Development of S-ARIMA Model for Forecasting Demand in a Beverage Supply Chain

NASA Astrophysics Data System (ADS)

Mircetic, Dejan; Nikolicic, Svetlana; Maslaric, Marinko; Ralevic, Nebojsa; Debelic, Borna

2016-11-01

Demand forecasting is one of the key activities in planning the freight flows in supply chains, and accordingly it is essential for planning and scheduling of logistic activities within observed supply chain. Accurate demand forecasting models directly influence the decrease of logistics costs, since they provide an assessment of customer demand. Customer demand is a key component for planning all logistic processes in supply chain, and therefore determining levels of customer demand is of great interest for supply chain managers. In this paper we deal with exactly this kind of problem, and we develop the seasonal Autoregressive IntegratedMoving Average (SARIMA) model for forecasting demand patterns of a major product of an observed beverage company. The model is easy to understand, flexible to use and appropriate for assisting the expert in decision making process about consumer demand in particular periods.

An Unconditional Test for Change Point Detection in Binary Sequences with Applications to Clinical Registries.

PubMed

Ellenberger, David; Friede, Tim

2016-08-05

Methods for change point (also sometimes referred to as threshold or breakpoint) detection in binary sequences are not new and were introduced as early as 1955. Much of the research in this area has focussed on asymptotic and exact conditional methods. Here we develop an exact unconditional test. An unconditional exact test is developed which assumes the total number of events as random instead of conditioning on the number of observed events. The new test is shown to be uniformly more powerful than Worsley's exact conditional test and means for its efficient numerical calculations are given. Adaptions of methods by Berger and Boos are made to deal with the issue that the unknown event probability imposes a nuisance parameter. The methods are compared in a Monte Carlo simulation study and applied to a cohort of patients undergoing traumatic orthopaedic surgery involving external fixators where a change in pin site infections is investigated. The unconditional test controls the type I error rate at the nominal level and is uniformly more powerful than (or to be more precise uniformly at least as powerful as) Worsley's exact conditional test which is very conservative for small sample sizes. In the application a beneficial effect associated with the introduction of a new treatment procedure for pin site care could be revealed. We consider the new test an effective and easy to use exact test which is recommended in small sample size change point problems in binary sequences.

Some Exact Conditional Tests of Independence for R X C Cross-Classification Tables

ERIC Educational Resources Information Center

Agresti, Alan; Wackerly, Dennis

1977-01-01

Exact conditional tests of independence in cross-classification tables are formulated based on chi square and other statistics with stronger operational interpretations, such as some nominal and ordinal measures of association. Guidelines for table dimensions and sample sizes for which the tests are economically implemented on a computer are…

Occupational accidents among mototaxi drivers.

PubMed

Amorim, Camila Rego; de Araújo, Edna Maria; de Araújo, Tânia Maria; de Oliveira, Nelson Fernandes

2012-03-01

The use of motorcycles as a means of work has contributed to the increase in traffic accidents, in particular, mototaxi accidents. The aim of this study was to estimate and characterize the incidence of occupational accidents among the mototaxis registered in Feira de Santana, BA. This is a cross-sectional study with descriptive and census data. Of the 300 professionals registered at the Municipal Transportation Service, 267 professionals were interviewed through a structured questionnaire. Then, a descriptive analysis was conducted and the incidence of accidents was estimated based on the variables studied. Relative risks were calculated and statistical significance was determined using the chi-square test and Fisher's exact test, considering p < 0.05. Logistic regression was used in order to perform simultaneous adjustment of variables. Occupational accidents were observed in 10.5% of mototaxis. There were mainly minor injuries (48.7%), 27% of them requiring leaves of absence from work. There was an association between the days of work per week, fatigue in lower limbs and musculoskeletal complaints, and accidents. Knowledge of the working conditions and accidents involved in this activity can be of great importance for the adoption of traffic education policies, and to help prevent accidents by improving the working conditions and lives of these professionals.

Comparison of exact pupil astigmatism conditions with Seidel approximations

NASA Astrophysics Data System (ADS)

Zhao, Chunyu; Burge, James H.

2002-12-01

The aberrations of axisymmetric imaging systems can be calculated to third order by use of the Seidel formulas. The Coddington equations give aberrations that have quadratic dependence on the pupil, for all field points. The pupil astigmatism conditions were recently developed to predict and control aberrations that have quadratic field dependence and arbitrary pupil dependence. We investigate the relationship between the exact pupil astigmatism conditions and the classical Seidel treatment of pupil aberrations.

Menstrual cycle phase and single tablet antiretroviral medication adherence in women with HIV.

PubMed

Hessol, Nancy A; Holman, Susan; Minkoff, Howard; Cohen, Mardge H; Golub, Elizabeth T; Kassaye, Seble; Karim, Roksana; Sosanya, Oluwakemi; Shaheen, Christopher; Merhi, Zaher

2016-01-01

Suboptimal adherence to antiretroviral (ARV) therapy among HIV-infected individuals is associated with increased risk of progression to AIDS and the development of HIV resistance to ARV medications. To examine whether the luteal phase of the menstrual cycle is independently associated with suboptimal adherence to single tablet regimen (STR) ARV medication, data were analyzed from a multicenter cohort study of HIV-infected women who reported regular menstrual cycles and were taking an STR. In a cross-sectional analysis, suboptimal adherence to an STR among women in their follicular phase was compared with suboptimal adherence among women in their luteal phase. In two-way crossover analyses, whereby the same woman was assessed for STR medication adherence in both her follicular and luteal phases, the estimated exact conditional odds of non-adherence to an STR was measured. In adjusted logistic regression analysis of the cross-sectional data (N=327), women with ≤12 years of education were more than three times more likely to have suboptimal adherence (OR=3.6, p=.04) compared to those with >12 years of education. Additionally, women with Center for Epidemiological Studies Depression Scale (CES-D) scores ≥23 were 2.5-times more likely to have suboptimal adherence (OR=2.6, p=.02) compared to those with CES-D scores <23. In conditional logistic regression analyses of the crossover data (N=184), having childcare responsibilities was associated with greater odds of ≤95% adherence. Menstrual cycle phase was not associated with STR adherence in either the cross-sectional or crossover analyses. The lack of association between phase of the menstrual cycle and adherence to an STR in HIV-infected women means attention can be given to other more important risk factors for suboptimal adherence, such as depression, level of education, and childcare responsibilities.

Analysis of Multiple Contingency Tables by Exact Conditional Tests for Zero Partial Association.

ERIC Educational Resources Information Center

Kreiner, Svend

The tests for zero partial association in a multiple contingency table have gained new importance with the introduction of graphical models. It is shown how these may be performed as exact conditional tests, using as test criteria either the ordinary likelihood ratio, the standard x squared statistic, or any other appropriate statistics. A…

Relative Moldiness Index as Predictor of Childhood Respiratory Illness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vesper, Sephen J.; McKinstry, Craig A.; Haugland, Richard A.

2007-01-01

This study compared two classification methods to evaluate the mold condition in 271 homes of infants, 144 of which later developed symptoms of respiratory illness. A method using on-site visual mold inspection was compared to another method using a quantitative index of moldiness, calculated from mold specific quantitative PCR (MSQPCR) measurements on the concentration of 36 species of molds in floor dust samples called the EPA relative moldiness index© (ERMI©). The binary classification of homes as either moldy or non-moldy by on-site visual home inspection was not predictive of the development of wheeze and/or rhinitis. The odds-ratio of moldy vs.more » non-moldy homes to experience respiratory illness was estimated at 1.33 (p=0.27, Fisher’s exact test). Further, this method offers little flexibility in how it may be applied in support of decisions on mold remediation. On the other hand, a method developed and validated in this paper using the ERMI© index fit to a logistic function, can be used to predict the occurrence of illness in homes and allows stake holders to choose among various levels of risk. An example is given where an ERMI© value of -4.29 is used as a threshold for binary classification of homes producing an odds ratio of 2.53 (p=0.003, Fisher’s exact test). The ERMI© based methods presented here provide a new and more flexible platform to support mold remediation decisions.« less

Coastal Asia as seen from the ISS

NASA Image and Video Library

2001-03-30

ISS01-E-5082 (December 2000) --- This image of coastal Asia was taken from the International Space Station with a digital still camera and a 400mm lens with a very narrow field of view. Early in the Space Station Program, communications with the crew are less direct, and the exact time that this image was taken could not be determined. Because there are relatively few photograph of Earth taken with this long lens, and because the times are not available to calculate the exact position of the Station over the Earth when the photograph was taken, the exact location of the photograph cannot be determined. Many of these logistical problems will be resolved as camera equipment is replaced and communications with the crew improve. Catalogers believe the coast most resembles Indonesia, and this determination will be maintained until future images allow correction and refinement of the location. The photograph is a striking example of the degree to which humans modify coastal environments. The large green squares in the image probably represent a combination of rice cultivation and aquaculture.

On estimating probability of presence from use-availability or presence-background data.

PubMed

Phillips, Steven J; Elith, Jane

2013-06-01

A fundamental ecological modeling task is to estimate the probability that a species is present in (or uses) a site, conditional on environmental variables. For many species, available data consist of "presence" data (locations where the species [or evidence of it] has been observed), together with "background" data, a random sample of available environmental conditions. Recently published papers disagree on whether probability of presence is identifiable from such presence-background data alone. This paper aims to resolve the disagreement, demonstrating that additional information is required. We defined seven simulated species representing various simple shapes of response to environmental variables (constant, linear, convex, unimodal, S-shaped) and ran five logistic model-fitting methods using 1000 presence samples and 10 000 background samples; the simulations were repeated 100 times. The experiment revealed a stark contrast between two groups of methods: those based on a strong assumption that species' true probability of presence exactly matches a given parametric form had highly variable predictions and much larger RMS error than methods that take population prevalence (the fraction of sites in which the species is present) as an additional parameter. For six species, the former group grossly under- or overestimated probability of presence. The cause was not model structure or choice of link function, because all methods were logistic with linear and, where necessary, quadratic terms. Rather, the experiment demonstrates that an estimate of prevalence is not just helpful, but is necessary (except in special cases) for identifying probability of presence. We therefore advise against use of methods that rely on the strong assumption, due to Lele and Keim (recently advocated by Royle et al.) and Lancaster and Imbens. The methods are fragile, and their strong assumption is unlikely to be true in practice. We emphasize, however, that we are not arguing against standard statistical methods such as logistic regression, generalized linear models, and so forth, none of which requires the strong assumption. If probability of presence is required for a given application, there is no panacea for lack of data. Presence-background data must be augmented with an additional datum, e.g., species' prevalence, to reliably estimate absolute (rather than relative) probability of presence.

Conditional Poisson models: a flexible alternative to conditional logistic case cross-over analysis.

PubMed

Armstrong, Ben G; Gasparrini, Antonio; Tobias, Aurelio

2014-11-24

The time stratified case cross-over approach is a popular alternative to conventional time series regression for analysing associations between time series of environmental exposures (air pollution, weather) and counts of health outcomes. These are almost always analyzed using conditional logistic regression on data expanded to case-control (case crossover) format, but this has some limitations. In particular adjusting for overdispersion and auto-correlation in the counts is not possible. It has been established that a Poisson model for counts with stratum indicators gives identical estimates to those from conditional logistic regression and does not have these limitations, but it is little used, probably because of the overheads in estimating many stratum parameters. The conditional Poisson model avoids estimating stratum parameters by conditioning on the total event count in each stratum, thus simplifying the computing and increasing the number of strata for which fitting is feasible compared with the standard unconditional Poisson model. Unlike the conditional logistic model, the conditional Poisson model does not require expanding the data, and can adjust for overdispersion and auto-correlation. It is available in Stata, R, and other packages. By applying to some real data and using simulations, we demonstrate that conditional Poisson models were simpler to code and shorter to run than are conditional logistic analyses and can be fitted to larger data sets than possible with standard Poisson models. Allowing for overdispersion or autocorrelation was possible with the conditional Poisson model but when not required this model gave identical estimates to those from conditional logistic regression. Conditional Poisson regression models provide an alternative to case crossover analysis of stratified time series data with some advantages. The conditional Poisson model can also be used in other contexts in which primary control for confounding is by fine stratification.

Presenilin E318G variant and Alzheimer's disease risk: the Cache County study.

PubMed

Hippen, Ariel A; Ebbert, Mark T W; Norton, Maria C; Tschanz, JoAnn T; Munger, Ronald G; Corcoran, Christopher D; Kauwe, John S K

2016-06-29

Alzheimer's disease is the leading cause of dementia in the elderly and the third most common cause of death in the United States. A vast number of genes regulate Alzheimer's disease, including Presenilin 1 (PSEN1). Multiple studies have attempted to locate novel variants in the PSEN1 gene that affect Alzheimer's disease status. A recent study suggested that one of these variants, PSEN1 E318G (rs17125721), significantly affects Alzheimer's disease status in a large case-control dataset, particularly in connection with the APOEε4 allele. Our study looks at the same variant in the Cache County Study on Memory and Aging, a large population-based dataset. We tested for association between E318G genotype and Alzheimer's disease status by running a series of Fisher's exact tests. We also performed logistic regression to test for an additive effect of E318G genotype on Alzheimer's disease status and for the existence of an interaction between E318G and APOEε4. In our Fisher's exact test, it appeared that APOEε4 carriers with an E318G allele have slightly higher risk for AD than those without the allele (3.3 vs. 3.8); however, the 95 % confidence intervals of those estimates overlapped completely, indicating non-significance. Our logistic regression model found a positive but non-significant main effect for E318G (p = 0.895). The interaction term between E318G and APOEε4 was also non-significant (p = 0.689). Our findings do not provide significant support for E318G as a risk factor for AD in APOEε4 carriers. Our calculations indicated that the overall sample used in the logistic regression models was adequately powered to detect the sort of effect sizes observed previously. However, the power analyses of our Fisher's exact tests indicate that our partitioned data was underpowered, particularly in regards to the low number of E318G carriers, both AD cases and controls, in the Cache county dataset. Thus, the differences in types of datasets used may help to explain the difference in effect magnitudes seen. Analyses in additional case-control datasets will be required to understand fully the effect of E318G on Alzheimer's disease status.

Given a one-step numerical scheme, on which ordinary differential equations is it exact?

NASA Astrophysics Data System (ADS)

Villatoro, Francisco R.

2009-01-01

A necessary condition for a (non-autonomous) ordinary differential equation to be exactly solved by a one-step, finite difference method is that the principal term of its local truncation error be null. A procedure to determine some ordinary differential equations exactly solved by a given numerical scheme is developed. Examples of differential equations exactly solved by the explicit Euler, implicit Euler, trapezoidal rule, second-order Taylor, third-order Taylor, van Niekerk's second-order rational, and van Niekerk's third-order rational methods are presented.

Approximate bilateral symmetry in evaporation-induced polycrystalline structures from droplets of wheat grain leakages and fluctuating asymmetry as quality indicator

NASA Astrophysics Data System (ADS)

Kokornaczyk, Maria Olga; Dinelli, Giovanni; Betti, Lucietta

2013-01-01

The present paper reports on an observation that dendrite-like polycrystalline structures from evaporating droplets of wheat grain leakages exhibit bilateral symmetry. The exactness of this symmetry, measured by means of fluctuating asymmetry, varies depending on the cultivar and stress factor influence, and seems to correspond to the seed germination rate. In the bodies of plants, animals, and humans, the exactness of bilateral symmetry is known to reflect the environmental conditions of an organism's growth, its health, and its success in sexual selection. In polycrystalline structures, formed under the same conditions, the symmetry exactness depends on the properties of the crystallizing solution such as the composition and viscosity; however, it has never been associated with sample quality. We hypothesize here that, as in living nature, the exactness of approximate bilateral symmetry might be considered a quality indicator also in crystallographic methods applied to food quality analysis.

Exact solution for four-order acousto-optic Bragg diffraction with arbitrary initial conditions.

PubMed

Pieper, Ron; Koslover, Deborah; Poon, Ting-Chung

2009-03-01

An exact solution to the four-order acousto-optic (AO) Bragg diffraction problem with arbitrary initial conditions compatible with exact Bragg angle incident light is developed. The solution, obtained by solving a 4th-order differential equation, is formalized into a transition matrix operator predicting diffracted light orders at the exit of the AO cell in terms of the same diffracted light orders at the entrance. It is shown that the transition matrix is unitary and that this unitary matrix condition is sufficient to guarantee energy conservation. A comparison of analytical solutions with numerical predictions validates the formalism. Although not directly related to the approach used to obtain the solution, it was discovered that all four generated eigenvalues from the four-order AO differential matrix operator are expressed simply in terms of Euclid's Divine Proportion.

Is there a relationship between periodontal conditions and number of medications among the elderly?

PubMed

Natto, Zuhair S; Aladmawy, Majdi; Alshaeri, Heba K; Alasqah, Mohammed; Papas, Athena

2016-03-01

To investigate possible correlations of clinical attachment level and pocket depth with number of medications in elderly individuals. Intra-oral examinations for 139 patients visiting Tufts dental clinic were done. Periodontal assessments were performed with a manual UNC-15 periodontal probe to measure probing depth (PD) and clinical attachment level (CAL) at 6 sites. Complete lists of patients' medications were obtained during the examinations. Statistical analysis involved Kruskal-Wallis, chi square and multivariate logistic regression analyses. Age and health status attained statistical significance (p< 0.05), in contingency table analysis with number of medications. Number of medications had an effect on CAL: increased attachment loss was observed when 4 or more medications were being taken by the patient. Number of medications did not have any effect on periodontal PD. In multivariate logistic regression analysis, 6 or more medications had a higher risk of attachment loss (>3mm) when compared to the no-medication group, in crude OR (1.20, 95% CI:0.22-6.64), and age adjusted (OR=1.16, 95% CI:0.21-6.45), but not with the multivariate model (OR=0.71, 95% CI:0.11-4.39). CAL seems to be more sensitive to the number of medications taken, when compared to PD. However, it is not possible to discriminate at exactly what number of drug combinations the breakdown in CAL will happen. We need to do further analysis, including more subjects, to understand the possible synergistic mechanisms for different drug and periodontal responses.

Performance comparison of a new hybrid conjugate gradient method under exact and inexact line searches

NASA Astrophysics Data System (ADS)

Ghani, N. H. A.; Mohamed, N. S.; Zull, N.; Shoid, S.; Rivaie, M.; Mamat, M.

2017-09-01

Conjugate gradient (CG) method is one of iterative techniques prominently used in solving unconstrained optimization problems due to its simplicity, low memory storage, and good convergence analysis. This paper presents a new hybrid conjugate gradient method, named NRM1 method. The method is analyzed under the exact and inexact line searches in given conditions. Theoretically, proofs show that the NRM1 method satisfies the sufficient descent condition with both line searches. The computational result indicates that NRM1 method is capable in solving the standard unconstrained optimization problems used. On the other hand, the NRM1 method performs better under inexact line search compared with exact line search.

Exact conditions on the temperature dependence of density functionals

DOE PAGES

Burke, K.; Smith, J. C.; Grabowski, P. E.; ...

2016-05-15

Universal exact conditions guided the construction of most ground-state density functional approximations in use today. Here, we derive the relation between the entropy and Mermin free energy density functionals for thermal density functional theory. Both the entropy and sum of kinetic and electron-electron repulsion functionals are shown to be monotonically increasing with temperature, while the Mermin functional is concave downwards. Analogous relations are found for both exchange and correlation. The importance of these conditions is illustrated in two extremes: the Hubbard dimer and the uniform gas.

Variational analysis of the coupling between a geometrically exact Cosserat rod and an elastic continuum

NASA Astrophysics Data System (ADS)

Sander, Oliver; Schiela, Anton

2014-12-01

We formulate the static mechanical coupling of a geometrically exact Cosserat rod to a nonlinearly elastic continuum. In this setting, appropriate coupling conditions have to connect a one-dimensional model with director variables to a three-dimensional model without directors. Two alternative coupling conditions are proposed, which correspond to two different configuration trace spaces. For both, we show existence of solutions of the coupled problems, using the direct method of the calculus of variations. From the first-order optimality conditions, we also derive the corresponding conditions for the dual variables. These are then interpreted in mechanical terms.

Solving Modal Equations of Motion with Initial Conditions Using MSC/NASTRAN DMAP. Part 2; Coupled Versus Uncoupled Integration

NASA Technical Reports Server (NTRS)

Barnett, Alan R.; Ibrahim, Omar M.; Abdallah, Ayman A.; Sullivan, Timothy L.

1993-01-01

By utilizing MSC/NASTRAN DMAP (Direct Matrix Abstraction Program) in an existing NASA Lewis Research Center coupled loads methodology, solving modal equations of motion with initial conditions is possible using either coupled (Newmark-Beta) or uncoupled (exact mode superposition) integration available within module TRD1. Both the coupled and newly developed exact mode superposition methods have been used to perform transient analyses of various space systems. However, experience has shown that in most cases, significant time savings are realized when the equations of motion are integrated using the uncoupled solver instead of the coupled solver. Through the results of a real-world engineering analysis, advantages of using the exact mode superposition methodology are illustrated.

Risk factors of fatal occupational accidents in Iran.

PubMed

Asady, Hadi; Yaseri, Mehdi; Hosseini, Mostafa; Zarif-Yeganeh, Morvarid; Yousefifard, Mahmoud; Haghshenas, Mahin; Hajizadeh-Moghadam, Parisa

2018-01-01

Occupational accidents are of most important consequences of globalization in developing countries. Therefore, investigating the causes of occupational accidents for improving the job situation and making operational policy is necessary. So the aim of this study was to investigate factors affecting the fatal occupational accidents and also calculate the years of life lost for dead workers. This cross-sectional study was conducted on data related to the 6052 injured workers that was registered in the 2013 registry system of the Ministry of Health and Medical Education of Iran. Variables including sex, education, age, job tenure, injury cause, referred location of injured workers, occupation, shift work, season, accident day, damaged part of the body were chosen as independent variables. The Chi-squared and Fisher exact tests were used for univariate analysis and then exact multiple logistic regression was carried out to identify independent risk factors of fatal occupational accidents. Finally, for dead workers, years of life lost, according to the injury causes was calculated. Among the 6052 accidents reported, 33 deaths were recorded. Chi-square and Fisher exact tests showed that factors including: current job tenure ( p  = 0.01), damaged parts of the body ( p  < 0.001) and injury cause ( p  < 0.001) are associated with the fatal accidents. Also exact multiple logistic regression analysis showed a significant association between electric shocks as a cause of injury (OR = 7.04; 95% CI: 1.01-43.74; p  = 0.02) and current job tenure more than 1 year (OR = 0.21; 95% CI: 0.05-0.70; p  = 0.005) with the fatal accidents. The total amount of years of life lost based on causes of injuries was estimated 1289.12 years. In Iran, fatal accident odds in workers with job tenure more than 1 year was less in comparing to the workers with job tenure less and equal to 1 year. Also odd of death for electrical shock was more than other causes of injuries. So it seems that employing of workers who have more than one-year work experience in a specific job and using of appropriate safeguards will be useful for the reducing of fatal occupational accidents.

21 CFR 330.1 - General conditions for general recognition as safe, effective and not misbranded.

Code of Federal Regulations, 2012 CFR

2012-04-01

... exact language where exact language has been established and identified by quotation marks in an... “minimize”. (64) “Referred to as” or “of”. (65) “Sensation” or “feeling”. (66) “Solution” or “liquid”. (67...

21 CFR 330.1 - General conditions for general recognition as safe, effective and not misbranded.

Code of Federal Regulations, 2013 CFR

2013-04-01

... exact language where exact language has been established and identified by quotation marks in an... “minimize”. (64) “Referred to as” or “of”. (65) “Sensation” or “feeling”. (66) “Solution” or “liquid”. (67...

21 CFR 330.1 - General conditions for general recognition as safe, effective and not misbranded.

Code of Federal Regulations, 2014 CFR

2014-04-01

... exact language where exact language has been established and identified by quotation marks in an... “minimize”. (64) “Referred to as” or “of”. (65) “Sensation” or “feeling”. (66) “Solution” or “liquid”. (67...

Risk Factors for Venous Thromboembolism After Spine Surgery

PubMed Central

Tominaga, Hiroyuki; Setoguchi, Takao; Tanabe, Fumito; Kawamura, Ichiro; Tsuneyoshi, Yasuhiro; Kawabata, Naoya; Nagano, Satoshi; Abematsu, Masahiko; Yamamoto, Takuya; Yone, Kazunori; Komiya, Setsuro

2015-01-01

Abstract The efficacy and safety of chemical prophylaxis to prevent the development of deep venous thrombosis (DVT) or pulmonary embolism (PE) following spine surgery are controversial because of the possibility of epidural hematoma formation. Postoperative venous thromboembolism (VTE) after spine surgery occurs at a frequency similar to that seen after joint operations, so it is important to identify the risk factors for VTE formation following spine surgery. We therefore retrospectively studied data from patients who had undergone spinal surgery and developed postoperative VTE to identify those risk factors. We conducted a retrospective clinical study with logistic regression analysis of a group of 80 patients who had undergone spine surgery at our institution from June 2012 to August 2013. All patients had been screened by ultrasonography for DVT in the lower extremities. Parameters of the patients with VTE were compared with those without VTE using the Mann–Whitney U-test and Fisher exact probability test. Logistic regression analysis was used to analyze the risk factors associated with VTE. A value of P < 0.05 was used to denote statistical significance. The prevalence of VTE was 25.0% (20/80 patients). One patient had sensed some incongruity in the chest area, but the vital signs of all patients were stable. VTEs had developed in the pulmonary artery in one patient, in the superficial femoral vein in one patient, in the popliteal vein in two patients, and in the soleal vein in 18 patients. The Mann–Whitney U-test and Fisher exact probability test showed that, except for preoperative walking disability, none of the parameters showed a significant difference between patients with and without VTE. Risk factors identified in the multivariate logistic regression analysis were preoperative walking disability and age. The prevalence of VTE after spine surgery was relatively high. The most important risk factor for developing postoperative VTE was preoperative walking disability. Gait training during the early postoperative period is required to prevent VTE. PMID:25654385

Electron correlation in Hooke's law atom in the high-density limit.

PubMed

Gill, P M W; O'Neill, D P

2005-03-01

Closed-form expressions for the first three terms in the perturbation expansion of the exact energy and Hartree-Fock energy of the lowest singlet and triplet states of the Hooke's law atom are found. These yield elementary formulas for the exact correlation energies (-49.7028 and -5.807 65 mE(h)) of the two states in the high-density limit and lead to a pair of necessary conditions on the exact correlation kernel G(w) in Hartree-Fock-Wigner theory.

Orthographic and Semantic Processing in Young Readers

ERIC Educational Resources Information Center

Polse, Lara R.; Reilly, Judy S.

2015-01-01

This investigation examined orthographic and semantic processing during reading acquisition. Children in first to fourth grade were presented with a target word and two response alternatives, and were asked to identify the semantic match. Words were presented in four conditions: an exact match and unrelated foil (STONE-STONE-EARS), an exact match…

Exact Tests for the Rasch Model via Sequential Importance Sampling

ERIC Educational Resources Information Center

Chen, Yuguo; Small, Dylan

2005-01-01

Rasch proposed an exact conditional inference approach to testing his model but never implemented it because it involves the calculation of a complicated probability. This paper furthers Rasch's approach by (1) providing an efficient Monte Carlo methodology for accurately approximating the required probability and (2) illustrating the usefulness…

Frequent hospital admissions in Singapore: clinical risk factors and impact of socioeconomic status.

PubMed

Low, Lian Leng; Tay, Wei Yi; Ng, Matthew Joo Ming; Tan, Shu Yun; Liu, Nan; Lee, Kheng Hock

2018-01-01

Frequent admitters to hospitals are high-cost patients who strain finite healthcare resources. However, the exact risk factors for frequent admissions, which can be used to guide risk stratification and design effective interventions locally, remain unknown. Our study aimed to identify the clinical and sociodemographic risk factors associated with frequent hospital admissions in Singapore. An observational study was conducted using retrospective 2014 data from the administrative database at Singapore General Hospital, Singapore. Variables were identified a priori and included patient demographics, comorbidities, prior healthcare utilisation, and clinical and laboratory variables during the index admission. Multivariate logistic regression analysis was used to identify independent risk factors for frequent admissions. A total of 16,306 unique patients were analysed and 1,640 (10.1%) patients were classified as frequent admitters. On multivariate logistic regression, 16 variables were independently associated with frequent hospital admissions, including age, cerebrovascular disease, history of malignancy, haemoglobin, serum creatinine, serum albumin, and number of specialist outpatient clinic visits, emergency department visits, admissions preceding index admission and medications dispensed at discharge. Patients staying in public rental housing had a 30% higher risk of being a frequent admitter after adjusting for demographics and clinical conditions. Our study, the first in our knowledge to examine the clinical risk factors for frequent admissions in Singapore, validated the use of public rental housing as a sensitive indicator of area-level socioeconomic status in Singapore. These risk factors can be used to identify high-risk patients in the hospital so that they can receive interventions that reduce readmission risk. Copyright: © Singapore Medical Association

Conditional spectrum computation incorporating multiple causal earthquakes and ground-motion prediction models

USGS Publications Warehouse

Lin, Ting; Harmsen, Stephen C.; Baker, Jack W.; Luco, Nicolas

2013-01-01

The conditional spectrum (CS) is a target spectrum (with conditional mean and conditional standard deviation) that links seismic hazard information with ground-motion selection for nonlinear dynamic analysis. Probabilistic seismic hazard analysis (PSHA) estimates the ground-motion hazard by incorporating the aleatory uncertainties in all earthquake scenarios and resulting ground motions, as well as the epistemic uncertainties in ground-motion prediction models (GMPMs) and seismic source models. Typical CS calculations to date are produced for a single earthquake scenario using a single GMPM, but more precise use requires consideration of at least multiple causal earthquakes and multiple GMPMs that are often considered in a PSHA computation. This paper presents the mathematics underlying these more precise CS calculations. Despite requiring more effort to compute than approximate calculations using a single causal earthquake and GMPM, the proposed approach produces an exact output that has a theoretical basis. To demonstrate the results of this approach and compare the exact and approximate calculations, several example calculations are performed for real sites in the western United States. The results also provide some insights regarding the circumstances under which approximate results are likely to closely match more exact results. To facilitate these more precise calculations for real applications, the exact CS calculations can now be performed for real sites in the United States using new deaggregation features in the U.S. Geological Survey hazard mapping tools. Details regarding this implementation are discussed in this paper.

On approximating guided waves in plates with thin anisotropic coatings by means of effective boundary conditions

PubMed

Niklasson; Datta; Dunn

2000-09-01

In this paper, effective boundary conditions for elastic wave propagation in plates with thin coatings are derived. These effective boundary conditions are used to obtain an approximate dispersion relation for guided waves in an isotropic plate with thin anisotropic coating layers. The accuracy of the effective boundary conditions is investigated numerically by comparison with exact solutions for two different material systems. The systems considered consist of a metallic core with thin superconducting coatings. It is shown that for wavelengths long compared to the coating thickness there is excellent agreement between the approximate and exact solutions for both systems. Furthermore, numerical results presented might be used to characterize coating properties by ultrasonic techniques.

Exact lower and upper bounds on stationary moments in stochastic biochemical systems

NASA Astrophysics Data System (ADS)

Ghusinga, Khem Raj; Vargas-Garcia, Cesar A.; Lamperski, Andrew; Singh, Abhyudai

2017-08-01

In the stochastic description of biochemical reaction systems, the time evolution of statistical moments for species population counts is described by a linear dynamical system. However, except for some ideal cases (such as zero- and first-order reaction kinetics), the moment dynamics is underdetermined as lower-order moments depend upon higher-order moments. Here, we propose a novel method to find exact lower and upper bounds on stationary moments for a given arbitrary system of biochemical reactions. The method exploits the fact that statistical moments of any positive-valued random variable must satisfy some constraints that are compactly represented through the positive semidefiniteness of moment matrices. Our analysis shows that solving moment equations at steady state in conjunction with constraints on moment matrices provides exact lower and upper bounds on the moments. These results are illustrated by three different examples—the commonly used logistic growth model, stochastic gene expression with auto-regulation and an activator-repressor gene network motif. Interestingly, in all cases the accuracy of the bounds is shown to improve as moment equations are expanded to include higher-order moments. Our results provide avenues for development of approximation methods that provide explicit bounds on moments for nonlinear stochastic systems that are otherwise analytically intractable.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Curchod, Basile F. E.; Agostini, Federica, E-mail: agostini@mpi-halle.mpg.de; Gross, E. K. U.

Nonadiabatic quantum interferences emerge whenever nuclear wavefunctions in different electronic states meet and interact in a nonadiabatic region. In this work, we analyze how nonadiabatic quantum interferences translate in the context of the exact factorization of the molecular wavefunction. In particular, we focus our attention on the shape of the time-dependent potential energy surface—the exact surface on which the nuclear dynamics takes place. We use a one-dimensional exactly solvable model to reproduce different conditions for quantum interferences, whose characteristic features already appear in one-dimension. The time-dependent potential energy surface develops complex features when strong interferences are present, in clear contrastmore » to the observed behavior in simple nonadiabatic crossing cases. Nevertheless, independent classical trajectories propagated on the exact time-dependent potential energy surface reasonably conserve a distribution in configuration space that mimics one of the exact nuclear probability densities.« less

Genetic prediction of type 2 diabetes using deep neural network.

PubMed

Kim, J; Kim, J; Kwak, M J; Bajaj, M

2018-04-01

Type 2 diabetes (T2DM) has strong heritability but genetic models to explain heritability have been challenging. We tested deep neural network (DNN) to predict T2DM using the nested case-control study of Nurses' Health Study (3326 females, 45.6% T2DM) and Health Professionals Follow-up Study (2502 males, 46.5% T2DM). We selected 96, 214, 399, and 678 single-nucleotide polymorphism (SNPs) through Fisher's exact test and L1-penalized logistic regression. We split each dataset randomly in 4:1 to train prediction models and test their performance. DNN and logistic regressions showed better area under the curve (AUC) of ROC curves than the clinical model when 399 or more SNPs included. DNN was superior than logistic regressions in AUC with 399 or more SNPs in male and 678 SNPs in female. Addition of clinical factors consistently increased AUC of DNN but failed to improve logistic regressions with 214 or more SNPs. In conclusion, we show that DNN can be a versatile tool to predict T2DM incorporating large numbers of SNPs and clinical information. Limitations include a relatively small number of the subjects mostly of European ethnicity. Further studies are warranted to confirm and improve performance of genetic prediction models using DNN in different ethnic groups. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Mixed conditional logistic regression for habitat selection studies.

PubMed

Duchesne, Thierry; Fortin, Daniel; Courbin, Nicolas

2010-05-01

1. Resource selection functions (RSFs) are becoming a dominant tool in habitat selection studies. RSF coefficients can be estimated with unconditional (standard) and conditional logistic regressions. While the advantage of mixed-effects models is recognized for standard logistic regression, mixed conditional logistic regression remains largely overlooked in ecological studies. 2. We demonstrate the significance of mixed conditional logistic regression for habitat selection studies. First, we use spatially explicit models to illustrate how mixed-effects RSFs can be useful in the presence of inter-individual heterogeneity in selection and when the assumption of independence from irrelevant alternatives (IIA) is violated. The IIA hypothesis states that the strength of preference for habitat type A over habitat type B does not depend on the other habitat types also available. Secondly, we demonstrate the significance of mixed-effects models to evaluate habitat selection of free-ranging bison Bison bison. 3. When movement rules were homogeneous among individuals and the IIA assumption was respected, fixed-effects RSFs adequately described habitat selection by simulated animals. In situations violating the inter-individual homogeneity and IIA assumptions, however, RSFs were best estimated with mixed-effects regressions, and fixed-effects models could even provide faulty conclusions. 4. Mixed-effects models indicate that bison did not select farmlands, but exhibited strong inter-individual variations in their response to farmlands. Less than half of the bison preferred farmlands over forests. Conversely, the fixed-effect model simply suggested an overall selection for farmlands. 5. Conditional logistic regression is recognized as a powerful approach to evaluate habitat selection when resource availability changes. This regression is increasingly used in ecological studies, but almost exclusively in the context of fixed-effects models. Fitness maximization can imply differences in trade-offs among individuals, which can yield inter-individual differences in selection and lead to departure from IIA. These situations are best modelled with mixed-effects models. Mixed-effects conditional logistic regression should become a valuable tool for ecological research.

Exact vibration analysis of a double-nanobeam-systems embedded in an elastic medium by a Hamiltonian-based method

NASA Astrophysics Data System (ADS)

Zhou, Zhenhuan; Li, Yuejie; Fan, Junhai; Rong, Dalun; Sui, Guohao; Xu, Chenghui

2018-05-01

A new Hamiltonian-based approach is presented for finding exact solutions for transverse vibrations of double-nanobeam-systems embedded in an elastic medium. The continuum model is established within the frameworks of the symplectic methodology and the nonlocal Euler-Bernoulli and Timoshenko beam beams. The symplectic eigenfunctions are obtained after expressing the governing equations in a Hamiltonian form. Exact frequency equations, vibration modes and displacement amplitudes are obtained by using symplectic eigenfunctions and end conditions. Comparisons with previously published work are presented to illustrate the accuracy and reliability of the proposed method. The comprehensive results for arbitrary boundary conditions could serve as benchmark results for verifying numerically obtained solutions. In addition, a study on the difference between the nonlocal beam and the nonlocal plate is also included.

Matched samples logistic regression in case-control studies with missing values: when to break the matches.

PubMed

Hansson, Lisbeth; Khamis, Harry J

2008-12-01

Simulated data sets are used to evaluate conditional and unconditional maximum likelihood estimation in an individual case-control design with continuous covariates when there are different rates of excluded cases and different levels of other design parameters. The effectiveness of the estimation procedures is measured by method bias, variance of the estimators, root mean square error (RMSE) for logistic regression and the percentage of explained variation. Conditional estimation leads to higher RMSE than unconditional estimation in the presence of missing observations, especially for 1:1 matching. The RMSE is higher for the smaller stratum size, especially for the 1:1 matching. The percentage of explained variation appears to be insensitive to missing data, but is generally higher for the conditional estimation than for the unconditional estimation. It is particularly good for the 1:2 matching design. For minimizing RMSE, a high matching ratio is recommended; in this case, conditional and unconditional logistic regression models yield comparable levels of effectiveness. For maximizing the percentage of explained variation, the 1:2 matching design with the conditional logistic regression model is recommended.

Communication: An exact bound on the bridge function in integral equation theories.

PubMed

Kast, Stefan M; Tomazic, Daniel

2012-11-07

We show that the formal solution of the general closure relation occurring in Ornstein-Zernike-type integral equation theories in terms of the Lambert W function leads to an exact relation between the bridge function and correlation functions, most notably to an inequality that bounds possible bridge values. The analytical results are illustrated on the example of the Lennard-Jones fluid for which the exact bridge function is known from computer simulations under various conditions. The inequality has consequences for the development of bridge function models and rationalizes numerical convergence issues.

Semi-implicit integration factor methods on sparse grids for high-dimensional systems

NASA Astrophysics Data System (ADS)

Wang, Dongyong; Chen, Weitao; Nie, Qing

2015-07-01

Numerical methods for partial differential equations in high-dimensional spaces are often limited by the curse of dimensionality. Though the sparse grid technique, based on a one-dimensional hierarchical basis through tensor products, is popular for handling challenges such as those associated with spatial discretization, the stability conditions on time step size due to temporal discretization, such as those associated with high-order derivatives in space and stiff reactions, remain. Here, we incorporate the sparse grids with the implicit integration factor method (IIF) that is advantageous in terms of stability conditions for systems containing stiff reactions and diffusions. We combine IIF, in which the reaction is treated implicitly and the diffusion is treated explicitly and exactly, with various sparse grid techniques based on the finite element and finite difference methods and a multi-level combination approach. The overall method is found to be efficient in terms of both storage and computational time for solving a wide range of PDEs in high dimensions. In particular, the IIF with the sparse grid combination technique is flexible and effective in solving systems that may include cross-derivatives and non-constant diffusion coefficients. Extensive numerical simulations in both linear and nonlinear systems in high dimensions, along with applications of diffusive logistic equations and Fokker-Planck equations, demonstrate the accuracy, efficiency, and robustness of the new methods, indicating potential broad applications of the sparse grid-based integration factor method.

Bifurcation approach to a logistic elliptic equation with a homogeneous incoming flux boundary condition

NASA Astrophysics Data System (ADS)

Umezu, Kenichiro

In this paper, we consider a semilinear elliptic boundary value problem in a smooth bounded domain, having the so-called logistic nonlinearity that originates from population dynamics, with a nonlinear boundary condition. Although the logistic nonlinearity has an absorption effect in the problem, the nonlinear boundary condition is induced by the homogeneous incoming flux on the boundary. The objective of our study is to analyze the existence of a bifurcation component of positive solutions from trivial solutions and its asymptotic behavior and stability. We perform this analysis using the method developed by Lyapunov and Schmidt, based on a scaling argument.

Classes of exact Einstein Maxwell solutions

NASA Astrophysics Data System (ADS)

Komathiraj, K.; Maharaj, S. D.

2007-12-01

We find new classes of exact solutions to the Einstein Maxwell system of equations for a charged sphere with a particular choice of the electric field intensity and one of the gravitational potentials. The condition of pressure isotropy is reduced to a linear, second order differential equation which can be solved in general. Consequently we can find exact solutions to the Einstein Maxwell field equations corresponding to a static spherically symmetric gravitational potential in terms of hypergeometric functions. It is possible to find exact solutions which can be written explicitly in terms of elementary functions, namely polynomials and product of polynomials and algebraic functions. Uncharged solutions are regainable with our choice of electric field intensity; in particular we generate the Einstein universe for particular parameter values.

The yield of colorectal cancer among fast track patients with normocytic and microcytic anaemia.

PubMed

Panagiotopoulou, I G; Fitzrol, D; Parker, R A; Kuzhively, J; Luscombe, N; Wells, A D; Menon, M; Bajwa, F M; Watson, M A

2014-05-01

We receive fast track referrals on the basis of iron deficiency anaemia (IDA) for patients with normocytic anaemia or for patients with no iron studies. This study examined the yield of colorectal cancer (CRC) among fast track patients to ascertain whether awaiting confirmation of IDA is necessary prior to performing bowel investigations. A review was undertaken of 321 and 930 consecutive fast track referrals from Centre A and Centre B respectively. Contingency tables were analysed using Fisher's exact test. Logistic regression analyses were performed to investigate significant predictors of CRC. Overall, 229 patients were included from Centre A and 689 from Centre B. The odds ratio for microcytic anaemia versus normocytic anaemia in the outcome of CRC was 1.3 (95% confidence interval [CI]: 0.5-3.9) for Centre A and 1.6 (95% CI: 0.8-3.3) for Centre B. In a logistic regression analysis (Centre B only), no significant difference in CRC rates was seen between microcytic and normocytic anaemia (adjusted odds ratio: 1.9, 95% CI: 0.9-3.9). There was no statistically significant difference in the yield of CRC between microcytic and normocytic anaemia (p=0.515, Fisher's exact test) in patients with anaemia only and no colorectal symptoms. Finally, CRC cases were seen in both microcytic and normocytic groups with or without low ferritin. There is no significant difference in the yield of CRC between fast track patients with microcytic and normocytic anaemia. This study provides insufficient evidence to support awaiting confirmation of IDA in fast track patients with normocytic anaemia prior to requesting bowel investigations.

Notes on the ExactPack Implementation of the DSD Rate Stick Solver

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaul, Ann

It has been shown above that the discretization scheme implemented in the ExactPack solver for the DSD Rate Stick equation is consistent with the Rate Stick PDE. In addition, a stability analysis has provided a CFL condition for a stable time step. Together, consistency and stability imply convergence of the scheme, which is expected to be close to first-order in time and second-order in space. It is understood that the nonlinearity of the underlying PDE will affect this rate somewhat. In the solver I implemented in ExactPack, I used the one-sided boundary condition described above at the outer boundary. Inmore » addition, I used 80% of the time step calculated in the stability analysis above. By making these two changes, I was able to implement a solver that calculates the solution without any arbitrary limits placed on the values of the curvature at the boundary. Thus, the calculation is driven directly by the conditions at the boundary as formulated in the DSD theory. The chosen scheme is completely coherent and defensible from a mathematical standpoint.« less

On the exact solvability of the anisotropic central spin model: An operator approach

NASA Astrophysics Data System (ADS)

Wu, Ning

2018-07-01

Using an operator approach based on a commutator scheme that has been previously applied to Richardson's reduced BCS model and the inhomogeneous Dicke model, we obtain general exact solvability requirements for an anisotropic central spin model with XXZ-type hyperfine coupling between the central spin and the spin bath, without any prior knowledge of integrability of the model. We outline basic steps of the usage of the operators approach, and pedagogically summarize them into two Lemmas and two Constraints. Through a step-by-step construction of the eigen-problem, we show that the condition gj‧2 - gj2 = c naturally arises for the model to be exactly solvable, where c is a constant independent of the bath-spin index j, and {gj } and { gj‧ } are the longitudinal and transverse hyperfine interactions, respectively. The obtained conditions and the resulting Bethe ansatz equations are consistent with that in previous literature.

76 FR 42119 - 36(b)(1) Arms Sales Notification

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-18

.... Government and contractor engineering and logistics support services, and other related elements of logistics... documentation, U.S. Government and contractor engineering and logistics support services, and other related... range of adverse battlefield conditions. The hardware itself is Unclassified. The engineering design and...

Higher symmetries and exact solutions of linear and nonlinear Schr{umlt o}dinger equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fushchych, W.I.; Nikitin, A.G.

1997-11-01

A new approach for the analysis of partial differential equations is developed which is characterized by a simultaneous use of higher and conditional symmetries. Higher symmetries of the Schr{umlt o}dinger equation with an arbitrary potential are investigated. Nonlinear determining equations for potentials are solved using reductions to Weierstrass, Painlev{acute e}, and Riccati forms. Algebraic properties of higher order symmetry operators are analyzed. Combinations of higher and conditional symmetries are used to generate families of exact solutions of linear and nonlinear Schr{umlt o}dinger equations. {copyright} {ital 1997 American Institute of Physics.}

Graph-associated entanglement cost of a multipartite state in exact and finite-block-length approximate constructions

NASA Astrophysics Data System (ADS)

Yamasaki, Hayata; Soeda, Akihito; Murao, Mio

2017-09-01

We introduce and analyze graph-associated entanglement cost, a generalization of the entanglement cost of quantum states to multipartite settings. We identify a necessary and sufficient condition for any multipartite entangled state to be constructible when quantum communication between the multiple parties is restricted to a quantum network represented by a tree. The condition for exact state construction is expressed in terms of the Schmidt ranks of the state defined with respect to edges of the tree. We also study approximate state construction and provide a second-order asymptotic analysis.

Asymptotically exact parabolic solutions of the generalized nonlinear Schrödinger equation with varying parameters

NASA Astrophysics Data System (ADS)

Kruglov, Vladimir I.; Harvey, John D.

2006-12-01

We present exact asymptotic similariton solutions of the generalized nonlinear Schrödinger equation (NLSE) with gain or loss terms for a normal-dispersion fiber amplifier with dispersion, nonlinearity, and gain profiles that depend on the propagation distance. Our treatment is based on the mapping of the NLSE with varying parameters to the NLSE with constant dispersion and nonlinearity coefficients and an arbitrary varying gain function. We formulate an effective procedure that leads directly, under appropriate conditions, to a wide range of exact asymptotic similariton solutions of NLSE demonstrating self-similar propagating regimes with linear chirp.

On the effects of nonlinear boundary conditions in diffusive logistic equations on bounded domains

NASA Astrophysics Data System (ADS)

Cantrell, Robert Stephen; Cosner, Chris

We study a diffusive logistic equation with nonlinear boundary conditions. The equation arises as a model for a population that grows logistically inside a patch and crosses the patch boundary at a rate that depends on the population density. Specifically, the rate at which the population crosses the boundary is assumed to decrease as the density of the population increases. The model is motivated by empirical work on the Glanville fritillary butterfly. We derive local and global bifurcation results which show that the model can have multiple equilibria and in some parameter ranges can support Allee effects. The analysis leads to eigenvalue problems with nonstandard boundary conditions.

The stationary sine-Gordon equation on metric graphs: Exact analytical solutions for simple topologies

NASA Astrophysics Data System (ADS)

Sabirov, K.; Rakhmanov, S.; Matrasulov, D.; Susanto, H.

2018-04-01

We consider the stationary sine-Gordon equation on metric graphs with simple topologies. Exact analytical solutions are obtained for different vertex boundary conditions. It is shown that the method can be extended for tree and other simple graph topologies. Applications of the obtained results to branched planar Josephson junctions and Josephson junctions with tricrystal boundaries are discussed.

Expanded solutions of force-free electrodynamics on general Kerr black holes

NASA Astrophysics Data System (ADS)

Li, Huiquan; Wang, Jiancheng

2017-07-01

In this work, expanded solutions of force-free magnetospheres on general Kerr black holes are derived through a radial distance expansion method. From the regular conditions both at the horizon and at spatial infinity, two previously known asymptotical solutions (one of them is actually an exact solution) are identified as the only solutions that satisfy the same conditions at the two boundaries. Taking them as initial conditions at the boundaries, expanded solutions up to the first few orders are derived by solving the stream equation order by order. It is shown that our extension of the exact solution can (partially) cure the problems of the solution: it leads to magnetic domination and a mostly timelike current for restricted parameters.

The power of exact conditions in electronic structure theory

NASA Astrophysics Data System (ADS)

Bartlett, Rodney J.; Ranasinghe, Duminda S.

2017-02-01

Once electron correlation is included in an effective one-particle operator, one has a correlated orbital theory (COT). One such theory is Kohn-Sham density functional theory (KS-DFT), but there are others. Such methods have the prospect to redefine traditional Molecular Orbital (MO) theory by building a quantitative component upon its conceptual framework. This paper asks the question what conditions should such a theory satisfy and can this be accomplished? One such condition for a COT is that the orbital eigenvalues should satisfy an ionization theorem that generalizes Koopmans' approximation to the exact principal ionization potentials for every electron in a molecule. Guided by this principle, minimal parameterizations of KS-DFT are made that provide a good approximation to a quantitative MO theory.

32 CFR 231.7 - Procedures-domestic credit unions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... of logistical support and space arrangements may be made through the Secretary of the Military... improvements and restore the land to its original condition. (d) Use of space, logistical support, and military...) Logistical support. When available, custodial and janitorial services to include garbage disposal and outdoor...

32 CFR 231.7 - Procedures-domestic credit unions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... of logistical support and space arrangements may be made through the Secretary of the Military... improvements and restore the land to its original condition. (d) Use of space, logistical support, and military...) Logistical support. When available, custodial and janitorial services to include garbage disposal and outdoor...

32 CFR 231.7 - Procedures-domestic credit unions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... of logistical support and space arrangements may be made through the Secretary of the Military... improvements and restore the land to its original condition. (d) Use of space, logistical support, and military...) Logistical support. When available, custodial and janitorial services to include garbage disposal and outdoor...

Management: A continuing literature survey with indexes

NASA Technical Reports Server (NTRS)

1978-01-01

This bibliography lists 782 reports, articles, and other documents introduced into the NASA scientific and technical information system in 1977. The citations, and abstracts when available, are reproduced exactly as they appeared originally in IAA and STAR, including the original accession numbers from the respective announcement journals. Topics cover the management of research and development contracts, production, logistics, personnel, safety, reliability and quality control citations. Includes references on: program, project and systems management; management policy, philosophy, tools, and techniques; decisionmaking processes for managers; technology assessment; management of urban problems; and information for managers on Federal resources, expenditures, financing, and budgeting.

Regularization Paths for Conditional Logistic Regression: The clogitL1 Package.

PubMed

Reid, Stephen; Tibshirani, Rob

2014-07-01

We apply the cyclic coordinate descent algorithm of Friedman, Hastie, and Tibshirani (2010) to the fitting of a conditional logistic regression model with lasso [Formula: see text] and elastic net penalties. The sequential strong rules of Tibshirani, Bien, Hastie, Friedman, Taylor, Simon, and Tibshirani (2012) are also used in the algorithm and it is shown that these offer a considerable speed up over the standard coordinate descent algorithm with warm starts. Once implemented, the algorithm is used in simulation studies to compare the variable selection and prediction performance of the conditional logistic regression model against that of its unconditional (standard) counterpart. We find that the conditional model performs admirably on datasets drawn from a suitable conditional distribution, outperforming its unconditional counterpart at variable selection. The conditional model is also fit to a small real world dataset, demonstrating how we obtain regularization paths for the parameters of the model and how we apply cross validation for this method where natural unconditional prediction rules are hard to come by.

Regularization Paths for Conditional Logistic Regression: The clogitL1 Package

PubMed Central

Reid, Stephen; Tibshirani, Rob

2014-01-01

We apply the cyclic coordinate descent algorithm of Friedman, Hastie, and Tibshirani (2010) to the fitting of a conditional logistic regression model with lasso (ℓ1) and elastic net penalties. The sequential strong rules of Tibshirani, Bien, Hastie, Friedman, Taylor, Simon, and Tibshirani (2012) are also used in the algorithm and it is shown that these offer a considerable speed up over the standard coordinate descent algorithm with warm starts. Once implemented, the algorithm is used in simulation studies to compare the variable selection and prediction performance of the conditional logistic regression model against that of its unconditional (standard) counterpart. We find that the conditional model performs admirably on datasets drawn from a suitable conditional distribution, outperforming its unconditional counterpart at variable selection. The conditional model is also fit to a small real world dataset, demonstrating how we obtain regularization paths for the parameters of the model and how we apply cross validation for this method where natural unconditional prediction rules are hard to come by. PMID:26257587

Flock-level prevalence, geographical distribution, and seasonal variation of avian reovirus among broiler flocks in Ontario.

PubMed

Nham, Eric G; Pearl, David L; Slavic, Durda; Ouckama, Rachel; Ojkic, Davor; Guerin, Michele T

2017-08-01

Avian reovirus (ARV) is an economically significant pathogen of broiler chickens. Our objective was to determine the prevalence, geographical distribution, and seasonal variation of ARV infection among commercial broiler flocks in Ontario, Canada during grow-out. A cross-sectional study of 231 randomly selected flocks was conducted from July 2010 to January 2012. Fifteen blood samples, 15 whole intestines, and 15 cloacal swabs per flock were collected at slaughter; ELISA and PCR were used to determine a flock's ARV exposure status. Avian reovirus prevalence was 91% (95% CI: 87 to 94). District alone did not significantly explain the overall variation in the prevalence of ARV (univariable logistic regression; P = 0.073), although geographical differences were identified. The odds of ARV presence were significantly lower in the summer/autumn compared to the winter/spring (univariable exact logistic regression; P < 0.001). There was no association between flock mortality and flock ELISA mean titer or PCR status.

Flock-level prevalence, geographical distribution, and seasonal variation of avian reovirus among broiler flocks in Ontario

PubMed Central

Nham, Eric G.; Pearl, David L.; Slavic, Durda; Ouckama, Rachel; Ojkic, Davor; Guerin, Michele T.

2017-01-01

Avian reovirus (ARV) is an economically significant pathogen of broiler chickens. Our objective was to determine the prevalence, geographical distribution, and seasonal variation of ARV infection among commercial broiler flocks in Ontario, Canada during grow-out. A cross-sectional study of 231 randomly selected flocks was conducted from July 2010 to January 2012. Fifteen blood samples, 15 whole intestines, and 15 cloacal swabs per flock were collected at slaughter; ELISA and PCR were used to determine a flock’s ARV exposure status. Avian reovirus prevalence was 91% (95% CI: 87 to 94). District alone did not significantly explain the overall variation in the prevalence of ARV (univariable logistic regression; P = 0.073), although geographical differences were identified. The odds of ARV presence were significantly lower in the summer/autumn compared to the winter/spring (univariable exact logistic regression; P < 0.001). There was no association between flock mortality and flock ELISA mean titer or PCR status. PMID:28761188

Risk Factors for Developing Scoliosis in Cerebral Palsy: A Cross-Sectional Descriptive Study.

PubMed

Bertoncelli, Carlo M; Solla, Federico; Loughenbury, Peter R; Tsirikos, Athanasios I; Bertoncelli, Domenico; Rampal, Virginie

2017-06-01

This study aims to identify the risk factors leading to the development of severe scoliosis among children with cerebral palsy. A cross-sectional descriptive study of 70 children (aged 12-18 years) with severe spastic and/or dystonic cerebral palsy treated in a single specialist unit is described. Statistical analysis included Fisher exact test and logistic regression analysis to identify risk factors. Severe scoliosis is more likely to occur in patients with intractable epilepsy ( P = .008), poor gross motor functional assessment scores ( P = .018), limb spasticity ( P = .045), a history of previous hip surgery ( P = .048), and nonambulatory patients ( P = .013). Logistic regression model confirms the major risk factors are previous hip surgery ( P = .001), moderate to severe epilepsy ( P = .007), and female gender ( P = .03). History of previous hip surgery, intractable epilepsy, and female gender are predictors of developing severe scoliosis in children with cerebral palsy. This knowledge should aid in the early diagnosis of scoliosis and timely referral to specialist services.

Epidemiologic programs for computers and calculators. A microcomputer program for multiple logistic regression by unconditional and conditional maximum likelihood methods.

PubMed

Campos-Filho, N; Franco, E L

1989-02-01

A frequent procedure in matched case-control studies is to report results from the multivariate unmatched analyses if they do not differ substantially from the ones obtained after conditioning on the matching variables. Although conceptually simple, this rule requires that an extensive series of logistic regression models be evaluated by both the conditional and unconditional maximum likelihood methods. Most computer programs for logistic regression employ only one maximum likelihood method, which requires that the analyses be performed in separate steps. This paper describes a Pascal microcomputer (IBM PC) program that performs multiple logistic regression by both maximum likelihood estimation methods, which obviates the need for switching between programs to obtain relative risk estimates from both matched and unmatched analyses. The program calculates most standard statistics and allows factoring of categorical or continuous variables by two distinct methods of contrast. A built-in, descriptive statistics option allows the user to inspect the distribution of cases and controls across categories of any given variable.

Exact folded-band chaotic oscillator.

PubMed

Corron, Ned J; Blakely, Jonathan N

2012-06-01

An exactly solvable chaotic oscillator with folded-band dynamics is shown. The oscillator is a hybrid dynamical system containing a linear ordinary differential equation and a nonlinear switching condition. Bounded oscillations are provably chaotic, and successive waveform maxima yield a one-dimensional piecewise-linear return map with segments of both positive and negative slopes. Continuous-time dynamics exhibit a folded-band topology similar to Rössler's oscillator. An exact solution is written as a linear convolution of a fixed basis pulse and a discrete binary sequence, from which an equivalent symbolic dynamics is obtained. The folded-band topology is shown to be dependent on the symbol grammar.

Exact relativistic Toda chain eigenfunctions from Separation of Variables and gauge theory

NASA Astrophysics Data System (ADS)

Sciarappa, Antonio

2017-10-01

We provide a proposal, motivated by Separation of Variables and gauge theory arguments, for constructing exact solutions to the quantum Baxter equation associated to the N-particle relativistic Toda chain and test our proposal against numerical results. Quantum Mechanical non-perturbative corrections, essential in order to obtain a sensible solution, are taken into account in our gauge theory approach by considering codimension two defects on curved backgrounds (squashed S 5 and degenerate limits) rather than flat space; this setting also naturally incorporates exact quantization conditions and energy spectrum of the relativistic Toda chain as well as its modular dual structure.

Regularization of moving boundaries in a laplacian field by a mixed Dirichlet-Neumann boundary condition: exact results.

PubMed

Meulenbroek, Bernard; Ebert, Ute; Schäfer, Lothar

2005-11-04

The dynamics of ionization fronts that generate a conducting body are in the simplest approximation equivalent to viscous fingering without regularization. Going beyond this approximation, we suggest that ionization fronts can be modeled by a mixed Dirichlet-Neumann boundary condition. We derive exact uniformly propagating solutions of this problem in 2D and construct a single partial differential equation governing small perturbations of these solutions. For some parameter value, this equation can be solved analytically, which shows rigorously that the uniformly propagating solution is linearly convectively stable and that the asymptotic relaxation is universal and exponential in time.

The optimal power puzzle: scrutiny of the monotone likelihood ratio assumption in multiple testing.

PubMed

Cao, Hongyuan; Sun, Wenguang; Kosorok, Michael R

2013-01-01

In single hypothesis testing, power is a non-decreasing function of type I error rate; hence it is desirable to test at the nominal level exactly to achieve optimal power. The puzzle lies in the fact that for multiple testing, under the false discovery rate paradigm, such a monotonic relationship may not hold. In particular, exact false discovery rate control may lead to a less powerful testing procedure if a test statistic fails to fulfil the monotone likelihood ratio condition. In this article, we identify different scenarios wherein the condition fails and give caveats for conducting multiple testing in practical settings.

ANALYZING NUMERICAL ERRORS IN DOMAIN HEAT TRANSPORT MODELS USING THE CVBEM.

USGS Publications Warehouse

Hromadka, T.V.

1987-01-01

Besides providing an exact solution for steady-state heat conduction processes (Laplace-Poisson equations), the CVBEM (complex variable boundary element method) can be used for the numerical error analysis of domain model solutions. For problems where soil-water phase change latent heat effects dominate the thermal regime, heat transport can be approximately modeled as a time-stepped steady-state condition in the thawed and frozen regions, respectively. The CVBEM provides an exact solution of the two-dimensional steady-state heat transport problem, and also provides the error in matching the prescribed boundary conditions by the development of a modeling error distribution or an approximate boundary generation.

An investigation of the accuracy of the Merkel equation for evaporative cooling tower calculations. Waste heat management

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadigaroglu, G.; Pastor, E.J.

