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

Prediction of Weld Strength in Power Ultrasonic Spot Welding Process Using Artificial Neural Network (ANN) and Back Propagation Method

In this presented work, the employment of artificial neural network (ANN) connected with back propagation method was performed to predict the strength of joining materials that carried out by using ultrasonic spot welding process. The models which created in this study were investigated and their process parameters were analysed. These parameters were classified and set as input variables like for example applying pressure, time of duration weld and trigger of vibrating amplitude while weld strength of joining dissimilar materials (Al-Cu) is set as output parameters. The identification from the process parameters are obtained using number of experiments and finite element analyses based prediction. The results of actual and numerical are accurate and reliability, however its complexity has significant effect due to sensitive to the condition variation of welding processes. Therefore, the needed for an efficient technique like artificial neural network coupled with back propagation method is required to use the experiments as an input data in simulation of ultrasonic welding process, finding the adequacy of modeling process in prediction of weld strength and to confirm the performance of using mathematical methods. The results of the selecting non-linear models show a noticeable potency when using ANN with back propagation method in providing high accuracy compared with other results obtained by conventional models

Design and Analysis of Ultrasonic Horns Operating in Multiple Vibration Modes

A number of recent studies have shown that combining different modal responses can provide opportunities to improve the vibration behaviour of the output faces of tuned ultrasonic horns to provide a more effective use of the ultrasonic energy. Investigation the benefits of combining different modal responses with a view to optimizing the energy transfer from a range of power ultrasonic devices that rely on tuned horns is essential. This research will therefore aim to investigate the use of combining and exciting different vibration modes in order to design more effective resonant horns for use in high power ultrasonics applications such as metal forming, welding, cleaning and surgical devices. The research is extended to study the possibility of design an ultrasonic transducer which can operate in multiple vibration modes by modify its geometric features. The longitudinal- torsional mode is selected first because of its wide applications in ultrasonic field. The effect of geometrical modifications of transducer's matching part is being analyzed analytically, numerically and experimentally. The suggested modifications are including cut of slots and reduce the cross sectional area so that the excited longitudinal vibrational mode can be regenerated into a longitudinal-torsional mode. The considerations of simplicity of manufacturing and exciting and the efficient of energy conversion are the main advantages of the proposed transducer. Keywords–ultrasonic transducer, design horn; resonant frequency; model and harmonic analysis DOI: 10.7176/JIEA/9-3-02 Publication date:May 31st 201

Long-term dynamic changes in the haemoparasites community, and description and characterization of a novel Babesia species and co-infecting blood parasites, of rodents from the Sinai massif (Egypt)

