917 research outputs found
Adverse birth outcome: a comparative analysis between cesarean section and vaginal delivery at Felegehiwot Referral Hospital, Northwest Ethiopia: a retrospective record review [Corrigendum]
No full textAbebe Eyowas F, Negasi AK, Aynalem GE, Worku AG. Pediatric Health, Medicine and Therapeutics. 2016;7:65–70On page 65 Abel Fekadu Dadi should have been listed as an author. The incorrect author list was:Fantu Abebe Eyowas1Ashebir Kidane Negasi1Gizachew Eyassu Aynalem1Abebaw Gebeyehu Worku2The correct author list should have been:Fantu Abebe Eyowas1Ashebir Kidane Negasi1Gizachew Eyassu Aynalem1Abebaw Gebeyehu Worku2Abel Fekadu Dadi2Read the original articl
Flexible two-piece distributions for right censored survival data
No full textAn important complexity in censored data is that only partial information on the variables of interest is observed. In recent years, a large family of asymmetric distributions and maximum likelihood estimation for the parameters in that family has been studied, in the complete data case. In this paper, we exploit the appealing family of quantile-based asymmetric distributions to obtain flexible distributions for modelling right censored survival data. The flexible distributions can be generated using a variety of symmetric distributions and monotonic link functions. The interesting feature of this family is that the location parameter coincides with an index-parameter quantile of the distribution. This family is also suitable to characterize different shapes of the hazard function (constant, increasing, decreasing, bathtub and upside-down bathtub or unimodal shapes). Statistical inference is done for the whole family of distributions. The parameter estimation is carried out by optimizing a non-differentiable likelihood function. The asymptotic properties of the estimators are established. The finite-sample performance of the proposed method and the impact of censorship are investigated via simulations. Finally, the methodology is illustrated on two real data examples (times to weaning in breast-fed data and German Breast Cancer data).sponsorship: The authors are grateful to the editor, and associate editor and reviewers for their valuable comments that led to an improvement of the manuscript. The second author gratefully acknowledge support from Research Grant FWO G0D6619N of the Flemish Science Foundation, and from the C16/20/002 project of the Research Fund KU Leuven. (Flemish Science Foundation|FWO G0D6619N, Research Fund KU Leuven|C16/20/002)status: Published onlin
A hybrid hazard-based model using two-piece distributions
No full textCox proportional hazards model is widely used to study the relationship between the survival time of an event and covariates. Its primary objective is parameter estimation assuming a constant relative hazard throughout the entire follow-up time. The baseline hazard is thus treated as a nuisance parameter. However, if the interest is to predict possible outcomes like specific quantiles of the distribution (e.g. median survival time), survival and hazard functions, it may be more convenient to use a parametric baseline distribution. Such a parametric model should however be flexible enough to allow for various shapes of e.g. the hazard function. In this paper we propose flexible hazard-based models for right censored data using a large class of two-piece asymmetric baseline distributions. The effect of covariates is characterized through timescale changes on hazard progression and on the relative hazard ratio; and can take three possible functional forms: parametric, semi-parametric (partly linear) and non-parametric. In the first case, the usual full likelihood estimation method is applied. In the semi-parametric and non-parametric settings a general profile (local) likelihood estimation approach is proposed. An extensive simulation study investigates the finite-sample performances of the proposed method. Its use in data analysis is illustrated in real data examples.The authors thank the reviewers for their valuable comments that led to an improvement
of the manuscript. The second author gratefully acknowledges support from Research Grant C16/20/002
project of the Research Fund KU Leuven
Two-piece distribution based semi-parametric quantile regression for right censored data
