Tilapia africana en el Lago de Nicaragua: ecosistema en transición.
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Jeffrey K. McCrary
1998-10-01
Full Text Available Los grandes lagos de Nicaragua, son comparables con el sistema de grandes lagos africanos. Contienen una gran diversidad de peces, incluyendo varios peces endémicos de la familia Cichlidae. La captura de peces en el Lago de Cocibolca, estandarizada en 100 metros de red, promedió 4.34 kilogramos en el área de Ometepe, en donde la tilapia constituyó el 1.5 % del peso total de la captura. Este promedio fue de 0.80 kilogramos en la costa septentrional, donde la tilapia constituyó 54% del peso total de la captura. Un estudio ruso efectuado en 1983 y desarrollado en todo el Lago, demostró que el promedio era de 4.66 kilogramos. Los autores del presente artículo recomiendan que en el Lago Cocibolca se implemente un plan de manejo adecuado para controlar la población de tilapia y rescatar un ecosistema en peligro de colapso
La ciudad como ecosistema urbano
Higueras García, Esther
2013-01-01
LA CIUDAD COMO ECOSISTEMA URBANO .- La ecología y los ecosistemas .- El ecosistema urbano, definición, alcance y oportunidad .- El metabolismo urbano .- Los síntomas de la patología urbana .- Los objetivos del nuevo ecosistema urbano .- Las aportaciones de los ecobarrios
Los ecosistemas marinos y costeros.
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Comité Editorial Gestión y Ambiente
2010-05-01
Full Text Available Apreciado lector. Como lo habíamos anunciado, este número de la Revista Gestión y Ambiente centra su atención en los ecosistemas acuáticos continentales y el último número del año 2008 se referirá a los ecosistemas marinos y costeros. El agua es un recurso esencial para los seres vivos; se compone de hidrógeno y de oxígeno, contiene gases y nutrientes, partículas suspendidas vivas y no vivas, y físicamente, es permeada por la luz y el calor. Sólo una parte pequeña del agua del planeta es dulce. Los ríos, lagos y ciénagas del paisaje terrestre son ecosistemas donde interactúan lo vivo y lo no- vivo; y a través del agua, se mueve la materia y fluye la energía. Lo vivo está influido por el agua, pero, a su vez. el agua también lo esta por lo vivo. El agua dulce está en riesgo por la actividad del hombre quien la requiere, la usa, la contamina y la descontamina. Por ello, el conocimiento de los ambientes acuáticos es fundamental. En esta perspectiva, el agua dulce requiere ser estudiada para su aprovechamiento sostenible. Sin embargo, los niveles actuales de contaminación hacen indispensable no sólo su estudio hidrológico- biológico- ecológico, sino también el análisis de la cantidad de agua, su calidad y los procesos de saneamiento. Es igualmente fundamental la gestión del recurso hídrico, teniendo en cuenta los aspectos humanos, económicos y socio- ambientales. Por lo anterior las ciencias naturales, las ingenierías sanitaria y ambiental, y las ciencias sociales deben unir esfuerzos para estudiar los ecosistemas acuáticos con miras a su sostenibilidad, uso, reuso y protección. Además, como temas complementarios, la Revista entrega artículos que amplían temas tratados en números anteriores: • La contaminación atmosférica, con los resultados de dos investigaciones desarrollados en el Area Metropolitana del Valle de Aburra, y • La problemática de los riesgos con un
UTILIZACIÓN DE SENSORES REMOTOS PARA EL ESTUDIO DE UN ECOSISTEMA LACUSTRE
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Marisa Cogliati
2006-12-01
Full Text Available La distribución de sustancias disueltas, nutrientes, microorganismos y plancton es influenciada por la circulación del agua en los lagos, por lo que el adecuado conocimiento de los movimientos del agua adquiere importancia en la caracterización de ecosistemas lacustres ya que además, inciden en la distribución del calor entre las distintas capas del lago. Una de las características más importantes del lago es su estructura térmica. El contenido de calor del cuerpo de agua es de vital importancia en los estudios de la calidad de agua en lagos. El metabolismo y el comportamiento de los organismos acuáticos están directamente relacionados con la temperatura del agua.
TERMODINAMICA DE ECOSISTEMAS UNA APROXIMACION
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Gómez Palacio Germán Raúl
1998-06-01
Full Text Available La ecología actual no es ya una ciencia puramente descriptiva y autosuficiente. Dada la naturaleza compleja de los ecosistemas, ha sido necesario recurrir a disciplinas como la física, la química, y a herramientas matemáticas como la teoría de catástrofes, la teoría de fractales, la cibernética y la teoría de redes, para el estudio y predicción de su comportamiento. La termodinámica -en sus distintos estadios -también aporta a esa visión pluralista, tal vez la única aproximada al comportamiento real de un ecosistema. Se presentan algunas ideas sobre la importancia que pueden tener conceptos como la energía, la entropía, la exergía, la información, el no equilibrio en el análisis de los procesos que tienen lugar en ecosistemas.
Estado del arte de la limnología de lagos de planos inundables (Ciénagas) en Colombia
Montoya Moreno Yimmy; Aguirre R Néstor
2011-01-01
Colombia es uno de los países con mayor diversidad de especies y de ecosistemas en el planeta. Los lagos ubicados en llanuras de inundación o «ciénagas» (como comúnmente se las conoce en Colombia) comprenden un tipo de ecosistema acuático, que, no obstante su elevada riqueza específica, han sido someramente estudiados. Las investigaciones básicas en estos ambientes son escasas, en su mayoría se hallan publicadas en la «literatura gris» y no existe una compilación actualizada de los di...
Directory of Open Access Journals (Sweden)
Joao Canavilhas
2011-06-01
Full Text Available Originalmente usado para describir la relación entre la blogosfera y la mediasfera, el concepto de Ecosistema Mediático se extendió a otro tipo de relaciones, pasando a designar todo el complejo sistema de relaciones entre los medios de comunicación. Las nuevas formas de interacción, con los contenidos y los cambios en el consumo mediático motivados por la movilidad y las nuevas interfaces, han producido alteraciones importantes en los propios medios de comunicación que han tenido que adaptarse a esta nueva realidad.Tomando como punto de partida el concepto original de Ecología, tratamos de identificar un conjunto de elementos que ayuden a aclarar el concepto de Ecosistema Mediático, en particular en lo que respecta a los diversos factores que influyen en él. Se trata de trazar un paralelo entre los dos ecosistemas –biológico y mediático– buscando formas de integrar las novedades relacionadas con la evolución técnica de los medios, las herramientas y aplicaciones que están cambiando las funciones y contenidos de los medios tradicionales, o alterando la forma de consumo mediático.La propuesta que se hace busca la integración de nuevos conceptos que ahora se estudian de forma fragmentada y, a veces, descontextualizada del nuevo entorno mediático.
El ecosistema pedagógico de los PLEs
Adell, Jordi; Castañeda Quintero, Linda Johanna
2013-01-01
Para citar: Adell, J. y Castañeda, L. (2013). El ecosistema pedagógico de los PLEs. En L. Castañeda y J. Adell (Eds.), Entornos Personales de Aprendizaje: Claves para el ecosistema educativo en red (pp. 29-51). Alcoy: Marfil.
African Journals Online (AJOL)
PROMOTING ACCESS TO AFRICAN RESEARCH ... Lagos Notes and Records is an annual, interdisciplinary journal of the humanities. ... Insuring the Nation: Europeans and the Emergence of Modern Insurance Business in Colonial Nigeria ...
Lagos Notes and Records: Editorial Policies
African Journals Online (AJOL)
Professor Tom Byers, University of Louisville Professor Olumuyiwa Alaba, University of Lagos Professor Karen King-Aribisala, University of Lagos Professor Samuel Ade Ojo, University of Lagos Professor Niyi Osundare, University of Lagos Professor Segun Awonusi, University of Lagos Professor Adebayo Lawal, University ...
African Journals Online (AJOL)
The Lagos Historical Review is an international and interdisciplinary journal publishing papers with a historical focus. The journal generates and participates in debates to advance the discipline of history and promote its relevance to development. The journal aims to serve the academic community with a bias towards ...
Onandia Bieco, Gabriela
2015-01-01
Los lagos someros son uno de los ecosistemas acuáticos más numerosos a nivel global y hacen posible el desarrollo de multitud de actividades de interés económico y recreativo. En las últimas décadas, gran parte de estos lagos se han visto sujetos a un proceso de eutrofización cultural que a menudo conlleva una transición desde un estado "claro" caracterizado por una alta transparencia del agua y gran abundancia de macrófitos, a un estado "turbio" caracterizado por una baja transparencia del a...
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Borrero H. José I.
1963-06-01
Full Text Available Puesto que el lago de Tola constituye hoy en día la única fuente de abastecimiento de agua para nuestra máxima industria nacional, como es Acerías de Paz del Río, porque esta industria depende en un ciento por ciento del lago de Tota para su desarrollo actual y ensanches futuros, según concepto de sus directivas además por ser este un lugar de incomparable belleza al cual debe dársele la importancia que merece, se ha resuelto escribir estas líneas, en las cuales el lector encontrará esbozados en la forma más sucinta posible una serie de hechos que a no dudar todos hemos observado al visitar el lago. No se pretende que este pequeño escrito abarque todo el problema que es de por sí muy vasto y que posiblemente ha sido tratado ya antes con mayor propiedad, pero sí se espera que produzca en cada uno de los lectores una reacción que sea lo suficientemente grande para que logre convertirlos en admiradores de Tota por consiguiente en sus perennes defensores. No tratamos tampoco de inculpar a nadie y menos a ninguna de las entidades nacionales responsables de la conservación de nuestros recursos naturales, sino simplemente de alertar a todos los directivos de esas entidades para que de común acuerdo logremos salvar el Lago de Tota.
J. A. Camargo; A. Alonso
2007-01-01
Los principales problemas medioambientales asociados a la contaminación por nitrógeno inorgánico en los ecosistemas acuáticos son: (1) acidificación de ríos y lagos con baja o reducida alcalinidad; (2) eutrofización de las aguas dulces y marinas (con el problema adicional de las algas tóxicas); y (3) toxicidad directa de los compuestos nitrogenadospara los animales acuáticos. Además, la contaminación por nitrógeno inorgánico podría inducir efectos perjudiciales sobre la salud humana. En b...
The Seis Lagos Carbonatite Complex
International Nuclear Information System (INIS)
Issler, R.S.; Silva, G.G. da.
1980-01-01
The Seis Lagos Carbonatite Complex located about 840 Km from Manaus, on the northwestern part of the Estado do Amazonas, Brazil is described. Geological reconnaissance mapping by Radam Project/DNPM, of the southwestern portion of the Guianes Craton, determined three circular features arranged in a north-south trend and outcroping as thick lateritic radioactive hills surrounded by gneisses and mignatites of the peneplained Guianense Complex. Results of core drilling samples analysis of the Seis Lagos Carbonatite Complex are compared with some igneous rocks and limestones of the world on the basis of abundance of their minor and trace elements. Log-log variation diagram of strontium and barium in carbonatite and limestone, exemplifield by South Africa and Angola carbonatites, are compared with the Seis Lagos Carbonatite Complex. The Seis Lagos Carbonatite Complex belongs to the siderite-soevite type. (E.G.) [pt
PRODUCTIVIDAD DE LOS ECOSISTEMAS EN LAS REGIONES ÁRIDAS
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M. Á. Hernández-García
2003-01-01
Full Text Available La producción de los ecosistemas terrestres está influida por el clima, especialmente por la temperatura y por las precipitaciones. La temperatura influye sobre la tasa de fotosíntesis, y la cantidad de agua disponible limita tanto la fotosíntesis como la cantidad de hojas que la planta puede sustentar y, consecuentemente, la producción total de las plantas. Las condiciones de altas temperaturas y escasa humedad hacen de los desiertos uno de los ecosistemas terrestres menos productivos. De esta manera, existe una relación casi lineal entre la pluviosidad y la productividad de los órganos aéreos de las plantas.
LA LLUVIA ÁCIDA Y LOS ECOSISTEMAS FORESTALES
D. Granados Sánchez; G. F. López Ríos; M. Á. Hernández García
2010-01-01
Por efecto de la civilización industrial y del desarrollo tecnológico de nuestros tiempos, se origina la "lluvia ácida", que es la precipitación en forma de lluvia, nieve, aguanieve, granizo o niebla con altas concentraciones de ácido sulfúrico (H2SO4), ácido nítrico (HNO3) y ácido carbónico (H2CO3). El aumento de la lluvia ácida ha tenido efectos considerables en los ecosistemas: los bosques del mundo se están muriendo y sus cuerpos de agua no pueden sostener a las poblaciones normales de pe...
LA LLUVIA ÁCIDA Y LOS ECOSISTEMAS FORESTALES
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D. Granados Sánchez
2010-01-01
Full Text Available Por efecto de la civilización industrial y del desarrollo tecnológico de nuestros tiempos, se origina la "lluvia ácida", que es la precipitación en forma de lluvia, nieve, aguanieve, granizo o niebla con altas concentraciones de ácido sulfúrico (H2SO4, ácido nítrico (HNO3 y ácido carbónico (H2CO3. El aumento de la lluvia ácida ha tenido efectos considerables en los ecosistemas: los bosques del mundo se están muriendo y sus cuerpos de agua no pueden sostener a las poblaciones normales de peces. Asimismo, disminuye el rendimiento agrícola y se corroen el mármol, metal y piedra en las ciudades.
Singular stochastic differential equations
Cherny, Alexander S
2005-01-01
The authors introduce, in this research monograph on stochastic differential equations, a class of points termed isolated singular points. Stochastic differential equations possessing such points (called singular stochastic differential equations here) arise often in theory and in applications. However, known conditions for the existence and uniqueness of a solution typically fail for such equations. The book concentrates on the study of the existence, the uniqueness, and, what is most important, on the qualitative behaviour of solutions of singular stochastic differential equations. This is done by providing a qualitative classification of isolated singular points, into 48 possible types.
AGRICULTURA SOSTENIBLE EN ECOSISTEMAS DE ALTA MONTAÑA
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DIANA MARCELA RUIZ O
Full Text Available La agricultura como principal actividad del desarrollo económico rural en Colombia ha sido implementada con diferentes estrategias desde la época precolombina. Los ecosistemas de la alta montaña no han sido ajenos a esta realidad, y particularmente en las zonas de Páramo del Cauca, el intento por favorecer la prevalencia de un modelo altamente productivo e intensivo en el uso del suelo ha conllevado al detrimento de la diversidad socio-ecológica, la rápida expansión de la frontera agropecuaria en áreas estratégicas, la pérdida del conocimiento tradicional sobre el uso de la tierra y el bajo rendimiento de los cultivos que ha implicado mayor incorporación de fertilizantes al suelo amenazando estos sistemas vulnerables en la alta montaña. Sin embargo, es común encontrar en diferentes localidades paramunas caucanas comunidades indígenas y campesinas que reconocen la necesidad de cambiar los sistemas productivos que han venido empleando debido a la disminución de la fertilidad del suelo que limita la comercialización de sus productos y a la problemática ambiental asociada, en este sentido, el acompañamiento institucional en este proceso es vital para favorecer la implementación de procesos sostenibles de forma integral.
Quantum evolution across singularities
International Nuclear Information System (INIS)
Craps, Ben; Evnin, Oleg
2008-01-01
Attempts to consider evolution across space-time singularities often lead to quantum systems with time-dependent Hamiltonians developing an isolated singularity as a function of time. Examples include matrix theory in certain singular time-dependent backgounds and free quantum fields on the two-dimensional compactified Milne universe. Due to the presence of the singularities in the time dependence, the conventional quantum-mechanical evolution is not well-defined for such systems. We propose a natural way, mathematically analogous to renormalization in conventional quantum field theory, to construct unitary quantum evolution across the singularity. We carry out this procedure explicitly for free fields on the compactified Milne universe and compare our results with the matching conditions considered in earlier work (which were based on the covering Minkowski space)
Ishii, Shihoko
2014-01-01
This book is an introduction to singularities for graduate students and researchers. It is said that algebraic geometry originated in the seventeenth century with the famous work Discours de la méthode pour bien conduire sa raison, et chercher la vérité dans les sciences by Descartes. In that book he introduced coordinates to the study of geometry. After its publication, research on algebraic varieties developed steadily. Many beautiful results emerged in mathematicians’ works. Most of them were about non-singular varieties. Singularities were considered “bad” objects that interfered with knowledge of the structure of an algebraic variety. In the past three decades, however, it has become clear that singularities are necessary for us to have a good description of the framework of varieties. For example, it is impossible to formulate minimal model theory for higher-dimensional cases without singularities. Another example is that the moduli spaces of varieties have natural compactification, the boundar...
Lagos Koolhaas and Partisan Politics in Nigeria
Fourchard, Laurent
2010-01-01
International audience; Architect Rem Koolhaas and his team from Harvard regard Lagos as an extreme and pathological form of the city in Africa and as a paradigmatic case of a modern avant-garde city. In rehabilitating the informality at work in Lagos, they put forward a romanticized vision of a self-regulatory system working outside state regulation and political influence. In this article I consider that the crisis of urban infrastructure in Lagos is less the result of the weakness of the N...
CIENCIA, TECNOLOGIA Y SOCIEDAD: REFLEXION DESDE EL USO DE LOS ECOSISTEMAS ESTRATÉGICOS
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Gloria Yaneth Florez Yepes
2013-10-01
Full Text Available El presente artículo presenta una reflexión sobre la influencia de la tecnología y la sociedad en los ecosistemas estratégicos, principalmente los humedales altoandinos. Los problemas ambientales están volviéndose más complejos, debido a variables climáticas y antropogénicas que contribuyen a la degradación del ecosistema. Se pueden encontrar soluciones factibles desde un punto de vista social y tecnológico, con base en la participación de las comunidades. Se toma un enfoque sistemático, teniendo en cuenta todos los factores que influyen en los problemas ambientales y la posibilidad de encontrar soluciones apropiadas con base en la participación de las comunidades. Los temas tratados son: i dimensiones de los sistemas tecnológicos, en los ecosistemas estratégicos, ii sistemas tecnológicos y su influencia en los ecosistemas vulnerables, iii contribución de las comunidades en el entendimiento del ecosistema y sus alrededores, iv apropiación de las comunidades de su entorno. La idea es mostrar el grave efecto del proceso de producción inadecuado en los ecosistemas estratégicos, y el hecho de que los procesos comunitarios de desarrollo motivan: i la apropiación de los ecosistemas por parte de las comunidades, ii la conciencia de las comunidades con respecto al efecto de la acción antropogénica sobre los problemas ambientales.
Properties of kinematic singularities
Energy Technology Data Exchange (ETDEWEB)
Coley, A A [Department of Mathematics and Statistics, Dalhousie University, Halifax, Nova Scotia B3H 3J5 (Canada); Hervik, S [Department of Mathematics and Natural Sciences, University of Stavanger, N-4036 Stavanger (Norway); Lim, W C [Albert-Einstein-Institut, Am Muehlenberg 1, D-14476 Potsdam (Germany); MacCallum, M A H, E-mail: aac@mathstat.dal.c, E-mail: sigbjorn.hervik@uis.n, E-mail: wclim@aei.mpg.d, E-mail: m.a.h.maccallum@qmul.ac.u [School of Mathematical Sciences, Queen Mary University of London, E1 4NS (United Kingdom)
2009-11-07
The locally rotationally symmetric tilted perfect fluid Bianchi type V cosmological model provides examples of future geodesically complete spacetimes that admit a 'kinematic singularity' at which the fluid congruence is inextendible but all frame components of the Weyl and Ricci tensors remain bounded. We show that for any positive integer n there are examples of Bianchi type V spacetimes admitting a kinematic singularity such that the covariant derivatives of the Weyl and Ricci tensors up to the nth order also stay bounded. We briefly discuss singularities in classical spacetimes.
Nonlinear singular elliptic equations
International Nuclear Information System (INIS)
Dong Minh Duc.
1988-09-01
We improve the Poincare inequality, the Sobolev imbedding theorem and the Trudinger imbedding theorem and prove a Mountain pass theorem. Applying these results we study a nonlinear singular mixed boundary problem. (author). 22 refs
International Nuclear Information System (INIS)
Berry, M.V.
2002-01-01
For illumination with white light, the spectra near a typical isolated phase singularity (nodal point of the component wavelengths) can be described by a universal function of position, up to linear distortion and a weak dependence on the spectrum of the source. The appearance of the singularity when viewed by a human observer is predicted by transforming the spectrum to trichromatic variables and chromaticity coordinates, and then rendering the colours, scaled to constant luminosity, on a computer monitor. The pattern far from the singularity is a white that depends on the source temperature, and the centre of the pattern is flanked by intensely coloured 'eyes', one orange and one blue, separated by red, and one of the eyes is surrounded by a bright white circle. Only a small range of possible colours appears near the singularity; in particular, there is no green. (author)
Ling, Eric
The big bang theory is a model of the universe which makes the striking prediction that the universe began a finite amount of time in the past at the so called "Big Bang singularity." We explore the physical and mathematical justification of this surprising result. After laying down the framework of the universe as a spacetime manifold, we combine physical observations with global symmetrical assumptions to deduce the FRW cosmological models which predict a big bang singularity. Next we prove a couple theorems due to Stephen Hawking which show that the big bang singularity exists even if one removes the global symmetrical assumptions. Lastly, we investigate the conditions one needs to impose on a spacetime if one wishes to avoid a singularity. The ideas and concepts used here to study spacetimes are similar to those used to study Riemannian manifolds, therefore we compare and contrast the two geometries throughout.
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Gabriel Martínez-Niconoff
2012-01-01
Full Text Available With the purpose to compare the physical features of the electromagnetic field, we describe the synthesis of optical singularities propagating in the free space and on a metal surface. In both cases the electromagnetic field has a slit-shaped curve as a boundary condition, and the singularities correspond to a shock wave that is a consequence of the curvature of the slit curve. As prototypes, we generate singularities that correspond to fold and cusped regions. We show that singularities in free space may generate bifurcation effects while plasmon fields do not generate these kinds of effects. Experimental results for free-space propagation are presented and for surface plasmon fields, computer simulations are shown.
International Nuclear Information System (INIS)
Goswami, Rituparno; Joshi, Pankaj S.; Vaz, Cenalo; Witten, Louis
2004-01-01
We construct a class of spherically symmetric collapse models in which a naked singularity may develop as the end state of collapse. The matter distribution considered has negative radial and tangential pressures, but the weak energy condition is obeyed throughout. The singularity forms at the center of the collapsing cloud and continues to be visible for a finite time. The duration of visibility depends on the nature of energy distribution. Hence the causal structure of the resulting singularity depends on the nature of the mass function chosen for the cloud. We present a general model in which the naked singularity formed is timelike, neither pointlike nor null. Our work represents a step toward clarifying the necessary conditions for the validity of the Cosmic Censorship Conjecture
Biomedical Science Technologists in Lagos Universities: Meeting ...
African Journals Online (AJOL)
Biomedical Science Technologists in Lagos Universities: Meeting Modern Standards ... like to see in biomedical science in Nigeria; 5) their knowledge of ten state-of-the-arts ... KEY WORDS: biomedical science, state-of-the-arts, technical staff ...
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Hans Schonemann
1996-12-01
Full Text Available Some algorithms for singularity theory and algebraic geometry The use of Grobner basis computations for treating systems of polynomial equations has become an important tool in many areas. This paper introduces of the concept of standard bases (a generalization of Grobner bases and the application to some problems from algebraic geometry. The examples are presented as SINGULAR commands. A general introduction to Grobner bases can be found in the textbook [CLO], an introduction to syzygies in [E] and [St1]. SINGULAR is a computer algebra system for computing information about singularities, for use in algebraic geometry. The basic algorithms in SINGULAR are several variants of a general standard basis algorithm for general monomial orderings (see [GG]. This includes wellorderings (Buchberger algorithm ([B1], [B2] and tangent cone orderings (Mora algorithm ([M1], [MPT] as special cases: It is able to work with non-homogeneous and homogeneous input and also to compute in the localization of the polynomial ring in 0. Recent versions include algorithms to factorize polynomials and a factorizing Grobner basis algorithm. For a complete description of SINGULAR see [Si].
Numerical method of singular problems on singular integrals
International Nuclear Information System (INIS)
Zhao Huaiguo; Mou Zongze
1992-02-01
As first part on the numerical research of singular problems, a numerical method is proposed for singular integrals. It is shown that the procedure is quite powerful for solving physics calculation with singularity such as the plasma dispersion function. Useful quadrature formulas for some class of the singular integrals are derived. In general, integrals with more complex singularities can be dealt by this method easily
HISTORIA AMBIENTAL DE UN LAGO ALPINO EN EL CENTRO DE MÉXICO (1230-2010
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Estela Cuna
2015-01-01
Full Text Available Los lagos de alta montaña, con una baja mineralización, alcalinidad y contenido de nutrientes, son ecosistemas sensibles a perturbaciones naturales o antropogénicas y en la actualidad están amenazados por el calentamiento global. En México existen dos lagos de alta montaña (> 3,800 m snm: La Luna y El Sol, en el cráter del Nevado de Toluca. Análisis de parámetros químicos y de diatomeas en sedimentos superficiales permiten identificar que La Luna es más ácido y menos mineralizado que El Sol y que a pesar de su proximidad geográfica cada lago tiene un conjunto de diatomeas característico, con menor abundancia y riqueza específica en La Luna. En este lago dominan Encyonema perpusillum y Psammothidium helveticum y en El Sol Cavinula pseudoscutiformis , Psammothidium levanderi y Aulacoseira distans. Con base en esta distribución se interpreta el registro de diatomeas de una secuencia sedimentaria de La Luna, de 57 cm, fechada con 210 Pb y 14 C en la que también se realizaron análisis de contenido de cladóceros y de susceptibilidad magnética. Todos estos indicadores permiten ubicar el inicio de una tendencia hacia climas secos y fríos alrededor de los años 1350 y 1510, que corresponde a la Pequeña Edad de Hielo (PEH, la cual tiene su máxima expresión entre los años 1660 y 1760, durante el mínimo de actividad solar de Maunder. Las características ambientales de sequía y frío se observan hasta principios del siglo XX. La comparación de este registro con otros disponibles permite concluir que durante la PEH hubo una tendencia regional en el centro de México hacia climas secos.
Procesos de regulación metacognitiva en el aprendizaje de ecosistemas terrestres
Salazar Oviedo, Vivian Lucy
2017-01-01
En los procesos de regulación metacognitiva en el aprendizaje de ecosistemas terrestres es importante contar con herramientas que permitan identificar las habilidades metacognitivas que poseen los estudiantes, ya que para los docentes contar con este resultado permite conocer hacia donde se deben enfocar las estrategias de aprendizaje. Para el análisis categoría de regulación del aprendizaje de ecosistemas terrestres la investigación se basó en tres subcategorías planificación, monitoreo, y e...
Lagos Journal of Library and Information Science: Site Map
African Journals Online (AJOL)
Lagos Journal of Library and Information Science: Site Map. Journal Home > About the Journal > Lagos Journal of Library and Information Science: Site Map. Log in or Register to get access to full text downloads.
Lagos Journal of Library and Information Science: Journal ...
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Singularities in FLRW spacetimes
het Lam, Huibert; Prokopec, Tomislav
2017-12-01
We point out that past-incompleteness of geodesics in FLRW spacetimes does not necessarily imply that these spacetimes start from a singularity. Namely, if a test particle that follows such a trajectory has a non-vanishing velocity, its energy was super-Planckian at some time in the past if it kept following that geodesic. That indicates a breakdown of the particle's description, which is why we should not consider those trajectories for the definition of an initial singularity. When one only considers test particles that do not have this breakdown of their trajectory, it turns out that the only singular FLRW spacetimes are the ones that have a scale parameter that vanishes at some initial time.
LAGO: The Latin American giant observatory
Sidelnik, Iván; Asorey, Hernán; LAGO Collaboration
2017-12-01
The Latin American Giant Observatory (LAGO) is an extended cosmic ray observatory composed of a network of water-Cherenkov detectors (WCD) spanning over different sites located at significantly different altitudes (from sea level up to more than 5000 m a.s.l.) and latitudes across Latin America, covering a wide range of geomagnetic rigidity cut-offs and atmospheric absorption/reaction levels. The LAGO WCD is simple and robust, and incorporates several integrated devices to allow time synchronization, autonomous operation, on board data analysis, as well as remote control and automated data transfer. This detection network is designed to make detailed measurements of the temporal evolution of the radiation flux coming from outer space at ground level. LAGO is mainly oriented to perform basic research in three areas: high energy phenomena, space weather and atmospheric radiation at ground level. It is an observatory designed, built and operated by the LAGO Collaboration, a non-centralized collaborative union of more than 30 institutions from ten countries. In this paper we describe the scientific and academic goals of the LAGO project - illustrating its present status with some recent results - and outline its future perspectives.
Pseudospherical surfaces with singularities
DEFF Research Database (Denmark)
Brander, David
2017-01-01
We study a generalization of constant Gauss curvature −1 surfaces in Euclidean 3-space, based on Lorentzian harmonic maps, that we call pseudospherical frontals. We analyse the singularities of these surfaces, dividing them into those of characteristic and non-characteristic type. We give methods...
Supersymmetry in singular spaces
Bergshoeff, Eric
2002-01-01
We discuss supersymmetry in spaces with a boundary, i.e. singular spaces. In particular, we discuss the situation in ten and five dimensions. In both these cases we review the construction of supersymmetric domain wall actions situated at the boundary. These domain walls act as sources inducing a
Singularities in FLRW Spacetimes
Lam, Huibert het; Prokopec, Tom
2017-01-01
We point out that past-incompleteness of geodesics in FLRW spacetimes does not necessarily imply that these spacetimes start from a singularity. Namely, if a test particle that follows such a trajectory has a non-vanishing velocity, its energy was super-Planckian at some time in the past if it kept
Charged singularities: repulsive effects
Energy Technology Data Exchange (ETDEWEB)
De Felice, F; Nobili, L [Padua Univ. (Italy). Ist. di Fisica; Calvani, M [Padua Univ. (Italy). Ist. di Astronomia
1980-07-01
The repulsive phenomena which a particle experiences in the vicinity of a naked singularity are investigated in the Kerr-Newman space-time. The aim is to extend the knowledge of this fact to charged solutions and to have a direct indication of how, in these situations, the gravitational and electrostatic interactions are competing.
Papapetrou's naked singularity is a strong curvature singularity
International Nuclear Information System (INIS)
Hollier, G.P.
1986-01-01
Following Papapetrou [1985, a random walk in General Relativity ed. J. Krishna-Rao (New Delhi: Wiley Eastern)], a spacetime with a naked singularity is analysed. This singularity is shown to be a strong curvature singularity and thus a counterexample to a censorship conjecture. (author)
Urban-Rural Temperature Differences in Lagos
Directory of Open Access Journals (Sweden)
Vincent N. Ojeh
2016-05-01
Full Text Available In this study, the hourly air temperature differences between City hall (urban and Okoafo (rural in Lagos, Nigeria, were calculated using one year of meteorological observations, from June 2014 to May 2015. The two sites considered for this work were carefully selected to represent their climate zones. The city core, City hall, is within the Local Climate Zone (LCZ 2 (Compact midrise while the rural location, Okoafo, falls within LCZ B (Scattered Trees in the south-western part on the outskirt of the city. This study is one of very few to investigate urban temperature conditions in Lagos, the largest city in Africa and one of the most rapidly urbanizing megacities in the world; findings show that maximum nocturnal UHI magnitudes in Lagos can exceed 7 °C during the dry season, and during the rainy season, wet soils in the rural environment supersede regional wind speed as the dominant control over UHI magnitude.
Singular potentials in quantum mechanics
International Nuclear Information System (INIS)
Aguilera-Navarro, V.C.; Koo, E. Ley
1995-10-01
This paper is a review of some mathematical methods as recently developed and applied to deal with singular potentials in Quantum Mechanics. Regular and singular perturbative methods as well as variational treatments are considered. (author). 25 refs
Singularities: the Brieskorn anniversary volume
National Research Council Canada - National Science Library
Brieskorn, Egbert; Arnolʹd, V. I; Greuel, G.-M; Steenbrink, J. H. M
1998-01-01
...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Main theorem ... 3 Ideals of ideal-unimodal plane curve singularities. . . . . . . . . . . . . . . . References ... Gert-Martin Greuel and Gerhard Pfister...
String theory and cosmological singularities
Indian Academy of Sciences (India)
Well-known examples are singularities inside black holes and initial or final singularities in expanding or contracting universes. In recent times, string theory is providing new perspectives of such singularities which may lead to an understanding of these in the standard framework of time evolution in quantum mechanics.
Holographic complexity and spacetime singularities
Energy Technology Data Exchange (ETDEWEB)
Barbón, José L.F. [Instituto de Física Teórica IFT UAM/CSIC,C/ Nicolás Cabrera 13, Campus Universidad Autónoma de Madrid,Madrid 28049 (Spain); Rabinovici, Eliezer [Racah Institute of Physics, The Hebrew University,Jerusalem 91904 (Israel); Laboratoire de Physique Théorique et Hautes Energies, Université Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris Cedex 05 (France)
2016-01-15
We study the evolution of holographic complexity in various AdS/CFT models containing cosmological crunch singularities. We find that a notion of complexity measured by extremal bulk volumes tends to decrease as the singularity is approached in CFT time, suggesting that the corresponding quantum states have simpler entanglement structure at the singularity.
Are naked singularities really visible
Energy Technology Data Exchange (ETDEWEB)
Calvani, M [Padua Univ. (Italy). Ist. di Astronomia; De Felice, F [Alberta Univ., Edmonton (Canada); Nobili, L [Padua Univ. (Italy). Ist. di Fisica
1978-12-09
The question whether a Kerr naked singularity is actually visible from infinity is investigated; it is shown that in fact any signal which could be emitted from the singularity is infinitely red-shifted. This implies that naked singularities would be indistinguishable from a black hole.
Holographic complexity and spacetime singularities
International Nuclear Information System (INIS)
Barbón, José L.F.; Rabinovici, Eliezer
2016-01-01
We study the evolution of holographic complexity in various AdS/CFT models containing cosmological crunch singularities. We find that a notion of complexity measured by extremal bulk volumes tends to decrease as the singularity is approached in CFT time, suggesting that the corresponding quantum states have simpler entanglement structure at the singularity.
Belinski, Vladimir
2018-01-01
Written for researchers focusing on general relativity, supergravity, and cosmology, this is a self-contained exposition of the structure of the cosmological singularity in generic solutions of the Einstein equations, and an up-to-date mathematical derivation of the theory underlying the Belinski–Khalatnikov–Lifshitz (BKL) conjecture on this field. Part I provides a comprehensive review of the theory underlying the BKL conjecture. The generic asymptotic behavior near the cosmological singularity of the gravitational field, and fields describing other kinds of matter, is explained in detail. Part II focuses on the billiard reformulation of the BKL behavior. Taking a general approach, this section does not assume any simplifying symmetry conditions and applies to theories involving a range of matter fields and space-time dimensions, including supergravities. Overall, this book will equip theoretical and mathematical physicists with the theoretical fundamentals of the Big Bang, Big Crunch, Black Hole singula...
Deformations of surface singularities
Szilárd, ágnes
2013-01-01
The present publication contains a special collection of research and review articles on deformations of surface singularities, that put together serve as an introductory survey of results and methods of the theory, as well as open problems, important examples and connections to other areas of mathematics. The aim is to collect material that will help mathematicians already working or wishing to work in this area to deepen their insight and eliminate the technical barriers in this learning process. This also is supported by review articles providing some global picture and an abundance of examples. Additionally, we introduce some material which emphasizes the newly found relationship with the theory of Stein fillings and symplectic geometry. This links two main theories of mathematics: low dimensional topology and algebraic geometry. The theory of normal surface singularities is a distinguished part of analytic or algebraic geometry with several important results, its own technical machinery, and several op...
DEFF Research Database (Denmark)
Somchaipeng, Kerawit; Sporring, Jon; Johansen, Peter
2007-01-01
We propose MultiScale Singularity Trees (MSSTs) as a structure to represent images, and we propose an algorithm for image comparison based on comparing MSSTs. The algorithm is tested on 3 public image databases and compared to 2 state-of-theart methods. We conclude that the computational complexity...... of our algorithm only allows for the comparison of small trees, and that the results of our method are comparable with state-of-the-art using much fewer parameters for image representation....
International Nuclear Information System (INIS)
Habis, M.; Robichon, F.; Demonet, J.F.
1996-01-01
Of late ten years, neurologists are studying the brain of the dyslectics. The cerebral imagery (NMR imaging, positron computed tomography) has allowed to confirm the anatomical particularities discovered by some of them: asymmetry default of cerebral hemispheres, size abnormally large of the white substance mass which connect the two hemispheres. The functional imagery, when visualizing this singular brain at work, allows to understand why it labors to reading. (O.M.)
Lagos Journal of Library and Information Science
African Journals Online (AJOL)
Lagos Journal of Library and Information Science (LJLIS) aims to publish articles, short communications and conference reports which will: raise the level of awareness within the international library and information community of the potential for change and innovation; assist policy and decision-making in the medium term ...
Automated acquisition: principles and practice | Ezomo | Lagos ...
African Journals Online (AJOL)
No Abstract. Lagos Journal of Library and Information Science Vol. 1(2) 2003: 120-124. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. Article Metrics. Metrics Loading ... Metrics powered by PLOS ALM · http://dx.doi.org/10.4314/ljlis.v1i2.35486 · AJOL African Journals ...
Directory of Open Access Journals (Sweden)
Gabriel A. Pinilla
2006-01-01
Full Text Available La relación entre la fluorescencia variable y la fluorescencia máxima (Fv/Fm de las comunidades de algas se ha utilizado comúnmente como una medida de la eficiencia fotosintética del fitoplancton. Dicha eficiencia puede estar afectada por la localización de los ambientes acuáticos en distintas provincias limnológicas. En este trabajo se quiso establecer la diferencia en la relación Fv/Fm entre el lago Boa (150 msnm, Amazonía colombiana y el lago Guatavita (3000 msnm, cordillera oriental de los Andes colombianos. Los promedios de las eficiencias medidas fueron en general bajos (0,212 a 0,367 y 0,089 a 0,32 en los lagos Boa y Guatavita, respectivamente, lo que señala estrés fisiológico para las algas. La eficiencia fue mayor en aguas intermedias y presentó cambios fuertes entre épocas de muestreo y entre ecosistemas. En aguas superficiales se presentó fotoinhibición, la cual fue más fuerte en Guatavita. La eficiencia fotosintética fue menor en el lago andino debido posiblemente a diferencias climáticas, de altura sobre el nivel del mar y de estratificación. Durante los ensayos de laboratorio se observó que la eficiencia disminuyó con el tiempo, lo cual pudo deberse a una aclimatación de las algas a la oscuridad. Los datos de laboratorio confirmaron que el fitoplancton epilimnético del lago Guatavita estuvo fotoinhibido en la época de estratificación.Commonly relation between variable fluorescence and maximum fluorescence (Fv/Fm of the algae community has been utilized like a measure of the phytoplanktonic photosynthetic efficiency. Such efficiency can be affected by the water bodies' location in different limnological provinces. The goal of this work was to establish the differences in the Fv/Fm rate between Lake Boa (150 masl Colombian Amazon and Lake Guatavita (3000 masl, East Range in the Colombian Andes. In general, averages of the photosynthetic efficiencies were low (0.212 to 0.367 and 0.089 to 0.32 in lakes Boa and
CSIR Research Space (South Africa)
Roux, FS
2013-09-01
Full Text Available Roux Presented at the International Conference on Correlation Optics 2013 Chernivtsi, Ukraine 18-20 September 2013 CSIR National Laser Centre, Pretoria, South Africa – p. 1/24 Contents ⊲ Defining Stochastic Singular Optics (SSO) ⊲ Tools of Stochastic... of vortices: topological charge ±1 (higher order are unstable). Positive and negative vortex densities np(x, y, z) and nn(x, y, z) ⊲ Vortex density: V = np + nn ⊲ Topological charge density: T = np − nn – p. 4/24 Subfields of SSO ⊲ Homogeneous, normally...
Cosmological models without singularities
International Nuclear Information System (INIS)
Petry, W.
1981-01-01
A previously studied theory of gravitation in flat space-time is applied to homogeneous and isotropic cosmological models. There exist two different classes of models without singularities: (i) ever-expanding models, (ii) oscillating models. The first class contains models with hot big bang. For these models there exist at the beginning of the universe-in contrast to Einstein's theory-very high but finite densities of matter and radiation with a big bang of very short duration. After short time these models pass into the homogeneous and isotropic models of Einstein's theory with spatial curvature equal to zero and cosmological constant ALPHA >= O. (author)
GESTIÓN AMBIENTAL DE LOS ECOSISTEMAS DE MANGLAR. APROXIMACIÓN AL CASO COLOMBIANO
Directory of Open Access Journals (Sweden)
URIBE PÉREZ JOLIANNA
2010-05-01
Full Text Available La presente investigación documental tiene como fin dará conocer, mediante un análisis claro y detallado, la información publicada acerca del estado actual ce los ecosistemas de manglar y su gestión. Para ello, se estableció un sistema categorial que facilitó el análisis de la información recopilada. En primera instancia, se examina la importancia de los ecosistemas de manglar, tanto a nivel soco- económico como biológico. Luego, se analizan las causas de su degradación ambiental. agrupadas en: cambio d mático global, desarrollos urbanísticos. Sobreexplotación de los recursos y cambios en el uso del suelo Igualmente, se revisan les efectos de la degradación ambiental de los manglares, resumidos en el deterioro de sus funciones biológicas y en la pérdida de los bienes y servicios, consumibles y no consumibles. Posteriormente, se analiza la gestión ambiental levada a cabo en los manglares, la cual implica, por un lado la normatividad (tanto nacional como internacional y por otro, las estrategias de manejo implementadas. Se identifican tendencias, vacíes y ambigüedades de la información recopilada, y se presentan algunas conclusiones y recomendaciones útiles para futuras tareas de gestión ambiental de ecosistemas demandar.
Plane waves with weak singularities
International Nuclear Information System (INIS)
David, Justin R.
2003-03-01
We study a class of time dependent solutions of the vacuum Einstein equations which are plane waves with weak null singularities. This singularity is weak in the sense that though the tidal forces diverge at the singularity, the rate of divergence is such that the distortion suffered by a freely falling observer remains finite. Among such weak singular plane waves there is a sub-class which does not exhibit large back reaction in the presence of test scalar probes. String propagation in these backgrounds is smooth and there is a natural way to continue the metric beyond the singularity. This continued metric admits string propagation without the string becoming infinitely excited. We construct a one parameter family of smooth metrics which are at a finite distance in the space of metrics from the extended metric and a well defined operator in the string sigma model which resolves the singularity. (author)
Factors Influencing Patronage Of Medical Tourism In Metropolitan Lagos Nigeria
Omisore; E.O.; Agbabiaka; H. I.
2015-01-01
Since medical tourism attract patient from various origin to seek medical services at different destinations it is paramount to consider the factors that motivate patrons decision on medical tourism. Hence this study assesses the factors influencing patronage of medical tourism in Lagos metropolis Nigeria. Lagos State is situated in the southwestern corner of Nigeria it lies within Latitudes 62N to 64N of the Equator and Longitudes 245E to 420E of the Greenwich meridian. Metropolitan Lagos is...
Major Sources of Worries and Concerns about Landfills in Lagos
African Journals Online (AJOL)
Choice-Academy
Department of Physical Development, Nigerian Institute of Social and Economic Research (NISER), Ibadan, Nigeria. ... Keywords: Landfills; Environment; Risk; Perception; Lagos. Introduction ... the popular media frequently contain accounts.
Residues and duality for singularity categories of isolated Gorenstein singularities
Murfet, Daniel
2009-01-01
We study Serre duality in the singularity category of an isolated Gorenstein singularity and find an explicit formula for the duality pairing in terms of generalised fractions and residues. For hypersurfaces we recover the residue formula of the string theorists Kapustin and Li. These results are obtained from an explicit construction of complete injective resolutions of maximal Cohen-Macaulay modules.
Bioremediación de lagos tropicales eutrofizados: estudio del Lago San Pablo (Ecuador)
Gómez Rosero, Tamia Gabriela
2017-01-01
En este trabajo se presenta la propuesta del Plan de Restauración Ambiental denominado "Guardianas/es del Lago" que, a través de la fitorremediación de las macrófitas y diseñado con la participación de la población, plantea disminuir la contaminación que actualmente existe en el lago San Pablo. Para que el diseño sea acorde a la realidad, se ha realizado un diagnóstico de las condiciones físico-químicas, identificación del plancton y de las macrófitas del lago, además una indagaci...
International Nuclear Information System (INIS)
Littlejohn, R.G.
