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Results for “Analytical Approach”

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PubMed2006

The role of trade-off shapes in the evolution of parasites in spatial host populations: an approximate analytical approach.

Given the substantial changes in mixing in many populations, there is considerable interest in the role that spatial structure can play in the evolution of disease. Here we examine the role of different trade-off shapes in the evolution of parasites in a spatially structured host population where infection can occur locally or globally. We develop an approximate adaptive dynamic analytical approach, to examine how the evolutionarily stable (ES) virulence depends not only on the fraction of global infection/transmission but also on the shape of the trade-off between transmission and virulence. Our analysis can successfully predict the ES virulence found previously by simulation of the full system. The analysis confirms that when there is a linear trade-off between transmission and virulence spatial structure may lead to an ES virulence that increases as the proportion of global transmission increases. However, we also show that the ESS disappears above a threshold level of global infection, leading to maximization. In addition just below this threshold, there is the possibility of evolutionary bi-stabilities. When we assume the realistic trade-off between transmission and virulence that results in an ESS in the classical mixed model, we find that spatial structure can increase or decrease the ES virulence. A relatively high proportion of local infection reduces virulence but intermediate levels can select for higher virulence. Our work not only emphasizes the importance of spatial structure to the evolution of parasites, but also makes it clear that situations between the local and the global need to be considered. We also emphasize the key role that the shape of trade-offs plays in evolutionary outcomes.

Adaptation, Physiological↗

PubMed2006

Uncertainties in workplace external dosimetry--an analytical approach.

The uncertainties associated with external dosimetry measurements at workplaces depend on the type of dosemeter used together with its performance characteristics and the information available on the measurement conditions. Performance characteristics were determined in the course of a type test and information about the measurement conditions can either be general, e.g. 'research' and 'medicine', or specific, e.g. 'X-ray testing equipment for aluminium wheel rims'. This paper explains an analytical approach to determine the measurement uncertainty. It is based on the Draft IEC Technical Report IEC 62461 Radiation Protection Instrumentation-Determination of Uncertainty in Measurement. Both this paper and the report cannot eliminate the fact that the determination of the uncertainty requires a larger effort than performing the measurement itself. As a counterbalance, the process of determining the uncertainty results not only in a numerical value of the uncertainty but also produces the best estimate of the quantity to be measured, which may differ from the indication of the instrument. Thus it also improves the result of the measurement.

Calibration↗

PubMed2000

An accessible analytical approach for investigating what happens between the rounds of a Delphi study.

The Delphi method is used to investigate consensus amongst a panel of experts using repeated rounds of a questionnaire, often in healthcare settings. However, many Delphi studies do not report any investigation into what happens to the stability of consensus or the convergence of agreement between the rounds in the study, which may be of importance. In this paper an accessible analytical approach is outlined using graphical presentations of means and standard deviations to identify what happens between rounds. For Delphi studies where the scale upon which experts are expressing their opinions can be considered to be interval, the mean will represent the group opinion whilst the standard deviation will represent the level of agreement. An example Delphi study from a healthcare setting is used to illustrate the methodology.

Attitude of Health Personnel↗

PubMed1988

Validating the components of a taxonomic system for rapists: a path analytic approach.

This study was part of a series designed to validate a classification system for rapists developed at the Massachusetts Treatment Center. This system (MTC:R2) determines subtypes according to three major dimensions: the meaning of the aggression in the rapist's offenses (expressive versus instrumental), the meaning of the sexual behavior (compensatory, exploitative, displaced anger, or sadistic), and the degree of general lifestyle impulsivity (low or high). A total of 201 rapists were subtyped using this system. A path analytic approach was used to relate family, juvenile, and adult histories to the main decisions of subtype assignment. The classification of an offender on each of the three dimensions was informed by a developmental perspective. Results provided support for the use of the discriminators used and highlighted the deficiencies in our current knowledge regarding developmental precursors. These results were integrated with the findings from other studies using MTC:R2 and suggestions for revisions to the current classification system were discussed.

Aggression↗

PubMedDate not supplied

Administrative days in acute care facilities: a queueing-analytic approach.

After acute care services are no longer required, a patient in an acute care hospital often must remain there while he or she awaits the provision of extended care services by a nursing home, through social support services, or by a home health care service. This waiting period is often referred to as "administrative days" because the time is spent in the acute facility not for medical reasons, but rather for administrative reasons. In this paper we use a queueing-analytic approach to describe the process by which patients await placement. We model the situation using a state-dependent placement rate for patients backed up in the acute care facility. We compare our model results with data collected from a convenience sample of 7 hospitals in New York State. We conclude with a discussion of the policy implications of our models.

