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At least 1,207 records · Page 67Linked to original sources
PubMed2002

S-matrix analysis of coincident measurement of two-electron energy distribution for double ionization of He in an intense laser field.

Analyses of two mechanisms of double ionization of He in an intense femtosecond laser pulse are made within the S-matrix theory. Their contributions are compared with each other and with the recent data of coincidence measurements for two-electron energy distributions. It is found that the correlated energy-sharing mechanism reproduces the data remarkably well and also confirms the so-called "excessive production" of hot electrons in the process. In contrast, the shakeoff mechanism is found to fail completely to account for either the strength or the trend of the data and is therefore ruled out.

Journal Article↗
PubMed1994

A test of the Markovian model of DNA evolution.

The Markov model of molecular evolution has recently received a significant amount of interest because its statistical nature allows for the testing of a number of evolutionary hypotheses. Here we propose a test which assesses whether data from two species sharing a common ancestor will fit a general Markovian model. We illustrate the test with two examples of data which appear at first glance not to fit a Markov model.

Animals↗
PubMed2000

Effects of stratification in the analysis of affected-sib-pair data: benefits and costs.

The benefits and costs of stratification of affected-sib-pair (ASP) data were examined in three situations: (1) when there is no difference in identity-by-descent (IBD) allele sharing between stratified and unstratified ASP data sets; (2) when there is an increase in IBD allele sharing in one of the stratified groups; and (3) when the data are stratified on the basis of IBD allele-sharing status at one locus, and the stratified ASPs are then analyzed for linkage at a second locus. When there is no difference in IBD sharing between strata, a penalty is always paid for stratifying the data. The loss of power to detect linkage in the stratified ASP data sets is the result of multiple testing and the smaller sample size within individual strata. In the case in which etiologic heterogeneity (i.e., severity of phenotype, age at onset) represents genetic heterogeneity, the power to detect linkage can be increased by stratifying the ASP data. This benefit is obtained when there is sufficient IBD allele sharing and sample sizes. Once linkage has been established for a given locus, data can be stratified on the basis of IBD status at this locus and can be tested for linkage at a second locus. When the relative risk is in the vicinity of 1, the power to detect linkage at the second locus is always greater for the unstratified ASP data set. Even for values of the relative risk that diverge sufficiently from 1, with adequate sample sizes and IBD allele sharing, the benefits of stratifying ASP data are minimal.

Age of Onset↗
PubMed1991

Conformational and structural characteristics of peptides binding to HLA-DR molecules.

A fundamental characteristic of MHC class I and class II proteins is their unusual capacity to form stable complexes with a wide spectrum of peptide ligands. In this study, sets of peptide analogues containing long chain-biotinylated lysine individually substituted for each amino acid in the sequence have been used to explore the structural requirements for the formation of peptide-MHC class II protein complexes. Based on the ability of the analogs to bind both the MHC protein and fluorescent streptavidin, receptor contact residues were identified and from their spacing the conformation of the bound peptides could be inferred. Six separate peptides were studied; three defined by HLA-DR1Dw1-restricted T cells, and three identified by T cells restricted through alleles other than HLA-DR1Dw1. The similar patterns of fluorescent signals observed when the former three peptides were studied indicated that they shared conformational features when bound to HLA-DR1Dw1. In contrast when the latter three peptides were examined, the data indicated that they shared some but not all of the conformational features characteristic of the peptides known to elicit HLA-DR1Dw1-restricted T cells. When the peptide sequences were aligned based on the critical contact residues, two positions of structural homology were apparent. In each sequence, an amino acid with a bulky hydrophobic side chain could be identified separated by four residues from a small amino acid. These minimal structural requirements were consistent with recent experiments demonstrating that only a small number of side chains in the peptide were necessary for binding to the MHC protein.

Amino Acid Sequence↗
PubMed1997

Obstacles encountered in application of the Centers for Disease Control and Prevention guidelines for control of tuberculosis in a large dental center.