1982-01-01
The Hamiltonian structures discovered by Morrison and Greene for various fluid equations were obtained by guessing a Hamiltonian and a suitable Poisson bracket formula, expressed in terms of noncanonical (but physical) coordinates. In general, such a procedure for obtaining a Hamiltonian system does not produce a Hamiltonian phase space in the usual sense (a symplectic manifold), but rather a family of symplectic manifolds. To state the matter in terms of a system with a finite number of degrees of freedom, the family of symplectic manifolds is parametrized by a set of Casimir functions, which are characterized by having vanishing Poisson brackets with all other functions. The number of independent Casimir functions is the corank of the Poisson tensor J/sup ij/, the components of which are the Poisson brackets of the coordinates among themselves. Thus, these Casimir functions exist only when the Poisson tensor is singular
Directory of Open Access Journals (Sweden)
Mariana Delgado-Jaramillo
2011-12-01
Full Text Available Los murciélagos constituyen el grupo de mamíferos más diversificado en la región neotropical y representan un componente clave en la dinámica de muchos ecosistemas terrestres. En este trabajo se describen los resultados de un estudio sobre la quiropterofauna del Parque Nacional Yurubí (ubicado en la zona montañosa del norte de Venezuela, se incluye un listado taxonómico y la caracterización de algunos atributos comunitarios en ambientes predominantemente boscosos. Los datos evaluados fueron obtenidos mediante la revisión de colecciones zoológicas y muestreos diversificados realizados entre febrero y julio del 2009, en un gradiente altitudinal (100-1 500m, que integra a tres unidades ecológicas: bosque semideciduo, bosque siempreverde y selva nublada. Se registraron 64 especies agrupadas en cinco familias, lo que constituye el 63% de los murciélagos conocidos en la Cordillera de la Costa. La familia Phyllostomidae fue dominante (42 especies; 66% del total, seguida por Vespertilionidae, Molossidae, Emballonuridae y Mormoopidae. La comunidad presente a baja elevación fue la más diversificada en términos taxonómicos, mientras que la del piso superior evidenció el menor grado de diversificación. Se identificaron 11 categorías tróficas, con dominancia de los insectívoros en cuanto a la riqueza taxonómica y de los frugívoros en lo que respecta a la abundancia. Nuestros resultados permiten inferir, en un contexto general, que los ecosistemas boscosos del área de estudio muestran un buen estado de conservación, en virtud de la presencia de una proporción relativamente alta de especies pertenecientes a la subfamilia Phyllostominae, cuyos componentes han sido considerados por otros autores como indicadores del grado de conservación de hábitats boscosos primarios, así como la presencia de otras especies con prioridades de conservación. Todos estos aspectos, le confieren a esta área protegida un alto valor proteccionista, en
Naked singularities are not singular in distorted gravity
Energy Technology Data Exchange (ETDEWEB)
Garattini, Remo, E-mail: Remo.Garattini@unibg.it [Università degli Studi di Bergamo, Facoltà di Ingegneria, Viale Marconi 5, 24044 Dalmine (Bergamo) (Italy); I.N.F.N. – sezione di Milano, Milan (Italy); Majumder, Barun, E-mail: barunbasanta@iitgn.ac.in [Indian Institute of Technology Gandhinagar, Ahmedabad, Gujarat 382424 (India)
2014-07-15
We compute the Zero Point Energy (ZPE) induced by a naked singularity with the help of a reformulation of the Wheeler–DeWitt equation. A variational approach is used for the calculation with Gaussian Trial Wave Functionals. The one loop contribution of the graviton to the ZPE is extracted keeping under control the UltraViolet divergences by means of a distorted gravitational field. Two examples of distortion are taken under consideration: Gravity's Rainbow and Noncommutative Geometry. Surprisingly, we find that the ZPE is no more singular when we approach the singularity.
Naked singularities are not singular in distorted gravity
Garattini, Remo; Majumder, Barun
2014-07-01
We compute the Zero Point Energy (ZPE) induced by a naked singularity with the help of a reformulation of the Wheele-DeWitt equation. A variational approach is used for the calculation with Gaussian Trial Wave Functionals. The one loop contribution of the graviton to the ZPE is extracted keeping under control the UltraViolet divergences by means of a distorted gravitational field. Two examples of distortion are taken under consideration: Gravity's Rainbow and Noncommutative Geometry. Surprisingly, we find that the ZPE is no more singular when we approach the singularity.
Naked singularities are not singular in distorted gravity
International Nuclear Information System (INIS)
Garattini, Remo; Majumder, Barun
2014-01-01
We compute the Zero Point Energy (ZPE) induced by a naked singularity with the help of a reformulation of the Wheeler–DeWitt equation. A variational approach is used for the calculation with Gaussian Trial Wave Functionals. The one loop contribution of the graviton to the ZPE is extracted keeping under control the UltraViolet divergences by means of a distorted gravitational field. Two examples of distortion are taken under consideration: Gravity's Rainbow and Noncommutative Geometry. Surprisingly, we find that the ZPE is no more singular when we approach the singularity
Breastfeeding practices of mothers of young children in Lagos, Nigeria
African Journals Online (AJOL)
Objective: To determine the breastfeeding practices (prevalence, initiation and exclusivity) of mothers of young children in Lagos. Methods: This was a communitybased, cross-sectional study carried out in 2010 in two Local Government Areas of Lagos State. Structured, intervieweradministered questionnaires were ...
Lago Agrio (Nueva Loja), Ecuador: A Strategic Black Spot?
2013-03-01
Lago Agrio (Nueva Loja ), Ecuador : A Strategic Black Spot? by Colonel John A. Conway United States Army...REPORT TYPE STRATEGY RESEARCH PROJECT .33 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Lago Agrio (Nueva Loja ), Ecuador : A...Agrio (Nueva Loja ), Ecuador : A Strategic Black Spot? by Colonel John A. Conway United States Army Colonel Juan C
Widening the tax net: Lessons from Lagos State, Nigeria | Abiola ...
African Journals Online (AJOL)
Pressure is on governments all over the world to increase revenue through taxation in order to provide better services within their jurisdictions. This study attempts to access the Lagos state's revenue performance under the internally generated revenue scheme. Lagos state total revenue data was collected from 2009 to ...
Road Traffic Accident Variations in Lagos State, Nigeria: A Synopsis ...
African Journals Online (AJOL)
FIRST LADY
The major objective of this research is to examine the variation patterns of road traffic .... situation in Lagos state is bad because of the absence of effective transport ... environment as judged by the investigating officers. Also .... pattern of road traffic accident occurrence over that part of Lagos State. For ... Ph.D Thesis.
459 Road Transport System Management and Traffic in Lagos ...
African Journals Online (AJOL)
User
2010-10-16
Oct 16, 2010 ... reason for this being the catalytic effect of transport development on socio- economic ... as well as in promoting regional cooperation. In Lagos State ... The primary road network (Federal and State roads) which link the major .... Recently, in 2002, when a survey of Lagos urban traffic was conducted, the.
Factors Affecting Tourist Satisfaction in Lagos State,Nigeria | Madu ...
African Journals Online (AJOL)
This paper tries to discover factors that are responsible for the poor development of recreational tourism in Lagos State of Nigeria, so as to be able to suggest improvement measures. The results show that the overall satisfaction of the business tourists is generally similar to that of the recreational group, and that Lagos State ...
Circulating Adipokine levels in Type 2 Diabetes Mellitus in Lagos ...
African Journals Online (AJOL)
Objective: This study was undertaken with the aim of investigating adipokine levels in the Type 2 Diabetes Mellitus. Methods: This is a cross sectional study conducted in Lagos University Teaching Hospital (LUTH), a-700 bed tertiary hospital centre in Lagos, Nigeria. 53 diabetic subjects and 27 non-diabetic controls with ...
Autopsy findings in sickle cell disease patients in Lagos State ...
African Journals Online (AJOL)
Autopsy findings in sickle cell disease patients in Lagos State University Teaching Hospital, Ikeja, Lagos, Nigeria. ... The study showed that the most common cause of sudden death was anemia-related (50%) while 21% were due to acute infections, 18.4 % were due to cardiovascular events and 4.6% were due to ...
Efecto de la radiación ultravioleta sobre los ecosistemas acuáticos
Zagarese, H.E.; Cravero, W.R.; Villafane, V.; Helbling, W.
1998-01-01
Hasta hace poco tiempo se consideraba que la radiación ultravioleta carecía de importancia como factor ambiental en los ecosistemas acuáticos, ya que se suponía que se absorbía totalmente en los primeros centímetros de la columna de agua. Gracias al desarrollo de mejores instrumentos de medición, hoy se sabe que la penetración de la radiación ultravioleta en el agua es mucho mayor que la estimada anteriormente, y que sus efectos biológicos resultan observables hasta decenas de metros de profu...
Inventory of fisheries and fishes of the Lagos Lagoon, Lagos, Nigeria
African Journals Online (AJOL)
The systematic literature of fishes and fisheries in Lagos Lagoon is scattered, hence there is need for a comprehensive documentation of the diverse fish species that ... artisanal fishery, points to environmental degradation and possible changes in water quality with biological consequences for the biota in this environment.
Loop quantum cosmology and singularities.
Struyve, Ward
2017-08-15
Loop quantum gravity is believed to eliminate singularities such as the big bang and big crunch singularity. This belief is based on studies of so-called loop quantum cosmology which concerns symmetry-reduced models of quantum gravity. In this paper, the problem of singularities is analysed in the context of the Bohmian formulation of loop quantum cosmology. In this formulation there is an actual metric in addition to the wave function, which evolves stochastically (rather than deterministically as the case of the particle evolution in non-relativistic Bohmian mechanics). Thus a singularity occurs whenever this actual metric is singular. It is shown that in the loop quantum cosmology for a homogeneous and isotropic Friedmann-Lemaître-Robertson-Walker space-time with arbitrary constant spatial curvature and cosmological constant, coupled to a massless homogeneous scalar field, a big bang or big crunch singularity is never obtained. This should be contrasted with the fact that in the Bohmian formulation of the Wheeler-DeWitt theory singularities may exist.
Singularity resolution in quantum gravity
International Nuclear Information System (INIS)
Husain, Viqar; Winkler, Oliver
2004-01-01
We examine the singularity resolution issue in quantum gravity by studying a new quantization of standard Friedmann-Robertson-Walker geometrodynamics. The quantization procedure is inspired by the loop quantum gravity program, and is based on an alternative to the Schroedinger representation normally used in metric variable quantum cosmology. We show that in this representation for quantum geometrodynamics there exists a densely defined inverse scale factor operator, and that the Hamiltonian constraint acts as a difference operator on the basis states. We find that the cosmological singularity is avoided in the quantum dynamics. We discuss these results with a view to identifying the criteria that constitute 'singularity resolution' in quantum gravity
The theory of singular perturbations
De Jager, E M
1996-01-01
The subject of this textbook is the mathematical theory of singular perturbations, which despite its respectable history is still in a state of vigorous development. Singular perturbations of cumulative and of boundary layer type are presented. Attention has been given to composite expansions of solutions of initial and boundary value problems for ordinary and partial differential equations, linear as well as quasilinear; also turning points are discussed. The main emphasis lies on several methods of approximation for solutions of singularly perturbed differential equations and on the mathemat
Van Hove singularities revisited
International Nuclear Information System (INIS)
Dzyaloshinskii, I.
1987-07-01
Beginning with the work of Hirsch and Scalapino the importance of ln 2 -Van Hove singularity in T c -enhancement in La 2 CuO 4 -based compounds was realized, which is nicely reviewed by Rice. However, the theoretical treatment carried out before is incomplete. Two things were apparently not paid due attention to: interplay of particle-particle and particle-hole channels and Umklapp processes. In what follows a two-dimensional weak coupling model of LaCuO 4 will be solved exactly in the ln 2 -approximation. The result in the Hubbard limit (one bare charge) is that the system is unstable at any sign of interaction. Symmetry breaking moreover is pretty peculiar. Of course, there are separate singlet superconducting pairings in the pp-channel (attraction) and SDW (repulsion) and CDW (attraction) in the ph-channel. It is natural that Umklapps produce an SDW + CDW mixture at either sign of the interaction. What is unusual is that both the pp-ph interplay and the Umklapps give rise to a monster-coherent SS + SDW + CDW mixture, again at either sign of the bare charge. In the general model where all 4 charges involved are substantially different, the system might remain metallic. A more realistic approach which takes into account dopping in La-M-Cu-O and interlayer interaction provides at least a qualitative understanding of the experimental picture. 10 refs, 5 figs
Singularity: Raychaudhuri equation once again
Indian Academy of Sciences (India)
Cosmology; Raychaudhuri equation; Universe; quantum gravity; loop quan- tum gravity ... than the observation verifying the prediction of theory. This gave .... which was now expanding, would have had a singular beginning in a hot Big Bang.
Directory of Open Access Journals (Sweden)
Rudy A Salas Tathum
2018-02-01
Full Text Available El estudio se realizó en el laboratorio natural Snaki ubicado en el la comunidad de Moss, municipio de Waspam, Región Autónoma de la Costa Caribe Norte. Se ha diagnosticado la ornitofauna en los ecosistemas bosque ripario, bosque latifoliado, área agrícola y área pecuaria del laboratorio natural Snaki-URACCAN. Se realizaron transectos lineales y entrevistas informales a cazadores de la zona que permitió crear un listado de aves y su estado de conservación. Los resultados de los diferentes ecosistemas re ejaron la existencia de 49 diferentes especies de aves, pertenecientes a 23 familias y 12 órde- nes. Las especies representativas son: Aratinga nana, Cyanocorax Morio, Ramphocelus Passerinii, Quiscalus nicaraguensis, Procnias tricarunculata, Tachyponus rufus. Al com- parar los índices de diversidad, Shannon y Simpson encontraron similitudes en sus resultados, existiendo una diversidad considerable en el bosque, principalmente en el de galería.
Local and nonlocal space-time singularities
International Nuclear Information System (INIS)
Konstantinov, M.Yu.
1985-01-01
The necessity to subdivide the singularities into two classes: local and nonlocal, each of them to be defined independently, is proved. Both classes of the singularities are defined, and the relation between the definitions introduced and the standard definition of singularities, based on space-time, incompleteness, is established. The relation between definitions introduced and theorems on the singularity existence is also established
ESTADO TRÓFICO DE UN LAGO TROPICAL DE ALTA MONTAÑA: CASO LAGUNA DE LA COCHA
Directory of Open Access Journals (Sweden)
Mery Liliana López Martínez
2015-01-01
Full Text Available Este artículo presenta los resultados de una investigación realizada con el fin de determinar el estado trófico de la laguna de La Cocha, cuerpo hídrico importante en Colombia y en el mundo, que hace parte del humedal Ramsar laguna de La Cocha, ecosistema que cumple distintas funciones y alberga una gran biodiversidad que se quiere proteger. Para lograr el propósito planteado, esta investigación se realizó entre enero y septiembre de 2013, determinando el estado trófico mediante los índices de Carlson, el índice desarrollado por la OCDE (Organización para la Cooperación y el Desarrollo Económico y el índice de Carlson modificado por Toledo. Los resultados permitieron clasificar a la laguna de La Cocha como oligotrófica y ultraoligotrófica, característica típica de lagos de alta montaña con bajos procesos de contaminación de origen aloctóno y autóctono.
On the singularities of solutions to singular perturbation problems
International Nuclear Information System (INIS)
Fruchard, A; Schaefke, R
2005-01-01
We consider a singularly perturbed complex first order ODE εu ' Φ(x, u, a, ε), x, u element of C, ε > 0 is a small complex parameter and a element of C is a control parameter. It is proven that the singularities of some solutions are regularly spaced and that they move from one to the next as a runs about a loop of index one around a value of overstability. This gives a positive answer to a question of J. L. Callot
On the singularities of solutions to singular perturbation problems
Energy Technology Data Exchange (ETDEWEB)
Fruchard, A [Laboratoire de Mathematiques, Informatique et Applications, Faculte des Sciences et Techniques, Universite de Haute Alsace, 4 rue des Freres Lumiere, 68093 Mulhouse cedex (France); Schaefke, R [Departement de Mathematiques, Universite Louis Pasteur, 7 rue Rene-Descartes, 67084 Strasbourg cedex (France)
2005-01-01
We consider a singularly perturbed complex first order ODE {epsilon}u ' {phi}(x, u, a, {epsilon}), x, u element of C, {epsilon} > 0 is a small complex parameter and a element of C is a control parameter. It is proven that the singularities of some solutions are regularly spaced and that they move from one to the next as a runs about a loop of index one around a value of overstability. This gives a positive answer to a question of J. L. Callot.
Emergency distress call system for automobiles in Lagos state, Nigeria
African Journals Online (AJOL)
Emergency distress call system for automobiles in Lagos state, Nigeria. ... PROMOTING ACCESS TO AFRICAN RESEARCH ... and communications technology capabilities to transportation and the medical care system in order to save lives, ...
Personnel Recruitment and Retention Strategies in Lagos State Civil ...
African Journals Online (AJOL)
Personnel Recruitment and Retention Strategies in Lagos State Civil Service of Nigeria. ... The results show that the strategy for personnel recruitment into the CS is based on mixtures of merit and political ... AJOL African Journals Online.
Understanding green and sustainable construction in Lagos, Nigeria ...
African Journals Online (AJOL)
Ethiopian Journal of Environmental Studies and Management. Journal Home ... Journal Home > Vol 8, No 1 (2015) >. Log in or ... Understanding green and sustainable construction in Lagos, Nigeria: Principles, attributes and framework.
Major Sources of Worries and Concerns about Landfills in Lagos
African Journals Online (AJOL)
Choice-Academy
Keywords: Landfills; Environment; Risk; Perception; Lagos. Introduction ... largely to the perception of risk to human health and the environment. ..... in turn pass the cost to consumers. Potential ... Environment and Behaviour, Vol. 32 No. 2 pp.
Level of awareness of genetic counselling in Lagos, Nigeria: its ...
African Journals Online (AJOL)
Level of awareness of genetic counselling in Lagos, Nigeria: its advocacy on the inheritance of sickle cell disease. ... and the level of awareness about genetic counseling in 30 hospitals were carried out. ... AJOL African Journals Online.
Pattern of Exodontia treatment need of adults attending the Lagos ...
African Journals Online (AJOL)
Aim and Objective: To determine the pattern of tooth loss among adults ... Dentistry of the Lagos University Teaching Hospital from September 2001 to April 2004. ... treatment recommended (i.e. periodontal, conservative dentistry, prosthetic, ...
Ecological assessment of a coastal shallow lagoon in Lagos, Nigeria
African Journals Online (AJOL)
Michael Horsfall
Nigerian Institute for Oceanography and Marine Research, P.M.B. 12729, Victoria Island, Lagos, Nigeria ... diversity observed in station B could be attributed to stress imposed by effluents from ..... of American Science 2010;6(1):42-48.
Social change and traditional gender roles in Lagos State, Nigeria ...
African Journals Online (AJOL)
Social change and traditional gender roles in Lagos State, Nigeria. ... twenty seven respondents consisted of 135 Females (59.5%) and 92 Males (40.5%) participated in the survey. The study adopted descriptive method of research design.
adaptation of plastic waste to energy development in lagos
African Journals Online (AJOL)
user
Keywords: Plastic wastes, Energy, Sustainable development, Environment, ... countries to be rationalising energy supply to their people. .... Managing waste in Lagos is may be a herculean task in ..... uncertainties in a life cycle perspective.
Trend of Heavy Metal Concentrations in Lagos Lagoon Ecosystem
African Journals Online (AJOL)
komla
The distribution and occurrence of heavy metals in the sediment, water and benthic animals of the Lagos lagoon ... The concentrations of the metals detected in the lagoon sediment and water ..... waste products contaminating water sources.
Experiencias dendroclimáticas con árboles de ecosistemas contrastantes de Colombia
Directory of Open Access Journals (Sweden)
Jorge Ignacio del Valle
2012-01-01
Full Text Available Este trabajo presenta los resultados de diferentes investigaciones dendroclimáticas realizadas en tres ecosistemas contrastantes de Colombia. Se emplearon técnicas dendrocronológicas y densitogramas computarizados para obtener las cronologías de crecimiento y densidad, respectivamente. Se encontraron asociaciones significativas entre las cronologías, las variables climáticas locales y el ENSO, por ejemplo: la densidad de los anillos de crecimiento de Rhizophora mangle con la precipitación; el ancho de los anillos de crecimiento de Parkinsonia praecox y Capparis odoratissima con la precipitación, la temperatura del aire y la temperatura superficial del mar, y el ancho de los anillos de crecimiento de Prioria copaifera con las alturas limnimétricas del río Atrato. Dichos resultados demuestran la aplicabilidad y el potencial de la dendroclimatología en regiones tropicales.
Experiencias dendroclimáticas con árboles de ecosistemas contrastantes de Colombia
Directory of Open Access Journals (Sweden)
Herrera David Andrés
2012-12-01
Full Text Available Este trabajo presenta los resultados de diferentes investigaciones dendroclimaticas realizadas en tres ecosistemas contrastantes de Colombia. Se emplearon técnicas dendrocronologicas y densitogramas computarizados para obtener las cronologías de crecimiento y densidad, respectivamente. Se encontraron asociaciones significativas entre las cronologías, las variables climáticas locales y el ENSO, por ejemplo: la densidad de los anillos de crecimiento de Rhizophora mangle con la precipitación; el ancho de los anillos de crecimiento de Parkinsonia praecox y Capparis odoratissima con la precipitación, la temperatura del aire y la temperatura superficial del mar, y el ancho de los anillos de crecimiento de Prioria copaifera con las alturas limnimetricas del rio Atrato. Dichos resultados demuestran la aplicabilidad y el potencial de la dendroclimatologia en regiones tropicales.
Experiencias dendroclimáticas con árboles de ecosistemas contrastantes de Colombia
Directory of Open Access Journals (Sweden)
Jorge Ignacio del Valle
2012-07-01
Full Text Available Este trabajo presenta los resultados de diferentes investigaciones dendroclimaticas realizadas en tres ecosistemas contrastantes de Colombia. Se emplearon técnicas dendrocronologicas y densitogramas computarizados para obtener las cronologías de crecimiento y densidad, respectivamente. Se encontraron asociaciones significativas entre las cronologías, las variables climáticas locales y el ENSO, por ejemplo: la densidad de los anillos de crecimiento de Rhizophora mangle con la precipitación; el ancho de los anillos de crecimiento de Parkinsonia praecox y Capparis odoratissima con la precipitación, la temperatura del aire y la temperatura superficial del mar, y el ancho de los anillos de crecimiento de Prioria copaifera con las alturas limnimetricas del rio Atrato. Dichos resultados demuestran la aplicabilidad y el potencial de la dendroclimatologia en regiones tropicales.
Is the cosmological singularity compulsory
International Nuclear Information System (INIS)
Bekenstein, J.D.; Meisels, A.
1980-01-01
The cosmological singularity is inherent in all conventional general relativistic cosmological models. There can be no question that it is an unphysical feature; yet there does not seem to be any convervative way of eliminating it. Here we present singularity-free isotropic cosmological models which are indistinguishable from general relativistic ones at late times. They are based on the general theory of variable rest masses that we developed recently. Outside cosmology this theory simulates general relativity well. Thus it provides a framework incorporating those features which have made geneal relativity so sucessful while providing a way out of singularity dilemma. The cosmological models can be made to incorporate Dirac's large numbers hypothesis. G(now)/G(0)approx.10 -38
A 1 + 5-dimensional gravitational-wave solution. Curvature singularity and spacetime singularity
Energy Technology Data Exchange (ETDEWEB)
Chen, Yu-Zhu [Tianjin University, Department of Physics, Tianjin (China); Li, Wen-Du [Tianjin University, Department of Physics, Tianjin (China); Nankai University, Theoretical Physics Division, Chern Institute of Mathematics, Tianjin (China); Dai, Wu-Sheng [Nankai University, Theoretical Physics Division, Chern Institute of Mathematics, Tianjin (China); Nankai University and Tianjin University, LiuHui Center for Applied Mathematics, Tianjin (China)
2017-12-15
We solve a 1 + 5-dimensional cylindrical gravitational-wave solution of the Einstein equation, in which there are two curvature singularities. Then we show that one of the curvature singularities can be removed by an extension of the spacetime. The result exemplifies that the curvature singularity is not always a spacetime singularity; in other words, the curvature singularity cannot serve as a criterion for spacetime singularities. (orig.)
Asymptomatic bacteriuria among antenatal women in Lagos.
Olamijulo, Joseph Ayodeji; Adewale, Chris Olu; Olaleye, Olalekan
2016-08-01
This cross-sectional study was undertaken to determine the prevalence of asymptomatic bacteriuria (ASB), the commonest bacterial isolates and the antibiotic sensitivity pattern among 556 pregnant women in Lagos University Teaching Hospital (LUTH), Nigeria. Women with a bacterial count over 100,000 colony-forming units per millilitre of the same organisms in paired urine samples were considered to have ASB. The prevalence of ASB was 14.6%. Klebsiella was the commonest micro-organism (39.2%) isolated. ASB was significantly associated with marital status, body mass index and parity. There was a significant relationship between urinary nitrites and ASB. The isolated organisms showed remarkable resistance to commonly prescribed antibiotics such as amoxicillin, cloxacillin and trimethoprim but good sensitivity to ofloxacin, gentamycin and ceftazidime. These facts have implications for the management of ASB in pregnancy.
Singularities in geodesic surface congruence
International Nuclear Information System (INIS)
Cho, Yong Seung; Hong, Soon-Tae
2008-01-01
In the stringy cosmology, we investigate singularities in geodesic surface congruences for the timelike and null strings to yield the Raychaudhuri type equations possessing correction terms associated with the novel features owing to the strings. Assuming the stringy strong energy condition, we have a Hawking-Penrose type inequality equation. If the initial expansion is negative so that the congruence is converging, we show that the expansion must pass through the singularity within a proper time. We observe that the stringy strong energy conditions of both the timelike and null string congruences produce the same inequality equation.
Singular perturbation of simple eigenvalues
International Nuclear Information System (INIS)
Greenlee, W.M.
1976-01-01
Two operator theoretic theorems which generalize those of asymptotic regular perturbation theory and which apply to singular perturbation problems are proved. Application of these theorems to concrete problems is involved, but the perturbation expansions for eigenvalues and eigenvectors are developed in terms of solutions of linear operator equations. The method of correctors, as well as traditional boundary layer techniques, can be used to apply these theorems. The current formulation should be applicable to highly singular ''hard core'' potential perturbations of the radial equation of quantum mechanics. The theorems are applied to a comparatively simple model problem whose analysis is basic to that of the quantum mechanical problem
Singularity Theory and its Applications
Stewart, Ian; Mond, David; Montaldi, James
1991-01-01
A workshop on Singularities, Bifuraction and Dynamics was held at Warwick in July 1989, as part of a year-long symposium on Singularity Theory and its applications. The proceedings fall into two halves: Volume I mainly on connections with algebraic geometry and volume II on connections with dynamical systems theory, bifurcation theory and applications in the sciences. The papers are original research, stimulated by the symposium and workshop: All have been refereed and none will appear elsewhere. The main topic of volume II is new methods for the study of bifurcations in nonlinear dynamical systems, and applications of these.
Ambient cosmology and spacetime singularities
International Nuclear Information System (INIS)
Antoniadis, Ignatios; Cotsakis, Spiros
2015-01-01
We present a new approach to the issues of spacetime singularities and cosmic censorship in general relativity. This is based on the idea that standard 4-dimensional spacetime is the conformal infinity of an ambient metric for the 5-dimensional Einstein equations with fluid sources. We then find that the existence of spacetime singularities in four dimensions is constrained by asymptotic properties of the ambient 5-metric, while the non-degeneracy of the latter crucially depends on cosmic censorship holding on the boundary. (orig.)
Ambient cosmology and spacetime singularities
Antoniadis, Ignatios
2015-01-01
We present a new approach to the issues of spacetime singularities and cosmic censorship in general relativity. This is based on the idea that standard 4-dimensional spacetime is the conformal infinity of an ambient metric for the 5-dimensional Einstein equations with fluid sources. We then find that the existence of spacetime singularities in four dimensions is constrained by asymptotic properties of the ambient 5-metric, while the non-degeneracy of the latter crucially depends on cosmic censorship holding on the boundary.
Singular moduli and Arakelov intersection
International Nuclear Information System (INIS)
Weng Lin.
1994-05-01
The value of the modular function j(τ) at imaginary quadratic arguments τ in the upper half plane is usually called singular moduli. In this paper, we use Arakelov intersection to give the prime factorizations of a certain combination of singular moduli, coming from the Hecke correspondence. Such a result may be considered as the degenerate one of Gross and Zagier on Heegner points and derivatives of L-series in their paper [GZ1], and is parallel to the result in [GZ2]. (author). 2 refs
Singularities in minimax optimization of networks
DEFF Research Database (Denmark)
Madsen, Kaj; Schjær-Jacobsen, Hans
1976-01-01
A theoretical treatment of singularities in nonlinear minimax optimization problems, which allows for a classification in regular and singular problems, is presented. A theorem for determining a singularity that is present in a given problem is formulated. A group of problems often used in the li......A theoretical treatment of singularities in nonlinear minimax optimization problems, which allows for a classification in regular and singular problems, is presented. A theorem for determining a singularity that is present in a given problem is formulated. A group of problems often used...
String theory and cosmological singularities
Indian Academy of Sciences (India)
recent times, string theory is providing new perspectives of such singularities which .... holes appear as stacks of a large number of D-branes wrapped in internal .... results into a well-known measure factor which makes the wave function into a.
Charged singularities: the causality violation
Energy Technology Data Exchange (ETDEWEB)
De Felice, F; Nobili, L [Padua Univ. (Italy). Ist. di Fisica; Calvani, M [Padua Univ. (Italy). Ist. di Astronomia
1980-12-01
A search is made for examples of particle trajectories which, approaching a naked singularity from infinity, make up for lost time before going back to infinity. In the Kerr-Newman metric a whole family of such trajectories is found showing that the causality violation is indeed a non-avoidable pathology.
Interval matrices: Regularity generates singularity
Czech Academy of Sciences Publication Activity Database
Rohn, Jiří; Shary, S.P.
2018-01-01
Roč. 540, 1 March (2018), s. 149-159 ISSN 0024-3795 Institutional support: RVO:67985807 Keywords : interval matrix * regularity * singularity * P-matrix * absolute value equation * diagonally singilarizable matrix Subject RIV: BA - General Mathematics Impact factor: 0.973, year: 2016
Computation at a coordinate singularity
Prusa, Joseph M.
2018-05-01
Coordinate singularities are sometimes encountered in computational problems. An important example involves global atmospheric models used for climate and weather prediction. Classical spherical coordinates can be used to parameterize the manifold - that is, generate a grid for the computational spherical shell domain. This particular parameterization offers significant benefits such as orthogonality and exact representation of curvature and connection (Christoffel) coefficients. But it also exhibits two polar singularities and at or near these points typical continuity/integral constraints on dependent fields and their derivatives are generally inadequate and lead to poor model performance and erroneous results. Other parameterizations have been developed that eliminate polar singularities, but problems of weaker singularities and enhanced grid noise compared to spherical coordinates (away from the poles) persist. In this study reparameterization invariance of geometric objects (scalars, vectors and the forms generated by their covariant derivatives) is utilized to generate asymptotic forms for dependent fields of interest valid in the neighborhood of a pole. The central concept is that such objects cannot be altered by the metric structure of a parameterization. The new boundary conditions enforce symmetries that are required for transformations of geometric objects. They are implemented in an implicit polar filter of a structured grid, nonhydrostatic global atmospheric model that is simulating idealized Held-Suarez flows. A series of test simulations using different configurations of the asymptotic boundary conditions are made, along with control simulations that use the default model numerics with no absorber, at three different grid sizes. Typically the test simulations are ∼ 20% faster in wall clock time than the control-resulting from a decrease in noise at the poles in all cases. In the control simulations adverse numerical effects from the polar
Remarks on gauge variables and singular Lagrangians
International Nuclear Information System (INIS)
Chela-Flores, J.; Janica-de-la-Torre, R.; Kalnay, A.J.; Rodriguez-Gomez, J.; Rodriguez-Nunez, J.; Tascon, R.
1977-01-01
The relevance is discussed of gauge theory, based on a singular Lagrangian density, to the foundations of field theory. The idea that gauge transformations could change the physics of systems where the Lagrangian is singular is examined. (author)
Singular multiparameter dynamic equations with distributional ...
African Journals Online (AJOL)
Singular multiparameter dynamic equations with distributional potentials on time scales. ... In this paper, we consider both singular single and several multiparameter ... multiple function which is of one sign and nonzero on the given time scale.
Eweka, O M; Ogundana, O M; Agbelusi, G A
2016-01-01
Temporomandibular joint pain dysfunction syndrome (TMJPDS) is the most common temporomandibular disorder. This condition presents with symptoms of pain, restricted jaw movement and joint noise. Other symptoms include otalgia, headache, neck pain and trismus. To determine the pattern of Temporomandibular joint pain dysfunction syndrome patients managed at the Lagos University Teaching Hospital, Lagos, Nigeria. A descriptive study of patients with signs and symptoms of Temporomandibular joint pain dysfunction syndrome attending the Oral Medicine Clinic of Lagos University Teaching Hospital. Twenty-one patients with Temporomandibular joint pain dysfunction syndrome were enrolled into the study, out of which 10(48%) were females and 11(52%) were males. The age range was 23-81years with a mean of 45.2 ± 18.9 years. Majority of the patients 20(95.2%) complained of pain around the joint, in the pre-auricular region, in the muscles of mastication and the ear. While 7(35%) complained of clicking sounds, 10(47.6%) complained of pain on mouth opening and during mastication only. In all 5(23.8%) had impaired movement of the jaws, mouth opening was normal in 18(85.7%) but reduced in 3(14.3%) patients. Over half of patients 12(57%) experienced clicking sounds, there was tenderness around the temporomandibular joint in 16(76.2%) cases, pain in the ear of 7(33.3%) patients and 13(61.9%) people presented with tenderness of the muscles of mastication. Conservative management of all the cases resulted in resolution of the symptoms. Temporomandibular joint pain dysfunction syndrome has diverse clinical presentation and though distressing, it responds to prompt and effective conservative management.
Analysis of singularity in redundant manipulators
International Nuclear Information System (INIS)
Watanabe, Koichi
2000-03-01
In the analysis of arm positions and configurations of redundant manipulators, the singularity avoidance problems are important themes. This report presents singularity avoidance computations of a 7 DOF manipulator by using a computer code based on human-arm models. The behavior of the arm escaping from the singular point can be identified satisfactorily through the use of 3-D plotting tools. (author)
Assessment of radiation protection practices among radiographers in Lagos, Nigeria.
Eze, Cletus Uche; Abonyi, Livinus Chibuzo; Njoku, Jerome; Irurhe, Nicholas Kayode; Olowu, Oluwabola
2013-11-01
Use of ionising radiation in diagnostic radiography could lead to hazards such as somatic and genetic damages. Compliance to safe work and radiation protection practices could mitigate such risks. The aim of the study was to assess the knowledge and radiation protection practices among radiographers in Lagos, Nigeria. The study was a prospective cross sectional survey. Convenience sampling technique was used to select four x-ray diagnostic centres in four tertiary hospitals in Lagos metropolis. Data were analysed with Epi- info software, version 3.5.1. Average score on assessment of knowledge was 73%. Most modern radiation protection instruments were lacking in all the centres studied. Application of shielding devices such as gonad shield for protection was neglected mostly in government hospitals. Most x-ray machines were quite old and evidence of quality assurance tests performed on such machines were lacking. Radiographers within Lagos metropolis showed an excellent knowledge of radiation protection within the study period. Adherence to radiation protection practices among radiographers in Lagos metropolis during the period studied was, however, poor. Radiographers in Lagos, Nigeria should embrace current trends in radiation protection and make more concerted efforts to apply their knowledge in protecting themselves and patients from harmful effects of ionising radiation.
Energy conditions and spacetime singularities
International Nuclear Information System (INIS)
Tipler, F.J.
1978-01-01
In this paper, a number of theorems are proven which collectively show that singularities will occur in spacetime under weaker energy conditions than the strong energy condition. In particular, the Penrose theorem, which uses only the weak energy condition but which applies only to open universes, is extended to all closed universes which have a Cauchy surface whose universal covering manifold is not a three-sphere. Furthermore, it is shown that the strong energy condition in the Hawking-Penrose theorem can be replaced by the weak energy condition and the assumption that the strong energy condition holds only on the average. In addition, it is demonstrated that if the Universe is closed, then the existence of singularities follows from the averaged strong energy condition alone. It is argued that any globally hyperbolic spacetime which satisfies the weak energy condition and which contains a black hole must be null geodesically incomplete
Multidimensional singular integrals and integral equations
Mikhlin, Solomon Grigorievich; Stark, M; Ulam, S
1965-01-01
Multidimensional Singular Integrals and Integral Equations presents the results of the theory of multidimensional singular integrals and of equations containing such integrals. Emphasis is on singular integrals taken over Euclidean space or in the closed manifold of Liapounov and equations containing such integrals. This volume is comprised of eight chapters and begins with an overview of some theorems on linear equations in Banach spaces, followed by a discussion on the simplest properties of multidimensional singular integrals. Subsequent chapters deal with compounding of singular integrals
Fundamental solutions of singular SPDEs
International Nuclear Information System (INIS)
Selesi, Dora
2011-01-01
Highlights: → Fundamental solutions of linear SPDEs are constructed. → Wick-convolution product is introduced for the first time. → Fourier transformation maps Wick-convolution into Wick product. → Solutions of linear SPDEs are expressed via Wick-convolution with fundamental solutions. → Stochastic Helmholtz equation is solved. - Abstract: This paper deals with some models of mathematical physics, where random fluctuations are modeled by white noise or other singular Gaussian generalized processes. White noise, as the distributional derivative od Brownian motion, which is the most important case of a Levy process, is defined in the framework of Hida distribution spaces. The Fourier transformation in the framework of singular generalized stochastic processes is introduced and its applications to solving stochastic differential equations involving Wick products and singularities such as the Dirac delta distribution are presented. Explicit solutions are obtained in form of a chaos expansion in the Kondratiev white noise space, while the coefficients of the expansion are tempered distributions. Stochastic differential equations of the form P(ω, D) ◊ u(x, ω) = A(x, ω) are considered, where A is a singular generalized stochastic process and P(ω, D) is a partial differential operator with random coefficients. We introduce the Wick-convolution operator * which enables us to express the solution as u = s*A ◊ I ◊(-1) , where s denotes the fundamental solution and I is the unit random variable. In particular, the stochastic Helmholtz equation is solved, which in physical interpretation describes waves propagating with a random speed from randomly appearing point sources.
Why the Singularity Cannot Happen
Modis, Theodore
2012-01-01
The concept of a Singularity as described in Ray Kurzweil's book cannot happen for a number of reasons. One reason is that all natural growth processes that follow exponential patterns eventually reveal themselves to be following S-curves thus excluding runaway situations. The remaining growth potential from Kurzweil's ''knee'', which could be approximated as the moment when an S-curve pattern begins deviating from the corresponding exponential, is a factor of only one order of magnitude grea...
Black holes, singularities and predictability
International Nuclear Information System (INIS)
Wald, R.M.
1984-01-01
The paper favours the view that singularities may play a central role in quantum gravity. The author reviews the arguments leading to the conclusion, that in the process of black hole formation and evaporation, an initial pure state evolves to a final density matrix, thus signaling a breakdown in ordinary quantum dynamical evolution. Some related issues dealing with predictability in the dynamical evolution, are also discussed. (U.K.)
On singularities of lattice varieties
Mukherjee, Himadri
2013-01-01
Toric varieties associated with distributive lattices arise as a fibre of a flat degeneration of a Schubert variety in a minuscule. The singular locus of these varieties has been studied by various authors. In this article we prove that the number of diamonds incident on a lattice point $\\a$ in a product of chain lattices is more than or equal to the codimension of the lattice. Using this we also show that the lattice varieties associated with product of chain lattices is smooth.
Quantum propagation across cosmological singularities
Gielen, Steffen; Turok, Neil
2017-05-01
The initial singularity is the most troubling feature of the standard cosmology, which quantum effects are hoped to resolve. In this paper, we study quantum cosmology with conformal (Weyl) invariant matter. We show that it is natural to extend the scale factor to negative values, allowing a large, collapsing universe to evolve across a quantum "bounce" into an expanding universe like ours. We compute the Feynman propagator for Friedmann-Robertson-Walker backgrounds exactly, identifying curious pathologies in the case of curved (open or closed) universes. We then include anisotropies, fixing the operator ordering of the quantum Hamiltonian by imposing covariance under field redefinitions and again finding exact solutions. We show how complex classical solutions allow one to circumvent the singularity while maintaining the validity of the semiclassical approximation. The simplest isotropic universes sit on a critical boundary, beyond which there is qualitatively different behavior, with potential for instability. Additional scalars improve the theory's stability. Finally, we study the semiclassical propagation of inhomogeneous perturbations about the flat, isotropic case, at linear and nonlinear order, showing that, at least at this level, there is no particle production across the bounce. These results form the basis for a promising new approach to quantum cosmology and the resolution of the big bang singularity.
El fitoplancton de un canal de Xochimilco y la importancia de estudiar ecosistemas acuáticos urbanos
Directory of Open Access Journals (Sweden)
Zitlali López-Mendoza
2015-01-01
Full Text Available El fitoplancton del canal El Bordo en Xochimilco se estudió durante la época de lluvias de 2008 y la época seca de 2009. El objetivo fue conocer la estabilidad de la flora de una zona que requiere medidas de remediación. Los resultados de este estudio mostraron una composición diversa del fitoplancton, en la que destacó el registro de varias especies no observadas previamente en México y concretamente en Xochimilco. Los resultados del monitoreo reflejan en los factores fisicoquímicos una proporción de variación baja (9-17%, a pesar de la intensidad de las actividades agropecuarias que prevalecen en la zona de estudio. Un tercer resultado fue la identificación de un grupo funcional que reúne especies que son típicas de cuerpos de agua someros, tropicales y eutróficos, como el canal El Bordo. Se discute la posibilidad de asociar este grupo funcional con un estado estable en el ecosistema, lo que puede aplicarse en medidas de remediación. Consideramos que es útil estudiar las comunidades de ecosistemas acuáticos urbanos con un alto grado de alteración, pues la cantidad de conocimiento acumulado en una región podría hacer la diferencia entre conservar o perder estos ecosistemas.
Degradación y rehabilitación de ecosistemas terrestres: estado de la cuestión
Montoya Greenheck, Felipe
2016-01-01
Este artículo presenta una visión panorámica sobre la degradación y la rehabilitación de los ecosistemas terrestres costarricenses. Se señalan el mal uso de los suelos, la destrucción de los bosques y el auge ganadero como los principales factores degradantes de los ecosistemas; por otra parte, se recomiendan prácticas como la designación de la capacidad de uso del suelo, la reforestación y las prácticas silvopastoriles como herramientas en pro de la rehabilitación de los ecosistemas y de ...
Directory of Open Access Journals (Sweden)
CORREA SANDRA LILIANA
2012-11-01
Full Text Available Los habitantes de las poblaciones costeras colombianas, la de El Valle, en el Pacífico, y la de Sapzurro, en el Darién (Caribe, poseen un conocimiento ecológico sobre los ecosistemas marinos y costeros que resulta de su relación permanente con el mar, a través de la pesca y la navegación. El mar constituye una fuente de alimentos y de recursos económicos, pero también es el ámbito donde se forja la personalidad masculina. El conocimiento preciso de los manglares, los corales, los arrecifes rocosos, las playas y los caladeros de pesca se ha visto enriquecido a través del diálogo entre los habitantes locales e investigadores en el campo de la biología de la conservación. Sin embargo, aún existen tensiones con dichos investigadores y con las autoridades ambientales. El artículo sugiere que el estudio del conocimiento ecológico local puede ser un punto de partida para sostener un diálogo más horizontal entre las autoridades ambientales, los investigadores y las poblaciones cuya subsistencia depende de la pesca.
Universidad, ecosistema de montaña y desarrollo sustentable: Resultados
Directory of Open Access Journals (Sweden)
Dr. C. Fernando C. Agüero Contreras
2018-01-01
Full Text Available Se ofrece una visión sintética de los resultados del trabajo realizado desde la Universidad de Cienfuegos, por algo más de dos décadas, en el ecosistema de montaña Guamuhaya, o Escambray. El objetivo es valorar las experiencias, resultados prácticos y metodológicos, mostrando momentos y etapas, la diversidad de procedimientos, para construir determinadas reflexiones teóricas que permitan el despliegue del trabajo sociocultural comunitario y, en función de la gestión del desarrollo sustentable. Ha significado laborar con actores sociales escuelas, empresas, familias, estructuras productivas, el gobierno local, Comisión del Plan Turquino (CPPT, y con pobladores de los asentamientos humanos. Se concluye como en la medida en que la universidad interviene en los procesos de la gestión del desarrollo sustentable se fortalece en sus quehaceres y prácticas, acrecientan y consolidan las funciones sustantivas que le caracterizan, se muestran los aportes esenciales de la universidad en el proceso del trabajo
Singularities in Free Surface Flows
Thete, Sumeet Suresh
Free surface flows where the shape of the interface separating two or more phases or liquids are unknown apriori, are commonplace in industrial applications and nature. Distribution of drop sizes, coalescence rate of drops, and the behavior of thin liquid films are crucial to understanding and enhancing industrial practices such as ink-jet printing, spraying, separations of chemicals, and coating flows. When a contiguous mass of liquid such as a drop, filament or a film undergoes breakup to give rise to multiple masses, the topological transition is accompanied with a finite-time singularity . Such singularity also arises when two or more masses of liquid merge into each other or coalesce. Thus the dynamics close to singularity determines the fate of about-to-form drops or films and applications they are involved in, and therefore needs to be analyzed precisely. The primary goal of this thesis is to resolve and analyze the dynamics close to singularity when free surface flows experience a topological transition, using a combination of theory, experiments, and numerical simulations. The first problem under consideration focuses on the dynamics following flow shut-off in bottle filling applications that are relevant to pharmaceutical and consumer products industry, using numerical techniques based on Galerkin Finite Element Methods (GFEM). The second problem addresses the dual flow behavior of aqueous foams that are observed in oil and gas fields and estimates the relevant parameters that describe such flows through a series of experiments. The third problem aims at understanding the drop formation of Newtonian and Carreau fluids, computationally using GFEM. The drops are formed as a result of imposed flow rates or expanding bubbles similar to those of piezo actuated and thermal ink-jet nozzles. The focus of fourth problem is on the evolution of thinning threads of Newtonian fluids and suspensions towards singularity, using computations based on GFEM and experimental
Evaluación de la contaminación en el lago Titicaca
Ministerio de Agricultura; Instituto Nacional de Recursos Naturales. Dirección General de Áreas Naturales Protegidas
1996-01-01
Contiene una relación de informes relacionados a la contaminación del lago Titicaca, tales como: Evaluación de la contaminación en el lago Titicaca y Evaluación ambiental del problema de contaminación que afecta al lago Titicaca (ambos de de setiembre de 1996), Informe sobre la grave contaminación ambiental que está afectando el lago Titicaca (marzo de 1996) y el Plan para descontaminar las aguas del lago Titicaca, Bahía Interior de Puno (julio de 1996).