1974-01-01

The exact differential equations governing heat and mass transfer and air flow in an evaporative, natural-draft cooling tower are presented. The Merkel equation is then derived starting from this exact formulation and showing all the approximations involved. The Merkel formulation lumps the sensible and the latent heat transfer together and considers a single enthalpy-difference driving force for the total heat transfer. The effect of the approximations inherent in the Merkel equation is investigated and analyzed by a series of parametric numerical calculations of cooling tower performance under various ambient conditions and load conditions.

Adding a solar-radiance function to the Hošek-Wilkie skylight model.

PubMed

Hošek, Lukáš; Wilkie, Alexander

2013-01-01

One prerequisite for realistic renderings of outdoor scenes is the proper capturing of the sky's appearance. Currently, an explicit simulation of light scattering in the atmosphere isn't computationally feasible, and won't be in the foreseeable future. Captured luminance patterns have proven their usefulness in practice but can't meet all user needs. To fill this capability gap, computer graphics technology has employed analytical models of sky-dome luminance patterns for more than two decades. For technical reasons, such models deal with only the sky dome's appearance, though, and exclude the solar disc. The widely used model proposed by Arcot Preetham and colleagues employed a separately derived analytical formula for adding a solar emitter of suitable radiant intensity. Although this yields reasonable results, the formula is derived in a manner that doesn't exactly match the conditions in their sky-dome model. But the more sophisticated a skylight model is and the more subtly it can represent different conditions, the more the solar radiance should exactly match the skylight's conditions. Toward that end, researchers propose a solar-radiance function that exactly matches a recently published high-quality analytical skylight model.

Identification of six polymorphisms as novel susceptibility loci for ischemic or hemorrhagic stroke by exome-wide association studies

PubMed Central

Yamada, Yoshiji; Sakuma, Jun; Takeuchi, Ichiro; Yasukochi, Yoshiki; Kato, Kimihiko; Oguri, Mitsutoshi; Fujimaki, Tetsuo; Horibe, Hideki; Muramatsu, Masaaki; Sawabe, Motoji; Fujiwara, Yoshinori; Taniguchi, Yu; Obuchi, Shuichi; Kawai, Hisashi; Shinkai, Shoji; Mori, Seijiro; Arai, Tomio; Tanaka, Masashi

2017-01-01

In this study, we performed exome-wide association studies (EWASs) to identify genetic variants that confer susceptibility to ischemic stroke, intracerebral hemorrhage (ICH), or subarachnoid hemorrhage (SAH). EWAS for ischemic stroke was performed using 1,575 patients with this condition and 9,210 controls, and EWASs for ICH and SAH were performed using 673 patients with ICH, 265 patients with SAH and 9,158 controls. Analyses were performed with Illumina HumanExome-12 DNA Analysis BeadChip or Infinium Exome-24 BeadChip arrays. The relation of allele frequencies for 41,339 or 41,332 single nucleotide polymorphisms (SNPs) that passed quality control to ischemic or hemorrhagic stroke, respectively, was examined with Fisher's exact test. Based on Bonferroni's correction, a P-value of <1.21×10−6 was considered statistically significant. EWAS for ischemic stroke revealed that 77 SNPs were significantly associated with this condition. Multivariable logistic regression analysis with adjustment for age, sex and the prevalence of hypertension and diabetes mellitus revealed that 4 of these SNPs [rs3212335 of GABRB3 (P=0.0036; odds ratio, 1.29), rs147783135 of TMPRSS7 (P=0.0024; odds ratio, 0.37), rs2292661 of PDIA5 (P=0.0054; odds ratio, 0.35) and rs191885206 of CYP4F12 (P=0.0082; odds ratio, 2.60)] were related (P<0.01) to ischemic stroke. EWASs for ICH or SAH revealed that 48 and 12 SNPs, respectively, were significantly associated with these conditions. Multivariable logistic regression analysis with adjustment for age, sex and the prevalence of hypertension revealed that rs138533962 of STYK1 (P<1.0×10−23; odds ratio, 111.3) was significantly (P<2.60×10−4) associated with ICH and that rs117564807 of COL17A1 (P=0.0009; odds ratio, 2.23×10−8) was significantly (P<0.0010) associated with SAH. GABRB3, TMPRSS7, PDIA5 and CYP4F12 may thus be novel susceptibility loci for ischemic stroke, whereas STYK1 and COL17A1 may be such loci for ICH and SAH, respectively. PMID:28487959

Asymptotic behavior of degenerate logistic equations

NASA Astrophysics Data System (ADS)

Arrieta, José M.; Pardo, Rosa; Rodríguez-Bernal, Aníbal

2015-12-01

We analyze the asymptotic behavior of positive solutions of parabolic equations with a class of degenerate logistic nonlinearities of the type λu - n (x)uρ. An important characteristic of this work is that the region where the logistic term n (ṡ) vanishes, that is K0 = { x : n (x) = 0 }, may be non-smooth. We analyze conditions on λ, ρ, n (ṡ) and K0 guaranteeing that the solution starting at a positive initial condition remains bounded or blows up as time goes to infinity. The asymptotic behavior may not be the same in different parts of K0.

A Formula to Calculate Standard Liver Volume Using Thoracoabdominal Circumference.

PubMed

Shaw, Brian I; Burdine, Lyle J; Braun, Hillary J; Ascher, Nancy L; Roberts, John P

2017-12-01

With the use of split liver grafts as well as living donor liver transplantation (LDLT) it is imperative to know the minimum graft volume to avoid complications. Most current formulas to predict standard liver volume (SLV) rely on weight-based measures that are likely inaccurate in the setting of cirrhosis. Therefore, we sought to create a formula for estimating SLV without weight-based covariates. LDLT donors underwent computed tomography scan volumetric evaluation of their livers. An optimal formula for calculating SLV using the anthropomorphic measure thoracoabdominal circumference (TAC) was determined using leave-one-out cross-validation. The ability of this formula to correctly predict liver volume was checked against other existing formulas by analysis of variance. The ability of the formula to predict small grafts in LDLT was evaluated by exact logistic regression. The optimal formula using TAC was determined to be SLV = (TAC × 3.5816) - (Age × 3.9844) - (Sex × 109.7386) - 934.5949. When compared to historic formulas, the current formula was the only one which was not significantly different than computed tomography determined liver volumes when compared by analysis of variance with Dunnett posttest. When evaluating the ability of the formula to predict small for size syndrome, many (10/16) of the formulas tested had significant results by exact logistic regression, with our formula predicting small for size syndrome with an odds ratio of 7.94 (95% confidence interval, 1.23-91.36; P = 0.025). We report a formula for calculating SLV that does not rely on weight-based variables that has good ability to predict SLV and identify patients with potentially small grafts.

The Effect of History of Abnormal Pap Smear or Preceding HPV infection on the Humoral Immune Response to Quadrivalent Human Papilloma virus (qHPV) Vaccine in Women with Systemic Lupus Erythematosus.

PubMed

Dhar, J Patricia; Essenmacher, Lynnette; Dhar, Renee; Magee, Ardella; Ager, Joel; Sokol, Robert J

2018-04-30

To determine if natural human papillomavirus (HPV) infection would induce an anamnestic response to quadrivalent (qHPV) vaccine in women with Systemic Lupus Erythematosus (SLE). Thirty four women (19-50 years) with mild to moderate and minimally active or inactive SLE received standard qHPV vaccine. Neutralizing antibody titers to HPV 6, 11, 16 and18 were evaluated pre- and post- vaccine using HPV competitive Luminex Immunoassay. For each HPV type, logistic regressions were performed to explore the relationship between a positive titer at baseline with their final geometric mean titer and with the rise in titer. Fisher's Exact Test was used to assess the association of at least one positive HPV antibody test at baseline and history of abnormal pap. History of abnormal pap smear/cervical neoplasia occurred in 52.9%. Baseline anti HPV antibody titers: 21% = negative for all 4 HPV types, 79% = positive for ≥1 of the HPV types. Statistical analysis showed: those with a history of abnormal pap smear/cervical neoplasia were likely to have a positive anti-HPV antibody result pre-vaccine to ≥ 1 of the 4 types, p = 0.035 Fisher's Exact Test. In general, HPV exposed women showed higher post vaccine GMTs than HPV unexposed women with higher point estimates. However, when examining the rise in titers using logistic regression, there was no evidence of an anamnestic response. Prior HPV infection and cervical neoplasia in SLE are linked with no anamnestic response to HPV vaccine. This supports not checking HPV-antibodies pre-vaccine. Women with SLE should be vaccinated for HPV.

Conformally symmetric traversable wormholes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boehmer, Christian G.; Harko, Tiberiu; Lobo, Francisco S. N.

2007-10-15

Exact solutions of traversable wormholes are found under the assumption of spherical symmetry and the existence of a nonstatic conformal symmetry, which presents a more systematic approach in searching for exact wormhole solutions. In this work, a wide variety of solutions are deduced by considering choices for the form function, a specific linear equation of state relating the energy density and the pressure anisotropy, and various phantom wormhole geometries are explored. A large class of solutions impose that the spatial distribution of the exotic matter is restricted to the throat neighborhood, with a cutoff of the stress-energy tensor at amore » finite junction interface, although asymptotically flat exact solutions are also found. Using the 'volume integral quantifier', it is found that the conformally symmetric phantom wormhole geometries may, in principle, be constructed by infinitesimally small amounts of averaged null energy condition violating matter. Considering the tidal acceleration traversability conditions for the phantom wormhole geometry, specific wormhole dimensions and the traversal velocity are also deduced.« less

Exact combinatorial approach to finite coagulating systems

NASA Astrophysics Data System (ADS)

Fronczak, Agata; Chmiel, Anna; Fronczak, Piotr

2018-02-01

This paper outlines an exact combinatorial approach to finite coagulating systems. In this approach, cluster sizes and time are discrete and the binary aggregation alone governs the time evolution of the systems. By considering the growth histories of all possible clusters, an exact expression is derived for the probability of a coagulating system with an arbitrary kernel being found in a given cluster configuration when monodisperse initial conditions are applied. Then this probability is used to calculate the time-dependent distribution for the number of clusters of a given size, the average number of such clusters, and that average's standard deviation. The correctness of our general expressions is proved based on the (analytical and numerical) results obtained for systems with the constant kernel. In addition, the results obtained are compared with the results arising from the solutions to the mean-field Smoluchowski coagulation equation, indicating its weak points. The paper closes with a brief discussion on the extensibility to other systems of the approach presented herein, emphasizing the issue of arbitrary initial conditions.

Period of vibration of axially vibrating truly nonlinear rod

NASA Astrophysics Data System (ADS)

Cveticanin, L.

2016-07-01

In this paper the axial vibration of a muscle whose fibers are parallel to the direction of muscle compression is investigated. The model is a clamped-free rod with a strongly nonlinear elastic property. Axial vibration is described by a nonlinear partial differential equation. A solution of the equation is constructed for special initial conditions by using the method of separation of variables. The partial differential equation is separated into two uncoupled strongly nonlinear second order differential equations. Both equations, with displacement function and with time function are exactly determined. Exact solutions are given in the form of inverse incomplete and inverse complete Beta function. Using boundary and initial conditions, the frequency of vibration is obtained. It has to be mentioned that the determined frequency represents the exact analytic description for the axially vibrating truly nonlinear clamped-free rod. The procedure suggested in this paper is applied for calculation of the frequency of the longissimus dorsi muscle of a cow. The influence of elasticity order and elasticity coefficient on the frequency property is tested.

Exact evaluation of the depletion force between nanospheres in a polydisperse polymer fluid under Θ conditions.

PubMed

Wang, Haiqiang; Woodward, Clifford E; Forsman, Jan

2014-05-21

We analyze a system consisting of two spherical particles immersed in a polydispersed polymer solution under theta conditions. An exact theory is developed to describe the potential of mean force between the spheres for the case where the polymer molecular weight dispersity is described by the Schulz-Flory distribution. Exact results can be derived for the protein regime, where the sphere radius (R(s)) is small compared to the average radius of gyration of the polymer (R(g)). Numerical results are relatively easily obtained in the cases where the sphere radius is increased. We find that even when q = R(g)/R(s) ⪆ 10, then the use of a monopole expansion for the polymer end-point distribution about the spheres is sufficient. For even larger spheres q ≈ 1, accuracy is maintained by including a dipolar correction. The implications of these findings on generating a full many-body effective interaction for a collection of N spheres imbedded in the polymer solution are discussed.

On the use and misuse of scalar scores of confounders in design and analysis of observational studies.

PubMed

Pfeiffer, R M; Riedl, R

2015-08-15

We assess the asymptotic bias of estimates of exposure effects conditional on covariates when summary scores of confounders, instead of the confounders themselves, are used to analyze observational data. First, we study regression models for cohort data that are adjusted for summary scores. Second, we derive the asymptotic bias for case-control studies when cases and controls are matched on a summary score, and then analyzed either using conditional logistic regression or by unconditional logistic regression adjusted for the summary score. Two scores, the propensity score (PS) and the disease risk score (DRS) are studied in detail. For cohort analysis, when regression models are adjusted for the PS, the estimated conditional treatment effect is unbiased only for linear models, or at the null for non-linear models. Adjustment of cohort data for DRS yields unbiased estimates only for linear regression; all other estimates of exposure effects are biased. Matching cases and controls on DRS and analyzing them using conditional logistic regression yields unbiased estimates of exposure effect, whereas adjusting for the DRS in unconditional logistic regression yields biased estimates, even under the null hypothesis of no association. Matching cases and controls on the PS yield unbiased estimates only under the null for both conditional and unconditional logistic regression, adjusted for the PS. We study the bias for various confounding scenarios and compare our asymptotic results with those from simulations with limited sample sizes. To create realistic correlations among multiple confounders, we also based simulations on a real dataset. Copyright © 2015 John Wiley & Sons, Ltd.

A Mathematical Motivation for Complex-Valued Convolutional Networks.

PubMed

Tygert, Mark; Bruna, Joan; Chintala, Soumith; LeCun, Yann; Piantino, Serkan; Szlam, Arthur

2016-05-01

A complex-valued convolutional network (convnet) implements the repeated application of the following composition of three operations, recursively applying the composition to an input vector of nonnegative real numbers: (1) convolution with complex-valued vectors, followed by (2) taking the absolute value of every entry of the resulting vectors, followed by (3) local averaging. For processing real-valued random vectors, complex-valued convnets can be viewed as data-driven multiscale windowed power spectra, data-driven multiscale windowed absolute spectra, data-driven multiwavelet absolute values, or (in their most general configuration) data-driven nonlinear multiwavelet packets. Indeed, complex-valued convnets can calculate multiscale windowed spectra when the convnet filters are windowed complex-valued exponentials. Standard real-valued convnets, using rectified linear units (ReLUs), sigmoidal (e.g., logistic or tanh) nonlinearities, or max pooling, for example, do not obviously exhibit the same exact correspondence with data-driven wavelets (whereas for complex-valued convnets, the correspondence is much more than just a vague analogy). Courtesy of the exact correspondence, the remarkably rich and rigorous body of mathematical analysis for wavelets applies directly to (complex-valued) convnets.

Performance Evaluation of the Q Exactive HF-X for Shotgun Proteomics.

PubMed

Kelstrup, Christian D; Bekker-Jensen, Dorte B; Arrey, Tabiwang N; Hogrebe, Alexander; Harder, Alexander; Olsen, Jesper V

2018-01-05

Progress in proteomics is mainly driven by advances in mass spectrometric (MS) technologies. Here we benchmarked the performance of the latest MS instrument in the benchtop Orbitrap series, the Q Exactive HF-X, against its predecessor for proteomics applications. A new peak-picking algorithm, a brighter ion source, and optimized ion transfers enable productive MS/MS acquisition above 40 Hz at 7500 resolution. The hardware and software improvements collectively resulted in improved peptide and protein identifications across all comparable conditions, with an increase of up to 50 percent at short LC-MS gradients, yielding identification rates of more than 1000 unique peptides per minute. Alternatively, the Q Exactive HF-X is capable of achieving the same proteome coverage as its predecessor in approximately half the gradient time or at 10-fold lower sample loads. The Q Exactive HF-X also enables rapid phosphoproteomics with routine analysis of more than 5000 phosphopeptides with short single-shot 15 min LC-MS/MS measurements, or 16 700 phosphopeptides quantified across ten conditions in six gradient hours using TMT10-plex and offline peptide fractionation. Finally, exciting perspectives for data-independent acquisition are highlighted with reproducible identification of 55 000 unique peptides covering 5900 proteins in half an hour of MS analysis.

Predictors of immunological failure of antiretroviral therapy among HIV infected patients in Ethiopia: a matched case-control study.

PubMed

Teshome, Wondu; Asefa, Anteneh; Assefa, Anteneh

2014-01-01

In resource constrained settings, immunological assessment through CD4 count is used to assess response to first line Highly Active Antiretroviral Therapy (HAART). In this study, we aim to investigate factors associated with immunological treatment failure. A matched case-control study design was used. Cases were subjects who already experienced immunological treatment failure and controls were those without immunological failure after an exactly or approximately equivalent duration of first line treatment with cases. Data were analyzed using SPSS v16.0. Conditional logistic regression was carried out. A total of 134 cases and 134 controls were included in the study. At baseline, the mean age ± 1 SD of cases was 37.5 ± 9.7 years whereas it was 36.9 ± 9.2 years among controls. The median baseline CD4 counts of cases and controls were 121.0 cells/µl (IQR: 47-183 cells/µl) and 122.0 cells/µl (IQR: 80.0-189.8 cells/µl), respectively. The median rate of CD4 cells increase was comparable for the two groups in the first six months of commencing HAART (P = 0.442). However, the median rate of CD4 increase was significantly different for the two groups in the next 6 months period (M6 to M12). The rate of increment was 8.8 (IQR: 0.5, 14.6) and 1.8 (IQR: 8.8, 11.3) cells/µl/month for controls and cases, respectively (Mann-Whitney U test, P = 0.003). In conditional logistic regressions grouped baseline CD4 count (P = 0.028), old age group and higher educational status (P<0.001) were significant predictors of immunological treatment failure. Subjects with immunological treatment failure have an optimal rate of immunological recovery in the first 6 months of treatment with first line HAART, but relative to the non-failing group the rate declines at a later period, notably between 6 and 12 months. Low baseline CD4 count, old age and higher educational status were associated with immunological treatment failure.

Solutal Convection Around Growing Protein Crystal and Diffusional Purification in Space

NASA Technical Reports Server (NTRS)

Chernov, A. A.; Lee, C. P.

2002-01-01

This work theoretically addressed two subjects: 1) onset of convection, 2) distribution of impurities. Onset of convection was considered analytically and numerically. Crystal growth was characterized by slow surface incorporation kinetics, i.e. growth kinetic coefficient beta (cm/s) small as compared to the typical bulk diffusion rate, D(sub 1)/h, where D(sub 1) is diffusivity of major crystallizing protein and h is the crystal size. Scaling type analysis predicted two laws on how the convection rate, v, essentially the Peclet number, Pe exactly equal to vh/D(sub 1), depends on dimensionless kinetic coefficient a exactly equal to beta h/D(sub 1). Namely: Pe = C(sub 2/5)(aRa(sup 2/5)) and Pe = C(sub 1) aRa. Here, Reynolds number Ra = rho(sub 1)(sup 0)gh(sup 3)(rho(sub p) - rho(sub w))/rho(sup p)rho(sub 1)vD(sub 1), v being solution viscosity. The constants C(sub 2/5), exactly equal to 0.28 and C(sub 1) exactly equal to 10(exp -2) found from the full scale computer simulation for a cylindrical crystal inside big cylindrical vessel. The linear boundary conditions connecting protein and impurity concentration at the interface with the flux to/from the interface was applied. No-slip condition for Navier-Shocker equations was employed. With these conditions, flow and concentration distributions were calculated. Validity of the Pe(Ra) dependencies follows for wide range of parameters for which numerical calculations have been accomplished and presented by various points.

The Use of Logistics n the Quality Parameters Control System of Material Flow

ERIC Educational Resources Information Center

Karpova, Natalia P.; Toymentseva, Irina A.; Shvetsova, Elena V.; Chichkina, Vera D.; Chubarkova, Elena V.

2016-01-01

The relevance of the research problem is conditioned on the need to justify the use of the logistics methodologies in the quality parameters control process of material flows. The goal of the article is to develop theoretical principles and practical recommendations for logistical system control in material flows quality parameters. A leading…

Exact semiclassical expansions for one-dimensional quantum oscillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delabaere, E.; Dillinger, H.; Pham, F.

1997-12-01

A set of rules is given for dealing with WKB expansions in the one-dimensional analytic case, whereby such expansions are not considered as approximations but as exact encodings of wave functions, thus allowing for analytic continuation with respect to whichever parameters the potential function depends on, with an exact control of small exponential effects. These rules, which include also the case when there are double turning points, are illustrated on various examples, and applied to the study of bound state or resonance spectra. In the case of simple oscillators, it is thus shown that the Rayleigh{endash}Schr{umlt o}dinger series is Borelmore » resummable, yielding the exact energy levels. In the case of the symmetrical anharmonic oscillator, one gets a simple and rigorous justification of the Zinn-Justin quantization condition, and of its solution in terms of {open_quotes}multi-instanton expansions.{close_quotes} {copyright} {ital 1997 American Institute of Physics.}« less

Dynamics of a stochastic HIV-1 infection model with logistic growth

NASA Astrophysics Data System (ADS)

Jiang, Daqing; Liu, Qun; Shi, Ningzhong; Hayat, Tasawar; Alsaedi, Ahmed; Xia, Peiyan

2017-03-01

This paper is concerned with a stochastic HIV-1 infection model with logistic growth. Firstly, by constructing suitable stochastic Lyapunov functions, we establish sufficient conditions for the existence of ergodic stationary distribution of the solution to the HIV-1 infection model. Then we obtain sufficient conditions for extinction of the infection. The stationary distribution shows that the infection can become persistent in vivo.

Periodic Heterogeneous Vehicle Routing Problem With Driver Scheduling

NASA Astrophysics Data System (ADS)

Mardiana Panggabean, Ellis; Mawengkang, Herman; Azis, Zainal; Filia Sari, Rina

2018-01-01

The paper develops a model for the optimal management of logistic delivery of a given commodity. The company has different type of vehicles with different capacity to deliver the commodity for customers. The problem is then called Periodic Heterogeneous Vehicle Routing Problem (PHVRP). The goal is to schedule the deliveries according to feasible combinations of delivery days and to determine the scheduling of fleet and driver and routing policies of the vehicles. The objective is to minimize the sum of the costs of all routes over the planning horizon. We propose a combined approach of heuristic algorithm and exact method to solve the problem.

Partition-free approach to open quantum systems in harmonic environments: An exact stochastic Liouville equation

NASA Astrophysics Data System (ADS)

McCaul, G. M. G.; Lorenz, C. D.; Kantorovich, L.

2017-03-01

We present a partition-free approach to the evolution of density matrices for open quantum systems coupled to a harmonic environment. The influence functional formalism combined with a two-time Hubbard-Stratonovich transformation allows us to derive a set of exact differential equations for the reduced density matrix of an open system, termed the extended stochastic Liouville-von Neumann equation. Our approach generalizes previous work based on Caldeira-Leggett models and a partitioned initial density matrix. This provides a simple, yet exact, closed-form description for the evolution of open systems from equilibriated initial conditions. The applicability of this model and the potential for numerical implementations are also discussed.

Exact synchronization bound for coupled time-delay systems.

PubMed

Senthilkumar, D V; Pesquera, Luis; Banerjee, Santo; Ortín, Silvia; Kurths, J

2013-04-01

We obtain an exact bound for synchronization in coupled time-delay systems using the generalized Halanay inequality for the general case of time-dependent delay, coupling, and coefficients. Furthermore, we show that the same analysis is applicable to both uni- and bidirectionally coupled time-delay systems with an appropriate evolution equation for their synchronization manifold, which can also be defined for different types of synchronization. The exact synchronization bound assures an exponential stabilization of the synchronization manifold which is crucial for applications. The analytical synchronization bound is independent of the nature of the modulation and can be applied to any time-delay system satisfying a Lipschitz condition. The analytical results are corroborated numerically using the Ikeda system.

Correlated electron-nuclear dynamics with conditional wave functions.

PubMed

Albareda, Guillermo; Appel, Heiko; Franco, Ignacio; Abedi, Ali; Rubio, Angel

2014-08-22

The molecular Schrödinger equation is rewritten in terms of nonunitary equations of motion for the nuclei (or electrons) that depend parametrically on the configuration of an ensemble of generally defined electronic (or nuclear) trajectories. This scheme is exact and does not rely on the tracing out of degrees of freedom. Hence, the use of trajectory-based statistical techniques can be exploited to circumvent the calculation of the computationally demanding Born-Oppenheimer potential-energy surfaces and nonadiabatic coupling elements. The concept of the potential-energy surface is restored by establishing a formal connection with the exact factorization of the full wave function. This connection is used to gain insight from a simplified form of the exact propagation scheme.

Symmetric tops in combined electric fields: Conditional quasisolvability via the quantum Hamilton-Jacobi theory

NASA Astrophysics Data System (ADS)

Schatz, Konrad; Friedrich, Bretislav; Becker, Simon; Schmidt, Burkhard

2018-05-01

We make use of the quantum Hamilton-Jacobi (QHJ) theory to investigate conditional quasisolvability of the quantum symmetric top subject to combined electric fields (symmetric top pendulum). We derive the conditions of quasisolvability of the time-independent Schrödinger equation as well as the corresponding finite sets of exact analytic solutions. We do so for this prototypical trigonometric system as well as for its anti-isospectral hyperbolic counterpart. An examination of the algebraic and numerical spectra of these two systems reveals mutually closely related patterns. The QHJ approach allows us to retrieve the closed-form solutions for the spherical and planar pendula and the Razavy system that had been obtained in our earlier work via supersymmetric quantum mechanics as well as to find a cornucopia of additional exact analytic solutions.

Penetrable square-well fluids: exact results in one dimension.

PubMed

Santos, Andrés; Fantoni, Riccardo; Giacometti, Achille

2008-05-01

We introduce a model of attractive penetrable spheres by adding a short-range attractive square well outside a penetrable core, and we provide a detailed analysis of structural and thermodynamical properties in one dimension using the exact impenetrable counterpart as a starting point. The model is expected to describe star polymers in regimes of good and moderate solvent under dilute conditions. We derive the exact coefficients of a low-density expansion up to second order for the radial distribution function and up to fourth order in the virial expansion. These exact results are used as a benchmark to test the reliability of approximate theories (Percus-Yevick and hypernetted chain). Notwithstanding the lack of an exact solution for arbitrary densities, our results are expected to be rather precise within a wide range of temperatures and densities. A detailed analysis of some limiting cases is carried out. In particular, we provide a complete solution of the sticky penetrable-sphere model in one dimension up to the same order in density. The issue of Ruelle's thermodynamics stability is analyzed and the region of a well-defined thermodynamic limit is identified.

Strength conditions for the elastic structures with a stress error

NASA Astrophysics Data System (ADS)

Matveev, A. D.

2017-10-01

As is known, the constraints (strength conditions) for the safety factor of elastic structures and design details of a particular class, e.g. aviation structures are established, i.e. the safety factor values of such structures should be within the given range. It should be noted that the constraints are set for the safety factors corresponding to analytical (exact) solutions of elasticity problems represented for the structures. Developing the analytical solutions for most structures, especially irregular shape ones, is associated with great difficulties. Approximate approaches to solve the elasticity problems, e.g. the technical theories of deformation of homogeneous and composite plates, beams and shells, are widely used for a great number of structures. Technical theories based on the hypotheses give rise to approximate (technical) solutions with an irreducible error, with the exact value being difficult to be determined. In static calculations of the structural strength with a specified small range for the safety factors application of technical (by the Theory of Strength of Materials) solutions is difficult. However, there are some numerical methods for developing the approximate solutions of elasticity problems with arbitrarily small errors. In present paper, the adjusted reference (specified) strength conditions for the structural safety factor corresponding to approximate solution of the elasticity problem have been proposed. The stress error estimation is taken into account using the proposed strength conditions. It has been shown that, to fulfill the specified strength conditions for the safety factor of the given structure corresponding to an exact solution, the adjusted strength conditions for the structural safety factor corresponding to an approximate solution are required. The stress error estimation which is the basis for developing the adjusted strength conditions has been determined for the specified strength conditions. The adjusted strength conditions presented by allowable stresses are suggested. Adjusted strength conditions make it possible to determine the set of approximate solutions, whereby meeting the specified strength conditions. Some examples of the specified strength conditions to be satisfied using the technical (by the Theory of Strength of Materials) solutions and strength conditions have been given, as well as the examples of stress conditions to be satisfied using approximate solutions with a small error.

Predicting 30-day Hospital Readmission with Publicly Available Administrative Database. A Conditional Logistic Regression Modeling Approach.

PubMed

Zhu, K; Lou, Z; Zhou, J; Ballester, N; Kong, N; Parikh, P

2015-01-01

This article is part of the Focus Theme of Methods of Information in Medicine on "Big Data and Analytics in Healthcare". Hospital readmissions raise healthcare costs and cause significant distress to providers and patients. It is, therefore, of great interest to healthcare organizations to predict what patients are at risk to be readmitted to their hospitals. However, current logistic regression based risk prediction models have limited prediction power when applied to hospital administrative data. Meanwhile, although decision trees and random forests have been applied, they tend to be too complex to understand among the hospital practitioners. Explore the use of conditional logistic regression to increase the prediction accuracy. We analyzed an HCUP statewide inpatient discharge record dataset, which includes patient demographics, clinical and care utilization data from California. We extracted records of heart failure Medicare beneficiaries who had inpatient experience during an 11-month period. We corrected the data imbalance issue with under-sampling. In our study, we first applied standard logistic regression and decision tree to obtain influential variables and derive practically meaning decision rules. We then stratified the original data set accordingly and applied logistic regression on each data stratum. We further explored the effect of interacting variables in the logistic regression modeling. We conducted cross validation to assess the overall prediction performance of conditional logistic regression (CLR) and compared it with standard classification models. The developed CLR models outperformed several standard classification models (e.g., straightforward logistic regression, stepwise logistic regression, random forest, support vector machine). For example, the best CLR model improved the classification accuracy by nearly 20% over the straightforward logistic regression model. Furthermore, the developed CLR models tend to achieve better sensitivity of more than 10% over the standard classification models, which can be translated to correct labeling of additional 400 - 500 readmissions for heart failure patients in the state of California over a year. Lastly, several key predictor identified from the HCUP data include the disposition location from discharge, the number of chronic conditions, and the number of acute procedures. It would be beneficial to apply simple decision rules obtained from the decision tree in an ad-hoc manner to guide the cohort stratification. It could be potentially beneficial to explore the effect of pairwise interactions between influential predictors when building the logistic regression models for different data strata. Judicious use of the ad-hoc CLR models developed offers insights into future development of prediction models for hospital readmissions, which can lead to better intuition in identifying high-risk patients and developing effective post-discharge care strategies. Lastly, this paper is expected to raise the awareness of collecting data on additional markers and developing necessary database infrastructure for larger-scale exploratory studies on readmission risk prediction.

Prehospital management and fluid resuscitation in hypotensive trauma patients admitted to Karolinska University Hospital in Stockholm.

PubMed

Talving, Peep; Pålstedt, Joakim; Riddez, Louis

2005-01-01

Few previous studies have been conducted on the prehospital management of hypotensive trauma patients in Stockholm County. The aim of this study was to describe the prehospital management of hypotensive trauma patients admitted to the largest trauma center in Sweden, and to assess whether prehospital trauma life support (PHTLS) guidelines have been implemented regarding prehospital time intervals and fluid therapy. In addition, the effects of the age, type of injury, injury severity, prehospital time interval, blood pressure, and fluid therapy on outcome were investigated. This is a retrospective, descriptive study on consecutive, hypotensive trauma patients (systolic blood pressure < or = 90 mmHg on the scene of injury) admitted to Karolinska University Hospital in Stockholm, Sweden, during 2001-2003. The reported values are medians with interquartile ranges. Basic demographics, prehospital time intervals and interventions, injury severity scores (ISS), type and volumes of prehospital fluid resuscitation, and 30-day mortality were abstracted. The effects of the patient's age, gender, prehospital time interval, type of injury, injury severity, on-scene and emergency department blood pressure, and resuscitation fluid volumes on mortality were analyzed using the exact logistic regression model. In 102 (71 male) adult patients (age > or = 15 years) recruited, the median age was 35.5 years (range: 27-55 years) and 77 patients (75%) had suffered blunt injury. The predominant trauma mechanisms were falls between levels (24%) and motor vehicle crashes (22%) with an ISS of 28.5 (range: 16-50). The on-scene time interval was 19 minutes (range: 12-24 minutes). Fluid therapy was initiated at the scene of injury in the majority of patients (73%) regardless of the type of injury (77 blunt [75%] / 25 penetrating [25%]) or injury severity (ISS: 0-20; 21-40; 41-75). Age (odds ratio (OR) = 1.04), male gender (OR = 3.2), ISS 21-40 (OR = 13.6), and ISS >40 (OR = 43.6) were the significant factors affecting outcome in the exact logistic regression analysis. The time interval at the scene of injury exceeded PHTLS guidelines. The vast majority of the hypotensive trauma patients were fluid-resuscitated on-scene regardless of the type, mechanism, or severity of injury. A predefined fluid resuscitation regimen is not employed in hypotensive trauma victims with different types of injuries. The outcome was worsened by male gender, progressive age, and ISS > 20 in the exact multiple regression analysis.

Solving modal equations of motion with initial conditions using MSC/NASTRAN DMAP. Part 1: Implementing exact mode superposition

NASA Technical Reports Server (NTRS)

Abdallah, Ayman A.; Barnett, Alan R.; Ibrahim, Omar M.; Manella, Richard T.

1993-01-01

Within the MSC/NASTRAN DMAP (Direct Matrix Abstraction Program) module TRD1, solving physical (coupled) or modal (uncoupled) transient equations of motion is performed using the Newmark-Beta or mode superposition algorithms, respectively. For equations of motion with initial conditions, only the Newmark-Beta integration routine has been available in MSC/NASTRAN solution sequences for solving physical systems and in custom DMAP sequences or alters for solving modal systems. In some cases, one difficulty with using the Newmark-Beta method is that the process of selecting suitable integration time steps for obtaining acceptable results is lengthy. In addition, when very small step sizes are required, a large amount of time can be spent integrating the equations of motion. For certain aerospace applications, a significant time savings can be realized when the equations of motion are solved using an exact integration routine instead of the Newmark-Beta numerical algorithm. In order to solve modal equations of motion with initial conditions and take advantage of efficiencies gained when using uncoupled solution algorithms (like that within TRD1), an exact mode superposition method using MSC/NASTRAN DMAP has been developed and successfully implemented as an enhancement to an existing coupled loads methodology at the NASA Lewis Research Center.

Improving approximate-optimized effective potentials by imposing exact conditions: Theory and applications to electronic statics and dynamics

NASA Astrophysics Data System (ADS)

Kurzweil, Yair; Head-Gordon, Martin

2009-07-01

We develop a method that can constrain any local exchange-correlation potential to preserve basic exact conditions. Using the method of Lagrange multipliers, we calculate for each set of given Kohn-Sham orbitals a constraint-preserving potential which is closest to the given exchange-correlation potential. The method is applicable to both the time-dependent (TD) and independent cases. The exact conditions that are enforced for the time-independent case are Galilean covariance, zero net force and torque, and Levy-Perdew virial theorem. For the time-dependent case we enforce translational covariance, zero net force, Levy-Perdew virial theorem, and energy balance. We test our method on the exchange (only) Krieger-Li-Iafrate (xKLI) approximate-optimized effective potential for both cases. For the time-independent case, we calculated the ground state properties of some hydrogen chains and small sodium clusters for some constrained xKLI potentials and Hartree-Fock (HF) exchange. The results (total energy, Kohn-Sham eigenvalues, polarizability, and hyperpolarizability) indicate that enforcing the exact conditions is not important for these cases. On the other hand, in the time-dependent case, constraining both energy balance and zero net force yields improved results relative to TDHF calculations. We explored the electron dynamics in small sodium clusters driven by cw laser pulses. For each laser pulse we compared calculations from TD constrained xKLI, TD partially constrained xKLI, and TDHF. We found that electron dynamics such as electron ionization and moment of inertia dynamics for the constrained xKLI are most similar to the TDHF results. Also, energy conservation is better by at least one order of magnitude with respect to the unconstrained xKLI. We also discuss the problems that arise in satisfying constraints in the TD case with a non-cw driving force.

Improving approximate-optimized effective potentials by imposing exact conditions: Theory and applications to electronic statics and dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurzweil, Yair; Head-Gordon, Martin

2009-07-15

We develop a method that can constrain any local exchange-correlation potential to preserve basic exact conditions. Using the method of Lagrange multipliers, we calculate for each set of given Kohn-Sham orbitals a constraint-preserving potential which is closest to the given exchange-correlation potential. The method is applicable to both the time-dependent (TD) and independent cases. The exact conditions that are enforced for the time-independent case are Galilean covariance, zero net force and torque, and Levy-Perdew virial theorem. For the time-dependent case we enforce translational covariance, zero net force, Levy-Perdew virial theorem, and energy balance. We test our method on the exchangemore » (only) Krieger-Li-Iafrate (xKLI) approximate-optimized effective potential for both cases. For the time-independent case, we calculated the ground state properties of some hydrogen chains and small sodium clusters for some constrained xKLI potentials and Hartree-Fock (HF) exchange. The results (total energy, Kohn-Sham eigenvalues, polarizability, and hyperpolarizability) indicate that enforcing the exact conditions is not important for these cases. On the other hand, in the time-dependent case, constraining both energy balance and zero net force yields improved results relative to TDHF calculations. We explored the electron dynamics in small sodium clusters driven by cw laser pulses. For each laser pulse we compared calculations from TD constrained xKLI, TD partially constrained xKLI, and TDHF. We found that electron dynamics such as electron ionization and moment of inertia dynamics for the constrained xKLI are most similar to the TDHF results. Also, energy conservation is better by at least one order of magnitude with respect to the unconstrained xKLI. We also discuss the problems that arise in satisfying constraints in the TD case with a non-cw driving force.« less

Mean effective size and refractive index of transparent atmospheric particulates

NASA Technical Reports Server (NTRS)

Fymat, A. L.

1975-01-01

It is demonstrated that the scattering ratio-principle originally restricted to exact forward and exact backward scattering, and to values of the size parameter and of the product (refractive index x size parameter) less than 0.8 has a much wider applicability. After relaxing these stringent conditions, it is also shown that this principle can be retained as the basis of an experimental technique for retrieving the mean effective size and refractive index of transparent atmospheric particulates.

Gödel metrics with chronology protection in Horndeski gravities

NASA Astrophysics Data System (ADS)

Geng, Wei-Jian; Li, Shou-Long; Lü, H.; Wei, Hao

2018-05-01

Gödel universe, one of the most interesting exact solutions predicted by General Relativity, describes a homogeneous rotating universe containing naked closed time-like curves (CTCs). It was shown that such CTCs are the consequence of the null energy condition in General Relativity. In this paper, we show that the Gödel-type metrics with chronology protection can emerge in Einstein-Horndeski gravity. We construct such exact solutions also in Einstein-Horndeski-Maxwell and Einstein-Horndeski-Proca theories.

Thermal stresses and deflections of cross-ply laminated plates using refined plate theories

NASA Technical Reports Server (NTRS)

Khdeir, A. A.; Reddy, J. N.

1991-01-01

Exact analytical solutions of refined plate theories are developed to study the thermal stresses and deflections of cross-ply rectangular plates. The state-space approach in conjunction with the Levy method is used to solve exactly the governing equations of the theories under various boundary conditions. Numerical results of the higher-order theory of Reddy for thermal stresses and deflections are compared with those obtained using the classical and first-order plate theories.

Variational dynamic background model for keyword spotting in handwritten documents

NASA Astrophysics Data System (ADS)

Kumar, Gaurav; Wshah, Safwan; Govindaraju, Venu

2013-12-01

We propose a bayesian framework for keyword spotting in handwritten documents. This work is an extension to our previous work where we proposed dynamic background model, DBM for keyword spotting that takes into account the local character level scores and global word level scores to learn a logistic regression classifier to separate keywords from non-keywords. In this work, we add a bayesian layer on top of the DBM called the variational dynamic background model, VDBM. The logistic regression classifier uses the sigmoid function to separate keywords from non-keywords. The sigmoid function being neither convex nor concave, exact inference of VDBM becomes intractable. An expectation maximization step is proposed to do approximate inference. The advantage of VDBM over the DBM is multi-fold. Firstly, being bayesian, it prevents over-fitting of data. Secondly, it provides better modeling of data and an improved prediction of unseen data. VDBM is evaluated on the IAM dataset and the results prove that it outperforms our prior work and other state of the art line based word spotting system.

Estimating raptor nesting success: old and new approaches

USGS Publications Warehouse

Brown, Jessi L.; Steenhof, Karen; Kochert, Michael N.; Bond, Laura

2013-01-01

Studies of nesting success can be valuable in assessing the status of raptor populations, but differing monitoring protocols can present unique challenges when comparing populations of different species across time or geographic areas. We used large datasets from long-term studies of 3 raptor species to compare estimates of apparent nest success (ANS, the ratio of successful to total number of nesting attempts), Mayfield nesting success, and the logistic-exposure model of nest survival. Golden eagles (Aquila chrysaetos), prairie falcons (Falco mexicanus), and American kestrels (F. sparverius) differ in their breeding biology and the methods often used to monitor their reproduction. Mayfield and logistic-exposure models generated similar estimates of nesting success with similar levels of precision. Apparent nest success overestimated nesting success and was particularly sensitive to inclusion of nesting attempts discovered late in the nesting season. Thus, the ANS estimator is inappropriate when exact point estimates are required, especially when most raptor pairs cannot be located before or soon after laying eggs. However, ANS may be sufficient to assess long-term trends of species in which nesting attempts are highly detectable.

Comparison of exact, efron and breslow parameter approach method on hazard ratio and stratified cox regression model

NASA Astrophysics Data System (ADS)

Fatekurohman, Mohamat; Nurmala, Nita; Anggraeni, Dian

2018-04-01

Lungs are the most important organ, in the case of respiratory system. Problems related to disorder of the lungs are various, i.e. pneumonia, emphysema, tuberculosis and lung cancer. Comparing all those problems, lung cancer is the most harmful. Considering about that, the aim of this research applies survival analysis and factors affecting the endurance of the lung cancer patient using comparison of exact, Efron and Breslow parameter approach method on hazard ratio and stratified cox regression model. The data applied are based on the medical records of lung cancer patients in Jember Paru-paru hospital on 2016, east java, Indonesia. The factors affecting the endurance of the lung cancer patients can be classified into several criteria, i.e. sex, age, hemoglobin, leukocytes, erythrocytes, sedimentation rate of blood, therapy status, general condition, body weight. The result shows that exact method of stratified cox regression model is better than other. On the other hand, the endurance of the patients is affected by their age and the general conditions.

Non-empirical exchange-correlation parameterizations based on exact conditions from correlated orbital theory.

PubMed

Haiduke, Roberto Luiz A; Bartlett, Rodney J

2018-05-14

Some of the exact conditions provided by the correlated orbital theory are employed to propose new non-empirical parameterizations for exchange-correlation functionals from Density Functional Theory (DFT). This reparameterization process is based on range-separated functionals with 100% exact exchange for long-range interelectronic interactions. The functionals developed here, CAM-QTP-02 and LC-QTP, show mitigated self-interaction error, correctly predict vertical ionization potentials as the negative of eigenvalues for occupied orbitals, and provide nice excitation energies, even for challenging charge-transfer excited states. Moreover, some improvements are observed for reaction barrier heights with respect to the other functionals belonging to the quantum theory project (QTP) family. Finally, the most important achievement of these new functionals is an excellent description of vertical electron affinities (EAs) of atoms and molecules as the negative of appropriate virtual orbital eigenvalues. In this case, the mean absolute deviations for EAs in molecules are smaller than 0.10 eV, showing that physical interpretation can indeed be ascribed to some unoccupied orbitals from DFT.

Non-empirical exchange-correlation parameterizations based on exact conditions from correlated orbital theory

NASA Astrophysics Data System (ADS)

Haiduke, Roberto Luiz A.; Bartlett, Rodney J.

2018-05-01

Some of the exact conditions provided by the correlated orbital theory are employed to propose new non-empirical parameterizations for exchange-correlation functionals from Density Functional Theory (DFT). This reparameterization process is based on range-separated functionals with 100% exact exchange for long-range interelectronic interactions. The functionals developed here, CAM-QTP-02 and LC-QTP, show mitigated self-interaction error, correctly predict vertical ionization potentials as the negative of eigenvalues for occupied orbitals, and provide nice excitation energies, even for challenging charge-transfer excited states. Moreover, some improvements are observed for reaction barrier heights with respect to the other functionals belonging to the quantum theory project (QTP) family. Finally, the most important achievement of these new functionals is an excellent description of vertical electron affinities (EAs) of atoms and molecules as the negative of appropriate virtual orbital eigenvalues. In this case, the mean absolute deviations for EAs in molecules are smaller than 0.10 eV, showing that physical interpretation can indeed be ascribed to some unoccupied orbitals from DFT.

Racial/ethnic and educational differences in the estimated odds of recent nitrite use among adult household residents in the United States: an illustration of matching and conditional logistic regression.

PubMed

Delva, J; Spencer, M S; Lin, J K

2000-01-01

This article compares estimates of the relative odds of nitrite use obtained from weighted unconditional logistic regression with estimates obtained from conditional logistic regression after post-stratification and matching of cases with controls by neighborhood of residence. We illustrate these methods by comparing the odds associated with nitrite use among adults of four racial/ethnic groups, with and without a high school education. We used aggregated data from the 1994-B through 1996 National Household Survey on Drug Abuse (NHSDA). Difference between the methods and implications for analysis and inference are discussed.

Simpson's paradox - aggregating and partitioning populations in health disparities of lung cancer patients.

PubMed

Fu, P; Panneerselvam, A; Clifford, B; Dowlati, A; Ma, P C; Zeng, G; Halmos, B; Leidner, R S

2015-12-01

It is well known that non-small cell lung cancer (NSCLC) is a heterogeneous group of diseases. Previous studies have demonstrated genetic variation among different ethnic groups in the epidermal growth factor receptor (EGFR) in NSCLC. Research by our group and others has recently shown a lower frequency of EGFR mutations in African Americans with NSCLC, as compared to their White counterparts. In this study, we use our original study data of EGFR pathway genetics in African American NSCLC as an example to illustrate that univariate analyses based on aggregation versus partition of data leads to contradictory results, in order to emphasize the importance of controlling statistical confounding. We further investigate analytic approaches in logistic regression for data with separation, as is the case in our example data set, and apply appropriate methods to identify predictors of EGFR mutation. Our simulation shows that with separated or nearly separated data, penalized maximum likelihood (PML) produces estimates with smallest bias and approximately maintains the nominal value with statistical power equal to or better than that from maximum likelihood and exact conditional likelihood methods. Application of the PML method in our example data set shows that race and EGFR-FISH are independently significant predictors of EGFR mutation. © The Author(s) 2011.

[Quantitative Evaluation of Intracardiac Blood Flow by Left Ventricle Dynamic Anatovy Based On Exact Solutions of Non-Stationary Navier-Stocks Equations for Selforganized tornado-Like Flows of Viscous Incompresssible Fluid].

PubMed

Talygin, E A; Zazybo, N A; Zhorzholiany, S T; Krestinich, I M; Mironov, A A; Kiknadze, G I; Bokerya, L A; Gorodkov, A Y; Makarenko, V N; Alexandrova, S A

2016-01-01

New approach to intracardiac blood flow condition analysis based on geometric parameters of left ventricle flow channel has been suggested. Parameters, that used in this method, follow from exact solutions of nonstationary Navier-Stocks equations for selforganized tornado-like flows of viscous incompressible fluid. The main advantage of this method is considering dynamic anatomy of intracardiac cavity and trabeculae relief of left ventricle streamlined surface, both registered in a common mri-process, as flow condition indicator. Calculated quantity options that characterizes blood flow condition can be use as diagnostic criterias for estimation of violation in blood circulation function which entails heart ejection reduction. Developed approach allows to clarify heart jet organization mechanism and estimate the share of the tornado-like flow self-organization in heart ejection structure.

Exact analytic solution for the spin-up maneuver of an axially symmetric spacecraft

NASA Astrophysics Data System (ADS)

Ventura, Jacopo; Romano, Marcello

2014-11-01

The problem of spinning-up an axially symmetric spacecraft subjected to an external torque constant in magnitude and parallel to the symmetry axis is considered. The existing exact analytic solution for an axially symmetric body is applied for the first time to this problem. The proposed solution is valid for any initial conditions of attitude and angular velocity and for any length of time and rotation amplitude. Furthermore, the proposed solution can be numerically evaluated up to any desired level of accuracy. Numerical experiments and comparison with an existing approximated solution and with the integration of the equations of motion are reported in the paper. Finally, a new approximated solution obtained from the exact one is introduced in this paper.

Earthworks logistics in the high density urban development conditions - case study

NASA Astrophysics Data System (ADS)

Sobotka, A.; Blajer, M.

2017-10-01

Realisation of the construction projects on highly urbanised areas carries many difficulties and logistic problems. Earthworks conducted in such conditions constitute a good example of how important it is to properly plan the works and use the technical means of the logistics infrastructure. The construction processes on the observed construction site, in combination with their external logistics service are a complex system, difficult for mathematical modelling and achievement of appropriate data for planning the works. The paper shows describe and analysis of earthworks during construction of the Centre of Power Engineering of AGH in Krakow for two stages of a construction project. At the planning stage in the preparatory phase (before realization) and in the implementation phase of construction works (foundation). In the first case, an example of the use of queuing theory for prediction of excavation time under random work conditions of the excavator and the associated trucks is provided. In the second case there is a change of foundation works technology resulting as a consequence of changes in logistics earthworks. Observation of the construction has confirmed that the use of appropriate methods of construction works management, and in this case agile management, the time and cost of the project have not been exceeded. The success of a project depends on the ability of the contractor to react quickly when changes occur in the design, technology, environment, etc.

Front and pulse solutions for the complex Ginzburg-Landau equation with higher-order terms.

PubMed

Tian, Huiping; Li, Zhonghao; Tian, Jinping; Zhou, Guosheng

2002-12-01

We investigate one-dimensional complex Ginzburg-Landau equation with higher-order terms and discuss their influences on the multiplicity of solutions. An exact analytic front solution is presented. By stability analysis for the original partial differential equation, we derive its necessary stability condition for amplitude perturbations. This condition together with the exact front solution determine the region of parameter space where the uniformly translating front solution can exist. In addition, stable pulses, chaotic pulses, and attenuation pulses appear generally if the parameters are out of the range. Finally, applying these analysis into the optical transmission system numerically we find that the stable transmission of optical pulses can be achieved if the parameters are appropriately chosen.

Exact solution of conductive heat transfer in cylindrical composite laminate

NASA Astrophysics Data System (ADS)

Kayhani, M. H.; Shariati, M.; Nourozi, M.; Karimi Demneh, M.

2009-11-01

This paper presents an exact solution for steady-state conduction heat transfer in cylindrical composite laminates. This laminate is cylindrical shape and in each lamina, fibers have been wound around the cylinder. In this article heat transfer in composite laminates is being investigated, by using separation of variables method and an analytical relation for temperature distribution in these laminates has been obtained under specific boundary conditions. Also Fourier coefficients in each layer obtain by solving set of equations that related to thermal boundary layer conditions at inside and outside of the cylinder also thermal continuity and heat flux continuity between each layer is considered. In this research LU factorization method has been used to solve the set of equations.

Hydrodynamics beyond Navier-Stokes: exact solution to the lattice Boltzmann hierarchy.

PubMed

Ansumali, S; Karlin, I V; Arcidiacono, S; Abbas, A; Prasianakis, N I

2007-03-23

The exact solution to the hierarchy of nonlinear lattice Boltzmann (LB) kinetic equations in the stationary planar Couette flow is found at nonvanishing Knudsen numbers. A new method of solving LB kinetic equations which combines the method of moments with boundary conditions for populations enables us to derive closed-form solutions for all higher-order moments. A convergence of results suggests that the LB hierarchy with larger velocity sets is the novel way to approximate kinetic theory.

An exact plane-stress solution for a class of problems in orthotropic elasticity

NASA Technical Reports Server (NTRS)

Erb, D. A.; Cooper, P. A.; Weisshaar, T. A.

1982-01-01

An exact solution for the stress field within a rectangular slab of orthotropic material is found using a two dimensional Fourier series formulation. The material is required to be in plane stress, with general stress boundary conditions, and the principle axes of the material must be parallel to the sides of the rectangle. Two load cases similar to those encountered in materials testing are investigated using the solution. The solution method has potential uses in stress analysis of composite structures.

Thermal stresses and deflections of cross-ply laminated plates using refined plate theories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khdeir, A.A.; Reddy, J.N.

1991-12-01

Exact analytical solutions of refined plate theories are developed to study the thermal stresses and deflections of cross-ply rectangular plates. The state-space approach in conjunction with the Levy method is used to solve exactly the governing equations of the theories under various boundary conditions. Numerical results of the higher-order theory of Reddy for thermal stresses and deflections are compared with those obtained using the classical and first-order plate theories. 14 refs.

Notes on the ExactPack Implementation of the DSD Explosive Arc Solver

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaul, Ann; Doebling, Scott William

It has been shown above that the discretization scheme implemented in the ExactPack solver for the DSD Explosive Arc equation is consistent with the Explosive Arc PDE. In addition, a stability analysis has provided a CFL condition for a stable time step. Together, consistency and stability imply convergence of the scheme, which is expected to be close to first-order in time and second-order in space. It is understood that the nonlinearity of the underlying PDE will affect this rate somewhat.

Exact-Output Tracking Theory for Systems with Parameter Jumps

NASA Technical Reports Server (NTRS)

Devasia, Santosh; Paden, Brad; Rossi, Carlo

1996-01-01

In this paper we consider the exact output tracking problem for systems with parameter jumps. Necessary and sufficient conditions are derived for the elimination of switching-introduced output transient. Previous works have studied this problem by developing a regulator that maintains exact tracking through parameter jumps (switches). Such techniques are, however, only applicable to minimum-phase systems. In contrast, our approach is applicable to nonminimum-phase systems and obtains bounded but possibly non-causal solutions. If the reference trajectories are generated by an exo-system, then we develop an exact-tracking controller in a feedback form. As in standard regulator theory, we obtain a linear map from the states of the exo-system to the desired system state which is defined via a matrix differential equation. The constant solution of this differential equation provides asymptotic tracking, and coincides with the feedback law used in standard regulator theory. The obtained results are applied to a simple flexible manipulator with jumps in the pay-load mass.

Exact-Output Tracking Theory for Systems with Parameter Jumps

NASA Technical Reports Server (NTRS)

Devasia, Santosh; Paden, Brad; Rossi, Carlo

1997-01-01

We consider the exact output tracking problem for systems with parameter jumps. Necessary and sufficient conditions are derived for the elimination of switching-introduced output transient. Previous works have studied this problem by developing a regulator that maintains exact tracking through parameter jumps (switches). Such techniques are, however, only applicable to minimum-phase systems. In contrast, our approach is applicable to non-minimum-phase systems and it obtains bounded but possibly non-causal solutions. If the reference trajectories are generated by an exosystem, then we develop an exact-tracking controller in a feed-back form. As in standard regulator theory, we obtain a linear map from the states of the exosystem to the desired system state which is defined via a matrix differential equation. The constant solution of this differential equation provides asymptotic tracking, and coincides with the feedback law used in standard regulator theory. The obtained results are applied to a simple flexible manipulator with jumps in the pay-load mass.

Exact solutions for postbuckling of a graded porous beam

NASA Astrophysics Data System (ADS)

Ma, L. S.; Ou, Z. Y.

2018-06-01

An exact, closed-form solution for the postbuckling responses of graded porous beams subjected to axially loading is obtained. It was assumed that the properties of the graded porous materials vary continuously through thickness of the beams, the equations governing the axial and transverse deformations are derived based on the classical beam theory and the physical neutral surface concept. The two equations are reduced to a single nonlinear fourth-order integral-differential equation governing the transverse deformations. The nonlinear equation is directly solved without any use of approximation and a closed-form solution for postbuckled deformation is obtained as a function of the applied load. The exact solutions explicitly describe the nonlinear equilibrium paths of the buckled beam and thus are able to provide insight into deformation problems. Based on the exact solutions obtained herein, the effects of various factors such as porosity distribution pattern, porosity coefficient and boundary conditions on postbuckling behavior of graded porous beams have been investigated.

Knowledge, Attitudes, and Substance Use Practices Among Street Children in Western Kenya

PubMed Central

Embleton, Lonnie; Ayuku, David; Atwoli, Lukoye; Vreeman, Rachel; Braitstein, Paula

2013-01-01

The study describes the knowledge of and attitudes toward substance use among street-involved youth in Kenya, and how they relate to their substance use practices. In 2011, 146 children and youth ages 10–19 years, classified as either children on the street or children of the street were recruited to participate in a cross-sectional survey in Eldoret, Kenya. Bivariate analysis using χ2 or Fisher’s Exact Test was used to test the associations between variables, and multiple logistic regression analysis was used to identify independent covariates associated with lifetime and current drug use. The study’s limitations and source of funding are noted. PMID:22780841

Sociodemographic factors associated with pregnant women's level of knowledge about oral health

PubMed Central

Barbieri, Wander; Peres, Stela Verzinhasse; Pereira, Carla de Britto; Peres, João; de Sousa, Maria da Luz Rosário; Cortellazzi, Karine Laura

2018-01-01

ABSTRACT Objective To evaluate knowledge on oral health and associated sociodemographic factors in pregnant women. Methods A cross-sectional study with a sample of 195 pregnant women seen at the Primary Care Unit Paraisópolis I, in São Paulo (SP), Brazil. For statistical analysis, χ2 or Fisher's exact test and multiple logistic regression were used. A significance level of 5% was used in all analyses. Results Schooling level equal to or greater than 8 years and having one or two children were associated with an adequate knowledge about oral health. Conclusion Oral health promotion strategies during prenatal care should take into account sociodemographic aspects. PMID:29694612

Critical fluctuations near the pitchfork bifurcations of period-doubling maps

NASA Astrophysics Data System (ADS)

Noble, Andrew; Karimeddiny, Saba; Hastings, Alan; Machta, Jonathan

2015-03-01

Period-doubling maps, such as the logistic map, have been a subject of intense study in both physics and biology. The period-doubling route to chaos proceeds through a sequence of supercritical pitchfork bifurcations. Here, motivated by applications to population ecology, we investigate the asymptotic behavior of period-doubling bifurcations subject to environmental or demographic noise. We demonstrate, analytically, that fluctuations in the vicinity of each noisy pitchfork bifurcation are described by finite-size mean-field theory. Our results establish an exact correspondence between the bifurcations of far-from-equilibrium systems and the mean-field critical phenomena of equilibrium systems. This material is based upon work supported by the National Science Foundation under INSPIRE Grant No. 1344187.

Incidence and predictors of onset of injection drug use in a San Francisco cohort of homeless youth.

PubMed

Parriott, Andrea M; Auerswald, Colette L

2009-01-01

Few studies document incidence of injection drug use among homeless youth. We followed a cohort of 70 street-recruited homeless youth in San Francisco, California who had never injected drugs for six months in 2004-5. We examined initiation of injection drug use and its predictors, informed by prior ethnographic findings. Data were analyzed using exact logistic regression. 11.4% of youth initiated injection drug use. Having no high school education, being over 21 years old, and being in disequilibrium predicted initiation. Limitations, implications and suggestions for future research are noted. Funding was provided by the National Institute for Child Health and Development.

Who Gets Promoted? Gender Differences in Science and Engineering Academia

NASA Astrophysics Data System (ADS)

Olson, Kristen

Using a nationally representative sample of doctoral academic scientists and engineers, this study examines gender differences in the likelihood of having tenure and senior faculty ranks after controlling for academic age, field, doctoral origins, employing educational institution, productivity, postdoctoral positions, work activities, and family characteristics. Logistic regressions show that many of these controls are significant; that biology and employment at comprehensive universities have a gender-specific advantage for women; and that postdoctoral positions, teaching instead of doing administrative work, and having children have a gender-specific disadvantage. Although the statistical methods employed here do not reveal the exact nature of how gender inequities in science and engineering careers arise, the author suggests that they exist.

Health and Behavioral Survey of over 8000 Finnish Cats

PubMed Central

Vapalahti, Katariina; Virtala, Anna-Maija; Joensuu, Tara A.; Tiira, Katriina; Tähtinen, Jaana; Lohi, Hannes

2016-01-01

A comprehensive feline health survey was conducted to reveal breed-specific inheritable diseases in Finnish pedigree cats for genetic research. Prevalence of 19 disease categories and 227 feline diseases were defined in a study population of 8175 cats belonging to 30 breeds. Dental and oral diseases, with a prevalence of 28%, and dental calculus and gingivitis (21 and 8%, respectively) were the most prevalent disease category and diseases among all cats and in most of the breeds. An exception was Korats, which were more often affected by the diseases of the respiratory tract (23%) and asthma (19%). Other prevalent disease categories affected various organ systems, such as the skin (12%), the urinary system (12%), the digestive tract (11%), eyes (10%), the musculoskeletal system (10%), and genitals of female cats (17%). Prevalent health or developmental issues included repetitive vomiting (4%), tail kink (4%), feline odontoclastic resorption lesion (4%), urinary tract infections (4%), as well as cesarean section (6%) and stillborn kittens (6%) among female cats. We found 57 breed-specific conditions by Fisher’s exact tests and logistic regression analyses, including 32 previously described and 19 new breed-specific diseases. The genetic defect has already been found in six of them: polycystic kidney disease, progressive retinal atrophy, hypertrophic cardiomyopathy, and three types of tail malformations. Behavioral profiling revealed breed-specific traits, such as an increased human avoidance in British Short and Longhairs and a higher level of aggression in Turkish vans. Our epidemiological study reveals the overall health profile in Finnish pure and mixed breed cats and identifies many breed-specific conditions without molecular identity for genetic research. PMID:27622188

Continuous thermographic observation may predict extravasation in chemotherapy-treated patients.

