Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Information Distribution”

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
PubMed2005

In vivo prostate magnetic resonance spectroscopic imaging using two-dimensional J-resolved PRESS at 3 T.

In vivo magnetic resonance spectroscopic imaging of the prostate using single-voxel and multivoxel two-dimensional (2D) J-resolved sequences is investigated at a main magnetic field strength of 3 T. Citrate, an important metabolite often used to aid the detection of prostate cancer in magnetic resonance spectroscopic exams, can be reliably detected along with the other metabolites using this method. We show simulations and measurements of the citrate metabolite using 2D J-resolved spectroscopy to characterize the spectral pattern. Furthermore, using spiral readout gradients, the single-voxel 2D J-resolved method is extended to provide the spatial distribution information as well all within a reasonable scan time (17 min). Phantom and in vivo data are presented to illustrate the multivoxel 2D J-resolved spiral chemical shift imaging sequence.

Choline↗
PubMed2006

Exploring series of multivariate censored temporal data through fuzzy coding and correspondence analysis.

We present an exploratory analysis methodology for a multiple series of multivariate temporal data subject to censoring, and thus requiring the introduction of a coding technique: fuzzy coding preserving a large amount of the distributional information is fully adapted. Correspondence analysis is performed on the array produced by fuzzy coding. Projections of mean paths on factorial mappings, according to subgroup characteristics, highlight the behaviour of the underlying process. This approach is illustrated with an application to a randomized controlled clinical trial designed for comparing non-diabetic chronic renal failure treatments. Our methodology has resulted in the identification of a difference between the treatments with an interpretation of the effects in subgroups of patients not obtainable with traditional survival methodology; it also provides some valuable insights for designing further studies on treatment of renal impairment.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

Bootstrapping Word Boundaries: A Bottom-up Corpus-Based Approach to Speech Segmentation

Speech is continuous, and isolating meaningful chunks for lexical access is a nontrivial problem. In this paper we use neural network models and more conventional statistics to study the use of sequential phonological probabilities in the segmentation of an idealized phonological transcription of the London-Lund Corpus; these speech data are representative of genuine conversational English. We demonstrate, first, that the distribution of phonetic segments in English is an important cue to segmentation, and, second, that the distributional information is such that it might allow the infant, beginning with only a sensitivity to the statistics of subsegmental primitives, to bootstrap into a series of increasingly sophisticated segmentation competences, ending with an adult competence. We discuss the relation between the behavior of the models and existing psycholinguistic studies of speech segmentation. In particular, we confirm the utility of the Metrical Segmentation Strategy (Cutler & Norris, 1988) and demonstrate a route by which this utility might be recognized by the infant, without requiring the prior specification of categories like "syllable" or "strong syllable."

Journal Article↗
PubMed1999

Gene expression profiling, genetic networks, and cellular states: an integrating concept for tumorigenesis and drug discovery.

Genome-wide expression monitoring, a novel tool of functional genomics, is currently used mainly to identify groups of coregulated genes and to discover genes expressed differentially in distinct situations that could serve as drug targets. This descriptive approach. however, fails to extract "distributed" information embedded in the genomic regulatory network and manifested in distinct gene activation profiles. A model based on the formalism of boolean genetic networks in which cellular states are represented by attractors in a discrete dynamic system can serve as a conceptual framework for an integrative interpretation of gene expression profiles. Such a global (genome-wide) view of "gene function" in the regulation of the dynamic relationship between proliferation, differentiation, and apoptosis can provide new insights into cellular homeostasis and the origins of neoplasia. Implications for a rational approach to the identification of new drug targets for cancer treatment are discussed.

Biotechnology↗
PubMed2001

Identifying influences on model uncertainty: an application using a forest carbon budget model.

Uncertainty is an important consideration for both developers and users of environmental simulation models. Establishing quantitative estimates of uncertainty for deterministic models can be difficult when the underlying bases for such information are scarce. We demonstrate an application of probabilistic uncertainty analysis that provides for refinements in quantifying input uncertainty even with little information. Uncertainties in forest carbon budget projections were examined with Monte Carlo analyses of the model FORCARB. We identified model sensitivity to range, shape, and covariability among model probability density functions, even under conditions of limited initial information. Distributional forms of probabilities were not as important as covariability or ranges of values. Covariability among FORCARB model parameters emerged as a very influential component of uncertainty, especially for estimates of average annual carbon flux.

Carbon↗
PubMed2007

[Validity of a web-based color vision test for screening examinations of color vision].

