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At least 1,711 records · Page 95Linked to original sources
PubMed2006

Embedded multiple description coding of video.

Real-time delivery of video over best-effort error-prone packet networks requires scalable erasure-resilient compression systems in order to 1) meet the users' requirements in terms of quality, resolution, and frame-rate; 2) dynamically adapt the rate to the available channel capacity; and 3) provide robustness to data losses, as retransmission is often impractical. Furthermore, the employed erasure-resilience mechanisms should be scalable in order to adapt the degree of resiliency against transmission errors to the varying channel conditions. Driven by these constraints, we propose in this paper a novel design for scalable erasure-resilient video coding that couples the compression efficiency of the open-loop architecture with the robustness provided by multiple description coding. In our approach, scalability and packet-erasure resilience are jointly provided via embedded multiple description scalar quantization. Furthermore, a novel channel-aware rate-allocation technique is proposed that allows for shaping on-the-fly the output bit rate and the degree of resiliency without resorting to channel coding. As a result, robustness to data losses is traded for better visual quality when transmission occurs over reliable channels, while erasure resilience is introduced when noisy links are involved. Numerical results clearly demonstrate the advantages of the proposed approach over equivalent codec instantiations employing 1) no erasure-resilience mechanisms, 2) erasure-resilience with nonscalable redundancy, or 3) data-partitioning principles.

Algorithms↗
PubMed2005

Reconstruction of optical properties of phantom and breast lesion in vivo from paraxial scanning data.

We report on the reconstruction of absorption and reduced scattering coefficients of breast tissue in vivo of a patient with mastopathic disease. Distributions of times of flight of photons through the compressed breast were recorded by paraxial scanning. From data measured at four different source-detector offsets optical properties were reconstructed within the linear Rytov approximation by a fast inverse Fourier space method. Low-pass filtering in Fourier space was employed to remove excessive noise from high spatial frequency components and to reduce the computational efforts by a factor of 3, typically. The mammograms displaying reconstructed absorption and reduced scattering coefficients were compared with projection mammograms either obtained by time-window analysis of experimental data or based on average absorption and reduced scattering coefficients which were derived from measured temporal point spread functions within a simple homogeneous model. All inhomogeneities which were visible in the projection mammograms and which could be associated with specific breast tissue compartments could be correlated with inhomogeneities in the reconstructed absorption coefficient. In particular, the mastopathic disease was detected in the reconstructed absorption mammogram. In order to assess reliability of optical properties reconstructed from data obtained by paraxial scanning, corresponding phantom experiments and reconstructions of phantom optical properties were carried out. Because of the limited angular range sampled by the in vivo and phantom measurements, considerable blurring of the absorption coefficient occurs along the compression direction, compromising longitudinal resolution.

Algorithms↗
PubMed2001

Symptoms and neurophysiological picture of carpal tunnel syndrome in pregnancy.

OBJECTIVE: To evaluate the incidence of carpal tunnel syndrome (CTS) in pregnancy through a validated and multiperspective assessment of CTS. METHODS: During 2000, the Italian CTS study group focussed on the occurrence of CTS in women during the final stages of pregnancy, enrolled in 7 Italian centers. In addition to the physician-centered and neurophysiologic traditional evaluations, we used a validated patient-oriented measurement to obtain more comprehensive and consistent data for severity of symptoms and functional impairment. RESULTS: In our study, CTS was clinically diagnosed in more than half of women (62%). Neurophysiological evaluation provided diagnosis of CTS in around half of women (43% were positive in one hand at least). Our study provides evidence, reported here for the first time, of a correlation between edema and neurophysiological picture. Similarly, our study provides a correlation between validated patient-oriented measurement and edema. Moreover, a significant correlation between a negative trend (subjectively assessed) and smoking and alcohol consumption was observed. CONCLUSIONS: Our observations confirm that the edema of the tissues in the carpal tunnel could induce a mechanical compression of the nerve. Moreover, our data suggest that smoking and alcohol consumption have a negative role in the evolution of the syndrome probably due to impairment of the microcirculation.

