SEARCH · PubMed Health

Results for “Methodology”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources

PubMed2006

Multiscale modelling methodology for virtual prototyping of effervescent tablets.

Computational methodology for virtual tablet prototyping has been developed. The methodology consists of two steps: construction of virtual particle compacts of varying composition using the discrete element method (DEM), and the simulation of their dissolution by eroding individual components from the tablet microstructure according to their intrinsic dissolution rates, using the volume-of-fluid (VOF) method. The effective erosion rate obtained from simulations at the particle assembly length-scale is used for the calculation of dissolution time at the tablet length-scale. The methodology is demonstrated on the case of a simple effervescent formulation consisting of sodium bicarbonate-acetic acid effervescent system, sodium chloride as a model active substance, and lactose filler. The experimentally measured dependence of tablet dissolution time on composition and compaction force was found to be in very good agreement with outputs from computer simulations.

Citric Acid↗

PubMed2005

New hyphenated methodologies in high-sensitivity glycoprotein analysis.

High-sensitivity glycoprotein analyses are of particular interest in modern biomedical and clinical research, as well as in the development of recombinant protein products. The evolution of new hyphenated methodologies in high-sensitivity glycoprotein analysis is highlighted in this thematic review. These methodologies include, in particular, capillary LC/MALDI/TOF/TOF MS in conjunction with online permethylation platform, and silica-based lectin microcolumns interfaced to MS. The potential of these methodologies in glycomic and glycoproteomic analysis is demonstrated for model glycoproteins as well as total glycomes and glycoproteomes derived from biological samples. Additionally, the applications of CE-MS, CEC, and nanoLC with graphitized carbon in the areas of glycomics and glycoproteomics are described.

Chromatography, Ion Exchange↗

PubMed1997

Observer performance methodologies for evaluating blood vessel visibility in MR angiograms using accurate geometric registration to high resolution x-ray angiograms.

Receiver operator characteristic (ROC) and two alternative forced choice (2AFC) methodologies for quantitatively assessing vessel visibility in MR angiography (MRA) were examined using x-ray angiography images as truth. The methodologies required MRA projection images with the same orientation and magnification as the x-ray images. Geometric distortions limited the quality of the registration. The observer performance measurements were compared to vessel contrast-to-noise ratio (CNR) measurements. Receiver bandwidth (RBW) and magnetization transfer (MT) effects in 3D time-of-flight MRA were evaluated. Overall, applying MT significantly increased all three measurements while decreasing the RBW significantly improved the 2AFC and CNR measurements. The relative importance of both effects on the 2AFC measure increased as vessel diameter decreased, although statistical significance was limited by small samples for diameters less than approximately 0.7 mm. These results demonstrate the usefulness of these observer performance methodologies for MRA technique assessment.

Angiography, Digital Subtraction↗

PubMed2004

Comparison of data mining methodologies using Japanese spontaneous reports.

PURPOSE: Five data mining methodologies for detecting a possible signal from spontaneous reports on adverse drug reactions (ADRs) were compared. METHODS: The five methodologies, the Bayesian method using the Gamma Poissson Shrinker (GPS), the method employed in the UK Medicines Control Agency (MCA), the Bayesian Confidence Propagation Neural Network (BCPNN), the method using the 95% confidence interval (CI) for the reporting odds ratio (RORCI) and that using the 95% CI of the proportional reporting ratio (PRRCI) were compared using Japanese data obtained between 1998 and 2000. RESULTS: There were all in all 38,731 drug-ADR combinations. The count of drug-ADR pairs was equal to 1 or 2 for 31,230 combinations and none of them were identified as a possible signal with the MCA or BCPNN. Similarly, the GPS detected a possible signal in none of the combinations where the count was equal to 1 but in 7.5% of the combinations where the count was equal to 2. The RORCI and PRRCI detected a possible signal in more than half of the combinations where the count was equal to 1 or 2. When the pairwise agreement on whether or not a drug-ADR combination satisfied the criteria for a possible signal was assessed for the 38,731 combinations, the concordance measure kappa was greater than 0.9 between the MCA and BCPNN and between the RORCI and PRRCI. Kappa was around 0.6 between the GPS and MCA and between the GPS and BCPNN. Otherwise, kappa was smaller than 0.2. CONCLUSIONS: The drug-ADR combinations detected as a possible signal vary between different methodologies.

Adverse Drug Reaction Reporting Systems↗

PubMed1994

A quantitative methodology for the de novo design of proteins.

