Influence of M-phase chromatin on the anisotropy of microtubule asters

In many eukaryotic cells going through M-phase, a bipolar spindle is formed by microtubules nucleated from centrosomes. These microtubules, in addition to being "captured" by kinetochores, may be stabilized by chromatin in two different ways: short-range stabilization effects may affect microtubules in close contact with the chromatin, while long-range stabilization effects may "guide" microtubule growth towards the chromatin (e.g., by introducing a diffusive gradient of an enzymatic activity that affects microtubule assembly). Here, we use both meiotic and mitotic extracts from Xenopus laevis eggs to study microtubule aster formation and microtubule dynamics in the presence of chromatin. In "low-speed" meiotic extracts, in the presence of salmon sperm chromatin, we find that short-range stabilization effects lead to a strong anisotropy of the microtubule asters. Analysis of the dynamic parameters of microtubule growth show that this anisotropy arises from a decrease in the catastrophe frequency, an increase in the rescue frequency and a decrease in the growth velocity. In this system we also find evidence for long-range "guidance" effects, which lead to a weak anisotropy of the asters. Statistically relevant results on these long-range effects are obtained in "high-speed" mitotic extracts in the presence of artificially constructed chromatin stripes. We find that aster anisotropy is biased in the direction of the chromatin and that the catastrophe frequency is reduced in its vicinity. In this system we also find a surprising dependence of the catastrophe and the rescue frequencies on the length of microtubules nucleated from centrosomes: the catastrophe frequency increase and the rescue frequency decreases with microtubule length

Lepton masses, mixings and FCNC in a minimal S_3-invariant extension of the Standard Model

The mass matrices of the charged leptons and neutrinos, previously derived in a minimal S_3-invariant extension of the Standard Model, were reparametrized in terms of their eigenvalues. We obtained explicit, analytical expressions for all entries in the neutrino mixing matrix, V_PMNS, the neutrino mixing angles and the Majorana phases as functions of the masses of charged leptons and neutrinos in excellent agreement with the latest experimental values. The resulting V_PMNS matrix is very close to the tri-bimaximal form of the neutrino mixing matrix. We also derived explicit analytical expressions for the matrices of the Yukawa couplings and computed the branching ratios of some selected flavour changing neutral current processes as functions of the masses of the charged leptons and the neutral Higgs bosons. We find that the S_3 x Z_2 flavour symmetry and the strong mass hierarchy of the charged leptons strongly suppress the FCNC processes in the leptonic sector well below the present experimental upper bounds by many orders of magnitude.Comment: One paragraph added with comparison to tri-bimaximal mixing, two lines changed in abstract, references added, typographical errors correcte

On the Rational Type 0f Moment Angle Complexes

In this note it is shown that the moment angle complexes Z(K;(D^2,,S^1)) which are rationally elliptic are a product of odd spheres and a diskComment: This version avoids the use of an incorrect result from the literature in the proof of Theorem 1.3. There is some text overlap with arXiv:1410.645

Características mecánicas de uñas acrílicas en el toque de guitarra

Los guitarristas sufren un importante desgaste en el contactode las uñas con las cuerdas de la guitarra y concretamentecon las tres cuerdas superiores de latón. Actualmentese colocan uñas llamadas de “porcelana”, o uñasesculpidas, las cuales dan un resultado aceptable en elapartado durabilidad, además de aportar un sonido aceptable.Sin embargo, en este trabajo se pretende medir lassolicitaciones que tiene la uña de Poli[metacrilato de etilo](PEMA) del guitarrista bajo la acción del toque de guitarra,ya que en este tipo de toque la uña está sometida a bastantemás tensión de lo habitual. Se parte de distintas formulacionesde PEMA y se ensaya el material para intentarimitar el movimiento natural de la uña y así cuantificar lassolicitaciones mecánicas en el uso de la misma. Se concluyeque es necesario una alta proporción de iniciador yPEMA para obtener una uña con adecuadas propiedadesmecánicas y de desgaste

Photon-Number-Splitting versus Cloning Attacks in Practical Implementations of the Bennett-Brassard 1984 protocol for Quantum Cryptography

