14,480 research outputs found

    Reply to Comments of Steuernagel on the Afshar's Experiment

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    We respond to criticism of our paper "Paradox in Wave-Paricle Duality for Non-Perturbative Measurements". We disagree with Steuernagel's derivation of the visibility of the Afshar experiment. To calculate the fringe visibility, Steuernagel utilizes two different experimental situations, i.e. the wire grid in the pattern minima and in the pattern maxima. In our assessment, this proceduere cannot lead to the correct result for the complementarity properties of wave-particle in one particular experimental set-up

    Lorentz contraction, Bell's spaceships, and rigid body motion in special relativity

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    The meaning of Lorentz contraction in special relativity and its connection with Bell's spaceships parable is discussed. The motion of Bell's spaceships is then compared with the accelerated motion of a rigid body. We have tried to write this in a simple form that could be used to correct students' misconceptions due to conflicting earlier treatments.Comment: Modified the discussion in Sec. 2. This version to be published in European Journal of Physic

    The Shape of Dark Matter Halos: Dependence on Mass, Redshift, Radius, and Formation

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    Using six high resolution dissipationless simulations with a varying box size in a flat LCDM universe, we study the mass and redshift dependence of dark matter halo shapes for M_vir = 9.0e11 - 2.0e14, over the redshift range z=0-3, and for two values of sigma_8=0.75 and 0.9. Remarkably, we find that the redshift, mass, and sigma_8 dependence of the mean smallest-to-largest axis ratio of halos is well described by the simple power-law relation = (0.54 +- 0.02)(M_vir/M_*)^(-0.050 +- 0.003), where s is measured at 0.3 R_vir and the z and sigma_8 dependences are governed by the characteristic nonlinear mass, M_*=M_*(z,sigma_8). We find that the scatter about the mean s is well described by a Gaussian with sigma ~ 0.1, for all masses and redshifts. We compare our results to a variety of previous works on halo shapes and find that reported differences between studies are primarily explained by differences in their methodologies. We address the evolutionary aspects of individual halo shapes by following the shapes of the halos through ~100 snapshots in time. We determine the formation scalefactor a_c as defined by Wechsler et al. (2002) and find that it can be related to the halo shape at z = 0 and its evolution over time.Comment: 18 pages, 21 figures, submitted to MNRA

    Precision stellar radial velocity measurements with FIDEOS at the ESO 1-m telescope of La Silla

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    We present results from the commissioning and early science programs of FIDEOS, the new high-resolution echelle spectrograph developed at the Centre of Astro Engineering of Pontificia Universidad Catolica de Chile, and recently installed at the ESO 1m telescope of La Silla. The instrument provides spectral resolution R = 43,000 in the visible spectral range 420-800 nm, reaching a limiting magnitude of 11 in V band. Precision in the measurement of radial velocity is guaranteed by light feeding with an octagonal optical fibre, suitable mechanical isolation, thermal stabilisation, and simultaneous wavelength calibration. Currently the instrument reaches radial velocity stability of = 8 m/s over several consecutive nights of observation

    Analysis of ASTEC-Na capabilities for simulating a loss of flow CABRI experiment

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    Abstract This paper presents simulation results of the CABRI BI1 test using the code ASTEC-Na, currently under development, as well as a comparison of the results with available experimental data. The EU-JASMIN project (7th FP of EURATOM) centres on the development and validation of the new severe accident analysis code ASTEC-Na (Accident Source Term Evaluation Code) for sodium-cooled fast reactors whose owner and developer is IRSN. A series of experiments performed in the past (CABRI/SCARABEE experiments) and new experiments to be conducted in the new experimental sodium facility KASOLA have been chosen to validate the developed ASTEC-Na code. One of the in-pile experiments considered for the validation of ASTEC-Na thermal–hydraulic models is the CABRI BI1 test, a pure loss-of-flow transient using a low burnup MOX fuel pin. The experiment resulted in a channel voiding as a result of the flow coast-down leading to clad melting. Only some fuel melting took place. Results from the analysis of this test using SIMMER and SAS-SFR codes are also presented in this work to check their suitability for further code benchmarking purposes

    Divergência entre acessos de tucumanzeiro por caracteres da inflorescência.