PubMed

Oya, Maiko; Murayama, Ryoko; Oe, Makoto; Yabunaka, Koichi; Tanabe, Hidenori; Takahashi, Toshiaki; Matsui, Yuko; Otomo, Eiko; Komiyama, Chieko; Sanada, Hiromi

2017-06-01

Extravasation, or leakage of vesicant drugs into subcutaneous tissues, causes serious complications such as induration and necrosis in chemotherapy-treated patients. As macroscopic observation may overlook symptoms during infusion, we focused on skin temperature changes at puncture sites and studied thermographic patterns related to induration or necrosis caused by extravasation. Outpatients undergoing chemotherapy using peripheral intravenous catheters were enrolled in this prospective observational study. We filmed and classified infrared thermography movies of puncture sites during infusion; ultrasonography was also utilized at puncture sites to observe the subcutaneous condition. Multiple logistic regression analysis was performed to examine the association of thermographic patterns with induration or necrosis observed on the next chemotherapy day. Differences in patient characteristics, puncture sites, and infusions were analyzed by Mann-Whitney's U test and Fisher's exact test according to thermographic patterns. Eight patients developed induration among 74 observations in 62 patients. Among six thermographic patterns, a fan-shaped lower temperature area gradually spreading from the puncture site (fan at puncture site) was significantly associated with induration. Ultrasonography revealed that catheters of patients with fan at puncture site remained in the vein at the end of infusion, indicating that the infusion probably leaked from the puncture site. Patients with fan at puncture site had no significant differences in characteristics and infusion conditions compared with those with the other five thermographic patterns. We determined that fan at puncture site was related to induration caused by extravasation. Continuous thermographic observation may enable us to predict adverse events of chemotherapy. Copyright © 2017. Published by Elsevier Ltd.

Unconditional or Conditional Logistic Regression Model for Age-Matched Case-Control Data?

PubMed

Kuo, Chia-Ling; Duan, Yinghui; Grady, James

2018-01-01

Matching on demographic variables is commonly used in case-control studies to adjust for confounding at the design stage. There is a presumption that matched data need to be analyzed by matched methods. Conditional logistic regression has become a standard for matched case-control data to tackle the sparse data problem. The sparse data problem, however, may not be a concern for loose-matching data when the matching between cases and controls is not unique, and one case can be matched to other controls without substantially changing the association. Data matched on a few demographic variables are clearly loose-matching data, and we hypothesize that unconditional logistic regression is a proper method to perform. To address the hypothesis, we compare unconditional and conditional logistic regression models by precision in estimates and hypothesis testing using simulated matched case-control data. Our results support our hypothesis; however, the unconditional model is not as robust as the conditional model to the matching distortion that the matching process not only makes cases and controls similar for matching variables but also for the exposure status. When the study design involves other complex features or the computational burden is high, matching in loose-matching data can be ignored for negligible loss in testing and estimation if the distributions of matching variables are not extremely different between cases and controls.

Unconditional or Conditional Logistic Regression Model for Age-Matched Case–Control Data?

PubMed Central

Kuo, Chia-Ling; Duan, Yinghui; Grady, James

2018-01-01

Matching on demographic variables is commonly used in case–control studies to adjust for confounding at the design stage. There is a presumption that matched data need to be analyzed by matched methods. Conditional logistic regression has become a standard for matched case–control data to tackle the sparse data problem. The sparse data problem, however, may not be a concern for loose-matching data when the matching between cases and controls is not unique, and one case can be matched to other controls without substantially changing the association. Data matched on a few demographic variables are clearly loose-matching data, and we hypothesize that unconditional logistic regression is a proper method to perform. To address the hypothesis, we compare unconditional and conditional logistic regression models by precision in estimates and hypothesis testing using simulated matched case–control data. Our results support our hypothesis; however, the unconditional model is not as robust as the conditional model to the matching distortion that the matching process not only makes cases and controls similar for matching variables but also for the exposure status. When the study design involves other complex features or the computational burden is high, matching in loose-matching data can be ignored for negligible loss in testing and estimation if the distributions of matching variables are not extremely different between cases and controls. PMID:29552553

Risk estimation using probability machines

PubMed Central

2014-01-01

Background Logistic regression has been the de facto, and often the only, model used in the description and analysis of relationships between a binary outcome and observed features. It is widely used to obtain the conditional probabilities of the outcome given predictors, as well as predictor effect size estimates using conditional odds ratios. Results We show how statistical learning machines for binary outcomes, provably consistent for the nonparametric regression problem, can be used to provide both consistent conditional probability estimation and conditional effect size estimates. Effect size estimates from learning machines leverage our understanding of counterfactual arguments central to the interpretation of such estimates. We show that, if the data generating model is logistic, we can recover accurate probability predictions and effect size estimates with nearly the same efficiency as a correct logistic model, both for main effects and interactions. We also propose a method using learning machines to scan for possible interaction effects quickly and efficiently. Simulations using random forest probability machines are presented. Conclusions The models we propose make no assumptions about the data structure, and capture the patterns in the data by just specifying the predictors involved and not any particular model structure. So they do not run the same risks of model mis-specification and the resultant estimation biases as a logistic model. This methodology, which we call a “risk machine”, will share properties from the statistical machine that it is derived from. PMID:24581306

Risk estimation using probability machines.

PubMed

Dasgupta, Abhijit; Szymczak, Silke; Moore, Jason H; Bailey-Wilson, Joan E; Malley, James D

2014-03-01

Logistic regression has been the de facto, and often the only, model used in the description and analysis of relationships between a binary outcome and observed features. It is widely used to obtain the conditional probabilities of the outcome given predictors, as well as predictor effect size estimates using conditional odds ratios. We show how statistical learning machines for binary outcomes, provably consistent for the nonparametric regression problem, can be used to provide both consistent conditional probability estimation and conditional effect size estimates. Effect size estimates from learning machines leverage our understanding of counterfactual arguments central to the interpretation of such estimates. We show that, if the data generating model is logistic, we can recover accurate probability predictions and effect size estimates with nearly the same efficiency as a correct logistic model, both for main effects and interactions. We also propose a method using learning machines to scan for possible interaction effects quickly and efficiently. Simulations using random forest probability machines are presented. The models we propose make no assumptions about the data structure, and capture the patterns in the data by just specifying the predictors involved and not any particular model structure. So they do not run the same risks of model mis-specification and the resultant estimation biases as a logistic model. This methodology, which we call a "risk machine", will share properties from the statistical machine that it is derived from.

Single-molecule stochastic times in a reversible bimolecular reaction

NASA Astrophysics Data System (ADS)

Keller, Peter; Valleriani, Angelo

2012-08-01

In this work, we consider the reversible reaction between reactants of species A and B to form the product C. We consider this reaction as a prototype of many pseudobiomolecular reactions in biology, such as for instance molecular motors. We derive the exact probability density for the stochastic waiting time that a molecule of species A needs until the reaction with a molecule of species B takes place. We perform this computation taking fully into account the stochastic fluctuations in the number of molecules of species B. We show that at low numbers of participating molecules, the exact probability density differs from the exponential density derived by assuming the law of mass action. Finally, we discuss the condition of detailed balance in the exact stochastic and in the approximate treatment.

Exact results for models of multichannel quantum nonadiabatic transitions

DOE PAGES

Sinitsyn, N. A.

2014-12-11

We consider nonadiabatic transitions in explicitly time-dependent systems with Hamiltonians of the form Hˆ(t)=Aˆ+Bˆt+Cˆ/t, where t is time and Aˆ,Bˆ,Cˆ are Hermitian N × N matrices. We show that in any model of this type, scattering matrix elements satisfy nontrivial exact constraints that follow from the absence of the Stokes phenomenon for solutions with specific conditions at t→–∞. This allows one to continue such solutions analytically to t→+∞, and connect their asymptotic behavior at t→–∞ and t→+∞. This property becomes particularly useful when a model shows additional discrete symmetries. Specifically, we derive a number of simple exact constraints and explicitmore » expressions for scattering probabilities in such systems.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Xin-Ping, E-mail: xuxp@mail.ihep.ac.cn; Ide, Yusuke

In the literature, there are numerous studies of one-dimensional discrete-time quantum walks (DTQWs) using a moving shift operator. However, there is no exact solution for the limiting probability distributions of DTQWs on cycles using a general coin or swapping shift operator. In this paper, we derive exact solutions for the limiting probability distribution of quantum walks using a general coin and swapping shift operator on cycles for the first time. Based on the exact solutions, we show how to generate symmetric quantum walks and determine the condition under which a symmetric quantum walk appears. Our results suggest that choosing various coinmore » and initial state parameters can achieve a symmetric quantum walk. By defining a quantity to measure the variation of symmetry, deviation and mixing time of symmetric quantum walks are also investigated.« less

Exact models for isotropic matter

NASA Astrophysics Data System (ADS)

Thirukkanesh, S.; Maharaj, S. D.

2006-04-01

We study the Einstein-Maxwell system of equations in spherically symmetric gravitational fields for static interior spacetimes. The condition for pressure isotropy is reduced to a recurrence equation with variable, rational coefficients. We demonstrate that this difference equation can be solved in general using mathematical induction. Consequently, we can find an explicit exact solution to the Einstein-Maxwell field equations. The metric functions, energy density, pressure and the electric field intensity can be found explicitly. Our result contains models found previously, including the neutron star model of Durgapal and Bannerji. By placing restrictions on parameters arising in the general series, we show that the series terminate and there exist two linearly independent solutions. Consequently, it is possible to find exact solutions in terms of elementary functions, namely polynomials and algebraic functions.

Structural factoring approach for analyzing stochastic networks

NASA Technical Reports Server (NTRS)

Hayhurst, Kelly J.; Shier, Douglas R.

1991-01-01

The problem of finding the distribution of the shortest path length through a stochastic network is investigated. A general algorithm for determining the exact distribution of the shortest path length is developed based on the concept of conditional factoring, in which a directed, stochastic network is decomposed into an equivalent set of smaller, generally less complex subnetworks. Several network constructs are identified and exploited to reduce significantly the computational effort required to solve a network problem relative to complete enumeration. This algorithm can be applied to two important classes of stochastic path problems: determining the critical path distribution for acyclic networks and the exact two-terminal reliability for probabilistic networks. Computational experience with the algorithm was encouraging and allowed the exact solution of networks that have been previously analyzed only by approximation techniques.

Asthma exacerbation and proximity of residence to major roads: a population-based matched case-control study among the pediatric Medicaid population in Detroit, Michigan

PubMed Central

2011-01-01

Background The relationship between asthma and traffic-related pollutants has received considerable attention. The use of individual-level exposure measures, such as residence location or proximity to emission sources, may avoid ecological biases. Method This study focused on the pediatric Medicaid population in Detroit, MI, a high-risk population for asthma-related events. A population-based matched case-control analysis was used to investigate associations between acute asthma outcomes and proximity of residence to major roads, including freeways. Asthma cases were identified as all children who made at least one asthma claim, including inpatient and emergency department visits, during the three-year study period, 2004-06. Individually matched controls were randomly selected from the rest of the Medicaid population on the basis of non-respiratory related illness. We used conditional logistic regression with distance as both categorical and continuous variables, and examined non-linear relationships with distance using polynomial splines. The conditional logistic regression models were then extended by considering multiple asthma states (based on the frequency of acute asthma outcomes) using polychotomous conditional logistic regression. Results Asthma events were associated with proximity to primary roads with an odds ratio of 0.97 (95% CI: 0.94, 0.99) for a 1 km increase in distance using conditional logistic regression, implying that asthma events are less likely as the distance between the residence and a primary road increases. Similar relationships and effect sizes were found using polychotomous conditional logistic regression. Another plausible exposure metric, a reduced form response surface model that represents atmospheric dispersion of pollutants from roads, was not associated under that exposure model. Conclusions There is moderately strong evidence of elevated risk of asthma close to major roads based on the results obtained in this population-based matched case-control study. PMID:21513554

Nonconvex Sparse Logistic Regression With Weakly Convex Regularization

NASA Astrophysics Data System (ADS)

Shen, Xinyue; Gu, Yuantao

2018-06-01

In this work we propose to fit a sparse logistic regression model by a weakly convex regularized nonconvex optimization problem. The idea is based on the finding that a weakly convex function as an approximation of the $\\ell_0$ pseudo norm is able to better induce sparsity than the commonly used $\\ell_1$ norm. For a class of weakly convex sparsity inducing functions, we prove the nonconvexity of the corresponding sparse logistic regression problem, and study its local optimality conditions and the choice of the regularization parameter to exclude trivial solutions. Despite the nonconvexity, a method based on proximal gradient descent is used to solve the general weakly convex sparse logistic regression, and its convergence behavior is studied theoretically. Then the general framework is applied to a specific weakly convex function, and a necessary and sufficient local optimality condition is provided. The solution method is instantiated in this case as an iterative firm-shrinkage algorithm, and its effectiveness is demonstrated in numerical experiments by both randomly generated and real datasets.

Nonlinear model of a rotating hub-beams structure: Equations of motion

NASA Astrophysics Data System (ADS)

Warminski, Jerzy

2018-01-01

Dynamics of a rotating structure composed of a rigid hub and flexible beams is presented in the paper. A nonlinear model of a beam takes into account bending, extension and nonlinear curvature. The influence of geometric nonlinearity and nonconstant angular velocity on dynamics of the rotating structure is presented. The exact equations of motion and associated boundary conditions are derived on the basis of the Hamilton's principle. The simplification of the exact nonlinear mathematical model is proposed taking into account the second order approximation. The reduced partial differential equations of motion together with associated boundary conditions can be used to study natural or forced vibrations of a rotating structure considering constant or nonconstant angular speed of a rigid hub and an arbitrary number of flexible blades.

Transverse vibration of Bernoulli Euler beams carrying point masses and taking into account their rotatory inertia: Exact solution

NASA Astrophysics Data System (ADS)

Maiz, Santiago; Bambill, Diana V.; Rossit, Carlos A.; Laura, P. A. A.

2007-06-01

The situation of structural elements supporting motors or engines attached to them is usual in technological applications. The operation of the machine may introduce severe dynamic stresses on the beam. It is important, then, to know the natural frequencies of the coupled beam-mass system, in order to obtain a proper design of the structural elements. An exact solution for the title problem is obtained in closed-form fashion, considering general boundary conditions by means of translational and rotatory springs at both ends. The model allows to analyze the influence of the masses and their rotatory inertia on the dynamic behavior of beams with all the classic boundary conditions, and also, as particular cases, to determine the frequencies of continuous beams.

Minimization theory of induced drag subject to constraint conditions

NASA Technical Reports Server (NTRS)

Deyoung, J.

1979-01-01

Exact analytical solutions in terms of induced drag influence coefficients can be attained which define the spanwise loading with minimized induced drag, subject to specified constraint conditions, for any nonplanar wing shape or number of lift plus wing bending moment about a given wing span station. Example applications of the theory are made to a biplane, a wing in ground effect, a cruciform wing, a V-wing, a planar-wing winglet, and linked wingtips in formation flying. For minimal induced drag, the spanwise loading, relative to elliptic, is outboard for the biplane and is inboard for the wing in ground effect and for the planar-wing winglet. A spinoff of the triplane solution provides mathematically exact equations for downwash and sidewash about a planar vorticity sheet having an arbitrary loading distribution.

Optimal Combination of Non-Invasive Tools for the Early Detection of Potentially Life-Threatening Emergencies in Gynecology

PubMed Central

Varas, Catalina; Ravit, Marion; Mimoun, Camille; Panel, Pierre; Huchon, Cyrille; Fauconnier, Arnaud

2016-01-01

Objectives Potentially life-threatening gynecological emergencies (G-PLEs) are acute pelvic conditions that may spontaneously evolve into a life-threatening situation, or those for which there is a risk of sequelae or death in the absence of prompt diagnosis and treatment. The objective of this study was to identify the best combination of non-invasive diagnostic tools to ensure an accurate diagnosis and timely response when faced with G-PLEs for patients arriving with acute pelvic pain at the Gynecological Emergency Department (ED). Methods The data on non-invasive diagnostic tools were sourced from the records of patients presenting at the ED of two hospitals in the Parisian suburbs (France) with acute pelvic pain between September 2006 and April 2008. The medical history of the patients was obtained through a standardized questionnaire completed for a prospective observational study, and missing information was completed with data sourced from the medical forms. Diagnostic tool categories were predefined as a collection of signs or symptoms. We analyzed the association of each sign/symptom with G-PLEs using Pearson’s Chi-Square or Fischer’s exact tests. Symptoms and signs associated with G-PLEs (p-value < 0.20) were subjected to logistic regression to evaluate the diagnostic value of each of the predefined diagnostic tools and in various combinations. Results The data of 365 patients with acute pelvic pain were analyzed, of whom 103 were confirmed to have a PLE. We analyzed five diagnostic tools by logistic regression: Triage Process, History-Taking, Physical Examination, Ultrasonography, and Biological Exams. The combination of History-Taking and Ultrasonography had a C-index of 0.83, the highest for a model combining two tools. Conclusions The use of a standardized self-assessment questionnaire for history-taking and focal ultrasound examination were found to be the most successful tool combination for the diagnosis of gynecological emergencies in a Gynecological ED. Additional tools, such as physical examination, do not add substantial diagnostic value. PMID:27583697

US-guided percutaneous cholecystostomy: features predicting culture-positive bile and clinical outcome.

PubMed

Sosna, Jacob; Kruskal, Jonathan B; Copel, Laurian; Goldberg, S Nahum; Kane, Robert A

2004-03-01

To assess sonographic and clinical features that might be used to predict infected bile and/or patient outcome from ultrasonography (US)-guided percutaneous cholecystostomy. Between February 1997 and August 2002 at one institution, 112 patients underwent US-guided percutaneous cholecystostomy (59 men, 53 women; average age, 69.3 years). All US images were scored on a defined semiquantitative scale according to preset parameters: (a) gallbladder distention, (b) sludge and/or stones, (c) wall appearance, (d) pericholecystic fluid, and (e) common bile duct size and/or choledocholithiasis. Separate and total scores were generated. Retrospective evaluation of (a) the bacteriologic growth of aspirated bile and its color and (b) clinical indices (fever, white blood cell count, bilirubin level, liver function test results) was conducted by reviewing medical records. For each patient, the clinical manifestation was classified into four groups: (a) localized right upper quadrant symptoms, (b) generalized abdominal symptoms, (c) unexplained sepsis, or (d) sepsis with other known infection. Logistic regression models, exact Wilcoxon-Mann-Whitney test, and the Kruskal-Wallis test were used. Forty-seven (44%) of 107 patients had infected bile. A logistic regression model showed that wall appearance, distention, bile color, and pericholecystic fluid were not individually significant predictors for culture-positive bile, leaving sludge and/or stones (P =.003, odds ratio = 1.647), common bile duct status (P =.02, odds ratio = 2.214), and total score (P =.007, odds ratio = 1.267). No US covariates or clinical indices predicted clinical outcome. Clinical manifestation was predictive of clinical outcome (P =.001) and aspirating culture-positive bile (P =.008); specifically, 30 (86%) of 35 patients with right upper quadrant symptoms had their condition improve, compared with one (7%) of 15 asymptomatic patients with other known causes of infection. US variables can be used to predict culture-positive bile but not patient outcome. Clinical manifestation is important because patients with right upper quadrant symptoms have the best clinical outcome. Copyright RSNA, 2004

Modeling logistic performance in quantitative microbial risk assessment.

PubMed

Rijgersberg, Hajo; Tromp, Seth; Jacxsens, Liesbeth; Uyttendaele, Mieke

2010-01-01

In quantitative microbial risk assessment (QMRA), food safety in the food chain is modeled and simulated. In general, prevalences, concentrations, and numbers of microorganisms in media are investigated in the different steps from farm to fork. The underlying rates and conditions (such as storage times, temperatures, gas conditions, and their distributions) are determined. However, the logistic chain with its queues (storages, shelves) and mechanisms for ordering products is usually not taken into account. As a consequence, storage times-mutually dependent in successive steps in the chain-cannot be described adequately. This may have a great impact on the tails of risk distributions. Because food safety risks are generally very small, it is crucial to model the tails of (underlying) distributions as accurately as possible. Logistic performance can be modeled by describing the underlying planning and scheduling mechanisms in discrete-event modeling. This is common practice in operations research, specifically in supply chain management. In this article, we present the application of discrete-event modeling in the context of a QMRA for Listeria monocytogenes in fresh-cut iceberg lettuce. We show the potential value of discrete-event modeling in QMRA by calculating logistic interventions (modifications in the logistic chain) and determining their significance with respect to food safety.

Exact analytical solution of shear-induced flexural vibration of functionally graded piezoelectric beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Pankaj, E-mail: psharma@rtu.ac.in; Parashar, Sandeep Kumar, E-mail: parashar2@yahoo.com

The priority of this paper is to obtain the exact analytical solution for free flexural vibration of FGPM beam actuated using the d{sub 15} effect. In piezoelectric actuators, the potential use of d{sub 15} effect has been of particular interest for engineering applications since shear piezoelectric coefficient d15 is much higher than the other piezoelectric coupling constants d{sub 31} and d{sub 33}. The applications of shear actuators are to induce and control the flexural vibrations of beams and plates. In this study, a modified Timoshenko beam theory is used where electric potential is assumed to vary sinusoidaly along the thicknessmore » direction. The material properties are assumed to be graded across the thickness in accordance with power law distribution. Hamilton's principle is employed to obtain the equations of motion along with the associated boundary conditions for FGPM beams. Exact analytical solution is derived thus obtained equations of motion. Results for clamped-clamped and clamped-free boundary conditions are presented. The presented result and method shell serve as benchmark for comparing the results obtained from the other approximate methods.« less

Exact solutions for the static bending of Euler-Bernoulli beams using Eringen's two-phase local/nonlocal model

NASA Astrophysics Data System (ADS)

Wang, Y. B.; Zhu, X. W.; Dai, H. H.

2016-08-01

Though widely used in modelling nano- and micro- structures, Eringen's differential model shows some inconsistencies and recent study has demonstrated its differences between the integral model, which then implies the necessity of using the latter model. In this paper, an analytical study is taken to analyze static bending of nonlocal Euler-Bernoulli beams using Eringen's two-phase local/nonlocal model. Firstly, a reduction method is proved rigorously, with which the integral equation in consideration can be reduced to a differential equation with mixed boundary value conditions. Then, the static bending problem is formulated and four types of boundary conditions with various loadings are considered. By solving the corresponding differential equations, exact solutions are obtained explicitly in all of the cases, especially for the paradoxical cantilever beam problem. Finally, asymptotic analysis of the exact solutions reveals clearly that, unlike the differential model, the integral model adopted herein has a consistent softening effect. Comparisons are also made with existing analytical and numerical results, which further shows the advantages of the analytical results obtained. Additionally, it seems that the once controversial nonlocal bar problem in the literature is well resolved by the reduction method.

Epidemiology of Human Papillomavirus Detected in the Oral Cavity and Fingernails of Mid-Adult Women.

PubMed

Fu, Tsung-chieh Jane; Hughes, James P; Feng, Qinghua; Hulbert, Ayaka; Hawes, Stephen E; Xi, Long Fu; Schwartz, Stephen M; Stern, Joshua E; Koutsky, Laura A; Winer, Rachel L

2015-12-01

Oral and fingernail human papillomavirus (HPV) detection may be associated with HPV-related carcinoma risk at these nongenital sites and foster transmission to the genitals. We describe the epidemiology of oral and fingernail HPV among mid-adult women. Between 2011 and 2012, 409 women aged 30 to 50 years were followed up for 6 months. Women completed health and behavior surveys and provided self-collected oral, fingernail, and vaginal specimens at enrollment and exit for type-specific HPV DNA testing. Concordance of type-specific HPV detection across anatomical sites was described with κ statistics. Using generalized estimating equations or exact logistic regression, we measured the univariate associations of various risk factors with type-specific oral and fingernail HPV detection. Prevalence of detecting HPV in the oral cavity (2.4%) and fingernails (3.8%) was low compared with the vagina (33.1%). Concordance across anatomical sites was poor (κ < 0.20 for all comparisons). However, concurrent vaginal infection with the same HPV type (odds ratio [OR], 101.0; 95% confidence interval [CI], 31.4-748.6) and vaginal HPV viral load (OR per 1 log10 viral load increase, 2.2; 95% CI, 1.5-5.5) were each associated with fingernail HPV detection. Abnormal Papanicolaou history (OR, 11.1; 95% CI, 2.8-infinity), lifetime number of male vaginal sex partners at least 10 (OR vs. 0-3 partners, 5.0; 95% CI, 1.2-infinity), and lifetime number of open-mouth kissing partners at least 16 (OR vs. 0-15 partners, infinity; 95% CI, 2.6-infinity, by exact logistic regression) were each associated with oral HPV detection. Although our findings support HPV DNA deposition or autoinoculation between anatomical sites in mid-adult women, the rarity of HPV in the oral cavity and fingernails suggests that oral/fingernail HPV does not account for a significant fraction of HPV in genital sites.

Epidemiology of Human Papillomavirus (HPV) Detected in the Oral Cavity and Fingernails of Mid-Adult Women

PubMed Central

Fu, Tsung-chieh (Jane); Hughes, James P.; Feng, Qinghua; Hulbert, Ayaka; Hawes, Stephen E.; Xi, Long Fu; Schwartz, Stephen M.; Stern, Joshua E.; Koutsky, Laura A.; Winer, Rachel L.

2015-01-01

Background Oral and fingernail human papillomavirus (HPV) detection may be associated with HPV-related carcinoma risk at these non-genital sites and foster transmission to the genitals. We describe the epidemiology of oral and fingernail HPV among mid-adult women. Methods Between 2011–2012, 409 women aged 30–50 years were followed for 6 months. Women completed health and behavior surveys and provided self-collected oral, fingernail, and vaginal specimens at enrollment and exit for type-specific HPV DNA testing. Concordance of type-specific HPV detection across anatomic sites was described with kappa statistics. Using generalized estimating equations or exact logistic regression, we measured the univariate associations of various risk factors with type-specific oral and fingernail HPV detection. Results Prevalence of detecting HPV in the oral cavity (2.4%) and fingernails (3.8%) was low compared to the vagina (33.1%). Concordance across anatomic sites was poor (kappa<.20 for all comparisons). However, concurrent vaginal infection with the same HPV type (OR=101.0;95%CI: 31.4–748.6) and vaginal HPV viral load (OR per one log10 viral load increase=2.2;95%CI:1.5–5.5) were each associated with fingernail HPV detection. Abnormal Pap history (OR=11.1;95%CI:2.8-infinity), lifetime number of male vaginal sex partners ≥10 (OR vs. 0–3 partners=5.0;95%CI:1.2-infinity), and lifetime number of open-mouth kissing partners ≥16 (OR vs. 0–15 partners=infinity;95%CI:2.6-infinity, by exact logistic regression) were each associated with oral HPV detection. Conclusions While our findings support HPV DNA deposition or autoinoculation between anatomic sites in mid-adult women, the rarity of HPV in the oral cavity and fingernails suggests that oral/fingernail HPV does not account for a significant fraction of HPV in genital sites. PMID:26562696

Using the Domenico Solution to Teach Contaminant Transport Modeling

ERIC Educational Resources Information Center

Devlin, J. F.; Brookfield, A.; Huang, B.; Schillig, P. C.

2012-01-01

The Domenico solution is a heuristic simplification of a solution to the transport equation. Although there is a growing consensus that the Domenico solution is undesirable for use in professional and research applications due to departures from exact solutions under certain conditions, it behaves well under conditions suitable for instruction.…

Variability in Second Language Learning: The Roles of Individual Differences, Learning Conditions, and Linguistic Complexity

ERIC Educational Resources Information Center

Tagarelli, Kaitlyn M.; Ruiz, Simón; Vega, José Luis Moreno; Rebuschat, Patrick

2016-01-01

Second language learning outcomes are highly variable, due to a variety of factors, including individual differences, exposure conditions, and linguistic complexity. However, exactly how these factors interact to influence language learning is unknown. This article examines the relationship between these three variables in language learners.…

Exact analytic solution for non-linear density fluctuation in a ΛCDM universe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoo, Jaiyul; Gong, Jinn-Ouk, E-mail: jyoo@physik.uzh.ch, E-mail: jinn-ouk.gong@apctp.org

We derive the exact third-order analytic solution of the matter density fluctuation in the proper-time hypersurface in a ΛCDM universe, accounting for the explicit time-dependence and clarifying the relation to the initial condition. Furthermore, we compare our analytic solution to the previous calculation in the comoving gauge, and to the standard Newtonian perturbation theory by providing Fourier kernels for the relativistic effects. Our results provide an essential ingredient for a complete description of galaxy bias in the relativistic context.

Volumetric formulation for a class of kinetic models with energy conservation.

PubMed

Sbragaglia, M; Sugiyama, K

2010-10-01

We analyze a volumetric formulation of lattice Boltzmann for compressible thermal fluid flows. The velocity set is chosen with the desired accuracy, based on the Gauss-Hermite quadrature procedure, and tested against controlled problems in bounded and unbounded fluids. The method allows the simulation of thermohydrodyamical problems without the need to preserve the exact space-filling nature of the velocity set, but still ensuring the exact conservation laws for density, momentum, and energy. Issues related to boundary condition problems and improvements based on grid refinement are also investigated.

Heun Polynomials and Exact Solutions for the Massless Dirac Particle in the C-Metric

NASA Astrophysics Data System (ADS)

Kar, Priyasri; Singh, Ritesh K.; Dasgupta, Ananda; Panigrahi, Prasanta K.

2018-03-01

The equation of motion of a massless Dirac particle in the C-metric leads to the general Heun equation (GHE) for the radial and the polar variables. The GHE, under certain parametric conditions, is cast in terms of a new set of su(1, 1) generators involving differential operators of degrees ±1/2 and 0. Additional Heun polynomials are obtained using this new algebraic structure and are used to construct some exact solutions for the radial and the polar parts of the Dirac equation.

An asymptotically exact reduced PDE model for the magnetorotational instability: derivation and numerical simulations

NASA Astrophysics Data System (ADS)

Jamroz, Ben; Julien, Keith; Knobloch, Edgar

2008-12-01

Taking advantage of disparate spatio-temporal scales relevant to astrophysics and laboratory experiments, we derive asymptotically exact reduced partial differential equation models for the magnetorotational instability. These models extend recent single-mode formulations leading to saturation in the presence of weak dissipation, and are characterized by a back-reaction on the imposed shear. Numerical simulations performed for a broad class of initial conditions indicate an initial phase of growth dominated by the optimal (fastest growing) magnetorotational instability fingering mode, followed by a vertical coarsening to a box-filling mode.

Maslov indices, Poisson brackets, and singular differential forms

NASA Astrophysics Data System (ADS)

Esterlis, I.; Haggard, H. M.; Hedeman, A.; Littlejohn, R. G.

2014-06-01

Maslov indices are integers that appear in semiclassical wave functions and quantization conditions. They are often notoriously difficult to compute. We present methods of computing the Maslov index that rely only on typically elementary Poisson brackets and simple linear algebra. We also present a singular differential form, whose integral along a curve gives the Maslov index of that curve. The form is closed but not exact, and transforms by an exact differential under canonical transformations. We illustrate the method with the 6j-symbol, which is important in angular-momentum theory and in quantum gravity.

Effects of partial slip boundary condition and radiation on the heat and mass transfer of MHD-nanofluid flow

NASA Astrophysics Data System (ADS)

Abd Elazem, Nader Y.; Ebaid, Abdelhalim

2017-12-01

In this paper, the effect of partial slip boundary condition on the heat and mass transfer of the Cu-water and Ag-water nanofluids over a stretching sheet in the presence of magnetic field and radiation. Such partial slip boundary condition has attracted much attention due to its wide applications in industry and chemical engineering. The flow is basically governing by a system of partial differential equations which are reduced to a system of ordinary differential equations. This system has been exactly solved, where exact analytical expression has been obtained for the fluid velocity in terms of exponential function, while the temperature distribution, and the nanoparticles concentration are expressed in terms of the generalized incomplete gamma function. In addition, explicit formulae are also derived from the rates of heat transfer and mass transfer. The effects of the permanent parameters on the skin friction, heat transfer coefficient, rate of mass transfer, velocity, the temperature profile, and concentration profile have been discussed through tables and graphs.

Ising antiferromagnet on a finite triangular lattice with free boundary conditions

NASA Astrophysics Data System (ADS)

Kim, Seung-Yeon

2015-11-01

The exact integer values for the density of states of the Ising model on an equilateral triangular lattice with free boundary conditions are evaluated up to L = 24 spins on a side for the first time by using the microcanonical transfer matrix. The total number of states is 2 N s = 2300 ≈ 2.037 × 1090 for L = 24, where N s = L( L+1)/2 is the number of spins. Classifying all 2300 spin states according to their energy values is an enormous work. From the density of states, the exact partition function zeros in the complex temperature plane of the triangular-lattice Ising model are evaluated. Using the density of states and the partition function zeros, we investigate the properties of the triangularlattice Ising antiferromagnet. The scaling behavior of the ground-state entropy and the form of the correlation length at T = 0 are studied for the triangular-lattice Ising antiferromagnet with free boundary conditions. Also, the scaling behavior of the Fisher edge singularity is investigated.

Exact sum rules for inhomogeneous drums

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amore, Paolo, E-mail: paolo.amore@gmail.com

2013-09-15

We derive general expressions for the sum rules of the eigenvalues of drums of arbitrary shape and arbitrary density, obeying different boundary conditions. The formulas that we present are a generalization of the analogous formulas for one dimensional inhomogeneous systems that we have obtained in a previous paper. We also discuss the extension of these formulas to higher dimensions. We show that in the special case of a density depending only on one variable the sum rules of any integer order can be expressed in terms of a single series. As an application of our result we derive exact summore » rules for the homogeneous circular annulus with different boundary conditions, for a homogeneous circular sector and for a radially inhomogeneous circular annulus with Dirichlet boundary conditions. -- Highlights: •We derive an explicit expression for the sum rules of inhomogeneous drums. •We discuss the extension to higher dimensions. •We discuss the special case of an inhomogeneity only along one direction.« less

Exact solution for a two-phase Stefan problem with variable latent heat and a convective boundary condition at the fixed face

NASA Astrophysics Data System (ADS)

Bollati, Julieta; Tarzia, Domingo A.

2018-04-01

Recently, in Tarzia (Thermal Sci 21A:1-11, 2017) for the classical two-phase Lamé-Clapeyron-Stefan problem an equivalence between the temperature and convective boundary conditions at the fixed face under a certain restriction was obtained. Motivated by this article we study the two-phase Stefan problem for a semi-infinite material with a latent heat defined as a power function of the position and a convective boundary condition at the fixed face. An exact solution is constructed using Kummer functions in case that an inequality for the convective transfer coefficient is satisfied generalizing recent works for the corresponding one-phase free boundary problem. We also consider the limit to our problem when that coefficient goes to infinity obtaining a new free boundary problem, which has been recently studied in Zhou et al. (J Eng Math 2017. https://doi.org/10.1007/s10665-017-9921-y).

Exact harmonic solutions to Guyer-Krumhansl-type equation and application to heat transport in thin films

NASA Astrophysics Data System (ADS)

Zhukovsky, K.; Oskolkov, D.

2018-03-01

A system of hyperbolic-type inhomogeneous differential equations (DE) is considered for non-Fourier heat transfer in thin films. Exact harmonic solutions to Guyer-Krumhansl-type heat equation and to the system of inhomogeneous DE are obtained in Cauchy- and Dirichlet-type conditions. The contribution of the ballistic-type heat transport, of the Cattaneo heat waves and of the Fourier heat diffusion is discussed and compared with each other in various conditions. The application of the study to the ballistic heat transport in thin films is performed. Rapid evolution of the ballistic quasi-temperature component in low-dimensional systems is elucidated and compared with slow evolution of its diffusive counterpart. The effect of the ballistic quasi-temperature component on the evolution of the complete quasi-temperature is explored. In this context, the influence of the Knudsen number and of Cauchy- and Dirichlet-type conditions on the evolution of the temperature distribution is explored. The comparative analysis of the obtained solutions is performed.

Waveguide effect under 'antiguiding' conditions in graded anisotropic media.

PubMed

Kozlov, A V; Mozhaev, V G; Zyryanova, A V

2010-02-24

A new wave confinement effect is predicted in graded crystals with a concave slowness surface under conditions of growth of the phase velocity with decreasing distance from the waveguide axis. This finding overturns the common notion about the guiding and 'antiguiding' profiles of wave velocity in inhomogeneous media. The waveguide effect found is elucidated by means of ray analysis and particular exact wave solutions. The exact solution obtained for localized flexural waves in thin plates of graded cubic and tetragonal crystals confirms the predicted effect. Since this solution is substantially different with respect to the existence conditions from all others yet reported, and it cannot be deduced from the previously known results, the predicted waves can be classified as a new type of waveguide mode in graded anisotropic media. Although the concrete calculations are given in the article for acoustic waves, its general predictions are expected to be valid for waves of various natures, including spin, plasma, and optical waves.

Could texture features from preoperative CT image be used for predicting occult peritoneal carcinomatosis in patients with advanced gastric cancer?

PubMed

Kim, Hae Young; Kim, Young Hoon; Yun, Gabin; Chang, Won; Lee, Yoon Jin; Kim, Bohyoung

2018-01-01

To retrospectively investigate whether texture features obtained from preoperative CT images of advanced gastric cancer (AGC) patients could be used for the prediction of occult peritoneal carcinomatosis (PC) detected during operation. 51 AGC patients with occult PC detected during operation from January 2009 to December 2012 were included as occult PC group. For the control group, other 51 AGC patients without evidence of distant metastasis including PC, and whose clinical T and N stage could be matched to those of the patients of the occult PC group, were selected from the period of January 2011 to July 2012. Each group was divided into test (n = 41) and validation cohort (n = 10). Demographic and clinical data of these patients were acquired from the hospital database. Texture features including average, standard deviation, kurtosis, skewness, entropy, correlation, and contrast were obtained from manually drawn region of interest (ROI) over the omentum on the axial CT image showing the omentum at its largest cross sectional area. After using Fisher's exact and Wilcoxon signed-rank test for comparison of the clinical and texture features between the two groups of the test cohort, conditional logistic regression analysis was performed to determine significant independent predictor for occult PC. Using the optimal cut-off value from receiver operating characteristic (ROC) analysis for the significant variables, diagnostic sensitivity and specificity were determined in the test cohort. The cut-off value of the significant variables obtained from the test cohort was then applied to the validation cohort. Bonferroni correction was used to adjust P value for multiple comparisons. Between the two groups, there was no significant difference in the clinical features. Regarding the texture features, the occult PC group showed significantly higher average, entropy, standard deviation, and significantly lower correlation (P value < 0.004 for all). Conditional logistic regression analysis demonstrated that entropy was significant independent predictor for occult PC. When the cut-off value of entropy (> 7.141) was applied to the validation cohort, sensitivity and specificity for the prediction of occult PC were 80% and 90%, respectively. For AGC patients whose PC cannot be detected with routine imaging such as CT, texture analysis may be a useful adjunct for the prediction of occult PC.

Identification of EGFLAM, SPATC1L and RNASE13 as novel susceptibility loci for aortic aneurysm in Japanese individuals by exome-wide association studies

PubMed Central

Yamada, Yoshiji; Sakuma, Jun; Takeuchi, Ichiro; Yasukochi, Yoshiki; Kato, Kimihiko; Oguri, Mitsutoshi; Fujimaki, Tetsuo; Horibe, Hideki; Muramatsu, Masaaki; Sawabe, Motoji; Fujiwara, Yoshinori; Taniguchi, Yu; Obuchi, Shuichi; Kawai, Hisashi; Shinkai, Shoji; Mori, Seijiro; Arai, Tomio; Tanaka, Masashi

2017-01-01

We performed an exome-wide association study (EWAS) to identify genetic variants - in particular, low-frequency or rare variants with a moderate to large effect size - that confer susceptibility to aortic aneurysm with 8,782 Japanese subjects (456 patients with aortic aneurysm, 8,326 control individuals) and with the use of Illumina HumanExome-12 DNA Analysis BeadChip or Infinium Exome-24 BeadChip arrays. The correlation of allele frequencies for 41,432 single nucleotide polymorphisms (SNPs) that passed quality control to aortic aneurysm was examined with Fisher's exact test. Based on Bonferroni's correction, a P-value of <1.21×10−6 was considered statistically significant. The EWAS revealed 59 SNPs that were significantly associated with aortic aneurysm. None of these SNPs was significantly (P<2.12×10−4) associated with aortic aneurysm by multivariable logistic regression analysis with adjustment for age, gender and hypertension, although 8 SNPs were related (P<0.05) to this condition. Examination of the correlation of these latter 8 SNPs to true or dissecting aortic aneurysm separately showed that rs1465567 [T/C (W229R)] of the EGF-like, fibronectin type III, and laminin G domains gene (EGFLAM) (dominant model; P=0.0014; odds ratio, 1.63) was significantly (P<0.0016) associated with true aortic aneurysm. We next performed EWASs for true or dissecting aortic aneurysm separately and found that 45 and 19 SNPs were significantly associated with these conditions, respectively. Multivariable logistic regression analysis with adjustment for covariates revealed that rs113710653 [C/T (E231K)] of the spermatogenesis- and centriole associated 1-like gene (SPATC1L) (dominant model; P=0.0002; odds ratio, 5.32) and rs143881017 [C/T (R140H)] of the ribonuclease A family member 13 gene (RNASE13) (dominant model; P=0.0006; odds ratio, 5.77) were significantly (P<2.78×10−4 or P<6.58×10−4, respectively) associated with true or dissecting aortic aneurysm, respectively. EGFLAM and SPATC1L may thus be susceptibility loci for true aortic aneurysm and RNASE13 may be such a locus for dissecting aneurysm in Japanese individuals. PMID:28339009

Development of Performance Assessments in Science: Conceptual, Practical, and Logistical Issues.

ERIC Educational Resources Information Center

Solano-Flores, Guillermo; Shavelson, Richard J.

1997-01-01

Conceptual, practical, and logistical issues in the development of science performance assessments (SPAs) are discussed. The conceptual framework identifies task, response format, and scoring system as components, and conceives of SPAs as tasks that attempt to recreate conditions in which scientists work. Developing SPAs is a sophisticated effort…

Computing exact bundle compliance control charts via probability generating functions.

PubMed

Chen, Binchao; Matis, Timothy; Benneyan, James

2016-06-01

Compliance to evidenced-base practices, individually and in 'bundles', remains an important focus of healthcare quality improvement for many clinical conditions. The exact probability distribution of composite bundle compliance measures used to develop corresponding control charts and other statistical tests is based on a fairly large convolution whose direct calculation can be computationally prohibitive. Various series expansions and other approximation approaches have been proposed, each with computational and accuracy tradeoffs, especially in the tails. This same probability distribution also arises in other important healthcare applications, such as for risk-adjusted outcomes and bed demand prediction, with the same computational difficulties. As an alternative, we use probability generating functions to rapidly obtain exact results and illustrate the improved accuracy and detection over other methods. Numerical testing across a wide range of applications demonstrates the computational efficiency and accuracy of this approach.

Details of Exact Low Prandtl Number Boundary-Layer Solutions for Forced and For Free Convection

NASA Technical Reports Server (NTRS)

Sparrow, E. M.; Gregg, J. L.

1959-01-01

A detailed report is given of exact (numerical) solutions of the laminar-boundary-layer equations for the Prandtl number range appropriate to liquid metals (0.003 to 0.03). Consideration is given to the following situations: (1) forced convection over a flat plate for the conditions of uniform wall temperature and uniform wall heat flux, and (2) free convection over an isothermal vertical plate. Tabulations of the new solutions are given in detail. Results are presented for the heat-transfer and shear-stress characteristics; temperature and velocity distributions are also shown. The heat-transfer results are correlated in terms of dimensionless parameters that vary only slightly over the entire liquid-metal range. Previous analytical and experimental work on low Prandtl number boundary layers is surveyed and compared with the new exact solutions.

40 CFR 147.2925 - Standard permit conditions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... three years. (3) Monitoring records shall include: (i) Date, exact place and time of sampling or... document and all attachments and that, based on my inquiry of those individuals immediately responsible for...

Functional determinants, index theorems, and exact quantum black hole entropy

NASA Astrophysics Data System (ADS)

Murthy, Sameer; Reys, Valentin

2015-12-01

The exact quantum entropy of BPS black holes can be evaluated using localization in supergravity. An important ingredient in this program, that has been lacking so far, is the one-loop effect arising from the quadratic fluctuations of the exact deformation (the QV operator). We compute the fluctuation determinant for vector multiplets and hyper multiplets around Q-invariant off-shell configurations in four-dimensional N=2 supergravity with AdS 2 × S 2 boundary conditions, using the Atiyah-Bott fixed-point index theorem and a subsequent zeta function regularization. Our results extend the large-charge on-shell entropy computations in the literature to a regime of finite charges. Based on our results, we present an exact formula for the quantum entropy of BPS black holes in N=2 supergravity. We explain cancellations concerning 1/8 -BPS black holes in N=8 supergravity that were observed in arXiv:1111.1161. We also make comments about the interpretation of a logarithmic term in the topological string partition function in the low energy supergravity theory.

Extension of many-body theory and approximate density functionals to fractional charges and fractional spins.

PubMed

Yang, Weitao; Mori-Sánchez, Paula; Cohen, Aron J

2013-09-14

The exact conditions for density functionals and density matrix functionals in terms of fractional charges and fractional spins are known, and their violation in commonly used functionals has been shown to be the root of many major failures in practical applications. However, approximate functionals are designed for physical systems with integer charges and spins, not in terms of the fractional variables. Here we develop a general framework for extending approximate density functionals and many-electron theory to fractional-charge and fractional-spin systems. Our development allows for the fractional extension of any approximate theory that is a functional of G(0), the one-electron Green's function of the non-interacting reference system. The extension to fractional charge and fractional spin systems is based on the ensemble average of the basic variable, G(0). We demonstrate the fractional extension for the following theories: (1) any explicit functional of the one-electron density, such as the local density approximation and generalized gradient approximations; (2) any explicit functional of the one-electron density matrix of the non-interacting reference system, such as the exact exchange functional (or Hartree-Fock theory) and hybrid functionals; (3) many-body perturbation theory; and (4) random-phase approximations. A general rule for such an extension has also been derived through scaling the orbitals and should be useful for functionals where the link to the Green's function is not obvious. The development thus enables the examination of approximate theories against known exact conditions on the fractional variables and the analysis of their failures in chemical and physical applications in terms of violations of exact conditions of the energy functionals. The present work should facilitate the calculation of chemical potentials and fundamental bandgaps with approximate functionals and many-electron theories through the energy derivatives with respect to the fractional charge. It should play an important role in developing accurate approximate density functionals and many-body theory.

Comment on "exact solutions of the derivative nonlinear Schrödinger equation for a nonlinear transmission line".

PubMed

Nickel, J; Schürmann, H W

2007-03-01

In a recent article Kengne and Liu [Phys. Rev. E 73, 026603 (2006)] have presented a number of exact elliptic solutions for a derivative nonlinear Schrödinger equation. It is the aim of this Comment to point out that all these solutions given in Secs. II and III of this article (referred to as KL in the following) are subcases of the general solution of Eq. (KL.9). Conditions for the parameters A-E of the solutions given by Kengne and Liu can be found from general conditions for solitary and periodic elliptic solutions as shown in the following. Positive and bounded solutions can be found by considering the phase diagram. Therefore, the comment of Kengne and Liu that "we find its particular positive bounded solutions" can be specified.

The Exact Solution for Linear Thermoelastic Axisymmetric Deformations of Generally Laminated Circular Cylindrical Shells

NASA Technical Reports Server (NTRS)

Nemeth, Michael P.; Schultz, Marc R.

2012-01-01

A detailed exact solution is presented for laminated-composite circular cylinders with general wall construction and that undergo axisymmetric deformations. The overall solution is formulated in a general, systematic way and is based on the solution of a single fourth-order, nonhomogeneous ordinary differential equation with constant coefficients in which the radial displacement is the dependent variable. Moreover, the effects of general anisotropy are included and positive-definiteness of the strain energy is used to define uniquely the form of the basis functions spanning the solution space of the ordinary differential equation. Loading conditions are considered that include axisymmetric edge loads, surface tractions, and temperature fields. Likewise, all possible axisymmetric boundary conditions are considered. Results are presented for five examples that demonstrate a wide range of behavior for specially orthotropic and fully anisotropic cylinders.

On the multiple depots vehicle routing problem with heterogeneous fleet capacity and velocity

NASA Astrophysics Data System (ADS)

Hanum, F.; Hartono, A. P.; Bakhtiar, T.

2018-03-01

This current manuscript concerns with the optimization problem arising in a route determination of products distribution. The problem is formulated in the form of multiple depots and time windowed vehicle routing problem with heterogeneous capacity and velocity of fleet. Model includes a number of constraints such as route continuity, multiple depots availability and serving time in addition to generic constraints. In dealing with the unique feature of heterogeneous velocity, we generate a number of velocity profiles along the road segments, which then converted into traveling-time tables. An illustrative example of rice distribution among villages by bureau of logistics is provided. Exact approach is utilized to determine the optimal solution in term of vehicle routes and starting time of service.

Exact solutions for unsteady free convection flow over an oscillating plate due to non-coaxial rotation.

PubMed

Mohamad, Ahmad Qushairi; Khan, Ilyas; Ismail, Zulkhibri; Shafie, Sharidan

2016-01-01

Non-coaxial rotation has wide applications in engineering devices, e.g. in food processing such as mixer machines and stirrers with a two-axis kneader, in cooling turbine blades, jet engines, pumps and vacuum cleaners, in designing thermal syphon tubes, and in geophysical flows. Therefore, this study aims to investigate unsteady free convection flow of viscous fluid due to non-coaxial rotation and fluid at infinity over an oscillating vertical plate with constant wall temperature. The governing equations are modelled by a sudden coincidence of the axes of a disk and the fluid at infinity rotating with uniform angular velocity, together with initial and boundary conditions. Some suitable non-dimensional variables are introduced. The Laplace transform method is used to obtain the exact solutions of the corresponding non-dimensional momentum and energy equations with conditions. Solutions of the velocity for cosine and sine oscillations as well as for temperature fields are obtained and displayed graphically for different values of time ( t ), the Grashof number ( Gr ), the Prandtl number ([Formula: see text]), and the phase angle ([Formula: see text]). Skin friction and the Nusselt number are also evaluated. The exact solutions are obtained and in limiting cases, the present solutions are found to be identical to the published results. Further, the obtained exact solutions also validated by comparing with results obtained by using Gaver-Stehfest algorithm. The interested physical property such as velocity, temperature, skin friction and Nusselt number are affected by the embedded parameters time ( t ), the Grashof number ( Gr ), the Prandtl number ([Formula: see text]), and the phase angle ([Formula: see text]).

Thermal density functional theory, ensemble density functional theory, and potential functional theory for warm dense matter

NASA Astrophysics Data System (ADS)

Pribram-Jones, Aurora

Warm dense matter (WDM) is a high energy phase between solids and plasmas, with characteristics of both. It is present in the centers of giant planets, within the earth's core, and on the path to ignition of inertial confinement fusion. The high temperatures and pressures of warm dense matter lead to complications in its simulation, as both classical and quantum effects must be included. One of the most successful simulation methods is density functional theory-molecular dynamics (DFT-MD). Despite great success in a diverse array of applications, DFT-MD remains computationally expensive and it neglects the explicit temperature dependence of electron-electron interactions known to exist within exact DFT. Finite-temperature density functional theory (FT DFT) is an extension of the wildly successful ground-state DFT formalism via thermal ensembles, broadening its quantum mechanical treatment of electrons to include systems at non-zero temperatures. Exact mathematical conditions have been used to predict the behavior of approximations in limiting conditions and to connect FT DFT to the ground-state theory. An introduction to FT DFT is given within the context of ensemble DFT and the larger field of DFT is discussed for context. Ensemble DFT is used to describe ensembles of ground-state and excited systems. Exact conditions in ensemble DFT and the performance of approximations depend on ensemble weights. Using an inversion method, exact Kohn-Sham ensemble potentials are found and compared to approximations. The symmetry eigenstate Hartree-exchange approximation is in good agreement with exact calculations because of its inclusion of an ensemble derivative discontinuity. Since ensemble weights in FT DFT are temperature-dependent Fermi weights, this insight may help develop approximations well-suited to both ground-state and FT DFT. A novel, highly efficient approach to free energy calculations, finite-temperature potential functional theory, is derived, which has the potential to transform the simulation of warm dense matter. As a semiclassical method, it connects the normally disparate regimes of cold condensed matter physics and hot plasma physics. This orbital-free approach captures the smooth classical density envelope and quantum density oscillations that are both crucial to accurate modeling of materials where temperature and pressure effects are influential.

Is autoimmune thyroid dysfunction a risk factor for gestational diabetes?

PubMed

Pascual Corrales, Eider; Andrada, Patricia; Aubá, María; Ruiz Zambrana, Alvaro; Guillén Grima, Francisco; Salvador, Javier; Escalada, Javier; Galofré, Juan C

2014-01-01

Some recent studies have related autoimmune thyroid dysfunction and gestational diabetes (GD). The common factor for both conditions could be the existence of pro-inflammatory homeostasis. The study objective was therefore to assess whether the presence of antithyroid antibodies is related to the occurrence of GD. Fifty-six pregnant women with serum TSH levels ≥ 2.5 mU/mL during the first trimester were retrospectively studied. Antithyroid antibodies were measured, and an O'Sullivan test was performed. GD was diagnosed based on the criteria of the Spanish Group on Diabetes and Pregnancy. Positive antithyroid antibodies were found in 21 (37.50%) women. GD was diagnosed in 15 patients, 6 of whom (10.71%) had positive antibodies, while 9 (16.07%) had negative antibodies. Data were analyzed using exact logistic regression by LogXact-8 Cytel; no statistically significant differences were found between GD patients with positive and negative autoimmunity (OR = 1.15 [95%CI = 0.28-4.51]; P=1.00). The presence of thyroid autoimmunity in women with TSH above the recommended values at the beginning of pregnancy is not associated to development of GD. However, GD prevalence was higher in these patients as compared to the Spanish general population, suggesting the need for closer monitoring in pregnant women with TSH levels ≥ 2.5 mU/mL. Copyright © 2013 SEEN. Published by Elsevier Espana. All rights reserved.

Comparison of Two Approaches for Handling Missing Covariates in Logistic Regression

ERIC Educational Resources Information Center

Peng, Chao-Ying Joanne; Zhu, Jin

2008-01-01

For the past 25 years, methodological advances have been made in missing data treatment. Most published work has focused on missing data in dependent variables under various conditions. The present study seeks to fill the void by comparing two approaches for handling missing data in categorical covariates in logistic regression: the…

Comparison of IRT Likelihood Ratio Test and Logistic Regression DIF Detection Procedures

ERIC Educational Resources Information Center

Atar, Burcu; Kamata, Akihito

2011-01-01

The Type I error rates and the power of IRT likelihood ratio test and cumulative logit ordinal logistic regression procedures in detecting differential item functioning (DIF) for polytomously scored items were investigated in this Monte Carlo simulation study. For this purpose, 54 simulation conditions (combinations of 3 sample sizes, 2 sample…

Classifying machinery condition using oil samples and binary logistic regression

NASA Astrophysics Data System (ADS)

Phillips, J.; Cripps, E.; Lau, John W.; Hodkiewicz, M. R.

2015-08-01

The era of big data has resulted in an explosion of condition monitoring information. The result is an increasing motivation to automate the costly and time consuming human elements involved in the classification of machine health. When working with industry it is important to build an understanding and hence some trust in the classification scheme for those who use the analysis to initiate maintenance tasks. Typically "black box" approaches such as artificial neural networks (ANN) and support vector machines (SVM) can be difficult to provide ease of interpretability. In contrast, this paper argues that logistic regression offers easy interpretability to industry experts, providing insight to the drivers of the human classification process and to the ramifications of potential misclassification. Of course, accuracy is of foremost importance in any automated classification scheme, so we also provide a comparative study based on predictive performance of logistic regression, ANN and SVM. A real world oil analysis data set from engines on mining trucks is presented and using cross-validation we demonstrate that logistic regression out-performs the ANN and SVM approaches in terms of prediction for healthy/not healthy engines.

Research design and statistical methods in Pakistan Journal of Medical Sciences (PJMS).

PubMed

Akhtar, Sohail; Shah, Syed Wadood Ali; Rafiq, M; Khan, Ajmal

2016-01-01

This article compares the study design and statistical methods used in 2005, 2010 and 2015 of Pakistan Journal of Medical Sciences (PJMS). Only original articles of PJMS were considered for the analysis. The articles were carefully reviewed for statistical methods and designs, and then recorded accordingly. The frequency of each statistical method and research design was estimated and compared with previous years. A total of 429 articles were evaluated (n=74 in 2005, n=179 in 2010, n=176 in 2015) in which 171 (40%) were cross-sectional and 116 (27%) were prospective study designs. A verity of statistical methods were found in the analysis. The most frequent methods include: descriptive statistics (n=315, 73.4%), chi-square/Fisher's exact tests (n=205, 47.8%) and student t-test (n=186, 43.4%). There was a significant increase in the use of statistical methods over time period: t-test, chi-square/Fisher's exact test, logistic regression, epidemiological statistics, and non-parametric tests. This study shows that a diverse variety of statistical methods have been used in the research articles of PJMS and frequency improved from 2005 to 2015. However, descriptive statistics was the most frequent method of statistical analysis in the published articles while cross-sectional study design was common study design.

Evaluating guideline adherence regarding empirical vancomycin use in patients with neutropenic fever.

PubMed

Chastain, Daniel B; Wheeler, Sarah; Franco-Paredes, Carlos; Olubajo, Babatunde; Hawkins, W Anthony

2018-04-01

The purpose of this study was to evaluate the use of empirical vancomycin for patients with neutropenic fever (NF) with regard to adherence to treatment guidelines. Adult patients with a diagnosis of neutropenia, who met the definition of NF as per treatment guidelines, were identified. Use of vancomycin was evaluated as part of empirical therapy and again after 72h. Outcomes were assessed using descriptive statistics, the Chi-square or Fisher's exact test, and univariate exact logistic regression analyses. Sixty-four patients were included. Overall, inappropriate empirical vancomycin use was observed in more than 30% of patients. Of 35 patients with indications for empirical vancomycin, only 68% received it. At 72h, appropriate vancomycin continuation, de-escalation, or discontinuation occurred in 21 of 33 patients. On univariate regression, hematological malignancy was associated with appropriate empirical vancomycin prescribing, whether initiating or withholding (odds ratio 4.0, 95% confidence interval 1.31-12.1). No variable was independently associated with inappropriate continuation at 72h. There is poor guideline adherence to vancomycin prescribing as empirical therapy and at 72-h reassessment in patients with NF. Further efforts are needed to foster a more rational use of vancomycin in patients with NF. Copyright © 2018. Published by Elsevier Ltd.

21 CFR 522.1020 - Gelatin.

Code of Federal Regulations, 2014 CFR

2014-04-01

...) Specifications. Each 100 milliliters contains 8 grams of gelatin in a 0.85 percent sodium chloride solution. (b) Sponsor. See No. 054771 in § 510.600(c) of this chapter. (c) Conditions of use—(1) Amount. The exact...

On High-Order Radiation Boundary Conditions

NASA Technical Reports Server (NTRS)

Hagstrom, Thomas

1995-01-01

In this paper we develop the theory of high-order radiation boundary conditions for wave propagation problems. In particular, we study the convergence of sequences of time-local approximate conditions to the exact boundary condition, and subsequently estimate the error in the solutions obtained using these approximations. We show that for finite times the Pade approximants proposed by Engquist and Majda lead to exponential convergence if the solution is smooth, but that good long-time error estimates cannot hold for spatially local conditions. Applications in fluid dynamics are also discussed.

Clinical and clinicopathologic abnormalities in young dogs with acquired and congenital portosystemic shunts: 93 cases (2003-2008).

PubMed

Adam, Fiona H; German, Alexander J; McConnell, J Fraser; Trehy, Mary R; Whitley, Nat; Collings, Alison; Watson, Penny J; Burrow, Rachel D

2012-09-15

To determine whether clinical and clinicopathologic data could assist differentiation of congenital portosystemic shunts (CPSSs) from acquired portosystemic shunts (APSSs) in young dogs. Retrospective case series. Dogs < 30 months of age with CPSSs (n = 62) or APSSs (31). Medical records from 3 referral centers identified 31 dogs with APSSs and 62 dogs with CPSSs diagnosed from July 2003 to July 2008. Signalment, clinical signs, physical examination, and clinicopathological data were recorded, and statistical analyses were performed to determine differences between groups. Univariable analysis showed APSS patients were older, heavier, and in poorer body condition, compared with CPSS patients. In CPSS patients, diarrhea was less prevalent, and neurologic signs were more prevalent. Ascites was more prevalent in APSS (Fisher exact test; OR, 50.2; 95% confidence interval [CI], 6.2 to 409.7), with no significant difference in albumin concentration between groups. The logistic regression model used to assess clinicopathological parameters showed lower Hct (OR, 1.42 × 10(-12); 95% CI, 1.42 × 10(-17) to 4.0 × 10(-6)), higher mean corpuscular volume (OR, 1.27; 95% CI, 1.08 to 1.50), and higher alanine aminotransferase concentrations (OR, 1.005; 95% CI, 1.001 to 1.009) were more likely in APSS patients. Several clinicopathologic differences between dogs with congenital and acquired shunts were identified; however, assessed alone, these would be unlikely to enable differentiation between the 2 conditions. Awareness of the rarity of ascites in CPSS cases should prompt recognition of a likely diagnosis of APSS, allowing the veterinarian to target further diagnostics and counsel the owner appropriately.

Patient Characteristics and Outcomes After Hemorrhagic Stroke in Pregnancy.

