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 217 records · Page 12Linked to original sources
PubMed1991

The effect of mechanical deformation on the movement of water in foods.

This study has shown the importance of relating NMR spectroscopic information on the water in model food structures to the mechanical properties of those structures. Analysis of the NMR relaxation data can be used to examine the distribution of water domain sizes, and this has been related to the mechanical properties of the samples. A novel NMR probe-head has been designed, which allows both the NMR and the mechanical data to be simultaneously measured during compression of the sample. This probe-head allows compressive stress/strain data to be obtained directly from the NMR sample, allowing changes in the distribution of the water to be directly correlated to changes in mechanical properties.

Chemical Phenomena↗
PubMed1989

Recurrent deep venous thrombosis: limitations of US.

Compression ultrasound (US) has become widely used to diagnose acute deep venous thrombosis (DVT). To determine the appearance of veins with previous DVT, 60 legs (58 patients) in which DVT had been diagnosed 6-31 months earlier (mean, 15.1 months) were reexamined with compression US. At reevaluation there was no indication of acute DVT. Thirty-two extremities had an appearance consistent with clot at the time of this study; 28 demonstrated normal findings. Variables that correlated with findings at follow-up US included age, location of clot, number of previous clots, pain, and augmentation of flow at compression. These preliminary data indicate that compression US may not be reliable as a follow-up study in patients in whom postphlebotic syndrome develops after an acute episode of DVT.

Follow-Up Studies↗
PubMed1992

An efficient algorithm for MR image reconstruction and compression.

In magnetic resonance imaging (MRI), the original data are sampled in the spatial frequency domain. The sampled data thus constitute a set of discrete Fourier transform (DFT) coefficients. The image is usually reconstructed by taking inverse DFT. The image data may then be efficiently compressed using the discrete cosine transform (DCT). We present here a method of using DCT to treat the sampled data, which combines two procedures, image reconstruction and data compression. This method may be particularly useful in medical picture archiving and communication systems (PACS) where both image reconstruction and compression are important issues.

Algorithms↗
PubMed1995

A model for acute, chronic, and delayed graded compression of the dog cauda equina. Neurophysiologic and histologic changes induced by acute, graded compression.

STUDY DESIGN: The results of acute compression on nerve function and morphology were analyzed in a recently developed model for graded cauda equina compression in the dog. OBJECTIVES: The model was developed to better mimic the clinical situation of cauda equina compression in association with spinal canal stenosis. SUMMARY OF BACKGROUND DATA: The compression of the cauda equina has been induced by metal clips, plastic bands, constrictors, and inflatable balloons. No model has used the intact spinal canal and induced compression by increasing the pressure per se in the canal. METHODS: An inflatable balloon with a diameter exceeding the diameter of the spinal canal was placed under the lamina of the L7 vertebra in the dog. The balloon was inflated to various pressures, and muscle action potential area and nerve conduction velocity were monitored during 2 hours of compression and 1.5 hours of recovery. Nerve root specimens were processed for light microscopic examination. RESULTS: There was a progressive reduction of muscle action potential area and nerve conduction velocity that was proportional to the applied pressure. Histologic evaluation revealed no nerve fiber damage but a slight intraneural edema after compression at 200 mg Hg. CONCLUSIONS: The presented model may provide reproducible results regarding neurophysiologic and morphologic effects after acute, graded compression of the dog cauda equina. Two additional conclusions can be made from this study. First, the area measurement of the MAP is probably well suited for recordings and analyses of changes in muscle action potentials. Second, the specific onset rate of this study, in relation to previous studies, indicates that there is a threshold for the compression onset rate for inducing additional nerve injury located in the interval 0.1-0.8 seconds. The results from the present study provides important baseline data for the continued studies on chronic and intermittent compression with the compression model.

Action Potentials↗
PubMed1990

Enhancement and compression of digital chest radiographs.

The application of digital technologies to chest radiography holds the promise of routine application of image processing techniques to effect image enhancement. Because of their inherent spatial resolution, however, digital chest images impose severe constraints on data storage devices. Compression of these images will relax such constraints and facilitate image transmission on a digital network. We evaluated an algorithm for enhancing digital chest images that has allowed significant data compression while improving the diagnostic quality of the image. This algorithm is based on the photographic technique of unsharp masking. Image quality was measured with respect to the task of tumor detection and compression ratios as high as 2:1 were achieved. This compression can be supplemented by irreversible methods.