No full textWidely used methods such as Cox proportional hazards, accelerated failure time, and Bennet proportional odds models do not model the quantiles directly, but rather allow to assess the influence of the covariates only on the location of the distribution. Quantile regression allows to assess the effects of covariates, not only on a location parameter (such as a mean or median) but also on specific percentiles of the conditional distribution. In recent years, a large family of flexible two-piece asymmetric distributions where the location parameter coincides with a specific quantile of the distribution has been studied. In a conditional (regression) setting the use of such a family of two-piece asymmetric distributions has only been investigated in the complete data case in the literature. In this paper, we propose a semi-parametric procedure to estimate the conditional quantile curves of two-piece asymmetric distributions based on right censored survival data. We use a local likelihood estimation technique in a multi-parameter functional form, via which the effect of a covariate on the location, scale, and index of the conditional survival distribution can be assessed. The finite sample performance of the estimators is investigated via simulations, and the methodology is illustrated on real data examples.The authors are grateful to an Associate Editor and two reviewers for their comments which led to an improvement of the manuscript. We thank the authors of Christou and Akritas (2019) to provide us with the R code to calculate their estimator in the SIQR model. The second author gratefully acknowledges support from Research Grant FWO G0D6619N of the Flemish Science Foundation, and from the C16/20/002 project of the Research Fund KU Leuven. The resources and services used in this work were provided by the VSC (Flemish Supercomputer Center), funded by the Research Foundation - Flanders (FWO) and the Flemish Government
T cell mediated immunity in malaria and mycobacterial infection : a protective role for gd+ T cells
No full textT cell mediated immunity is essential against intracellular infections. Studies of cell mediated immunity are important for the optimal design and development of effective vaccines. Identifying correlates of protective immunity will also enable measurement of vaccine efficiency. This thesis includes studies of T cell mediated immune protection against malaria and mycobacterial infections. A major focus of this work was the investigation of the role of [gamma][delta]+ T cell responses. In an initial study of lymphocyte subset compositions, a higher percentage of cytotoxic T cells were found in the peripheral blood of healthy adults from Ethiopia and Bangladesh than from Sweden. This suggested the involvement of environmental and/or genetic factors on the adaptation of the cellular immune system.During acute malaria illness there was a complex pattern of changes in lymphocyte subset distribution and activation that appeared to be different in P. falciparum infection compared to P. vivax. During acute P. falciparum illness an increase in level and activation of [gamma][delta]+ T cells, that was mostly due to increase in V[delta]1+ cells was found. However, during both infections increased numbers of CD4+, CD8+ and [gamma][delta]+ T cells in peripheral blood were expressing the proliferation marker Ki-67. These results suggest that all T cells are activated and that lymphocyte redistribution and /or activation driven apoptosis may be the cause of the altered phenotypic profiles in peripheral blood.An in vitro assay was developed to study the functional significance of [gamma][delta]+ T cells. Generally activated [gamma][delta]+ T cells of both V[delta]1+ and V[delta]2+ subsets but not similarly activated [alpha][beta] T cells from non-malaria exposed individuals inhibited the in vitro growth of asexual blood stages of P. falciparum parasite. The inhibition was correlated to the number of [gamma][delta]+ T cells and required cell-to-cell contact. Kinetic analysis suggested the likely targets to be the late infected erythrocyte (schizonts) or extracellular merozoites. These results suggest [gamma][delta]+ T cells may have a protective role during malaria infection independent of previous exposure to malaria.An in vitro assay was also developed to measure T cell mediated inhibition of mycobacterial growth. Both [alpha][beta]+ and [gamma][delta]+ T cells from PPD positive individuals inhibited intracellular growth of BCG, but only when activated by mycobacterial antigens. The mycobacterial growth inhibition capacity was up regulated by BCG vaccination and required cell-to-cell contact. These results suggest a role for [gamma][delta]+ T cells in the memory responses against mycobacteria.Expressions of proinflammatory cytokines and cytolytic molecules such as perforin, granzymes, granulysin and Fas/Fas ligand, were characteristic of both malaria and BCG growth inhibitory T cells. However, expression of these molecules in