Abstract First section: Long-term dynamics of haemoparasite infections in spiny mice A. dimidiatus Long-term field studies of parasite communities provide a powerful insight into the ecological processes shaping host-parasite interactions. The aim of the study was to monitor long-term trends in the haemoparasite communities of spiny mice (Acomys dimidiatus) over a 12 year period. We sampled four semi-isolated populations of mice (n = 835) in 2000, 2004, 2008 and 2012 in four montane valleys (Wadis) in the Sinai Massif, Egypt. Overall 76.2 % of spiny mice carried at least one of parasite genera (Babesia, Bartonella, Haemobartonella, Hepatozoon, Trypanosoma). I observed a decrease in the prevalence of haemoparasites over successive years of the study. The highest prevalence was recorded in 2004, while the lowest was in 2012. I observed also marked differences in the prevalence of haemoparasites in spiny mice from different valleys– the highest prevalence was in W. Tlah and the lowest in W. Arbaein. Species richness was highest among mice from W. Tlah and peaked in age class 2 (young adults). In four of the five genera we observed a significant drop in prevalence or/and abundance since 2004, the exception being Hepatozoon sp. During the 12-year-long period of study in the Sinai, we observed dynamic changes in prevalence and abundance of infections which differed depending on parasite species. Although the exact reasons cannot be identified at this time, we hypothesize that the effects of a 15-year-long scarcity of rainfall in the local environment and a fall in host densities over the period of study may have been responsible for a drop in transmission rates, possibly by a negative impact on vector survival. Second section: description of a new species of Babesia (Babesia behnkei) from D. dasyurus Although a number of new species of Babesia/Theileria have been described recently, there are still relatively few reports of species from Africa. Based on the evaluation of morphology and phylogenetic relationships, we describe a novel species Babesia behnkei n. sp. from Wagner’s gerbil. The overall prevalence of Babesia spp. was highest in the Wagner’s gerbil (Dipodillus dasyurus; 38.7%) in comparison to the prevalence in two mice species. Thirty-two isolates derived from D. dasyurus in a period 2004-2012 from two wadies (29 isolates from W. Gebal and 3 from W. Arbaein) were investigated by microscopic, molecular and phylogenetic analyses. A near-full-length sequence of the 18S rRNA gene and the first and second internal transcribed spacer (ITS1, ITS2) region were amplified, sequenced and used for the construction of phylogenetic trees. Phylogenetic analyses revealed that B. behnkei n. sp. is most closely related to B. lengau from cheetahs and belong to phylogenetic ‘Duncani’ group, and is distant to the cosmopolitan rodent B. microti. Babesia behnkei n. sp. is a novel species of Babesia.Część I: wieloletnia dynamika zarażeń hemopasożytami u kolcomyszy arabskiej A. dimidiatus (Alsarraf et al. 2016) Wieloletnie parazytologiczne badania środowiskowe pozwalają na szeroki wgląd 
w ekologiczne i ewolucyjne kształtowanie się układu pasożyt-żywiciel. Celem badań było określenie dynamiki zespołu pasożytów krwi u A. dimidiatus na przestrzeni 12 lat badań. Do realizacji tego celu zbadałem 835 kolcomyszy arabskich z czterech odizolowanych dolin górskich (W. Arbaein, W. Gebal, W. Gharaba i W. Tlah) z Masywu Synaju (Egipt) w latach 2000, 2004, 2008 i 2012. Ogólna ekstensywność zarażenia pasożytami krwi u A. dimidiatus wynosiła 76.2%, gdzie przynajmniej jeden z pięciu pasożytów (Babesia, Bartonella, Haemobartonella, Hepatozoon, Trypanosoma) występował u danego gryzonia. Na przestrzeni lat zaobserwowałem istotny spadek ekstensywności zarażenia hemopasożytami– najwyższą ekstensywność zarażenia odnotowałem w roku 2004, natomiast najniższą w roku 2012. Zaobserwowałem różnice w ekstensywności zarażenia hemopasożytami pomiędzy populacjami kolcomyszy z różnych dolin badań – najwyższą ekstensywność odnotowałem w W. Tlah, a najniższą w W. Arbaein. Najwyższe bogactwo gatunkowe odnotowałem u gryzoni z W. Tlah i w klasie wiekowej młodych-dorosłych. Zaobserwowałem istotny spadek w ekstensywności i intensywności zarażenia większości pasożytów, oprócz Hepatozoon, od roku 2004. Obecnie dokładne przyczyny tego zjawiska nie mogą być zidentyfikowane, choć można postawić hipotezę, że efekty 15-letniego niedoboru opadów w środowisku lokalnym oraz spadek zagęszczeń żywicieli mogą być odpowiedzialne za spadek transmisji pasożytów, prawdopodobnie poprzez negatywny wpływ na przeżycie wektorów.Część II: Opis nowego gatunku Babesia (Babesia behnkei) u D. dasyurusPomimo opisania kilku nowych gatunków Babesia/ Theileria, wciąż jest niewiele badań nad gatunkami Babesia z Afryki. Na podstawie analizy morfologicznej i filogenetycznej opisaliśmy nowy gatunek Babesia: Babesia behnkei n. sp., występujący u myszoskocza arabskiego Dipodillus dasyurus. Ogólna ekstensywność zarażenia Babesia spp. była najwyższa (38.7%) u myszoskocza, w porównaniu do dwóch gatunków kolcomyszy. Dla 32 izolatów Babesia z D. dasyurus z lat 2004-2012, z dwóch dolin (29 z W. Gebal i 3 izolaty z W. Arbaein) wykonano analizy mikroskopowe, molekularne i filogenetyczne. Do analizy molekularnej i filogenetycznej wykorzystałem prawie cały gen 18S rRNA i rejony ITS1 i ITS2. Analiza filogenetyczna dla genu 18S rRNA i rejonu ITS2 wykazała, że B.behnkei n. sp. jest blisko spokrewniona z B.lengau od geparda, należy do grupy filognetycznej ‘Duncani’ i jest odległa od kosmopolitycznego gatunku B. microti, występującego u gryzoni. B.behnkei n. sp. jest nowym gatunkiem Babesia

