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PubMed1986

The metro rating game: what can be learned from the recent migrants?

The authors examine nine indicators of quality of life in the 277 U.S. Standard Metropolitan Statistical Areas (SMSAs) in terms of their impact on the decision to migrate. The factors considered were utilized in the 1985 publication "Places Rated Almanac" and include climate, housing, health care, crime, transportation, education, recreation, arts, and economics. "The purpose of this paper is both to analyze several alternative methods by which the nine 'Places Rated' indicators have been combined in previous studies, and to estimate a new system of weights for combining such indicators from a multivariate model of metropolitan out-migration." In this article, the authors examine out-migration of metropolitan households during the years 1975-1980. "Coefficient estimates from a multivariate model of out-migration form the basis for a ranking of metropolitan areas in the third section. Also included are comparisons among this and other studies of both the implicit weights employed against the 'Places Rated' scores...to derive both overall measures of urban life quality, and how such quality varies by city size."

Americas↗
PubMed2006

Random sampling of evolution time space and Fourier transform processing.

Application of Fourier Transform for processing 3D NMR spectra with random sampling of evolution time space is presented. The 2D FT is calculated for pairs of frequencies, instead of conventional sequence of one-dimensional transforms. Signal to noise ratios and linewidths for different random distributions were investigated by simulations and experiments. The experimental examples include 3D HNCA, HNCACB and (15)N-edited NOESY-HSQC spectra of (13)C (15)N labeled ubiquitin sample. Obtained results revealed general applicability of proposed method and the significant improvement of resolution in comparison with conventional spectra recorded in the same time.

Fourier Analysis↗
PubMed2005

From acute to chronic pain after laparoscopic cholecystectomy: a prospective follow-up analysis.

OBJECTIVE: The pathogenesis and risk of chronic pain after cholecystectomy are unknown. In this prospective study of 150 consecutive patients undergoing laparoscopic cholecystectomy, the preoperative clinical data, cold pressor test, state of neuroticism and early postoperative pain intensity were assessed. MATERIAL AND METHODS: Follow-up questionnaires were sent to all patients 1 year after surgery. Patients with moderate/severe chronic pain were interviewed and invited to participate in a structured examination programme. RESULTS: The questionnaire response rate was 100%. Twenty patients reported moderate or severe chronic pain. The 1-year in-office interview revealed that two patients without chronic pain had misinterpreted the questionnaire. Sixteen patients were enrolled for the examination programme. Demonstrable pathology explained the aetiology of chronic pain in 8 patients (5%); another 8 patients with moderate (n=6) or severe (n=2) chronic pain were without pathological findings. In total, 132 patients had no chronic pain. Chronic pain patients suffered significantly more intense acute postoperative pain compared with those without chronic pain (p < or =0.05). The incidence of chronic pain patients was higher in the group of patients with intense acute postoperative pain than in patients with low acute postoperative pain (p = 0.030-0.063). Development of chronic pain was not statistically related to a preoperative cold pressor nociceptive stimulus, preoperative state of neuroticism or to any other variables examined. CONCLUSIONS: The risk of significant chronic pain after laparoscopic cholecystectomy for symptomatic cholecystolithiasis is low but was significantly associated with the intensity of acute postoperative pain. Patients should be carefully examined to exclude somatic causes of chronic pain after laparoscopic cholecystectomy.

Acute Disease↗
PubMed2005

Scaling exponents and probability distributions of DNA end-to-end distance.

The scaling of the average gyration radius of polymers as a function of their length can be experimentally determined from ensemble measurements, such as light scattering, and agrees with analytical estimates. Ensemble techniques, yet, do not give access to the full probability distributions. Single molecule techniques, instead, can deliver information on both average quantities and distribution functions. Here we exploit the high resolution of atomic force microscopy over long DNA molecules adsorbed on a surface to measure the average end-to-end distance as a function of the DNA length, and its full distribution function. We find that all the scaling exponents are close to the predicted 3D values (upsilon=0.589+/-0.006 and delta=2.58+/-0.77). These results suggest that the adsorption process is akin to a geometric projection from 3D to 2D, known to preserve the scaling properties of fractal objects of dimension df<2.

Computer Simulation↗
PubMed2005

Maximum likelihood segmentation of ultrasound images with Rayleigh distribution.

