Relativistic effects on LEED intensities from Au(111)

Comparison of relativistically and nonrelativistically calculated intensity versus energy profiles in low energy electron diffraction (LEED) from the (111) surface of Au (Z = 79) reveals that relativistic corrections are quite significant. They can however, be obtained in very good approximation by quasirelativistic calculations, in which spin-averaged relativistic phase shifts are used as input for the nonrelativistic multiple scattering formalism. Further, relativistic effects on intensities are found to be comparable to differences arising from different approximations to the exchange part of the ion core potential

Common Core State Standards and Assessments: Background and Issues

Over the last two decades, there has been interest in developing federal policies that focus on student outcomes in elementary and secondary education. Perhaps most prominently, the enactment of the No Child Left Behind Act of 2001 (NCLB; P.L. 107-110), which amended and reauthorized the Elementary and Secondary Education Act (ESEA), marked a dramatic expansion of the federal government’s role in supporting standards-based instruction and test-based accountability, thereby increasing the federal government’s involvement in decisions that directly affect teaching and learning. Under the ESEA, states are required to have standards in reading and mathematics for specified grade levels in order to receive funding under Title I-A of the ESEA. In response to this requirement, all 50 states and the District of Columbia have adopted and implemented standards that meet the requirements of the ESEA. Since the ESEA was last comprehensively reauthorized by NCLB, three major changes have taken place that have possibly played a role in the selection of reading and mathematics standards by states: (1) the development and release of the Common Core State Standards; (2) the Race to the Top (RTT) State Grant competition and RTT Assessment Grants competition; and (3) the ESEA flexibility package provided by ED to states with approved applications. As of August 2014, 43 states, the District of Columbia, 4 outlying areas, and the Department of Defense Education Activity (DODEA) had at some point adopted the Common Core State Standards. Indiana and Oklahoma recently became the first states to adopt and subsequently discontinue use of the Common Core State Standards. South Carolina has indicated that the Common Core State Standards will be fully implemented for the 2014-2015 school year but will be replaced by new standards in the 2015-2016 school year. This report examines each of the aforementioned changes and discusses how they are interrelated. More specifically, it provides (1) background information on current law, (2) a discussion of the development of the Common Core State Standards and state adoption of the standards, (3) an analysis of the RTT State Grant competition and how the structure of the grant application process may have incentivized state adoption of the Common Core State Standards, (4) an examination of the RTT Assessment Grants competition and the federal funds provided to support the development of assessments aligned with the Common Core State Standards, and (5) an analysis of the ESEA flexibility package and how the conditions that states had to meet to receive waivers of ESEA accountability provisions may have incentivized state implementation of the Common Core State Standards. This report also examines prohibitions in the ESEA and the General Education Provisions Act related to standards, assessments, and curriculum. Additionally, it includes a brief discussion of the relationship between teacher and school leader evaluation systems that are being developed by states and the Common Core State Standards. Finally, the report examines issues that have arisen in relation to the Common Core State Standards, including the following: • whether states were incentivized by the Administration to adopt and implement the Common Core State Standards; • whether state adoption and implementation of the Common Core State Standards could result in a national assessment and national standards; • whether state adoption and implementation of the Common Core State Standards could lead to the development of a national curriculum; •possible issues that may need to be addressed if a state chooses to discontinue its use of the Common Core State Standards; • possible issues related to teacher evaluation and the Common Core State Standards; • possible technology issues related to implementation of the Common Core State Standards; and • possible issues related to the long-term maintenance of the Common Core State Standards