In practical quantum cryptography, the source sometimes produces multi-photon pulses, thus enabling the eavesdropper Eve to perform the powerful photon-number-splitting (PNS) attack. Recently, it was shown by Curty and Lutkenhaus [Phys. Rev. A 69, 042321 (2004)] that the PNS attack is not always the optimal attack when two photons are present: if errors are present in the correlations Alice-Bob and if Eve cannot modify Bob's detection efficiency, Eve gains a larger amount of information using another attack based on a 2->3 cloning machine. In this work, we extend this analysis to all distances Alice-Bob. We identify a new incoherent 2->3 cloning attack which performs better than those described before. Using it, we confirm that, in the presence of errors, Eve's better strategy uses 2->3 cloning attacks instead of the PNS. However, this improvement is very small for the implementations of the Bennett-Brassard 1984 (BB84) protocol. Thus, the existence of these new attacks is conceptually interesting but basically does not change the value of the security parameters of BB84. The main results are valid both for Poissonian and sub-Poissonian sources.Comment: 11 pages, 5 figures; "intuitive" formula (31) adde

Equivariant Poincar\'e series of filtrations and topology

Earlier, for an action of a finite group $G$ on a germ of an analytic variety, an equivariant $G$-Poincar\'e series of a multi-index filtration in the ring of germs of functions on the variety was defined as an element of the Grothendieck ring of $G$-sets with an additional structure. We discuss to which extend the $G$-Poincar\'e series of a filtration defined by a set of curve or divisorial valuations on the ring of germs of analytic functions in two variables determines the (equivariant) topology of the curve or of the set of divisors

Guidelines to improve sustainability and cultural integration of temporary housing units

Unfortunately, natural disasters have drastically increased over the last decades causing extensive material and non-­material damages. The destruction of houses and the number of homeless people are some of the most visible effects of post-­disaster scenarios. Housing is one of the people’s most important needs and it is also essential for their well-­being. After a disaster it is crucial to supply temporary accommodation in order to provide victims with comfort, protection, and privacy until they have a permanent house. Temporary housing is an extremely important solution of temporary accommodation allowing victims to gradually return to their normal life activities during the reconstruction process. Although it has been widely used after the most large-scale disasters, the urgent need of fast solutions has not led to effective options. Therefore, temporary housing solutions have been greatly criticized mainly for being unsustainable, and also culturally and locally inadequate. Through literature review and case-­studies’ analysis the research points out the main factors and reasons that cause the problems of temporary housing units. It also refers to possible solutions to overcome or minimize those problems, offering guidelines based on concepts that have been proved effective in previous studies. The guidelines focus on useful concepts in the development of more sustainable, locally sensitive and culturally integrated solutions. It was found that an essential change is needed in the development of temporary housing solutions. These solutions should be developed through a people-­oriented strategy rather than focusing on the technical aspects of the units. The suggested guidelines have that objective

Sistemas em madeira e derivados na reabilitação urbana em situações pós-catástrofe

Os centros históricos são elementos importantes e fundamentais de muitas cidades. Representam a sua história e evolução, sendo por isso parte essencial do Património Cultural. São contudo elementos extremamente vulneráveis, sendo vários os exemplos ao longo da história de situações imprevistas como terramotos, tsunamis, cheias, vulcões, incêndios, etc., que provocaram danos significativos nos edifícios e monumentos de cidades históricas importantes. Após um desastre destes, a situação é previsivelmente crítica e torna-se urgente proteger os monumentos e demais edifícios históricos. Deverá evitar-se a propagação e avanço dos danos, prevenindo colapsos locais e falhas globais. Neste cenário, torna-se crucial a utilização de sistemas de construção rápidos baseados em elementos leves e pequenos. Estes elementos devem permitir uma instalação fácil e rápida, bem como proporcionar a resistência suficiente para prevenir o aumento das perdas. Por outro lado, é fundamental que estes sistemas tenham em linha de conta a manutenção da traça arquitectónica, através de soluções que preservem as características estéticas e materiais dos edifícios. Este artigo apresenta uma primeira abordagem ao uso de sistemas à base de madeira e derivados em situações pós-catástrof

Temporary housing after disasters: a state of the art survey

The number of natural disasters has drastically increased, causing great damages on buildings. A large number of houses have suffered damage and become unusable, causing a high number of homeless people. Housing reconstruction programmes play a decisive role on the disaster recovery and providing temporary housing is a crucial step of these programmes. During the reconstruction of permanent housing, it allows victims to have a private and secure place to return to their normal lives. This has been widely used after the largest scale disasters but it has also been greatly criticised, mainly for being unsustainable and culturally inadequate. The study aims to present a state-of-the-art survey on the topic, as well as to identify the main problems, their origin and the existing proposals to avoid them. The research also proposes some guidelines that can reduce the effects of those problems