This study presents a geometric model and a computational algorithm for segmentation of ultrasound images. A partial differential equation (PDE)-based flow is designed in order to achieve a maximum likelihood segmentation of the target in the scene. The flow is derived as the steepest descent of an energy functional taking into account the density probability distribution of the gray levels of the image as well as smoothness constraints. To model gray level behavior of ultrasound images, the classic Rayleigh probability distribution is considered. The steady state of the flow presents a maximum likelihood segmentation of the target. A finite difference approximation of the flow is derived, and numerical experiments are provided. Results are presented on ultrasound medical images as fetal echography and echocardiography.

Algorithms↗
PubMed1999

The ideal free distribution in humans: an experimental test.

How the distribution of resources affects the spatial distribution of animals is a central concern of behavioral ecology. One influential model relating population dynamics to individual foraging behavior is that of ideal free distribution (Fretwell & Lucas, 1970). This model assumes foragers of equal competitive abilities, moving freely from one habitat to another, the choices made by each individual subject are supposed to equalize gains across habitats. The resulting distribution at the group level, or ideal free distribution, has been tested with various animal species. Here we report an experimental test with human subjects competing for money. The results approximate those predicted by the ideal free model, the degree of approximation being consistent with that obtained in other species. This similarity of results supports the application of behavioral ecology models to humanperformance.

Competitive Behavior↗
PubMed1978

Immunohistological studies on the distribution of cytochrome b3 reductase in rat liver microsomes.

The distribution of cytochrome b5 reductase in rat liver microsomes purified by density gradient centrifugation was studied using anti-cytochrome b5 reductase/anti-ferritin hybrid antibodies labeled with ferritin. Electron micrographs show that the outer surface and the polar cap of tangential sections of essentially all vesicles derived from endoplasmic reticulum are specifically marked with a few ferritin grains which are not localized in large patches but arranged randomly. This finding was correlated with morphometrical and biochemical measurements. The results, supporting our earlier investigations, suggest that cytochrome b5 reductase may be clustered at the most in very small assemblies consisting of a few molecules which, in turn, are statistically uniformly distributed over the total membrane system.

Animals↗
PubMed2005

Determination of orientation distribution function of anisotropic paramagnetic species by analysis of ESR spectra angular dependence.

A method has been developed to determine orientation distribution function (ODF) of anisotropic paramagnetic species by analysis of the angular dependence of the ESR spectra. The method is based on computational spectra simulation. The ODF is represented as an expansion in terms of orthonormal functions. The expansion coefficients are determined through minimization of discrepancies between simulated spectra and experimental ones. By means of the suggested method we have determined the orientation distribution functions for radical probe 2,2,6,6-tetramethyl-4-ol-piperidinooxyl in 4-n-amyl-4'-cyanobiphenyl aligned by magnetic field and 2-septadecyl-2,3,4,5,5-pentamethylimidazolidine in polyethylene stretched films. In each case, thermal evolution of the ODF has been investigated.

Algorithms↗
PubMed2004

Genetic networks with canalyzing Boolean rules are always stable.

We determine stability and attractor properties of random Boolean genetic network models with canalyzing rules for a variety of architectures. For all power law, exponential, and flat in-degree distributions, we find that the networks are dynamically stable. Furthermore, for architectures with few inputs per node, the dynamics of the networks is close to critical. In addition, the fraction of genes that are active decreases with the number of inputs per node. These results are based upon investigating ensembles of networks using analytical methods. Also, for different in-degree distributions, the numbers of fixed points and cycles are calculated, with results intuitively consistent with stability analysis; fewer inputs per node implies more cycles, and vice versa. There are hints that genetic networks acquire broader degree distributions with evolution, and hence our results indicate that for single cells, the dynamics should become more stable with evolution. However, such an effect is very likely compensated for by multicellular dynamics, because one expects less stability when interactions among cells are included. We verify this by simulations of a simple model for interactions among cells.

Animals↗
PubMed2006

Deterministic approach to robust adaptive learning of fuzzy models.

This study is concerned with the adaptive learning of an interpretable Sugeno-type fuzzy inference system, in a deterministic framework, in the presence of data uncertainties and modeling errors. The authors explore the use of Hinfinity estimation theory and least squares estimation for online learning of membership functions and consequent parameters without making any assumption and requiring a priori knowledge of upper bounds, statistics, and distribution of data uncertainties and modeling errors. The issues of data uncertainties, modeling errors, and time variations have been considered mathematically in a sensible way. The proposed robust approach to the adaptive learning of fuzzy models has been illustrated through the examples of adaptive system identification, time-series prediction, and estimation of an uncertain process.

