Nanociència : l'important no rau en la noblesa

La nanociència avança dia a dia en el que és el seu camp amb més projecció: les nanopartícules metàl·liques (NPMs). Les excepcionals propietats físico-químiques que les caracteritzen fan possible les seves aplicacions electroquímiques. Aquestes però, poden veure's afectades degut a la tendència de les NPMs a agregar-se, perdent així, la seva forma original. Estabilitzant-les en matrius polimèriques, no només s'ha aconseguit controlar les seves mides i velocitat de creixement, sinó que també poden ser emmagatzemades en forma sòlida i líquida, gràcies a la solubilitat dels polímers. Aquestes aplicacions electroquímiques, tal i com s'explica en el següent article, es basen en l'ús de metalls nobles (partícules monometàl·liques), la qual cosa encareix molt el procés. D'aquí que un dels objectius sigui decréixer la quantitat d'aquests metalls -sense perdre la seva capacitat electrocatalítica- i preparar nanopartícules del tipus nucli-embolcall (bimetàl·liques). Aquestes posseeixen un nucli de metall econòmic recobert per un altre de noble, i han demostrat ser més estables en quant a mida i forma, a més de presentar una activitat electrocatalítica superior.La nanociencia avanza día a día en el que es su campo con más proyección: las nanopartículas metálicas (NPMs). Las excepcionales propiedades físico-químicas que las caracterizan hacen posible sus aplicaciones electroquímicas. Éstas, sin embargo, pueden verse afectadas debido a la tendencia de las NPMs a agregarse, perdiendo, así, su forma original. Estabilizándolas en matrices poliméricas, no sólo se ha conseguido controlar su tamaño y velocidad de crecimiento, sino que también pueden ser almacenadas en forma sólida y líquida, gracias a la solubilidad de los polímeros. Estas aplicaciones electroquímicas, tal como se explica en el siguiente artículo, se basan en el uso de metales nobles (partículas monometálicas), lo que encarece mucho el proceso. De aquí que uno de los objetivos sea disminuir la cantidad de estos metales -sin perder su capacidad electrocatalítica- y preparar nanopartículas del tipo núcleo-envoltorio (bimetálicas). Éstas poseen un núcleo de metal económico recubierto por otro que es noble, y han demostrado ser más estables en cuanto a tamaño y forma, además de presentar una actividad electrocatalítica superior, siempre y cuando se mantenga la misma cantidad de metal noble.The field of metallic nanoparticles (MNP), one of the nanoscience fields with most projection, advances daily. The exceptional characteristic physical and chemical properties of these particles make it possible to use them in electrochemical applications. However, this can be affected by the tendency of MNPs to group together and thus lose their original form. By stabilising the particles in polymeric matrices it is possible not only to control their size and speed of growth, but to store them in solid and liquid forms due to the solubility of polymers. As explained in the following article, noble metals (monometallic particles) are used in electrochemical applications, which make the process extremely expensive. The objective therefore is to reduce the quantity of noble metal used -without compromising electrocatalytic capacity -and add core-shell (bimetallic) nanoparticles. These possess a more economical metal core covered by a noble metal shell. They have been proved to be more stable in both size and shape, and display greater electrocatalytic activity

Efectos del clima y la estructura del rodal sobre procesos de mortalidad en los bosques ibéricos.

Herrero A & Zavala MA, editores (2015) Los Bosques y la Biodiversidad frente al Cambio Climático: Impactos, Vulnerabilidad y Adaptación en España. Ministerio de Agricultura, Alimentación y Medio Ambiente, Madrid.Peer Reviewe

Calculation of the interventilatory threshold area: a method for examining the aerobic-anaerobic transition

El objetivo fue determinar la relación entre el área interumbrales (ITA) [la zona comprendida entre el primer y el segundo umbral ventilatorio (VT1 y VT2) en la función VO2/VE, Carga/VO2 y Carga/VE] y las variables ergoespirométricas. Treinta y tres hombres realizaron un test incremental. El ITA se calculó: 1) como la integral definida por el área entre VT1 y VT2 bajo las curvas de VO2/VE, Carga/VO2 y Carga/VE y 2) como la suma de las áreas descritas por el triángulo y rectángulo entre los mismos puntos. El ITA para la función Carga/VE se correlacionó positivamente (p<0,01) con la carga en VT2 (r = 0,831) y la ventilación en VT2 (r = 0,799). El ITA para la función VO2/VE fue significativamente mayor en los ciclistas que en los estudiantes. La determinación del ITA es un método simple para evaluar la transición aeróbica-anaeróbica durante las pruebas de esfuerzo incremental.The aim was to determine the relationship between the interthreshold area (ITA) [the area between the first and second ventilatory threshold (VT1 and VT2) for the function VO2/VE, load/VO2 and load/VE] and the traditional variables measured. Thirty-three men underwent an incremental test. The ITA was calculated: 1) as the integral defined by the area between VT1 and VT2 under the curves for the functions VO2/VE, load/VO2 and load/VE and 2) as the simple sum of the areas described by the triangle and rectangle between the same points. The mean ITA for the function load/VE was positively correlated (p<0.01) with load at VT2 (r=0.831) and ventilation at VT2 (r=0.799). The mean ITA for the function VO2/VE was significantly greater in the cyclists than in the students. The ITA for the function load/VE differed between March and July as training progressed. The determination of the ITA is a simple method of assessing the aerobic-anaerobic transition process during incremental exercise tests