PubMed

Leffert, Lisa R; Clancy, Caitlin R; Bateman, Brian T; Cox, Margueritte; Schulte, Phillip J; Smith, Eric E; Fonarow, Gregg C; Schwamm, Lee H; Kuklina, Elena V; George, Mary G

2015-10-01

Hospitalizations for pregnancy-related stroke are rare but increasing. Hemorrhagic stroke (HS), ie, subarachnoid hemorrhage and intracerebral hemorrhage, is more common than ischemic stroke in pregnant versus nonpregnant women, reflecting different phenotypes or risk factors. We compared stroke risk factors and outcomes in pregnant versus nonpregnant HS in the Get With The Guidelines-Stroke Registry. Using medical history or International Classification of Diseases-Ninth Revision codes, we identified 330 pregnant and 10 562 nonpregnant female patients aged 18 to 44 years with HS in Get With The Guidelines-Stroke (2008-2014). Differences in patient and care characteristics were compared by χ(2) or Fisher exact test (categorical variables) or Wilcoxon rank-sum (continuous variables) tests. Conditional logistic regression assessed the association of pregnancy with outcomes conditional on categorical age and further adjusted for patient and hospital characteristics. Pregnant versus nonpregnant HS patients were younger with fewer pre-existing stroke risk factors and medications. Pregnant versus nonpregnant subarachnoid hemorrhage patients were less impaired at arrival, and less than half met blood pressure criteria for severe preeclampsia. In-hospital mortality was lower in pregnant versus nonpregnant HS patients: adjusted odds ratios (95% CI) for subarachnoid hemorrhage 0.17 (0.06-0.45) and intracerebral hemorrhage 0.57 (0.34-0.94). Pregnant subarachnoid hemorrhage patients also had a higher likelihood of home discharge (2.60 [1.67-4.06]) and independent ambulation at discharge (2.40 [1.56-3.70]). Pregnant HS patients are younger and have fewer risk factors than their nonpregnant counterparts, and risk-adjusted in-hospital mortality is lower. Our findings suggest possible differences in underlying disease pathophysiology and challenges to identifying at-risk patients. © 2015 American Heart Association, Inc.

Conservative corrections to the innermost stable circular orbit (ISCO) of a Kerr black hole: A new gauge-invariant post-Newtonian ISCO condition, and the ISCO shift due to test-particle spin and the gravitational self-force

DOE Office of Scientific and Technical Information (OSTI.GOV)

Favata, Marc

2011-01-15

The innermost stable circular orbit (ISCO) delimits the transition from circular orbits to those that plunge into a black hole. In the test-mass limit, well-defined ISCO conditions exist for the Kerr and Schwarzschild spacetimes. In the finite-mass case, there are a large variety of ways to define an ISCO in a post-Newtonian (PN) context. Here I generalize the gauge-invariant ISCO condition of Blanchet and Iyer [Classical Quantum Gravity 20, 755 (2003)] to the case of spinning (nonprecessing) binaries. The Blanchet-Iyer ISCO condition has two desirable and unexpected properties: (1) it exactly reproduces the Schwarzschild ISCO in the test-mass limit, andmore » (2) it accurately approximates the recently calculated shift in the Schwarzschild ISCO frequency due to the conservative-piece of the gravitational self-force [L. Barack and N. Sago, Phys. Rev. Lett. 102, 191101 (2009)]. The generalization of this ISCO condition to spinning binaries has the property that it also exactly reproduces the Kerr ISCO in the test-mass limit (up to the order at which PN spin corrections are currently known). The shift in the ISCO due to the spin of the test-particle is also calculated. Remarkably, the gauge-invariant PN ISCO condition exactly reproduces the ISCO shift predicted by the Papapetrou equations for a fully relativistic spinning particle. It is surprising that an analysis of the stability of the standard PN equations of motion is able (without any form of 'resummation') to accurately describe strong-field effects of the Kerr spacetime. The ISCO frequency shift due to the conservative self-force in Kerr is also calculated from this new ISCO condition, as well as from the effective-one-body Hamiltonian of Barausse and Buonanno [Phys. Rev. D 81, 084024 (2010)]. These results serve as a useful point of comparison for future gravitational self-force calculations in the Kerr spacetime.« less

Exact short-time height distribution for the flat Kardar-Parisi-Zhang interface

NASA Astrophysics Data System (ADS)

Smith, Naftali R.; Meerson, Baruch

2018-05-01

We determine the exact short-time distribution -lnPf(" close=")H ,t )">H ,t =Sf(H )/√{t } of the one-point height H =h (x =0 ,t ) of an evolving 1 +1 Kardar-Parisi-Zhang (KPZ) interface for flat initial condition. This is achieved by combining (i) the optimal fluctuation method, (ii) a time-reversal symmetry of the KPZ equation in 1 +1 dimension, and (iii) the recently determined exact short-time height distribution -lnPst(H ) of the latter, one encounters two branches: an analytic and a nonanalytic. The analytic branch is nonphysical beyond a critical value of H where a second-order dynamical phase transition occurs. Here we show that, remarkably, it is the analytic branch of Sst(H ) which determines the large-deviation function Sf(H ) of the flat interface via a simple mapping Sf(H )=2-3 /2SstThe exact solutions and approximate analytic solutions of the (2 + 1)-dimensional KP equation based on symmetry method.

PubMed

Gai, Litao; Bilige, Sudao; Jie, Yingmo

2016-01-01

In this paper, we successfully obtained the exact solutions and the approximate analytic solutions of the (2 + 1)-dimensional KP equation based on the Lie symmetry, the extended tanh method and the homotopy perturbation method. In first part, we obtained the symmetries of the (2 + 1)-dimensional KP equation based on the Wu-differential characteristic set algorithm and reduced it. In the second part, we constructed the abundant exact travelling wave solutions by using the extended tanh method. These solutions are expressed by the hyperbolic functions, the trigonometric functions and the rational functions respectively. It should be noted that when the parameters are taken as special values, some solitary wave solutions are derived from the hyperbolic function solutions. Finally, we apply the homotopy perturbation method to obtain the approximate analytic solutions based on four kinds of initial conditions.

Quantum recurrence and fractional dynamic localization in ac-driven perfect state transfer Hamiltonians

DOE Office of Scientific and Technical Information (OSTI.GOV)

Longhi, Stefano, E-mail: stefano.longhi@fisi.polimi.it

Quantum recurrence and dynamic localization are investigated in a class of ac-driven tight-binding Hamiltonians, the Krawtchouk quantum chain, which in the undriven case provides a paradigmatic Hamiltonian model that realizes perfect quantum state transfer and mirror inversion. The equivalence between the ac-driven single-particle Krawtchouk Hamiltonian H{sup -hat} (t) and the non-interacting ac-driven bosonic junction Hamiltonian enables to determine in a closed form the quasi energy spectrum of H{sup -hat} (t) and the conditions for exact wave packet reconstruction (dynamic localization). In particular, we show that quantum recurrence, which is predicted by the general quantum recurrence theorem, is exact for themore » Krawtchouk quantum chain in a dense range of the driving amplitude. Exact quantum recurrence provides perfect wave packet reconstruction at a frequency which is fractional than the driving frequency, a phenomenon that can be referred to as fractional dynamic localization.« less

Some exact velocity profiles for granular flow in converging hoppers

NASA Astrophysics Data System (ADS)

Cox, Grant M.; Hill, James M.

2005-01-01

Gravity flow of granular materials through hoppers occurs in many industrial processes. For an ideal cohesionless granular material, which satisfies the Coulomb-Mohr yield condition, the number of known analytical solutions is limited. However, for the special case of the angle of internal friction δ equal to ninety degrees, there exist exact parametric solutions for the governing coupled ordinary differential equations for both two-dimensional wedges and three-dimensional cones, both of which involve two arbitrary constants of integration. These solutions are the only known analytical solutions of this generality. Here, we utilize the double-shearing theory of granular materials to determine the velocity field corresponding to these exact parametric solutions for the two problems of gravity flow through converging wedge and conical hoppers. An independent numerical solution for other angles of internal friction is shown to coincide with the analytical solution.

Exact time-dependent nonlinear dispersive wave solutions in compressible magnetized plasmas exhibiting collapse.

PubMed

Chakrabarti, Nikhil; Maity, Chandan; Schamel, Hans

2011-04-08

Compressional waves in a magnetized plasma of arbitrary resistivity are treated with the lagrangian fluid approach. An exact nonlinear solution with a nontrivial space and time dependence is obtained with boundary conditions as in Harris' current sheet. The solution shows competition among hydrodynamic convection, magnetic field diffusion, and dispersion. This results in a collapse of density and the magnetic field in the absence of dispersion. The dispersion effects arrest the collapse of density but not of the magnetic field. A possible application is in the early stage of magnetic star formation.

Zone clearance in an infinite TASEP with a step initial condition

NASA Astrophysics Data System (ADS)

Cividini, Julien; Appert-Rolland, Cécile

2017-06-01

The TASEP is a paradigmatic model of out-of-equilibrium statistical physics, for which many quantities have been computed, either exactly or by approximate methods. In this work we study two new kinds of observables that have some relevance in biological or traffic models. They represent the probability for a given clearance zone of the lattice to be empty (for the first time) at a given time, starting from a step density profile. Exact expressions are obtained for single-time quantities, while more involved history-dependent observables are studied by Monte Carlo simulation, and partially predicted by a phenomenological approach.

Exact solution for the layered convection of a viscous incompressible fluid at specified temperature gradients and tangential forces on the free boundary

NASA Astrophysics Data System (ADS)

Burmasheva, N. V.; Prosviryakov, E. Yu.

2017-12-01

A new exact analytical solution of a system of thermal convection equations in the Boussinesq approximation describing layered flows in an incompressible viscous fluid is obtained. A fluid flow in an infinite layer is considered. Convection in the fluid is induced by tangential stresses specified on the upper non-deformable boundary. At the fixed lower boundary, the no-slip condition is satisfied. Temperature corrections are given on the both boundaries of the fluid layer. The possibility of physical field stratification is investigated.

Numerical Solution of the Electron Transport Equation in the Upper Atmosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Woods, Mark Christopher; Holmes, Mark; Sailor, William C

A new approach for solving the electron transport equation in the upper atmosphere is derived. The problem is a very stiff boundary value problem, and to obtain an accurate numerical solution, matrix factorizations are used to decouple the fast and slow modes. A stable finite difference method is applied to each mode. This solver is applied to a simplifieed problem for which an exact solution exists using various versions of the boundary conditions that might arise in a natural auroral display. The numerical and exact solutions are found to agree with each other to at least two significant digits.

The exact fundamental solution for the Benes tracking problem

NASA Astrophysics Data System (ADS)

Balaji, Bhashyam

2009-05-01

The universal continuous-discrete tracking problem requires the solution of a Fokker-Planck-Kolmogorov forward equation (FPKfe) for an arbitrary initial condition. Using results from quantum mechanics, the exact fundamental solution for the FPKfe is derived for the state model of arbitrary dimension with Benes drift that requires only the computation of elementary transcendental functions and standard linear algebra techniques- no ordinary or partial differential equations need to be solved. The measurement process may be an arbitrary, discrete-time nonlinear stochastic process, and the time step size can be arbitrary. Numerical examples are included, demonstrating its utility in practical implementation.

Exact coupling threshold for structural transition reveals diversified behaviors in interconnected networks.

PubMed

Darabi Sahneh, Faryad; Scoglio, Caterina; Van Mieghem, Piet

2015-10-01

An interconnected network features a structural transition between two regimes [F. Radicchi and A. Arenas, Nat. Phys. 9, 717 (2013)]: one where the network components are structurally distinguishable and one where the interconnected network functions as a whole. Our exact solution for the coupling threshold uncovers network topologies with unexpected behaviors. Specifically, we show conditions that superdiffusion, introduced by Gómez et al. [Phys. Rev. Lett. 110, 028701 (2013)], can occur despite the network components functioning distinctly. Moreover, we find that components of certain interconnected network topologies are indistinguishable despite very weak coupling between them.

Comment on "Exact solution of resonant modes in a rectangular resonator".

PubMed

Gutiérrez-Vega, Julio C; Bandres, Miguel A

2006-08-15

We comment on the recent Letter by J. Wu and A. Liu [Opt. Lett. 31, 1720 (2006)] in which an exact scalar solution to the resonant modes and the resonant frequencies in a two-dimensional rectangular microcavity were presented. The analysis is incorrect because (a) the field solutions were imposed to satisfy simultaneously both Dirichlet and Neumann boundary conditions at the four sides of the rectangle, leading to an overdetermined problem, and (b) the modes in the cavity were expanded using an incorrect series ansatz, leading to an expression for the mode fields that does not satisfy the Helmholtz equation.

Regression approaches in the test-negative study design for assessment of influenza vaccine effectiveness.

PubMed

Bond, H S; Sullivan, S G; Cowling, B J

2016-06-01

Influenza vaccination is the most practical means available for preventing influenza virus infection and is widely used in many countries. Because vaccine components and circulating strains frequently change, it is important to continually monitor vaccine effectiveness (VE). The test-negative design is frequently used to estimate VE. In this design, patients meeting the same clinical case definition are recruited and tested for influenza; those who test positive are the cases and those who test negative form the comparison group. When determining VE in these studies, the typical approach has been to use logistic regression, adjusting for potential confounders. Because vaccine coverage and influenza incidence change throughout the season, time is included among these confounders. While most studies use unconditional logistic regression, adjusting for time, an alternative approach is to use conditional logistic regression, matching on time. Here, we used simulation data to examine the potential for both regression approaches to permit accurate and robust estimates of VE. In situations where vaccine coverage changed during the influenza season, the conditional model and unconditional models adjusting for categorical week and using a spline function for week provided more accurate estimates. We illustrated the two approaches on data from a test-negative study of influenza VE against hospitalization in children in Hong Kong which resulted in the conditional logistic regression model providing the best fit to the data.

An exact solution on unsteady MHD free convection chemically reacting silver nanofluid flow past an exponentially accelerated vertical plate through porous medium

NASA Astrophysics Data System (ADS)

Kumaresan, E.; Vijaya Kumar, A. G.; Rushi Kumar, B.

2017-11-01

This article studies, an exact solution of unsteady MHD free convection boundary-layer flow of a silver nanofluid past an exponentially accelerated moving vertical plate through aporous medium in the presence of thermal radiation, transverse applied amagnetic field, radiation absorption and Heat generation or absorption with chemical reaction are investigated theoretically. We consider nanofluids contain spherical shaped nanoparticle of silverwith a nanoparticle volume concentration range smaller than or equal to 0.04. This phenomenon is modeled in the form of partial differential equations with initial boundary conditions. Some suitable dimensional variables are introduced. The corresponding dimensionless equations with boundary conditions are solved by using Laplace transform technique. The exact solutions for velocity, energy, and species are obtained, also the corresponding numerical values of nanofluid velocity, temperature and concentration profiles are represented graphically. The expressions for skin friction coefficient, the rate of heat transfer and mass transfer are derived. The present study finds applications involving heat transfer, enhancement of thermal conductivity and other applications like transportation, industrial cooling applications, heating buildings and reducing pollution, energy applications and solar absorption. The effect of heat transfer is found to be more pronounced in a silver-water nanofluid than in the other nanofluids.

Exact semi-separation of variables in waveguides with non-planar boundaries

NASA Astrophysics Data System (ADS)

Athanassoulis, G. A.; Papoutsellis, Ch. E.

2017-05-01

Series expansions of unknown fields Φ =∑φn Zn in elongated waveguides are commonly used in acoustics, optics, geophysics, water waves and other applications, in the context of coupled-mode theories (CMTs). The transverse functions Zn are determined by solving local Sturm-Liouville problems (reference waveguides). In most cases, the boundary conditions assigned to Zn cannot be compatible with the physical boundary conditions of Φ, leading to slowly convergent series, and rendering CMTs mild-slope approximations. In the present paper, the heuristic approach introduced in Athanassoulis & Belibassakis (Athanassoulis & Belibassakis 1999 J. Fluid Mech. 389, 275-301) is generalized and justified. It is proved that an appropriately enhanced series expansion becomes an exact, rapidly convergent representation of the field Φ, valid for any smooth, non-planar boundaries and any smooth enough Φ. This series expansion can be differentiated termwise everywhere in the domain, including the boundaries, implementing an exact semi-separation of variables for non-separable domains. The efficiency of the method is illustrated by solving a boundary value problem for the Laplace equation, and computing the corresponding Dirichlet-to-Neumann operator, involved in Hamiltonian equations for nonlinear water waves. The present method provides accurate results with only a few modes for quite general domains. Extensions to general waveguides are also discussed.

RT DDA: A hybrid method for predicting the scattering properties by densely packed media

NASA Astrophysics Data System (ADS)

Ramezan Pour, B.; Mackowski, D.

2017-12-01

The most accurate approaches to predicting the scattering properties of particulate media are based on exact solutions of the Maxwell's equations (MEs), such as the T-matrix and discrete dipole methods. Applying these techniques for optically thick targets is challenging problem due to the large-scale computations and are usually substituted by phenomenological radiative transfer (RT) methods. On the other hand, the RT technique is of questionable validity in media with large particle packing densities. In recent works, we used numerically exact ME solvers to examine the effects of particle concentration on the polarized reflection properties of plane parallel random media. The simulations were performed for plane parallel layers of wavelength-sized spherical particles, and results were compared with RT predictions. We have shown that RTE results monotonically converge to the exact solution as the particle volume fraction becomes smaller and one can observe a nearly perfect fit for packing densities of 2%-5%. This study describes the hybrid technique composed of exact and numerical scalar RT methods. The exact methodology in this work is the plane parallel discrete dipole approximation whereas the numerical method is based on the adding and doubling method. This approach not only decreases the computational time owing to the RT method but also includes the interference and multiple scattering effects, so it may be applicable to large particle density conditions.

Testing Gene-Gene Interactions in the Case-Parents Design

PubMed Central

Yu, Zhaoxia

2011-01-01

The case-parents design has been widely used to detect genetic associations as it can prevent spurious association that could occur in population-based designs. When examining the effect of an individual genetic locus on a disease, logistic regressions developed by conditioning on parental genotypes provide complete protection from spurious association caused by population stratification. However, when testing gene-gene interactions, it is unknown whether conditional logistic regressions are still robust. Here we evaluate the robustness and efficiency of several gene-gene interaction tests that are derived from conditional logistic regressions. We found that in the presence of SNP genotype correlation due to population stratification or linkage disequilibrium, tests with incorrectly specified main-genetic-effect models can lead to inflated type I error rates. We also found that a test with fully flexible main genetic effects always maintains correct test size and its robustness can be achieved with negligible sacrifice of its power. When testing gene-gene interactions is the focus, the test allowing fully flexible main effects is recommended to be used. PMID:21778736

Chilblains

MedlinePlus

... to rule out other conditions. If you have diabetes or poor circulation, healing may be impaired. Be cautious and seek care. Causes No one knows exactly what causes chilblains. They may be an abnormal reaction of your body to cold exposure followed by ...

Conditions where random phase approximation becomes exact in the high-density limit

NASA Astrophysics Data System (ADS)

Morawetz, Klaus; Ashokan, Vinod; Bala, Renu; Pathak, Kare Narain

2018-04-01

It is shown that, in d -dimensional systems, the vertex corrections beyond the random phase approximation (RPA) or G W approximation scales with the power d -β -α of the Fermi momentum if the relation between Fermi energy and Fermi momentum is ɛf˜pfβ and the interacting potential possesses a momentum power law of ˜p-α . The condition d -β -α <0 specifies systems where RPA is exact in the high-density limit. The one-dimensional structure factor is found to be the interaction-free one in the high-density limit for contact interaction. A cancellation of RPA and vertex corrections render this result valid up to second order in contact interaction. For finite-range potentials of cylindrical wires a large-scale cancellation appears and is found to be independent of the width parameter of the wire. The proposed high-density expansion agrees with the quantum Monte Carlo simulations.

Role of protein fluctuation correlations in electron transfer in photosynthetic complexes.

PubMed

Nesterov, Alexander I; Berman, Gennady P

2015-04-01

We consider the dependence of the electron transfer in photosynthetic complexes on correlation properties of random fluctuations of the protein environment. The electron subsystem is modeled by a finite network of connected electron (exciton) sites. The fluctuations of the protein environment are modeled by random telegraph processes, which act either collectively (correlated) or independently (uncorrelated) on the electron sites. We derived an exact closed system of first-order linear differential equations with constant coefficients, for the average density matrix elements and for their first moments. Under some conditions, we obtained analytic expressions for the electron transfer rates and found the range of parameters for their applicability by comparing with the exact numerical simulations. We also compared the correlated and uncorrelated regimes and demonstrated numerically that the uncorrelated fluctuations of the protein environment can, under some conditions, either increase or decrease the electron transfer rates.

ANALYZING NUMERICAL ERRORS IN DOMAIN HEAT TRANSPORT MODELS USING THE CVBEM.

USGS Publications Warehouse

Hromadka, T.V.; ,

1985-01-01

Besides providing an exact solution for steady-state heat conduction processes (Laplace Poisson equations), the CVBEM (complex variable boundary element method) can be used for the numerical error analysis of domain model solutions. For problems where soil water phase change latent heat effects dominate the thermal regime, heat transport can be approximately modeled as a time-stepped steady-state condition in the thawed and frozen regions, respectively. The CVBEM provides an exact solution of the two-dimensional steady-state heat transport problem, and also provides the error in matching the prescribed boundary conditions by the development of a modeling error distribution or an approximative boundary generation. This error evaluation can be used to develop highly accurate CVBEM models of the heat transport process, and the resulting model can be used as a test case for evaluating the precision of domain models based on finite elements or finite differences.

Violation of the continuity equation in the Krieger-Li-Iafrate approximation for current-density functional theory

NASA Astrophysics Data System (ADS)

Siegmund, Marc; Pankratov, Oleg

2011-01-01

We show that the exchange-correlation scalar and vector potentials obtained from the optimized effective potential (OEP) equations and from the Krieger-Li-Iafrate (KLI) approximation for the current-density functional theory (CDFT) change under a gauge transformation such that the energy functional remains invariant. This alone does not assure, however, the theory’s compliance with the continuity equation. Using the model of a quantum ring with a broken angular symmetry which is penetrated by a magnetic flux we demonstrate that the physical current density calculated with the exact-exchange CDFT in the KLI approximation violates the continuity condition. In contrast, the current found from a solution of the full OEP equations satisfies this condition. We argue that the continuity violation stems from the fact that the KLI potentials are not (in general) the exact functional derivatives of a gauge-invariant exchange-correlation functional.

Grazing-incidence X-ray diffraction from a crystal with subsurface defects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaevskii, A. Yu., E-mail: transilv@mail.ru; Golentus, I. E.

2015-03-15

The diffraction of X rays incident on a crystal surface under grazing angles under conditions of total external reflection has been investigated. An approach is proposed in which exact solutions to the dynamic problem of grazing-incidence diffraction in an ideal crystal are used as initial functions to calculate the diffuse component of diffraction in a crystal with defects. The diffuse component of diffraction is calculated for a crystal with surface defects of a dilatation-center type. Exact formulas of the continuum theory which take into account the mirror-image forces are used for defect-induced atomic displacements. Scattering intensity maps near Bragg peaksmore » are constructed for different scan modes, and the conditions for detecting primarily the diffuse component are determined. The results of dynamic calculations of grazing-incidence diffraction in defect-containing crystals are compared with calculations in the kinematic approximation.« less

Exact cone beam reconstruction formulae for functions and their gradients for spherical and flat detectors

NASA Astrophysics Data System (ADS)

Louis, Alfred K.

2016-11-01

We derive unified inversion formulae for the cone beam transform similar to the Radon transform. Reinterpreting Grangeat’s formula we find a relation between the Radon transform of the gradient of the searched-for function and a quantity computable from cone beam data. This gives a uniqueness result for the cone beam transform of compactly supported functions under much weaker assumptions than the Tuy-Kirillov condition. Furthermore this relation leads to an exact formula for the direct calculation of derivatives of the density distribution; but here, similar to the classical Radon transform, complete Radon data are needed, hence the Tuy-Kirillov condition has to be imposed. Numerical experiments reported in Hahn B N et al (2013 Meas. Sci. Technol. 24 125601) indicate that these calculations are less corrupted by beam-hardening noise. Finally, we present flat detector versions for these results, which are mathematically less attractive but important for applications.

Network-based regularization for matched case-control analysis of high-dimensional DNA methylation data.

PubMed

Sun, Hokeun; Wang, Shuang

2013-05-30

The matched case-control designs are commonly used to control for potential confounding factors in genetic epidemiology studies especially epigenetic studies with DNA methylation. Compared with unmatched case-control studies with high-dimensional genomic or epigenetic data, there have been few variable selection methods for matched sets. In an earlier paper, we proposed the penalized logistic regression model for the analysis of unmatched DNA methylation data using a network-based penalty. However, for popularly applied matched designs in epigenetic studies that compare DNA methylation between tumor and adjacent non-tumor tissues or between pre-treatment and post-treatment conditions, applying ordinary logistic regression ignoring matching is known to bring serious bias in estimation. In this paper, we developed a penalized conditional logistic model using the network-based penalty that encourages a grouping effect of (1) linked Cytosine-phosphate-Guanine (CpG) sites within a gene or (2) linked genes within a genetic pathway for analysis of matched DNA methylation data. In our simulation studies, we demonstrated the superiority of using conditional logistic model over unconditional logistic model in high-dimensional variable selection problems for matched case-control data. We further investigated the benefits of utilizing biological group or graph information for matched case-control data. We applied the proposed method to a genome-wide DNA methylation study on hepatocellular carcinoma (HCC) where we investigated the DNA methylation levels of tumor and adjacent non-tumor tissues from HCC patients by using the Illumina Infinium HumanMethylation27 Beadchip. Several new CpG sites and genes known to be related to HCC were identified but were missed by the standard method in the original paper. Copyright © 2012 John Wiley & Sons, Ltd.

Prevalence of abortion and stillbirth in a beef cattle system in Southeastern Mexico.

PubMed

Segura-Correa, José C; Segura-Correa, Victor M

2009-12-01

Prenatal mortality is an important cause of production losses in the livestock industry. This study estimates the prevalences of abortion and stillbirth in a beef cattle system and determines the significance of some risk factors, in the tropics of Mexico. Data were obtained from a Zebu cattle herd and their crosses with Bos taurus breeds, in Yucatan, Mexico. The logit of the probability of an abortion or stillbirth was modeled using binary logistic regression. The risk factors tested were: year of abortion (or calving), season of abortion (or calving), parity number and dam breed group. The effect of twins on stillbirth was tested using Fisher exact test. Of the 4175 calvings studied 49 were abortions (1.17%). Significant factors in the logistic regression analysis for abortions were season of abortion and parity number. The risk of abortion was lower in the dry seasons compared to the rainy and windy seasons (P = 0.009). The risk of abortion was higher in second parity cows followed by the third and first parity cows, as compared to older cows (P = 0.015). Of the 4126 births, 87 were stillbirths (2.11%). Significant factors in the logistic regression analysis for stillbirth were year of calving (P = 0.0001) and parity number (P < 0.001). The risk of stillbirth in first parity cows was 2.6 times that of old cows. Of the total births, 15 were twins (0.36%) of which 7 were born dead calves. Herd owners must focus on the significant risk factors under their control to reduce the prevalence of prenatal mortality.

Effects of Social Class and School Conditions on Educational Enrollment and Achievement of Boys and Girls in Rural Viet Nam

ERIC Educational Resources Information Center

Nguyen, Phuong L.

2006-01-01

This study examines the effects of parental SES, school quality, and community factors on children's enrollment and achievement in rural areas in Viet Nam, using logistic regression and ordered logistic regression. Multivariate analysis reveals significant differences in educational enrollment and outcomes by level of household expenditures and…

Application of fuzzy neural network technologies in management of transport and logistics processes in Arctic

NASA Astrophysics Data System (ADS)

Levchenko, N. G.; Glushkov, S. V.; Sobolevskaya, E. Yu; Orlov, A. P.

2018-05-01

The method of modeling the transport and logistics process using fuzzy neural network technologies has been considered. The analysis of the implemented fuzzy neural network model of the information management system of transnational multimodal transportation of the process showed the expediency of applying this method to the management of transport and logistics processes in the Arctic and Subarctic conditions. The modular architecture of this model can be expanded by incorporating additional modules, since the working conditions in the Arctic and the subarctic themselves will present more and more realistic tasks. The architecture allows increasing the information management system, without affecting the system or the method itself. The model has a wide range of application possibilities, including: analysis of the situation and behavior of interacting elements; dynamic monitoring and diagnostics of management processes; simulation of real events and processes; prediction and prevention of critical situations.

Effect of Initial Conditions on Reproducibility of Scientific Research

PubMed Central

Djulbegovic, Benjamin; Hozo, Iztok

2014-01-01

Background: It is estimated that about half of currently published research cannot be reproduced. Many reasons have been offered as explanations for failure to reproduce scientific research findings- from fraud to the issues related to design, conduct, analysis, or publishing scientific research. We also postulate a sensitive dependency on initial conditions by which small changes can result in the large differences in the research findings when attempted to be reproduced at later times. Methods: We employed a simple logistic regression equation to model the effect of covariates on the initial study findings. We then fed the input from the logistic equation into a logistic map function to model stability of the results in repeated experiments over time. We illustrate the approach by modeling effects of different factors on the choice of correct treatment. Results: We found that reproducibility of the study findings depended both on the initial values of all independent variables and the rate of change in the baseline conditions, the latter being more important. When the changes in the baseline conditions vary by about 3.5 to about 4 in between experiments, no research findings could be reproduced. However, when the rate of change between the experiments is ≤2.5 the results become highly predictable between the experiments. Conclusions: Many results cannot be reproduced because of the changes in the initial conditions between the experiments. Better control of the baseline conditions in-between the experiments may help improve reproducibility of scientific findings. PMID:25132705

Effect of initial conditions on reproducibility of scientific research.

PubMed

Djulbegovic, Benjamin; Hozo, Iztok

2014-06-01

It is estimated that about half of currently published research cannot be reproduced. Many reasons have been offered as explanations for failure to reproduce scientific research findings- from fraud to the issues related to design, conduct, analysis, or publishing scientific research. We also postulate a sensitive dependency on initial conditions by which small changes can result in the large differences in the research findings when attempted to be reproduced at later times. We employed a simple logistic regression equation to model the effect of covariates on the initial study findings. We then fed the input from the logistic equation into a logistic map function to model stability of the results in repeated experiments over time. We illustrate the approach by modeling effects of different factors on the choice of correct treatment. We found that reproducibility of the study findings depended both on the initial values of all independent variables and the rate of change in the baseline conditions, the latter being more important. When the changes in the baseline conditions vary by about 3.5 to about 4 in between experiments, no research findings could be reproduced. However, when the rate of change between the experiments is ≤2.5 the results become highly predictable between the experiments. Many results cannot be reproduced because of the changes in the initial conditions between the experiments. Better control of the baseline conditions in-between the experiments may help improve reproducibility of scientific findings.

Event-driven Monte Carlo: Exact dynamics at all time scales for discrete-variable models

NASA Astrophysics Data System (ADS)

Mendoza-Coto, Alejandro; Díaz-Méndez, Rogelio; Pupillo, Guido

2016-06-01

We present an algorithm for the simulation of the exact real-time dynamics of classical many-body systems with discrete energy levels. In the same spirit of kinetic Monte Carlo methods, a stochastic solution of the master equation is found, with no need to define any other phase-space construction. However, unlike existing methods, the present algorithm does not assume any particular statistical distribution to perform moves or to advance the time, and thus is a unique tool for the numerical exploration of fast and ultra-fast dynamical regimes. By decomposing the problem in a set of two-level subsystems, we find a natural variable step size, that is well defined from the normalization condition of the transition probabilities between the levels. We successfully test the algorithm with known exact solutions for non-equilibrium dynamics and equilibrium thermodynamical properties of Ising-spin models in one and two dimensions, and compare to standard implementations of kinetic Monte Carlo methods. The present algorithm is directly applicable to the study of the real-time dynamics of a large class of classical Markovian chains, and particularly to short-time situations where the exact evolution is relevant.

Exact theory of freeze-out

NASA Astrophysics Data System (ADS)

Cannoni, Mirco

2015-03-01

We show that the standard theory of thermal production and chemical decoupling of WIMPs is incomplete. The hypothesis that WIMPs are produced and decouple from a thermal bath implies that the rate equation the bath particles interacting with the WIMPs is an algebraic equation that constraints the actual WIMPs abundance to have a precise analytical form down to the temperature . The point , which coincides with the stationary point of the equation for the quantity , is where the maximum departure of the WIMPs abundance from the thermal value is reached. For each mass and total annihilation cross section , the temperature and the actual WIMPs abundance are exactly known. This value provides the true initial condition for the usual differential equation that have to be integrated in the interval . The matching of the two abundances at is continuous and differentiable. The dependence of the present relic abundance on the abundance at an intermediate temperature is an exact result. The exact theory suggests a new analytical approximation that furnishes the relic abundance accurate at the level of 1-2 % in the case of -wave and -wave scattering cross sections. We conclude the paper studying the evolution of the WIMPs chemical potential and the entropy production using methods of non-equilibrium thermodynamics.

Exact Solutions of Linear Reaction-Diffusion Processes on a Uniformly Growing Domain: Criteria for Successful Colonization

PubMed Central

Simpson, Matthew J

2015-01-01

Many processes during embryonic development involve transport and reaction of molecules, or transport and proliferation of cells, within growing tissues. Mathematical models of such processes usually take the form of a reaction-diffusion partial differential equation (PDE) on a growing domain. Previous analyses of such models have mainly involved solving the PDEs numerically. Here, we present a framework for calculating the exact solution of a linear reaction-diffusion PDE on a growing domain. We derive an exact solution for a general class of one-dimensional linear reaction—diffusion process on 0

Exact solutions of linear reaction-diffusion processes on a uniformly growing domain: criteria for successful colonization.

PubMed

Simpson, Matthew J

2015-01-01

Many processes during embryonic development involve transport and reaction of molecules, or transport and proliferation of cells, within growing tissues. Mathematical models of such processes usually take the form of a reaction-diffusion partial differential equation (PDE) on a growing domain. Previous analyses of such models have mainly involved solving the PDEs numerically. Here, we present a framework for calculating the exact solution of a linear reaction-diffusion PDE on a growing domain. We derive an exact solution for a general class of one-dimensional linear reaction-diffusion process on 0

Cosmological Perturbation Theory and the Spherical Collapse model - I. Gaussian initial conditions

NASA Astrophysics Data System (ADS)

Fosalba, Pablo; Gaztanaga, Enrique

1998-12-01

We present a simple and intuitive approximation for solving the perturbation theory (PT) of small cosmic fluctuations. We consider only the spherically symmetric or monopole contribution to the PT integrals, which yields the exact result for tree-graphs (i.e. at leading order). We find that the non-linear evolution in Lagrangian space is then given by a simple local transformation over the initial conditions, although it is not local in Euler space. This transformation is found to be described by the spherical collapse (SC) dynamics, as it is the exact solution in the shearless (and therefore local) approximation in Lagrangian space. Taking advantage of this property, it is straightforward to derive the one-point cumulants, xi_J, for both the unsmoothed and smoothed density fields to arbitrary order in the perturbative regime. To leading-order this reproduces, and provides us with a simple explanation for, the exact results obtained by Bernardeau. We then show that the SC model leads to accurate estimates for the next corrective terms when compared with the results derived in the exact perturbation theory making use of the loop calculations. The agreement is within a few per cent for the hierarchical ratios S_J=xi_J/xi^J-1_2. We compare our analytic results with N-body simulations, which turn out to be in very good agreement up to scales where sigma~1. A similar treatment is presented to estimate higher order corrections in the Zel'dovich approximation. These results represent a powerful and readily usable tool to produce analytical predictions that describe the gravitational clustering of large-scale structure in the weakly non-linear regime.

Use and interpretation of logistic regression in habitat-selection studies

USGS Publications Warehouse

Keating, Kim A.; Cherry, Steve

2004-01-01

 Logistic regression is an important tool for wildlife habitat-selection studies, but the method frequently has been misapplied due to an inadequate understanding of the logistic model, its interpretation, and the influence of sampling design. To promote better use of this method, we review its application and interpretation under 3 sampling designs: random, case-control, and use-availability. Logistic regression is appropriate for habitat use-nonuse studies employing random sampling and can be used to directly model the conditional probability of use in such cases. Logistic regression also is appropriate for studies employing case-control sampling designs, but careful attention is required to interpret results correctly. Unless bias can be estimated or probability of use is small for all habitats, results of case-control studies should be interpreted as odds ratios, rather than probability of use or relative probability of use. When data are gathered under a use-availability design, logistic regression can be used to estimate approximate odds ratios if probability of use is small, at least on average. More generally, however, logistic regression is inappropriate for modeling habitat selection in use-availability studies. In particular, using logistic regression to fit the exponential model of Manly et al. (2002:100) does not guarantee maximum-likelihood estimates, valid probabilities, or valid likelihoods. We show that the resource selection function (RSF) commonly used for the exponential model is proportional to a logistic discriminant function. Thus, it may be used to rank habitats with respect to probability of use and to identify important habitat characteristics or their surrogates, but it is not guaranteed to be proportional to probability of use. Other problems associated with the exponential model also are discussed. We describe an alternative model based on Lancaster and Imbens (1996) that offers a method for estimating conditional probability of use in use-availability studies. Although promising, this model fails to converge to a unique solution in some important situations. Further work is needed to obtain a robust method that is broadly applicable to use-availability studies.

Identification of the population density of a species model with nonlocal diffusion and nonlinear reaction

NASA Astrophysics Data System (ADS)

Tuan, Nguyen Huy; Van Au, Vo; Khoa, Vo Anh; Lesnic, Daniel

2017-05-01

The identification of the population density of a logistic equation backwards in time associated with nonlocal diffusion and nonlinear reaction, motivated by biology and ecology fields, is investigated. The diffusion depends on an integral average of the population density whilst the reaction term is a global or local Lipschitz function of the population density. After discussing the ill-posedness of the problem, we apply the quasi-reversibility method to construct stable approximation problems. It is shown that the regularized solutions stemming from such method not only depend continuously on the final data, but also strongly converge to the exact solution in L 2-norm. New error estimates together with stability results are obtained. Furthermore, numerical examples are provided to illustrate the theoretical results.

Careful with Those Priors: A Note on Bayesian Estimation in Two-Parameter Logistic Item Response Theory Models

ERIC Educational Resources Information Center

Marcoulides, Katerina M.

2018-01-01

This study examined the use of Bayesian analysis methods for the estimation of item parameters in a two-parameter logistic item response theory model. Using simulated data under various design conditions with both informative and non-informative priors, the parameter recovery of Bayesian analysis methods were examined. Overall results showed that…

Estimation of Logistic Regression Models in Small Samples. A Simulation Study Using a Weakly Informative Default Prior Distribution

ERIC Educational Resources Information Center

Gordovil-Merino, Amalia; Guardia-Olmos, Joan; Pero-Cebollero, Maribel

2012-01-01

In this paper, we used simulations to compare the performance of classical and Bayesian estimations in logistic regression models using small samples. In the performed simulations, conditions were varied, including the type of relationship between independent and dependent variable values (i.e., unrelated and related values), the type of variable…

dLOGIS: Disaster Logistics Information System

NASA Astrophysics Data System (ADS)

Koesuma, Sorja; Riantana, Rio; Siswanto, Budi; Aji Purnomo, Fendi; Lelono, Sarjoko

2017-11-01

There are three timing of disaster mitigation which is pre-disaster, emergency response and post-disaster. All of those is important in disaster mitigation, but emergency response is important when we are talking about time. Emergency response has limited time when we should give help. Rapid assessment of kind of logistic, the number of survivors, number children and old people, their gender and also for difable person. It should be done in emergency response time. Therefore we make a mobile application for logistics management system. The name of application is dLOGIS, i.e. Disaster Logistics Information System. The application is based on Android system for mobile phone. Otherwise there is also website version. The website version is for maintenance, data input and registration. So the people or government can use it directly when there is a disaster. After login in dLOGIS, there is five main menus. The first main menu shows disaster information, refugees conditions, logistics needed, available logistics stock and already accepted logistics. In the second menu is used for entering survivors data. The field coordinator can enter survivors data based on the rapid assessment in disaster location. The third menu is used for entering kind of logistic. Number and kind of logistics are based on the BNPB needed standard for the survivor. The fourth menu displays the logistics stock available in field coordinator. And the last menu displays the logistics help that already accepted and sent by donation. By using this application when a disaster happened, field coordinator or local government can use maintenance distribution of logistics base on their needs. Also for donor people who will give help to survivor, they can give logistics with the corresponding of survivor needs.

Effect of zone size on the convergence of exact solutions for diffusion in single phase systems with planar, cylindrical or spherical geometry

NASA Technical Reports Server (NTRS)

Unnam, J.; Tenney, D. R.

1981-01-01

Exact solutions for diffusion in single phase binary alloy systems with constant diffusion coefficient and zero-flux boundary condition have been evaluated to establish the optimum zone size of applicability. Planar, cylindrical and spherical interface geometry, and finite, singly infinite, and doubly infinite systems are treated. Two solutions are presented for each geometry, one well suited to short diffusion times, and one to long times. The effect of zone-size on the convergence of these solutions is discussed. A generalized form of the diffusion solution for doubly infinite systems is proposed.

Explicit least squares system parameter identification for exact differential input/output models

NASA Technical Reports Server (NTRS)

Pearson, A. E.

1993-01-01

The equation error for a class of systems modeled by input/output differential operator equations has the potential to be integrated exactly, given the input/output data on a finite time interval, thereby opening up the possibility of using an explicit least squares estimation technique for system parameter identification. The paper delineates the class of models for which this is possible and shows how the explicit least squares cost function can be obtained in a way that obviates dealing with unknown initial and boundary conditions. The approach is illustrated by two examples: a second order chemical kinetics model and a third order system of Lorenz equations.

Work performance decrements are associated with Australian working conditions, particularly the demand to work longer hours.

PubMed

Holden, Libby; Scuffham, Paul A; Hilton, Michael F; Vecchio, Nerina N; Whiteford, Harvey A

2010-03-01

To demonstrate the importance of including a range of working conditions in models exploring the association between health- and work-related performance. The Australian Work Outcomes Research Cost-benefit study cross-sectional screening data set was used to explore health-related absenteeism and work performance losses on a sample of approximately 78,000 working Australians, including available demographic and working condition factors. Data collected using the World Health Organization Health and Productivity Questionnaire were analyzed with negative binomial logistic regression and multinomial logistic regressions for absenteeism and work performance, respectively. Hours expected to work, annual wage, and job insecurity play a vital role in the association between health- and work-related performance for both work attendance and self-reported work performance. Australian working conditions are contributing to both absenteeism and low work performance, regardless of health status.

Space Operations Center orbit altitude selection strategy

NASA Technical Reports Server (NTRS)

Indrikis, J.; Myers, H. L.

1982-01-01

The strategy for the operational altitude selection has to respond to the Space Operation Center's (SOC) maintenance requirements and the logistics demands of the missions to be supported by the SOC. Three orbit strategies are developed: two are constant altitude, and one variable altitude. In order to minimize the effect of atmospheric uncertainty the dynamic altitude method is recommended. In this approach the SOC will operate at the optimum altitude for the prevailing atmospheric conditions and logistics model, provided that mission safety constraints are not violated. Over a typical solar activity cycle this method produces significant savings in the overall logistics cost.

Scale-invariance underlying the logistic equation and its social applications

NASA Astrophysics Data System (ADS)

Hernando, A.; Plastino, A.

2013-01-01

On the basis of dynamical principles we i) advance a derivation of the Logistic Equation (LE), widely employed (among multiple applications) in the simulation of population growth, and ii) demonstrate that scale-invariance and a mean-value constraint are sufficient and necessary conditions for obtaining it. We also generalize the LE to multi-component systems and show that the above dynamical mechanisms underlie a large number of scale-free processes. Examples are presented regarding city-populations, diffusion in complex networks, and popularity of technological products, all of them obeying the multi-component logistic equation in an either stochastic or deterministic way.

Embryonic stem cells: testing the germ-cell theory.

PubMed

Hochedlinger, Konrad

2011-10-25

The exact cellular origin of embryonic stem cells remains elusive. Now a new study provides compelling evidence that embryonic stem cells, established under conventional culture conditions, originate from a transient germ-cell state. Copyright © 2011 Elsevier Ltd. All rights reserved.

Use of the micro-deval test for assessing Alaska aggregates : [summary].

DOT National Transportation Integrated Search

2012-12-01

Choosing the right material is half the battle in building roads for Alaska. The extreme conditions typical to cold regions require a : durable, abrasion resistant and freeze-thaw resistant aggregate. Recently the state has been wondering exactly how...

Integral Equations and Scattering Solutions for a Square-Well Potential.

ERIC Educational Resources Information Center

Bagchi, B.; Seyler, R. G.

1979-01-01

Derives Green's functions and integral equations for scattering solutions subject to a variety of boundary conditions. Exact solutions are obtained for the case of a finite spherical square-well potential, and properties of these solutions are discussed. (Author/HM)

Variation in the prevalence of chronic bronchitis among smokers: a cross-sectional study.

PubMed

Mahesh, P A; Jayaraj, B S; Chaya, S K; Lokesh, K S; McKay, A J; Prabhakar, A K; Pape, U J

2014-07-01

Given the wide variations in prevalence of chronic obstructive pulmonary disease observed between populations with similar levels of exposure to tobacco smoke, we aimed to investigate the possibility of variations in prevalence of chronic bronchitis (CB) between two geographically distinct smoking populations in rural Karnataka, India. The Burden of Obstructive Lung Disease (BOLD) questionnaire was administered to all men aged >30 years in a cross-sectional survey. The χ(2) and Fisher's exact tests were used to compare CB prevalence in the two populations. Logistic regression was used to analyse the impact of multiple variables on the occurrence of CB. Two samples of 2322 and 2182 subjects were included in the study. In non-smokers, CB prevalence did not differ between the populations. However, it was significantly different between smoking populations (44.79% vs. 2.13%, P < 0.0001). Logistic regression indicated that, in addition to smoking, region, age, occupational dust exposure and type of house were associated with higher likelihood of CB. An interaction between smoking and area of residence was found (P < 0.001) and appeared to explain the effect of region (without interaction). A significant difference in CB prevalence was observed between male populations from two areas of Karnataka state, including when stratified by smoking status. No significant difference was observed between non-smokers.

[Diabetic Foot Neuropathy and Related Factors in Patients With Type 2 Diabetes Mellitus].

PubMed

Chen, Tzu-Yu; Lin, Chia-Huei; Chang, Yue-Cune; Wang, Chih-Hsin; Hung, Yi-Jen; Tzeng, Wen-Chii

2018-06-01

Patients with type 2 diabetes mellitus (T2DM) face a higher risk of diabetic foot neuropathy, which increases the risk of death. The early detection of factors that influence diabetic neuropathy reduces the risk of foot lesions, including foot ulcerations, lower extremity amputation, and mortality. To explore the demographic, disease-characteristic, health-literacy, and foot-self-care-behavior factors that affect diabetic foot neuropathy in patients with T2DM. A case-control study design was employed in which cases (Michigan Neuropathy Screening Instrument, MNSI) ≥ 2 were matched to controls based on age and gender in a medical center. A total of 114 patients diagnosed with T2DM in a medical center were recruited as participants. Data were collected using a structured questionnaire. The collected data were analyzed using Fisher's exact test, Mann-Whitney U test, and logistic regression. The results of multiple logistic regression showed that glycated hemoglobin (B = 1.696, p = .041) and communication and critical health literacy (B = -0.082, p = .034) were significant factors of diabetic foot neuropathy. The findings of this study suggest that nurses should assess the health literacy of patients with T2DM before providing health education and should develop a specific foot-care intervention for individuals with poor glycemic control.

An improved plate theory of order (1,2) for thick composite laminates

NASA Technical Reports Server (NTRS)

Tessler, A.

1992-01-01

A new (1,2)-order theory is proposed for the linear elasto-static analysis of laminated composite plates. The basic assumptions are those concerning the distribution through the laminate thickness of the displacements, transverse shear strains and the transverse normal stress, with these quantities regarded as some weighted averages of their exact elasticity theory representations. The displacement expansions are linear for the inplane components and quadratic for the transverse component, whereas the transverse shear strains and transverse normal stress are respectively quadratic and cubic through the thickness. The main distinguishing feature of the theory is that all strain and stress components are expressed in terms of the assumed displacements prior to the application of a variational principle. This is accomplished by an a priori least-square compatibility requirement for the transverse strains and by requiring exact stress boundary conditions at the top and bottom plate surfaces. Equations of equilibrium and associated Poisson boundary conditions are derived from the virtual work principle. It is shown that the theory is particularly suited for finite element discretization as it requires simple C(sup 0)- and C(sup -1)-continuous displacement interpolation fields. Analytic solutions for the problem of cylindrical bending are derived and compared with the exact elasticity solutions and those of our earlier (1,2)-order theory based on the assumed displacements and transverse strains.

Ergonomics, automation and logistics: practical and effective combination of working methods, a case study of a baking company.

PubMed

Quintana, Leonardo; Arias, Claudia; Cordoba, Jorge; Moroy, Magda; Pulido, Jean; Ramirez, Angela

2012-01-01

The aim of this study was to combine three different analytical methods from three different disciplines to diagnose the ergonomic conditions, manufacturing and supply chain operation of a baking company. The study explores a summary of comprehensive working methods that combines the ergonomics, automation and logistics study methods in the diagnosis of working conditions and productivity. The participatory approach of this type of study that involves the feelings and first-hand knowledge of workers of the operation are determining factors in defining points of action and ergonomic interventions, as well as defining opportunities in the automation of manufacturing and logistics, to cope with the needs of the company. The study identified an ergonomic situation (high prevalence of wrist-hand pain), and the combination of interdisciplinary techniques applied allowed to improve this condition in the company. This type of study allows a primary basis of the opportunities presented by the combination of specialized methods of different disciplines, for the definition of comprehensive action plans for the company. Additionally, it outlines opportunities for improvement and recommendations to mitigate the burden associated with occupational diseases and as an end result improve the quality of life and productivity of workers.

Collapse susceptibility mapping in karstified gypsum terrain (Sivas basin - Turkey) by conditional probability, logistic regression, artificial neural network models

NASA Astrophysics Data System (ADS)

Yilmaz, Isik; Keskin, Inan; Marschalko, Marian; Bednarik, Martin

2010-05-01

This study compares the GIS based collapse susceptibility mapping methods such as; conditional probability (CP), logistic regression (LR) and artificial neural networks (ANN) applied in gypsum rock masses in Sivas basin (Turkey). Digital Elevation Model (DEM) was first constructed using GIS software. Collapse-related factors, directly or indirectly related to the causes of collapse occurrence, such as distance from faults, slope angle and aspect, topographical elevation, distance from drainage, topographic wetness index- TWI, stream power index- SPI, Normalized Difference Vegetation Index (NDVI) by means of vegetation cover, distance from roads and settlements were used in the collapse susceptibility analyses. In the last stage of the analyses, collapse susceptibility maps were produced from CP, LR and ANN models, and they were then compared by means of their validations. Area Under Curve (AUC) values obtained from all three methodologies showed that the map obtained from ANN model looks like more accurate than the other models, and the results also showed that the artificial neural networks is a usefull tool in preparation of collapse susceptibility map and highly compatible with GIS operating features. Key words: Collapse; doline; susceptibility map; gypsum; GIS; conditional probability; logistic regression; artificial neural networks.

A Bayesian goodness of fit test and semiparametric generalization of logistic regression with measurement data.

PubMed

Schörgendorfer, Angela; Branscum, Adam J; Hanson, Timothy E

2013-06-01

Logistic regression is a popular tool for risk analysis in medical and population health science. With continuous response data, it is common to create a dichotomous outcome for logistic regression analysis by specifying a threshold for positivity. Fitting a linear regression to the nondichotomized response variable assuming a logistic sampling model for the data has been empirically shown to yield more efficient estimates of odds ratios than ordinary logistic regression of the dichotomized endpoint. We illustrate that risk inference is not robust to departures from the parametric logistic distribution. Moreover, the model assumption of proportional odds is generally not satisfied when the condition of a logistic distribution for the data is violated, leading to biased inference from a parametric logistic analysis. We develop novel Bayesian semiparametric methodology for testing goodness of fit of parametric logistic regression with continuous measurement data. The testing procedures hold for any cutoff threshold and our approach simultaneously provides the ability to perform semiparametric risk estimation. Bayes factors are calculated using the Savage-Dickey ratio for testing the null hypothesis of logistic regression versus a semiparametric generalization. We propose a fully Bayesian and a computationally efficient empirical Bayesian approach to testing, and we present methods for semiparametric estimation of risks, relative risks, and odds ratios when parametric logistic regression fails. Theoretical results establish the consistency of the empirical Bayes test. Results from simulated data show that the proposed approach provides accurate inference irrespective of whether parametric assumptions hold or not. Evaluation of risk factors for obesity shows that different inferences are derived from an analysis of a real data set when deviations from a logistic distribution are permissible in a flexible semiparametric framework. © 2013, The International Biometric Society.

Bohr-Sommerfeld quantization condition for Dirac states derived from an Ermakov-type invariant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thylwe, Karl-Erik; McCabe, Patrick

2013-05-15

It is shown that solutions of the second-order decoupled radial Dirac equations satisfy Ermakov-type invariants. These invariants lead to amplitude-phase-type representations of the radial spinor solutions, with exact relations between their amplitudes and phases. Implications leading to a Bohr-Sommerfeld quantization condition for bound states, and a few particular atomic/ionic and nuclear/hadronic bound-state situations are discussed.

Helping the Hyperactive Child.

ERIC Educational Resources Information Center

Texas State Dept. of Mental Health and Mental Retardation, Austin.

This brief booklet discusses the characteristics, causes, and treatments of attention deficit disorders with hyperactivity. Although children with this condition may be overly active, fidgety, distractible, aggressive, impulsive, and have difficulty learning, the primary problem is their inability to concentrate and pay attention. The exact origin…

Rainfall-runoff response informed by exact solutions of Boussinesq equation on hillslopes

NASA Astrophysics Data System (ADS)

Bartlett, M. S., Jr.; Porporato, A. M.

2017-12-01

The Boussinesq equation offers a powerful approach forunderstanding the flow dynamics of unconfined aquifers. Though this nonlinear equation allows for concise representation of both soil and geomorphological controls on groundwater flow, it has only been solved exactly for a limited number of initial and boundary conditions. These solutions do not include source/sink terms (evapotranspiration, recharge, and seepage to bedrock) and are typically limited to horizontal aquifers. Here we present a class of exact solutions that are general to sloping aquifers and a time varying source/sink term. By incorporating the source/sink term, they may describe aquifers with both time varying recharge over seasonal or weekly time scales, as well as a loss of water from seepage to the bedrock interface, which is a common feature in hillslopes. These new solutions shed light on the hysteretic relationship between streamflow and groundwater and the behavior of the hydrograph recession curves, thus providing a robust basis for deriving a runoff curves for the partition of rainfall into infiltration and runoff.

Exact mapping between different dynamics of isotropically trapped quantum gases

NASA Astrophysics Data System (ADS)

Wamba, Etienne; Pelster, Axel; Anglin, James R.

2016-05-01

Experiments on trapped quantum gases can probe challenging regimes of quantum many-body dynamics, where strong interactions or non-equilibrium states prevent exact theoretical treatment. In this talk, we present a class of exact mappings between all the observables of different experiments, under the experimentally attainable conditions that the gas particles interact via a homogeneously scaling two-body potential which is in general time-dependent, and are confined in an isotropic harmonic trap. We express our result through an identity relating second-quantized field operators in the Heisenberg picture of quantum mechanics which makes it general. It applies to arbitrary measurements on possibly multi-component Bose or Fermi gases in arbitrary initial quantum states, no matter how highly excited or far from equilibrium. We use an example to show how the results of two different and currently feasible experiments can be mapped onto each other by our spacetime transformation. DAMOP sorting category: 6.11 Nonlinear dynamics and out-of-equilibrium trapped gases EW acknowledge the financial support from the Alexander von Humboldt foundation.

Configuring Airspace Sectors with Approximate Dynamic Programming

NASA Technical Reports Server (NTRS)

Bloem, Michael; Gupta, Pramod

2010-01-01

In response to changing traffic and staffing conditions, supervisors dynamically configure airspace sectors by assigning them to control positions. A finite horizon airspace sector configuration problem models this supervisor decision. The problem is to select an airspace configuration at each time step while considering a workload cost, a reconfiguration cost, and a constraint on the number of control positions at each time step. Three algorithms for this problem are proposed and evaluated: a myopic heuristic, an exact dynamic programming algorithm, and a rollouts approximate dynamic programming algorithm. On problem instances from current operations with only dozens of possible configurations, an exact dynamic programming solution gives the optimal cost value. The rollouts algorithm achieves costs within 2% of optimal for these instances, on average. For larger problem instances that are representative of future operations and have thousands of possible configurations, excessive computation time prohibits the use of exact dynamic programming. On such problem instances, the rollouts algorithm reduces the cost achieved by the heuristic by more than 15% on average with an acceptable computation time.

Research design and statistical methods in Pakistan Journal of Medical Sciences (PJMS)

PubMed Central

Akhtar, Sohail; Shah, Syed Wadood Ali; Rafiq, M.; Khan, Ajmal

2016-01-01

Objective: This article compares the study design and statistical methods used in 2005, 2010 and 2015 of Pakistan Journal of Medical Sciences (PJMS). Methods: Only original articles of PJMS were considered for the analysis. The articles were carefully reviewed for statistical methods and designs, and then recorded accordingly. The frequency of each statistical method and research design was estimated and compared with previous years. Results: A total of 429 articles were evaluated (n=74 in 2005, n=179 in 2010, n=176 in 2015) in which 171 (40%) were cross-sectional and 116 (27%) were prospective study designs. A verity of statistical methods were found in the analysis. The most frequent methods include: descriptive statistics (n=315, 73.4%), chi-square/Fisher’s exact tests (n=205, 47.8%) and student t-test (n=186, 43.4%). There was a significant increase in the use of statistical methods over time period: t-test, chi-square/Fisher’s exact test, logistic regression, epidemiological statistics, and non-parametric tests. Conclusion: This study shows that a diverse variety of statistical methods have been used in the research articles of PJMS and frequency improved from 2005 to 2015. However, descriptive statistics was the most frequent method of statistical analysis in the published articles while cross-sectional study design was common study design. PMID:27022365

Two models for evaluating landslide hazards

USGS Publications Warehouse

Davis, J.C.; Chung, C.-J.; Ohlmacher, G.C.

2006-01-01

Two alternative procedures for estimating landslide hazards were evaluated using data on topographic digital elevation models (DEMs) and bedrock lithologies in an area adjacent to the Missouri River in Atchison County, Kansas, USA. The two procedures are based on the likelihood ratio model but utilize different assumptions. The empirical likelihood ratio model is based on non-parametric empirical univariate frequency distribution functions under an assumption of conditional independence while the multivariate logistic discriminant model assumes that likelihood ratios can be expressed in terms of logistic functions. The relative hazards of occurrence of landslides were estimated by an empirical likelihood ratio model and by multivariate logistic discriminant analysis. Predictor variables consisted of grids containing topographic elevations, slope angles, and slope aspects calculated from a 30-m DEM. An integer grid of coded bedrock lithologies taken from digitized geologic maps was also used as a predictor variable. Both statistical models yield relative estimates in the form of the proportion of total map area predicted to already contain or to be the site of future landslides. The stabilities of estimates were checked by cross-validation of results from random subsamples, using each of the two procedures. Cell-by-cell comparisons of hazard maps made by the two models show that the two sets of estimates are virtually identical. This suggests that the empirical likelihood ratio and the logistic discriminant analysis models are robust with respect to the conditional independent assumption and the logistic function assumption, respectively, and that either model can be used successfully to evaluate landslide hazards. ?? 2006.

A revised approach for an exact analytical solution for thermal response in biological tissues significant in therapeutic treatments.

PubMed

Dutta, Jaideep; Kundu, Balaram

2017-05-01

The genesis of the present research paper is to develop a revised exact analytical solution of thermal profile of 1-D Pennes' bioheat equation (PBHE) for living tissues influenced in thermal therapeutic treatments. In order to illustrate the temperature distribution in living tissue both Fourier and non-Fourier model of 1-D PBHE has been solved by 'Separation of variables' technique. Till date most of the research works have been carried out with the constant initial steady temperature of tissue which is not at all relevant for the biological body due to its nonhomogeneous living cells. There should be a temperature variation in the body before the therapeutic treatment. Therefore, a coupled heat transfer in skin surface before therapeutic heating must be taken account for establishment of exact temperature propagation. This approach has not yet been considered in any research work. In this work, an initial condition for solving governing differential equation of heat conduction in biological tissues has been represented as a function of spatial coordinate. In a few research work, initial temperature distribution with PBHE has been coupled in such a way that it eliminates metabolic heat generation. The study has been devoted to establish the comparison of thermal profile between present approach and published theoretical approach for particular initial and boundary conditions inflicted in this investigation. It has been studied that maximum temperature difference of existing approach for Fourier temperature distribution is 19.6% while in case of non-Fourier, it is 52.8%. We have validated our present analysis with experimental results and it has been observed that the temperature response based on the spatial dependent variable initial condition matches more accurately than other approaches. Copyright © 2017 Elsevier Ltd. All rights reserved.

Guidelines for Use of the Approximate Beta-Poisson Dose-Response Model.

