200 research outputs found
Conservação de esporos, germinação e desenvolvimento gametofítico de Pleopeltis lepidopteris: análises morfofisiológicas e ultraestruturais
Full text linkDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Programa de Pós-Graduação em Biologia de Fungos, Algas e Plantas, Florianópolis, 2015.Pleopeltis lepidopteris (Langsd. & Fisch) de la Sota (Polypodiaceae) é uma samambaia endêmica importante da vegetação de restingas do sul do Brasil. A vegetação de restinga vem sofrendo fortes ameaças com o aumento da especulação imobiliária, ocupação humana, a poluição e a extração. Esporos de P. lepidopteris foram coletados em setembro de 2013 e março de 2014 nas Dunas da Praia da Joaquina, Florianópolis, SC, Brasil. Para preservar eficazmente esporos de P. lepidopteris foram avaliados os efeitos de diferentes tratamentos na viabilidade dos esporos e desenvolvimento gametofítico. Foi analisada a viabilidade de esporos recém coletados em setembro de 2013. Os esporos foram armazenados: por um e oito meses nas frondes à temperatura ambiente; sob-refrigeração 7±1ºC; imersos em nitrogênio líquido (-196ºC) não esterilizados e esterilizados superficialmente após degelo. Foram realizadas análises morfológicas de esporos e gametófitos por meio de microscopia de luz (ML), microscopia confocal de varredura a laser (MCVL), microscopia eletrônica de varredura (MEV) e microscopia eletrônica de transmissão (MET). Análises de conteúdo de pigmentos fotossintetizantes e fluorescência da clorofila a foram realizadas em gametófitos de 150 dias. Esporos de P. lepidopteris perdem rapidamente a viabilidade dentro de um mês e morrem após oito meses, quando armazenados à temperatura ambiente. Houve grande redução da viabilidade quando os esporos foram armazenados a 7±1ºC após oito meses. Em contraste, esporos sobreviveram e apresentaram as mais altas porcentagens de germinação quando armazenados em nitrogênio líquido indiferentemente da época de coleta. Esporos criopreservados analisados em MEV apresentaram a superfície e as ornamentações mais ásperas do que os esporos controles. A criopreservação aparentemente escarificou a superfície dos esporos. Houve aceleração e desenvolvimento normal de gametófitos oriundos de esporos criopreservados e surgimento antecipado de estruturas reprodutivas. Não houve diferença na ultraestrutura de esporos e gametófitos de ambos os tratamentos e nem nos conteúdos de pigmentos fotossintetizantes e nos parâmetros fotossintéticos obtidos a partir da análise da fluorescência da clorofila a. A criopreservação mostrou-se eficaz para a conservação ex situ em bancos de germoplasma de esporos de Pleopeltis lepidopteris, mantendo sua viabilidade e integridade fisiológica.Abstract : Pleopeltis lepidopteris (Langsd. & Fisch) de la Sota (Polypodiaceae) is an important endemic fern of the dunes vegetation of southern Brazil. The ?restinga? vegetation has been suffering strong threats with the human occupation, pollution and extraction. Spores of P. lepidopteris were collected in September 2013 and March 2014 in the dunes of Joaquina Beach, Florianópolis, SC, Brazil. To effectively preserve P. lepidopteris spores the effects of different treatments of conservation were analised. The viability of spores collected in September 2013 were analised and compared to different methods of conservation: spores stored for eight months in the fronds at room temperature, spores stored under refrigeration at 7±1ºC, spores immersed in liquid nitrogen (-196ºC) non-sterile or surface steriled after thaw. Morphological analysis of spores and gametophytes were performed by light microscopy (ML), confocal laser scanning microscopy (CLSM), scanning electronic microscopy (SEM) and transmission electronic microscopy (MET). Analisys of photosynthetic pigmens and fluorescence of chlorophyll a were performed in gametophytes of 150 days. Spores of P. lepidopteris rapidly lose viability within a month and die after eight months when stored at room temperature. There was a great reduction of viability when the spores were stored at 7±1ºC after eight months. In contrast, spores survived and presented the highest percentage of germination when stored in liquid nitrogen regardless the period of collection. The surface of the cryopreserved spores analyzed by SEM was rougher than that of controls. Cryopreservation apparently scarified spore surface. There was acceleration of development of gametophyte grown from criopreserved spores and early onset of reproductive structures. There were no differences in the ultrastructure of spores and gametophytes of both treatments or in the photosynthetic pigment content and the photosynthetic parameters obtained from the analysis of chlorophyll a fluorescence. Cryopreservation was effective for the ?ex situ? conservation in germplasm banks of spores of Pleopeltis lepidopteris spores, maintaining their viability and physiological integrity