Multiple abiotic and biotic pathways shape biomass demographic processes in temperate forests

International audienceForests play a key role in regulating the global carbon cycle, and yet the abiotic and biotic conditions that drive the demographic processes that underpin forest carbon dynamics remain poorly understood in natural ecosystems. To address this knowledge gap, we used repeat forest inventory data from 92,285 trees across four large permanent plots (4-25 ha in size) in temperate mixed forests in northeast China to ask the following questions: (1) How do soil conditions and stand age drive biomass demographic processes? (2) How do vegetation quality (i.e., functional trait diversity and composition) and quantity (i.e., initial biomass stocks) influence biomass demographic processes independently from soil conditions and stand age? (3) What is the relative contribution of growth, recruitment, and mortality to net biomass change? Using structural equation modeling, we showed that all three demographic processes were jointly constrained by multiple abiotic and biotic factors and that mortality was the strongest determinant on net biomass change over time. Growth and mortality, as well as functional trait diversity and the community-weighted mean of specific leaf area (CWM SLA), declined with stand age. By contrast, high soil phosphorous concentrations were associated with greater functional diversity and faster dynamics (i.e., high growth and mortality rates), but associated with lower CWM SLA and initial biomass stock. More functionally diverse communities also had higher recruitment rates, but did not exhibit faster growth and mortality. Instead, initial biomass stocks and CWM SLA were stronger predictors of biomass growth and mortality, respectively. By integrating the full spectrum of abiotic and biotic drivers of forest biomass dynamics, our study provides critical system-level insights needed to predict the possible consequences of regional changes in forest diversity, composition, structure and function in the context of global change

SARS-CoV-2 immunochromatographic IgM/IgG rapid test in pregnancy: A false friend?

Background: An increasing body of evidence has revealed that SARS-CoV-2 infection in pregnant women could increase the risk of adverse maternal and fetal outcomes. Careful monitoring of pregnancies with COVID-19 and measures to prevent neonatal infection are warranted. Therefore, rapid antibody tests have been suggested as an efficient screening tool during pregnancy. Cases: We analysed the clinical performance during pregnancy of a rapid, lateral-flow immunochromatographic assay for qualitative detection of SARS-CoV-2 IgG/IgM antibodies. We performed a universal screening including 169 patients during their last trimester of pregnancy. We present a series of 14 patients with positive SARS-CoV-2 immunochromatographic assay rapid test result. Immunochromatographic assay results were always confirmed by chemiluminescent microparticle immunoassays for quantitative detection of SARS-CoV-2 IgG and IgM+IgA antibodies as the gold standard. We observed a positive predictive value of 50% and a false positive rate of 50% in pregnant women, involving a significantly lower diagnostic performance than reported in non-pregnant patients. Discussion: Our data suggest that although immunochromatographic assay rapid tests may be a fast and profitable screening tool for SARS-CoV-2 infection, they may have a high false positive rate and low positive predictive value in pregnant women. Therefore, immunochromatographic assay for qualitative detection of SARS-CoV-2 IgG/IgM antibodies must be verified by other test in pregnant patients

Screening of autochthonous lactic acid bacteria strains from artisanal soft cheese: probiotic characteristics and prebiotic metabolism

Today's growing interest in functional foods is due to their positive impacts on human health. The aim of this study was to evaluate the probiotic properties and prebiotic metabolism of autochthonous lactic acid bacteria from artisanal Serpa cheese. Twenty strains presented better tolerance to stress conditions found in the gastrointestinal tract, highlighting Lactobacillus brevis C1Lb21 for its adequate auto-aggregating ability and significantly higher hydrophobicity. However, eight strains were discarded for their antibiotic resistance and biogenic amine production. Finally, prebiotic fermentation study showed that lactulose supported better growth of lactobacilli and induced the production of short-chain fatty acids (SCFA). During lactulose fermentation, Lb. pentosus G4Lb7 produced statistically more SCFA, and Lb. plantarum G1Lb5 lactic acid. Thus, Lb. brevis C1Lb21, Lb. plantarum G1Lb5 and Lb. pentosus G4Lb7 are promising probiotic candidates, and in combination with lactulose could be used for developing a symbiotic cheese