PubMed

Xie, Gang; Roiko, Anne; Stratton, Helen; Lemckert, Charles; Dunn, Peter K; Mengersen, Kerrie

2017-07-01

For dose-response analysis in quantitative microbial risk assessment (QMRA), the exact beta-Poisson model is a two-parameter mechanistic dose-response model with parameters α>0 and β>0, which involves the Kummer confluent hypergeometric function. Evaluation of a hypergeometric function is a computational challenge. Denoting PI(d) as the probability of infection at a given mean dose d, the widely used dose-response model PI(d)=1-(1+dβ)-α is an approximate formula for the exact beta-Poisson model. Notwithstanding the required conditions α<β and β>1, issues related to the validity and approximation accuracy of this approximate formula have remained largely ignored in practice, partly because these conditions are too general to provide clear guidance. Consequently, this study proposes a probability measure Pr(0 < r < 1 | α̂, β̂) as a validity measure (r is a random variable that follows a gamma distribution; α̂ and β̂ are the maximum likelihood estimates of α and β in the approximate model); and the constraint conditions β̂>(22α̂)0.50 for 0.02<α̂<2 as a rule of thumb to ensure an accurate approximation (e.g., Pr(0 < r < 1 | α̂, β̂) >0.99) . This validity measure and rule of thumb were validated by application to all the completed beta-Poisson models (related to 85 data sets) from the QMRA community portal (QMRA Wiki). The results showed that the higher the probability Pr(0 < r < 1 | α̂, β̂), the better the approximation. The results further showed that, among the total 85 models examined, 68 models were identified as valid approximate model applications, which all had a near perfect match to the corresponding exact beta-Poisson model dose-response curve. © 2016 Society for Risk Analysis.

An Experimental Realization of a Chaos-Based Secure Communication Using Arduino Microcontrollers.

PubMed

Zapateiro De la Hoz, Mauricio; Acho, Leonardo; Vidal, Yolanda

2015-01-01

Security and secrecy are some of the important concerns in the communications world. In the last years, several encryption techniques have been proposed in order to improve the secrecy of the information transmitted. Chaos-based encryption techniques are being widely studied as part of the problem because of the highly unpredictable and random-look nature of the chaotic signals. In this paper we propose a digital-based communication system that uses the logistic map which is a mathematically simple model that is chaotic under certain conditions. The input message signal is modulated using a simple Delta modulator and encrypted using a logistic map. The key signal is also encrypted using the same logistic map with different initial conditions. In the receiver side, the binary-coded message is decrypted using the encrypted key signal that is sent through one of the communication channels. The proposed scheme is experimentally tested using Arduino shields which are simple yet powerful development kits that allows for the implementation of the communication system for testing purposes.

Noise-induced hearing loss still a problem in shipbuilders: a cross-sectional study in goa, India.

PubMed

Bhumika, N; Prabhu, Gv; Ferreira, Am; Kulkarni, Mk

2013-01-01

Workplace safety regulations seek to mitigate noise-induced hearing loss (NIHL), conventionally associated with the shipbuilding industry. Despite this, are workers still predisposed to NIHL? To study the prevalence of NIHL among noise-exposed subjects in the shipbuilding industry in Goa and to compare it with that among the non-exposed population working in the same industry in relation to certain relevant factors. This is a cross-sectional study in the shipbuilding industry, Goa This study examined 552 workers: 276 shipbuilders and 276 office staff, of similar age, duration of employment and socio-economic status working at a shipbuilding enterprise. An interviewer-administered questionnaire was followed by audiometry. Values were presented as percentages, Mean (SD) and odds ratio (OR) and its 95% confidence interval (CI) (Woolfe's method). Fisher's exact test and binary logistic regression were used. P value of < 0.05 was taken as significant. SPSS version 16 was used. NIHL was found in 17 (6%) shipbuilders, while no office staff was detected to have this condition (OR = 37.29, 95% CI 22.42-62.18). The shipbuilders with NIHL were 52.5 years of age and had been employed for 30.4 years, on an average. None of the 17 cases of NIHL were found to be using earplugs consistently; 11 reported using them "sometimes" and six "never" used them. NIHL continues to affect shipbuilders, owing their non-compliance to workplace regulation. Health education is the need of the hour.

The alarming problems of confounding equivalence using logistic regression models in the perspective of causal diagrams.

PubMed

Yu, Yuanyuan; Li, Hongkai; Sun, Xiaoru; Su, Ping; Wang, Tingting; Liu, Yi; Yuan, Zhongshang; Liu, Yanxun; Xue, Fuzhong

2017-12-28

Confounders can produce spurious associations between exposure and outcome in observational studies. For majority of epidemiologists, adjusting for confounders using logistic regression model is their habitual method, though it has some problems in accuracy and precision. It is, therefore, important to highlight the problems of logistic regression and search the alternative method. Four causal diagram models were defined to summarize confounding equivalence. Both theoretical proofs and simulation studies were performed to verify whether conditioning on different confounding equivalence sets had the same bias-reducing potential and then to select the optimum adjusting strategy, in which logistic regression model and inverse probability weighting based marginal structural model (IPW-based-MSM) were compared. The "do-calculus" was used to calculate the true causal effect of exposure on outcome, then the bias and standard error were used to evaluate the performances of different strategies. Adjusting for different sets of confounding equivalence, as judged by identical Markov boundaries, produced different bias-reducing potential in the logistic regression model. For the sets satisfied G-admissibility, adjusting for the set including all the confounders reduced the equivalent bias to the one containing the parent nodes of the outcome, while the bias after adjusting for the parent nodes of exposure was not equivalent to them. In addition, all causal effect estimations through logistic regression were biased, although the estimation after adjusting for the parent nodes of exposure was nearest to the true causal effect. However, conditioning on different confounding equivalence sets had the same bias-reducing potential under IPW-based-MSM. Compared with logistic regression, the IPW-based-MSM could obtain unbiased causal effect estimation when the adjusted confounders satisfied G-admissibility and the optimal strategy was to adjust for the parent nodes of outcome, which obtained the highest precision. All adjustment strategies through logistic regression were biased for causal effect estimation, while IPW-based-MSM could always obtain unbiased estimation when the adjusted set satisfied G-admissibility. Thus, IPW-based-MSM was recommended to adjust for confounders set.

COMPRESSIBLE FLOW, ENTRAINMENT, AND MEGAPLUME

EPA Science Inventory

It is generally believed that low Mach number, i.e., low-velocity, flow may be assumed to be incompressible flow. Under steady-state conditions, an exact equation of continuity may then be used to show that such flow is non-divergent. However, a rigorous, compressible fluid-dynam...

Anisotropic strange star with Tolman V potential

NASA Astrophysics Data System (ADS)

Shee, Dibyendu; Deb, Debabrata; Ghosh, Shounak; Ray, Saibal; Guha, B. K.

In this paper, we present a strange stellar model using Tolman V-type metric potential employing simplest form of the MIT bag equation of state (EOS) for the quark matter. We consider that the stellar system is spherically symmetric, compact and made of an anisotropic fluid. Choosing different values of n we obtain exact solutions of the Einstein field equations and finally conclude that for a specific value of the parameter n = 1/2, we find physically acceptable features of the stellar object. Further, we conduct different physical tests, viz., the energy condition, generalized Tolman-Oppeheimer-Volkoff (TOV) equation, Herrera’s cracking concept, etc., to confirm the physical validity of the presented model. Matching conditions provide expressions for different constants whereas maximization of the anisotropy parameter provides bag constant. By using the observed data of several compact stars, we derive exact values of some of the physical parameters and exhibit their features in tabular form. It is to note that our predicted value of the bag constant satisfies the report of CERN-SPS and RHIC.

Multiple imputation of missing covariates for the Cox proportional hazards cure model

PubMed Central

Beesley, Lauren J; Bartlett, Jonathan W; Wolf, Gregory T; Taylor, Jeremy M G

2016-01-01

We explore several approaches for imputing partially observed covariates when the outcome of interest is a censored event time and when there is an underlying subset of the population that will never experience the event of interest. We call these subjects “cured,” and we consider the case where the data are modeled using a Cox proportional hazards (CPH) mixture cure model. We study covariate imputation approaches using fully conditional specification (FCS). We derive the exact conditional distribution and suggest a sampling scheme for imputing partially observed covariates in the CPH cure model setting. We also propose several approximations to the exact distribution that are simpler and more convenient to use for imputation. A simulation study demonstrates that the proposed imputation approaches outperform existing imputation approaches for survival data without a cure fraction in terms of bias in estimating CPH cure model parameters. We apply our multiple imputation techniques to a study of patients with head and neck cancer. PMID:27439726

A comparison of exact tests for trend with binary endpoints using Bartholomew's statistic.

PubMed

Consiglio, J D; Shan, G; Wilding, G E

2014-01-01

Tests for trend are important in a number of scientific fields when trends associated with binary variables are of interest. Implementing the standard Cochran-Armitage trend test requires an arbitrary choice of scores assigned to represent the grouping variable. Bartholomew proposed a test for qualitatively ordered samples using asymptotic critical values, but type I error control can be problematic in finite samples. To our knowledge, use of the exact probability distribution has not been explored, and we study its use in the present paper. Specifically we consider an approach based on conditioning on both sets of marginal totals and three unconditional approaches where only the marginal totals corresponding to the group sample sizes are treated as fixed. While slightly conservative, all four tests are guaranteed to have actual type I error rates below the nominal level. The unconditional tests are found to exhibit far less conservatism than the conditional test and thereby gain a power advantage.

Time-Accurate, Unstructured-Mesh Navier-Stokes Computations with the Space-Time CESE Method

NASA Technical Reports Server (NTRS)

Chang, Chau-Lyan

2006-01-01

Application of the newly emerged space-time conservation element solution element (CESE) method to compressible Navier-Stokes equations is studied. In contrast to Euler equations solvers, several issues such as boundary conditions, numerical dissipation, and grid stiffness warrant systematic investigations and validations. Non-reflecting boundary conditions applied at the truncated boundary are also investigated from the stand point of acoustic wave propagation. Validations of the numerical solutions are performed by comparing with exact solutions for steady-state as well as time-accurate viscous flow problems. The test cases cover a broad speed regime for problems ranging from acoustic wave propagation to 3D hypersonic configurations. Model problems pertinent to hypersonic configurations demonstrate the effectiveness of the CESE method in treating flows with shocks, unsteady waves, and separations. Good agreement with exact solutions suggests that the space-time CESE method provides a viable alternative for time-accurate Navier-Stokes calculations of a broad range of problems.

[Optimization for MSW logistics of new Xicheng and new Dongcheng districts in Beijing based on the maximum capacity of transfer stations].

PubMed

Yuan, Jing; Li, Guo-xue; Zhang, Hong-yu; Luo, Yi-ming

2013-09-01

It is necessary to achieve the optimization for MSW logistics based on the new Xicheng (combining the former Xicheng and the former Xuanwu districts) and the new Dongcheng (combining the former Dongcheng and the former Chongwen districts) districts of Beijing. Based on the analysis of current MSW logistics system, transfer station's processing capacity and the terminal treatment facilities' conditions of the four former districts and other districts, a MSW logistics system was built by GIS methods considering transregional treatment. This article analyzes the MSW material balance of current and new logistics systems. Results show that the optimization scheme could reduce the MSW collection distance of the new Xicheng and the new Dongcheng by 9.3 x 10(5) km x a(-1), reduced by 10% compared with current logistics. Under the new logistics solution, considering transregional treatment, can reduce landfill treatment of untreated MSW about 28.3%. If the construction of three incineration plants finished based on the new logistics, the system's optimal ratio of incineration: biochemical treatment: landfill can reach 3.8 : 4.5 : 1.7 compared with 1 : 4.8 : 4.2, which is the ratio of current MSW logistics. The ratio of the amount of incineration: biochemical treatment: landfill approximately reach 4 : 3 : 3 which is the target for 2015. The research results are benefit in increasing MSW utilization and reduction rate of the new Dongcheng and Xicheng districts and nearby districts.

Synchronization in complex oscillator networks and smart grids.

PubMed

Dörfler, Florian; Chertkov, Michael; Bullo, Francesco

2013-02-05

The emergence of synchronization in a network of coupled oscillators is a fascinating topic in various scientific disciplines. A widely adopted model of a coupled oscillator network is characterized by a population of heterogeneous phase oscillators, a graph describing the interaction among them, and diffusive and sinusoidal coupling. It is known that a strongly coupled and sufficiently homogeneous network synchronizes, but the exact threshold from incoherence to synchrony is unknown. Here, we present a unique, concise, and closed-form condition for synchronization of the fully nonlinear, nonequilibrium, and dynamic network. Our synchronization condition can be stated elegantly in terms of the network topology and parameters or equivalently in terms of an intuitive, linear, and static auxiliary system. Our results significantly improve upon the existing conditions advocated thus far, they are provably exact for various interesting network topologies and parameters; they are statistically correct for almost all networks; and they can be applied equally to synchronization phenomena arising in physics and biology as well as in engineered oscillator networks, such as electrical power networks. We illustrate the validity, the accuracy, and the practical applicability of our results in complex network scenarios and in smart grid applications.

Construction of constant curvature punctured Riemann surfaces with particle-scattering interpretation

NASA Astrophysics Data System (ADS)

Bilal, Adel; Gervais, Jean-Loup

A class of punctured constant curvature Riemann surfaces, with boundary conditions similar to those of the Poincaré half plane, is constructed. It is shown to describe the scattering of particle-like objects in two Euclidian dimensions. The associated time delays and classical phase shifts are introduced and connected to the behaviour of the surfaces at their punctures. For each such surface, we conjecture that the time delays are partial derivatives of the phase shift. This type of relationship, already known to be correct in other scattering problems, leads to a general integrability condition concerning the behaviour of the metric in the neighbourhood of the punctures. The time delays are explicitly computed for three punctures, and the conjecture is verified. The result, reexpressed as a product of Riemann zeta-functions, exhibits an intringuing number-theoretic structure: a p-adic product formula holds and one of Ramanujan's identities applies. An ansatz is given for the corresponding exact quantum S-matrix. It is such that the integrability condition is replaced by a finite difference relation only involving the exact spectrum already derived, in the associated Liouville field theory, by Gervais and Neveu.

Binary Logistic Regression Analysis for Detecting Differential Item Functioning: Effectiveness of R[superscript 2] and Delta Log Odds Ratio Effect Size Measures

ERIC Educational Resources Information Center

Hidalgo, Mª Dolores; Gómez-Benito, Juana; Zumbo, Bruno D.

2014-01-01

The authors analyze the effectiveness of the R[superscript 2] and delta log odds ratio effect size measures when using logistic regression analysis to detect differential item functioning (DIF) in dichotomous items. A simulation study was carried out, and the Type I error rate and power estimates under conditions in which only statistical testing…

Lay Consultations in Heart Failure Symptom Evaluation.

PubMed

Reeder, Katherine M; Sims, Jessica L; Ercole, Patrick M; Shetty, Shivan S; Wallendorf, Michael

2017-01-01

Lay consultations can facilitate or impede healthcare. However, little is known about how lay consultations for symptom evaluation affect treatment decision-making. The purpose of this study was to explore the role of lay consultations in symptom evaluation prior to hospitalization among patients with heart failure. Semi-structured interviews were conducted with 60 patients hospitalized for acute decompensated heart failure. Chi-square and Fisher's exact tests, along with logistic regression were used to characterize lay consultations in this sample. A large proportion of patients engaged in lay consultations for symptom evaluation and decision-making before hospitalization. Lay consultants provided attributions and advice and helped make the decision to seek medical care. Men consulted more often with their spouse than women, while women more often consulted with adult children. Findings have implications for optimizing heart failure self-management interventions, improving outcomes, and reducing hospital readmissions.

A refined analysis of composite laminates. [theory of statics and dynamics

NASA Technical Reports Server (NTRS)

Srinivas, S.

1973-01-01

The purpose of this paper is to develop a sufficiently accurate analysis, which is much simpler than exact three-dimensional analysis, for statics and dynamics of composite laminates. The governing differential equations and boundary conditions are derived by following a variational approach. The displacements are assumed piecewise linear across the thickness and the effects of transverse shear deformations and rotary inertia are included. A procedure for obtaining the general solution of the above governing differential equations in the form of hyperbolic-trigonometric series is given. The accuracy of the present theory is assessed by obtaining results for free vibrations and flexure of simply supported rectangular laminates and comparing them with results from exact three-dimensional analysis.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sinitsyn, N. A.

We consider nonadiabatic transitions in explicitly time-dependent systems with Hamiltonians of the form Hˆ(t)=Aˆ+Bˆt+Cˆ/t, where t is time and Aˆ,Bˆ,Cˆ are Hermitian N × N matrices. We show that in any model of this type, scattering matrix elements satisfy nontrivial exact constraints that follow from the absence of the Stokes phenomenon for solutions with specific conditions at t→–∞. This allows one to continue such solutions analytically to t→+∞, and connect their asymptotic behavior at t→–∞ and t→+∞. This property becomes particularly useful when a model shows additional discrete symmetries. Specifically, we derive a number of simple exact constraints and explicitmore » expressions for scattering probabilities in such systems.« less

Solution of the advection-dispersion equation: Continuous load of finite duration

USGS Publications Warehouse

Runkel, R.L.

1996-01-01

Field studies of solute fate and transport in streams and rivers often involve an. experimental release of solutes at an upstream boundary for a finite period of time. A review of several standard references on surface-water-quality modeling indicates that the analytical solution to the constant-parameter advection-dispersion equation for this type of boundary condition has been generally overlooked. Here an exact analytical solution that considers a continuous load of unite duration is compared to an approximate analytical solution presented elsewhere. Results indicate that the exact analytical solution should be used for verification of numerical solutions and other solute-transport problems wherein a high level of accuracy is required. ?? ASCE.

Characterization of topological phases of dimerized Kitaev chain via edge correlation functions

NASA Astrophysics Data System (ADS)

Wang, Yucheng; Miao, Jian-Jian; Jin, Hui-Ke; Chen, Shu

2017-11-01

We study analytically topological properties of a noninteracting modified dimerized Kitaev chain and an exactly solvable interacting dimerized Kitaev chain under open boundary conditions by analyzing two introduced edge correlation functions. The interacting dimerized Kitaev chain at the symmetry point Δ =t and the chemical potential μ =0 can be exactly solved by applying two Jordan-Wigner transformations and a spin rotation, which permits us to calculate the edge correlation functions analytically. We demonstrate that the two edge correlation functions can be used to characterize the trivial, Su-Schrieffer-Heeger-like topological and topological superconductor phases of both the noninteracting and interacting systems and give their phase diagrams.

Exact computation of the maximum-entropy potential of spiking neural-network models.

PubMed

Cofré, R; Cessac, B

2014-05-01

Understanding how stimuli and synaptic connectivity influence the statistics of spike patterns in neural networks is a central question in computational neuroscience. The maximum-entropy approach has been successfully used to characterize the statistical response of simultaneously recorded spiking neurons responding to stimuli. However, in spite of good performance in terms of prediction, the fitting parameters do not explain the underlying mechanistic causes of the observed correlations. On the other hand, mathematical models of spiking neurons (neuromimetic models) provide a probabilistic mapping between the stimulus, network architecture, and spike patterns in terms of conditional probabilities. In this paper we build an exact analytical mapping between neuromimetic and maximum-entropy models.

Lack of consensus in social systems

NASA Astrophysics Data System (ADS)

Benczik, I. J.; Benczik, S. Z.; Schmittmann, B.; Zia, R. K. P.

2008-05-01

We propose an exactly solvable model for the dynamics of voters in a two-party system. The opinion formation process is modeled on a random network of agents. The dynamical nature of interpersonal relations is also reflected in the model, as the connections in the network evolve with the dynamics of the voters. In the infinite time limit, an exact solution predicts the emergence of consensus, for arbitrary initial conditions. However, before consensus is reached, two different metastable states can persist for exponentially long times. One state reflects a perfect balancing of opinions, the other reflects a completely static situation. An estimate of the associated lifetimes suggests that lack of consensus is typical for large systems.

Caudal Regression Syndrome with Partial Agenesis of the Corpus callosum and Partial Lobar Holoprosencephaly

PubMed Central

Hashami, Hilal Al; Bataclan, Maria F; Mathew, Mariam; Krishnan, Lalitha

2010-01-01

Caudal regression syndrome is a rare fetal condition of diabetic pregnancy. Although the exact mechanism is not known, hyperglycaemia during embryogenesis seems to act as a teratogen. Independently, caudal regression syndrome (CRS), agenesis of the corpus callosum (ACC) and partial lobar holoprosencephaly (HPE) have been reported in infants of diabetic mothers. To our knowledge, a combination of all these three conditions has not been reported so far. PMID:21509087

Caudal Regression Syndrome with Partial Agenesis of the Corpus callosum and Partial Lobar Holoprosencephaly: Case report.

PubMed

Hashami, Hilal Al; Bataclan, Maria F; Mathew, Mariam; Krishnan, Lalitha

2010-04-01

Caudal regression syndrome is a rare fetal condition of diabetic pregnancy. Although the exact mechanism is not known, hyperglycaemia during embryogenesis seems to act as a teratogen. Independently, caudal regression syndrome (CRS), agenesis of the corpus callosum (ACC) and partial lobar holoprosencephaly (HPE) have been reported in infants of diabetic mothers. To our knowledge, a combination of all these three conditions has not been reported so far.

Dispersion-relation-preserving finite difference schemes for computational acoustics

NASA Technical Reports Server (NTRS)

Tam, Christopher K. W.; Webb, Jay C.

1993-01-01

Time-marching dispersion-relation-preserving (DRP) schemes can be constructed by optimizing the finite difference approximations of the space and time derivatives in wave number and frequency space. A set of radiation and outflow boundary conditions compatible with the DRP schemes is constructed, and a sequence of numerical simulations is conducted to test the effectiveness of the DRP schemes and the radiation and outflow boundary conditions. Close agreement with the exact solutions is obtained.

Integral Method of Boundary Characteristics: Neumann Condition

NASA Astrophysics Data System (ADS)

Kot, V. A.

2018-05-01

A new algorithm, based on systems of identical equalities with integral and differential boundary characteristics, is proposed for solving boundary-value problems on the heat conduction in bodies canonical in shape at a Neumann boundary condition. Results of a numerical analysis of the accuracy of solving heat-conduction problems with variable boundary conditions with the use of this algorithm are presented. The solutions obtained with it can be considered as exact because their errors comprise hundredths and ten-thousandths of a persent for a wide range of change in the parameters of a problem.

Study on site selection of cold chain logistics in northwest territories

NASA Astrophysics Data System (ADS)

Liu, Yubin; Ren, Zongwei

2017-08-01

In this research, we mainly studied the Site selection problem of cold chain logistics in northwest of China. In the first place, we counted the demands of cold chain products in northwest territories, and then classified it into the Site selection problem in five provinces in northwest territories(Xinjiang, Qinghai, Gansu, Ningxia, Shanxi); Next, we used the Center of gravity Method to select initial location; Finally, we established the location of distribution by using Analytic Hierarchy Process (AHP)and fuzzy comprehensive evaluation method. Comparing with the traditional method, this method not only considered the cost of transportation and distance, but also deliberated the physical condition, social environment and economics condition which associated with Site selection problem.

Impact of clinical status and salivary conditions on xerostomia and oral health-related quality of life of adolescents with type 1 diabetes mellitus.

PubMed

Busato, Ivana Maria Saes; Ignácio, Sérgio Aparecido; Brancher, João Armando; Moysés, Simone Tetu; Azevedo-Alanis, Luciana Reis

2012-02-01

To investigate the influence of clinical status and salivary conditions on the presence of xerostomia on adolescents with and without type 1 diabetes mellitus (DM1), and further to investigate the influence of clinical status, salivary conditions and xerostomia on oral health-related quality of life (OHQoL) of those with DM1. A cross-sectional study was performed on 102 adolescents, 51 with DM1 and 51 nondiabetics. Xerostomia was detected by asking a question about the sensation of having 'dry mouth', and Oral Health Impact Profile-14 was used to measure the impact of xerostomia on OHQoL. The clinical status was assessed by using decayed, missing or filled and Community Periodontal indices, and by evaluating oral manifestations; and the following salivary conditions were evaluated: stimulated salivary flow, pH, buffer capacity, total protein, amylase, urea, calcium, and glucose salivary concentrations. Multiple logistic regression analysis was used to evaluate the influence of clinical status and salivary conditions on xerostomia and the impact of xerostomia on the OHQoL of adolescents with DM1. Clinical status and salivary conditions was shown to have no influence on the presence of xerostomia. Bivariate (P = 0.00) and logistic regression (P = 0.01) analysis showed a significant association between DM1 and xerostomia. Logistic regression analysis showed association between xerostomia (P = 0.00) and OHQoL, and caries experience (P = 0.03) and OHQoL. DM1 showed to be predictive of a high prevalence of xerostomia in adolescents. Caries experience and xerostomia showed to have a negative impact on the OHQoL of adolescents with DM1. © 2011 John Wiley & Sons A/S.

Role of 5-HTTLPR polymorphism in the development of the inward/outward personality organization: a genetic association study.

PubMed

Nardi, Bernardo; Marini, Alessandra; Turchi, Chiara; Arimatea, Emidio; Tagliabracci, Adriano; Bellantuono, Cesario

2013-01-01

Reciprocity with primary caregivers affects subjects' adaptive abilities toward the construction of the most useful personal meaning organization (PMO) with respect to their developmental environment. Within cognitive theory the post-rationalist approach has outlined two basic categories of identity construction and of regulation of cognitive and emotional processes: the Outward and the Inward PMO. The presence of different, consistent clinical patterns in Inward and Outward subjects is paralleled by differences in cerebral activation during emotional tasks on fMRI and by different expression of some polymorphisms in serotonin pathways. Since several lines of evidence support a role for the 5-HTTLPR polymorphism in mediating individual susceptibility to environmental emotional stimuli, this study was conducted to investigate its influence in the development of the Inward/Outward PMO. PMO was assessed and the 5-HTTLPR polymorphism investigated in 124 healthy subjects who were subdivided into an Inward (n = 52) and an Outward (n = 72) group. Case-control comparisons of short allele (S) frequencies showed significant differences between Inwards and Outwards (p = 0.036, χ2 test; p = 0.026, exact test). Genotype frequencies were not significantly different although values slightly exceeded p ≤ 0.05 (p = 0.056, χ2 test; p = 0.059, exact test). Analysis of the 5-HTTLPR genotypes according to the recessive inheritance model showed that the S/S genotype increased the likelihood of developing an Outward PMO (p = 0.0178, χ2 test; p = 0.0143, exact test; OR = 3.43, CI (95%) = 1.188-9.925). A logistic regression analysis confirmed the association between short allele and S/S genotypes with the Outward PMO also when gender and age were considered. However none of the differences remained significant after correction for multiple testing, even though using the recessive model they approach significance. Overall our data seem to suggest a putative genetic basis for interindividual differences in PMO development.

Role of 5-HTTLPR Polymorphism in the Development of the Inward/Outward Personality Organization: A Genetic Association Study

PubMed Central

Nardi, Bernardo; Marini, Alessandra; Turchi, Chiara; Arimatea, Emidio; Tagliabracci, Adriano; Bellantuono, Cesario

2013-01-01

Reciprocity with primary caregivers affects subjects' adaptive abilities toward the construction of the most useful personal meaning organization (PMO) with respect to their developmental environment. Within cognitive theory the post-rationalist approach has outlined two basic categories of identity construction and of regulation of cognitive and emotional processes: the Outward and the Inward PMO. The presence of different, consistent clinical patterns in Inward and Outward subjects is paralleled by differences in cerebral activation during emotional tasks on fMRI and by different expression of some polymorphisms in serotonin pathways. Since several lines of evidence support a role for the 5-HTTLPR polymorphism in mediating individual susceptibility to environmental emotional stimuli, this study was conducted to investigate its influence in the development of the Inward/Outward PMO. PMO was assessed and the 5-HTTLPR polymorphism investigated in 124 healthy subjects who were subdivided into an Inward (n = 52) and an Outward (n = 72) group. Case-control comparisons of short allele (S) frequencies showed significant differences between Inwards and Outwards (p = 0.036, χ2 test; p = 0.026, exact test). Genotype frequencies were not significantly different although values slightly exceeded p≤0.05 (p = 0.056, χ2 test; p = 0.059, exact test). Analysis of the 5-HTTLPR genotypes according to the recessive inheritance model showed that the S/S genotype increased the likelihood of developing an Outward PMO (p = 0.0178, χ2 test; p = 0.0143, exact test; OR = 3.43, CI (95%) = 1.188–9.925). A logistic regression analysis confirmed the association between short allele and S/S genotypes with the Outward PMO also when gender and age were considered. However none of the differences remained significant after correction for multiple testing, even though using the recessive model they approach significance. Overall our data seem to suggest a putative genetic basis for interindividual differences in PMO development. PMID:24358153

Relation Between Firing Statistics of Spiking Neuron with Delayed Fast Inhibitory Feedback and Without Feedback

NASA Astrophysics Data System (ADS)

Vidybida, Alexander; Shchur, Olha

We consider a class of spiking neuronal models, defined by a set of conditions typical for basic threshold-type models, such as the leaky integrate-and-fire or the binding neuron model and also for some artificial neurons. A neuron is fed with a Poisson process. Each output impulse is applied to the neuron itself after a finite delay Δ. This impulse acts as being delivered through a fast Cl-type inhibitory synapse. We derive a general relation which allows calculating exactly the probability density function (pdf) p(t) of output interspike intervals of a neuron with feedback based on known pdf p0(t) for the same neuron without feedback and on the properties of the feedback line (the Δ value). Similar relations between corresponding moments are derived. Furthermore, we prove that the initial segment of pdf p0(t) for a neuron with a fixed threshold level is the same for any neuron satisfying the imposed conditions and is completely determined by the input stream. For the Poisson input stream, we calculate that initial segment exactly and, based on it, obtain exactly the initial segment of pdf p(t) for a neuron with feedback. That is the initial segment of p(t) is model-independent as well. The obtained expressions are checked by means of Monte Carlo simulation. The course of p(t) has a pronounced peculiarity, which makes it impossible to approximate p(t) by Poisson or another simple stochastic process.

Focused Logistics and Support for Force Projection in Force XXI and Beyond

DTIC Science & Technology

1999-12-09

business system linking trading partners with point of sale demand and real time manufacturing for clothing items.17 Quick Response achieved $1.7...be able to determine the real - time status and supply requirements of units. With "distributed logistics system software model hosts൨ and active...location, quantity, condition, and movement of assets. The system is designed to be fully automated, operate in near- real time with an open-architecture

Hierarchic models for laminated plates. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Actis, Ricardo Luis

1991-01-01

Structural plates and shells are three-dimensional bodies, one dimension of which happens to be much smaller than the other two. Thus, the quality of a plate or shell model must be judged on the basis of how well its exact solution approximates the corresponding three-dimensional problem. Of course, the exact solution depends not only on the choice of the model but also on the topology, material properties, loading and constraints. The desired degree of approximation depends on the analyst's goals in performing the analysis. For these reasons models have to be chosen adaptively. Hierarchic sequences of models make adaptive selection of the model which is best suited for the purposes of a particular analysis possible. The principles governing the formulation of hierarchic models for laminated plates are presented. The essential features of the hierarchic models described models are: (1) the exact solutions corresponding to the hierarchic sequence of models converge to the exact solution of the corresponding problem of elasticity for a fixed laminate thickness; and (2) the exact solution of each model converges to the same limit as the exact solution of the corresponding problem of elasticity with respect to the laminate thickness approaching zero. The formulation is based on one parameter (beta) which characterizes the hierarchic sequence of models, and a set of constants whose influence was assessed by a numerical sensitivity study. The recommended selection of these constants results in the number of fields increasing by three for each increment in the power of beta. Numerical examples analyzed with the proposed sequence of models are included and good correlation with the reference solutions was found. Results were obtained for laminated strips (plates in cylindrical bending) and for square and rectangular plates with uniform loading and with homogeneous boundary conditions. Cross-ply and angle-ply laminates were evaluated and the results compared with those of MSC/PROBE. Hierarchic models make the computation of any engineering data possible to an arbitrary level of precision within the framework of the theory of elasticity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manjunath, Naren; Samajdar, Rhine; Jain, Sudhir R., E-mail: srjain@barc.gov.in

Recently, the nodal domain counts of planar, integrable billiards with Dirichlet boundary conditions were shown to satisfy certain difference equations in Samajdar and Jain (2014). The exact solutions of these equations give the number of domains explicitly. For complete generality, we demonstrate this novel formulation for three additional separable systems and thus extend the statement to all integrable billiards.

Across-Task Conflict Regulation: A Replication Failure

ERIC Educational Resources Information Center

Runger, Dennis; Schwager, Sabine; Frensch, Peter A.

2010-01-01

Fernandez-Duque and Knight (2008, Experiment 4) described an across-task effect of endogenously generated, anticipatory control: A cue that predicted conflict in an upcoming Eriksen flanker task modulated conflict regulation in a subsequent number Stroop task. In 3 experiments, 1 of which included an exact replication condition, we failed to…

Magnetically recyclable magnetite-ceria (Nanocat-Fe-Ce) nanocatalysts - applications in multicomponent reactions under benign conditions

EPA Science Inventory

A novel magnetite nanoparticle-supported ceria catalyst (Nanocat-Fe-Ce) has been successfully prepared by simple impregnation method and was well characterized by XRD, SIMS, FEG-SEM-EDS, and TEM. The exact nature of Nanocat-Fe-Ce was confirmed by X-ray photoelectron spectroscopy ...

Acute esophageal necrosis and liver pathology, a rare combination

PubMed Central

Khan, Amir Maqbul; Hundal, Rangit; Ramaswamy, Vijaya; Korsten, Mark; Dhuper, Sunil

2004-01-01

Acute esophageal necrosis (AEN) or “black esophagus” is a clinical condition found at endoscopy. It is a rare entity the exact etiology of which remains unknown. We describe a case of ‘black esophagus’, first of its kind, in the setting of liver cirrhosis and hepatic encephalopathy. PMID:15285044

Use of multivariable asymptotic expansions in a satellite theory

NASA Technical Reports Server (NTRS)

Dallas, S. S.

1973-01-01

Initial conditions and perturbative force of satellite are restricted to yield motion of equatorial satellite about oblate body. In this manner, exact analytic solution exists and can be used as standard of comparison in numerical accuracy comparisons. Detailed numerical accuracy studies of uniformly valid asymptotic expansions were made.

Factors Predisposing Drug Abuse.

ERIC Educational Resources Information Center

Cheney, Carl D.; Phelps, Brady J.

The exact nature of the events which may predispose a person to substance abuse is not known. This paper provides a theoretical discussion and review which emphasizes three contexts which have been shown to predispose on individual to drug abuse: (1) prenatal exposure to a given substance; (2) environmental conditions present upon first exposure…

Burnout in Counselors and Organizations.

ERIC Educational Resources Information Center

Moracco, John C.

Burnout is a condition that exacts a heavy toll on individual and organizational effectiveness. In this paper stress and burnout are defined and their relationship to each other is identified. A model for stress is developed so that intervention strategies can be based on practical and conceptual grounds. Burnout in human service organizations is…

Aerodynamic beam generator for large particles

DOEpatents

Brockmann, John E.; Torczynski, John R.; Dykhuizen, Ronald C.; Neiser, Richard A.; Smith, Mark F.

2002-01-01

A new type of aerodynamic particle beam generator is disclosed. This generator produces a tightly focused beam of large material particles at velocities ranging from a few feet per second to supersonic speeds, depending on the exact configuration and operating conditions. Such generators are of particular interest for use in additive fabrication techniques.

Multiple shooting algorithms for jump-discontinuous problems in optimal control and estimation

NASA Technical Reports Server (NTRS)

Mook, D. J.; Lew, Jiann-Shiun

1991-01-01

Multiple shooting algorithms are developed for jump-discontinuous two-point boundary value problems arising in optimal control and optimal estimation. Examples illustrating the origin of such problems are given to motivate the development of the solution algorithms. The algorithms convert the necessary conditions, consisting of differential equations and transversality conditions, into algebraic equations. The solution of the algebraic equations provides exact solutions for linear problems. The existence and uniqueness of the solution are proved.

Livestock transport from the perspective of the pre-slaughter logistic chain: a review.

PubMed

Miranda-de la Lama, G C; Villarroel, M; María, G A

2014-09-01

New developments in livestock transport within the pre-slaughter chain are discussed in terms of three logistic nodes: origin, stopovers and slaughterhouse. Factors as transport cost, haulier, truck specifications, micro-environment conditions, loading density, route planning, vehicle accidents and journey length are discussed as well as causes of morbidity, mortality, live weight and carcass damage. Taking into account current trends towards increased transport times, logistics stopovers and mixed transport, there is a need to develop systems of evaluation and decision-making that provide tools and protocols that can minimize the biological cost to animals, which may have been underestimated in the past. Copyright © 2014 Elsevier Ltd. All rights reserved.

Molybdenum Accumulation in Marine Sediments as an Indicator of Hypoxic Water Conditions (NACAETAC)

EPA Science Inventory

Direct monitoring of hypoxic water column conditions over large spatial and temporal extents is difficult due to the substantial logistical and financial investment required. Recent studies have indicated that concentrations of molybdenum (Mo) in marine sediments may serve as a u...

[Application of SAS macro to evaluated multiplicative and additive interaction in logistic and Cox regression in clinical practices].

PubMed

Nie, Z Q; Ou, Y Q; Zhuang, J; Qu, Y J; Mai, J Z; Chen, J M; Liu, X Q

2016-05-01

Conditional logistic regression analysis and unconditional logistic regression analysis are commonly used in case control study, but Cox proportional hazard model is often used in survival data analysis. Most literature only refer to main effect model, however, generalized linear model differs from general linear model, and the interaction was composed of multiplicative interaction and additive interaction. The former is only statistical significant, but the latter has biological significance. In this paper, macros was written by using SAS 9.4 and the contrast ratio, attributable proportion due to interaction and synergy index were calculated while calculating the items of logistic and Cox regression interactions, and the confidence intervals of Wald, delta and profile likelihood were used to evaluate additive interaction for the reference in big data analysis in clinical epidemiology and in analysis of genetic multiplicative and additive interactions.

Estimating the exceedance probability of rain rate by logistic regression

NASA Technical Reports Server (NTRS)

Chiu, Long S.; Kedem, Benjamin

1990-01-01

Recent studies have shown that the fraction of an area with rain intensity above a fixed threshold is highly correlated with the area-averaged rain rate. To estimate the fractional rainy area, a logistic regression model, which estimates the conditional probability that rain rate over an area exceeds a fixed threshold given the values of related covariates, is developed. The problem of dependency in the data in the estimation procedure is bypassed by the method of partial likelihood. Analyses of simulated scanning multichannel microwave radiometer and observed electrically scanning microwave radiometer data during the Global Atlantic Tropical Experiment period show that the use of logistic regression in pixel classification is superior to multiple regression in predicting whether rain rate at each pixel exceeds a given threshold, even in the presence of noisy data. The potential of the logistic regression technique in satellite rain rate estimation is discussed.

Integrated Systems Health Management as an Enabler for Condition Based Maintenance and Autonomic Logistics

DTIC Science & Technology

2015-09-17

turbines , SHM tools, maintenance scheduling, and performance of the SHM system determine the added value of the system of systems (A. Van Horenbeek...J. R., & Pintelon, L. (2013). Quantifying the added value of an imperfectly performing condition monitoring system— Application to a wind turbine ...INTEGRATED SYSTEMS HEALTH MANAGEMENT AS AN ENABLER FOR CONDITION BASED MAINTENANCE AND AUTONOMIC

Neumann boundary controllability of the Gear-Grimshaw system with critical size restrictions on the spatial domain

NASA Astrophysics Data System (ADS)

Capistrano-Filho, Roberto A.; Gallego, Fernando A.; Pazoto, Ademir F.

2016-10-01

In this paper, we study the boundary controllability of the Gear-Grimshaw system posed on a finite domain (0, L), with Neumann boundary conditions: ut + uu_x+u_{xxx} + a v_{xxx} + a_1vv_x+a_2 (uv)_x =0, & {in} (0,L)× (0,T), c v_t +rv_x +vv_x+abu_{xxx} +v_{xxx}+a_2buu_x+a_1b(uv)_x =0, &{in} (0,L)× (0,T), u_{xx}(0,t)=h_0(t), u_x(L,t)=h_1(t), u_{xx}(L,t)=h_2(t), &{in} (0,T), v_{xx}(0,t)=g_0(t), v_x(L,t)=g_1(t), v_{xx}(L,t)=g_2(t), &{in} (0,T), u(x,0)= u^0(x), quad v(x,0)= v^0(x), & {in} (0,L). We first prove that the corresponding linearized system around the origin is exactly controllable in {(L^2(0,L))^2} when h 2( t) = g 2( t) = 0. In this case, the exact controllability property is derived for any L > 0 with control functions {h_0, g_0 in H^{-1/3}(0,T)} and {h_1, g_1in L^2(0,T)}. If we change the position of the controls and consider {h_0(t)=h_2(t)=0} (resp. {g_0(t)=g_2(t)=0)}, we obtain the result with control functions {g_0, g_2in H^{-1/3}(0,T)} and {h_1, g_1in L^2(0,T)} if and only if the length L of the spatial domain (0, L) does not belong to a countable set. In all cases, the regularity of the controls are sharp in time. If only one control act in the boundary condition, {h_0(t)=g_0(t)=h_2(t)=g_2(t)=0} and g 1( t) = 0 (resp. h 1( t) = 0), the linearized system is proved to be exactly controllable for small values of the length L and large time of control T. Finally, the nonlinear system is shown to be locally exactly controllable via the contraction mapping principle, if the associated linearized systems are exactly controllable.

Addition by subtraction in coupled-cluster theory: a reconsideration of the CC and CI interface and the nCC hierarchy.

PubMed

Bartlett, Rodney J; Musiał, Monika

2006-11-28

The nCC hierarchy of coupled-cluster approximations, where n guarantees exactness for n electrons and all products of n electrons are derived and applied to several illustrative problems. The condition of exactness for n=2 defines nCCSD=2CC, with nCCSDT=3CC and nCCSDTQ=4CC being exact for three and four electrons. To achieve this, the minimum number of diagrams is evaluated, which is less than in the corresponding CC model. For all practical purposes, nCC is also the proper definition of a size-extensive CI. 2CC is also an orbitally invariant coupled electron pair approximation. The numerical results of nCC are close to those for the full CC variant, and in some cases are closer to the full CI reference result. As 2CC is exact for separated electron pairs, it is the natural zeroth-order approximation for the correlation problem in molecules with other effects introduced as these units start to interact. The nCC hierarchy of approximations has all the attractive features of CC including its size extensivity, orbital invariance, and orbital insensitivity, but in a conceptually appealing form suited to bond breaking, while being computationally less demanding. Excited states from the equation of motion (EOM-2CC) are also reported, which show results frequently approaching those of EOM-CCSDT.

A 3-Year Study of Predictive Factors for Positive and Negative Appendicectomies.

PubMed

Chang, Dwayne T S; Maluda, Melissa; Lee, Lisa; Premaratne, Chandrasiri; Khamhing, Srisongham

2018-03-06

Early and accurate identification or exclusion of acute appendicitis is the key to avoid the morbidity of delayed treatment for true appendicitis or unnecessary appendicectomy, respectively. We aim (i) to identify potential predictive factors for positive and negative appendicectomies; and (ii) to analyse the use of ultrasound scans (US) and computed tomography (CT) scans for acute appendicitis. All appendicectomies that took place at our hospital from the 1st of January 2013 to the 31st of December 2015 were retrospectively recorded. Test results of potential predictive factors of acute appendicitis were recorded. Statistical analysis was performed using Fisher exact test, logistic regression analysis, sensitivity, specificity, and positive and negative predictive values calculation. 208 patients were included in this study. 184 patients had histologically proven acute appendicitis. The other 24 patients had either nonappendicitis pathology or normal appendix. Logistic regression analysis showed statistically significant associations between appendicitis and white cell count, neutrophil count, C-reactive protein, and bilirubin. Neutrophil count was the test with the highest sensitivity and negative predictive values, whereas bilirubin was the test with the highest specificity and positive predictive values (PPV). US and CT scans had high sensitivity and PPV for diagnosing appendicitis. No single test was sufficient to diagnose or exclude acute appendicitis by itself. Combining tests with high sensitivity (abnormal neutrophil count, and US and CT scans) and high specificity (raised bilirubin) may predict acute appendicitis more accurately.

Risk factors for indications of intraoperative blood transfusion among patients undergoing surgical treatment for colorectal adenocarcinoma.

PubMed

Gonçalves, Iara; Linhares, Marcelo; Bordin, Jose; Matos, Delcio

2009-01-01

Identification of risk factors for requiring transfusions during surgery for colorectal cancer may lead to preventive actions or alternative measures, towards decreasing the use of blood components in these procedures, and also rationalization of resources use in hemotherapy services. This was a retrospective case-control study using data from 383 patients who were treated surgically for colorectal adenocarcinoma at 'Fundação Pio XII', in Barretos-SP, Brazil, between 1999 and 2003. To recognize significant risk factors for requiring intraoperative blood transfusion in colorectal cancer surgical procedures. Univariate analyses were performed using Fisher's exact test or the chi-squared test for dichotomous variables and Student's t test for continuous variables, followed by multivariate analysis using multiple logistic regression. In the univariate analyses, height (P = 0.06), glycemia (P = 0.05), previous abdominal or pelvic surgery (P = 0.031), abdominoperineal surgery (P<0.001), extended surgery (P<0.001) and intervention with radical intent (P<0.001) were considered significant. In the multivariate analysis using logistic regression, intervention with radical intent (OR = 10.249, P<0.001, 95% CI = 3.071-34.212) and abdominoperineal amputation (OR = 3.096, P = 0.04, 95% CI = 1.445-6.623) were considered to be independently significant. This investigation allows the conclusion that radical intervention and the abdominoperineal procedure in the surgical treatment of colorectal adenocarcinoma are risk factors for requiring intraoperative blood transfusion.

Factors associated with abnormal eating attitudes among Greek adolescents.

PubMed

Bilali, Aggeliki; Galanis, Petros; Velonakis, Emmanuel; Katostaras, Theofanis

2010-01-01

To estimate the prevalence of abnormal eating attitudes among Greek adolescents and identify possible risk factors associated with these attitudes. Cross-sectional, school-based study. Six randomly selected schools in Patras, southern Greece. The study population consisted of 540 Greek students aged 13-18 years, and the response rate was 97%. The dependent variable was scores on the Eating Attitudes Test-26, with scores > or = 20 indicating abnormal eating attitudes. Bivariate analysis included independent Student t test, chi-square test, and Fisher's exact test. Multivariate logistic regression analysis was applied for the identification of the predictive factors, which were associated independently with abnormal eating attitudes. A 2-sided P value of less than .05 was considered statistically significant. The prevalence of abnormal eating attitudes was 16.7%. Multivariate logistic regression analysis demonstrated that females, urban residents, and those with a body mass index outside normal range, a perception of being overweight, body dissatisfaction, and a family member on a diet were independently related to abnormal eating attitudes. The results indicate that a proportion of Greek adolescents report abnormal eating attitudes and suggest that multiple factors contribute to the development of these attitudes. These findings are useful for further research into this topic and would be valuable in designing preventive interventions. Copyright 2010 Society for Nutrition Education. Published by Elsevier Inc. All rights reserved.

Prevalence of Tobacco Smoking and Factors Associated with the Initiation of Smoking among University Students in Dhaka, Bangladesh.

PubMed

Hossain, Sahadat; Hossain, Shakhaoat; Ahmed, Fahad; Islam, Rabiul; Sikder, Tajuddin; Rahman, Abdur

2017-01-01

Tobacco smoking is considered to be the key preventable risk factor for morbidity and mortality at the global level. The aim of this study was to determine the prevalence of tobacco smoking and factors associated with the initiation of smoking among university students in Dhaka, Bangladesh. A cross-sectional survey study was conducted with 264 students of Jahangirnagar University, Dhaka, Bangladesh in 2015. A standard, self-administered questionnaire consisting of questions on socio-demographic variables, tobacco smoking status, family and peer tobacco smoking history, attitudes and beliefs about tobacco smoking, as well as knowledge about the negative health consequences of tobacco smoking was administered to participants. Data were analyzed using logistic regression models, chi square, and Fisher exact tests. The overall prevalence of tobacco smoking was 60.2%, where males smoked at higher rates than females (68.81% and 19.56%, respectively). The influence of friends was the most significant reason for initiating tobacco smoking (OR: 0.862; CI: 0.810-0.917). Perception regarding tobacco smoking was significantly related to continuing tobacco use. Logistic regression models identified that smoking-related attitudes, potential health problems, and family members dying from cardiovascular disease and cancer were significantly associated with tobacco smoking. The current tobacco smoking prevalence among university students in Bangladesh is over 60%. We suggest adopting WHO Framework Convention on Tobacco Control (FCTC) policies, especially for university students.

Three friendly walkers

NASA Astrophysics Data System (ADS)

Jensen, Iwan

2017-01-01

More than 15 years ago Guttmann and Vöge (2002 J. Stat. Plan. Inference 101 107), introduced a model of friendly walkers. Since then it has remained unsolved. In this paper we provide the exact solution to a closely allied model which essentially only differs in the boundary conditions. The exact solution is expressed in terms of the reciprocal of the generating function for vicious walkers which is a D-finite function. However, ratios of D-finite functions are inherently not D-finite and in this case we prove that the friendly walkers generating function is the solution to a non-linear differential equation with polynomial coefficients, it is in other words D-algebraic. We find using numerically exact calculations a conjectured expression for the generating function of the original model as a ratio of a D-finite function and the generating function for vicious walkers. We obtain an expression for this D-finite function in terms of a {{}2}{{F}1} hypergeometric function with a rational pullback and its first and second derivatives. Dedicated to Tony Guttmann on the occasion of his 70th birthday.

Exact analytic solution of position-dependent mass Schrödinger equation

NASA Astrophysics Data System (ADS)

Rajbongshi, Hangshadhar

2018-03-01

Exact analytic solution of position-dependent mass Schrödinger equation is generated by using extended transformation, a method of mapping a known system into a new system equipped with energy eigenvalues and corresponding wave functions. First order transformation is performed on D-dimensional radial Schrödinger equation with constant mass by taking trigonometric Pöschl-Teller potential as known system. The exactly solvable potentials with position-dependent mass generated for different choices of mass functions through first order transformation are also taken as known systems in the second order transformation performed on D-dimensional radial position-dependent mass Schrödinger equation. The solutions are fitted for "Zhu and Kroemer" ordering of ambiguity. All the wave functions corresponding to nonzero energy eigenvalues are normalizable. The new findings are that the normalizability condition of the wave functions remains independent of mass functions, and some of the generated potentials show a family relationship among themselves where power law potentials also get related to non-power law potentials and vice versa through the transformation.

Connecting numbers to discrete quantification: a step in the child's construction of integer concepts.

PubMed

Slusser, Emily; Ditta, Annie; Sarnecka, Barbara

2013-10-01

The present study asks when young children understand that number words quantify over sets of discrete individuals. For this study, 2- to 4-year-old children were asked to extend the number word five or six either to a cup containing discrete objects (e.g., blocks) or to a cup containing a continuous substance (e.g., water). In Experiment 1, only children who knew the exact meanings of the words one, two and three extended higher number words (five or six) to sets of discrete objects. In Experiment 2, children who only knew the exact meaning of one extended higher number words to discrete objects under the right conditions (i.e., when the problem was first presented with the number words one and two). These results show that children have some understanding that number words pertain to discrete quantification from very early on, but that this knowledge becomes more robust as children learn the exact, cardinal meanings of individual number words. Copyright © 2013 Elsevier B.V. All rights reserved.

Feedback controlled optics with wavefront compensation

NASA Technical Reports Server (NTRS)

Breckenridge, William G. (Inventor); Redding, David C. (Inventor)

1993-01-01

The sensitivity model of a complex optical system obtained by linear ray tracing is used to compute a control gain matrix by imposing the mathematical condition for minimizing the total wavefront error at the optical system's exit pupil. The most recent deformations or error states of the controlled segments or optical surfaces of the system are then assembled as an error vector, and the error vector is transformed by the control gain matrix to produce the exact control variables which will minimize the total wavefront error at the exit pupil of the optical system. These exact control variables are then applied to the actuators controlling the various optical surfaces in the system causing the immediate reduction in total wavefront error observed at the exit pupil of the optical system.

Note on the equivalence of a barotropic perfect fluid with a k-essence scalar field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arroja, Frederico; Sasaki, Misao

In this brief report, we obtain the necessary and sufficient condition for a class of noncanonical single scalar field models to be exactly equivalent to barotropic perfect fluids, under the assumption of an irrotational fluid flow. An immediate consequence of this result is that the nonadiabatic pressure perturbation in this class of scalar field systems vanishes exactly at all orders in perturbation theory and on all scales. The Lagrangian for this general class of scalar field models depends on both the kinetic term and the value of the field. However, after a field redefinition, it can be effectively cast inmore » the form of a purely kinetic k-essence model.« less

Unsteady aerodynamic modeling and active aeroelastic control

NASA Technical Reports Server (NTRS)

Edwards, J. W.

1977-01-01

Unsteady aerodynamic modeling techniques are developed and applied to the study of active control of elastic vehicles. The problem of active control of a supercritical flutter mode poses a definite design goal stability, and is treated in detail. The transfer functions relating the arbitrary airfoil motions to the airloads are derived from the Laplace transforms of the linearized airload expressions for incompressible two dimensional flow. The transfer function relating the motions to the circulatory part of these loads is recognized as the Theodorsen function extended to complex values of reduced frequency, and is termed the generalized Theodorsen function. Inversion of the Laplace transforms yields exact transient airloads and airfoil motions. Exact root loci of aeroelastic modes are calculated, providing quantitative information regarding subcritical and supercritical flutter conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prakash, S. Arun; Malathi, V.; Mani Rajan, M. S., E-mail: senthilmanirajanofc@gmail.com

We obtain the bright similariton solutions for generalized inhomogeneous nonlinear Schrödinger equation (GINLSE) which governs the pulse propagation in a tapered graded index diffraction decreasing waveguide (DDW). The exact solutions have been worked out by employing similarity transformations which involve the mapping of the GINLSE to standard NLSE for the certain conditions of the parameters. By making use of the exact analytical solutions, we have investigated the dynamical behavior of optical similariton pairs and have suggested the methods to control them as they propagate through DDW. Moreover, pulse width of similariton is controlled through various profiles. These results are helpfulmore » to understand the similaritons in DDW and can be potentially useful for future experiments in optical communications which involve optical amplifiers and long-haul telecommunication networks.« less

Evaluating penalized logistic regression models to predict Heat-Related Electric grid stress days

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bramer, L. M.; Rounds, J.; Burleyson, C. D.

Understanding the conditions associated with stress on the electricity grid is important in the development of contingency plans for maintaining reliability during periods when the grid is stressed. In this paper, heat-related grid stress and the relationship with weather conditions is examined using data from the eastern United States. Penalized logistic regression models were developed and applied to predict stress on the electric grid using weather data. The inclusion of other weather variables, such as precipitation, in addition to temperature improved model performance. Several candidate models and datasets were examined. A penalized logistic regression model fit at the operation-zone levelmore » was found to provide predictive value and interpretability. Additionally, the importance of different weather variables observed at different time scales were examined. Maximum temperature and precipitation were identified as important across all zones while the importance of other weather variables was zone specific. The methods presented in this work are extensible to other regions and can be used to aid in planning and development of the electrical grid.« less

Evaluating penalized logistic regression models to predict Heat-Related Electric grid stress days

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bramer, Lisa M.; Rounds, J.; Burleyson, C. D.

Understanding the conditions associated with stress on the electricity grid is important in the development of contingency plans for maintaining reliability during periods when the grid is stressed. In this paper, heat-related grid stress and the relationship with weather conditions were examined using data from the eastern United States. Penalized logistic regression models were developed and applied to predict stress on the electric grid using weather data. The inclusion of other weather variables, such as precipitation, in addition to temperature improved model performance. Several candidate models and combinations of predictive variables were examined. A penalized logistic regression model which wasmore » fit at the operation-zone level was found to provide predictive value and interpretability. Additionally, the importance of different weather variables observed at various time scales were examined. Maximum temperature and precipitation were identified as important across all zones while the importance of other weather variables was zone specific. In conclusion, the methods presented in this work are extensible to other regions and can be used to aid in planning and development of the electrical grid.« less

Evaluating penalized logistic regression models to predict Heat-Related Electric grid stress days

DOE PAGES

Bramer, Lisa M.; Rounds, J.; Burleyson, C. D.; ...

2017-09-22

Understanding the conditions associated with stress on the electricity grid is important in the development of contingency plans for maintaining reliability during periods when the grid is stressed. In this paper, heat-related grid stress and the relationship with weather conditions were examined using data from the eastern United States. Penalized logistic regression models were developed and applied to predict stress on the electric grid using weather data. The inclusion of other weather variables, such as precipitation, in addition to temperature improved model performance. Several candidate models and combinations of predictive variables were examined. A penalized logistic regression model which wasmore » fit at the operation-zone level was found to provide predictive value and interpretability. Additionally, the importance of different weather variables observed at various time scales were examined. Maximum temperature and precipitation were identified as important across all zones while the importance of other weather variables was zone specific. In conclusion, the methods presented in this work are extensible to other regions and can be used to aid in planning and development of the electrical grid.« less

An Experimental Realization of a Chaos-Based Secure Communication Using Arduino Microcontrollers

PubMed Central

Zapateiro De la Hoz, Mauricio; Vidal, Yolanda

2015-01-01

Security and secrecy are some of the important concerns in the communications world. In the last years, several encryption techniques have been proposed in order to improve the secrecy of the information transmitted. Chaos-based encryption techniques are being widely studied as part of the problem because of the highly unpredictable and random-look nature of the chaotic signals. In this paper we propose a digital-based communication system that uses the logistic map which is a mathematically simple model that is chaotic under certain conditions. The input message signal is modulated using a simple Delta modulator and encrypted using a logistic map. The key signal is also encrypted using the same logistic map with different initial conditions. In the receiver side, the binary-coded message is decrypted using the encrypted key signal that is sent through one of the communication channels. The proposed scheme is experimentally tested using Arduino shields which are simple yet powerful development kits that allows for the implementation of the communication system for testing purposes. PMID:26413563

Identification of nine genes as novel susceptibility loci for early-onset ischemic stroke, intracerebral hemorrhage, or subarachnoid hemorrhage.

PubMed

Yamada, Yoshiji; Kato, Kimihiko; Oguri, Mitsutoshi; Horibe, Hideki; Fujimaki, Tetsuo; Yasukochi, Yoshiki; Takeuchi, Ichiro; Sakuma, Jun

2018-07-01

Given that substantial genetic components have been shown in ischemic stroke, intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH), heritability may be higher in early-onset than late-onset individuals with these conditions. Although genome-wide association studies (GWASs) have identified various genes and loci significantly associated with ischemic stroke, ICH, or intracranial aneurysm mainly in European ancestry populations, genetic variants that contribute to susceptibility to these disorders remain to be identified definitively. We performed exome-wide association studies (EWASs) to identify genetic variants that confer susceptibility to ischemic stroke, ICH, or SAH in early-onset subjects with these conditions. A total of 6,649 individuals aged ≤65 years were examined. For the EWAS of ischemic or hemorrhagic stroke, 6,224 individuals (450 subjects with ischemic stroke, 5,774 controls) or 6,179 individuals (261 subjects with ICH, 176 subjects with SAH, 5,742 controls), respectively, were examined. EWASs were performed with the use of Illumina Human Exome-12 v1.2 DNA Analysis BeadChip or Infinium Exome-24 v1.0 BeadChip. To compensate for multiple comparisons of allele frequencies with ischemic stroke, ICH, or SAH, we applied a false discovery rate (FDR) of <0.05 for statistical significance of association. The association of allele frequencies of 31,245 single nucleotide polymorphisms (SNPs) that passed quality control to ischemic stroke was examined with Fisher's exact test, and 31 SNPs were significantly (FDR <0.05) associated with ischemic stroke. The association of allele frequencies of 31,253 or 30,970 SNPs to ICH or SAH, respectively, was examined with Fisher's exact test, and six or two SNPs were significantly associated with ICH or SAH, respectively. Multivariable logistic regression analysis with adjustment for age, sex, and the prevalence of hypertension and diabetes mellitus revealed that 12 SNPs were significantly [P<0.0004 (0.05/124)] related to ischemic stroke. Similar analysis with adjustment for age, sex, and the prevalence of hypertension revealed that six or two SNPs were significantly [P<0.0016 (0.05/32)] related to ICH or SAH, respectively. After examination of linkage disequilibrium of identified SNPs and results of previous GWASs, we identified HHIPL2, CTNNA3, LOC643770, UTP20 , and TRIB3 as susceptibility loci for ischemic stroke, DNTTIP2 and FAM205A as susceptibility loci for ICH, and FAM160A1 and OR52E4 as such loci for SAH. Therefore, to the best of our knowledge, we have newly identified nine genes that confer susceptibility to early-onset ischemic stroke, ICH, or SAH. Determination of genotypes for the SNPs in these genes may prove informative for assessment of the genetic risk for ischemic stroke, ICH, or SAH in Japanese.

Attack to AN Image Encryption Based on Chaotic Logistic Map

NASA Astrophysics Data System (ADS)

Wang, Xing-Yuan; Chen, Feng; Wang, Tian; Xu, Dahai; Ma, Yutian

2013-10-01

This paper offers two different attacks on a freshly proposed image encryption based on chaotic logistic map. The cryptosystem under study first uses a secret key of 80-bit and employed two chaotic logistic maps. We derived the initial conditions of the logistic maps from using the secret key by providing different weights to all its bits. Additionally, in this paper eight different types of procedures are used to encrypt the pixels of an image in the proposed encryption process of which one of them will be used for a certain pixel which is determined by the product of the logistic map. The secret key is revised after encrypting each block which consisted of 16 pixels of the image. The encrypting process have weakness, worst of which is that every byte of plaintext is independent when substituted, so the cipher text of the byte will not change even the other bytes have changed. As a result of weakness, a chosen plaintext attack and a chosen cipher text attack can be completed without any knowledge of the key value to recuperate the ciphered image.

