1,138 research outputs found
On generalized Sethi-Vafa-Witten formulas
We present a formula for computing proper pushforwards of classes in the Chow
ring of a projective bundle under the projection \pi:\Pbb(\Escr)\rightarrow
B, for a non-singular compact complex algebraic variety of any dimension.
Our formula readily produces generalizations of formulas derived by Sethi,Vafa,
and Witten to compute the Euler characteristic of elliptically fibered
Calabi-Yau fourfolds used for F-theory compactifications of string vacua. The
utility of such a formula is illustrated through applications, such as the
ability to compute the Chern numbers of any non-singular complete intersection
in such a projective bundle in terms of the Chern class of a line bundle on
Lemme de Fatou pour l'intégrale de Pettis
The purpose of this paper is to present Fatou type results for a sequence of Pettis integrable functions and multifunctions. We prove the non vacuity of the weak upper limit of a sequence of Pettis integrable functions taking their values in a locally convex space and we deduce a Fatou's lemma for a sequence of convex weak compact valued Pettis integrable multifunctions. We prove as well a Lebesgue theorem for a sequence of Pettis integrable multifunctions with values in the space of convex compact sets of a separable Banach space
Pbp1p, a factor interacting with Saccharomyces cerevisiae poly(A)-binding protein, regulates polyadenylation
The poly(A) tail of an mRNA is believed to influence the initiation of translation, and the rate at which the poly(A) tail is removed is thought to determine how fast an mRNA is degraded. One key factor associated with this 3\u27-end structure is the poly(A)-binding protein (Pab1p) encoded by the PAB1 gene in Saccharomyces cerevisiae. In an effort to learn more about the functional role of this protein, we used a two-hybrid screen to determine the factor(s) with which it interacts. We identified five genes encoding factors that specifically interact with the carboxy terminus of Pab1p. Of a total of 44 specific clones identified, PBP1 (for Pab1p-binding protein) was isolated 38 times. Of the putative interacting genes examined, PBP1 promoted the highest level of resistance to 3-aminotriazole (\u3e100 mM) in constructs in which HIS3 was used as a reporter. We determined that a fraction of Pbp1p cosediments with polysomes in sucrose gradients and that its distribution is very similar to that of Pab1p. Disruption of PBP1 showed that it is not essential for viability but can suppress the lethality associated with a PAB1 deletion. The suppression of pab1Delta by pbp1Delta appears to be different from that mediated by other pab1 suppressors, since disruption of PBP1 does not alter translation rates, affect accumulation of ribosomal subunits, change mRNA poly(A) tail lengths, or result in a defect in mRNA decay. Rather, Pbp1p appears to function in the nucleus to promote proper polyadenylation. In the absence of Pbp1p, 3\u27 termini of pre-mRNAs are properly cleaved but lack full-length poly(A) tails. These effects suggest that Pbp1p may act to repress the ability of Pab1p to negatively regulate polyadenylation
La maladie de Fanconi: à propos d’une nouvelle observation
La maladie de Fanconi ou l'anémie de Fanconi (AF) est une maladie génétique rare à transmission autosomique récessive. Elle est marquée parune hétérogénéité phénotypique. Certains symptômes et notamment la triade classique faite d'une petite taille, d'un syndrome malformatif varié et parfois discret et d'une insuffisance médullaire d'apparition précoce, doivent faire évoquer le diagnostic. Nous rapportons le cas d'un enfant âgé de sept ans, suivi et traité pour une luxation congénitale des hanches, qui présentait une pancytopénie avec à l'examen clinique on note un faciès dysmorphique triangulaire, une duplication du pouce droit, une surélévation de l'épaule gauche et un retard staturo-pondéral
Pluie de solitons dans un laser à fibre co-dopée Er:Yb en forme de huit
Nous rapportons ici l\u27observation expérimentale d\u27un comportement collectif d\u27un ensemble de soliton,
appelé pluie de solitons, dans un laser à fibre en forme de huit avec un miroir à boucle non linéaire
(NOLM). Cette dynamique non linéaire a été précédemment observée dans un laser à fibre verrouillé
passivement par la technique de rotation de polarisation non linéaire. A partir d\u27un fond continu, des
solitons se créent et dérivent vers la phase condensée de plusieurs solitons. L\u27observation de cette
dynamique tend Ă renforcer l\u27idĂ©e de l\u27universalitĂ© du comportement collectif des solitons.Â
Soliton pattern formation in figure-of-eight laser
We investigate the soliton pattern formation in an erbium-doped figure-of-eight double-clad fiber laser. The mode-locking is realized with a nonlinear amplifying loop mirror. Different soliton complexes have been obtained similar to those obtained when the mode-locking is achieved through the nonlinear polarization rotation technique
Dissipative Soliton Resonance in Passive Mode-Locked Lasers
By numerical simulation it is found that the dissipative soliton resonance prevents to an appearance in generation of new pulses with increasing pump power. It can be used for generation of high-energy pulses
Hémophilie B mineure révélée par une hémorragie cérébrale: à propos d’un cas
L'hémorragie intracrânienne (HIC) du nouveau-né à terme est une pathologie rare, leur prévalence est estimée à 2% des naissances vivantes. Les manifestations cliniques sont variables et non spécifique. Les causes d'HIC sont multiples et souvent intriquées, les mécanismes physiopathologiques principaux sont la dysrégulation du débit cérébral, une obstruction des vaisseaux ou une coagulation intravasculaire; ou une lésion directe par traumatisme. Nous rapportons le cas d'un nourrisson d'un mois qui a été admis dans notre service pour prendre en charge des convulsions associées à une pâleur cutanéomuqueuse, suite à laquelle l'examen biologique a mis fortuitement en faveur une hémophilie mineure sur une maladie hémorragique tardive
A Three-Dimensional TLM Simulation Method for Thermal Effect in PV-Solar Cells
Temperature rising is a negative factor in almost all systems. It could cause by self heating or ambient temperature. In solar photovoltaic cells this temperature rising affects on the behavior of cells. The ability of a PV module to withstand the effects of periodic hot-spot heating that occurs when cells are operated under reverse biased conditions is closely related to the properties of the cell semi-conductor material. In addition, the thermal effect also influences the estimation of the maximum power point (MPP) and electrical parameters for the PV modules, such as maximum output power, maximum conversion efficiency, internal efficiency, reliability, and lifetime. The cells junction temperature is a critical parameter that significantly affects the electrical characteristics of PV modules. For practical applications of PV modules, it is very important to accurately estimate the junction temperature of PV modules and analyze the thermal characteristics of the PV modules. Once the temperature variation is taken into account, we can then acquire a more accurate MPP for the PV modules, and the maximum utilization efficiency of the PV modules can also be further achieved. In this paper, the three-Dimensional Transmission Line Matrix (3D-TLM) method was used to map the surface temperature distribution of solar cells while in the reverse bias mode. It was observed that some cells exhibited an inhomogeneity of the surface temperature resulting in localized heating (hot-spot). This hot-spot heating causes irreversible destruction of the solar cell structure. Hot spots can have a deleterious impact on the total solar modules if individual solar cells are heated. So, the results show clearly that the solar cells are capable of self-generating considerable amounts of heat that should be dissipated very quickly to increase PV module's lifetime
Analysis of Soliton Complexes in High Power Fiber Lasers
We consider a fibre laser operating in a regime where thousands of solitons coexist in the cavity. Because of the soliton interaction, different soliton patterns or complexes are generated depending on the laser parameters. We point out an analogy between soliton complexes and the states of the matter: soliton gas, soliton supersonic flow, soliton liquid, soliton polycrystal and soliton crystal
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