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At least 1,027 records · Page 57Linked to original sources
PubMed1999

Applicability of CATALYST in ecotoxicology, a new promising tool for 3D-QSAR: study of chlorophenols.

With the aim of applying recent quantitative structure-activity relationship (QSAR) descriptors coming from the pharmaceutical sciences to the modelization of ecotoxicity data, this work deals with the establishment of 3D-QSAR on chlorophenols by using for the first time in this field the recent CATALYST software. The training set has been intentionally chosen simply because of its homogeneous character and the abundance of reliable experimental values. Among 69 data sets collected in the literature on these chemicals, 9 were selected to have fulfilled CATALYST simulation conditions. The principle of CATALYST is briefly described. The different investigations have led to nine 3D-QSAR called "hypotheses," meeting the criteria of high statistical significance attested by costs and correlation coefficient values. The ecotoxicity values calculated from the 9 models established in this study. Analysis of the graphical representations of hypotheses led to hypotheses about the toxicity mechanisms. A comparison is finally made between the CATALYST models and those previously derived by other modeling methods.

Animals↗
PubMed1994

A dynamic model of reaction time in a short-term memory task.

In this article we hypothesized that the trial to trial variability in speed of access to recently presented information is deterministic in nature and that it reflects important properties of immediate memory. Application of analytic techniques emerging from the science of nonlinear dynamical systems to data obtained from the Sternberg (1966, 1970) short-term memory task corroborates the view. A simple nonlinear difference equation, consistent with fuzzy-trace theory (Brainerd & Reyna, 1992), was then proposed to describe the dynamics underlying reaction time (RT) on the Sternberg task. The model posits that RT is a function of the interaction of two control parameters: susceptibility to interference (SI) and episodic activation (EA). Evaluation of the model indicated an exceptionally good fit with the raw empirical observations. Age comparisons of the model parameters revealed that adults exhibited higher levels of SI and EA. Although the finding that adults exhibited higher levels of SI than children runs counter to theory and other empirical results, further analysis revealed that adults exhibited lower levels of SI relative to EA than children. Thus, children may exhibit slower disintegration of verbatim memory traces than adults due to interference; however, adults may be more efficient at redintegrating verbatim memory traces than children.

Adult↗
PubMedDate not supplied

Proposal for a new distributed database of macromolecular and subcellular structures from different areas of microscopy.

In this work we address the problem of information access that arises in the field of three-dimensional structure determination, by means of image processing, from data obtained by various types of microscopy. A prototype of a distributed database containing three-dimensional structural information is presented. In this database the volume information is linked, if possible, to other sources of catalogued information such as sequence data, atomic coordinates, and bibliographies. The solution we propose is sufficiently general to be applicable to data in other fields of biomedical science.

Computer Communication Networks↗
PubMed1994

A comparison of liver tumor diagnoses from seven PCB studies in rats.

Through a policy assumption, all polychlorinated biphenyls (PCBs) are considered probable human carcinogens by most regulatory agencies based on experimental studies in rodents where an increased incidence of liver tumors has been observed. Recognizing that new consensus criteria for the diagnoses of liver tumors in rats had been promulgated, a reevaluation of liver tumor diagnoses from seven PCB studies in rats was undertaken. These seven studies, in which rats were fed PCB mixtures containing 42, 54, or 60% chlorine, were considered to be the best studies from which to evaluate the cancer potential of PCB mixtures. The reevaluation results, where consistent diagnoses now exist across all studies, clearly indicate major differences in carcinogenic potential based on degree of chlorination. Studies of mixtures with 60% chlorination consistently resulted in a high incidence of liver tumors, whereas studies in which rats were fed mixtures with 54 or 42% chlorination showed no statistically significant increases in liver tumors. These data indicate that continuation of a science policy of assuming that all PCBs are probable human carcinogens with a potency equivalent to the mixture that contains 60% chlorine has no scientific foundation and should be reconsidered.

Animals↗
PubMed1982

[Online literature searches--a new dimension in mastering the information avalanche? A demonstration using examples].

