323 research outputs found
Multiple-locus heterozygosity, physiology and growth at two different stages in the life cycle of the Chilean oyster Ostrea chilensis
A random sample of 150 individuals of a laboratory-produced cohort of Ostrea chilensis Philippi, 1845 was taken at 10 and 36 mo of age to estimate physiological variables and individual heterozygosity using 4 loci (Lap, Pgi, Pgm and Ca). Juveniles of 10 mo of age showed a mean D value of 0.134 (p > 0.05) and a positive correlation between oyster size and multiple-locus heterozygosity (MLH) (p 0.05), oxygen consumption rate (p < 0.05) and MLH was found. The K2 value (standardized net growth efficiency) was positively correlated (p < 0.05) with MLH. At 36 mo a heterozygote deficiency was present with a mean value D = -0.431 (p < 0.05). No relationship between standard dry weight and MLH and also a negative correlation between the scope for growth and MLH were found. The oxygen consumption and excretion rates also showed an increase in large size individuals. The slopes for filtration and excretion rates against MLH were negative and not statistically significant. However, ingestion and absorption rates showed significant (p < 0.05) decrease with an increase in heterozygosity. The results seem to indicate that within sexually immature individuals of O. chilensis, a positive correlation between growth rate and MLH can be found, while in adults the higher energy allocation for reproduction precludes the detection of this relationship
Cálculo de los factores de intensificación de tensiones generalizados en uniones adhesivas metal-composite
VI CONGRESO NACIONAL DE MATERIALES COMPUESTOS. Celebrado en Valencia del 27-29 de junio de 2005Las uniones adhesivas entre materiales metálicos y compuestos generan puntos críticos
donde la geometría y/o las propiedades de los materiales cambian bruscamente. El
estado tensional que predice la Teoría de la Elasticidad lineal en estos puntos es
singular (el valor de las tensiones no está acotado). La caracterización completa de estos
estados tensionales no acotados se consigue con el cálculo de los exponentes
característicos (órdenes de singularidad de tensiones), las funciones características y los
Factores de Intensificación de Tensiones Generalizados (FITG). En este trabajo se
presenta un procedimiento para el cálculo de los FITG basado en un ajuste por mínimos
cuadrados y el empleo de modelos numéricos de las uniones utilizando el Método de los
Elementos de Contorno (MEC). Se presentan comparaciones para problemas con
solución analítica y ejemplos de aplicación.Ministerio de Ciencia y Tecnología MAT2003-0331
Resolving the Azimuthal Ambiguity in Vector Magnetogram Data with the Divergence-Free Condition: Application to Discrete Data
We investigate how the divergence-free property of magnetic fields can be
exploited to resolve the azimuthal ambiguity present in solar vector
magnetogram data, by using line-of-sight and horizontal heliographic derivative
information as approximated from discrete measurements. Using synthetic data we
test several methods that each make different assumptions about how the
divergence-free property can be used to resolve the ambiguity. We find that the
most robust algorithm involves the minimisation of the absolute value of the
divergence summed over the entire field of view. Away from disk centre this
method requires the sign and magnitude of the line-of-sight derivatives of all
three components of the magnetic field vector.Comment: Solar Physics, in press, 20 pages, 11 figure
Identification and characterization of a nodH ortholog from the alfalfa-nodulating Or191-like rhizobia
Nodulation of Medicago sativa (alfalfa) is known to be restricted to Sinorhizobium meliloti and a few other rhizobia that include the poorly characterized isolates related to Rhizobium sp. strain Or191. Distinctive features of the symbiosis between alfalfa and S. meliloti are the marked specificity from the plant to the bacteria and the strict requirement for the presence of sulfated lipochitooligosaccharides (Nod factors [NFs]) at its reducing end. Here, we present evidence of the presence of a functional nodH-encoded NF sulfotransferase in the Or191-like rhizobia. The nodH gene, present in single copy, maps to a high molecular weight megaplasmid. As in S. meliloti, a nodF homolog was identified immediately upstream of nodH that was transcribed in the opposite direction (local synteny). This novel nodH ortholog was cloned and shown to restore both NF sulfation and the Nif +Fix+ phenotypes when introduced into an S. meliloti nodH mutant. Unexpectedly, however, nodH disruption in the Or191-like bacteria did not abolish their ability to nodulate alfalfa, resulting instead in a severely delayed nodulation. In agreement with evidence from other authors, the nodH sequence analysis strongly supports the idea that the Or191-like rhizobia most likely represent a genetic mosaic resulting from the horizontal transfer of symbiotic genes from a sinorhizobial megaplasmid to a not yet clearly identified ancestor.Instituto de Biotecnologia y Biologia Molecula
Spectral Line Selection for HMI: A Comparison of Fe I 6173 and Ni I 6768
We present a study of two spectral lines, Fe I 6173 Angstroms and Ni I 6768
Angstroms, that were candidates to be used in the Helioseismic and Magnetic
Imager (HMI) for observing Doppler velocity and the vector magnetic field. The
line profiles were studied using the Mt. Wilson Observatory, the Advanced
Stokes Polarimeter and the Kitt Peak McMath telescope and one meter Fourier
transform spectrometer atlas. Both Fe I and Ni I profiles have clean continua
and no blends that threaten instrument performance. The Fe I line is 2% deeper,
15% narrower and has a 6% smaller equivalent width than the Ni I line. The
potential of each spectral line to recover pre-assigned solar conditions is
tested using a least-squares minimization technique to fit Milne-Eddington
models to tens of thousands of line profiles that have been sampled at five
spectral positions across the line. Overall, the Fe I line has a better
performance than the Ni I line for vector magnetic field retrieval. We selected
the Fe I spectral line for use in HMI due to its better performance for
magnetic diagnostics while not sacrificing velocity information
Modeling the Subsurface Structure of Sunspots
While sunspots are easily observed at the solar surface, determining their
subsurface structure is not trivial. There are two main hypotheses for the
subsurface structure of sunspots: the monolithic model and the cluster model.
