292 research outputs found
Linear Regression from Strategic Data Sources
Linear regression is a fundamental building block of statistical data
analysis. It amounts to estimating the parameters of a linear model that maps
input features to corresponding outputs. In the classical setting where the
precision of each data point is fixed, the famous Aitken/Gauss-Markov theorem
in statistics states that generalized least squares (GLS) is a so-called "Best
Linear Unbiased Estimator" (BLUE). In modern data science, however, one often
faces strategic data sources, namely, individuals who incur a cost for
providing high-precision data.
In this paper, we study a setting in which features are public but
individuals choose the precision of the outputs they reveal to an analyst. We
assume that the analyst performs linear regression on this dataset, and
individuals benefit from the outcome of this estimation. We model this scenario
as a game where individuals minimize a cost comprising two components: (a) an
(agent-specific) disclosure cost for providing high-precision data; and (b) a
(global) estimation cost representing the inaccuracy in the linear model
estimate. In this game, the linear model estimate is a public good that
benefits all individuals. We establish that this game has a unique non-trivial
Nash equilibrium. We study the efficiency of this equilibrium and we prove
tight bounds on the price of stability for a large class of disclosure and
estimation costs. Finally, we study the estimator accuracy achieved at
equilibrium. We show that, in general, Aitken's theorem does not hold under
strategic data sources, though it does hold if individuals have identical
disclosure costs (up to a multiplicative factor). When individuals have
non-identical costs, we derive a bound on the improvement of the equilibrium
estimation cost that can be achieved by deviating from GLS, under mild
assumptions on the disclosure cost functions.Comment: This version (v3) extends the results on the sub-optimality of GLS
(Section 6) and improves writing in multiple places compared to v2. Compared
to the initial version v1, it also fixes an error in Theorem 6 (now Theorem
5), and extended many of the result
Opportunities for a Truffle-based Golo Interpreter
Golo is a simple dynamically-typed language for the Java Virtual Machine.
Initially implemented as a ahead-of-time compiler to JVM bytecode, it leverages
invokedy-namic and JSR 292 method handles to implement a reasonably efficient
runtime. Truffle is emerging as a framework for building interpreters for JVM
languages with self-specializing AST nodes. Combined with the Graal compiler,
Truffle offers a simple path towards writing efficient interpreters while
keeping the engineering efforts balanced. The Golo project is interested in
experimenting with a Truffle interpreter in the future, as it would provides
interesting comparison elements between invokedynamic versus Truffle for
building a language runtime
Исследование сезонной изменчивости циркуляции вод Южной Атлантики по данным спутниковой альтиметрии
Исследован сезонный цикл течений на поверхности Южной Атлантики по данным спутниковой альтиметрии за период с 1992 по 2002 гг. Показано, что западные и восточные течения усиливаются с фазовой разницей в несколько месяцев, тогда как их широтные смещения квазисинхронны. Для течений тропической зоны наблюдается запаздывание сезонного сигнала с запада на восток в среднем на 2 – 3 месяца, в полярных широтах оно увеличивается до 6 месяцев.Seasonal cycle of the currents on the South Atlantic surface is investigated using the satellite altimetry data from 1992 to 2002. It is shown that the western and the eastern currents increase with phase difference in several months whereas their latitudinal displacements are quasi-synchronous. For the currents of the tropical zone the seasonal signal delay from the west to the east on average for 2 – 3 months can be observed; at polar latitudes it increases up to 6 months
Fairness in Selection Problems with Strategic Candidates
To better understand discriminations and the effect of affirmative actions in
selection problems (e.g., college admission or hiring), a recent line of
research proposed a model based on differential variance. This model assumes
that the decision-maker has a noisy estimate of each candidate's quality and
puts forward the difference in the noise variances between different
demographic groups as a key factor to explain discrimination. The literature on
differential variance, however, does not consider the strategic behavior of
candidates who can react to the selection procedure to improve their outcome,
which is well-known to happen in many domains.