Adult↗
PubMed2005

Free-response receiver operating characteristic evaluation of lossy JPEG2000 and object-based set partitioning in hierarchical trees compression of digitized mammograms.

PURPOSE: To assess the effects of two irreversible wavelet-based compression algorithms--Joint Photographic Experts Group (JPEG) 2000 and object-based set partitioning in hierarchical trees (SPIHT)--on the detection of clusters of microcalcifications and masses on digitized mammograms. MATERIALS AND METHODS: The use of the images in this retrospective image-collection study was approved by the institutional review board, and patient informed consent was not required. One hundred twelve mammographic images (28 with one or two clusters of microcalcifications, 19 with one mass, 17 with both abnormal findings, and 48 with normal findings) obtained in 60 women who ranged in age from 25 to 79 years were digitized and compressed at 40:1 and 80:1 by using the JPEG2000 and object-based SPIHT methods. Five experienced radiologists were asked to locate and rate clusters of microcalcifications and masses on the original and compressed images in a free-response receiver operating characteristic (FROC) data acquisition paradigm. Observer performance was evaluated with the jackknife FROC method. RESULTS: The mean FROC figures of merit for detecting clusters of microcalcifications, masses, and both radiographic findings on uncompressed images were 0.80, 0.81, and 0.72, respectively. With object-based SPIHT 80:1 compression, the corresponding values were larger than the values for uncompressed images by 0.005, 0.009, and -0.005, respectively. The 95% confidence interval for the differences in figures of merit between compressed and uncompressed images was -0.039, 0.033 for the microcalcification finding; -0.055, 0.034 for the mass finding; and -0.039, 0.030 for both findings. Because each of these confidence intervals includes zero, no significant difference in detection accuracy between uncompressed and object-based SPIHT 80:1 compression was observed at a P value of 5%. The F test of the null hypothesis that all of the modes (uncompressed and four compressed modes) were equivalent yielded the following results: F = 0.255, P = .903 for the microcalcification finding; F = 0.340, P = .848 for the mass finding; and F = 0.122, P = .975 for both findings. CONCLUSION: To within the accuracy of these measurements, lossy compression of digital mammographic data at 80:1 with JPEG2000 or the object-based SPIHT algorithm can be performed without decreasing the rate of detection of clusters of microcalcifications and masses.

Adult↗
PubMed1984

Adverse effects of the management of malignant spinal cord compression.

As a prelude to further work which attempts to improve the management of metastatic spinal cord compression the efficacy and adverse effects of existing therapy has been assessed. All papers dealing with the management of malignant spinal cord compression since 1960 have been reviewed. Data from this review is presented in a novel manner in order to identify not only the degree of successful return to ambulation achieved but more importantly the extent of the adverse effects which occur during existing management. It is seen that, while in general some 35% of patients treated in any manner retain or return to the ability to walk, some 20% to 25% sustain major neurological deterioration. In addition, those patients treated by laminectomy who do deteriorate may be subject to a significant rate of perioperative mortality and major structural complications related to the surgical wounds. In the light of the adverse factors described, the role of laminectomy as first-line management of malignant cord compression is questioned. Alternative modes of treatment are discussed and a tentative scheme of management described which it is hoped will lead to a better quality of survival of the group as a whole in addition to maintaining, or perhaps, improving the rate of successful return to ambulation.

Combined Modality Therapy↗
PubMed2002

The effects of the simulated Valsalva maneuver, liver compression, and/or Trendelenburg position on the cross-sectional area of the internal jugular vein in infants and young children.

