45 research outputs found
El tiempo principia en XibalbĂĄ: claves mĂticas y realidad socio-polĂtica
El tiempo principia en XibalbĂĄ is considered as the best expression achieved in contemporary Guatemalan indigenous novels. Written in 1972 by Luis de LiĂłn, this novel displays a rich diversity of social, cultural and political resonances whose meaning is relevant to understand the problems of a broken society due to deep social divisions. This brief analysis merely indicates how the mythical elements of the novel strategies articulate certain social critic whose political importance is undeniable. Following Hans Blumenberg (2004: 103), I would like to show how the poetic and mythic potential of this novel helps to destabilize the powers of an exclusive society.El tiempo principia en XibalbĂĄ se considera como la manifestaciĂłn mejor lograda de la novelĂstica indĂgena guatemalteca contemporĂĄnea. Escrita en 1972 por Luis de LiĂłn, esta novela despliega una rica pluralidad de resonancias sociales, culturales y polĂticas cuya significaciĂłn es relevante para entender los problemas de una sociedad cruzada por profundas fracturas sociales. Asumiendo como horizonte la riqueza de estos aspectos, este breve anĂĄlisis se limita a señalar cĂłmo los elementos mĂticos de esta novela articulan ciertas estrategias de crĂtica social cuya importancia polĂtica es innegable. Siguiendo a Hans Blumenberg (2004: 103), quisiera mostrar cĂłmo el potencial poĂ©tico y mĂtico de esta novela contribuye a desestabilizar los poderes de una sociedad excluyente
Finding lower bounds on the complexity of secret sharing schemes by linear programming
Optimizing the maximum, or average, length of the shares in relation to the length of the secret for every given access structure is a difficult and long-standing open problem in cryptology. Most of the known lower bounds on these parameters have been obtained by implicitly or explicitly using that every secret sharing scheme defines a polymatroid related to the access structure. The best bounds that can be obtained by this combinatorial method can be determined by using linear programming, and this can be effectively done for access structures on a small number of participants.
By applying this linear programming approach, we improve some of the known lower bounds for the access structures on five participants and the graph access structures on six participants for which these parameters were still undetermined. Nevertheless, the lower bounds that are obtained by this combinatorial method are not tight in general. For some access structures, they can be improved by adding to the linear program non-Shannon information inequalities as new constraints. We obtain in this way new separation results for some graph access structures on eight participants and for some ports of non-representable matroids. Finally, we prove that, for two access structures on five participants, the combinatorial lower bound cannot be attained by any linear secret sharing schemePeer ReviewedPostprint (author's final draft
On the optimization of bipartite secret sharing schemes
Optimizing the ratio between the maximum length of the shares and the length of the secret value in secret sharing schemes for general access structures is an extremely difficult and long-standing open problem. In this paper, we study it for bipartite access structures, in which the set of participants is divided in two parts, and all participants in each part play an equivalent role. We focus on the search of lower bounds by using a special class of polymatroids that is introduced here, the tripartite ones. We present a method based on linear programming to compute, for every given bipartite access structure, the best lower bound that can be obtained by this combinatorial method. In addition, we obtain some general lower bounds that improve the previously known ones, and we construct optimal secret sharing schemes for a family of bipartite access structures.Peer ReviewedPostprint (author's final draft
Defining a novel leptinâmelanocortinâkisspeptin pathway involved in the metabolic control of puberty
Objective
Puberty is a key developmental phenomenon highly sensitive to metabolic modulation. Worrying trends of changes in the timing of puberty have been reported in humans. These might be linked to the escalating prevalence of childhood obesity and could have deleterious impacts on later (cardio-metabolic) health, but their underlying mechanisms remain unsolved. The neuropeptide α-MSH, made by POMC neurons, plays a key role in energy homeostasis by mediating the actions of leptin and likely participates in the control of reproduction. However, its role in the metabolic regulation of puberty and interplay with kisspeptin, an essential puberty-regulating neuropeptide encoded by Kiss1, remain largely unknown. We aim here to unveil the potential contribution of central α-MSH signaling in the metabolic control of puberty by addressing its role in mediating the pubertal effects of leptin and its potential interaction with kisspeptin.
Methods
Using wild type and genetically modified rodent models, we implemented pharmacological studies, expression analyses, electrophysiological recordings, and virogenetic approaches involving DREADD technology to selectively inhibit Kiss1 neurons, in order to interrogate the physiological role of a putative leptinâα-MSHâkisspeptin pathway in the metabolic control of puberty.
