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Search Results: 1 - 10 of 815 matches for " Uriel Kaufmann "
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Existence of strictly positive solutions for sublinear elliptic problems in bounded domains
Tomas Godoy,Uriel Kaufmann
Mathematics , 2013,
Abstract: Let $\Omega$ be a smooth bounded domain in $\mathbb{R}^{N}$ and let $m$ be a possibly discontinuous and unbounded function that changes sign in $\Omega$. Let $f:\left[ 0,\infty\right) \rightarrow\left[ 0,\infty\right) $ be a continuous function such that $k_{1}\xi^{p}\leq f\left(\xi\right) \leq k_{2}\xi^{p}$ for all $\xi\geq0$ and some $k_{1},k_{2}>0$ and $p\in\left(0,1\right) $. We study existence and nonexistence of strictly positive solutions for nonlinear elliptic problems of the form $-\Delta u=m\left(x\right) f\left(u\right) $ in $\Omega$, $u=0$ on $\partial\Omega$.
Strictly positive solutions for one-dimensional nonlinear problems involving the p-Laplacian
Uriel Kaufmann,Ivan Medri
Mathematics , 2013, DOI: 10.1017/S0004972713000725
Abstract: Let $\Omega$ be a bounded open interval, and let $p>1$ and $q\in\left(0,p-1\right) $. Let $m\in L^{p^{\prime}}\left(\Omega\right) $ and $0\leq c\in L^{\infty}\left(\Omega\right) $. We study existence of strictly positive solutions for elliptic problems of the form $-\left(\left\| u^{\prime}\right\|^{p-2}u^{\prime}\right) ^{\prime}+c\left(x\right) u^{p-1}=m\left(x\right) u^{q}$ in $\Omega$, $u=0$ on $\partial\Omega$. We mention that our results are new even in the case $c\equiv0$.
Strictly positive solutions for one-dimensional nonlinear elliptic problems
Uriel Kaufmann,Ivan Medri
Mathematics , 2014,
Abstract: We study existence and nonexistence of strictly positive solutions for the elliptic problems of the form $Lu=m\left( x\right) u^{p}$ in a bounded open interval, with zero boundary conditions, where $L$ is a strongly uniformly elliptic differential operator, $p\in\left( 0,1\right) $, and $m$ is a function that changes sign. We also characterize the set of values $p$ for which the problem admits a solution, and in addition an existence result for other nonlinearities is presented.
On Dirichlet problems with singular nonlinearity of indefinite sign
Tomás Godoy,Uriel Kaufmann
Mathematics , 2014,
Abstract: Let $\Omega$ be a smooth bounded domain in $\mathbb{R}^{N}$, $N\geq1$, let $K$, $M$ be two nonnegative functions and let $\alpha,\gamma>0$. We study existence and nonexistence of positive solutions for singular problems of the form $-\Delta u=K\left( x\right) u^{-\alpha}-\lambda M\left( x\right) u^{-\gamma}$ in $\Omega$, $u=0$ on $\partial\Omega$, where $\lambda>0$ is a real parameter. We mention that as a particular case our results apply to problems of the form $-\Delta u=m\left( x\right) u^{-\gamma}$ in $\Omega$, $u=0$ on $\partial\Omega$, where $m$ is allowed to change sign in $\Omega$.
One-dimensional singular problems involving the p-Laplacian and nonlinearities indefinite in sign
Uriel Kaufmann,Iván Medri
Mathematics , 2015,
Abstract: Let $\Omega$ be a bounded open interval, let $p>1$ and $\gamma>0$, and let $m:\Omega\rightarrow\mathbb{R}$ be a function that may change sign in $\Omega $. In this article we study the existence and nonexistence of positive solutions for one-dimensional singular problems of the form $-(\left\vert u^{\prime}\right\vert ^{p-2}u^{\prime})^{\prime}=m\left( x\right) u^{-\gamma}$ in $\Omega$, $u=0$ on $\partial\Omega$. As a consequence we also derive existence results for other related nonlinearities.
Syntactic and Lexico-Semantic Variations in Nigerian English: Implications and Chal-lenges in the ESL Classroom  [PDF]
Uriel Okunrinmeta
Open Journal of Modern Linguistics (OJML) , 2014, DOI: 10.4236/ojml.2014.42026

The present study traces the poor performance of Nigerian students in English to the sole use of British English for teaching and evaluation purposes in the Nigerian ESL classroom thereby neglecting the local Nigerian variations which, as it should be expected, reflect the linguistic and cultural contexts that English must, as a necessary condition, accommodate if it must function effectively in Nigeria’s multilingual socio-cultural setting. The study, after presenting some syntactic and lexico-semantic variations in Nigerian English and highlighting their appropriateness within the Nigerian socio-cultural context, argues that, if students must perform well in English and even in other subjects taught and examined in English, it is necessary to teach them and evaluate their performances by using an endonormative model (that is, Standard Nigerian English), which is capable of reflecting the local variations that English has, in a bid to satisfy the demands for communicative appropriateness, manifested in the Nigerian setting. This is so because Standard Nigerian English as an endonormative model is, because of its ability to appropriately reflect the Nigerian experience, more supportive to the students in the Nigerian ESL classroom than the foreign British model which, though used as the standard in Nigeria as a former British colony, is culturally inappropriate in the Nigerian context and does not, therefore, appeal to the sensibilities of the students who, in their quest for communicative appropriateness in English in the Nigerian socio-cultural setting, have to use the language to reflect the Nigerian worldview.