UNLABELLED: We calculated the effects of the simulated Valsalva (V), liver (L) compression, and Trendelenburg (T) position on the cross-sectional area (CSA) of the right internal jugular vein by using planimetry (Aloka ultrasound machine) in 84 infants and young children. Eight combinations of positions and interventions were studied for each patient, with the patient supine, in the T position, during the simulated V maneuver, with L compression and a combination of maneuvers. Data were analyzed by using Friedman's chi(2) test and Wilcoxon's signed rank test. An increase of >25% in the CSA of the internal jugular vein was considered significant. In infants, the maximal mean increase achieved with the combination of all 3 maneuvers was only 17.4% +/- 16.1%. As a single maneuver, the simulated V was the most effective (11.6% +/- 11.5%). In children, the combination of all 3 maneuvers performed simultaneously produced a mean 65.9% (SD +/- 44.7%) increase in the CSA, which was larger than the increase by all other maneuvers alone or in a single combination (Friedman's test, P < 0.001 and Wilcoxon's test, P < 0.002). As a single maneuver, V produced the most increase (40.4% +/- 32.2%) compared with L compression (14.3% +/- 18.9%) or T position (24.3% +/- 27.1%). IMPLICATIONS: The combinations of simulated Valsalva, liver compression, and Trendelenburg maneuvers produce the maximal mean increase in the size of the internal jugular vein in infants and young children, with the Valsalva maneuver being the most effective single maneuver. This increase is significant in young children, but negligible in infants.

Catheterization, Central Venous↗
PubMedDate not supplied

Mechanical properties of trabecular bone from the proximal femur: a quantitative CT study.

We have investigated the relationships between trabecular bone compressive strength and elastic modulus and the directly measured apparent density and noninvasively measured CT equivalent mineral density for 49 cylindrical specimens harvested from fresh human proximal femora. Compressive strength demonstrated a high positive correlation with both densities, being proportional to the apparent density raised to the 1.8 power (R2 = 0.93) and equivalent mineral density to the 1.5 power (R2 = 0.89). Similarly, the compressive modulus demonstrated a high correlation with both density measures, being proportional to the apparent density raised to the 1.4 power (R2 = 0.91) and CT equivalent mineral density to the 1.2 power (R2 = 0.90). Though variations in architecture and bone marrow fat were observed to influence trabecular properties, the data presented here demonstrate that apparent density, compressive strength, and elastic modulus can be determined accurately using single energy quantitative CT. We expect that the use of these noninvasive data will result in improved estimates of that component of hip fracture risk that is attributable to bone strength.

Biomechanical Phenomena↗
PubMed2001

Molecular dynamics studies of sequence-directed curvature in bending locus of trypanosome kinetoplast DNA.

The macroscopic curvature induced in the double helical B-DNA by regularly repeated adenine tracts (A-tracts) plays an exceptional role in structural studies of DNA because this effect presents the most well documented example of sequence specific conformational modulations. Recently, a new hypothesis of its physical origin has been put forward. According to it, the intrinsic bends in B-DNA may represent one of the consequences of the compressed frustrated state of its backbone. The compressed backbone hypothesis agrees with many data and explains some controversial experimental observations. The original arguments of this theory came out from MD simulations of a DNA fragment with a strong bending propensity. Its sequence, however, was not experimental. It was constructed empirically so as to maximize the magnitude of bending in calculations. To make sure that our computations reproduce the experimental effect we carried out similar simulations with an A-tract repeat of a natural base pair sequence found in a bent locus of a minicircle DNA. We demonstrate spontaneous development of static curvature in the course of MD simulations excluding any initial bias except the base pair sequence. Its direction and magnitude agree with experimental estimates. The results confirm earlier qualitative conclusions and agree with the hypothesis of a compressed backbone as the origin of static bending in B-DNA.

Animals↗
PubMed2005

What is the optimal chest compression-ventilation ratio?

