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

High-dose chemoradiotherapy followed by surgery versus surgery alone in esophageal cancer: a retrospective cohort study

<p>Abstract</p> <p>Background</p> <p>We aimed to assess whether high-dose preoperative chemoradiotherapy (CRT) improves outcome in esophageal cancer patients compared to surgery alone and to define possible prognostic factors for overall survival.</p> <p>Methods</p> <p>Hundred-and-seven patients with disease stage IIA - III were treated with either surgery alone (n = 45) or high-dose preoperative CRT (n = 62). The data were collected retrospectively. Sixty-seven patients had adenocarcinomas, 39 squamous cell carcinomas and one undifferentiated carcinoma. CRT was given as three intensive chemotherapy courses by cisplatin 100 mg/m²on day 1 and 5-fluorouracil 1000 mg/m²/day, from day 1 through day 5 as continuous infusion. One course was given every 21 days. The last two courses were given concurrent with high-dose radiotherapy, 2 Gy/fraction and a median dose of 66 Gy. Kaplan-Meier survival analysis with log rank test was used to obtain survival data and Cox Regression multivariate analysis was used to define prognostic factors for overall survival.</p> <p>Results</p> <p>Toxicity grade 3 of CRT occurred in 30 (48.4%) patients and grade 4 in 24 (38.7%) patients of 62 patients. One patient died of neutropenic infection (grade 5). Fifty percent (31 patients) in the CRT group did undergo the planned surgery. Postoperative mortality rate was 9% and 10% in the surgery alone and CRT+ surgery groups, respectively (p = 1.0). Median overall survival was 11.1 and 31.4 months in the surgery alone and CRT+ surgery groups, respectively (log rank test, p = 0.042). In the surgery alone group one, 3 and 5 year survival rates were 44%, 24% and 16%, respectively and in the CRT+ surgery group they were 68%, 44% and 29%, respectively. By multivariate analysis we found that age of patient, performance status, alcoholism and > = 4 pathological positive lymph nodes in resected specimen were significantly associated with overall survival, whereas high-dose preoperative CRT was not.</p> <p>Conclusion</p> <p>We found no significant survival advantage in esophageal cancer stage IIA-III following preoperative high-dose CRT compared to surgery alone. Patient's age, performance status, alcohol abuse and number of positive lymph nodes were prognostic factors for overall survival.</p

Phase II study of induction chemotherapy with TPF followed by radioimmunotherapy with Cetuximab and intensity-modulated radiotherapy (IMRT) in combination with a carbon ion boost for locally advanced tumours of the oro-, hypopharynx and larynx - TPF-C-HIT

<p>Abstract</p> <p>Background</p> <p>Long-term locoregional control in locally advanced squamous cell carcinoma of the head and neck (SCCHN) remains challenging. While recent years have seen various approaches to improve outcome by intensification of treatment schedules through introduction of novel induction and combination chemotherapy regimen and altered fractionation regimen, patient tolerance to higher treatment intensities is limited by accompanying side-effects. Combined radioimmunotherapy with cetuximab as well as modern radiotherapy techniques such as intensity-modulated radiotherapy (IMRT) and carbon ion therapy (C12) are able to limit toxicity while maintaining treatment effects. In order to achieve maximum efficacy with yet acceptable toxicity, this sequential phase II trial combines induction chemotherapy with docetaxel, cisplatin, and 5-FU (TPF) followed by radioimmunotherapy with cetuximab as IMRT plus carbon ion boost. We expect this approach to result in increased cure rates with yet manageable accompanying toxicity.</p> <p>Methods/design</p> <p>The TPF-C-HIT trial is a prospective, mono-centric, open-label, non-randomized phase II trial evaluating efficacy and toxicity of the combined treatment with IMRT/carbon ion boost and weekly cetuximab in 50 patients with histologically proven locally advanced SCCHN following TPF induction chemotherapy. Patients receive 24 GyE carbon ions (8 fractions) and 50 Gy IMRT (2.0 Gy/fraction) in combination with weekly cetuximab throughout radiotherapy. Primary endpoint is locoregional control at 12 months, secondary endpoints are disease-free survival, progression-free survival, overall survival, acute and late radiation effects as well as any adverse events of the treatment as well as quality of life (QoL) analyses.</p> <p>Discussion</p> <p>The primary objective of TPF-C-HIT is to evaluate efficacy and toxicity of cetuximab in combination with combined IMRT/carbon ion therapy following TPF induction in locally advanced SCCHN.</p> <p>Trial Registration</p> <p>Clinical Trial Identifier: <a href="http://www.clinicaltrials.gov/ct2/show/NCT01245985">NCT01245985</a> (clinicaltrials.gov)</p> <p>EudraCT number: 2009 - 016489- 10</p

Effect of high-pressure torsion on microstructure, mechanical properties and corrosion resistance of cast pure Mg

© 2018, The Author(s). High-pressure torsion (HPT) processing was applied to cast pure magnesium, and the effects of the deformation on the microstructure, hardness, tensile properties and corrosion resistance were evaluated. The microstructures of the processed samples were examined by electron backscatter diffraction, and the mechanical properties were determined by Vickers hardness and tensile testing. The corrosion resistance was studied using electrochemical impedance spectroscopy in a 3.5% NaCl solution. The results show that HPT processing effectively refines the grain size of Mg from millimeters in the cast structure to a few micrometers after processing and also creates a basal texture on the surface. It was found that one or five turns of HPT produced no significant difference in the grain size of the processed Mg and the hardness was a maximum after one turn due to recovery in some grains. Measurements showed that the yield strength of the cast Mg increased by about seven times whereas the corrosion resistance was not significantly affected by the HPT processing