Algorithms↗
PubMed2002

Heart rate variability after coronary artery bypass graft surgery: a prospective 3-year follow-up study.

BACKGROUND: Autonomic heart rate control is impaired after CABG. The aim of this study was to establish the temporal pattern of change in the decrease of HRV observed after CABG. METHODS AND RESULTS: Twelve patients with coronary artery disease were assessed with 24-hour Holter recordings 2 days before CABG and 1 week, 3 months, 6 months, 1 year, and 3 years after CABG. All the time-domain and frequency-domain HRV parameters decreased precipitately after CABG and were mostly recovered 3 months after CABG except mean NN, rMSSD, and pNN50. The ratio of LF to HF showed a slight decrease after surgery, recovered to preoperative values after 3 months, surpassed, and continued to increase 6 months after surgery. At 3 years of follow-up the recovery was complete. The rate of change of time-domain and frequency-domain parameters were calculated and their correlation with aortic cross-clamping time, number of vessels bypassed, the amount of cardioplegic used were sought and no statistically significant correlation was found. CONCLUSION: The recovery of HRV regardless to the preoperative state of the patients and their postoperative course implies that the early drop of HRV after CABG was related to the acute effects of surgery. Late complete recovery of HRV may be due to resolution of ischemia or use of angiotensin-converting enzyme inhibitor.

Adult↗
PubMed1988

Risk factors for type 2 (non-insulin-dependent) diabetes mellitus. Thirteen and one-half years of follow-up of the participants in a study of Swedish men born in 1913.

This report presents data on antecedents of Type 2 (non-insulin-dependent) diabetes mellitus in a homogeneous sample of randomly selected 54-year-old men from an urban Swedish population with a diabetes incidence of 6.1% during 13.5 years of follow-up. The increased risk leading to diabetes for those in the top quintile compared to the lowest quintile of the distribution of statistically significant risk factors were: body mass index = 21.7, triglycerides = 13.5, waist-to-hip circumference ratio = 9.6, diastolic blood pressure = 6.7, uric acid = 5.8, glutamic pyruvic transaminase = 3.9, bilirubin = 3.2, blood glucose = 2.7, lactate = 2.4 and glutamic oxaloacetic transaminase = 2.0. Those with a positive family history of diabetes had 2.4-fold higher risk for developing diabetes than those without such a history. In a multivariate analysis glutamic pyruvic transaminase, blood glucose, body mass index, bilirubin, systolic blood pressure, uric acid and a family history of diabetes were all significantly associated with the development of diabetes. Our study demonstrates the great importance of adiposity and body fat distribution for the risk of diabetes. A number of established risk factors for coronary heart disease are risk factors for diabetes as well. Disturbed liver function and increased levels of lactate are early risk factors for diabetes - presumably indicators of the presence of impaired glucose tolerance and/or hyperinsulinaemia.

Alanine Transaminase↗
PubMed2005

Fisher information matrix of the Dirichlet-multinomial distribution.

In this paper we derive explicit expressions for the elements of the exact Fisher information matrix of the Dirichlet-multinomial distribution. We show that exact calculation is based on the beta-binomial probability function rather than that of the Dirichlet-multinomial and this makes the exact calculation quite easy. The exact results are expected to be useful for the calculation of standard errors of the maximum likelihood estimates of the beta-binomial parameters and those of the Dirichlet-multinomial parameters for data that arise in practice in toxicology and other similar fields. Standard errors of the maximum likelihood estimates of the beta-binomial parameters and those of the Dirichlet-multinomial parameters, based on the exact and the asymptotic Fisher information matrix based on the Dirichlet distribution, are obtained for a set of data from Haseman and Soares (1976), a dataset from Mosimann (1962) and a more recent dataset from Chen, Kodell, Howe and Gaylor (1991). There is substantial difference between the standard errors of the estimates based on the exact Fisher information matrix and those based on the asymptotic Fisher information matrix.

Abnormalities, Drug-Induced↗
PubMed1999

Spontaneous subcapital femoral neck fracture complicating a healed intertrochanteric fracture.

