Seeding approach to bubble nucleation in superheated Lennard-Jones fluids

We investigate vapor homogeneous nucleation in a superheated Lennard-Jones liquid with computer simulations. Special simulation techniques are required to address this study since the nucleation of a critical vapor bubble-one that has an equal chance to grow or shrink-in a moderately superheated liquid is a rare event. We use the Seeding method, which combines Classical Nucleation Theory with computer simulations of a liquid containing a vapor bubble to provide bubble nucleation rates in a wide temperature range. Seeding has been successfully applied to investigate the nucleation of crystals in supercooled fluids, and here we apply it to the liquid-to-vapor transition. We find that the Seeding method provides nucleation rates that are consistent with independent calculations not based on the assumptions of Classical Nucleation Theory. Different criteria to determine the radius of the critical bubble give different rate values. The accuracy of each criterion depends of the degree of superheating. Moreover, seeding simulations show that the surface tension depends on pressure for a given temperature. Therefore, using Classical Nucleation Theory with the coexistence surface tension does not provide good estimates of the nucleation rate

In vitro caecal fermentation of carbohydrate-rich feedstuffs in rabbits as affected by substrate pre-digestion and donors' diet

[EN] The influence of substrate pre-digestion and donors’ diet on in vitro caecal fermentation of different substrates in rabbits was investigated. Eight crossbreed rabbits were fed 2 experimental diets containing either low (LSF; 84.0 g/kg dry matter [DM]) or high soluble fibre (HSF; 130 g/kg DM) levels. In vitro incubations were conducted using batch cultures with soft faeces as inoculum and four fibrous or fibre-derived, low-starch and low-protein substrates: D-cellobiose (CEL), sugar beet pectin (PEC), sugar beet pulp (SBP) and wheat straw (WS). Substrates in half of the cultures were subjected to a 2-step pepsin/pancreatin in vitro digestion without filtration, and the whole residue (soluble, insoluble and added enzymes) was incubated at 39°C. Gas production was measured until 144 h, and volatile fatty acid (VFA) production at 24 h incubation was determined. Cultures without substrate (blanks) were included to correct gas production values for gas released from endogenous substrates and added enzymes. Pre-digestion had no influence on in vitro gas production kinetic of WS, and only reduced the time before gas production begins (lag time; by 31%; P=0.042) for SBP, but for both substrates the pre-digestion decreased the molar proportion of acetate (by 9%; P≤0.003) and increased those of propionate and butyrate (P≤0.014). For CEL, the pre-digestion increased the gas and total VFA production (by 30 and 114%), shortened the lag time (by 32%), and only when it was combined with LSF inoculum 38 percentage units of acetate were replaced by butyrate (P≤0.039). Treatments had a minor influence on in vitro fermentation traits of SBP pectin. The results showed that the pre-digestion process influenced the in vitro caecal fermentation in rabbits, but the effects were influenced by donors’ diet and the incubated substrate. Pre-digestion of substrate is recommended before conducting in vitro caecal fermentations. The level of soluble fibre in the donors’ diet also influenced the in vitro caecal fermentation, but its effect depended on the type of substrate.Funding from the Spanish Ministry of Economy and Competitiveness (Projects AGL2011-23885 and AGL2011-22628) and the Comunidad Autónoma de Madrid (CAM; Project MEDGAN ABI-2913) is gratefully acknowledged.Ocasio-Vega, C.; Abad-Guamán, R.; Delgado, R.; Carabaño, R.; Carro, M.; García, J. (2018). In vitro caecal fermentation of carbohydrate-rich feedstuffs in rabbits as affected by substrate pre-digestion and donors' diet. World Rabbit Science. 26(1):15-25. https://doi.org/10.4995/wrs.2018.7854SWORD152526

Toxicity study in a pig model of intraperitoneal collagenase as an “enzymatic scalpel” directed to break stroma in order to generate a new perspective for peritoneal carcinomatosis approach: an experimental research

Background: This study aimed to measure the toxicity resulting from collagenase administration to the peritoneal cavity in a pig model as a preliminary step to break down the stroma surrounding tumors. Methods: Eight pigs were treated with 2 different collagenase concentrations previously tested in rats by our group. Time and temperature were controlled using a peritoneal lavage system (PRS System, Combat Medical Ltd.) identical to that used in human surgeries through hyperthermic intraperitoneal chemotherapy (HIPEC); 2 additional pigs were treated with peritoneal lavage only. Samples of blood and peritoneal fluid were collected pre-treatment, immediately after treatment, and 24 h postoperatively. In addition, histological studies and blood collagenase levels were measured. Results: No complications were observed during the surgeries. Intraoperative images evidenced the release of peritoneal tissue during collagenase treatment. After surgery, the animals showed no signs of pain. Diet and mobility were normal at 4 h postoperatively, and there were no significant differences in hematologic or biochemical parameters. Quantification of MMP1 and MMP2 in all samples as measured by absorbance showed no differences in blood collagenase levels between pre-treatment, post-treatment, and 24 h postoperatively. None of the animals treated with collagenase showed peritoneal adhesions during the second surgery. Histologically, peritoneal organs and serous structures did not show any microscopic alterations associated with collagenase treatment in any group. Conclusion: Lavage of the peritoneal cavity with doses of up to 100,000 collagen digestion units/animal for 30 min is safe and removes connective tissue from the peritoneal cavity