BACKGROUND: The Centers for Disease Control and Prevention (CDC) and the Occupational Safety and Health Administration have designated five categories of workplaces as carrying higher than normal risk for exposure to tuberculosis (TB); "health care facilities" is one of these categories. To assist all health care facilities in developing an appropriate and effective control plan, the CDC has listed various components to be included in the overall plan-however, the components needed cannot be determined until the level of risk has been determined. The published criteria for risk assessment are more appropriately applicable to a hospital-based facility. In complying with CDC's guidelines and adopting the recommended components of the TB control program at a large, educational, ambulatory care dental facility, several obstacles were identified. METHODS: As part of the risk assessment for TB transmission and to determine the significance of purified protein derivative of tuberculin (PPD) skin-test conversions observed among the student and employee populations, we implemented a strategy that consisted of surveying all accredited dental schools in the country, performing a controlled PPD screening study involving predoctoral dental students in their junior year, and reviewing and evaluating all patient registration records for the same period. RESULTS: Forty-four percent of the dental schools contacted agreed to participate in the survey. Of these, 58% had no information available on student PPD conversion rates and 29% either had no data available yet or were unwilling to share their information. Three schools (12%) that had some data and were willing to share it reported PPD conversion rates for faculty, students, or staff of 1% to 2%. The student PPD study showed a 10.7% conversion rate, but the registration record reviews showed no convincing evidence of patients with active TB having been registered at the dental school for the period of the student PPD study. CONCLUSION: Development of a TB control program relies heavily on assessment of risk within a health care facility. The sporadic reports of PPD conversion rates among dental care workers are not adequate to determine the magnitude of exposure to TB in educational dental settings. Further studies are necessary to establish the true risk and to assist dental care facilities in developing TB control programs.

Centers for Disease Control and Prevention, U.S.↗
PubMed2006

Rimes are not necessarily favored by prereaders: evidence from meta- and epilinguistic phonological tasks.

This article explores young children's facility in phonological awareness tasks requiring either the detection or the articulation of head, coda, onset, and rime subsyllabic units shared in word pairs. Data are reported from 70 nonreading children and 21 precocious readers attending preschools. Prereading children were able to articulate shared heads, codas, and onsets, although rimes rarely were articulated. Precocious readers were able to articulate shared rimes, but articulation performance was still most accurate for onsets and codas. Rimes and heads were equally accessible in the detection task and were identified more often than onsets and codas (nonreaders) and codas (readers). It is concluded that the articulation advantage for nonrime units cannot simply reflect early reading instruction. This disjoint pattern of phonological awareness in detection and production tasks does not support Goswami's phonological status hypothesis. Results may instead reflect quite distinct influences on epilinguistic and metalinguistic phonological development.

Analysis of Variance↗
PubMed2002

Allele sharing and allelic association I: sib pair tests with increased power.

Affected sib pair data contain information about allele sharing and allelic association. Either of these features can point to the presence of a risk-related gene. This study introduces the elliptical sib pair test, a generalization of traditional sib pair tests. The proposed test can be implemented using any of three strategies, the choice of which depends on the anticipated combination of sharing and association. The elliptical sib pair test can achieve substantial gains in power relative to traditional tests for likely alternative hypotheses at little or no cost for other alternatives. The proposed test is valid under most models of genetic risk, disease etiology, and genotype-haplotype distributions. This study also provides new insight into the trade-off between tests of allelic association and tests of allele sharing.

Alleles↗
PubMed2004

Pediatric pharmacokinetic data: implications for environmental risk assessment for children.

