Elimination of extremal index zeroes from generic paths of closed 1-forms

Let $\alpha$ be a Morse closed $1$-form of a smooth $n$-dimensional manifold $M$. The zeroes of $\alpha$ of index $0$ or $n$ are called \emph{centers}. It is known that every non-vanishing de Rham cohomology class $u$ contains a Morse representative without centers. The result of this paper is the one-parameter analogue of the last statement: every generic path $(\alpha_t)_{t\in [0,1]}$ of closed $1$-forms in a fixed class $u\neq 0$ such that $\alpha_0, \alpha_1$ have no centers, can be modified relatively to its extremities to another such path $(\beta_t)_{t\in [0,1]}$ having no center at all.Comment: Mathematische Zeitschrift (2014) 25 p

An enhanced worst-case end-to-end evaluation method for SpaceWire networks

The SpaceWire network is scheduled to be used as the sole on-board network for future ESA satellites. However, at the moment, network designers do not have tools to ensure that critical temporal deadlines are met when using best-effort wormhole networks like SpaceWire. In a previous paper, we have presented a first method to compute an upper-bound on the worst-case end-to-end delay of flows traversing such networks. However, its scope was limited by restrictive assumptions on the traffic patterns. Thus, in this paper, we propose a new network model that removes those limitations and allows worst-case delay analysis on SpaceWire networks with any traffic pattern

Reintroduint la marmota alpina als Pirineus

Malgrat la manca de planificació i de seguiment, la reintroducció de la marmota alpina als Pirienus ha estat un èxit. Tot i així, les poblacions reintroduïdes a Andorra, la Cerdanya i el Ripollès tenen molt poca diversitat genètica, un aspecte crucial per adaptar-se al nou ambient. Només el temps dirà si aquest aspecte les perjudica al adaptar-se a les noves condicions que genera el canvi climàtic.Pese a la falta de planificación y seguimiento, la reintroducción de la marmota alpina en los Pirineos ha sido un éxito. Sin embargo, las poblaciones reintroducidas en Andorra, la Cerdanya y el Ripollès tienen muy poca diversidad genética, un aspecto crucial para adaptarse al nuevo ambiente. El tiempo dirá si este aspecto las perjudica al adaptarse a las nuevas condiciones que genera el cambio climático.Despite a lack of planning and monitoring, the reintroduction of the alpine marmot in the Pyrenees has been a success. However, reintroduced populations of Andorra, La Cerdanya and El Ripollès have low genetic diversity. Only time will tell whether this inconvenience will influence their adaptation to the new conditions climate change is generating

Worst-case end-to-end delays evaluation for SpaceWire networks

SpaceWire is a standard for on-board satellite networks chosen by the ESA as the basis for multiplexing payload and control traffic on future data-handling architectures. However, network designers need tools to ensure that the network is able to deliver critical messages on time. Current research fails to address this needs for SpaceWire networks. On one hand, many papers only seek to determine probabilistic results for end-to-end delays on Wormhole networks like SpaceWire. This does not provide sufficient guarantee for critical traffic. On the other hand, a few papers give methods to determine maximum latencies on wormhole networks that, unlike SpaceWire, have dedicated real-time mechanisms built-in. Thus, in this paper, we propose an appropriate method to compute an upper-bound on the worst-case end-to-end delay of a packet in a SpaceWire network

A method of computation for worst-case delay analysis on SpaceWire networks

SpaceWire is a standard for on-board satellite networks chosen by the ESA as the basis for future data-handling architectures. However, network designers need tools to ensure that the network is able to deliver critical messages on time. Current research only seek to determine probabilistic results for end-to-end delays on Wormhole networks like SpaceWire. This does not provide sufficient guarantee for critical traffic. Thus, in this paper, we propose a method to compute an upper-bound on the worst-case end-to-end delay of a packet in a SpaceWire network

Modeling SpaceWire networks with network calculus

The SpaceWire network standard is promoted by the ESA and is scheduled to be used as the sole on-board network for future satellites. This network uses a wormhole routing mechanism that can lead to packet blocking in routers and consequently to variable end-to-end delays. As the network will be shared by real-time and non real-time traffic, network designers require a tool to check that temporal constraints are verified for all the critical messages. Network Calculus can be used for evaluating worst-case end-to-end delays. However, we first have to model SpaceWire components through the definition of service curves. In this paper, we propose a new Network Calculus element that we call the Wormhole Section. This element allows us to better model a wormhole network than the usual multiplexer and demultiplexer elements used in the context of usual Store-and-Forward networks. Then, we show how to combine Wormhole Section elements to compute the end-to-end service curve offered to a flow and illustrate its use on a industrial case study

Selecció sexual: per què els mascles lluiten i les femelles trien?