Methanol and ammonia as emerging green fuels: Evaluation of a new power generation paradigm

[EN]In the current context of the energy transition, the use of liquid fuels is attracting attention to be used as energy storage, due to the inherent fluctuations of the main renewable energy sources. In addition, these liquid fuels have also been proposed as energy carriers, to introduce renewables in hard-to-electrify applications. Methanol and ammonia emerge as the two most promising green liquid fuels for energy purposes. In this work, a systematic assessment of the transformation of methanol/ammonia into power is performed. Two different routes have been studied: thermochemical (through fuel combustion) and electrochemical (using fuel cells). From a technical analysis, the methanol process reaches the highest efficiency, around 38%. In general, thermochemical processes show better performance in terms of energy efficiency. From an economic perspective, the current costs of the thermochemical route are around 0.3 €/kWh and 0.6-1 €/kWh for the electrochemical. Electricity cost is expected to be reduced as process efficiency increases down to values of around 0.1 €/kWh. A progressive introduction of these green liquid fuels will be necessary to achieve a 100% renewable energy system in all areas, guaranteeing the long-term sustainability of the planet

Conjugation of cell-penetrating peptides with poly(Lactic-co-glycolic acid)-polyethylene glycol nanoparticles improves ocular drug delivery

In this work, a peptide for ocular delivery (POD) and human immunodeficiency virus transactivator were conjugated with biodegradable poly(lactic-co-glycolic acid) (PGLA)- polyethylene glycol (PEG)-nanoparticles (NPs) in an attempt to improve ocular drug bioavail- ability. The NPs were prepared by the solvent displacement method following two different pathways. One involved preparation of PLGA NPs followed by PEG and peptide conjugation (PLGA-NPs-PEG-peptide); the other involved self-assembly of PLGA-PEG and the PLGA-PEG- peptide copolymer followed by NP formulation. The conjugation of the PEG and the peptide was confrmed by a colorimetric test and proton nuclear magnetic resonance spectroscopy. Flur- biprofen was used as an example of an anti-inflammatory drug. The physicochemical properties of the resulting NPs (morphology, in vitro release, cell viability, and ocular tolerance) were studied. In vivo anti-inflammatory effcacy was assessed in rabbit eyes after topical instillation of sodium arachidonate. Of the formulations developed, the PLGA-PEG-POD NPs were the smaller particles and exhibited greater entrapment effciency and more sustained release. The positive charge on the surface of these NPs, due to the conjugation with the positively charged peptide, facilitated penetration into the corneal epithelium, resulting in more effective preven- tion of ocular inflammation. The in vitro toxicity of the NPs developed was very low; no ocular irritation in vitro (hen’s egg test-chorioallantoic membrane assay) or in vivo (Draize test) was detected. Taken together, these data demonstrate that PLGA-PEG-POD NPs are promising vehicles for ocular drug delivery.This work was supported by the Cooperation Research Program CSIC-CITMA and a project (MAT2011-26994) funded by the Spanish Ministry of Science and Technology. AV is a recipient of a PhD grant from the CSIC. The authors thank Nacho Pérez of the IQAC-CSIC for performing the cytotoxicity assays.Peer reviewe

Calibration of semi-analytic models of galaxy formation using Particle Swarm Optimization

We present a fast and accurate method to select an optimal set of parameters in semi-analytic models of galaxy formation and evolution (SAMs). Our approach compares the results of a model against a set of observables applying a stochastic technique called Particle Swarm Optimization (PSO), a self-learning algorithm for localizing regions of maximum likelihood in multidimensional spaces that outperforms traditional sampling methods in terms of computational cost. We apply the PSO technique to the SAG semi-analytic model combined with merger trees extracted from a standard $\Lambda$CDM N-body simulation. The calibration is performed using a combination of observed galaxy properties as constraints, including the local stellar mass function and the black hole to bulge mass relation. We test the ability of the PSO algorithm to find the best set of free parameters of the model by comparing the results with those obtained using a MCMC exploration. Both methods find the same maximum likelihood region, however the PSO method requires one order of magnitude less evaluations. This new approach allows a fast estimation of the best-fitting parameter set in multidimensional spaces, providing a practical tool to test the consequences of including other astrophysical processes in SAMs.Comment: 11 pages, 4 figures, 1 table. Accepted for publication in ApJ. Comments are welcom