Appointments and Schedules↗

PubMed1996

The meta-analytic approach to research integration.

A quantitative research method for aggregating findings from empirical research, meta-analysis is useful for systematically integrating findings gleaned from individual studies. Meta-analysis goes beyond the mere summarization and critique of research findings, to conducting statistical analyses on the outcomes of similar studies. Overall, meta-analysis represents a vast improvement over traditional methods of research review, by providing a more thorough description of the current status of research in an area and a more precise estimate of the effects of treatments or interventions. This article describes the meta-analytic approach to research integration, discusses the advantages that it offers for integrating nursing research, and highlights some of the methodological issues surrounding this approach.

Data Interpretation, Statistical↗

PubMed2005

An analytical approach to the rise velocity of periodic bubble trains in non-Newtonian fluids.

The present study aims at providing insight into the acceleration mechanism of a bubble chain rising in shear-thinning viscoelastic fluids. The experimental investigation by the Particle Image Velocimetry (PIV), birefringence visualisation and rheological simulation shows that two aspects are central to bubble interactions in such media: the stress creation by the passage of bubbles, and their relaxation due to the fluid's memory forming an evanescent corridor of reduced viscosity. Interactions between bubbles were taken into account mainly through a linear superposition of the stress evolution behind each bubble. An analytical approach together with the rheological consideration was developed to compute the rise velocity of a bubble chain in function of the injection period and bubble volume. The model predictions compare satisfactorily with the experimental investigation.

Computer Simulation↗

PubMed2001

Estimation of growth hormone secretion rate: impact of kinetic assumptions intrinsic to the analytical approach.

We compared four common mathematical techniques to determine daily endogenous growth hormone (GH) secretion rates from diurnal plasma GH concentration profiles in 24 women (16 upper- or lower-body obese and 8 normal-weight individuals). Two forms of deconvolution analysis and two techniques based on a priori determined GH clearance estimates were employed. Deconvolution analyses revealed significant differences in the 24-h GH secretion rate between normal-weight and upper-body obese women, whereas the other two techniques did not. Moreover, deconvolution analyses predicted that the reduction in mean plasma GH concentrations in upper-body obese women was accounted for by impaired GH secretion, whereas the other methods suggested that obesity increases GH metabolic clearance. Thus we infer that disparate conclusions concerning GH secretion can be drawn from the same primary data set. The different inferences likely reflect dissimilar kinetic assumptions and the particular limitations intrinsic to each analytical approach. Accordingly, we urge caution in the facile comparison of calculated GH secretion data in humans, especially when kinetic and secretion measurements are performed under different conditions. The most appropriate way to determine the GH secretion rate in humans must be balanced by the exact intent of the experiment and the acceptability of different assumptions in that context.

Adult↗

PubMed1995

Working with anger in groups: a modern analytic approach.

The development of Modern Psychoanalytic psychotherapy with schizophrenic and borderline patients is briefly traced, and the major themes of the treatment approach that derived from that early work are discussed with attention to their application in group therapy. These themes include the concepts of the narcissistic defense, narcissistic transference, joining or reinforcing defenses, emotional communication, and a shift away from the classical psychoanalytic emphasis on interpretation and insight to a strategy of helping the patient put all his or her thoughts and feelings into language in a constructive manner. These principles are discussed in connection with three kinds of problems involving anger in therapy groups: members' anger destructively turned against their own egos, anger expressed toward the leader within a negative transference, and anger destructively expressed toward others in the group. Lastly, consideration is given to the group leader's anger and its expression within the group. Some contrasts are made between the Modern Analytic approach and the classical Freudian position as well as Kohut's self psychology.

Anger↗

PubMed2006

Linkage of cell cycle kinetics between embryonic and adult stroke models: an analytical approach.

In the adult brain, neurogenesis occurs in the subventricular zone (SVZ) of the lateral ventricle. The proliferating population and the cell cycle kinetics in the ventricular zone regulate cortical neurogenesis during the development. Using the embryonic model, we investigated kinetics of SVZ cells in adult rats after stroke, incorporating migration of SVZ cells to the ischemic boundary. Concurrent linear regressions were considered through iteration to improve precision of parameter estimation. We found no model-fit difference in stroke with and without the migration (p=0.31), suggesting no migration effect on assessment of the cell kinetics. Stroke increased SVZ cell proliferation (20% in non-stroke and 31% in stroke p<0.01). Cell cycle durations in stroke were reduced for the total cycle length (19h for non-stroke and 15.3h for stroke, p<0.05), in G1 phase (12.6 h for non-stroke and 9.6 h for stroke, p<0.01), but were the same in S, M2, and in G2 phases compared to non-stroke, indicating that stroke reduces the total cell cycle length, specially in G1 phase. We conclude that cell cycle kinetic models for cortical development can be adapted to the kinetics of adult SVZ cells after stroke. The analytical approach may be useful for studying neural progenitor cell proliferation under different treatments.