Mathematical models with singularities a zoo of singular creatures
Torres, Pedro J
2015-01-01
The book aims to provide an unifying view of a variety (a 'zoo') of mathematical models with some kind of singular nonlinearity, in the sense that it becomes infinite when the state variable approaches a certain point. Up to 11 different concrete models are analyzed in separate chapters. Each chapter starts with a discussion of the basic model and its physical significance. Then the main results and typical proofs are outlined, followed by open problems. Each chapter is closed by a suitable list of references. The book may serve as a guide for researchers interested in the modelling of real world processes.
On important precursor of singular optics (tutorial)
Polyanskii, Peter V.; Felde, Christina V.; Bogatyryova, Halina V.; Konovchuk, Alexey V.
2018-01-01
The rise of singular optics is usually associated with the seminal paper by J. F. Nye and M. V. Berry [Proc. R. Soc. Lond. A, 336, 165-189 (1974)]. Intense development of this area of modern photonics has started since the early eighties of the XX century due to invention of the interfrence technique for detection and diagnostics of phase singularities, such as optical vortices in complex speckle-structured light fields. The next powerful incentive for formation of singular optics into separate area of the science on light was connectected with discovering of very practical technique for creation of singular optical beams of various kinds on the base of computer-generated holograms. In the eghties and ninetieth of the XX century, singular optics evolved, almost entirely, under the approximation of complete coherency of light field. Only at the threshold of the XXI century, it has been comprehended that the singular-optics approaches can be fruitfully expanded onto partially spatially coherent, partially polarized and polychromatic light fields supporting singularities of new kinds, that has been resulted in establishing of correlation singular optics. Here we show that correlation singular optics has much deeper roots, ascending to "pre-singular" and even pre-laser epoch and associated with the concept of partial coherence and polarization. It is remarcable that correlation singular optics in its present interpretation has forestalled the standard coherent singular optics. This paper is timed to the sixtieth anniversary of the most profound precursor of modern correlation singular optics [J. Opt. Soc. Am., 47, 895-902 (1957)].
Symmetry generators in singular theories
International Nuclear Information System (INIS)
Lavrov, P.M.; Tyutin, I.V.
1989-01-01
It is proved that in the singular nondegenerate theories any symmetry of the lagrangian under non-point transformations of lagrangian variables with the open (in the general case) algebra in the hamiltonian approach generates corresponding transformations of canonical variables the generator of which is the Noether charge with respect to the Dirac brackets. On the surface of all constraints these transformations leave the hamiltonian invariant and the algebra of the Noether charges is closed. As a consequence it is shown that the nilpotent BRST charge operator always exists in gauge theories of the general form (if possible anomalies are not taken into account)
Topological resolution of gauge theory singularities
Saracco, Fabio; Tomasiello, Alessandro; Torroba, Gonzalo
2013-08-01
Some gauge theories with Coulomb branches exhibit singularities in perturbation theory, which are usually resolved by nonperturbative physics. In string theory this corresponds to the resolution of timelike singularities near the core of orientifold planes by effects from F or M theory. We propose a new mechanism for resolving Coulomb branch singularities in three-dimensional gauge theories, based on Chern-Simons interactions. This is illustrated in a supersymmetric SU(2) Yang-Mills-Chern-Simons theory. We calculate the one-loop corrections to the Coulomb branch of this theory and find a result that interpolates smoothly between the high-energy metric (that would exhibit the singularity) and a regular singularity-free low-energy result. We suggest possible applications to singularity resolution in string theory and speculate a relationship to a similar phenomenon for the orientifold six-plane in massive IIA supergravity.
Topological resolution of gauge theory singularities
Energy Technology Data Exchange (ETDEWEB)
Saracco, Fabio; Tomasiello, Alessandro; Torroba, Gonzalo
2013-08-21
Some gauge theories with Coulomb branches exhibit singularities in perturbation theory, which are usually resolved by nonperturbative physics. In string theory this corresponds to the resolution of timelike singularities near the core of orientifold planes by effects from F or M theory. We propose a new mechanism for resolving Coulomb branch singularities in three-dimensional gauge theories, based on Chern-Simons interactions. This is illustrated in a supersymmetric S U ( 2 ) Yang-Mills-Chern-Simons theory. We calculate the one-loop corrections to the Coulomb branch of this theory and find a result that interpolates smoothly between the high-energy metric (that would exhibit the singularity) and a regular singularity-free low-energy result. We suggest possible applications to singularity resolution in string theory and speculate a relationship to a similar phenomenon for the orientifold six-plane in massive IIA supergravity.
Singularities of Type-Q ABS Equations
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James Atkinson
2011-07-01
Full Text Available The type-Q equations lie on the top level of the hierarchy introduced by Adler, Bobenko and Suris (ABS in their classification of discrete counterparts of KdV-type integrable partial differential equations. We ask what singularities are possible in the solutions of these equations, and examine the relationship between the singularities and the principal integrability feature of multidimensional consistency. These questions are considered in the global setting and therefore extend previous considerations of singularities which have been local. What emerges are some simple geometric criteria that determine the allowed singularities, and the interesting discovery that generically the presence of singularities leads to a breakdown in the global consistency of such systems despite their local consistency property. This failure to be globally consistent is quantified by introducing a natural notion of monodromy for isolated singularities.
The geometry of warped product singularities
Stoica, Ovidiu Cristinel
In this article, the degenerate warped products of singular semi-Riemannian manifolds are studied. They were used recently by the author to handle singularities occurring in General Relativity, in black holes and at the big-bang. One main result presented here is that a degenerate warped product of semi-regular semi-Riemannian manifolds with the warping function satisfying a certain condition is a semi-regular semi-Riemannian manifold. The connection and the Riemann curvature of the warped product are expressed in terms of those of the factor manifolds. Examples of singular semi-Riemannian manifolds which are semi-regular are constructed as warped products. Applications include cosmological models and black holes solutions with semi-regular singularities. Such singularities are compatible with a certain reformulation of the Einstein equation, which in addition holds at semi-regular singularities too.
The dominant balance at cosmological singularities
International Nuclear Information System (INIS)
Cotsakis, Spiros; Barrow, John D
2007-01-01
We define the notion of a finite-time singularity of a vector field and then discuss a technique suitable for the asymptotic analysis of vector fields and their integral curves in the neighborhood of such a singularity. Having in mind the application of this method to cosmology, we also provide an analysis of the time singularities of an isotropic universe filled with a perfect fluid in general relativity
Exact solutions and singularities in string theory
International Nuclear Information System (INIS)
Horowitz, G.T.; Tseytlin, A.A.
1994-01-01
We construct two new classes of exact solutions to string theory which are not of the standard plane wave of gauged WZW type. Many of these solutions have curvature singularities. The first class includes the fundamental string solution, for which the string coupling vanishes near the singularity. This suggests that the singularity may not be removed by quantum corrections. The second class consists of hybrids of plane wave and gauged WZW solutions. We discuss a four-dimensional example in detail
Dressing up a Kerr naked singularity
Energy Technology Data Exchange (ETDEWEB)
Calvani, M [Padua Univ. (Italy). Ist. di Astronomia; Nobili, L [Padua Univ. (Italy). Ist. di Fisica
1979-06-11
The evolution of a naked singularity surrounded by an accreting disk of matter is studied; two kinds of disks are considered: the standard thin-disk model and the thick barytropic model, for several initial conditions. It is shown that any Kerr naked singularity slows down in a finite time to a maximal Kerr black hole. The final mass, the luminosity and the time of evolution of the singularity are evaluated.
Naked singularity, firewall, and Hawking radiation.
Zhang, Hongsheng
2017-06-21
Spacetime singularity has always been of interest since the proof of the Penrose-Hawking singularity theorem. Naked singularity naturally emerges from reasonable initial conditions in the collapsing process. A recent interesting approach in black hole information problem implies that we need a firewall to break the surplus entanglements among the Hawking photons. Classically, the firewall becomes a naked singularity. We find some vacuum analytical solutions in R n -gravity of the firewall-type and use these solutions as concrete models to study the naked singularities. By using standard quantum theory, we investigate the Hawking radiation emitted from the black holes with naked singularities. Here we show that the singularity itself does not destroy information. A unitary quantum theory works well around a firewall-type singularity. We discuss the validity of our result in general relativity. Further our result demonstrates that the temperature of the Hawking radiation still can be expressed in the form of the surface gravity divided by 2π. This indicates that a naked singularity may not compromise the Hakwing evaporation process.
Spacetime averaging of exotic singularity universes
International Nuclear Information System (INIS)
Dabrowski, Mariusz P.
2011-01-01
Taking a spacetime average as a measure of the strength of singularities we show that big-rips (type I) are stronger than big-bangs. The former have infinite spacetime averages while the latter have them equal to zero. The sudden future singularities (type II) and w-singularities (type V) have finite spacetime averages. The finite scale factor (type III) singularities for some values of the parameters may have an infinite average and in that sense they may be considered stronger than big-bangs.
On local invariants of singular symplectic forms
Domitrz, Wojciech
2017-04-01
We find a complete set of local invariants of singular symplectic forms with the structurally stable Martinet hypersurface on a 2 n-dimensional manifold. In the C-analytic category this set consists of the Martinet hypersurface Σ2, the restriction of the singular symplectic form ω to TΣ2 and the kernel of ω n - 1 at the point p ∈Σ2. In the R-analytic and smooth categories this set contains one more invariant: the canonical orientation of Σ2. We find the conditions to determine the kernel of ω n - 1 at p by the other invariants. In dimension 4 we find sufficient conditions to determine the equivalence class of a singular symplectic form-germ with the structurally smooth Martinet hypersurface by the Martinet hypersurface and the restriction of the singular symplectic form to it. We also study the singular symplectic forms with singular Martinet hypersurfaces. We prove that the equivalence class of such singular symplectic form-germ is determined by the Martinet hypersurface, the canonical orientation of its regular part and the restriction of the singular symplectic form to its regular part if the Martinet hypersurface is a quasi-homogeneous hypersurface with an isolated singularity.
Music education and musical activities in Lagos: then and now ...
African Journals Online (AJOL)
This article is a historical excursion into the musical activities in Lagos from around 600 to 1800, which it classifies as the first phase, from around 1800 to 1914, the second period, and third period, from around 1914 up to date and how they have affected music education in the area. The study also highlights the roles played ...
Quality of gari (roasted cassava mash) in Lagos State, Nigeria ...
African Journals Online (AJOL)
Gari is creamy-white, partially gelatinized roasted free flowing granular flour made from cassava roots. It is a major staple consumed in both urban and rural areas due to its convenience. Quality of Gari (roasted cassava mash) in Lagos, Nigeria was investigated. Gari samples were collected at random from different ...
An institutional survey of female genital mutilation in Lagos, South ...
African Journals Online (AJOL)
Background: Female genital mutilation (FGM) as a procedure can have serious physical and psychological health consequences in girls and women. Objectives: To determine the prevalence of FGM and the socio-demographic factors which influence the practice among women in Lagos State. Methods: This was a ...
The Prevalence of Cardiovascular Disease in the Lagos State, Nigeria
African Journals Online (AJOL)
The analysis, which examines the prevalence of cardiovascular diseases (ICD 9: 390-459) in Lagos State of Nigeria, was based on records obtained from the register of deaths in four Local Government Areas of the State. The result shows that there is general increase in death rates due to cardiovascular diseases over the ...
Gender and Campus Violence: A Study of University of Lagos ...
African Journals Online (AJOL)
This research is an attempt to investigate the incidence of violence among university students using University of Lagos as a case study. A questionnaire on different kinds of violence was administered to 446 students of the university. In addition, four focus group discussion sessions were conducted to assess the types of ...
subsurface sequence delineation and saline water mapping of lagos
African Journals Online (AJOL)
A subsurface sequence delineation and saline water mapping of Lagos State was carried out. Ten (10) deep boreholes with average depth of 300 m were drilled within the sedimentary basin. The boreholes were lithologically and geophysically logged. The driller's lithological logs aided by gamma and resistivity logs, ...
Development Control in Lagos State: an Assessment of Public ...
African Journals Online (AJOL)
This submission also contains an assessment of the town planning regulation, level of compliance to building regulation and technical skills of personals monitoring compliance to space standards as specified by Urban and Regional Planning Law Decree 88 of 1992, the Lagos Planning Law of 2005 and under the Urban ...
Genetic diversity of Chrysichthys nigrodigitatus in the Lagos lagoon ...
African Journals Online (AJOL)
s
2012-11-13
Nov 13, 2012 ... 1Key Laboratory of Mariculture, Ministry of Education of China, Ocean University ... 3Department of Marine Sciences, Faculty of Science, University of Lagos, ... degradation and possible changes in water quality ... MATERIALS AND METHODS ... was subsequently resuspended in 100 µl of distilled water for.
Fish resources of Lagos State coastal wetlands | Ayodele | African ...
African Journals Online (AJOL)
Fishing is the major occupation of the people found along the coastal wetland of Lagos State. Fishing is carried out all the year round. This study examines the fishing Activities, Gear composition and fishing methods in order to obtain the fish species and harvest composition of the study area. This paper is based on the ...
Attitude and Perceptions of Clinicians in Lagos to Autopsy Practice ...
African Journals Online (AJOL)
Using pretested questionnaire instrument, a cross sectional survey of clinicians working in the Lagos University Teaching Hospital to obtain their attitudes and perception towards autopsy practice. 230 questionnaires were administered and the response rate was 80.7% . 41.5% of respondents often requested for autopsy.
Evaluation of measles vaccine cold chain in Lagos State, Nigeria ...
African Journals Online (AJOL)
The National (level 1), State (L2), and Local government vaccine cold stores (L3) as well as some vaccination centres (L4) were physically inspected in Lagos State, Nigeria and the potency of the live-attenuated measles vaccine was tested. Both the L1 and L2 storage facilities were formally adequately equipped and ...
Perinatal Mortality Among Twins In Lagos University Teaching ...
African Journals Online (AJOL)
Background: Perinatal mortality rate is reported to be higher in twins than in singletons. More than two decades ago, Abudu and Agarin reported a twinning rate of 21.1/1000 maternities and perinatal mortality rate of 142.6/1000 among twins in Lagos. Objective: To determine the current perinatal mortality rate and risk factors ...
Geophysical study of saline water intrusion in Lagos municipality
African Journals Online (AJOL)
aghomotsegin
1Department of Applied Geophysics, Federal University of Technology, Akure, Ondo State, Nigeria. 2Lagos State ... E'. C. C'. N070 00'. E0020 300'. N060 15'. E0020 300'. N070 00'. E0040 30' ..... coastal aquifer, Youngkwang-gun, Korea.
Prevalence and trends in breast cancer in Lagos state, Nigeria ...
African Journals Online (AJOL)
The study examined the trends in the prevalence of breast cancer in Lagos State, Nigeria. A sample of 1000 subjects was taken from a population consisting of women between the ages of 15 and 60 years spread across the 20 Local Government Areas (LGAs) of the State. Fifty questionnaires were distributed in each LGA.
Radiographic diagnosis of skeletal diseases among dogs in Lagos ...
African Journals Online (AJOL)
Case records of dogs presented with signs of skeletal injuries at the Veterinary Teaching Hospital, Federal University of Agriculture, Abeokuta, Ogun State and Petcare Animal Hospital, Ikeja, Lagos between January, 2010 and December, 2011 were reviewed. Data recorded included breed, sex and age of the dogs, ...
236 Effective Social Work Practice in Lagos: An Emerging
African Journals Online (AJOL)
User
2010-10-17
Oct 17, 2010 ... social work profession; institutional perspective is the modern approach that is currently put in place, that ... Lagos had for long been in the fore-front of the development of social work in Nigeria .... organization has crises within or without or both; ... newly learnt ways of solving problems, so, learning effective.
Ectopic Pregnancy in Lagos State University Teaching Hospital ...
African Journals Online (AJOL)
We set out to determine the socio-demographic factors,pattern of presentation and management of ectopic pregnancy in a University Teaching Hospital in Lagos, Nigeria. A retrospective descriptive analysis of all cases of ectopic pregnancy over a 2-year period was carried out. The case notes were retrieved from the ...
Traditional Music and Dance: An Appreciation | Adedeji | Lagos ...
African Journals Online (AJOL)
Lagos Notes and Records. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 17 (2011) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register. DOWNLOAD FULL TEXT Open Access DOWNLOAD FULL TEXT ...
A Review of Nosocomial Infection at the Lagos university Teaching ...
African Journals Online (AJOL)
The infection control program of the Lagos Universityteaching hospital was started in 1974 with an Infection Control team reporting to an Infection Control Committee. There is currently no functioning ... were the most common pathogens accounting for 75% of all organisms isolated. The prevalence of Staphylococcus aureus ...
A prospective study of Vitamin A Utilization in Lagos, Nigeria ...
African Journals Online (AJOL)
Also, drug utilization studies are primary in establishing mechanisms to promote the use of this vitamin. Hence, we investigated the use of Vitamin A in 4 referral paediatric units in Lagos, Nigeria. The study was prospective with the use of questionnaires administered to those patients placed on Vitamin A therapy among 380 ...
John Lyons' Chomsky: A Review Essay | Eleshin | Lagos Notes and ...
African Journals Online (AJOL)
Lagos Notes and Records. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 18, No 1 (2012) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register. DOWNLOAD FULL TEXT Open Access DOWNLOAD FULL ...
Cost of Care Among Patients With Pulmonary Tuberculosis in Lagos ...
African Journals Online (AJOL)
Tuberculosis (TB) is a global health challenge. Currently it is the 7th leading cause of death worldwide, and Nigeria ranks fourth amongst 22 high-burden countries for the disease. This study sought to appraise the direct and indirect costs borne by TB patients attending the Chest Clinics at the Lagos State University ...
Ambient air particulate matter in Lagos, Nigeria: A study using ...
African Journals Online (AJOL)
chemical mass balance model was used for source apportionment. ... world are: soil or entrained dust, vehicular exhaust, marine (in a city situated close ... Mn is a marker element for steel industry and can also be attributed to .... The high enrichment of Br and Pb at the three sites in Lagos is believed to be due to the heavy.
Correlates of Abortion Related Maternal Mortality at the Lagos State ...
African Journals Online (AJOL)
This study was carried out to highlight the probable correlates of mortality among patients managed for abortion related complications at the Lagos State University Teaching Hospital, Ikeja. All patients managed for abortion related complications between 1st January 2000 and 31st December 2003 were studied. Certain ...
Patent Medicine Vendors in Rural Areas of Lagos Nigeria ...
African Journals Online (AJOL)
Purpose: To determine the compliance of patent medicine vendors (PMVs) in rural areas of Lagos State, Nigeria with set guidelines to regulate their practice and its implications for malaria control. Methods: A baseline cross-sectional study was conducted as part of an intervention study in two rural local government areas ...
Childhood Renal Neoplasms in Lagos Nigera- A 28 Year Review ...
African Journals Online (AJOL)
Childhood Renal Neoplasms in Lagos Nigera- A 28 Year Review. ... Most of the patients presented with abdominal mass with a unilaterally enlarged kidney, abdominal pain, haematuria and weight loss. All of them had nephrectomy as initial treatment followed by radiotherapy and chemotherapy. Nigerian Quarterly Journal ...
Cytomegalovirus antibodies among healthy blood donors at Lagos ...
African Journals Online (AJOL)
Objectives. Cytomegalovirus (CMV) is found worldwide in all geographical locations and socio-economic groups and is the virus most frequently transmitted to a developing child before birth. This study aimed to determine the prevalence and risk factors for CMV antibodies among healthy blood donors at Lagos University ...
Temporal variation in the ecology of Kuramo water, Lagos Nigeria ...
African Journals Online (AJOL)
Temporal variation in the ecology of Kuramo water was studied in the Lagos lagoon complex. Physicochemical parameters and heavy metals concentration were analyzed. Eight sites were marked using the geographical positioning system (GPS model-12). Water chemistry was determined for 8 months and sampling was ...
Road Traffic Accident Variations in Lagos State, Nigeria: A Synopsis ...
African Journals Online (AJOL)
The major objective of this research is to examine the variation patterns of road traffic accident in Lagos State. The study used mostly secondary data; accident records and vehicular situation were obtained from the Nigeria police force and Federal Road Safety Commission. The data were obtained for a period of thirty two ...
Urban Renewal and Associated Problems in Lagos, 1924 – 1990 ...
African Journals Online (AJOL)
... traffic congestion, increase in traffic noise, air pollution, flooding, and decadent infrastructure among others. Urban/municipal infrastructure which involves specifying, designing, constructing, and maintaining several services has never had it so good in Lagos. The coordination of these infrastructure networks and services, ...
Scintigraphic analysis of thyroid diseases at the Lagos University ...
African Journals Online (AJOL)
This paper presents a retrospective analysis of randomly selected clinical scintigraphic records at the College of Medicine/Lagos University Teaching Hospital, Nigeria. Out of the 436 patients scanned for various thyroid abnormalities, 266 (61.0%) were used for the analysis due to insufficient data and parameters required ...
Comparative Study of Teenage Pregnancy in Lagos State University ...
African Journals Online (AJOL)
... a comparative study of the obstetric performance of primiparous teenagers and ... 2006-31st December, 2007) in Lagos State University Teaching Hospital,Ikeja. ... The incidence of teenage pregnancy in the study population was 1.01% with ...
The pattern and challenges of infertility management in Lagos, Nigeria
African Journals Online (AJOL)
Background: Infertility remains a threat to successful reproduction by couples desirous of pregnancy. Objective: To determine the pattern of infertility cases amongst infertile couples seeking care in Lagos University Teaching Hospital as well as challenges in their management. Methods: A review of the management of ...
Knowledge And Attitude Of Youth Corps Members In Lagos To ...
African Journals Online (AJOL)
Sickle cell disease has remained a public health problem in Nigeria. This study was carried out to determine the knowledge and attitudes of unmarried NYSC members in Lagos State to sickle cell disease and screening. This study was a cross sectional study. Multistage sampling technique was used to select the ...
The pattern and challenges of infertility management in Lagos, Nigeria
African Journals Online (AJOL)
EB
Abstract. Background: Infertility remains a threat to successful reproduction by couples desirous of pregnancy. Objective: To determine the pattern of infertility cases amongst infertile couples seeking care in Lagos University Teaching. Hospital as well as challenges in their management. Methods: A review of the ...
Pattern of juvenile periodontitis in Lagos University Teaching ...
African Journals Online (AJOL)
Objective: The aim of the survey was to study the pattern of juvenile periodontitis patients that presented at the Lagos University Teaching Hospital Dental Centre from November 1999 to March 2004. Methods: Through review of case files of patients, twenty six juvenile periodontitis patients, within the age range of 18 and 30 ...
MUSIC EDUCATION AND MUSICAL ACTIVITIES IN LAGOS: THEN ...
African Journals Online (AJOL)
This article is a historical excursion into the musical activities in Lagos from around ... development in virtually all areas of life; political, religious, social and .... children' As an example, the cited a song composed on the occasion of the victory ..... missionaries surfaced in the church when the Pan-Africanist movement became.
Coupled singular and non singular thermoelastic system and double lapalce decomposition methods
Hassan Gadain; Hassan Gadain
2016-01-01
In this paper, the double Laplace decomposition methods are applied to solve the non singular and singular one dimensional thermo-elasticity coupled system and. The technique is described and illustrated with some examples
Cuentas Romero, María Alejandra; Salazar Toledo, Arturo Ítalo
2017-01-01
El artículo muestra la relevancia de una especie clave —Prosopis pallida— en el desarrollo ecológico del bosque seco costero, y cómo dicha importancia también influye en el desarrollo humano, pues con el tiempo se ha ido fortaleciendo el vínculo social con los ecosistemas forestales. Mediante el método de muestreo por transectos (punto-centro-cuadrado) y el valor obtenido por medio del Índice de Valor de Importancia (IVI) aplicados al Área de Conservación Regional (ACR) Huacrupe La Calera (Ol...
Papapetrou's naked singularity is a strong curvature singularity
Energy Technology Data Exchange (ETDEWEB)
Hollier, G.P.
1986-11-01
Following Papapetrou (1985, a random walk in General Relativity ed. J. Krishna-Rao (New Delhi: Wiley Eastern)), a spacetime with a naked singularity is analysed. This singularity is shown to be a strong curvature singularity and thus a counterexample to a censorship conjecture.
Directory of Open Access Journals (Sweden)
Christian Chigozie Makwe
2012-12-01
Conclusion: The knowledge of and the perceived susceptibility to HPV infection and HPV-related diseases among female students in the University of Lagos were generally low. The need for a well-designed HPV-educational program to bridge the knowledge gap cannot be overemphasized.
Análisis de contenidos de ecosistemas y ciclos geoquímicos en los manuales portugueses
Directory of Open Access Journals (Sweden)
Rosa Branca Cameira TRACANA
2015-03-01
Full Text Available Son muchos los estudios, en los últimos tiempos, sobre el tema Ecosistemas y ciclos geoquímicos. Pretendemos analizar la transposición didáctica del tema Ecosistemas y ciclos geoquímicos, en los manuales escolares, en el sistema de enseñanza portugués. Fueron analizados manuales de ciencias naturales, ciencia de la naturaleza, biología, geología y geografía, en el sistema educativo portugués y aun estudios sociales, química, biología, ciencias naturales, geología, geografía y ecología. En lo que se refiere a los manuales, constatamos que los del Tiempo I (1991-2000 se presentan más desarrollados en la presentación de los temas cuando se comparan con los del Tiempo II (2000-2006. En el tema Ecosistemas y ciclos geoquímicos, el abordaje de los manuales es esencialmente ecocéntrico. Sin embargo, nuestros resultados llevan a cuestionar la calidad de los manuales al respecto de este tema, porque no sólo es necesario tratarlo de modo más profundo, sino también se deben incluir en los manuales las competencias en educación ambiental para así poder transmitirlas a las generaciones futuras, y de este modo contribuir a una mejora de la calidad de vida en la Tierra.
The Semantics of Plurals: A Defense of Singularism
Florio, Salvatore
2010-01-01
In this dissertation, I defend "semantic singularism", which is the view that syntactically plural terms, such as "they" or "Russell and Whitehead", are semantically singular. A semantically singular term is a term that denotes a single entity. Semantic singularism is to be distinguished from "syntactic singularism", according to which…
Stable singularities in string theory
International Nuclear Information System (INIS)
Aspinwall, P.S.; Morrison, D.R.; Gross, M.
1996-01-01
We study a topological obstruction of a very stringy nature concerned with deforming the target space of an N=2 non-linear σ-model. This target space has a singularity which may be smoothed away according to the conventional rules of geometry, but when one studies the associated conformal field theory one sees that such a deformation is not possible without a discontinuous change in some of the correlation functions. This obstruction appears to come from torsion in the homology of the target space (which is seen by deforming the theory by an irrelevant operator). We discuss the link between this phenomenon and orbifolds with discrete torsion as studied by Vafa and Witten. (orig.). With 3 figs
Directory of Open Access Journals (Sweden)
Elvio Alccinelli
2001-07-01
Full Text Available En este artículo pretendemos mostrar que le conjunto de las economías singulares, si bien pequeño desde el punto de vista de la topología y/o desde el punto de vista de la teoría de la medida, tiene importantes efectos en el desarrollo de los regímenes económicos. Es el responsable de los cambios abruptos en los estados de equilibrio y de la multiplicidad de tales estados. Permite además establecer a partir de los tipos de singularidades posibles, una partición del conjunto de economías según tenga lugar uno u otro tipo de singularidad cuya presencia o no, caracteriza el comportamiento posible de la economía en cuestión.
Quantum transitions through cosmological singularities
Energy Technology Data Exchange (ETDEWEB)
Bramberger, Sebastian F.; Lehners, Jean-Luc [Max Planck Institute for Gravitational Physics (Albert Einstein Institute), 14476 Potsdam-Golm (Germany); Hertog, Thomas; Vreys, Yannick, E-mail: sebastian.bramberger@aei.mpg.de, E-mail: thomas.hertog@kuleuven.be, E-mail: jlehners@aei.mpg.de, E-mail: yannick.vreys@kuleuven.be [Institute for Theoretical Physics, KU Leuven, 3001 Leuven (Belgium)
2017-07-01
In a quantum theory of cosmology spacetime behaves classically only in limited patches of the configuration space on which the wave function of the universe is defined. Quantum transitions can connect classical evolution in different patches. Working in the saddle point approximation and in minisuperspace we compute quantum transitions connecting inflationary histories across a de Sitter like throat or a singularity. This supplies probabilities for how an inflating universe, when evolved backwards, transitions and branches into an ensemble of histories on the opposite side of a quantum bounce. Generalising our analysis to scalar potentials with negative regions we identify saddle points describing a quantum transition between a classically contracting, crunching ekpyrotic phase and an inflationary universe.
Coulomb branches with complex singularities
Argyres, Philip C.; Martone, Mario
2018-06-01
We construct 4d superconformal field theories (SCFTs) whose Coulomb branches have singular complex structures. This implies, in particular, that their Coulomb branch coordinate rings are not freely generated. Our construction also gives examples of distinct SCFTs which have identical moduli space (Coulomb, Higgs, and mixed branch) geometries. These SCFTs thus provide an interesting arena in which to test the relationship between moduli space geometries and conformal field theory data. We construct these SCFTs by gauging certain discrete global symmetries of N = 4 superYang-Mills (sYM) theories. In the simplest cases, these discrete symmetries are outer automorphisms of the sYM gauge group, and so these theories have lagrangian descriptions as N = 4 sYM theories with disconnected gauge groups.
Quantum transitions through cosmological singularities
International Nuclear Information System (INIS)
Bramberger, Sebastian F.; Lehners, Jean-Luc; Hertog, Thomas; Vreys, Yannick
2017-01-01
In a quantum theory of cosmology spacetime behaves classically only in limited patches of the configuration space on which the wave function of the universe is defined. Quantum transitions can connect classical evolution in different patches. Working in the saddle point approximation and in minisuperspace we compute quantum transitions connecting inflationary histories across a de Sitter like throat or a singularity. This supplies probabilities for how an inflating universe, when evolved backwards, transitions and branches into an ensemble of histories on the opposite side of a quantum bounce. Generalising our analysis to scalar potentials with negative regions we identify saddle points describing a quantum transition between a classically contracting, crunching ekpyrotic phase and an inflationary universe.
Discrete variable representation for singular Hamiltonians
DEFF Research Database (Denmark)
Schneider, B. I.; Nygaard, Nicolai
2004-01-01
We discuss the application of the discrete variable representation (DVR) to Schrodinger problems which involve singular Hamiltonians. Unlike recent authors who invoke transformations to rid the eigenvalue equation of singularities at the cost of added complexity, we show that an approach based...
Building Reproducible Science with Singularity Containers
CERN. Geneva
2018-01-01
Michael Bauer first began working with containers at GSI national lab in Darmstadt, Germany, in 2017 while taking a semester off of school at the University of Michigan. Michael met Greg Kurtzer, project lead of Singularity, during his time at GSI and he began contributing heavily to the Singularity project. At the start of summer 2017, Greg hired Michael to work at the ...
Reasons for singularity in robot teleoperation
DEFF Research Database (Denmark)
Marhenke, Ilka; Fischer, Kerstin; Savarimuthu, Thiusius Rajeeth
2014-01-01
In this paper, the causes for singularity of a robot arm in teleoperation for robot learning from demonstration are analyzed. Singularity is the alignment of robot joints, which prevents the configuration of the inverse kinematics. Inspired by users' own hypotheses, we investigated speed and dela...
The Geometry of Black Hole Singularities
Directory of Open Access Journals (Sweden)
Ovidiu Cristinel Stoica
2014-01-01
Full Text Available Recent results show that important singularities in General Relativity can be naturally described in terms of finite and invariant canonical geometric objects. Consequently, one can write field equations which are equivalent to Einstein's at nonsingular points but, in addition remain well-defined and smooth at singularities. The black hole singularities appear to be less undesirable than it was thought, especially after we remove the part of the singularity due to the coordinate system. Black hole singularities are then compatible with global hyperbolicity and do not make the evolution equations break down, when these are expressed in terms of the appropriate variables. The charged black holes turn out to have smooth potential and electromagnetic fields in the new atlas. Classical charged particles can be modeled, in General Relativity, as charged black hole solutions. Since black hole singularities are accompanied by dimensional reduction, this should affect Feynman's path integrals. Therefore, it is expected that singularities induce dimensional reduction effects in Quantum Gravity. These dimensional reduction effects are very similar to those postulated in some approaches to make Quantum Gravity perturbatively renormalizable. This may provide a way to test indirectly the effects of singularities, otherwise inaccessible.
Singularities in the nonisotropic Boltzmann equation
International Nuclear Information System (INIS)
Garibotti, C.R.; Martiarena, M.L.; Zanette, D.
1987-09-01
We consider solutions of the nonlinear Boltzmann equation (NLBE) with anisotropic singular initial conditions, which give a simplified model for the penetration of a monochromatic beam on a rarified target. The NLBE is transformed into an integral equation which is solved iteratively and the evolution of the initial singularities is discussed. (author). 5 refs
Cold atoms in singular potentials
International Nuclear Information System (INIS)
Denschlag, J. P.
1998-09-01
We studied both theoretically and experimentally the interaction between cold Li atoms from a magnetic-optical trap (MOT) and a charged or current-carrying wire. With this system, we were able to realize 1/r 2 and 1/r potentials in two dimensions and to observe the motion of cold atoms in both potentials. For an atom in an attractive 1/r 2 potential, there exist no stable trajectories, instead there is a characteristic class of trajectories for which atoms fall into the singularity. We were able to observe this falling of atoms into the center of the potential. Moreover, by probing the singular 1/r 2 potential with atomic clouds of varying size and temperature we extracted scaling properties of the atom-wire interaction. For very cold atoms, and very thin wires the motion of the atoms must be treated quantum mechanically. Here we predict that the absorption cross section for the 1/r 2 potential should exhibit quantum steps. These quantum steps are a manifestation of the quantum mechanical decomposition of plane waves into partial waves. For the second part of this work, we realized a two dimensional 1/r potential for cold atoms. If the potential is attractive, the atoms can be bound and follow Kepler-like orbits around the wire. The motion in the third dimension along the wire is free. We were able to exploit this property and constructed a novel cold atom guide, the 'Kepler guide'. We also demonstrated another type of atom guide (the 'side guide'), by combining the magnetic field of the wire with a homogeneous offset magnetic field. In this case, the atoms are held in a potential 'tube' on the side of the wire. The versatility, simplicity, and scaling properties of this guide make it an interesting technique. (author)
An adaptive singular ES-FEM for mechanics problems with singular field of arbitrary order
Nguyen-Xuan, H.; Liu, G. R.; Bordas, Stéphane; Natarajan, S.; Rabczuk, T.
2013-01-01
This paper presents a singular edge-based smoothed finite element method (sES-FEM) for mechanics problems with singular stress fields of arbitrary order. The sES-FEM uses a basic mesh of three-noded linear triangular (T3) elements and a special layer of five-noded singular triangular elements (sT5) connected to the singular-point of the stress field. The sT5 element has an additional node on each of the two edges connected to the singular-point. It allows us to represent simple and efficient ...
DEFF Research Database (Denmark)
Cappellin, Cecilia; Breinbjerg, Olav; Frandsen, Aksel
2008-01-01
An effective technique for extracting the singularity of plane wave spectra in the computation of antenna aperture fields is proposed. The singular spectrum is first factorized into a product of a finite function and a singular function. The finite function is inverse Fourier transformed...... numerically using the Inverse Fast Fourier Transform, while the singular function is inverse Fourier transformed analytically, using the Weyl-identity, and the two resulting spatial functions are then convolved to produce the antenna aperture field. This article formulates the theory of the singularity...
Biclustering via Sparse Singular Value Decomposition
Lee, Mihee
2010-02-16
Sparse singular value decomposition (SSVD) is proposed as a new exploratory analysis tool for biclustering or identifying interpretable row-column associations within high-dimensional data matrices. SSVD seeks a low-rank, checkerboard structured matrix approximation to data matrices. The desired checkerboard structure is achieved by forcing both the left- and right-singular vectors to be sparse, that is, having many zero entries. By interpreting singular vectors as regression coefficient vectors for certain linear regressions, sparsity-inducing regularization penalties are imposed to the least squares regression to produce sparse singular vectors. An efficient iterative algorithm is proposed for computing the sparse singular vectors, along with some discussion of penalty parameter selection. A lung cancer microarray dataset and a food nutrition dataset are used to illustrate SSVD as a biclustering method. SSVD is also compared with some existing biclustering methods using simulated datasets. © 2010, The International Biometric Society.
One dimensional systems with singular perturbations
International Nuclear Information System (INIS)
Alvarez, J J; Gadella, M; Nieto, L M; Glasser, L M; Lara, L P
2011-01-01
This paper discusses some one dimensional quantum models with singular perturbations. Eventually, a mass discontinuity is added at the points that support the singular perturbations. The simplest model includes an attractive singular potential with a mass jump both located at the origin. We study the form of the only bound state. Another model exhibits a hard core at the origin plus one or more repulsive deltas with mass jumps at the points supporting these deltas. We study the location and the multiplicity of these resonances for the case of one or two deltas and settle the basis for a generalization. Finally, we consider the harmonic oscillator and the infinite square well plus a singular potential at the origin. We see how the energy of bound states is affected by the singular perturbation.
Noncrossing timelike singularities of irrotational dust collapse
International Nuclear Information System (INIS)
Liang, E.P.T.
1979-01-01
Known naked singularities in spherical dust collapse are either due to shell-crossing or localized to the central world line. They will probably be destroyed by pressure gradients or blue-shift instabilities. To violate the cosmic censorship hypothesis in a more convincing and general context, collapse solutions with naked singularities that are at least nonshell-crossing and nonlocalized need to be constructed. Some results concerning the probable structure of a class of nonshellcrossing and nonlocalized timelike singularities are reviewed. The cylindrical dust model is considered but this model is not asymptotically flat. To make these noncrossing singularities viable counter examples to the cosmic censorship hypothesis, the occurrence of such singularities in asymptotically flat collapse needs to be demonstrated. (UK)
Recursos hídricos en los Andes: Lago Titicaca
Directory of Open Access Journals (Sweden)
1995-01-01
Full Text Available RESSOURCES EN EAUX DANS LES ANDES : LAC TITICACA. Une analyse par régression a été menée entre les variations de niveau du Lac Titicaca et les entrées du système (apports des affluents et précipitations. Les coefficients de corrélation, quoique relativement faibles, montrent aux abords du lac un effet de persistance qui diminue lorsque les stations sont éloignées du plan deau. Linertie du lac se manifeste lannée suivante pour les affluents du lac et évidemment pour le lac lui-même. Ces résultats confirment la présence dun mécanisme de rétro alimentation (effet boomerang. Cela montre que le système du Lac Titicaca est fragile, face à une utilisation excessive de ses eaux. Las regresiones estudiadas de cambios de nivel en el lago Titicaca contra precipitaciones y aportes en su cuenca, aunque relativamente bajas, muestran un efecto de persistencia en las proximidades del lago que decrece conforme las estaciones se alejan de éste. Lo que evidencia que la inercia del lago se manifiesta en el período siguiente (lag uno en los afluentes del lago y obviamente en el propio lago, fenómeno que parece confirmar la presencia de un mecanismo de retroalimentación (efecto boomerang. Este comportamiento muestra la fragilidad del lago frente a un aprovechamiento consuntivo excesivo. WATER RESOURCES IN THE ANDES: LAKE TITICACA. The studied regressions of the level changes in the Lake Titicaca versus the rainfall and the runoff in the basin, even being relatively low, show an effect of persistence in the proximity of the lake which decreases as we go away from it. This makes evident that the lake inertia manifests itself the following period (lag one in the lake tributaries and obviously in the lake itself, phenomenon which seems to confirm the presence of a feedback mechanism (boomerang effect. This behaviour shows the fragility of the lake against the excessive consumptive uses of the waters in its basin.
Road Traffic Injury in Lagos, Nigeria: Assessing Prehospital Care.
Ibrahim, Nasiru A; Ajani, Abdul Wahab O; Mustafa, Ibrahim A; Balogun, Rufai A; Oludara, Mobolaji A; Idowu, Olufemi E; Solagberu, Babatunde A
2017-08-01
Introduction Injuries are the third most important cause of overall deaths globally with one-quarter resulting from road traffic crashes. Majority of these deaths occur before arrival in the hospital and can be reduced with prompt and efficient prehospital care. The aim of this study was to highlight the burden of road traffic injury (RTI) in Lagos, Nigeria and assess the effectiveness of prehospital care, especially the role of Lagos State Ambulance Service (LASAMBUS) in providing initial care and transportation of the injured to the hospital. A three-year, retrospective review of road traffic injured patients seen at the Surgical Emergency Room (SER) of the Lagos State University Teaching Hospital (LASUTH), Ikeja, Nigeria, from January 1, 2012 to December 31, 2014 was conducted. Parameters extracted from the Institution Trauma Registry included bio-data, date and time of injury, date and time of arrival in SER, host status, type of vehicle involved, and region(s) injured. Information on how patients came to the hospital and outcome in SER also were recorded. Results were analyzed using Statistical Package for Social Sciences (SPSS; IBM Corporation; Armonk, New York USA) version 16. A total of 23,537 patients were seen during the study period. Among them, 16,024 (68.1%) had trauma. Road traffic crashes were responsible in 5,629 (35.0%) of trauma cases. Passengers constituted 42.0% of the injured, followed by pedestrians (34.0%). Four wheelers were the most frequent vehicle type involved (54.0%), followed by motor cycles (30.0%). Regions mainly affected were head and neck (40.0%) and lower limb (29.0%). Less than one-quarter (24.0%) presented to the emergency room within an hour, while one-third arrived between one and six hours following injury. Relatives brought 55.4%, followed by bystanders (21.4%). Only 2.3% had formal prehospital care and were brought to the hospital by LASAMBUS. They also had significantly shorter arrival time. One hundred and nine patients
Ezenwa, Beatrice N; Balogun, Mobolanle R; Okafor, Ifeoma P
2013-01-01
Beatrice N Ezenwa,1 Mobolanle R Balogun,2 Ifeoma P Okafor2 1Department of Pediatrics, 68 Nigerian Army Reference Hospital, Lagos State, Nigeria; 2Department of Community Health and Primary Care, College of Medicine, University of Lagos, Lagos State, Nigeria Introduction: Human papillomavirus (HPV) is one of the most common sexually transmitted infections in sexually active adolescents and young women and has been implicated as a cause of the majority of cases of cervical cancer, which is the...
Directory of Open Access Journals (Sweden)
Ana María Osorio Guzmán
2015-01-01
Full Text Available El municipio de Santa Cruz de Mompox (Departamento de Bolívar, Colombia cuyo centro históricofue declarado Patrimonio de la Humanidad por la UNESCO en 1995, da su nombre a la regiónconocida como Depresión Momposina, a veces confundida con la región de La Mojana ¿Esla Depresión Momposina la misma región de La Mojana? ¿Qué área comprende? Por una parte,se consultan varias fuentes y se identifican diferencias en la delimitación de la región (o regionesque llevan estos nombres y que varían según los actores que las delimiten y la finalidad perseguida.Por otra parte, se propone la aproximación territorial al Ecosistema Cultural Momposinobasada en una propuesta teórica y metodológica que articula las demandas del Centro Históricoal territorio -aquellas relacionadas a las expresiones culturales patrimoniales-, como aporte a lavaloración, protección y gestión patrimonial así como a la planificación regional. Este artículo seenmarca en la investigación Centro histórico y territorio: Ecosistema cultural momposino.
Minimal solution for inconsistent singular fuzzy matrix equations
Directory of Open Access Journals (Sweden)
M. Nikuie
2013-10-01
Full Text Available The fuzzy matrix equations $Ailde{X}=ilde{Y}$ is called a singular fuzzy matrix equations while the coefficients matrix of its equivalent crisp matrix equations be a singular matrix. The singular fuzzy matrix equations are divided into two parts: consistent singular matrix equations and inconsistent fuzzy matrix equations. In this paper, the inconsistent singular fuzzy matrix equations is studied and the effect of generalized inverses in finding minimal solution of an inconsistent singular fuzzy matrix equations are investigated.
Chamorro, Alan; Contreras, Christian; Raschio, Giancarlo
2014-01-01
La Planta Pampa Melchorita de Perú LNG se establece sobre un ecosistema costero árido el cual limita por el oeste con un acantilado rocoso y cuyas condiciones ambientales corresponden a un ecosistema marino con playas, un litoral rocoso y una zona pelágica; las tres sub-unidades han sufrido modificaciones físicas, donde estas modificaciones podrían haber generado variaciones en la biodiversidad local. El principal objetivo del presente estudio es describir las principales características b...
Hidalgo Mogollón, Auberto
2008-01-01
Con el propósito de determinar el impacto de la actividad langostinera, extractiva y agrícola sobre el ecosistema de manglar de Tumbes (Perú), se evaluó sus componentes más importantes, en los canales de marea el Bendito, Jelí, Puerto Rico y estero Corrales ubicados en la Región Tumbes. Se tomaron muestras de agua y sedimento, se hicieron entrevistas, observaciones in situ y acopio de información en instituciones públicas y privadas, comprometidas con el ecosistema de manglar. Los valores de...