The struggle to reproduce is a key part of the existence of any organism. For sexually reproductive species, reproduction is more difficult because they need to find another individual willing to mate. Charles Darwin was the first to study mating systems from an evolutionary point of view and he laid the first stone of sexual selection theory. More than one century was needed to convince the scientific community of its validity, but it has become one of the most active areas in the field of evolutionary biology. According to the theory, the traits that give individuals higher reproductive output, though they often compromise their survival, may be selected by two different mechanisms. First, individuals of the same sex compete with each other to copulate with the other sex, so any character that makes them good competitors should be selected. Second, the individuals of a given sex, usually the females, are able to choose which individual they prefer to mate with, so they can select attractive traits in the eyes of the other sex. From this perspective, sexual selection theory has explained why males usually fight and females are the choosy sex. In addition, it has increased understanding of a great variety of extravagant behaviours in the context of sex: furtive mating, cross-dressing lovers, nuptial gifts and sexual suicide. Everything counts in the struggle for reproduction!La lluita per aconseguir reproduir-se és una part essencial de l’existència de qualsevol organisme. Per als animals sexuats, l’afer es veu complicat per la necessitat de trobar un altre individu disposat a aparellar-se. Charles Darwin va ser el primer que va estudiar els sistemes d’aparellament des d’una òptica evolutiva i va posar la primera pedra de la teoria de la selecció sexual. Tot i que va caldre més d’un segle per convèncer els científics de la seva validesa, ha esdevingut una de les àrees més fecundes en el camp de la biologia evolutiva. Segons la teoria, els caràcters que confereixen als individus més possibilitats de deixar descendència, malgrat que puguin comprometre la seva supervivència, seran seleccionats per dos mecanismes diferents. Per una banda, els individus d’un mateix sexe competiran entre si per aconseguir aparellar-se amb l’altre sexe, de manera que se seleccionaran caràcters que els facin bons competidors. Per altra banda, els individus d’un sexe, generalment les femelles, podran elegir quin individu els fa més el pes per aparellar-s’hi, de manera que es podran seleccionar trets que per alguna raó fan els individus més atractius a ulls de l’altre sexe. Sota aquesta perspectiva, la teoria de la selecció sexual ha mirat d’explicar perquè són els mascles els que normalment lluiten i perquè les femelles les que majoritàriament són més exigents a l’hora d’escollir parella. A més, ha permès entendre una gran varietat de comportaments extravagants en el context del sexe: còpules furtives, amants transvestits, regals nupcials o suïcidis sexuals. Tot s’hi val en la lluita per la reproducció

On the decorrelation filtering of RL05 GRACE data for global applications

In autumn 2012, the new release 05 (RL05) of monthly geopotencial spherical harmonics Stokes coefficients (SC) from GRACE (Gravity Recovery and Climate Experiment) mission was published. This release reduces the noise in high degree and order SC, but they still need to be filtered. One of the most common filtering processing is the combination of decorrelation and Gaussian filters. Both of them are parameters dependent and must be tuned by the users. Previous studies have analyzed the parameters choice for the RL05 GRACE data for oceanic applications, and for RL04 data for global application. This study updates the latter for RL05 data extending the statistics analysis. The choice of the parameters of the decorrelation filter has been optimized to: (1) balance the noise reduction and the geophysical signal attenuation produced by the filtering process; (2) minimize the differences between GRACE and model-based data; (3) maximize the ratio of variability between continents and oceans. The Gaussian filter has been optimized following the latter criteria. Besides, an anisotropic filter, the fan filter, has been analyzed as an alternative to the Gauss filter, producing better statistics.This work has been partly supported by two Spanish Projects from CGL2010-12153-E and AYA2010-22039-C02-01; and two from Generalitat Valenciana, GV/2013/144 and ACOMP-2013-068

Redundant regulation of meristem identity and plant architecture by FRUITFULL, APETALA1 and CAULIFLOWER

The transition from vegetative to reproductive phases during Arabidopsis development is the result of a complex interaction of environmental and endogenous factors. One of the key regulators of this transition is LEAFY (LFY), whose threshold levels of activity are proposed to mediate the initiation of flowers. The closely related APETALA1 (AP1) and CAULIFLOWER (CAL) meristem identity genes are also important for flower initiation, in part because of their roles in upregulating LFY expression. We have found that mutations in the FRUITFULL (FUL) MADS-box gene, when combined with mutations in AP1 and GAL, lead to a dramatic non-flowering phenotype in which plants continuously elaborate leafy shoots in place of flowers. We demonstrate that this phenotype is caused both by the lack of LFY upregulation and by the ectopic expression of the TERMINAL FLOWER1 (TFL1) gene. Our results suggest that the FUL, AP1 and CAL genes act redundantly to control inflorescence architecture by affecting the domains of LFY and TFL1 expression as well as the relative levels of their activities