SEARCH · PubMed Health

Results for “Deterministic Measurement”

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 73 records · Page 4Linked to original sources

PubMed1980

Physical causality and brain theories.

The history of deterministic theories in physics is reviewed, and four levels of determinism are found: 1) absolute, 2) asymptotic, 3) probabilistic, and 4) absolute indeterminism. Nagel's view that all causal laws are deterministic in the frame of the state descriptions to which they refer is acknowledged, but the inevitability of macroscopic measurement noise may hint that dynamical laws are innately noisy. Quantum mechanical effects are not the noise source. Symmetry and broken symmetry are introduced as physical concepts that can account both for lawfulness, and for the hierarchical nature of the universe. Physical ideas are chosen over those of formal systems with indirect self-reference as the basis of a global theory of brains. By exclusion it is concluded that only a statistical thermodynamics, combined with nonlinear mechanics, has the features needed for theorizing about brains in a physical sense. Quantum mechanics is judged not to be relevant. New statistical thermodynamic theories are briefly described, and their strengths and weaknesses noted. The question, "Why should neuroscience look to physics for its theories?" is raised and answered. Some concrete objectives for a program of theoretical research are stated.

Brain↗

PubMed1997

A dynamic mechanical model for hand force in right angle nutrunner operation.

A deterministic mechanical model based on physical tool parameters was used for estimating static and dynamic hand forces from kinematic measurements. We investigated the effects of target torque (25, 40, and 55 Nm) and threaded fastener joint hardness (35-, 150-, 300-, 500-, and 900-ms torque buildup time) on hand force. Estimated hand force was affected by target torque and joint hardness. Peak and average dynamic hand force was least for the hard joint (35-ms buildup) and greatest for the medium hardness joint (150-ms buildup). Tool inertia played the major role in reducing hand reaction force. Estimated hand force decreased when the inertial force component increased. Inertial force decreased by 366% when buildup time increased from 35 to 300 ms. Static modeling overestimated hand force; the error ranged from 10% for a soft joint to 40% for a hard joint. Results from direct hand force measurements using a strain gauge dynamometer showed that the dynamic model overestimated peak hand force by 9%. However, average hand force and force impulse were not significantly overestimated.

Hand Strength↗

PubMed1998

Efficiency of multistage marker-assisted selection in the improvement of multiple quantitative traits.

The application of marker-assisted selection (MAS) to breeding programmes depends on its relative cost and the expected economic return compared to conventional phenotypic selection. The relative efficiency of MAS can be increased through a two-stage selection scheme or through marker-based, multiple-trait improvement. However, the effectiveness of these alternatives has not been quantified. In this study, we evaluate the efficiency of MAS relative to conventional phenotypic selection and marker-only selection in multistage selection for the improvement of multiple traits. We further incorporate the costs of obtaining measurements on phenotypic characters and marker loci into the objective function to evaluate the efficiency of MAS with respect to the gain per unit cost. Deterministic analyses indicate that excluding costs, multiple-trait MAS can be used to increase the aggregate breeding values in quantitative characters and is expected to be more effective than conventional selection or single-trait MAS. Two-stage MAS has a slightly reduced gain because of culling in the first stage. If the objective function is to maximize the gain per unit cost, multiple-trait MAS is inferior to phenotypic selection in most of the selection schemes investigated when the cost ratio (r) of obtaining measurements on phenotypic characters to scoring marker loci is less than unity (r < or = 1.0) and the heritability (h2) is greater than 0.3. The efficiency of MAS increases as r increases and h2 decreases. For MAS to be more effective, it is necessary to decrease further the cost associated with molecular marker assays.

Chromosome Mapping↗

PubMed1991

Risk prevention and policy-making in automatic systems.

