934 research outputs found
Two-Loop Renormalization of Heavy--Light Currents at Order 1/m_Q in the Heavy-Quark Expansion
We present exact results, at next-to-leading order in renormalization-group
improved perturbation theory, for the Wilson coefficients appearing at order
1/m_Q in the heavy-quark expansion of heavy-light current operators. To this
end, we complete the calculation of the corresponding two-loop anomalous
dimension matrix. Our results are important for determinations of |V_{ub}|
using exclusive and inclusive semileptonic B decays. They are also relevant to
computations of the decay constant f_B based on a heavy-quark expansion.Comment: 16 pages, 2 figures; third author added and one reference updated,
results unchange
The SU(2) and SU(3) chiral phase transitions within Chiral Perturbation Theory
The SU(2) and SU(3) chiral phase transitions in a hot gas made of pions,
kaons and etas are studied within the framework of Chiral Perturbation Theory.
By using the meson meson scattering phase shifts in a second order virial
expansion, we are able to describe the temperature dependence of the quark
condensates. We have estimated the critical temperatures where the different
condensates melt. In particular, the SU(3) formalism yields a lower critical
temperature for the non-strange condensates than within SU(2), and also
suggests that the strange condensate may melt at a somewhat higher temperature,
due to the different strange and non-strange quark masses.Comment: 4 pages, two figures. Final version to appear in Phys Rev D. Complete
model independent calculation. Unitarized ChPt only used to check
extrapolation at high T. References added and numerical bug correcte
"Romanticizing Penniless Entrepreneurs?" The Relationship between Start-Ups and Human Wellbeing across Countries
We study the effect of entrepreneurship and its allocation between necessity and opportunity entrepreneurship on three indicators of countries' wellbeing: monetary wellbeing, non-monetary wellbeing and our own indicator of a country's ability to translate economic growth into non-monetary wellbeing. We take into consideration that there is a feedback effect from monetary and non-monetary wellbeing to entrepreneurial allocation. Using data from the Global Entrepreneurship Monitor we establish that opportunity entrepreneurship may contribute towards national wellbeing and that better wellbeing in turn may stimulate opportunity entrepreneurship. Hence, entrepreneurship may contribute towards countries' wellbeing in a broad sense, and countries with higher levels of wellbeing may contribute towards opportunity entrepreneurship
Aplasia del arco posterior del Atlas
Las anomalías congénitas del arco posterior del Atlas son poco frecuentes. Se
presenta el caso de una paciente, que tras sufrir un accidente se diagnosticó de aplasia parcial
del atlas. Esta lesión es considerada como una variante anatómica benigna de la región cráneovertebral.
Se expone el desarrollo y el significado de esta anomalía.Congenital anomalies of the posterior arch of the atlas are uncommon. This
paper presents the case of a patient who, as result of an accident, was diagnosed as having a
congenital partial agenesia of the posterior arch of the atlas. This finding is considered as a
benign anatomical variation of the craniovertebral junction region. The development and clinical
significance of this anomaly are discussed
Fracturas diafisarias de húmero en adultos: estudio retrospectivo de 53 casos
Se estudian retrospectivamente 53 pacientes adultos con fractura diafisaria de
húmero, 36 de los cuales siguieron el tratamiento ortopédico funcional. En otros 17 casos,
pacientes politraumatizados o con fracturas de tercio medio transversas, realizamos tratamiento
quirúrgico. La edad media de los pacientes fue 48 ± 2 2 años. Se afectó más el lado derecho,
siendo el antecedente etiológico más frecuente el accidente casual. No hubo diferencia entre
el tiempo de consolidación con el tratamiento ortopédico-funcional (60 ± 14 días) y el tratamiento
quirúrgico (56 ±1 2 días). Como complicaciones hubo 7 pseudoartrosis (4 tras tratamiento
ortopédico-funcional y 3 tratamiento quirúrgico). La edad media de los pacientes con
pseudoartrosis fue superior a la de los pacientes con consolidación completa. Ocho casos cursaron
con lesión del nervio radial, obteniendo una recuperación funcional del 100% en un
tiempo medio de 38 ± 30 semanas. Valorando los resultados con arreglo a los criterios de Gayet,
hemos obtenido un 80% de buenos y muy buenos resultados con tratamiento ortopédico
funcional y un 70% con tratamiento quirúrgico.Fifty three adult patients with fracture of the humeral shaft were retrospectively
studied. Orthopaedic-functional treatment was applied in 36 cases. Seventeen patients with
either multiple injuries or transverse middle-shaft fractures were surgically treated. The mean
age of patients was 48 ± 21 years. Right side was most frecuently affected and casual fall was
the predominated etiology. There were no differences regarding the average consolidation period
between fractures treated conservatively (60 ± 14 days) and those undergoing surgery (56 ± 12
days). As complications, there were 7 monounions (4 conservative and 3 operative treatment).
The mean age of patients with non-unions was higther than those with complete fracture consolidation.