We have developed a general quantitative methodology for designing proteins de novo, which automatically produces sequences for any given plausible protein structure. The method incorporates statistical information, a theoretical description of protein structure, and motifs described in the literature. A model system embodying a portion of the quantitative methodology has been used to design many protein sequences for the phage 434 Cro and fibronectin type III domain folds, as well as several other structures. Residue sequences selected by this prototype share no significant identity with any natural protein. Nonetheless, 3-dimensional models of the designed sequences appear generally plausible. When examined using secondary structure prediction methods and profile analysis, the designed sequences generally score considerably better than the natural ones. The designed sequences are also in reasonable agreement with a sequence template. This quantitative methodology is likely to be capable of successfully designing new proteins and yielding fundamental insights about the determinants of protein structure.

Amino Acid Sequence↗

PubMedDate not supplied

Methodological issues with adaptation of clinical trial design.

Adaptation of clinical trial design generates many issues that have not been resolved for practical applications, though statistical methodology has advanced greatly. This paper focuses on some methodological issues. In one type of adaptation such as sample size re-estimation, only the postulated value of a parameter for planning the trial size may be altered. In another type, the originally intended hypothesis for testing may be modified using the internal data accumulated at an interim time of the trial, such as changing the primary endpoint and dropping a treatment arm. For sample size re-estimation, we make a contrast between an adaptive test weighting the two-stage test statistics with the statistical information given by the original design and the original sample mean test with a properly corrected critical value. We point out the difficulty in planning a confirmatory trial based on the crude information generated by exploratory trials. In regards to selecting a primary endpoint, we argue that the selection process that allows switching from one endpoint to the other with the internal data of the trial is not very likely to gain a power advantage over the simple process of selecting one from the two endpoints by testing them with an equal split of alpha (Bonferroni adjustment). For dropping a treatment arm, distributing the remaining sample size of the discontinued arm to other treatment arms can substantially improve the statistical power of identifying a superior treatment arm in the design. A common difficult methodological issue is that of how to select an adaptation rule in the trial planning stage. Pre-specification of the adaptation rule is important for the practicality consideration. Changing the originally intended hypothesis for testing with the internal data generates great concerns to clinical trial researchers.

Clinical Trials as Topic↗

PubMed1997

The origin of life and its methodological challenge.

The problem of the origin of life is discussed from a methodological point of view as an encounter between the teleological thinking of the historian and the mechanistic thinking of the chemist; and as the Kantian task of replacing teleology by mechanism. It is shown how the Popperian situational logic of historic understanding and the Popperian principle of explanatory power of scientific theories, when jointly applied to biochemistry, lead to a methodology of biochemical retrodiction, whereby common precursor functions are constructed for disparate successor functions. This methodology is exemplified by central tenets of the theory of the chemo-autotrophic origin of life: the proposal of a surface metabolism with a two-dimensional order; the basic polarity of life with negatively charged constituents on positively charged mineral surfaces; the surface-metabolic origin of phosphorylated sugar metabolism and nucleic acids; the origin of membrane lipids and of chemi-osmosis on pyrite surfaces; and the principles of the origin of the genetic machinery. The theory presents the early evolution of life as a process that begins with chemical necessity and winds up in genetic chance.

Animals↗

PubMed1994

Differences in indirect risk methodologies: dioxin emissions from combustion facilities.

Guidance for performing indirect risk evaluations is in a state of flux; yet, EPA and the public are insisting that estimates of indirect risks associated with combustion of industrial wastes must be derived. Two different guidance documents exist for estimating these risks: one that focuses on dioxin exposures and one that has a more general application. This paper evaluates the differences in indirect risk estimates derived from methodologies presented in these two documents and discusses those assumptions that may contribute to these differences. The influence of an individual exposure pathway on indirect risk estimates varies depending on the methodology applied. Indirect risk estimates differ by 30-fold for the same exposure pathway when comparing these methodologies. Assumptions about vapor uptake, food consumption rates, and the fraction of local food consumption appear to drive final estimates. A major discrepancy between these two documents is differences in assumptions about soil dermal contact for children. Many EPA default assumptions and values are extremely conservative and often unrealistic; therefore, use of site-specific data will be essential when estimating indirect risks associated with combustor emissions. Also, application of a toxic equivalency approach may have some benefit; risk estimates are reduced 16- to 18-fold using this approach.

Air Pollutants, Occupational↗

PubMed1987

The evaluation of biological interactions using response surface methodology.