Vehicle Scheduling Schemes for Commercial and Emergency Logistics Integration

PubMed Central

Li, Xiaohui; Tan, Qingmei

2013-01-01

In modern logistics operations, large-scale logistics companies, besides active participation in profit-seeking commercial business, also play an essential role during an emergency relief process by dispatching urgently-required materials to disaster-affected areas. Therefore, an issue has been widely addressed by logistics practitioners and caught researchers' more attention as to how the logistics companies achieve maximum commercial profit on condition that emergency tasks are effectively and performed satisfactorily. In this paper, two vehicle scheduling models are proposed to solve the problem. One is a prediction-related scheme, which predicts the amounts of disaster-relief materials and commercial business and then accepts the business that will generate maximum profits; the other is a priority-directed scheme, which, firstly groups commercial and emergency business according to priority grades and then schedules both types of business jointly and simultaneously by arriving at the maximum priority in total. Moreover, computer-based simulations are carried out to evaluate the performance of these two models by comparing them with two traditional disaster-relief tactics in China. The results testify the feasibility and effectiveness of the proposed models. PMID:24391724

Vehicle scheduling schemes for commercial and emergency logistics integration.

PubMed

Li, Xiaohui; Tan, Qingmei

2013-01-01

In modern logistics operations, large-scale logistics companies, besides active participation in profit-seeking commercial business, also play an essential role during an emergency relief process by dispatching urgently-required materials to disaster-affected areas. Therefore, an issue has been widely addressed by logistics practitioners and caught researchers' more attention as to how the logistics companies achieve maximum commercial profit on condition that emergency tasks are effectively and performed satisfactorily. In this paper, two vehicle scheduling models are proposed to solve the problem. One is a prediction-related scheme, which predicts the amounts of disaster-relief materials and commercial business and then accepts the business that will generate maximum profits; the other is a priority-directed scheme, which, firstly groups commercial and emergency business according to priority grades and then schedules both types of business jointly and simultaneously by arriving at the maximum priority in total. Moreover, computer-based simulations are carried out to evaluate the performance of these two models by comparing them with two traditional disaster-relief tactics in China. The results testify the feasibility and effectiveness of the proposed models.

Combination of a Stressor-Response Model with a Conditional Probability Analysis Approach for Developing Candidate Criteria from MBSS

EPA Science Inventory

I show that a conditional probability analysis using a stressor-response model based on a logistic regression provides a useful approach for developing candidate water quality criteria from empirical data, such as the Maryland Biological Streams Survey (MBSS) data.

A Comparison of Strategies for Estimating Conditional DIF

ERIC Educational Resources Information Center

Moses, Tim; Miao, Jing; Dorans, Neil J.

2010-01-01

In this study, the accuracies of four strategies were compared for estimating conditional differential item functioning (DIF), including raw data, logistic regression, log-linear models, and kernel smoothing. Real data simulations were used to evaluate the estimation strategies across six items, DIF and No DIF situations, and four sample size…

Guidance of Nonlinear Nonminimum-Phase Dynamic Systems

NASA Technical Reports Server (NTRS)

Devasia, Santosh

1996-01-01

The research work has advanced the inversion-based guidance theory for: systems with non-hyperbolic internal dynamics; systems with parameter jumps; and systems where a redesign of the output trajectory is desired. A technique to achieve output tracking for nonminimum phase linear systems with non-hyperbolic and near non-hyperbolic internal dynamics was developed. This approach integrated stable inversion techniques, that achieve exact-tracking, with approximation techniques, that modify the internal dynamics to achieve desirable performance. Such modification of the internal dynamics was used (a) to remove non-hyperbolicity which is an obstruction to applying stable inversion techniques and (b) to reduce large preactuation times needed to apply stable inversion for near non-hyperbolic cases. The method was applied to an example helicopter hover control problem with near non-hyperbolic internal dynamics for illustrating the trade-off between exact tracking and reduction of preactuation time. Future work will extend these results to guidance of nonlinear non-hyperbolic systems. The exact output tracking problem for systems with parameter jumps was considered. Necessary and sufficient conditions were derived for the elimination of switching-introduced output transient. While previous works had studied this problem by developing a regulator that maintains exact tracking through parameter jumps (switches), such techniques are, however, only applicable to minimum-phase systems. In contrast, our approach is also applicable to nonminimum-phase systems and leads to bounded but possibly non-causal solutions. In addition, for the case when the reference trajectories are generated by an exosystem, we developed an exact-tracking controller which could be written in a feedback form. As in standard regulator theory, we also obtained a linear map from the states of the exosystem to the desired system state, which was defined via a matrix differential equation.

OPTRAN- OPTIMAL LOW THRUST ORBIT TRANSFERS

NASA Technical Reports Server (NTRS)

Breakwell, J. V.

1994-01-01

OPTRAN is a collection of programs that solve the problem of optimal low thrust orbit transfers between non-coplanar circular orbits for spacecraft with chemical propulsion systems. The programs are set up to find Hohmann-type solutions, with burns near the perigee and apogee of the transfer orbit. They will solve both fairly long burn-arc transfers and "divided-burn" transfers. Program modeling includes a spherical earth gravity model and propulsion system models for either constant thrust or constant acceleration. The solutions obtained are optimal with respect to fuel use: i.e., final mass of the spacecraft is maximized with respect to the controls. The controls are the direction of thrust and the thrust on/off times. Two basic types of programs are provided in OPTRAN. The first type is for "exact solution" which results in complete, exact tkme-histories. The exact spacecraft position, velocity, and optimal thrust direction are given throughout the maneuver, as are the optimal thrust switch points, the transfer time, and the fuel costs. Exact solution programs are provided in two versions for non-coplanar transfers and in a fast version for coplanar transfers. The second basic type is for "approximate solutions" which results in approximate information on the transfer time and fuel costs. The approximate solution is used to estimate initial conditions for the exact solution. It can be used in divided-burn transfers to find the best number of burns with respect to time. The approximate solution is useful by itself in relatively efficient, short burn-arc transfers. These programs are written in FORTRAN 77 for batch execution and have been implemented on a DEC VAX series computer with the largest program having a central memory requirement of approximately 54K of 8 bit bytes. The OPTRAN program were developed in 1983.

Cerebrovascular accidents in patients treated for choroidal neovascularization with ranibizumab in randomized controlled trials.

PubMed

Bressler, Neil M; Boyer, David S; Williams, David F; Butler, Steven; Francom, Steven F; Brown, Benton; Di Nucci, Flavia; Cramm, Timothy; Tuomi, Lisa L; Ianchulev, Tsontcho; Rubio, Roman G

2012-10-01

To analyze cerebrovascular accidents (CVAs) pooled from large, randomized, controlled clinical trials of ranibizumab treatment for neovascular age-related macular degeneration. Events in five trials (FOCUS, MARINA, ANCHOR, PIER, and SAILOR) were analyzed using a standard safety monitoring process. Exact methods, stratified by study, were used to test for treatment differences based on odds ratios. A stepwise logistic regression model was fit to classify subjects' risk for CVA based on medical history. Treatment differences in CVA rates at 1 year or 2 years were evaluated within risk groups using stratified exact methods. Pooled 2-year CVA rates were <3%; odds ratios (95% confidence intervals) for CVA risk were 1.2 (0.4-4.4) for ranibizumab 0.3-mg versus control, 2.2 (0.8-7.1) for 0.5 mg versus control, and 1.5 (0.8-3.0) for 0.5-mg versus 0.3-mg ranibizumab. No substantial increased risk of CVA for 0.5 mg versus 0.3 mg was identified in pooled analyses or any of the individual trials. In pooled analyses, the difference between 0.5-mg ranibizumab and control was larger (7.7 [1.2-177]) among high-risk CVA patients. This analysis provided some evidence, although not definitive, of a potential increased risk of CVA with ranibizumab versus control or with 0.5-mg versus 0.3-mg ranibizumab. Continued monitoring for CVA within clinical trials seems warrented.

Causal Effect of Self-esteem on Cigarette Smoking Stages in Adolescents: Coarsened Exact Matching in a Longitudinal Study.

PubMed

Khosravi, Ahmad; Mohammadpoorasl, Asghar; Holakouie-Naieni, Kourosh; Mahmoodi, Mahmood; Pouyan, Ali Akbar; Mansournia, Mohammad Ali

2016-12-01

Identification of the causal impact of self-esteem on smoking stages faces seemingly insurmountable problems in observational data, where self-esteem is not manipulable by the researcher and cannot be assigned randomly. The aim of this study was to find out if weaker self-esteem in adolescence is a risk factor of cigarette smoking in a longitudinal study in Iran. In this longitudinal study, 4,853 students (14-18 years) completed a self-administered multiple-choice anonym questionnaire. The students were evaluated twice, 12 months apart. Students were matched based on coarsened exact matching on pretreatment variables, including age, gender, smoking stages at the first wave of study, socioeconomic status, general risk-taking behavior, having a smoker in the family, having a smoker friend, attitude toward smoking, and self-injury, to ensure statistically equivalent comparison groups. Self-esteem was measured using the Rosenberg 10-item questionnaire and were classified using a latent class analysis. After matching, the effect of self-esteem was evaluated using a multinomial logistic model. In the causal fitted model, for adolescents with weaker self-esteem relative to those with stronger self-esteem, the relative risk for experimenters and regular smokers relative to nonsmokers would be expected to increase by a factor of 2.2 (1.9-2.6) and 2.0 (1.5-2.6), respectively. Using a causal approach, our study indicates that low self-esteem is consistently associated with progression in cigarette smoking stages.

Grading system to categorize breast MRI using BI-RADS 5th edition: a statistical study of non-mass enhancement descriptors in terms of probability of malignancy.

PubMed

Asada, Tatsunori; Yamada, Takayuki; Kanemaki, Yoshihide; Fujiwara, Keishi; Okamoto, Satoko; Nakajima, Yasuo

2018-03-01

To analyze the association of breast non-mass enhancement descriptors in the BI-RADS 5th edition with malignancy, and to establish a grading system and categorization of descriptors. This study was approved by our institutional review board. A total of 213 patients were enrolled. Breast MRI was performed with a 1.5-T MRI scanner using a 16-channel breast radiofrequency coil. Two radiologists determined internal enhancement and distribution of non-mass enhancement by consensus. Corresponding pathologic diagnoses were obtained by either biopsy or surgery. The probability of malignancy by descriptor was analyzed using Fisher's exact test and multivariate logistic regression analysis. The probability of malignancy by category was analyzed using Fisher's exact and multi-group comparison tests. One hundred seventy-eight lesions were malignant. Multivariate model analysis showed that internal enhancement (homogeneous vs others, p < 0.001, heterogeneous and clumped vs clustered ring, p = 0.003) and distribution (focal and linear vs segmental, p < 0.001) were the significant explanatory variables. The descriptors were classified into three grades of suspicion, and the categorization (3, 4A, 4B, 4C, and 5) by sum-up grades showed an incremental increase in the probability of malignancy (p < 0.0001). The three-grade criteria and categorization by sum-up grades of descriptors appear valid for non-mass enhancement.

Autism in children and correlates in Lebanon: a pilot case-control study.

PubMed

Hamadé, Aline; Salameh, Pascale; Medlej-Hashim, Myrna; Hajj-Moussa, Elie; Saadallah-Zeidan, Nina; Rizk, Francine

2013-09-17

Autism spectrum disorder (ASD) is a neurological disorder typically appearing before the age of three. The exact cause of autism remains uncertain, and several factors may be involved in its onset: genetic factors and possible environmental factors. The aim of this study was to assess the correlates of autism in the Lebanese population. We investigated the association of autism with several factors in 86 autism cases from specialized schools for children with developmental disabilities and 172 control children from regular public schools in the same regions. Several risk factors for autism were investigated after comparison with a cohort control on parental age, sex, maternal unhappy feeling during pregnancy, consanguineous marriage, and province of residence. The Chi-square test was used to compare nominal variables, and Fisher exact test was used in case expected values within cells were inferior to five. For quantitative variables, we used t-test to compare means between two groups, after checking their distribution normality. For multivariate analysis, we used a forward stepwise likelihood ratio logistic regression. We observed male predominance (79.1%) among autistic infants. There was a significant association between autism and older parents age (OR=1.27), male sex (OR=3.38), unhappy maternal feeling during pregnancy (OR=5.77), living close to industry (OR=6.58), previous childhood infection (OR=8.85), but none concerning maternal age, paternal age and consanguinity. In this pilot epidemiological study of autism in Lebanon, we found several prenatal and perinatal risk factors for autism that could be modified.

Iterative solution of the inverse Cauchy problem for an elliptic equation by the conjugate gradient method

NASA Astrophysics Data System (ADS)

Vasil'ev, V. I.; Kardashevsky, A. M.; Popov, V. V.; Prokopev, G. A.

2017-10-01

This article presents results of computational experiment carried out using a finite-difference method for solving the inverse Cauchy problem for a two-dimensional elliptic equation. The computational algorithm involves an iterative determination of the missing boundary condition from the override condition using the conjugate gradient method. The results of calculations are carried out on the examples with exact solutions as well as at specifying an additional condition with random errors are presented. Results showed a high efficiency of the iterative method of conjugate gradients for numerical solution

Novel third-order Lovelock wormhole solutions

NASA Astrophysics Data System (ADS)

Mehdizadeh, Mohammad Reza; Lobo, Francisco S. N.

2016-06-01

In this work, we consider wormhole geometries in third-order Lovelock gravity and investigate the possibility that these solutions satisfy the energy conditions. In this framework, by applying a specific equation of state, we obtain exact wormhole solutions, and by imposing suitable values for the parameters of the theory, we find that these geometries satisfy the weak energy condition in the vicinity of the throat, due to the presence of higher-order curvature terms. Finally, we trace out a numerical analysis, by assuming a specific redshift function, and find asymptotically flat solutions that satisfy the weak energy condition throughout the spacetime.

Lay Consultations in Heart Failure Symptom Evaluation

PubMed Central

Reeder, Katherine M.; Sims, Jessica L.; Ercole, Patrick M.; Shetty, Shivan S.; Wallendorf, Michael

2017-01-01

Purpose Lay consultations can facilitate or impede healthcare. However, little is known about how lay consultations for symptom evaluation affect treatment decision-making. The purpose of this study was to explore the role of lay consultations in symptom evaluation prior to hospitalization among patients with heart failure. Methods Semi-structured interviews were conducted with 60 patients hospitalized for acute decompensated heart failure. Chi-square and Fisher’s exact tests, along with logistic regression were used to characterize lay consultations in this sample. Results A large proportion of patients engaged in lay consultations for symptom evaluation and decision-making before hospitalization. Lay consultants provided attributions and advice and helped make the decision to seek medical care. Men consulted more often with their spouse than women, while women more often consulted with adult children. Conclusions Findings have implications for optimizing heart failure self-management interventions, improving outcomes, and reducing hospital readmissions. PMID:29399657

Discrete Optimization Model for Vehicle Routing Problem with Scheduling Side Cosntraints

NASA Astrophysics Data System (ADS)

Juliandri, Dedy; Mawengkang, Herman; Bu'ulolo, F.

2018-01-01

Vehicle Routing Problem (VRP) is an important element of many logistic systems which involve routing and scheduling of vehicles from a depot to a set of customers node. This is a hard combinatorial optimization problem with the objective to find an optimal set of routes used by a fleet of vehicles to serve the demands a set of customers It is required that these vehicles return to the depot after serving customers’ demand. The problem incorporates time windows, fleet and driver scheduling, pick-up and delivery in the planning horizon. The goal is to determine the scheduling of fleet and driver and routing policies of the vehicles. The objective is to minimize the overall costs of all routes over the planning horizon. We model the problem as a linear mixed integer program. We develop a combination of heuristics and exact method for solving the model.

Urban parasitology: visceral leishmaniasis in Brazil.

PubMed

Harhay, Michael O; Olliaro, Piero L; Costa, Dorcas Lamounier; Costa, Carlos Henrique Nery

2011-09-01

Since the early 1980s, visceral leishmaniasis (VL) which is, in general, a rural zoonotic disease, has spread to the urban centers of the north, and now the south and west of Brazil. The principal drivers differ between cities, though human migration, large urban canid populations (animal reservoir), and a decidedly peripatetic and adaptable sand fly vector are the primary forces. The exact number of urban cases remains unclear as a result of challenges with surveillance. However, the number of urban cases registered continues to increase annually. Most control initiatives (e.g. culling infected dogs and household spraying to kill the sand fly) could be effective, but have proven hard to maintain at large scales due to logistical, financial and other reasons. In this article, the urbanization of VL in Brazil is reviewed, touching on these and other topics related to controlling VL within and outside Brazil. Copyright © 2011 Elsevier Ltd. All rights reserved.

An assessment of primary care attributes from the perspective of female healthcare users1

PubMed Central

Lima, Eliane de Fátima Almeida; Sousa, Ana Inês; Primo, Cândida Caniçali; Leite, Francielie Marabotti Costa; Lima, Rita de Cassia Duarte; Maciel, Ethel Leonor Nóia

2015-01-01

OBJECTIVE: this study sought to assess the quality of the Family Health Strategy (FHS) and investigated the association between primary care attributes (PCAs) and the sociodemographic characteristics of users. METHOD: a total of 215 female FHS users were interviewed for this descriptive and cross-sectional study. The Primary Care Assessment Tool (PCATool), Adult Edition was used, and the results were analyzed using Fisher's exact tests, Pearson's chi-square tests and logistic regressions. RESULTS: the lowest average score corresponded to the dimension "accessibility" (1.80), and the highest score corresponded to "access" (8.76). The results corresponding to the attributes "longitudinality", "coordination", "comprehensiveness", and "orientation" were not significant. No association was found between the participants' sociodemographic characteristics and the essential, derivative, and general attributes (p>0.05). CONCLUSION: several attributes must be improved across all the investigated services from the perspective of female FHS users. PMID:26155006

Motivations and Predictors of Cheating in Pharmacy School

PubMed Central

Nguyen, Kathy; Shah, Bijal M.; Doroudgar, Shadi; Bidwal, Monica K.

2016-01-01

Objective. To assess the prevalence, methods, and motivations for didactic cheating among pharmacy students and to determine predictive factors for cheating in pharmacy colleges and schools. Methods. A 45-item cross-sectional survey was conducted at all four doctor of pharmacy programs in Northern California. For data analysis, t test, Fisher exact test, and logistic regression were used. Results. Overall, 11.8% of students admitted to cheating in pharmacy school. Primary motivations for cheating included fear of failure, procrastination, and stress. In multivariate analysis, the only predictor for cheating in pharmacy school was a history of cheating in undergraduate studies. Conclusion. Cheating occurs in pharmacy schools and is motivated by fear of failure, procrastination, and stress. A history of past cheating predicts pharmacy school cheating. The information presented may help programs better understand their student population and lead to a reassessment of ethical culture, testing procedures, and prevention programs. PMID:27899829

Financial Care for Older Adults With Dementia.

PubMed

Pan, Xi; Lee, Yeonjung; Dye, Cheryl; Roley, Laurie Theriot

2017-06-01

This article describes an examination of the sociodemographic characteristics of adult children, particularly Baby Boomer caregivers, who provide financial care to older parents with dementia. The sample including 1,011adult children dementia caregivers aged 50 to 64 years is selected from a nationally representative sample in the 2010 Health and Retirement Study. Exact logistic regression revealed that race, provision of financial assistance to caregiver children, and the number of their children are significantly associated with financial caregiving of parents. Non-White caregivers are more likely to provide financial care to their parents or parents-in-law with dementia; those who have more children and provide financial assistance to their children are less likely to provide financial care to parents with dementia. The current findings present valuable new information on the sociodemographic characteristics of adult children who provide financial assistance to parents with dementia and inform research, programs, and services on dementia caregiving.

Improved data reduction algorithm for the needle probe method applied to in-situ thermal conductivity measurements of lunar and planetary regoliths

NASA Astrophysics Data System (ADS)

Nagihara, Seiichi; Hedlund, Magnus; Zacny, Kris; Taylor, Patrick T.

2014-03-01

The needle probe method (also known as the ‘hot wire’ or ‘line heat source’ method) is widely used for in-situ thermal conductivity measurements on terrestrial soils and marine sediments. Variants of this method have also been used (or planned) for measuring regolith on the surfaces of extra-terrestrial bodies (e.g., the Moon, Mars, and comets). In the near-vacuum condition on the lunar and planetary surfaces, the measurement method used on the earth cannot be simply duplicated, because thermal conductivity of the regolith can be ~2 orders of magnitude lower. In addition, the planetary probes have much greater diameters, due to engineering requirements associated with the robotic deployment on extra-terrestrial bodies. All of these factors contribute to the planetary probes requiring a much longer time of measurement, several tens of (if not over a hundred) hours, while a conventional terrestrial needle probe needs only 1 to 2 min. The long measurement time complicates the surface operation logistics of the lander. It also negatively affects accuracy of the thermal conductivity measurement, because the cumulative heat loss along the probe is no longer negligible. The present study improves the data reduction algorithm of the needle probe method by shortening the measurement time on planetary surfaces by an order of magnitude. The main difference between the new scheme and the conventional one is that the former uses the exact mathematical solution to the thermal model on which the needle probe measurement theory is based, while the latter uses an approximate solution that is valid only for large times. The present study demonstrates the benefit of the new data reduction technique by applying it to data from a series of needle probe experiments carried out in a vacuum chamber on a lunar regolith simulant, JSC-1A. The use of the exact solution has some disadvantage, however, in requiring three additional parameters, but two of them (the diameter and the volumetric heat capacity of the probe) can be measured and the other (the volumetric heat capacity of the regolith/stimulant) may be estimated from the surface geologic observation and temperature measurements. Therefore, overall, the new data reduction scheme would make in-situ thermal conductivity measurement more practical on planetary missions.

Improved Data Reduction Algorithm for the Needle Probe Method Applied to In-Situ Thermal Conductivity Measurements of Lunar and Planetary Regoliths

NASA Technical Reports Server (NTRS)

Nagihara, S.; Hedlund, M.; Zacny, K.; Taylor, P. T.

2013-01-01

The needle probe method (also known as the' hot wire' or 'line heat source' method) is widely used for in-situ thermal conductivity measurements on soils and marine sediments on the earth. Variants of this method have also been used (or planned) for measuring regolith on the surfaces of extra-terrestrial bodies (e.g., the Moon, Mars, and comets). In the near-vacuum condition on the lunar and planetary surfaces, the measurement method used on the earth cannot be simply duplicated, because thermal conductivity of the regolith can be approximately 2 orders of magnitude lower. In addition, the planetary probes have much greater diameters, due to engineering requirements associated with the robotic deployment on extra-terrestrial bodies. All of these factors contribute to the planetary probes requiring much longer time of measurement, several tens of (if not over a hundred) hours, while a conventional terrestrial needle probe needs only 1 to 2 minutes. The long measurement time complicates the surface operation logistics of the lander. It also negatively affects accuracy of the thermal conductivity measurement, because the cumulative heat loss along the probe is no longer negligible. The present study improves the data reduction algorithm of the needle probe method by shortening the measurement time on planetary surfaces by an order of magnitude. The main difference between the new scheme and the conventional one is that the former uses the exact mathematical solution to the thermal model on which the needle probe measurement theory is based, while the latter uses an approximate solution that is valid only for large times. The present study demonstrates the benefit of the new data reduction technique by applying it to data from a series of needle probe experiments carried out in a vacuum chamber on JSC-1A lunar regolith stimulant. The use of the exact solution has some disadvantage, however, in requiring three additional parameters, but two of them (the diameter and the volumetric heat capacity of the probe) can be measured and the other (the volumetric heat capacity of the regolith/stimulant) may be estimated from the surface geologic observation and temperature measurements. Therefore, overall, the new data reduction scheme would make in-situ thermal conductivity measurement more practical on planetary missions.

Relating induced in situ conditions of raw chicken breast meat to pinking.

PubMed

Holownia, K; Chinnan, M S; Reynolds, A E; Davis, J W

2004-01-01

Our objective was to simulate the pink color defect in cooked chicken breast meat with treatment combinations that would induce measurable changes in the conditions of raw meat. In addition, the feasibility of using induced raw meat conditions to develop a logistic regression model for prediction of pinking was studied. Approximately 960 breast fillets from 2 plants with 2 replications were used for inducing in situ conditions with 16 combinations of sodium chloride, sodium tripolyphosphate, sodium erythorbate, and sodium nitrite (present and not present). Muscles in all treatments were subjected to individual injections, followed by tumbling, cooking, and chilling. Raw samples were analyzed for pH, oxidation-reduction potential, and pigment evaluation. Results indicated a significant role of induced in situ conditions of raw meat in the occurrence of pinking. Presence of 1 ppm or more of sodium nitrite in raw meat produced significant pinking of cooked meat. The light muscle color group was least affected and the dark group was most affected by induced pH, oxidation-reduction potential conditions, and metmyoglobin and nitrosopigment content. The predictive ability of the logistic model was more than 90% with nitrosopigment, pH, and reducing conditions being the most important factors. Moreover, validation of the model was confirmed by close association between observed pink samples and those predicted as pink.

Gradient Boosting for Conditional Random Fields

DTIC Science & Technology

2014-09-23

221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257...length around 208. We use exactly the same features and data split step as [22]. The resulting data set contains 5600 sequences as training set, 256 ...1097–1104. [16] F. Sha and F. Pereira. Shallow parsing with conditional random fields. In Proceedings of the 2003 Conference of the North American

Verification of the proteus two-dimensional Navier-Stokes code for flat plate and pipe flows

NASA Technical Reports Server (NTRS)

Conley, Julianne M.; Zeman, Patrick L.

1991-01-01

The Proteus Navier-Stokes Code is evaluated for 2-D/axisymmetric, viscous, incompressible, internal, and external flows. The particular cases to be discussed are laminar and turbulent flows over a flat plate, laminar and turbulent developing pipe flows, and turbulent pipe flow with swirl. Results are compared with exact solutions, empirical correlations, and experimental data. A detailed description of the code set-up, including boundary conditions, initial conditions, grid size, and grid packing is given for each case.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burke, K.; Smith, J. C.; Grabowski, P. E.

Universal exact conditions guided the construction of most ground-state density functional approximations in use today. Here, we derive the relation between the entropy and Mermin free energy density functionals for thermal density functional theory. Both the entropy and sum of kinetic and electron-electron repulsion functionals are shown to be monotonically increasing with temperature, while the Mermin functional is concave downwards. Analogous relations are found for both exchange and correlation. The importance of these conditions is illustrated in two extremes: the Hubbard dimer and the uniform gas.

Integrable Time-Dependent Quantum Hamiltonians

NASA Astrophysics Data System (ADS)

Sinitsyn, Nikolai A.; Yuzbashyan, Emil A.; Chernyak, Vladimir Y.; Patra, Aniket; Sun, Chen

2018-05-01

We formulate a set of conditions under which the nonstationary Schrödinger equation with a time-dependent Hamiltonian is exactly solvable analytically. The main requirement is the existence of a non-Abelian gauge field with zero curvature in the space of system parameters. Known solvable multistate Landau-Zener models satisfy these conditions. Our method provides a strategy to incorporate time dependence into various quantum integrable models while maintaining their integrability. We also validate some prior conjectures, including the solution of the driven generalized Tavis-Cummings model.

Physical Performance Characteristics of Military Aircraft Maintenance Personnel Resistant to Work-Related Musculoskeletal Disorders of the Hand and Wrist

DTIC Science & Technology

2006-01-01

neuropathy . Arthritis is an example of a degenerative condition. Though exact symptoms vary by conditions and the individual, some are common to most...depending upon the part and the access area (J. Warsinske, personal communication, July, 6, 2006). 12 Air Force WMSD iniury data Two jet engine repair...facilities were responsible for receiving, inspecting, and repairing jet engines, tasks that are comparable to the duties of the aircraft maintainers

Accumulation of a novel glycolipid and a betaine lipid in cells of Rhodobacter sphaeroides grown under phosphate limitation.

PubMed

Benning, C; Huang, Z H; Gage, D A

1995-02-20

Cells of the photosynthetic bacterium Rhodobacter sphaeroides grown under phosphate-limiting conditions accumulated nonphosphorous glycolipids and lipids carrying head groups derived from amino acids. Concomitantly, the relative amount of phosphoglycerolipids decreased from 90 to 22 mol% of total polar lipids in the membranes. Two lipids, not detectable in cells grown under standard conditions, were synthesized during phosphate-limited growth. Fast atom bombardment mass spectroscopy, exact mass measurements, 1H NMR spectroscopy, sugar composition analysis, and methylation analysis of the predominant glycolipid led to the identification of the novel compound 1,2-di-O-acyl-3-O-[alpha-D-glucopyranosyl-(1-->4)-O-beta-D-galactopyr anosyl]glycerol. The second lipid was identified as the betaine lipid 1,2-di-O-acyl-[4'-(N,N,N-trimethyl)-homoserine]glycerol by cochromatography employing an authentic standard from Chlamydomonas reinhardtii, fast atom bombardment mass spectroscopy, exact mass measurements, and 1H NMR spectroscopy. Prior to this observation, the occurrence of this lipid was thought to be restricted to lower plants and algae. Apparently, these newly synthesized nonphosphorous lipids, in addition to the sulfo- and the ornithine lipid also found in R. sphaeroides grown under optimal conditions, take over the role of phosphoglycerolipids in phosphate-deprived cells.

Mechanical failure of fine root cortical cells initiates plant hydraulic decline during drought

USDA-ARS?s Scientific Manuscript database

Root systems perform the crucial task of absorbing water from the soil to meet the demands of a transpiring canopy. Roots are thought to operate like electrical fuses, which break when carrying an excessive load under conditions of drought stress. Yet the exact site and sequence of this dysfunction ...

Site-Species Relationships for Southern Hardwoods

Treesearch

B. G. Blackmon

1978-01-01

The high cost of land and forest management make selection of sites suitable for planting hardwoods particularly important. Hardwoods have exacting soil requirements, and productivity can change significantly with small changes in conditions. The purpose of this paper is to review some of the attempts to evaluate sites for southern hardwoods, with emphasis on an...

Syndrome by Any Other Name. . .

ERIC Educational Resources Information Center

Bowers, Drew

2008-01-01

The word "syndrome" is one of those words that has slipped into one's vocabulary with few realizing what exactly it means or all the implications it carries. The word "syndrome" can be defined as "a group of signs and symptoms that occur together and characterize a particular abnormality or condition." Typically, a syndrome will be defined by…

Research and Teaching PA: Towards Research as Teaching

ERIC Educational Resources Information Center

van der Meer, Frans-Bauke; Marks, Peter

2016-01-01

Research and teaching are core business of academic institutions. The research context is thought to be fruitful for teaching and learning, and students may contribute to research. But how exactly does the interplay between research and teaching take place and how, in what respects and under which conditions, does this contribute to the quality of…

Mathematical Analysis of a Multiple-Look Concept Identification Model.

ERIC Educational Resources Information Center

Cotton, John W.

The behavior of focus samples central to the multiple-look model of Trabasso and Bower is examined by three methods. First, exact probabilities of success conditional upon a certain brief history of stimulation are determined. Second, possible states of the organism during the experiment are defined and a transition matrix for those states…

Regression sampling: some results for resource managers and researchers

Treesearch

William G. O' Regan; Robert W. Boyd

1974-01-01

Regression sampling is widely used in natural resources management and research to estimate quantities of resources per unit area. This note brings together results found in the statistical literature in the application of this sampling technique. Conditional and unconditional estimators are listed and for each estimator, exact variances and unbiased estimators for the...

The "Ass" Camouflage Construction: Masks as Parasitic Heads

ERIC Educational Resources Information Center

Levine, Robert D.

2010-01-01

Collins et al. 2008 offers a principles-and-parameters-based analysis of an AAVE construction first described in Spears 1998, in which nominal phrases such as "John's ass" appear to have exactly the same denotation, and behavior with respect to familiar conditions on anaphora, as the possessor ["John," and similarly for pronominal possessors.…

48 CFR 22.406-2 - Wages, fringe benefits, and overtime.

Code of Federal Regulations, 2010 CFR

2010-10-01

... exact cash amounts. In these cases, the hourly cash equivalent of the cost of these items shall be... the contractor's contributions, costs, or payment of cash equivalents for fringe benefits. Overtime... cash to the laborer or mechanic, or deducted from payments under the conditions set forth in 29 CFR 3.5...

Explicit Solutions and Bifurcations for a Class of Generalized Boussinesq Wave Equation

NASA Astrophysics Data System (ADS)

Ma, Zhi-Min; Sun, Yu-Huai; Liu, Fu-Sheng

2013-03-01

In this paper, the generalized Boussinesq wave equation utt — uxx + a(um)xx + buxxxx = 0 is investigated by using the bifurcation theory and the method of phase portraits analysis. Under the different parameter conditions, the exact explicit parametric representations for solitary wave solutions and periodic wave solutions are obtained.

Can Higher Education Foster Economic Growth? Chicago Fed Letter. Number 229

ERIC Educational Resources Information Center

Mattoon, Richard H.

2006-01-01

Not all observers agree that higher education and economic growth are obvious or necessary complements to each other. The controversy may be exacerbated because of the difficulty of measuring the exact contribution of colleges and universities to economic growth. Recognizing that a model based on local conditions and higher education's response…

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Y. B.; Zhu, X. W., E-mail: xiaowuzhu1026@znufe.edu.cn; Dai, H. H.

Though widely used in modelling nano- and micro- structures, Eringen’s differential model shows some inconsistencies and recent study has demonstrated its differences between the integral model, which then implies the necessity of using the latter model. In this paper, an analytical study is taken to analyze static bending of nonlocal Euler-Bernoulli beams using Eringen’s two-phase local/nonlocal model. Firstly, a reduction method is proved rigorously, with which the integral equation in consideration can be reduced to a differential equation with mixed boundary value conditions. Then, the static bending problem is formulated and four types of boundary conditions with various loadings aremore » considered. By solving the corresponding differential equations, exact solutions are obtained explicitly in all of the cases, especially for the paradoxical cantilever beam problem. Finally, asymptotic analysis of the exact solutions reveals clearly that, unlike the differential model, the integral model adopted herein has a consistent softening effect. Comparisons are also made with existing analytical and numerical results, which further shows the advantages of the analytical results obtained. Additionally, it seems that the once controversial nonlocal bar problem in the literature is well resolved by the reduction method.« less

Exact solutions for discrete breathers in a forced-damped chain.

PubMed

Gendelman, O V

2013-06-01

Exact solutions for symmetric on-site discrete breathers (DBs) are obtained in a forced-damped linear chain with on-site vibro-impact constraints. The damping in the system is caused by inelastic impacts; the forcing functions should satisfy conditions of periodicity and antisymmetry. Global conditions for existence and stability of the DBs are established by a combination of analytic and numeric methods. The DB can lose its stability through either pitchfork, or Neimark-Sacker bifurcations. The pitchfork bifurcation is related to the internal dynamics of each individual oscillator. It is revealed that the coupling can suppress this type of instability. To the contrary, the Neimark-Sacker bifurcation occurs for relatively large values of the coupling, presumably due to closeness of the excitation frequency to a boundary of the propagation zone of the chain. Both bifurcation mechanisms seem to be generic for the considered type of forced-damped lattices. Some unusual phenomena, like nonmonotonous dependence of the stability boundary on the forcing amplitude, are revealed analytically for the initial system and illustrated numerically for small periodic lattices.

A new model for impregnation mechanisms in different GF/PP commingled yarns

NASA Astrophysics Data System (ADS)

Klinkmüller, V.; Um, M.-K.; Steffens, M.; Friedrich, K.; Kim, B.-S.

1994-09-01

Impregnation mechanisms of different kinds of GF/PP commingled yarns have been studied. As the reinforcing fibres were always the same, a global description has been worked out. Two different mathematical approaches for fibre bed permeability (Kozeny-Carman and Gutowski) were compared. The constants of the applied mathematical models have to stay the same if the fibre reeinforcement and the fibre arrangement is the same. Neither the kind of matrix, nor the fibre volume content may change these constants. Differences in the degree of impregnation after the same process conditions can be only due to different sizes of fibre agglomerations, thus the initial distribution of reinforcing fibres and matrix. For an exact determination of impregnation times and conditions the exact distribution of fibres in the intermediate material and after processing has to be known. This distribution is determined by SEM microscopy and data given from the material supplier. The importance of different process parameters, such as temperature, pressure, processing time is weighted by determining the density and mechanical properties of the specimens.

Quantum dynamical framework for Brownian heat engines

NASA Astrophysics Data System (ADS)

Agarwal, G. S.; Chaturvedi, S.

2013-07-01

We present a self-contained formalism modeled after the Brownian motion of a quantum harmonic oscillator for describing the performance of microscopic Brownian heat engines such as Carnot, Stirling, and Otto engines. Our theory, besides reproducing the standard thermodynamics results in the steady state, enables us to study the role dissipation plays in determining the efficiency of Brownian heat engines under actual laboratory conditions. In particular, we analyze in detail the dynamics associated with decoupling a system in equilibrium with one bath and recoupling it to another bath and obtain exact analytical results, which are shown to have significant ramifications on the efficiencies of engines involving such a step. We also develop a simple yet powerful technique for computing corrections to the steady state results arising from finite operation time and use it to arrive at the thermodynamic complementarity relations for various operating conditions and also to compute the efficiencies of the three engines cited above at maximum power. Some of the methods and exactly solvable models presented here are interesting in their own right and could find useful applications in other contexts as well.

Self-similar solutions to isothermal shock problems

NASA Astrophysics Data System (ADS)

Deschner, Stephan C.; Illenseer, Tobias F.; Duschl, Wolfgang J.

We investigate exact solutions for isothermal shock problems in different one-dimensional geometries. These solutions are given as analytical expressions if possible, or are computed using standard numerical methods for solving ordinary differential equations. We test the numerical solutions against the analytical expressions to verify the correctness of all numerical algorithms. We use similarity methods to derive a system of ordinary differential equations (ODE) yielding exact solutions for power law density distributions as initial conditions. Further, the system of ODEs accounts for implosion problems (IP) as well as explosion problems (EP) by changing the initial or boundary conditions, respectively. Taking genuinely isothermal approximations into account leads to additional insights of EPs in contrast to earlier models. We neglect a constant initial energy contribution but introduce a parameter to adjust the initial mass distribution of the system. Moreover, we show that due to this parameter a constant initial density is not allowed for isothermal EPs. Reasonable restrictions for this parameter are given. Both, the (genuinely) isothermal implosion as well as the explosion problem are solved for the first time.

Analysis of electroluminescence images in small-area circular CdTe solar cells

NASA Astrophysics Data System (ADS)

Bokalič, Matevž; Raguse, John; Sites, James R.; Topič, Marko

2013-09-01

The electroluminescence (EL) imaging process of small area solar cells is investigated in detail to expose optical and electrical effects that influence image acquisition and corrupt the acquired image. An approach to correct the measured EL images and to extract the exact EL radiation as emitted from the photovoltaic device is presented. EL images of circular cadmium telluride (CdTe) solar cells are obtained under different conditions. The power-law relationship between forward injection current and EL emission and a negative temperature coefficient of EL radiation are observed. The distributed Simulation Program with Integrated Circuit Emphasis (SPICE®) model of the circular CdTe solar cell is used to simulate the dark J-V curve and current distribution under the conditions used during EL measurements. Simulation results are presented as circularly averaged EL intensity profiles, which clearly show that the ratio between resistive parameters determines the current distribution in thin-film solar cells. The exact resistance values for front and back contact layers and for CdTe bulk layer are determined at different temperatures, and a negative temperature coefficient for the CdTe bulk resistance is observed.

Hierarchical Bayesian Logistic Regression to forecast metabolic control in type 2 DM patients.

PubMed

Dagliati, Arianna; Malovini, Alberto; Decata, Pasquale; Cogni, Giulia; Teliti, Marsida; Sacchi, Lucia; Cerra, Carlo; Chiovato, Luca; Bellazzi, Riccardo

2016-01-01

In this work we present our efforts in building a model able to forecast patients' changes in clinical conditions when repeated measurements are available. In this case the available risk calculators are typically not applicable. We propose a Hierarchical Bayesian Logistic Regression model, which allows taking into account individual and population variability in model parameters estimate. The model is used to predict metabolic control and its variation in type 2 diabetes mellitus. In particular we have analyzed a population of more than 1000 Italian type 2 diabetic patients, collected within the European project Mosaic. The results obtained in terms of Matthews Correlation Coefficient are significantly better than the ones gathered with standard logistic regression model, based on data pooling.

Medical Logistics Lessons Observed During Operations Enduring Freedom and Iraqi Freedom.

PubMed

Dole, Mark J; Kissane, Jonathan M

2016-01-01

Medical Logistics (MEDLOG) is a function of the Army's integrated System for Health that provides the medical products and specialized logistics services required to deliver health protection and care under all operational conditions. In unified land operations, MEDLOG is an inherent function of Health Service Support (HSS), which also includes casualty care and medical evacuation. This paper focuses on a few key lessons observed during Operations Enduring Freedom and Iraqi Freedom with direct implications for the support of HSS in future operations as envisioned in the Army Operating Concept and the Joint Concept for Health Services. It also examines a few key enablers that helped mitigate these challenges that are not yet fully acknowledged in Army Medical Department doctrine, policy, and planning.

Methodologic considerations in the design and analysis of nested case-control studies: association between cytokines and postoperative delirium.

PubMed

Ngo, Long H; Inouye, Sharon K; Jones, Richard N; Travison, Thomas G; Libermann, Towia A; Dillon, Simon T; Kuchel, George A; Vasunilashorn, Sarinnapha M; Alsop, David C; Marcantonio, Edward R

2017-06-06

The nested case-control study (NCC) design within a prospective cohort study is used when outcome data are available for all subjects, but the exposure of interest has not been collected, and is difficult or prohibitively expensive to obtain for all subjects. A NCC analysis with good matching procedures yields estimates that are as efficient and unbiased as estimates from the full cohort study. We present methodological considerations in a matched NCC design and analysis, which include the choice of match algorithms, analysis methods to evaluate the association of exposures of interest with outcomes, and consideration of overmatching. Matched, NCC design within a longitudinal observational prospective cohort study in the setting of two academic hospitals. Study participants are patients aged over 70 years who underwent scheduled major non-cardiac surgery. The primary outcome was postoperative delirium from in-hospital interviews and medical record review. The main exposure was IL-6 concentration (pg/ml) from blood sampled at three time points before delirium occurred. We used nonparametric signed ranked test to test for the median of the paired differences. We used conditional logistic regression to model the risk of IL-6 on delirium incidence. Simulation was used to generate a sample of cohort data on which unconditional multivariable logistic regression was used, and the results were compared to those of the conditional logistic regression. Partial R-square was used to assess the level of overmatching. We found that the optimal match algorithm yielded more matched pairs than the greedy algorithm. The choice of analytic strategy-whether to consider measured cytokine levels as the predictor or outcome-- yielded inferences that have different clinical interpretations but similar levels of statistical significance. Estimation results from NCC design using conditional logistic regression, and from simulated cohort design using unconditional logistic regression, were similar. We found minimal evidence for overmatching. Using a matched NCC approach introduces methodological challenges into the study design and data analysis. Nonetheless, with careful selection of the match algorithm, match factors, and analysis methods, this design is cost effective and, for our study, yields estimates that are similar to those from a prospective cohort study design.

Global boundedness to a chemotaxis system with singular sensitivity and logistic source

NASA Astrophysics Data System (ADS)

Zhao, Xiangdong; Zheng, Sining

2017-02-01

We consider the parabolic-parabolic Keller-Segel system with singular sensitivity and logistic source: u_t=Δ u-χ nabla \\cdot (u/vnabla v) +ru-μ u^2, v_t=Δ v-v+u under the homogeneous Neumann boundary conditions in a smooth bounded domain Ω subset {R}^2, χ ,μ >0 and rin {R}. It is proved that the system exists globally bounded classical solutions if r>χ ^2/4 for 0<χ ≤ 2, or r>χ -1 for χ >2.

NDIA 34th Annual National Logistics Forum: Logistics Innovation to Ensure Global Readiness. Held in Tampa, Florida on 15-16 May 2018

DTIC Science & Technology

2018-05-16

KEYNOTE ADDRESS BAYSHORE 1-3 Ward Heinke Vice President, Strategic Alliances, Government Markets , Forcepoint 9:45 – 10:15 am NETWORKING BREAK GALLERIA B 6...or conditions of sale (including allowances, credit terms, and warranties); allocation of markets or customers or division of territories; or refusals...Army War College. 11 WARD HEINKE Vice President, Strategic Alliances, Government Markets Forcepoint Ward is VP for Strategic Alliances, Government

Addressing data privacy in matched studies via virtual pooling.

PubMed

Saha-Chaudhuri, P; Weinberg, C R

2017-09-07

Data confidentiality and shared use of research data are two desirable but sometimes conflicting goals in research with multi-center studies and distributed data. While ideal for straightforward analysis, confidentiality restrictions forbid creation of a single dataset that includes covariate information of all participants. Current approaches such as aggregate data sharing, distributed regression, meta-analysis and score-based methods can have important limitations. We propose a novel application of an existing epidemiologic tool, specimen pooling, to enable confidentiality-preserving analysis of data arising from a matched case-control, multi-center design. Instead of pooling specimens prior to assay, we apply the methodology to virtually pool (aggregate) covariates within nodes. Such virtual pooling retains most of the information used in an analysis with individual data and since individual participant data is not shared externally, within-node virtual pooling preserves data confidentiality. We show that aggregated covariate levels can be used in a conditional logistic regression model to estimate individual-level odds ratios of interest. The parameter estimates from the standard conditional logistic regression are compared to the estimates based on a conditional logistic regression model with aggregated data. The parameter estimates are shown to be similar to those without pooling and to have comparable standard errors and confidence interval coverage. Virtual data pooling can be used to maintain confidentiality of data from multi-center study and can be particularly useful in research with large-scale distributed data.

Automated outreach to increase primary adherence to cholesterol-lowering medications.

PubMed

Derose, Stephen F; Green, Kelley; Marrett, Elizabeth; Tunceli, Kaan; Cheetham, T Craig; Chiu, Vicki Y; Harrison, Teresa N; Reynolds, Kristi; Vansomphone, Southida S; Scott, Ronald D

2013-01-14

Primary nonadherence occurs when new prescriptions are not dispensed. Little is known about how to reduce primary nonadherence. We performed a randomized controlled trial to evaluate an automated system to decrease primary nonadherence to statins for lowering cholesterol. Adult members of Kaiser Permanente Southern California with no history of statin use within the past year who did not fill a statin prescription after 1 to 2 weeks were passively enrolled. The intervention group received automated telephone calls followed 1 week later by letters for continued nonadherence; the control group received no outreach. The primary outcome was a statin dispensed up to 2 weeks after delivery of the letter. Secondary outcomes included refills at intervals up to 1 year. Intervention effectiveness was determined by intent-to-treat analysis and Fisher exact test. Subgroups were examined using logistic regression. There were 2606 participants in the intervention group and 2610 in the control group. Statins were dispensed to 42.3% of intervention participants and 26.0% of control participants (absolute difference, 16.3%; P < .001). The relative risk for the intervention vs control group was 1.63 (95% CI, 1.50-1.76). Intervention effectiveness varied slightly by age (P = .045) but was effective across all age strata. Differences in the frequency of statin dispensations persisted up to 1 year (P < .001). The intervention was effective in reducing primary nonadherence to statin medications. Because of low marginal costs for outreach, this strategy appears feasible for reducing primary nonadherence. This approach may generalize well to other medications and chronic conditions.

Dried blood spot measurement of pregnancy-associated plasma protein A (PAPP-A) and free β-subunit of human chorionic gonadotropin (β-hCG) from a low-resource setting.

PubMed

Browne, J L; Schielen, P C J I; Belmouden, I; Pennings, J L A; Klipstein-Grobusch, K

2015-06-01

The objectives of the article is to compare pregnancy-associated plasma protein A (PAPP-A) and free β-subunit of human chorionic gonadotropin (β-hCG) concentrations in dried blood spots (DBSs) with serum of samples obtained from a public hospital in a low-resource setting and to evaluate their stability. Serum and DBS samples were obtained by venipuncture and finger prick from 50 pregnant participants in a cohort study in a public hospital in Accra, Ghana. PAPP-A and β-hCG concentrations from serum and DBS were measured with an AutoDELFIA® (PerkinElmer, PerkinElmer, Turku, Finland) automatic immunoassay. Correlation and Passing-Bablok regression analyses were performed to compare marker levels. High correlation (>0.9) was observed for PAPP-A and β-hCG levels between various sampling techniques. The β-hCG concentration was stable between DBS and serum, PAPP-A concentration consistently lower in DBS. Our findings suggest that β-hCG can be reliably collected from DBS in low-resource tropical settings. The exact conditions of the clinical workflow necessary for reliable PAPP-A measurement in these settings need to be further developed in the future. These findings could have implications for prenatal screening programs feasibility in low-income and middle-income countries, as DBS provides an alternative minimally invasive sampling method, with advantages in sampling technique, stability, logistics, and potential application in low-resource settings. © 2015 John Wiley & Sons, Ltd.

Noise-Induced Hearing Loss Still a Problem in Shipbuilders: A Cross-Sectional Study in Goa, India

PubMed Central

Bhumika, N; Prabhu, GV; Ferreira, AM; Kulkarni, MK

2013-01-01

Background: Workplace safety regulations seek to mitigate noise-induced hearing loss (NIHL), conventionally associated with the shipbuilding industry. Despite this, are workers still predisposed to NIHL? Aims: To study the prevalence of NIHL among noise-exposed subjects in the shipbuilding industry in Goa and to compare it with that among the non-exposed population working in the same industry in relation to certain relevant factors. Subjects and Methods: This is a cross-sectional study in the shipbuilding industry, Goa This study examined 552 workers: 276 shipbuilders and 276 office staff, of similar age, duration of employment and socio-economic status working at a shipbuilding enterprise. An interviewer-administered questionnaire was followed by audiometry. Values were presented as percentages, Mean (SD) and odds ratio (OR) and its 95% confidence interval (CI) (Woolfe's method). Fisher's exact test and binary logistic regression were used. P value of < 0.05 was taken as significant. SPSS version 16 was used. Results: NIHL was found in 17 (6%) shipbuilders, while no office staff was detected to have this condition (OR = 37.29, 95% CI 22.42-62.18). The shipbuilders with NIHL were 52.5 years of age and had been employed for 30.4 years, on an average. None of the 17 cases of NIHL were found to be using earplugs consistently; 11 reported using them “sometimes” and six “never” used them. Conclusions: NIHL continues to affect shipbuilders, owing their non-compliance to workplace regulation. Health education is the need of the hour. PMID:23634321

Utility of gastric aspirates for diagnosing tuberculosis in children in a low prevalence area: predictors of positive cultures and significance of non-tuberculous mycobacteria.

PubMed

Kordy, Faisal; Richardson, Susan E; Stephens, Derek; Lam, Ray; Jamieson, Frances; Kitai, Ian

2015-01-01

In countries with low rates of tuberculosis (TB), yields of gastric aspirates (GAs) for Mycobacterium tuberculosis (MTB) culture are low. The significance of non-tuberculous mycobacteria (NTM) isolated from GA is uncertain. We reviewed clinical, microbiologic and radiologic data for children who underwent GA between 1999 and 2011 at Sick Kids, Toronto. Radiologic features of cases were compared with those of age matched controls. 785 GAs were obtained from 285 patients of whom 20 (7%) had positive MTB cultures: in 15 patients the GA was the only positive culture for MTB. Of 15 culture-positive patients who underwent exactly 3 GAs, MTB was isolated from the first lavage in 10 (67%), only from the second in 3 (20%) and only from the third in 2 (13%). On univariate analysis, miliary disease and intrathoracic lymphadenopathy were associated with a positive GA MTB culture. On multiple conditional logistic regression analysis, adenopathy remained significant (OR 10.2 [95% CI 2.0-51.4] p =0.005). Twelve patients had NTM isolated, most commonly M. avium complex: none had evidence of invasive NTM disease during a median duration of 12 months of follow-up. Causal pathogens different from the GA NTM culture were isolated from biopsies or bronchoalveolar lavage in 3. GAs continue to be important for TB diagnosis in children. Three GAs have a yield better than 1. Those with miliary or disseminated TB and intrathoracic lymphadenopathy have highest yields. NTM isolates from GA are likely unimportant and can be clinically misleading.

Hospital readmission and parent perceptions of their child's hospital discharge

PubMed Central

Berry, Jay G.; Ziniel, Sonja I.; Freeman, Linda; Kaplan, William; Antonelli, Richard; Gay, James; Coleman, Eric A.; Porter, Stephanie; Goldmann, Don

2013-01-01

Objective To describe parent perceptions of their child's hospital discharge and assess the relationship between these perceptions and hospital readmission. Design A prospective study of parents surveyed with questions adapted from the care transitions measure, an adult survey that assesses components of discharge care. Participant answers, scored on a 5-point Likert scale, were compared between children who did and did not experience a readmission using a Fisher's exact test and logistic regression that accounted for patient characteristics associated with increased readmission risk, including complex chronic condition and assistance with medical technology. Setting A tertiary-care children's hospital. Participants: A total of 348 parents surveyed following their child's hospital discharge between March and October 2010. Intervention None. Main Outcome Measure Unplanned readmission within 30 days of discharge. Results There were 28 children (8.1%) who experienced a readmission. Children had a lower readmission rate (4.4 vs. 11.3%, P = 0.004) and lower adjusted readmission likelihood [odds ratio 0.2 (95% confidence interval 0.1, 0.6)] when their parents strongly agreed (n = 206) with the statement, ‘I felt that my child was healthy enough to leave the hospital’ from the index admission. Parent perceptions relating to care management responsibilities, medications, written discharge plan, warning signs and symptoms to watch for and primary care follow-up were not associated with readmission risk in multivariate analysis. Conclusions Parent perception of their child's health at discharge was associated with the risk of a subsequent, unplanned readmission. Addressing concerns with this perception prior to hospital discharge may help mitigate readmission risk in children. PMID:23962990

A weighted exact test for mutually exclusive mutations in cancer

PubMed Central

Leiserson, Mark D.M.; Reyna, Matthew A.; Raphael, Benjamin J.

2016-01-01

Motivation: The somatic mutations in the pathways that drive cancer development tend to be mutually exclusive across tumors, providing a signal for distinguishing driver mutations from a larger number of random passenger mutations. This mutual exclusivity signal can be confounded by high and highly variable mutation rates across a cohort of samples. Current statistical tests for exclusivity that incorporate both per-gene and per-sample mutational frequencies are computationally expensive and have limited precision. Results: We formulate a weighted exact test for assessing the significance of mutual exclusivity in an arbitrary number of mutational events. Our test conditions on the number of samples with a mutation as well as per-event, per-sample mutation probabilities. We provide a recursive formula to compute P-values for the weighted test exactly as well as a highly accurate and efficient saddlepoint approximation of the test. We use our test to approximate a commonly used permutation test for exclusivity that conditions on per-event, per-sample mutation frequencies. However, our test is more efficient and it recovers more significant results than the permutation test. We use our Weighted Exclusivity Test (WExT) software to analyze hundreds of colorectal and endometrial samples from The Cancer Genome Atlas, which are two cancer types that often have extremely high mutation rates. On both cancer types, the weighted test identifies sets of mutually exclusive mutations in cancer genes with fewer false positives than earlier approaches. Availability and Implementation: See http://compbio.cs.brown.edu/projects/wext for software. Contact: braphael@cs.brown.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:27587696

Non-equilibrium steady states in the Klein-Gordon theory

NASA Astrophysics Data System (ADS)

Doyon, Benjamin; Lucas, Andrew; Schalm, Koenraad; Bhaseen, M. J.

2015-03-01

We construct non-equilibrium steady states in the Klein-Gordon theory in arbitrary space dimension d following a local quench. We consider the approach where two independently thermalized semi-infinite systems, with temperatures {{T}L} and {{T}R}, are connected along a d-1-dimensional hypersurface. A current-carrying steady state, described by thermally distributed modes with temperatures {{T}L} and {{T}R} for left and right-moving modes, respectively, emerges at late times. The non-equilibrium density matrix is the exponential of a non-local conserved charge. We obtain exact results for the average energy current and the complete distribution of energy current fluctuations. The latter shows that the long-time energy transfer can be described by a continuum of independent Poisson processes, for which we provide the exact weights. We further describe the full time evolution of local observables following the quench. Averages of generic local observables, including the stress-energy tensor, approach the steady state with a power-law in time, where the exponent depends on the initial conditions at the connection hypersurface. We describe boundary conditions and special operators for which the steady state is reached instantaneously on the connection hypersurface. A semiclassical analysis of freely propagating modes yields the average energy current at large distances and late times. We conclude by comparing and contrasting our findings with results for interacting theories and provide an estimate for the timescale governing the crossover to hydrodynamics. As a modification of our Klein-Gordon analysis we also include exact results for free Dirac fermions.

Leavers, Movers, and Stayers: The Role of Workplace Conditions in Teacher Mobility Decisions

ERIC Educational Resources Information Center

Kukla-Acevedo, Sharon

2009-01-01

The author explored whether 3 workplace conditions were related to teacher mobility decisions. The modeling strategy incorporated a series of binomial and multinomial logistic models to estimate the effects of administrative support, classroom control, and behavioral climate on teachers' decisions to quit teaching or switch schools. The results…

Combination of a Stresor-Response Model with a Conditional Probability Anaylsis Approach to Develop Candidate Criteria from Empirical Data

EPA Science Inventory

We show that a conditional probability analysis that utilizes a stressor-response model based on a logistic regression provides a useful approach for developing candidate water quality criterai from empirical data. The critical step in this approach is transforming the response ...

Female sex workers use power over their day-to-day lives to meet the condition of a conditional cash transfer intervention to incentivize safe sex.

PubMed

Cooper, Jan E; Dow, William H; de Walque, Damien; Keller, Ann C; McCoy, Sandra I; Fernald, Lia C H; Balampama, Marianna P; Kalolella, Admirabilis; Packel, Laura J; Wechsberg, Wendee M; Ozer, Emily J

2017-05-01

Female Sex Workers are a core population in the HIV epidemic, and interventions such as conditional cash transfers (CCTs), effective in other health domains, are a promising new approach to reduce the spread of HIV. Here we investigate how a population of Tanzanian female sex workers, though constrained in many ways, experience and use their power in the context of a CCT intervention that incentivizes safe sex. We analyzed 20 qualitative in-depth interviews with female sex workers enrolled in a randomized-controlled CCT program, the RESPECT II pilot, and found that while such women have limited choices, they do have substantial power over their work logistics that they leveraged to meet the conditions of the CCT and receive the cash award. It was through these decisions over work logistics, such as reducing the number of workdays and clients, that the CCT intervention had its greatest impact on modifying female sex workers' behavior. Copyright © 2017. Published by Elsevier Ltd.

The association of corporate work environment factors, health risks, and medical conditions with presenteeism among Australian employees.

PubMed

Musich, Shirley; Hook, Dan; Baaner, Stephanie; Spooner, Michelle; Edington, Dee W

2006-01-01

To investigate the impact of selected corporate environment factors, health risks, and medical conditions on job performance using a self-reported measure of presenteeism. A cross-sectional survey utilizing health risk appraisal (HRA) data merging presenteeism with corporate environment factors, health risks, and medical conditions. Approximately 8000 employees across ten diverse Australian corporations. Employees (N = 1523; participation rate, 19%) who completed an HRA questionnaire. Self-reported HRA data were used to test associations of defined adverse corporate environment factors with presenteeism. Stepwise multivariate logistic regression modeling assessed the relative associations of corporate environment factors, health risks, and medical conditions with increased odds of any presenteeism. Increased presenteeism was significantly associated with poor working conditions, ineffective management/leadership, and work/life imbalance (adjusting for age, gender, health risks, and medical conditions). In multivariate logistic regression models, work/life imbalance, poor working conditions, life dissatisfaction, high stress, back pain, allergies, and younger age were significantly associated with presenteeism. Although the study has some limitations, including a possible response bias caused by the relatively low participation rate across the corporations, the study does demonstrate significant associations between corporate environment factors, health risks, and medical conditions and self-reported presenteeism. The study provides initial evidence that health management programming may benefit on-the-job productivity outcomes if expanded to include interventions targeting work environments.

Quantum lattice representations for vector solitons in external potentials

NASA Astrophysics Data System (ADS)

Vahala, George; Vahala, Linda; Yepez, Jeffrey

2006-03-01

A quantum lattice algorithm is developed to examine the effect of an external potential well on exactly integrable vector Manakov solitons. It is found that the exact solutions to the coupled nonlinear Schrodinger equations act like quasi-solitons in weak potentials, leading to mode-locking, trapping and untrapping. Stronger potential wells will lead to the emission of radiation modes from the quasi-soliton initial conditions. If the external potential is applied to that particular mode polarization, then the radiation will be trapped within the potential well. The algorithm developed leads to a finite difference scheme that is unconditionally stable. The Manakov system in an external potential is very closely related to the Gross-Pitaevskii equation for the ground state wave functions of a coupled BEC state at T=0 K.

New envelope solitons for Gerdjikov-Ivanov model in nonlinear fiber optics

NASA Astrophysics Data System (ADS)

Triki, Houria; Alqahtani, Rubayyi T.; Zhou, Qin; Biswas, Anjan

2017-11-01

Exact soliton solutions in a class of derivative nonlinear Schrödinger equations including a pure quintic nonlinearity are investigated. By means of the coupled amplitude-phase formulation, we derive a nonlinear differential equation describing the evolution of the wave amplitude in the non-Kerr quintic media. The resulting amplitude equation is then solved to get exact analytical chirped bright, kink, antikink, and singular soliton solutions for the model. It is also shown that the nonlinear chirp associated with these solitons is crucially dependent on the wave intensity and related to self-steepening and group velocity dispersion parameters. Parametric conditions on physical parameters for the existence of chirped solitons are also presented. These localized structures exist due to a balance among quintic nonlinearity, group velocity dispersion, and self-steepening effects.

Automation: Decision Aid or Decision Maker?

NASA Technical Reports Server (NTRS)

Skitka, Linda J.

