First-principles investigation of Ag-Cu alloy surfaces in an oxidizing environment

In this paper we investigate by means of first-principles density functional theory calculations the (111) surface of the Ag-Cu alloy under varying conditions of pressure of the surrounding oxygen atmosphere and temperature. This alloy has been recently proposed as a catalyst with improved selectivity for ethylene epoxidation with respect to pure silver, the catalyst commonly used in industrial applications. Here we show that the presence of oxygen leads to copper segregation to the surface. Considering the surface free energy as a function of the surface composition, we construct the convex hull to investigate the stability of various surface structures. By including the dependence of the free surface energy on the oxygen chemical potential, we are able compute the phase diagram of the alloy as a function of temperature, pressure and surface composition. We find that, at temperature and pressure typically used in ethylene epoxidation, a number of structures can be present on the surface of the alloy, including clean Ag(111), thin layers of copper oxide and thick oxide-like structures. These results are consistent with, and help explain, recent experimental results.Comment: 10 pages, 6 figure

Effective differentiation Practices:A systematic review and meta-analysis of studies on the cognitive effects of differentiation practices in primary education

This systematic review gives an overview of the effects of differentiation practices on language and math performance in primary education, synthesizing the results of empirical studies (n = 21) on this topic since 1995. We extracted 78 effect sizes from the included studies. We found that using computerized systems as a differentiation tool and using differentiation as part of a broader program or reform had small to moderate positive effects on students’ performance. Between- or within-class homogeneous ability grouping had a small negative effect on low-ability students, but no effect on others. The finding that computer technology can be a useful tool to facilitate differentiated instruction is not covered in earlier reviews. Moreover, our findings emphasize that homogeneous ability grouping alone is not enough to guarantee differentiated instruction. This stresses the importance of embedding differentiation practices in a broader educational context

Reverse Shock Emission Revealed in Early Photometry in the Candidate Short GRB 180418A

We present observations of the possible short GRB 180418A in $\gamma$-rays, X-rays, and in the optical. Early optical photometry with the TAROT and RATIR instruments show a bright peak ($\approx$ 14.2 AB mag) between $T+28$ and $T+90$ seconds that we interpret as the signature of a reversal shock. Later observations can be modeled by a standard forward shock model and show no evidence of jet break, allowing us to constrain the jet collimation to $\theta_j> 7^\circ$. Using deep late-time optical observations we place an upper limit of $r>24$ AB mag on any underlying host galaxy. The detection of the afterglow in the \textit{Swift} UV filters constrains the GRB redshift to $z<1.3$ and places an upper bound on the $\gamma$-ray isotropic equivalent energy $E_{\rm{\gamma,iso}} < 3 \times 10^{51}$ erg. The properties of this GRB (e.g. duration, hardness ratio, energetic, and environment) lie at the intersection between short and long bursts, and we can not conclusively identify its type. We estimate that the probability that it is drawn from the population of short GRBs is 10\%-30\%.Comment: Accepted por publication in Ap

Decreased kainate receptors in the hippocampus of apolipoprotein D knockout mice

Producción CientíficaApolipoprotein D (ApoD) has many actions critical to maintaining mammalian CNS function. It is therefore significant that levels of ApoD have been shown to be altered in the CNS of subjects with schizophrenia, suggesting a role for ApoD in the pathophysiology of the disorder. There is also a large body of evidence that cortical and hippocampal glutamatergic, serotonergic and cholinergic systems are affected by the pathophysiology of schizophrenia. Thus, we decided to use in vitro radioligand binding and autoradiography tomeasure levels of ionotropic glutamate, somemuscarinic and serotonin 2Areceptors in theCNS ofApoD-/- and isogenic wild-type mice. These studies revealed a 20% decrease(mean±SEM: 104±10.2 vs. 130±10.4 fmol/mg ETE) in the density of kainate receptors in the CA 2–3 of the ApoD-/- mice. In addition therewas a global decrease inAMPA receptors (F1,214=4.67, pb0.05) and a global increase in muscarinic M2/M4 receptors (F1,208=22.77, pb0.0001) in the ApoD-/- mice that did not reach significance in any single cytoarchitectural region. We conclude that glutamatergic pathways seem to be particularly affected in ApoD-/- mice and this may contribute to the changes in learning and memory, motor tasks and orientation-based tasks observed in these animals, all of which involve glutamatergic neurotransmission

Depression and treatment with anti-calcitonin gene related peptide (CGRP) (ligand or receptor) antibodies for migraine

Background and purpose: The aim was to evaluate the effect of anti-calcitonin gene related peptide (CGRP) (ligand or receptor) antibodies on depressive symptoms in subjects with migraine and to determine whether depressive symptoms predict treatment response. Methods: Patients with migraine treated with erenumab and fremanezumab at the Leiden Headache Centre completed daily E-headache diaries. A control group was included. Depressive symptoms were assessed using the Hospital Anxiety and Depression Scale (HADS) and the Center for Epidemiological Studies Depression Scale (CES-D) questionnaires at baseline (T0) and after 3 months (T1). First, the effect of treatment on the reduction in HADS-D and CES-D scores was assessed, with reduction in depression scores as the dependent variable and reduction in monthly migraine days (MMD) and treatment with anti-CGRP medication as independent variables. Second, depression as a predictor of treatment response was investigated, using the absolute reduction in MMD as a dependent variable and age, gender, MMD, active depression, impact, stress and locus of control scores as independent variables. Results: In total, n = 108 patients were treated with erenumab, n = 90 with fremanezumab and n = 68 were without active treatment. Treatment with anti-CGRP medication was positively associated with a reduction in the HADS-D (β = 1.65, p = 0.01) compared to control, independent of MMD reduction. However, the same effect was not found for the CES-D (β = 2.15, p = 0.21). Active depression predicted poorer response to erenumab (p = 0.02) but not to fremanezumab (p = 0.09). Conclusion: Anti-CGRP (ligand or receptor) monoclonals lead to improvement of depressive symptoms in individuals with migraine, independent of migraine reduction. Depression may predict treatment response to erenumab but not to fremanezumab.</p