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At least 721 records · Page 40Linked to original sources
PubMed1994

Use of isotope-dilution phenomenon to advantage in the determination of kinetic constants Km and Kcat for BamHI restriction endonuclease: an empirical and iterative approach.

An assay using a very small amount of 35S-labeled deoxyoligonucleotide as a substrate for the determination of Km and Kcat for the restriction enzyme BamHI is described. Two synthetic deoxyoligonucleotides, ATGGCGGATCCGC and ATGGCGGAGCCGC, containing the cognate and a mismatch BamHI sequence, respectively, were labeled by an end-filling reaction using the Klenow fragment of DNA polymerase and [35S]dATP to generate the labeled self-complementary substrates. The dependence of BamHI hydrolysis on substrate concentration was investigated using mixtures of a fixed amount of radiolabeled substrate and varying amounts of cold-labeled substrate over a wide range. The apparent competitive inhibition observed due to the phenomenon of carrier dilution was analytically corrected by an empirical as well as an iterative approach to give Km values comparable to those reported in the literature. We have found that the values obtained using the empirical formula are very close to the precise values obtained through iteration. Our procedure has used isotopic dilution to advantage to make the assay less expensive and can be applied effectively to any enzyme-substrate reaction in which the substrate and the product have radioactive labels. The method would be especially useful for a rapid analysis and comparison of kinetic constants of various mutant enzymes or substrates.

Base Sequence↗
PubMed1975

Empirical quantum chemical approach to structure-gas chromatographic retention index relationship. I. Sterol acetates.

It has been found possible to correlate chromatographic retention parameters directly with molecular electronic structure by means of a linear relationship. The empirical parameters used are total energy and localized charge, calculated by the method of Del Re. They are deduced directly from the molecular structure and they permit the retention index to be calculated theoretically with an acceptable error.

Acetates↗
PubMed1992

Psychiatric diagnosis and racial bias: empirical and interpretative approaches.

Understanding of psychiatric illness among Britain's Black and ethnic minority population has shifted from an emphasis on cultural difference to one on racism within psychiatric theory and practice. In spite of this apparent turn, the explanations put forward remain within an empirical framework of methodological individualism, reflecting the background and training of British psychiatrists themselves. How racism may be actually demonstrated in individual clinical practice remains elusive. The standard hypotheses are examined here through a conventional clinical vignette study: this suggests medical education does not in itself now involve any specific racist psychiatric assumptions. Fuller understanding of the exercise of social power within this particular domain requires not only more complex interactive studies, preferably derived from a variety of clinical and social contexts, but a more developed interpretation of psychiatric practice and ideology within the social system.

Adult↗
PubMed2006

Sensitivity analysis of thermodynamic properties of liquid water: a general approach to improve empirical potentials.

A sensitivity analysis of bulk water thermodynamics is presented in an effort to understand the relation between qualitative features of molecular potentials and properties that they predict. The analysis is incorporated in molecular dynamics simulations and investigates the sensitivity of the Helmholtz free energy, internal energy, entropy, heat capacity, pressure, thermal pressure coefficient, and static dielectric constant to components of the potential rather than the parameters of a given functional form. The sensitivities of the properties are calculated with respect to the van der Waals repulsive and the attractive parts, plus short- and long-range Coulomb parts of three four site empirical water potentials: TIP4P, Dang-Chang and TTM2R. The polarization sensitivity is calculated for the polarizable Dang-Chang and TTM2R potentials. This new type of analysis allows direct comparisons of the sensitivities for different potentials that use different functional forms. The analysis indicates that all investigated properties are most sensitive to the van der Waals repulsive, the short-range Coulomb and the polarization components of the potentials. When polarization is included in the potentials, the magnitude of the sensitivity of the Helmholtz free energy, internal energy, and entropy with respect to this part of the potential is comparable in magnitude to the other electrostatic components. In addition similarities in trends of observed sensitivities for nonpolarizable and polarizable potentials lead to the conclusion that the complexity of the model is not of critical importance for the calculation of these thermodynamic properties for bulk water. The van der Waals attractive and the long-range Coulomb sensitivities are relatively small for the entropy, heat capacity, thermal pressure coefficient and the static dielectric constant, while small changes in any of the potential contributions will significantly affect the pressure. The analysis suggests a procedure for modification of the potentials to improve predictions of thermodynamic properties and we demonstrate this general approach for modifying potentials for one of the potentials.

Journal Article↗
PubMed2001

The UHP ultrasound protocol: a novel ultrasound approach to the empiric evaluation of the undifferentiated hypotensive patient.

This report describes a novel sonographic protocol for the evaluation of the undifferentiated hypotensive patient. This protocol combines components of 3 sonographic applications: free fluid, cardiac, and abdominal aorta into a single protocol. We believe this protocol and its underlying principles should be a routine part of the empiric evaluation of the patient with undifferentiated hypotension or pulseless electrical activity.

Adult↗
PubMed1982

Interaction of afferent and efferent signals underlying joint position sense: empirical and theoretical approaches.

A model of joint position sense is considered based on the concept that central motor commands are adequately expressed in terms of shifts of the so-called invariant length-tension characteristics for agonist and antagonist muscles. The main points of this concept are discussed to clarify them and to prevent misunderstanding. The basic idea of the model is that the efferent copy of the central motor commands plays the role of a reference frame for evaluation of afferent proprioceptive discharges. An experiment with reproduction of constrained movements was performed in order to investigate the influence of voluntary flexor or extensor muscle tension on position sense in the elbow joint. The results demonstrate adequate perception of joint position on the background of voluntary muscle tension and thus are quite consistent with the model. The role of afferent and efferent signals in position sense is discussed with special reference to views expressed recently by different authors. The interrelation between position sense and sense of effort is considered, based on a concept of senso-motor space.

