Magnetism and Magnetic Isomers in Free Chromium Clusters

We have used the Stern-Gerlach deflection technique to study magnetism in chromium clusters of 20-133 atoms. Between 60 K and 100 K, we observe that these clusters have large magnetic moments and respond superparamagnetically to applied magnetic fields. Using superparamagnetic theory, we have determined the moment per atom for each cluster size and find that it often far exceeds the moment per atom present anywhere in the bulk antiferromagnetic lattice. Remarkably, our cluster beam contains two magnetically distinguishable forms of each cluster size with >= 34 atoms. We attribute this observation to structural isomers

Identifying hotspots of land use cover change under socioeconomic and climate change scenarios in Mexico

This study identifies the hotspots of land use cover change (LUCC) under two socioeconomic and climate change scenarios [business as usual (BAU) and a pessimistic scenario] at the national level for Mexico for three-time periods. Modelling suggests that by 2050 grassland and tropical evergreen forest will be the most endangered ecosystems, having lost 20–33% (BAU) or 43–46% (pessimistic scenario) of their extent in comparison to 1993. Agricultural expansion would be the major driver of LUCC, increasing from 24.4% of the country in 1993 to 30% (BAU) or 34% (pessimistic) in 2050. The most influential variables were distance from roads and human settlements, slope, aridity, and evapotranspiration. The hotspots of LUCC were influenced by environmental constraints and socioeconomic activities more than by climate change. These findings could be used to build proposals to reduce deforestation, including multiple feedbacks among urbanization, industrialization and food consumption

Improved Performance of an Epoxy Matrix as a Result of Combining Graphene Oxide and Reduced Graphene

We present an easy and effective way to improve the mechanical properties of an epoxy matrix by reinforcing it with a combination of graphene oxide (GO) and reduced graphene oxide (RGO). These nanocomposites were prepared with different load of nanofillers: 0.1, 0.4, 0.7, 1.0 wt% and a neat epoxy. Ratios of graphene oxide and reduced graphene (GO : RGO) employed were: 0 : 1, 0.25 : 0.75, 0.5 : 0.5, 0.75 : 0.25, and 1 : 0. Results show that with only 0.4 wt% and a ratio 0.2 : 0.75 of GO : RGO, tensile strength and tensile toughness are 52% and 152% higher than neat epoxy while modulus of elasticity was improved ~20%. The obtained results suggest that it is possible achieve advantageous properties by combining graphene in oxidized and reduced conditions as it shows a synergic effect by the presence of both nanofillers

Proyecciones poblacionales y económicas bajo diferentes escenarios para México [Population and economic projections under different scenarios for Mexico]

Los escenarios existentes que incluyen proyecciones poblacionales y económicas no permiten ser utilizados a niveles sub-nacionales. En países en desarrollo la información a nivel sub-nacional y la contextualización de escenarios es escasa. El objetivo de este trabajo es mostrar cómo pueden superarse estas limitaciones desarrollando: 1) proyecciones demográficas (probabilísticas y determinísticas) y económicas (probabilísticas) bajo diferentes escenarios y escalas temporales y espaciales, y 2) espacializar la distribución de la población a una resolución de un km2. Los resultados indican que para el 2050, la población mexicana podría ser entre 22 a 55 por ciento más grande que en el 2010 y tener un crecimiento del PIB entre 0.54 y 2.5 por ciento. Este estudio muestra cómo los escenarios socioeconómicos sub-nacionales son necesarios para la evaluación de la vulnerabilidad de los sistemas socio-ecológicos

Allosteric modulation of the GTPase activity of a bacterial LRRK2 homolog by conformation-specific Nanobodies

