In vitro monitoring of surface mechanical properties of poly(L-lactic acid) using microhardness

Poly(L-lactic acid) (PLLA) was immersed in a simulated body fluid (SBF) solution at 37.58C for distinct times. The variation of the surface mechanical properties of PLLA samples with immersion time was followed by microhardness. These measurements showed that PLLA microhardness decreased significantly ( 60%) after only 30 days of immersion. The results were explained in terms of hydrolytic degradation of the samples. The dependence of microhardness with the applied dwell time was also analyzed. The creep curves were successfully described by a power law. A decrease of the creep constant k as the immersion time increased was found. Differential scanning calorimetry was also used to analyze the changes in the physical properties of PLLA, namely in crystallinity degree (Xc) and glass transition temperature (Tg), as a function of the immersion time in SBF. A significant variation in the crystallinity degree of PLLA, initially nearly amorphous (Xc 5 9%), was detected after only 3 days of immersion (Xc 5 37%). The interpretation of this behavior was based on the hydrolysis process suffered by PLLA

Microhardness of starch based biomaterials in simulated physiological conditions

In this work the variation of the surface mechanical properties of starch-based biomaterials with immersion time was followed using microhardness measurements. Two blends with very distinct water uptake capabilities, starch/cellulose acetate (SCA) and starch/poly- (e-caprolactone) (SPCL), were immersed in a phosphate buffer solution (PBS) at 37.5 C for various times. The microhardness of the blends decreased significantly ( 50% for SPCL and 94% for SCA), within a time period of 30 days of immersion, reflecting the different hydrophilic character of the synthetic components of the blends. The dependence of microhardness on the applied loading time and load was also analysed and showed a power law dependency for SCA. Water uptake and weight loss measurements were performed for the same immersion times used in the microhardness experiments. The different swelling/degradation behaviour presented by the blends was related to the respective variation in microhardness. Moreover, complementary characterization of the mechanical properties of SCA and SPCL was accomplished by dynamic mechanical analysis (DMA) and creep measurements. Microhardness measurements proved to be a useful technique for characterizing the mechanical behaviour near the surface of polymeric biomaterials, including in simulated physiological conditions

Understanding Mechanical Response of Elastomeric Graphene Networks

Ultra-light porous networks based on nano-carbon materials (such as graphene or carbon nanotubes) have attracted increasing interest owing to their applications in wide fields from bioengineering to electrochemical devices. However, it is often difficult to translate the properties of nanomaterials to bulk three-dimensional networks with a control of their mechanical properties. In this work, we constructed elastomeric graphene porous networks with well-defined structures by freeze casting and thermal reduction, and investigated systematically the effect of key microstructural features. The porous networks made of large reduced graphene oxide flakes (>20 μm) are superelastic and exhibit high energy absorption, showing much enhanced mechanical properties than those with small flakes (<2 μm). A better restoration of the graphitic nature also has a considerable effect. In comparison, microstructural differences, such as the foam architecture or the cell size have smaller or negligible effect on the mechanical response. The recoverability and energy adsorption depend on density with the latter exhibiting a minimum due to the interplay between wall fracture and friction during deformation. These findings suggest that an improvement in the mechanical properties of porous graphene networks significantly depend on the engineering of the graphene flake that controls the property of the cell walls

International Variations in Surgical Morbidity and Mortality Post Gynaecological Oncology Surgery: A Global Gynaecological Oncology Surgical Outcomes Collaborative Led Study (GO SOAR1)

Gynaecological malignancies affect women in low and middle income countries (LMICs) at disproportionately higher rates compared with high income countries (HICs) with little known about variations in access, quality, and outcomes in global cancer care. Our study aims to evaluate international variation in post-operative morbidity and mortality following gynaecological oncology surgery between HIC and LMIC settings. Study design consisted of a multicentre, international prospective cohort study of women undergoing surgery for gynaecological malignancies (NCT04579861). Multilevel logistic regression determined relationships within three-level nested-models of patients within hospitals/countries. We enrolled 1820 patients from 73 hospitals in 27 countries. Minor morbidity (Clavien-Dindo I-II) was 26.5% (178/672) and 26.5% (267/1009), whilst major morbidity (Clavien-Dindo III-V) was 8.2% (55/672) and 7% (71/1009) for LMICs/HICs, respectively. Higher minor morbidity was associated with pre-operative mechanical bowel preparation (OR = 1.474, 95%CI = 1.054-2.061, p = 0.023), longer surgeries (OR = 1.253, 95%CI = 1.066-1.472, p = 0.006), greater blood loss (OR = 1.274, 95%CI = 1.081-1.502, p = 0.004). Higher major morbidity was associated with longer surgeries (OR = 1.37, 95%CI = 1.128-1.664, p = 0.002), greater blood loss (OR = 1.398, 95%CI = 1.175-1.664, p ≤ 0.001), and seniority of lead surgeon, with junior surgeons three times more likely to have a major complication (OR = 2.982, 95%CI = 1.509-5.894, p = 0.002). Of all surgeries, 50% versus 25% were performed by junior surgeons in LMICs/HICs, respectively. We conclude that LMICs and HICs were associated with similar post-operative major morbidity. Capacity to rescue patients from surgical complications is a tangible opportunity for meaningful intervention

