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 1,387 records · Page 77Linked to original sources
PubMed2003

Identification of PINCH in Schwann cells and DRG neurons: shuttling and signaling after nerve injury.

Particularly interesting new cysteine-histidine rich protein (PINCH) is a double zinc finger domain (LIM)-only adapter protein that functions to recruit the integrin-linked kinase (ILK) to sites of integrin activation. Genetic studies have shown that PINCH and ILK are required for integrin signaling. Since integrin activation is associated with Schwann cell migration, neurite outgrowth and regeneration, this study examined PINCH in the normal peripheral nervous system and after chronic constriction injury (CCI) in adult Sprague-Dawley rats. Immunohistochemistry identified PINCH immunoreactivity in cell bodies of dorsal root ganglia (DRG) neurons, axons, satellite cells, and Schwann cells. PINCH immunostaining was localized to the membrane of uninjured DRG cell bodies consistent with its localization at a site of integrin activation. In contrast, 5 days following CCI, PINCH immunostaining was diffuse throughout the DRG cell cytoplasm. Confocal microscopy of primary and transformed Schwann cells localized PINCH in cytoplasmic, perinuclear and nuclear areas. Examination of the PINCH sequence revealed a putative leucine-rich nuclear export signal (NES) and an overlapping basic nuclear localization signal (NLS). To demonstrate nuclear export of PINCH, rabbit anti-PINCH IgG was microinjected into Schwann cell nuclei and allowed to combine with PINCH contained within the nucleus. Immunofluorescence showed that the PINCH and anti-PINCH IgG complex rapidly translocated to the cytoplasm. Treatment with leptomycin B caused nuclear accumulation of PINCH, indicating that the CRM1 pathway mediates nuclear export of PINCH. ILK activity in Schwann cells was enhanced by platelet-derived growth factor (PDGF) and tumor necrosis factor alpha. PINCH immunoprecipitates from PDGF- and TNFalpha-stimulated Schwann cells contained several high-molecular-weight threonine-phosphorylated proteins. Taken together, these results indicate that PINCH is an abundant shuttling/signaling protein in Schwann cells and DRG neurons.

Active Transport, Cell Nucleus↗
PubMed1994

Intravascular stents for management of pulmonary artery and right ventricular outflow obstruction.

This study was performed to determine the efficacy of balloon-expandable stents in the treatment of branch pulmonary artery-stenoses and conduit stenosis in children. A total of eight stainless steel stents were implanted in seven patients. Three patients had tetralogy of Fallot with pulmonary artery stenosis following total correction, one patient had conduit stenosis following correction of transposition of the great arteries, one patient had intra-cardiac conduit stenosis after septation for single left ventricle, and two patients had pulmonary artery stenosis after Fontan operation. Six stents were placed in the branch pulmonary arteries, one in the extracardiac conduit, and one in the intracardiac conduit. The mean age at implantation was 13 +/- 3 years and the mean weight 37 +/- 12 kg. Follow-up time ranged from 0.3-2 years. The diameter of pulmonary arteries with stenoses increased from 5.6 +/- 2.2 mm to 10.6 +/- 1.8 mm (n = 7). The systolic pressure gradient decreased from 56 +/- 26 mmHg to 22 +/- 16 mmHg (n = 5). No embolization or thrombotic event has been noted. One stent placed in the intracardiac conduit was compressed and fractured. These data indicate that balloon-expandable stents are useful in the treatment of pulmonary artery branch stenoses and extracardiac conduit stenosis in children. The use of stents for intracardiac stenosis may result in stent fracture.

Adolescent↗
PubMed1984

Effect of excitatory amino acid antagonists on the high pressure neurological syndrome in rats.

The onset pressures for the tremor, myoclonus and convulsions seen in the high pressure neurological syndrome (HPNS) are increased following cis-2,3-piperidine dicarboxylic acid 1 mmol/kg in the rat. Glutamic acid diethyl ester 1-3 mmol/kg has no effect on tremor or myoclonus, but increases the convulsion pressure when 3 mmol/kg is given immediately before compression. These and earlier data with 2-amino-7-phosphonoheptanoic acid suggest that excitation at the N-methyl-D-aspartate receptor is important in HPNS tremor, and that excitation at the quisqualate receptor contributes to HPNS convulsions.