non-inhibitory activated cells were also seen, suggesting that growth inhibition requires restricted recognition of target cells by specific effectors. Our results indicate that [gamma][delta]+ T cells may represent an important component of the primary immune defense against P. falciparum infection and the memory immune defense against mycobacterial infection.List of scientific papersI. Worku S, Christensson B, Bjorkman A, Islam D (1997). "Higher proportion of CD8+ T cells in the blood in healthy adults from Ethiopia and Bangladesh compared with Sweden" Trans R Soc Trop Med Hyg 91(5): 618-22 https://pubmed.ncbi.nlm.nih.gov/98124846II. Worku S, Bjorkman A, Troye-Blomberg M, Jemaneh L, Farnert A, Christensson B (1997). "Lymphocyte activation and subset redistribution in the peripheral blood in acute malaria illness: distinct gammadelta+ T cell patterns in Plasmodium falciparum and P. vivax infections" Clin Exp Immunol 108(1): 34-41 https://pubmed.ncbi.nlm.nih.gov/97252339III. Worku S, Troye-Blomberg M, Christensson B, Bjorkman A, Fehniger T (2000). "Activation of T cells in the blood of patients with acute malaria, Proliferative activity as indicated by Ki 67 expression" Scand J Immunol (In Print)IV. Troye-Blomberg M, Worku S, Tangteerawatana P, Jamshaid R, Soderstrom K, Elghazali G, Moretta L, Hammarstrom M, Mincheva-Nilsson L (1999). "Human gamma delta T cells that inhibit the in vitro growth of the asexual blood stages of the Plasmodium falciparum parasite express cytolytic and proinflammatory molecules" Scand J Immunol 50(6): 642-50 https://pubmed.ncbi.nlm.nih.gov/20075382V. Worku S, Hoft DF (2000). "In vitro measurement of protective mycobacterial immunity: antigen-specific expansion of T cells capable of inhibiting intracellular growth of bacille Calmette-Guerin" Clin Infect Dis Suppl 3: S257-61 https://pubmed.ncbi.nlm.nih.gov/20336492VI. Worku S, Hoft DF (2000). "Differential effects of antigen specific and control T cells on intracellular mycobacterial growth, in vitro models of protective immunity and mycobacterial persistence" (Submitted)</p
Left in Limbo: UNHCR's Study on the Implementation of the Dublin III Regulation, United Nations High Commissioner for Refugees
No full textAcknowledgements: This research was coordinated by Silvia Cravesana in UNHCR’s Bureau for Europe (Policy and Legal Support Unit). This report was written by Silvia Cravesana and Maria Hennessy. This report brings together the main findings of national reports produced by Lucienne Joergensen (Denmark), Claire Callejon (France), Aida Worku (Germany), Aliki-Eleni Georgiadi (Greece), Pietro Sullo (Italy), Paolo Biondi (Malta), Vigdis Vevstad (Norway), Marta Gorczynska (Poland), Cynthia Orchard and Helen-Marie Fraher (United Kingdom)Particular thanks go to staff in UNHCR’s national offices in France, Germany, Greece, Italy, Malta, Poland and the United Kingdom, and in the Regional Representations for Western and Northern Europe for their important contributions. Appreciation is also extended to Reem Alsalem, Lucie Bichet, Sam Boutruche, Zoé Campiglia, Elena Colunga Caballero, Kate Connelly, Cathryn Costello, Alexander de Châlus, Yolande Ditewig, Madeline Garlick, Kristof Gombeer, Sophie Magennis, Hugh Massey, Maeve Patterson, Cornelia Schick, Juliette Tassy, Andrea Vonkeman and Cornelis Wouters for their inputs and support. Particular thanks also go to the colleagues in other organizations who provided advice and inputs in the initial phase of this research: Anneliese Baldaccini (Amnesty International), Daphné Bouteillet (ECRE) and Marc Provera (JRS). Finally, UNHCR expresses its sincere gratitude to Member State officials, representatives of organizations, lawyers, asylum-seekers and many others who agreed to be interviewed and provided information in the course of this research
Teacher-learner behaviour and classroom processes in large ESL classes in Pakistan
No full textThe thesis presents a descriptive-interpretive account of teacher-learner behaviour and classroom processes in large ESL classes in Pakistan. The fieldwork for the study was
done in 6 secondary schools in Karachi, Pakistan; a total of 232 classes of varying size were observed; furthermore, 20 teachers and 21 groups of learners from the same classes
were interviewed. The major findings of the study are as follows:
1) Numbers seem to be necessary but not sufficient for defining class size. Other factors which influence participants' perceptions of class size include participants' previous experience, the average class size in the immediate educational context, the size of the
room and the ease or difficulty of doing certain activity types in the classroom.