Quantum cosmology and late-time singularities
International Nuclear Information System (INIS)
Kamenshchik, A Yu
2013-01-01
The development of dark energy models has stimulated interest to cosmological singularities, which differ from the traditional Big Bang and Big Crunch singularities. We review a broad class of phenomena connected with soft cosmological singularities in classical and quantum cosmology. We discuss the classification of singularities from the geometrical point of view and from the point of view of the behavior of finite size objects, crossing such singularities. We discuss in some detail quantum and classical cosmology of models based on perfect fluids (anti-Chaplygin gas and anti-Chaplygin gas plus dust), of models based on the Born–Infeld-type fields and of the model of a scalar field with a potential inversely proportional to the field itself. We dwell also on the phenomenon of the phantom divide line crossing in the scalar field models with cusped potentials. Then we discuss the Friedmann equations modified by quantum corrections to the effective action of the models under considerations and the influence of such modification on the nature and the existence of soft singularities. We review also quantum cosmology of models, where the initial quantum state of the universe is presented by the density matrix (mixed state). Finally, we discuss the exotic singularities arising in the braneworld cosmological models. (topical review)
Atmospheric turbidity and the diffuse irradiance in Lagos, Nigeria
International Nuclear Information System (INIS)
Maduekwe, A.A.L.; Chendo, M.A.C.
1994-06-01
The relationships between the total hemispherical irradiance reaching the earth surface in Lagos, Nigeria and the turbidity coefficients at two wavelengths namely λ(500) and λ(880) measured with a Volz sun photometer have been investigated. Using simple piecewise linear regression relationships between the atmospheric turbidity using Angstrom turbidity coefficients and the diffuse components of solar radiation are presented. (author). 18 refs, 11 figs, 3 tabs
Nigerian medical libraries in a digital age | Ibegwam | Lagos Journal ...
African Journals Online (AJOL)
No Abstract. Lagos Journal of Library and Information Science Vol. 1(2) 2003: 129-135. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT · http://dx.doi.org/10.4314/ljlis.v1i2.35488 · AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians ...
Assessment of radiation protection practices among radiographers in Lagos, Nigeria
Eze, Cletus Uche; Abonyi, Livinus Chibuzo; Njoku, Jerome; Irurhe, Nicholas Kayode; Olowu, Oluwabola
2013-01-01
Background: Use of ionising radiation in diagnostic radiography could lead to hazards such as somatic and genetic damages. Compliance to safe work and radiation protection practices could mitigate such risks. The aim of the study was to assess the knowledge and radiation protection practices among radiographers in Lagos, Nigeria. Materials and Methods: The study was a prospective cross sectional survey. Convenience sampling technique was used to select four x-ray diagnostic centres in four te...
Initial singularity and pure geometric field theories
Wanas, M. I.; Kamal, Mona M.; Dabash, Tahia F.
2018-01-01
In the present article we use a modified version of the geodesic equation, together with a modified version of the Raychaudhuri equation, to study initial singularities. These modified equations are used to account for the effect of the spin-torsion interaction on the existence of initial singularities in cosmological models. Such models are the results of solutions of the field equations of a class of field theories termed pure geometric. The geometric structure used in this study is an absolute parallelism structure satisfying the cosmological principle. It is shown that the existence of initial singularities is subject to some mathematical (geometric) conditions. The scheme suggested for this study can be easily generalized.
Discrete variable representation for singular Hamiltonians
DEFF Research Database (Denmark)
Schneider, B. I.; Nygaard, Nicolai
2004-01-01
We discuss the application of the discrete variable representation (DVR) to Schrodinger problems which involve singular Hamiltonians. Unlike recent authors who invoke transformations to rid the eigenvalue equation of singularities at the cost of added complexity, we show that an approach based...... solely on an orthogonal polynomial basis is adequate, provided the Gauss-Lobatto or Gauss-Radau quadrature rule is used. This ensures that the mesh contains the singular points and by simply discarding the DVR functions corresponding to those points, all matrix elements become well behaved. the boundary...
Transmutation of singularities in optical instruments
Energy Technology Data Exchange (ETDEWEB)
Tyc, Tomas [Institute of Theoretical Physics and Astrophysics, Masaryk University, Kotlarska 2, 61137 Brno (Czech Republic); Leonhardt, Ulf [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom)], E-mail: tomtyc@physics.muni.cz
2008-11-15
We propose a method for eliminating a class of singularities in optical media where the refractive index goes to zero or infinity at one or more isolated points. Employing transformation optics, we find a refractive index distribution equivalent to the original one that is nonsingular but shows a slight anisotropy. In this way, the original singularity is 'transmuted' into another, weaker type of singularity where the permittivity and permeability tensors are discontinuous at one point. The method is likely to find applications in designing and improving optical devices by making them easier to implement or to operate in a broad band of the spectrum.
Quantum dress for a naked singularity
Directory of Open Access Journals (Sweden)
Marc Casals
2016-09-01
Full Text Available We investigate semiclassical backreaction on a conical naked singularity space–time with a negative cosmological constant in (2+1-dimensions. In particular, we calculate the renormalized quantum stress–energy tensor for a conformally coupled scalar field on such naked singularity space–time. We then obtain the backreacted metric via the semiclassical Einstein equations. We show that, in the regime where the semiclassical approximation can be trusted, backreaction dresses the naked singularity with an event horizon, thus enforcing (weak cosmic censorship.
Cirant, Marco; Gomes, Diogo A.; Pimentel, Edgard A.; Sá nchez-Morgado, Hé ctor
2016-01-01
Here, we prove the existence of smooth solutions for mean-field games with a singular mean-field coupling; that is, a coupling in the Hamilton-Jacobi equation of the form $g(m)=-m^{-\\alpha}$. We consider stationary and time-dependent settings. The function $g$ is monotone, but it is not bounded from below. With the exception of the logarithmic coupling, this is the first time that MFGs whose coupling is not bounded from below is examined in the literature. This coupling arises in models where agents have a strong preference for low-density regions. Paradoxically, this causes the agents to spread and prevents the creation of solutions with a very-low density. To prove the existence of solutions, we consider an approximate problem for which the existence of smooth solutions is known. Then, we prove new a priori bounds for the solutions that show that $\\frac 1 m$ is bounded. Finally, using a limiting argument, we obtain the existence of solutions. The proof in the stationary case relies on a blow-up argument and in the time-dependent case on new bounds for $m^{-1}$.
Cirant, Marco
2016-11-22
Here, we prove the existence of smooth solutions for mean-field games with a singular mean-field coupling; that is, a coupling in the Hamilton-Jacobi equation of the form $g(m)=-m^{-\\\\alpha}$. We consider stationary and time-dependent settings. The function $g$ is monotone, but it is not bounded from below. With the exception of the logarithmic coupling, this is the first time that MFGs whose coupling is not bounded from below is examined in the literature. This coupling arises in models where agents have a strong preference for low-density regions. Paradoxically, this causes the agents to spread and prevents the creation of solutions with a very-low density. To prove the existence of solutions, we consider an approximate problem for which the existence of smooth solutions is known. Then, we prove new a priori bounds for the solutions that show that $\\\\frac 1 m$ is bounded. Finally, using a limiting argument, we obtain the existence of solutions. The proof in the stationary case relies on a blow-up argument and in the time-dependent case on new bounds for $m^{-1}$.
Behavioral pattern of commercial public transport passengers in Lagos metropolis
Directory of Open Access Journals (Sweden)
Oluwaseyi Joseph Afolabi
2017-05-01
Full Text Available This study examined the travel behavior of commercial public transport passengers in Lagos State, Nigeria. The descriptive research survey was used in order to assess the opinions of the respondents using the questionnaire. A total of 84 samples were used as representative population, while two null hypotheses were formulated and tested using the Pearson Product Moment Correlation Coefficient at 0.05 level of significant. The results that were obtained indicated that a positive correlation exists between frequency of travel and commuters income in Lagos Metropolis and also that a positive correlation exists between frequency of travel and distance covered by commuters in Lagos Metropolis. Secondary data was also sourced to serve as complement to the primary data, thus allowing for a robust research. Descriptive statistical tools such as percentages were also adopted to present the socio-economic characteristics in the area. Findings showed that about 57% of sampled population are male, 62 % are civil servants, 48% of respondents travel for business purposes. Also, that majority of the respondents (50% said that the commercial public transport is highly prone to accident, while about 64% of the respondents commute on daily basis. It was established that lack of transport infrastructure coupled with poor road maintenance were seen as the leading causes of inaccessibility of the area.
Halitosis amongst students in tertiary institutions in Lagos state.
Arinola, J E; Olukoju, O O
2012-12-01
Halitosis is defined as a noticeable unpleasant odor from the mouth. It is a medico-social problem that affects a significant number of people around the world. Research reveals that nearly 50% of the adult population has halitosis. To determine level of awareness of halitosis and prevalence of the condition amongst students in tertiary institutions as a baseline survey. For this project, 100 students from three tertiary institutions in Lagos state were chosen: University of Lagos, Lagos State University, Ojo campus and Yaba College of Technology. A semi-structured questionnaire and practical testing/diagnostic tool were utilized. Data collected was collated and analyzed using Microsoft Excel 2007 and SPSS statistical software. Most of the respondents were single and Christian. Level of awareness of halitosis was high. Results showed that 15%, 2% and 22% from UNILAG, LASU and YCT respectively said they had halitosis. Using the diagnostic tool, 6%, 8% and 2% respectively were positive for halitosis. There is high level of awareness of halitosis among the respondents. The prevalence of the disorder is low, however, it is recommended that enlightenment campaigns be mounted in schools to improve level of awareness and treatment seeking.
Responsabilidad Social Empresarial. Caso Centro Comercial Lago Mall
Directory of Open Access Journals (Sweden)
Carlos E. Torres Geisse
2011-01-01
Full Text Available El objetivo del artículo es el análisis de la responsabilidad empresarial para el centro comercial Lago Mall. El tipo de investigación fue un proyecto factible, descriptivo y de campo, con un diseño de tipo no experimental y transeccional. Se consideró como población al gerente de mercadeo del C.C Lago Mall, a quince (15 miembros de la comunidad interna, y a noventa (90 miembros de la comunidad externa del mismo. Las técnicas de recolección de datos aplicadas fueron: la encuesta y la entrevista. Los instrumentos fueron validados por cinco (5 expertos en gerencia social, obteniendo una confiabilidad de 0,99. Los resultados indican que en ambas dimensiones de la RSE los elementos que la integran no constituían un marco ideal para considerar a la empresa C.C. Lago Mall como socialmente responsable. Se concluye que el mismo carece de programas formales de responsabilidad social empresarial; sin embargo demuestra un compromiso con los principios de la empresa y con los valores de los empleados, donde se destacan la dignidad, identidad e integridad por los grupos de interés que se han denominado internos y externos.
Singularities in cosmologies with interacting fluids
International Nuclear Information System (INIS)
Cotsakis, Spiros; Kittou, Georgia
2012-01-01
We study the dynamics near finite-time singularities of flat isotropic universes filled with two interacting but otherwise arbitrary perfect fluids. The overall dynamical picture reveals a variety of asymptotic solutions valid locally around the spacetime singularity. We find the attractor of all solutions with standard decay, and for ‘phantom’ matter asymptotically at early times. We give a number of special asymptotic solutions describing universes collapsing to zero size and others ending at a big rip singularity. We also find a very complicated singularity corresponding to a logarithmic branch point that resembles a cyclic universe, and give an asymptotic local series representation of the general solution in the neighborhood of infinity.
Singularities: the state of the art
International Nuclear Information System (INIS)
Clarke, C.J.S.; Schmidt, B.G.
1977-01-01
A brief, but precise and unified account is given of the results that have been rigorously established at the time of writing concerning the existence and nature of singularities in classical relativity. (author)
Technological Singularity: What Do We Really Know?
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Alexey Potapov
2018-04-01
Full Text Available The concept of the technological singularity is frequently reified. Futurist forecasts inferred from this imprecise reification are then criticized, and the reified ideas are incorporated in the core concept. In this paper, I try to disentangle the facts related to the technological singularity from more speculative beliefs about the possibility of creating artificial general intelligence. I use the theory of metasystem transitions and the concept of universal evolution to analyze some misconceptions about the technological singularity. While it may be neither purely technological, nor truly singular, we can predict that the next transition will take place, and that the emerged metasystem will demonstrate exponential growth in complexity with a doubling time of less than half a year, exceeding the complexity of the existing cybernetic systems in few decades.
Algunas aclaraciones acerca del conocimiento del singular.
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Carlos Llano Cifuentes
2013-11-01
Full Text Available Llano tries to explain the main purpose of El Conocimiento del Singular, showing how the individuals about which the book is concerned are basically human individuals: people as decision makers.
Topological Signals of Singularities in Ricci Flow
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Paul M. Alsing
2017-08-01
Full Text Available We implement methods from computational homology to obtain a topological signal of singularity formation in a selection of geometries evolved numerically by Ricci flow. Our approach, based on persistent homology, produces precise, quantitative measures describing the behavior of an entire collection of data across a discrete sample of times. We analyze the topological signals of geometric criticality obtained numerically from the application of persistent homology to models manifesting singularities under Ricci flow. The results we obtain for these numerical models suggest that the topological signals distinguish global singularity formation (collapse to a round point from local singularity formation (neckpinch. Finally, we discuss the interpretation and implication of these results and future applications.
Asymptotic safety, singularities, and gravitational collapse
International Nuclear Information System (INIS)
Casadio, Roberto; Hsu, Stephen D.H.; Mirza, Behrouz
2011-01-01
Asymptotic safety (an ultraviolet fixed point with finite-dimensional critical surface) offers the possibility that a predictive theory of quantum gravity can be obtained from the quantization of classical general relativity. However, it is unclear what becomes of the singularities of classical general relativity, which, it is hoped, might be resolved by quantum effects. We study dust collapse with a running gravitational coupling and find that a future singularity can be avoided if the coupling becomes exactly zero at some finite energy scale. The singularity can also be avoided (pushed off to infinite proper time) if the coupling approaches zero sufficiently rapidly at high energies. However, the evolution deduced from perturbation theory still implies a singularity at finite proper time.
Stable computation of generalized singular values
Energy Technology Data Exchange (ETDEWEB)
Drmac, Z.; Jessup, E.R. [Univ. of Colorado, Boulder, CO (United States)
1996-12-31
We study floating-point computation of the generalized singular value decomposition (GSVD) of a general matrix pair (A, B), where A and B are real matrices with the same numbers of columns. The GSVD is a powerful analytical and computational tool. For instance, the GSVD is an implicit way to solve the generalized symmetric eigenvalue problem Kx = {lambda}Mx, where K = A{sup {tau}}A and M = B{sup {tau}}B. Our goal is to develop stable numerical algorithms for the GSVD that are capable of computing the singular value approximations with the high relative accuracy that the perturbation theory says is possible. We assume that the singular values are well-determined by the data, i.e., that small relative perturbations {delta}A and {delta}B (pointwise rounding errors, for example) cause in each singular value {sigma} of (A, B) only a small relative perturbation {vert_bar}{delta}{sigma}{vert_bar}/{sigma}.
Factors Influencing Patronage Of Medical Tourism In Metropolitan Lagos Nigeria
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Omisore
2015-08-01
Full Text Available Since medical tourism attract patient from various origin to seek medical services at different destinations it is paramount to consider the factors that motivate patrons decision on medical tourism. Hence this study assesses the factors influencing patronage of medical tourism in Lagos metropolis Nigeria. Lagos State is situated in the southwestern corner of Nigeria it lies within Latitudes 62N to 64N of the Equator and Longitudes 245E to 420E of the Greenwich meridian. Metropolitan Lagos is a statistical division and not an administrative unit it extends over 16 of the 20 LGAs of Lagos State it contains 88 of the population of Lagos State and includes semi-rural areas. Data were collected from primary source. Primary data collection was carried out through the use of structured questionnaire. Systematic sampling technique was employed to select 15 specialized private hospitals and 14 Public hospitals in the study area resulting to a sample size of 29 hospitals. Ten 10 patrons were contacted in each of the selected hospitals consequently 290 patrons were sampled. The study revealed three factors influencing patronage of medical tourism in the study area to be service related economic and facilities. These were further established by factor analysis result which combine service related economic factor as factor one with 29.5 variance explained and Eigen value of 5.605 Facility factor as factor two with 28.6 variance explained and Eigen value of 5.435 Service related factor as factor three with 14.7 variance explained and Eigen value of 2.788 and Economic factor as factor four with 9.2 variance explained and Eigen value of 1.754. The relevant authority in charge of health facilities in the study area would have to employ adequate manpower in-terms of doctors and other healthcare personnel across the public hospital while also regulating the scale of charges of the registered private hospitals in the study area. There is need to improve upon the
Bacteriana en el suelo en ecosistemas oligotróficos: una revisión crítica
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Yunuen Tapia Torres
2013-07-01
Full Text Available El fósforo (P es un elemento esencial para la vida, por lo cual entender los mecanismos que permiten su disponibilidad en el suelo es prioritario. Debido a la complejidad de la dinámica de este nutriente, aún existen varios procesos que no están claramente entendidos, principalmente en los ecosistemas oligotróficos. En la presente revisión se analiza literatura relacionada con procesos involucrados en la disponibilidad del P, dándole énfasis al papel de las bacterias. La forma química disponible del P es el ortofosfato, pero por su alta reactividad y demanda de la biota, esta forma es rápidamente disminuida de la solución del suelo. Por lo que es necesario que la biota adquiera este elemento de otras formas químicas. Entre ellas, las formas orgánicas representan la principal fuente de este nutriente mediante la mineralización bioquímica producto principalmente de la comunidad bacteriana del suelo. Entre los compuestos organofosforados, los ésteres de fosfatos son los más fáciles de mineralizar, por la poca demanda energética en la producción de las enzimas involucradas en dicho proceso. Por otro lado, la mineralización de los fosfonatos puede representar una fuente alternativa de P disponible, a pesar de que se había considerado que esta forma química no era accesible por la complejidad de sus moléculas. En general, una estrategia exitosa para la adquisición de P en ecosistemas donde dicho elemento es limitado, depende de la presencia de una maquinaria genética capaz de sintetizar las diferentes enzimas que mineralizan compuestos orgánicos con demandas energéticas diferentes (fosfohidrolasas, fosfonatasas y C-P liasas, además de la presencia de transportadores específicos de membrana y la disponibilidad de C como fuente de energía. Aún faltan estudios integrados que permitan elucidar el movimiento del P en los ecosistemas y cómo esto puede ser controlado y llevado a cabo por las bacterias que habitan en el suelo.
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Alfredo Ramos Moreno
2012-01-01
Full Text Available En este estudio se realizó una descripción y análisis, en primera aproximación, de la oferta en diversidad de aves en el predio La Primavera, vereda Estambul, municipio de Teruel, departamento del Huila. A partir de la información generada, se procedió a comparar los resultados obtenidos con los reportes de aves inventariadas en el estudio GEMA (2006 desarrollado por el Instituto de Investigación de Recursos Biológicos Alexander Von Humboldt, en el Corredor Biológico entre los PNN Puracé y Cueva de Los Guácharos, con el fin de determinar la relación entre estos espacios naturales a partir del concepto de interacción entre ecosistemas, entendido como las relaciones de suministro, flujo e intercambio de materiales, energía o información, que para el casoque compete al estudio se refiere al movimiento de aves de un ecosistema a otro. El predio La Primavera, ubicado en el municipio de Teruel en el occidentedel departamento del Huila, a una altitud promedio de 900 m. s. n. m., perteneciente a la zona de vida de bosque seco tropical, sirvió de sitio de trabajo para la identificación de 32 especies de aves medianteobservación visual directa y captura con redes de niebla, de las cuales hubo dos familias que resultaron comunes a los dos estudios, pertenecientes a laThraupinae (tángaras y Tyrannidae (atrapamoscas, lo cual indica su capacidad de adaptación a pisos altitudinales diferentes. Caso particular merece la especie Tangara vitriolina (tángara rastrojera, la cual está considerada casi endémica, lo que se traduce en una alta vulnerabilidad y de especial cuidado yvigilancia. Se sugiere la realización de otras valoraciones similares en sitios que permitan establecer esta conexión ecosistémica con el fin de identificar aquellas especies que presenten características comunes para ecosistemas diferentes.
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Ricardo Rangel
2012-12-01
Full Text Available Los Scolytinae son insectos comúnmente conocidos como coleópteros descortezadores o ambrosiales debido a su forma de alimentarse. Existen especies que restringen su actividad reproductiva a una planta huésped o a un número reducido de ellas, otras son altamente polífagas. Se estudiaron las poblaciones de Scolytinae con el objetivo de conocer la fluctuación poblacional de X. ferrugineus y X. affinis en ecosistemas de Tabasco, México durante noviembre 2010-julio 2011, febrero 2010-enero 2011 y 2007. Los métodos de captura utilizados fueron trampa de alcohol, trampa de luz y captura directa sobre sus plantas huésped. Se recolectaron 688 especímenes de X. ferrugineus y 3 911 de X. affinis. La fluctuación poblacional de X. ferrugineus mostró de manera general poblaciones bajas en los ecosistemas estudiados sin alguna estacionalidad marcada, registrándose los máximos picos poblacionales tanto en época seca (marzo-mayo como lluviosa (septiembre-diciembre. A diferencia de las poblaciones de X. affinis que fueron más abundantes y mostraron en la mayoría de los sitios (excepto en el Jardín Botánico José Narciso Rovirosa que se presentó en mayo picos poblacionales en época lluviosa. Las trampas de alcohol y de luz son métodos de recolecta que pueden ser complementarios para el monitoreo de las poblaciones de estos insectos, los cuales se encuentran presentes durante la mayor parte del año y su fluctuación poblacional es dependiente de los recursos alimenticios y sobre todo de factores ambientales como la temperatura y humedad. Se sugiere que X. affinis se ha adaptado y explotado los recursos de mejor manera que X. ferrugineus en estos ecosistemas, a juzgar por la abundancia observada. Las correlaciones entre la abundancia y los factores climáticos presentaron valores positivos y negativos. Los resultados reflejan el comportamiento de las poblaciones, sin embargo, hace falta evaluar de manera detallada algunos factores biol
On Borel singularities in quantum field theory
International Nuclear Information System (INIS)
Chadha, S.; Olesen, P.
1977-10-01
The authors consider the effective one-loop Lagrangian in a constant electric field. It is shown that perturbation theory behaves as n factorial giving rise to singularities in the Borel plane. Comparing with the known exact result it is shown how to integrate these singularities. It is suggested that renormalons in QED and QCD should be integrated in a similar way. A speculation is made on a possible interpretation of this integration. (Auth.)
Singularity theorems from weakened energy conditions
International Nuclear Information System (INIS)
Fewster, Christopher J; Galloway, Gregory J
2011-01-01
We establish analogues of the Hawking and Penrose singularity theorems based on (a) averaged energy conditions with exponential damping; (b) conditions on local stress-energy averages inspired by the quantum energy inequalities satisfied by a number of quantum field theories. As particular applications, we establish singularity theorems for the Einstein equations coupled to a classical scalar field, which violates the strong energy condition, and the nonminimally coupled scalar field, which also violates the null energy condition.
Directory of Open Access Journals (Sweden)
Ing. Nelvis Fernández García
2018-04-01
Full Text Available El estudio se realizó en cuatro ecosistemas del Consejo Popular “Horquita”, municipio Abreus, provincia Cienfuegos. Se caracterizaron desde el punto de vista microbiológico las mieles de colmenas de Abejas Meliponas. Mediante un diseño completamente aleatorizado para cada ecosistema se tomaron de cinco colmenas muestras de miel (250 ml, todas ellas de cajas, modalidad Nogueira-Neto, 1997. Las muestras fueron enviadas al Centro Provincial de Higiene y Epidemiología de la provincia Santa Clara donde fueron analizadas. En todos los ecosistemas existió integración agricultura-ganadería o crianza de traspatio, y en algunos casos aguas residuales dentro del rango de vuelo de las abejas. Las mieles analizadas cumplieron con las exigencias internacionales presentando, en todos los casos, características microbiológicas óptimas para su consumo y comercialización. Se propone como parámetros microbiológicos para la miel en el territorio menos de 10 UFC/g, tanto para microorganismos a 30oC (bacterias, hongos y levaduras como para coliformes totales. Palabras clave: Ecosistemas, miel, bacterias, hongos, levaduras.
Observational constraints on cosmological future singularities
Energy Technology Data Exchange (ETDEWEB)
Beltran Jimenez, Jose [Aix Marseille Univ, Universite de Toulon CNRS, CPT, Marseille (France); Lazkoz, Ruth [Euskal Herriko Unibertsitatea, Fisika Teorikoaren eta Zientziaren Historia Saila, Zientzia eta Teknologia Fakultatea, Bilbao (Spain); Saez-Gomez, Diego [Faculdade de Ciencias da Universidade de Lisboa, Departamento de Fisica, Instituto de Astrofisica e Ciencias do Espaco, Lisbon (Portugal); Salzano, Vincenzo [University of Szczecin, Institute of Physics, Szczecin (Poland)
2016-11-15
In this work we consider a family of cosmological models featuring future singularities. This type of cosmological evolution is typical of dark energy models with an equation of state violating some of the standard energy conditions (e.g. the null energy condition). Such a kind of behavior, widely studied in the literature, may arise in cosmologies with phantom fields, theories of modified gravity or models with interacting dark matter/dark energy. We briefly review the physical consequences of these cosmological evolution regarding geodesic completeness and the divergence of tidal forces in order to emphasize under which circumstances the singularities in some cosmological quantities correspond to actual singular spacetimes. We then introduce several phenomenological parameterizations of the Hubble expansion rate to model different singularities existing in the literature and use SN Ia, BAO and H(z) data to constrain how far in the future the singularity needs to be (under some reasonable assumptions on the behavior of the Hubble factor). We show that, for our family of parameterizations, the lower bound for the singularity time cannot be smaller than about 1.2 times the age of the universe, what roughly speaking means ∝2.8 Gyrs from the present time. (orig.)
Observational constraints on cosmological future singularities
International Nuclear Information System (INIS)
Beltran Jimenez, Jose; Lazkoz, Ruth; Saez-Gomez, Diego; Salzano, Vincenzo
2016-01-01
In this work we consider a family of cosmological models featuring future singularities. This type of cosmological evolution is typical of dark energy models with an equation of state violating some of the standard energy conditions (e.g. the null energy condition). Such a kind of behavior, widely studied in the literature, may arise in cosmologies with phantom fields, theories of modified gravity or models with interacting dark matter/dark energy. We briefly review the physical consequences of these cosmological evolution regarding geodesic completeness and the divergence of tidal forces in order to emphasize under which circumstances the singularities in some cosmological quantities correspond to actual singular spacetimes. We then introduce several phenomenological parameterizations of the Hubble expansion rate to model different singularities existing in the literature and use SN Ia, BAO and H(z) data to constrain how far in the future the singularity needs to be (under some reasonable assumptions on the behavior of the Hubble factor). We show that, for our family of parameterizations, the lower bound for the singularity time cannot be smaller than about 1.2 times the age of the universe, what roughly speaking means ∝2.8 Gyrs from the present time. (orig.)
Naked singularities and cosmic censorship: comment on the current situation
International Nuclear Information System (INIS)
Seifert, H.J.
1979-01-01
The current discussion is mainly concerned with how, or indeed, whether space-times possessing naked singularities can be ruled out as being too unrealistic or not being singular at all. The present position is summarized, with references, under the following headings: the Hawking-Penrose existence theorems, hydrodynamical singularities and the strength of naked singularities. (UK)
AbdulAzeez, Abbas Tunde
2016-01-01
This research investigated total quality management practices and quality teacher education in public tertiary institutions in Lagos State. The study was therefore designed to analyse management practices in Lagos state tertiary institutions through total quality management structural framework. The selected public tertiary institutions in Lagos…
Migration and Social Change in the Eastern District of Lagos: The ...
African Journals Online (AJOL)
The lagoon serves as a catalyst for economic development in the transformation of Lagos, most especially the eastern district. Fishing is central to the economy of Epe and the entire eastern section of Lagos. However, the fishing industry benefitted immensely from the migrating pattern and economic practices of the Mahin ...
Infertility in Women: Hysterosalpingographic Assessment of the Fallopian Tubes in Lagos, Nigeria
Akinola, R. A.; Akinola, O. I.; Fabamwo, A. O.
2009-01-01
Tubal disease constitutes a major factor in infertility especially in developing countries. This study was undertaken to assess the hysterosalpingographic patterns seen in infertile patients in an urban centre in Lagos. Two hundred and twenty patients who reported from the gynaecology clinic to the radiology department of Lagos State University…
Cosmologies with quasiregular singularities. II. Stability considerations
International Nuclear Information System (INIS)
Konkowski, D.A.; Helliwell, T.M.
1985-01-01
The stability properties of a class of spacetimes with quasiregular singularities is discussed. Quasiregular singularities are the end points of incomplete, inextendible geodesics at which the Riemann tensor and its derivatives remain at least bounded in all parallel-propagated orthonormal (PPON) frames; observers approaching such a singularity would find that their world lines come to an end in a finite proper time. The Taub-NUT (Newman-Unti-Tamburino)-type cosmologies investigated are R 1 x T 3 and R 3 x S 1 flat Kasner spacetimes, the two-parameter family of spatially homogeneous but anisotropic Bianchi type-IX Taub-NUT spacetimes, and an infinite-dimensional family of Einstein-Rosen-Gowdy spacetimes studied by Moncrief. The behavior of matter near the quasiregular singularity in each of these spacetimes is explored through an examination of the behavior of the stress-energy tensors and scalars for conformally coupled and minimally coupled, massive and massless scalar waves as observed in both coordinate and PPON frames. A conjecture is postulated concerning the stability of the nature of the singularity in these spacetimes. The conjecture for a Taub-NUT-type background spacetime is that if a test-field stress-energy tensor evaluated in a PPON frame mimics the behavior of the Riemann tensor components which indicate a particular type of singularity (quasiregular, nonscalar curvature, or scalar curvature), then a complete nonlinear backreaction calculation, in which the fields are allowed to influence the geometry, would show that this type of singularity actually occurs. Evidence supporting the conjecture is presented for spacetimes whose symmetries are unchanged when fields with the same symmetries are added
Sedimentation Survey of Lago La Plata, Puerto Rico, July 2006
Soler-López, Luis R.
2008-01-01
Lago La Plata dam is located between the municipalities of Naranjito and Toa Alta in north central Puerto Rico, about 5 kilometers south of the town of Toa Alta and about 5 kilometers north of the town of Naranjito. The reservoir impounds the waters of the Rio de La Plata, the Rio Guadiana, and the Rio Ca?as, and is part of the San Juan Metropolitan Water District, which provides about 35 percent of the total water demand for the area (Soler-Lopez and others, 2000). The reservoir has a drainage area of about 469 square kilometers. The dam was constructed in 1974 and is a concrete gravity structure with a normal pool elevation of 52.00 meters above mean sea level (Puerto Rico Electric Power Authority, 1979). During October 1998, the U.S. Geological Survey (USGS), Caribbean Water Science Center, in cooperation with the Puerto Rico Aqueduct and Sewer Authority (PRASA) conducted a bathymetric survey of Lago La Plata to assess the impact of Hurricane Georges on the storage capacity of the reservoir. Between July 17 and 20, 2006, the USGS and the PRASA conducted an additional bathymetric survey of Lago La Plata to update the reservoir storage capacity and determine the reservoir sedimentation rate by comparing the 2006 survey data with the 1998 survey data.. The purpose of this report is to update the reservoir storage capacity, sedimentation rates, and areas of substantial sediment accumulation since 1998. Historical (1974) data are referenced as needed to account for long-term storage capacity loss trends...
Generalized teleparallel cosmology and initial singularity crossing
Energy Technology Data Exchange (ETDEWEB)
Awad, Adel; Nashed, Gamal, E-mail: Adel.Awad@bue.edu.eg, E-mail: gglnashed@sci.asu.edu.eg [Center for Theoretical Physics, the British University in Egypt, Suez Desert Road, Sherouk City 11837 (Egypt)
2017-02-01
We present a class of cosmological solutions for a generalized teleparallel gravity with f ( T )= T +α̃ (− T ) {sup n} , where α̃ is some parameter and n is an integer or half-integer. Choosing α̃ ∼ G {sup n} {sup −1}, where G is the gravitational constant, and working with an equation of state p = w ρ, one obtains a cosmological solution with multiple branches. The dynamics of the solution describes standard cosmology at late times, but the higher-torsion correction changes the nature of the initial singularity from big bang to a sudden singularity. The milder behavior of the sudden singularity enables us to extend timelike or lightlike curves, through joining two disconnected branches of solution at the singularity, leaving the singularity traversable. We show that this extension is consistent with the field equations through checking the known junction conditions for generalized teleparallel gravity. This suggests that these solutions describe a contracting phase a prior to the expanding phase of the universe.
Phylogeny of Lagos bat virus: challenges for lyssavirus taxonomy.
Markotter, W; Kuzmin, I; Rupprecht, C E; Nel, L H
2008-07-01
Lagos bat virus (LBV) belongs to genotype 2 of the Lyssavirus genus. The complete nucleoprotein (N), phosphoprotein (P), matrixprotein (M) and glycoprotein (G) genes of 13 LBV isolates were sequenced and phylogenetically compared with other lyssavirus representatives. The results identified three different lineages of LBV. One of these lineages demonstrated sufficient sequence diversity to be considered a new lyssavirus genotype (Dakar bat lyssavirus). The suggested quantitative separation of lyssavirus genotypes using the N, P, M and G genes was also investigated using P-distances matrixes. Results indicated that the current criteria should be revised since overlaps between intergenotypic and intragenotypic variation occur.
Vestígios da cultura popular em Angela Lago
Silva, Celso Sisto
2004-01-01
Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão. Programa de Pós-graduação em Literatura A presente dissertação elabora, sob o domínio da cultura popular, e configura, sob o viés do conto popular recontado, a leitura de algumas obras da escritora brasileira para crianças, Angela Lago. Pretende-se, em primeiro lugar, identificar nos recontos da escritora, a persistência dos modelos narrativos que a tradição popular de cunho escrito mantev...
Phantom cosmology without Big Rip singularity
Energy Technology Data Exchange (ETDEWEB)
Astashenok, Artyom V. [Baltic Federal University of I. Kant, Department of Theoretical Physics, 236041, 14, Nevsky st., Kaliningrad (Russian Federation); Nojiri, Shin' ichi, E-mail: nojiri@phys.nagoya-u.ac.jp [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Odintsov, Sergei D. [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Institucio Catalana de Recerca i Estudis Avancats - ICREA and Institut de Ciencies de l' Espai (IEEC-CSIC), Campus UAB, Facultat de Ciencies, Torre C5-Par-2a pl, E-08193 Bellaterra (Barcelona) (Spain); Tomsk State Pedagogical University, Tomsk (Russian Federation); Yurov, Artyom V. [Baltic Federal University of I. Kant, Department of Theoretical Physics, 236041, 14, Nevsky st., Kaliningrad (Russian Federation)
2012-03-23
We construct phantom energy models with the equation of state parameter w which is less than -1, w<-1, but finite-time future singularity does not occur. Such models can be divided into two classes: (i) energy density increases with time ('phantom energy' without 'Big Rip' singularity) and (ii) energy density tends to constant value with time ('cosmological constant' with asymptotically de Sitter evolution). The disintegration of bound structure is confirmed in Little Rip cosmology. Surprisingly, we find that such disintegration (on example of Sun-Earth system) may occur even in asymptotically de Sitter phantom universe consistent with observational data. We also demonstrate that non-singular phantom models admit wormhole solutions as well as possibility of Big Trip via wormholes.
Radioanatomy of the singular nerve canal
Energy Technology Data Exchange (ETDEWEB)
Muren, C. [Dept. of Diagnostic Radiology, Sabbatsbergs Hospital, Stockholm (Sweden); Wadin, K. [University Hospital, Uppsala (Sweden); Dimopoulos, P. [University Hospital, Uppsala (Sweden)
1991-08-01
The singular canal conveys vestibular nerve fibers from the ampulla of the posterior semicircular canal to the posteroinferior border of the internal auditory meatus. Radiographic identification of this anatomic structure helps to distinguish it from a fracture. It is also a landmark in certain surgical procedures. Computed tomography (CT) examinations of deep-frozen temporal bone specimens were compared with subsequently prepared plastic casts of these bones, showing good correlation between the anatomy and the images. The singular canal and its variable anatomy were studied in CT examinations of 107 patients. The singular canal could be identified, in both the axial and in the coronal planes. Its point of entry into the internal auditory meatus varied considerably. (orig.)
Enveloping branes and brane-world singularities
Energy Technology Data Exchange (ETDEWEB)
Antoniadis, Ignatios; Cotsakis, Spiros [CERN-Theory Division, Department of Physics, Geneva 23 (Switzerland); Klaoudatou, Ifigeneia [University of the Aegean, Research Group of Geometry, Dynamical Systems and Cosmology, Department of Information and Communication Systems Engineering, Samos (Greece)
2014-12-01
The existence of envelopes is studied for systems of differential equations in connection with the method of asymptotic splittings which allows one to determine the singularity structure of the solutions. The result is applied to brane-worlds consisting of a 3-brane in a five-dimensional bulk, in the presence of an analog of a bulk perfect fluid parameterizing a generic class of bulk matter. We find that all flat brane solutions suffer from a finite-distance singularity contrary to previous claims. We then study the possibility of avoiding finite-distance singularities by cutting the bulk and gluing regular solutions at the position of the brane. Further imposing physical conditions such as finite Planck mass on the brane and positive energy conditions on the bulk fluid, excludes, however, this possibility as well. (orig.)
Phantom cosmology without Big Rip singularity
International Nuclear Information System (INIS)
Astashenok, Artyom V.; Nojiri, Shin'ichi; Odintsov, Sergei D.; Yurov, Artyom V.
2012-01-01
We construct phantom energy models with the equation of state parameter w which is less than -1, w<-1, but finite-time future singularity does not occur. Such models can be divided into two classes: (i) energy density increases with time (“phantom energy” without “Big Rip” singularity) and (ii) energy density tends to constant value with time (“cosmological constant” with asymptotically de Sitter evolution). The disintegration of bound structure is confirmed in Little Rip cosmology. Surprisingly, we find that such disintegration (on example of Sun-Earth system) may occur even in asymptotically de Sitter phantom universe consistent with observational data. We also demonstrate that non-singular phantom models admit wormhole solutions as well as possibility of Big Trip via wormholes.
Global embeddings for branes at toric singularities
Balasubramanian, Vijay; Braun, Volker; García-Etxebarria, Iñaki
2012-01-01
We describe how local toric singularities, including the Toric Lego construction, can be embedded in compact Calabi-Yau manifolds. We study in detail the addition of D-branes, including non-compact flavor branes as typically used in semi-realistic model building. The global geometry provides constraints on allowable local models. As an illustration of our discussion we focus on D3 and D7-branes on (the partially resolved) (dP0)^3 singularity, its embedding in a specific Calabi-Yau manifold as a hypersurface in a toric variety, the related type IIB orientifold compactification, as well as the corresponding F-theory uplift. Our techniques generalize naturally to complete intersections, and to a large class of F-theory backgrounds with singularities.
Holographic subregion complexity for singular surfaces
Energy Technology Data Exchange (ETDEWEB)
Bakhshaei, Elaheh [Isfahan University of Technology, Department of Physics, Isfahan (Iran, Islamic Republic of); Mollabashi, Ali [Institute for Research in Fundamental Sciences (IPM), School of Physics, Tehran (Iran, Islamic Republic of); Shirzad, Ahmad [Isfahan University of Technology, Department of Physics, Isfahan (Iran, Islamic Republic of); Institute for Research in Fundamental Sciences (IPM), School of Particles and Accelerators, Tehran (Iran, Islamic Republic of)
2017-10-15
Recently holographic prescriptions were proposed to compute the quantum complexity of a given state in the boundary theory. A specific proposal known as 'holographic subregion complexity' is supposed to calculate the complexity of a reduced density matrix corresponding to a static subregion. We study different families of singular subregions in the dual field theory and find the divergence structure and universal terms of holographic subregion complexity for these singular surfaces. We find that there are new universal terms, logarithmic in the UV cut-off, due to the singularities of a family of surfaces including a kink in (2 + 1) dimensions and cones in even dimensional field theories. We also find examples of new divergent terms such as squared logarithm and negative powers times the logarithm of the UV cut-off parameter. (orig.)
Singularity hypotheses a scientific and philosophical assessment
Moor, James; Søraker, Johnny; Steinhart, Eric
2012-01-01
Singularity Hypotheses: A Scientific and Philosophical Assessment offers authoritative, jargon-free essays and critical commentaries on accelerating technological progress and the notion of technological singularity. It focuses on conjectures about the intelligence explosion, transhumanism, and whole brain emulation. Recent years have seen a plethora of forecasts about the profound, disruptive impact that is likely to result from further progress in these areas. Many commentators however doubt the scientific rigor of these forecasts, rejecting them as speculative and unfounded. We therefore invited prominent computer scientists, physicists, philosophers, biologists, economists and other thinkers to assess the singularity hypotheses. Their contributions go beyond speculation, providing deep insights into the main issues and a balanced picture of the debate.
Percepción ecológica y calidad de vida. El caso de Santa María del Lago, Bogotá
Directory of Open Access Journals (Sweden)
Leonardo Garavito González
2004-11-01
Full Text Available Este artículo propone que cuando aumenta la percepción de conectividad de los individuos de una población con su entorno también aumenta su capacidad de lograr bienestar personal y colectivo. La percepción de conexión con los elementos del entorno implica un proceso de reconocimiento de la responsabilidad que comparte cada ser humano con los otros seres humanos y no humanos en el mantenimiento de la vida. En este sentido, la habilidad de percibir ecológicamente se refiere al proceso de tomar conciencia respecto a los múltiples vínculos entre el individuo y su entorno, y las potencialidades y límites que éstos configuran. Mientras más conciencia posea un individuo sobre las múltiples formas de su conexión dinámica con el entorno, será mayor su capacidad para asumir la incertidumbre del entorno y, por lo tanto, actuar sobre su calidad de vida y la de otros seres. Esta hipótesis se contrastará con la información recogida de la población vecina al humedal de Santa María del Lago, en la localidad de Engativá en Bogotá. En este sentido se construirá una red de narraciones a partir de las interpretaciones individuales respecto a la conexión entre la propia calidad de vida y las formas de vivir de otros seres humanos, no humanos y el ecosistema del humedal. No obstante que los resultados finales se encuentran en proceso, en este artículo se enfatiza en la propuesta metodológica.
Singularities in four-body final-state amplitudes
International Nuclear Information System (INIS)
Adhikari, S.K.
1978-01-01
Like three-body amplitudes, four-body amplitudes have subenergy threshold singularities over and above total-energy singularities. In the four-body problem we encounter a new type of subenergy singularity besides the usual two- and three-body subenergy threshold singularities. This singularity will be referred to as ''independent-pair threshold singularity'' and involves pair-subenergy threshold singularities in each of the two independent pair subenergies in four-body final states. We also study the particularly interesting case of resonant two- and three-body interactions in the four-body isobar model and the rapid (singular) dependence of the isobar amplitudes they generate in the four-body phase space. All these singularities are analyzed in the multiple-scattering formalism and it is shown that they arise from the ''next-to-last'' rescattering and hence may be represented correctly by an approximate amplitude which has that rescattering
Endpoint singularities in unintegrated parton distributions
Hautmann, F
2007-01-01
We examine the singular behavior from the endpoint region x -> 1 in parton distributions unintegrated in both longitudinal and transverse momenta. We identify and regularize the singularities by using the subtraction method, and compare this with the cut-off regularization method. The counterterms for the distributions with subtractive regularization are given in coordinate space by compact all-order expressions in terms of eikonal-line operators. We carry out an explicit calculation at one loop for the unintegrated quark distribution. We discuss the relation of the unintegrated parton distributions in subtractive regularization with the ordinary parton distributions.
Characteristic classes, singular embeddings, and intersection homology.
Cappell, S E; Shaneson, J L
1987-06-01
This note announces some results on the relationship between global invariants and local topological structure. The first section gives a local-global formula for Pontrjagin classes or L-classes. The second section describes a corresponding decomposition theorem on the level of complexes of sheaves. A final section mentions some related aspects of "singular knot theory" and the study of nonisolated singularities. Analogous equivariant analogues, with local-global formulas for Atiyah-Singer classes and their relations to G-signatures, will be presented in a future paper.
Cosmic censorship and the strengths of singularities
International Nuclear Information System (INIS)
Newman, R.P.