Journal Article↗
PubMed2004

Ethical issues in public health: a qualitative study of public health practice in Scotland.

STUDY OBJECTIVE: To identify ethical issues encountered by staff in the development and implementation of public health activities at two sites in Scotland. DESIGN: Qualitative research study involving face to face semi-structured interviews with participants. SETTING: A public health directorate in a National Health Service Trust, and a public health demonstration project in child health. PARTICIPANTS: Health promotion specialists, managers, nurses, public health consultants and specialists, researchers, trainees, and other public health staff. MAIN RESULTS: Three main categories of ethical issues were identified: paternalism, responsibilities, and ethical decision making. Consulting with the community and sharing information raised issues of paternalism and honesty. Participants identified multiple and sometimes conflicting responsibilities. Barriers to fulfilling responsibilities included meeting targets, working with partners, and political influences. Defining the limits of responsibilities posed challenges. Participants identified values for ideal decision making, but lack of time often led to a more pragmatic approach. CONCLUSION: These empirical findings complement and extend existing discussions of public health ethics, emphasising the complex nature of ethical issues in public health. The implications for public health policy and future research are discussed.

Child↗
PubMed2006

The relation between temperature, ozone, and mortality in nine French cities during the heat wave of 2003.

BACKGROUND: During August 2003, record high temperatures were observed across Europe, and France was the country most affected. During this period, elevated ozone concentrations were measured all over the country. Questions were raised concerning the contribution of O3 to the health impact of the summer 2003 heat wave. METHODS: We used a time-series design to analyze short-term effects of temperature and O3 pollution on mortality. Counts of deaths were regressed on temperatures and O3 levels, controlling for possible confounders: long-term trends, season, influenza outbreaks, day of the week, and bank holiday effects. For comparison with previous results of the nine cities, we calculated pooled excess risk using a random effect approach and an empirical Bayes approach. FINDINGS: For the nine cities, the excess risk of death is significant (1.01% ; 95% confidence interval, 0.58-1.44) for an increase of 10 microg/m3 in O3 level. For the 3-17 August 2003 period, the excess risk of deaths linked to O3 and temperatures together ranged from 10.6% in Le Havre to 174.7% in Paris. When we compared the relative contributions of O3 and temperature to this joint excess risk, the contribution of O3 varied according to the city, ranging from 2.5% in Bordeaux to 85.3% in Toulouse. INTERPRETATION: We observed heterogeneity among the nine cities not only for the joint effect of O3 and temperatures, but also for the relative contribution of each factor. These results confirmed that in urban areas O3 levels have a non-negligible impact in terms of public health.

Cities↗
PubMed2006

A hybrid empirical-mechanistic modeling approach for extrapolating biota-sediment accumulation factors and bioaccumulation factors across species, time, and/or ecosystems.

An approach is presented for extrapolating field-measured biota-sediment accumulation factors (BSAFs) and bioaccumulation factors (BAFs) across species, time, and/or ecosystems. This approach, called the hybrid bioaccumulation modeling approach, uses mechanistic bioaccumulation models to extrapolate field-measured bioaccumulation data (i.e., BSAFs and BAFs) to new sets of ecological conditions. The hybrid approach predicts relative differences in bioaccumulation using food web models with two sets of ecological conditions and parameters: One set for the ecosystem where the BSAFs and/or BAFs were measured, and the other set for the ecological conditions and parameters for which the extrapolated BSAFs and/or BAFs are desired. The field-measured BSAF (or BAF) is extrapolated by adjusting the measured BSAF (or BAF) by the predicted relative difference, which is derived from two separate solutions of the food web model. Extrapolations of polychlorinated biphenyl BSAFs and BAFs for lake trout (Salvelinus namaycush) from southern Lake Michigan to Green Bay of Lake Michigan (Green Bay, WI, USA) walleye (Stizostedion vitreum) and brown trout (Salmo trutta), as well as Hudson River largemouth bass (Micropterus salmoides) and yellow perch (Perca flavescens), resulted in generally better agreement between measured and predicted BSAFs and BAFs with the hybrid approach.

Animals↗
PubMed1984

[Drug abuse in youth.].

In an on-going review of the literature dealing with the assessment of drug abuse treatment and prevention programs, the authors indicate that changes are occurring in basic concepts : the concept of addiction has been expanded and a more systemic approach to drug use and abuse is more prevalent. An examination of the relationship between adolescent drug use and the related psychosocial images leads to an outline of two main evaluative approaches : the moralistic a priori approach and the empirical social approach. To efficiently prevent youthful drug abuse, they propose that primary preventive actions should focus on demand factors and be complemented with secondary preventive actions focused on supply factors.

English Abstract↗
PubMedDate not supplied

[Life cycle strategies: a synthesis of empirical and theoretical approaches].

A scheme of relationships among life-history characters is developed on assumptions of determinate growth and dependence of juvenile mortality on the specific growth rate. It is shown that constraints on the relative neonate size, (W0/W infinity), and minimum value of the biotic potential, (rmax), lead to "triangular" shape of life history set on the plain defined by juvenile and adult mortality. This completely coincides with the Ramenskiĭ++--Grime (C-S-R) classification of life-history strategies. Phylogenetic constraints can reduce this set to a relatively narŕow r/K-continuum specifically oriented for a certain taxon. Similar restrictions generate models of life history optimization which predict interspecific allometries between life-history traits.

Aging↗