Statistical mechanics and the description of the early universe II. Principle of detailed balance and primordial 4He formation

If the universe is slightly non-extensive, and the distribution functions are not exactly given by those of Boltzmann-Gibbs, the primordial production of light elements will be non-trivially modified. In particular, the principle of detailed balance (PDB), of fundamental importance in the standard analytical analysis, is no longer valid, and a non-extensive correction appears. This correction is computed and its influence is studied and compared with previous works, where, even when the universe was considered as an slightly non-extensive system, the PDB was assumed valid. We analytically track the formation of Helium and Deuterium, and study the kind of deviation one could expect from the standard regime. The correction to the capture time, the moment in which Deuterium can no longer be substantially photo-disintegrated, is also presented. This allows us to take into account the process of the free decay of neutrons, which was absent in all previous treatments of the topic. We show that even when considering a first (linear) order correction in the quantum distribution functions, the final output on the primordial nucleosynthesis yields cannot be reduced to a linear correction in the abundances. We finally obtain new bounds upon the non-extensive parameter, both comparing the range of physical viability of the theory, and using the latest observational data.Comment: 24 pages, to appear in Physica A (2001

Techno-economic analysis of a hybrid CO2 capture system for natural gas combined cycles with selective exhaust gas recirculation

© 2018 Elsevier Ltd This work analyses the implementation of CO 2 capture in natural gas combined cycle (NGCC) power plants using a hybrid system integrated by an amine scrubbing plant and a CO 2 selective membrane. In this configuration, the membrane unit operates at close to atmospheric pressure and it is used to selectively recycle CO 2 back to the inlet of the compressor, therefore increasing the CO 2 content of the flue gas entering the capture system. A novel integration between the amine capture plant and the selective membrane is analysed here, which aims at exploiting the benefits of both the parallel and series selective exhaust gas recirculation (S-EGR) existing options. The mass and energy balances performed on this system indicate that the new configuration generates a flue gas with a CO 2 -enhanced concentration of 18%vol., which leads to a decrease in the energy demand in the reboiler by 6% with respect to an amine scrubbing system coupled to a conventional NGCC plant without S-EGR. Moreover, a reduction of 77% is achieved in the gas flowrate fed to the absorber of the amine plant, thus significantly reducing its size and cost. The calculated net electrical efficiency of the plant is 50.3%, which is 0.5 net percentage points higher than that of a conventional NGCC with amine-based capture and slightly lower than that of a reference plant with exhaust gas recirculation (EGR). These values are dependent on the pressure drop associated with the membrane system, which has a large influence on the energy balance of the plant. Therefore, higher efficiency improvements can be achieved if membrane module designs with reduced pressure drop are used. A techno-economic evaluation reveals that the cost of the membrane system has a strong effect on the capital costs of the plant and thus, on the cost of electricity and the cost of CO 2 avoided. These values vary between $81.9 and$93.9 per MWh and $82.6 and$121.8 per tonne of CO 2 avoided, respectively, for the S-EGR cases studied at a reference capacity factor of 0.85. A sensitivity analysis shows that it is necessary to reduce the costs of the reference hybrid S-EGR system in order to make it competitive against current benchmark options. Therefore, further ongoing development towards membrane units with high CO 2 permeance, limited pressure drop and reduced costs is particularly interesting for the S-EGR system studied in this work. The obtained results also indicate the targeted values of these parameters that can make the cost of the S-EGR configuration to be below that of conventional systems with amine capture and EGR options for CO 2 capture in NGCC power plants under different scenarios

Evaluation of the performance and economic viability of a novel low temperature carbon capture process

A novel Advanced Cryogenic Carbon Capture (A3C) process is being developed using low cost but high intensity heat transfer to achieve high CO2 capture efficiencies with a much reduced energy consumption and process equipment size. These characteristics, along with the purity of CO2 product and absence of process chemicals, offer the potential for application across a range of sectors. This work presents a techno-economic evaluation for applications ranging from 3% to 35%vol. CO2 content. The A3C process is evaluated against an amine-based CO2 capture process for three applications; an oil-fired boiler, a combined cycle gas turbine (CCGT) and a biogas upgrading plant. The A3C process has shown a modest life cost advantage over the mature MEA technology for the larger selected applications, and substantially lower costs in the smaller biogas application. Enhanced energy recovery and optimization offer significant opportunities for further reductions in cost

