Production of new neutron-rich isotopes of heavy elements in fragmentation reactions of 238^{238}U projectiles at 1 A GeV

The production of heavy neutron-rich nuclei has been investigated using cold fragmentation reactions of $^{238}$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: $^{205}$Pt, $^{207-210}$Au, $^{211-216}$Hg, $^{213-217}$Tl, $^{215-220}$Pb, $^{219-224}$Bi, $^{221-227}$Po, $^{224-229}$At, $^{229-231}$Rn and $^{233}$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 ($z>3$) 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 $\gamma$-ray emitting BL Lac object, 4FGL~J1219.0+3653 (J1219), beyond $z=3$, 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 $\sim$3.5 A supporting its BL Lac nature. The detection of a strong Lyman-$\alpha$ break at $\sim$5570 A, on the other hand, confirms that J2119 is indeed a high-redshift ($z\sim3.59$) 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 $z=3.5$. Future identifications of more $z>3$ $\gamma$-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 ⁷H 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&nbsp;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&nbsp;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