5,994 research outputs found
Equity of Attention: Amortizing Individual Fairness in Rankings
Rankings of people and items are at the heart of selection-making,
match-making, and recommender systems, ranging from employment sites to sharing
economy platforms. As ranking positions influence the amount of attention the
ranked subjects receive, biases in rankings can lead to unfair distribution of
opportunities and resources, such as jobs or income.
This paper proposes new measures and mechanisms to quantify and mitigate
unfairness from a bias inherent to all rankings, namely, the position bias,
which leads to disproportionately less attention being paid to low-ranked
subjects. Our approach differs from recent fair ranking approaches in two
important ways. First, existing works measure unfairness at the level of
subject groups while our measures capture unfairness at the level of individual
subjects, and as such subsume group unfairness. Second, as no single ranking
can achieve individual attention fairness, we propose a novel mechanism that
achieves amortized fairness, where attention accumulated across a series of
rankings is proportional to accumulated relevance.
We formulate the challenge of achieving amortized individual fairness subject
to constraints on ranking quality as an online optimization problem and show
that it can be solved as an integer linear program. Our experimental evaluation
reveals that unfair attention distribution in rankings can be substantial, and
demonstrates that our method can improve individual fairness while retaining
high ranking quality.Comment: Accepted to SIGIR 201
Dynamic treatment of vibrational energy relaxation in a heterogeneous and fluctuating environment
A computational approach to describe the energy relaxation of a
high-frequency vibrational mode in a fluctuating heterogeneous environment is
outlined. Extending previous work [H. Fujisaki, Y. Zhang, and J.E. Straub, J.
Chem. Phys. {\bf 124}, 144910 (2006)], second-order time-dependent perturbation
theory is employed which includes the fluctuations of the parameters in the
Hamiltonian within the vibrational adiabatic approximation. This means that the
time-dependent vibrational frequencies along an MD trajectory are obtained via
a partial geometry optimization of the solute with fixed solvent and a
subsequent normal mode calculation. Adopting the amide I mode of
N-methylacetamide in heavy water as a test problem, it is shown that the
inclusion of dynamic fluctuations may significantly change the vibrational
energy relaxation. In particular, it is found that relaxation occurs in two
phases, because for short times ( 200 fs) the spectral density
appears continuous due to the frequency-time uncertainty relation, while at
longer times the discrete nature of the bath becomes apparent. Considering the
excellent agreement between theory and experiment, it is speculated if this
behavior can explain the experimentally obtained biphasic relaxation the amide
I mode of N-methylacetamide.Comment: 24 pages, 7 figures, submitted to J. Chem. Phy
From algebra to logic: there and back again -- the story of a hierarchy
This is an extended survey of the results concerning a hierarchy of languages
that is tightly connected with the quantifier alternation hierarchy within the
two-variable fragment of first order logic of the linear order.Comment: Developments in Language Theory 2014, Ekaterinburg : Russian
Federation (2014
Phase behaviour of a symmetrical binary fluid mixture
We have investigated the phase behaviour of a symmetrical binary fluid
mixture for the situation where the chemical potentials and of
the two species differ. Attention is focused on the set of interparticle
interaction strengths for which, when , the phase diagram exhibits
both a liquid-vapor critical point and a tricritical point. The corresponding
phase behaviour for the case is investigated via
integral-equation theory calculations within the mean spherical approximation
(MSA), and grand canonical Monte Carlo (GCMC) simulations. We find that two
possible subtypes of phase behaviour can occur, these being distinguished by
the relationship between the critical lines in the full phase diagram in the
space of temperature, density, and concentration. We present the detailed form
of the phase diagram for both subtypes and compare with the results from GCMC
simulations, finding good overall agreement. The scenario via which one subtype
evolves into the other, is also studied, revealing interesting features.Comment: 22 pages, 13 figure
Monitoramento da qualidade da água de igarapés da Amazônia Oriental em unidades demonstrativas de recuperação de áreas de preservação permanente.
