblad method was used to obtain the combined estimates of sensitivity and specificity for the performance of US. RESULTS: Twenty-two articles (2,643 patients) fulfilled all inclusion criteria. The estimate of d calculated by combining the sensitivity and specificity was 2.0054 (95% confidence interval [CI]: 1.8553, 2.1554) by a random effects model. The overall sensitivity and specificity (95% CI) were 86.7% (85.4 to 88.0), and 90.0% (88.9 to 91.2), respectively. According to the subgroup meta-analysis by patients' characteristics, the d estimate (95% CI) of dominantly younger age, male, and highly clinical suggestive group for US was 2.2388 (1.8758 to 2.6019), 2.7131 (2.2493 to 3.1770), and 2.4582 (1.7387 to 3.1777), respectively. Also, according to subgroup meta-analysis by researchers' characteristics, the d value (95% CI) for US done by diagnostic radiologists and gray-scale was 2.0195 (1.7942 to 2.2447) and 2.2630 (1.8444 to 2.6815). CONCLUSION: This evidence suggests that US may be useful for the diagnosis of acute appendicitis, especially when patients are younger age, male, and highly clinical suggestive.

Acute Disease↗
PubMed1999

Pressor response to compression of the ventrolateral medulla mediated by glutamate receptors.

The rostral ventrolateral medulla (RVLM) is considered a major center for the regulation of sympathetic and cardiovascular activities. Several clinical studies have indicated a possible causal relationship between neurovascular contact of the left RVLM and essential hypertension, and some investigators have suggested that the left RVLM is more sensitive to pulsatile compression than the right RVLM. Previously, we reported that pulsatile compression of the RVLM elevates arterial pressure by enhancing sympathetic outflow in rats; however, we have not investigated the laterality of the responses to the compression. In addition, it remains to be elucidated whether RVLM neurons are activated by compression and, if so, how they are activated. Therefore, we performed compression experiments in rats to investigate these issues. Pulsatile compression was performed on the unilateral RVLM with a pulsating probe in anesthetized and artificially ventilated rats. Pulsatile compression of the unilateral RVLM increased arterial pressure, heart rate, and sympathetic nerve activity. The pressor response to compression was inhibited significantly after local microinjection of glutamate receptor antagonists. Pulsatile compression of the RVLM increased Fos immunoreactivitiy, a marker of neuronal activation, within the nuclei of postsynaptic RVLM neurons. All results were observed symmetrically. The data indicate that the responses to pulsatile compression of the unilateral RVLM are similar on both sides. They also suggest that pulsatile compression of the RVLM increases sympathetic and cardiovascular activities by activating postsynaptic RVLM neurons through the stimulation of the local glutamate receptors in rats.

Animals↗
PubMed2003

The 3-D model: comparison of parameters obtained from and by simulating different tableting machines.

The aim of this study is to apply 3-D modeling to data obtained from different tableting machines and for different compression wheels on a linear rotary tableting machine replicator. A new analysis technique to interpret these data by 3-D parameter plots is presented. Tablets were produced on an instrumented eccentric tableting machine and on a linear rotary tableting machine replicator. The materials used were dicalcium phosphate dihydrate (DCPD), spray-dried lactose, microcrystalline cellulose (MCC), hydroxypropyl methylcellulose (HPMC), and theophylline monohydrate. Tableting was performed to different maximum relative densities (rho (rel, max)). Force, time, and displacement were recorded during compaction. The 3-D data plots were prepared using pressure, normalized time, and porosity according to Heckel. A twisted plane was fitted to these data according to the 3-D modeling technique. The resulting parameters were analyzed in a 3-D parameter plot. The results show that the 3-D modeling technique can be applied to compaction cycles from different tableting machines as different as eccentric and rotary tableting machines (simulated). The relation of the data to each other is the same even when the absolute values are different. This is also true for different compression wheels used on the linear rotary tableting machine replicator. By using compression wheels of different sizes on this simulator, mainly time plasticity changes. By using bigger compression wheels for simulation, the materials deform slower at lower densification and they deform faster at higher densification. For brittle materials, the stages of higher densification are influenced; for plastically deforming materials, the stages of lower and higher densification can be influenced.

Computer Simulation↗
PubMed2001

Interobserver and intraobserver reliability of the japanese orthopaedic association scoring system for evaluation of cervical compression myelopathy.