Coronary artery bypass grafting in a patient with polycythaemia rubra vera - a rare indication with a spectrum of complication: a case report

Coronary artery bypass surgery for coronary artery thrombosis in patients with polycythaemia rubra vera has been rarely described. The main issue with such patients is their risk of both bleeding and thrombosis and as such the ideal postoperative management of such cases is unknown. Hereby, we describe a case of a 62-year-old man with polycythaemia rubra vera who underwent coronary artery bypass surgery. Although his initial postoperative course was complicated, his long-term outcome was good

Skin Lightening as An Image Enhancing Phenomenon: Investigating Risks, Motivations, and Underlying Psychological Factors

Background: Skin lightening phenomenon is a widely growing trend with serious side effects. Its history spans many decades and affects different cultures and regions globally. So far it has been marginally investigated and the full extent of its reasoning and motives are still poorly understood. Aim: to enhance the existing knowledge and increase public and professional awareness about this phenomenon through identifying the most at risk, exploring the underlying motivations, and analysing users’ experiences amongst multicultural populations in clinical and non-clinical settings. Methods: a mixed method approach was developed and comprised in four interconnected studies. Study one involved a comprehensive literature review which laid out the foundation for the following studies. Study two was a quantitative cross-sectional investigation based on semi-structured questionnaire distributed among 500 participants in clinical and non-clinical settings. Data were analysed using SPSS software where descriptive statistics and binary logistic regression were utilized. Study three was centered on semi-structured interviews with dermatological patients. The qualitative data obtained were analysed and coded using N Vivo software where themes and subthemes were generated. Study four focused on qualitative online data extracted from skin lightening related fora. Codes and themes were developed using N Vivo software. Results: Skin lightening use is considered as a mean to gain sociocultural benefits despite the well documented adverse effects. Colorism and prejudice against dark skin also helped fuel this practice. In addition, the role of online platforms in promoting “ideal beauty of fair skin” was a major factor driving skin lightening use. The results showed that Asian, females, 25 to 34 years old with medium coloured skin are the most likely group to use skin lightening products. Alarmingly, 51.8% of users reported side effects and 18.3% have purchased their skin lightening products online. The extracted motivational factors are sociocultural, skin conditions related, and psychological which are potentially integrated with each other. Accordingly, it was revealed that skin lightening users are more likely to have self-esteem issues. The online experience of skin lightening users emphasized the revealed motivations, side effects and ease of access to skin lightening products. Conclusion: The key issues that have been identified in this research reinforce the fact that skin lightening is a common and dangerous practice. This research identifies those most at risks and sheds new lights on the underlying risks factors associated with this behaviour in both clinical and non-clinical population. It provides some initial and unprecedented evidence to inform policy makers and regulators and help improve clinical practice in dermatology, psychology, and psychiatry. In addition, one of the goals of this research is to raise public awareness and tackle the dominance of harmful body image ideals

Sternotomy after retrosternal esophagogastric anastomotic disruption: a case report

Disruption of cervical esophagogastric anastomosis after retrosternal stomach transposition remains a dangerous complication. We report a case of cervical gastric disruption after retrosternal gastric transposition in a 36-year-old man that required sternotomy for reanastomosis. After sternotomy, gastric mobilization was possible, in order to gain sufficient length for a new cervical esophagogastric anastomosis