Several examples of online literature searches in the Chemical Abstracts, Science Citation Index, and Biological Abstracts data bases are discussed to demonstrate that online searching is a powerful and very useful tool for retrieving information faster and more efficiently than before. This article attempts to stimulate scientists to familiarize themselves with this new technique and gain some personal experience, because online searching for information will probably become indispensable in scientific research and teaching in the near future.

Animals↗
PubMed2002

Beyond spike timing: the role of nonlinear plasticity and unreliable synapses.

Spike-timing-dependent plasticity (STDP) strengthens synapses that are activated immediately before a postsynaptic spike, and weakens those that are activated after a spike. To prevent an uncontrolled growth of the synaptic strengths, weakening must dominate strengthening for uncorrelated spike times. However, this weight-normalization property would preclude Hebbian potentiation when the pre- and postsynaptic neurons are strongly active without specific spike-time correlations. We show that nonlinear STDP as inherent in the data of Markram et al. [(1997) Science 275:213-215] can preserve the benefits of both weight normalization and Hebbian plasticity, and hence can account for learning based on spike-time correlations and on mean firing rates. As examples we consider the moving-threshold property of the Bienenstock-Cooper-Munro rule, the development of direction-selective simple cells by changing short-term synaptic depression, and the joint adaptation of axonal and dendritic delays. Without threshold nonlinearity at low frequencies, the development of direction selectivity does not stabilize in a natural stimulation environment. Without synaptic unreliability there is no causal development of axonal and dendritic delays.

Action Potentials↗
PubMed2006

Item response theory test equating in health sciences education.

In the context of health sciences education, and education in general, the knowledge or ability of one or several subjects in a specific area is frequently compared using different forms of a test, or by means of different instruments aimed at measuring this knowledge or ability. In such cases, test scores must be equated so that they can be properly compared. The present article aims to explain the equating of scores within the framework of item response theory (IRT), special emphasis being placed on its application in the field of health sciences education. Although there are many data collection designs that can be used within the framework of score equating, the three most widely used designs are single group, randomly equivalent groups and non-equivalent groups with anchor test. Likewise, there are different equating procedures within IRT, such as the mean/mean and mean/sigma methods, or methods based on the characteristic curve. The equating of scores must ensure that examinees taking a test do so under the same conditions; however, the procedure is also highly useful in creating a bank of items that can be used subsequently in new tests.

Educational Measurement↗
PubMedDate not supplied

Robust alternatives to traditional analysis of variance: Welch W*, James J I*, James J II*, Brown-Forsythe BF*.

Contaminated data sets commonly appear in biomedical sciences. Traditional statistical analyses are based on a 'normality' assumption and homogeneity of variances assumption. If either or both assumptions are violated, traditional statistical procedures may give an inflated type I error rate and are then not robust. Robust alternatives to traditional one-way analysis of variance have better power curves and protect against inflated type I error rates.

Analysis of Variance↗
PubMed1992

Patient-number-based computerized medical records in Crete. A tool for planning and assessment of primary health care.

Primary Health Care (PHC) in Crete is in a state of rapid development. The strategy for introducing PHC involves an orientation towards the population and the creation of possibilities for evaluation. A case records system, "Egino", was installed in the University of Heraklion and at the Health Centre in Spili in 1988, and was further developed according to local needs during 1989, when also a Greek version of the statistical system, "DoIt", was installed. The main reasons for establishing a computerized medical information system were (i) to assess the health needs in Crete, (ii) to monitor activities of the primary health care organizations, and (iii) to introduce epidemiological research into primary health care in Greece. The information system was based on specially assigned patient numbers containing several pieces of information about the individual; the system was developed at the Dalby Health Sciences Centre in Sweden. Each month, data were extracted in Spili Health Centre, and these data were regularly used to present incidence and prevalence indices. Some of the data extracted were reported to the health authorities in Greece. "EginO" and "DoIt" gave possibilities to evaluate health services by following the morbidity, while also making it possible to describe and analyse health needs in the population of Spili and other primary health care catchment areas in Greece.