Rural extension services

The authors analyze the considerations that lead policymakers to undertake extension investments as a key public responsibility, as well as the complex set of factors and intra-agency incentives that explain why different extension systems'performance vary. The authors provide a conceptual framework outlining farmers'demand for information, the welfare economic characterizations of extension services, and the organizational and political attributes that govern the performance of extension systems. They use the conceptual framework to examine several extension modalities and to analyze their likely and actual effectiveness. Specifically, the modalities reviewed include"training and visit"extension, decentralized systems,"fee-for-service"and privatized extension, and farmer-field-schools. The authors also discuss methodological issues pertaining to the assessment of extension outcomes and review the empirical literature on extension impact. They emphasize the efficiency gains that can come from locally decentralized delivery systems with incentive structures based largely on private provision that in most poorer countries is still publicly-funded. In wealthier countries, and for particular higher income farmer groups, extension systems will likely evolve into fee-for-service organizations.Decentralization,Agricultural Knowledge&Information Systems,Environmental Economics&Policies,ICT Policy and Strategies,Health Economics&Finance,Agricultural Knowledge&Information Systems,ICT Policy and Strategies,Environmental Economics&Policies,Health Economics&Finance,Knowledge Economy

Influence of the scattering potential model on low energy electron diffraction from Cu(001)−c(2 × 2)-Pb

A dynamical LEED intensity analysis is reported for Cu(001)−c(2 × 2)-Pb. The adsorbate layer distance from the substrate is determined as 2.29 Å, and the topmost interlayer spacing for the substrate is the same as in bulk Cu, in contrast to a contraction for clean Cu(001). This structural result is, within the accuracy reached, insensitive to changes in the assumed scattering potential models. The r-factors suggest a weak preference for an energy-dependent exchange correlation and a moderate one for adding a localized adsorption part inside the muffin-tin spheres. The sensitivity of spectra and r-factors to changes in the assumed isotropic Debye temperature for Pb suggests that vibrational anisotropy should be taken into account in order to improve the accuracy of the analysis. Calculated spin polarization spectra are very sensitive to the exchange approximation, the localized absorption and the Debye temperature. Together with experimental data, they should be useful in particular for determining the vibrational anisotropy

Constraint Satisfaction with Counting Quantifiers

We initiate the study of constraint satisfaction problems (CSPs) in the presence of counting quantifiers, which may be seen as variants of CSPs in the mould of quantified CSPs (QCSPs). We show that a single counting quantifier strictly between exists^1:=exists and exists^n:=forall (the domain being of size n) already affords the maximal possible complexity of QCSPs (which have both exists and forall), being Pspace-complete for a suitably chosen template. Next, we focus on the complexity of subsets of counting quantifiers on clique and cycle templates. For cycles we give a full trichotomy -- all such problems are in L, NP-complete or Pspace-complete. For cliques we come close to a similar trichotomy, but one case remains outstanding. Afterwards, we consider the generalisation of CSPs in which we augment the extant quantifier exists^1:=exists with the quantifier exists^j (j not 1). Such a CSP is already NP-hard on non-bipartite graph templates. We explore the situation of this generalised CSP on bipartite templates, giving various conditions for both tractability and hardness -- culminating in a classification theorem for general graphs. Finally, we use counting quantifiers to solve the complexity of a concrete QCSP whose complexity was previously open

The rise and fall of training and visit extension : an Asian mini-drama with an African epilogue

The paper reviews the origins and evolution of the Training and Visit (T&V) extension system, which was promoted by the World Bank in 1975-98 in over 50 developing countries. The discussion seeks to clarify the context within which the approach was implemented, and to analyze the causes for its lack of sustainability and its ultimate abandonment. The paper identifies some of the challenges faced by the T&V approach as being typical of a large public extension system, where issues of scale, interaction with the agricultural research systems, inability to attribute benefits, weak accountability, and lack of political support tend to lead to incentive problems among staff and managers of extension, and limited budgetary resources. The different incentives and outlook of domestic stakeholders and external donor agencies are also reviewed. The main cause of the T&V system's disappearance is attributed to the incompatibility of its high recurrent costs with the limited budgets available domestically, leading to fiscal unsustainability. The paper concludes with some lessons that apply to donor-driven public extension initiatives, and more generally to rural development fads. The role of timely, independent, and rigorous evaluative studiesis specifically highlighted.Agricultural Knowledge&Information Systems,Rural Development Knowledge&Information Systems,Rural Poverty Reduction,ICT Policy and Strategies,Banks&Banking Reform

