The Non-Mesonic Weak Decay of Double-Lambda Hypernuclei: A Microscopic Approach

The non--mesonic weak decay of double--$\Lambda$ hypernuclei is studied within a microscopic diagrammatic approach. Besides the nucleon--induced mechanism, $\Lambda N\to nN$, widely studied in single--$\Lambda$ hypernuclei, additional hyperon--induced mechanisms, $\Lambda \Lambda\to \Lambda n$, $\Lambda \Lambda\to \Sigma^0 n$ and $\Lambda \Lambda\to \Sigma^-p$, are accessible in double--$\Lambda$ hypernuclei and are investigated here. As in previous works on single--$\Lambda$ hypernuclei, we adopt a nuclear matter formalism extended to finite nuclei via the local density approximation and a one--meson exchange weak transition potential (including the ground state pseudoscalar and vector octets mesons) supplemented by correlated and uncorrelated two--pion--exchange contributions. The weak decay rates are evaluated for hypernuclei in the region of the experimentally accessible light hypernuclei $^{10}_{\Lambda\Lambda}$Be and $^{13}_{\Lambda\Lambda}$B. Our predictions are compared with a few previous evaluations. The rate for the $\Lambda \Lambda\to \Lambda n$ decay is dominated by $K$--, $K^*$-- and $\eta$--exchange and turns out to be about 2.5\% of the free $\Lambda$ decay rate, $\Gamma_{\Lambda}^{\rm free}$, while the total rate for the $\Lambda \Lambda\to \Sigma^0 n$ and $\Lambda \Lambda\to \Sigma^- p$ decays, dominated by $\pi$--exchange, amounts to about 0.25\% of $\Gamma_{\Lambda}^{\rm free}$. The experimental measurement of these decays would be essential for the beginning of a systematic study of the non--mesonic decay of strangeness $-2$ hypernuclei. This field of research could also shed light on the possible existence and nature of the $H$--dibaryon.Comment: 17 pages, 2 figure

High-performance functional renormalization group calculations for interacting fermions

We derive a novel computational scheme for functional Renormalization Group (fRG) calculations for interacting fermions on 2D lattices. The scheme is based on the exchange parametrization fRG for the two-fermion interaction, with additional insertions of truncated partitions of unity. These insertions decouple the fermionic propagators from the exchange propagators and lead to a separation of the underlying equations. We demonstrate that this separation is numerically advantageous and may pave the way for refined, large-scale computational investigations even in the case of complex multiband systems. Furthermore, on the basis of speedup data gained from our implementation, it is shown that this new variant facilitates efficient calculations on a large number of multi-core CPUs. We apply the scheme to the $t$,$t'$ Hubbard model on a square lattice to analyze the convergence of the results with the bond length of the truncation of the partition of unity. In most parameter areas, a fast convergence can be observed. Finally, we compare to previous results in order to relate our approach to other fRG studies.Comment: 26 pages, 9 figure

The molecular environment of the pillar-like features in the HII region G46.5-0.2

At the interface of HII regions and molecular gas peculiar structures appear, some of them with pillar-like shapes. Understanding their origin is important for characterizing triggered star formation and the impact of massive stars on the interstellar medium. In order to study the molecular environment and the influence of the radiation on two pillar-like features related to the HII region G46.5-0.2, we performed molecular line observations with the Atacama Submillimeter Telescope Experiment, and spectroscopic optical observations with the Isaac Newton Telescope. From the optical observations we identified the star that is exciting the HII region as a spectral type O4-6. The molecular data allowed us to study the structure of the pillars and a HCO+ cloud lying between them. In this HCO+ cloud, which have not any well defined 12CO counterpart, we found direct evidence of star formation: two molecular outflows and two associated near-IR nebulosities. The outflows axis orientation is perpendicular to the direction of the radiation flow from the HII region. Several Class I sources are also embedded in this HCO+ cloud, showing that it is usual that the YSOs form large associations occupying a cavity bounded by pillars. On the other hand, it was confirmed that the RDI process is not occurring in one of the pillar tips.Comment: Accepted in MNRAS (2017 June 13

Incidencia de alteraciones cardiovasculares en caballos criollos colombianos mediante diagnóstico ecocardiográfico