The added value of 18f-FDG PET/CT in the assessment of onset and steroid resistant polimyalgia rheumatica

PMR is a common inflammatory rheumatic disease. Although its clinical characteristics are fully recognized, no specific test for its diagnosis has been established to date. Several studies have described a wide variety of diseases that present with polymyalgic symptoms. A 18FDG-PET/CT scan could help to deal with these differential diagnoses. The goal of our study is to describe the findings of the 18FDG-PET/CT scan in a cohort of PMR patients and to detail how the 18FDG-PET/CT scan improves accuracy when diagnosing other underlying conditions. This cross-sectional study enrolled patients with a diagnosis of PMR who underwent to a 18FDG-PET/CT scan to rule out other diagnosis. The 18FDG-PET/CT scan was performed either following clinical criteria at the onset of clinical symptoms or when the patient became PMR steroid resistant. Patients' demographic, clinical and analytical data at the moment of the 18FDG-PET/CT scan were recorded. The final diagnosis was confirmed according to clinical judgement. A total of 103 patients with PMR were included. In 49.51% of patients, the 18FDG-PET/CT scan was ordered to study resistance to steroid therapy. The final diagnoses of patients were PMR in 70.9% patients, large vessel vasculitis in 15.5%, neoplasms 4.8% and another diagnosis in the rest. The 18FDG-PET/CT scan is a very useful technique for the study of Polymyalgia Rheumatica, not only to help in the diagnostic process, but also due to its role in the identification of a variety of PMR-like patrons

El aclareo en fruto: ¿una nueva fuente de compuestos funcionales?

Estudio del contenido en compuestos antioxidantes de los frutos preocedentes del aclareo del melocotón, nectarina y paraguay

Testing postcombustion CO2 capture with CaO in a 1.7 MWt pilot facility

AbstractCalcium looping, CaL, is a new and rapidly developing technology that makes use of CaO as a high temperature regenerable sorbent of CO2. Previous theoretical and lab scale studies have shown that this technology could lead to a substantial reduction in the cost of CO2 capture and energy penalties because heat can be effectively recovered from this high temperature solid looping system. We report in this paper on the first results from a pilot plant designed to demonstrate the viability of postcombustion capture of CO2 using CaL under conditions comparable to those expected in a large scale plant. The pilot includes two interconnected circulating fluidized bed reactors of 15 m height: a CO2 absorber (carbonator) able to treat up to 2400kg/h (equivalent to about 1.7 MWth), and an oxy-fired CFB calciner with a firing power between 1-3 MWth. CO2 capture efficiencies over 90% have been experimentally observed, including continuous operation with highly cycled solids in the system (i.e. with modest CO2 carrying capacities). SO2 capture is shown to be extremely high, with concentrations of SO2 well below 10 ppmv at the exit of the carbonator. Closure of carbon and sulfur balances is satisfactory. These results should be valuable base for model validation and scaling up purposes in future stages of the EU FP7 “CaOling” project, under which this investigation has been carried out

Spatially Explicit Modeling Reveals Cephalopod Distributions Match Contrasting Trophic Pathways in the Western Mediterranean Sea

Populations of the same species can experience different responses to the environment throughout their distributional range as a result of spatial and temporal heterogeneity in habitat conditions. This highlights the importance of understanding the processes governing species distribution at local scales. However, research on species distribution often averages environmental covariates across large geographic areas, missing variability in population- environment interactions within geographically distinct regions. We used spatially explicit models to identify interactions between species and environmental, including chlorophyll a (Chla) and sea surface temperature (SST), and trophic (prey density) conditions, along with processes governing the distribution of two cephalopods with contrasting life-histories (octopus and squid) across the western Mediterranean Sea. This approach is relevant for cephalopods, since their population dynamics are especially sensitive to variations in habitat conditions and rarely stable in abundance and location. The regional distributions of the two cephalopod species matched two different trophic pathways present in the western Mediterranean Sea, associated with the Gulf of Lion upwelling and the Ebro river discharges respectively. The effects of the studied environmental and trophic conditions were spatially variant in both species, with usually stronger effects along their distributional boundaries. We identify areas where prey availability limited the abundance of cephalopod populations as well as contrasting effects of temperature in the warmest regions. Despite distributional patterns matching productive areas, a general negative effect of Chla on cephalopod densities suggests that competition pressure is common in the study area. Additionally, results highlight the importance of trophic interactions, beyond other common environmental factors, in shaping the distribution of cephalopod populations. Our study presents a valuable approach for understanding the spatially variant ecology of cephalopod populations, which is important for fisheries and ecosystem management.Versión del editor4,411