Local helioseismology is the only means by which we can investigate
subphotospheric structure. However, as current linear inversion techniques do
not yet allow helioseismology to probe the internal structure with sufficient
confidence to distinguish between the monolith and cluster models, the
development of physically realistic sunspot models are a priority for
helioseismologists. This is because they are not only important indicators of
the variety of physical effects that may influence helioseismic inferences in
active regions, but they also enable detailed assessments of the validity of
helioseismic interpretations through numerical forward modeling. In this paper,
we provide a critical review of the existing sunspot models and an overview of
numerical methods employed to model wave propagation through model sunspots. We
then carry out an helioseismic analysis of the sunspot in Active Region 9787
and address the serious inconsistencies uncovered by
\citeauthor{gizonetal2009}~(\citeyear{gizonetal2009,gizonetal2009a}). We find
that this sunspot is most probably associated with a shallow, positive
wave-speed perturbation (unlike the traditional two-layer model) and that
travel-time measurements are consistent with a horizontal outflow in the
surrounding moat.Comment: 73 pages, 19 figures, accepted by Solar Physic
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC
Measurements of inclusive jet suppression in heavy ion collisions at the LHC
provide direct sensitivity to the physics of jet quenching. In a sample of
lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated
luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with
a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the
transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the
anti-kt algorithm with values for the distance parameter that determines the
nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of
the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp.
Jet production is found to be suppressed by approximately a factor of two in
the 10% most central collisions relative to peripheral collisions. Rcp varies
smoothly with centrality as characterized by the number of participating
nucleons. The observed suppression is only weakly dependent on jet radius and
transverse momentum. These results provide the first direct measurement of
inclusive jet suppression in heavy ion collisions and complement previous
measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables,
submitted to Physics Letters B. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02
Identification and characterization of a nodH ortholog from the alfalfa-nodulating Or191-like rhizobia
Nodulation of Medicago sativa (alfalfa) is known to be restricted to Sinorhizobium meliloti and a few other rhizobia that include the poorly characterized isolates related to Rhizobium sp. strain Or191. Distinctive features of the symbiosis between alfalfa and S. meliloti are the marked specificity from the plant to the bacteria and the strict requirement for the presence of sulfated lipochitooligosaccharides (Nod factors [NFs]) at its reducing end. Here, we present evidence of the presence of a functional nodH-encoded NF sulfotransferase in the Or191-like rhizobia. The nodH gene, present in single copy, maps to a high molecular weight megaplasmid. As in S. meliloti, a nodF homolog was identified immediately upstream of nodH that was transcribed in the opposite direction (local synteny). This novel nodH ortholog was cloned and shown to restore both NF sulfation and the Nif +Fix+ phenotypes when introduced into an S. meliloti nodH mutant. Unexpectedly, however, nodH disruption in the Or191-like bacteria did not abolish their ability to nodulate alfalfa, resulting instead in a severely delayed nodulation. In agreement with evidence from other authors, the nodH sequence analysis strongly supports the idea that the Or191-like rhizobia most likely represent a genetic mosaic resulting from the horizontal transfer of symbiotic genes from a sinorhizobial megaplasmid to a not yet clearly identified ancestor.Instituto de Biotecnologia y Biologia Molecula
Enhancing studies of the connectome in autism using the autism brain imaging data exchange II
The second iteration of the Autism Brain Imaging Data Exchange (ABIDE II) aims to enhance the scope of brain connectomics research in Autism Spectrum Disorder (ASD). Consistent with the initial ABIDE effort (ABIDE I), that released 1112 datasets in 2012, this new multisite open-data resource is an aggregate of resting state functional magnetic resonance imaging (MRI) and corresponding structural MRI and phenotypic datasets. ABIDE II includes datasets from an additional 487 individuals with ASD and 557 controls previously collected across 16 international institutions. The combination of ABIDE I and ABIDE II provides investigators with 2156 unique cross-sectional datasets allowing selection of samples for discovery and/or replication. This sample size can also facilitate the identification of neurobiological subgroups, as well as preliminary examinations of sex differences in ASD. Additionally, ABIDE II includes a range of psychiatric variables to inform our understanding of the neural correlates of co-occurring psychopathology; 284 diffusion imaging datasets are also included. It is anticipated that these enhancements will contribute to unraveling key sources of ASD heterogeneity
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