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At least 73 records · Page 4Linked to original sources
PubMed2005

Henry's law constants for hexachlorobenzene, p,p'-DDE and components of technical chlordane and estimates of gas exchange for Lake Ontario.

The Henry's law constants (HLC) for trans- and cis-chlordane (TC, CC), trans-nonachlor (TN), hexachlorobenzene (HCB) and p,p'-DDE were determined by the gas-stripping method over a temperature range of 5-35 degrees C. The HLC variation versus temperature (K) was described by logH=m/T+b. Parameters of this equation were (with standard deviations) TC: m=-1524+/-158, b=6.58+/-0.54; CC: m=-1786+/-209, b=7.42+/-0.71; TN m=-2068+/-284, b=8.44+/-0.97; HCB: m=-3013+/-174, b=11.60+/-0.59 and p,p'-DDE: m=-2043+/-240, b=8.37+/-0.82. The HLCs (Pa m3 mol(-1)) at 25 degrees C (298.15 K) were: TC=29; CC=27; TN=32; p,p'-DDE=33 and HCB=35. These HLCs values were used to calculate fugacity ratios from paired air and water data from Lake Ontario, July 1998. The resulting fugacity ratios predict that volatilization was occurring for all compounds during that month.

Air Pollutants↗
PubMed1981

[Serological diagnosis of human brucellosis by means of an immunoenzymatic technic (ELISA). I.--Estimate of some parameters of the reaction and practical application (author's transl)].

The authors propose a new immunoenzymatic method (ELISA) for human brucellosis diagnosis. They study in a logical way some of the parameters of the reaction realizable by macro- or microassay. The all method requires less than six hours. They use OMS recommended brucella suspension as antigen. The conjugate enzyme is peroxydase and human anti-immunoglobulins are either complete or specific IgM. The revelating substrate is obtained by association of hydrogen peroxyde with 5 amino-salicylic acid which gives the best colorimetric stability. The reading is made at 450 nm : automatically by micro-assay. Using only one sample dilution, serum quantification may be hazardous.

Brucellosis↗
PubMedDate not supplied

[Review of a technic for the estimation of area under the concentration curve in pharmacokinetic analysis].

The determination of the area under concentration-time curve (AUC) is the most important parameter of a non-compartmental pharmacokinetic analysis. The calculation of AUC is usually performed by the trapezoidal rule. The aim of this work is to examine the reliability of this method still considered as a reference. The trapezoidal rule was compared to a selection of calculation methods often owning to other fields of research i.e., rectangular rule, Simpson and Tchebychev rules and log trapezoidal rule. The specific interest and limits of each method were discussed according to the kind and the type of pharmacokinetic profiles i.e., logarithmic or nonlogarithmic and the number of concentration-time couples. We obtained the following results: 1) The rectangular rule is the most simple and less effective method. 2) The trapezoidal rule remains an interesting method particularly when the profile is monologarithmic or nonlogarithmic. The efficacy of this method increases with the number of points of the pharmacokinetic profile. 3) The Simpson and the Tchebychev rules give very good results particularly when the number of points is higher than 7 and 6 respectively. 4) The log trapezoidal rule is an excellent method for the treatment of a logarithmic profile. 5) Both Tchebychev and log trapezoidal rules give accurate results when compared to the true AUC values. Further, it must be pointed out that this determination is depending on an arbitrary choice of points. Finally, the trapezoidal rule is not always the best method to determine AUC. If the analyst has only a pocket-calculator, he will obtain best results with the Simpson method than with the trapezoidal rule.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1979

[Estimation of survival rates: technics used (author's transl)].

The direct method and life-table methods (actuarial and Kaplan-Meier) for estimating survival rates are described here. The difference between direct method and lifetable method is the use of information about the patients who are still alive. Practical examples of calculation are given with recommandations for graphical displays.

Actuarial Analysis↗
PubMed1992

The validation of interviews for estimating morbidity.

Health interview surveys have been widely used to measure morbidity in developing countries, particularly for infectious diseases. Structured questionnaires using algorithms which derive sign/symptom-based diagnoses seem to be the most reliable but there have been few studies to validate them. The purpose of validation is to evaluate the sensitivity and specificity of brief algorithms (combinations of signs/symptoms) which can then be used for the rapid assessment of community health problems. Validation requires a comparison with an external standard such as physician or serological diagnoses. There are several potential pitfalls in assessing validity, such as selection bias, differences in populations and the pattern of diseases in study populations compared to the community. Validation studies conducted in the community may overcome bias caused by case selection. Health centre derived estimates can be adjusted and applied to the community with caution. Further study is needed to validate algorithms for important diseases in different cultural settings. Community-based studies need to be conducted, and the utility of derived algorithms for tracking disease frequency explored further.

Algorithms↗
PubMed1989

Estimation of adult male mortality in Turkey by the widowhood method.

"In this paper, the [widowhood] method is applied to Turkish data to estimate adult male mortality. First, the method and its assumptions are briefly discussed. Secondly, the data source and its major characteristics are described and the method is applied; the resulting mortality measures estimated with the method are compared with findings from other sources, and the reliability of the results, the applicability of the method to the Turkish case, and possible biases risked with the application of the method are elaborated in the final section of the paper." (SUMMARY IN TUR)

Asia↗
PubMed1987

[The registration of deaths in Venezuela: an evaluation of coverage].