Degradación y utilización de la hemicelulosa contenida en especies forrajeras por Pseudobutyrivibrio xylanivorans aislado del rumen de cabras criollas

Los estudios realizados en el Noreste de Mendoza acerca de la composición botánica de la ingesta caprina indican que existe un predominio de especies arbustivas nativas, tales como Prosopis flexuosa, Atriplex lampa, Tricomaria usillo, Geoffroea decorticans, Mimosa ephedroides y Capparis atamisquea, las que constituyen una importante oferta de fibra vegetal. Por lo tanto, el rol de las bacterias y enzimas fibrolíticas (celulolíticas y hemicelulolíticas) implicadas en la fermentación ruminal adquiere importancia en los sistemas de producción caprina en nuestro país. Recientemente, Grilli et al. (2012) reportaron el aislamiento de Pseudobutyrivibrio xylanivorans a partir del rumen de cabras criollas alimentadas con especies forrajeras nativas. Posteriormente, Grilli et al. (2013) evaluaron la degradación y utilización del xilano, el principal componente de la hemicelulosa sintética, y demostraron que la P. xylanivorans posee una importante actividad hemicelulolítica. Además se identificó en esta cepa uno de los genes que codifican para la enzima hemicelulasa implicada en la digestión de este sustrato. Estos antecedentes proporcionan un marco para profundizar los estudios necesarios para lograr la manipulación de la fermentación ruminal en las cabras criollas. La actividad hemicelulolítica en el ambiente ruminal podría ser modificada mediante la incorporación de la cepa P. xylanivorans al rumen de los caprinos criollos. Para eso serán necesarios estudios que determinen la capacidad probiótica de la cepa. Evaluar la degradación y utilización de la hemicelulosa presente en especies forrajeras nativas y tradicionales por P. xylanivorans. De esta manera, se avanzará en el conocimiento del aprovechamiento de los nutrientes contenidos en estos forrajes para determinar la capacidad probiótica de esa cepa

Identificación de Xilanasas GH10 en las cepas 2 y Mz5 de Pseudobutyrivibrio xylanivorans

El rumen contiene una población bacteriana encargada de la degradación del xilano, el principal componente de la hemicelulosa presente en la pared celular vegetal de los forrajes que consumen las cabras. Las bacterias del rumen, principalmente los géneros Butyrivibrio y Pseudobutyrivibrio, sintetizan una gama de enzimas xilanolíticas para la digestión eficaz de los componentes de la pared celular. Los genes que codifican para xilanasas pertenecientes a la familia glicosil hidrolasa 11 (GH11) y la actividad xilanasa asociada han sido identificados en la cepa tipo (Mz5) de P. xylanivorans. Por el contrario, poco se sabe acerca de la diversidad y distribución de los genes xilanasa GH10 en otras cepas de Pseudobutyrivibrio. // El objetivo del presente estudio fue identificar genes xilanasa GH10 en P. ruminis 153, P. xylanivorans 2 y Mz5. Además, se evaluó la degradación y utilización de xilano por las cepas aisladas del rumen de cabras Criollas. Se identificó un gen xilanasa (xynAPx) en P. xylanivorans 2 y otro gen xilanasa diferente (xynBMz5) en P. xylanivorans Mz5. Estos genes se relacionaron con enzimas presentes en especies de Butyrivibrio. P. xylanivorans 2 fue capaz de utilizar hasta el 53% de las pentosas totales presentes en el xilano de la madera de abedul (BWX) y utilizar hasta el 62% del BWX. // La presencia de genes xilanasas GH10 y la actividad xilanasa reportada en P. xylanivorans 2, permitió concluir el rol funcional de esta cepa en la degradación de la hemicelulosa presente en forrajes con abundante contenido de fibra vegetal. Esta característica podría ser uno de los mecanismos de adaptación de los caprinos Criollos para el aprovechamiento de forrajes de baja calidad nutricional que consumen en el campo natural