Adolescent↗
PubMed1994

A survey of the teaching and learning of biological sciences on undergraduate nursing courses.

Curriculum planners developing degree courses in nursing have to decide how much time to allocate to each of the academic disciplines including biological sciences. There is no research-based evidence to suggest what depth and detail of knowledge of biological sciences is required to support nursing practice. There is also some debate about the teaching methods used and who should teach the biological sciences. This paper reports the results of a small survey investigating the teaching of biological sciences on 16 nursing degree courses in the UK. The survey uncovered great variation in the number of hours spent on biological sciences in the different universities and in the science entry requirements of the different universities. Most teachers of biological sciences had a first degree in the subject but few were nurses. The possible implications of these findings are discussed. Problems associated with shared learning and didactic teaching methods are also highlighted. Although the biological sciences input will largely be a matter of institutional preferences, nursing needs to develop a research-based framework to aid curriculum planning.

Biological Science Disciplines↗
PubMed1989

AIDS: methodological problems in studying its prevention and spread.

This paper outlines some problems in conducting AIDS research in developing countries, discusses the impact of the socio-cultural setting on study efforts, and emphasizes the need for adopting methodological approaches that are highly sensitive to the environment. The importance of seeing AIDS as a disease that affects humans not merely biologically, but also socially--in terms of their conceptions of sexual behavior and their belief systems of disease, illness and sickness--is considered. The potential of scientists to disregard this facet in the study of AIDS is stressed. The imperatives for interdisciplinary collaboration between the medical and social scientists are examined to argue that without combining research agendas, significant variables will be ignored in the search for ways to control AIDS. Special attention is given to the limitations of several methods that are employed by medical and social science researchers, including research designs, sampling, data collection and analysis, to suggest that with AIDS research these may be difficult to operationalize. The ethical implications of some of these are weighed. The interaction of economic and political conditions of the context with research activity is explored. Suggestions are given which take cognizance of the fact that it is human beings and Third World conditions, as well as the complexities of HIV and AIDS, that make AIDS research so problematic.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Effectiveness of immune globulins in preventing infectious hepatitis and hepatitis A: a systematic review.

OBJECTIVE: To assess the effectiveness and safety of immune globulins in preventing infectious hepatitis and hepatitis A. STUDY DESIGN: Systematic review with meta-analysis. DATA SOURCES: We searched the Cochrane Library, MEDLINE, EMBASE, Biological Abstracts and Science Citation Index to December 2002. Vaccine manufacturers were contacted for additional data. REVIEW METHODS: We included randomised controlled trials comparing effectiveness of hepatitis A immune globulins with no intervention or placebo, and carried out a meta-analysis. RESULTS: We included six studies (two in Russian). Tested immune globulins show higher effectiveness than placebo or do-nothing against infectious hepatitis both in primary prevention and in prevention after exposure (effectiveness 83%; RR: 0.17; 95% CI: 0.15-0.19; and effectiveness 69%; RR: 0.31; 95% CI: 0.20-0.47, respectively). We found considerable heterogeneity among studies, possibly due to different methodology, background rates of disease and immune globulins dosage and concentrations. No safety data were reported in the studies. CONCLUSIONS: Immune globulins are efficacious in preventing infectious hepatitis and hepatitis A, but included studies do not report data about their safety. Average length of passive protection was three months. Given the notable heterogeneity of performance of immune globulins, short protection conferred and absence of trial safety data, the only indications for the use of immune globulins may be in situations in which inadequate supplies of vaccine are available or when the eight-day window of opportunity for vaccine use is past.

Chi-Square Distribution↗
PubMed2005

Vocal fold wound healing: a review for clinicians.

SUMMARY: The basic science of wound healing is largely omitted from the curriculum of many voice clinicians. This fact is relatively disheartening as most therapeutic manipulation in the realm of laryngology and voice disorders deals with injured tissue. Therefore, the selection of therapeutic tasks for persons with vocal injury should ideally be informed by basic science in wound healing. Recently, several investigators have initiated lines of research to determine the course of vocal fold wound healing and the potential role of therapeutic agents, including behavioral agents. The current review seeks to provide a foundation of basic wound healing science and present the most current data regarding the wound healing process in the vocal folds.