Results
Stimulation of central α-MSH signaling robustly activated the reproductive axis in pubertal rats, whereas chronic inhibition of melanocortin receptors MC3/4R, delayed puberty, and prevented the permissive effect of leptin on puberty onset. Central blockade of MC3/4R or genetic elimination of kisspeptin receptors from POMC neurons did not affect kisspeptin effects. Conversely, congenital ablation of kisspeptin receptors or inducible, DREADD-mediated inhibition of arcuate nucleus (ARC) Kiss1 neurons resulted in markedly attenuated gonadotropic responses to MC3/4R activation. Furthermore, close appositions were observed between POMC fibers and ARC Kiss1 neurons while blockade of α-MSH signaling suppressed Kiss1 expression in the ARC of pubertal rats.
Conclusions
Our physiological, virogenetic, and functional genomic studies document a novel α-MSHâkisspeptinâGnRH neuronal signaling pathway involved in transmitting the permissive effects of leptin on pubertal maturation, which is relevant for the metabolic (and, eventually, pharmacological) regulation of puberty onsetThis work was supported by grants BFU2011-025021 & BFU2014-57581-P (Ministerio de EconomĂa y Competitividad, Spain; co-funded with EU funds from FEDER Program); project PIE-00005 (Flexi-Met, Instituto de Salud Carlos III, Ministerio de Sanidad, Spain); Projects P08-CVI-03788 and P12-FQM-01943 (Junta de AndalucĂa, Spain); EU research contract DEER FP7-ENV-2007-1 and the New Zealand Health Research Council. CIBER FisiopatologĂa de la Obesidad y NutriciĂłn is an initiative of Instituto de Salud Carlos III. Senior authors are indebted with Dr. R.A. Steiner (University of Washington, Seattle, USA) and Dr. U. Boehm (University of Saarland School of Medicine, Homburg, Germany) for provision of relevant mouse lines, essential for conduction of some of the experiments included in this studyS
Democracia en el Estado de MĂ©xico: fortalezas y debilidades
En toda interacciĂłn humana puede estar presente el poder. Por tanto, todas las formas de interacciĂłn humana son susceptibles de catalogarse como democrĂĄticas o como autoritarias (e incluso hĂbridas, cuando conjugan elementos democrĂĄticos y autoritarios). En la interacciĂłn democrĂĄtica o bien estĂĄ ausente el poder o bien Ă©ste es ejercido con tolerancia y con apego a normas preestablecidas. En la interacciĂłn autoritaria prevalece la intolerancia, la arbitrariedad y la violencia
Verbeia: Journal of english and spanish studies
Verbeia nace con la finalidad de contagiarnos con la pasiĂłn de la FilologĂa. Durante este año hemos crecido, nuestro ComitĂ© CientĂfico aumenta y con Ă©l las esperanzas de estabilidad. Todos sabemos lo que cuesta llegar hasta aquĂ, y hoy llegamos con artĂculos escritos por profesores e investigadores de distintas universidades del planeta
GestiĂłn del conocimiento. Perspectiva multidisciplinaria. Volumen 8
El libro âGestiĂłn del Conocimiento. Perspectiva Multidisciplinariaâ, volumen 8, de la ColecciĂłn UniĂłn Global, es resultado de investigaciones. Los capĂtulos del libro, son resultados de investigaciones desarrolladas por sus autores. El libro es una publicaciĂłn internacional, seriada, continua, arbitrada de acceso abierto a todas las ĂĄreas del conocimiento, que cuenta con el esfuerzo de investigadores de varios paĂses del mundo, orientada a contribuir con procesos de gestiĂłn del conocimiento cientĂfico, tecnolĂłgico y humanĂstico que consoliden la transformaciĂłn del conocimiento en diferentes escenarios, tanto organizacionales como universitarios, para el desarrollo de habilidades cognitivas del quehacer diario. La gestiĂłn del conocimiento es un camino para consolidar una plataforma en las empresas pĂșblicas o privadas, entidades educativas, organizaciones no gubernamentales, ya sea generando polĂticas para todas las jerarquĂas o un modelo de gestiĂłn para la administraciĂłn, donde es fundamental articular el conocimiento, los trabajadores, directivos, el espacio de trabajo, hacia la creaciĂłn de ambientes propicios para el desarrollo integral de las instituciones
Miradas y voces de la investigaciĂłn educativa I
Fil: Ferreyra, Horacio Ademar. Universidad CatĂłlica de CĂłrdoba. Facultad de EducaciĂłn; ArgentinaFil: Calneggia, MarĂa Isabel. Universidad CatĂłlica de CĂłrdoba. Facultad de EducaciĂłn; ArgentinaFil: Di Francesco, Adriana Carlota. Universidad CatĂłlica de CĂłrdoba. Facultad de EducaciĂłn; Argentin
Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic
This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic