Resultados versus desempenho “impacto de longo prazo de professores”

The authors of the study “The Long-Term Impact of Teachers” claim that their study shows that increases in teacher value-added lead to significant and lasting increases in test scores and significant increases in income that will last throughout adulthood. Instead, I show that these claims are false because they are contradicted by the findings of the study itself. In fact, the results of the Chetty et al. study raise serious questions about the benefits of using the value-added method for evaluating teachers.Los autores del estudio "El impacto a largo plazo de maestros" (original en inglés “The Long-Term Impact of Teachers”) afirman que su estudio demuestra que aumentos en el valor agregado de los docentes conducen a aumentos significativos y duraderos en pruebas de resultados académicos y aumentos significativos en los ingresos económicos a lo largo de la edad adulta. Por el contrario, mostramos que estas afirmaciones son falsas, ya que se contradicen con las conclusiones del propio estudio. Así, los resultados del estudio de Chetty et al. plantean serias dudas sobre los beneficios de usar el método de valor agregado para la evaluación de los docentes.Os autores do estudo "O impacto de longo prazo de professores" dizem que seu estudo mostra que os aumentos no valor agregado dos professores leva a aumentos significativos e duradouros em provas de desempenho acadêmico e aumentos significativos de renda durante a vida adulta. Contrariamente nós mostramos que essas alegações são falsas, e que contradizem as conclusões do próprio estudo. Assim, os resultados do estudo Chetty et al. levantam sérias dúvidas sobre os benefícios de usar modelos de valor agregado para avaliar os professores

NEPC Review: Measuring the Impacts of Teachers I: Evaluating Bias in Teacher Value-Added Estimates and Measuring the Impacts of Teachers II: Teacher Value-Added and Student Outcomes in Adulthood

Can the quality of teachers be measured the way that a person&rsquo;s weight or height is measured? Some economists have tried, but the &ldquo;value-added&rdquo; they have attempted to measure has proven elusive. The results have not been consistent over tests or over time. Nevertheless, a two-part report by Raj Chetty and his colleagues claims that higher value-added scores for teachers lead to greater economic success for their students later in life. This review of the methods of Chetty et al. focuses on their most important result: that teacher value-added affects income in adulthood. Five key problems with the research emerge. First, their own results show that the calculation of teacher value-added is unreliable. Second, their own research also generated a result that contradicts their main claim&mdash;but the report pushed that inconvenient result aside. Third, the trumpeted result is based on an erroneous calculation. Fourth, the report incorrectly assumes that the (miscalculated) result holds across students&rsquo; lifetimes despite the authors&rsquo; own research indicating otherwise. Fifth, the report cites studies as support for the authors&rsquo; methodology, even though they don&rsquo;t provide that support. Despite widespread references to this study in policy circles, the shortcomings and shaky extrapolations make this report misleading and unreliable for determining educational policy.</p

Critical Behavior of the Random-Field Ising Model

We study the critical properties of the random field Ising model in general dimension d using high-temperature expansions for the susceptibility, χ=∑j[〈σiσj⟩T-〈σi⟩T〈σj⟩T]h and the structure factor, G=∑j[〈σiσj⟩T]h, where 〈⟩T indicates a canonical average at temperature T for an arbitrary configuration of random fields and [ ]h indicates an average over random fields. We treated two distributions of random fields, the bimodal in which each hi=±h0 and a Gaussian distribution in which each hi has variance h02. We obtained series for χ and G in the form ∑n=1,15an(g,d)(J/T)n, where J is the exchange constant and the coefficients an(g,d) are polynomials in g≡h02/J2 and in d. We assume that as T approaches its critical value, Tc, one has χ~(T-Tc)−γ and G~(T-Tc)−γ. For dimensions above d=2 we find a range of values of g for which the critical exponents obtained from our series seem not to depend on g. For large values of g our results show a g dependence which is attributable to either a tricritical point or a first-order transition. All our results for critical exponents suggest that γ¯=2γ, in agreement with the two-exponent scaling picture. In addition we have also constructed series for the amplitude ratio, A=(G/χ2)(T2)/(gJ2). We find that A approaches a constant value as T→Tc (consistent with γ¯=2γ) with A~1. It appears that A is somewhat larger for the bimodal than for the Gaussian model, in agreement with a recent analysis at high d

Evidence for Two Exponent Scaling in the Random Field Ising Model

Novel methods were used to generate and analyze new 15 term high temperature series for both the (connected) susceptibility χ and the structure factor (disconnected susceptibility) χd for the random field Ising model with dimensionless coupling K=J/kT, in general dimension d. For both the bimodal and the Gaussian field distributions, with mean square field J2g, we find that (χd-χ)/K2gχ2=1 as T→Tc(g), for a range of [h2]=J2g and d=3,4,5. This confirms the exponent relation γ¯=2γ (where χd~t−γ¯, χ~t−γ, t=T-Tc) providing that random field exponents are determined by two (and not three) independent exponents. We also present new accurate values for γ

Theta dependence of SU(N) gauge theories in the presence of a topological term

We review results concerning the theta dependence of 4D SU(N) gauge theories and QCD, where theta is the coefficient of the CP-violating topological term in the Lagrangian. In particular, we discuss theta dependence in the large-N limit. Most results have been obtained within the lattice formulation of the theory via numerical simulations, which allow to investigate the theta dependence of the ground-state energy and the spectrum around theta=0 by determining the moments of the topological charge distribution, and their correlations with other observables. We discuss the various methods which have been employed to determine the topological susceptibility, and higher-order terms of the theta expansion. We review results at zero and finite temperature. We show that the results support the scenario obtained by general large-N scaling arguments, and in particular the Witten-Veneziano mechanism to explain the U(1)_A problem. We also compare with results obtained by other approaches, especially in the large-N limit, where the issue has been also addressed using, for example, the AdS/CFT correspondence. We discuss issues related to theta dependence in full QCD: the neutron electric dipole moment, the dependence of the topological susceptibility on the quark masses, the U(1)_A symmetry breaking at finite temperature. We also consider the 2D CP(N) model, which is an interesting theoretical laboratory to study issues related to topology. We review analytical results in the large-N limit, and numerical results within its lattice formulation. Finally, we discuss the main features of the two-point correlation function of the topological charge density.Comment: A typo in Eq. (3.9) has been corrected. An additional subsection (5.2) has been inserted to demonstrate the nonrenormalizability of the relevant theta parameter in the presence of massive fermions, which implies that the continuum (a -> 0) limit must be taken keeping theta fixe

Gene Expression Analysis in Rats Treated with Experimental Acetyl-Coenzyme A Carboxylase Inhibitors Suggests Interactions with the Peroxisome Proliferator-Activated Receptor ␣ Pathway

ABSTRACT Acetyl CoA carboxylase (ACC) 2, which catalyzes the carboxylation of acetyl-CoA to form malonyl-CoA, has been identified as a potential target for type 2 diabetes and obesity. Small-molecule inhibitors of ACC2 would be expected to reduce de novo lipid synthesis and increase lipid oxidation. Treatment of ob/ob mice with compound A-908292 (S) ({(S)-3-[2-(4-isopropoxy-phenoxy)-thiazol-5-yl]-1-methylprop-2-ynyl}-carbamic acid methyl ester), a small-molecule inhibitor with an IC 50 of 23 nM against ACC2, resulted in a reduction of serum glucose and triglyceride levels. However, compound A-875400 (R) ({(R)-3-[2-(4-isopropoxy-phenoxy)-thiazol-5-yl]-1-methyl-prop-2-ynyl}-carbamic acid methyl ester), an inactive enantiomer of A-908292 (S) with approximately 50-fold less activity against ACC2, also caused a similar reduction in glucose and triglycerides, suggesting that the glucose-lowering effects in ob/ob mice may be mediated by other metabolic pathways independent of ACC2 inhibition. To characterize the pharmacological activity of these experimental compounds at a transcriptional level, rats were orally dosed for 3 days with either A-908292 (S) or A-875400 (R), and gene expression analysis was performed. Gene expression analysis of livers showed that treatment with A-908292 (S) or A-875400 (R) resulted in gene expression profiles highly similar to known peroxisome proliferator-activated receptor (PPAR)-␣ activators. The results suggest that, in vivo, both A-908292 (S) and A-875400 (R) stimulated the PPAR-␣-dependent signaling pathway. These results were further supported by both an in vitro genomic evaluation using rat hepatocytes and immunohistochemical evaluation using 70-kDa peroxisomal membrane protein. Overall, the gene expression analysis suggests a plausible mechanism for the similar pharmacological findings with active and inactive enantiomers of an ACC2 inhibitor

Half a century of amyloids: past, present and future

Amyloid diseases are global epidemics with profound health, social and economic implications and yet remain without a cure. This dire situation calls for research into the origin and pathological manifestations of amyloidosis to stimulate continued development of new therapeutics. In basic science and engineering, the cross-ß architecture has been a constant thread underlying the structural characteristics of pathological and functional amyloids, and realizing that amyloid structures can be both pathological and functional in nature has fuelled innovations in artificial amyloids, whose use today ranges from water purification to 3D printing. At the conclusion of a half century since Eanes and Glenner's seminal study of amyloids in humans, this review commemorates the occasion by documenting the major milestones in amyloid research to date, from the perspectives of structural biology, biophysics, medicine, microbiology, engineering and nanotechnology. We also discuss new challenges and opportunities to drive this interdisciplinary field moving forward. This journal i

Can Economic Growth Save Social Security?

Here is a fascinating issue. If, because of economic growth, median incomes rise rapidly in the future, won't social security benefits have to be raised as well? As the author explains, growth will create a wealth of new and better goods. Thus, unless the level of social security's real benefits grows at the same rate as the economy, retirees will have to choose between the samesize basket of the goods that growth will have rendered stale and a smaller basket of the new goods. The only way that growth can "save" the social security system is by making retirees poorer.