Properties of estimators of parameters in logistic regression models

Properties of various types of estimators of the regression coefficients in linear logistic regression models are considered. The estimators include those based on maximum likelihood, minimum chi-square and weighted least squares. Theoretical approximations to the biases of the estimators are developed. The results of a large scale simulation investigation evaluating the moment properties of the estimators are presented for the case of a logistic model with a single explanatory variable

The extreme residuals in logistic regression models

Goodness of fit tests for logistic regression models using extreme residuals are considered. Moment properties of the Pearson residuals are developed and used to define modified residuals, for the cases when the model fit is made by maximum likelihood, minimum chi-square and weighted least squares. Approximations to the critical values of the extreme statistics based on the ordinary and modified Pearson residuals are developed and assessed for the case when the logistic regression model has a single explanatory variable

Null distribution of some goodness of fit statistics for logistic regression

The null distribution moment and percentile properties of several goodness of fit statistics for logistic regression models are considered. Small sample approximations to the critical values of the statistics are evaluated for the case of a single explanatory variable with equally spaced values

Flexural Behavior of Self-Compacting RC Continuous Beams Strengthened by CFRP Sheets

قدم هذا البحث دراسة عملية لتقصي سلوك انحناء العتبات الخرسانية المسلحة المستمرة ذاتية الرص المدعمة خارجيا بشرائح الياف الكربون البوليمرية. الدراسة العملية اشتملت على ثمانية اعتاب خرسانية ذاتية الرص مسلحة مستمرة مكونة من فضائين كل فضاء بطول 1500 مليمتر بابعاد (150*250). تم تقوية سبعة من هذه العتبات الخرسانية المسلحة خارجيا باستخدام شرائح من الياف الكربون البوليمرية مع استعمال او بدون استعمال الارساء الخارجي. المتغيرات الرئيسية تضمنت موقع شرائح الياف الكربون البوليمرية ونوع الارساء في النهائيات. اظهرت النتائج العملية بان الاعتاب المقواة خارجيا بشرائح الياف الكربون البوليمرية ابدت زيادات ملحوظة في الاحمال القصوى. بلغت الزيادة في الحمال الاقصى الى (60.71%) بالمقارنة مع العتبة المرجعية غير المقواة بشرائح الياف الكربون البوليمرية. ان الارساء بالياف الكربون البوليمرية فعال جدا اكثر من جعل شريحة الياف الكربون البوليمرية تمتد تحت المساند او الحمل المركز (في زيادة الحمل النهائي وتقليل هطول الاعتاب). وان التقوية في الجوانب طريقة فعالة جدا في زيادة احمال التشقق الاولي وصلت الى (125%) بالمقارنة مع العتبة المرجعية غير المقواة بشرائح الياف الكربون البوليمرية.This search presented an experimental study of the flexural behavior of self-compacting reinforced concrete continuous beams externally strengthened by carbon fiber reinforced polymer (CFRP) Sheets. The practical study contained eight self-compacting reinforced concrete continuous beams (with two span), each span had (1500) mm length and (150x250) mm cross sectional dimensions. Seven of these beams strengthened externally by CFRP sheets with and without external anchorage. The experimental variables included location of CFRP sheets and anchor type and location. The results, shows that the beams strengthened externally by CFRP sheets provided improvement in ultimate loads reached (60.71%). The usage of CFRP in the anchorage zone indicated an effective method in comparison to increasing the CFRP sheets lengths or extending them up to the support or under the loading points. Test results also showed that side strengthening provided an effective tool for increasing the load at the cracking stage and also the load capacity and reducing flexural crack widths