Aging↗

PubMed1986

31P NMR studies of the intact perfused rat heart: a novel analytical approach for determining functional-metabolic correlates, temporal relationships, and intracellular actions of cardiotoxic chemicals nondestructively in an intact organ model.

Intact hearts isolated from adult male, Sprague-Dawley rats were perfused under standardized conditions in an apparatus designed for use in a high-resolution nuclear magnetic resonance (NMR) spectrometer system. Myocardial phosphate metabolite concentrations (ATP, PCr, Pi, and phosphomonoesters) and intracellular pH were determined sequentially at timed intervals coincident with the functional assessments of the intact heart by phosphorus-31 (31P) NMR spectroscopic methods. Myocardial functional and metabolic parameters were unaffected by sustained control perfusion (2 hr). The negative inotropic actions of cadmium were associated with significant changes in the chemical environment of inorganic phosphate (Pi) within the cells. This initial cellular response to cadmium, which correlated with the onset and magnitude of the contractile disturbances, appeared to represent the formation of an acidic, intracellular Pi pool (pH, 6.0). This pH compartment reached a steady state during the period in which maximal changes in contractile function were manifested, and before cellular ATP and PCr concentrations were altered. These findings are consistent with the interpretation that the functional deficits caused by cadmium originated primarily from changes in the chemical environment experienced by intracellular metabolites, rather than changes in the amounts of cellular high energy substrates. In contrast, the time-dependent negative inotropic effects of arsenate were proportional to the loss of cellular ATP stores. Intracellular pH was not affected in these hearts. A distinctive metabolic finding associated with the cardiotoxicity of arsenate was the time-dependent accumulation of previously undetected phosphate metabolites in the arsenate-treated hearts. Efforts to chemically identify these metabolites proved inconclusive; however, existing evidence suggests the possibility that these phosphorus-containing compounds may be arsenophosphate derivatives of naturally occurring cellular metabolites. The present findings provide experimental evidence demonstrating that toxicologic assessments in an intact organ model are feasible using whole organ 31P NMR spectroscopic methods and that meaningful, new insights regarding the biochemical mechanisms responsible for the cardiotoxic actions of xenobiotic agents can be obtained by this analytical approach.

Animals↗

PubMed2003

Salivary metal levels of orthodontic patients: a novel methodological and analytical approach.

The purpose of this study was to qualitatively and quantitatively assess the nickel, chromium, and ferrous levels in a population of 17 orthodontic patients undergoing treatment, compared with seven untreated individuals, employing a novel methodological approach and a new analytical technique. Salivary samples obtained from patients before and after rinsing with double distilled water were processed for Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) for simultaneous estimation of the concentration of the metallic elements. No statistically significant difference was detected between control and patient groups with respect to salivary metal content, regardless of element. The range of salivary metal levels found did not exceed those of daily intake through food and air. The lack of a continuous monitoring scheme for salivary metal concentrations in real time may impose substantial obstacles to defining the release rate of metals in vivo. The results of this study emphasize the necessity of incorporating the dimension of time in assessing the release potential of orthodontic alloys.

Adolescent↗

PubMed1998

Validation of home blood glucose meters with respect to clinical and analytical approaches.

OBJECTIVE: To evaluate the clinical and analytical accuracy of home blood glucose meters. RESEARCH DESIGN AND METHODS: Six blood glucose meters--Reflolux S (Boehringer Mannheim, Mannheim, Germany), One Touch II (LifeScan, Milpitas, CA), Glucocard Memory (Menarini, Florence, Italy), Precision QID (Medisense, Cambridge, U.K.), HaemoCue (HaemoCue, Angelholm, Sweden), and Accutrend alpha (Boehringer Mannheim, Mannheim, Germany)--were compared with a reference method (Beckman Glucose Analyzer II) under controlled conditions (glucose clamp technique). Validation of the blood glucose meters was accomplished by clinically oriented approaches (error grid analysis), statistical approaches (variance components analysis), and by the criteria of the American Diabetes Association (ADA), which recommend a target variability of < 5%. RESULTS: A total of 1,794 blood glucose monitor readings and 299 reference values ranging from 2.2 to 18.2 mmol/l were analyzed (705 readings < 3.89 mmol/l, 839 readings between 3.89 and 9.99 mmol/l, and 250 readings > 9.99 mmol/l). According to error grid analysis, only Reflolux S and Glucocard M had 100% of estimations within the clinically acceptable zones A and B. Assessment of analytical accuracy revealed substantial differences between the glucose meters after separation of the data into defined glycemic ranges. None of the devices met the ADA criteria. CONCLUSIONS: To evaluate accuracy of blood glucose meters, error grid analysis, as well as statistical models, are helpful means and should be performed together. Analytical performance of currently available home blood glucose meters differs substantially within defined glycemic ranges.