Animals↗
PubMed1991

Strength of phosphate-bonded investments at high temperature.

There has been little reported on the strength of phosphate-bonded investments, and in particular the role of 'special liquids' in this context is poorly understood. Using a novel test design, sequential testing of an investment diaphragm using a variable casting metal mass, a measure of the effect of 'special liquid' on strength under actual casting conditions has been obtained. The use of special liquid was found to increase substantially the strength of the four products tested. This test may provide more useful data than the conventional compressive strength test, which may give misleading information, especially if performed at room temperature.

Dental Bonding↗
PubMed1986

Visco-elastic properties of dental elastomeric impression materials.

The visco-elastic properties of a number of set elastomeric impression materials were determined using a torsional pendulum apparatus, i.e. the real (G1) and imaginary (G2) parts of the complex shear modulus and the mechanical loss tangent (Tan delta). Comparison with published data on tension and compression set for these materials showed that whilst there was no correlation between Tan delta and tension set, there was significant (greater than 99%) correlation with compression set. Treating a permanent set test as the application of a rectangular stress pulse of duration tau, and assuming (i) linear visco-elasticity theory and (ii) that G1 and G2 are independent of frequency. Fourier integral analysis predicts that Tan delta should be proportional to permanent set. Tension set does not conform to this prediction because the deformation is nonlinear. The compression set test is shown to involve shear strains and elastomers generally are Hookean in shear. Whilst the theoretical treatment applies qualitatively, there are major quantitative disparities, the reasons for which are discussed.

Dental Impression Materials↗
PubMed1993

A hydromechanical model of the cochlea with nonlinear feedback using PVF2 bending transducers.

A single-channel hydromechanical model of the human cochlea with nonlinear feedback on the membrane is introduced. The piezoelectric transducers for displacement measurement and force exertion on the membrane are constructed of PVF2 in the bimorph bending type. The passive response shows high-frequency slopes of about 60 dB/oct and a shortest wavelength of about 17 mm corresponding to 0.9 Bark in the human cochlea. High-frequency slopes and Q10 dB with one feedback loop are within the range of animal data, where as dynamic compression does not exceed 20 dB. Input impedance and phase response are in good agreement with nature, which is ascribed to longitudinal stiffness of the membrane.

Acoustic Stimulation↗
PubMed2005

Deformation, yielding, fracture and fatigue behavior of conventional and highly cross-linked ultra high molecular weight polyethylene.

Medical grade ultra high molecular weight polyethylene (UHMWPE) has been used as the bearing surface of total joint replacements for over four decades. These polymeric devices are susceptible to accumulated cyclic damage in vivo. Wear debris formation that ultimately leads to a need for revision surgery is linked to the plasticity, fatigue and fracture mechanisms of UHMWPE. This paper examines the deformation, yielding, fracture and fatigue behavior of conventional and highly cross-linked medical grade UHMWPE. Such properties play an important role in determining the long-term success of orthopedic devices. The mechanical properties discussed include the deformation behavior of UHMWPE, the yielding associated with quasi-static tension and compression, fracture toughness, cyclic loading, and fatigue resistance.

Biocompatible Materials↗
PubMed2004

Robust denoising of electrophoresis and mass spectrometry signals with minimum description length principle.

The need for high-throughput assays in molecular biology places increasing requirements on the applied signal processing and modelling methods. In order to be able to extract useful information from the measurements, the removal of undesirable signal characteristics such as random noise is required. This can be done in a quite elegant and efficient way by the minimum description length (MDL) principle, which treats and separates 'noise' from the useful information as that part in the data that cannot be compressed. In its current form the MDL denoising method assumes the Gaussian noise model but does not require any ad hoc parameter settings. It provides a basis for high-speed automated processing systems without requiring continual user interventions to validate the results as in the conventional signal processing methods. Our analysis of the denoising problem in mass spectrometry, capillary electrophoresis genotyping, and sequencing signals suggests that the MDL denoising method produces robust and intuitively appealing results sometimes even in situations where competing approaches perform poorly.

