Factorization theorems for exclusive heavy-quarkonium production

We outline the proofs of the factorization theorems for exclusive two-body charmonium production in B-meson decay and e^+e^- annihilation to all orders in perturbation theory in quantum chromodynamics. We find that factorized expressions hold up to corrections of order m_c/m_b in B-meson decay and corrections of order m_c^2/s in e^+e^- annihilation, where m_c is the charm-quark mass, m_b is the bottom-quark mass, and root-s is the e^+e^- center-of-momentum energy.Comment: 4 pages, 2 figure

Factorization of low-energy gluons in exclusive processes

We outline a proof of factorization in exclusive processes, taking into account the presence of soft and collinear modes of arbitrarily low energy, which arise when the external lines of the process are taken on shell. Specifically, we examine the process of e^+e^- annihilation through a virtual photon into two light mesons. In an intermediate step, we establish a factorized form that contains a soft function that is free of collinear divergences. In contrast, in soft-collinear effective theory, the low-energy collinear modes factor most straightforwardly into the soft function. We point out that the cancellation of the soft function, which relies on the color-singlet nature of the external hadrons, fails when the soft function contains low-energy collinear modes.Comment: 18 pages, 10 figures, 2 tables, version published in Physical Review

Effects of woody vegetation patches on species composition in Stipa tenacissima steppes

Stipa tenacissima steppes cover 70, 000 km2 in the Mediterranean basin. In these habitats, resprouting shrubs form woody patches that were removed in the past to promote fiber and forage production. Patches are recovering after decades of abandonment. Patches enhance plant richness and affect ecosystem functioning. Yet, they have been commonly considered as a single entity, paying scarce attention to patch heterogeneity, patch dynamics and their impact on community composition. We describe the physical and biotic structure of 450 patches in 15 catchments along a climate gradient in southeastern Spain, and analyze the drivers of overstory and understory composition and recruitment of patch-forming species. Patches were formed by one to six species (Quercus coccifera, Juniperus oxycedrus, Rhamnus lycioides, Ephedra fragilis, Pistacia lentiscus and Osyris lanceolata). Climate determined the species composition in each patch, their physical characteristics and the recruitment of patch-forming species. Species cover and richness depended on the dominant species. Our results suggest that patches dominated by Quercus coccifera and Juniperus oxycedrus may decline and patches dominated by Rhamnus lycioides and Ephedra fragilis may expand as climate warms. They also provide new insights on the interactions in patch communities very relevant for the conservation and management of S. tenacissima steppes

Factorization in exclusive quarkonium production

We present factorization theorems for two exclusive heavy-quarkonium production processes: production of two quarkonia in e^+e^- annihilation and production of a quarkonium and a light meson in B-meson decays. We describe the general proofs of factorization and supplement them with explicit one-loop analyses, which illustrate some of the features of the soft-gluon cancellations. We find that violations of factorization are generally suppressed relative to the factorized contributions by a factor v^2m_c/Q for each S-wave charmonium and a factor m_c/Q for each L-wave charmonium with L>0. Here, v is the velocity of the heavy quark or antiquark in the quarkonium rest frame, Q=sqrt{s} for e^+e^- annihilation, Q=m_B for B-meson decays, sqrt{s} is the e^+e^- center-of-momentum energy, m_c is the charm-quark mass, and m_B is the B-meson mass. There are modifications to the suppression factors if quantum-number restrictions apply for the specific process.Comment: 69 pages, 12 figures, 2 tables. v2: Version published in Physical Review

Michel decay spectrum for a muon bound to a nucleus

The spectrum of electrons from muons decaying in an atomic bound state is significantly modified by their interaction with the nucleus. Somewhat unexpectedly, its first measurement, at the Canadian laboratory TRIUMF, differed from basic theory. We show, using a combination of techniques developed in atomic, nuclear, and high-energy physics, that radiative corrections eliminate the discrepancy. In addition to solving that outstanding problem, our more precise predictions are potentially useful for interpreting future high-statistics muon experiments that aim to search for exotic interactions at $10^{-16}$ sensitivity.Comment: 6 pages, 4 figures, Alberta Thy 7-14 v2: Expanded discussion. Journal versio

The use of branch piles to assist in the restoration of degraded semiarid steppes

Desertification is a major environmental problem in arid and semiarid regions. Tree plantation has been commonly employed to foster the recovery of degraded areas. However, this technique is costly, and their outcomes are often uncertain. Therefore, we evaluated an alternative method for the restoration of degraded semiarid steppes that involved the construction of branch piles to attract frugivores as potential seed-dispersing birds, promoting seed rain, and fostering the formation of woody patches. We measured the success of branch piles in terms of the number of bird visits and seed input compared to naturally occurring shrub patches. Generally, frugivorous birds visited branch piles less frequently than shrub patches. Yet, branch piles accumulated seeds of patch-forming shrub species. Seed rain was higher under patches of the dominant shrub Rhamnus lycioides than under branch piles. In contrast, woody patches and branch piles did not differ in seed input of the less abundant Pistacia lentiscus shrub. Our study demonstrates that branch piles are used by frugivorous birds and accumulate seeds of patch-forming shrubs. Branch piles may be a suitable method to promote the expansion of bird-dispersed plant species and restore semiarid wooded steppes. However, their efficiency largely depends on pile persistence and economic cost

Muon decay in orbit spectra for muon-electron conversion experiments

We have determined in detail the electron spectrum in the decay of bound muons. These results are especially relevant for the upcoming muon-electron conversion experiments.Comment: submitted to Proceedings of the International Conference on Exotic Atoms and Related Topics (EXA 2011