2) Participants tend to view their difficulties in teaching-learning in large classes in relation to the ease in doing the same kinds of activity types in classes of a smaller
size.
3) All teachers use a set of 'core' activity types and accompanying teacher-learner behaviours in their classrooms, irrespective of the size of their classes. This indicates the presence of a shared culture of teaching and learning in school classes in Pakistan which cuts across the variable of class size. On the other hand, though enhancing activity types are used by different teachers in both larger and smaller size classes, individual teachers seem to find it more difficult to use enhancing activities in larger as compared to smaller classes.
4) It seems that teachers do not change their teaching style if two (or more) classes are perceived by them to be in the same 'size category' in regard to their threshold levels of class size.
5) In large classes, the location of the students in the front or the back of the classroom seems to affect the pattern of teacher-learner interaction and the degree of learner participation in the classroom. This, in turn, has consequences for the classroom behaviour, and the motivation and learning of students at varied locations in the classroom
Human gamma delta T cells that inhibit the in vitro growth of the asexual blood stages of the Plasmodium falciparum parasite express cytolytic and proinflammatory molecules.
No full textEffect of Different Levels of Dried Sugar Cane Tops Inclusion on the Performance of Washera Sheep Fed Basal Diet of Grass Hay, Ethiopia
No full textCopyright: © 2015 Worku A, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Background: Ruminants feed largely on crop resides as their basal diet. Despite their vast use as a livestock feed, crop residues are naturally of low quality and do not fulfill the nutrient requirement of animals. Thus, the deficit in the basal feed of quantity can be covered with sugar cane tops that are potential feed for better performance of animals. This study aimed with to evaluate the effect of different level of Dried Sugar Can tops inclusion on carcass characteristics and Economic Feasibility of Washera sheep fed a basal diet of grass hay. Methodology: A study was conducted at Bure Agricultural Technical Vocational Educational Training (ATVET) College using twenty yearling Washera sheep with initial body weight (BW) of 18.15 ± 1.85 (mean ± SD). The experimental design was randomized complete block design, and sheep were blocked into five blocks of four animals based on their initial BW and randomly assigned to one of the treatments within a block. Treatments were hay ad libitum+100 g/head/d CM for T1 and an additional 120 g, 240 g and 360 g SCT per head/day on dry matter basis for T2, T3 and T4, respectively. The experiment consisted 90 days of Growth trials followed by evaluation of carcass components at the end
Dynamics of the Volterra-type integral and differentiation operators on generalized Fock spaces
No full text[EN] Various dynamical properties of the differentiation and Volterra-type integral operators on generalized Fock spaces are studied. We show that the differentiation operator is always supercyclic on these spaces. We further characterize when it is hypercyclic, power bounded and uniformly mean ergodic. We prove that the operator satisfies the Ritt's resolvent condition if and only if it is power bounded and uniformly mean ergodic. Some similar results are obtained for the Volterra-type and Hardy integral operators.J. Bonet was partially supported by the research projects MTM2016-76647-P and GV Prometeo 2017/102 (Spain). M. Worku is supported by ISP project, Addis Ababa University, Ethiopia.Bonet Solves, JA.; Mengestie, T.; Worku, M. (2019). Dynamics of the Volterra-type integral and differentiation operators on generalized Fock spaces. Results in Mathematics. 