2,481 research outputs found
Adaptive methodology for meshless finite point method
In this work, a posteriori error estimator and an adaptive refinement process for the meshless finite point method (FPM), which is based on point collocation, are presented. The error indicator is formulated by the least-squares functional evaluation, used in the shape function development. New degrees of freedom or additional points can be incorporated without difficulty, in zones where the error estimator presents a high value, by means of h–p refinement processes. The validity of the proposed error estimator can be demonstrated by developments of numerical problems in mechanics of solids, using an adaptive refinement process of the solution
Symmetries in Fluctuations Far from Equilibrium
Fluctuations arise universally in Nature as a reflection of the discrete
microscopic world at the macroscopic level. Despite their apparent noisy
origin, fluctuations encode fundamental aspects of the physics of the system at
hand, crucial to understand irreversibility and nonequilibrium behavior. In
order to sustain a given fluctuation, a system traverses a precise optimal path
in phase space. Here we show that by demanding invariance of optimal paths
under symmetry transformations, new and general fluctuation relations valid
arbitrarily far from equilibrium are unveiled. This opens an unexplored route
toward a deeper understanding of nonequilibrium physics by bringing symmetry
principles to the realm of fluctuations. We illustrate this concept studying
symmetries of the current distribution out of equilibrium. In particular we
derive an isometric fluctuation relation which links in a strikingly simple
manner the probabilities of any pair of isometric current fluctuations. This
relation, which results from the time-reversibility of the dynamics, includes
as a particular instance the Gallavotti-Cohen fluctuation theorem in this
context but adds a completely new perspective on the high level of symmetry
imposed by time-reversibility on the statistics of nonequilibrium fluctuations.
The new symmetry implies remarkable hierarchies of equations for the current
cumulants and the nonlinear response coefficients, going far beyond Onsager's
reciprocity relations and Green-Kubo formulae. We confirm the validity of the
new symmetry relation in extensive numerical simulations, and suggest that the
idea of symmetry in fluctuations as invariance of optimal paths has
far-reaching consequences in diverse fields.Comment: 8 pages, 4 figure
Related Message Attacks to Public Key Encryption Schemes: Relations among Security Notions
Consider a scenario in which an adversary, attacking a certain public key encryption scheme, gains knowledge of several ciphertexts
which underlying plaintext are meaningfully related with a given target ciphertext. This kind of
related message attack has been proved
successful against several public key encryption schemes; widely
known is the Franklin-Reiter attack to RSA with low exponent and
its subsequent improvement by Coppersmith. However, to the best of
our knowledge no formal treatment of these type of attacks has to
date been done, and as a result, it has not been rigorously studied which of the ``standard\u27\u27 security notions
imply resilience to them.
We give formal definitions of several security
notions capturing the resistance to this kind of attacks. For
passive adversaries we prove that, for the case of
indistinguishability, security against related message attacks is
equivalent to standard CPA security. On the other hand,
one-wayness robust schemes in this sense can be seen as
strictly between OW-CPA and IND-CPA secure schemes.
Furthermore, we prove that the same holds for active (CCA)
adversaries
Group key exchange protocols withstanding ephemeral-key reveals
When a group key exchange protocol is executed, the session key is typically extracted from two types of secrets; long-term keys (for authentication) and freshly generated (often random) values. The leakage of this latter so-called ephemeral keys has been extensively analyzed in the 2-party case, yet very few works are concerned with it in the group setting. We provide a generic {group key exchange} construction that is strongly secure, meaning that the attacker is allowed to learn both long-term and ephemeral keys (but not both from the same participant, as this would trivially disclose the session key). Our design can be seen as a compiler, in the sense that it builds on a 2-party key exchange protocol which is strongly secure and transforms it into a strongly secure group key exchange protocol by adding only one extra round of communication. When applied to an existing 2-party protocol from Bergsma et al., the result is a 2-round group key exchange protocol which is strongly secure in the standard model, thus yielding the first construction with this property
Human bocavirus infections in Spanish 0-14 year-old: clinical and epidemiological characteristics of an emerging respiratory virus