Algorithms↗
PubMed2003

Combined effects of dynamic tissue shear deformation and insulin-like growth factor I on chondrocyte biosynthesis in cartilage explants.

Biophysical forces and biochemical factors play crucial roles in the maintenance of the integrity of articular cartilage. In this study, we explored the effect of dynamic tissue shear deformation and insulin-like growth factor I (IGF-I) on matrix synthesis by chondrocytes within native cartilage explants. Dynamic tissue shear in the range of 0.5-6% strain amplitude at 0.1 Hz was applied to cartilage explants cultured in serum-free medium. Dynamic tissue shear above 1.5% strain amplitude significantly stimulated protein and proteoglycan synthesis, by maximum values of 35 and 25%, respectively, over statically held control specimens. In the absence of tissue shear, IGF-I augmented protein and proteoglycan synthesis up to twofold at IGF-I concentrations in the range of 100-300 ng/ml. When tissue shear and IGF-I stimuli were combined, matrix biosynthesis levels were significantly higher than the maximal effect caused by either stimulus alone. However, there was no significant interaction between tissue shear and IGF-I as determined by two-way ANOVA. We then quantified the effect of dynamic tissue shear on the transport of IGF-I into and within cartilage explants. [125I]IGF-I was added to the medium, and the levels of intratissue [125I]IGF-I were directly measured as a function of time over 48 h in the presence and absence of continuous dynamic shear strain. Dynamic shear did not alter the rate of uptake of [125I]IGF-I into the explants, suggesting that convective diffusion of [125I]IGF-I is negligible under the shear strain conditions used. This is in marked contrast to the enhancement of transport reported in response to uniaxial dynamic compression. Taken together, these data suggest that (1) the stimulatory effect of tissue shear is via mechanotransduction pathways and not by facilitated transport of biochemical factors and (2) chondrocytes may possess complementary signal transduction pathways for biophysical and biochemical factors leading to changes in metabolic activity.

Analysis of Variance↗
PubMed2000

Characterisation of three novel cationic lipids as liposomal complexes with DNA.

Cationic lipids (CLs) are being increasingly exploited as transfection vectors for the delivery of DNA into eukaryotic cells. To obtain further insight to the complex formation and interactions between cationic liposomes and DNA, we characterised three novel cationic lipids, viz. bis[2-(11-phenoxyundecanoate)ethyl]-dimethylammonium bromide, N-hexadecyl-N-¿10-[O-(4-acetoxy)-phenylundecanoate]ethyl¿- dimethylammonium bromide, and bis[2-(11-butyloxyundecanoate)ethyl]dimethylammonium bromide. These lipids bear the same charged headgroup yet have different hydrophobic parts. Accordingly, we may anticipate their electrostatic interactions with DNA to be similar while differing in both thermal phase behaviour and physicochemical properties of their complexes with DNA. In keeping with the above all three lipids formed complexes with DNA as evidenced by light scattering, fluorescence spectroscopy and Langmuir film balance. Differential scanning calorimetry revealed very different phase behaviours for the binary mixtures of the three CLs with dimyristoylphosphatidylcholine and also provided evidence for DNA-induced lipid phase separation. These data were confirmed by compression isotherms and fluorescence microscopy of monolayers residing on an aqueous buffer, recorded both in the presence and absence of DNA. Importantly, binding to cationic liposomes appears to prevent thermal denaturation of DNA upon heating of the complexes. Likewise, renaturation of heat-treated DNA complexed with the cationic liposomes appears to be abolished as well.

Cations↗
PubMed1993

Cross-bridge scheme and force per cross-bridge state in skinned rabbit psoas muscle fibers.