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    O Astrocaryum vulgare, Mart. popularmente conhecido como tucumã, é uma palmeira comumente encontrada nos estados da região norte do Brasil, onde seus frutos são bastante apreciados na culinária local e mais recentemente como matéria prima na produção de biocombustível. Estudos quanto à domesticação e utilização desta planta, ainda são escassos. Objetivou-se avaliar a divergência entre acessos de tucumanzeiro por caracteres da inflorescência. Foram coletadas inflorescências de 29 acessos conservados no Banco Ativo de Germoplasma da Embrapa Amazônia Oriental para a avaliação de doze caracteres. Os caracteres foram submetidos a análise de multivariada. O caráter número de flores masculinas foi o que mais contribuiu para a divergência entre os acessos, com os demais sendo responsáveis por 0,76 %. As distâncias Euclidianas médias entre os pares de acessos variaram de 0,47 a 3,4 com média de 1,31. Os acessos 16 e 20 se mostraram menos divergentes, enquanto os acessos 11 e 27 os mais distantes. Os 29 acessos formaram seis e dois grupos divergentes pelos métodos de Tocher e UPGMA, respectivamente. Assim sendo, pelo menos seis acessos divergentes podem ser indicados para programas de melhoramento genética dessa palmeira

    Kinematic modelling of a 3-axis NC machine tool in linear and circular interpolation

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    Machining time is a major performance criterion when it comes to high-speed machining. CAM software can help in estimating that time for a given strategy. But in practice, CAM-programmed feed rates are rarely achieved, especially where complex surface finishing is concerned. This means that machining time forecasts are often more than one step removed from reality. The reason behind this is that CAM routines do not take either the dynamic performances of the machines or their specific machining tolerances into account. The present article seeks to improve simulation of high-speed NC machine dynamic behaviour and machining time prediction, offering two models. The first contributes through enhanced simulation of three-axis paths in linear and circular interpolation, taking high-speed machine accelerations and jerks into account. The second model allows transition passages between blocks to be integrated in the simulation by adding in a polynomial transition path that caters for the true machining environment tolerances. Models are based on respect for path monitoring. Experimental validation shows the contribution of polynomial modelling of the transition passage due to the absence of a leap in acceleration. Simulation error on the machining time prediction remains below 1%

    The enzymes LSD1 and Set1A cooperate with the viral protein HBx to establish an active hepatitis B viral chromatin state

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    Indexación: Web of ScienceWith about 350 million people chronically infected around the world hepatitis B is a major health problem. Template for progeny HBV synthesis is the viral genome, organized as a minichromosome (cccDNA) inside the hepatocyte nucleus. How viral cccDNA gene expression is regulated by its chromatin structure; more importantly, how the modulation of this structure impacts on viral gene expression remains elusive. Here, we found that the enzyme SetDB1 contributes to setting up a repressed cccDNA chromatin state. This repressive state is activated by the histone lysine demethylase-1 (LSD1). Consistently, inhibiting or reducing LSD1 levels led to repression of viral gene expression. This correlates with the transcriptionally repressive mark H3K9 methylation and reduction on the activating marks H3 acetylation and H3K4 methylation on viral promoters. Investigating the importance of viral proteins we found that LSD1 recruitment to viral promoters was dependent on the viral transactivator protein HBx. Moreover, the histone methyltransferase Set1A and HBx are simultaneously bound to the core promoter, and Set1A expression correlates with cccDNA H3K4 methylation. Our results shed light on the mechanisms of HBV regulation mediated by the cccDNA chromatin structure, offering new therapeutic targets to develop drugs for the treatment of chronically infected HBV patients.http://www.nature.com/articles/srep2590

    Correlação fenotípica entre caracteres em variedades e híbridos de mandioca (Manihot esculenta Crantz).

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    A mandioca se destaca por ser uma das culturas mais consumidas e de maior importância no mundo, sendo cultivada principalmente, por pequenos e médios produtores rurais. É uma das culturas agrícolas de maior expressão no Brasil, sendo cultivada em todo o território nacional (APLEVICZ e DEMIATE, 2007). Apesar de ser cultivada por pequenos produtores, a cultura da mandioca vem despertando interesses cada vez maiores da indústria. Dentre os subprodutos de maior relevância, podemos destacar a obtenção do amido e a produção de farinha e fécula. Estudos recentes indicam, ainda, o potencial da cultura para a produção de etanol (MORALES et al., 2009). Mesmo sendo uma cultura bastante estudada, as informações quanto às relações entre os caracteres de importância para o melhoramento, são escassos. Assim, faz-se necessário o estudo de correlação fenotípica entre os caracteres. O estudo de correlação tem como propósito, mensurar a alteração em um caráter quando se altera outro. Ao determinar a magnitude desta alteração e a significância das associações entre as características, podemse descriminar quais influenciam na produção (VENCOVSKY e BARRIGA, 1992). Assim, este trabalho objetivou estimar a correlação fenotípica entre o teor de amido e os demais caracteres, em variedades e híbridos de mandioca

    Bubble formation in ϕ6\phi^6 potential

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    Scalar field theory with an asymmetric potential is studied at zero temperature and high-temperature for ϕ6\phi^6 potential. The equations of motion are solved numerically to obtain O(4) spherical symmetric and O(3) cylindrical symmetric bounce solutions. These solutions control the rates for tunneling from the false vacuum to the true vacuum by bubble formation. The range of validity of the thin-wall approximation (TWA) is investigated. An analytical solution for the bounce is presented, which reproduces the action in the thin-wall as well as the thick-wall limits.Comment: 22 pag
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