[ES] Introducción: En el año 2005 se ha clonado un nuevo virus respiratorio, llamado bocavirus humano (HBoV) de muestras respiratorias procedentes de lactantes y niños suecos con infección respiratoria de vías bajas. Objetivos: Determinar si HBoV ha circulado en España, estimar la frecuencia de infecciones por HBoV en los niños hospitalizados por infección respiratoria y describir sus características clínicas y epidemiológicas. Pacientes y métodos: Estudio descriptivo, prospectivo de las infecciones confirmadas por HBoV en niños menores de 14 años, hospitalizados por infección respiratoria desde octubre de 2004 a junio de 2005. Para el diagnóstico virológico se realizó reacción en cadena de la polimerasa-transcripción inversa (RT-PCR) múltiple para virus respiratorio sincitial (VRS) A y B, influenza A, B y C, parainfluenza 1-4, adenovirus y rinovirus; PCR para metapneumovirus humano (hMPV) y PCR para HBoV en aspirado nasofaríngeo. Se describen las características clínicas y epidemiológicas de los pacientes. Resultados: Se detectaron 52 casos de infección por HBoV, lo que supuso el 17,1 % (IC [intervalo de confianza] 95 %: 13 a 21) de los pacientes hospitalizados por procesos respiratorios. HBoV fue el tercer agente viral tras el VRS (30 %) y el rinovirus (25 %). En 39 casos (71,1 %) se detectó coinfección con otro virus respiratorio. El 50 % de los pacientes eran menores de 13,6 meses y el 75% menores de 2 años. Los diagnósticos más frecuentes fueron sibilancias recurrentes (55,8 %), bronquiolitis (21,2 %) y neumonía (15,4 %). Dos niños presentaron sepsis clínica con exantema petequial. El 71,2 % presentó fiebre superior a 38 °C e infiltrado radiológico el 44 %. Presentaron hipoxia el 55,8 % de los niños. Dos pacientes presentaron aislamientos positivos para HBoV en distintos episodios. Las coinfecciones fueron similares a las infecciones simples, excepto que presentaron hipoxia con más frecuencia, p = 0,038. Conclusiones: HBoV es uno de los virus más frecuentes en las infecciones respiratorias graves de los niños, sólo precedido por VRS y rinovirus. Las coinfecciones son muy frecuentes. La mayoría de los niños son lactantes con sibilancias recurrentes y bronquiolitis. [EN] Introduction: In 2005 a new respiratory virus, called human bocavirus (HBoV), was cloned from respiratory samples from Swedish infants and children with lower respiratory tract infections. Objectives: To determine whether HBoV has circulated in Spain, estimate the frequency of HBoV infections in patients hospitalized for respiratory infection and describe the clinical and epidemiological characteristics of these patients. Patients and methods: We performed a descriptive prospective study of confirmed HBoV infections in patients aged 38 degrees C was found in 72.1% and radiological infiltrate in 44%. Hypoxia was present in 55.8 % of the patients. HBoV was isolated in distinct episodes in two patients. Coinfections were similar to simple infections except that hypoxia was more frequent in the former (p = 0.038). Conclusions: HBoV is one of the most frequent viruses in severe respiratory infections in patients aged less than 14 years old. Only RSV and rhinovirus are more frequent. Coinfections are highly frequent. Most patients are infants with recurrent wheezing and bronchiolitis.Estudio parcialmente financiado por el Fondo de Investigaciones Sanitarias. FIS N.º 98/0310.S
RNase H2, mutated in Aicardi-Goutières syndrome, promotes LINE-1 retrotransposition
Long INterspersed Element class 1 (LINE-1) elements are a type of
abundant retrotransposons active in mammalian genomes. An
average human genome contains ~100 retrotransposition-competent
LINE-1s, whose activity is influenced by the combined action
of cellular repressors and activators. TREX1, SAMHD1 and ADAR1
are known LINE-1 repressors and when mutated cause the autoinflammatory
disorder Aicardi-Goutières syndrome (AGS). Mutations
in RNase H2 are the most common cause of AGS, and its activity
was proposed to similarly control LINE-1 retrotransposition. It has
therefore been suggested that increased LINE-1 activity may be
the cause of aberrant innate immune activation in AGS. Here, we
establish that, contrary to expectations, RNase H2 is required for
efficient LINE-1 retrotransposition. As RNase H1 overexpression
partially rescues the defect in RNase H2 null cells, we propose a
model in which RNase H2 degrades the LINE-1 RNA after reverse
transcription, allowing retrotransposition to be completed. This
also explains how LINE-1 elements can retrotranspose efficiently
without their own RNase H activity. Our findings appear to be at
odds with LINE-1-derived nucleic acids driving autoinflammation
in AGS.M.B.-G. is funded by a “Formacion Profesorado
Universitario” (FPU) PhD fellowship from the Government of Spain (MINECO,
Ref FPU15/03294), and this paper is part of her thesis project (“Epigenetic
control of the mobility of a human retrotransposon”). R.V.-A. is funded by a
PFIS Fellowship from the Government of Spain (ISCiii, FI16/00413). O.M. is
funded by an EMBO Long-Term Fellowship (ALTF 7-2015), the European
Commission FP7 (Marie Curie Actions, LTFCOFUND2013, GA-2013-609409) and
the Swiss National Science Foundation (P2ZHP3_158709). S.R.H. is funded by
the Government of Spain (MINECO, RYC-2016-21395 and SAF2015-71589-P).