1986-01-01
This paper considers the principal definitions concerning limiting curvature strength on geodesics, and on non-spacelike geodesics in particular. They are formulated in terms of focussing conditions. Two definitions suggest themselves, and these are given in terms of a concept of a generalized Jacobi field. An historical survey is presented on some important developments concerning examples of naked singularities. The historical context is recalled in which these models, and cosmic censorship in general, have arisen. It is the author's opinion that one can expect to obtain theoretical limitations on the strengths of any naked singularities which do occur
Iron stores in regular blood donors in Lagos, Nigeria
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Adediran A
2013-06-01
Full Text Available Adewumi Adediran,1 Ebele I Uche,2 Titilope A Adeyemo,1 Dapus O Damulak,3 Akinsegun A Akinbami,4 Alani S Akanmu1 1Department of Hematology and Blood Transfusion, University of Lagos, Lagos, Nigeria; 2Department of Hematology and Blood Transfusion, Lagos University Teaching Hospital, Lagos, Nigeria; 3Department of Hematology and Blood Transfusion, Jos University Teaching Hospital, Jos, Nigeria; 4Department of Hematology and Blood Transfusion, Lagos State University, Ikeja, Nigeria Background: Apart from challenging the bone marrow to increase its red cell production, thereby producing more blood for the donor, regular blood donation has been shown to have several benefits, one of which is preventing accumulation of body iron which can cause free radical formation in the body. This study was carried out to assess body iron stores in regular blood donors. Methods: A total of 52 regular (study and 30 first-time (control volunteer blood donors were studied prospectively. Twenty milliliters of venous blood was drawn from each subject, 5 mL of which was put into sodium ethylenediamine tetra-acetic acid specimen bottles for a full blood count, including red blood cell indices. The remaining sample was allowed to clot in a plain container, and the serum was then retrieved for serum ferritin, serum iron, and serum transferrin receptor measurement by enzyme-linked immunosorbent assay. Results: Mean hemoglobin and packed cell volume in the study group (13.47 ± 2.36 g/dL and 42.00 ± 7.10, respectively, P = 0.303 were not significantly higher than in the control group (12.98 ± 1.30 g/dL and 39.76 ± 4.41, respectively, P = 0.119. Mean serum ferritin was 102.46 ± 80.26 ng/mL in the control group and 41.46 ± 40.33 ng/mL in the study group (P = 0.001. Mean serum ferritin for women in the study group (28.02 ± 25.00 ng/mL was significantly lower than for women in the control group (56.35 ± 34.03 ng/mL, P = 0.014. Similarly, men in the study group had a lower
Directory of Open Access Journals (Sweden)
ADRIANA E ROVERE
2011-12-01
Full Text Available La restauración ecológica es una disciplina que intenta recuperar atributos perdidos en un ecosistema (diversidad de especies, estructura y función. El objetivo de este trabajo fue evaluar la diversidad de musgos y sus formas de vida en tres ambientes con diferentes niveles de degradación y los sustratos en los que estos se desarrollan. El área de estudio corresponde a un sector que se está restaurando dentro de la Reserva Nacional Lago Puelo. En ella se encuentran tres ambientes distintos: (1 área remanente de bosque maduro de Nothofagus dombeyi, (2 bosque secundario de Austrocedrus chilensis, y (3 matorral dominado por especies exóticas. Se recorrió cada uno de los ambientes, registrando los sustratos con musgos, formas de vida y géneros. Los resultados evidencian una reducción de los sustratos disponibles y de las especies presentes conforme avanza el grado de alteración, desde el área de bosque maduro de N. dombeyi (9 sustratos: 17 géneros: 7 formas de vida, al sector de bosque secundario de A. chilensis (6 sustratos: 8 géneros: 5 formas de vida, siendo menor en el matorral dominado por especies exóticas (1 sustrato: 4 géneros: 3 formas de vida. Los musgos desempeñan funciones importantes en los ecosistemas, son fundamentales en el balance hídrico, pioneros en suelos inestables controlando la erosión y colonizando sitios alterados, sirven como hábitat y alimento para invertebrados, y también constituyen sitios propicios para la germinación de plantas vasculares. Si bien algunas especies leñosas ven afectada su germinación por la presencia de musgos, estos facilitan la germinación de otras especies arbóreas de los bosques templados. Los resultados podrían ser utilizados en restauración, ya sea recreando los sustratos ausentes o realizando traslado de sustratos con musgos, a fin de favorecer la recuperación de áreas boscosas degradadas considerando la biodiversidad original.Ecological restoration is a discipline
Energy Technology Data Exchange (ETDEWEB)
Spezzano, P.; Cerea, E.; Massironi, L.; Olivetta, A.; Bortoluzzi, S.; Nocente, M.; Berton, G. [ENEA, Centro Ricerche Saluggia, Vercelli (Italy). Dip. Ambiente
1998-12-31
For the evaluation of long term behaviour of {sup 137}Cs in a lacustrine ecosystem, for ten years after the Chernobyl nuclear accident several experimental studies have been conducted in the Viverone lake, a small, eutrophic, monomictic lake situated between Turin and Vercelli, in North-West Italy. Radiocaesium activities were measured in different components of the ecosystem, i.e. soil, water, sediment and biotas, and have been related with main environmental physico-chemical parameters. Changes in radiocaesium content with time provided information about transfer processes of this radionuclide into the lacustrine ecosystem. Levels of {sup 137}Cs in lake water after several years from deposition can be ascribed to the migration from catchment basin and to the remobilization from bottom sediments. However, experimental results do not allow to ascertain which of these two factors prevails over the other.
Singular Linear Differential Equations in Two Variables
Braaksma, B.L.J.; Put, M. van der
2008-01-01
The formal and analytic classification of integrable singular linear differential equations has been studied among others by R. Gerard and Y. Sibuya. We provide a simple proof of their main result, namely: For certain irregular systems in two variables there is no Stokes phenomenon, i.e. there is no
Singular continuous spectrum for palindromic Schroedinger operators
International Nuclear Information System (INIS)
Hof, A.; Knill, O.; Simon, B.
1995-01-01
We give new examples of discrete Schroedinger operators with potentials taking finitely many values that have purely singular continuous spectrum. If the hull X of the potential is strictly ergodic, then the existence of just one potential x in X for which the operator has no eigenvalues implies that there is a generic set in X for which the operator has purely singular continuous spectrum. A sufficient condition for the existence of such an x is that there is a z element of X that contains arbitrarily long palindromes. Thus we can define a large class of primitive substitutions for which the operators are purely singularly continuous for a generic subset in X. The class includes well-known substitutions like Fibonacci, Thue-Morse, Period Doubling, binary non-Pisot and ternary non-Pisot. We also show that the operator has no absolutely continuous spectrum for all x element of X if X derives from a primitive substitution. For potentials defined by circle maps, x n =l J (θ 0 +nα), we show that the operator has purely singular continuous spectrum for a generic subset in X for all irrational α and every half-open interval J. (orig.)
'Footballs', conical singularities, and the Liouville equation
International Nuclear Information System (INIS)
Redi, Michele
2005-01-01
We generalize the football shaped extra dimensions scenario to an arbitrary number of branes. The problem is related to the solution of the Liouville equation with singularities, and explicit solutions are presented for the case of three branes. The tensions of the branes do not need to be tuned with each other but only satisfy mild global constraints
Mobile communications technology: The singular factor responsible ...
African Journals Online (AJOL)
This paper investigated the factors responsible for the growth of Internet usage on the African continent. The principal finding was that increasing growth of Internet usage is also down to one singular factor: mobile communications technology. The proliferation of mobile phone usage in Africa has resulted in the sustained ...
Diamagnetism of quantum gases with singular potentials
DEFF Research Database (Denmark)
Briet, Philippe; Cornean, Horia; Savoie, Baptiste
2010-01-01
We consider a gas of quasi-free quantum particles confined to a finite box, subjected to singular magnetic and electric fields. We prove in great generality that the finite volume grand-canonical pressure is analytic with respect to the chemical potential and the intensity of the external magnetic...
Supersymmetric quantum mechanics under point singularities
International Nuclear Information System (INIS)
Uchino, Takashi; Tsutsui, Izumi
2003-01-01
We provide a systematic study on the possibility of supersymmetry (SUSY) for one-dimensional quantum mechanical systems consisting of a pair of lines R or intervals [-l, l] each having a point singularity. We consider the most general singularities and walls (boundaries) at x = ±l admitted quantum mechanically, using a U(2) family of parameters to specify one singularity and similarly a U(1) family of parameters to specify one wall. With these parameter freedoms, we find that for a certain subfamily the line systems acquire an N = 1 SUSY which can be enhanced to N = 4 if the parameters are further tuned, and that these SUSY are generically broken except for a special case. The interval systems, on the other hand, can accommodate N = 2 or N = 4 SUSY, broken or unbroken, and exhibit a rich variety of (degenerate) spectra. Our SUSY systems include the familiar SUSY systems with the Dirac δ(x)-potential, and hence are extensions of the known SUSY quantum mechanics to those with general point singularities and walls. The self-adjointness of the supercharge in relation to the self-adjointness of the Hamiltonian is also discussed
A singularity theorem based on spatial averages
Indian Academy of Sciences (India)
journal of. July 2007 physics pp. 31–47. A singularity theorem based on spatial ... In this paper I would like to present a result which confirms – at least partially – ... A detailed analysis of how the model fits in with the .... Further, the statement that the spatial average ...... Financial support under grants FIS2004-01626 and no.
Symmetries and singularities in Hamiltonian systems
International Nuclear Information System (INIS)
Miranda, Eva
2009-01-01
This paper contains several results concerning the role of symmetries and singularities in the mathematical formulation of many physical systems. We concentrate in systems which find their mathematical model on a symplectic or Poisson manifold and we present old and new results from a global perspective.
Singular interactions supported by embedded curves
International Nuclear Information System (INIS)
Kaynak, Burak Tevfik; Turgut, O Teoman
2012-01-01
In this work, singular interactions supported by embedded curves on Riemannian manifolds are discussed from a more direct and physical perspective, via the heat kernel approach. We show that the renormalized problem is well defined, the ground state is finite and the corresponding wavefunction is positive. The renormalization group invariance of the model is also discussed. (paper)
Resolving curvature singularities in holomorphic gravity
Mantz, C.L.M.; Prokopec, T.
2011-01-01
We formulate a holomorphic theory of gravity and study how the holomorphy symmetry alters the two most important singular solutions of general relativity: black holes and cosmology. We show that typical observers (freely) falling into a holomorphic black hole do not encounter a curvature
Classical resolution of singularities in dilaton cosmologies
Bergshoeff, EA; Collinucci, A; Roest, D; Russo, JG; Townsend, PK
2005-01-01
For models of dilaton gravity with a possible exponential potential, such as the tensor-scalar sector of ITA supergravity, we show how cosmological solutions correspond to trajectories in a 2D Milne space (parametrized by the dilaton and the scale factor). Cosmological singularities correspond to
Normal forms of Hopf-zero singularity
International Nuclear Information System (INIS)
Gazor, Majid; Mokhtari, Fahimeh
2015-01-01
The Lie algebra generated by Hopf-zero classical normal forms is decomposed into two versal Lie subalgebras. Some dynamical properties for each subalgebra are described; one is the set of all volume-preserving conservative systems while the other is the maximal Lie algebra of nonconservative systems. This introduces a unique conservative–nonconservative decomposition for the normal form systems. There exists a Lie-subalgebra that is Lie-isomorphic to a large family of vector fields with Bogdanov–Takens singularity. This gives rise to a conclusion that the local dynamics of formal Hopf-zero singularities is well-understood by the study of Bogdanov–Takens singularities. Despite this, the normal form computations of Bogdanov–Takens and Hopf-zero singularities are independent. Thus, by assuming a quadratic nonzero condition, complete results on the simplest Hopf-zero normal forms are obtained in terms of the conservative–nonconservative decomposition. Some practical formulas are derived and the results implemented using Maple. The method has been applied on the Rössler and Kuramoto–Sivashinsky equations to demonstrate the applicability of our results. (paper)
Normal forms of Hopf-zero singularity
Gazor, Majid; Mokhtari, Fahimeh
2015-01-01
The Lie algebra generated by Hopf-zero classical normal forms is decomposed into two versal Lie subalgebras. Some dynamical properties for each subalgebra are described; one is the set of all volume-preserving conservative systems while the other is the maximal Lie algebra of nonconservative systems. This introduces a unique conservative-nonconservative decomposition for the normal form systems. There exists a Lie-subalgebra that is Lie-isomorphic to a large family of vector fields with Bogdanov-Takens singularity. This gives rise to a conclusion that the local dynamics of formal Hopf-zero singularities is well-understood by the study of Bogdanov-Takens singularities. Despite this, the normal form computations of Bogdanov-Takens and Hopf-zero singularities are independent. Thus, by assuming a quadratic nonzero condition, complete results on the simplest Hopf-zero normal forms are obtained in terms of the conservative-nonconservative decomposition. Some practical formulas are derived and the results implemented using Maple. The method has been applied on the Rössler and Kuramoto-Sivashinsky equations to demonstrate the applicability of our results.
A Systolic Architecture for Singular Value Decomposition,
1983-01-01
Presented at the 1 st International Colloquium on Vector and Parallel Computing in Scientific Applications, Paris, March 191J Contract N00014-82-K.0703...Gene Golub. Private comunication . given inputs x and n 2 , compute 2 2 2 2 /6/ G. H. Golub and F. T. Luk : "Singular Value I + X1 Decomposition
Sporadic simple groups and quotient singularities
International Nuclear Information System (INIS)
Cheltsov, I A; Shramov, C A
2013-01-01
We show that if a faithful irreducible representation of a central extension of a sporadic simple group with centre contained in the commutator subgroup gives rise to an exceptional (resp. weakly exceptional but not exceptional) quotient singularity, then that simple group is the Hall-Janko group (resp. the Suzuki group)
Singularity is the Future of ICT Research
African Journals Online (AJOL)
PROF. OLIVER OSUAGWA
2014-06-01
Jun 1, 2014 ... innovation if the black race are not to be left one hundred years ... aspects of innovation in mechatronics design philosophy which illustrate the benefits obtainable by an a priori ..... An overview of models of technological singularity ... the Singularity—representing a profound and disruptive transformation in.
Longe, Ezechiel O
2012-06-01
A survey of healthcare waste management practices and their implications for health and the environment was carried out. The study assessed waste management practices in 20 healthcare facilities ranging in capacity from 40 to 600 beds in Ikorodu and metropolitan Lagos, Lagos State, Nigeria. The prevailing healthcare waste management status was analysed. Management issues on quantities and proportion of different constituents of waste, segregation, collection, handling, transportation, treatment and disposal methods were assessed. The waste generation averaged 0.631 kg bed(-1) day(-1) over the survey area. The waste stream from the healthcare facilities consisted of general waste (59.0%), infectious waste (29.7%), sharps and pathological (8.9%), chemical (1.45%) and others (0.95%). Sharps/pathological waste includes disposable syringes. In general, the waste materials were collected in a mixed form, transported and disposed of along with municipal solid waste with attendant risks to health and safety. Most facilities lacked appropriate treatment systems for a variety of reasons that included inadequate funding and little or no priority for healthcare waste management as well as a lack of professionally competent waste managers among healthcare providers. Hazards associated with healthcare waste management and shortcomings in the existing system were identified.
Directory of Open Access Journals (Sweden)
Sandra Milena Arias
2011-03-01
Conclusiones. Se señala la presencia de focos de Paragonimus sp. en la parte alta del río Medellín; por lo tanto, el municipio de Caldas debe incluirse en los programas de prevención y control. La población estudiantil requiere nuevos programas educativos para mejorar la interacción con los ecosistemas acuáticos y disminuir el deterioro de su salud.
Generalized Parton Distributions and their Singularities
Energy Technology Data Exchange (ETDEWEB)
Anatoly Radyushkin
2011-04-01
A new approach to building models of generalized parton distributions (GPDs) is discussed that is based on the factorized DD (double distribution) Ansatz within the single-DD formalism. The latter was not used before, because reconstructing GPDs from the forward limit one should start in this case with a very singular function $f(\\beta)/\\beta$ rather than with the usual parton density $f(\\beta)$. This results in a non-integrable singularity at $\\beta=0$ exaggerated by the fact that $f(\\beta)$'s, on their own, have a singular $\\beta^{-a}$ Regge behavior for small $\\beta$. It is shown that the singularity is regulated within the GPD model of Szczepaniak et al., in which the Regge behavior is implanted through a subtracted dispersion relation for the hadron-parton scattering amplitude. It is demonstrated that using proper softening of the quark-hadron vertices in the regions of large parton virtualities results in model GPDs $H(x,\\xi)$ that are finite and continuous at the "border point'' $x=\\xi$. Using a simple input forward distribution, we illustrate the implementation of the new approach for explicit construction of model GPDs. As a further development, a more general method of regulating the $\\beta=0$ singularities is proposed that is based on the separation of the initial single DD $f(\\beta, \\alpha)$ into the "plus'' part $[f(\\beta,\\alpha)]_{+}$ and the $D$-term. It is demonstrated that the "DD+D'' separation method allows to (re)derive GPD sum rules that relate the difference between the forward distribution $f(x)=H(x,0)$ and the border function $H(x,x)$ with the $D$-term function $D(\\alpha)$.
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Hilda Machado
2008-12-01
Full Text Available La conservación de los ecosistemas agrícolas o agroecosistemas reviste una gran importancia para la seguridad alimentaria del planeta, por cuanto ellos contienen los elementos necesarios (suelo, agua y biodiversidad que son consustanciales a la producción agropecuaria. Aunque la agricultura es una forma necesaria en el uso de las tierras que se encuentra en oposición a los ecosistemas, debido a que las decisiones sobre las prácticas de manejo y uso del suelo influyen en los procesos ecológicos y en las interacciones suelo-agua-plantas, estas decisiones deben tener en cuenta que la calidad de vida de las personas y su bienestar dependen en última instancia del bienestar del ecosistema. Este artículo hace un llamado a la reflexión sobre la responsabilidad que tienen los decisores en cuanto al uso de la tierra para garantizar la seguridad alimentaria de forma sostenible.
São Carlos Workshop on Real and Complex Singularities
Ruas, Maria
2007-01-01
The São Carlos Workshop on Real and Complex Singularities is the longest running workshop in singularities. It is held every two years and is a key international event for people working in the field. This volume contains papers presented at the eighth workshop, held at the IML, Marseille, July 19–23, 2004. The workshop offers the opportunity to establish the state of the art and to present new trends, new ideas and new results in all of the branches of singularities. This is reflected by the contributions in this book. The main topics discussed are equisingularity of sets and mappings, geometry of singular complex analytic sets, singularities of mappings, characteristic classes, classification of singularities, interaction of singularity theory with some of the new ideas in algebraic geometry imported from theoretical physics, and applications of singularity theory to geometry of surfaces in low dimensional euclidean spaces, to differential equations and to bifurcation theory.
Singularly perturbed Burger-Huxley equation: Analytical solution ...
African Journals Online (AJOL)
user
solutions of singularly perturbed nonlinear differential equations. ... for solving generalized Burgers-Huxley equation but this equation is not singularly ...... Solitary waves solutions of the generalized Burger Huxley equations, Journal of.
EDITORIAL: The plurality of optical singularities
Berry, Michael; Dennis, Mark; Soskin, Marat
2004-05-01
This collection of papers arose from an Advanced Research Workshop on Singular Optics, held at the Bogolyubov Institute in Kiev, Ukraine, during 24-28 June 2003. The workshop was generously financed by NATO, with welcome additional support from Institute of Physics Publishing and the National Academy of Sciences of Ukraine. There had been two previous international meetings devoted to singular optics, in Crimea in 1997 and 2000, reflecting the strong involvement of former Soviet Union countries in this research. Awareness of singular optics is growing within the wider optics community, indicated by symposia on the subject at several general optics meetings. As the papers demonstrate, the field of singular optics has reached maturity. Although the subject originated in an observation on ultrasound, it has been largely theory-driven until recently. Now, however, there is close contact between theory and experiment, and we speculate that this is one reason for its accelerated development. To single out particular papers for mention here would be invidious, and since the papers speak for themselves it is not necessary to describe them all. Instead, we will confine ourselves to a brief description of the main areas included in singular optics, to illustrate the broad scope of the subject. Optical vortices are lines of phase singularity: nodal lines where the intensity of the light, represented by a complex scalar field, vanishes. The subject has emerged from flatland, where the vortices are points characterized by topological charges, into the much richer world of vortex lines in three dimensions. By combining Laguerre-Gauss or Bessel beams, or reflecting light from plates with spiral steps, intricate arrangements can be generated, with vortices that are curved, looped, knotted, linked or braided. With light whose state of polarization varies with position, different singularities occur, associated with the vector nature of light. These are also lines, on which the
Directory of Open Access Journals (Sweden)
ÁLVARO GIRALDO-CARDONA
2014-06-01
Full Text Available Se analizaron taxonómicamente por medio de caracteres de la concha 233 especímenes del género Echinolittorina (familia Littorinidae recolectados en ecosistemas rocosos del Pacífico colombiano. Los especímenes revisados se encuentran depositados en la Colección de Referencia de Biología Marina de la Universidad del Valle (CRBMUV y provienen de localidades en los departamentos de Valle del Cauca (Bahía Málaga, Bahía de Buenaventura, Cauca (Isla Gorgona, Guapi y Nariño (Mulatos, Parque Nacional Natural Sanquianga. Hasta este trabajo, se pensaba que esta familia estaba representada solamente por tres especies en el Pacifico colombiano y en este estudio se registran seis especies: Echinolittorina apicina, E. atrata, E. conspersa, E. dubiosa, E. paytensis, y E. tenuistriata. Se incluye una descripción morfológica de cada una de ellas para facilitar su identificación.
Salar de Surire un ecosistema altoandino en peligro, frente a escenario del cambio climático
Directory of Open Access Journals (Sweden)
Ingrid Garcés
2011-12-01
Full Text Available Este trabajo realiza un análisis al salar de Surire desde el punto de vista de la biodiversidad y sus implicancias producto del cambio climático. Como resultado se predice que los próximos años serán secos y la temperatura podría ir en aumento, lo cual afectará notablemente a la flora y fauna del altiplano. El salar de Surire es un cuerpo salino ubicado en el altiplano andino chileno, en un entorno geológico de características volcánicas. La climatología actual de aridez no permite una acumulación de agua superficial de gran extensión, y por lo tanto es posible diferenciar tres tipos principales de aguas: los aportes de drenaje, las acumulaciones de agua en la aureola pantanosa externa o “bofedales”, y las aguas del interior del cuerpo salino (surgencias termales y salmueras. Estas condiciones hidrológicas afectan factores abióticos, como anaerobiosis de suelos, disposición de nutrientes y salinidad, factores determinantes del desarrollo de la flora y fauna. Palabras claves: Salar de Surire; Biodiversidad andina; Cambio climático; Ecosistema andino
Shapefile of the bathymetric contours of Lago Lucchetti, Puerto Rico, September 2013-May 2014
Department of the Interior — The U.S. Geological Survey conducted a sedimentation survey of Lago Lucchetti, Yauco, Puerto Rico, in 2013–14 in cooperation with the Puerto Rico Aqueduct and Sewer...
Economic Analysis of the Marketing of Fruit in Lagos State of Nigeria ...
African Journals Online (AJOL)
Economic Analysis of the Marketing of Fruit in Lagos State of Nigeria (A case study of Oyingbo, Oshodi and Ikotun ... PROMOTING ACCESS TO AFRICAN RESEARCH ... This implies a wide gap in prices between wholesalers and retailers.
Prevalence of Low Back Pain Among Traffic Wardens in Lagos State ...
African Journals Online (AJOL)
to determine the prevalence of low back pain and its associated risk factors among traffic wardens. ... in regulating traffic also has a significant influence on the severity of LBP. ... wardens in Lagos State, who assume a standing position for.
Focalización y modalidad en el "Lanzarote del Lago" (ms. 9611 BNE
Directory of Open Access Journals (Sweden)
Antonio Contreras Martín
2009-12-01
Full Text Available The purpose of this paper is to analise the point of view and the varitions of the speech in Lanzarote del Lago (BNE ms 9611 to observe how the compilator worked the French source, Lancelot en prose.
LBA-ECO LC-07 Bathymetric Survey of Floodplain Lake, Lago Curuai, Para, Brazil: 2004
National Aeronautics and Space Administration — The bathymetry data provided represent a continuous surface of interpolated point measurements of depth values of Lago Curuai, an Amazon River floodplain lake,...
LBA-ECO LC-07 Bathymetric Survey of Floodplain Lake, Lago Curuai, Para, Brazil: 2004
National Aeronautics and Space Administration — ABSTRACT: The bathymetry data provided represent a continuous surface of interpolated point measurements of depth values of Lago Curuai, an Amazon River floodplain...
On Weakly Singular Versions of Discrete Nonlinear Inequalities and Applications
Directory of Open Access Journals (Sweden)
Kelong Cheng
2014-01-01
Full Text Available Some new weakly singular versions of discrete nonlinear inequalities are established, which generalize some existing weakly singular inequalities and can be used in the analysis of nonlinear Volterra type difference equations with weakly singular kernels. A few applications to the upper bound and the uniqueness of solutions of nonlinear difference equations are also involved.
THE EXT RACORPOREAL FERTILIZATION TECHNOLOGIES AND THE SINGULARITY PROBLEMS
Directory of Open Access Journals (Sweden)
S. V. Denysenko
2013-05-01
Full Text Available The peculiarities of modern medicine development connected with the technological and informative singularity are analyzed. The risks of realization of extracorporeal fertilization are examined from positions of development of informative singularity. The warning problems of origin of singularity are discussed on t h e base of t h e newest technologies development.
On the nature of naked singularities in Vaidya spacetimes
Energy Technology Data Exchange (ETDEWEB)
Dwivedi, I.H. (Aligarh Muslim Univ. (India). Dept. of Physics); Joshi, P.S. (Tata Inst. of Fundamental Research, Bombay (India))
1989-11-01
The Vaidya-Papapetrou model containing a naked singularity is analysed for outgoing causal geodesics joining the singularity. The curvature growth along these trajectories is examined to show that this is a strong curvature singularity, providing a counter-example to certain forms of cosmic censorship hypotheses. (author).
On the nature of naked singularities in Vaidya spacetimes
International Nuclear Information System (INIS)
Dwivedi, I.H.
1989-01-01
The Vaidya-Papapetrou model containing a naked singularity is analysed for outgoing causal geodesics joining the singularity. The curvature growth along these trajectories is examined to show that this is a strong curvature singularity, providing a counter-example to certain forms of cosmic censorship hypotheses. (author)
7 CFR 1200.50 - Words in the singular form.
2010-01-01
... 7 Agriculture 10 2010-01-01 2010-01-01 false Words in the singular form. 1200.50 Section 1200.50 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING....50 Words in the singular form. Words in this subpart in the singular form shall be deemed to import...
7 CFR 900.1 - Words in the singular form.
2010-01-01
... 7 Agriculture 8 2010-01-01 2010-01-01 false Words in the singular form. 900.1 Section 900.1 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing... Words in the singular form. Words in this subpart in the singular form shall be deemed to import the...
7 CFR 900.20 - Words in the singular form.
2010-01-01
... 7 Agriculture 8 2010-01-01 2010-01-01 false Words in the singular form. 900.20 Section 900.20 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing... § 900.20 Words in the singular form. Words in this subpart in the singular form shall be deemed to...
7 CFR 900.36 - Words in the singular form.
2010-01-01
... 7 Agriculture 8 2010-01-01 2010-01-01 false Words in the singular form. 900.36 Section 900.36 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing... Marketing Orders § 900.36 Words in the singular form. Words in this subpart in the singular form shall be...
7 CFR 900.100 - Words in the singular form.
2010-01-01
... 7 Agriculture 8 2010-01-01 2010-01-01 false Words in the singular form. 900.100 Section 900.100 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing... Words in the singular form. Words in this subpart in the singular form shall be deemed to import the...
7 CFR 46.1 - Words in singular form.
2010-01-01
... 7 Agriculture 2 2010-01-01 2010-01-01 false Words in singular form. 46.1 Section 46.1 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Words in singular form. Words in this part in the singular form shall be deemed to import the plural...
7 CFR 900.50 - Words in the singular form.
2010-01-01
... 7 Agriculture 8 2010-01-01 2010-01-01 false Words in the singular form. 900.50 Section 900.50 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing... Words in the singular form. Words in this subpart in the singular form shall be deemed to import the...
7 CFR 61.1 - Words in singular form.
2010-01-01
... 7 Agriculture 3 2010-01-01 2010-01-01 false Words in singular form. 61.1 Section 61.1 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Words in singular form. Words used in the regulations in this subpart in the singular form shall be...
Singularities and the geometry of spacetime
Hawking, Stephen
2014-11-01
The aim of this essay is to investigate certain aspects of the geometry of the spacetime manifold in the General Theory of Relativity with particular reference to the occurrence of singularities in cosmological solutions and their relation with other global properties. Section 2 gives a brief outline of Riemannian geometry. In Section 3, the General Theory of Relativity is presented in the form of two postulates and two requirements which are common to it and to the Special Theory of Relativity, and a third requirement, the Einstein field equations, which distinguish it from the Special Theory. There does not seem to be any alternative set of field equations which would not have some undeseriable features. Some exact solutions are described. In Section 4, the physical significance of curvature is investigated using the deviation equation for timelike and null curves. The Riemann tensor is decomposed into the Ricci tensor which represents the gravitational effect at a point of matter at that point and the Welyl tensor which represents the effect at a point of gravitational radiation and matter at other points. The two tensors are related by the Bianchi identities which are presented in a form analogous to the Maxwell equations. Some lemmas are given for the occurrence of conjugate points on timelike and null geodesics and their relation with the variation of timelike and null curves is established. Section 5 is concerned with properties of causal relations between points of spacetime. It is shown that these could be used to determine physically the manifold structure of spacetime if the strong causality assumption held. The concepts of a null horizon and a partial Cauchy surface are introduced and are used to prove a number of lemmas relating to the existence of a timelike curve of maximum length between two sets. In Section 6, the definition of a singularity of spacetime is given in terms of geodesic incompleteness. The various energy assumptions needed to prove
Kalmar, Boldizsar
2006-01-01
We give a Pontryagin-Thom-Szucs type construction for non-positive codimensional singular maps, and obtain results about cobordism and bordism groups of -1 codimensional stable maps with prescribed singular fibers.
Rabia transmitida por murciélagos en Brasil
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Willian Oliveira Fahl
2015-09-01
Full Text Available Frente al desafío que la rabia representa para la industria pecuaria y la salud pública en América Latina, el presente artículo tiene como objetivo hacer una revisión de literatura amplia y crítica sobre la epidemiología de la rabia transmitida por murciélagos en Brasil. El tema es abordado inicialmente desde una perspectiva histórica hasta la caracterización molecular de aislamientos del virus, para finalmente contrastar con la situación de otros países de las Américas. La información referente a Brasil es presentada de manera separada debido a la gran abundancia de especies de murciélagos de diversos hábitos alimenticios, implicadas en la transmisión del virus de la rabia y las complejas relaciones entre los ciclos epidemiológicos revelados por estudios de tipificación antigénica y análisis filogenético, lo cual ha permitido reconocer con más nitidez, la importancia de los quirópteros como reservorios y transmisores de esta enfermedad. Este nuevo escenario epidemiológico exige reexaminar las medidas de control aplicadas hasta el momento, desde un abordaje multidisciplinar, así como cooperación intersectorial y participación por parte de la comunidad.
Friedmann-like cosmological models without singularity
International Nuclear Information System (INIS)
Kuchowicz, B.
1978-01-01
The Einstein-Cartan theory of gravitation ('general relativity with spin') provides a specific spin-spin contact interaction of matter, in addition to the usual long-range gravity. This new interaction enables us to prevent singularities in cosmological models. it is shown how this mechanism works in the case when the standard Einstein-Cartan equations are valid at a micro-physical level, and some spin-spin terms remain from the averaging procedure for randomly distributed spins. In contrast with the case of aligned spin distributions, it is possible to take over the isotropic and spatially homogeneous (i.e., Friedmannian) models into the Einstein-Cartan theory. These models can be made free from singularity, thanks to the self-interaction of spinning fluid. (author)
Singularities in the general theory of relativity
International Nuclear Information System (INIS)
Treder, H.J.
1980-01-01
'Regular solutions of Einstein's equations' mean very different things. In the case of the empty-space equations, Rsub(ik) = o, such solutions must be metrics gsub(ik)(xsup(l)) without additionaly singular 'field sources' (Einstein's 'Particle problem'). However the 'phenomenological matter' is defined by the Einstein equations Rsub(ik) - 1/2gsub(ik)R = -kappaTsub(ik) itselves. Therefore if 10 regular functions gsub(ik)(xsup(l)) are given (which the inequalities of Lorentz-signature fulfil) then these gsub(ik) define 10 functions Tsub(ik)(xsup(l)) without singularities. But, the matter-tensor Tsub(ik) must fulfil the two inequalities T >= o, T 0 0 >= 1/2 T only and therefore the Einstein-equations with 'phenomenological matter' mean the two inequalities R >= o, R 0 0 <= o which are incompatible with a permanently regular metric with Lorentz-signature, generally. (author)
Singularity theory and equivariant symplectic maps
Bridges, Thomas J
1993-01-01
The monograph is a study of the local bifurcations of multiparameter symplectic maps of arbitrary dimension in the neighborhood of a fixed point.The problem is reduced to a study of critical points of an equivariant gradient bifurcation problem, using the correspondence between orbits ofa symplectic map and critical points of an action functional. New results onsingularity theory for equivariant gradient bifurcation problems are obtained and then used to classify singularities of bifurcating period-q points. Of particular interest is that a general framework for analyzing group-theoretic aspects and singularities of symplectic maps (particularly period-q points) is presented. Topics include: bifurcations when the symplectic map has spatial symmetry and a theory for the collision of multipliers near rational points with and without spatial symmetry. The monograph also includes 11 self-contained appendices each with a basic result on symplectic maps. The monograph will appeal to researchers and graduate student...
Dirac operator on spaces with conical singularities
International Nuclear Information System (INIS)
Chou, A.W.
1982-01-01
The Dirac operator on compact spaces with conical singularities is studied via the separation of variables formula and the functional calculus of the Dirac Laplacian on the cone. A Bochner type vanishing theorem which gives topological obstructions to the existence of non-negative scalar curvature k greater than or equal to 0 in the singular case is proved. An index formula relating the index of the Dirac operator to the A-genus and Eta-invariant similar to that of Atiyah-Patodi-Singer is obtained. In an appendix, manifolds with boundary with non-negative scalar curvature k greater than or equal to 0 are studied, and several new results on constructing complete metrics with k greater than or equal to on them are obtained
Further holographic investigations of big bang singularities
Energy Technology Data Exchange (ETDEWEB)
Engelhardt, Netta [Department of Physics, UCSB,Santa Barbara, CA 93106 (United States); Hertog, Thomas [Institute for Theoretical Physics, KU Leuven,3001 Leuven (Belgium); Horowitz, Gary T. [Department of Physics, UCSB,Santa Barbara, CA 93106 (United States)
2015-07-09
We further explore the quantum dynamics near past cosmological singularities in anisotropic Kasner-AdS solutions using gauge/gravity duality. The dual description of the bulk evolution involves N=4 super Yang-Mills on the contracting branch of an anisotropic de Sitter space and is well defined. We compute two-point correlators of Yang-Mills operators of large dimensions using spacelike geodesics anchored on the boundary. The correlator between two points separated in a direction with negative Kasner exponent p always exhibits a pole at horizon scales, in any dimension, which we interpret as a dual signature of the classical bulk singularity. This indicates that the geodesic approximation selects a non-normalizable Yang-Mills state.
Further holographic investigations of big bang singularities
Engelhardt, Netta; Hertog, Thomas; Horowitz, Gary T.
2015-07-01
We further explore the quantum dynamics near past cosmological singularities in anisotropic Kasner-AdS solutions using gauge/gravity duality. The dual description of the bulk evolution involves super Yang-Mills on the contracting branch of an anisotropic de Sitter space and is well defined. We compute two-point correlators of Yang-Mills operators of large dimensions using spacelike geodesics anchored on the boundary. The correlator between two points separated in a direction with negative Kasner exponent p always exhibits a pole at horizon scales, in any dimension, which we interpret as a dual signature of the classical bulk singularity. This indicates that the geodesic approximation selects a non-normalizable Yang-Mills state.
Singular tachyon kinks from regular profiles
International Nuclear Information System (INIS)
Copeland, E.J.; Saffin, P.M.; Steer, D.A.
2003-01-01
We demonstrate how Sen's singular kink solution of the Born-Infeld tachyon action can be constructed by taking the appropriate limit of initially regular profiles. It is shown that the order in which different limits are taken plays an important role in determining whether or not such a solution is obtained for a wide class of potentials. Indeed, by introducing a small parameter into the action, we are able circumvent the results of a recent paper which derived two conditions on the asymptotic tachyon potential such that the singular kink could be recovered in the large amplitude limit of periodic solutions. We show that this is explained by the non-commuting nature of two limits, and that Sen's solution is recovered if the order of the limits is chosen appropriately
The technological singularity and exponential medicine
Iraj Nabipour; Majid Assadi
2016-01-01
The "technological singularity" is forecasted to occur in 2045. It is a point when non-biological intelligence becomes more intelligent than humans and each generation of intelligent machines re-designs itself smarter. Beyond this point, there is a symbiosis between machines and humans. This co-existence will produce incredible impacts on medicine that its sparkles could be seen in healthcare industry and the future medicine since 2025. Ray Kurzweil, the great futurist, suggested th...
Non-singular spiked harmonic oscillator
International Nuclear Information System (INIS)
Aguilera-Navarro, V.C.; Guardiola, R.
1990-01-01
A perturbative study of a class of non-singular spiked harmonic oscillators defined by the hamiltonian H = d sup(2)/dr sup(2) + r sup(2) + λ/r sup(α) in the domain [0,∞] is carried out, in the two extremes of a weak coupling and a strong coupling regimes. A path has been found to connect both expansions for α near 2. (author)
Singular reduction of Nambu-Poisson manifolds
Das, Apurba
The version of Marsden-Ratiu Poisson reduction theorem for Nambu-Poisson manifolds by a regular foliation have been studied by Ibáñez et al. In this paper, we show that this reduction procedure can be extended to the singular case. Under a suitable notion of Hamiltonian flow on the reduced space, we show that a set of Hamiltonians on a Nambu-Poisson manifold can also be reduced.
Constraint theory, singular lagrangians and multitemporal dynamics
International Nuclear Information System (INIS)
Lusanna, L.
1988-01-01
Singular Lagrangians and constraint theory permeate theoretical physics, as shown by the relevance of gauge theories, string models and general relativity. Their study used finite---dimensional models as a guide to develop the theory, but their main use was in classical field theory, due to the necessity of understanding their quantization. The covariant quantization of singular Lagrangians led to the BRST approach and to the theory of the effective action. On the other hand their phase---space formulation, culminated with the BFV approach for first class, second class and reducible constraints. It, in turn, gave new insights in the theory of singular Lagrangians and constraints and in their cohomological aspects. However the Hamiltonian approach to field theory is highly nontrivial, is open to criticism due to its problems with locality, geometry and manifest covariance and its canonical quantization has still to be developed, because there is no proof of the renormalizability of the Schroedinger representation of field theory. This paper discusses how, notwithstanding these developments, there is still a big amount of ambiguity at every level of the theory
An Exact Solution of the Binary Singular Problem
Directory of Open Access Journals (Sweden)
Baiqing Sun
2014-01-01
Full Text Available Singularity problem exists in various branches of applied mathematics. Such ordinary differential equations accompany singular coefficients. In this paper, by using the properties of reproducing kernel, the exact solution expressions of dual singular problem are given in the reproducing kernel space and studied, also for a class of singular problem. For the binary equation of singular points, I put it into the singular problem first, and then reuse some excellent properties which are applied to solve the method of solving differential equations for its exact solution expression of binary singular integral equation in reproducing kernel space, and then obtain its approximate solution through the evaluation of exact solutions. Numerical examples will show the effectiveness of this method.
Singular Spectrum Near a Singular Point of Friedrichs Model Operators of Absolute Type
International Nuclear Information System (INIS)
Iakovlev, Serguei I.
2006-01-01
In L 2 (R) we consider a family of self adjoint operators of the Friedrichs model: A m =|t| m +V. Here |t| m is the operator of multiplication by the corresponding function of the independent variable t element of R, and (perturbation) is a trace-class integral operator with a continuous Hermitian kernel ν(t,x) satisfying some smoothness condition. These absolute type operators have one singular point of order m>0. Conditions on the kernel ν(t,x) are found guaranteeing the absence of the point spectrum and the singular continuous one of such operators near the origin. These conditions are actually necessary and sufficient. They depend on the finiteness of the rank of a perturbation operator and on the order of singularity. The sharpness of these conditions is confirmed by counterexamples
Directory of Open Access Journals (Sweden)
Mariana Delgado-Jaramillo
2011-12-01
Full Text Available Los murciélagos constituyen el grupo de mamíferos más diversificado en la región neotropical y representan un componente clave en la dinámica de muchos ecosistemas terrestres. En este trabajo se describen los resultados de un estudio sobre la quiropterofauna del Parque Nacional Yurubí (ubicado en la zona montañosa del norte de Venezuela, se incluye un listado taxonómico y la caracterización de algunos atributos comunitarios en ambientes predominantemente boscosos. Los datos evaluados fueron obtenidos mediante la revisión de colecciones zoológicas y muestreos diversificados realizados entre febrero y julio del 2009, en un gradiente altitudinal (100-1 500m, que integra a tres unidades ecológicas: bosque semideciduo, bosque siempreverde y selva nublada. Se registraron 64 especies agrupadas en cinco familias, lo que constituye el 63% de los murciélagos conocidos en la Cordillera de la Costa. La familia Phyllostomidae fue dominante (42 especies; 66% del total, seguida por Vespertilionidae, Molossidae, Emballonuridae y Mormoopidae. La comunidad presente a baja elevación fue la más diversificada en términos taxonómicos, mientras que la del piso superior evidenció el menor grado de diversificación. Se identificaron 11 categorías tróficas, con dominancia de los insectívoros en cuanto a la riqueza taxonómica y de los frugívoros en lo que respecta a la abundancia. Nuestros resultados permiten inferir, en un contexto general, que los ecosistemas boscosos del área de estudio muestran un buen estado de conservación, en virtud de la presencia de una proporción relativamente alta de especies pertenecientes a la subfamilia Phyllostominae, cuyos componentes han sido considerados por otros autores como indicadores del grado de conservación de hábitats boscosos primarios, así como la presencia de otras especies con prioridades de conservación. Todos estos aspectos, le confieren a esta área protegida un alto valor proteccionista, en
Directory of Open Access Journals (Sweden)
J. Cabello
2016-06-01
Full Text Available La gestión de las áreas protegidas en el actual contexto de cambio global requiere de aproximaciones que permitan caracterizar y seguir el funcionamiento de los ecosistemas. La teledetección ofrece herramientas para ello, ya que proporciona índices que informan reiteradamente y para grandes porciones de territorio, de los intercambios de materia y energía que tienen lugar entre la biota y la superficie terrestre. Considerando este principio, y la cada vez mayor disponibilidad de información satelital de calidad y facilidad de uso, desarrollamos junto con el Organismo Autónomo de Parques Nacionales de España (OAPN, un sistema de seguimiento que complementa a otras iniciativas desarrolladas por este organismo para informar del estado de conservación de los parques nacionales. El sistema, denominado REMOTE, se basa en el empleo de los índices de vegetación espectrales (IVs de uso más extendido (EVI -índice de vegetación mejorado- y NDVI -índice de vegetación normalizado-, derivados de la serie temporal de imágenes satelitales del sensor MODIS-Terra. El sistema permite avanzar en la identificación de las condiciones de referencia para la comprensión y predicción de las respuestas de los ecosistemas frente a perturbaciones e intervenciones, y de los cambios direccionales que éstos están experimentando (tendencias. Así mismo ayuda a la detección de anomalías recientes que alertan de cambios bruscos en el funcionamiento de los ecosistemas. REMOTE se caracteriza porque usa como indicadores tres atributos relacionados con las ganancias de carbono anuales (productividad primaria neta por parte del dosel vegetal, su estacionalidad y fenología. Además, está diseñado y programado con software libre y gratuito, lo que permitirá modificar o implementar mejoras en él fácilmente. Su implementación tiene como objetivo informar a los tomadores de decisiones y gestores de la Red de Parques Nacionales de España de la salud y estado
Tello García, Elena; Rodríguez Ortega, Tamara; Ripoll Bosch, Raimon; Casasús Pueyo, Isabel; Bernués Jal, Alberto
2015-01-01
El objetivo de este trabajo fue conocer las percepciones sociales sobre las relaciones entre la ganadería y el medio ambiente en agro-ecosistemas mediterráneos de montaña. Para ello, se desarrollaron dos dinámicas de grupo con ganaderos y tres con ciudadanos sobre aspectos generales de ganadería y medio ambiente. Las dinámicas fueron analizadas mediante un análisis inductivo del contenido que ayudó, por un lado, a clasificar las ideas en prácticas agrarias y servicios de los ecosi...
Sardans Galobart, Jordi; Peñuelas Reixach, Josep
2005-01-01
Siguiendo el consejo repetido del profesor Margalef, estos últimos años hemos estudiado la disponibilidad y la acumulación del fósforo en los ecosistemas terrestres mediterráneos. Presentamos aquí un resumen de los resultados enmarcados en las ideas y consejos del profesor. En ellos hemos comprobado que algunos cambios ambientales actuales, como el calentamiento y la sequía, acentúan la limitación por fósforo; pero, por otra parte, que las especies arbóreas y arbustivas mediterráneas...
Almacenes y flujos de carbono en ecosistemas áridos y semiáridos de México: síntesis y perspectivas
Directory of Open Access Journals (Sweden)
Noé Manuel Montaño
2016-01-01
Full Text Available Los ecosistemas áridos y semiáridos constituyen un tercio de la superficie terrestre global y un 60% del territorio mexicano, pero poco se sabe sobre su importancia en el ciclo del carbono (C. Este trabajo sintetiza y analiza la información disponible sobre almacenes, flujos y controles de la dinámica del C en las regiones áridas y semiáridas de México. En estos ecosistemas, la productividad neta del ecosistema, la respiración del suelo, la producción y la descomposición de la hojarasca están determinadas por la variabilidad de la precipitación, aunque la descomposición depende también de la radiación solar y temperatura. El suelo es el principal almacén de C, representa 45 y 90% del C en la biomasa del matorral y pastizal, respectivamente. Las regiones semiáridas podrían almacenar más C orgánico e inorgánico que las regiones áridas. El cambio de uso de suelo disminuye hasta en 50% el C orgánico del suelo (COS, pero las especies vegetales formadoras de islas de fertilidad y de recursos amortiguan el impacto de la perturbación en el almacenamiento del C, al actuar como “hotspots” de conservación y trasformación del COS. Las biocostras también controlan la acumulación del COS, debido a su rápida respuesta a la humedad que potencia los flujos del C y la transformación de los nutrimentos en el suelo. El COS controla la estequiometría microbiana que regula la disponibilidad de otros nutrimentos en el suelo. La información sobre la dinámica del C para las regiones áridas y semiáridas de México es aún escasa y fragmentada, ya que la mayoría se limita al COS, en los primeros 30 cm del perfil, sin considerar el C inorgánico del suelo. En consecuencia, es necesario y urgente estandarizar metodologías para cuantificar los almacenes y flujos a diferentes escalas espacio-temporales en los ecosistemas áridos y semiáridos del país.