PURPOSE OF REVIEW: Despite a more widespread knowledge of basic cardiopulmonary resuscitation maneuvers in the community, the survival rate for patients with cardiac arrest has remained essentially unchanged in the past 30 years. Over the past few decades, many different compression-ventilation ratios have been studied in terms of best coronary and cerebral oxygen delivery, restoration of spontaneous circulation, and neurologic outcome. This article summarizes the recent evidence presented at the International Consensus on Resuscitation Science in January 2005. RECENT FINDINGS: Recent data from animal and mathematical models suggest a move to a higher compression-ventilation ratio to maximize coronary and cerebral oxygen delivery during cardiac arrest and long-term neurologic outcome. Prospective randomized human data on alternative compression-ventilation ratios are missing and new evidence seems to indicate the inadequacy of both lay and professional rescuers in providing chest compression and ventilating the victim in cardiac arrest. Finally, observational and animal studies highlight the hidden danger of inadvertent hyperventilation during advanced cardiac life support as a reduction of both coronary and perfusion pressure secondary to increased intrathoracic pressure and decreased venous return. SUMMARY: The optimal compression-ventilation ratio is still unknown and the best tradeoff between oxygenation and organ perfusion during cardiopulmonary resuscitation is probably different for each patient and scenario. A discrepancy between what is recommended by the current guidelines and the 'real world' of cardiopulmonary resuscitation has resulted in a near flat survival rate from cardiac arrest in the past few years.

Cardiopulmonary Resuscitation↗
PubMed2004

Bone scintigraphy predicts the risk of spinal cord compression in hormone-refractory prostate cancer.

In prostate cancer, confirmation of metastatic involvement of the skeleton has traditionally been achieved by bone scintigraphy, although the widespread availability of prostate-specific antigen (PSA) measurements has tended to eliminate the need for this investigation. The potential of bone scintigraphy to predict skeletal-related events, particularly spinal cord compression, after the onset of hormone refractoriness has never been investigated. The aim of this study was to establish whether a new method of evaluating bone scintigraphy would offer a better predictive value for this complication of the metastatic process than is achieved with currently available grading methods. We studied 84 patients with hormone-refractory prostate cancer who had undergone bone scintigraphy at the time of hormone escape. Tumour grading and parameters of tumour load (PSA and alkaline phosphatase activity) were available in all patients. The incidence of spinal cord compression was documented and all patients were followed up until death. Bone scintigraphy was evaluated by the conventional Soloway grading and by an additional analysis determining total or partial involvement of individual vertebrae. In contrast to the Soloway method, the new method was able to predict spinal cord compression at various spinal levels. Our data suggest that there is still a place for bone scintigraphy in the management of hormone-refractory prostate cancer.

Antineoplastic Agents, Hormonal↗
PubMed1999

The optimal radiologic method for assessing spinal canal compromise and cord compression in patients with cervical spinal cord injury. Part II: Results of a multicenter study.

STUDY DESIGN: A multicenter, retrospective study using computed tomographic and magnetic resonance imaging data to establish quantitative, reliable criteria of canal compromise and cord compression in patients with cervical spinal cord injury. OBJECTIVES: To develop and validate a radiologic assessment tool of spinal canal compromise and cord compression in cervical spinal cord injury for use in clinical trials. SUMMARY OF BACKGROUND DATA: There are few quantitative, reliable criteria for radiologic measurement of cervical spinal canal compromise or cord compression after acute spinal cord injury. METHODS: The study included 71 patients (55 men, 16 women; mean age, 39.7 +/- 18.7 years) with acute cervical spinal cord injury. Causes of spinal cord injury included motor vehicle accidents (n = 36), falls (n = 20), water-related injuries (n = 8), sports (n = 5), assault (n = 1), and farm accidents (n = 1). Canal compromise was measured on computed tomographic scan and T1- and T2-weighted magnetic resonance imaging, and cord compression at the level of maximum injury was measured on T1- and T2-weighted magnetic resonance imaging. All films were assessed by two independent observers. RESULTS: There was a strong correlation of canal compromise and/or cord compression measurements between axial and midsagittal computed tomography, and between axial and midsagittal T2-weighted magnetic resonance imaging. Spinal canal compromise assessed by computed tomography showed a significant although moderate correlation with spinal cord compression assessed by T1- and T2-weighted magnetic resonance imaging. Virtually all patients with canal compromise of 25% or more on computed tomographic scan had evidence of some degree of cord compression on magnetic resonance imaging, but a large number of patients with less than 25% canal compromise on computed tomographic scan also had evidence on magnetic resonance imaging of cord compression. CONCLUSIONS: In patients with cervical spinal cord injury, the midsagittal T1- and T2-weighted magnetic resonance imaging provides an objective, quantifiable, and reliable assessment of spinal cord compression that cannot be adequately assessed by computed tomography alone.