BACKGROUND: With standardized examination conditions, a web-based color vision test using pseudoisochromatic color plates can deliver test results comparable to those yielded by conventional color vision tests. The aim of the study is to analyze to what extent a web-based color vision test can be used as a screening test on the internet after visual monitor calibration. METHODS: A German-language web-based color vision test with 25 pseudoisochromatic color plates based on the color plates of Velhagen and Broschmann and of Ishihara was developed, which can be seen at http://www.farbsehtest.de. Volunteers were recruited by means of specific information distributed on the internet, in various print media, and on the radio. RESULTS: Over a period of 12 months, 2,126 of the initial volunteers [541 women and 1,588 men; mean age 34.27 (+/-14.1) years] with a valid test result for 25 color plates performed the web-based color vision test, 1,700 (506 women and 1,194 men) of whom passed it. Of the 426 volunteers who did not pass the test, 32 were women and 394, men. Counter-testing was performed on 101 volunteers (34 women and 67 men) with a mean age of 36.74 (+/-11.6) years. CONCLUSIONS: The results recorded in the patients who underwent counter-testing suggest that, if handled correctly, the web-based color vision test can be used as a color vision screening test on the internet.

Adolescent↗
PubMed1995

A representational analysis of numeration systems.

This article explores the representational structures of numeration systems and the cognitive factors of the representational effect in numerical tasks, focusing on external representations and their interactions with internal representations. Numeration systems are analyzed at four levels: dimensionally, dimensional representations, bases, and symbol representations. The representational properties at these levels affect the processes of numerical tasks in different ways and are responsible for different aspects of the representational effect. This hierarchical structure is also a cognitive taxonomy that can classify nearly all numeration systems that have been invented across the world. Multiplication is selected as an example to demonstrate that complex numerical tasks require the interwoven processing of information distributed across internal and external representations. Finally, a model of distributed numerical cognition is proposed and an answer to the question of why Arabic numerals are so special is provided.

Cognition↗
PubMed1988

Study and performance evaluation of statistical methods in image processing.

Two statistical image processing formalisms involving the entropy concept and Bayesian analysis are studied. Iterative imaging algorithms of the formalisms are formulated by employing, for the purpose of performance evaluation and easy implementation, the steepest descent method for the solution of entropy concept and the expectation maximization technique for the solution of Bayesian analysis. Quantitative evaluation and comparison of the convergence performance of the iterative algorithms on computer generated ideal and experimental radioisotope phantom imaging noisy data are given. The study concludes that the entropy algorithm can converge relatively fast, but it is very sensitive to noise in measured data due to the ill-posed nature of inverse problems and its lack of ability to consider the statistics of data fluctuation; while the Bayesian algorithm converges monotonically even with noisy data and has the advantage of considering both the a priori source distribution information and the statistical fluctuation of measured data.

Algorithms↗
PubMed1995

Compliance and oral contraceptives: a review.

Compliance difficulties are more common among oral contraceptive (OC) users than generally appreciated by clinicians, in part because unintended pregnancy is a relatively infrequent consequence and in part because more common manifestations such as spotting and bleeding may not be recognized as resulting from poor compliance. While improving compliance is a shared responsibility of patients, clinicians, and manufacturers, the clinician is the focal point for these efforts. Counseling must be individualized, which requires knowledge of factors that predict compliance and an understanding of the patient's decision-making process as it relates to medications. Most OC compliance research has focused on adolescents, where predictors of poor compliance include multiple sex partners, low evaluation of personal health, degree of concern about pregnancy, and previous abortion. Good compliance has been linked with patient satisfaction with the clinician, the absence of certain side effects, establishing a regular daily routine to take OCs, and reading information distributed with OC packaging.

Contraceptives, Oral↗
PubMed1977

Tritium nuclear magnetic resonance spectroscopy. Distribution patterns and nuclear Overhauser enhancements in some tritiated steroids.

The distribution of tritium atoms in some labeled steroids has been determined by tritium nuclear magnetic resonance spectroscopy. In addition, the distribution of molecular types (mono vs. polytritiated) and nuclear Overhauser enhancements have been determined. As near maximal NOE's were observed, quantitative distribution information was derived from NOE suppressed spectra.

Estradiol↗
PubMed1991

Spatial regulation of photosynthetic development in C4 plants.

Leaf development in C4 plants requires the morphological and functional differentiation of two photosynthetic cell types (bundle sheath and mesophyll). Photosynthetic reactions are split between bundle sheath and mesophyll cells, with each cell type accumulating a specific complement of photosynthetic enzymes. Current evidence suggests that in order to activate this cell-specific expression of photosynthetic genes, bundle sheath and mesophyll cells must interpret positional information distributed locally around each vein.

Carbon Dioxide↗
PubMed1993

Advances in 3-dimensional radiation treatment planning systems: room-view display with real time interactivity.

