399 research outputs found

    Subadditivity of syzygies of Koszul algebras

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    Estimates are obtained for the degrees of minimal syzygies of quotient algebras of polynomial rings. For a class that includes Koszul algebra in almost all characteristics, these degrees are shown to increase by at most 2 from one syzygy module to the next one. Even slower growth is proved if, in addition, the algebra satisfies Green and Lazarsfeld's condition N_q with q > 1.Comment: 19 page

    Asymptotics for models of non-stationary diffusion in domains with a surface distribution of obstacles

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    We consider a time-dependent model for the diffusion of a substance through an incompressible fluid in a perforated domain ??, urn:x-wiley:mma:media:mma5323:mma5323-math-0001 with n?=?3,4. The fluid flows in a domain containing a periodical set of ?obstacles? (?\??) placed along an inner (n???1)?dimensional manifold urn:x-wiley:mma:media:mma5323:mma5323-math-0002. The size of the obstacles is much smaller than the size of the characteristic period ?. An advection term appears in the partial differential equation linking the fluid velocity with the concentration, while we assume a nonlinear adsorption law on the boundary of the obstacles. This law involves a monotone nonlinear function ? of the concentration and a large adsorption parameter. The ?critical adsorption parameter? depends on the size of the obstacles , and, for different sizes, we derive the time?dependent homogenized models. These models contain a ?strange term? in the transmission conditions on ?, which is a nonlinear function and inherits the properties of ?. The case in which the fluid velocity and the concentration do not interact is also considered for n???3.The authors would like to thank the anonymous referees for their careful reading of the manupscript and useful comments. The work has been partially supported by MINECO, MTM2013-44883-P

    Brillouin light scattering study of Co2_{2}Cr0.6_{0.6}Fe0.4_{0.4}Al and Co2_{2}FeAl Heusler compounds

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    The thermal magnonic spectra of Co2_{2}Cr0.6_{0.6}Fe0.4_{0.4}Al (CCFA) and Co2_2FeAl were investigated using Brillouin light scattering spectroscopy (BLS). For CCFA, the exchange constant A (exchange stiffness D) is found to be 0.48 Ό\muerg/cm (203 meV A2^2), while for Co2_2FeAl the corresponding values of 1.55 Ό\muerg/cm (370 meV A2^2) were found. The observed asymmetry in the BLS spectra between the Stokes and anti-Stokes frequencies was assigned to an interplay between the asymmetrical profiles of hybridized Damon-Esbach and perpendicular standing spin-wave modes, combined with the optical sensitivity of the BLS signal to the upper side of the CCFA or Co2_2FeAl film

    Pragmatic

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    A npresentation of Pragmatic 2014

    Functional consequences of mutations in CDKL5, an X-linked gene involved in infantile spasms and mental retardation

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    Mutations in the X-linked cyclin-dependent kinase-like 5 (CDKL5) gene have been identified in patients with Rett syndrome, West syndrome, and X-linked infantile spasms sharing the common features of generally intractable early seizures and mental retardation. Disease-causing mutations are distributed in both the catalytic domain and in the large COOH terminus. In this report, we examine the functional consequences of some Rett mutations of CDKL5 together with some synthetically designed derivatives useful to underline the functional domains of the protein. The mutated CDKL5 derivatives have been subjected to in vitro kinase assays and analyzed for phosphorylation of the TEY (Thr-Glu-Tyr) motif within the activation loop, their subcellular localization, and the capacity of CDKL5 to interact with itself. Whereas wild-type CDKL5 autophosphorylates and mediates the phosphorylation of the methyl-CpG-binding protein 2 (MeCP2) in vitro, Rett-mutated proteins show both impaired and increased catalytic activity suggesting that a tight regulation of CDKL5 is required for correct brain functions. Furthermore, we show that CDKL5 can self-associate and mediate the phosphorylation of its own TEY (Thr-Glu-Tyr) motif. Eventually, we show that the COOH terminus regulates CDKL5 properties; in particular, it negatively influences the catalytic activity and is required for its proper sub-nuclear localization. We propose a model in which CDKL5 phosphorylation is required for its entrance into the nucleus whereas a portion of the COOH-terminal domain is responsible for a stable residency in this cellular compartment probably through protein-protein interactions