A spontaneous subcapital femoral neck fracture is an uncommon complication of a healed intertrochanteric hip fracture. To determine the etiology of this complication, 274 patients who had been treated for intertrochanteric hip fractures were followed up over an 8-year period from June 1988 to June 1996. We found 7 fractures of the subcapital femoral neck without a history of a trauma. The remaining 267 patients were defined as the control group. All seven patients with fractures of the subcapital femoral neck were women, and their average age at the time of compression hip screw (CHS) fixation was 83 years (range 74-92 years). The subcapital fractures occurred between 4 and 36 months after CHS fixation. The difference in the Singh index between the patient and control groups was statistically significant (P < 0.01). However, with regard to the position of the screw, spinal score, age, ambulatory ability, height, weight, and intertrochanteric fracture type (Jensen type), the differences between the patient and control groups were not statistically significant. Based on our findings, we conclude that a high grade of osteoporosis is the most important predisposing factor in the spontaneous development of a subcapital femoral neck fracture after a healed intertrochanteric hip fracture.

Aged↗
PubMed2005

Is there a relation between irritable Bowel syndrome and urinary stone disease?

Our aim was to investigate the role of renal colic, a clinical condition characterized by excruciating pain, in the etiopathogenesis of irritable bowel syndrome (IBS). Two groups of patients were enrolled in the study. Group I consisted of 59 patients (33 male and 26 female) with a median age of 41.9 (18 to 58) years. The patients in group I were admitted to our clinic with urinary stone disease and with a medical history of acute renal colic. Group II consisted of 55 patients (25 male and 30 female) with a median age of 40.1 (18 to 56) years, complaining of urologic abnormalities other than stone disease. IBS was diagnosed using Rome criteria. Metabolic analysis for stone disease was performed on patients in group I. The incidence of five metabolic abnormalities--low urine volume, hypercalciuria, hyperoxaluria, hyperuricosuria and hypocitraturia--in patients with and without irritable bowel disease was investigated. IBS was found in 16 of the 59 patients (27.1%) in group I and in 6 of the 55 patients (10.9%) in group II. The difference was statistically significant (P < 0.05). Relative risk of developing IBS was 2.48 times higher in patients with urinary stone disease than in those without stone disease. There was no statistically significant difference in the metabolic analysis of patients with and without IBS in group I. IBS causes great suffering. Urinary stone disease should be considered as an etiological factor during management of IBS patients. In the presence of gastrointestinal symptoms, a patient with a medical history of acute renal colic might be referred to a gastroenterologist.

Adolescent↗
PubMed2005

Verification of the Crooks fluctuation theorem and recovery of RNA folding free energies.

Atomic force microscopes and optical tweezers are widely used to probe the mechanical properties of individual molecules and molecular interactions, by exerting mechanical forces that induce transitions such as unfolding or dissociation. These transitions often occur under nonequilibrium conditions and are associated with hysteresis effects-features usually taken to preclude the extraction of equilibrium information from the experimental data. But fluctuation theorems allow us to relate the work along nonequilibrium trajectories to thermodynamic free-energy differences. They have been shown to be applicable to single-molecule force measurements and have already provided information on the folding free energy of a RNA hairpin. Here we show that the Crooks fluctuation theorem can be used to determine folding free energies for folding and unfolding processes occurring in weak as well as strong nonequilibrium regimes, thereby providing a test of its validity under such conditions. We use optical tweezers to measure repeatedly the mechanical work associated with the unfolding and refolding of a small RNA hairpin and an RNA three-helix junction. The resultant work distributions are then analysed according to the theorem and allow us to determine the difference in folding free energy between an RNA molecule and a mutant differing only by one base pair, and the thermodynamic stabilizing effect of magnesium ions on the RNA structure.

Base Pairing↗
PubMed2002

The limitations of a 'high-risk' approach for the prevention of dental caries.

The decline in the prevalence of caries has lead several authors to advocate the adoption of a 'high-risk' approach for caries preventive strategies. This paper analyses such an approach. It argues that the distribution of caries within a population follows certain laws: first, the mean caries score is a function of the prevalence; second, the variance is a function of the mean; and third, for a particular mean score, the distribution within the population is predetermined. Using data from the National Preventive Dentistry Demonstration Programme (NPDDP) in the US and the British Association for the Study of Community Dentistry (BASCD) epidemiological programmes in the UK the functions determining the distribution of caries within the population are examined. The findings indicate the changes in caries experience observed occurred throughout populations and are not confined to subgroups. Strategies limited to individuals 'at risk' would fail to deal with the majority of new lesions. The main emphasis should be centred on a population approach.

Adolescent↗