Data Aggregation: A Proposed Psychometric IPD Meta-Analysis  [PDF]
Esther Kaufmann
Open Journal of Statistics (OJS) , 2018, DOI: 10.4236/ojs.2018.81004
Abstract: Individual participant data (IPD) meta-analysis was developed to overcome several meta-analytical pitfalls of classical meta-analysis. One advantage of classical psychometric meta-analysis over IPD meta-analysis is the corrections of the aggregated unit of studies, namely study differences, i.e., artifacts, such as measurement error. Without these corrections on a study level, meta-analysts may assume moderator variables instead of artifacts between studies. The psychometric correction of the aggregation unit of individuals in IPD meta-analysis has been neglected by IPD meta-analysts thus far. In this paper, we present the adaptation of a psychometric approach for IPD meta-analysis to account for the differences in the aggregation unit of individuals to overcome differences between individuals. We introduce the reader to this approach using the aggregation of lens model studies on individual data as an example, and lay out different application possibilities for the future (e.g., big data analysis). Our suggested psychometric IPD meta-analysis supplements the meta-analysis approaches within the field and is a suitable alternative for future analysis.
Polyamines and Carcinogenesis
Uriel Bachrach
Acta Facultatis Medicae Naissensis , 2012,
Abstract: The naturally occurring polyamines, spermine, spermidine and the diamine putrescine are widespread in nature. They have been implicated in growth and differentiation processes. In 1967, we reported that cancer cells are rich in polyamines. Subsequently, it has been shown that polyamines are released from cancer cells and may be detected in body fluids such as urine, blood and cerebrospinal fluids. It has also been demonstrated that the increase in cellular polyamine levels is an early and an obligatory event in the process of malignant transformation. This increase in cellular polyamine concentration is due to the activation of ornithine decarboxylase (ODC), which catalyses the rate limiting step in polyamine synthesis by converting ornithine to putrescine. Assays of urinary and blood polyamines have been used to detect cancer and to determine the success of therapy. A sensitive, rapid, chemiluminescence-based method for the determination of diamines and polyamines was developed and 2.000 urine samples were tested. An interesting "gene therapy" system for injecting amine oxidases into normal and transformed cells was developed as follows: serum amine oxidase and porcine kidney damine oxidase were trapped within reconstituted Sendai virus envelopes. Chick or rat fibroblasts, transformed by Rous sarcoma virus, were more susceptible to the injected enzymes, compared to the normal culture, when macromolecular synthesis was tested. An in vitro chemosensitivity assay for the testing of the sensitivity of cancer cells from individual patients ("tailored treatment") was also developed. All these studies stress the importance of polyamines in carcinogenesis.
Journal of Community Positive Practices , 2013,
Abstract: While hierarchical structures have many advantages for the effective running of organizations, they also pose major drawbacks both for organizations and for individuals lower in a hierarchy. Research in kibbutz industry and in its social organizations shows that kibbutzim are not much different from other organizations because within kibbutzim hierarchical structures are common, differentials in power and control are correlated with hierarchical position, differential rewards are correlated with position, and health symptoms and indicators for well being are correlated with hierarchical position. Yet kibbutzim managed to solve the paradox of having organizations that are hierarchically structured and show all the features of hierarchical organizations yet keep up with the principles of equality and democracy. I explain and describe seven different counterbalancing mechanisms employed by kibbutzim to alleviate the drawbacks of hierarchy and yet preserve its advantages. Recently, many kibbutzim went through major structural transformations, and most mechanisms to counterbalance the ill effects of hierarchy were among the "victims" of these structural changes. Results of research show both in the economic sphere and in the social sphere how giving up on the counterbalancing mechanisms brings about deterioration in positive outcomes. The last part of the paper discusses reasons for the deterioration in effectiveness and then discusses possible generalization from kibbutz research to other societies.
Las balanzas fiscales de las Comunidades Autónomas
Ezequiel Uriel
Investigaciones Regionales , 2006,
Abstract: En este artículo se examina la elaboración de las balanzas fiscales de las Comunidades Autónomas con respecto a la Administración Pública Central. Después de analizar los problemas metodológicos, se examinan los resultados obtenidos por el autor y se comparan con los obtenidos con simulaciones basadas en criterios normativos. Finalmente, en las conclusiones se hace una especial referencia a la interpretación de los saldos de balanzas fiscales obtenidos con los enfoques carga-beneficio (utilizado por el autor) y flujo-monetario. En opinión del autor no son comparables los resultados con los dos enfoques. Además, el enfoque de flujo monetario no tiene una interpretación clara, a diferencia del enfoque carga beneficio que sí la tiene.
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