6,421 research outputs found
Analysis of the elastic scattering measured with a 23.7 MeV 7Be beam on a 9Be target.
We present new data for the reaction 7Be+9Be measured at Elab =23.7 MeV. The elastic
scattering angular distribution has been analyzed using the phenomenological optical model and
the coupled-channels method. In the latter approach, we assumed a two-cluster model of the 7Be nucleus, and we included explicitly the ground state and first excited state of this nucleus. The contribution of the inelastic excitation of the 7Be nucleus to the quasielastic cross sections has been investigated.Ministerio de Educación y Ciencia (MEC). España FPA2006-13807-c02-01Spanish Consolider-Ingenio programme CPAN CSD2007-0004
Search for new resonant states in 10C and 11C and their impact on the cosmological lithium problem
The observed primordial 7Li abundance in metal-poor halo stars is found to be
lower than its Big-Bang nucleosynthesis (BBN) calculated value by a factor of
approximately three. Some recent works suggested the possibility that this
discrepancy originates from missing resonant reactions which would destroy the
7Be, parent of 7Li. The most promising candidate resonances which were found
include a possibly missed 1- or 2- narrow state around 15 MeV in the compound
nucleus 10C formed by 7Be+3He and a state close to 7.8 MeV in the compound
nucleus 11C formed by 7Be+4He. In this work, we studied the high excitation
energy region of 10C and the low excitation energy region in 11C via the
reactions 10B(3He,t)10C and 11B(3He,t)11C, respectively, at the incident energy
of 35 MeV. Our results for 10C do not support 7Be+3He as a possible solution
for the 7Li problem. Concerning 11C results, the data show no new resonances in
the excitation energy region of interest and this excludes 7Be+4He reaction
channel as an explanation for the 7Li deficit.Comment: Accepted for publication in Phys. Rev. C (Rapid Communication
The AMS-02 RICH Imager Prototype - In-Beam Tests with 20 GeV/c per Nucleon Ions -
A prototype of the AMS Cherenkov imager (RICH) has been tested at CERN by
means of a low intensity 20 GeV/c per nucleon ion beam obtained by
fragmentation of a primary beam of Pb ions. Data have been collected with a
single beam setting, over the range of nuclear charges 2<Z<~45 in various beam
conditions and using different radiators. The charge Z and velocity beta
resolutions have been measured.Comment: 4 pages, contribution to the ICRC 200
The Ring Imaging Cherenkov detector (RICH) of the AMS experiment
The Alpha Magnetic Spectrometer (AMS) experiment to be installed on the
International Space Station (ISS) will be equipped with a proximity focusing
Ring Imaging Cherenkov (RICH) detector for measuring the electric charge and
velocity of the charged cosmic particles. A RICH prototype consisting of 96
photomultiplier units, including a piece of the conical reflector, was built
and its performance evaluated with ion beam data. Preliminary results of the
in-beam tests performed with ion fragments resulting from collisions of a 158
GeV/c/nuc primary beam of Indium ions (CERN SPS) on a Pb target are reported.
The collected data included tests to the final front-end electronics and to
different aerogel radiators. Cherenkov rings for a large range of charged
nuclei and with reflected photons were observed. The data analysis confirms the
design goals. Charge separation up to Fe and velocity resolution of the order
of 0.1% for singly charged particles are obtained.Comment: 29th International Conference on Cosmic Rays (Pune, India
Phenotypic Characteristics and Copy Number Variants in a Cohort of Colombian Patients with VACTERL Association
VACTERL association (OMIM 192350) is a heterogeneous clinical condition characterized by congenital structural defects that include at least 3 of the following features: vertebral abnormalities, anal atresia, heart defects, tracheoesophageal fistula, renal malformations, and limb defects. The nonrandom occurrence of these malformations and some familial cases suggest a possible association with genetic factors such as chromosomal alterations, gene mutations, and inherited syndromes such as Fanconi anemia (FA). In this study, the clinical phenotype and its relationship with the presence of chromosomal abnormalities and FA were evaluated in 18 patients with VACTERL association. For this, a G-banded karyotype, array-comparative genomic hybridization, and chromosomal fragility test for FA were performed. All patients (10 female and 8 male) showed a broad clinical spectrum: 13 (72.2%) had vertebral abnormalities, 8 (44.4%) had anal atresia, 14 (77.8%) had heart defects, 8 (44.4%) had esophageal atresia, 10 (55.6%) had renal abnormalities, and 10 (55.6%) had limb defects. Chromosomal abnormalities and FA were ruled out. In 2 cases, the finding of microalterations, namely del(15)(q11.2) and dup(17)(q12), explained the phenotype; in 8 cases, copy number variations were classified as variants of unknown significance and as not yet described in VACTERL. These variants comprise genes related to important cellular functions and embryonic development
Probing proton halo effects in the 8B+64Zn collision around the Coulomb barrier