Mutations in the Parkinson's disease (PD)-associated protein leucine-rich repeat kinase 2 (LRRK2) commonly lead to a reduction of GTPase activity and increase in kinase activity. Therefore, strategies for drug development have mainly been focusing on the design of LRRK2 kinase inhibitors. We recently showed that the central RocCOR domains (Roc: Ras of complex proteins; COR: C-terminal of Roc) of a bacterial LRRK2 homolog cycle between a dimeric and monomeric form concomitant with GTP binding and hydrolysis. PD-associated mutations can slow down GTP hydrolysis by stabilizing the protein in its dimeric form. Here, we report the identification of two Nanobodies (NbRoco1 and NbRoco2) that bind the bacterial Roco protein (CtRoco) in a conformation-specific way, with a preference for the GTP-bound state. NbRoco1 considerably increases the GTP turnover rate of CtRoco and reverts the decrease in GTPase activity caused by a PD-analogous mutation. We show that NbRoco1 exerts its effect by allosterically interfering with the CtRoco dimer–monomer cycle through the destabilization of the dimeric form. Hence, we provide the first proof of principle that allosteric modulation of the RocCOR dimer–monomer cycle can alter its GTPase activity, which might present a potential novel strategy to overcome the effect of LRRK2 PD mutations

Acceleration of Solar Wind Ions by Nearby Interplanetary Shocks: Comparison of Monte Carlo Simulations with Ulysses Observations

The most stringent test of theoretical models of the first-order Fermi mechanism at collisionless astrophysical shocks is a comparison of the theoretical predictions with observational data on particle populations. Such comparisons have yielded good agreement between observations at the quasi-parallel portion of the Earth's bow shock and three theoretical approaches, including Monte Carlo kinetic simulations. This paper extends such model testing to the realm of oblique interplanetary shocks: here observations of proton and alpha particle distributions made by the SWICS ion mass spectrometer on Ulysses at nearby interplanetary shocks are compared with test particle Monte Carlo simulation predictions of accelerated populations. The plasma parameters used in the simulation are obtained from measurements of solar wind particles and the magnetic field upstream of individual shocks. Good agreement between downstream spectral measurements and the simulation predictions are obtained for two shocks by allowing the the ratio of the mean-free scattering length to the ionic gyroradius, to vary in an optimization of the fit to the data. Generally small values of this ratio are obtained, corresponding to the case of strong scattering. The acceleration process appears to be roughly independent of the mass or charge of the species.Comment: 26 pages, 6 figures, AASTeX format, to appear in the Astrophysical Journal, February 20, 199

Rumen fermentation and diet degradability in sheep fed sugarcane (Saccharum officinarum) silage supplemented with Tithonia diversifolia or alfalfa (Medicago sativa) and rice polishing

The objective of this study was to evaluate ruminal fermentation (i.e. pH, ammonia, and volatile fatty acid concentrations) and in situ degradability of diets in sheep fed sugarcane silage (SCS) supplemented with Tithonia diversifolia (Td) or alfalfa (Medicago sativa) hay (A), with or without rice (Oriza sativa) polishing (RP) as an energy source. Four Blackbelly sheep (35 kg average body weight) with rumen cannula were used. The experimental diets were (g/kg of dry matter): Diet 1) SCS (686) + Td (294), Diet 2) SCS (460) + Td (226) + RP (294), Diet 3) SCS (637) + A (343), and Diet 4) SCS (441) + A (245) + RP (294). The remainder (20 g/kg of dry matter) was composed by minerals supplement and salt. Samples of diets were incubated into rumen for 3, 6, 9, 12, 24, 30, 36, 48, and 72 h to determine in situ degradability. Data were analysed with a linear mixed model. The lamb, period and lamb nested in period*diet were considered as a random variable. The inclusion of RP improved the degradability of diets and ammonia production in the rumen. The acetic, propionic, and butyric acid concentrations (mmol/100 mL) in rumen increased (P<0.03) when diets with alfalfa and RP were provided. The degradability of diets based on sugarcane silage supplemented with either alfalfa or Tithonia diversifolia was improved (P<0.05) with the rice polishing inclusion, with no difference (P>0.05) between these forages. In conclusion, energy supplementation, not necessarily from starch, is important to improve rumen fermentation and degradability of diets based on sugarcane silage