Pharmacology and toxicology share a common interest in pharmacokinetic data, especially as it is available in pediatric populations. These data have been critical to the clinical pharmacologist for many years in designing age-specific dosing regimens. Now they are being used increasingly by toxicologists to understand the ontogeny of physiologic parameters that may affect the metabolism and clearance of environmental toxicants. This article reviews a wide range of physiologic and metabolic factors that are present in utero and in early postnatal life and that can affect the internal dose of an absorbed chemical and its metabolites. It also presents a child/adult pharmacokinetic database that includes data for 45 therapeutic drugs organized into specific children's age groupings and clearance pathways. Analysis of these data suggests that substantial child/adult differences in metabolism and clearance are likely for a variety of drugs and environmental chemicals in the early postnatal period. These results are also relevant to in utero exposures, where metabolic systems are even more immature, but exposures are greatly modified by the maternal system and placental metabolism. The implications of these child/adult differences for assessing children's risks from environmental toxicants is discussed with special focus on physiologically based pharmacokinetic modeling strategies that could simulate children's abilities to metabolize and eliminate chemicals at various developmental stages.

Adolescent↗
PubMed1997

Database challenges and solutions in neuroscientific applications.

In the scientific community, the quality and progress of various endeavors depend in part on the ability of researchers to share and exchange large quantities of heterogeneous data with one another efficiently. This requires controlled sharing and exchange of information among autonomous, distributed, and heterogeneous databases. In this paper, we focus on a neuroscience application, Neuroanatomical Rat Brain Viewer (NeuART Viewer) to demonstrate alternative database concepts that allow neuroscientists to manage and exchange data. Requirements for the NeuART application, in combination with an underlying network-aware database, are described at a conceptual level. Emphasis is placed on functionality from the user's perspective and on requirements that the database must fulfill. The most important functionality required by neuroscientists is the ability to construct brain models using information from different repositories. To accomplish such a task, users need to browse remote and local sources and summaries of data and capture relevant information to be used in building and extending the brain models. Other functionalities are also required, including posing queries related to brain models, augmenting and customizing brain models, and sharing brain models in a collaborative environment. An extensible object-oriented data model is presented to capture the many data types expected in this application. After presenting conceptual level design issues, we describe several known database solutions that support these requirements and discuss requirements that demand further research. Data integration for heterogeneous databases is discussed in terms of reducing or eliminating semantic heterogeneity when translations are made from one system to another. Performance enhancement mechanisms such as materialized views and spatial indexing for three-dimensional objects are explained and evaluated in the context of browsing, incorporating, and sharing. Policies for providing the system with fault tolerance and avoiding possible intellectual property abuses are presented. Finally, two existing systems are evaluated and compared using the identified requirements.

Animals↗
PubMed2006

Surgical site infection surveillance: analysis of adherence to recommendations for routine infection control practices.

OBJECTIVE: To evaluate the application of surgical site infection control procedures in general surgery departments in hospitals in the Piemonte region of Italy. DESIGN: The descriptive study entailed 1 week of observation in the general surgery departments and 1 week of observation in the operating rooms of 49 hospitals in Piemonte; the survey was conducted in 2003. METHODS: Data collection forms were designed to record information about presurgical patient preparation (form 1) and infection control practices routinely used by surgical teams (form 2). RESULTS: A total of 856 patients were observed; 88% of operations were surgical wound class I or II; 70.6% of patients had hair removed, 28.8% showered the day before the operation; antimicrobial prophylaxis was administered in 63.3% of cases (68.4% on induction of anesthesia and 26% on the day of the operation) and was continued into the postoperative period in 43% of cases. A total of 799 operations were observed; the mean number of healthcare personnel in the operating room was 6; doors were opened an average of 12 times during an operation; 88% of the surgical team members wore a cap/hood and mask correctly; 25% of surgeons and 41% of instrument nurses wore an eye shield; preoperative hand and forearm scrubbing technique was correct in 78% of cases (surgeons, 74.6%; instrument nurses, 86.6%; and anesthesiologists, 73%). CONCLUSIONS: A comparison between the survey data and the international recommendations for SSI prevention highlighted practices that could be improved with corrective interventions. The study provided an opportunity for sharing feedback on appropriate data with healthcare personnel and was an effective instrument to audit infection control practices.