The rate and association constants (kinetic constants) which comprise a seven state cross-bridge scheme were deduced by sinusoidal analysis in chemically skinned rabbit psoas muscle fibers at 20 degrees C, 200 mM ionic strength, and during maximal Ca2+ activation (pCa 4.54-4.82). The kinetic constants were then used to calculate the steady state probability of cross-bridges in each state as the function of MgATP, MgADP, and phosphate (Pi) concentrations. This calculation showed that 72% of available cross-bridges were (strongly) attached during our control activation (5 mM MgATP, 8 mM Pi), which agreed approximately with the stiffness ratio (active:rigor, 69 +/- 3%); active stiffness was measured during the control activation, and rigor stiffness after an induction of the rigor state. By assuming that isometric tension is a linear combination of probabilities of cross-bridges in each state, and by measuring tension as the function of MgATP, MgADP, and Pi concentrations, we deduced the force associated with each cross-bridge state. Data from the osmotic compression of muscle fibers by dextran T500 were used to deduce the force associated with one of the cross-bridge states. Our results show that force is highest in the AM*ADP.Pi state (A = actin, M = myosin). Since the state which leads into the AM*ADP.Pi state is the weakly attached AM.ADP.Pi state, we confirm that the force development occurs on Pi isomerization (AM.ADP.Pi --> AM*ADP.Pi). Our results also show that a minimal force change occurs with the release of Pi or MgADP, and that force declines gradually with ADP isomerization (AM*ADP -->AM.ADP), ATP isomerization (AM+ATP-->AM*ATP), and with cross-bridge detachment. Force of the AM state agreed well with force measured after induction of the rigor state, indicating that the AM state is a close approximation of the rigor state. The stiffness results obtained as functions of MgATP, MgADP, and Pi concentrations were generally consistent with the cross-bridge scheme.

Adenosine Diphosphate↗
PubMed1999

Adjustment of the human melatonin and cortisol rhythms to shortening of the natural summer photoperiod.

Fifteen human subjects were exposed to natural outdoor summer light from 0415 h until 2000 h for 4 days and then from 0800 h until 1600 h for another 4 days. Following shortening of the natural summer photoperiod, times of the morning salivary melatonin decline and cortisol rise did not change whereas the time of the evening melatonin rise phase advanced by about 1.5 h within 1 day and further did not change significantly. Consequently, the melatonin signal duration extended markedly within 1 day. The data show that the compressed melatonin rhythm waveform in humans experiencing a long natural summer photoperiod from sunrise until sunset may change rapidly following a shortening of the photoperiod.

Adolescent↗
PubMed2004

Digital video for the documentation of colonoscopy.

BACKGROUND: The aim of this study was to determine whether digital video is suitable for the documentation of colonoscopy. Standards are required for the visual documentation of endoscopic findings and to optimize image quality while limiting file size and bandwidth requirements. METHODS: Video recordings of colonoscopy procedures were encoded using a common video compression method at selected data rates and resolutions. Twelve reviewers were selected, each of whom was assigned 8 video review sessions, each consisting of 5 colonoscopy procedures. The reviewers rated the following: level of confidence that the cecum was demonstrated, subjective quality of the video compared with actual videocolonoscopy, and whether the video was of "diagnostic quality." RESULTS: Reviewers were confident that the cecum was demonstrated in all cases except at the lowest data rate. The 1.0 Mbps standard interchange format video provided an optimal balance between quality and file size. CONCLUSIONS: For the documentation of colonoscopy, 1.0 Mbps is acceptable and results in a file size of 7.5 Mbytes/min, which is manageable for most modern hospital and telehealth networks.

Colonoscopy↗
PubMed1994

Posterior fossa neurovascular anomalies in essential hypertension.