Bermúdez Acosta, Jelvys; González Delgado, Alejandro; Castro Hernández, Yoelvis; Ortiz Guilarte, Eudalys; Núñez Moreira, Roberto; Oramas García, Julio; García García, Yaliany
2014-01-01
El propósito de esta investigación fue estudiar la contaminación de un ecosistema de manglar impactado con hidrocarburos en el sector centro sur de Cayo Santa María, Jardines del Rey, Cuba. Para el estudio de los indicadores microbiológicos y fisicoquímicos fue diseñado un muestreo estratificado, donde se seleccionaron dos estratos y diez estaciones de muestreo, considerando los patrones de flujos de marea en pleamar y bajamar, así como el impacto perceptible de la contaminación. La determina...
Spectral asymptotics for nonsmooth singular Green operators
DEFF Research Database (Denmark)
Grubb, Gerd
2014-01-01
is a singular Green operator. It is well-known in smooth cases that when G is of negative order −t on a bounded domain, its eigenvalues ors-numbers have the behavior (*)s j (G) ∼ cj −t/(n−1) for j → ∞, governed by the boundary dimension n − 1. In some nonsmooth cases, upper estimates (**)s j (G) ≤ Cj −t/(n−1...
Singularity spectrum of self-organized criticality
International Nuclear Information System (INIS)
Canessa, E.
1992-10-01
I introduce a simple continuous probability theory based on the Ginzburg-Landau equation that provides for the first time a common analytical basis to relate and describe the main features of two seemingly different phenomena of condensed-matter physics, namely self-organized criticality and multifractality. Numerical support is given by a comparison with reported simulation data. Within the theory the origin of self-organized critical phenomena is analysed in terms of a nonlinear singularity spectrum different form the typical convex shape due to multifractal measures. (author). 29 refs, 5 figs
Singularity Structure of Maximally Supersymmetric Scattering Amplitudes
DEFF Research Database (Denmark)
Arkani-Hamed, Nima; Bourjaily, Jacob L.; Cachazo, Freddy
2014-01-01
We present evidence that loop amplitudes in maximally supersymmetric (N=4) Yang-Mills theory (SYM) beyond the planar limit share some of the remarkable structures of the planar theory. In particular, we show that through two loops, the four-particle amplitude in full N=4 SYM has only logarithmic ...... singularities and is free of any poles at infinity—properties closely related to uniform transcendentality and the UV finiteness of the theory. We also briefly comment on implications for maximal (N=8) supergravity theory (SUGRA)....
The Singularity May Never Be Near
Walsh, Toby
2017-01-01
There is both much optimisim and pessimism around artificial intelligence (AI) today. The optimists are investing millions of dollars, and even in some cases billions of dollars into AI. The pessimists, on the other hand, predict that AI will end many things: jobs, warfare, and even the human race. Both the optimists and the pessimists often appeal to the idea of a technological singularity, a point in time where machine intelligence starts to run away, and a new, more in- telligent “species”...
Compacted dimensions and singular plasmonic surfaces
Pendry, J. B.; Huidobro, Paloma Arroyo; Luo, Yu; Galiffi, Emanuele
2017-11-01
In advanced field theories, there can be more than four dimensions to space, the excess dimensions described as compacted and unobservable on everyday length scales. We report a simple model, unconnected to field theory, for a compacted dimension realized in a metallic metasurface periodically structured in the form of a grating comprising a series of singularities. An extra dimension of the grating is hidden, and the surface plasmon excitations, though localized at the surface, are characterized by three wave vectors rather than the two of typical two-dimensional metal grating. We propose an experimental realization in a doped graphene layer.
Beyond the singularity of the 2-D charged black hole
International Nuclear Information System (INIS)
Giveon, Amit; Rabinovici, Eliezer; Sever, Amit
2003-01-01
Two dimensional charged black holes in string theory can be obtained as exact SL(2,R) x U(1)/U(1) quotient CFTs. The geometry of the quotient is induced from that of the group, and in particular includes regions beyond the black hole singularities. Moreover, wavefunctions in such black holes are obtained from gauge invariant vertex operators in the SL(2,R) CFT, hence their behavior beyond the singularity is determined. When the black hole is charged we find that the wavefunctions are smooth at the singularities. Unlike the uncharged case, scattering waves prepared beyond the singularity are not fully reflected; part of the wave is transmitted through the singularity. Hence, the physics outside the horizon of a charged black hole is sensitive to conditions set behind the past singularity. (author)
Directory of Open Access Journals (Sweden)
Saray Sánchez
2011-12-01
Full Text Available En Cuba, debido a la degradación que presentan los suelos, se requiere de un manejo integrado para potenciar su capacidad productiva en beneficio del hombre y lograr el desarrollo sostenible y la seguridad alimentaria. Esta situación demanda que los profesionales, técnicos y responsables de la producción agropecuaria amplíen sus conocimientos relacionados con el manejo y conservación de este recurso, de modo que con su trabajo se pueda lograr un equilibrio en el sistema suelo-planta-animal, que posibilite mejorar el medio ambiente, lograr producciones más ecológicas y obtener mayores beneficios económicos y sociales para el país. En este artículo se presentan algunos resultados generados en diferentes instituciones científicas en cuanto al uso de tecnologías adecuadas en el manejo de la fertilidad del suelo en ecosistemas agropecuarios, así como las experiencias de su introducción en la práctica productiva con el fin de contribuir al desarrollo sostenible y la seguridad alimentaria en Cuba.In Cuba, due to soil degradation, integrated management is required to enhance their productive capacity in benefit of man and achieve sustainable development and the necessary food security. This situation demands that the professionals, technicians and people responsible for livestock production increase their knowledge related to the management and conservation of this resource, so that with their work balance can be achieved in the soil-plant-animal system, which allows improving the environment, achieving more ecological productions, and attaining higher economic and social benefits for the country. In this paper some results are shown generated in different scientific institutions regarding the use of adequate technologies of soil fertility management in agricultural and livestock production ecosystems, as well as the experiences of their introduction in productive practice in order to contribute to sustainable development and food
Examination of Estate Marketing Practices in Ikeja, Lagos, Nigeria
Directory of Open Access Journals (Sweden)
Joseph Oyewale Oyedeji
2017-09-01
Full Text Available Estate marketing is an aspect of the profession of Estate Surveying and Valuation in Nigeria. Previous studies on estate marketing identified that there are challenges affecting estate marketing and the resultant effect on these challenges affects the credibility of the profession of Estate Surveying and Valuation in Nigeria. This necessitates the need to examine the practice of estate marketing in Nigeria. This study examined estate marketing practice among estate surveyors and valuers in Ikeja, Lagos Nigeria. The sample size for the study is the 64 registered Estate Surveying and Valuation firms in the study area. Data gathered were analyzed using descriptive statistics and 5-point likert ordinal scale. Findings from the study revealed that the use of brochure or bulletin is the most common estate marketing method in the study area. Also, it was revealed from the study that the use of press is the most cost effective method of estate marketing in the study area. The study identified the various challenges of estate marketing. However, collection of double professional fees is the most prevalent challenge of estate marketing in the study area. Finally, aggressive marketing which leads to unethical practices is the most prevalent mitigating measures adopted by Estate Surveyors and Valuers in the study area. Recommendations were made on how to review the ethical regulations guiding the practice of Estate Surveying and Valuation which will consequently improve marketing in the study area.
Congenital club foot in a teaching hospital in Lagos, Nigeria.
Adewole, O A; Giwa, S O; Kayode, M O; Shoga, M O; Balogun, R A
2009-06-01
Congenital club foot has been sparsely reported in literature in Nigeria, although it has been reported as the commonest congenital musculoskeletal abnormality. This study enumerates the point prevalence of this disease in a university teaching hospital in Lagos. Better understanding of the epidemiology in our community should improve awareness, and influence management. Between June 2005 and July 2006, 72 consecutive patients with congenital club feet were seen in the orthopaedic clinic of our Hospital. Demographic data, birth weight, family history, birth facility, maternal age and associated congenital anomalies were recorded and analysed using Statistical Programme for Social Sciences (SPSS) version 15. A total of 72 patients were seen, 28 of whom had bilateral club feet resulting in a total of 100 feet. There were 38 males and 34 females. Only 29% presented in the first month of life and 28% in the second month. Maternal ages ranged between 19 and 38 years and no family history of congenital club foot was given,. Babies delivered outside the orthodox medical system (churches, traditional healers, home etc) constituted 28%. The commonest associated congenital anomalies were tibia hemimelia, hydrocephalus, inguinal hernia and umbilical hernia. A default rate of 28% was observed during treatment. Congenital club foot may not be uncommon in Nigeria. Late presentation and high default rate before correction of the deformity were observed. Establishment of special club foot clinics should reduce the default rate. Training of healthcare workers in maternity units as well as Public awareness should encourage early referral to specialists.
Logarithmic of mass singularities theorem in non massive quantum electrodynamics
International Nuclear Information System (INIS)
Mares G, R.; Luna, H.
1997-01-01
We give an explicit example of the use of dimensional regularization to calculate in a unified approach, all the ultraviolet, infrared and mass singularities, by considering the LMS (logarithms of mass singularities) theorem in the frame of massless QED (Quantum electrodynamics). In the calculation of the divergent part of the cross section, all singularities are found to cancel provided soft and hard photon emission are both taken into account. (Author)
Singular vectors of Malikov-Fagin-Fux in topological theories
International Nuclear Information System (INIS)
Semikhatov, A.M.
1993-01-01
Coincidence of singular vectors in relation to the sl(2) Katza-Mudi algebra and the algebra of the N=2 (twisted) supersymmetry is established. On the base of the Kazama-Suzuki simplest model is obtained a representation for the sl(2) currents in terms of an interacting with mater gravitation. From the Malikov-Fagin-Fux formulae for the sl(2) singular currents is obtained the general expression for singular vectors in topological theories
Observer-dependent sign inversions of polarization singularities.
Freund, Isaac
2014-10-15
We describe observer-dependent sign inversions of the topological charges of vector field polarization singularities: C points (points of circular polarization), L points (points of linear polarization), and two virtually unknown singularities we call γ(C) and α(L) points. In all cases, the sign of the charge seen by an observer can change as she changes the direction from which she views the singularity. Analytic formulas are given for all C and all L point sign inversions.
Transmutation of planar media singularities in a conformal cloak.
Liu, Yichao; Mukhtar, Musawwadah; Ma, Yungui; Ong, C K
2013-11-01
Invisibility cloaking based on optical transformation involves materials singularity at the branch cut points. Many interesting optical devices, such as the Eaton lens, also require planar media index singularities in their implementation. We show a method to transmute two singularities simultaneously into harmless topological defects formed by anisotropic permittivity and permeability tensors. Numerical simulation is performed to verify the functionality of the transmuted conformal cloak consisting of two kissing Maxwell fish eyes.
Deficiency indices and singular boundary conditions in quantum mechanics
International Nuclear Information System (INIS)
Bulla, W.
1984-01-01
We consider Schroedinger operators H in L 2 (Rsup(n)), n from IN, with countably infinitely many local singularities of the potential which are separated from each other by a positive distance. It is proved that due to locality each singularity yields a separate contribution to the deficiency index of H. In the special case where the singularities are pointlike and the potential exhibits certain symmetries near these points we give an explicit construction of self-adjoint boundary conditions
Naked singularities in self-similar spherical gravitational collapse
International Nuclear Information System (INIS)
Ori, A.; Piran, T.
1987-01-01
We present general-relativistic solutions of self-similar spherical collapse of an adiabatic perfect fluid. We show that if the equation of state is soft enough (Γ-1<<1), a naked singularity forms. The singularity resembles the shell-focusing naked singularities that arise in dust collapse. This solution increases significantly the range of matter fields that should be ruled out in order that the cosmic-censorship hypothesis will hold
7 CFR 900.80 - Words in the singular form.
2010-01-01
... 7 Agriculture 8 2010-01-01 2010-01-01 false Words in the singular form. 900.80 Section 900.80....C. 608b(b) and 7 U.S.C. 608e Covering Fruits, Vegetables, and Nuts § 900.80 Words in the singular form. Words in this subpart in the singular form shall be deemed to import the plural, and vice versa...
Directory of Open Access Journals (Sweden)
Mercedes Camargo Velandia
2016-12-01
lleguen al archipiélago en busca de oportunidades de trabajo. Los encuestados no notan que haya un deterioro importante de los ecosistemas y reconocen que ellos no tienen una cultura ambiental para proteger las playas. La comunidad local utiliza y valora 14 servicios ecosistémicos, especialmente los de provisión, soporte y cultural, que forman parte de sus estrategias y medios de vida. Los operadores turísticos valoran seis servicios, específicamente de provisión, regulación y cultura, que están estrechamente ligados al desarrollo de la actividad turística, el acceso y la oportunidad de integrarse a la labor turística. También se descubre que las mujeres, en general, reciben menos ingresos que los hombres.
Quantum singularities in the FRW universe revisited
International Nuclear Information System (INIS)
Letelier, Patricio S.; Pitelli, Joao Paulo M.
2010-01-01
The components of the Riemann tensor in the tetrad basis are quantized and, through the Einstein equation, we find the local expectation value in the ontological interpretation of quantum mechanics of the energy density and pressure of a perfect fluid with equation of state p=(1/3)ρ in the flat Friedmann-Robertson-Walker quantum cosmological model. The quantum behavior of the equation of state and energy conditions are then studied, and it is shown that the energy conditions are violated since the singularity is removed with the introduction of quantum cosmology, but in the classical limit both the equation of state and the energy conditions behave as in the classical model. We also calculate the expectation value of the scale factor for several wave packets in the many-worlds interpretation in order to show the independence of the nonsingular character of the quantum cosmological model with respect to the wave packet representing the wave function of the Universe. It is also shown that, with the introduction of nonnormalizable wave packets, solutions of the Wheeler-DeWitt equation, the singular character of the scale factor, can be recovered in the ontological interpretation.
Finite-time singularity signature of hyperinflation
Sornette, D.; Takayasu, H.; Zhou, W.-X.
2003-07-01
We present a novel analysis extending the recent work of Mizuno et al. (Physica A 308 (2002) 411) on the hyperinflations of Germany (1920/1/1-1923/11/1), Hungary (1945/4/30-1946/7/15), Brazil (1969-1994), Israel (1969-1985), Nicaragua (1969-1991), Peru (1969-1990) and Bolivia (1969-1985). On the basis of a generalization of Cagan's model of inflation based on the mechanism of “inflationary expectation” of positive feedbacks between realized growth rate and people's expected growth rate, we find that hyperinflations can be characterized by a power law singularity culminating at a critical time tc. Mizuno et al.'s double-exponential function can be seen as a discrete time-step approximation of our more general non-linear ODE formulation of the price dynamics which exhibits a finite-time singular behavior. This extension of Cagan's model, which makes natural the appearance of a critical time tc, has the advantage of providing a well-defined end of the clearly unsustainable hyperinflation regime. We find an excellent and reliable agreement between theory and data for Germany, Hungary, Peru and Bolivia. For Brazil, Israel and Nicaragua, the super-exponential growth seems to be already contaminated significantly by the existence of a cross-over to a stationary regime.
Consideration on Singularities in Learning Theory and the Learning Coefficient
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Miki Aoyagi
2013-09-01
Full Text Available We consider the learning coefficients in learning theory and give two new methods for obtaining these coefficients in a homogeneous case: a method for finding a deepest singular point and a method to add variables. In application to Vandermonde matrix-type singularities, we show that these methods are effective. The learning coefficient of the generalization error in Bayesian estimation serves to measure the learning efficiency in singular learning models. Mathematically, the learning coefficient corresponds to a real log canonical threshold of singularities for the Kullback functions (relative entropy in learning theory.
Identification of discrete chaotic maps with singular points
Directory of Open Access Journals (Sweden)
P. G. Akishin
2001-01-01
Full Text Available We investigate the ability of artificial neural networks to reconstruct discrete chaotic maps with singular points. We use as a simple test model the Cusp map. We compare the traditional Multilayer Perceptron, the Chebyshev Neural Network and the Wavelet Neural Network. The numerical scheme for the accurate determination of a singular point is also developed. We show that combining a neural network with the numerical algorithm for the determination of the singular point we are able to accurately approximate discrete chaotic maps with singularities.
Numerical investigation of stress singularities in cracked bimaterial body
Czech Academy of Sciences Publication Activity Database
Náhlík, Luboš; Šestáková, Lucie; Hutař, Pavel
2008-01-01
Roč. 385-387, - (2008), s. 125-128 ISSN 1013-9826. [International Conference on Fracture and Damage Mechanics /7./. Seoul, 09.09.2008-11.09.2008] R&D Projects: GA AV ČR(CZ) KJB200410803; GA ČR GP106/06/P239; GA ČR GA106/08/1409 Institutional research plan: CEZ:AV0Z20410507 Keywords : bimaterial interface * stress singularity exponent * corner singularity * vertex singularity * general singular stress concentrator Subject RIV: JL - Materials Fatigue, Friction Mechanics
The road to singularities, and the roses on the way
International Nuclear Information System (INIS)
Collins, C.B.
1978-01-01
A survey of current investigations of space-time singularities is given. The different approaches adopted by various research schools is discussed, and an analogy is drawn between this study and the mounting of an expedition that sets out on a long trail of discovery. A heuristic discussion is given of the latest classification of singularities and some brief comments are made on how physically relevant each type of singularity is. Roughly speaking, it seems that the milder types (at which quantities remain well behaved) are pathological cases, whereas the crude 'big-bang' type of singularity is more generic. (author)
Can non-commutativity resolve the big-bang singularity?
Energy Technology Data Exchange (ETDEWEB)
Maceda, M.; Madore, J. [Laboratoire de Physique Theorique, Universite de Paris-Sud, Batiment 211, 91405, Orsay (France); Manousselis, P. [Department of Engineering Sciences, University of Patras, 26110, Patras (Greece); Physics Department, National Technical University, Zografou Campus, 157 80, Zografou, Athens (Greece); Zoupanos, G. [Physics Department, National Technical University, Zografou Campus, 157 80, Zografou, Athens (Greece); Theory Division, CERN, 1211, Geneva 23 (Switzerland)
2004-08-01
A possible way to resolve the singularities of general relativity is proposed based on the assumption that the description of space-time using commuting coordinates is not valid above a certain fundamental scale. Beyond that scale it is assumed that the space-time has non-commutative structure leading in turn to a resolution of the singularity. As a first attempt towards realizing the above programme a modification of the Kasner metric is constructed which is commutative only at large time scales. At small time scales, near the singularity, the commutation relations among the space coordinates diverge. We interpret this result as meaning that the singularity has been completely delocalized. (orig.)
La Sabana de Bogotá y su lago en el Pleniglacial Medio
Directory of Open Access Journals (Sweden)
Hamenn Thomas Van Der
1986-12-01
Full Text Available Durante buena parte del Pleistoceno (últimos 2.5 millones de años, la Sabana de Bogotá fue un lago. En su extensa historia presenta cambios frecuentes de nivel, especialmente durante las épocas interglaciales en las cuales el lago se contraía y dejaba una amplia zona pantanosa y boscosa entre su orilla y el pie de los cerros (VAN DER HAMMEN & GONZÁLEZ 1960-1963; HOOGHIEMSTRA,1984. Durante el último interglacial y en los interestadiales y estadiales de la parte temprana del último glacial existía un lago relativamente grande; en los bordes y especialmente en la parte baja de los valles que desembocan a la Sabana (como el de Tenjo se encontraba vegetación pantanosa, especialmente con Alnus acuminata (Aliso acompañado en ocasiones de Weinmannia sp. y Vallea stipularis.
Directory of Open Access Journals (Sweden)
José G. Vargas-Hernández
2017-12-01
Full Text Available Este trabajo entrega una revisión crítica respecto de la literatura especializada existente acerca de algunas características importantes de los espacios verdes urbanos, como los componentes, funciones, servicios, participación comunitaria, iniciativas y acciones desde una perspectiva eco sistémica. El análisis parte del supuesto de que los espacios verdes urbanos son ecosistemas de vital importancia para mejorar la calidad de vida en un entorno urbano y para proporcionar servicios ecosistémicos, como la biodiversidad y la regulación del clima. Por lo tanto, el espacio verde urbano es un componente esencial de un ecosistema en cualquier desarrollo comunitario. Satisfacer las necesidades de los usuarios está relacionado con las funciones y servicios que los espacios verdes urbanos proporcionan a las comunidades. La participación, el compromiso y el desarrollo de la comunidad requieren mecanismos para asegurar el cumplimiento de las necesidades y aspiraciones de los usuarios locales en la comunidad. Los métodos empleados en este análisis son la revisión de literatura y de documentos secundarios, el análisis de datos existentes acerca de usos y usuarios, y entrevistas con autoridades. Como conclusiones, el documento sugiere iniciativas ambientales, económicas y sociales para las autoridades locales y las comunidades que se pueden aplicar a todas las partes interesadas representadas e involucradas.
Amirjanyan, A. A.; Sahakyan, A. V.
2017-08-01
A singular integral equation with a Cauchy kernel and a logarithmic singularity on its righthand side is considered on a finite interval. An algorithm is proposed for the numerical solution of this equation. The contact elasticity problem of a П-shaped rigid punch indented into a half-plane is solved in the case of a uniform hydrostatic pressure occurring under the punch, which leads to a logarithmic singularity at an endpoint of the integration interval. The numerical solution of this problem shows the efficiency of the proposed approach and suggests that the singularity has to be taken into account in solving the equation.
Medina Rodriguez, Oscar Alfonso; Ospino Nuñez, Natalia Carolina
2018-01-01
Este trabajo de grado pretende presentar una aproximación teórica del negocio del fútbol profesional colombiano en el contexto actual, desde la perspectiva de los ecosistemas de los negocios. Específicamente, este documento estudia la influencia que ejerce la estructura organizacional del negocio del fútbol en Colombia en el enfoque estratégico de los clubes de primera división, comprendiendo y sintetizando las relaciones existentes entre los distintos actores del ecosistema.
Directory of Open Access Journals (Sweden)
Gerardo Umaña
2014-08-01
Full Text Available Esta localizado a 650m sobre el nivel del mar en el límite entre las llanuras del Norte y la vertiente del Pacífico en la Cordillera de Guanacaste, Costa Rica. Al inicio de la década de 1980 se construyó una represa en el río de desagüe y el caudal de salida fue desviado hacia el Embalse Arenal. Se realizó un primer estudio entre 1990 y 1991, y luego en el año 2001 antes de que se construyera una nueva modificación del lago mediante el levantamiento del nivel de la presa en un metro con el fin de utilizar la descarga para la producción de energía hidroeléctrica. Del 2002 al 2010 se realizó un monitoreo limnológico dos veces al año. Aquí se presenta un análisis de las principales características y de los cambios a través del tiempo. El lago es polimíctico discontinuo y desarrolla una termoclina intermitente a 6m de profundidad, la cual puede perdurar por varios días o semanas a juzgar por el desarrollo de una capa anóxica cercana al fondo. Desde su modificación la temperatura superficial del lago ha alcanzado valores mayores a los reportados con anterioridad. El hipolimnion muestra periodos de hipoxia a anoxia que se han vuelto más frecuentes. A pesar de la turbidez del lago, la concentración de nutrientes y de clorofila a son bajos. La tendencia en tiempos recientes es a una reducción de la clorofila a y un aumento en la trasparencia del agua. Estos cambios son similares a los observados en lagos donde se ha logrado atribuirlos al cambio climático global. También se pueden deber a la modificación del flujo del efluente por la operación intermitente de la planta hidroeléctrica, que favorece la acumulación de calor en la columna de agua. Esto debido a que otros factores, como el cambio en el uso del suelo en los alrededores del lago ocurrieron en la década de 1980, por lo que no se les puede atribuir una influencia en los cambios observados en los últimos 10 años.
Metric dimensional reduction at singularities with implications to Quantum Gravity
International Nuclear Information System (INIS)
Stoica, Ovidiu Cristinel
2014-01-01
A series of old and recent theoretical observations suggests that the quantization of gravity would be feasible, and some problems of Quantum Field Theory would go away if, somehow, the spacetime would undergo a dimensional reduction at high energy scales. But an identification of the deep mechanism causing this dimensional reduction would still be desirable. The main contribution of this article is to show that dimensional reduction effects are due to General Relativity at singularities, and do not need to be postulated ad-hoc. Recent advances in understanding the geometry of singularities do not require modification of General Relativity, being just non-singular extensions of its mathematics to the limit cases. They turn out to work fine for some known types of cosmological singularities (black holes and FLRW Big-Bang), allowing a choice of the fundamental geometric invariants and physical quantities which remain regular. The resulting equations are equivalent to the standard ones outside the singularities. One consequence of this mathematical approach to the singularities in General Relativity is a special, (geo)metric type of dimensional reduction: at singularities, the metric tensor becomes degenerate in certain spacetime directions, and some properties of the fields become independent of those directions. Effectively, it is like one or more dimensions of spacetime just vanish at singularities. This suggests that it is worth exploring the possibility that the geometry of singularities leads naturally to the spontaneous dimensional reduction needed by Quantum Gravity. - Highlights: • The singularities we introduce are described by finite geometric/physical objects. • Our singularities are accompanied by dimensional reduction effects. • They affect the metric, the measure, the topology, the gravitational DOF (Weyl = 0). • Effects proposed in other approaches to Quantum Gravity are obtained naturally. • The geometric dimensional reduction obtained
Using satellite images to monitor glacial-lake outburst floods: Lago Cachet Dos drainage, Chile
Friesen, Beverly A.; Cole, Christopher J.; Nimick, David A.; Wilson, Earl M.; Fahey, Mark J.; McGrath, Daniel J.; Leidich, Jonathan
2015-01-01
The U.S. Geological Survey (USGS) is monitoring and analyzing glacial-lake outburst floods (GLOFs) in the Colonia valley in the Patagonia region of southern Chile. A GLOF is a type of flood that occurs when water impounded by a glacier or a glacial moraine is released catastrophically. In the Colonia valley, GLOFs originating from Lago Cachet Dos, which is dammed by the Colonia Glacier, have recurred periodically since 2008. The water discharged during these GLOFs flows under or through the Colonia Glacier, into Lago Colonia and then the Río Colonia, and finally into the Río Baker—Chile's largest river in terms of volume of water.
Utilization of Oral Health Care Services by University Undergraduates in Lagos, Nigeria.
Makanjuola, J O; Uti, O G; Sofola, O O
2015-01-01
Data on the utilization of the available oral health facilities by university undergraduates is scarce in Nigeria. To determine the level of utilization of oral health care services and to identify the barriers to seeking treatment among University of Lagos students. A cross-sectional survey was carried out among University of Lagos undergraduates. Systematic sampling was used to select participants after randomly selecting a male and female hostel. Self-administered questionnaires were distributed to participants and collected immediately. The data was analyzed using Epi info version 6.04 software. Statistical significance was evaluated with chi square test and p-value facilities.
Lagos bat virus transmission in an Eidolon helvum bat colony, Ghana.
Freuling, Conrad M; Binger, Tabea; Beer, Martin; Adu-Sarkodie, Yaw; Schatz, Juliane; Fischer, Melina; Hanke, Dennis; Hoffmann, Bernd; Höper, Dirk; Mettenleiter, Thomas C; Oppong, Samual K; Drosten, Christian; Müller, Thomas
2015-12-02
A brain sample of a straw-coloured fruit bat (Eidolon helvum) from Ghana without evident signs of disease tested positive by generic Lyssavirus RT-PCR and direct antigen staining. Sequence analysis confirmed the presence of a Lagos bat virus belonging to phylogenetic lineage A. Virus neutralization tests using the isolate with sera from the same group of bats yielded neutralizing antibodies in 74% of 567 animals. No cross-neutralization was observed against a different Lagos bat virus (lineage B). Copyright © 2015 Elsevier B.V. All rights reserved.
Planeamiento estratégico de la empresa ABR Lagos S.A.C.
Zuloeta Lagos, Bujarin Jaime
2016-01-01
La presente investigación tiene por finalidad desarrollar un Plan Estratégico para la empresa ABR Lagos S.A.C. para el periodo 2016-2020, con lo cual se busca consolidar su permanencia en el mercado peruano, incrementar su rentabilidad y mejorar la calidad del servicio. ABR Lagos S.A.C. es una empresa especializada en la fabricación e instalación de estructuras metálicas, la cual con casi siete años en el mercado ha mostrado un significativo crecimiento en las ventas. Para el logro del objeti...
A vida singular de um jovem militante
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Áurea Maria Guimarães
2012-01-01
Full Text Available Esse artigo é fruto de uma pesquisa realizada no período de 2007 a 2010, junto a jovens militantes da cidade de Campinas, com o objetivo de compreender as diferentes maneiras que conduziam esses jovens tanto a reproduzir um modelo de vida quanto a criar outras possibilidades de militância na relação com esse modelo. Entre as histórias orais de vida narradas por jovens que militavam em diferentes grupos ou instituições, escolhi a vida de Biula, representante do movimento estudantil secundarista, procurando evidenciar que a singularidade desta vida, como também e a de outros jovens, estava conectada à problematização que faziam no interior de certas práticas, histórica e culturalmente constituídas, possibilitando a criação de novas formas de subjetivação nas quais se modificava a experiência que tinham deles mesmos na relação com os seus heróis ou modelos de referência. Palavras-chave: história oral – transcriação – heróis – resistência - processos de singularização. THE SINGULAR LIFE OF A YOUNG MILITANT ABSTRACT This article is the result of a research carried out from 2007 to 2010 with young militants in the city of Campinas, aiming to understand the different ways which conducted these youngsters to both reproduce a life model and create other possibilities of militancy in the relationship with this model. Among oral stories narrated by young militants from different groups or institutions, I have chosen the life of Biula, a representative of the secondary students’ movement, trying to show that the singularity of this life and other youngsters’ lives was connected to the problematization they promoted within certain practices, historically and culturally built, thus enabling the creation of new subjectification modes in which the experience they had of themselves in the relationship with their heroes or reference models has changed. Key words: oral history - transcreation – heroes
The technological singularity and exponential medicine
Directory of Open Access Journals (Sweden)
Iraj Nabipour
2016-01-01
Full Text Available The "technological singularity" is forecasted to occur in 2045. It is a point when non-biological intelligence becomes more intelligent than humans and each generation of intelligent machines re-designs itself smarter. Beyond this point, there is a symbiosis between machines and humans. This co-existence will produce incredible impacts on medicine that its sparkles could be seen in healthcare industry and the future medicine since 2025. Ray Kurzweil, the great futurist, suggested that three revolutions in science and technology consisting genetic and molecular science, nanotechnology, and robotic (artificial intelligence provided an exponential growth rate for medicine. The "exponential medicine" is going to create more disruptive technologies in healthcare industry. The exponential medicine shifts the paradigm of medical philosophy and produces significant impacts on the healthcare system and patient-physician relationship.
Dual Vector Spaces and Physical Singularities
Rowlands, Peter
Though we often refer to 3-D vector space as constructed from points, there is no mechanism from within its definition for doing this. In particular, space, on its own, cannot accommodate the singularities that we call fundamental particles. This requires a commutative combination of space as we know it with another 3-D vector space, which is dual to the first (in a physical sense). The combination of the two spaces generates a nilpotent quantum mechanics/quantum field theory, which incorporates exact supersymmetry and ultimately removes the anomalies due to self-interaction. Among the many natural consequences of the dual space formalism are half-integral spin for fermions, zitterbewegung, Berry phase and a zero norm Berwald-Moor metric for fermionic states.
String wave function across a Kasner singularity
International Nuclear Information System (INIS)
Copeland, Edmund J.; Niz, Gustavo; Turok, Neil
2010-01-01
A collision of orbifold planes in 11 dimensions has been proposed as an explanation of the hot big bang. When the two planes are close to each other, the winding membranes become the lightest modes of the theory, and can be effectively described in terms of fundamental strings in a ten-dimensional background. Near the brane collision, the 11-dimensional metric is a Euclidean space times a 1+1-dimensional Milne universe. However, one may expect small perturbations to lead into a more general Kasner background. In this paper we extend the previous classical analysis of winding membranes to Kasner backgrounds, and using the Hamiltonian equations, solve for the wave function of loops with circular symmetry. The evolution across the singularity is regular, and explained in terms of the excitement of higher oscillation modes. We also show there is finite particle production and unitarity is preserved.
Fixed drug eruption at a dermatology clinic in Lagos, Nigeria
Directory of Open Access Journals (Sweden)
Olusola Olabisi Ayanlowo
2015-01-01
Full Text Available Background: Fixed drug eruption (FDE is common cutaneous drug eruption characterized by the development of one or more annular, oval, erythematous, and hyperpigmented patches as a result of systemic exposure to a drug. Drugs causing FDE vary with prevailing diseases and prescription pattern in different parts of the world. This study is aimed at reviewing cases of FDE seen at the dermatology outpatient clinic of Lagos University Teaching Hospital (LUTH over a 9-year period, highlighting the spectrum of drugs implicated and the clinical characteristics. Materials and Methods: Data were obtained from the clinic records and patients' case notes. These included the demographic details, duration of presentation, drugs implicated, and clinical characteristics. Results: FDE was diagnosed in 1.8% (295/16,160 of patients seen. There was a slight female preponderance. Antimalarials were the commonest group of medications implicated (51.0% followed by antibiotics (27.9%; analgesics (10.2%, herbal toothpaste (6.1%, and oral hypoglycemic agents (4.1%. Sulfonamides were the commonest group of drugs found in 78 patients (53.1% predominantly as sulfadoxine/pyrimethamine antimalarials and trimethoprim/sulfamethoxazole antibiotics (co-trimoxazole. Conclusion: Concerted efforts are needed to discourage over-the-counter sales and purchase of nonprescription sulfonamide-based medications. A change in prescription pattern from sulfonamides to other classes of antimalarials and antibiotics is desirable and/or recommended. Patients should inform their caregivers at any point of care about their reaction to drugs. It is advised that they have a list of common implicating drugs and they wear a medic alert or carry an ID card bearing this information.
Herbal medicine use among urban residents in Lagos, Nigeria
2011-01-01
Background Over three-quarter of the world's population is using herbal medicines with an increasing trend globally. Herbal medicines may be beneficial but are not completely harmless. This study aimed to assess the extent of use and the general knowledge of the benefits and safety of herbal medicines among urban residents in Lagos, Nigeria. Methods The study involved 388 participants recruited by cluster and random sampling techniques. Participants were interviewed with a structured open- and close-ended questionnaire. The information obtained comprises the demography and types of herbal medicines used by the respondents; indications for their use; the sources, benefits and adverse effects of the herbal medicines they used. Results A total of 12 herbal medicines (crude or refined) were used by the respondents, either alone or in combination with other herbal medicines. Herbal medicines were reportedly used by 259 (66.8%) respondents. 'Agbo jedi-jedi' (35%) was the most frequently used herbal medicine preparation, followed by 'agbo-iba' (27.5%) and Oroki herbal mixture® (9%). Family and friends had a marked influence on 78.4% of the respondents who used herbal medicine preparations. Herbal medicines were considered safe by half of the respondents despite 20.8% of those who experienced mild to moderate adverse effects. Conclusions Herbal medicine is popular among the respondents but they appear to be ignorant of its potential toxicities. It may be necessary to evaluate the safety, efficacy and quality of herbal medicines and their products through randomised clinical trial studies. Public enlightenment programme about safe use of herbal medicines may be necessary as a means of minimizing the potential adverse effects. PMID:22117933
Self-medication for infants with colic in Lagos, Nigeria
Directory of Open Access Journals (Sweden)
Oshikoya Kazeem A
2009-02-01
Full Text Available Abstract Background Infantile colic is a self-limiting condition that is distributed worldwide. It is often misdiagnosed as an organic disease for which an infant is admitted to the hospital. Many studies have described the aetiopathogenesis, pharmacologic and non-pharmacologic management of colic but none has evaluated self-medication for infants with colic. The aim of this study was therefore to determine the knowledge of Nigerian mothers about colic, their home-based management, extent of self-medication for the infants with colic and the types of medicines involved. Methods It is a prospective study conducted at the vaccination clinics of 20 primary health care centres, each from different Local Government Areas in Lagos, Nigeria. Eight hundred mothers that brought their infants for vaccination between April and September, 2006 were interviewed with open-and close-ended questionnaire. Results Six hundred and eighty three (85.4% mothers claimed they had a good knowledge of colic. Incessant and excessive cry was the main clinical feature of colic identified by 430(62.9% mothers. Three hundred and seventy eight (67.7% infants were treated by self-medication, 157 (28.1% sought medical intervention and 17 (3.1% were treated at a traditional birth attendant home. Herbal medicines constituted 51.8% of the self-medicated medicines, of which 48 (26.2% were "Ororo Ogiri". Nospamin® (49.5% and Gripe water® (43.0% were the two frequently prescribed and self-medicated medicines for infants with colic. Conclusion Nigerian mothers are deficient in their knowledge of colic. Self-medication was the most frequently used home-based intervention. Health education would appear necessary to improve parental management of this self-limiting condition.
Branes at Singularities in Type 0 String Theory
Alishahiha, M; Brandhuber, A; Oz, Y
1999-01-01
We consider Type 0B D3-branes placed at conical singularities and analyze in detail the conifold singularity. We study the non supersymmetric gauge theories on their worldvolume and their conjectured dual gravity descriptions. In the ultraviolet the solutions exhibit a logarithmic running of the gauge coupling. In the infrared we find confining solutions and IR fixed points.
Eigenstructure of of singular systems. Perturbation analysis of simple eigenvalues
García Planas, María Isabel; Tarragona Romero, Sonia
2014-01-01
The problem to study small perturbations of simple eigenvalues with a change of parameters is of general interest in applied mathematics. After to introduce a systematic way to know if an eigenvalue of a singular system is simple or not, the aim of this work is to study the behavior of a simple eigenvalue of singular linear system family
Singularities of elastic scattering amplitude by long-range potentials
International Nuclear Information System (INIS)
Kvitsinsky, A.A.; Komarov, I.V.; Merkuriev, S.P.
1982-01-01
The angular peculiarities and the zero energy singularities of the elastic scattering amplitude by a long-range potential are described. The singularities of the elastic (2 → 2) scattering amplitude for a system of three Coulomb particles are considered [ru
Singularly perturbed volterra integro-differential equations | Bijura ...
African Journals Online (AJOL)
Several investigations have been made on singularly perturbed integral equations. This paper aims at presenting an algorithm for the construction of asymptotic solutions and then provide a proof asymptotic correctness to singularly perturbed systems of Volterra integro-differential equations. Mathematics Subject
Non-uniqueness of the source for singular gauge fields
International Nuclear Information System (INIS)
Lanyi, G.; Pappas, R.
1977-01-01
It is shown that the singular Wu-Yang solution for SU(2) gauge fields may be interpreted as due to a point source at the origin. However, the electric or magnetic nature of the source depends on whether one approaches the singularity by means of a 'smeared' potential or a 'smeared' field strength. (Auth.)
Solitary wave solution to a singularly perturbed generalized Gardner ...
Indian Academy of Sciences (India)
2017-03-24
Mar 24, 2017 ... Abstract. This paper is concerned with the existence of travelling wave solutions to a singularly perturbed gen- eralized Gardner equation with nonlinear terms of any order. By using geometric singular perturbation theory and based on the relation between solitary wave solution and homoclinic orbits of the ...
K3-fibered Calabi-Yau threefolds II, singular fibers
Hunt, Bruce
1999-01-01
In part I of this paper we constructed certain fibered Calabi-Yaus by a quotient construction in the context of weighted hypersurfaces. In this paper look at the case of K3 fibrations more closely and study the singular fibers which occur. This differs from previous work since the fibrations we discuss have constant modulus, and the singular fibers have torsion monodromy.
Some BMO estimates for vector-valued multilinear singular integral ...
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
the multilinear operator related to some singular integral operators is obtained. The main purpose of this paper is to establish the BMO end-point estimates for some vector-valued multilinear operators related to certain singular integral operators. First, let us introduce some notations [10,16]. Throughout this paper, Q = Q(x,r).
Infinite derivative gravity : non-singular cosmology & blackhole solutions
Mazumdar, Anupam
2017-01-01
Both Einstein's theory of General Relativity and Newton's theory of gravity possess a short dis- tance and small time scale catastrophe. The blackhole singularity and cosmological Big Bang singularity problems highlight that current theories of gravity are incomplete description at early times and
A Note on Inclusion Intervals of Matrix Singular Values
Directory of Open Access Journals (Sweden)
Shu-Yu Cui
2012-01-01
Full Text Available We establish an inclusion relation between two known inclusion intervals of matrix singular values in some special case. In addition, based on the use of positive scale vectors, a known inclusion interval of matrix singular values is also improved.
Simpson's neutrino and the singular see-saw
International Nuclear Information System (INIS)
Allen, T.J.; Johnson, R.; Ranfone, S.; Schechter, J.; Walle, J.W.F.
1991-01-01
The authors of this paper derive explicit forms for the neutrino and lepton mixing-matrices which describe the generic singular see-saw model. The dependence on the hierarchy parameter is contrasted with the non-singular case. Application is made to Simpson's 17 keV neutrino
On reliability of singular-value decomposition in attractor reconstruction
International Nuclear Information System (INIS)
Palus, M.; Dvorak, I.
1990-12-01
Applicability of singular-value decomposition for reconstructing the strange attractor from one-dimensional chaotic time series, proposed by Broomhead and King, is extensively tested and discussed. Previously published doubts about its reliability are confirmed: singular-value decomposition, by nature a linear method, is only of a limited power when nonlinear structures are studied. (author). 29 refs, 9 figs
One Critical Case in Singularly Perturbed Control Problems
Sobolev, Vladimir
2017-02-01
The aim of the paper is to describe the special critical case in the theory of singularly perturbed optimal control problems. We reduce the original singularly perturbed problem to a regularized one such that the existence of slow integral manifolds can be established by means of the standard theory. We illustrate our approach by an example of control problem.
7 CFR 1200.1 - Words in the singular form.
2010-01-01
... 7 Agriculture 10 2010-01-01 2010-01-01 false Words in the singular form. 1200.1 Section 1200.1 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (MARKETING... Governing Proceedings To Formulate and Amend an Order § 1200.1 Words in the singular form. Words in this...
Periodic solutions to second-order indefinite singular equations
Czech Academy of Sciences Publication Activity Database
Hakl, Robert; Zamora, M.
2017-01-01
Roč. 263, č. 1 (2017), s. 451-469 ISSN 0022-0396 Institutional support: RVO:67985840 Keywords : degree theory * indefinite singularity * periodic solution * singular differential equation Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 1.988, year: 2016 http://www.sciencedirect.com/science/article/pii/S0022039617301134
Non-singular cosmologies in the conformally invariant gravitation theory
International Nuclear Information System (INIS)
Kembhavi, A.K.
1976-01-01
It is shown that in the framework of a conformally invariant gravitation theory, the singularity which is present in some anisotropic universes in general relativity is due to a wrong choice of conformal frame. Frames exist in which these models can be made singularity free. (author)
A numerical method for solving singular De`s
Energy Technology Data Exchange (ETDEWEB)
Mahaver, W.T.
1996-12-31
A numerical method is developed for solving singular differential equations using steepest descent based on weighted Sobolev gradients. The method is demonstrated on a variety of first and second order problems, including linear constrained, unconstrained, and partially constrained first order problems, a nonlinear first order problem with irregular singularity, and two second order variational problems.
ANALYTICAL SOLUTIONS OF SINGULAR ISOTHERMAL QUADRUPOLE LENS
International Nuclear Information System (INIS)
Chu Zhe; Lin, W. P.; Yang Xiaofeng
2013-01-01
Using an analytical method, we study the singular isothermal quadrupole (SIQ) lens system, which is the simplest lens model that can produce four images. In this case, the radial mass distribution is in accord with the profile of the singular isothermal sphere lens, and the tangential distribution is given by adding a quadrupole on the monopole component. The basic properties of the SIQ lens have been studied in this Letter, including the deflection potential, deflection angle, magnification, critical curve, caustic, pseudo-caustic, and transition locus. Analytical solutions of the image positions and magnifications for the source on axes are derived. We find that naked cusps will appear when the relative intensity k of quadrupole to monopole is larger than 0.6. According to the magnification invariant theory of the SIQ lens, the sum of the signed magnifications of the four images should be equal to unity, as found by Dalal. However, if a source lies in the naked cusp, the summed magnification of the left three images is smaller than the invariant 1. With this simple lens system, we study the situations where a point source infinitely approaches a cusp or a fold. The sum of the magnifications of the cusp image triplet is usually not equal to 0, and it is usually positive for major cusps while negative for minor cusps. Similarly, the sum of magnifications of the fold image pair is usually not equal to 0 either. Nevertheless, the cusp and fold relations are still equal to 0 in that the sum values are divided by infinite absolute magnifications by definition.