Radial nerve injury was seen in 8 cases. In all there patients, a complete functional
were recovery was obtained with a mean average time of 38 ± 30 weeks. When evaluating functional
results according to Gayet, satisfactory results were found in 80 per cent of patients with
conservative treatment and 70 per cent of those surgically treated
Development of a critical structure state alarm system based on the instrumentation of the Botafoc breakwater nº 8 caisson
Balearic Port Authority has developed an instrumentation system for the #8 caisson of the Botafoc breakwater that integrates 12 pressure sensors located at three surfaces, two in contact with the sea water and another with the bottom. This design was completed with an inertial system that measures the angular velocities and the accelerations over the three Cartesian axes. Consequently, the system measures actions (pressures) and reactions (movements and accelerations) experimented by the caisson, due to sea waves and/or other service loads. R+D department of the Port Authority and Polytechnic University of Madrid are working on two directions, the development of new theories on vertical breakwater design that go beyond Goda and Sainflou, and on the creation of a real-time critical structure alarm system, based on the instrumentation installed. This alarm system has two main parts: the instrumentation itself that collects data and processes it on real-time (the data processing compares the pressure law suffered by the caisson in every step process with the design critical state of the caisson, in this case the Goda pressure law for a 6.5 m wave), giving a security coefficient that points out the risk level on real-time; and the alarm system consisting of a monitoring panel located in the Port Control Center that shows the risk level and advises in case of an incidental evacuation of this critical portuary installation
Osteosíntesis con tornillos de Kadar en las fracturas de cuello femoral
Se estudian retrospectivamente 30 pacientes con fractura de cuello femoral, tipo
I y II de Garden, tratadas con osteosíntesis a compresión mediante tornillos de esponjosa tipo
Kadar. La edad media de los pacientes fue de 70±19 años, siendo el accidente casual la
etiología de todas ellas. Se valoró la calidad de la reducción y de la fijación mediante criterios
radiográficos, siendo la reducción óptima en el 93 % de los pacientes y la fijación en el 50%.
Como complicaciones hubo 2 desplazamientos precoces de la fractura. No ha habido ninguna
pseudoartrosis ni necrosis avascular. Valorando los resultados con arreglo a los criterios de
Merle d'Aubigné, hemos obtenidos un 84% de buenos resultados. Creemos que el factor pronóstico
más importante es la reducción anatómica de la fractura.Thirty patients with Garden's type I and II femoral neck fracture treated by
Kadar's spongiosa compressive screws were retrospectively studied. The mean age of patients
was 70±9 years. In all cases, the etiology was a casual accident. Fracture reduction and positioning
of the osteosynthesis were assessed by radiographic criteria. Satisfactory reduction was
achieved in 93 percent of the patients, and the osteosynthesis was accurate in 50 per cent. As
for complications, there were 2 early fracture redisplacement. There were neither non-union
nor avascular necrosis. When evaluating functional results according to Merle d'Aubigné criteria,
satisfactory results were found in 84 per cent of patients. In our opinion, the more important
pronostic factor is the anatomic reduction of the fracture
Integration of modular process simulators under the Generalized Disjunctive Programming framework for the structural flowsheet optimization
The optimization of chemical processes where the flowsheet topology is not kept fixed is a challenging discrete-continuous optimization problem. Usually, this task has been performed through equation based models. This approach presents several problems, as tedious and complicated component properties estimation or the handling of huge problems (with thousands of equations and variables). We propose a GDP approach as an alternative to the MINLP models coupled with a flowsheet program. The novelty of this approach relies on using a commercial modular process simulator where the superstructure is drawn directly on the graphical use interface of the simulator. This methodology takes advantage of modular process simulators (specially tailored numerical methods, reliability, and robustness) and the flexibility of the GDP formulation for the modeling and solution. The optimization tool proposed is successfully applied to the synthesis of a methanol plant where different alternatives are available for the streams, equipment and process conditions.Spanish Ministry of Science and Innovation (CTQ2012-37039-C02-02)
A new technique for recovering energy in thermally coupled distillation using vapor recompression cycles
Even though it has been proved that a fully thermally coupled distillation (TCD) system minimizes the energy used by a sequence of columns, it is well-known that vapor/liquid transfers between different sections produce an unavoidable excess of vapor (liquid) in some of them, increasing both the investment and operating costs. It is proposed here to take advantage of this situation by extracting the extra vapor/liquid and subjecting it to a direct/reverse vapor compression cycle. This new arrangement restores the optimal operating conditions of some of the affected sections with energy savings of around 20–30% compared with conventional TCD columns. Various examples, including the direct and reverse vapor recompression cycles, are presented. Furthermore, in each example, all possible modes of distillation (direct, indirect and Petlyuk distillation) with and without vapor recompression cycles (VRC) are compared to ensure that this approach delivers the best results.The authors would like to acknowledge financial support from the Spanish Ministerio de Ciencias e Innovación (PPQ, CTQ2009–14420-C02-02 and CTQ2012–37039-C02-02)
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