Accidents with automatic production systems are reported to be on the order of one in a hundred or thousand robot-years, while fatal accidents are found to occur one or two orders of magnitude less frequently. Traditions in occupational safety tend to seek for safety targets in terms of zero severe accidents for automatic systems. Decision-making requires a risk assessment balancing potential risk reduction measures and costs within the cultural environment of a production company. This paper presents a simplified procedure which acts as a decision tool. The procedure is based on a risk concept approaching prevention both in a deterministic and in a probabilistic manner. Eight accident scenarios are shown to represent the potential accident processes involving robot interactions with people. Seven prevention policies are shown to cover the accident scenarios in principle. An additional probabilistic approach may indicate which extra safety measures can be taken against what risk reduction and additional costs. The risk evaluation process aims at achieving a quantitative acceptable risk level. For that purpose, three risk evaluation methods are discussed with respect to reaching broad consensus on the safety targets.

Accidents, Occupational↗

PubMed1979

Computer simulation of the effectiveness of male-linked translocations for the control of Anopheles albimanus Wiedemann.

A deterministic simulation model was used to establish the potential value of releasing male-linked translocation heterozygotes as a control measure for Anopheles albimanus Wiedemann. Theoretical population reductions exceeding 90% were obtained within 90 and 120 days after releases at initial ratios of 5 translocation males (TM): 1 normal male (NM) and 1 TM: 1 NM, respectively. Additional simulations emphasized the importance of the need for a method that would eliminate females from the release material. Releases containing 15% females were less effective than those with none. When a malaria subroutine was included in the model, the calculations showed that all the theoretical releases greatly reduced the number of malaria-infective females and therefore would have a profound effect on transmission of the disease. The number of malaria-infective females present was eliminated completely when only translocation males were released; however, a small number were present when the releases contained 15% females. Male-linked translocation males required longer periods of time to bring about population control than males that were completely sterile.

Animals↗

PubMed1997

Nonlinear deterministic analysis of tissue texture: a stereological study on mastopathic and mammary cancer tissue using chaos theory.

Signals from some dynamical systems look like stochastic processes although their latent mechanism is deterministic. When such systems show sensitive dependence on small changes of initial conditions, they are denoted as deterministic chaos. Motivated by recent advances in statistical inference methods for chaotic systems and by the concept of spatial chaos, we present a deterministic approach to the study of epithelial tissue texture. Methods for estimation of the autocorrelation function, for evaluation of the power spectrum, for attractor reconstruction, for estimation of the Lyapunov exponent and of the correlation dimension, and for the generation of surrogate data sets are outlined. In our biological example, these methods are applied to 20 cases of mastopathy as compared to 20 cases of mammary cancer. The input signals for the analysis were estimates of epithelial fraction measured at low magnification within 5100 equally spaced line segments per case perpendicular to an arbitrarily directed axis. The results suggest the existence of a low-dimensional deterministic attractor in mastopathic tissue texture, which is replaced by coloured noise in the majority of mammary carcinomas. Biological mechanisms for this finding and scale effects are discussed, and some methodological aspects and possible extensions of our approach are outlined.

Breast Neoplasms↗

PubMed1991

A stochastic model for the development of an AIDS epidemic in a heterosexual population.

A non-age-dependent model, describing the evolution of a bisexual population, is developed in this paper and applied to projecting an AIDS epidemic in a heterosexual population. Included in the formulation are frequency- and non-frequency-dependent rules of partnership formation as well as five states of HIV disease, affecting the probability of infection per sexual contact. Results from computer experiments, designed to study the development of an AIDS epidemic in a heterosexual population fed by single males with a 50% prevalence of HIV infection prior to becoming active in heterosexual partnerships, are reported. In these experiments, the only source of HIV infection for females was sexual contacts with infected males within partnerships. Data on the probability of infection per sexual contact with an infected partner and the number of sexual contacts per month were incorporated into the model. However, the numbers used for the initial population of singles, couples, and those becoming sexually active per month were hypothetical. Even though the prevalence of HIV infection among males entering heterosexual partnerships was high, after 30 years the projected prevalence of HIV infection among females ranged from about 10 to 15% depending in part on the expected duration of partnerships and on whether the frequency- or non-frequency-dependent model was used. In these experiments, solutions of the embedded, nonlinear, deterministic equations for the incidence of HIV infection and the cumulative number of deaths due to AIDS proved to be good measures of central tendency for the sample functions of the stochastic population process.

Acquired Immunodeficiency Syndrome↗

PubMedDate not supplied

Non-deterministic individual responses to receptor-selective opioid agonists.