Response surface methodology was employed in the statistical analysis of the combination exposures of genotoxic agents, bischloroethylnitrosourea with cis-diamminedichloroplatinum (II) and cis-diamminedichloroplatinum (II) with X rays. The measured endpoint in each case was sister chromatid exchanges in V79 Chinese hamster cells. The combination experiments employed a factorial design in which cells were treated, in various concentration combinations, with two agents simultaneously. Bis-chloroethylnitrosourea and cis-diamminedichloroplatinum (II) each exhibited curvilinear concentration-related increases in sister chromatid exchanges. X rays exhibited a dose-dependent increase in sister chromatid exchanges. For the cis-diamminedichloroplatinum (II)/X ray combinations, response surface methodology indicates a less-than-additive interaction, suggested by the non-parallel concentration-response curves of one agent at varying concentrations of the other, and a slight dose-dependent increase in sister chromatid exchanges due to X rays alone. Both cis-diamminedichloroplatinum and bis-chloroethylnitrosourea exhibited concentration-related increases in sister chromatid exchanges, cis-diamminedichloroplatinum (II) being 8-10 times (dependent on what level of effect was compared) more potent than bis-chloroethylnitrosourea. For the cis-diamminedichloroplatinum (II)/bis-chloroethylnitrosourea combinations, an increasingly less-than-additive interaction was detected. The analysis of these combinations demonstrates the strength of response surface methodology, a collection of mathematical and statistical techniques for detecting, analyzing and describing the biological effects resulting from exposures to multiple cytotoxic agents. The descriptive ability of these procedures is shown to be useful in that it leads to the suggestion of hypotheses regarding mechanisms of action.

Animals↗

PubMed1993

Evaluation of the methodological quality of clinical trial protocols. A preliminary experience in Spain.

The methodological quality of 50 clinical trial protocols submitted to our hospital has been assessed by means of a check-list. The most frequent methodological deficiencies found were related to statistical analysis, selection criteria, sample size, incorrect use of placebo, homogeneity of the groups, concomitant medication, randomisation plan, monitoring of adverse events and study design. Lack of insurance for the patients and inadequacies in the investigators' brochure and case report forms were observed in a significant number of cases. The results suggest the importance of a multidisciplinary team in the elaboration of clinical trial protocols to prevent methodological errors.

Clinical Protocols↗

PubMed1995

Method and methodology in medical ethics: inaugurating another new section.

This essay announces the inauguration of a section of Theoretical Medicine and invites submissions on the topic "Method and Methodology in Medical Ethics." It offers some sketches of plausible meanings of "method" and "methodology" and their relationships as these might apply to work in biomedical ethics. It suggests a broad range of issues, dilemmas or conflicts that may be addressed for help via method and/or methodology.

Ethical Analysis↗

PubMed1978

Methodological issues in alpha biofeedback training.

Current controversies concerning outcomes of EEG alpha feedback training are at least in part due to methodological differences among different studies. The aim of this paper is to provide future and present researchers in this field with an analysis of methods used in most of the studies published from 1968 to 1976, and to comment on those methodological issues we think most important. These include alpha assessment, training schedules, and uni- versus bidirectional training. This analysis is accomplished in part by a series of tables listing 45 studies and the detailed methodologies used. It is believed that the probabilities of successful feedback enhancement of alpha can be substantially improved by incorporating the following suggestions: (a) employing at least four training sessions, (b) the use of continuous rather than dichotomous feedback, supplemented by periodic quantitative scores of progress, and (c) using training trials of at least 10 minutes' duration.

Alpha Rhythm↗

PubMed1976

Adult-child interaction analysis: methodology and case application.

A revised methodology for analyzing adult-child interactions incorporating the use of videotape is presented. Results obtained from the application of this methodology to a successfully treated case of prolonged subsistence on pureed foods demonstrate that it is valid and useful. Objective confirmation of previous subjective clinical impressions and judgments was provided, and previously unnoted behavioral characteristics of mother, child and therapist were revealed. The clinical, research, and training potential of this comprehensive yet unobtrusive methodology is discussed.

Behavior Therapy↗

PubMed1995

Adolescent schizophrenia: a methodologic review of the current neuroimaging and neuropsychologic literature.

This paper reviews all relevant articles that reported structural neuroimaging or neuropsychological data in adolescent patients with schizophrenia. These papers were subsequently examined from a methodological perspective. Few papers have been written that have examined whether adolescent schizophrenia is associated with structural neuroimaging abnormalities or cognitive dysfunction. In these studies, major methodologic issues exist. Therefore, at present, firm conclusions cannot be made regarding the presence or absence of neuropsychologic dysfunction or structural neuroimaging abnormalities in this population. Attention to certain methodologic issues may improve future studies of this topic.

Adolescent↗

PubMed1984

A taxonomy: hospital information systems evaluation methodologies.