Extracellular Matrix↗
PubMed2003

Tinnitus: clinical measurement.

Clinical measurement of tinnitus is necessary for (1) establishing adequate diagnostic information, (2) selection of appropriate treatment, and (3) quantitative documentation of treatment effects. This article describes standardized methods for measuring tinnitus pitch, loudness, maskability, and residual inhibition. These methods have been used in the Tinnitus Clinic, Oregon Health & Science University, since the 1970s. Summary data for all four measures, obtained from over 1600 Tinnitus Clinic patients, are presented here in tabular form to demonstrate the nature and range of variability within the tinnitus patient population.

Humans↗
PubMed2003

Recent water quality trends in the Schuylkill River, Pennsylvania, USA: a preliminary assessment of the relative influences of climate, river discharge and suburban development.

Climate, flow rate and land use are all known drivers of water quality in river systems, but determining the relative influences of these factors remains a significant challenge for aquatic science and management. Long-term data from the Schuylkill River at Philadelphia is assessed here in an attempt to ascertain the separate and combined influence of these major drivers on water quality in a developed watershed. Water quality measures including nutrients, conservative solutes and bacteria all elicited distinct seasonal patterns driven primarily by river discharge. Mass transport rates of sodium and chloride have increased with time, and were elevated in winter, presumably as a function of road salt deposition. A steady increase in developed land area in the watershed has occurred in recent decades, which allowed the use of time as a surrogate parameter for regional development in the construction of multiple factor linear models predicting the relative influences of precipitation, river discharge and developed land area on river water quality. Linear models predicting annually averaged water quality measures showed the effects of precipitation, discharge and developed land area to be of nearly equal importance in regulating levels of conductivity, alkalinity, sodium, and chloride in the river. Models predicting water quality variables for discrete samples demonstrated that river flow was the major determinant of daily variability in alkalinity, conductivity, hardness and calcium levels, while still resolving the highly significant influence of watershed development on water quality. Increases in solute transport in the Schuylkill River in recent decades appear to be the direct result of modern suburban development in the watershed.

Cities↗
PubMed2003

Molecular staging and pharmacogenomics. Clinical implications: from lab to patients and back.

The complexities of human cancer have frustrated attempts to understand its genetic underpinnings and explain the unpredictable behavior of individual tumors. Advances in robotics and computer science, as well as the sequence data from the human genome project are now allowing us to begin to glean useful information from the simultaneous analysis of thousands of data elements from hundreds of tumors. Through the sophisticated analysis of patterns in these complex data sets, we are seeing clues that we may be able to predict the behavior of individual tumors as well as to define novel biomarkers and therapeutic targets. In this review, we will discuss the application of these high-throughput technologies for the study of human lung cancer.

Antineoplastic Agents↗
PubMed2003

Initial closed operation of the CELSS Test Facility Engineering Development Unit.

As part of the NASA Advanced Life Support Flight Program, a Controlled Ecological Life Support System (CELSS) Test Facility Engineering Development Unit has been constructed and is undergoing initial operational testing at NASA Ames Research Center. The Engineering Development Unit (EDU) is a tightly closed, stringently controlled, ground-based testbed which provides a broad range of environmental conditions under which a variety of CELSS higher plant crops can be grown. Although the EDU was developed primarily to provide near-term engineering data and a realistic determination of the subsystem and system requirements necessary for the fabrication of a comparable flight unit, the EDU has also provided a means to evaluate plant crop productivity and physiology under controlled conditions. This paper describes the initial closed operational testing of the EDU, with emphasis on the hardware performance capabilities. Measured performance data during a 28-day closed operation period are compared with the specified functional requirements, and an example of inferring crop growth parameters from the test data is presented. Plans for future science and technology testing are also discussed.

Air Conditioning↗