Proton halo effects in the 8B+64Zn reaction at an energy around 1.5 times the Coulomb barrier have been studied at HIE-ISOLDE CERN using, for the first time, the only existing postaccelerated 8B beam. This, together with the use of a high granularity and large solid angle detection system, allowed for a careful mapping of the elastic angular distribution, especially in the Coulomb-nuclear interference region. Contrary to what is observed for the one-neutron halo nucleus 11Be on the same target in a similar energy range, the analysis of the elastic scattering angular distribution shows only a modest suppression of the Coulomb-nuclear interference peak, with no remarkable enhancement of the total reaction cross-section. Inclusive angular and energy distributions of 7Be produced in direct reaction processes have also been measured. The comparison of these data with the results of theoretical calculations for the elastic and non-elastic breakup contributions indicate that both processes are important. Overall, the experimental data suggest a 8B collision dynamics at the barrier very different from the one of neutron halo nuclei, showing only modest effects of coupling to continuum. This behaviour can be interpreted as due to the presence of the additional Coulomb interactions halo-core and halo-target together with the presence of the centrifugal barrier felt by the valence proton of 8B
RNase H2, mutated in Aicardi-GoutiĂšres 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-GoutiĂšres 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 âFormacion Profesorado
Universitarioâ (FPU) PhD fellowship from the Government of Spain (MINECO,
Ref FPU15/03294), and this paper is part of her thesis project (âEpigenetic
control of the mobility of a human retrotransposonâ). 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.Jâs laboratory is supported by the UK Medical Research Council (MRC University Unit grant U127527202). J.L.G.Pâs 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)
Nanoinformatics: developing new computing applications for nanomedicine
Nanoinformatics has recently emerged to address the need of computing applications at the nano level. In this regard, the authors have participated in various initiatives to identify its concepts, foundations and challenges. While nanomaterials open up the possibility for developing new devices in many industrial and scientific areas, they also offer breakthrough perspectives for the prevention, diagnosis and treatment of diseases. In this paper, we analyze the different aspects of nanoinformatics and suggest five research topics to help catalyze new research and development in the area, particularly focused on nanomedicine. We also encompass the use of informatics to further the biological and clinical applications of basic research in nanoscience and nanotechnology, and the related concept of an extended ?nanotype? to coalesce information related to nanoparticles. We suggest how nanoinformatics could accelerate developments in nanomedicine, similarly to what happened with the Human Genome and other -omics projects, on issues like exchanging modeling and simulation methods and tools, linking toxicity information to clinical and personal databases or developing new approaches for scientific ontologies, among many others
The Spectral Energy Distribution of Fermi bright blazars
(Abridged) We have conducted a detailed investigation of the broad-band
spectral properties of the \gamma-ray selected blazars of the Fermi LAT Bright
AGN Sample (LBAS). By combining our accurately estimated Fermi gamma-ray
spectra with Swift, radio, infra-red, optical and other hard X-ray/gamma-ray
data, collected within three months of the LBAS data taking period, we were
able to assemble high-quality and quasi-simultaneous Spectral Energy
Distributions (SED) for 48 LBAS blazars.The SED of these gamma-ray sources is
similar to that of blazars discovered at other wavelengths, clearly showing, in
the usual Log - Log F representation, the typical broad-band
spectral signatures normally attributed to a combination of low-energy
synchrotron radiation followed by inverse Compton emission of one or more
components. We have used these SEDs to characterize the peak intensity of both
the low and the high-energy components. The results have been used to derive
empirical relationships that estimate the position of the two peaks from the
broad-band colors (i.e. the radio to optical and optical to X-ray spectral
slopes) and from the gamma-ray spectral index. Our data show that the
synchrotron peak frequency is positioned between 10 and
10 Hz in broad-lined FSRQs and between and Hz in
featureless BL Lacertae objects.We find that the gamma-ray spectral slope is
strongly correlated with the synchrotron peak energy and with the X-ray
spectral index, as expected at first order in synchrotron - inverse Compton
scenarios. However, simple homogeneous, one-zone, Synchrotron Self Compton
(SSC) models cannot explain most of our SEDs, especially in the case of FSRQs
and low energy peaked (LBL) BL Lacs. (...)Comment: 85 pages, 38 figures, submitted to Ap
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