STUDY DESIGN: The inter- and intraobserver reliabilities of an assessment scale for cervical compression myelopathy were examined statistically. This scoring system consists of seven categories: motor function of fingers, shoulder and elbow, and lower extremity; sensory function of upper extremity, trunk and lower extremity; and function of the bladder. It evaluates the severity of myelopathy by allocating points based on degree of dysfunction in each category. OBJECTIVES: To determine the inter- and intraobserver reliabilities of the revised scoring system (17 - 2 points) for cervical compression myelopathy proposed by the Japanese Orthopedic Association. SUMMARY OF BACKGROUND DATA: Several scales to assess clinical outcome from treatment of cervical compression myelopathy have been proposed. Most of these scales include items evaluated by observers. However, no system, including the Japanese Orthopedic Association scoring system, has yet been validated in terms of interobserver reliability. METHODS: From five different university hospitals, 10 spine surgery specialists, 10 orthopedic surgeons who had just passed the board examination of the Japanese Orthopedic Association, and 13 residents in the first or second year of orthopedic residency programs were chosen. The participants in this study were 29 patients with myelopathy secondary to ossification of the posterior longitudinal ligament selected from five participating university hospitals. Several surgeons interviewed each patient twice at intervals of 1 to 6 weeks. Inter- and intraobserver reliabilities of the total score for all categories were evaluated by the intraclass correlation coefficient. The extension of the kappa coefficient of Kraemer also was calculated for each category to assess reliability of multivariate categorical data. RESULTS: The interobserver reliability of the total score for the first interview (intraclass correlation coefficient = 0.813) and the intra- and interobserver reliabilities of the total score (intraclass correlation coefficient = 0.826) were high. The level of experience and the hospital slightly affected the reliability of the Japanese Orthopedic Association scoring system. The kappa values for intraobserver data generally were high in each category, whereas the kappa values for interobserver data were relatively low for the categories of shoulder-elbow motor function and lower extremity sensory function. CONCLUSIONS: The inter- and intraobserver reliabilities of the Japanese Orthopedic Association scoring system for cervical myelopathy were high, suggesting that this system is useful for assessment of cervical myelopathy in comparative studies of treatment.

Activities of Daily Living↗
PubMed1996

Impact of information compression on intellectual activities in the brain.

Imaging and modeling represent an action of information compression, which is inevitable for a complex system in order to process and communicate data. Humans are such complex systems. Sensational and body reaction information is processed by the brain, the overall information rate being 10(11)-10(12) bit/s. Consciousness is the result of massive information compression, the attentional data rate being 10-14 bit/s. The primary purpose of the conscious state is to control the interaction with the environment. In humans, this ability facilitates the projection of the future horizon far away from the next instant. Thinking and reasoning can be thought of as a process of retrospective control. Retrospective in the sense that the sub-conscious has already decided what is to come next. In the long run, however, conscious thought influences the cortical context potentiation, thus providing steering to the associative process. The paper emphasizes that all cognitive operations are restricted to the bioelectrical signal processing of the brain. Accordingly, mental models and scientific theories will always be constrained by this fact. The last subject of this paper deals with the interaction between the brain, the glands and the rest of the body. It is interpreted that qualia are the result of a complex feedback interaction between those parts, a self-supported process close to a singularity point.

Brain↗
PubMed1976

Partial specific volume, expansibility, compressibility, and heat capacity of aqueous lysozyme solutions.

Density measurements have been made on aqueous lysozyme solutions at 20, 25, and 30 degrees. The apparent specific volumes, phi v, and expansibilities, phi e, have been determined from the density measurements and fitted to a function of concentration (weight per cent). Sound velocities and heat capacities have also been measured for various concentrations of lysozyme-water solutions at 25 degrees. From the density, expansibility, heat capacity, and sound velocity data at 25 degrees, the isothermal compressibility, phi k, for the lysozyme solutions have been calculated over a range of concentrations. All the physicochemical properties measured were found to be a linear function of the weight per cent of lysozyme. The number of water molecules hydrated to 1 mol of lysozyme was estimated from the volume and compressibility and found to be 162 at 25 degrees.

Mathematics↗
PubMed1995

Effects of selected thermal variables on the mechanical properties of trabecular bone.

Osteoarticular allografts are commonly used in the treatment of segmental bone loss due to a wide resection of tumour. While the use of such grafts has met with considerable clinical success, fractures are a recognized complication of allograft use. Although trabecular bone can play an important structural role in the function of segmental allografts, few data exist on the effects of common storage and sterilization procedures on the mechanical properties of trabecular bone. To this end, we investigated with these experiments the effects of freezing at -20 degrees C, freezing at -70 degrees C, eight freeze-thaw cycles at -20 degrees C, freeze-drying, boiling and autoclaving on the compressive modulus and strength of bovine trabecular bone. Of these treatments, boiling and autoclaving were the only treatments to alter the properties of bovine trabecular bone, resulting in 26 and 58% reductions in strength, respectively. Autoclaving also significantly reduced the compressive modulus by 59%. From these data, freezing at temperatures between -20 and -70 degrees C does not appear to compromise the structural integrity of trabecular bone.