Blood Glucose Self-Monitoring↗

PubMed1985

Analytical approaches for biomedical elemental analysis.

Several different analytical systems are available for biomedical elemental analysis related to human nutrition. The principle, detection limits, analytical artifacts, and applications are presented for the following analytical systems for elemental analysis classified by sample volume: macro volume systems--flame atomic absorption spectroscopy (FAAS) and inductively coupled plasma (ICP); micro volume systems--electrothermal atomization (graphite furnace) atomic absorption spectroscopy (ETA-AAS) and x-ray fluorescence (XRF); and ultramicro volume systems--electron probe x-ray microanalysis (EPX) and laser microprobe mass analysis (LAMMA).

Electron Probe Microanalysis↗

PubMed1998

Optimal design of planar-concave collimators for SPECT--an analytical approach.

In this paper we present an analytical tool for the design and optimization of planar-concave collimators for SPECT. We conclude that a single general planar-concave collimator that eliminates the non-isotropic blurring for all SPECT applications does not exist. On the other hand, it is possible to achieve pseudo-optimal collimators for different clinical applications by a careful choice of the design parameters. By classifying the clinical applications into two groups, for instance body and brain studies, the non-isotropic blurring for most SPECT situations may be dramatically reduced by means of planar-concave collimators. The results based on Monte Carlo simulations show that the shape of the point source response function of the reconstructed image obtained from the planar-concave collimator is more isotropic than that obtained from a conventional parallel-hole collimator. Specifically, the ratio of the FWHM of the reconstructed point response function in the radial and tangential direction is increased from 0.5 for the parallel-hole to 0.85 for the planar-concave collimator for sources 200 mm away from the centre of rotation.

Algorithms↗

PubMed1980

A decision analytic approach to cleft palate treatment evaluation.

An analytic methodology, developed from the field of decision analysis, is presented for the evaluation of treatment alternatives. The management of velopharyngeal incompetence illustrates the method. Nasal quality is utilized as a primary means of measuring outcome. Results indicate that treatment alternatives can be preferentially ordered using analytic methods which incorporate costs, benefits, and probabilities of successful and unsuccessful outcomes. Extensions of the mathematical formulations are discussed in relationship to treatment outcomes.

Cleft Palate↗

PubMedDate not supplied

The analytical approach to the nature of lipofuscin (age pigment).

Analytical studies of three lipopigments show that much can be achieved. Lipopigment from ovine ceroid-lipofuscinosis is composed of discrete protein and lipid molecules in orderly arrays and lipid peroxidation is not involved in its formation. Subunit c of mitochondrial ATP synthase accounts for approximately 50% of accumulated material and is specific to the disease process in this and other forms of the disease. Lipofuscin from bovine heart was mostly soluble and also contained discrete proteins, lipids and metals. Equine thyroid lipofuscin was less soluble but also had a relatively high protein content, probably derived from thyroglobulin. Although sugar could not be measured quantitatively, staining reactions and elemental analyses suggested it could also be a significant component. Some may be present as derivatives in the form of advanced glycation products. It is proposed that protein, the dominant molecular species present, is the important constituent in lipofuscinogenesis rather than lipid peroxidation. Whereas this latter may play some part in the maturation of lipofuscin, this has not been shown experimentally and is not likely to be the initiating mechanism.

Journal Article↗

PubMed2001

An accurate analytical approach to electron crystallography.

A much more accurate analytical expression of dynamical electron diffraction than the phase object approximation (POA) formula has been derived in this paper which decreases the restriction of sample thickness up to almost one order of magnitude compared to POA theory. The importance of the new expression is twofold. First, a sample with such a thickness that new expression remains valid can be prepared experimentally. Second, the new expression reveals a clear and straightforward relationship between the wave function and crystal potential. In the expression, the effect of dynamical diffraction on wave function can be simply attributed to two factors TP(D) = (sin(lambda pi zg2))/(4pi2g2) and TA(D) = [1 - cos(lambda pi zg2)]/4pi2g2. Compared to the effect of transfer functions of an electron microscope on wave function, we found that TP(d) and TA(d) play the same role as transfer function but are independent of the instrument. For this reason, we here call the former as "extrinsic transfer functions" and the latter as "intrinsic" ones. In principle, one should correct not only extrinsic transfer functions but also intrinsic ones if one desires to achieve higher resolution.

Journal Article↗