952 research outputs found
Production of new neutron-rich isotopes of heavy elements in fragmentation reactions of U projectiles at 1 A GeV
The production of heavy neutron-rich nuclei has been investigated using cold
fragmentation reactions of U projectiles at relativistic energies. The
experiment performed at the high-resolving-power magnetic spectrometer FRS at
GSI allowed to identify 45 new heavy neutron-rich nuclei: Pt,
Au, Hg, Tl, Pb, Bi,
Po, At, Rn and Fr. The production
cross sections of these nuclei were also determined and used to benchmark
reaction codes that predict the production of nuclei far from stability.Comment: 5 pages, 2 figure
The First Gamma-ray Emitting BL Lacertae Object at the Cosmic Dawn
One of the major challenges in studying the cosmic evolution of relativistic
jets is the identification of the high-redshift () BL Lacertae objects, a
class of jetted active galactic nuclei characterized by their quasi-featureless
optical spectra. Here we report the identification of the first -ray
emitting BL Lac object, 4FGL~J1219.0+3653 (J1219), beyond , i.e., within
the first two billion years of the age of the Universe. The optical and
near-infrared spectra of J1219 taken from 10.4 m Gran Telescopio Canarias
exhibit no emission lines down to an equivalent width of 3.5 A supporting
its BL Lac nature. The detection of a strong Lyman- break at 5570
A, on the other hand, confirms that J2119 is indeed a high-redshift
() quasar. Based on the prediction of a recent BL Lac evolution
model, J1219 is one of the only two such objects expected to be present within
the comoving volume at . Future identifications of more
-ray emitting BL Lac sources, therefore, will be crucial to verify the
theories of their cosmic evolution.Comment: Accepted for publication in The Astrophysical Journal Letter
Experimental investigation of ground-state properties of <sup>7</sup>H with transfer reactions
The properties of nuclei with extreme neutron–to–proton ratios, far from those naturally occurring on Earth, are key to understand nuclear forces and how nucleons hold together to form nuclei. 7H, with six neutrons and a single proton, is the nuclear system with the most unbalanced neutron–to–proton ratio known so far. However, its sheer existence and properties are still a challenge for experimental efforts and theoretical models. Here we report experimental evidences on the formation of 7H as a resonance, detected with independent observables, and the first measurement of the structure of its ground state. The resonance is found at ∼0.7 MeV above the 3H+4n mass, with a narrow width of ∼0.2 MeV and a 1/2+ spin and parity. These data are consistent with a 7H as a 3H core surrounded by an extended four-neutron halo, with a unique four-neutron decay and a relatively long half-life thanks to neutron pairing; a prime example of new phenomena occurring in what would be the most pure-neutron nuclear matter we can access in the laboratory.</p
Mudanças na resistência compreensiva do ionômero de vidro ao ser gravado com ácido ortofosfórico
Introduction: Resin-modified glass ionomers are materials used as an intermediate base in some dental procedures. Our objective was to evaluate the changes that occur in resistance to compression in a light-cured resin-modified glass ionomer after etching it with 37% orthophosphoric acid.
Materials and methods: We carried out an experimental study in vitro. We prepared forty thermoformed molds. The control group (cg) consisted of 20 samples to which no phosphoric acid was applied and the experimental group (ge) included 20 samples that were etched with 37% orthophosphoric acid for 15 seconds and rinsed with water for 40 seconds. All samples were subjected to a compressive test using an Instron universal testing machine. 10 samples of each group were stored in a water bath. For the analysis we used spss version 19. Tukey and Anova tests were performed.
Results: There were statistically significant differences between the groups with and without acid at 15 minutes with respect to the groups with and without acid at 48 hours. (P = 0.01).
Conclusions: The application of 37% phosphoric acid for 15 seconds does not affect the resistance to compression strength of a lightcured resin-modified glass ionomer. Reduction in resistance to compression might be associated with storing the samples in a wet environment.Introducción: los ionómeros de vidrio resinomodificados son materiales usados como base intermedia en procedimientos dentales. El objetivo fue evaluar los cambios que ocurren en la resistencia compresiva de un ionómero de vidrio resinomodificado después de ser grabado con ácido ortofosfórico al 37%.
Materiales y métodos: Estudio experimental in vitro. Se prepararon 40 moldes termoformados, 20 muestras en el grupo experimental (ge) a las que se les aplicó ácido fosfórico durante 15 s y fueron lavadas durante 40 s, y 20 muestras en el grupo control (cg). Diez muestras de cada grupo se almacenaron por 48 horas al baño maría. Todas las muestras fueron sometidas a una fuerza compresiva usando una máquina universal de prueba. El análisis se realizó en el programa estadístico spss versión 19. Se realizaron las pruebas de Tukey y Anova.
Resultados: hubo diferencias estadísticamente significativas entre los grupos con y sin ácido a los 15 minutos con respecto a los grupos con y sin ácido a las 48 horas (P = 0,01).