In this paper, we study how the strategic aspect affects fairness in
selection problems. We propose to model selection problems with strategic
candidates as a contest game: A population of rational candidates compete by
choosing an effort level to increase their quality. They incur a cost-of-effort
but get a (random) quality whose expectation equals the chosen effort. A
Bayesian decision-maker observes a noisy estimate of the quality of each
candidate (with differential variance) and selects the fraction of
best candidates based on their posterior expected quality; each selected
candidate receives a reward . We characterize the (unique) equilibrium of
this game in the different parameters' regimes, both when the decision-maker is
unconstrained and when they are constrained to respect the fairness notion of
demographic parity. Our results reveal important impacts of the strategic
behavior on the discrimination observed at equilibrium and allow us to
understand the effect of imposing demographic parity in this context. In
particular, we find that, in many cases, the results contrast with the
non-strategic setting.Comment: Accepted for publication in the proceedings of the Twenty-Third ACM
Conference on Economics and Computation (EC'22
Towards a Decoupled Context-Oriented Programming Language for the Internet of Things
Easily programming behaviors is one major issue of a large and reconfigurable
deployment in the Internet of Things. Such kind of devices often requires to
externalize part of their behavior such as the sensing, the data aggregation or
the code offloading. Most existing context-oriented programming languages
integrate in the same class or close layers the whole behavior. We propose to
abstract and separate the context tracking from the decision process, and to
use event-based handlers to interconnect them. We keep a very easy declarative
and non-layered programming model. We illustrate by defining an extension to
Golo-a JVM-based dynamic language
T regulatory cells disrupt the CCL20-CCR6 axis driving Th17 homing to the gut
Background: During HIV-1 infection, the integrity of the intestinal immune barrier is disrupted due to a deep depletion of CD4 + T cells in the gut. The translocation of microbial products from the gut lumen into the bloodstream has been linked with systemic inflammation. Despite long-term effective cART, CD4 + T cells in the lamina propria
are incompletely restored in most individuals.
Aims: Among the chemotactic axes involved in CD4 + T cell homing to the gut, we focused on the CCR6-CCL20 axis as it governs Th17 cells homing, a T cell subset exerting a major role in antimicrobial immunity. We aimed to assess the factors regulating the expression of CCL20 by the enterocytes, and notably the role of the cytokines produced by Treg and Th17 cells.
Methods: Small bowel biopsies were obtained by endoscopy in 20 HIV-1 + and 10 HIV-1-individuals. Intestinal lymphocytes phenotype was analyzed by flow cytometry. CCL20 mRNA was quantified by qRT-PCR. The effect of PRR ligands and cytokines on CCL20 expression was explored using an ex-vivosystem of human primary enterocytes. A coculture was done between the enterocytes and Th17/Treg cells. The expression of CCL20 by the enterocytes was evaluated by qRT-PCR and ELISA
The Price of Local Fairness in Multistage Selection
International audienc
Verruculogen associated with Aspergillus fumigatus hyphae and conidia modifies the electrophysiological properties of human nasal epithelial cells
BACKGROUND: The role of Aspergillus fumigatus mycotoxins in the colonization of the respiratory tract by conidia has not been studied extensively, even though patients at risk from invasive aspergillosis frequently exhibit respiratory epithelium damage. In a previous study, we found that filtrates of A. fumigatus cultures can specifically alter the electrophysiological properties of human nasal epithelial cells (HNEC) compared to those of non pathogenic moulds. RESULTS: We fractionated the organic phase of filtrate from 3-day old A. fumigatus cultures using high-performance liquid chromatography. The different fractions were tested for their ability to modify the electrophysiological properties of HNEC in an in vitro primary culture model. The fraction collected between 20 and 30 min mimicked the effects of the whole filtrate, i.e. decrease of transepithelial resistance and increase of potential differences, and contained secondary metabolites such as helvolic acid, fumagillin, and verruculogen. Only verruculogen (10(-8 )M) had effects similar to the whole filtrate. We verified that verruculogen was produced by a collection of 67 human, animal, plant and environmental A. fumigatus isolates. Using MS-MS analysis, we found that verruculogen was associated with both mycelium and conidia extracts. CONCLUSION: Verruculogen is a secondary metabolite that modifies the electrophysiological properties of HNEC. The role of these modifications in the colonization and invasion of the respiratory epithelium by A. fumigatus on first contact with the epithelium remains to be determined
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