Intraoperative observations, necropsy, and angiographic studies support the presumption that neurovascular compression of the left ventrolateral medulla may cause neurogenic hypertension. Pulsatile irritation of the ventrolateral medulla at the root-entry zone of cranial nerves IX and X increases blood pressure in animals. To identify and assess the distribution of neurovascular compression at the ventrolateral medulla in human beings, we did a prospective single-blind study in 24 patients with essential hypertension, in 14 patients with renal hypertension, and in 14 normal subjects. To detect neurovascular compression, we used axial and coronal double-echo and magnetic-resonance angiography sequences. Blood pressure control and duration of hypertension were not different in the two groups of patients. 20 patients with essential hypertension had magnetic tomographic evidence of left-sided neurovascular compression at the ventrolateral medulla; 2 patients with renal hypertension and 1 of the normal subjects had a positive finding on the left. On the right side, we found signs of neurovascular compression in 4 patients with essential hypertension, in 4 with renal hypertension, and in 2 of the normal subjects. With magnetic resonance tomography, it is possible to evaluate the neurovascular relations in the posterior fossa and detect neurovascular compression at the ventrolateral medulla. These data in living subjects give further evidence of an association between neurovascular compression at the left ventrolateral medulla and essential hypertension.

Adult↗
PubMed1999

Visualisation of biomedical datasets by use of growing cell structure networks: a novel diagnostic classification technique.

BACKGROUND: Medical research produces large multivariable datasets that are difficult to visualise and interpret intuitively. We describe a novel growing cell structure (GCS) technique that compresses multidimensional datasets into two dimensional maps with colour overlays that can be visually interpreted. METHODS: The two-dimensional map is self-discovered from the training set by distribution of cases to different nodes according to similarity between the cases at each node. Nodes are added to the map until there is no further significant reduction in error. The Parzen window method is used to estimate the probability distribution of the training cases, and this probability is converted to posterior class probabilities by use of Bayes' theorem. Classification performance can be assessed by means of receiver operating characteristic (ROC) curves. Colour maps of the values of each input variable at each node are constructed, which illustrate the relation between each input variable and the overall distribution of cases in the network map. FINDINGS: From a dataset of 11 input variables from 692 fine-needle aspirate samples from breast lesions, a 32-node network produced an area under the ROC curve of 0.96, which was not significantly different from that for logistic regression (0.98, z=1.09, p>0.05). Colour maps of the input variables showed that some variables had discrete distributions over exclusively benign or malignant areas of the network, and were thus discriminant, whereas others, such as foamy macrophages, covered both benign and malignant regions. INTERPRETATION: This technique produces dimensional compression that allows multidimensional data to be displayed as two-dimensional colour images. This envisioning of information allows the highly developed visuospatial abilities of human observers to perceive subtle inter-relations in the dataset.

Artificial Intelligence↗
PubMed1994

Use of supplemental oxygen during bystander-initiated CPR.

STUDY OBJECTIVE: To evaluate the efficacy of three methods by which rescuers can breathe supplemental oxygen to increase their delivered oxygen concentration (FDO2) during single-rescuer, bystander-initiated CPR. DESIGN: Controlled, randomized, crossover study. SETTING: Simulation in laboratory setting using a CPR manikin. SUBJECTS: Thirteen-volunteer convenience sample group. INTERVENTIONS: Volunteers trained only in basic life support performed ventilation only and full CPR on a CPR manikin using room air and each of three supplemental oxygen delivery methods: nasal cannula, oxygen supply tube, and demand valve. The volunteers received minimal instruction on how to use the supplemental oxygen delivery methods. MAIN OUTCOME MEASURES: Peak FDO2 and peak carbon dioxide concentration; American Heart Association-defined ventilation and CPR compression performance indices. The data were analyzed using Duncan's method of analysis of variance. RESULTS: The mean peak FDO2 during ventilation-only/full CPR for the baseline (room air ventilation) and each supplemental oxygen delivery method (at specified flow rate) was: baseline (room air), -17.96% +/- 0.56%/16.77% +/- 0.56%; nasal cannula (at 10 L/min), -31.77% +/- 3.06%/27.01% +/- 3.68%; oxygen supply tubing (at 15 L/min), -36.82% +/- 9.93%/30.41% +/- 4.88%; and demand valve, -78.17% +/- 9.10%/68.22% +/- 7.10%. CPR performance was not hampered by the use of the supplemental oxygen methods. CONCLUSION: The use of supplemental oxygen increases the rescuer's FDO2 during ventilation-only and full CPR without interfering with CPR performance.

