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Search Results: 1 - 10 of 1504 matches for " Sabrina Selk "
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Community Violence as Psychosocial Stressor:The Case of Childhood Asthma in Boston  [PDF]
Gonzalo Bacigalupe, Takeo Fujiwara, Sabrina Selk, Meghan Woo
Psychology (PSYCH) , 2010, DOI: 10.4236/psych.2010.11005
Abstract: Childhood asthma is a critical public health problem of urban centers in the United States and other industrialized nations. Population-based and laboratory research studies indicate that psychosocial stress differentially affects asthma expression. Witnessing or experiencing community violence is a psychosocial stressor that results in long-term biological changes that may in turn contribute to asthma morbidity. This is a review of the literature that examines the exposure to violence as a psychosocial stressor that is independently associated with asthma morbidity even after adjustment for income, housing, and other adverse life events. In addition to acting as a physiological trigger for the disease, community violence can also impact health behaviors and exposure to other unknown environmental risk factors. This connection leads the authors to suggest that reducing violence and the amelioration of its impact has implications beyond public health. The City of Boston in Massachusetts serves as the context to contextualize a series of recommendations that may ameliorate and/or prevent asthma incidence and prevalence. The reduction of poverty, unemployment, substandard housing, and high crime/violence rates can have significant health implications for children asthma and a decline on asthma hospitalization.
Testing for a change of the innovation distribution in nonparametric autoregression - the sequential empirical process approach
Leonie Selk,Natalie Neumeyer
Statistics , 2012,
Abstract: We consider a nonparametric autoregression model under conditional heteroscedasticity with the aim to test whether the innovation distribution changes in time. To this end we develop an asymptotic expansion for the sequential empirical process of nonparametrically estimated innovations (residuals). We suggest a Kolmogorov-Smirnov statistic based on the difference of the estimated innovation distributions built from the first ns and the last n-ns residuals, respectively. Weak convergence of the underlying stochastic process to a Gaussian process is proved under the null hypothesis of no change point. The result implies that the test is asymptotically distribution-free. Consistency against fixed alternatives is shown. The small sample performances of the proposed test is investigated in a simulation study and the test is applied to data examples.
A note on nonparametric testing for Gaussian innovations in AR-ARCH models
Natalie Neumeyer,Leonie Selk
Statistics , 2012,
Abstract: In this paper we consider autoregressive models with conditional autoregressive variance, including the case of homoscedastic AR-models and the case of ARCH models. Our aim is to test the hypothesis of normality for the innovations in a completely nonparametric way, i. e. without imposing parametric assumptions on the conditional mean and volatility functions. To this end the Cram\'er-von Mises test based on the empirical distribution function of nonparametrically estimated residuals is shown to be asymptotically distribution-free. We demonstrate its good performance for finite sample sizes in a simulation study.
Efficient estimation of functionals in nonparametric boundary models
Markus Rei?,Leonie Selk
Statistics , 2014,
Abstract: For nonparametric regression with one-sided errors and a boundary curve model for Poisson point processes we consider the problem of efficient estimation for linear functionals. The minimax optimal rate is obtained by an unbiased estimation method which nevertheless depends on a H\"older condition or monotonicity assumption for the underlying regression or boundary function. We first construct a simple blockwise estimator and then build up a nonparametric maximum-likelihood approach for exponential noise variables and the point process model. In that approach also non-asymptotic efficiency is obtained (UMVU: uniformly minimum variance among all unbiased estimators).The proofs rely essentially on martingale stopping arguments for counting processes and the point process geometry. The estimators are easily computable and a small simulation study confirms their applicability.
Human Resources Information System (HRIS): A Theoretical Perspective  [PDF]
Sabrina Sabrina Jahan
Journal of Human Resource and Sustainability Studies (JHRSS) , 2014, DOI: 10.4236/jhrss.2014.22004
Abstract: HRIS is one of the major modern HR tools. In developed countries, it became popular since the be-ginning of this century. In Bangladesh, corporate organizations have started to implement HRIS in last 5 years. But still its implementation is limited within the big corporate houses. Small corporate houses and public organizations have failed to realize the benefits of HRIS and taken hardly any initiative to implement the system. The major barrier to success of HRIS is the lack of management commitment. The major limitation is the high cost. But the benefits of the HRIS are more than the limitations. Once it is implemented in any organization, employees and management have accepted and realized the benefits. But to get it implemented is a challenge. This study is an attempt to provide a theoretical analysis of the HRIS implementation with analysis of benefits, limitations and barriers. A case study was prepared to provide a better understanding of the topic in a real life context.
Evaluation of Durability Conferred by an Oleothermic Treatment on Chestnut and Douglas fir through Laboratory and in Field Tests  [PDF]
Sabrina Palanti
Open Journal of Forestry (OJF) , 2013, DOI: 10.4236/ojf.2013.32011

The research evaluated two wood species, chestnut and Douglas fir, that are widespread in Tuscany, treated with an oleothermicprocess. Efficacy of this treatment against fungal decay was assessed through laboratory and field tests. The aim of this research was to investigate if an oleothermic process could add value to these natural resources when utilized in Use Class 4 (EN 335) for agricultural purposes such as vineyard poles. The treatment was effective on sapwood of both wood species in laboratory test, giving a protection similar to the untreated heartwood but in case of chestnut, it was easily washed away. In field test the leaching during the outdoor exposure reduced the resistance to fungal decay in both species.