High pressure metamorphism of ophiolites in Cuba

High-pressure metamorphic complexes of ophiolitic material in Cuba trace the evolution of the northern margin of the Caribbean Plate during the Mesozoic. In the northern ophiolite belt of western and central Cuba, these complexes document cold (i.e., mature) subduction of oceanic lithosphere. Age data indicate subduction during pre-Aptian times followed by mélange formation and uplift during the Aptian-Albian. The P-T evolution is clockwise with relatively hot geothermal gradient during exhumation (i.e., "Alpine-type"), suggesting that exhumation may have been triggered by unroofing processes ensuing arrest of subduction. It is hypothesized that tectonic processes related to termination of subduction led to formation of characteristic oscillatory zoning of garnet recorded in blocks separated by ca. 800 km along strike of the belt. In eastern Cuba, the complexes document hot subduction with peak conditions at ca. 750 ºC, 15-18 kbar followed by near-isobaric cooling (i.e., counterclockwise P-T path). The contrasting petrologic evolution in the two regions indicates that the correlation of eastern and western-central Cuban mélanges is doubtful. The age and tectonic context of formation of these hot-subduction complexes is uncertain, but available data are consistent with formation during the Aptian-Albian due to a) the birth of a new subduction zone and/or b) subduction of young oceanic lithosphere or a ridge. Furthermore, tectonic juxtaposition of high-pressure ophiolitic material and subducted platform metasediments in the Escambray complex (central Cuba) that were decompressed under relatively cold geothermal gradients ("Franciscan-type" P-T paths) indicates syn-subduction exhumation during the uppermost Cretaceous (ca. 70 Ma). The diversity of P-T paths, ages and tectonic settings of formation of the high-pressure complexes of ophiolitic material in Cuba document a protracted history of subduction at the northern margin of the Caribbean Plate during the Mesozoic

Are you ready for retirement? The influence of values on membership in voluntary organizations in midlife and old age

Membership in voluntary organizations is associated with individual and social benefits. Due to the negative consequences of the global pandemic on older people, and the governmental challenges posed by population aging, voluntary membership is of great importance to society. To effectively promote volunteering among older people, it is necessary to understand the determinants of voluntary membership. This study analyses the influence of individual values—secular/traditional and survival/self-expression–on voluntary membership among European adults (N = 31,985). Specifically, it examines which values orient two age groups (middle age: 50–64 and old age: 65–79), as well as men and women toward a certain type of association (Social Awareness; Professional and Political; Education and Leisure; Religion). The sample of 31,985 comprises 60% of adults aged 50–64 and 40% aged 65–79; of which 56% are women and 44% men. The empirical estimation considers different levels of data aggregation: individual, national and welfare system, therefore multilevel analysis is used as an analytical strategy. Individual-level variables from the Integrated Values Survey (2005/09, 2010/14, and 2017/20) and national-level variables (Gini Index and Gross Domestic Product Per Capita) from the World Bank and Eurostat are used. The results indicate that traditional and self-expression values promote membership in voluntary organizations in general more than secular and survival values. However, there are differences according to the type of organization. Furthermore, values are found to moderate the effect of age and gender on voluntary membership

Methodology to determine operating times for the implantation of Prosopis alba in Santiago del Estero

La necesidad de calcular los costos en las actividades de plantación llevadas a cabo en el Programa Forestal Santiagueño (PFS) exige disponer previamente de datos técnicos de tiempos operativos de dichas actividades. El objetivo de este trabajo es describir la metodología que se siguió para calcular los tiempos de las labores manuales y mecanizadas que efectivamente se realizaron en el marco del PFS para lograr plantaciones forestales. Para conformar la muestra de estudio se seleccionaron seis pequeños productores que forestaro con algarrobo blanco (Prosopis alba) en la zona de riego de Santiago del Estero. Si bien las unidades de muestreo son escasas, representan el 40 % de productores que alcanzó el Programa durante el período 2017-2018 y el 34 % de las hectáreas forestadas. El trabajo de campo permitió registrar la forma de ejecutar las labores de implantación y medir el rendimiento de las mismas.The need for estimating costs in the forest activities carried out in the Santiagueño Forest Programme (SFP) requires the prior availability of technical data concerning the operating times involved. The aim of this work is to describe the methodology used to calculate the times of both manual and mechanized tasks effectively performed within the SFP frame to achieve forest plantations. In order to define the study sample, six small producers who forested with white carob (Prosopis alba) in the irrigation area of Santiago del Estero were selected. Although scarce, the sampling units represent 40 % of the producers reached by the Programme during the 2017-2018 period and 34 % of the forested hectares. From this work it was possible to record how implantation tasks should be carried out and determine how their performance should be measured.Fil: García, Jorge Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Santiago del Estero. Facultad de Ciencias Forestales; ArgentinaFil: Sanchez Ugalde, Rocio. Universidad Nacional de Santiago del Estero. Facultad de Ciencias Forestales; ArgentinaFil: García, J.. Universidad Nacional de Santiago del Estero. Facultad de Ciencias Forestales; ArgentinaFil: Veliz, A.. No especifíca;Fil: Vega, C.. No especifíca;Fil: Sarmiento, M.. Universidad Nacional de Santiago del Estero. Facultad de Ciencias Forestales; Argentin