Adolescent↗
PubMed1994

Microvascular compression during myocardial ischemia: mechanistic basis for no-reflow phenomenon.

Alterations in fiber size and capillary diameter were highly correlated with perfusion deficits after myocardial ischemia. After 5 (n = 3) and 30 (n = 5) min of global normothermic ischemia, isolated rabbit hearts were perfused with India ink and then with glutaraldehyde. Morphometric techniques were used to determine mean fiber cross-sectional area [a(f)], mean effective capillary diameter [d(c)], total and perfused capillary number per fiber area, and capillary length per fiber volume in subepicardium (Epi) and subendocardium (Endo). Sarcomere length was measured to differentiate between effects of fiber shortening and intracellular edema on a(f). After 30 min of ischemia, a(f) increased 41 (Epi) and 36% (Endo). Of these percentages, fiber shortening accounted for 2 (Epi) and 25% (Endo). Decreased d(c) was correlated with increased a(f) as well as reductions in perfused capillary number and length. Whereas intracellular edema had the greatest overall effect on a(f), fiber shortening accounted for a significant increase of a(f) in Endo, where perfusion deficits were most pronounced. These data support the hypothesis that microvascular compression consequent to increased a(f) contributes to perfusion deficits after myocardial ischemia.

Animals↗
PubMed2005

Fabrication using a rapid prototyping system and in vitro characterization of PEG-PCL-PLA scaffolds for tissue engineering.

In the field of tissue engineering new polymers are needed to fabricate scaffolds with specific properties depending on the targeted tissue. This work aimed at designing and developing a 3D scaffold with variable mechanical strength, fully interconnected porous network, controllable hydrophilicity and degradability. For this, a desktop-robot-based melt-extrusion rapid prototyping technique was applied to a novel tri-block co-polymer, namely poly(ethylene glycol)-block-poly(epsilon-caprolactone)-block-poly(DL-lactide), PEG-PCL-P(DL)LA. This co-polymer was melted by electrical heating and directly extruded out using computer-controlled rapid prototyping by means of compressed purified air to build porous scaffolds. Various lay-down patterns (0/30/60/90/120/150 degrees, 0/45/90/135 degrees, 0/60/120 degrees and 0/90 degrees) were produced by using appropriate positioning of the robotic control system. Scanning electron microscopy and micro-computed tomography were used to show that 3D scaffold architectures were honeycomb-like with completely interconnected and controlled channel characteristics. Compression tests were performed and the data obtained agreed well with the typical behavior of a porous material undergoing deformation. Preliminary cell response to the as-fabricated scaffolds has been studied with primary human fibroblasts. The results demonstrated the suitability of the process and the cell biocompatibility of the polymer, two important properties among the many required for effective clinical use and efficient tissue-engineering scaffolding.

Adult↗
PubMedDate not supplied

Monitoring of cerebral perfusion during anesthesia by time-compressed Fourier analysis of the electroencephalogram.

Time-compressed Fourier analysis of the electroencephalogram has proven to be a useful analytical procedure during anesthesia and surgery which simplifies data interpretation by presenting the EEG in a time-compressed frequency domain rather than the conventional time domain. This method of data analysis graphically accentuates the electroencephalographic correlates of ischemia-induced cerebral dysfunction and other cerebral oxygen consumption abnormalities. The ability to accentuate trends in frequency and power is derived from sequential plotting of spectra to produce a graph with three dimensional axes of frequency, time, and power. In carotid endarterectomies the system has proven more useful than the conventional EEG in assessing the need for a vascular shunt to maintain internal carotid flow during endarterectomy. In open-heart surgery time-compressed EEG spectral analysis has allowed early recognition of cerebral ischemia resulting from arterial hypotension and venous hypertension. Five cases are presented which demonstrate the ability of our system to reflect developing cerebral ischemia.

