2,018 research outputs found
Absence Of Adamts13 On A Vwf Deficient Background Is No Longer Prothrombotic In A Murine Model Of Arterial Thrombosis
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106148/1/jth00411.pd
Scale invariance in coarsening of binary and ternary fluids
Phase separation in binary and ternary fluids is studied using a two
dimensional Lattice Gas Automata. The lengths, given by the the first zero
crossing point of the correlation function and the total interface length is
shown to exhibit power law dependence on time. In binary mixtures, our data
clearly indicate the existence of a regime having more than one length scale
where the coarsening process proceeds through the rupture and reassociation of
domains. In ternary fluids; in the case of symmetric mixtures there exists a
regime with a single length scale having dynamic exponent 1/2, while in
asymmetric mixtures our data establish the break down of scale invariance.Comment: 20 pages, 13 figure
Where Power Resides in Committees
The power to control decisions is rarely distributed equally in committees. In a small
voting committee, in which members have conflicting interests, we study how the decision
right to break ties (formal power) translates into effective control over outcomes (real
power). Two controlled experiments show that the level of real power held by the chair
is larger than predicted by rational-choice theory. We also provide causal evidence that
the legitimacy, but not the salience, of holding formal tie-breaking power affects voting
behavior and thus the distribution of real power in the committee. Attitudinal measures
related to the perceived attractiveness of the decision right to break ties exhibit a strong
asymmetry between the one holding the decision right and those who do not
Classical Structures Based on Unitaries
Starting from the observation that distinct notions of copying have arisen in
different categorical fields (logic and computation, contrasted with quantum
mechanics) this paper addresses the question of when, or whether, they may
coincide. Provided all definitions are strict in the categorical sense, we show
that this can never be the case. However, allowing for the defining axioms to
be taken up to canonical isomorphism, a close connection between the classical
structures of categorical quantum mechanics, and the categorical property of
self-similarity familiar from logical and computational models becomes
apparent.
The required canonical isomorphisms are non-trivial, and mix both typed
(multi-object) and untyped (single-object) tensors and structural isomorphisms;
we give coherence results that justify this approach.
We then give a class of examples where distinct self-similar structures at an
object determine distinct matrix representations of arrows, in the same way as
classical structures determine matrix representations in Hilbert space. We also
give analogues of familiar notions from linear algebra in this setting such as
changes of basis, and diagonalisation.Comment: 24 pages,7 diagram
Elastic interactions of active cells with soft materials
Anchorage-dependent cells collect information on the mechanical properties of
the environment through their contractile machineries and use this information
to position and orient themselves. Since the probing process is anisotropic,
cellular force patterns during active mechanosensing can be modelled as
anisotropic force contraction dipoles. Their build-up depends on the mechanical
properties of the environment, including elastic rigidity and prestrain. In a
finite sized sample, it also depends on sample geometry and boundary conditions
through image strain fields. We discuss the interactions of active cells with
an elastic environment and compare it to the case of physical force dipoles.
Despite marked differences, both cases can be described in the same theoretical
framework. We exactly solve the elastic equations for anisotropic force
contraction dipoles in different geometries (full space, halfspace and sphere)
and with different boundary conditions. These results are then used to predict
optimal position and orientation of mechanosensing cells in soft material.Comment: Revtex, 38 pages, 8 Postscript files included; revised version,
accepted for publication in Phys. Rev.
