1,521,585 research outputs found
Counterfactual Risk Minimization: Learning from Logged Bandit Feedback
We develop a learning principle and an efficient algorithm for batch learning
from logged bandit feedback. This learning setting is ubiquitous in online
systems (e.g., ad placement, web search, recommendation), where an algorithm
makes a prediction (e.g., ad ranking) for a given input (e.g., query) and
observes bandit feedback (e.g., user clicks on presented ads). We first address
the counterfactual nature of the learning problem through propensity scoring.
Next, we prove generalization error bounds that account for the variance of the
propensity-weighted empirical risk estimator. These constructive bounds give
rise to the Counterfactual Risk Minimization (CRM) principle. We show how CRM
can be used to derive a new learning method -- called Policy Optimizer for
Exponential Models (POEM) -- for learning stochastic linear rules for
structured output prediction. We present a decomposition of the POEM objective
that enables efficient stochastic gradient optimization. POEM is evaluated on
several multi-label classification problems showing substantially improved
robustness and generalization performance compared to the state-of-the-art.Comment: 10 page
Tips for Transitional Jobs Programs Serving People Experiencing Homelessness
This brief offers recommendations for employment programs using the TJ model to serve jobseekers who are experiencing or at risk of homelessness. These recommendations reflect the most relevant research findings as well as the experiences of expert TJ practitioners
Polarization restricts hepatitis C virus entry into HepG2 hepatoma cells
The primary reservoir for hepatitis C virus (HCV) replication is believed to be hepatocytes, which are highly polarized with tight junctions (TJ) separating their basolateral and apical domains. HepG2 cells develop polarity over time, resulting in the formation and remodeling of bile canalicular (BC) structures. HepG2 cells expressing CD81 provide a model system to study the effects of hepatic polarity on HCV infection. We found an inverse association between HepG2-CD81 polarization and HCV pseudoparticle entry. As HepG2 cells polarize, discrete pools of claudin-1 (CLDN1) at the TJ and basal/lateral membranes develop, consistent with the pattern of receptor staining observed in liver tissue. The TJ and nonjunctional pools of CLDN1 show an altered association with CD81 and localization in response to the PKA antagonist Rp-8-Br-cyclic AMPs (cAMPs). Rp-8-Br-cAMPs reduced CLDN1 expression at the basal membrane and inhibited HCV infection, supporting a model where the nonjunctional pools of CLDN1 have a role in HCV entry. Treatment of HepG2 cells with proinflammatory cytokines, tumor necrosis factor alpha and gamma interferon, perturbed TJ integrity but had minimal effect(s) on cellular polarity and HCV infection, suggesting that TJ integrity does not limit HCV entry into polarized HepG2 cells. In contrast, activation of PKC with phorbol ester reduced TJ integrity, ablated HepG2 polarity, and stimulated HCV entry. Overall, these data show that complex hepatocyte-like polarity alters CLDN1 localization and limits HCV entry, suggesting that agents which disrupt hepatocyte polarity may promote HCV infection and transmission within the liver
The Transitional Jobs Reentry Demonstration: Advancing the Field of Transitional Jobs
The field of Transitional Jobs (TJ) is committed to providing employment opportunities to people throughout our nation who have struggled to find or keep a job. The National Transitional Jobs Network is committed to helping practitioners implement tested best practices to improve TJ program outcomes
Effective Job Development Strategies for Working with the Hardest to Employ
Effective job development -- creating opportunity for subsidized employees to move into the unsubsidized labor market -- is integral to the goals and successful outcomes of the Transitional Jobs (TJ) strategy. It is also one of the most challenging aspects of TJ program delivery, especially during times of high unemployment
Electron Bernstein waves emission in the TJ-II Stellarator
Taking advantage of the electron Bernstein waves heating (EBWH) system of the
TJ-II stellarator, an electron Bernstein emission (EBE) diagnostic was
installed. Its purpose is to investigate the B-X-O radiation properties in the
zone where optimum theoretical EBW coupling is predicted. An internal movable
mirror shared by both systems allows us to collect the EBE radiation along the
same line of sight that is used for EBW heating. The theoretical EBE has been
calculated for different orientations of the internal mirror using the TRUBA
code as ray tracer. A comparison with experimental data obtained in NBI
discharges is carried out. The results provide a valuable information regarding
the experimental O-X mode conversion window expected in the EBW heating
experiments. Furthermore, the characterization of the radiation polarization
shows evidence of the underlying B-X-O conversion process.Comment: 21 pages, 14 figure
On kinetic energy stabilized superconductivity in cuprates
The possibility of kinetic energy driven superconductivity in cuprates as was
recently found in the model is discussed. We argue that the violation of
the virial theorem implied by this result is serious and means that the
description of superconductivity within the model is pathological.Comment: 3 pages, v2 includes additional reference
Collaborer pour s’insérer ?: analyse des pratiques collaboratives des enseignants débutants
En Suisse romande et italienne, la situation de l’emploi amène beaucoup d’enseignants débutants à amorcer leur carrière par un ou plusieurs emplois à temps partiel, ce qui rend la collaboration au sein de duos pédagogiques incontournable. Dès lors, les collaborations que les enseignants débutants établissent au cours de leurs premières années de pratique constituent un enjeu central tant pour leur insertion professionnelle que pour l’exercice futur de leur profession. Cette étude interroge différents aspects des collaborations des enseignants débutants à travers une analyse qualitative d’entretiens conduits auprès d’enseignants débutants primaires (élèves de 6 à 13 ans) de Suisse romande et italienne en lien avec leur développement professionnel. Les principaux résultats sont présentés autour de quatre thèmes : les objets de la collaboration, ses enjeux du point de vue des enseignants débutants, ses conditions et ses effets
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