Site‐dependent vibrational coupling of CO adsorbates on well‐defined step and terrace sites of monocrystalline platinum: Mixed‐isotope studies at Pt(335) and Pt(111) in the aqueous electrochemical environment

Infrared spectroscopy is applied to probe qualitative structural features of the adlayers formed by CO at step sites and on terrace planes of Pt(335){Pt(S)‐[4(111)×(100)]} in the aqueous electrochemical environment. The C–O stretching vibrational features are reported for adlayers formed from 12CO/13CO isotopic mixtures over a wide range of CO surface coverages. At saturation, the predominant spectral features are associated with the vibrational modes of terrace‐CO in terminal (atop) coordination environments. The position of the 12CO and 13CO spectral features and their relative intensity are examined for several 12CO/13CO fractions, and they are shown to display the characteristics of a strongly coupled system.In comparison with corresponding mixed isotope spectra for CO at Pt(111) electrodes, intermolecular coupling for terrace‐CO on the (111) surface planes of Pt(335) is observed to be significantly stronger, reflecting the higher CO surface coverages on the edge sites and the terrace sites of the Pt(335) surface plane. At low coverages, spectral features associated with edge‐CO are discerned, and the intermolecular coupling for atop CO is weaker than for corresponding coverages of CO at Pt(111). The weak coupling at low coverages is attributed to the exclusive CO occupation at the step edges, which confines the intermolecular coupling to one dimension, in the direction along the step edges. For all coverages, values are determined for the dynamic dipole–dipole coupling parameter (Δνd) and the chemical (static–dipole) shift parameter (Δνs). Values for Δνs are generally small at all coverages. Values for Δνd are small (<8 cm−1) at low coverages, where CO forms one‐dimensional structures along the step edges, and they increase to large values (∼42 cm−1) at coverages that coincide with the growth of two‐dimensional structures on the terrace planes. The majority of measurements were made for the Pt(335) electrode at potentials in the classical double‐layer region, although dipole coupling parameters are also reported for Pt(335)/CO at potentials in the hydrogen adsorption region, where Δνd approaches zero at low coverages.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70025/2/JCPSA6-101-10-9113-1.pd

Site specific co‐adsorption at Pt(335) as probed by infrared spectroscopy: Structural alterations in the CO adlayer under aqueous electrochemical conditions

Experiments probe the effect of hydrogen co‐adsorption on the infrared spectral features of carbon monoxide adsorbed at Pt(335) {Pt(S)‐[4(111)×(100)]} under aqueous electrochemical conditions. Using intermediate CO coverages, where it is possible to discern infrared spectral features for CO bound terminally (atop) at edge sites and at terrace sites, the present experiments observe greater alterations in the atop CO population at the step edge compared to the atop CO population on the terrace plane when hydrogen is co‐adsorbed under aqueous electrochemical conditions. These findings suggest that hydrogen is preferentially adsorbed at step sites on the Pt(335) surface plane and they coincide with what has been revealed by recent UHV experiments which probed the effect of co‐adsorbing oxygen at Pt(335) in the presence of a partial CO monolayer.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70726/2/JCPSA6-100-1-628-1.pd

Ikaros has a crucial role in regulation of B cell receptor signaling

transcription factor Ikaros, a key regulator of hematopoiesis, has an essential role in lymphocyte development. In mice, fetal lymphoid differentiation is blocked in the absence of Ikaros, and whereas T cells develop postnatally, B cells are totally absent. The significance of Ikaros in the B cell development is evident, but how Ikaros regulates B cell function has neither been established nor previously been studied with B cells that lack Ikaros expression. Here we show that disruption of Ikaros in the chicken B cell line DT40 induces a B cell receptor (BCR) signaling defect with reduced phospholipase C gamma 2 phosphorylation and impaired intracellular calcium mobilization, which is restored by Ikaros reintroduction. Furthermore, we show that lack of Ikaros induces hyperphosphorylation of Casitas B lymphoma protein subsequent to BCR activation. These results indicate that the absolute need of Ikaros for development, cell fate decisions and maintenance of B cells is due to the enhancement of BCR signaling

Schools Without Diversity: Education Management Organizations, Charter Schools, and the Demographic Stratification of the American School System