Aged↗
PubMed2003

Early versus deferred treatment for early stage multiple myeloma.

BACKGROUND: Early stage multiple myeloma (MM) represents about 20% of MM. Most of the patients are asymptomatic. Thus, it is far less dramatic than advanced disease and may require different treatment strategies. For these patients, it is not clear whether it is better to start chemotherapy right after the diagnosis or to delay the treatment until symptoms become obvious as the disease progresses. OBJECTIVES: To identify and synthesize all available research evidence on whether early treatment intervention results in improved clinical outcomes when compared with observation alone. The main outcomes of interest that were examined included mortality, disease progression, response rate, and toxicity of early treatment. SEARCH STRATEGY: Searches of the following electronic databases were undertaken: MEDLINE, EMBASE, CANCERLIT, LILLIACS and Cochrane Database of RCTs. We have recently compiled a comprehensive database of RCTs in myeloma. This search was updated and supplemented by hand-search of abstracts from main society meetings such as the ASH (American Society of Hematology), ASCO (American Society of Clinical Oncology), and EHA (European Haematology Association). In addition, we compared our list with a list of RCTs maintained by the Oxford Clinical Trial Service Unit. SELECTION CRITERIA: Randomized controlled trials (RCT) with a parallel design that compared early versus deferred treatment of patients with early stage multiple myeloma based on Durie-Salmon (D-S) staging system. We also considered those trials that did not define early stage myeloma according to D-S staging system, but enrolled patients according to clinical uncertainty about the benefits of immediate intervention. DATA COLLECTION AND ANALYSIS: Data synthesis was performed for all studies and according to the defined quality criteria. The first reviewer and the contact reviewer of this proposal independently extracted data. Disagreement was resolved by consensus. Revman software (ver 4.1) was used to combine results from all studies and expressed as an overall odds ratio or Peto's Odds Ratio, with 95% confidence interval. MAIN RESULTS: Three trials were included with a total of 131 patients in each of the early treatment and deferred treatment groups. Early MM is asymptomatic stage I in these trials. All trials used standard Melphalan treatment but not stem cell transplantation. No statistically significant heterogeneity among the studies was detected. Beneficial effects of early treatment were seen in delay of myeloma progression (Peto's OR = 0.16, 95% CI: 0.09-0.29), and reduced vertebral compression (OR = 0.18, 95%CI: 0.02-1.59, NNT = 23, 95% CI: an NNT of 11, via infinity, to an NNH of 50). No significant effects on mortality and response rate were seen (Peto's OR = 1.11, 95% CI: 0.67-1.84, and OR = 0.63, 95% CI: 0.33-1.23, respectively). Early treatment may increase the risk of acute leukemia (Peto's OR = 3.20, 95% CI: 0.55-18.73, NNH = 44, 95% CI: an NNT of 63, via infinity, to an NNH of 15). REVIEWER'S CONCLUSIONS: Early treatment of early stage multiple myeloma inhibits disease progression, and may reduce vertebral compression. However, early treatment may increase the risk of acute leukemia. However, the data on vertebral compression and leukaemic transformation may not be interpretable due to very small numbers. Based on the current evidence, mortality and response rate are not significantly affected by introducing early treatment in the progression of myeloma. However, it is quite possible that the lack of beneficial effects of early intervention in myeloma is a false negative result due to the paucity of the existing evidence. In addition, data on quality of life and toxicity were sparsely reported adding to additional difficulties about management decisions in early stage myeloma.