To assess within a single rat strain individual variability of analgesic responses to sub-ED50 doses of receptor-selective opioids, we measured: 1) tail flick latency (TFL) responses after intrathecal (ith) injection of delta, mu, and kappa agonists administered serially; 2) TFL and tail pinch latencies (TPch) after intravenous (iv) mu and kappa agonists; and 3) TFL and TPch after iv agonists of mu or combined mu + delta selectivity. Mean values in each study confirmed an analgesic response, but individual TFL and TPch responses were chaotic and, within each study, rank order correlations between TFL and TPch values within or between drugs were insignificant. Our results suggest a hypothesis that such responses are intrinsically nondeterministic because--resembling other complex dynamic systems--they are generated by stochastic receptor-transmitter interactions that in turn evoke a series of nonlinearly coupled cellular and neural events.

Amino Acid Sequence↗

PubMedDate not supplied

Evaluating the quality of anonymous record linkage using deterministic procedures with the New York State AIDS registry and a hospital discharge file.

Linkage of same-person records across multiple databases relies on high-quality, uniformly available identifying information. These data quality issues become increasingly important when personal names are not available for record linkage. Using deterministic decision criteria, we linked records from two population-based files in the absence of personal names. The sensitivity of anonymous record linkage procedures ranged from 32 to 85 per cent for the two years studied, and the positive predictive value (PPV) ranged from 14 to 99 per cent. Decreasing sensitivity and PPV were primarily attributed to (1) errors in computerized identifying information and (2) the deterministic decision criteria specified for record linkage. An evaluation of the contribution of personal names to the quality of record linkage found no measurable impact.

Acquired Immunodeficiency Syndrome↗

PubMedDate not supplied

Economic value of caregiver effort in maintaining long-term ventilator-assisted individuals at home.

OBJECTIVE: To estimate the economic value of caregivers' efforts in maintaining ventilator-assisted individuals at home. DESIGN: Nonexperimental, cross-sectional survey. SETTING: Households of home-based ventilator-assisted individuals residing in 37 states. PARTICIPANTS: Caregivers of 1404 ventilator-assisted individuals; 277 (19.7%) responses were received. OUTCOME MEASURES: The Home Ventilator Care Cost and Utilization Survey and the Modified Katz Index. METHODS: The economic value of caregiver effort was estimated deterministically by opportunity cost, aggregated market value, and aggregated replacement cost and estimated stochastically by ordinary least squares regression. Cost of formal home care services was estimated with the Medicare Schedule of Limits for Home Health Agency Costs. Estimates of total cost of home care for each method of valuing caregiver effort were calculated by summing the cost of formal home care services with the value of caregiver effort. RESULTS: The average monthly cost of formal home care services was estimated to be $6411 (SD, $8490; median, $2006; range, $0 to $38,607). After adding various values of caregiver effort to the cost of formal home care services, the average cost of home care increases by $960 to $12,483, depending on the method used to calculate the value of the caregiver's time; the median total cost of home care increased by $1403 to $17,793. Data also showed that, depending on the figure used to estimate the cost of long-term care and which method was used to calculate caregiver value, home care was more expensive for at least 4.6% of ventilator-assisted individuals and for as many as 36.7%. CONCLUSIONS: The incorporation of the caregiver's time value into cost estimates did not substantially reduce the proportion of patients for whom home care was the least expensive alternative, except when caregiver effort was valued at a registered nurse's wage rate. However, the methods used to place an economic value on caregiver effort did not take into consideration the long-term economic impact on caregivers who reduce their work hours or forego employment or educational opportunities, nor did they take into account the lost wages of the ventilator-assisted individual or the extent to which the caregiver was financially dependent on the ventilator-assisted individual.

Adult↗

PubMed1995

Parathyroid hormone secretion and serum calcium concentration--a deterministic view of its regulation.