    The environmental security debate and its significance for climate change

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    Policymakers, military strategists and academics all increasingly hail climate change as a security issue. This article revisits the (comparatively) long-standing “environmental security debate” and asks what lessons that earlier debate holds for the push towards making climate change a security issue. Two important claims are made. First, the emerging climate security debate is in many ways a re-run of the earlier dispute. It features many of the same proponents and many of the same disagreements. These disagreements concern, amongst other things, the nature of the threat, the referent object of security and the appropriate policy responses. Second, given its many different interpretations, from an environmentalist perspective, securitisation of the climate is not necessarily a positive development

    A Kato type Theorem for the inviscid limit of the Navier-Stokes equations with a moving rigid body

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    The issue of the inviscid limit for the incompressible Navier-Stokes equations when a no-slip condition is prescribed on the boundary is a famous open problem. A result by Tosio Kato says that convergence to the Euler equations holds true in the energy space if and only if the energy dissipation rate of the viscous flow in a boundary layer of width proportional to the viscosity vanishes. Of course, if one considers the motion of a solid body in an incompressible fluid, with a no-slip condition at the interface, the issue of the inviscid limit is as least as difficult. However it is not clear if the additional difficulties linked to the body's dynamic make this issue more difficult or not. In this paper we consider the motion of a rigid body in an incompressible fluid occupying the complementary set in the space and we prove that a Kato type condition implies the convergence of the fluid velocity and of the body velocity as well, what seems to indicate that an answer in the case of a fixed boundary could also bring an answer to the case where there is a moving body in the fluid

    Existence of global strong solutions to a beam-fluid interaction system

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    We study an unsteady non linear fluid-structure interaction problem which is a simplified model to describe blood flow through viscoleastic arteries. We consider a Newtonian incompressible two-dimensional flow described by the Navier-Stokes equations set in an unknown domain depending on the displacement of a structure, which itself satisfies a linear viscoelastic beam equation. The fluid and the structure are fully coupled via interface conditions prescribing the continuity of the velocities at the fluid-structure interface and the action-reaction principle. We prove that strong solutions to this problem are global-in-time. We obtain in particular that contact between the viscoleastic wall and the bottom of the fluid cavity does not occur in finite time. To our knowledge, this is the first occurrence of a no-contact result, but also of existence of strong solutions globally in time, in the frame of interactions between a viscous fluid and a deformable structure

    Pautas pedagógicas y comunicacionales para la educación en tiempos de emergencia: la enseñanza en la virtualidad

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    La medida de aislamiento establecida ante la propagaciĂłn del coronavirus nos sorprendiĂł a todos. Bajo la consigna de dar continuidad a la actividad docente en el grado, sin la posibilidad de una mĂ­nima organizaciĂłn y sin demasiada experiencia previa, debimos asumir el desarrollo de la enseñanza en espacios virtuales. Nos encontramos ahora ante la proximidad del inicio del segundo semestre del año, que se estima se desarrollarĂĄ bajo condiciones de una “nueva normalidad”. Esto implicarĂĄ el regreso a las aulas bajo condiciones restrictivas en cuanto a espacios y cantidad de personas presentes por clase, lo cual darĂĄ lugar a la continuidad de la enseñanza virtual, bien sea a travĂ©s de un formato totalmente en lĂ­nea, o bajo la posibilidad de un formato mixto, que combine instancias presenciales y en lĂ­nea. Estamos, por tanto, ante el desafĂ­o de planear una propuesta que suponga la genuina integraciĂłn de ambas instancias.publishedVersionRezzĂłnico, M. S. Universidad Nacional de CĂłrdoba. Facultad de OdontologĂ­a. AsesorĂ­a PedagĂłgica; Argentina.Castillo, B. Universidad Nacional de CĂłrdoba. Facultad de OdontologĂ­a. AsesorĂ­a PedagĂłgica; Argentina.Tessio Conca, A. Universidad Nacional de CĂłrdoba. Facultad de OdontologĂ­a. AsesorĂ­a PedagĂłgica; Argentina.Allende Posse, M. Universidad Nacional de CĂłrdoba. Facultad de OdontologĂ­a. AsesorĂ­a PedagĂłgica; Argentina.Justiniano, M. S. Universidad Nacional de CĂłrdoba. Facultad de OdontologĂ­a. AsesorĂ­a PedagĂłgica; Argentina
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