Aplicación de TICS (Formulario on-line) como metodología docente activa en estudios de postgrado

In the current Information Society there is a growing number of free or low-cost technological tools that can be used to improve training processes in higher education. This is the case of the online forms (Google Forms), which can be filled in with any mobile device, such as smartphones, tablets, computers... instruments that are used by students today permanently. Students are often not fully conscious of the progress in the acquisition of knowledge or skills involved in their participation in formal education. For this reason, in the context of an official postgraduate teaching degree recently introduced at the University of León, the University Master’s Degree in Sports Training and Performance, a technological instrument has been applied (on-line forms for collecting information) aimed at making students aware of their learning and progress in their competences related to the subjects they are studying. These forms have allowed those in charge of the subjects taught in these studies to collect information that can be quickly used in decision-making to adapt the training process to the needs and realities of the students, as well as to optimise and improve it. This initiative has been very well received by students and teaching staff, with a great participation and acceptance, providing a very positive image of innovation and current relevance of this official title of the University of León. This study has been developed within the Plan of support for teaching innovation of the University of León (PAID 2017), under the title “Application of ICTs (On-Line Forms) as an active teaching methodology in the Master’s Degree in Sports Training and Performance”.En la actual Sociedad de la Información existe un número creciente de herramientas tecnológicas gratuitas o de bajo coste que pueden ser empleadas para la mejora de los procesos formativos en la enseñanza superior. Éste es el caso de los formularios on-line (Google Forms), los cuales pueden ser cumplimentados haciendo uso de cualquier dispositivo móvil, tales como smartphone, tablets, ordenadores, … instrumentos que hoy en día son usados permanentemente por los alumnos/ as. Con frecuencia, los estudiantes no son totalmente conscientes de los progresos en la adquisición de conocimientos o competencias que conlleva su participación en enseñanzas oficiales. Es por ello, que el en contexto de un título oficial de enseñanza de posgrado de reciente implantación en la Universidad de León, el Máster Universitario en Entrenamiento y Rendimiento Deportivo, se ha aplicado un instrumento tecnológico (formularios on-line de recogida de información) encaminado a que los alumnos/as hagan consciente sus aprendizajes y progresos en sus competencias vinculados con las materias que cursan. Estos formularios, a su vez han permitido a los responsables de las asignaturas impartidas en estos estudios, recoger información que podrá ser rápidamente empleada en la toma de decisiones para adaptar/adecuar el proceso formativo a las necesidades y realidades de los estudiantes, así como para la optimización y mejora del mismo. Esta iniciativa ha tenido muy buena acogida tanto por los estudiantes como por el equipo docente, con una gran participación y aceptación, aportado una imagen muy positiva de innovación y actualidad de este título oficial de la Universidad de León. Este estudio se ha desarrollado dentro del Plan de apoyo a la innovación docente de la Universidad de León (PAID 2017), bajo el título “Aplicación de TICs (Formularios On-Line) como metodología docente activa en el Máster Universitario en Entrenamiento y Rendimiento Deportivo”

Phage inducible islands in the gram-positive cocci

The SaPIs are a cohesive subfamily of extremely common phage-inducible chromosomal islands (PICIs) that reside quiescently at specific att sites in the staphylococcal chromosome and are induced by helper phages to excise and replicate. They are usually packaged in small capsids composed of phage virion proteins, giving rise to very high transfer frequencies, which they enhance by interfering with helper phage reproduction. As the SaPIs represent a highly successful biological strategy, with many natural Staphylococcus aureus strains containing two or more, we assumed that similar elements would be widespread in the Gram-positive cocci. On the basis of resemblance to the paradigmatic SaPI genome, we have readily identified large cohesive families of similar elements in the lactococci and pneumococci/streptococci plus a few such elements in Enterococcus faecalis. Based on extensive ortholog analyses, we found that the PICI elements in the four different genera all represent distinct but parallel lineages, suggesting that they represent convergent evolution towards a highly successful lifestyle. We have characterized in depth the enterococcal element, EfCIV583, and have shown that it very closely resembles the SaPIs in functionality as well as in genome organization, setting the stage for expansion of the study of elements of this type. In summary, our findings greatly broaden the PICI family to include elements from at least three genera of cocci

Rotura de vástago femoral de prótesis total de cadera enteramente recubierta de hidroxiapatita. Presentación de tres casos.

Presentamos la descripción de tres casos de rotura de vástago femoral de una prótesis total de cadera enteramente recubierta de hidroxiapatita (Furlong, JRI limited, London), sin antecedente traumático. En dos pacientes el tiempo de evolución fue de 7 años tras el implante primario, y en un caso la rotura del vástago se produjo a los 5 años. El fallo del implante se produjo en todos los casos a nivel de la zona de transición metafiso-diafisaria- infundibulo-. La osteointegración del implante en la porción distal del vástago, favorecida por el recubrimiento de hidroxiapatita produce una transmisión anómala de cargas a nivel de la unión metafisodiafisaria y aumenta el riesgo de fallo del material en los casos descritos.We are describing 3 cases of femoral component failure of a total hip arthroplasty with fully coated hidroxiapa- tite (Furlong, JRI limited, London), without any traumatic event. The follow-up before failure was 7 and 5 years. The fracture of femoral stem was always just distal to the metap- hisal cone. The ingrowth of the distal portion of the femoral component increased by hidrixiapatite causes abnormal transmission of biomechanical forces in the metafiso-diafisal union increasing the risk of material failure