Singular Null Hypersurfaces in General Relativity
International Nuclear Information System (INIS)
Dray, T
2006-01-01
Null hypersurfaces are a mathematical consequence of the Lorentzian signature of general relativity; singularities in mathematical models usually indicate where the interesting physics takes place. This book discusses what happens when you combine these ideas. Right from the preface, this is a no-nonsense book. There are two principal approaches to singular shells, one distributional and the other 'cut and paste'; both are treated in detail. A working knowledge of GR is assumed, including familiarity with null tetrads, differential forms, and 3 + 1 decompositions. Despite my own reasonably extensive, closely related knowledge, there was material unfamiliar to me already in chapter 3, although I was reunited with some old friends in later chapters. The exposition is crisp, with a minimum of transition from chapter to chapter. In fact, my main criticism is that there is no clear statement of the organization of the book, nor is there an index. Everything is here, and the story is compelling if you know what to look for, although it is less easy to follow the story if you are not already familiar with it. But this is really a book for experts, and the authors certainly qualify, having played a significant role in developing and extending the results they describe. It is also entirely appropriate that the book is dedicated to Werner Israel, who pioneered the thin-shell approach to (non-null) singular surfaces and later championed the use of similar methods for analysing null shells. After an introductory chapter on impulsive signals, the authors show how the Bianchi identities can be used to classify spacetimes with singular null hypersurfaces. This approach, due to the authors, generalizes the framework originally proposed by Penrose. While astrophysical applications are discussed only briefly, the authors point out that detailed physical characteristics of signals from isolated sources can be determined in this manner. In particular, they describe the behaviour of
Complexity, Analysis and Control of Singular Biological Systems
Zhang, Qingling; Zhang, Xue
2012-01-01
Complexity, Analysis and Control of Singular Biological Systems follows the control of real-world biological systems at both ecological and phyisological levels concentrating on the application of now-extensively-investigated singular system theory. Much effort has recently been dedicated to the modelling and analysis of developing bioeconomic systems and the text establishes singular examples of these, showing how proper control can help to maintain sustainable economic development of biological resources. The book begins from the essentials of singular systems theory and bifurcations before tackling the use of various forms of control in singular biological systems using examples including predator-prey relationships and viral vaccination and quarantine control. Researchers and graduate students studying the control of complex biological systems are shown how a variety of methods can be brought to bear and practitioners working with the economics of biological systems and their control will also find the ...
Managing focal fields of vector beams with multiple polarization singularities.
Han, Lei; Liu, Sheng; Li, Peng; Zhang, Yi; Cheng, Huachao; Gan, Xuetao; Zhao, Jianlin
2016-11-10
We explore the tight focusing behavior of vector beams with multiple polarization singularities, and analyze the influences of the number, position, and topological charge of the singularities on the focal fields. It is found that the ellipticity of the local polarization states at the focal plane could be determined by the spatial distribution of the polarization singularities of the vector beam. When the spatial location and topological charge of singularities have even-fold rotation symmetry, the transverse fields at the focal plane are locally linearly polarized. Otherwise, the polarization state becomes a locally hybrid one. By appropriately arranging the distribution of the polarization singularities in the vector beam, the polarization distributions of the focal fields could be altered while the intensity maintains unchanged.
Workshop on Singularities in Geometry, Topology, Foliations and Dynamics
Lê, Dung; Oka, Mutsuo; Snoussi, Jawad
2017-01-01
This book features state-of-the-art research on singularities in geometry, topology, foliations and dynamics and provides an overview of the current state of singularity theory in these settings. Singularity theory is at the crossroad of various branches of mathematics and science in general. In recent years there have been remarkable developments, both in the theory itself and in its relations with other areas. The contributions in this volume originate from the “Workshop on Singularities in Geometry, Topology, Foliations and Dynamics”, held in Merida, Mexico, in December 2014, in celebration of José Seade’s 60th Birthday. It is intended for researchers and graduate students interested in singularity theory and its impact on other fields.
Cusp singularities in f(R) gravity: pros and cons
International Nuclear Information System (INIS)
Chen, Pisin; Yeom, Dong-han
2015-01-01
We investigate cusp singularities in f(R) gravity, especially for Starobinsky and Hu-Sawicki dark energy models. We illustrate that, by using double-null numerical simulations, a cusp singularity can be triggered by gravitational collapses. This singularity can be cured by adding a quadratic term, but this causes a Ricci scalar bump that can be observed by an observer outside the event horizon. Comparing with cosmological parameters, it seems that it would be difficult to see super-Planckian effects by astrophysical experiments. On the other hand, at once there exists a cusp singularity, it can be a mechanism to realize a horizon scale curvature singularity that can be interpreted by a firewall
Fold points and singularity induced bifurcation in inviscid transonic flow
International Nuclear Information System (INIS)
Marszalek, Wieslaw
2012-01-01
Transonic inviscid flow equation of elliptic–hyperbolic type when written in terms of the velocity components and similarity variable results in a second order nonlinear ODE having several features typical of differential–algebraic equations rather than ODEs. These features include the fold singularities (e.g. folded nodes and saddles, forward and backward impasse points), singularity induced bifurcation behavior and singularity crossing phenomenon. We investigate the above properties and conclude that the quasilinear DAEs of transonic flow have interesting properties that do not occur in other known quasilinear DAEs, for example, in MHD. Several numerical examples are included. -- Highlights: ► A novel analysis of inviscid transonic flow and its similarity solutions. ► Singularity induced bifurcation, singular points of transonic flow. ► Projection method, index of transonic flow DAEs, linearization via matrix pencil.
Czech Academy of Sciences Publication Activity Database
Knésl, Zdeněk; Klusák, Jan; Náhlík, Luboš
2007-01-01
Roč. 14, č. 6 (2007), s. 399-408 ISSN 1802-1484 R&D Projects: GA ČR(CZ) GA101/05/0320; GA ČR GA101/05/0227 Institutional research plan: CEZ:AV0Z20410507 Keywords : fracture mechanics * stability criteria * singular stress concentrations * crack initiation * critical stress Subject RIV: JL - Materials Fatigue, Friction Mechanics
3rd Singularity Theory Meeting of Northeast region & the Brazil-Mexico 2nd Meeting on Singularities
Neto, Aurélio; Mond, David; Saia, Marcelo; Snoussi, Jawad; BMMS 2/NBMS 3; ENSINO; Singularities and foliations geometry, topology and applications
2018-01-01
This proceedings book brings selected works from two conferences, the 2nd Brazil-Mexico Meeting on Singularity and the 3rd Northeastern Brazilian Meeting on Singularities, that were hold in Salvador, in July 2015. All contributions were carefully peer-reviewed and revised, and cover topics like Equisingularity, Topology and Geometry of Singularities, Topological Classification of Singularities of Mappings, and more. They were written by mathematicians from several countries, including Brazil, Spain, Mexico, Japan and the USA, on relevant topics on Theory of Singularity, such as studies on deformations, Milnor fibration, foliations, Catastrophe theory, and myriad applications. Open problems are also introduced, making this volume a must-read both for graduate students and active researchers in this field.
Akinnubi, Caroline Funmbi
2016-01-01
This study examined the day caring methods among the civil servants of reproductive age with children between three months to four years in Lagos State Nigeria. The research design employed for this study was a descriptive research design. A total number of 212 teachers and 128 ministry workers making a total of 340 reproductive age mothers were…
Ecological health status of the Lagos wetland ecosystems: Implications for coastal risk reduction
Agboola, Julius I.; Ndimele, Prince E.; Odunuga, Shakirudeen; Akanni, Adeniran; Kosemani, Bosede; Ahove, Michael A.
2016-12-01
Lagos, a major urban agglomeration in the world is characterized by wetlands and basin for upstream rivers such as Ogun, Oshun and Yewa Rivers. Ongoing environmental pressures exerted by large-scale land reclamation for residential quarters, refuse and sewage dumping, and other uses, however, are suspected to have had a substantial impact on ecological health of the Lagos wetland ecosystems over the last few decades. To determine the impact of these pressures, we examined spatial changes in three wetlands areas- Badore/Langbasa (BL), Festac/Iba/Ijegun (FI) and Ologe/Otto-Awori (OO) through field sample collection and analyses of surface water, sediments, air-water interface gas fluxes and vegetations. Surface water conductivity, total suspended solids (TSS), alkalinity, chloride, biological oxygen demand (BOD), nitrate, phosphate and heavy metals (Zn, Cu, Fe, Na, Mn, Pb, Cd, K and Ni) exhibited relative spatial stability while other water quality parameters varied significantly (P International Union for Conservation of Nature (IUCN). There are indications of steady rise in greenhouse gas levels in Lagos since air CO2 value at BL have reached global threshold of 400 ppm with OO and FI closely approaching. We conclude that the Lagos wetland ecosystems, especially OO and FI still have some semblance of natural habitat. However, further destruction and unwise use of the resources could cause damage to physical, chemical, geological and biological processes in nature, which could result to grave socio-economic and cultural consequences to the local communities whose livelihood and lifestyle depend on these valued wetlands.
Agboola, Julius I.; Ndimele, Prince E.; Odunuga, Shakirudeen; Akanni, Adeniran; Kosemani, Bosede; Ahove, Michael A.
2016-12-01
Lagos, a major urban agglomeration in the world is characterized by wetlands and basin for upstream rivers such as Ogun, Oshun and Yewa Rivers. Ongoing environmental pressures exerted by large-scale land reclamation for residential quarters, refuse and sewage dumping, and other uses, however, are suspected to have had a substantial impact on ecological health of the Lagos wetland ecosystems over the last few decades. To determine the impact of these pressures, we examined spatial changes in three wetlands areas- Badore/Langbasa (BL), Festac/Iba/Ijegun (FI) and Ologe/Otto-Awori (OO) through field sample collection and analyses of surface water, sediments, air-water interface gas fluxes and vegetations. Surface water conductivity, total suspended solids (TSS), alkalinity, chloride, biological oxygen demand (BOD), nitrate, phosphate and heavy metals (Zn, Cu, Fe, Na, Mn, Pb, Cd, K and Ni) exhibited relative spatial stability while other water quality parameters varied significantly (P International Union for Conservation of Nature (IUCN). There are indications of steady rise in greenhouse gas levels in Lagos since air CO2 value at BL have reached global threshold of 400 ppm with OO and FI closely approaching. We conclude that the Lagos wetland ecosystems, especially OO and FI still have some semblance of natural habitat. However, further destruction and unwise use of the resources could cause damage to physical, chemical, geological and biological processes in nature, which could result to grave socio-economic and cultural consequences to the local communities whose livelihood and lifestyle depend on these valued wetlands.
A Ten-Year Review of Childhood Renal Admissions into the Lagos ...
African Journals Online (AJOL)
Background: The exact burden of childhood renal disease among Nigerians, particularly in the Lagos environment is not known. Local literature by focusing on the nephortic syndrome seemingly gives the impression that it constitutes the most important and perhaps the most common of these diseases. In practices however ...
El ultrasonido: desde el murciélago hasta la cardiología no invasiva
Directory of Open Access Journals (Sweden)
Fabián Dávila
2017-03-01
Conclusiones: Grandes avances se han logrado en consecuencia con la evolución del ultrasonido en medicina, su inicio en la ecolocalización descrita en los murciélagos hasta la ultrasonografía cardiaca en 3 D, han permitido el desarrollo de nuevas no invasivas en la medicina cardiovascular.
Floral diversity in the wetlands of Ibeju-Lekki Area, Lagos, Nigeria ...
African Journals Online (AJOL)
Until very recently poor attention has been given to the management of wetlands in Nigeria despite their significance in the global food and water supply, energy needs and disaster management. Due to the rapid development of the Lagos coastal areas for commerce and industrial purposes, the natural coastal vegetation ...
Exploitation of Factory Workers: A Study of Union Dicon Salt, Lagos ...
African Journals Online (AJOL)
The study examined labour exploitation in Nigeria with particular reference to Union Dicon Salt Plc., Lagos. The review of literature points to the fact that exploitation of the factory workers in the long run leads to strained relationships between management and staff. The situation becomes conflictual to the extent that both ...
Decision scenario analysis for addressing sediment accumulation in Lago Lucchetti, Puerto Rico
A Bayesian belief network (BBN) was used to characterize the effects of sediment accumulation on water storage capacity of a reservoir (Lago Lucchetti) in southwest Puerto Rico and the potential of different management options to increase reservoir life expectancy. Water and sedi...
Levels of Job Satisfaction and Performance of Sports Officers in Lagos State Secondary Schools
Onifade, Ademola; Keinde, Idou; Kehinde, Eunice
2009-01-01
The purpose of this paper was to examine the relationship between job satisfaction levels of sports officers and sports performance of secondary schools in Lagos State. Data were collected from 200 subjects across 10 Local Education Districts. Job Descriptive Index was used to determine job satisfaction while performance in the Principals' Soccer…
Investigation into ivory trade in selected markets and hotels in Lagos ...
African Journals Online (AJOL)
The market growth for wildlife trophy collection is gradually leading to a decline in animal population. Thus, trade in ivory constitutes a potential threat to biodiversity conservation. The extent of this treat was therefore investigated via a 3-month survey of trade in ivory in selected markets and hotels in Lagos, Nigeria.
An Examination of Tenure Security for Urban Crop Farming in Lagos ...
African Journals Online (AJOL)
The study examined issues surrounding tenure security of land for urban crop farming and identified constraints that must be dealt with in order to facilitate land accessibility and productivity of urban crop farmers in the Lagos metropolis. 475 respondents of seven communities were selected through simple random sampling ...
Selenium deficiency and pregnancy outcome in pregnant women with HIV in Lagos, Nigeria.
Okunade, Kehinde S; Olowoselu, Olusola F; Osanyin, Gbemisola E; John-Olabode, Sarah; Akanmu, Sulaimon A; Anorlu, Rose I
2018-04-16
To investigate the prevalence of maternal selenium deficiency and its effects on pregnancy outcomes in pregnant women with HIV in Lagos, Nigeria. The present descriptive cross-sectional study enrolled women aged 15-49 years with HIV who were at 14-26 weeks of a singleton pregnancy and were attending Lagos University Teaching Hospital, Lagos, Nigeria, between August 1, 2016, and April 30, 2017. Participants were selected by consecutive sampling and baseline data were collected through interviews. Venous blood samples were obtained to measure selenium concentrations, and associations between low maternal selenium concentrations (defined as <0.89 μmol/L) and pregnancy outcomes were examined using bivariate and multivariate analysis. The final analysis included 113 patients; selenium deficiency was recorded in 23 (20.4%) patients. Women with selenium deficiency had an approximately eight-fold higher risk of preterm delivery (adjusted odds ratio 7.61, 95% confidence interval 4.37-18.89; P=0.031) and of delivering a term neonate with a low delivery weight (adjusted odds ratio 8.11, 95% confidence interval 3.27-17.22; P=0.012), compared with women with a normal selenium concentration. The prevalence of selenium deficiency among pregnant women with HIV in Lagos was relatively high. The significant associations observed between maternal selenium deficiency and adverse pregnancy outcomes could have implications for the future management of HIV in pregnancy. © 2018 International Federation of Gynecology and Obstetrics.
PMN-Portuguese Meteor Network and OLA-Observatório do Lago Alqueva agreement
Saraiva, C.
2018-01-01
The PMN-Portuguese Meteor Network has two new video meteor detecting systems at OLA- Observartório do Lago Alqueva, situated at the South East Portuguese territory with a pristine night sky and more than 290 clear nights each year.
a multi-period markov model for monthly rainfall in lagos, nigeria
African Journals Online (AJOL)
PUBLICATIONS1
A twelve-period. Markov model has been developed for the monthly rainfall data for Lagos, along the coast of .... autoregressive process to model river flow; Deo et al. (2015) utilized an ...... quences for the analysis of river basins by simulation.
Seccional del Lago Lleu Lleu extracto del resumen ejecutivo del estudio
Directory of Open Access Journals (Sweden)
Manuel Durán
2000-08-01
Full Text Available En el siguiente reportaje se presentan los estudios contratados por el MINVU Planes Seccionales del Lago Lleu Lleu y del Lago Pangue; realizados por las oficinas de Manuel Durán y Lira y Peña Asoc. A continuación entrevistamos al Sr. Tito Rojas, ex Director Regional de SERNATUR y actual Gobernador de la Provincia de Arauco, y a Patricio Aguirre, Director de la Carrera de Turismo del DUOC-UC sede Concepción. Mientras que los instrumentos de planificación desarrollan estrategias específicas para potenciar el turismo aprovechando las potencialidades del recurso lacustre; los entrevistados nos dan su opinión en cuanto a diversos aspectos relacionados con el turismo y los lagos de esta zona: el delicado equilibrio entre turismo y protección de los recursos; las potencialidades de las áreas aledañas a los lagos Pangue y Lleu Lleu; el patrimonio paisajístico y cultural de la provincia de Arauco, entre otros, son los aspectos que se exponen en las próximas páginas.
Brydges, Colton; Mkandawire, Paul
2017-01-01
This article examines the perceptions of inclusive education in Lagos, Nigeria, based upon in-depth interviews conducted with students with visual impairments during the month of July 2013. The results and discussions are situated within critical disability theory. Despite decades of inclusive education policies, the findings of the study show…
The Influence of Travel Time on Accessibility in Lagos Island | Atubi ...
African Journals Online (AJOL)
The aim of this paper is to establish the influence of time on accessibility in Lagos Island, Nigeria. It was observed that generally, average driving speed was observed to be lower over short than over long distance routes. High speeds tend to be concentrated within a distance band of over 2.7km but beyond 6.0km average ...
Work-Life Balance among academic staff of the University of Lagos ...
African Journals Online (AJOL)
Work-Life Balance among academic staff of the University of Lagos. ... Abstract. Work-life balance is associated with the maintenance of stability in both one's professional and personal life. It is key to the welfare and, subsequently, job satisfaction and productivity of employees. It is against this understanding that this study ...
Trust in government and the politics of fuel subsidy removal in Lagos
African Journals Online (AJOL)
JOHNSON-AYODELE
It covered the three senatorial districts in Lagos using data obtained from 220 .... data in Africa, there is a significant impact of trust in government on citizens' beliefs that .... about a quarter of Nigeria's total gross domestic product, in the face of oil ... 40.0. 10.0. 100.0. Religion. Christianity. Islam. Traditional/Others. Total. 180.
Within salvation: girl hawkers and the colonial state in development era Lagos.
George, Abosede
2011-01-01
For almost two decades between the close of the Second World War and Nigerian independence in 1960, the British colonial state which faced a crisis of legitimacy in Lagos upheld city ordinances that made itinerant trading by young children in Lagos a punishable status offense. Although anti-trading regulations were gender-neutral in their language, girls were disproportionately sanctioned for engaging in street trading and related activities. In defending their concentration on girl sellers over boy sellers, colonial welfare officials painted a picture of the urban context as an inherently dangerous context and of girls as being particularly at risk of violent assault in the city, making them particularly in need of protection from town life. Sources which show that parents generally resisted or ignored the street trading regulations and continued permitting their daughters to sell despite entreaties, warnings, or fines from colonial officials, suggest that African parents and British colonial officials may have had conflicting views on the inherent danger of the city, on what constituted child endangerment, and on the gendered nature of childhood. This article argues that the girl saving campaigns of development era Lagos were as much about the legitimization of a colonial state facing a crisis of legitimacy as they were about debates between African parents and colonial welfare officials in Lagos concerning ideas of children and childhood and the dangers of street trading by African girls.
Coastal Dump Sites in the Lagos lagoon and toxicity of their ...
African Journals Online (AJOL)
An assessment of the coastal dumpsites and their impacts on shrimp mortality in the Lagos lagoon was investigated. The study involved a census of dumpsites in the major sections of the coastline associated with anthropogenic activities, followed by specific bioassay to determine the acute toxicity of leachates from one of ...
The Succession Dispute to the Throne of Lagos and the British ...
African Journals Online (AJOL)
info
the early years of his reign Adele won popularity by making lavish gifts to his chiefs. This royal largesse ..... thousand followers had left Lagos in about fifty or sixty canoes to Badone, a village on ..... their influence in a more spectacular fashion.
Ocular findings seen among the staff of an institution in Lagos, Nigeria
African Journals Online (AJOL)
Background:The degree to which ocular morbidity affects workers productivity in the developing countries has not been studied adequately. A federal government research institute based in Lagos introduced an annual health screen for all its workers, which included eye tests. This provided an opportunity to study the ...
Transnational business and family strategies among Chinese/Nigerian couples in Guangzhou and Lagos
Lan, S.
2015-01-01
Based on ethnographic fieldwork in Guangzhou and Lagos, this paper explores transnational trade activities and family strategies among Chinese/Nigerian interracial couples in the context of growing China/Africa trade relations and the recent tightening of China's immigration control. It examines how
Long stay patients in a psychiatric hospital in Lagos, Nigeria | Taiwo ...
African Journals Online (AJOL)
Objective: In the face of recently introduced government health reform and the dwindling number of available beds for acutely ill patients, a cross sectional study was carried out on long-stay patients at the 100 years old psychiatric hospital Yaba, Lagos, Nigeria with a view to discharging most of them. Method: Necessary ...
Reparación del cartílago articular con injerto libre de pericondrio estudio experimental
Ballesteros Vazquez, P.; Carranza Bencano, Andrés; Armas Padrón, J. R.; Saenz López de Rueda, F.
1994-01-01
Ante la incapacidad de regeneración espontánea de lesiones profundas y amplias del cartílago articular, estudiamos la reparación cartilaginosa con plastias de pericondrio tomadas de la región condro-costal e implantándolas con su cara condrogénica sobre una lesión osteocondral realizada en la superficie articular rotuliana. Macroscópica e histológicamente, a la octava semana, el neocartílago formado tenía igual apariencia que el cartílago hialino normal, no existiendo separació...
Virtual Singular Scattering of Electromagnetic Waves in Transformation Media Concept
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M. Y. Barabanenkov
2012-07-01
Full Text Available If a scatterer and an observation point (receive both approach the so-called near field zone of a source of electromagnetic waves, the scattering process becomes singular one which is mathematically attributed to the spatial singularity of the free space Green function at the origin. Starting from less well known property of left-handed material slab to transfer the singularity of the free space Green function by implementing coordinate transformation, we present a phenomenon of virtual singular scattering of electromagnetic wave on an inhomogeneity located in the volume of left – handed material slab. Virtual singular scattering means that a scatterer is situated only virtually in the near field zone of a source, being, in fact, positioned in the far field zone. Such a situation is realized if a scatterer is embedded into a flat Veselago’s lens and approaches the lens’s inner focus because a slab of Veselago medium produces virtual sources inside and behind the slab and virtual scatterer (as a source of secondary waves from both slab sides. Considering a line-like dielectric scatterer we demonstrate that the scattering efficiency is proportional to product of singular quasistatic parts of two empty space Green functions that means a multiplicative quasistatic singularity of the Green function for a slab of inhomogeneous Veselago medium. We calculate a resonance value of the scattering amplitude in the regime similar to the known Mie resonance scattering.
Solutions of dissimilar material singularity and contact problems
International Nuclear Information System (INIS)
Yang, Y.
2003-09-01
Due to the mismatch of the material properties of joined components, after a homogeneous temperature change or under a mechanical loading, very high stresses occur near the intersection of the interface and the outer surface, or near the intersection of two interfaces. For most material combinations and joint geometries, there exists even a stress singularity. These high stresses may cause fracture of the joint. The investigation of the stress situation near the singular point, therefore, is of great interest. Especially, the relationship between the singular stress exponent, the material data and joint geometry is important for choosing a suitable material combination and joint geometry. In this work, the singular stress field is described analytically in case of the joint having a real and a complex eigenvalue. Solutions of different singularity problems are given, which are two dissimilar materials joint with free edges; dissimilar materials joint with edge tractions; joint with interface corner; joint with a given displacement at one edge; cracks in dissimilar materials joint; contact problem in dissimilar materials and logarithmic stress singularity. For an arbitrary joint geometry and material combination, the stress singular exponent, the angular function and the regular stress term can be calculated analytically. The stress intensity factors for a finite joint can be determined applying numerical methods, e.g. the finite element method (FEM). The method to determine more than one stress intensity factor is presented. The characteristics of the eigenvalues and the stress intensity factors are shown for different joint conditions. (orig.)
Boundary singularities produced by the motion of soap films.
Goldstein, Raymond E; McTavish, James; Moffatt, H Keith; Pesci, Adriana I
2014-06-10
Recent work has shown that a Möbius strip soap film rendered unstable by deforming its frame changes topology to that of a disk through a "neck-pinching" boundary singularity. This behavior is unlike that of the catenoid, which transitions to two disks through a bulk singularity. It is not yet understood whether the type of singularity is generally a consequence of the surface topology, nor how this dependence could arise from an equation of motion for the surface. To address these questions we investigate experimentally, computationally, and theoretically the route to singularities of soap films with different topologies, including a family of punctured Klein bottles. We show that the location of singularities (bulk or boundary) may depend on the path of the boundary deformation. In the unstable regime the driving force for soap-film motion is the mean curvature. Thus, the narrowest part of the neck, associated with the shortest nontrivial closed geodesic of the surface, has the highest curvature and is the fastest moving. Just before onset of the instability there exists on the stable surface the shortest closed geodesic, which is the initial condition for evolution of the neck's geodesics, all of which have the same topological relationship to the frame. We make the plausible conjectures that if the initial geodesic is linked to the boundary, then the singularity will occur at the boundary, whereas if the two are unlinked initially, then the singularity will occur in the bulk. Numerical study of mean curvature flows and experiments support these conjectures.
Quantum healing of classical singularities in power-law spacetimes
Energy Technology Data Exchange (ETDEWEB)
Helliwell, T M [Department of Physics, Harvey Mudd College, Claremont, CA 91711 (United States); Konkowski, D A [Department of Mathematics, US Naval Academy, Annapolis, MD 21402 (United States)
2007-07-07
We study a broad class of spacetimes whose metric coefficients reduce to powers of a radius r in the limit of small r. Among these four-parameter 'power-law' metrics, we identify those parameters for which the spacetimes have classical singularities as r {yields} 0. We show that a large set of such classically-singular spacetimes is nevertheless non-singular quantum mechanically, in that the Hamiltonian operator is essentially self-adjoint, so that the evolution of quantum wave packets lacks the ambiguity associated with scattering off singularities. Using these metrics, the broadest class yet studied to compare classical with quantum singularities, we explore the physical reasons why some that are singular classically are 'healed' quantum mechanically, while others are not. We show that most (but not all) of the remaining quantum-mechanically singular spacetimes can be excluded if either the weak energy condition or the dominant energy condition is invoked, and we briefly discuss the effect of this work on the strong cosmic censorship conjecture.
A clinicopathological study of dyspeptic subjects in Lagos, Nigeria
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Ladi Hameed
2012-05-01
Full Text Available The clinicopathological and endoscopic features of dyspepsia have not been well studied in Nigeria due to the high cost of gastroscopes and lack of the relevant expertise. This study was designed to highlight these features and possible risk factors. This prospective study was conducted on adult dyspeptic patients who fulfilled the study criteria from November 2007 to December 2008 at a University hospital in Lagos, Nigeria. Demographic and clinical presentation including possible risk factors were obtained through a questionnaire administered by an interviewer followed by an upper gastrointestinal endoscopy and gastric biopsy. Of the 123 subjects who took part in the study, 100 gave their consent to an upper gastrointestinal endoscopy and biopsy. The male:female ratio was 1:1, mean age was 44.98 (SD 15.4 years and the modal age group was 38-47years. The prevalence of dyspepsia was 29% and epigastric pain was the most common presentation. Endoscopic findings were superficial mucosal lesion (21%, peptic ulcer (16%, features of gastroesophageal reflux disease (10%, and gastric cancer (2%, as well normal findings (44%. Non-steroidal antiinflammatory drug (NSAID use as a risk factor had a significant association with positive endoscopic findings; relative risk for development of positive endoscopic findings was 1.5% (P =0.03. Histology showed rates of chronic gastritis to be 91% and normal values 9%. The most common type of gastritis was the non-specific form (59.3%, followed by H. Pylori-associated gastritis (36.3%. The topography of gastritis was mainly pangastritis (68.1% and antral predominant in 23.1%. The prevalence of H. pylori by histology was 41%. The presence of H. pylori was not associated with severity, location or duration of symptoms. H. pylori was, however, found to be a significant contributor to the development of positive endoscopic findings (P=0.01; OR 2.92 95% CI 1.50-3.17. Alarm symptoms were found to be important markers of
Diverticular disease at colonoscopy in Lagos State, Nigeria.
Oluyemi, Aderemi; Odeghe, Emuobor
2016-01-01
The upsurge in the reported cases of diverticular disease (DD) has led to a re-appraisal of the earlier held views that it was a rare entity in Nigeria. The advent of colonoscopy has contributed in no small way to this change. We sought to determine the clinical characteristics, indications for colonoscopy, and intra-procedural findings among these patients. A retrospective cross-sectional study was carried out on the colonoscopy records from four private endoscopy units based in Lagos State, Nigeria. The records were drawn from a 5-year period (August 2010 to July 2015). The endoscopy logs and reports were reviewed, and the bio data, indications, and colonoscopy findings were gleaned. A total of 265 colonoscopies were carried out in the stated period. Of these, 28 (10.6%) had DD. Of the patients with DD, 5 (17.9%) were females while 23 (82.1%) were males. Their ages ranged from 46 to 94 years (mean = 68.2 ± 11 years). Fifteen patients had been referred for the procedure on account of hematochezia alone (15 = 53.6%). Other reasons for referral included abdominal pain alone (2 = 7%), hematochezia plus abdominal pain (5 = 17.9%), and change in bowel habits (3 = 10.8%). Ten (35%) patients had pan-colonic involvement. Regional disease involved the right side alone in only one case (3.5%) while the other combinations of sites are as follows; 6 (21.4%) in the sigmoid colon alone, 2 (7%) in the descending colon alone, 5 (17.9%) in the sigmoid-descending colon, 4 (14.3%) in the sigmoid-descending-transverse colon, thus the sigmoid colon was involved in 25 (89.3%) cases. Five cases (17.9%) had endoscopic features suggestive of diverticulitis. DD should no longer be regarded as a rare problem in the Nigerian patient. The study findings support the notion of higher prevalence among the elderly, in males, and of sigmoid colon involvement.
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Adeteju A Adedini
2016-01-01
Full Text Available Background and Objective: According to the World Health Organization, the number of obese children would increase to 70 million by 2025 if no intervention is made. An increase in the prevalence of overweight and obesity among school children in Lagos State, Nigeria has been established, but specific factors promoting its prevalence are unknown. The aim of this study was to elicit the views of stakeholders on the perceived causes for the rise in child overweight and obesity. Methods: Five focus group discussions were conducted with different groups of stakeholders involved in child care, namely: Parents, teachers, and healthcare givers. Participants were recruited using a purposive sampling method; a structured question guide was employed for the discussion sessions. The discussions were recorded, collated, and analyzed using grounded theory to extract themes. Results: Six themes emerged as factors responsible for the rise, of which civilization and lifestyle imbalance of the populace emerged as the prominent cause. Of the fifty respondents, 76% of respondents identified parents (particularly young mothers as major contributors to the prevalence of overweight and obesity in children of Lagos State; and 52.3% of the participants reported that a direct relationship exists between income class of parent and weight of a child resident in Lagos. Conclusion: Civilization and lifestyle imbalance, insecurity and congestion, low level of public awareness, inadequate educative and enlightenment programs, myths and societal perception were factors identified to responsible for the rise in the prevalence of child obesity in Lagos, Nigeria. Preventive strategies to control the prevalence of overweight and obesity in children residing in Lagos State should be considered for further studies.
The realities of Lagos urban development vision on livelihoods of the urban poor
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Oluwafemi Ayodeji Olajide
2018-04-01
Full Text Available Similar to many other cities in sub-Saharan African countries, the struggle between urban development policies and the livelihoods of the urban poor is one of the urban development challenges facing Lagos. This paper examines the realities of the Lagos urban development policies and intiatives on the livelihoods of the urban poor. The state government embarked on series of what it calls sustainable urban transformation policies towards making Lagos ‘an African model megacity’ and a global economic and financial hub that is safe, secure, functional and productive, with a view to achieving poverty alleviation and sustainable development. This paper, through the lens of theoretical and analytical underpinnings of Sustainable Livelihoods Framework, however, argues that the actions of the state government contradict the whole essence of sustainable urban development and poverty alleviation, but reflect an agenda deliberately targeted to further impoverish the poor. While the Sustainable Livelihood was used as the theoretical and analytical framework, this paper essentially focuses on the Policies, Institutions and Processes component of the framework. This provides a unique entry point for understanding the implications of the Lagos urban development aspirations on the livelihoods of the urban poor. The research uses mixed methods research design with a broad range of data-collection methods, including household surveys, interviews, direct observation and photography, documentary review and policy document analysis. The study reveals that there is a disconnection between urban development policies and realities of the poor. The implementation of urban development projects and policies works against the urban poor and resulted in more hardship, through reduction in livelihood opportunities or complete loss of livelihoods. This study, therefore, suggests that one important element in reducing poverty in Lagos’ informal settlements is a policy
Assessing the deep drilling potential of Lago de Tota, Colombia, with a seismic survey
Bird, B. W.; Wattrus, N. J.; Fonseca, H.; Velasco, F.; Escobar, J.
2015-12-01
Reconciling orbital-scale patterns of inter-hemispheric South American climate during the Quaternary requires continuous, high-resolution paleoclimate records that span multiple glacial cycles from both hemispheres. Southern Andean Quaternary climates are represented by multi-proxy results from Lake Titicaca (Peru-Bolivia) spanning the last 400 ka and by pending results from the Lago Junin Drilling Project (Peru). Although Northern Andean sediment records spanning the last few million years have been retrieved from the Bogota and Fúquene Basins in the Eastern Cordillera of the Colombian Andes, climatic reconstructions based on these cores have thus far been limited to pollen-based investigations. When viewed together with the Southern Hemisphere results, these records suggest an anti-phased hemispheric climatic response during glacial cycles. In order to better assess orbital-scale climate responses, however, independent temperature and hydroclimate proxies from the Northern Hemisphere are needed in addition to vegetation histories. As part of this objective, an effort is underway to develop a paleoclimate record from Lago de Tota (3030 m asl), the largest lake in Colombia and the third largest lake in the Andes. One of 17 highland tectonic basins in Eastern Cordillera, Lago de Tota formed during Tertiary uplift that deformed pre-foreland megasequences, synrift and back-arc megasequences. The precise age and thickness of sediments in the Lago de Tota basin has not previously been established. Here, we present results from a recent single-channel seismic reflection survey collected with a small (5 cubic inch) air gun and high-resolution CHIRP sub-bottom data. With these data, we examine the depositional history and sequence stratigraphy of Lago de Tota and assess its potential as a deep drilling target.
Sedimentation survey of Lago Cerrillos, Ponce, Puerto Rico, April-May 2008
Soler-López, Luis R.
2011-01-01
Lago Cerrillos dam, located in the municipality of Ponce in southern Puerto Rico, was constructed in 1991 as part of the multipurpose Rio Portugues and Bucana Project. This project provides flood protection, water supply, and recreation facilities for the municipio of Ponce. The reservoir had an original storage capacity of 38.03 million cubic meters at maximum conservation pool elevation of 174.65 meters above mean sea level and a drainage area of 45.32 square kilometers. Sedimentation in Lago Cerrillos reservoir has reduced the storage capacity from 38.03 million cubic meters in 1991 to 37.26 million cubic meters in 2008, which represents a total storage loss of about 2 percent. During July 29 to August 23, 2002, 8,492 cubic meters of sediment were removed from the Rio Cerrillos mouth of the reservoir. Taking into account this removed material, the total water-storage loss as of 2008 is 778,492 cubic meters, and the long-term annual water-storage capacity loss rate is about 45,794 cubic meters per year or about 0.12 percent per year. The Lago Cerrillos net sediment-contributing drainage area has an average sediment yield of about 1,069 cubic meters per square kilometer per year. Sediment accumulation in Lago Cerrillos is not uniformly distributed and averages about 3 meters in thickness. This represents a sediment deposition rate of about 18 centimeters per year. On the basis of the 2008 reservoir storage capacity of 37.26 million cubic meters per year and a long-term sedimentation rate of 45,794 cubic meters per year, Lago Cerrillos is estimated to have a useful life of about 814 years or until the year 2822.
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Ezenwa BN
2013-07-01
Full Text Available Beatrice N Ezenwa,1 Mobolanle R Balogun,2 Ifeoma P Okafor2 1Department of Pediatrics, 68 Nigerian Army Reference Hospital, Lagos State, Nigeria; 2Department of Community Health and Primary Care, College of Medicine, University of Lagos, Lagos State, Nigeria Introduction: Human papillomavirus (HPV is one of the most common sexually transmitted infections in sexually active adolescents and young women and has been implicated as a cause of the majority of cases of cervical cancer, which is the second most common cancer in women in Nigeria. HPV is preventable with the use of HPV vaccines. Objectives: The objective of this study was to assess mothers' HPV knowledge and their willingness to vaccinate their adolescent daughters in Lagos, Nigeria. Materials and methods: This study was a community-based, descriptive cross-sectional study carried out in July, 2012 in Shomolu Local Government Area (LGA of Lagos State, Nigeria. Multistage sampling method was employed to select the 290 respondents who participated in the study. Structured, pretested, interviewer-administered questionnaires were used for data collection. Data was analyzed with Epi-Info™ version 7. Results: The study revealed low awareness of HPV (27.9% and HPV vaccines (19.7% among the mothers that participated. There was a high awareness for cervical cancer but little knowledge of its link to HPV. Awareness and utilization of HPV vaccines increased with increasing educational level (P<0.05. There was a high willingness and intention among the mothers to vaccinate their girls (88.9% and to recommend the vaccine to others (91.0%. Accessibility and affordability of the HPV vaccines were found to be possible barriers to future utilization of the vaccines. Conclusion: Despite low knowledge about HPV and HPV vaccines, mothers were willing to vaccinate their daughters. We recommend improving mothers' knowledge by education and the possible inclusion of the vaccine in the national immunization
The Effect of Manpower Planning and Development in Lagos State (Nigeria Civil Service Performance
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Chinyeaka J. Igbokwe-Ibeto
2015-12-01
Full Text Available The study examined effects of manpower planning and development in Lagos state civil service performance. Lagos state civil service is the greatest asset of the state in its quest for socio-economic development. The primary question that was explored is whether the nature of manpower planning and development curriculum in Lagos state civil service has effect on the service performance and the attainment of state objective. The study relied on primary and secondary data, and multiple stage sampling technique was used to select the sample population. The data collected was presented in frequency bar chart and simple percentage. Pearson’s Product Moment Correlation Coefficient (PPMC statistical tool was used to test the hypotheses. Findings of the study show that the nature of manpower planning and development curriculum has a positive effect on the Lagos state civil performance. It also reveals that the manpower planning and development has a positive effect on the attainment of Lagos state objective. To achieve better performance in the service, it should among others, improve on the current manpower planning strategy and continue to update its manpower development curriculum in line with the global best practices. Given the pivotal role that technology plays in the 21st century, the service should avail itself the windows of opportunities that information technology provides in its drive to enhance employees’ skills, knowledge and abilities that will invariably improve the service performance. Yet, the service should imbibe the prescripts of New PublicManagement theory (NPM, and that goals and targets should be defined and measurable as indicators of organizational performance.
Tangled nonlinear driven chain reactions of all optical singularities
Vasil'ev, V. I.; Soskin, M. S.
2012-03-01
Dynamics of polarization optical singularities chain reactions in generic elliptically polarized speckle fields created in photorefractive crystal LiNbO3 was investigated in details Induced speckle field develops in the tens of minutes scale due to photorefractive 'optical damage effect' induced by incident beam of He-Ne laser. It was shown that polarization singularities develop through topological chain reactions of developing speckle fields driven by photorefractive nonlinearities induced by incident laser beam. All optical singularities (C points, optical vortices, optical diabolos,) are defined by instantaneous topological structure of the output wavefront and are tangled by singular optics lows. Therefore, they have develop in tangled way by six topological chain reactions driven by nonlinear processes in used nonlinear medium (photorefractive LiNbO3:Fe in our case): C-points and optical diabolos for right (left) polarized components domains with orthogonally left (right) polarized optical vortices underlying them. All elements of chain reactions consist from loop and chain links when nucleated singularities annihilated directly or with alien singularities in 1:9 ratio. The topological reason of statistics was established by low probability of far enough separation of born singularities pair from existing neighbor singularities during loop trajectories. Topology of developing speckle field was measured and analyzed by dynamic stokes polarimetry with few seconds' resolution. The hierarchy of singularities govern scenario of tangled chain reactions was defined. The useful space-time data about peculiarities of optical damage evolution were obtained from existence and parameters of 'islands of stability' in developing speckle fields.
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CORTÉS-PÉREZ FRANCISCO
2003-12-01
Full Text Available Se presentan algunos aspectos del ciclo de vida de la hormiga arriera Atta laevigata,en especial el vuelo nupcial, con notas ecológicas de interés, el perfil modal desuelos afectados por la actividad de las arrieras y se analiza su contenido denutrientes. Se detalla el funcionamiento y la estructura de las colonias de arrierascon especial énfasis en el transporte y la acumulación de nutrientes y semillas en lossitios de establecimiento de la colonia; se explica el establecimiento de las matas demonte a partir de estos sitios ricos en nutrientes y semillas. Con base en estosaspectos se plantea un modelo funcional del papel que cumplen las colonias dearrieras en los ecosistemas de sabana estacional.
León, Juan Diego; González, María Isabel; Gallardo, Juan Fernando
2011-01-01
La caída y descomposición de hojarasca representan los principales ingresos de materia orgánica y nutrientes a los ecosistemas forestales. Se estudiaron la caída y acumulación de hojarasca fina y el retorno de nutrientes, en un robledal (Quercus humboldtii) y en plantaciones de pino (Pinus patula) y ciprés (Cupressus lusitanica) en tierras altas de Colombia. La caída de hojarasca fina fue similar entre el robledal (7.5Mg/ha.a) y el pinar (7.8Mg/ha.a), y muy inferior en el cipresal (3.5Mg/ha.a...
From Fourier Transforms to Singular Eigenfunctions for Multigroup Transport
International Nuclear Information System (INIS)
Ganapol, B.D.
2001-01-01
A new Fourier transform approach to the solution of the multigroup transport equation with anisotropic scattering and isotropic source is presented. Through routine analytical continuation, the inversion contour is shifted from the real line to produce contributions from the poles and cuts in the complex plane. The integrand along the branch cut is then recast in terms of matrix continuum singular eigenfunctions, demonstrating equivalence of Fourier transform inversion and the singular eigenfunction expansion. The significance of this paper is that it represents the initial step in revealing the intimate connection between the Fourier transform and singular eigenfunction approaches as well as serves as a basis for a numerical algorithm
Repulsive and attractive timelike singularities in vacuum cosmologies
International Nuclear Information System (INIS)
Miller, B.D.
1979-01-01
Spherically symmetric cosmologies whose big bang is partially spacelike and partially timelike are constrained to occur only in the presence of certain types of matter, and in such cosmologies the timelike part of the big bang is a negative-mass singularity. In this paper examples are given of cylindrically symmetric cosmologies whose big bang is partially spacelike and partially timelike. These cosmologies are vacuum. In some of them, the timelike part of the big bang is clearly a (generalized) negative-mass singularity, while in others it is a (generalized) positive-mass singularity
On the singular perturbations for fractional differential equation.
Atangana, Abdon
2014-01-01
The goal of this paper is to examine the possible extension of the singular perturbation differential equation to the concept of fractional order derivative. To achieve this, we presented a review of the concept of fractional calculus. We make use of the Laplace transform operator to derive exact solution of singular perturbation fractional linear differential equations. We make use of the methodology of three analytical methods to present exact and approximate solution of the singular perturbation fractional, nonlinear, nonhomogeneous differential equation. These methods are including the regular perturbation method, the new development of the variational iteration method, and the homotopy decomposition method.
An investigation of singular Lagrangians as field systems
International Nuclear Information System (INIS)
Rabei, E.M.
1995-07-01
The link between the treatment of singular Lagrangians as field systems and the general approach is studied. It is shown that singular Lagrangians as field systems are always in exact agreement with the general approach. Two examples and the singular Lagrangian with zero rank Hessian matrix are studied. The equations of motion in the field systems are equivalent to the equations which contain acceleration, and the constraints are equivalent to the equations which do not contain acceleration in the general approach treatment. (author). 10 refs
Singularity, initial conditions and quantum tunneling in modern cosmology
International Nuclear Information System (INIS)
Khalatnikov, I M; Kamenshchik, A Yu
1998-01-01
The key problems of modern cosmology, such as the cosmological singularity, initial conditions, and the quantum tunneling hypothesis, are discussed. The relationship between the latest cosmological trends and L D Landau's old ideas is analyzed. Particular attention is given to the oscillatory approach to singularity; quantum tunneling processes determining wave function of the Universe in the presence of a compex scalar field; and the role of quantum corrections in these processes. The classical dynamics of closed models with a real scalar field is investigated from the standpoint of chaotic, fractal, and singularity-avoiding properties. (special issue)
On the Singular Perturbations for Fractional Differential Equation
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Abdon Atangana
2014-01-01
Full Text Available The goal of this paper is to examine the possible extension of the singular perturbation differential equation to the concept of fractional order derivative. To achieve this, we presented a review of the concept of fractional calculus. We make use of the Laplace transform operator to derive exact solution of singular perturbation fractional linear differential equations. We make use of the methodology of three analytical methods to present exact and approximate solution of the singular perturbation fractional, nonlinear, nonhomogeneous differential equation. These methods are including the regular perturbation method, the new development of the variational iteration method, and the homotopy decomposition method.
Finger image quality based on singular point localization
DEFF Research Database (Denmark)
Wang, Jinghua; Olsen, Martin A.; Busch, Christoph
2014-01-01
Singular points are important global features of fingerprints and singular point localization is a crucial step in biometric recognition. Moreover the presence and position of the core point in a captured fingerprint sample can reflect whether the finger is placed properly on the sensor. Therefore...... and analyze the importance of singular points on biometric accuracy. The experiment is based on large scale databases and conducted by relating the measured quality of a fingerprint sample, given by the positions of core points, to the biometric performance. The experimental results show the positions of core...