The Structure of Optimal and Near Optimal Target Sets in Consensus Models
No full textWe consider the problem of identifying a subset of nodes in a network that will enable the fastest spread of information in a decentralized environment.In a model of communication based on a random walk on an undirected graph, the optimal set over all sets of the same or smaller cardinality minimizes the sum of the mean first arrival times to the set by walkers starting at nodes outside the set. The problem originates from the study of the spread of information or consensus in a network and was introduced in this form by V.Borkar et al. in 2010. More generally, the work of A. Clark et al. in 2012 showed that estimating the fastest rate of convergence to consensus of so-called leader follower systems leads to a consideration of the same optimization problem. The set function F to be minimized is supermodular and therefore the greedy algorithm is commonly used to construct optimal sets or their approximations. In this paper, the problem is reformulated so that the search for solutions is restricted to optimal and near optimal subsets of the graph. We prove sufficient conditions for the existence of a greedoid structure that contains feasible optimal and near optimal sets. It is therefore possible we conjecture, to search for optimal or near optimal sets by local moves in a stepwise manner to obtain near optimal sets that are better approximations than the factor (1−1/e) degree of optimality guaranteed by the use of the greedy algorithm. A simple example illustrates aspects of the method. 1 Random Walk Consensus Model Given a connected graph G = (V,E), with vertices or nodes V and edges E, we imagine a random walker situated at a node i ∈ V, moving to another node j ∈ V in a single discrete time step. The choice of j is random and has probability, Prob{i → j} = pij> 0, if (i, j) ∈ E pij = 0 otherwise. (1) The matrix P = (pij)i,j=1···N is the transition matrix of a Markov chain which in this paper, is assumed to be irreducible and aperiodic ([7]). N is the number of nodes and as in [1] the spread of information is described in terms of a process that is dual to the movement from informed to uninformed nodes. A random walk begins outside a pre-determined set A of informed target nodes 1 ar X i
Violence de l'adolescent et angoisse de démembrement
No full textFern Nevjinsky, Adolescent violence and dismemberment anxiety.
By following the evolution of approximately forty adolescents for the past few years, we have been able to determine the signs which are frequently linked to the occurrence of violent acts. Starting from the interpretation of these data, the author has hypothesized that for these adolescents, the work of mourning cannot be accomplished normally and is replaced by a work of melancholy which appears during a massive narcissistic regression. The encounter between aggressive maternal introjects and the presence of a "clinging" maternal imago can generate "dismemberment anxiety", a consequence of instinctual disentanglement and the failure to establish a primary erogenous masochistic core.
Key-words : Adolescence, dismemberment anxiety, masochism, death instinct, work of melancholy.Le suivi d'une quarantaine d'adolescents pendant plusieurs années a permis de déterminer les indices fréquemment liés à la survenue de passages à l'acte violents. A partir de l'interprétation de ces données, l'auteur fait l'hypothèse que pour ces adolescents, le travail de deuil ne peut s'effectuer normalement et est remplacé par un travail de mélancolie qui intervient lors d'une régression narcissique massive. La rencontre d'introjects maternels agressifs avec la présence d'une imago maternelle "accolée" est génératrice d'une "angoisse de démembrement", conséquence d'une désintrication pulsionnelle et de défaillances dans l'établissement du noyau masochique érogène primaire.
Mots-clés : Adolescence, angoisse de démembrement, masochisme, pulsion de mort, travail de mélancolie.Fern Nevjinsky, Violencias del adolescente y angustia de desmembramiento.