In seven normal men we investigated the basal secretion of PTH by blood sampling in 30 sec intervals for estimation of intact PTH and at 2-min intervals for measurement of ionized calcium. In 4 of these subjects we also investigated the PTH-secretion under conditions of intermittent hypercalcemia and hypocalcemia. Our measurements demonstrate the existence of three time scales in the secretion of PTH, viz. short-term pulses (faster than 2 min), an intermediate pattern of adjusting PTH levels to changed Ca2+ averages, and finally a long-term coupling between PTH and Ca2+ averages after 20 min. Ionized calcium controls the long-term regulation and intermediate adaptation mechanisms, but the short-term fluctuations seem to be due to spontaneous secretion.

Adult↗

PubMed1997

Nutrient flows in agriculture in The Netherlands with special emphasis on pig production.

Annual nitrogen (N), phosphorus (P), and potassium (K) flows in agriculture in The Netherlands were identified and quantified in 1990, with special emphasis on pig production. Also, the effects that various management strategies in pig production have on NPK emission in 1990 were compared using a static deterministic simulation model. Ammonia emission from pig production in 1990 (60.9 Gg N) exceeded the defined target for the year 2000 (12.7 Gg N). Measures that affect volatilization of ammonia directly (i.e., introduction of low-emission stables, manure storage facilities, or manure application techniques) reduced ammonia emission most effectively. These measures, however, should be combined with a reduction in application of artificial N fertilizer to avoid an increase in N losses through leaching, run-off, or denitrification. Targets for ammonia emission in the year 2010 require a reduction in the pig population of 24 to 62%, in addition to implications of measures described in this article. National NPK losses in 1990 through leaching, run-off, or denitrification, predicted at 223.5 kg/ha for N, 32.7 kg/ha for P, and 67 kg/ha for K, exceeded government targets for the year 2010 (185 kg N/ha; 8.7 kg P/ha; norm not set for K). Reducing application of artificial NPK fertilizer reduced national NPK losses most effectively. For P, use of phytase and feeding pigs in accordance with their P requirements is required, in addition to limited use of artificial P fertilizer to meet targets for the year 2010. Hence, from an environmental point of view, pig production in The Netherlands is limited primarily by ammonia emission targets for the year 2010.

Ammonia↗

PubMed1998

On the holistic approach in cellular and cancer biology: nonlinearity, complexity, and quasi-determinism of the dynamic cellular network.

A keystone of the molecular reductionist approach to cellular biology is a specific deductive strategy relating genotype to phenotype-two distinct categories. This relationship is based on the assumption that the intermediary cellular network of actively transcribed genes and their regulatory elements is deterministic (i.e., a link between expression of a gene and a phenotypic trait can always be identified, and evolution of the network in time is predetermined). However, experimental data suggest that the relationship between genotype and phenotype is nonbijective (i.e., a gene can contribute to the emergence of more than just one phenotypic trait or a phenotypic trait can be determined by expression of several genes). This implies nonlinearity (i.e., lack of the proportional relationship between input and the outcome), complexity (i.e. emergence of the hierarchical network of multiple cross-interacting elements that is sensitive to initial conditions, possesses multiple equilibria, organizes spontaneously into different morphological patterns, and is controlled in dispersed rather than centralized manner), and quasi-determinism (i.e., coexistence of deterministic and nondeterministic events) of the network. Nonlinearity within the space of the cellular molecular events underlies the existence of a fractal structure within a number of metabolic processes, and patterns of tissue growth, which is measured experimentally as a fractal dimension. Because of its complexity, the same phenotype can be associated with a number of alternative sequences of cellular events. Moreover, the primary cause initiating phenotypic evolution of cells such as malignant transformation can be favored probabilistically, but not identified unequivocally. Thermodynamic fluctuations of energy rather than gene mutations, the material traits of the fluctuations alter both the molecular and informational structure of the network. Then, the interplay between deterministic chaos, complexity, self-organization, and natural selection drives formation of malignant phenotype. This concept offers a novel perspective for investigation of tumorigenesis without invalidating current molecular findings. The essay integrates the ideas of the sciences of complexity in a biological context.

Genotype↗

PubMed1976

Cytophotometric analysis of basic nuclear proteins during gametogenesis in the free-living nematode Panagrellus silusiae.