Data Collection↗
PubMed2005

Midkine, a newly discovered regulator of the renin-angiotensin pathway in mouse aorta: significance of the pleiotrophin/midkine developmental gene family in angiotensin II signaling.

We previously demonstrated that pleiotrophin (PTN the protein, Ptn the gene) highly regulates the levels of expression of the genes encoding the proteins of the renin-angiotensin pathway in mouse aorta. We now demonstrate that the levels of expression of these same genes are significantly regulated in mouse aorta by the PTN family member midkine (MK the protein, Mk the gene); a 3-fold increase in expression of renin, an 82-fold increase in angiotensinogen, a 6-fold decrease in the angiotensin converting enzyme, and a 6.5-fold increase in the angiotensin II type 1 and a 9-fold increase in the angiotensin II type 2 receptor mRNAs were found in Mk-/- mouse aorta in comparison with the wild type (WT, +/+). The results in Mk-/- mice are remarkably similar to those previously reported in Ptn-/- mouse aorta, with the single exception of that the levels of the angiotensinogen gene expression in Ptn-/- mice are equal to those in WT+/+ mouse aorta, and thus, in contrast to Mk gene expression unaffected by levels of Ptn gene expression. The data indicate that MK and PTN share striking but not complete functional redundancy. These data support potentially high levels importance of MK and the MK/PTN developmental gene family in downstream signals initiated by angiotensin II either in development or in the many pathological conditions in which MK expression levels are increased, such as atherosclerosis and many human neoplasms that acquire constitutive endogenous Mk gene expression by mutation during tumor progression and potentially provide a target through the renin-angiotensin pathway to treat advanced malignancies.

Angiotensin II↗
PubMed2002

Lack of therapeutic interchangeability of HMG-CoA reductase inhibitors.

OBJECTIVE: To review relevant literature and provide an opinion on the class effect of hydroxymethylglutaryl coenzyme A reductase inhibitors (statins). DATA SOURCES: Primary and review articles were identified by MEDLINE search (1990-July 2002). STUDY SELECTION AND DATA EXTRACTION: Editorials, studies, and review articles related to the class effect or therapeutic interchangeability of statins were reviewed. Also included was information that is relevant to this topic. DATA SYNTHESIS: Although statins share common main actions, they may have clinically important differences in terms of efficacy and safety. At fixed or allowable dosages, rosuvastatin, atorvastatin, and simvastatin produced greater low-density lipoprotein cholesterol-lowering effects compared with other statins. Some statins have shown reduction in either cardiovascular and/or total mortality. Statins also differ in their structure, pharmacokinetics, potency, and rate of metabolism, any or all of which may have clinical significance. Although inconclusive, subtle differences in nonlipid effects of some statins may have contributed to positive benefits observed in clinical studies. As a result of drug-related deaths, cerivastatin was withdrawn voluntarily from the market, which may raise the question whether there is therapeutic interchangeability (due to class effect) among statins. CONCLUSIONS: Despite the competition for market share and strategies attempting to identify differences in therapeutic value, few head-to-head comparisons between statins have been performed. The limited, available data suggest that statins are not therapeutically interchangeable.

Drug Interactions↗
PubMed2001

Psychological mechanisms in hyperactivity: II. The role of genetic factors.

The main aim of this study was to combine two research approaches to hyperactivity: the behaviour genetic approach and the testing of psychological theories of hyperactivity. For a sample of 268 twin pairs aged 7-11 years we obtained ratings on the Conners' scales from both teachers (CTRS-28) and parents (CPRS-48). Forty-six hyperactive twin pairs (pairs in which at least one twin was pervasively hyperactive) and 47 control twin pairs were assessed on a psychological test battery. Confirming findings from previous twin studies, a substantial proportion of the variance in hyperactivity considered as a dimension was due to genetic effects. There was significant evidence of genetic effects also on extreme hyperactivity, although the present group heritability estimates were somewhat lower than those reported in most previous studies. We investigated the possibility that the psychological mechanisms we reported to be associated with hyperactivity (Kuntsi, Oosterlaan, & Stevenson, 2001) share common genetic factors with hyperactive behaviour. The data produced significant evidence of such shared genetic effects only on hyperactivity and the variability of reaction times. Given that the high variability in speed of responding would indicate a state-regulation problem, this is the psychological mechanism that could possibly be the "link" between genetic effects and hyperactive behaviour.