São apresentadas ações de monitoramento de qualidade de água fluvial ao longo de áreas de preservação permanente revegetadas ou a serem revegetadas em zonas ripárias de igarapés da Amazônia Oriental. O delineamento de amostragem será do tipo BACI (antes-depois-controle-impacto). As variáveis a serem monitoradas em cada estação serão: sedimentos em suspensão (nível de base e pico de vazão), parâmetros físicos e químicos da água, coliformes totais e fecais e biota aquática (avaliação rápida baseada em peixes e libélulas). O monitoramento será iniciado no primeiro trimestre de 2014. Serão tomadas amostras trimestrais durante três anos
Budding and vesiculation induced by conical membrane inclusions
Conical inclusions in a lipid bilayer generate an overall spontaneous
curvature of the membrane that depends on concentration and geometry of the
inclusions. Examples are integral and attached membrane proteins, viruses, and
lipid domains. We propose an analytical model to study budding and vesiculation
of the lipid bilayer membrane, which is based on the membrane bending energy
and the translational entropy of the inclusions. If the inclusions are placed
on a membrane with similar curvature radius, their repulsive membrane-mediated
interaction is screened. Therefore, for high inclusion density the inclusions
aggregate, induce bud formation, and finally vesiculation. Already with the
bending energy alone our model allows the prediction of bud radii. However, in
case the inclusions induce a single large vesicle to split into two smaller
vesicles, bending energy alone predicts that the smaller vesicles have
different sizes whereas the translational entropy favors the formation of
equal-sized vesicles. Our results agree well with those of recent computer
simulations.Comment: 11 pages, 12 figure
Diet of Astyanax paranae (Characidae) in streams with different riparian land covers in the Passa-Cinco River basin, southeastern Brazil.
A análise da dieta de Astyanax paranae Eigenmann, 1914 em nove riachos localizados na bacia do rio Passa-Cinco, sistema do alto rio Paraná, foi realizada com o objetivo de investigar os hábitos alimentares desta espécie, verificar possíveis variações espaciais na dieta e investigar a influência da vegetação ripária na composição da dieta. Foram analisados 243 estômagos através dos métodos de frequência relativa de ocorrência e volumétrico, e a dieta caracterizada através do índice alimentar (AIi). A espécie apresentou hábito alimentar insetívoro, com o predomínio de insetos terrestres e aquáticos na dieta, variando de acordo com o local. Na maioria dos riachos, os recursos mais consumidos foram os de origem alóctone. A participação de insetos aquáticos e vegetais terrestres foram elevadas na maioria dos riachos, enquanto que insetos e invertebrados terrestres apresentaram maior contribuição nos riachos com maior presença de floresta ripária. Os dois riachos drenando áreas de pastagens foram os únicos locais onde A. paranae consumiu algas e fragmentos de macrófitas. Esses resultados são corroborados pela análise de similaridade (ANOSIM), onde o descritor ambiental "porcentagem de floresta ripária" foi aquele de maior influencia na dieta de A. paranae. O estudo mostra que a porcentagem de floresta na zona ripária define a composição da dieta da espécie naquele trecho de riacho, mas que A. paranae também é capaz de obter recursos alimentares em uma variedade de ambientes degradados
Full-analytic frequency-domain 1pN-accurate gravitational wave forms from eccentric compact binaries
The article provides ready-to-use 1pN-accurate frequency-domain gravitational
wave forms for eccentric nonspinning compact binaries of arbitrary mass ratio
including the first post-Newtonian (1pN) point particle corrections to the
far-zone gravitational wave amplitude, given in terms of tensor spherical
harmonics. The averaged equations for the decay of the eccentricity and growth
of radial frequency due to radiation reaction are used to provide stationary
phase approximations to the frequency-domain wave forms.Comment: 28 pages, submitted to PR
The Geometric Maximum Traveling Salesman Problem
We consider the traveling salesman problem when the cities are points in R^d
for some fixed d and distances are computed according to geometric distances,
determined by some norm. We show that for any polyhedral norm, the problem of
finding a tour of maximum length can be solved in polynomial time. If
arithmetic operations are assumed to take unit time, our algorithms run in time
O(n^{f-2} log n), where f is the number of facets of the polyhedron determining
the polyhedral norm. Thus for example we have O(n^2 log n) algorithms for the
cases of points in the plane under the Rectilinear and Sup norms. This is in
contrast to the fact that finding a minimum length tour in each case is
NP-hard. Our approach can be extended to the more general case of quasi-norms
with not necessarily symmetric unit ball, where we get a complexity of
O(n^{2f-2} log n).
For the special case of two-dimensional metrics with f=4 (which includes the
Rectilinear and Sup norms), we present a simple algorithm with O(n) running
time. The algorithm does not use any indirect addressing, so its running time
remains valid even in comparison based models in which sorting requires Omega(n
\log n) time. The basic mechanism of the algorithm provides some intuition on
why polyhedral norms allow fast algorithms.
Complementing the results on simplicity for polyhedral norms, we prove that
for the case of Euclidean distances in R^d for d>2, the Maximum TSP is NP-hard.
This sheds new light on the well-studied difficulties of Euclidean distances.Comment: 24 pages, 6 figures; revised to appear in Journal of the ACM.
(clarified some minor points, fixed typos
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