This study, Schools Without Diversity: Education Management Organizations, Charter Schools, and the Demographic Stratification of the American School System, explores the hotly debated question as to whether charter schools increase or decrease school segregation. This research used a national database of schools operated by Education Management Organizations (EMO), 95% of which are charter schools. The research question was whether these EMO-operated charter schools integrate or segregate students by four key demographic characteristics: ethnic/minority classification, socioeconomic status, disabling condition and English language facility. The analysis found that, as compared with the public school district in which the charter school resided, the charter schools were substantially more segregated by race, wealth, disabling condition, and language. While charter schools have rapidly grown, the strong segregative pattern found in 2001 is virtually unchanged through 2007

Isoscalar-isovector mass splittings in excited mesons

Mass splittings between the isovector and isoscalar members of meson nonets arise in part from hadronic loop diagrams which violate the Okubo-Zweig-Iizuka rule. Using a model for these loop processes which works qualitatively well in the established nonets, I tabulate predictions for the splittings and associated isoscalar mixing angles in the remaining nonets below about 2.5 GeV, and explain some of their systematic features. The results for excited vector mesons compare favorably with experiment.Comment: 8 RevTeX pages, including 1 LaTeX figure. CMU-HEP93-23/DOE-ER-40682-4

The effects of meson mixing on dilepton spectra

The effect of scalar and vector meson mixing on the dilepton radiation from hot and dense hadronic matter is estimated in different isospin channels. In particular, we study the effect of $\sigma$-$\omega$ and $\rho-a_0$ mixing and calculate the corresponding rates. Effects are found to be significant compared to standard $\pi$-$\pi$ and $K$-${\bar K}$ annihilations. While the mixing in the isoscalar channel mostly gives a contribution in the invariant mass range between the two-pion threshold and the $\omega$ peak, the isovector channel mixing induces an additional peak just below that of the $\phi$. Experimentally, the dilepton signals from $\rho$-$a_0$ mixing seem to be more tractable than those from $\sigma$-$\omega$ mixing.Comment: 10 pages, 9 figure

Changes in Soil Organic Carbon and Nitrogen Stocks in Long-Term Experiments in Southern Brazil Simulated with Century 4.5

ABSTRACT The Century model has successfully simulated soil organic matter dynamics in many agroecosystems. However, initial applications in southern Brazil produced mixed results. The objective of this study was to calibrate and validate Century 4.5 to simulate soil carbon (C) and nitrogen (N) dynamics under diverse soil management practices in subtropical Brazil. Soil C and N data from two long-term experiments established on a degraded Acrisol in the early 1980s were used. Treatments were conventional or no-tillage; grass or grass/legume cropping systems; and corn with or without mineral N fertilizer. The calibration process iteratively modified model parameters to match simulated values of C additions and Soil Organic Carbon (SOC) and Soil Organic Nitrogen (SON) stocks to field data measured throughout the 25 years of the experiments. Improved fit between measured and observed data was obtained after key parameter changes. Soil C and N stocks were simulated accurately after these modifications were implemented. Other experimental treatments were used to validate the model. Century successfully simulated increases in C and N stocks under no-tillage cropping systems including legumes. However, the model overestimated Soil Organic Matter (SOM) decomposition in treatments with low N availability, like oat/corn without N fertilizer. Overall, Century version 4.5 showed adequate performance in simulating C and N trajectories of contrasting cropping systems commonly found in southern Brazil. The few discrepancies between measured and modeled SOC stocks do not preclude using Century in regional-scale applications to assess impacts of agricultural practices on soil C and N in southern Brazil

Bringing together Brazilian soil scientists to share soil data.

Brazilian soil scientists have recently created a soil data repository using community-built standards and following open data policies in an attempt to address the issues mentioned above. The Free Brazilian Repository for Open Soil Data - febr -, accessible through www.ufsm.br/febr, is a centralized repository targeted at storing open soil data and serving it in a standardized and harmonized format, for various applications. This paper describes the features of febr and the opportunities that it creates for soil science.Na publicação: Wenceslau Teixeira

Elements of Good Training in Anatomic Pathology

The American College of Veterinary Pathologists’ (ACVP’s) 2007–2012 strategic plan recognized the crisis confronting academic training programs and formed a task force to address these concerns. One area of concern identified by the ACVP Training Program Development Task Force was the lack of guidelines to make training more consistent across all programs and provide justification for maintaining or increasing faculty numbers and training resources. Training guidelines for clinical pathology have been outlined in three publications.1,2,4 The current document addresses the need for training guidelines in veterinary anatomic pathology