A.P.J’s laboratory is supported by the UK Medical Research Council (MRC University Unit grant U127527202). J.L.G.P’s laboratory is supported by CICEFEDER-
P12-CTS-2256, Plan Nacional de I+D+I 2008-2011 and 2013-2016 (FISFEDER-
PI14/02152), PCIN-2014-115-ERA-NET NEURON II, the European
Research Council (ERC-Consolidator ERC-STG-2012-233764), by an International
Early Career Scientist grant from the Howard Hughes Medical Institute
(IECS-55007420), by The Wellcome Trust-University of Edinburgh Institutional
Strategic Support Fund (ISFF2) and by a private donation from Ms Francisca
Serrano (Trading y Bolsa para Torpes, Granada, Spain)
Uncovering Suitable Reference Proteins for Expression Studies in Human Adipose Tissue with Relevance to Obesity
Protein expression studies based on the two major intra-abdominal human fat depots, the subcutaneous and the omental fat, can shed light into the mechanisms involved in obesity and its co-morbidities. Here we address, for the first time, the identification and validation of reference proteins for data standardization, which are essential for accurate comparison of protein levels in expression studies based on fat from obese and non-obese individuals.To uncover adipose tissue proteins equally expressed either in omental and subcutaneous fat depots (study 1) or in omental fat from non-obese and obese individuals (study 2), we have reanalyzed our previously published data based on two-dimensional fluorescence difference gel electrophoresis. Twenty-four proteins (12 in study 1 and 12 in study 2) with similar expression levels in all conditions tested were selected and identified by mass spectrometry. Immunoblotting analysis was used to confirm in adipose tissue the expression pattern of the potential reference proteins and three proteins were validated: PARK7, ENOA and FAA. Western Blot analysis was also used to test customary loading control proteins. ENOA, PARK7 and the customary loading control protein Beta-actin showed steady expression profiles in fat from non-obese and obese individuals, whilst FAA maintained steady expression levels across paired omental and subcutaneous fat samples.ENOA, PARK7 and Beta-actin are proper reference standards in obesity studies based on omental fat, whilst FAA is the best loading control for the comparative analysis of omental and subcutaneous adipose tissues either in obese and non-obese subjects. Neither customary loading control proteins GAPDH and TBB5 nor CALX are adequate standards in differential expression studies on adipose tissue. The use of the proposed reference proteins will facilitate the adequate analysis of proteins differentially expressed in the context of obesity, an aim difficult to achieve before this study
Observation of Pulsed Gamma-rays Above 25 GeV from the Crab Pulsar with MAGIC
One fundamental question about pulsars concerns the mechanism of their pulsed
electromagnetic emission. Measuring the high-end region of a pulsar's spectrum
would shed light on this question. By developing a new electronic trigger, we
lowered the threshold of the Major Atmospheric gamma-ray Imaging Cherenkov
(MAGIC) telescope to 25 GeV. In this configuration, we detected pulsed
gamma-rays from the Crab pulsar that were greater than 25 GeV, revealing a
relatively high cutoff energy in the phase-averaged spectrum. This indicates
that the emission occurs far out in the magnetosphere, hence excluding the
polar-cap scenario as a possible explanation of our measurement. The high
cutoff energy also challenges the slot-gap scenario.Comment: Slight modification of the analysis: Fitting a more general function
to the combined data set of COMPTEL, EGRET and MAGIC. Final result and
conclusion is unchange
First bounds on the high-energy emission from isolated Wolf-Rayet binary systems
High-energy gamma-ray emission is theoretically expected to arise in tight
binary star systems (with high mass loss and high velocity winds), although the
evidence of this relationship has proven to be elusive so far. Here we present
the first bounds on this putative emission from isolated Wolf-Rayet (WR) star
binaries, WR 147 and WR 146, obtained from observations with the MAGIC
telescope.Comment: (Authors are the MAGIC Collaboration.) Manuscript in press at The
Astrophysical Journal Letter
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