Surface Screening in the Casimir Force

We calculate the corrections to the Casimir force between two metals due to the spatial dispersion of their response functions. We employ model-independent expressions for the force in terms of the optical coefficients. We express the non-local corrections to the Fresnel coefficients employing the surface $d_\perp$ parameter, which accounts for the distribution of the surface screening charge. Within a self-consistent jellium calculation, spatial dispersion increases the Casimir force significatively for small separations. The nonlocal correction has the opposite sign than previously predicted employing hydrodynamic models and assuming abruptly terminated surfaces.Comment: 5 pages, 2 figure

Twentieth century increase of Scots pine radial growth in NE Spain shows strong climate interactions

Stem radial growth responds to environmental conditions, and has been widely used as a proxy to study long-term patterns of tree growth and to assess the impact of environmental changes on growth patterns. In this study, we use a tree ring dataset from the Catalan Ecological and Forest Inventory to study the temporal variability of Scots pine (Pinus sylvestris L.) stem growth during the 20th century across a relatively large region (Catalonia, NE Spain) close to the southern limit of the distribution of the species. Basal area increment (BAI) was modelled as a function of tree size and environmental variables by means of mixed effects models. Our results showed an overall increase of 84% in Scots pine BAI during the 20th century, consistent with most previous studies for temperate forests. This trend was associated with increased atmospheric CO2 concentrations and, possibly, with a general increase in nutrient availability, and we interpreted it as a fertilization effect. Over the same time period, there was also a marked increase in temperature across the study region (0.19 °C per decade on average). This warming had a negative impact on radial growth, particularly at the drier sites, but its magnitude was not enough to counteract the fertilization effect. In fact, the substantial warming observed during the 20th century in the study area did not result in a clear pattern of increased summer drought stress because of the large variability in precipitation, which did not show any clear time trend. But the situation may change in the future if temperatures continue to rise and/or precipitation becomes scarcer. Such a change could potentially reverse the temporal trend in growth, particularly at the driest sites, and is suggested in our data by the relative constancy of radial growth after ca. 1975, coinciding with the warmer period. If this situation is representative of other relatively dry, temperate forests, the implications for the regional carbon balance would be substantial

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Determinación de glucógeno en músculo de bovinos. Una propuesta de medición rápida

A practical, rapid and inexpensive method for muscle glucose determination is proposed. The method is based on acid digestion of the sample, followed by neutralization of the solution and the subsequent glucose determination using a domestic glucometer for human blood glucose level control. In a pre-experimental phase, the accuracy of this methodology and the titration method was determined, comparing results to pre-established glucose concentrations. There were significant differences between the glucose reading given by the glucometer and the pre-established glucose concentrations and the results given by the titration method. Nevertheless, when discrepancies (bias) were identified, differences resulted non-significant (P = 0.85). Subsequently, muscle glucose concentration (n = 24) was validated in the experimental phase and significant differences were shown between glucose concentration values given by the glucometer and the titration method, the latter considered as a standard method or as a reference (P < 0.0001). Once the sources of discrepancies were identified and removed, the differences observed between the values given by the two methods were not statistically significant (P = 0.99). It was concluded that the glucometer is a potential method for muscle glucose determination, but must be improved.Se propuso un método práctico, rápido y de bajo costo, para determinar glucosa en músculo, basado en una digestión ácida de la muestra de músculo, seguida por una neutralización de la solución y posterior determinación de glucosa, utilizando un glucómetro doméstico, para el control de la glicemia sanguínea. En una etapa pre-experimental se determinó la exactitud de esta metodología respecto al método de titulación, comparando sus lecturas, con concentraciones conocidas de glucosa a través de la dócima de exactitud, resultando diferencias significativas entre las lecturas de glucosa, las concentraciones de glucosa conocidas y las entregadas por el método de titulación. Sin embargo, identificadas las causas de las discrepancias (sesgos), las diferencias resultaron no significativas (P = 0,84 y P = 0,86, para ambos casos, respectivamente). En la etapa experimental, se validaron las concentraciones de glucosa en músculo (n = 24), resultando valores diferentes entre concentraciones de glucosa y la obtenida por el método de titulación, considerado como método de referencia o estándar (P < 0,0001). Una vez identificada y removida la fuente de las discrepancias, los valores entregados por ambos métodos fueron similares (P = 0,99). Se concluyó que el glucómetro es un método potencial para la determinación de glucosa en músculo, más aún cuando se afine la técnica en relación al procesamiento de las muestras, tanto en la extracción de la glucosa desde el músculo, como en el método de comparación de los valores entregados por el glucómetro