Algorithms↗
PubMed1976

[The nasopharynx in jaw compression--craniometric and rhinologic data].

113 patients-7 to 29 years old-of the orthodontic department of the School of Dentistry, University of Minnesota, were studied. 51 patients had a high SN-MP angle (a long face) and 62 a low SN-MP angle (a broad face). As compared to the broad-faced group the probands with a long face showed, on the average, a narrower palatal arch, a more posteriorly postitioned hard palate, a smaller nasopharynx (measured in the sagittal plane), and more frequent nasopharyngeal problems. According to our statistical evaluation, a narrower maxillary dental arch and clinical apparent adenoid hypertrophy do not appear to be connected to each other in a cause-and-effect relationship. They rather seem to be two independent symptoms found frequently, though not necessarily in combination with each other, in persons with a long face.

Adolescent↗
PubMed1992

Compression and reconstruction of MRI images using 2D DCT.

In magnetic resonance imaging (MRI), the original data are sampled in the spatial frequency domain. The sampled data thus constitute a set of discrete Fourier transform (DFT) coefficients. The image is usually reconstructed by taking inverse DFT. The image data may then be compressed using the discrete cosine transform (DCT). We present here a method of treating the data that combines two procedures, image reconstruction and data compression. This method may be particularly useful in medical picture archiving and communication systems (PACS) where both image reconstruction and compression are important issues.

Fourier Analysis↗
PubMed1987

On the use of statistics for representing the knowledge acquired from experts in a medical consulting system.

For making medical consulting systems, it is important and significant to select and devise the method for representing the knowledge acquired from professional experts. As quantities of data required for consultation are increasing according to the progress of medical science, we have to introduce some new kinds of statistics into a medical consultation system. From another point of view, since the process of diagnosis of experts is considered to be a kind of effective model for compressing (or condensing) data quantitatively and qualitatively, we discuss the use of statistics for representing the knowledge acquired from experts from the standpoint of data compression.

Adult↗
PubMed1996

Factors affecting performance of PACS.

We experimentally constructed a personal-computer-based Picture Archiving and Communication System (PACS) for color images of dermatology clinics. This system should especially satisfy such a demand as to be able to retrieve an image within a few seconds from the database residing in a remote server. Our two objectives in the experiment were: To examine how much time was consumed in each part of PACS while it does a series of jobs, from the requesting of an image to its display on the screen of the workstation of the user. The other objective was to see if a personal-computer-based PACS could satisfy our criteria. Total retrieving time, data reading time, data transporting time and image displaying time were measured. Total retrieving time can be divided into three procedures: Data reading time, data transporting time, image displaying time. Data reading time was about 0.6 second for reading an image with the size of 1 mega bytes (MB). Data reading time and the size of data were linearly correlated. Data transporting time was about 11 seconds for transporting an image with the size of 1 MB through EtherTalk, and 66 seconds through LocalTalk. Data transporting time and the size of the data were also linearly correlated. Data reading time and data transporting time was able to be reduced largely by compression technique. However, smaller data give other important effects to the network system besides reducing the time of data reading, data transporting and data displaying. Most Local Area using image Network (LAN) systems, such as EtherTalk, adopt Carrier Sense Multiple Access with Collision Detection (CSMA/CD) for the way of accessing to other computer. In CSMA/CD, transporting performance suddenly declines if the congestion of signal in a network gets beyond a critical level. This situation fatally impairs the performance of a network. We concluded that data compression plays an important role to improve the performances of PACS, especially those of a server and the network system. A personal-computer-based PACS with EtherTalk and an image compression/decompression hardware, e.g., CL550A chip, satisfies our criteria.

Dermatology↗
PubMed1986

Compression of nucleic acid and protein sequence data.

This paper describes the application of text compression methods to machine-readable files of nucleic acid and protein sequence data. Two main methods are used to reduce the storage requirements of such files, these being n-gram coding and run-length coding. A Pascal program combining both of these techniques resulted in a compression figure of 74.6% for the GenBank data-base and a program that used only n-gram coding gave a compression figure of 42.8% for the Protein Identification Resource database.