During the past decade, computers and information systems and their resultant products have pervaded hospitals. Not only have the number of and investments in computers and their associated systems increased, but the types of hospital systems and affected functions have also multiplied. Unfortunately, methodologies to measure impacts of these systems have not evolved at the same pace. There have been few developments of new techniques. Existing techniques have not been adapted for use in hospitals. As a result, evaluations are not performed or are based upon generalizations, often with users minimally involved, if at all. Most techniques emphasize the cost-benefit approach, but this should not be the only tool used. This paper presents a taxonomy of methodologies for the evaluation of hospital information systems. The analyses of methodologies and systems are accomplished from user's perspectives. Effectiveness of system products is emphasized. Users are provided with an additional tool to plan, organize, control, and direct the information resources and achieve the hospital's goals and objectives.

Classification↗

PubMed1995

System impact and methodological issues in the development of an empirical typology of psychiatric hospital residents.

The identification and categorization of similar objects or individuals into groups is a universal theme that permeates science and provides a conceptual framework to facilitate comprehension. For mental health administrators, a sound methodology to group individuals in a meaningful way would prove useful in the areas of general system understanding, as well as staffing, program planning and evaluation, and service system research, to name a few. Cluster analysis is a set of techniques that approach this grouping process empirically. Within the context of a large psychiatric hospital system, both the methodological processes involved in the application of cluster analysis and the resulting utility of such an analysis are discussed. Issues fundamental to the understanding of such a system are addressed. Special emphasis is placed on methodological issues regarding the application of cluster analytic techniques, which have left such techniques open for criticism. The value of such analyses, when used appropriately, is illustrated by the development of a stable, five-group typology of psychiatric hospital residents whose group characteristics are particularly germane to service system understanding. The implications of such a model for administration, planning, and research in a psychiatric hospital system are also addressed.

Cluster Analysis↗

PubMed1991

Methodological error and spatial variability of organ blood flow measurements using radiolabeled microspheres.

The quantitative analysis of the spatial variability of organ blood flow by means of radiolabeled microspheres (MS) requires that the methodological variability ("error") of the technique (RDmeth.) is known in each individual organ. Therefore, RDmeth. was quantified (eight to nine nuclides) in 6941 tissue samples from 13 organs of three anesthetized dogs, and the relative importance of errors originating from both the stochastic nature of MS distribution (RDtheo.) and the process of quantitation of MS radioactivity (RDcounting) was assessed under varying conditions (high/low specific MS activity (SAMS); inaccurate separation of gamma spectra; large sample size). At "minimized" methodological error (experiment 2), RDmeth. of samples trapping approximately 375 MS/nuclide was 5.8% and only slightly exceeded RDtheo. (5%). RDmeth. varied in the range 2.7-7.8% in individual organs and contributed little (3.5%) to the organs' observed spatial variability of flow. In contrast, RDmeth.--due to increased RDcounting--considerably exceeded RDtheo. when SAMS was low (experiment 3), overlap of two nuclides' main photopeaks was critical (experiment 1), or counting geometry was inappropriate (pulmonary tissue samples). At the same time, the contribution of RDmeth. to spatial flow variability rose to 7.9% (experiment 3), 26.9% (experiment 1), and 15-23% (lungs). Completely artifactual measurements, as indicated by an extremely high RDmeth. of sample flow, were rarely observed (less than 0.1%). In general, our data suggest that blood flow can be measured reproducibly and with low methodological error using up to 8 nuclides, RDmeth. does not essentially contribute to the observed spatial variability of organ blood flow, and, hence, organ flow variability may be accurately quantified using the MS technique. However, if sources of error as indicated above are present, the practice of using RDtheo. as a measure of RDmeth. (thereby neglecting RDcounting) may notably underestimate true MS error and result in an overestimation of spatial heterogeneity of organ blood flow. RDmeth., therefore, should be quantified separately in each region of interest prior to the onset of a new study.

Animals↗

PubMed1996

Synthesis of fat in response to alterations in diet: insights from new stable isotope methodologies.

Synthesis of fatty acids, or de novo lipogenesis (DNL), is an intensively researched metabolic pathway whose functional significance and metabolic role have nevertheless remained uncertain. Methodologic problems that limited previous investigations of DNL in vivo and recent methodologic advances that address these problems are discussed here. In particular, deuterated water incorporation and mass isotopomer distribution analysis techniques are described. Recent experimental results in humans based on these techniques are reviewed, emphasizing dietary and hormonal factors that modulate DNL and quantitative significance of DNL under various conditions, including carbohydrate overfeeding. The somewhat surprising finding that DNL appears not to be a quantitatively major pathway even under conditions of surplus carbohydrate energy intake, at least in normal adults on typical Western diets, is discussed in depth. Nutritional and metabolic implications of these results are also noted, and some speculations on possible functional roles of DNL in normal physiology and disease states are presented in this context. In summary, methodologic advances have added to our understanding of DNL and its regulation, but many questions concerning quantitation and function remain unanswered.

Calorimetry, Indirect↗