Attention Deficit Disorder with Hyperactivity↗
PubMed1994

Analysis, requirements and development of a collaborative social and medical services data model.

In any medical and social service setting, patient data must be readily shared among multiple providers for delivery of expeditious, quality care. This paper describes the development and implementation of a generalized social and medical services data model for an ambulatory population. The model, part of the Collaborative Social and Medical Services System Project, is based on the data needs of the Baylor College of Medicine Teen Health Clinics and follows the guidelines of the ANSI HISPP/MSDS JWG for a Common Data Model. Design details were determined by informal staff interviews, operational observations, and examination of clinic guidelines and forms. The social and medical services data model is implemented using object-oriented data modeling techniques and will be implemented in C++ using an Object-Oriented Database Management System.

Adolescent↗
PubMed2005

Understanding the covariation among childhood externalizing symptoms: genetic and environmental influences on conduct disorder, attention deficit hyperactivity disorder, and oppositional defiant disorder symptoms.

Conduct disorder (CD), attention deficit hyperactivity disorder (ADHD), and oppositional defiant disorder (ODD) are common childhood externalizing disorders that frequently co-occur. However, the causes of their comorbidity are not well understood. To address that question, we analyzed data from >600 Finnish twin pairs, who completed standardized interviews at age 14. Behavior genetic methods were used to examine how genetic/environmental factors contribute to each disorder's symptoms and to their covariation. We found significant genetic effects on each disorder with only modest evidence of shared environmental influences. Our data suggest the comorbidity among CD, ADHD, and ODD is primarily explained by shared genetic influences; however, each disorder was also under unique genetic influence, supporting the distinction of each disorder.

Adolescent↗
PubMed2005

Research protocol: EB-GIS4HEALTH UK - foundation evidence base and ontology-based framework of modular, reusable models for UK/NHS health and healthcare GIS applications.

EB-GIS4HEALTH UK aims at building a UK-oriented foundation evidence base and modular conceptual models for GIS applications and programmes in health and healthcare to improve the currently poor GIS state of affairs within the NHS; help the NHS understand and harness the importance of spatial information in the health sector in order to better respond to national health plans, priorities, and requirements; and also foster the much-needed NHS-academia GIS collaboration. The project will focus on diabetes and dental care, which together account for about 11% of the annual NHS budget, and are thus important topics where GIS can help optimising resource utilisation and outcomes. Virtual e-focus groups will ensure all UK/NHS health GIS stakeholders are represented. The models will be built using Protege ontology editor http://protege.stanford.edu/ based on the best evidence pooled in the project's evidence base (from critical literature reviews and e-focus groups). We will disseminate our evidence base, GIS models, and documentation through the project's Web server. The models will be human-readable in different ways to inform NHS GIS implementers, and it will be possible to also use them to generate the necessary template databases (and even to develop "intelligent" health GIS solutions using software agents) for running the modelled applications. Our products and experience in this project will be transferable to address other national health topics based on the same principles. Our ultimate goal is to provide the NHS with practical, vendor-neutral, modular workflow models, and ready-to-use, evidence-based frameworks for developing successful GIS business plans and implementing GIS to address various health issues. NHS organisations adopting such frameworks will achieve a common understanding of spatial data and processes, which will enable them to efficiently and effectively share, compare, and integrate their data silos and results for more informed planning and better outcomes.

Journal Article↗