1998-01-01

This study clarified that automation bias is something unique to automated decision making contexts, and is not the result of a general tendency toward complacency. By comparing performance on exactly the same events on the same tasks with and without an automated decision aid, we were able to determine that at least the omission error part of automation bias is due to the unique context created by having an automated decision aid, and is not a phenomena that would occur even if people were not in an automated context. However, this study also revealed that having an automated decision aid did lead to modestly improved performance across all non-error events. Participants in the non- automated condition responded with 83.68% accuracy, whereas participants in the automated condition responded with 88.67% accuracy, across all events. Automated decision aids clearly led to better overall performance when they were accurate. People performed almost exactly at the level of reliability as the automation (which across events was 88% reliable). However, also clear, is that the presence of less than 100% accurate automated decision aids creates a context in which new kinds of errors in decision making can occur. Participants in the non-automated condition responded with 97% accuracy on the six "error" events, whereas participants in the automated condition had only a 65% accuracy rate when confronted with those same six events. In short, the presence of an AMA can lead to vigilance decrements that can lead to errors in decision making.

A general probabilistic model for group independent component analysis and its estimation methods

PubMed Central

Guo, Ying

2012-01-01

SUMMARY Independent component analysis (ICA) has become an important tool for analyzing data from functional magnetic resonance imaging (fMRI) studies. ICA has been successfully applied to single-subject fMRI data. The extension of ICA to group inferences in neuroimaging studies, however, is challenging due to the unavailability of a pre-specified group design matrix and the uncertainty in between-subjects variability in fMRI data. We present a general probabilistic ICA (PICA) model that can accommodate varying group structures of multi-subject spatio-temporal processes. An advantage of the proposed model is that it can flexibly model various types of group structures in different underlying neural source signals and under different experimental conditions in fMRI studies. A maximum likelihood method is used for estimating this general group ICA model. We propose two EM algorithms to obtain the ML estimates. The first method is an exact EM algorithm which provides an exact E-step and an explicit noniterative M-step. The second method is an variational approximation EM algorithm which is computationally more efficient than the exact EM. In simulation studies, we first compare the performance of the proposed general group PICA model and the existing probabilistic group ICA approach. We then compare the two proposed EM algorithms and show the variational approximation EM achieves comparable accuracy to the exact EM with significantly less computation time. An fMRI data example is used to illustrate application of the proposed methods. PMID:21517789

Ambient air monitoring of Beijing MSW logistics facilities in 2006.

PubMed

Li, Chun-Ping; Li, Guo-Xue; Luo, Yi-Ming; Li, Yan-Fu

2008-11-01

In China, "green" integrated waste management methods are being implemented in response to environmental concerns. We measured the air quality at several municipal solid waste (MSW) sites to provide information for the incorporation of logistics facilities within the current integrated waste management system. We monitored ambient air quality at eight MSW collecting stations, five transfer stations, one composting plant, and five disposal sites in Beijing during April 2006. Composite air samples were collected and analyzed for levels of odor, ammonia (NH3), hydrogen sulfide (H2S), total suspended particles (TSPs), carbon monoxide (CO), sulfur dioxide (SO2), and nitrogen dioxide (NO2). The results of our atmospheric monitoring demonstrated that although CO and SO2 were within acceptable emission levels according to ambient standards, levels of H2S, TSP, and NO2 in the ambient air at most MSW logistics facilities far exceeded ambient limits established for China. The primary pollutants in the ambient air at Beijing MSW logistics facilities were H2S, TSPs, NO2, and odor. To improve current environmental conditions at MSW logistics facilities, the Chinese government encourages the separation of biogenic waste from MSW at the source.

Complementary nonparametric analysis of covariance for logistic regression in a randomized clinical trial setting.

PubMed

Tangen, C M; Koch, G G

1999-03-01

In the randomized clinical trial setting, controlling for covariates is expected to produce variance reduction for the treatment parameter estimate and to adjust for random imbalances of covariates between the treatment groups. However, for the logistic regression model, variance reduction is not obviously obtained. This can lead to concerns about the assumptions of the logistic model. We introduce a complementary nonparametric method for covariate adjustment. It provides results that are usually compatible with expectations for analysis of covariance. The only assumptions required are based on randomization and sampling arguments. The resulting treatment parameter is a (unconditional) population average log-odds ratio that has been adjusted for random imbalance of covariates. Data from a randomized clinical trial are used to compare results from the traditional maximum likelihood logistic method with those from the nonparametric logistic method. We examine treatment parameter estimates, corresponding standard errors, and significance levels in models with and without covariate adjustment. In addition, we discuss differences between unconditional population average treatment parameters and conditional subpopulation average treatment parameters. Additional features of the nonparametric method, including stratified (multicenter) and multivariate (multivisit) analyses, are illustrated. Extensions of this methodology to the proportional odds model are also made.

A deeper look at two concepts of measuring gene-gene interactions: logistic regression and interaction information revisited.

PubMed

Mielniczuk, Jan; Teisseyre, Paweł

2018-03-01

Detection of gene-gene interactions is one of the most important challenges in genome-wide case-control studies. Besides traditional logistic regression analysis, recently the entropy-based methods attracted a significant attention. Among entropy-based methods, interaction information is one of the most promising measures having many desirable properties. Although both logistic regression and interaction information have been used in several genome-wide association studies, the relationship between them has not been thoroughly investigated theoretically. The present paper attempts to fill this gap. We show that although certain connections between the two methods exist, in general they refer two different concepts of dependence and looking for interactions in those two senses leads to different approaches to interaction detection. We introduce ordering between interaction measures and specify conditions for independent and dependent genes under which interaction information is more discriminative measure than logistic regression. Moreover, we show that for so-called perfect distributions those measures are equivalent. The numerical experiments illustrate the theoretical findings indicating that interaction information and its modified version are more universal tools for detecting various types of interaction than logistic regression and linkage disequilibrium measures. © 2017 WILEY PERIODICALS, INC.

Some Considerations on the Fundamentals of Chemical Kinetics: Steady State, Quasi-Equilibrium, and Transition State Theory

ERIC Educational Resources Information Center

Perez-Benito, Joaquin F.

2017-01-01

The elementary reaction sequence A ? I ? Products is the simplest mechanism for which the steady-state and quasi-equilibrium kinetic approximations can be applied. The exact integrated solutions for this chemical system allow inferring the conditions that must fulfill the rate constants for the different approximations to hold. A graphical…

Young Children Sympathize Less in Response to Unjustified Emotional Distress

ERIC Educational Resources Information Center

Hepach, Robert; Vaish, Amrisha; Tomasello, Michael

2013-01-01

Three-year-old children saw an adult displaying the exact same distress in 3 different conditions: (a) the adult's distress was appropriate to a genuine harm, (b) the adult's distress was an overreaction to a minor inconvenience, and (c) there was no apparent cause for the adult's distress. Children who witnessed the adult being appropriately…

Quantum field between moving mirrors: A three dimensional example

NASA Technical Reports Server (NTRS)

Hacyan, S.; Jauregui, Roco; Villarreal, Carlos

1995-01-01

The scalar quantum field uniformly moving plates in three dimensional space is studied. Field equations for Dirichlet boundary conditions are solved exactly. Comparison of the resulting wavefunctions with their instantaneous static counterpart is performed via Bogolubov coefficients. Unlike the one dimensional problem, 'particle' creation as well as squeezing may occur. The time dependent Casimir energy is also evaluated.

[Fixation of patients during irradiation of the neurocranium and visceral cranium].

PubMed

Bohndorf, W; Richter, E

1983-12-01

Only few patients are able to exactly maintain during the irradiation a given position of the head without fixation. However, every movement of the head leads to a dose decrease up to 50% within the target volume. Today, fixation and reproducible field adjustment are the conditions of curative radiotherapy. The Würzburg model is presented.

Health-related productivity losses increase when the health condition is co-morbid with psychological distress: findings from a large cross-sectional sample of working Australians.

PubMed

Holden, Libby; Scuffham, Paul A; Hilton, Michael F; Ware, Robert S; Vecchio, Nerina; Whiteford, Harvey A

2011-05-31

The health condition of workers is known to impact on productivity outcomes. The relationship between health and productivity is of increasing interest amid the need to increase productivity to meet global financial challenges. Prevalence of psychological distress is also of growing concern in Australia with a two-fold increase in the prevalence of psychological distress in Australia from 1997-2005. We used the cross-sectional data set from the Australian Work Outcomes Research Cost-benefit (WORC) study to explore the impacts of health conditions with and without co-morbid psychological distress, compared to those with neither condition, in a sample of approximately 78,000 working Australians. The World Health Organisation Health and Performance Questionnaire was used which provided data on demographic characteristics, health condition and working conditions. Data were analysed using negative binomial logistic regression and multinomial logistic regression models for absenteeism and presenteeism respectively. For both absenteeism and presenteeism productivity measures there was a greater risk of productivity loss associated when health conditions were co-morbid with psychological distress. For some conditions this risk was much greater for those with co-morbid psychological distress compared to those without. Co-morbid psychological distress demonstrates an increased risk of productivity loss for a range of health conditions. These findings highlight the need for further research to determine whether co-morbid psychological distress potentially exacerbates lost productivity.

Optimization of lipids' ultrasonic extraction and production from Chlorella sp. using response-surface methodology.

PubMed

Hadrich, Bilel; Akremi, Ismahen; Dammak, Mouna; Barkallah, Mohamed; Fendri, Imen; Abdelkafi, Slim

2018-04-17

Three steps are very important in order to produce microalgal lipids: (1) controlling microalgae cultivation via experimental and modeling investigations, (2) optimizing culture conditions to maximize lipids production and to determine the fatty acid profile the most appropriate for biodiesel synthesis, and (3) optimizing the extraction of the lipids accumulated in the microalgal cells. Firstly, three kinetics models, namely logistic, logistic-with-lag and modified Gompertz, were tested to fit the experimental kinetics of the Chlorella sp. microalga culture established on standard conditions. Secondly, the response-surface methodology was used for two optimizations in this study. The first optimization was established for lipids production from Chlorella sp. culture under different culture conditions. In fact, different levels of nitrate concentrations, salinities and light intensities were applied to the culture medium in order to study their influences on lipids production and determine their fatty acid profile. The second optimization was concerned with the lipids extraction factors: ultrasonic's time and temperature, and chloroform-methanol solvent ratio. All models (logistic, logistic-with-lag and modified Gompertz) applied for the experimental kinetics of Chlorella sp. show a very interesting fitting quality. The logistic model was chosen to describe the Chlorella sp. kinetics, since it yielded the most important statistical criteria: coefficient of determination of the order of 94.36%; adjusted coefficient of determination equal to 93.79% and root mean square error reaching 3.685 cells · ml - 1 . Nitrate concentration and the two interactions involving the light intensity (Nitrate concentration × light intensity, and salinities × light intensity) showed a very significant influence on lipids production in the first optimization (p < 0.05). Yet, only the quadratic term of chloroform-methanol solvent ratio showed a significant influence on lipids extraction relative to the second step of optimization (p < 0.05). The two most abundant fatty acid methyl esters (≈72%) derived from the Chlorella sp. microalga cultured in the determined optimal conditions are: palmitic acid (C16:0) and oleic acid (C18:1) with the corresponding yields of 51.69% and 20.55% of total fatty acids, respectively. Only the nitrate deficiency and the high intensity of light can influence the microalgal lipids production. The corresponding fatty acid methyl esters composition is very suitable for biodiesel production. Lipids extraction is efficient only over long periods of time when using a solvent with a 2/1 chloroform/methanol ratio.

Multilocus lod scores in large pedigrees: combination of exact and approximate calculations.

PubMed

Tong, Liping; Thompson, Elizabeth

2008-01-01

To detect the positions of disease loci, lod scores are calculated at multiple chromosomal positions given trait and marker data on members of pedigrees. Exact lod score calculations are often impossible when the size of the pedigree and the number of markers are both large. In this case, a Markov Chain Monte Carlo (MCMC) approach provides an approximation. However, to provide accurate results, mixing performance is always a key issue in these MCMC methods. In this paper, we propose two methods to improve MCMC sampling and hence obtain more accurate lod score estimates in shorter computation time. The first improvement generalizes the block-Gibbs meiosis (M) sampler to multiple meiosis (MM) sampler in which multiple meioses are updated jointly, across all loci. The second one divides the computations on a large pedigree into several parts by conditioning on the haplotypes of some 'key' individuals. We perform exact calculations for the descendant parts where more data are often available, and combine this information with sampling of the hidden variables in the ancestral parts. Our approaches are expected to be most useful for data on a large pedigree with a lot of missing data. (c) 2007 S. Karger AG, Basel

Multilocus Lod Scores in Large Pedigrees: Combination of Exact and Approximate Calculations

PubMed Central

Tong, Liping; Thompson, Elizabeth

2007-01-01

To detect the positions of disease loci, lod scores are calculated at multiple chromosomal positions given trait and marker data on members of pedigrees. Exact lod score calculations are often impossible when the size of the pedigree and the number of markers are both large. In this case, a Markov Chain Monte Carlo (MCMC) approach provides an approximation. However, to provide accurate results, mixing performance is always a key issue in these MCMC methods. In this paper, we propose two methods to improve MCMC sampling and hence obtain more accurate lod score estimates in shorter computation time. The first improvement generalizes the block-Gibbs meiosis (M) sampler to multiple meiosis (MM) sampler in which multiple meioses are updated jointly, across all loci. The second one divides the computations on a large pedigree into several parts by conditioning on the haplotypes of some ‘key’ individuals. We perform exact calculations for the descendant parts where more data are often available, and combine this information with sampling of the hidden variables in the ancestral parts. Our approaches are expected to be most useful for data on a large pedigree with a lot of missing data. PMID:17934317

Immunodepletion Plasma Proteomics by TripleTOF 5600 and Orbitrap Elite/LTQ-Orbitrap Velos/Q Exactive Mass Spectrometers

PubMed Central

Patel, Bhavinkumar B.; Kelsen, Steven G.; Braverman, Alan; Swinton, Derrick J.; Gafken, Philip R.; Jones, Lisa A.; Lane, William S.; Neveu, John M.; Leung, Hon-Chiu E.; Shaffer, Scott A.; Leszyk, John D.; Stanley, Bruce A.; Fox, Todd E.; Stanley, Anne; Hall, Michael J.; Hampel, Heather; South, Christopher D.; de la Chapelle, Albert; Burt, Randall W.; Jones, David A.; Kopelovich, Levy; Yeung, Anthony T.

2013-01-01

Plasma proteomic experiments performed rapidly and economically using several of the latest high-resolution mass spectrometers were compared. Four quantitative hyperfractionated plasma proteomics experiments were analyzed in replicates by two AB SCIEX TripleTOF 5600 and three Thermo Scientific Orbitrap (Elite/LTQ-Orbitrap Velos/Q Exactive) instruments. Each experiment compared two iTRAQ isobaric-labeled immunodepleted plasma proteomes, provided as 30 labeled peptide fractions. 480 LC-MS/MS runs delivered >250 GB of data in two months. Several analysis algorithms were compared. At 1 % false discovery rate, the relative comparative findings concluded that the Thermo Scientific Q Exactive Mass Spectrometer resulted in the highest number of identified proteins and unique sequences with iTRAQ quantitation. The confidence of iTRAQ fold-change for each protein is dependent on the overall ion statistics (Mascot Protein Score) attainable by each instrument. The benchmarking also suggested how to further improve the mass spectrometry parameters and HPLC conditions. Our findings highlight the special challenges presented by the low abundance peptide ions of iTRAQ plasma proteome because the dynamic range of plasma protein abundance is uniquely high compared with cell lysates, necessitating high instrument sensitivity. PMID:24004147

Localized solutions of Lugiato-Lefever equations with focused pump.

PubMed

Cardoso, Wesley B; Salasnich, Luca; Malomed, Boris A

2017-12-04

Lugiato-Lefever (LL) equations in one and two dimensions (1D and 2D) accurately describe the dynamics of optical fields in pumped lossy cavities with the intrinsic Kerr nonlinearity. The external pump is usually assumed to be uniform, but it can be made tightly focused too-in particular, for building small pixels. We obtain solutions of the LL equations, with both the focusing and defocusing intrinsic nonlinearity, for 1D and 2D confined modes supported by the localized pump. In the 1D setting, we first develop a simple perturbation theory, based in the sech ansatz, in the case of weak pump and loss. Then, a family of exact analytical solutions for spatially confined modes is produced for the pump focused in the form of a delta-function, with a nonlinear loss (two-photon absorption) added to the LL model. Numerical findings demonstrate that these exact solutions are stable, both dynamically and structurally (the latter means that stable numerical solutions close to the exact ones are found when a specific condition, necessary for the existence of the analytical solution, does not hold). In 2D, vast families of stable confined modes are produced by means of a variational approximation and full numerical simulations.

Discrete Radon transform has an exact, fast inverse and generalizes to operations other than sums along lines

PubMed Central

Press, William H.

2006-01-01

Götz, Druckmüller, and, independently, Brady have defined a discrete Radon transform (DRT) that sums an image's pixel values along a set of aptly chosen discrete lines, complete in slope and intercept. The transform is fast, O(N2log N) for an N × N image; it uses only addition, not multiplication or interpolation, and it admits a fast, exact algorithm for the adjoint operation, namely backprojection. This paper shows that the transform additionally has a fast, exact (although iterative) inverse. The inverse reproduces to machine accuracy the pixel-by-pixel values of the original image from its DRT, without artifacts or a finite point-spread function. Fourier or fast Fourier transform methods are not used. The inverse can also be calculated from sampled sinograms and is well conditioned in the presence of noise. Also introduced are generalizations of the DRT that combine pixel values along lines by operations other than addition. For example, there is a fast transform that calculates median values along all discrete lines and is able to detect linear features at low signal-to-noise ratios in the presence of pointlike clutter features of arbitrarily large amplitude. PMID:17159155

Discrete Radon transform has an exact, fast inverse and generalizes to operations other than sums along lines.

PubMed

Press, William H

2006-12-19

Götz, Druckmüller, and, independently, Brady have defined a discrete Radon transform (DRT) that sums an image's pixel values along a set of aptly chosen discrete lines, complete in slope and intercept. The transform is fast, O(N2log N) for an N x N image; it uses only addition, not multiplication or interpolation, and it admits a fast, exact algorithm for the adjoint operation, namely backprojection. This paper shows that the transform additionally has a fast, exact (although iterative) inverse. The inverse reproduces to machine accuracy the pixel-by-pixel values of the original image from its DRT, without artifacts or a finite point-spread function. Fourier or fast Fourier transform methods are not used. The inverse can also be calculated from sampled sinograms and is well conditioned in the presence of noise. Also introduced are generalizations of the DRT that combine pixel values along lines by operations other than addition. For example, there is a fast transform that calculates median values along all discrete lines and is able to detect linear features at low signal-to-noise ratios in the presence of pointlike clutter features of arbitrarily large amplitude.

U.S. Emergency Department Admissions for Nontraumatic Dental Conditions for Individuals with Intellectual and Developmental Disabilities

ERIC Educational Resources Information Center

Chi, Donald L.; Masterson, Erin E.; Wong, Jacqueline J.

2014-01-01

The authors hypothesized that individuals with intellectual and developmental disabilities (IDDs) are more likely to have an emergency department (ED) admission for nontraumatic dental conditions (NTDCs). The authors analyzed 2009 U.S. National Emergency Department Sample data and ran logistic regression models for children ages 3-17 years and…

Habituation and desensitization as methods for reducing fearful behavior in singly housed rhesus macaques.

PubMed

Clay, Andrea W; Bloomsmith, Mollie A; Marr, M Jackson; Maple, Terry L

2009-01-01

Operant conditioning using positive reinforcement techniques has been used extensively in the management of nonhuman primates in both zoological and laboratory settings. This research project was intended to test the usefulness of counter-conditioning techniques in reducing the fear-responses of singly housed male rhesus macaques living in the laboratory environment. A total of 18 male rhesus macaques (Macaca mulatta) were selected for this project and randomly assigned to one of three groups: a desensitization training group, a husbandry training group, or a control group. Behavioral data were collected before and after a 6 weeks training and/or habituation period during which the first two groups received a total of 125 min of positive reinforcement training (and also were assumed to undergo habituation to the environment) and the control group experienced only simple habituation to the environment. Based on a Wilcoxon Matched-Pairs Sign Test, we found that a significant proportion of animals exposed to desensitization training showed a reduction in the rate at which they engaged in cringing toward humans (exact significance=0.016, one-tailed, N-ties=6), cringing in general (exact significance=0.016, one-tailed, N-ties=6), and in stress-related behaviors (exact significance=0.016, one-tailed, N-ties=6). This was not the case for animals exposed to basic husbandry training or animals in the control group. A significant proportion of desensitization-exposed animals also showed a reduction in the duration of time spent cringing toward humans (exact significance=0.016, one-tailed, N-ties=6), but not in cringing behaviors in general or in stress-related behaviors. There were not a significant proportion of animals in either the husbandry training group or the control group that showed a decrease in duration of these behaviors. Results of this study could enhance both laboratory animal welfare and laboratory animal research, and could be a first step in developing techniques for reducing fearful behavior in rhesus monkeys in the laboratory environment. (c) 2008 Wiley-Liss, Inc.

Non-linear analysis of wave progagation using transform methods and plates and shells using integral equations

NASA Astrophysics Data System (ADS)

Pipkins, Daniel Scott

Two diverse topics of relevance in modern computational mechanics are treated. The first involves the modeling of linear and non-linear wave propagation in flexible, lattice structures. The technique used combines the Laplace Transform with the Finite Element Method (FEM). The procedure is to transform the governing differential equations and boundary conditions into the transform domain where the FEM formulation is carried out. For linear problems, the transformed differential equations can be solved exactly, hence the method is exact. As a result, each member of the lattice structure is modeled using only one element. In the non-linear problem, the method is no longer exact. The approximation introduced is a spatial discretization of the transformed non-linear terms. The non-linear terms are represented in the transform domain by making use of the complex convolution theorem. A weak formulation of the resulting transformed non-linear equations yields a set of element level matrix equations. The trial and test functions used in the weak formulation correspond to the exact solution of the linear part of the transformed governing differential equation. Numerical results are presented for both linear and non-linear systems. The linear systems modeled are longitudinal and torsional rods and Bernoulli-Euler and Timoshenko beams. For non-linear systems, a viscoelastic rod and Von Karman type beam are modeled. The second topic is the analysis of plates and shallow shells under-going finite deflections by the Field/Boundary Element Method. Numerical results are presented for two plate problems. The first is the bifurcation problem associated with a square plate having free boundaries which is loaded by four, self equilibrating corner forces. The results are compared to two existing numerical solutions of the problem which differ substantially.

Inflow/Outflow Boundary Conditions with Application to FUN3D

NASA Technical Reports Server (NTRS)

Carlson, Jan-Renee

2011-01-01

Several boundary conditions that allow subsonic and supersonic flow into and out of the computational domain are discussed. These boundary conditions are demonstrated in the FUN3D computational fluid dynamics (CFD) code which solves the three-dimensional Navier-Stokes equations on unstructured computational meshes. The boundary conditions are enforced through determination of the flux contribution at the boundary to the solution residual. The boundary conditions are implemented in an implicit form where the Jacobian contribution of the boundary condition is included and is exact. All of the flows are governed by the calorically perfect gas thermodynamic equations. Three problems are used to assess these boundary conditions. Solution residual convergence to machine zero precision occurred for all cases. The converged solution boundary state is compared with the requested boundary state for several levels of mesh densities. The boundary values converged to the requested boundary condition with approximately second-order accuracy for all of the cases.

Lubrication of rigid ellipsida solids

NASA Technical Reports Server (NTRS)

Hamrock, B. J.; Dowson, D.

1982-01-01

The influence of geometry on the isothermal hydrodynamic film separating two rigid solids was investigated. The minimum film thickness is derived for fully flooded conjunctions by using the Reynolds boundary conditions. It was found that the minimum film thickness had the same speed, viscosity, and load dependence as Kapitza' classical solution. However, the incorporation of Reynolds boundary conditions resulted in an additional geometry effect. Solutions using the parabolic film approximation are compared by using the exact expression for the film in the analysis. Contour plots are known that indicate in detail the pressure developed between the solids.

Microwave imaging by three-dimensional Born linearization of electromagnetic scattering

NASA Astrophysics Data System (ADS)

Caorsi, S.; Gragnani, G. L.; Pastorino, M.

1990-11-01

An approach to microwave imaging is proposed that uses a three-dimensional vectorial form of the Born approximation to linearize the equation of electromagnetic scattering. The inverse scattering problem is numerically solved for three-dimensional geometries by means of the moment method. A pseudoinversion algorithm is adopted to overcome ill conditioning. Results show that the method is well suited for qualitative imaging purposes, while its capability for exactly reconstructing the complex dielectric permittivity is affected by the limitations inherent in the Born approximation and in ill conditioning.

Radiation Boundary Conditions for Maxwell’s Equations: A Review of Accurate Time-Domain Formulations

DTIC Science & Technology

2007-01-01

conditions have only been constructed for the case ne = 0. Lastly we note that exact reflection formulas have recently been derived by Diaz and Joly [20, 21...SIAM J. Numer. Anal. 41 (2003), 287–305. 6. E. Bécache and P. Joly , On the analysis of Bérenger’s perfectly matched layers for Maxwell’s equations...Computational Wave Propagation (M. Ainsworth, P. Davies, D. Duncan, P. Martin , and B. Rynne, eds.), Springer-Verlag, 2003, pp. 43–82. 13. O. Bruno and D. Hoch

Anal Fissure

PubMed Central

Beaty, Jennifer Sam; Shashidharan, M.

2016-01-01

Anal fissure (fissure-in-ano) is a very common anorectal condition. The exact etiology of this condition is debated; however, there is a clear association with elevated internal anal sphincter pressures. Though hard bowel movements are implicated in fissure etiology, they are not universally present in patients with anal fissures. Half of all patients with fissures heal with nonoperative management such as high fiber diet, sitz baths, and pharmacological agents. When nonoperative management fails, surgical treatment with lateral internal sphincterotomy has a high success rate. In this chapter, we will review the symptoms, pathophysiology, and management of anal fissures. PMID:26929749

Path-integral representation for the relativistic particle propagators and BFV quantization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fradkin, E.S.; Gitman, D.M.

1991-11-15

The path-integral representations for the propagators of scalar and spinor fields in an external electromagnetic field are derived. The Hamiltonian form of such expressions can be interpreted in the sense of Batalin-Fradkin-Vilkovisky quantization of one-particle theory. The Lagrangian representation as derived allows one to extract in a natural way the expressions for the corresponding gauge-invariant (reparametrization- and supergauge-invariant) actions for pointlike scalar and spinning particles. At the same time, the measure and ranges of integrations, admissible gauge conditions, and boundary conditions can be exactly established.

Condition for confinement in non-Abelian gauge theories

NASA Astrophysics Data System (ADS)

Chaichian, Masud; Frasca, Marco

2018-06-01

We show that a criterion for confinement, based on the BRST invariance, holds in four dimensions, by solving a non-Abelian gauge theory with a set of exact solutions. The confinement condition we consider was obtained by Kugo and Ojima some decades ago. The current understanding of gauge theories permits us to apply the techniques straightforwardly for checking the validity of this criterion. In this way, we are able to show that the non-Abelian gauge theory is confining and that confinement is rooted in the BRST invariance and asymptotic freedom.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bian, Lei, E-mail: bianlei@pku.edu.cn; Pang, Gang, E-mail: 1517191281@qq.com; Tang, Shaoqiang, E-mail: maotang@pku.edu.cn

For the Schrödinger–Poisson system, we propose an ALmost EXact (ALEX) boundary condition to treat accurately the numerical boundaries. Being local in both space and time, the ALEX boundary conditions are demonstrated to be effective in suppressing spurious numerical reflections. Together with the Crank–Nicolson scheme, we simulate a resonant tunneling diode. The algorithm produces numerical results in excellent agreement with those in Mennemann et al. [1], yet at a much reduced complexity. Primary peaks in wave function profile appear as a consequence of quantum resonance, and should be considered in selecting the cut-off wave number for numerical simulations.

Strip Yield Model Numerical Application to Different Geometries and Loading Conditions

NASA Technical Reports Server (NTRS)

Hatamleh, Omar; Forman, Royce; Shivakumar, Venkataraman; Lyons, Jed

2006-01-01

A new numerical method based on the strip-yield analysis approach was developed for calculating the Crack Tip Opening Displacement (CTOD). This approach can be applied for different crack configurations having infinite and finite geometries, and arbitrary applied loading conditions. The new technique adapts the boundary element / dislocation density method to obtain crack-face opening displacements at any point on a crack, and succeeds by obtaining requisite values as a series of definite integrals, the functional parts of each being evaluated exactly in a closed form.

Satisfying positivity requirement in the Beyond Complex Langevin approach

NASA Astrophysics Data System (ADS)

Wyrzykowski, Adam; Ruba, Błażej Ruba

2018-03-01

The problem of finding a positive distribution, which corresponds to a given complex density, is studied. By the requirement that the moments of the positive distribution and of the complex density are equal, one can reduce the problem to solving the matching conditions. These conditions are a set of quadratic equations, thus Groebner basis method was used to find its solutions when it is restricted to a few lowest-order moments. For a Gaussian complex density, these approximate solutions are compared with the exact solution, that is known in this special case.

Elastic properties of rigid fiber-reinforced composites

NASA Astrophysics Data System (ADS)

Chen, J.; Thorpe, M. F.; Davis, L. C.

1995-05-01

We study the elastic properties of rigid fiber-reinforced composites with perfect bonding between fibers and matrix, and also with sliding boundary conditions. In the dilute region, there exists an exact analytical solution. Around the rigidity threshold we find the elastic moduli and Poisson's ratio by decomposing the deformation into a compression mode and a rotation mode. For perfect bonding, both modes are important, whereas only the compression mode is operative for sliding boundary conditions. We employ the digital-image-based method and a finite element analysis to perform computer simulations which confirm our analytical predictions.

A tunable few electron triple quantum dot

NASA Astrophysics Data System (ADS)

Gaudreau, L.; Kam, A.; Granger, G.; Studenikin, S. A.; Zawadzki, P.; Sachrajda, A. S.

2009-11-01

In this paper, we report on a tunable few electron lateral triple quantum dot design. The quantum dot potentials are arranged in series. The device is aimed at studies of triple quantum dot properties where knowing the exact number of electrons is important as well as quantum information applications involving electron spin qubits. We demonstrate tuning strategies for achieving required resonant conditions such as quadruple points where all three quantum dots are on resonance. We find that in such a device resonant conditions at specific configurations are accompanied by complex charge transfer behavior.

Incidence of and risk factors for postoperative regurgitation and vomiting in dogs: 244 cases (2000-2012).

PubMed

Davies, John A; Fransson, Boel A; Davis, Anastacia M; Gilbertsen, Aaron M; Gay, John M

2015-02-01

To determine the incidence of and risk factors for postoperative regurgitation and vomiting (PORV) in dogs. Retrospective cohort study. 244 client-owned dogs. Dogs referred for nonelective surgery in the first 3 months of 2000 and 2012 were included. Breed; sex; age; weight; body condition score; emergency status; food withholding status; history of vomiting or regurgitation; American Society of Anesthesiologists score; presence of diabetes or hypothyroidism; preoperative PCV and total solids concentration; anesthesia protocol; corticosteroid, opioid, neuromuscular blocking agent, and nitrous oxide usage; anesthesia time; surgery time; type of surgery; and occurrence of vomiting or regurgitation within 24 hours after recovery from anesthesia were recorded. Data were analyzed by means of the Fisher exact test, Wilcoxon rank sum test, and logistic regression. 30 of 244 (12.3%) dogs meeting study inclusion criteria developed PORV. There was no significant difference in the incidence of PORV between the 2000 (12/111 [10.8%]) and 2012 (18/133 [13.5%]) cohorts, although the incidence of regurgitation was higher in 2012. Univariate logistic regression identified the most significant risk factors as gastrointestinal surgery (OR, 11.15; 95% confidence interval [CI], 3.11 to 40.03), premedication without strong sedatives including either an α2-adrenoceptor agonist or acepromazine (OR, 5.36; 95% CI, 1.89 to 15.17), American Society of Anesthesiologists score of 4 (OR, 5.25; 95% CI, 1.05 to 26.15), history of vomiting or regurgitation (OR, 5.12; 95% CI, 1.83 to 14.31), emergency surgery (OR, 4.08; 95% CI, 1.29 to 12.90), neurologic surgery (OR, 3.18; 95% CI, 1.02 to 9.92), sevoflurane inhalation anesthesia (OR, 2.78; 95% CI, 1.25 to 6.13), and being sexually intact (OR, 2.37; 95% CI, 1.07 to 5.27). Multivariate analysis was not clinically useful owing to the low sensitivity and specificity of the model. Between 2000 and 2012, there was no change in the incidence of PORV for dogs undergoing neurologic, orthopedic, and soft tissue surgical procedures; however, the proportion of dogs that regurgitated increased significantly in 2012. Preoperative antiemetic prophylaxis should be considered in dogs undergoing gastrointestinal surgery and in those in which other risk factors are present.

Reliability estimation of a N- M-cold-standby redundancy system in a multicomponent stress-strength model with generalized half-logistic distribution

NASA Astrophysics Data System (ADS)

Liu, Yiming; Shi, Yimin; Bai, Xuchao; Zhan, Pei

2018-01-01

In this paper, we study the estimation for the reliability of a multicomponent system, named N- M-cold-standby redundancy system, based on progressive Type-II censoring sample. In the system, there are N subsystems consisting of M statistically independent distributed strength components, and only one of these subsystems works under the impact of stresses at a time and the others remain as standbys. Whenever the working subsystem fails, one from the standbys takes its place. The system fails when the entire subsystems fail. It is supposed that the underlying distributions of random strength and stress both belong to the generalized half-logistic distribution with different shape parameter. The reliability of the system is estimated by using both classical and Bayesian statistical inference. Uniformly minimum variance unbiased estimator and maximum likelihood estimator for the reliability of the system are derived. Under squared error loss function, the exact expression of the Bayes estimator for the reliability of the system is developed by using the Gauss hypergeometric function. The asymptotic confidence interval and corresponding coverage probabilities are derived based on both the Fisher and the observed information matrices. The approximate highest probability density credible interval is constructed by using Monte Carlo method. Monte Carlo simulations are performed to compare the performances of the proposed reliability estimators. A real data set is also analyzed for an illustration of the findings.

Landscape Analysis of Global Health Tracks in United States Pediatric Residencies: Moving Toward Standards.

PubMed

Watts, Jennifer; Russ, Christiana; St Clair, Nicole E; Uwemedimo, Omolara Thomas

2018-03-28

The number of pediatric Global Health (GH) tracks has more than doubled in less than 10 years. The goal of this study was to describe the characteristics of the pediatric GH tracks to identify commonalities and differences in track structure, funding, and education. In addition, we also identified demographic, institutional, and residency-related factors that were significantly associated with educational offerings and logistical challenges. A cross-sectional survey was electronically administered to pediatric residency programs with GH tracks. Statistical analyses included frequencies to describe GH track characteristics. Fisher's exact tests were used to identify bivariate associations between track structure and funding with educational offerings and logistical challenges. Leaders of 32 pediatric GH tracks (67%) completed the survey. The majority of GH tracks were completed within the 3 years of residency (94%) and identified a GH track director (100%); however, tracks varied in size, enrollment methods, domestic and international partnerships, funding, and evaluations. Dedicated faculty time and GH track budget amounts were associated with more robust infrastructure pertaining to resident international electives, including funding and mentorship. Many tracks did not meet American Academy of Pediatrics recommended standards for clinical international rotations. Despite the presence of multiple similarities among pediatric GH tracks, there are large variations in track structure, education, and funding. The results from this study support the proposal of a formal definition and minimum standards for a GH track, which may provide a framework for quality, consistency, and comparison of GH tracks. Copyright © 2018. Published by Elsevier Inc.

Magnetic Resonance Imaging Findings Predict the Recurrence of Chronic Subdural Hematoma

PubMed Central

GOTO, Haruo; ISHIKAWA, Osamu; NOMURA, Masashi; TANAKA, Kentaro; NOMURA, Seiji; MAEDA, Keiichiro

2015-01-01

The exact predictive factors for postoperative recurrence of chronic subdural hematoma (CSDH) are still unknown. Based on the preoperative magnetic resonance imaging (MRI), low recurrence rate of T1-hyperintensity hematoma was previously reported. We investigated the other types of radiological findings which are related to the recurrence rate of CSDH in large number of patients analyzed by multivariate logistic regression model. Preoperative MRI and postoperative computed tomography (CT) were performed and the influence of the preoperative use of antiplatelet or anticoagulant drugs was also studied. The overall recurrence rate was 9.3% (47 of 505 hematomas). The MRI T1-iso/hypointensity group showed a significantly higher recurrence rate (18.2%, 29 of 159) compared to the other groups (5.2%, 18 of 346; p < 0.001). Multivariate logistic regression analysis showed T1 classification was the solo significant prognostic predictor among various factors such as bilateral hematoma, antiplatelet or anticoagulant drug usage, residual hematoma on postoperative CT, and MRI classification (p < 0.001): adjusted odds ratio for the recurrence in T1-iso/hypointensity group relative to the T1-hyperintensity group was 5.58 [95% confidence interval (CI), 2.09–14.86] (p = 0.001). Postoperative residual hematoma and antiplatelet or anticoagulant drug usage did not increase the recurrence risk. The preoperative MRI findings, especially T1WI findings, have predictive value for postoperative recurrence of CSDH and the T1-iso/hypointensity group can be assumed to be a high recurrence risk group. PMID:25746312

Epidemiological characteristics and deaths of premature infants in a referral hospital for high-risk pregnancies

PubMed Central

de Freitas, Brunnella Alcantara Chagas; Sant'Ana, Luciana Ferreira da Rocha; Longo, Giana Zarbato; Siqueira-Batista, Rodrigo; Priore, Silvia Eloiza; Franceschin, Sylvia do Carmo Castro

2012-01-01

Objective To analyze the process of care provided to premature infants in a neonatal intensive care unit and the factors associated with their mortality. Methods Cross-sectional retrospective study of premature infants in an intensive care unit between 2008 and 2010. The characteristics of the mothers and premature infants were described, and a bivariate analysis was performed on the following characteristics: the study period and the "death" outcome (hospital, neonatal and early) using Pearson's chi-square test, Fisher's exact test or a chi-square test for linear trends. Bivariate and multivariable logistic regression analyses were performed using a stepwise backward logistic regression method between the variables with p<0.20 and the "death" outcome. A p value <0.05 was considered to be significant. Results In total, 293 preterm infants were studied. Increased access to complementary tests (transfontanellar ultrasound and Doppler echocardiogram) and breastfeeding rates were indicators of improving care. Mortality was concentrated in the neonatal period, especially in the early neonatal period, and was associated with extreme prematurity, small size for gestational age and an Apgar score <7 at 5 minutes after birth. The late-onset sepsis was also associated with a greater chance of neonatal death, and antenatal corticosteroids were protective against neonatal and early deaths. Conclusions Although these results are comparable to previous findings regarding mortality among premature infants in Brazil, the study emphasizes the need to implement strategies that promote breastfeeding and reduce neonatal mortality and its early component. PMID:23917938

Fibrinogen: cardiometabolic risk marker in obese or overweight children and adolescents.

PubMed

Azevedo, Waldeneide F; Cantalice, Anajás S C; Gonzaga, Nathalia C; Simões, Mônica O da S; Guimarães, Anna Larissa V; Carvalho, Danielle F de; Medeiros, Carla Campos Muniz

2015-01-01

To determine the prevalence of increased serum fibrinogen levels and its association with cardiometabolic risk factors in overweight or obese children and adolescents. Cross-sectional study with 138 children and adolescents (overweight or obese) followed at a reference outpatient clinic of the public health care network. Fibrinogen concentration was divided into quartiles, and values above or equal to the third quartile were considered high. The association between high fibrinogen values and cardiometabolic risk factors was assessed using Pearson's chi-squared test or Fisher's exact test, as necessary. Logistic regression was used to adjust variables predictive of fibrinogen levels. Analyses were performed using SPSS version 22.0 and SAS software, considering a confidence interval of 95%. Serum fibrinogen levels were elevated in 28.3% of individuals, showing association with the presence of high CRP (p=0.003, PR: 2.41, 95% CI: 1.30-4.46) and the presence of four or more risk factors (p=0.042; PR: 1.78, 95% CI: 1.00-3.17). After a logistic regression, only elevated CRP remained associated with altered fibrinogen levels (p=0.024; PR: 1.32; 95% CI: 1.09-5.25). Increased fibrinogen was prevalent in the study population and was associated with ultrasensitive C-reactive protein and the presence of four or more cardiovascular risk factors; it should be included in the assessment of individuals at risk. Copyright © 2015 Sociedade Brasileira de Pediatria. Published by Elsevier Editora Ltda. All rights reserved.

On the accurate long-time solution of the wave equation in exterior domains: Asymptotic expansions and corrected boundary conditions

NASA Technical Reports Server (NTRS)

Hagstrom, Thomas; Hariharan, S. I.; Maccamy, R. C.

1993-01-01

We consider the solution of scattering problems for the wave equation using approximate boundary conditions at artificial boundaries. These conditions are explicitly viewed as approximations to an exact boundary condition satisfied by the solution on the unbounded domain. We study the short and long term behavior of the error. It is provided that, in two space dimensions, no local in time, constant coefficient boundary operator can lead to accurate results uniformly in time for the class of problems we consider. A variable coefficient operator is developed which attains better accuracy (uniformly in time) than is possible with constant coefficient approximations. The theory is illustrated by numerical examples. We also analyze the proposed boundary conditions using energy methods, leading to asymptotically correct error bounds.

Discrete transparent boundary conditions for the mixed KDV-BBM equation

NASA Astrophysics Data System (ADS)

Besse, Christophe; Noble, Pascal; Sanchez, David

2017-09-01

In this paper, we consider artificial boundary conditions for the linearized mixed Korteweg-de Vries (KDV) and Benjamin-Bona-Mahoney (BBM) equation which models water waves in the small amplitude, large wavelength regime. Continuous (respectively discrete) artificial boundary conditions involve non local operators in time which in turn requires to compute time convolutions and invert the Laplace transform of an analytic function (respectively the Z-transform of an holomorphic function). In this paper, we propose a new, stable and fairly general strategy to carry out this crucial step in the design of transparent boundary conditions. For large time simulations, we also introduce a methodology based on the asymptotic expansion of coefficients involved in exact direct transparent boundary conditions. We illustrate the accuracy of our methods for Gaussian and wave packets initial data.

Testing the non-unity of rate ratio under inverse sampling.

PubMed

Tang, Man-Lai; Liao, Yi Jie; Ng, Hong Keung Tony; Chan, Ping Shing

2007-08-01

Inverse sampling is considered to be a more appropriate sampling scheme than the usual binomial sampling scheme when subjects arrive sequentially, when the underlying response of interest is acute, and when maximum likelihood estimators of some epidemiologic indices are undefined. In this article, we study various statistics for testing non-unity rate ratios in case-control studies under inverse sampling. These include the Wald, unconditional score, likelihood ratio and conditional score statistics. Three methods (the asymptotic, conditional exact, and Mid-P methods) are adopted for P-value calculation. We evaluate the performance of different combinations of test statistics and P-value calculation methods in terms of their empirical sizes and powers via Monte Carlo simulation. In general, asymptotic score and conditional score tests are preferable for their actual type I error rates are well controlled around the pre-chosen nominal level, and their powers are comparatively the largest. The exact version of Wald test is recommended if one wants to control the actual type I error rate at or below the pre-chosen nominal level. If larger power is expected and fluctuation of sizes around the pre-chosen nominal level are allowed, then the Mid-P version of Wald test is a desirable alternative. We illustrate the methodologies with a real example from a heart disease study. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Semiparametric time varying coefficient model for matched case-crossover studies.

PubMed

Ortega-Villa, Ana Maria; Kim, Inyoung; Kim, H

2017-03-15

In matched case-crossover studies, it is generally accepted that the covariates on which a case and associated controls are matched cannot exert a confounding effect on independent predictors included in the conditional logistic regression model. This is because any stratum effect is removed by the conditioning on the fixed number of sets of the case and controls in the stratum. Hence, the conditional logistic regression model is not able to detect any effects associated with the matching covariates by stratum. However, some matching covariates such as time often play an important role as an effect modification leading to incorrect statistical estimation and prediction. Therefore, we propose three approaches to evaluate effect modification by time. The first is a parametric approach, the second is a semiparametric penalized approach, and the third is a semiparametric Bayesian approach. Our parametric approach is a two-stage method, which uses conditional logistic regression in the first stage and then estimates polynomial regression in the second stage. Our semiparametric penalized and Bayesian approaches are one-stage approaches developed by using regression splines. Our semiparametric one stage approach allows us to not only detect the parametric relationship between the predictor and binary outcomes, but also evaluate nonparametric relationships between the predictor and time. We demonstrate the advantage of our semiparametric one-stage approaches using both a simulation study and an epidemiological example of a 1-4 bi-directional case-crossover study of childhood aseptic meningitis with drinking water turbidity. We also provide statistical inference for the semiparametric Bayesian approach using Bayes Factors. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Conditional entropy in variation-adjusted windows detects selection signatures associated with expression quantitative trait loci (eQTLs)

PubMed Central

2015-01-01

Background Over the past 50,000 years, shifts in human-environmental or human-human interactions shaped genetic differences within and among human populations, including variants under positive selection. Shaped by environmental factors, such variants influence the genetics of modern health, disease, and treatment outcome. Because evolutionary processes tend to act on gene regulation, we test whether regulatory variants are under positive selection. We introduce a new approach to enhance detection of genetic markers undergoing positive selection, using conditional entropy to capture recent local selection signals. Results We use conditional logistic regression to compare our Adjusted Haplotype Conditional Entropy (H|H) measure of positive selection to existing positive selection measures. H|H and existing measures were applied to published regulatory variants acting in cis (cis-eQTLs), with conditional logistic regression testing whether regulatory variants undergo stronger positive selection than the surrounding gene. These cis-eQTLs were drawn from six independent studies of genotype and RNA expression. The conditional logistic regression shows that, overall, H|H is substantially more powerful than existing positive-selection methods in identifying cis-eQTLs against other Single Nucleotide Polymorphisms (SNPs) in the same genes. When broken down by Gene Ontology, H|H predictions are particularly strong in some biological process categories, where regulatory variants are under strong positive selection compared to the bulk of the gene, distinct from those GO categories under overall positive selection. . However, cis-eQTLs in a second group of genes lack positive selection signatures detectable by H|H, consistent with ancient short haplotypes compared to the surrounding gene (for example, in innate immunity GO:0042742); under such other modes of selection, H|H would not be expected to be a strong predictor.. These conditional logistic regression models are adjusted for Minor allele frequency(MAF); otherwise, ascertainment bias is a huge factor in all eQTL data sets. Relationships between Gene Ontology categories, positive selection and eQTL specificity were replicated with H|H in a single larger data set. Our measure, Adjusted Haplotype Conditional Entropy (H|H), was essential in generating all of the results above because it: 1) is a stronger overall predictor for eQTLs than comparable existing approaches, and 2) shows low sequential auto-correlation, overcoming problems with convergence of these conditional regression statistical models. Conclusions Our new method, H|H, provides a consistently more robust signal associated with cis-eQTLs compared to existing methods. We interpret this to indicate that some cis-eQTLs are under positive selection compared to their surrounding genes. Conditional entropy indicative of a selective sweep is an especially strong predictor of eQTLs for genes in several biological processes of medical interest. Where conditional entropy is a weak or negative predictor of eQTLs, such as innate immune genes, this would be consistent with balancing selection acting on such eQTLs over long time periods. Different measures of selection may be needed for variant prioritization under other modes of evolutionary selection. PMID:26111110

Fermionic edge states and new physics

NASA Astrophysics Data System (ADS)

Govindarajan, T. R.; Tibrewala, Rakesh

2015-08-01

We investigate the properties of the Dirac operator on manifolds with boundaries in the presence of the Atiyah-Patodi-Singer boundary condition. An exact counting of the number of edge states for boundaries with isometry of a sphere is given. We show that the problem with the above boundary condition can be mapped to one where the manifold is extended beyond the boundary and the boundary condition is replaced by a delta function potential of suitable strength. We also briefly highlight how the problem of the self-adjointness of the operators in the presence of moving boundaries can be simplified by suitable transformations which render the boundary fixed and modify the Hamiltonian and the boundary condition to reflect the effect of moving boundary.

Predictors of timing of pregnancy discovery.

PubMed

McCarthy, Molly; Upadhyay, Ushma; Biggs, M Antonia; Anthony, Renaisa; Holl, Jennifer; Roberts, Sarah Cm

2018-04-01

Earlier pregnancy discovery is important in the context of prenatal and abortion care. We evaluated characteristics associated with later pregnancy discovery among women seeking abortion care. Data come from a survey of women seeking abortion care at four family planning facilities in Utah. The participants completed a survey during the state-mandated abortion information visit they are required to complete prior to having an abortion. The outcome in this study was pregnancy discovery before versus after 6 weeks since respondents' last menstrual period (LMP). We used logistic regression to estimate the relationship between sociodemographic and health-related independent variables of interest and pregnancy discovery before versus after 6 weeks. Among the 458 women in the sample, 28% discovered their pregnancy later than 6 weeks since LMP. Most (n=366, 80%) knew the exact date of their LMP and a significant minority estimated it (n=92, 20%). Those who estimated the date of their LMP had higher odds of later pregnancy discovery than those who knew the exact date (adjusted odds ratio (aOR)=1.81[1.07-3.07]). Those who used illicit drugs weekly, daily, or almost daily had higher odds of later pregnancy discovery (aOR=6.33[2.44, 16.40]). Women who did not track their menstrual periods and those who frequently used drugs had higher odds of discovering their pregnancies later. Women who estimated the date of their LMP and who frequently used drugs may benefit from strategies to help them recognize their pregnancies earlier and link them to care when they discover their pregnancies later. Copyright © 2017 Elsevier Inc. All rights reserved.

Non-equilibrium dynamics from RPMD and CMD.

PubMed

Welsch, Ralph; Song, Kai; Shi, Qiang; Althorpe, Stuart C; Miller, Thomas F

2016-11-28

We investigate the calculation of approximate non-equilibrium quantum time correlation functions (TCFs) using two popular path-integral-based molecular dynamics methods, ring-polymer molecular dynamics (RPMD) and centroid molecular dynamics (CMD). It is shown that for the cases of a sudden vertical excitation and an initial momentum impulse, both RPMD and CMD yield non-equilibrium TCFs for linear operators that are exact for high temperatures, in the t = 0 limit, and for harmonic potentials; the subset of these conditions that are preserved for non-equilibrium TCFs of non-linear operators is also discussed. Furthermore, it is shown that for these non-equilibrium initial conditions, both methods retain the connection to Matsubara dynamics that has previously been established for equilibrium initial conditions. Comparison of non-equilibrium TCFs from RPMD and CMD to Matsubara dynamics at short times reveals the orders in time to which the methods agree. Specifically, for the position-autocorrelation function associated with sudden vertical excitation, RPMD and CMD agree with Matsubara dynamics up to O(t 4 ) and O(t 1 ), respectively; for the position-autocorrelation function associated with an initial momentum impulse, RPMD and CMD agree with Matsubara dynamics up to O(t 5 ) and O(t 2 ), respectively. Numerical tests using model potentials for a wide range of non-equilibrium initial conditions show that RPMD and CMD yield non-equilibrium TCFs with an accuracy that is comparable to that for equilibrium TCFs. RPMD is also used to investigate excited-state proton transfer in a system-bath model, and it is compared to numerically exact calculations performed using a recently developed version of the Liouville space hierarchical equation of motion approach; again, similar accuracy is observed for non-equilibrium and equilibrium initial conditions.

Optimization of biogas production using MEMS based near infrared inline-sensor

NASA Astrophysics Data System (ADS)

Saupe, Ray; Seider, Thomas; Stock, Volker; Kujawski, Olaf; Otto, Thomas; Gessner, Thomas

2013-03-01

Due to climate protection and increasing oil prices, renewable energy is becoming extremely important. Anaerobic digestion is a particular environmental and resource-saving way of heat and power production in biogas plants. These plants can be operated decentralized and independent of weather conditions and allow peak load operation. To maximize energy production, plants should be operated at a high efficiency. That means the entire installed power production capacity (e.g. CHP) and biogas production have to be used. However, current plant utilization in many areas is significantly lower, which is economically and environmentally inefficient, since the biochemical process responds to fluctuations in boundary conditions, e.g. mixing in the conditions and substrate composition. At present only a few easily accessible parameters such as fill level, flow rates and temperature are determined on-line. Monitoring of substrate composition occurs only sporadically with the help of laboratory methods. Direct acquisition of substrate composition combined with a smart control and regulation concept enables significant improvement in plant efficiency. This requires a compact, reliable and cost-efficient sensor. It is for this reason that a MEMS sensor system based on NIR spectroscopy has been developed. Requirements are high accuracy, which is the basic condition for exact chemometric evaluation of the sample as well as optimized MEMS design and packaging in order to work in poor environmental conditions. Another issue is sample presentation, which needs an exact adopted optical-mechanical system. In this paper, the development and application of a MEMS-based analyzer for biogas plants will be explained. The above mentioned problems and challenges will be discussed. Measurement results will be shown to demonstrate its performance.

Relative Positioning Evaluation of a Tetrahedral Flight Formation’s Satellites

NASA Astrophysics Data System (ADS)

Mahler, W. F. C.; Rocco, E. M.; Santos, D. P. S.

2017-10-01

This paper presents a study about the tetrahedral layout of four satellites in a way that every half-orbital period this set groups together while flying in formation. The formation is calculated analyzing the problem from a geometrical perspective and disposed by precisely adjusting the orbital parameters of each satellite. The dynamic modelling considers the orbital motion equations. The results are analyzed, compared and discussed. A detection algorithm is used as flag to signal the regular tetrahedron’s exact moments of occurrence. To do so, the volume calculated during the simulation is compared to the real volume, based on the initial conditions of the exact moment of formation and respecting a tolerance. This tolerance value is stablished arbitrarily depending on the mission and the formation’s geometrical parameters. The simulations will run on a computational environment.

Universal adiabatic quantum computation via the space-time circuit-to-Hamiltonian construction.

PubMed

Gosset, David; Terhal, Barbara M; Vershynina, Anna

2015-04-10

We show how to perform universal adiabatic quantum computation using a Hamiltonian which describes a set of particles with local interactions on a two-dimensional grid. A single parameter in the Hamiltonian is adiabatically changed as a function of time to simulate the quantum circuit. We bound the eigenvalue gap above the unique ground state by mapping our model onto the ferromagnetic XXZ chain with kink boundary conditions; the gap of this spin chain was computed exactly by Koma and Nachtergaele using its q-deformed version of SU(2) symmetry. We also discuss a related time-independent Hamiltonian which was shown by Janzing to be capable of universal computation. We observe that in the limit of large system size, the time evolution is equivalent to the exactly solvable quantum walk on Young's lattice.

Analysis of Dynamic Geometric Configuration of the Aortic Channel from the Perspective of Tornado-Like Flow Organization of Blood Flow.

PubMed

Zhorzholiani, Sh T; Mironov, A A; Talygin, E A; Tsyganokov, Yu M; Agafonov, A M; Kiknadze, G I; Gorodkov, A Yu; Bokeriya, L A

2018-03-01

Analysis of the data of morphometry of aortic casts, aortography at different pressures, and multispiral computer tomography of the aorta with contrast and normal pulse pressure showed that geometric configuration of the flow channel of the aorta during the whole cardiac cycle corresponded to the conditions of self-organization of tornado-like quasipotential flow described by exact solutions of the Navier-Stokes equation and continuity of viscous fluid typical for this type of fluid flows. Increasing pressure in the aorta leads to a decrease in the degree of approximation of the channel geometry to the ratio of exact solution and increases the risk of distortions in the structure of the flow. A mechanism of evolution of tornado-like flow in the aorta was proposed.

Exact solution for heat transfer free convection flow of Maxwell nanofluids with graphene nanoparticles

NASA Astrophysics Data System (ADS)

Aman, Sidra; Zuki Salleh, Mohd; Ismail, Zulkhibri; Khan, Ilyas

2017-09-01

This article focuses on the flow of Maxwell nanofluids with graphene nanoparticles over a vertical plate (static) with constant wall temperature. Possessing high thermal conductivity, engine oil is useful to be chosen as base fluid with free convection. The problem is modelled in terms of PDE’s with boundary conditions. Some suitable non-dimensional variables are interposed to transform the governing equations into dimensionless form. The generated equations are solved via Laplace transform technique. Exact solutions are evaluated for velocity and temperature. These solutions are significantly controlled by some parameters involved. Temperature rises with elevation in volume fraction while Velocity decreases with increment in volume fraction. A comparison with previous published results are established and discussed. Moreover, a detailed discussion is made for influence of volume fraction on the flow and heat profile.

Flexible rotor balancing by the influence coefficient method. Part 1: Evaluation of the exact point-speed and least squares procedures

NASA Technical Reports Server (NTRS)

Tessarzik, J. M.

1972-01-01

The practical aspects of balancing real, flexible rotors were investigated through inclusion of rotor out-of-roundness data at the measurement probe locations. The computer program was demonstrated to be fully capable of handling out-of-roundness data in the investigation. Testing was performed predominantly with a machine having a 41-inch long, 126-pound rotor. This rotor was operated over a speed range encompassing three rotor-bearing system critical speeds. Both balancing procedures were evaluated for several different conditions of initial rotor unbalance. Safe (and slow) passage through all the critical speeds was obtained after two or three balancing runs in most cases. The Least Squares procedure was found to be generally equivalent in capability to the Exact Point-Speed procedure for the configurations studies. (U)

A critical evaluation of two-equation models for near wall turbulence

NASA Technical Reports Server (NTRS)

Speziale, Charles G.; Anderson, E. Clay; Abid, Ridha

1990-01-01

A basic theoretical and computational study of two-equation models for near-wall turbulent flows was conducted. Two major problems established for the K-epsilon model are discussed, the lack of natural boundary conditions for the dissipation rate and the appearance of higher-order correlations in the balance of terms for the dissipation rate at the wall. The K-omega equation is shown to have two problems also: an exact viscous term is missing, and the destruction of the dissipation term is not properly damped near the wall. A new K-tau model (where tau = 1/omega is the turbulent time scale) was developed by inclusion of the exact viscous term, and by introduction of new wall damping functions with improved asymptotic behavior. A preliminary test of the new model yields improved predictions for the flat-plate turbulent boundary layer.

Allowable Trajectory Variations for Space Shuttle Orbiter Entry-Aeroheating CFD

NASA Technical Reports Server (NTRS)

Wood, William A.; Alter, Stephen J.

2008-01-01

Reynolds-number criteria are developed for acceptable variations in Space Shuttle Orbiter entry trajectories for use in computational aeroheating analyses. The criteria determine if an existing computational fluid dynamics solution for a particular trajectory can be extrapolated to a different trajectory. The criteria development begins by estimating uncertainties for seventeen types of computational aeroheating data, such as boundary layer thickness, at exact trajectory conditions. For each type of datum, the allowable uncertainty contribution due to trajectory variation is set to be half of the value of the estimated exact-trajectory uncertainty. Then, for the twelve highest-priority datum types, Reynolds-number relations between trajectory variation and output uncertainty are determined. From these relations the criteria are established for the maximum allowable trajectory variations. The most restrictive criterion allows a 25% variation in Reynolds number at constant Mach number between trajectories.

A fast exact simulation method for a class of Markov jump processes.

PubMed

Li, Yao; Hu, Lili

2015-11-14

A new method of the stochastic simulation algorithm (SSA), named the Hashing-Leaping method (HLM), for exact simulations of a class of Markov jump processes, is presented in this paper. The HLM has a conditional constant computational cost per event, which is independent of the number of exponential clocks in the Markov process. The main idea of the HLM is to repeatedly implement a hash-table-like bucket sort algorithm for all times of occurrence covered by a time step with length τ. This paper serves as an introduction to this new SSA method. We introduce the method, demonstrate its implementation, analyze its properties, and compare its performance with three other commonly used SSA methods in four examples. Our performance tests and CPU operation statistics show certain advantages of the HLM for large scale problems.

Memory effects on a resonate-and-fire neuron model subjected to Ornstein-Uhlenbeck noise

NASA Astrophysics Data System (ADS)

Paekivi, S.; Mankin, R.; Rekker, A.

2017-10-01

We consider a generalized Langevin equation with an exponentially decaying memory kernel as a model for the firing process of a resonate-and-fire neuron. The effect of temporally correlated random neuronal input is modeled as Ornstein-Uhlenbeck noise. In the noise-induced spiking regime of the neuron, we derive exact analytical formulas for the dependence of some statistical characteristics of the output spike train, such as the probability distribution of the interspike intervals (ISIs) and the survival probability, on the parameters of the input stimulus. Particularly, on the basis of these exact expressions, we have established sufficient conditions for the occurrence of memory-time-induced transitions between unimodal and multimodal structures of the ISI density and a critical damping coefficient which marks a dynamical transition in the behavior of the system.

Exact solution of two interacting run-and-tumble random walkers with finite tumble duration

NASA Astrophysics Data System (ADS)

Slowman, A. B.; Evans, M. R.; Blythe, R. A.

2017-09-01

We study a model of interacting run-and-tumble random walkers operating under mutual hardcore exclusion on a one-dimensional lattice with periodic boundary conditions. We incorporate a finite, poisson-distributed, tumble duration so that a particle remains stationary whilst tumbling, thus generalising the persistent random walker model. We present the exact solution for the nonequilibrium stationary state of this system in the case of two random walkers. We find this to be characterised by two lengthscales, one arising from the jamming of approaching particles, and the other from one particle moving when the other is tumbling. The first of these lengthscales vanishes in a scaling limit where the continuous-space dynamics is recovered whilst the second remains finite. Thus the nonequilibrium stationary state reveals a rich structure of attractive, jammed and extended pieces.

