355 research outputs found
MeV Neutron Production from Thermal Neutron Capture in {6}^Li Simulated with Geant4
Various Li compounds are commonly used at neutron facilities as neutron
absorbers. These compounds provide one of the highest ratios of neutron
attenuation to -ray production. Unfortunately, the usage of these
compounds can also give rise to fast neutron emission with energies up to
almost 16 MeV. Historically, some details in this fast neutron production
mechanism can be absent from some modeling packages under some optimization
scenarios. In this work, we tested Geant4 to assess the performance of this
simulation toolkit for the fast neutron generation mechanism. We compare the
results of simulations performed with Geant4 to available measurements. The
outcome of our study shows that results of the Geant4 simulations are in good
agreement with the available measurements for Li fast neutron production,
and suitable for neutron instrument background evaluation at spallation neutron
sources.Comment: 6 pages, 3 figures, Proceeding of The Sixth European Conference on
Neutron Scattering, Zaragoza Spain, August 30 to September 4 201
Evidence of Helicobacter sp. in dental plaque of captive dolphins (Tursiops gephyreus)
Gastrointestinal lesions have been extensively reported in wild and captive marine mammals. However, their etiology remains unclear. In humans and other animals, chronic gastritis and peptic ulcers have been associated with Helicobacter sp. Therefore, the aim of our study was to investigate the presence of Helicobacter sp. in the gastric juice, dental plaque, and saliva of marine mammals living in a controlled environment. Five dolphins (Tursiops gephyreus), one killer whale (Orcinus orca), one false killer whale (Pseudorca crassidens), three sea lions (Otaria flavescens), two elephant seals (Mirounga leonina), and two fur seals (Arctocephalus australis) were studied. Saliva, dental plaque, and gastric juice samples were examined for Helicobacter sp. using polymerase chain reaction. None of the gastric juice or saliva samples were positive for Helicobacter sp. However, Helicobacter sp. DNA was detected in dental plaque from two dolphins, suggesting the oral cavity might be a reservoir of this bacterium.Fil: Goldman, Cinthia Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Loureiro, Julio D.. Fundación Mundo Marino; ArgentinaFil: Quse, Viviana. Fundación Mundo Marino; ArgentinaFil: Corach, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Calderon, Enrique. Fundación Mundo Marino; ArgentinaFil: Caro, Ricardo A.. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Boccio, José. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Heredia, Sergio Rodríguez. Fundación Mundo Marino; ArgentinaFil: Di Carlo, Maria Beatriz. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Zubillaga, Marcela Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentin
Understanding Dwarf Galaxies in order to Understand Dark Matter
Much progress has been made in recent years by the galaxy simulation
community in making realistic galaxies, mostly by more accurately capturing the
effects of baryons on the structural evolution of dark matter halos at high
resolutions. This progress has altered theoretical expectations for galaxy
evolution within a Cold Dark Matter (CDM) model, reconciling many earlier
discrepancies between theory and observations. Despite this reconciliation, CDM
may not be an accurate model for our Universe. Much more work must be done to
understand the predictions for galaxy formation within alternative dark matter
models.Comment: Refereed contribution to the Proceedings of the Simons Symposium on
Illuminating Dark Matter, to be published by Springe
Mutations in the Cholesterol Transporter Gene ABCA5 Are Associated with Excessive Hair Overgrowth
Inherited hypertrichoses are rare syndromes characterized by excessive hair growth that does not result from androgen stimulation, and are often associated with additional congenital abnormalities. In this study, we investigated the genetic defect in a case of autosomal recessive congenital generalized hypertrichosis terminalis (CGHT) (OMIM135400) using whole-exome sequencing. We identified a single base pair substitution in the 5′ donor splice site of intron 32 in the ABC lipid transporter gene ABCA5 that leads to aberrant splicing of the transcript and a decrease in protein levels throughout patient hair follicles. The homozygous recessive disruption of ABCA5 leads to reduced lysosome function, which results in an accumulation of autophagosomes, autophagosomal cargos as well as increased endolysosomal cholesterol in CGHT keratinocytes. In an unrelated sporadic case of CGHT, we identified a 1.3 Mb cryptic deletion of chr17q24.2-q24.3 encompassing ABCA5 and found that ABCA5 levels are dramatically reduced throughout patient hair follicles. Collectively, our findings support ABCA5 as a gene underlying the CGHT phenotype and suggest a novel, previously unrecognized role for this gene in regulating hair growth
The HIBEAM program: search for neutron oscillations at the ESS
With the construction of the European Spallation Source, a remarkable
opportunity has emerged to conduct high sensitivity searches for neutron
oscillations, including a first search for thirty years for free neutrons
converting to antineutrons. Furthermore, searches can be made for transitions
of neutrons and antineutrons to sterile neutron states. The HIBEAM program
provides an increase in sensitivity of an order of magnitude compared to
previous work.
The HIBEAM program corresponds to baryon number violation by one and two
units. The observation of a process satisfying a Sakharov condition addresses
the open question of the origin of the matter-antimatter asymmetry in the
Universe. Sterile neutron states would belong to a `dark' sector of particles
which may explain dark matter. As electrically neutral, meta-stable objects
that can be copiously produced and studied, neutrons represent an attractive
portal to a `dark' sector.
This paper describes the capability, design, infrastructure, and potential of
the HIBEAM program. This includes a dedicated beamline, neutron optical system,
magnetic shielding and control, and detectors for neutrons and antineutrons.Comment: 41 pages, 12 figure
GATA2 Promotes Hematopoietic Development and Represses Cardiac Differentiation of Human Mesoderm.
In vertebrates, GATA2 is a master regulator of hematopoiesis and is expressed throughout embryo development and in adult life. Although the essential role of GATA2 in mouse hematopoiesis is well established, its involvement during early human hematopoietic development is not clear. By combining time-controlled overexpression of GATA2 with genetic knockout experiments, we found that GATA2, at the mesoderm specification stage, promotes the generation of hemogenic endothelial progenitors and their further differentiation to hematopoietic progenitor cells, and negatively regulates cardiac differentiation. Surprisingly, genome-wide transcriptional and chromatin immunoprecipitation analysis showed that GATA2 bound to regulatory regions, and repressed the expression of cardiac development-related genes. Moreover, genes important for hematopoietic differentiation were upregulated by GATA2 in a mostly indirect manner. Collectively, our data reveal a hitherto unrecognized role of GATA2 as a repressor of cardiac fates, and highlight the importance of coordinating the specification and repression of alternative cell fates.Ramón y Cajal Program, Spanish Ministry of Economy, Industry, and Competitiveness, Spanish Cancer Association, FERO, Instituto de Salud Carlos III, European Social Fund, MINECO, PERIS Program of the Generalitat de Catalunya, Obra Social la Caixa-Fundacion Josep Carreras, Spanish Institute of Health Carlos III, Wellcome Trust, MRC, CRUK, NIH-NIDD
The Development of the NNBAR Experiment
The NNBAR experiment for the European Spallation Source will search for free
neutrons converting to antineutrons with a sensitivity improvement of three
orders of magnitude compared to the last such search. This paper describes
progress towards a conceptual design report for NNBAR. The design of a
moderator, neutron reflector, beamline, shielding and annihilation detector is
reported. The simulations used form part of a model which will be used for
optimisation of the experiment design and quantification of its sensitivity.Comment: 30 pages, 26 figures, accepted for publication in Journal of
Instrumentation (JINST
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