The commissioning of CMS sites: improving the site reliability

The computing system of the CMS experiment works using distributed resources from more than 60 computing centres worldwide. These centres, located in Europe, America and Asia are interconnected by the Worldwide LHC Computing Grid. The operation of the system requires a stable and reliable behaviour of the underlying infrastructure. CMS has established a procedure to extensively test all relevant aspects of a Grid site, such as the ability to efficiently use their network to transfer data, the functionality of all the site services relevant for CMS and the capability to sustain the various CMS computing workflows at the required scale. This contribution describes in detail the procedure to rate CMS sites depending on their performance, including the complete automation of the program, the description of monitoring tools, and its impact in improving the overall reliability of the Grid from the point of view of the CMS computing system

Estudio preliminar del impacto óptico del soiling en testigos de vidrio, en un área semiurbana de Madrid, para aplicación en sistemas fotovoltaicos

CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia SolarRESUMEN: El ensuciamiento (soiling) de los paneles solares disminuye la producción energética de las instalaciones fotovoltaicas. Dentro del proyecto PVCastSOIL, que investiga el soiling desde varias perspectivas, este trabajo presenta los resultados preliminares del estudio del impacto óptico del soiling en un sistema fotovoltaico experimental, no conectado a red, situado en la periferia de Madrid (España). Con el objeto de estimar cuánta luz solar incidente no alcanza las células solares de losmódulos fotovoltaicos debido al soiling, se instaló un mini-soporte que ha permitido exponer, con una inclinación de 35º, una serie de testigos de vidrio durante casi once meses. Midiendo sus espectros de transmitancia, se ha determinado que durante ese periodo el grado de soiling fue bajo (1-3% de pérdida de transmitancia). Por último, se comentan las mejoras aplicadas para continuar este estudio durante 2020, destacándose que el nuevo banco de pruebas de soiling permitirá exponer testigos de vidrio de mayor tamaño y comparar el grado de ensuciamiento para dos inclinaciones diferentes (8º y 35º).ABSTRACT: Soiling on solar panels hinders the energy production of photovoltaic facilities. Within the PVCastSOIL project, which researches soiling from several perspectives, this work presents the early results of the study of the optical impairment due to soiling on an off-grid experimental photovoltaic system located in the urban fringe of Madrid (Spain). In order to estimate how much incoming sunlight does not reach the solar cells of the photovoltaic modules due to soiling, a 35º-tilted mini-mount was installed for the outdoor exposure of a series of glass coupons during almost eleven months. From their transmission spectra measurements, it was concluded that during such period the degree of soiling was low (1-3% of transmission loss). Finally, some improvements adopted for the continuation of this study during 2020 are commented, highlighting among them a new soiling test bench which will allow using larger glass coupons as well as comparing the degree of soiling for two different tilt angles (i.e. 8º and 35º).info:eu-repo/semantics/publishedVersio

Filling a blank on the map: 60 years of fisheries in Equatorial Guinea

Despite a scarcity of pertinent information, it has been possible to reconstruct time series of marine fisheries catches for Equatorial Guinea from 1950 to 2010 using per capita fish consumption and population numbers for small-scale fisheries, catch rates and number of vessels for industrial fisheries and discard rates to estimate the discarded bycatch. Small-scale fisheries, industrial large-scale fisheries, domestic and legal and illegal foreign fisheries and their discards are all included. Total catches were estimated at 2.7 million tonnes over the time period considered, of which 653 000 t were caught domestically compared to 187 000 t reported by FAO. This shows that fisheries have more importance for Equatorial Guinea's food security than the official data suggest. In contrast to what is suggested by official figures, fisheries were shown to be strongly impacted by civil and political unrest; notably, they declined overall because of civil and political conflicts, socio-demographic dynamics, and a growing role of the newly discovered oil resources, which directly and indirectly threaten the food security of the people of Equatorial Guinea