74(4):1-15. https://doi.org/10.1007/s00025-019-1123-7S115744Abanin, A.V., Tien, P.T.: Differentiation and integration operators on weighted Banach spaces of holomorphic functions. Math. Nachr. 290(8–9), 1144–1162 (2017)Atzmon, A., Brive, B.: Surjectivity and invariant subspaces of differential operators on weighted Bergman spaces of entire functions, Bergman spaces and related topics in complex analysis, Contemp. Math., vol. 404, Amer. Math. Soc., Providence, RI, pp. 27–39 (2006)Bayart, F., Matheron, E.: Dynamics of Linear Operators, Cambridge Tracts in Math, vol. 179. Cambridge Univ. Press, Cambridge (2009)Bermúdez, T., Bonilla, A., Peris, A.: On hypercyclicity and supercyclicity criteria. Bull. Austral. Math. Soc. 70, 45–54 (2004)Beltrán, M.J.: Dynamics of differentiation and integration operators on weighted space of entire functions. Studia Math. 221, 35–60 (2014)Beltrán, M.J., Bonet, J., Fernández, C.: Classical operators on weighted Banach spaces of entire functions. Proc. Am. Math. Soc. 141, 4293–4303 (2013)Bès, J., Peris, A.: Hereditarily hypercyclic operators. J. Funct. Anal. 167, 94–112 (1999)Bonet, J.: Dynamics of the differentiation operator on weighted spaces of entire functions. Math. Z. 26, 649–657 (2009)Bonet, J.: The spectrum of Volterra operators on weighted Banach spaces of entire functions. Q. J. Math. 66, 799–807 (2015)Bonet, J., Bonilla, A.: Chaos of the differentiation operator on weighted Banach spaces of entire functions. Complex Anal. Oper. Theory 7, 33–42 (2013)Bonet, J., Taskinen, J.: A note about Volterra operators on weighted Banach spaces of entire functions. Math. Nachr. 288, 1216–1225 (2015)Constantin, O., Persson, A.-M.: The spectrum of Volterra-type integration operators on generalized Fock spaces. Bull. Lond. Math. Soc. 47, 958–963 (2015)Constantin, O., Peláez, J.-Á.: Integral operators, embedding theorems and a Littlewood–Paley formula on weighted Fock spaces. J. Geom. Anal. 26, 1109–1154 (2016)De La Rosa, M., Read, C.: A hypercyclic operator whose direct sum is not hypercyclic. J. Oper. Theory 61, 369–380 (2009)Dunford, N.: Spectral theory. I. Convergence to projections. Trans. Am. Math. Soc. 54, 185–217 (1943)Grosse-Erdmann, K.G., Peris Manguillot, A.: Linear Chaos. Springer, New York (2011)Harutyunyan, A., Lusky, W.: On the boundedness of the differentiation operator between weighted spaces of holomorphic functions. Studia Math. 184, 233–247 (2008)Krengel, U.: Ergodic Theorems. Walter de Gruyter, Berlin (1985)Lyubich, Yu.: Spectral localization, power boundedness and invariant subspaces under Ritt’s type condition. Studia Mathematica 143(2), 153–167 (1999)Mengestie, T.: A note on the differential operator on generalized Fock spaces. J. Math. Anal. Appl. 458(2), 937–948 (2018)Mengestie, T.: Spectral properties of Volterra-type integral operators on Fock–Sobolev spaces. J. Kor. Math. Soc. 54(6), 1801–1816 (2017)Mengestie, T.: On the spectrum of volterra-type integral operators on Fock–Sobolev spaces. Complex Anal. Oper. Theory 11(6), 1451–1461 (2017)Mengestie, T., Ueki, S.: Integral, differential and multiplication operators on weighted Fock spaces. Complex Anal. Oper. Theory 13, 935–95 (2019)Mengestie, T., Worku, M.: Isolated and essentially isolated Volterra-type integral operators on generalized Fock spaces. Integr. Transf. Spec. Funct. 30, 41–54 (2019)Nagy, B., Zemanek, J.A.: A resolvent condition implying power boundedness. Studia Math. 134, 143–151 (1999)Nevanlinna, O.: Convergence of iterations for linear equations. Lecture Notes in Mathematics. ETH Zürich, Birkhäuser, Basel (1993)Ritt, R.K.: A condition that . Proc. Am. Math. Soc. 4, 898–899 (1953)Ueki, S.: Characterization for Fock-type space via higher order derivatives and its application. Complex Anal. Oper. Theory 8, 1475–1486 (2014)Yosida, K.: Functional Analysis. Springer, Berlin (1978)Yosida, K., Kakutani, S.: Operator-theoretical treatment of Marko’s process and mean ergodic theorem. Ann. Math. 42(1), 188–228 (1941
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