Influence of Anchorage on the Behavior of CFRP RC Beams in Flexure

This research study involves experimental and theoretical investigations of thebehavior of flexural debonding of carbon fiber reinforced polymer (CFRP) laminateswith steel anchorages. A total of nine reinforced concrete beam specimens with crosssection of (150mm width by 250mm height and 2000mm length) were investigated inthis study to observe the flexural strength of each one. Eight beam specimens werestrengthened with CFRP laminates and one beam specimen was tested withoutstrengthening. The experimental results showed that the use of CFRP strips as externalstrengthening has significant positive effect on ultimate loads, crack patterns anddeflections. The percent of increasing of the ultimate load capacity can be increased byabout 65% when using two layers of CFRP strips instead of one layer. The ultimateload is increased by about 118% for the beams strengthened with bonded CFRP andexternal anchorage with respect to the reference beam. Three-dimensional nonlinearfinite element analysis (i.e. ANSYS - version 9.0 computer program ) is used toinvestigate the performance of reinforced concrete beams strengthened with CFRP.The comparison between the numerical and the experimental results asserted that goodvalidity of the numerical analysis and the methodology developed in this study

Behavior of Short Span Composite Beams Strengthened with CFRP Strips

The experimental program in this paper is divided into two groups: the firstone consists of seven composite beams; six of them were strengthened with oneand two CFRP strips and with three different percentages of full beam length(40%, 60%, and 100%). The second group consists of five composite beamsstrengthened at the face of the bottom flange with CFRP strips fastened to the steelsection by steel bolts with two different length proportion of CFRP strips to beamsoffit (60%, and 100%).The analytical investigation included the use of three dimensionalnonlinear finite elements to model the performance of the composite beams using(ANSYS 8.0) computer program

Spread of imipenem-resistant Acinetobacter baumannii co-expressing OXA-23 and GES-11 carbapenemases in Lebanon

© 2015 The Authors. Objectives: The acquisition of carbapenemases by Acinetobacter baumannii is reported increasingly worldwide, but data from Lebanon are limited. The aims of this study were to evaluate the prevalence of imipenem-resistant A. baumannii in Lebanon, identify resistance determinants, and detect clonal relatedness. Methods: Imipenem-resistant A. baumannii were collected from nine Lebanese hospitals during 2012. Antimicrobial susceptibility, the cloxacillin effect, and ethylenediaminetetraacetic acid (EDTA) synergy were determined. Genes encoding carbapenemases and insertion sequence IS. Aba1 were screened via PCR sequencing. IS. Aba1 position relative to genes encoding Acinetobacter-derived cephalosporinases (ADCs) and OXA-23 was studied by PCR mapping. Clonal linkage was examined by enterobacterial repetitive intergenic consensus PCR (ERIC-PCR). Results: Out of 724 A. baumannii isolated in 2012, 638 (88%) were imipenem-resistant. Of these, 142 were analyzed. Clavulanic acid-imipenem synergy suggested carbapenem-hydrolyzing extended-spectrum β-lactamase. A positive cloxacillin test indicated ADCs, while EDTA detection strips were negative. Genotyping indicated that 90% of isolates co-harbored blaOXA-23 and blaGES-11. The remaining strains had blaOXA-23, blaOXA-24, blaGES-11, or blaOXA-24 with blaGES-11. ISAba1 was located upstream of blaADC and blaOXA-23 in 97% and 100% of isolates, respectively. ERIC-PCR fingerprinting revealed 18 pulsotypes spread via horizontal gene transfer and clonal dissemination. Conclusion: This survey established baseline evidence of OXA-23 and GES-11-producing A. baumannii in Lebanon, indicating the need for further surveillance

Impact of Radiotherapy, Chemotherapy and Surgery in Multimodal Treatment of Locally Advanced Esophageal Cancer

Objectives: It was the aim of this study to assess our institutional experience with definitive chemoradiation (CRT) versus induction chemotherapy followed by CRT with or without surgery (C-CRT/S) in esophageal cancer. Methods: We retrospectively analyzed 129 institutional patients with locally advanced esophageal cancer who had been treated by either CRT in analogy to the RTOG 8501 trial (n = 78) or C-CRT/S (n = 51). Results: The median, 2-and 5-year overall survival (OS) of the entire collective was 17.6 months, 42 and 24%, respectively, without a significant difference between the CRT and C-CRT/S groups. In C-CRT/S patients, surgery statistically improved the locoregional control (LRC) rates (2-year LRC 73.6 vs. 21.2%; p = 0.003); however, this was translated only into a trend towards improved OS (p = 0.084). The impact of escalated radiation doses (>= 60.0 vs. <60.0 Gy) on LRC was detectable only in T1-3 N0-1 M0 patients of the CRT group (2-year LRC 77.8 vs. 42.3%; p = 0.036). Conclusion: Definitive CRT and a trimodality approach including surgery (C-CRT/S) had a comparable outcome in this unselected patient collective. Surgery and higher radiation doses improve LRC rates in subgroups of patients, respectively, but without effect on OS. Copyright (C) 2012 S. Karger AG, Base