Páginas 61-68Recurso ElectrónicoEl trabajo se realizó en la ciudad de Ibagué con 47 caballos criollos colombianos con un peso medio de 282 ± 20 kg con una edad media de 6 ± 1,4 años. Todos sospechosos de padecer alteraciones cardiacas, con tos persistente, disnea e intolerancia al ejercicio. En el examen semiológico, mediante toma de pulso, frecuencia cardiaca, auscultación de sonidos cardiacos y pulmonares para determinar signología que reflejarán una afección cardiovascular, resultaron 25 equinos con signos evidentes de padecer alteraciones cardiacas. Se hizo evaluación con ecocardiografías en modo B y M, con el animal en reposo físico. Posteriormente se procedió a ejercitarlos, por veinte minutos, para tomar nuevamente y en forma inmediata el pulso, la frecuencia cardiaca, hacer auscultación cardiopulmonar y ecocardiografía en modo B y M, con el fin de detectar anormalidades cardiacas que no fueron mostradas por el animal en reposo. De estos, cinco mostraron insuficiencia mitral y dos presentaron arritmias cardiacas. Se construyeron intervalos de confianza, usando distribución de probabilidad exacta para una binomial, determinando así la probabilidad de que un equino sospechoso manifestara insuficiencia mitral (entre el 3,55 % y 23,10 %) o de que apareciera arritmia (entre el 0,05 % y el 11,29 %), igual probabilidad para la arritmia por vagotonía.ABSTRACT. The work was carried out in Ibague, with 47 Colombian Creole horses, between 250 and 350 kg with 6 ± 1,4 years-old, suspected of suffering cardiac alterations, persistent cough, dyspnea and exercise intolerance. After the semiological examination, with taking the pulse, heart rate, auscultation of heart and lung sounds to determine signs that reflected a cardiovascular affection, twenty-five horses showed evident signs of suffering heart alterations, evaluating them with B and M mode echocardiography and with the animal in physical rest, proceeding to exercise them for twenty minutes and taking the pulse and the heart frequency immediately, auscultating the heart again to detect heart abnormalities that were not shown by the animal in rest. According to test results, five showed mitral insufficiency and two had cardiac arrhythmias. As the sample size of the equine cardiac diseases is small, intervals of trust were built using distribution of exact probability for a binomial one, determining the probability that a suspected equine manifested mitral insufficiency it would be between 3,55 % and 23,10 %; or that arrhythmia appeared (between 0,05 % and 11,29 %),the same probability for the arrhythmia by vagotonia

Mapping participatory planning in Havana: patchwork legacies for a strengthened local governance

In 2019, Cuba approved a new political constitution that calls for deepening citizen participation to strengthen local governance. The emerging decentralization processes and the role of new actors in urban development open new possibilities for inclusive planning. While citizen participation is widely documented in the global South and under Western liberal democracy regimes, participatory urban planning in the context of Southern socialist cities such as Havana has been less scrutinized. This paper aims at mapping the framings, trajectories and legacies of such participatory planning initiatives. Based on mapping workshops and desktop research, we find that participatory initiatives within Havana are spatially dispersed, sporadic, lacking at the city level, and occurring in isolation at the neighbourhood level. We argue that establishing sustained participatory urban planning practices in Havana requires decision makers to scale outwards and upwards the lessons learned from existing initiatives to foster a city-wide participatory planning strategy

Northern hemisphere stratospheric pathway of different El Niño Flavors in stratosphere-resolving CMIP5 models

AbstractThe Northern Hemisphere (NH) stratospheric signals of eastern Pacific (EP) and central Pacific (CP) El Niño events are investigated in stratosphere-resolving historical simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), together with the role of the stratosphere in driving tropospheric El Niño teleconnections in NH climate. The large number of events in each composite addresses some of the previously reported concerns related to the short observational record. The results shown here highlight the importance of the seasonal evolution of the NH stratospheric signals for understanding the EP and CP surface impacts. CMIP5 models show a significantly warmer and weaker polar vortex during EP El Niño. No significant polar stratospheric response is found during CP El Niño. This is a result of differences in the timing of the intensification of the climatological wavenumber 1 through constructive interference, which occurs earlier in EP than CP events, related to the anomalous enhancement and earlier development of the Pacific–North American pattern in EP events. The northward extension of the Aleutian low and the stronger and eastward location of the high over eastern Canada during EP events are key in explaining the differences in upward wave propagation between the two types of El Niño. The influence of the polar stratosphere in driving tropospheric anomalies in the North Atlantic European region is clearly shown during EP El Niño events, facilitated by the occurrence of stratospheric summer warmings, the frequency of which is significantly higher in this case. In contrast, CMIP5 results do not support a stratospheric pathway for a remote influence of CP events on NH teleconnections

Hydrochemical characterization of a mine water geothermal energy resource in NW Spain

Abandoned and flooded mine networks provide underground reservoirs of mine water that can be used as a renewable geothermal energy source. A complete hydrochemical characterization of mine water is required to optimally design the geothermal installation, understand the hydraulic behavior of the water in the reservoir and prevent undesired effects such as pipe clogging via mineral precipitation. Water pumped from the Barredo-Figaredo mining reservoir (Asturias, NW Spain), which is currently exploited for geothermal use, has been studied and compared to water from a separate, nearby mountain mine and a river that receives mine water discharge and partially infiltrates into the mine workings. Although the hydrochemistry was altered during the flooding process, the deep mine waters are currently near neutral, net alkaline, high metal waters of Na-HCO3 type. Isotopic values suggest that mine waters are closely related to modern meteoric water, and likely correspond to rapid infiltration. Suspended and dissolved solids, and particularly iron content, of mine water results in some scaling and partial clogging of heat exchangers, but water temperature is stable (22 °C) and increases with depth, so, considering the available flow (> 100 L s− 1), the Barredo-Figaredo mining reservoir represents a sustainable, long-term resource for geothermal use