"This paper presents six indirect techniques for estimating the degree of death coverage as applied to vital statistics information in Venezuela between 1960 and 1982, collected by two public institutions, namely, the 'Oficina Central de Estadistica e Informatica' (OCEI) and the Ministry of Health and Social Assistance (MSAS).... The results show remarkable improvements in the death registry coverage for both institutions, that amount to 97 or 98 per cent at the beginning of the 80's. Nevertheless, great differences can be observed between them regarding both structure and volume of deaths by sex and age." Among the problems discussed are the impact of immigration and errors in age reporting. (SUMMARY IN ENG)

Age Factors↗
PubMed1987

Intercensal change and the indirect estimation of mortality: the case of Pakistan.

"In a country such as Pakistan, where there is no vital registration system, estimating mortality levels and trends can be difficult. One way we can learn about mortality is to use indirect estimation techniques on census age distributions. This paper applies some of these techniques and evaluates the quality of the census data in the process." Problems of relative coverage in the 1972 and 1981 censuses and changes in age-reporting preferences are discussed. Comments by Mohammad Afzal are included (pp. 583-5).

Age Distribution↗
PubMed1989

The estimation of moments: a technical note.

The calculation of several common pharmacokinetic parameters requires estimates of both the area under the curve of the concentration of the drug in a sampled fluid vs. time, and also the first moment about t = 0 of this area. It is proposed that the methods used to estimate these quantities should make consistent assumptions about the concentration of the drug. There appears to be an inconsistency in the standard published formulas in the case where concentration is interpolated linearly. A more consistent formula is derived.

Mathematics↗
PubMed1981

Sources of variance in the double normalized value: an evaluation of its reproducibility as a measure on HLA-D locus identity.

Two different sets of mixed lymphocyte culture (MLC) experiments were performed using HLA-D homozygous typing cells (HTC). In all stimulator-responder combinations the median cpm's of four replicate cultures were reduced into double normalized values (DNV). In the first experimental set the responder panel was unselected, whereas the responders for the second set were chosen on the basis of either sharing an HLA-D determinant with the stimulator (ID) or not (non-ID). The experiments were designed: Set 1: To estimate the technical variability in the DNV's and to observe the distribution of this variability. The standard deviation of an observation on a stimulator-responder combination was approximately 24 DNV units. Thus, by running 6 experiments on each responder we would have a mean DNV with a standard error of 10 DNV units. Set 2: To determine whether stimulators typing for the same Dw specificity had the same distribution of DNV's and to investigate the variability between responders, between experiments and within experiments. Although the mean DNV is the same for all HTC's, the variability in observations was greater for some HTC's than for others. The variability may be completely technical for some HTC's, whereas for other HTC's there is evidence of responder variability and between experiment variability. Important implications of these results are: (1) that in using a single cut-off value of 60 for all HTC to define typing responses one will have a very high misclassification rate for a large percentage of ID responders; (2) for some HTC this error rate can be reduced through repeating the experiment 4 times and raising the cut-off point; (3) this error, together with the technical and/or experimental variance can be further reduced by using 2 or more HTC's of the same specificity in each experiment and by combing their data; (4) misclassification can be reduced in every situation by doing 4 experiments, using 2 HTC per responder and computing a cut-off which gives a misclassification rate for each Dw type of 10% in ID's and in non-ID's. Thus the best approach to achieving Dw locus typing with a desirable low rate of misclassification would be to do similar control studies of every HTC, to estimate technical experimental and responder variance and then use this information to determine a cut-of value and the number of HTC's and experiments per responder required to keep the error rate at a satisfactory level.

Cells, Cultured↗
PubMed1998

Direct and indirect estimates of HIV-1 incidence in a high-prevalence population.

While the worldwide AIDS epidemic continues to expand, directly measured incidence data are difficult to obtain. Methods to reliably estimate human immunodeficiency virus type 1 (HIV-1) incidence from more easily available data are particularly relevant in those parts of the world where prevalence is rising in heterosexually exposed populations. The authors set out to estimate HIV-1 incidence in a population of heterosexual sexually transmitted disease clinic attendees in Trinidad who had a known high prevalence of HIV-1 subtype B. Over the period 1987-1995, HIV-1 incidence estimates from serial cross-sectional studies of HIV-1 prevalence, passive follow-up of clinic recidivists, modeling of early markers of HIV-1 infection (p24 antigen screening), and a cohort study of seronegative genital ulcer disease cases were compared. Measuring incidence density in the genital ulcer disease cases directly gave the highest estimate, 6.9% per annum. Screening for the detection of early HIV-1 markers yielded an incidence of 5.0% per annum, while estimating incidence from serial cross-sectional prevalence data and clinic recidivists gave estimates of 3.5% and 4.5% per annum, respectively. These results were found to be internally consistent. Indirect estimates of incidence based on prevalence data can give accurate surrogates of true incidence. Within limitations, even crude measures of incidence are robust enough for health planning and evaluation purposes. For planning vaccine efficacy trials, consistent conservative estimates may be used to evaluate populations before targeting them for cohort studies.

Blotting, Western↗