Algorithms↗
PubMedDate not supplied

Effect of the Harrington compression system on the correction of the rib hump in spinal instrumentation for idiopathic scoliosis.

To analyze the effect of the Harrington compression system on the rib hump in thoracic idiopathic scoliosis, intraoperative measurements were made on 21 cases during correction with the distraction system and after addition of the compression system. The data show that the compression system makes a major contribution to the correction of total rib deformity in over two-thirds of the patients, and the correction of the rib valley is much more significant than correction of the rib hump. Analysis of postoperative spine roentgenograms seems to indicate that the extent of the rib correction does not correlate with spine derotation as measured by the system of Nash and Moe. The improvement in rib correction achieved by addition of the compression system appears to result from changes centered about the costovertebral joints.

Adolescent↗
PubMed1994

Hydration and partial compressibility of biological compounds.

We review the results of compressibility studies on proteins, nucleic acids, and systematically altered low molecular weight compounds that model the constituents of these biopolymers. The model compound data allow one to define the compressibility properties of water surrounding charged, polar, and nonpolar groups. These results, in conjunction with compressibility data on proteins and nucleic acids, were used to define the properties of water that is perturbed by the presence of these biopolymers in aqueous solutions. Throughout this review, we emphasize the importance of compressibility data for characterizing the hydration properties of solutes (particularly, proteins, nucleic acids, and their constituents), while describing how such data can be interpreted to gain insight into role that hydration can play in modulating the stability of and recognition between biologically important compounds.

Animals↗
PubMed2026

RSHash: a fast and space-efficient hash table for k-mers.

SUMMARY: Large genomic data collections can be viewed as a continuous string of DNA characters. The essential operations for data structures indexing the k-mer content of such a string are lookup and locate. Lookup determines whether a query k-mer q exists in the string and locate returns all locations in the string where q is present. High-throughput DNA sequencing generates very many k-mer sets of size exceeding billions of characters. In such scenarios, memory consumption and query efficiency pose significant challenges to a data structure supporting the above mentioned queries. To address this problem, we describe a simple, compressed, static data structure for k-mers that answers lookup and can be extended for supporting locate. The general scheme follows the use of minimizers like the state-of-the art SSHash. However, instead of using minimum perfect hash functions our solution (RSHash for Rank-Select Hash) relies on bitvectors with rank and select support, a multiple layered minimizer scheme, and a clever buffering strategy. We can show that RSHash is on average 40% and in some cases up to two times faster than SSHash while having the same memory requirements. Indeed we can go as low as 8 bits per canonical 31-mer on a human dataset. AVAILABILITY: https://github.com/jonsmcode/rshash.

Sequence Analysis, DNA↗
PubMed1977

[Simplification of gamma-ray spectral data by using Fourier transform].

A method is proposed to represent gamma-ray response spectra by Fourier series for the purpose of compressing spectral data. The usefulness of the method was confirmed by applying it to a spectral library of a NaI detector. In the method, a response spectrum as a wave is described by superposition of sine (cosine) waves with low frequencies, whose coefficient parameters can be obtained by a Fast Fourier Transform program. The relation between the number of parameters and the fitting error is discussed, and as the result, it is shown that the number of parameters can be reduced to about a half. The merits and features are presented in practical application of the method to the analysis of gamma-ray spectra.

Fourier Analysis↗
PubMed1991

Effect of fitting adjustments on compressive strength of a new foil crown system.

The effect of die spacing and precementation internal adjustments on the compressive strength of a new ceramic foil crown system was examined in vitro. Twenty-four ceramic foil crowns were made for identical stylized master dies made of polycarbonate filled with 30 wt% carbon. One half of the stone working dies were coated with die spacer and the remaining were left untreated. A special foil used for these crowns was adapted to the working dies under 2500 psi loading. A sculpturing device was used to standardize the size and shape of the ceramic foil crowns. Only crowns made on dies coated with die spacer received precementation fitting adjustment. All crowns in the two groups were cemented with zinc phosphate cement and were subjected to compressive force until fracture occurred. Compressive strength data were analyzed and compared. Results showed that the use of die spacer and internal adjustments increased the compressive strength of the new ceramic foil crown.

Crowns↗