PURPOSE: We describe our 3-dimensional (3-D) radiation treatment planning system for external photon and electron beam 3-D treatment planning which provides high performance computational speed and a real-time display which we have named "room-view" in which the simulated target volumes, critical structures, skin surfaces, radiation beams and/or dose surfaces can be viewed on the display monitor from any arbitrary viewing position. METHODS AND MATERIALS: We have implemented the 3-D planning system on a graphics superworkstation with parallel processing. Patient's anatomical features are extracted from contiguous computed tomography scan images and are displayed as wireloops or solid surfaces. Radiation beams are displayed as a set of diverging rays plus the polygons formed by the intersection of these rays with planes perpendicular to the beam axis. Controls are provided for each treatment machine motion function. Photon dose calculations are performed using an effective pathlength algorithm modified to accommodate 3-D off-center ratios. Electron dose calculations are performed using a 3-D pencil beam model. RESULTS: Dose distribution information can be displayed as 3-D dose surfaces, dose-volume histograms, or as isodoses superimposed on 2-D gray scale images of the patient's anatomy. Tumor-control-probabilities, normal-tissue-complication probabilities and a figure-of-merit score function are generated to aid in plan evaluation. A split-screen display provides a beam's-eye-view for beam positioning and design of patient shielding block apertures and a concurrent "room-view" display of the patient and beam icon for viewing multiple beam set-ups, beam positioning, and plan evaluation. Both views are simultaneously interactive. CONCLUSION: The development of an interactive 3-D radiation treatment planning system with a real-time room-view display has been accomplished. The concurrent real-time beam's-eye-view and room-view display significantly improves the efficacy of the 3-D planning process.

Computer Systems↗
PubMed1989

Improving medical communication with facsimile (fax) transmission.

Facsimile machines (fax) used intensely in business, send copies of documents from one location to another. The medical potential for fax has not been fully explored. A general background in fax and the potential uses for fax between hospitals and within hospitals are described. Fax permits small hospitals to share the resources of larger hospitals and permits a large hospital to share resources more efficiently among its departments. The cost of a fax unit is small compared with the amount of work and time it can save. Clinics and private physicians may also find fax units cost effective. Fax boards, which provide fax capability to personal computers, are also described. The use of fax could streamline the process of patient transfer, telephone patient consultation, medical records retrieval, ECG interpretation, central information distribution, retrieval of medical literature, inpatient pharmacy orders, etc.

Copying Processes↗
PubMed2006

Comparison of quantitative computed tomography-based measures in predicting vertebral compressive strength.

Patient-specific measures derived from quantitative computed tomography (QCT) scans are currently being developed as a clinical tool for vertebral strength prediction. QCT-based measurement techniques vary greatly in structural complexity and generally fall into one of three categories: (1) bone mineral density (BMD), (2) "mechanics of solids" (MOS) models, such as minimum axial rigidity (the product of axial stiffness and vertebral height), or (3) three-dimensional finite element (FE) models. There is no clear consensus as to the relative performance of these measures due to differences in experimental protocols, sample sizes and demographics, and outcome metrics. The goal of this study was to directly compare the performance of QCT-based assessment techniques of varying degrees of structural sophistication in predicting experimental vertebral compressive strength. Eighty-one human thoracic vertebrae (T6-T10) from 44 donors cadavers (F=32, M=12; 85+/-8 years old, max=97 years old, min=54 years old) were QCT scanned and destructively tested in uniaxial compression. The QCT scans were processed to generate FE models and various BMD and MOS measures, including trabecular bone mineral density (tBMD), integral bone mineral density (iBMD), and axial rigidity. Bone mineral density was weakly to moderately predictive of compressive strength (R(2)=0.16 and 0.62 for tBMD and iBMD, respectively). In vitro vertebral strength was strongly correlated with both axial rigidity (R(2)=0.81) and FE strength measurements (R(2)=0.80), and the predictive capabilities of these two metrics were statistically equivalent (p>0.05 for differences between FE and axial rigidity). The results of this study indicate that non-invasive predictive measures of vertebral strength should include some level of structural sophistication, specifically, gross geometric and material property distribution information. For uniaxial compression of isolated vertebrae, which is the current biomechanical testing paradigm for new non-invasive strength assessment techniques, QCT-based FE and axial rigidity measures are equivalent predictors of experimental strength. However, before abandoning the FE method in favor of more simplistic techniques, future work should investigate the performance of the FE method versus MOS measures for more physiologically representative loading conditions, e.g., anterior bending or in situ loading with intervertebral discs intact.

Aged↗
PubMed2005

Laterotopic representation of left-right information onto the dorso-ventral axis of a zebrafish midbrain target nucleus.