Adult↗
PubMed2002

Tabletting of pellet-matrix systems: ability of parameters from dynamic and kinetic models to elucidate the densification of matrix formers and of pellets.

Two different types of pellets, i.e. drug-free sugar spheres, and pellets, spray-layered with crystalline theophylline and coated with Eudragit RS/RL, were tabletted each in combination with matrix-forming powder mixtures of Avicel PH200 and PEG 4000. The die fills from pellets and powder mixtures were regarded as two-compartment systems with a volume fraction of the pellets being limited to 0.52 corresponding to a cubic lattice, and the maximum degrees of densifications were adjusted related to the matrix. To data measured during single compression cycles on an instrumented eccentric tabletting machine and transformed appropriately, the Kawakita equation, the Heckel function, and a modified Weibull function were fitted, and the total work of compression was calculated. The Kawakita model fitted well systems with both types of pellets. Its parameters reflected the additional densification of the theophylline pellets separately from that of the matrix formers. The Heckel function could only be applied to systems containing non-porous sugar spheres, since the theophylline pellets underwent considerable densification and deformation. Only, when the Heckel porosity function was related to the volume fraction of the matrix, excluding the sugar spheres, the approximately linear regions for mixtures with increasing volume proportions of sugar spheres occured in comparable regions of densification. Parameters of the modified Weibull function demonstrated an increasing resistance against densification with increasing amounts of pellets. The total work of compression increased steeply with increasing volume fractions for pellets from 0.42 to 0.46 indicating, that the resistance against densification already rose when the pellets were still isolated. In conclusion, the combination of dynamic and kinetic models provides a comprehensible insight into the process of tabletting powder mixtures with pellets. Particularly, the Kawakita model was a suitable tool to differentiate the actual changes in porosity during compression from the compressibility of such complex systems.

Compressive Strength↗
PubMed2003

The level of compressive load affects conclusions from statistical analyses to determine whether a lateral meniscal autograft restores tibial contact pressure to normal: a study in human cadaveric knees.

This study addressed the question of whether the level of compressive load would affect the conclusions from statistical analyses aimed at determining how well a lateral meniscal autograft restores tibial contact (as indicated by the maximum contact pressure, mean pressure, and contact area) to that of the intact knee. If statistical analyses indicated that normal tibial contact was not restored with a higher, more physiologic load, then a secondary question was whether an autograft surgically implanted with bone plugs would improve tibial contact compared to that in a meniscectomized knee. Nine, fresh-frozen human cadaveric knees were subjected to a low, non-physiologic compressive load of 400 N and a higher, more physiologic compressive load of 1200 N under three conditions (lateral meniscus intact, lateral meniscus removed and reimplanted as an autograft, and lateral meniscus removed). Contact pressure on the lateral plateau was measured with pressure sensitive film at 0 degrees, 15 degrees, 30 degrees, and 45 degrees of flexion. At 400 N, p-values from statistical analyses indicated that both the maximum and mean pressures with the autograft were comparable to those of the intact knee (p> or =0.685). However, at 1200 N, p-values from statistical analyses indicated that both the maximum and mean pressures with the autograft were significantly greater than those of the intact knee (p< or =0.0001). Therefore studies designed to evaluate tibial contact pressure for a meniscal transplant should use a higher, more physiologic compressive load, because lower loads overestimate the transplant's effectiveness. Although none of the contact variables was restored to normal when the compressive load was increased to 1200 N, all of the contact variables were more normal than those of the meniscectomized knee. Thus, lateral meniscal allografts implanted using bone plugs can significantly improve contact pressure relative to a meniscectomized knee at the time of implantation.

Adult↗