Statistical properties of Joule heating rate, electric field and conductances at high latitudes
A. T. Aikio ,A. Selk l
Annales Geophysicae (ANGEO) , 2009,
Abstract: Statistical properties of Joule heating rate, electric field and conductances in the high latitude ionosphere are studied by a unique one-month measurement made by the EISCAT incoherent scatter radar in Troms (66.6 cgmlat) from 6 March to 6 April 2006. The data are from the same season (close to vernal equinox) and from similar sunspot conditions (about 1.5 years before the sunspot minimum) providing an excellent set of data to study the MLT and Kp dependence of parameters with high temporal and spatial resolution. All the parameters show a clear MLT variation, which is different for low and high Kp conditions. Our results indicate that the response of morning sector conductances and conductance ratios to increased magnetic activity is stronger than that of the evening sector. The co-location of Pedersen conductance maximum and electric field maximum in the morning sector produces the largest Joule heating rates 03–05 MLT for Kp≥3. In the evening sector, a smaller maximum occurs at 18 MLT. Minimum Joule heating rates in the nightside are statistically observed at 23 MLT, which is the location of the electric Harang discontinuity. An important outcome of the paper are the fitted functions for the Joule heating rate as a function of electric field magnitude, separately for four MLT sectors and two activity levels (Kp<3 and Kp≥3). In addition to the squared electric field, the fit includes a linear term to study the possible anticorrelation or correlation between electric field and conductance. In the midday sector, positive correlation is found as well as in the morning sector for the high activity case. In the midnight and evening sectors, anticorrelation between electric field and conductance is obtained, i.e. high electric fields are associated with low conductances. This is expected to occur in the return current regions adjacent to auroral arcs as a result of ionosphere-magnetosphere coupling, as discussed by Aikio et al. (2004) In addition, a part of the anticorrelation may come from polarization effects inside high-conductance regions, e.g. auroral arcs. These observations confirm the speculated effect of small scale electrodynamics, which is not included in most of the global modeling efforts of Joule heating rate.
Hypotheses tests in boundary regression models
Holger Drees,Natalie Neumeyer,Leonie Selk
Statistics , 2014,
Abstract: We consider a nonparametric regression model with one-sided errors and regression function in a general H\"older class. Our aim is inference on the error distribution. To this end we estimate the regression function via minimization of the local integral of a polynomial approximation. We show uniform rates of convergence for the simple regression estimator as well as for a smooth version. Those rates continue to hold in mean regression models with symmetric and bounded error distribution. Here one obtains faster rates of convergence compared to optimal rates in mean regression when the error distribution is irregular in the sense that sufficient mass is concentrated near the endpoints. The results are applied to prove asymptotic $\sqrt{n}$-equivalence of a residual-based empirical distribution function to the empirical distribution function of unobserved errors in the case of irregular error distributions. This result is remarkably different from corresponding results in mean regression with regular errors. It can readily be applied to develop goodness-of-fit tests for the error distribution. We present some examples and investigate the small sample performance in a simulation study.
Seroprevalence of Toxoplasma Gondii Infection in Dogs in Tehran, Iran
M Hosseininejad,A Malmasi,F Hosseini,M Selk-Ghaffari
Iranian Journal of Parasitology , 2011,
Abstract: Background: Toxoplasma gondii infects a wide range of animals; felines are definitive hosts and other animals including the dogs are intermediate hosts. The aim of this study was to determine the seroprevalence of T. gondii infection in dogs in Tehran, capital of Iran and to investigate possi-ble associated risk factors.Methods: Three hundreds ninety six serum samples were collected during 2007-8 from the dogs. Col-lected samples were tested using an indirect fluorescent antibody test (IFAT) in dilutions of 1:16 and more. All procedures were carried out in Shahrekord University, Iran. All the data were analyzed using SPSS software, qui square test with confidence interval of 0.95.Results: From evaluated samples, 89 (22.47%) were positive in titers of at least 1:16. further evalua-tions in other dilutions showed positive results in dilutions of maximum 1:16 , 1:32, 1:64, 1:128 and 1:256 in 38, 29, 15, 2 and 5 dogs respectively. Investigation of the role of risk factors showed no sex predisposition while infection rate was significantly higher in dogs older than one year old. Living places were of significant importance; infection rate was significantly higher in stray or guard dogs in compare with household dogs (P<0.05). Conclusion: Relatively high seroprevalence of T. gondii infection in dogs in Tehran shows high environmental contamination. It is recommended that the dogs with suspected clinical signs be tested for T. gondii infection.
Public Policy Making in the Coastal Zone of the Venice Lagoon: Is There a Good Balance between Economic Development, the Social Dimension and Environmental Protection?  [PDF]
Maria Sabrina De Gobbi
Open Journal of Political Science (OJPS) , 2013, DOI: 10.4236/ojps.2013.34019

This paper shows how much citizens’ views are taken into account in local policy decision-making concerning the management of the coastal area of the Venice Lagoon. Through the application of a somewhat innovative version of the contingent valuation method (CVM), it is possible to understand how to set a good balance among economic development, the social dimension and environmental protection in a coastal zone. The methodology allows for a clear assessment of the economic value of non-use values. In 2010, an online survey was conducted in the Venice area to find out how local much citizens value two protected areas in the Venice Lagoon. Four hypotheses were tested to find out whether the age of respondents, the municipality where they live, their income level, and the visited and protected sites are factors determining a different willingness to pay for environmental protection. The economic, social and environmental situation of the coastal zone of the Venice Lagoon in 2010 was then compared to that of 2012 to try to draw conclusions on the level of sustainability of the management of the Venice coastal area. The comparison indicates that there have been some improvements in citizens’ participation in decision-making

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