The habenulae are part of an evolutionarily highly conserved limbic-system conduction pathway that connects telencephalic nuclei to the interpeduncular nucleus (IPN) of the midbrain . In zebrafish, unilateral activation of the Nodal signaling pathway in the left brain specifies the laterality of the asymmetry of habenular size . We show "laterotopy" in the habenulo-interpeduncular projection in zebrafish, i.e., the stereotypic, topographic projection of left-sided habenular axons to the dorsal region of the IPN and of right-sided habenular axons to the ventral IPN. This asymmetric projection is accounted for by a prominent left-right (LR) difference in the size ratio of the medial and lateral habenular sub-nuclei, each of which specifically projects either to ventral or dorsal IPN targets. Asymmetric Nodal signaling directs the orientation of laterotopy but is dispensable for the establishment of laterotopy itself. Our results reveal a mechanism by which information distributed between left and right sides of the brain can be transmitted bilaterally without loss of LR coding, which may play a crucial role in functional lateralization of the vertebrate brain .

Animals↗
PubMed2006

Current challenges and developments in GC-MS based metabolite profiling technology.

Gas chromatography-mass spectrometry (GC-MS) based metabolite profiling of biological samples is one of the key technologies for metabolite profiling and substantially contributes to our understanding of the metabolome. While the technology is in increasing use it is challenged with novel demands. Increasing the number of metabolite identifications within existing profiling platforms is prerequisite for a substantially improved scope of profiling studies. Clear, reproducible strategies for metabolite identification and exchange of identifications between laboratories will facilitate further developments, such as the extension of profiling technologies towards metabolic signals and other technically demanding trace compound analysis. Using GC-MS technology as an example the concept of mass spectral tags (MSTs) is presented. A mass spectral tag is defined by the chemometric properties, molecular mass to charge ratio, chromatographic retention index and an induced mass fragmentation pattern such as an electron impact mass spectrum (EI-MS) or secondary fragmentation (MS(2)). These properties if properly documented will allow identification of hitherto non-identified MSTs by standard addition experiments of authenticated reference substances even years after first MST description. Strategies are discussed for MST identification and enhanced MST characterization utilizing experimental schemes such as in vivo stable isotope labelling of whole organisms and open access information distribution, for example the GMG internet platform initiated in 2004 (GMD, http://www.csbdb.mpimp-golm.mpg.de/gmd.html).

Carbohydrate Metabolism↗
PubMed2006

Flashing liquid jets and two-phase droplet dispersion I. Experiments for derivation of droplet atomisation correlations.

The large-scale release of a liquid contained at upstream conditions above its local atmospheric boiling point is a scenario often given consideration in process industry risk analysis. Current-hazard quantification software often employs simplistic equilibrium two-phase approaches. Scaled water experiments have been carried out measuring droplet velocity and droplet size distributions for a range of exit orifice aspect ratios (L/d) and conditions representing low to high superheat. 2D Phase-Doppler Anemometry has been utilised to characterise droplet kinematics and spray quality. Droplet size correlations have been developed for non-flashing, the transition between non-flashing and flashing, and fully flashing jets. Using high-speed shadowography, transition between regimes is defined in terms of criteria identified in the external flow structure. An overview companion paper provides a wider overview of the problem and reports implementation of these correlations into consequence models and subsequent validation. The fluid utilised throughout is water, hence droplet correlations are developed in non-dimensional form to allow extrapolation to other fluids through similarity scaling, although verification of model performance for other fluids is required in future studies. Data is reduced via non-dimensionalisation in terms of the Weber number and Jakob number, essentially representing the fluid mechanics and thermodynamics of the system, respectively. A droplet-size distribution correlation has also been developed, conveniently presented as a volume undersize distribution based on the Rosin-Rammler distribution. Separate correlations are provided for sub-cooled mechanical break-up and fully flashing jets. This form of correlation facilitates rapid estimates of likely mass rainout quantities, as well as full distribution information for more rigorous two-phase thermodynamic modelling in the future.

Aerosol Propellants↗
PubMed2006

Health literacy in the field of infectious diseases: the paradigm of brucellosis.

OBJECTIVES: Treatment outcome for infectious diseases, including brucellosis, may be influenced by patient awareness of the disease itself, as well as by compounding socioeconomic factors. We attempted to evaluate parameters of patient awareness and disease perception in brucellosis and the ways they influence outcome. METHODS: We used a specifically developed questionnaire assessing various parameters of patient literacy on brucellosis in 70 patients with a new diagnosis of brucellosis. Patients were assessed by interviewing at the time of diagnosis and during follow-up. Awareness and perception of the disease, willingness for epidemiologic surveillance, mode of referral, treatment preferences, and adherence were evaluated. RESULTS: Although basic disease awareness is high, willingness to collaborate in epidemiologic surveillance is limited. Patient education may improve adherence to treatment and willingness to undergo surveillance, but may also result in many false referrals for relapse. Level of academic education does not influence the results. Convenience is the major factor when determining treatment preferences. CONCLUSION: Improving health literacy may result in improved treatment outcome and improved control of disease incidence. There is a need for constant evaluation of the quality and quantity of information distributed in order to reduce transmission of misinformation and occurrences of public anxiety.

Brucellosis↗