El seguimiento de unos cuarenta adolescentes durante varios anos, permitiô determinar los indices ligados frecuentemente a la apariciôn de pasajes al acto violentos. A partir de la interpretacion de estos datos, el autor hace la hipétesis que para estos adolescentes, el trabajo de duelo no se puede efectuar normalmente y es reemplazado por un trabajo de melancolia que interviene en el momento de una regresiôn narcisistica masiva. El encuentro de introyecciones maternas agresivas con la presencia de una imagen materna "apegada", es generadora de una "angustia de desmembramiento", consecuencia de una desintricaciôn pulsional y de fallas en el establecimiento del nûcleo masoquista erôgeno primario.
Palabras-clave : Adolescencia, Angustia de desmembramiento, Masoquismo, Pulsion de muerte, Trabajo de melancolfa.Nevjinsky Fern. Violence de l'adolescent et angoisse de démembrement. In: Psychologie clinique et projective, vol. 2 n°1, 1996. Violences. pp. 93-112
Violence de l'adolescent et angoisse de démembrement
No full textFern Nevjinsky, Adolescent violence and dismemberment anxiety.
By following the evolution of approximately forty adolescents for the past few years, we have been able to determine the signs which are frequently linked to the occurrence of violent acts. Starting from the interpretation of these data, the author has hypothesized that for these adolescents, the work of mourning cannot be accomplished normally and is replaced by a work of melancholy which appears during a massive narcissistic regression. The encounter between aggressive maternal introjects and the presence of a "clinging" maternal imago can generate "dismemberment anxiety", a consequence of instinctual disentanglement and the failure to establish a primary erogenous masochistic core.
Key-words : Adolescence, dismemberment anxiety, masochism, death instinct, work of melancholy.Le suivi d'une quarantaine d'adolescents pendant plusieurs années a permis de déterminer les indices fréquemment liés à la survenue de passages à l'acte violents. A partir de l'interprétation de ces données, l'auteur fait l'hypothèse que pour ces adolescents, le travail de deuil ne peut s'effectuer normalement et est remplacé par un travail de mélancolie qui intervient lors d'une régression narcissique massive. La rencontre d'introjects maternels agressifs avec la présence d'une imago maternelle "accolée" est génératrice d'une "angoisse de démembrement", conséquence d'une désintrication pulsionnelle et de défaillances dans l'établissement du noyau masochique érogène primaire.
Mots-clés : Adolescence, angoisse de démembrement, masochisme, pulsion de mort, travail de mélancolie.Fern Nevjinsky, Violencias del adolescente y angustia de desmembramiento.
El seguimiento de unos cuarenta adolescentes durante varios anos, permitiô determinar los indices ligados frecuentemente a la apariciôn de pasajes al acto violentos. A partir de la interpretacion de estos datos, el autor hace la hipétesis que para estos adolescentes, el trabajo de duelo no se puede efectuar normalmente y es reemplazado por un trabajo de melancolia que interviene en el momento de una regresiôn narcisistica masiva. El encuentro de introyecciones maternas agresivas con la presencia de una imagen materna "apegada", es generadora de una "angustia de desmembramiento", consecuencia de una desintricaciôn pulsional y de fallas en el establecimiento del nûcleo masoquista erôgeno primario.
Palabras-clave : Adolescencia, Angustia de desmembramiento, Masoquismo, Pulsion de muerte, Trabajo de melancolfa.Nevjinsky Fern. Violence de l'adolescent et angoisse de démembrement. In: Psychologie clinique et projective, vol. 2 n°1, 1996. Violences. pp. 93-112
On bifurcated supertasks and related questions
Full text linkBifurcated supertasks entail the actual infinite division of time (accelerated system of reference) as well as the existence of half-curves of infinite length (supertask system of reference). This paper analyzes both issues from a critique perspective. It also analyzes a conflictive case of hypercomputation performed by means of a bifurcated supertask. The results of these analyzes suggest the convenience of reviewing certain foundational aspects of infinitist theories
Spectral based Methods that Streamline the Search for Failure Scenarios in Large-Scale Distributed Systems
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