Animals↗
PubMed2002

Shock compression of deuterium near 100 GPa pressures.

The shock-compression curve (Hugoniot) of D2 near 100 GPa pressures (1 Mbar) has been contro-versial because the two published measurements have limiting compressions of fourfold and sixfold. Our purpose is to examine published experimental results to decide which, if either, is probably correct. The published Hugoniot data of low-Z diatomic molecules have a universal behavior. The deuterium data of Knudson et al. (fourfold limiting compression) have this universal behavior, which suggests that Knudson et al. are correct and shows that deuterium behaves as other low-Z elements at high tem-peratures. In D2, H2, N2, CO, and O2, dissociation completes and average kinetic energy dominates average potential energy above approximately 60 GPa. Below approximately 30 GPa, D2, H2, N2, CO, and O2 are diatomic. D2 dissociation is accompanied by a temperature-driven nonmetal-metal transition at approximately 50 GPa.

Journal Article↗
PubMed2000

Extracranial vertebral artery dissection causing cervical root lesion.

The authors report an unusual manifestation of extracranial vertebral artery dissection (VAD), presenting with a predominantly motor radicular manifestation. Cervical magnetic resonance imaging (MRI) revealed the intramural hematoma in the dissected vessel wall, compressing mainly the segmental motor root and, to a lesser degree, the sensory ganglion. In the digital subtraction angiography (DSA), a circumscribed narrowing of the incriminated vessel was demonstrated. Color-coded Duplex imaging (CDDI) revealed complete recanalization after a few days of anticoagulation treatment. Complete neurologic recovery was seen after 3 months. Considering the MRI data, the likely pathogenetic mechanism was compression of the nerve root by the intramural hematoma. The synopsis with similar cases in the literature points to the characteristic features, i.e., the association of neck pain with radicular motor deficit and the absence of degenerative disk disease. The respective syndrome should raise the suspicion of vertebral artery dissection, especially in young individuals.

Adult↗
PubMed1999

Application of near-infrared spectroscopy in the pharmaceutical solid dosage form.

Near-infrared (NIR) spectroscopy, one of the most rapidly growing methodologies in pharmaceutical analysis, has been used to analyze the pharmaceutical solid dosage form. The objective of this study was to examine the information that can be gathered from NIR spectroscopy and demonstrate the potential utility of the technique as an alternative to current methods of tablet performance testing. The tablet formulation included active drug (acetaminophen or theophylline), binder (hydroxyethylcellulose), filler (lactose, calcium sulfate, dibasic calcium phosphate dihydrate, or microcrystalline cellulose), and lubricant (magnesium stearate). The compression forces were varied from 5 to 25 kN. A Foss/NIRSystems scanning near-infrared spectrometer was used to measure the diffuse reflectance from the tablet surface. Each tablet was scanned on opposite sides to reduce the effects of positioning. First derivative and multiplicative scatter correction data treatments were explored. A calibration for compression force, independent of the filler, was developed. In addition, the spectra were able to distinguish among the fillers used. A comparison of these spectra with data collected earlier suggests that the technique could differentiate among drugs as well. Near-infrared diffuse reflection spectroscopy, when properly calibrated, can determine the compression force used to prepare a tablet. This measurement may be independent of the different active drugs or fillers used in the tablet formulations.

Spectroscopy, Near-Infrared↗
PubMed2005

Influence of the pressure on the properties of chromatographic columns .III. retention volume of thiourea, hold-up volume, and compressibility of the C18-bonded layer.

The influence of the average column pressure (ACP) on the elution volume of thiourea was measured on two RPLC columns, packed with Resolve-C18 (surface coverage 2.45 micromol/m2) and Symmetry-C18 (surface coverage 3.18 micromol/m2), and it was compared to that measured under the same conditions on an underivatized silica (Resolve). Five different methanol-water mixtures (20, 40, 60, 80 and 100% methanol, v/v) were used. Once corrected for the compressibility of the mobile phase, the data show that the elution volume of thiourea increases between 3 and 7% on the C18-bonded columns when the ACP increases from 50 to 350 bar, depending on the methanol content of the eluent. No such increase is observed on the underivatized Resolve silica column. This increase is too large to be ascribed to the compressibility of the stationary phase (silica + C18 bonded chains) which accounts for less than 5% of the variation of the retention factor. It is shown that the reason for this effect is of thermodynamic origin, the difference between the partial molar volume of the solute in the stationary and the mobile phase, Delta V, controlling the retention volume of thiourea. While Delta V is nearly constant for all mobile phase compositions on Resolve silica (with Delta V approximately equal to -4 mL/mol), on RPLC phases, it significantly increases with increasing methanol content, particularly above 60% methanol. It varies between -5 mL/mol and -17 mL/mol on Resolve-C18 and between -9 mL/mol and -25 mL/mol on Symmetry-C18. The difference in surface coverage between these two RP-HPLC stationary phases increases the values of Delta V by about 5 mL/mol.

Chromatography, Liquid↗
PubMed2002

Indirect digital images: limit of image compression for diagnosis in endodontics.

AIM: To analyse the impact of the loss of information that results from the compression of a file containing a radiographic image. METHODOLOGY: Fourteen intraoral radiographs were digitized employing an AGFA ARCUS II scanner at an optical resolution of 300 ppi and with a grey scale of 8 bytes. The images were stored in Tagged Image File Format (TIFF). The files were compressed with no information loss with the WinZip 8.0 program. Compression with information loss was performed using the Photoshop 5.0 program (Adobe Systems Inc., San José, CA. USA) and the Joint Photograph Expert (Group (JPEG) format. Each of the images was compressed to one of the 11 qualities available (10-0). An expert performed the qualitative analysis. The quantitative analysis involved digital subtraction with each of the JPEG images to yield a new image using Photoshop 5.). The histograms of grey values were submitted to statistical analysis. The mean and standard deviation were calculated for each image. RESULTS: The data revealed that a JPEG lossy compression, six times smaller than the original TIFF, is compatible with diagnostic applications. CONCLUSIONS: The compression ratio calculated as the quotient between the file sizes and the standard deviation of the values corresponding to the image that resulted from digital subtraction may be employed to assess the outcome of the compression process and guarantee adequate quality.

Artifacts↗
PubMed1991

Compressive neuropathy of spinal nerve roots. A mechanical or biological problem?

Pathophysiologically, nerve root pain production is a complex issue. For many years, mechanical compression has been regarded as the sole cause for such pain. There are indications, however, that other factors, such as intraneural inflammation, may be of importance in this context. In this article, four cases are presented in which nerve root related pain gradually resolved without any proven change in the mechanical deformation of the involved nerve root. The data presented here suggest that mechanical compression, per se, may not always be the sole cause of radicular pain and dysfunction. These findings suggest that improvement is needed in our understanding of the pathophysiology of nerve root compression and inflammation.

Adult↗
PubMed1995

Comparing recognition of distorted speech using an equivalent signal-to-noise ratio index.

An index of equivalent performance in noise was developed to compare recognition in different forms of speech distortion. Speech-recognition performance of young and elderly listeners with and without hearing loss was evaluated for undistorted speech presented in quiet and noise, and for speech distorted by four time-compression ratios and by four reverberation times. The data obtained in noise on young subjects with normal hearing served to generate a normalized regression equation, which was used to convert percent-correct performance in different distortion conditions to equivalent performance for undistorted speech at a particular S/N ratio. Comparisons of the equivalent S/N ratios obtained in the various conditions allowed rank-ordering of speech recognition performance in different types of degradation. The data also show that age and hearing loss affect recognition of speech degraded by reverberation or time compression. However, age effects are evident primarily in the most severe distortion conditions. Recognition of undistorted speech in noise was affected by hearing loss but not by age. These findings support a hypothesis that stipulates that increased age produces a reduction in the functional S/N ratio.

Adolescent↗
PubMed1987

[Serum thiopental values, spontaneous frontal muscle electromyography activity and compressed EEG amplitudes and frequency values in thiopental infusion anesthesia].

Serum thiopentone (S-Thiop) was estimated every 10 minutes using a new high performance liquid chromatographic method during fentanyl-bolus-complemented (0.01 mg) thiopentone infusion anaesthesia (bolus of 5 mg/kg, infusion dosis 23.7 mg/min) for laryngo-microscopic procedures. Before stopping the infusion after 18/17 min (SD 8/5) (male/female) S-Thiop was (mean (SD) range) 16.0/12.4 (4.6/5.7) 5.9-26.8/5.1-26.6 mg/l; after stop of the infusion 12.8/10.5 (4.5/5.3) 7.6-25.5/4.5-23.4 mg/l. Patients reacted to verbal command after 11.5 (10.3) 11-81 min. There were no clinically relevant correlations between S-Thiop and frontal EMG and compressed 1-channel-EEG (ABM, Datex, Helsinki), nor with data recorded during recovery. Reasons may be: the total depolarisation block caused by succinylcholine; the method of compressing the EEG; subjective influences on the recording of recovery data; sampling in intervals of 10 min instead of at certain points of the anaesthesia course. We still recommend this total i.v.-anaesthesia for the short time endolaryngeal procedures need; before using this method for longer periods additional pharmacokinetic studies should be performed.

Adult↗
PubMed1993

An EMG-assisted model of loads on the lumbar spine during asymmetric trunk extensions.

An EMG-assisted, low-back, lifting model is presented which simulates spinal loading as a function of dynamic, asymmetric, lifting exertions. The purpose of this study has been to develop a model which overcomes the limitations of previous models including static or isokinetic mechanics, inaccurate predictions of muscle coactivity, static interpretation of myoelectric activity, and physiologically unrealistic or variable muscle force per unit area. The present model predicts individual muscle forces from processed EMG data, normalized as a function of trunk angle and asymmetry, and modified to account for muscle length and velocity artifacts. The normalized EMGs are combined with muscle cross-sectional area and intrinsic strength capacity as determined on a per subject basis, to represent tensile force amplitudes. Dynamic internal and external force vectors are employed to predict trunk moments, spinal compression, lateral and anterior shear forces. Data from 20 subjects performing a total of 2160 exertions showed good agreement between predicted and measured values under all trunk angle, asymmetry, velocity, and acceleration conditions. The design represents a significant step toward accurate, fully dynamic modeling of the low-back in multiple dimensions. The benefits of such a model are the insights provided into the effects of motion induced, muscle co-activity on spinal loading in multiple dimensions.

Adult↗
PubMedDate not supplied

[Lhermitte's sign in three oncological patients].

INTRODUCTION: Lhermitte's sign was first described by Pierre Marie and Chatelin in 1917. Lhermitte published his report in 1920 and reviewed this in 1924. This phenomenon is characterized by the occurrence of an electric shock-like sensation going along the spine in a cervico-caudal direction with flexion of the neck, and may also be felt in the upper and lower limbs. Clinical cases. Case 1. A 49 year-old woman diagnosed as having breast cancer and being treated with cisplatin presented with Lhermitte's sign. On physical examination the osteotendinous reflexes were absent but the abdominal cutaneous reflexes were present. There was reduced sensitivity to vibration. Case 2. An 80 year-old man, previously operated on for adenocarcinoma of the colon, without further treatment, presented with progressive weakness of all four limbs and Lhermitte's syndrome. On examination there was obvious weakness of all four limbs, with the sensory level at C3. A cervical MR scan showed a metastasis in the vertebral body of C3 with epidural involvement and compression of the spinal cord. Case 3. A 54 year-old man was being treated by radiotherapy for cancer of the larynx. He presented at the onset of Lhermitte's sign but MR and physical examination were normal. CONCLUSION: Lhermitte's sign is non-specific, although in oncological patients a detailed clinical history and examination should be done seeking data regarding chemotherapy, radiotherapy and spinal compression.

Aged↗
PubMed1999

Sciatica caused by cervical and thoracic spinal cord compression.

STUDY DESIGN: Two case reports of sciatica that was considered to be caused by cervical and thoracic spinal cord compression. OBJECTIVES: To point out that sciatica can be an initial major symptom in patients with cervical or thoracic spinal cord lesions. SUMMARY OF BACKGROUND DATA: Usually, tract pain caused by cord compression is considered to be diffuse and does not resemble sciatica. METHODS: Medical history, physical findings, and the results of imaging studies were reviewed in one case of cervical cord tumor and one case of thoracic kyphosis. RESULTS: In both cases, sciatica was the initial and major symptom. Imaging studies showed no lesion in the lumbar spine. In one patient, a cervical dumbbell tumor was found to compress the cervical cord, and in the other the spinal cord was severely compressed at the thoracic kyphosis. The sciatica disappeared immediately after decompression surgery in both cases. CONCLUSIONS: Leg pain resembling sciatica can be caused by cord compression at the cervical and thoracic level. Thoracic kyphosis may be a causative factor in sciatica, in addition to spinal cord tumor and disc herniation, which have been reported previously.

Adult↗