Countrywide spread of OXA-48 carbapenemase in Lebanon: Surveillance and genetic characterization of carbapenem-non-susceptible Enterobacteriaceae in 10 hospitals over a one-year period

© 2014 The Authors. Objectives: To detect, characterize, and assess the genetic clonality of carbapenem-non-susceptible Enterobacteriaceae in 10 Lebanese hospitals in 2012. Methods: Selected Enterobacteriaceae isolates with reduced susceptibility to carbapenems were subject to phenotypic study including antibiotic susceptibility, cloxacillin effect, modified Hodge test, and activity of efflux pump inhibitor. Carbapenemase genes were detected using PCR; clonal relatedness was studied by pulsed field gel electrophoresis. Results: Out of 8717 Enterobacteriaceae isolated in 2012, 102 (1.2%) showed reduced susceptibility to carbapenems. Thirty-one (70%) of the 44 studied clinical isolates harbored blaOXA-48, including 15 Klebsiella pneumoniae, eight Escherichia coli, four Serratia marcescens, three Enterobacter cloacae, and one Morganella morganii. The majority of OXA-48 producers co-secreted an extended-spectrum beta-lactamase, while one had an acquired AmpC of the ACC type. In the non-OXA-48 producers, carbapenem resistance was attributed to the production of acquired AmpC cephalosporinases of MOX or CIT type, outer membrane impermeability, and/or efflux pump overproduction. DNA fingerprints revealed that OXA-48 producers were different, except for clonal relatedness among four K. pneumoniae, two E. coli, two E. cloacae, and three S. marcescens. Conclusions: Nosocomial carbapenem-non-susceptible Enterobacteriaceae are moderately spread in Lebanon and the predominant mechanism is OXA-48 production

Prevalence and correlates of psychiatric disorders in a national survey of Iranian children and adolescents

Objective: Considering the impact of rapid sociocultural, political, and economical changes on societies and families, population-based surveys of mental disorders in different communities are needed to describe the magnitude of mental health problems and their disabling effects at the individual, familial, and societal levels. Method: A population-based cross sectional survey (IRCAP project) of 30 532 children and adolescents between 6 and 18 years was conducted in all provinces of Iran using a multistage cluster sampling method. Data were collected by 250 clinical psychologists trained to use the validated Persian version of the semi-structured diagnostic interview Kiddie-Schedule for Affective Disorders and Schizophrenia-PL (K-SADS-PL). Results: In this national epidemiological survey, 6209 out of 30 532 (22.31%) were diagnosed with at least one psychiatric disorder. The anxiety disorders (14.13%) and behavioral disorders (8.3%) had the highest prevalence, while eating disorders (0.13%) and psychotic symptoms (0.26%) had the lowest. The prevalence of psychiatric disorders was significantly lower in girls (OR = 0.85; 95% CI: 0.80-0.90), in those living in the rural area (OR = 0.80; 95% CI: 0.73-0.87), in those aged 15-18 years (OR = 0.92; 95% CI: 0.86-0.99), as well as that was significantly higher in those who had a parent suffering from mental disorders (OR = 1.96; 95% CI: 1.63-2.36 for mother and OR = 1.33; 95% CI: 1.07-1.66 for father) or physical illness (OR = 1.26; 95% CI: 1.17-1.35 for mother and OR = 1.19; 95% CI: 1.10-1.28 for father). Conclusion: About one fifth of Iranian children and adolescents suffer from at least one psychiatric disorder. Therefore, we should give a greater priority to promoting mental health and public health, provide more accessible services and trainings, and reduce barriers to accessing existing services. © 2019 Tehran University of Medical Scienc