Naked singularities in higher dimensional Vaidya space-times
International Nuclear Information System (INIS)
Ghosh, S. G.; Dadhich, Naresh
2001-01-01
We investigate the end state of the gravitational collapse of a null fluid in higher-dimensional space-times. Both naked singularities and black holes are shown to be developing as the final outcome of the collapse. The naked singularity spectrum in a collapsing Vaidya region (4D) gets covered with the increase in dimensions and hence higher dimensions favor a black hole in comparison to a naked singularity. The cosmic censorship conjecture will be fully respected for a space of infinite dimension
Directory of Open Access Journals (Sweden)
Rocio Becerril-Piña
2014-01-01
Full Text Available En las últimas décadas se han propuesto diversas ecuaciones alométricas (EA para especies tropicales y subtropicales a fin de estimar el contenido de carbono (CC en la biomasa aérea, sin embargo, los ecosistemas semiáridos han sido poco estudiados a pesar de constituir cerca del 40 % de la superficie de México. El objetivo de este estudio fue desarrollar EA para determinar el CC en la biomasa aérea en mezquite (Prosopis laevigata, huizache (Acacia farnesiana y herbáceas representativas de una región semiárida del centro del país. Se seleccionaron y muestrearon por método destructivo cinco individuos de cada especie para estimar biomasa seca total y por componente (hojas, ramas y fuste, los cuales se correlacionaron con parámetros de fácil medición en campo: cobertura de la copa, radio de la copa, altura total y volumen, encontrándose valores de R2 entre 0.96 y 0.80 dependiendo de la especie. Mediante información satelital se estimó la distribución espacial del CC en la Cuenca Dolores Hidalgo (Guanajuato, localizada en la región semiárida del centro de México. La cobertura vegetal del área de estudio se reclasificó en tres tipos: abierta, semiabierta y cerrada. El contenido de carbono en la cobertura abierta fue de 2.4 Mg C ha-1, semiabierta 10.26 Mg C ha-1 y cerrada de 21.20 Mg C ha-1. Los resultados sugieren que los ecosistemas semiáridos de la zona central de México representan un potencial considerable como sumideros de carbono con un promedio de 11 Mg C ha-1.
Singular Value Decomposition and Ligand Binding Analysis
Directory of Open Access Journals (Sweden)
André Luiz Galo
2013-01-01
Full Text Available Singular values decomposition (SVD is one of the most important computations in linear algebra because of its vast application for data analysis. It is particularly useful for resolving problems involving least-squares minimization, the determination of matrix rank, and the solution of certain problems involving Euclidean norms. Such problems arise in the spectral analysis of ligand binding to macromolecule. Here, we present a spectral data analysis method using SVD (SVD analysis and nonlinear fitting to determine the binding characteristics of intercalating drugs to DNA. This methodology reduces noise and identifies distinct spectral species similar to traditional principal component analysis as well as fitting nonlinear binding parameters. We applied SVD analysis to investigate the interaction of actinomycin D and daunomycin with native DNA. This methodology does not require prior knowledge of ligand molar extinction coefficients (free and bound, which potentially limits binding analysis. Data are acquired simply by reconstructing the experimental data and by adjusting the product of deconvoluted matrices and the matrix of model coefficients determined by the Scatchard and McGee and von Hippel equation.
Singular limits in thermodynamics of viscous fluids
Feireisl, Eduard
2017-01-01
This book is about singular limits of systems of partial differential equations governing the motion of thermally conducting compressible viscous fluids. "The main aim is to provide mathematically rigorous arguments how to get from the compressible Navier-Stokes-Fourier system several less complex systems of partial differential equations used e.g. in meteorology or astrophysics. However, the book contains also a detailed introduction to the modelling in mechanics and thermodynamics of fluids from the viewpoint of continuum physics. The book is very interesting and important. It can be recommended not only to specialists in the field, but it can also be used for doctoral students and young researches who want to start to work in the mathematical theory of compressible fluids and their asymptotic limits." Milan Pokorný (zbMATH) "This book is of the highest quality from every point of view. It presents, in a unified way, recent research material of fundament al importance. It is self-contained, thanks to Chapt...
Singularity fitting in hydrodynamical calculations II
International Nuclear Information System (INIS)
Richtmyer, R.D.; Lazarus, R.B.
1975-09-01
This is the second report in a series on the development of techniques for the proper handling of singularities in fluid-dynamical calculations; the first was called Progress Report on the Shock-Fitting Project. This report contains six main results: derivation of a free-surface condition, which relates the acceleration of the surface with the gradient of the square of the sound speed just behind it; an accurate method for the early and middle stages of the development of a rarefaction wave, two orders of magnitude more accurate than a simple direct method used for comparison; the similarity theory of the collapsing free surface, where it is shown that there is a two-parameter family of self-similar solutions for γ = 3.9; the similarity theory for the outgoing shock, which takes into account the entropy increase; a ''zooming'' method for the study of the asymptotic behavior of solutions of the full initial boundary-value problem; comparison of two methods for determining the similarity parameter delta by zooming, which shows that the second method is preferred. Future reports in the series will contain discussions of the self-similar solutions for this problem, and for that of the collapsing shock, in more detail and for the full range (1, infinity) of γ; the values of certain integrals related to neutronic and thermonuclear rates near collapse; and methods for fitting shocks, contact discontinuities, interfaces, and free surfaces in two-dimensional flows
Singular perturbation in the physical sciences
Neu, John C
2015-01-01
This book is the testimony of a physical scientist whose language is singular perturbation analysis. Classical mathematical notions, such as matched asymptotic expansions, projections of large dynamical systems onto small center manifolds, and modulation theory of oscillations based either on multiple scales or on averaging/transformation theory, are included. The narratives of these topics are carried by physical examples: Let's say that the moment when we "see" how a mathematical pattern fits a physical problem is like "hitting the ball." Yes, we want to hit the ball. But a powerful stroke includes the follow-through. One intention of this book is to discern in the structure and/or solutions of the equations their geometric and physical content. Through analysis, we come to sense directly the shape and feel of phenomena. The book is structured into a main text of fundamental ideas and a subtext of problems with detailed solutions. Roughly speaking, the former is the initial contact between mathematics and p...
International Nuclear Information System (INIS)
Bamba, Kazuharu; Odintsov, Sergei D.; Sebastiani, Lorenzo; Zerbini, Sergio
2010-01-01
We study all four types of finite-time future singularities emerging in the late-time accelerating (effective quintessence/phantom) era from F(R,G)-gravity, where R and G are the Ricci scalar and the Gauss-Bonnet invariant, respectively. As an explicit example of F(R,G)-gravity, we also investigate modified Gauss-Bonnet gravity, so-called F(G)-gravity. In particular, we reconstruct the F(G)-gravity and F(R,G)-gravity models where accelerating cosmologies realizing the finite-time future singularities emerge. Furthermore, we discuss a possible way to cure the finite-time future singularities in F(G)-gravity and F(R,G)-gravity by taking into account higher-order curvature corrections. The example of non-singular realistic modified Gauss-Bonnet gravity is presented. It turns out that adding such non-singular modified gravity to singular Dark Energy makes the combined theory a non-singular one as well. (orig.)
Ostrácodos no-marinos de lagos en el altiplano este-centro de México
Directory of Open Access Journals (Sweden)
Liseth Pérez
2015-06-01
Full Text Available La fauna de ostrácodos de la zona de transición néartica-neotropical ha sido poco estudiada hasta este estudio. En el este-centro de México, habitan diez especies de ostrácodos en diez lagos: cinco lagos maar (originados por explosiones freáticas/freato-magmáticas, un lago volcánico-tectónico, tres embalses naturales y un embalse artificial. De la parte más profunda y de las zonas litorales de todos los lagos estudiados se recolectaron sedimentos superficiales para el análisis de ostrácodos. También se midieron in situ las variables ambientales: pH, temperatura, oxígeno disuelto, conductividad, SDT, además se recolectaron muestras de agua paralelas para análisis químico con el objetivo de describir el hábitat. Especies con una amplia distribución en el área de estudio (≥5 lagos incluyen: Cypridopsis vidua, Darwinula stevensoni y Eucandona cf. patzcuaro. Limnocytherina axalapasco es una especie endémica y fue recolectada en tres lagos maar y en el embalse artificial. Especies raras incluyeron: Chlamydotheca arcuata?, Fabaeformiscandona acuminata?, Ilyocypris gibba?, Limnocythere friabilis?, Potamocypris smaragdina? y Potamocypris unicaudata? La riqueza de especies más alta (6 spp. se encontró en el lago más extenso y somero, lago Metztitlán (2.6km², 5.5m de profundidad, con el tipo de agua HCO3->>SO4²->Cl--- Ca2+>Na+>Mg2+. El resto de lagos estudiados (<63m, <27km² presentaron no más de tres especies. Por ejemplo, solamente dos especies de ostrácodos fueron recolectadas en el lago Alchichica, el cual es el más extenso, profundo y salino entre los lagos maar estudiados.
Dam failure analysis for the Lago El Guineo Dam, Orocovis, Puerto Rico
Gómez-Fragoso, Julieta; Heriberto Torres-Sierra,
2016-08-09
The U.S. Geological Survey, in cooperation with the Puerto Rico Electric Power Authority, completed hydrologic and hydraulic analyses to assess the potential hazard to human life and property associated with the hypothetical failure of the Lago El Guineo Dam. The Lago El Guineo Dam is within the headwaters of the Río Grande de Manatí and impounds a drainage area of about 4.25 square kilometers.The hydrologic assessment was designed to determine the outflow hydrographs and peak discharges for Lago El Guineo and other subbasins in the Río Grande de Manatí hydrographic basin for three extreme rainfall events: (1) a 6-hour probable maximum precipitation event, (2) a 24-hour probable maximum precipitation event, and (3) a 24-hour, 100-year recurrence rainfall event. The hydraulic study simulated a dam failure of Lago El Guineo Dam using flood hydrographs generated from the hydrologic study. The simulated dam failure generated a hydrograph that was routed downstream from Lago El Guineo Dam through the lower reaches of the Río Toro Negro and the Río Grande de Manatí to determine water-surface profiles developed from the event-based hydrologic scenarios and “sunny day” conditions. The Hydrologic Engineering Center’s Hydrologic Modeling System (HEC–HMS) and Hydrologic Engineering Center’s River Analysis System (HEC–RAS) computer programs, developed by the U.S. Army Corps of Engineers, were used for the hydrologic and hydraulic modeling, respectively. The flow routing in the hydraulic analyses was completed using the unsteady flow module available in the HEC–RAS model.Above the Lago El Guineo Dam, the simulated inflow peak discharges from HEC–HMS resulted in about 550 and 414 cubic meters per second for the 6- and 24-hour probable maximum precipitation events, respectively. The 24-hour, 100-year recurrence storm simulation resulted in a peak discharge of about 216 cubic meters per second. For the hydrologic analysis, no dam failure conditions are
Singularly perturbed Burger-Huxley equation: Analytical solution ...
African Journals Online (AJOL)
user
numbers, Navier-Stokes flows with large Reynolds numbers, chemical reactor ... It is to observe the layer behavior of the solution for smaller values of ε leading to singular ...... Burger equation, momentum gas equation and heat equation.
Coulomb singularity effects in tunnelling spectroscopy of individual impurities
Arseyev, P. I.; Maslova, N. S.; Panov, V. I.; Savinov, S. V.
2002-01-01
Non-equilibrium Coulomb effects in resonant tunnelling processes through deep impurity states are analyzed. It is shown that Coulomb vertex corrections to the tunnelling transfer amplitude lead to a power-law singularity in current- voltage characteristics
Singularities of robot mechanisms numerical computation and avoidance path planning
Bohigas, Oriol; Ros, Lluís
2017-01-01
This book presents the singular configurations associated with a robot mechanism, together with robust methods for their computation, interpretation, and avoidance path planning. Having such methods is essential as singularities generally pose problems to the normal operation of a robot, but also determine the workspaces and motion impediments of its underlying mechanical structure. A distinctive feature of this volume is that the methods are applicable to nonredundant mechanisms of general architecture, defined by planar or spatial kinematic chains interconnected in an arbitrary way. Moreover, singularities are interpreted as silhouettes of the configuration space when seen from the input or output spaces. This leads to a powerful image that explains the consequences of traversing singular configurations, and all the rich information that can be extracted from them. The problems are solved by means of effective branch-and-prune and numerical continuation methods that are of independent interest in themselves...
M theory and singularities of exceptional holonomy manifolds
International Nuclear Information System (INIS)
Acharya, Bobby S.; Gukov, Sergei
2004-12-01
M theory compactifications on G 2 holonomy manifolds, whilst supersymmetric, require singularities in order to obtain non-Abelian gauge groups, chiral fermions and other properties necessary for a realistic model of particle physics. We review recent progress in understanding the physics of such singularities. Our main aim is to describe the techniques which have been used to develop our understanding of M theory physics near these singularities. In parallel, we also describe similar sorts of singularities in Spin(7) holonomy manifolds which correspond to the properties of three dimensional field theories. As an application, we review how various aspects of strongly coupled gauge theories, such as confinement, mass gap and non-perturbative phase transitions may be given a simple explanation in M theory. (author)
Dark energy and dark matter perturbations in singular universes
International Nuclear Information System (INIS)
Denkiewicz, Tomasz
2015-01-01
We discuss the evolution of density perturbations of dark matter and dark energy in cosmological models which admit future singularities in a finite time. Up to now geometrical tests of the evolution of the universe do not differentiate between singular universes and ΛCDM scenario. We solve perturbation equations using the gauge invariant formalism. The analysis shows that the detailed reconstruction of the evolution of perturbations within singular cosmologies, in the dark sector, can exhibit important differences between the singular universes models and the ΛCDM cosmology. This is encouraging for further examination and gives hope for discriminating between those models with future galaxy weak lensing experiments like the Dark Energy Survey (DES) and Euclid or CMB observations like PRISM and CoRE
Quantum gravitational collapse: non-singularity and non-locality
International Nuclear Information System (INIS)
Greenwood, Eric; Stojkovic, Dejan
2008-01-01
We investigate gravitational collapse in the context of quantum mechanics. We take primary interest in the behavior of the collapse near the horizon and near the origin (classical singularity) from the point of view of an infalling observer. In the absence of radiation, quantum effects near the horizon do not change the classical conclusions for an infalling observer, meaning the horizon is not an obstacle for him. However, quantum effects are able to remove the classical singularity at the origin, since the wave function is non-singular at the origin. Also, near the classical singularity, some non-local effects become important. In the Schrodinger equation describing behavior near the origin, derivatives of the wave function at one point are related to the value of the wave function at some other distant point.
Phase Singularities and Termination of Spiral Wave Reentry
National Research Council Canada - National Science Library
Eason, James
2001-01-01
In order to elucidate the mechanisms by which a strong shock terminates reentrant wavefronts, we employed phase analysis techniques to study phase singularity dynamics in a finite element model of cardiac tissue...
A singular value sensitivity approach to robust eigenstructure assignment
DEFF Research Database (Denmark)
Søgaard-Andersen, Per; Trostmann, Erik; Conrad, Finn
1986-01-01
A design technique for improving the feedback properties of multivariable state feedback systems designed using eigenstructure assignment is presented. Based on a singular value analysis of the feedback properties a design parameter adjustment procedure is outlined. This procedure allows...
Normal families and isolated singularities of meromorphic functions
International Nuclear Information System (INIS)
Chee, P.S.; Subramaniam, A.
1985-06-01
Based on the criterion of Zalcman for normal families, a generalization of a well-known result relating normal families and isolated essential singularities of meromorphic functions is proved, using a theorem of Lehto and Virtanen on normal functions. (author)
Well-Being of Lagos Urban Mini-Bus Drivers: The Influence of Age and Marital Status
Bolajoko I. Malomo; Maryam O. Yusuf
2015-01-01
Lagos urban mini bus drivers play a critical role in the transportation sector. The current major mode of transportation within Lagos metropolis remains road transportation and this confirms the relevance of urban mini-bus drivers in transporting the populace to their various destinations. Other modes of transportation such as the train and waterways are currently inadequate. Various threats to the well-being of urban bus drivers include congested traffic typical of moder...
Singularity confinement for maps with the Laurent property
International Nuclear Information System (INIS)
Hone, A.N.W.
2007-01-01
The singularity confinement test is very useful for isolating integrable cases of discrete-time dynamical systems, but it does not provide a sufficient criterion for integrability. Quite recently a new property of the bilinear equations appearing in discrete soliton theory has been noticed: The iterates of such equations are Laurent polynomials in the initial data. A large class of non-integrable mappings of the plane are presented which both possess this Laurent property and have confined singularities
On the collinear singularity problem of hot QCD
International Nuclear Information System (INIS)
Candelpergher, B.; Grandou, T.
2002-01-01
The collinear singularity problem of hot QCD is revisited within a perturbative resummation scheme (PR) of the leading thermal fluctuations. On the basis of actual calculations, new aspects are discovered concerning the origin of the singularity plaguing the soft real photon emission rate out of a quark-gluon plasma at thermal equilibrium, when the latter is calculated by means of the Resummation Program (RP)
Classical resolution of black hole singularities via wormholes
Energy Technology Data Exchange (ETDEWEB)
Olmo, Gonzalo J. [Universidad de Valencia, Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Valencia (Spain); Universidade Federal da Paraiba, Departamento de Fisica, Joao Pessoa, Paraiba (Brazil); Rubiera-Garcia, D. [Universidade de Lisboa, Faculdade de Ciencias, Instituto de Astrofisica e Ciencias do Espaco, Lisbon (Portugal); Fudan University, Department of Physics, Center for Field Theory and Particle Physics, Shanghai (China); Sanchez-Puente, A. [Universidad de Valencia, Departamento de Fisica Teorica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Valencia (Spain)
2016-03-15
In certain extensions of General Relativity, wormholes generated by spherically symmetric electric fields can resolve black hole singularities without necessarily removing curvature divergences. This is shown by studying geodesic completeness, the behavior of time-like congruences going through the divergent region, and by means of scattering of waves off the wormhole. This provides an example of the logical independence between curvature divergences and space-time singularities, concepts very often identified with each other in the literature. (orig.)
Dimension counts for singular rational curves via semigroups
Cotterill, Ethan; Feital, Lia; Martins, Renato Vidal
2015-01-01
We study singular rational curves in projective space, deducing conditions on their parametrizations from the value semigroups $\\sss$ of their singularities. In particular, we prove that a natural heuristic for the codimension of the space of nondegenerate rational curves of arithmetic genus $g>0$ and degree $d$ in $\\mb{P}^n$, viewed as a subspace of all degree-$d$ rational curves in $\\mb{P}^n$, holds whenever $g$ is small.
Modified Differential Transform Method for Two Singular Boundary Values Problems
Directory of Open Access Journals (Sweden)
Yinwei Lin
2014-01-01
Full Text Available This paper deals with the two singular boundary values problems of second order. Two singular points are both boundary values points of the differential equation. The numerical solutions are developed by modified differential transform method (DTM for expanded point. Linear and nonlinear models are solved by this method to get more reliable and efficient numerical results. It can also solve ordinary differential equations where the traditional one fails. Besides, we give the convergence of this new method.
Propagation of singularities for linearised hybrid data impedance tomography
DEFF Research Database (Denmark)
Bal, Guillaume; Hoffmann, Kristoffer; Knudsen, Kim
2017-01-01
For a general formulation of linearised hybrid inverse problems in impedance tomography, the qualitative properties of the solutions are analysed. Using an appropriate scalar pseudo-differential formulation, the problems are shown to permit propagating singularities under certain non-elliptic con......For a general formulation of linearised hybrid inverse problems in impedance tomography, the qualitative properties of the solutions are analysed. Using an appropriate scalar pseudo-differential formulation, the problems are shown to permit propagating singularities under certain non...
Singular f-sum rule for superfluid 4He
International Nuclear Information System (INIS)
Wong, V.K.
1979-01-01
The validity and applicability to inelastic neutron scattering of a singular f-sum rule for superfluid helium, proposed by Griffin to explain the rhosub(s) dependence in S(k, ω) as observed by Woods and Svensson, are examined in the light of similar sum rules rigorously derived for anharmonic crystals and Bose liquids. It is concluded that the singular f-sum rules are only of microscopic interest. (Auth,)
The Notion of 'Singularity' in the Work of Gilles Deleuze
DEFF Research Database (Denmark)
Borum, Peter
2017-01-01
In Deleuze, singularity replaces generality in the economy of thought. A Deleuzian singularity is an event, but the notion comprises the effectuation of the event into form. The triptych émission–distribution–répartition itself distributes the dimensions of the passage from form-giving event to t......-drama-different/ciation’. The essay concludes that it is art that may let us consciously contemplate our pre-individual differences....
On singular interaction potentials in classical statistical mechanics
International Nuclear Information System (INIS)
Zagrebnov, V.A.; Pastur, L.A.
1978-01-01
A classical system of particles with stable two-body interaction potential is considered. It is shown that for a certain class of highly singular stable two-body potentials a cut-off procedure preserves the stability of the potential. The thermodynamical potentials (pressure and free energy density) and correlation functions are proved to have the property of asymptotic independence with respect to the continuation of the interaction potentials near singularity
Multifractal signal reconstruction based on singularity power spectrum
International Nuclear Information System (INIS)
Xiong, Gang; Yu, Wenxian; Xia, Wenxiang; Zhang, Shuning
2016-01-01
Highlights: • We propose a novel multifractal reconstruction method based on singularity power spectrum analysis (MFR-SPS). • The proposed MFR-SPS method has better power characteristic than the algorithm in Fraclab. • Further, the SPS-ISE algorithm performs better than the SPS-MFS algorithm. • Based on the proposed MFR-SPS method, we can restructure singularity white fractal noise (SWFN) and linear singularity modulation (LSM) multifractal signal, in equivalent sense, similar with the linear frequency modulation(LFM) signal and WGN in the Fourier domain. - Abstract: Fractal reconstruction (FR) and multifractal reconstruction (MFR) can be considered as the inverse problem of singularity spectrum analysis, and it is challenging to reconstruct fractal signal in accord with multifractal spectrum (MFS). Due to the multiple solutions of fractal reconstruction, the traditional methods of FR/MFR, such as FBM based method, wavelet based method, random wavelet series, fail to reconstruct fractal signal deterministically, and besides, those methods neglect the power spectral distribution in the singular domain. In this paper, we propose a novel MFR method based singularity power spectrum (SPS). Supposing the consistent uniform covering of multifractal measurement, we control the traditional power law of each scale of wavelet coefficients based on the instantaneous singularity exponents (ISE) or MFS, simultaneously control the singularity power law based on the SPS, and deduce the principle and algorithm of MFR based on SPS. Reconstruction simulation and error analysis of estimated ISE, MFS and SPS show the effectiveness and the improvement of the proposed methods compared to those obtained by the Fraclab package.
Removal of apparent singularity in grid computations
International Nuclear Information System (INIS)
Jakubovics, J.P.
1993-01-01
A self-consistency test for magnetic domain wall models was suggested by Aharoni. The test consists of evaluating the ratio S = var-epsilon wall /var-epsilon wall , where var-epsilon wall is the wall energy, and var-epsilon wall is the integral of a certain function of the direction cosines of the magnetization, α, β, γ over the volume occupied by the domain wall. If the computed configuration is a good approximation to one corresponding to an energy minimum, the ratio is close to 1. The integrand of var-epsilon wall contains terms that are inversely proportional to γ. Since γ passes through zero at the centre of the domain wall, these terms have a singularity at these points. The integral is finite and its evaluation does not usually present any problems when the direction cosines are known in terms of continuous functions. In many cases, significantly better results for magnetization configurations of domain walls can be obtained by computations using finite element methods. The direction cosines are then only known at a set of discrete points, and integration over the domain wall is replaced by summation over these points. Evaluation of var-epsilon wall becomes inaccurate if the terms in the summation are taken to be the values of the integrand at the grid points, because of the large contribution of points close to where γ changes sign. The self-consistency test has recently been generalised to a larger number of cases. The purpose of this paper is to suggest a method of improving the accuracy of the evaluation of integrals in such cases. Since the self-consistency test has so far only been applied to two-dimensional magnetization configurations, the problem and its solution will be presented for that specific case. Generalisation to three or more dimensions is straight forward
Singular vectors, predictability and ensemble forecasting for weather and climate
International Nuclear Information System (INIS)
Palmer, T N; Zanna, Laure
2013-01-01
The local instabilities of a nonlinear dynamical system can be characterized by the leading singular vectors of its linearized operator. The leading singular vectors are perturbations with the greatest linear growth and are therefore key in assessing the system’s predictability. In this paper, the analysis of singular vectors for the predictability of weather and climate and ensemble forecasting is discussed. An overview of the role of singular vectors in informing about the error growth rate in numerical models of the atmosphere is given. This is followed by their use in the initialization of ensemble weather forecasts. Singular vectors for the ocean and coupled ocean–atmosphere system in order to understand the predictability of climate phenomena such as ENSO and meridional overturning circulation are reviewed and their potential use to initialize seasonal and decadal forecasts is considered. As stochastic parameterizations are being implemented, some speculations are made about the future of singular vectors for the predictability of weather and climate for theoretical applications and at the operational level. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Lyapunov analysis: from dynamical systems theory to applications’. (review)
Singular spectrum analysis of sleep EEG in insomnia.
Aydın, Serap; Saraoǧlu, Hamdi Melih; Kara, Sadık
2011-08-01
In the present study, the Singular Spectrum Analysis (SSA) is applied to sleep EEG segments collected from healthy volunteers and patients diagnosed by either psycho physiological insomnia or paradoxical insomnia. Then, the resulting singular spectra computed for both C3 and C4 recordings are assigned as the features to the Artificial Neural Network (ANN) architectures for EEG classification in diagnose. In tests, singular spectrum of particular sleep stages such as awake, REM, stage1 and stage2, are considered. Three clinical groups are successfully classified by using one hidden layer ANN architecture with respect to their singular spectra. The results show that the SSA can be applied to sleep EEG series to support the clinical findings in insomnia if ten trials are available for the specific sleep stages. In conclusion, the SSA can detect the oscillatory variations on sleep EEG. Therefore, different sleep stages meet different singular spectra. In addition, different healthy conditions generate different singular spectra for each sleep stage. In summary, the SSA can be proposed for EEG discrimination to support the clinical findings for psycho-psychological disorders.
Curing Black Hole Singularities with Local Scale Invariance
Directory of Open Access Journals (Sweden)
Predrag Dominis Prester
2016-01-01
Full Text Available We show that Weyl-invariant dilaton gravity provides a description of black holes without classical space-time singularities. Singularities appear due to the ill behaviour of gauge fixing conditions, one example being the gauge in which theory is classically equivalent to standard General Relativity. The main conclusions of our analysis are as follows: (1 singularities signal a phase transition from broken to unbroken phase of Weyl symmetry; (2 instead of a singularity, there is a “baby universe” or a white hole inside a black hole; (3 in the baby universe scenario, there is a critical mass after which reducing mass makes the black hole larger as viewed by outside observers; (4 if a black hole could be connected with white hole through the “singularity,” this would require breakdown of (classical geometric description; (5 the singularity of Schwarzschild BH solution is nongeneric and so it is dangerous to rely on it in deriving general results. Our results may have important consequences for resolving issues related to information loss puzzle. Though quantum effects are still crucial and may change the proposed classical picture, a position of building quantum theory around essentially regular classical solutions normally provides a much better starting point.
Modelamiento y simulación para analizar la contaminación del lago Titicaca aplicando lógica difusa
Benites Noriega, Juan
2007-01-01
El trabajo de investigación titulado "MODELAMIENTO Y SIMULACIÓN PARA ANALIZAR LA CONTAMINACIÓN DEL LAGO TITICACA, APLICANDO LÓGICA DIFUSA", se ha realizado en la ciudad de Puno con la finalidad de modelar y analizar la contaminación del Lago Titicaca, aplicando la lógica difusa para la conservación del medio ambiente y la sociedad; localizar las fuentes generadoras de la contaminación del Lago Titicaca, y mencionar como afecta la contaminación del Lago Titicaca en la salud de los habitantes q...
Segmentation of singularity maps in the context of soil porosity
Martin-Sotoca, Juan J.; Saa-Requejo, Antonio; Grau, Juan; Tarquis, Ana M.
2016-04-01
Geochemical exploration have found with increasingly interests and benefits of using fractal (power-law) models to characterize geochemical distribution, including concentration-area (C-A) model (Cheng et al., 1994; Cheng, 2012) and concentration-volume (C-V) model (Afzal et al., 2011) just to name a few examples. These methods are based on the singularity maps of a measure that at each point define areas with self-similar properties that are shown in power-law relationships in Concentration-Area plots (C-A method). The C-A method together with the singularity map ("Singularity-CA" method) define thresholds that can be applied to segment the map. Recently, the "Singularity-CA" method has been applied to binarize 2D grayscale Computed Tomography (CT) soil images (Martin-Sotoca et al, 2015). Unlike image segmentation based on global thresholding methods, the "Singularity-CA" method allows to quantify the local scaling property of the grayscale value map in the space domain and determinate the intensity of local singularities. It can be used as a high-pass-filter technique to enhance high frequency patterns usually regarded as anomalies when applied to maps. In this work we will put special attention on how to select the singularity thresholds in the C-A plot to segment the image. We will compare two methods: 1) cross point of linear regressions and 2) Wavelets Transform Modulus Maxima (WTMM) singularity function detection. REFERENCES Cheng, Q., Agterberg, F. P. and Ballantyne, S. B. (1994). The separation of geochemical anomalies from background by fractal methods. Journal of Geochemical Exploration, 51, 109-130. Cheng, Q. (2012). Singularity theory and methods for mapping geochemical anomalies caused by buried sources and for predicting undiscovered mineral deposits in covered areas. Journal of Geochemical Exploration, 122, 55-70. Afzal, P., Fadakar Alghalandis, Y., Khakzad, A., Moarefvand, P. and Rashidnejad Omran, N. (2011) Delineation of mineralization zones in
International Nuclear Information System (INIS)
Cao, Yi; Zhou, Hui; Li, Baokun; Shen, Long
2011-01-01
This paper presents a new principle and method of kinematics to analyze the singularity of Stewart-Gough parallel manipulators and addresses the property identification of the position-singularity loci of the 6-3 Stewart-Gough manipulators for special orientations. Based on the kinematic relationship of a rigid body, a necessary and sufficient condition that three velocities of three non-collinear points in a moving rigid body can determine a screw motion is addressed and some typical singular configurations of the 6-3 Stewart-Gough parallel manipulators are also addressed in detail. With the above-mentioned condition, a symbolic analytical polynomial expression of degree three in the moving platform position parameters, representing the position-singularity locus of the 6-3 Stewart-Gough manipulators for special orientations, is derived: and the property identification of the position-singularity loci of the 6-3 Stewart-Gough manipulator for these special orientations is investigated at length. It is shown that position-singularity loci of the 6-3 Stewart-Gough parallel manipulator for these special orientations will be a plane and a hyperbolic paraboloid, even three intersecting planes
Efecto de la impermeabilidad del Mucílago de Nopal en bloques de tierra comprimidos
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Yolanda Guadalupe Aranda Jiménez
2013-01-01
Full Text Available La arquitectura de tierra1 es conocida desde hace siglos, sin embargo, actualmente es poco utilizada comparado con los sistemas constructivos comunes. Los bloques de tierra comprimido (BTC son elementos constructivos con un potencial elevado para ser utilizado en las construcciones de vivienda en México, principalmente por su similitud con los bloques tradicionales, siendo conveniente mejorar sus características a partir de un estabilizante. Se realizó el estudio de BTC estabilizados con cemento y una sustancia proveniente de las pencas maduras de nopal. Se encontró que al añadir mucílago de nopal se observa un incremento significativo de la resistencia a la compresión húmeda y seca, lo cual estar relacionado con una disminución de la porosidad; se ofrecen algunas relaciones del efecto del mucílago en el sólido analizado.
Murciélagos asociados a una finca ganadera en Córdoba (Colombia
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Berta Calonge C
2010-04-01
Full Text Available Objetivo. Conocer las especies de murciélagos asociadas a remanentes de bosque seco tropical en un sistema de ganadería extensiva en una finca del departamento de Córdoba. Materiales y métodos. Se realizó un muestreo de 35 noches, durante la época seca (enero-marzo de 2009, empleando 10 redes de niebla (3x6 m ubicadas en un diseño por conglomerados las cuales fueron abiertas desde las 18:00 hasta las 06:00 horas. Resultados. Se encontraron 20 especies de murciélagos, se capturaron un total de 614 individuos. Conclusiones. Se encontraron especies de las familias Phyllostomidae, Noctilionidae, Vespertilionidae y Emballonuridae. La especie Lasiurus ega se constituye en un nuevo reporte para el departamento de Córdoba.
growth pattern and the industrial development of the lagos region, nigeria
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Dickson Dare Ajayi
2013-07-01
Full Text Available This paper examines the nature, growth and spatial pattern of industries within the Lagos Region. Industrial activities in this region grew progressively over the year from mere brickwork, palm oil mills, printing press, soap factory, and metal container factory to capital intensive manufacturing. Indeed, the number of industrial establishments increased from 122 in 1962 to 637 in 1993. Lagos developed into Nigeria's leading industrial center; especially following the expansion in its service and administrative sectors. Whereas, chemicals and pharmaceutical; and basic metal, iron and steel and fabricated metal products industry groups dominate in industrial scene, wood and wood products (including furniture; and non-metallic mineral products are rare. The spatial pattern shows that industrial establishments vary amongst the industrial estates/areas, and also among the industry groups. Ikeja/Ogballsheri industrial estate/area dominates the industrial scene.
Travel Characteristics and Commuting Pattern of Lagos Metropolis Residents: an Assessment
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OSOBA, Samson Babatunde
2015-06-01
Full Text Available Urban travel is not solely the function of travel, but also on people’s participation in activities and how these were done. This study utilized 2,500 households’ samples in Lagos metropolis. The questionnaire about intra-city trip patterns was administered in direct proportion to the population size of each Local Government Areas (LGAs. Systematic sampling technique was used to select every tenth building on the identified streets. lt is observed that more than 95% of residents depends on roads, while less than 5% depends on Rail and Ferry. Work and business trips characterized the weekdays, while social, shopping and recreation trips dominate the weekends. This situation leads to too many vehicular traffic on the roads during the peak periods, leading to congestion and loss of valuable man-hours. Transportation planners in Lagos need to develop alternative intra-city transportation systems.
Subordinación local al manejo territorial globalizado de la ribera del lago de Chapala
Adriana Hernández
2017-01-01
El presente artículo aborda el proceso de reapropiación del lago de Chapala, México. En las últimas décadas se han venido transformando el suelo y la producción agrícola en los municipios ribereños del lago de Chapala debido a la introducción de cultivos de exportación mediante sistemas modernos de producción tecnificada. Por lo que los cultivos tradicionales han ido disminuyendo o se producen con mayor uso de pesticidas, fertilizantes y agroquímicos. El papel del campesino ribereño también s...
An Audit of Anaesthesia Record-keeping at the Lagos University ...
African Journals Online (AJOL)
An Audit of Anaesthesia Record-keeping at the Lagos University Teaching Hospital. ... in the re-audit were Pre-operative history (51% to 91% p<0.0001), blood pressure (65% to 78% p=0.04), pulse rate (47% to 65% p=0.015), administration of premedication (30% to 63% p<0.001), and ASA score (60% to 78%, p=0.009).
Evaluation of Railway Level Crossing Attributes on Accident Causation in Lagos, Nigeria.
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Adeolu O Dina
2017-01-01
Full Text Available Abstract The study examines the contribution of Railway Level Crossing (RLCphysical attributes to accident occurrence using the12 major level crossings within the Lagos metropolis. The 48km single track mainline section under consideration which barely make up 1.1% of the entire narrow gauge track network of the country within a 5 year period contributed about 45% of the total National crossing accidents recorded in Nigeria. The method of investigation involved recording the individual attributes of each RLC such asgates, pedestrian traffic, car traffic light, proximity of signage to crossing, vehicular traffic as dummy variables.The regression analysis was used to measure their effect on accidents.The result indicates gates, pedestrians and the location of signage had significant impact on accidents occurrence at level crossings within Lagos metropolis. Based on the findings, enhancement of active warning systems among other recommendations was suggested as potent counter measures for RLC accident reduction. Abstrak Penelitian menguji tingkat kontribusi atribut fisik dari perlintasan jalan kereta api terhadap kejadian kecelakaan menggunakan 12 perlintasan utama dalam kota metropolis Lagos. 48 km jalan utama tunggal menjadi pertimbangan yang hampir meningkat 1.1% dari seluruh trek sempit jaringan negara dalam jangka waktu 5 tahun menyumbang sekitar 45% dari total kecelakaan perlintasan secara Nasional di Nigeria. Metode penelitian melibatkan catatan dari masing-masing atribut RLC seperti pintu gerbang, pejalan kaki, lampu lalu lintas mobil, kedekatan tanda penyebarangan, lalu lintas kendaraan sebagai variabel dumi. Analisis regresi digunakan untuk mengukur pengaruh dari atribut terhadap kecelakaan. Hasilnya menunjukkan pintu gerbang, pejalan kaki, dan lokasi tanda perlintasan mempunyai dampak signifikan pada kecelakaan dalam kota metropolis Lagos.Berdasarkan penemuan tersebut, perbaikan dari sistem peringatan aktif disarankan sebagai upaya
Fivelman, Quinton L; Butcher, Geoffrey A; Adagu, Ipemida S; Warhurst, David C; Pasvol, Geoffrey
2002-01-01
Abstract We report the first in vitro and genetic confirmation of Malarone® (GlaxoSmithKline; atovaquone and proguanil hydrochloride) resistance in Plasmodium falciparum acquired in Africa. On presenting with malaria two weeks after returning from a 4-week visit to Lagos, Nigeria without prophylaxis, a male patient was given a standard 3-day treatment course of Malarone®. Twenty-eight days later the parasitaemia recrudesced. Parasites were cultured from the blood and the isolate (NGATV01) was...
Investigating last mile distribution challenges of wine suppliers in Lagos, Nigeria
2014-01-01
M.Com. (Business Management) The last mile distribution is the final link of successful supply chain operations. The high demand for products, lead time uncertainties and replenishment time complicate the distribution task. In order to achieve a competitive business edge, suppliers need to work at developing and improving their last mile distribution link. The aim of this study was to investigate the effectiveness of the last mile wine distribution in Lagos Island, Nigeria, and to determin...
Population dynamics and ecology of Tilapia rendalli in Lago Sauce (Peru)
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Wosnitza-Mendo, C.
1980-01-01
This is a practical contribution to development aid in Peru. It was to provide a basis for farming of Lago Sauce and similar lakes and introduce young Peruvian fishery biologists to practical and theoretical work with populations of freshwater fish. Various methods of biomass determination have been compared in order to find out why only small specimens of Tilapia rendalli have been caught and what ichthyobiomass was in the lake.
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Adenike O. Omosun
2011-10-01
Full Text Available Background: Child adoption is a recommended alternative form of infertility management. Infertility is of public health importance in Nigeria and many other developing nations. This is a result of its high prevalence and especially because of its serious social implications as the African society places a passionate premium on procreation in any family setting. Objectives: The aim of this study was to determine the knowledge, attitude and practice of child adoption amongst women attending infertility clinics in teaching hospitals in Lagos State and to determine the factors that influence their attitude and practice towards it. Method: A cross-sectional descriptive design was used. Data were collected by using a structured questionnaire which was interviewer-administered. The study was conducted in the two teaching hospitals in Lagos State (LUTH [Lagos University Teaching Hospital] and LASUTH [Lagos State University Teaching Hospital] from amongst 350 women attending the gynaecological clinics. All the patients under management for infertility at the gynaecology clinics during the period of the study were interviewed. Results: Many respondents (85.7% had heard of child adoption and 59.3% of them knew the correct meaning of the term. More than half of the respondents (68.3% said that they could love an adopted child but less than half of them (33.7% were willing to consider adoption. Only 13.9% has ever adopted a child. The major reason given for their unwillingness to adopt was their desire to have their own biological child. Factors that were favourable towards child adoption were Igbo tribe identity, an age above 40 years, duration of infertility above 15 years, and knowing the correct meaning of child adoption. Conclusion: There is a poor attitude to adoption even amongst infertile couples. Interventions need to be implemented to educate the public on child adoption, to improve their attitude towards adoption and to make it more acceptable.
Murciélagos hematófagos como reservorios de la rabia
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Karin Corrêa Scheffer
Full Text Available La rabia continua siendo un desafío para las autoridades de salud pública y una limitante para la industria ganadera en América Latina. Caninos silvestres y domésticos, así como murciélagos hematófagos son las principales especies transmisoras y reservorios de la enfermedad. Actualmente, se observa variaciones en el perfil epidemiológico de la rabia, donde la especie de murciélago hematófago Desmodus rotundus se constituye en la principal especie transmisora. A lo largo del tiempo se ha acumulado conocimiento sobre la ecología, biología y comportamiento de esta especie y sobre la historia natural de la rabia, lo cual debe conducir a una continua evolución de los métodos de control poblacional de D. rotundus, prevención y técnicas de diagnóstico. Aún se desconoce la relación ecológica de esta especie con otras hematófagas y no hematófagas, y queda mucho por mejorar en los sistemas de notificación y vigilancia epidemiológica, así como crear una mayor conciencia entre los ganaderos ante el tema. La comprensión del impacto que las modificaciones ambientales inducidas por el hombre ejercen sobre la dinámica de infección del virus de la rabia en los murciélagos debe ser motivo de investigaciones posteriores. Esto requerirá la combinación de estudios de campo con modelos matemáticos y nuevas herramientas diagnósticas. La presente revisión pretende presentar los aspectos más relevantes sobre el rol de los murciélagos hematófagos como reservorios y transmisores del virus de la rabia
Consumers’Willingness to Pay for Safety Attributes of Bread in Lagos Metropolis, Nigeria
Anyam, Osemeke E.; Fashogbon, Ayodele E.; Oni, Omobowale A.
2013-01-01
This study examined consumer’s willingness to pay for food safety attributes in bread in Lagos metropolis. It empirically analyzed the factors driving willingness to pay for improved bread and the effect of attributes on willingness to pay and mean willingness to pay for improved bread. The data for the study using a well-structured questionnaire containing Choice Experiment (CE) questions for eliciting willingness to pay was collected from 150 respondents using a two-stage random sampling te...
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Elba De la Cruz
2016-03-01
Full Text Available En el período que va de 1992 a 1997, Costa Rica importó alrededor de 41 millones de kilogramos de i.a. La cantidad total de i.a. importada en 1997 es un 61% mayor que la importada en 1992. La cantidad de i.a. utilizada por hectárea de tierra cultivada también aumentó durante ese período. El 80% de la cantidad importada entre 1995 y 1997 lo constituyeron 17 ingredientes activos. El grupo biocida más importante fue el de los fungicidas (47%, seguido por los herbicidas (26%, los insecticidas/nematicidas (16%, y otros grupos incluyendo los fumigantes (10%. Los principales cultivos de Costa Rica durante 1995 fueron: banano, café, arroz, vegetales, frutas, plantas ornamentales, tubérculos, caña de azúcar, otros granos y pastos. Casi todas las etapas del ciclo de cultivos de estos productos utilizan plaguicidas, dando como resultado un uso intenso, extenso y sostenido de estas sustancias, a lo largo del año. Las actividades agrícolas, que se llevan a cabo cerca de cuerpos de agua de las regiones costeras, influencian los ecosistemas de agua dulce y marinos con residuos de plaguicidas, principalmente porque: grandes extensiones de terreno son dedicadas al cultivo; la mayoría de los cultivos utilizan gran cantidad de plaguicidas; los plaguicidas son aplicados cerca o sobre los ecosistemas acuáticos; la mayoría de plaguicidas utilizados son tóxicos para los organismos acuáticos; el tipo de aplicación puede favorecer la dispersión, si es aérea las corrientes de viento los puede transportar hacia los cuerpos de agua y si es manual los procesos de escorrentía y erosión los transportan a través de los sistemas de canales y drenajes de las plantaciones a los sistemas fluviales de la zona, los estuarios y al mar. Lo anterior aunado a frecuentes e intensos períodos de lluvia que caracterizan ciertas regiones del país, facilitan el transporte de estas sustancias a los ecosistemas acuáticos. El impacto ambiental de una sustancia no
Calidad del agua y sedimento en el lago de Maracaibo, estado Zulia
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Giovany José-Bracho
2016-03-01
Full Text Available Se analizó el agua y el sedimento del lago de Maracaibo en seis estaciones de muestreo distribuidas de norte a sur del lago. Los parámetros físicoquímicos y ambientales fueron determinados y establecidas las relaciones entre estos y las áreas afectadas por descargas de aguas residuales, depósitos de basura, residuos industriales líquidos y sólidos, actividad petrolera y agrícola y materiales orgánicos acarreados por ríos y drenajes pluviales. Se evidenció la contaminación por incremento de utrientes(nitrógeno y fósforo en las zonas influenciadas por los ríos y vertederos de agua residual y se validó la presencia de una cuña salina por la penetración al lago de las aguas del golfo de Venezuela. Las concentraciones de metalespesados están por debajo de los límites permisibles para el agua; en los sedimentos es muy heterogénea.
Lago artificial de Martiánez Canarias – España
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Amigó, Juan A.
1980-06-01
Full Text Available In this article a technical description is given of the works of the Artificial Lake of Martiánez.
This work that was executed after gaining some 33,000 m^{2} from the sea mainly consisted of creating a small artificial lake of seawater surrounded by solariums, beaches and gardens.
Inside the lake — that has an area of some 15,000 m^{2} — five natural islands were formed, most of which have tourist complexes built on them, consisting of: night club, restaurants, bars, terraces, etc.
En este artículo se hace una descripción técnica de las obras del Lago Artificial de Martiánez.
Esta obra, realizada tras ganar al mar unos 33.000 m^{2} consistió, principalmente, en la creación de un pequeño lago artificial de agua de mar rodeado de solarios, playas y jardines.
En el interior del lago —cuya superficie es de unos 15.000 m^{2}— se formaron cinco islas naturales, en la mayor de las cuales se construyó un complejo turístico que consta de: sala de fiestas, restaurantes, bares, terrazas, etc.