Conclusiones: la aplicación de ácido fosfórico al 37% no afecta la resistencia compresiva de los ionómeros de vidrio resinomodificados. La reducción en la resistencia compresiva podría estar asociada al almacenamiento en medio húmedo.Introdução: os ionômeros de vidro resinomodificados são materiais usados como base intermediária em procedimentos dentais. O objetivo foi avaliar as mudanças que ocorrem na resistência compreensiva de um ionômero de vidro resinomodificado depois de ser gravado com ácido ortofosfórico a 37%. Materiais e métodos: estudo experimental in vitro. Prepararam-se 40 moldes termoformados, 20 amostras no grupo experimental (ge), às quais foi aplicado ácido fosfórico durante 15s e foram lavadas durante 40s, e 20 amostras no grupo controle (gc). Dez amostras de cada grupo se armazenaram por 48 horas em banho-maria. Todas as amostras foram submetidas a uma forca compreensiva ao usar uma máquina universal de prova. A análise se realizou no programa estatístico spss versão 19. Realizaram-se as provas de Tukey e Anova. Resultados: houve diferenças estatisticamente significativas entre os grupos com e sem ácido aos 15 minutos com relação aos grupos com e sem ácido às 48 horas (P = 0,01). Conclusões: a aplicação de ácido fosfórico a 37% não afeta a resistência compreensiva dos ionômeros de vidro resinomodificados. A redução na resistência compreensiva poderia estar associada ao armazenamento em meio úmido
Chiral three-nucleon forces and bound excited states in neutron-rich oxygen isotopes
We study the spectra of neutron-rich oxygen isotopes based on chiral two- and
three-nucleon interactions. First, we benchmark our many-body approach by
comparing ground-state energies to coupled-cluster results for the same
two-nucleon interaction, with overall good agreement. We then calculate bound
excited states in 21,22,23O, focusing on the role of three-nucleon forces, in
the standard sd shell and an extended sdf7/2p3/2 valence space. Chiral
three-nucleon forces provide important one- and two-body contributions between
valence neutrons. We find that both these contributions and an extended valence
space are necessary to reproduce key signatures of novel shell evolution, such
as the N = 14 magic number and the low-lying states in 21O and 23O, which are
too compressed with two-nucleon interactions only. For the extended space
calculations, this presents first work based on nuclear forces without
adjustments. Future work is needed and open questions are discussed.Comment: 6 pages, 4 figures, published versio
The Evolution of Compact Binary Star Systems
We review the formation and evolution of compact binary stars consisting of
white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and
BHs are thought to be the primary astrophysical sources of gravitational waves
(GWs) within the frequency band of ground-based detectors, while compact
binaries of WDs are important sources of GWs at lower frequencies to be covered
by space interferometers (LISA). Major uncertainties in the current
understanding of properties of NSs and BHs most relevant to the GW studies are
discussed, including the treatment of the natal kicks which compact stellar
remnants acquire during the core collapse of massive stars and the common
envelope phase of binary evolution. We discuss the coalescence rates of binary
NSs and BHs and prospects for their detections, the formation and evolution of
binary WDs and their observational manifestations. Special attention is given
to AM CVn-stars -- compact binaries in which the Roche lobe is filled by
another WD or a low-mass partially degenerate helium-star, as these stars are
thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure
Search for New Physics with Jets and Missing Transverse Momentum in pp collisions at sqrt(s) = 7 TeV
A search for new physics is presented based on an event signature of at least
three jets accompanied by large missing transverse momentum, using a data
sample corresponding to an integrated luminosity of 36 inverse picobarns
collected in proton--proton collisions at sqrt(s)=7 TeV with the CMS detector
at the LHC. No excess of events is observed above the expected standard model
backgrounds, which are all estimated from the data. Exclusion limits are
presented for the constrained minimal supersymmetric extension of the standard
model. Cross section limits are also presented using simplified models with new
particles decaying to an undetected particle and one or two jets
In-house coordination project for organ and tissue procurement: social responsibility and promising results
Abstract Objectives: to report the results of evaluation regarding changes in the number of potential donor referrals, actual donors, and conversion rates after the implementation of an in-house organ and tissue donation for transplantation coordination project. Methods: epidemiological study, both retrospective and transversal, was performed with organ donation data from the Secretariat of Health for the State and the in-house organ donation coordination project of a beneficent hospital. The data was compared using nonparametric statistical Mann-Whitney test, and the Student's t-test, considering a significance level of 5% (p <0.05). Results: there were statistically significant differences (p < 0.05), before and after the implementation of the project on the number of potential donor notification/month (3.05 - 4.7 ), number of actual donor/month (0.78 to 1.60) and rate of conversion ( 24.7 to 34.8 %). The hospitals 1, 2, 7 and 8 had significant results in potential donor, actual donor or conversion rate. Conclusion: the presence of an in-house coordinator is promising and beneficial, the specialist is important to change the indicators of efficiency, which consequently reduces the waiting lists for organ transplants
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