Duct-lining materials and concepts

Acoustic characteristics evaluation of duct lining materials and design of acoustically absorptive aircraft inlets and fan duct

Promises and realities of community-based agricultural extension

In view of the market failures and the state failures inherent in providing agricultural extension, community-based approaches, which involve farmers‘ groups, have gained increasing importance in recent years as a third way to provide this service. The paper discusses the conceptual underpinnings of community-based extension approaches, highlights theoretical and practical challenges inherent in their design, and assesses the evidence available so far on their performance. The paper reviews both quantitative and qualitative studies, focusing on three examples that contain important elements of community-based extension: the National Agricultural Advisory Services program of Uganda, the agricultural technology management agency model of India, and the farmer field school approach. The review finds that in the rather few cases where performance has been relatively carefully studied, elite capture was identified as a major constraint. Other challenges that empirical studies found include a limited availability of competent service providers, deep-seated cultural attitudes that prevent an effective empowerment of farmers, and difficulties in implementing farmers‘ control of service providers‘ contracts. The paper concludes that, just as for the state and the market, communities can also fail in extension delivery. Hence, the challenge for innovative approaches in agricultural extension is to identify systems that use the potential of the state, the market, and communities to create checks and balances to overcome the failures inherent in all of them.agricultural extension, Agricultural technology, community-based development, empowerment of farmers, innovative approaches, market failures, National Agricultural Advisory Services program,

Early-type galaxies in the Chandra COSMOS Survey

We study a sample of 69 X-ray detected Early Type Galaxies (ETGs), selected from the Chandra COSMOS survey, to explore the relation between the X-ray luminosity of hot gaseous halos (L_X, gas) and the integrated stellar luminosity (L_K) of the galaxies, in a range of redshift extending out to z=1.5. In the local universe a tight steep relationship has been stablished between these two quantities (L_X,gas~ L_K^4.5) suggesting the presence of largely virialized halos in X-ray luminous systems. We use well established relations from the study of local universe ETGs, together with the expected evolution of the X-ray emission, to subtract the contribution of low mass X-ray binary populations (LMXBs) from the X-ray luminosity of our sample. Our selection minimizes the presence of active galactic nuclei (AGN), yielding a sample representative of normal passive COSMOS ETGs; therefore the resulting luminosity should be representative of gaseous halos, although we cannot exclude other sources such as obscured AGN, or enhanced X-ray emission connected with embedded star formation in the higher z galaxies. We find that most of the galaxies with estimated L_X<10^42 erg/s and z<0.55 follow the L_X,gas- L_K relation of local universe ETGs. For these galaxies, the gravitational mass can be estimated with a certain degree of confidence from the local virial relation. However, the more luminous (10^42<L_X<10^43.5 erg/s) and distant galaxies present significantly larger scatter; these galaxies also tend to have younger stellar ages. The divergence from the local L_X,gas - L_K relation in these galaxies implies significantly enhanced X-ray emission, up to a factor of 100 larger than predicted from the local relation. We discuss the implications of this result for the presence of hidden AGN, and the evolution of hot halos, in the presence of nuclear and star formation feedback.Comment: 29 pages, 10 figures, accepted for publication on ApJ on May 27 201

New universality class for the three-dimensional XY model with correlated impurities: Application to 4^4He in aerogels

Encouraged by experiments on $^4$He in aerogels, we confine planar spins in the pores of simulated aerogels (diffusion limited cluster-cluster aggregation) in order to study the effect of quenched disorder on the critical behavior of the three-dimensional XY model. Monte Carlo simulations and finite-size scaling are used to determine critical couplings $K_c$ and exponents. In agreement with experiments, clear evidence of change in the thermal critical exponents $\nu$ and $\alpha$ is found at nonzero volume fractions of impurities. These changes are explained in terms of {\it hidden} long-range correlations within disorder distributions.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let