The cytochemical staining characteristics of basic nuclear proteins during gametogenesis in both sexes of the free-living nematode Panagrellus silusiae were monitored by absorption microspectrophotometry. During spermatogenesis, the levels of both of the nuclear-bound Sakaguchi and 1-fluoro-2, 4-dinitrobenzene (FDNB) reagents per Feulgen-DNA content increase prior to meiosis and subsequently drop off during spermiogenesis. During oogenesis, the amount of Sakaguchi-protein to DNA ratio rises slightly whereas the FDNB-protein to DNA ratio undergoes a meagre decline. Since the oocyte of Panagrellus accumulates DNA in excess of a 4C DNA equivalent, the relative constancy of the ratio of basic nuclear protein content to DNA amount during oogenesis signifies that these proteins are being continously produced during oocyte maturation. After treatment with alkaline fast green (pH 8.1) the cytoplasmic and nuclear regions of the gonocytes of both sexes yield such an intense reaction that microspectrophotometric measurements could not be taken. The basis of the cytoplasmic staining reaction to the fast green (pH 8.1) dye was not determined. The rapid, highly deterministic programme of embryogenesis in Panagrellus may require a substantial stockpiling of basic nuclear proteins during oogenesis.

Animals↗

PubMedDate not supplied

Discriminating deterministic versus stochastic dynamics in neuronal activity.

An approach to discriminating deterministic versus stochastic dynamics from neuronal data is presented. Direct tests for determinism are emphasized, as well as using time series with clear physical correlates measured from small ensembles of neurons. Surrogate data are used to provide null hypotheses that the dynamics in our data could be accounted for by linear stochastic systems. Algorithms are given in full, and the analysis of an experimental example is given.

Algorithms↗

PubMed1995

A survey of films for use as dosimeters in interventional radiology.

Analysis of radiation doses in interventional radiological procedures that can lead to deterministic radiation effects such as erythema and epilation would assist physicians in planning patients care after exposure and in reducing doses. Photographic films used to measure skin exposure in the past are too sensitive for the high doses involved in interventional procedures. Seventeen different types of films, many of which are generally available in hospitals, were surveyed to see if any would meet the demands of interventional radiology. Sensitometric curves obtained demonstrate that most films are inappropriate for high dose procedures. Using Kodak Fine Grain Positive and Dupont duplicating films and automatic processing, doses as high as 2.8 Gy could be measured with reasonable accuracy. Similar results can be obtained by manually processing Kodak XV-2 verification film at room temperature.

Automation↗

PubMed1995

EEG dipole localization bounds and MAP algorithms for head models with parameter uncertainties.

The Cramer-Rao bound for unbiased dipole location estimation is derived under the assumption of a general head model parameterized by deterministic and stochastic parameters. The expression thus characterizes fundamental limits on EEG dipole localization performance due to the effects of both model uncertainty and statistical measurements noise. Expressions are derived for the cases of multivariate Gaussian and gamma distribution priors, and examples are given to illustrate the derived bounds when the radii and conductivities of a four-concentric sphere head model are allowed to be random. The joint MAP estimate of location/model parameters is then examined as a means of achieving robustness to deviations from an ideal head model. Random variations in both the multiple sphere radii and the layer conductivities are shown, via the stochastic Cramer-Rao bounds and Monte Carlo simulation of the MAP estimator, to have the most impact on localization performance in high SNR regions, where finite sample effects are not the limiting factors. This corresponds most often to spatial regions that are close to the scalp electrodes.

Algorithms↗

PubMed1996

Dynamics of ongoing activity: explanation of the large variability in evoked cortical responses.

Evoked activity in the mammalian cortex and the resulting behavioral responses exhibit a large variability to repeated presentations of the same stimulus. This study examined whether the variability can be attributed to ongoing activity. Ongoing and evoked spatiotemporal activity patterns in the cat visual cortex were measured with real-time optical imaging; local field potentials and discharges of single neurons were recorded simultaneously, by electrophysiological techniques. The evoked activity appeared deterministic, and the variability resulted from the dynamics of ongoing activity, presumably reflecting the instantaneous state of cortical networks. In spite of the large variability, evoked responses in single trials could be predicted by linear summation of the deterministic response and the preceding ongoing activity. Ongoing activity must play an important role in cortical function and cannot be ignored in exploration of cognitive processes.

Animals↗