Universal Adiabatic Quantum Computation via the Space-Time Circuit-to-Hamiltonian Construction

NASA Astrophysics Data System (ADS)

Gosset, David; Terhal, Barbara M.; Vershynina, Anna

2015-04-01

We show how to perform universal adiabatic quantum computation using a Hamiltonian which describes a set of particles with local interactions on a two-dimensional grid. A single parameter in the Hamiltonian is adiabatically changed as a function of time to simulate the quantum circuit. We bound the eigenvalue gap above the unique ground state by mapping our model onto the ferromagnetic X X Z chain with kink boundary conditions; the gap of this spin chain was computed exactly by Koma and Nachtergaele using its q -deformed version of SU(2) symmetry. We also discuss a related time-independent Hamiltonian which was shown by Janzing to be capable of universal computation. We observe that in the limit of large system size, the time evolution is equivalent to the exactly solvable quantum walk on Young's lattice.

How mutation affects evolutionary games on graphs

PubMed Central

Allen, Benjamin; Traulsen, Arne; Tarnita, Corina E.; Nowak, Martin A.

2011-01-01

Evolutionary dynamics are affected by population structure, mutation rates and update rules. Spatial or network structure facilitates the clustering of strategies, which represents a mechanism for the evolution of cooperation. Mutation dilutes this effect. Here we analyze how mutation influences evolutionary clustering on graphs. We introduce new mathematical methods to evolutionary game theory, specifically the analysis of coalescing random walks via generating functions. These techniques allow us to derive exact identity-by-descent (IBD) probabilities, which characterize spatial assortment on lattices and Cayley trees. From these IBD probabilities we obtain exact conditions for the evolution of cooperation and other game strategies, showing the dual effects of graph topology and mutation rate. High mutation rates diminish the clustering of cooperators, hindering their evolutionary success. Our model can represent either genetic evolution with mutation, or social imitation processes with random strategy exploration. PMID:21473871

Trail impacts in Sagarmatha (Mt. Everest) National Park, Nepal: a logistic regression analysis.

PubMed

Nepal, S K

2003-09-01

A trail study was conducted in the Sagarmatha (Mt. Everest) National Park, Nepal, during 1997-1998. Based on that study, this paper examines the spatial variability of trail conditions and analyzes factors that influence trail conditions. Logistic regression (multinomial logit model) is applied to examine the influence of use and environmental factors on trail conditions. The assessment of trail conditions is based on a four-class rating system: (class I, very little damaged; class II, moderately damaged, class III, heavily damaged; and class IV, severely damaged). Wald statistics and a model classification table have been used for data interpretation. Results indicate that altitude, trail gradient, hazard potential, and vegetation type are positively associated with trail condition. Trails are more degraded at higher altitude, on steep gradients, in areas with natural hazard potential, and within shrub/grassland zones. Strong correlations between high levels of trail degradation and higher frequencies of visitors and lodges were found. A detailed analysis of environmental and use factors could provide valuable information to park managers in their decisions about trail design, layout and maintenance, and efficient and effective visitor management strategies. Comparable studies on high alpine environments are needed to predict precisely the effects of topographic and climatic extremes. More refined approaches and experimental methods are necessary to control the effects of environmental factors.

Association between bullous pemphigoid and neurologic diseases: a case-control study.

PubMed

Casas-de-la-Asunción, E; Ruano-Ruiz, J; Rodríguez-Martín, A M; Vélez García-Nieto, A; Moreno-Giménez, J C

2014-11-01

In the past 10 years, bullous pemphigoid has been associated with other comorbidities and neurologic and psychiatric conditions in particular. Case series, small case-control studies, and large population-based studies in different Asian populations, mainland Europe, and the United Kingdom have confirmed this association. However, no data are available for the Spanish population. This was an observational, retrospective, case-control study with 1:2 matching. Fifty-four patients with bullous pemphigoid were selected. We compared the percentage of patients in each group with concurrent neurologic conditions, ischemic heart disease, diabetes, chronic obstructive pulmonary disease, and solid tumors using univariate logistic regression. An association model was constructed with conditional multiple logistic regression. The case group had a significantly higher percentage of patients with cerebrovascular accident and/or transient ischemic attack (odds ratio [OR], 3.06; 95% CI, 1.19-7.87], dementia (OR, 5.52; 95% CI, 2.19-13.93), and Parkinson disease (OR, 5; 95% CI, 1.57-15.94). A significantly higher percentage of cases had neurologic conditions (OR, 6.34; 95% CI, 2.89-13.91). Dementia and Parkinson disease were independently associated with bullous pemphigoid in the multivariate analysis. Patients with bullous pemphigoid have a higher frequency of neurologic conditions. Copyright © 2013 Elsevier España, S.L.U. and AEDV. All rights reserved.

Focal Uncaging of GABA Reveals a Temporally Defined Role for GABAergic Inhibition during Appetitive Associative Olfactory Conditioning in Honeybees

ERIC Educational Resources Information Center

Raccuglia, Davide; Mueller, Uli

2013-01-01

Throughout the animal kingdom, the inhibitory neurotransmitter ?-aminobutyric acid (GABA) is a key modulator of physiological processes including learning. With respect to associative learning, the exact time in which GABA interferes with the molecular events of learning has not yet been clearly defined. To address this issue, we used two…

Polynomial modal analysis of lamellar diffraction gratings in conical mounting.

PubMed

Randriamihaja, Manjakavola Honore; Granet, Gérard; Edee, Kofi; Raniriharinosy, Karyl

2016-09-01

An efficient numerical modal method for modeling a lamellar grating in conical mounting is presented. Within each region of the grating, the electromagnetic field is expanded onto Legendre polynomials, which allows us to enforce in an exact manner the boundary conditions that determine the eigensolutions. Our code is successfully validated by comparison with results obtained with the analytical modal method.

Medial Prefrontal Cortex Is Selectively Involved in Response Selection Using Visual Context in the Background

ERIC Educational Resources Information Center

Lee, Inah; Shin, Ji Yun

2012-01-01

The exact roles of the medial prefrontal cortex (mPFC) in conditional choice behavior are unknown and a visual contextual response selection task was used for examining the issue. Inactivation of the mPFC severely disrupted performance in the task. mPFC inactivations, however, did not disrupt the capability of perceptual discrimination for visual…

Second-order numerical solution of time-dependent, first-order hyperbolic equations

NASA Technical Reports Server (NTRS)

Shah, Patricia L.; Hardin, Jay

1995-01-01

A finite difference scheme is developed to find an approximate solution of two similar hyperbolic equations, namely a first-order plane wave and spherical wave problem. Finite difference approximations are made for both the space and time derivatives. The result is a conditionally stable equation yielding an exact solution when the Courant number is set to one.

A first-order k-space model for elastic wave propagation in heterogeneous media.

PubMed

Firouzi, K; Cox, B T; Treeby, B E; Saffari, N

2012-09-01

A pseudospectral model of linear elastic wave propagation is described based on the first order stress-velocity equations of elastodynamics. k-space adjustments to the spectral gradient calculations are derived from the dyadic Green's function solution to the second-order elastic wave equation and used to (a) ensure the solution is exact for homogeneous wave propagation for timesteps of arbitrarily large size, and (b) also allows larger time steps without loss of accuracy in heterogeneous media. The formulation in k-space allows the wavefield to be split easily into compressional and shear parts. A perfectly matched layer (PML) absorbing boundary condition was developed to effectively impose a radiation condition on the wavefield. The staggered grid, which is essential for accurate simulations, is described, along with other practical details of the implementation. The model is verified through comparison with exact solutions for canonical examples and further examples are given to show the efficiency of the method for practical problems. The efficiency of the model is by virtue of the reduced point-per-wavelength requirement, the use of the fast Fourier transform (FFT) to calculate the gradients in k space, and larger time steps made possible by the k-space adjustments.

The Finite-Surface Method for incompressible flow: a step beyond staggered grid

NASA Astrophysics Data System (ADS)

Hokpunna, Arpiruk; Misaka, Takashi; Obayashi, Shigeru

2017-11-01

We present a newly developed higher-order finite surface method for the incompressible Navier-Stokes equations (NSE). This method defines the velocities as a surface-averaged value on the surfaces of the pressure cells. Consequently, the mass conservation on the pressure cells becomes an exact equation. The only things left to approximate is the momentum equation and the pressure at the new time step. At certain conditions, the exact mass conservation enables the explicit n-th order accurate NSE solver to be used with the pressure treatment that is two or four order less accurate without loosing the apparent convergence rate. This feature was not possible with finite volume of finite difference methods. We use Fourier analysis with a model spectrum to determine the condition and found that the range covers standard boundary layer flows. The formal convergence and the performance of the proposed scheme is compared with a sixth-order finite volume method. Finally, the accuracy and performance of the method is evaluated in turbulent channel flows. This work is partially funded by a research colloaboration from IFS, Tohoku university and ASEAN+3 funding scheme from CMUIC, Chiang Mai University.

Impact of uncertainties in free stream conditions on the aerodynamics of a rectangular cylinder

NASA Astrophysics Data System (ADS)

Mariotti, Alessandro; Shoeibi Omrani, Pejman; Witteveen, Jeroen; Salvetti, Maria Vittoria

2015-11-01

The BARC benchmark deals with the flow around a rectangular cylinder with chord-to-depth ratio equal to 5. This flow configuration is of practical interest for civil and industrial structures and it is characterized by massively separated flow and unsteadiness. In a recent review of BARC results, significant dispersion was observed both in experimental and numerical predictions of some flow quantities, which are extremely sensitive to various uncertainties, which may be present in experiments and simulations. Besides modeling and numerical errors, in simulations it is difficult to exactly reproduce the experimental conditions due to uncertainties in the set-up parameters, which sometimes cannot be exactly controlled or characterized. Probabilistic methods and URANS simulations are used to investigate the impact of the uncertainties in the following set-up parameters: the angle of incidence, the free stream longitudinal turbulence intensity and length scale. Stochastic collocation is employed to perform the probabilistic propagation of the uncertainty. The discretization and modeling errors are estimated by repeating the same analysis for different grids and turbulence models. The results obtained for different assumed PDF of the set-up parameters are also compared.

Accounting for center in the Early External Cephalic Version trials: an empirical comparison of statistical methods to adjust for center in a multicenter trial with binary outcomes.

PubMed

Reitsma, Angela; Chu, Rong; Thorpe, Julia; McDonald, Sarah; Thabane, Lehana; Hutton, Eileen

2014-09-26

Clustering of outcomes at centers involved in multicenter trials is a type of center effect. The Consolidated Standards of Reporting Trials Statement recommends that multicenter randomized controlled trials (RCTs) should account for center effects in their analysis, however most do not. The Early External Cephalic Version (EECV) trials published in 2003 and 2011 stratified by center at randomization, but did not account for center in the analyses, and due to the nature of the intervention and number of centers, may have been prone to center effects. Using data from the EECV trials, we undertook an empirical study to compare various statistical approaches to account for center effect while estimating the impact of external cephalic version timing (early or delayed) on the outcomes of cesarean section, preterm birth, and non-cephalic presentation at the time of birth. The data from the EECV pilot trial and the EECV2 trial were merged into one dataset. Fisher's exact method was used to test the overall effect of external cephalic version timing unadjusted for center effects. Seven statistical models that accounted for center effects were applied to the data. The models included: i) the Mantel-Haenszel test, ii) logistic regression with fixed center effect and fixed treatment effect, iii) center-size weighted and iv) un-weighted logistic regression with fixed center effect and fixed treatment-by-center interaction, iv) logistic regression with random center effect and fixed treatment effect, v) logistic regression with random center effect and random treatment-by-center interaction, and vi) generalized estimating equations. For each of the three outcomes of interest approaches to account for center effect did not alter the overall findings of the trial. The results were similar for the majority of the methods used to adjust for center, illustrating the robustness of the findings. Despite literature that suggests center effect can change the estimate of effect in multicenter trials, this empirical study does not show a difference in the outcomes of the EECV trials when accounting for center effect. The EECV2 trial was registered on 30 July 30 2005 with Current Controlled Trials: ISRCTN 56498577.

Uniqueness of boundary blow-up solutions on exterior domain of RN

NASA Astrophysics Data System (ADS)

Dong, Wei; Pang, Changci

2007-06-01

In this paper, we consider the existence and uniqueness of positive solutions of the degenerate logistic type elliptic equation where N[greater-or-equal, slanted]2, D[subset of]RN is a bounded domain with smooth boundary and a(x), b(x) are continuous functions on RN with b(x)[greater-or-equal, slanted]0, b(x)[not identical with]0. We show that under rather general conditions on a(x) and b(x) for large x, there exists a unique positive solution. Our results improve the corresponding ones in [W. Dong, Y. Du, Unbounded principal eigenfunctions and the logistic equation on RN, Bull. Austral. Math. Soc. 67 (2003) 413-427] and [Y. Du, L. Ma, Logistic type equations on RN by a squeezing method involving boundary blow-up solutions, J. London Math. Soc. (2) 64 (2001) 107-124].

Nowcasting of Low-Visibility Procedure States with Ordered Logistic Regression at Vienna International Airport

NASA Astrophysics Data System (ADS)

Kneringer, Philipp; Dietz, Sebastian; Mayr, Georg J.; Zeileis, Achim

2017-04-01

Low-visibility conditions have a large impact on aviation safety and economic efficiency of airports and airlines. To support decision makers, we develop a statistical probabilistic nowcasting tool for the occurrence of capacity-reducing operations related to low visibility. The probabilities of four different low visibility classes are predicted with an ordered logistic regression model based on time series of meteorological point measurements. Potential predictor variables for the statistical models are visibility, humidity, temperature and wind measurements at several measurement sites. A stepwise variable selection method indicates that visibility and humidity measurements are the most important model inputs. The forecasts are tested with a 30 minute forecast interval up to two hours, which is a sufficient time span for tactical planning at Vienna Airport. The ordered logistic regression models outperform persistence and are competitive with human forecasters.

Logistics engineering education from the point of view environment

NASA Astrophysics Data System (ADS)

Bányai, Ágota

2010-05-01

A new field of MSc programme offered by the Faculty of Mechanical Engineering and Informatics of the University of Miskolc is represented by the programme in logistics engineering. The Faculty has always laid great emphasis on assigning processes connected with environment protection and globalisation issues the appropriate weight in its programmes. This is based on the fact that the Faculty has initiated and been involved in a great number of research and development projects with a substantial emphasis on the fundamental principles of sustainable development. The objective of the programme of logistics engineering is to train engineers who, in possession of the science, engineering, economic, informatics and industrial, transportation technological knowledge related to the professional field of logistics, are able to analyse, design, organise, and control logistics processes and systems (freight transportation, materials handling, storage, commissioning, loading, purchasing, distribution and waste management) as well as to design and develop machinery and equipment as the elements of logistic systems and also to be involved in their manufacture and quality control and are able to control their operation. The programme prepares its students for performing the logistics management tasks in a company, for creative participation in solving research and development problems in logistics and for pursuing logistics studies in doctoral programmes. There are several laboratories available for practice-oriented training. The 'Integrated Logistics Laboratory' consists of various fixed and mobile, real industrial, i.e. not model-level equipment, the integration of which in one system facilitates not only the presentation, examination and development of the individual self-standing facilities, but the study of their interaction as well in terms of mechatronics, engineering, control engineering, informatics, identification technology and logistics. The state-of-the-art, reliable, automated mechatronics-material flow system with its single control engineering system provides the academic staff with up-to-date research facilities, and enables the students to study sophisticated equipment and systems that could also operate under industrial conditions, thus offering knowledge that can be efficiently utilised in the industry after graduation. The laboratory measurements of the programme in logistics engineering are performed in this laboratory, and they are supplemented by the theoretical and practical measurements in the ‘Robotic Technology Assembly Laboratory', the ‘Power Electronics Laboratory', the ‘Mechatronics Laboratory', the ‘CAD/CAM Laboratory' and the ‘Acoustics and Product Laboratory'. The bodies of knowledge connected with environment protection and sustainable development can be grouped around three large topic areas. In environmental economics the objective is to present the corporate-organisational aspects of environmental management. Putting environmental management in the focal point, the objective of the programme is to impart knowledge that can be utilised in practice which can be used to shift the relation between the organisation and its environment in the direction of sustainability. The tools include environmental controlling, environmental marketing and various solutions of environmental performance evaluation. The second large topic area is globalization and its logistic aspects. In the field of global logistics the following knowledge carries special weight: logistic challenges in a globalised world; the concept of global logistics, its conditions and effects; delayed manufacture, assembly, packaging; the economic investigation of delayed assembly; globalised purchase and distribution in logistics; the logistic features of the globalised production supply/distribution chain; meta-logistics systems; logistics-related EU harmonisation issues; the effect of e-commerce on the global logistic system; logistic centres, connecting virtual logistic companies in a network; the environmental harmonisation of international transportation. The third large area is recycling logistics. Here the bodies of knowledge are as follows: the concept of developing a ‘closed-loop economy'; stages in the progress of products after discarding, connections between the uses of waste collection, processing, selection, deposition or reuse processes; features of European recommendations (e.g. EMAS), harmonisation of national practices and global solutions; presenting the logistics part-processes of recycling; presenting process organisation procedures for the foundation of designing one-route, multi-route, replacement container waste collecting and distributing part systems; recycling strategies with consideration of logistically serving the separation and storage of waste to be deposited, the technological processing systems of recyclable materials; presenting dismantling and product and material identification technologies, presenting logistics part-tasks, analysis of technical solutions; IT solutions for identifying products and their elements to be distributed and withdrawn from distribution after use (e.g. RFID systems) and monitoring their material flow; methodology of using efficiency analyses and incentive systems in the decision making processes of recycling processes, risk analysis for evaluating typical part processes; the methodology of recycling-oriented product design for specific product groups. Graduates of the Master programmes are able to use and utilise the knowledge obtained in practice, use problem-solving techniques; process the information, new problems and new phenomena arising in the border areas of the professional experience gained the discipline; formulate substantial criticism and opinions as far as possible, make decisions and draw conclusions; comprehending and solving the problems arising, suggesting original ideas; plan and perform tasks independently at a high professional standard; improve themselves, develop their knowledge to higher levels; view the management of technical/engineering - economic - human resources in a complex way; design complex systems in a global way based on a system-oriented and process-oriented way of thinking; use integrated knowledge from the professional fields of transport, mobile machinery, process theory, industrial production processes, electronics and informatics; combine the part processes of logistics systems and the part units performing their physical realisation (materials handling equipment, sensors, actuators, control systems, and database systems, etc.); perform state evaluations depending on their specialisation, use them to elaborate evaluations and recommendations, develop complex logistic systems, design, organise and control them at the highest level. This work was implemented with support by the European Union and co-funding of the European Social Fund.

Influence of municipal- and individual-level socioeconomic conditions on mortality in Japan.

PubMed

Honjo, Kaori; Iso, Hiroyasu; Fukuda, Yoshiharu; Nishi, Nobuo; Nakaya, Tomoki; Fujino, Yoshihisa; Tanabe, Naohito; Suzuki, Sadao; Subramanian, S V; Tamakoshi, Akiko

2014-01-01

The health effect of area socioeconomic conditions has been evident especially in Western countries; however, limited research has focused on the effect of municipal-level socioeconomic conditions, especially in Asia. Multilevel research using data from the Japan Collaborative Cohort Study, a large cohort study followed from 1990 to 2006, was conducted to examine individual as well as municipal socioeconomic conditions on risk of death, adjusting for each other. We included 24,460 men and 32,649 women aged 40 to 65 years at baseline in 35 municipalities as our study population. Primary predictors were municipal socioeconomic conditions (proportion of college graduates, per capita income, unemployment rate, and proportion of households receiving public assistance) and individual socioeconomic conditions (education level and occupation). Among men, the multilevel logistic estimate (standard errors) of proportion of college graduates and unemployment rate for mortality from cardiovascular disease were -0.399 (0.094) and -0.343 (0.122), respectively. Among women, the multilevel logistic estimate (standard errors) of proportion of college graduates and per capita annual income for mortality from injuries were -0.386 (0.171) and -1.069 (0.407). Individual education level and occupation were associated with all-cause mortality, in particular, mortality from cardiovascular disease or injuries. Interactions between individual education level and indicators of municipal socioeconomic conditions were observed for mortality from cancer and cardiovascular disease among men and mortality from injuries among women. Municipal and individual socioeconomic conditions were independently and interactively associated with premature death; this suggests that reducing social inequalities in health demands a focus on municipal conditions in addition to those of individuals.

Multinomial logistic regression modelling of obesity and overweight among primary school students in a rural area of Negeri Sembilan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghazali, Amirul Syafiq Mohd; Ali, Zalila; Noor, Norlida Mohd

Multinomial logistic regression is widely used to model the outcomes of a polytomous response variable, a categorical dependent variable with more than two categories. The model assumes that the conditional mean of the dependent categorical variables is the logistic function of an affine combination of predictor variables. Its procedure gives a number of logistic regression models that make specific comparisons of the response categories. When there are q categories of the response variable, the model consists of q-1 logit equations which are fitted simultaneously. The model is validated by variable selection procedures, tests of regression coefficients, a significant test ofmore » the overall model, goodness-of-fit measures, and validation of predicted probabilities using odds ratio. This study used the multinomial logistic regression model to investigate obesity and overweight among primary school students in a rural area on the basis of their demographic profiles, lifestyles and on the diet and food intake. The results indicated that obesity and overweight of students are related to gender, religion, sleep duration, time spent on electronic games, breakfast intake in a week, with whom meals are taken, protein intake, and also, the interaction between breakfast intake in a week with sleep duration, and the interaction between gender and protein intake.« less

Multinomial logistic regression modelling of obesity and overweight among primary school students in a rural area of Negeri Sembilan

NASA Astrophysics Data System (ADS)

Ghazali, Amirul Syafiq Mohd; Ali, Zalila; Noor, Norlida Mohd; Baharum, Adam

2015-10-01

Multinomial logistic regression is widely used to model the outcomes of a polytomous response variable, a categorical dependent variable with more than two categories. The model assumes that the conditional mean of the dependent categorical variables is the logistic function of an affine combination of predictor variables. Its procedure gives a number of logistic regression models that make specific comparisons of the response categories. When there are q categories of the response variable, the model consists of q-1 logit equations which are fitted simultaneously. The model is validated by variable selection procedures, tests of regression coefficients, a significant test of the overall model, goodness-of-fit measures, and validation of predicted probabilities using odds ratio. This study used the multinomial logistic regression model to investigate obesity and overweight among primary school students in a rural area on the basis of their demographic profiles, lifestyles and on the diet and food intake. The results indicated that obesity and overweight of students are related to gender, religion, sleep duration, time spent on electronic games, breakfast intake in a week, with whom meals are taken, protein intake, and also, the interaction between breakfast intake in a week with sleep duration, and the interaction between gender and protein intake.

A regression technique for evaluation and quantification for water quality parameters from remote sensing data

NASA Technical Reports Server (NTRS)

Whitlock, C. H.; Kuo, C. Y.

1979-01-01

The objective of this paper is to define optical physics and/or environmental conditions under which the linear multiple-regression should be applicable. An investigation of the signal-response equations is conducted and the concept is tested by application to actual remote sensing data from a laboratory experiment performed under controlled conditions. Investigation of the signal-response equations shows that the exact solution for a number of optical physics conditions is of the same form as a linearized multiple-regression equation, even if nonlinear contributions from surface reflections, atmospheric constituents, or other water pollutants are included. Limitations on achieving this type of solution are defined.

Reliability and degradation of oxide VCSELs due to reaction to atmospheric water vapor

NASA Astrophysics Data System (ADS)

Dafinca, Alexandru; Weidberg, Anthony R.; McMahon, Steven J.; Grillo, Alexander A.; Farthouat, Philippe; Ziolkowski, Michael; Herrick, Robert W.

2013-03-01

850nm oxide-aperture VCSELs are susceptible to premature failure if operated while exposed to atmospheric water vapor, and not protected by hermetic packaging. The ATLAS detector in CERN's Large Hadron Collider (LHC) has had approximately 6000 channels of Parallel Optic VCSELs fielded under well-documented ambient conditions. Exact time-to-failure data has been collected on this large sample, providing for the first time actual failure data at use conditions. In addition, the same VCSELs were tested under a variety of accelerated conditions to allow us to construct a more accurate acceleration model. Failure analysis information will also be presented to show what we believe causes corrosion-related failure for such VCSELs.

A hybrid solution approach for a multi-objective closed-loop logistics network under uncertainty

NASA Astrophysics Data System (ADS)

Mehrbod, Mehrdad; Tu, Nan; Miao, Lixin

2015-06-01

The design of closed-loop logistics (forward and reverse logistics) has attracted growing attention with the stringent pressures of customer expectations, environmental concerns and economic factors. This paper considers a multi-product, multi-period and multi-objective closed-loop logistics network model with regard to facility expansion as a facility location-allocation problem, which more closely approximates real-world conditions. A multi-objective mixed integer nonlinear programming formulation is linearized by defining new variables and adding new constraints to the model. By considering the aforementioned model under uncertainty, this paper develops a hybrid solution approach by combining an interactive fuzzy goal programming approach and robust counterpart optimization based on three well-known robust counterpart optimization formulations. Finally, this paper compares the results of the three formulations using different test scenarios and parameter-sensitive analysis in terms of the quality of the final solution, CPU time, the level of conservatism, the degree of closeness to the ideal solution, the degree of balance involved in developing a compromise solution, and satisfaction degree.

Length bias correction in gene ontology enrichment analysis using logistic regression.

PubMed

Mi, Gu; Di, Yanming; Emerson, Sarah; Cumbie, Jason S; Chang, Jeff H

2012-01-01

When assessing differential gene expression from RNA sequencing data, commonly used statistical tests tend to have greater power to detect differential expression of genes encoding longer transcripts. This phenomenon, called "length bias", will influence subsequent analyses such as Gene Ontology enrichment analysis. In the presence of length bias, Gene Ontology categories that include longer genes are more likely to be identified as enriched. These categories, however, are not necessarily biologically more relevant. We show that one can effectively adjust for length bias in Gene Ontology analysis by including transcript length as a covariate in a logistic regression model. The logistic regression model makes the statistical issue underlying length bias more transparent: transcript length becomes a confounding factor when it correlates with both the Gene Ontology membership and the significance of the differential expression test. The inclusion of the transcript length as a covariate allows one to investigate the direct correlation between the Gene Ontology membership and the significance of testing differential expression, conditional on the transcript length. We present both real and simulated data examples to show that the logistic regression approach is simple, effective, and flexible.

Food Service Management

NASA Technical Reports Server (NTRS)

Rappole, C. L.; Louvier, S. A.

1985-01-01

A study to design a food service system using current technology to serve a small scale Space Station was conducted. The psychological, sociological and nutritional factors affecting feeding in microgravity conditions was investigated. The logistics of the food service system was defined.

The effective boundary conditions and their lifespan of the logistic diffusion equation on a coated body

NASA Astrophysics Data System (ADS)

Li, Huicong; Wang, Xuefeng; Wu, Yanxia

2014-11-01

We consider the logistic diffusion equation on a bounded domain, which has two components with a thin coating surrounding a body. The diffusion tensor is isotropic on the body, and anisotropic on the coating. The size of the diffusion tensor on these components may be very different; within the coating, the diffusion rates in the normal and tangent directions may be in different scales. We find effective boundary conditions (EBCs) that are approximately satisfied by the solution of the diffusion equation on the boundary of the body. We also prove that the lifespan of each EBC, which measures how long the EBC remains effective, is infinite. The EBCs enable us to see clearly the effect of the coating and ease the difficult task of solving the PDE in a thin region with a small diffusion tensor. The motivation of the mathematics includes a nature reserve surrounded by a buffer zone.

Access to Care and Satisfaction Among Health Center Patients With Chronic Conditions.

PubMed

Shi, Leiyu; Lee, De-Chih; Haile, Geraldine Pierre; Liang, Hailun; Chung, Michelle; Sripipatana, Alek

This study examined access to care and satisfaction among health center patients with chronic conditions. Data for this study were obtained from the 2009 Health Center Patient Survey. Dependent variables of interest included 5 measures of access to and satisfaction with care, whereas the main independent variable was number of chronic conditions. Results of bivariate analysis and multiple logistic regressions showed that patients with chronic conditions had significantly higher odds of reporting access barriers than those without chronic conditions. Our results suggested that additional efforts and resources are necessary to address the needs of health center patients with chronic conditions.

PREVALENCE OF SCOLIOSIS IN PUBLIC ELEMENTARY SCHOOL STUDENTS

PubMed Central

Ciaccia, Maria Célia Cunha; de Castro, Julia Silvestre; Rahal, Mariana Abduch; Penatti, Barbarah Silveira; Selegatto, Iara Borin; Giampietro, João Lucas Morette; Rullo, Vera Esteves Vagnozzi

2017-01-01

ABSTRACT Objective: To evaluate the prevalence of scoliosis and the risk factors in elementary school students. Methods: A cross-sectional study was carried out in 954 students in 2015. The instrument involved was a questionnaire on postural habits, socioeconomic conditions, and demographic factors. The anthropometric measurements, including height and weight, a visual inspection of the deformity of the vertebral column, the leveling of shoulders, and the Adam’s test were obtained. The sample was calculated in the expected frequency of 12.3%, acceptable error rate of 2.0% and confidence level of 95.0%. To compare the proportions, the chi-square test or Fisher’s exact test was applied. The association between scoliosis and risk factors was evaluated by logistic regression, being significant p <0.05. Results: The prevalence of scoliosis was 24.3%, higher in obese patients and students who adopted a sitting position for a long period of time. Obese students showed a 1.8 times higher chance of testing positive Adam’s Forward Bend Test when compared to normal-weight/lean and 2.1 times higher chance compared to overweight students. The sitting position for watching television increases the chance of testing positive Adam’s test in 38.0%, when compared to the lying position. Obesity increases the risk of testing positive Adam’s test in 74.0 and 98.0%, when compared, respectively, to the underweight/normal weight and overweight. Conclusions: There was a high prevalence of scoliosis in students from public elementary schools in Santos. The most influential factors for this deviation of the spine were obesity and the position adopted by students to watch television. PMID:28977336

Frequency of urinary tract infection in dogs with inflammatory skin disorders treated with ciclosporin alone or in combination with glucocorticoid therapy: a retrospective study.

PubMed

Peterson, Andrea L; Torres, Sheila M F; Rendahl, Aaron; Koch, Sandra N

2012-06-01

Few studies have investigated the frequency of urinary tract infection (UTI) in dogs receiving long-term ciclosporin therapy. The goal of the study was to investigate the frequency of UTI in dogs receiving ciclosporin with or without glucocorticoids. A secondary goal was to determine whether bacteriuria, pyuria and urine specific gravity were good predictors of UTI, and if ciclosporin dose, concurrent ketoconazole therapy, sex or duration of therapy affected the frequency of UTI. Animals -  Eighty-seven dogs with various inflammatory skin disorders and 59 control dogs with inflammatory skin conditions that had not received glucocorticoids or ciclosporin for 6 months were enrolled. This study was retrospective. The first urine culture from dogs receiving ciclosporin was compared with control dogs using Fisher's exact test. A logistic mixed model was used to test for association between a positive bacterial culture and duration of treatment, dose of ciclosporin, concurrent ketoconazole therapy and sex. The sensitivities and specificities for bacteriuria, pyuria and urine specific gravity were determined. Twenty-six of 87 (30%) ciclosporin-treated dogs had at least one positive culture. Compared with 3% positive control samples, 15% were positive in treated dogs (P=0.027). The sensitivity and specificity were, respectively, 64.1 and 98.1% for bacteriuria, 74.4 and 70.9% for pyuria, and 56.4 and 65.3% for urine specific gravity. All other analysed parameters were not significantly different. The results suggest that routine urine cultures and assessment of bacteriuria by cystocentesis should be part of the monitoring for dogs on long-term ciclosporin with and without glucocorticoids. © 2012 The Authors. Veterinary Dermatology. © 2012 ESVD and ACVD.

Risk of breast cancer with CXCR4-using HIV defined by V3 loop sequencing.

PubMed

Goedert, James J; Swenson, Luke C; Napolitano, Laura A; Haddad, Mojgan; Anastos, Kathryn; Minkoff, Howard; Young, Mary; Levine, Alexandra; Adeyemi, Oluwatoyin; Seaberg, Eric C; Aouizerat, Bradley; Rabkin, Charles S; Harrigan, P Richard; Hessol, Nancy A

2015-01-01

Evaluate the risk of female breast cancer associated with HIV-CXCR4 (X4) tropism as determined by various genotypic measures. A breast cancer case-control study, with pairwise comparisons of tropism determination methods, was conducted. From the Women's Interagency HIV Study repository, one stored plasma specimen was selected from 25 HIV-infected cases near the breast cancer diagnosis date and 75 HIV-infected control women matched for age and calendar date. HIV-gp120 V3 sequences were derived by Sanger population sequencing (PS) and 454-pyro deep sequencing (DS). Sequencing-based HIV-X4 tropism was defined using the geno2pheno algorithm, with both high-stringency DS [false-positive rate (3.5) and 2% X4 cutoff], and lower stringency DS (false-positive rate, 5.75 and 15% X4 cutoff). Concordance of tropism results by PS, DS, and previously performed phenotyping was assessed with kappa (κ) statistics. Case-control comparisons used exact P values and conditional logistic regression. In 74 women (19 cases, 55 controls) with complete results, prevalence of HIV-X4 by PS was 5% in cases vs 29% in controls (P = 0.06; odds ratio, 0.14; confidence interval: 0.003 to 1.03). Smaller case-control prevalence differences were found with high-stringency DS (21% vs 36%, P = 0.32), lower stringency DS (16% vs 35%, P = 0.18), and phenotyping (11% vs 31%, P = 0.10). HIV-X4 tropism concordance was best between PS and lower stringency DS (93%, κ = 0.83). Other pairwise concordances were 82%-92% (κ = 0.56-0.81). Concordance was similar among cases and controls. HIV-X4 defined by population sequencing (PS) had good agreement with lower stringency DS and was significantly associated with lower odds of breast cancer.

Contingency management improves smoking cessation treatment outcomes among highly impulsive adolescent smokers relative to cognitive behavioral therapy.

PubMed

Morean, Meghan E; Kong, Grace; Camenga, Deepa R; Cavallo, Dana A; Carroll, Kathleen M; Pittman, Brian; Krishnan-Sarin, Suchitra

2015-03-01

Impulsive adolescents have difficulty quitting smoking. We examined if treatments that provide behavioral incentives for abstinence improve treatment outcomes among impulsive adolescent smokers, who have been shown to be highly sensitive to reward. We ran secondary data analyses on 64 teen smokers (mean age=16.36 [1.44]; cigarettes/day=13.97 [6.61]; 53.1% female; 90.6% Caucasian) who completed a four-week smoking cessation trial to determine whether impulsive adolescents differentially benefit from receiving cognitive behavioral therapy (CBT), contingency management (CM), or the combination of the two (CM/CBT). Indices of treatment efficacy included self-report percent days abstinent and end of treatment biochemically-confirmed 7-day point prevalence abstinence (EOT abstinence). We assessed self-reported impulsivity using the Brief Barratt Impulsiveness Scale. We used univariate Generalized Linear Modeling to examine main effects and interactions of impulsivity and treatment condition as predictors of self-reported abstinence, and exact logistic regression to examine EOT abstinence. CM/CBT and CM were comparably effective in promoting abstinence, so analyses were conducted comparing the efficacy of CBT to treatments with a CM component (i.e., CM and CM/CBT). CBT and deficient self-regulation predicted lower self-reported abstinence rates within the total analytic sample. Treatments containing CM were more effective than CBT in predicting 1) self-reported abstinence among behaviorally impulsive adolescents (% days abstinent: CM 77%; CM/CBT 81%; CBT 30%) and 2) EOT point prevalence abstinence among behaviorally impulsive adolescents and adolescents with significant deficits in self-regulation. CM-based interventions may improve the low smoking cessation rates previously observed among impulsive adolescent smokers. Copyright © 2014 Elsevier Ltd. All rights reserved.

Association of complementary and alternative medicine use with symptoms and physical functional performance among adults with arthritis.

PubMed

Sharpe, Patricia A; Wilcox, Sara; Schoffman, Danielle E; Hutto, Brent; Ortaglia, Andrew

2016-01-01

Research shows high prevalence of complementary and alternative medicine (CAM) use in individuals with arthritis. Little is known about CAM use and objectively measured physical functional performance. The main objective was to determine if CAM use was associated with self-reported symptoms and physical functional performance in adults with arthritis. The secondary objectives were to describe the perceived helpfulness and correlates of CAM use. We analyzed cross-sectional data from a self-administered questionnaire and objectively measured physical functional performance prior to randomization to a self-paced exercise program or control condition (n = 401). We used the Fisher's exact test, analysis of variance, and general linear models to examine the association of CAM use with socio-demographic characteristics, symptoms and functional performance. Logistic regression computed the odds of perceiving CAM as helpful by level of use. Most respondents had used CAM (76%). Dietary supplements were the most-used (53.1%). Female gender and college education predicted greater number of modalities used. Compared to non-users, use of any CAM was associated with greater fatigue and lower grip strength; relaxation techniques with lower walk distance and gait speed; dietary change with greater pain and stiffness and lower walk distance; and yoga with lower pain and stiffness, greater walk distance, chair stands, seated reach and gait, but lower grip strength. Perceived help was positively associated with the number of modalities used. Associations between CAM and symptoms or functional performance were mixed. Only yoga showed positive associations; however, yoga practitioners were more physically active overall than non-practitioners. Copyright © 2016 Elsevier Inc. All rights reserved.

Serum uric acid levels correlate with benign paroxysmal positional vertigo.

PubMed

Celikbilek, A; Gencer, Z K; Saydam, L; Zararsiz, G; Tanik, N; Ozkiris, M

2014-01-01

Benign paroxysmal positional vertigo (BPPV) is a frequently encountered condition that can severely affect the quality of life. In this study, we aimed to assess the possible relations between serum uric acid (SUA) levels and BPPV. Fifty patients with BPPV, and 40 age- and sex-matched control subjects were enrolled in the study. All the patients and controls underwent a complete audio-vestibular test battery including the Dix-Hallpike maneuver and supine roll test for posterior semicircular canal (PSC) and horizontal semicircular canal, respectively. Routine hematological and biochemical analyses were performed in both groups. In the BPPV group, measurements of SUA levels were repeated 1 month after the vertigo attack. The lipid profiles and SUA levels were higher in patients with BPPV than detected in controls (P < 0.05 and P < 0.001, respectively). Albumin and SUA values were independently associated with BPPV in multiple logistic regression models (P < 0.05 and P < 0.001, respectively). A cutoff value of 4 for SUA level with a sensitivity of 0.72 (0.58-0.84) and a specificity of 0.60 (0.43-0.75) was obtained in the receiver operating characteristic analyses. There was a significant decrement in SUA level 1 month after the vertigo attack compared with the values obtained during the attack (P < 0.001). Among the most involved type of BPPV (PSC BPPV), the right side was affected in 26 patients (57.8%) and the left side in 19 patients (42.2%). SUA levels did not differ statistically in patients with PSC BPPV for either the right or left sides (P > 0.05). Elevated SUA is positively correlated with BPPV, requiring further efforts to clarify the exact mechanism. © 2013 The Author(s) European Journal of Neurology © 2013 EFNS.

Ureteral Injury After Laparoscopic Versus Open Colectomy

PubMed Central

Ahaghotu, Chiledum A.; Libuit, Laura; Ortega, Gezzer; Coleman, Pamela W.; Cornwell, Edward E.; Tran, Daniel D.; Fullum, Terrence M.

2014-01-01

Background and Objectives: Ureteral injury is an infrequent but potentially lethal complication of colectomy. We aimed to determine the incidence of intraoperative ureteral injury after laparoscopic and open colectomy and to determine the independent morbidity and mortality rates associated with ureteral injury. Methods: We analyzed data from the National Surgical Quality Improvement Program for the years 2005–2010. All patients undergoing colectomy for benign, neoplastic, or inflammatory conditions were selected. Patients undergoing laparoscopic colectomy versus open colectomy were matched on disease severity and clinical and demographic characteristics. Multivariate logistic regression analyses and coarsened exact matching were used to determine the independent difference in the incidence of ureteral injury between the 2 groups. Multivariate models were also used to determine the independent association between postoperative complications associated with ureteral injury. Results: Of a total of 94 526 colectomies, 33 092 (35%) were completed laparoscopically. Ureteral injury occurred in a total of 585 patients (0.6%). The crude incidence in the open group was higher than that in the laparoscopic group (0.66% versus 0.53%, P = .016). CEM produced 14 630 matching pairs. Matched analysis showed the likelihood of ureteral injury after laparoscopic colectomy to be 30% less than after open colectomy (odds ratio, 0.70; 95% confidence interval, 0.51–0.96). Patients with ureteral injury were independently more likely to have septic complications and have longer lengths of hospital stay than those without ureteral injury. Conclusion: Laparoscopic colectomy is associated with a lower incidence of intraoperative ureteral injury when compared with open procedures. Ureteral injury leads to significant postoperative morbidity even if identified and repaired during the colectomy. PMID:25392666

Malocclusion, dental aesthetic self-perception and quality of life in a 18 to 21 year-old population: a cross section study.

PubMed

Claudino, Dikson; Traebert, Jefferson

2013-01-07

Aesthetic alterations in the face can be self-perceived and can affect quality of life. For young people, physical attractiveness is an important factor affecting social relationships. The aim of this study was to estimate the prevalence of malocclusion, identify the most common types and test its association with oral aesthetic self-perception in 18 to 21 year-old population of male young adults. A cross-sectional study was carried out involving 138 Brazilian Army soldiers. Data collection included socio demographic profile, malocclusion status through the Dental Aesthetic Index (DAI) and oral aesthetic self-perception as indicated by the Oral Aesthetic Subjective Impact Scale (OASIS). The chi-square and Fisher's exact test were used to test for homogeneity of proportions. The stepwise multivariate logistic regression analysis was used to test for the relationship between the poorer oral aesthetic self-perception and parental and soldier's education, per capita income, history of caries in all teeth and only on anterior teeth, dental trauma, previous orthodontic treatment and malocclusion. The prevalence of malocclusion was 45.6%. Incisor teeth crowding and misalignment of lower incisors were the most common types of malocclusions. A statistically significant and independent association between malocclusion and poorer oral aesthetic self-perception in the multivariate analysis was observed. Subjects with severe malocclusion conditions showed 88% higher prevalence [prevalence ratio =1.88 (95% CI, 1.30 - 2.72); p = 0.001] of poorer aesthetic self-perception comparing to those with minor malocclusion. A high prevalence of malocclusion was observed. The young adults presenting severe malocclusion had a higher and independent prevalence of poorer oral aesthetic self-perception.

Risk factors for new-onset late postpartum preeclampsia in women without a history of preeclampsia.

PubMed

Bigelow, Catherine A; Pereira, Guilherme A; Warmsley, Amber; Cohen, Jennifer; Getrajdman, Chloe; Moshier, Erin; Paris, Julia; Bianco, Angela; Factor, Stephanie H; Stone, Joanne

2014-04-01

Risk factors for the development of new-onset late postpartum preeclampsia (LPP) in women without any history of preeclampsia are not known. Because identification of women who are at risk may lead to an earlier diagnosis of disease and improved maternal outcomes, this study identified risk factors (associated patient characteristics) for new-onset LPP. A case-control study of 34 women with new-onset LPP and 68 women without new-onset LPP after normal delivery, who were matched on date of delivery, was conducted at Mount Sinai Hospital, New York, NY. Data were collected by chart review. Exact conditional logistic regression identified patient characteristics that were associated with new-onset LPP. New-onset LPP was associated with age ≥40 years (adjusted odds ratio, 24.83; 95% confidence interval [CI], 1.43-infinity; P = .03), black race (adjusted odds ratio, 78.35; 95% CI, 7.25-infinity; P < .001), Latino ethnicity (adjusted odds ratio, 19.08; 95% CI, 2.73-infinity; P = .001), final pregnancy body mass index of ≥30 kg/m(2) (adjusted odds ratio, 13.38; 95% CI, 1.87-infinity; P = .01), and gestational diabetes mellitus (adjusted odds ratio, 72.91; 95% CI, 5.52-infinity; P < .001). As predictive tests for new-onset LPP, the sensitivity and specificity of having ≥1 of these characteristics was 100% and 59%, respectively, and the sensitivity and specificity of having ≥2 was 56% and 93%, respectively. Older age, black race, Latino ethnicity, obesity, and a pregnancy complicated by gestational diabetes mellitus all are associated positively with the development of new-onset LPP. Closer observation may be warranted in these populations. Copyright © 2014 Mosby, Inc. All rights reserved.

The diagnostic accuracy of the mediastinal width on supine anteroposterior chest radiographs with nontraumatic Stanford type A acute aortic dissection.

PubMed

Funakoshi, Hiraku; Mizobe, Michiko; Homma, Yosuke; Nakashima, Yoshiyuki; Takahashi, Jin; Shiga, Takashi

2018-03-01

Nontraumatic Stanford type A acute aortic dissection is a life-threatening condition; thus, the ability to make a precise diagnosis of nontraumatic Stanford type A acute aortic dissection is essential for the emergency physician. Several reports have shown that the mediastinal widening on a chest radiograph is useful for the diagnosis of nontraumatic Stanford type A acute aortic dissection; however, the exact cutoff value of the mediastinal width on plain radiographs is rarely defined. A single-center retrospective case-control study was conducted between October 1, 2013, and March 31, 2015. We evaluated the maximal mediastinal width of the anteroposterior chest X-ray at the level of the aortic knob in the supine position between patient groups with and without nontraumatic Stanford type A acute aortic dissection. We enrolled 72 patients (36 patients with nontraumatic Stanford type A acute aortic dissection and 36 patients without nontraumatic Stanford type A acute aortic dissection). The median mediastinal width of patients with nontraumatic Stanford type A acute aortic dissection was significantly larger than that of patients without nontraumatic Stanford type A acute aortic dissection (100.7 mm vs 77.7 mm, P  < .01). The optimal cutoff level was 87 mm (sensitivity, 81%; specificity, 89%). Using multivariable logistic regression, the odds ratio of a mediastinal width of >87 mm for a diagnosis nontraumatic Stanford type A acute aortic dissection was 57.1 (95% confidence interval, 11.2-290.2). A mediastinal width of >87 mm showed high sensitivity in the diagnosis of probable nontraumatic Stanford type A acute aortic dissection.

Effectiveness of palliative care services: A population-based study of end-of-life care for cancer patients.

PubMed

De Palma, Rossana; Fortuna, Daniela; Hegarty, Sarah E; Louis, Daniel Z; Melotti, Rita Maria; Moro, Maria Luisa

2018-06-01

Multiple studies demonstrate substantial utilization of acute hospital care and, potentially excessive, intensive medical and surgical treatments at the end-of-life. To evaluate the relationship between the use of home and facility-based hospice palliative care for patients dying with cancer and service utilization at the end of life. Retrospective, population-level study using administrative databases. The effect of palliative care was analyzed between coarsened exact matched cohorts and evaluated through a conditional logistic regression model. The study was conducted on the cohort of 34,357 patients, resident in Emilia-Romagna Region, Italy, admitted to hospital with a diagnosis of metastatic or poor-prognosis cancer during the 6 months before death between January 2013 and December 2015. Patients who received palliative care experienced significantly lower rates of all indicators of aggressive care such as hospital admission (odds ratio (OR) = 0.05, 95% confidence interval (CI): 0.04-0.06), emergency department visits (OR = 0.23, 95% CI: 0.21-0.25), intensive care unit stays (OR = 0.29, 95% CI: 0.26-0.32), major operating room procedures (OR = 0.22, 95% CI: 0.21-0.24), and lower in-hospital death (OR = 0.11, 95% CI: 0.10-0.11). This cohort had significantly higher rates of opiate prescriptions (OR = 1.27, 95% CI: 1.21-1.33) ( p < 0.01 for all comparisons). Use of palliative care at the end of life for cancer patients is associated with a reduction of the use of high-cost, intensive services. Future research is necessary to evaluate the impact of increasing use of palliative care services on other health outcomes. Administrative databases linked at the patient level are a useful data source for assessment of care at the end of life.

Impaired Decision-Making in Adolescent Suicide Attempters

PubMed Central

Bridge, Jeffrey A.; McBee-Strayer, Sandra M.; Cannon, Elizabeth A.; Sheftall, Arielle H.; Reynolds, Brady; Campo, John V.; Pajer, Kathleen A.; Barbe, Rémy P.; Brent, David A.

2012-01-01

Objective Decision-making deficits have been linked to suicidal behavior in adults. However, it remains unclear whether impaired decision-making plays a role in the etiopathogenesis of youth suicidal behavior. The purpose of this study was to examine decision-making processes in adolescent suicide attempters and never-suicidal comparison subjects. Method Using the Iowa Gambling Task, the authors examined decision-making in 40 adolescent suicide attempters, ages 13–18, and 40 never-suicidal, demographically-matched psychiatric comparison subjects. Results Overall, suicide attempters performed significantly worse on the Iowa Gambling Task than comparison subjects. This difference in overall task performance between the groups persisted in an exact conditional logistic regression analysis that controlled for affective disorder, current psychotropic medication use, impulsivity, and hostility (adjusted odds ratio=0.96, 95% confidence interval=0.90–0.99, p<.05). A two-way repeated-measures analysis of variance revealed a significant group-by-block interaction, demonstrating that attempters failed to learn during the task, picking approximately the same proportion of disadvantageous cards in the first and final blocks of the task. In contrast, comparison subjects picked proportionately fewer cards from the disadvantageous decks as the task progressed. Within the attempter group, overall task performance did not correlate with any characteristic of the index attempt or with the personality dimensions of impulsivity, hostility, and emotional lability. Conclusions Similar to findings in adults, impaired decision-making is associated with suicidal behavior in adolescents. Longitudinal studies are needed to elucidate the temporal relationship between decision-making processes and suicidal behavior and help frame potential targets for early identification and preventive interventions to reduce youth suicide and suicidal behavior. PMID:22449645

Trust in health information sources differs between young/middle and oldest old.

PubMed

Le, Thai; Chaudhuri, Shomir; White, Cathy; Thompson, Hilaire; Demiris, George

2014-01-01

Examine differences in trust of health information sources between the oldest old and young/middle old. Cross-sectional survey using convenience sampling. Eleven retirement communities. Older adults ≥65 years (N = 353). Self-rated trust in health information sources. Mann-Whitney U-test or Fisher exact test to compare trust between age groups; multinomial ordered logistic regression analyses to model trust in Internet information sources. The overall survey response rate was 26.6%. Differences in trust were identified between oldest old (n = 108) and young/middle old (n = 245) for pharmacist (p < .05), Internet (p < .001), television (p < .05), radio (p < .001), and newspaper (p < .05) sources. In the oldest old, we found associations between levels of trust in Internet sources and frequency of Internet use (β = 4.13, p < .001). Understanding where differences in trust arise can inform the design of resources to support the information-seeking process. When planning widespread distribution of health information to these distinct groups, program developers need to consider these differences.

Clinicopathological correlation of psychosis and brain vascular changes in Alzheimer's disease.

PubMed

Ting, Simon Kang Seng; Hao, Ying; Chia, Pei Shi; Tan, Eng-King; Hameed, Shahul

2016-02-12

Psychosis is common in Alzheimer's disease (AD). However, studies on neuropathology in vascular etiology contributing to psychosis in AD is lacking to date. The aim of this study was to investigate neuropathological vascular related changes in Alzheimer's disease with psychosis. Data of patients with AD from the National Alzheimer's Coordinating Center between 2005 to September 2013 was accessed and reviewed. Presence of psychosis was determined based on Neuropsychiatric Inventory Questionnaire taken from the last visit within one year prior to death, and patients were divided into psychosis positive and negative group. Comparison of clinical details and neuropathological vascular changes between the groups was performed using Wilcoxon rank sum test and Chi-square/ Fisher's exact test. Significant variables were further included in a multivariate logistic model. Overall, 145 patients was included. Of these, 50 patients were psychosis positive. Presence of one or more cortical microinfarcts and moderate to severe arteriosclerosis was found to be positively associated with psychosis. Our results suggest vascular changes correlate with psychosis in Alzheimer's disease.

Haemodialysis, nutritional disorders and hypoglycaemia in critical care.

PubMed

Crespo, Jeiel Carlos Lamonica; Gomes, Vanessa Rossato; Barbosa, Ricardo Luís; Padilha, Katia Grillo; Secoli, Silvia Regina

2017-03-09

This study aimed to determine hypoglycemia incidence and associated factors in critically ill patients. It looked at a retrospective cohort with 106 critically ill adult patients with 48 hours of glycaemic control and 72 hours of follow up. The dependent variable, hypoglycaemia (≤70 mg/dl), was assessed with respect to independent variables: age, diet, insulin, catecholamines, haemodialysis, nursing workload and the Simplified Acute Physiology Score. Statistical analysis was performed using Student's t-test, Fisher's exact test and logistic regression at 5% significance level. Incidence of hypoglycaemia was 14.2%. Hypoglycaemia was higher in the group of patients on catecholamines (p=0.040), with higher glycaemic variability (p<0.001) and death in the intensive care unit (p=0.008). Risk factors were identified as absence of oral diet (OR 5.11; 95% CI 1.04-25.10) and haemodialysis (OR 4.28; 95% CI 1.16-15.76). Patients on haemodialysis and with no oral diet should have their glycaemic control intensified in order to prevent and/or manage hypoglycaemic episodes.

Human Infection with Highly Pathogenic Avian Influenza Virus (H5N1) in Northern Vietnam, 2004–2005

PubMed Central

Hien, Nguyen Duc; Ha, Nguyen Hong; Van, Nguyen Tuong; Ha, Nguyen Thi Minh; Lien, Trinh Thi Minh; Thai, Nguyen Quoc; Trang, Van Dinh; Takahashi, Yoshimitsu; Kato, Yasuyuki; Kawana, Akihiko; Akita, Samu; Kudo, Koichiro

2009-01-01

We performed a retrospective case-series study of patients with influenza A (H5N1) admitted to the National Institute of Infectious and Tropical Diseases in Hanoi, Vietnam, from January 2004 through July 2005 with symptoms of acute respiratory tract infection, a history of high-risk exposure or chest radiographic findings such as pneumonia, and positive findings for A/H5 viral RNA by reverse transcription–PCR. We investigated data from 29 patients (mean age 35.1 years) of whom 7 (24.1%) had died. Mortality rates were 20% (5/25) and 50% (2/4) among patients treated with or without oseltamivir (p = 0.24), respectively, and were 33.3% (5/15) and 14.2% (2/14) among patients treated with and without methylprednisolone (p = 0.39), respectively. After exact logistic regression analysis was adjusted for variation in severity, no significant effectiveness for survival was observed among patients treated with oseltamivir or methylprednisolone. PMID:19116044

Influence of gender on office staff management in orthodontics.

PubMed

Holmes, Patrick B; Shroff, Bhavna; Best, Al M; Lindauer, Steven J

2010-11-01

To examine the gender differences in managing practice and staff members in orthodontic practices. All orthodontists in Virginia and Maryland (n = 427) were surveyed and demographic information was collected. For the crude analyses of the data, a Fisher's exact test or chi(2) test was performed. For the adjusted analyses, genders were compared using a logistic regression or analysis of covariance. The covariates were adjusted for age, program length, years in practice, number of years since graduation, and practice state. The length of the residency program attended did not differ with gender. No gender differences in practice ownership or creating the practice were observed. There was a significant gender difference in implementation of performance reviews: female orthodontists were more likely to provide performance reviews and tended to accept more poor reviews before staff termination than male orthodontists. However, when provided, no gender difference was observed in the number of performance reviews. Gender has a significant impact on the implementation of performance reviews in practices. Practice ownership status was not influenced by providers' gender.

A Comparison of Methods for Estimating Conditional Item Score Differences in Differential Item Functioning (DIF) Assessments. Research Report. ETS RR-10-15

ERIC Educational Resources Information Center

Moses, Tim; Miao, Jing; Dorans, Neil

2010-01-01

This study compared the accuracies of four differential item functioning (DIF) estimation methods, where each method makes use of only one of the following: raw data, logistic regression, loglinear models, or kernel smoothing. The major focus was on the estimation strategies' potential for estimating score-level, conditional DIF. A secondary focus…

Infrastructure, logistics and regulation of transplantation: UNOS.

PubMed

Heimbach, Julie K

2013-12-01

Organ transplantation has evolved into the standard of care for patients with end-stage organ failure. Despite considering increasingly complex transplant recipients for organs recovered from donors with increasing comorbid conditions, 1-year patient survival following kidney transplantation is 97% in the United States, whereas liver transplant recipient 1-year survival is 90%. There were 16,485 kidney recipients in the United States in 2012, and 6256 patients who underwent liver transplantation. The intent of this review is to highlight the logistics required for transplantation as well as reviewing the current oversight of transplantation. Copyright © 2013 Elsevier Inc. All rights reserved.

A study on identification of bacteria in environmental samples using single-cell Raman spectroscopy: feasibility and reference libraries.

PubMed

Baritaux, Jean-Charles; Simon, Anne-Catherine; Schultz, Emmanuelle; Emain, C; Laurent, P; Dinten, Jean-Marc

2016-05-01

We report on our recent efforts towards identifying bacteria in environmental samples by means of Raman spectroscopy. We established a database of Raman spectra from bacteria submitted to various environmental conditions. This dataset was used to verify that Raman typing is possible from measurements performed in non-ideal conditions. Starting from the same dataset, we then varied the phenotype and matrix diversity content included in the reference library used to train the statistical model. The results show that it is possible to obtain models with an extended coverage of spectral variabilities, compared to environment-specific models trained on spectra from a restricted set of conditions. Broad coverage models are desirable for environmental samples since the exact conditions of the bacteria cannot be controlled.

Exact solution and precise asymptotics of a Fisher-KPP type front

NASA Astrophysics Data System (ADS)

Berestycki, Julien; Brunet, Éric; Derrida, Bernard

2018-01-01

The present work concerns a version of the Fisher-KPP equation where the nonlinear term is replaced by a saturation mechanism, yielding a free boundary problem with mixed conditions. Following an idea proposed in Brunet and Derrida (2015 J. Stat. Phys. 161 801), we show that the Laplace transform of the initial condition is directly related to some functional of the front position μt . We then obtain precise asymptotics of the front position by means of singularity analysis. In particular, we recover the so-called Ebert and van Saarloos correction (Ebert and van Saarloos 2000 Physica D 146 1), we obtain an additional term of order log t /t in this expansion, and we give precise conditions on the initial condition for those terms to be present.

The sine method as a more accurate height predictor for hardwoods

Treesearch

Don C. Bragg

2007-01-01

Most hypsometers apply a mathematical technique that utilizes the tangent of angles and a horizontal distance to deliver the exact height of a tree under idealized circumstances. Unfortunately, these conditions are rarely met for hardwoods in the field. A “new” predictor based on sine and slope distance and discussed here does not require the same assumptions for...

Plasmon resonances, anomalous transparency, and reflectionless absorption in overdense plasmas

NASA Astrophysics Data System (ADS)

Smolyakov, A.; Sternberg, N.

2018-03-01

The structure of the surface and standing wave resonances and their coupling in the configuration of the overdense plasma slab with a single diffraction grating are studied, using impedance matching techniques. Analytical criteria and exact expressions are obtained for plasma and diffraction grating parameters which define resonance conditions for absolute transparency in the ideal plasma and reflectionless absorption in a plasma with dissipation.

Site-Based Teacher Education for Enhanced Community Knowledge and Culture: Creating the Conditions for "Philosophical Project Knowledge"

ERIC Educational Resources Information Center

Arnold, J.; Edwards, T.; Hooley, N.; Williams, J.

2013-01-01

Teacher education is in a state of uncertainty around the world including the more wealthy and less wealthy countries. If it is generally accepted that teacher education can make a difference in the educational lives of all students regardless of cultural and educational background, then how exactly to arrange the detail of schooling is not. Under…

Numerical investigation of sixth order Boussinesq equation

NASA Astrophysics Data System (ADS)

Kolkovska, N.; Vucheva, V.

2017-10-01

We propose a family of conservative finite difference schemes for the Boussinesq equation with sixth order dispersion terms. The schemes are of second order of approximation. The method is conditionally stable with a mild restriction τ = O(h) on the step sizes. Numerical tests are performed for quadratic and cubic nonlinearities. The numerical experiments show second order of convergence of the discrete solution to the exact one.

Sets of Mutually Orthogonal Sudoku Latin Squares

ERIC Educational Resources Information Center

Vis, Timothy; Petersen, Ryan M.

2009-01-01

A Latin square of order "n" is an "n" x "n" array using n symbols, such that each symbol appears exactly once in each row and column. A set of Latin squares is c ordered pairs of symbols appearing in the cells of the array are distinct. The popular puzzle Sudoku involves Latin squares with n = 9, along with the added condition that each of the 9…

Exact Analytical Solution of the Peristaltic Nanofluids Flow in an Asymmetric Channel with Flexible Walls and Slip Condition: Application to the Cancer Treatment

PubMed Central

Ebaid, Abdelhalim; Aly, Emad H.

2013-01-01

In the cancer treatment, magnetic nanoparticles are injected into the blood vessel nearest to the cancer's tissues. The dynamic of these nanoparticles occurs under the action of the peristaltic waves generated on the flexible walls of the blood vessel. Studying such nanofluid flow under this action is therefore useful in treating tissues of the cancer. In this paper, the mathematical model describing the slip peristaltic flow of nanofluid was analytically investigated. Exact expressions were deduced for the temperature distribution and nano-particle concentration. In addition, the effects of the slip, thermophoresis, and Brownian motion parameters on the temperature and nano-particle concentration profiles were discussed and further compared with other approximate results in the literatures. In particular, these results have been obtained at the same values of the physical examined parameters that was considered in Akbar et al., “Peristaltic flow of a nanofluid with slip effects,” 2012. The results reveal that remarkable differences are detected between the exact current results and those approximately obtained in the literatures for behaviour of the temperature profile and nano-particles concentration. Accordingly, the current analysis and results are considered as optimal and therefore may be taken as a base for any future comparisons. PMID:24151526