Disease Progression↗
PubMed1995

Hemodynamic mechanisms responsible for reduced subendocardial coronary reserve in dogs with severe left ventricular hypertrophy.

BACKGROUND: Reduced subendocardial coronary reserve is a hallmark of left ventricular hypertrophy (LVH). The goal of this study was to determine whether hemodynamic, as opposed to structural, mechanisms were responsible for the reduced subendocardial coronary reserve. METHODS AND RESULTS: The effects of near-maximal vasodilation with adenosine were examined in 10 conscious dogs with LVH (79% increase in ratio of LV weight to body weight) induced by aortic banding in puppies with and without preload reduction. At baseline, LV end-diastolic pressure, LV end-diastolic circumferential and compressive radial wall stresses, and LV myocardial blood flow were similar in dogs with LVH and sham-operated controls, while LV end-systolic circumferential wall stress tended to be greater in the LVH group compared with the control group. In control dogs, adenosine reduced LV circumferential end-systolic and end-diastolic wall stresses and compressive radial subendocardial wall stress; LV subendocardial blood flow increased (from 1.41 +/- 0.16 to 3.58 +/- 0.27 mL.min-1.g-1) and the ratio of subendocardial to subepicardial blood flow decrease from 1.30 +/- 0.07 to 0.69 +/- 0.05. In dogs with LVH, during adenosine infusion, LV circumferential end-systolic and end-diastolic wall stresses and LV radial subendocardial wall stresses remained elevated, the increase in LV subendocardial blood flow was significantly smaller (from 1.11 +/- 0.11 to 2.27 +/- 0.24 mL.min-1.g-1, P < .05), and the subendocardial/epicardial ratio fell to a lower level (from 1.22 +/- 0.17 to 0.35 +/- 0.03, P < .05). When LV wall stresses during adenosine were reduced in a subgroup of 5 dogs with LVH, the endocardium/epicardium ratio during adenosine infusion was no longer different from that in control dogs (0.63 +/- 0.11), nor was the level of subendocardial blood flow different (3.42 +/- 0.60 mL.min-1.g-1). CONCLUSIONS: These data suggest that hemodynamic factors, eg, compressive forces, are an important component of the reduced subendocardial coronary reserve as opposed to structural alterations, even in the presence of severe LVH.

Adenosine↗
PubMed1990

Density fluctuations in saturated phospholipid bilayers increase as the acyl-chain length decreases.

A systematic computer simulation study is conducted for a model of the main phase transition of fully hydrated saturated diacyl phosphatidylcholine bilayers (DMPC, DPPC, and DSPC). With particular focus on the fluctuation effects on the thermal properties in the transition region, the study yields data for the specific heat, the lateral compressibility, and the lipid-domain size distribution. Via a simple model assumption the transmembrane passive ion permeability is derived from the lipid-domain interfacial measure. A comparative analysis of the various data shows, in agreement with a number of experiments, that the lateral density fluctuations and hence the response functions increase as the acyl-chain length is decreased.

Biophysical Phenomena↗
PubMed2000

Electronic transmission of digital echocardiographic studies: effects of MPEG compression.

The acquisition, storage and retrieval of digital echocardiographic studies greatly facilitates image review and quantitation and permits the transmission of studies electronically. However, the considerable size of digital echocardiographic data files makes transmission over existing networks slow and impractical. Reduction in the size of these data files can be accomplished with digital image compression. We sought to evaluate the effects of MPEG-1 compression on the transfer time of digital echocardiographic studies over currently available network connections. Ninety consecutive routine clinical echocardiographic studies were randomly compressed at one of three compression ratios 60:1, 80:1, or 120:1 and sent to a receiving terminal using simulated transmission rates. Compression of digital echocardiographic studies at these ratios which, have been shown to maintain diagnostic image quality, reduced the size of digital echocardiographic studies to less than 1% of their original sizes which allowed transmission of echocardiographic studies over networks using 3ISDN or T1 lines with minimal waiting time.

Echocardiography↗