Secure Data Aggregation in Wireless Sensor Networks. Homomorphism versus Watermarking Approach
International audienceWireless sensor networks are now in widespread use to monitor regions, detect events and acquire information. Since the deployed nodes are separated, they need to cooperatively communicate sensed data to the base station. Hence, transmissions are a very energy consuming operation. To reduce the amount of sending data, an aggregation approach can be applied along the path from sensors to the sink. However, usually the carried information contains confidential data. Therefore, an end-to-end secure aggregation approach is required to ensure a healthy data reception. End-to-end encryption schemes that support operations over cypher-text have been proved important for private party sensor network implementations. These schemes offer two main advantages: end-to-end concealment of data and ability to operate on cipher text, then no more decryption is required for aggregation. Unfortunately, nowadays these methods are very complex and not suitable for sensor nodes having limited resources. In this paper, we propose a secure end-to-end encrypted-data aggregation scheme. It is based on elliptic curve cryptography that exploits a smaller key size. Additionally, it allows the use of higher number of operations on cypher-texts and prevents the distinction between two identical texts from their cryptograms. These properties permit to our approach to achieve higher security levels than existing cryptosystems in sensor networks. Our experiments show that our proposed secure aggregation method significantly reduces computation and communication overhead and can be practically implemented in on-the-shelf sensor platforms. By using homomorphic encryption on elliptic curves, we thus have realized an efficient and secure data aggregation in sensor networks. Lastly, to enlarge the aggregation functions that can be used in a secure wireless sensor network, a watermarking-based authentication scheme is finally proposed
Proximity to sports facilities and sports participation for adolescents in Germany
Objectives: To assess the relationship between proximity to specific sports facilities and participation in the corresponding
sports activities for adolescents in Germany.
Methods: A sample of 1,768 adolescents aged 11–17 years old and living in 161 German communities was examined.
Distances to the nearest sports facilities were calculated as an indicator of proximity to sports facilities using Geographic
Information Systems (GIS). Participation in specific leisure-time sports activities in sports clubs was assessed using a selfreport
questionnaire and individual-level socio-demographic variables were derived from a parent questionnaire.
Community-level socio-demographics as covariates were selected from the INKAR database, in particular from indicators
and maps on land development. Logistic regression analyses were conducted to examine associations between proximity to
the nearest sports facilities and participation in the corresponding sports activities.
Results: The logisitic regression analyses showed that girls residing longer distances from the nearest gym were less likely to
engage in indoor sports activities; a significant interaction between distances to gyms and level of urbanization was
identified. Decomposition of the interaction term showed that for adolescent girls living in rural areas participation in indoor
sports activities was positively associated with gym proximity. Proximity to tennis courts and indoor pools was not
associated with participation in tennis or water sports, respectively.
Conclusions: Improved proximity to gyms is likely to be more important for female adolescents living in rural areas
Preference reversals: Time and again
This paper sheds new light on the preference reversal phenomenon by analyzing decision times in the choice task. In a first experiment, we replicated the standard reversal pattern and found that choices associated with reversals take significantly longer than non-reversals, and non-reversal choices take longer whenever long-shot lotteries are selected. These results can be explained by a combination of noisy lottery evaluations (imprecise preferences) and an overpricing phenomenon associated with the compatibility hypothesis. The first cause explains the existence of reversals, while the second explains the predominance of a particular type thereof. A second experiment showed that the overpricing phenomenon can be shut down, greatly reducing reversals, by using ranking-based, ordinally-framed evaluation tasks. This experiment also disentangled the two determinants of reversals, because imprecise evaluations still deliver testable predictions on decision times even in the absence of the overpricing phenomenon. Strikingly, when unframed ranking tasks were used, decision times in the choice phase were greatly reduced, even though this phase was identical across treatments. This observation is consistent with psychological insights on conflicting decision processes
Model-independent extraction of matrix elements from top-quark measurements at hadron colliders
Current methods to extract the quark-mixing matrix element from
single-top production measurements assume that : top quarks decay into quarks with 100% branching fraction,
s-channel single-top production is always accompanied by a quark and
initial-state contributions from and quarks in the -channel
production of single top quarks are neglected. Triggered by a recent
measurement of the ratio
performed by the D0 collaboration, we consider a extraction method
that takes into account non zero d- and s-quark contributions both in
production and decay. We propose a strategy that allows to extract consistently
and in a model-independent way the quark mixing matrix elements ,
, and from the measurement of and from single-top
measured event yields. As an illustration, we apply our method to the Tevatron
data using a CDF analysis of the measured single-top event yield with two jets
in the final state one of which is identified as a -quark jet. We constrain
the matrix elements within a four-generation scenario by combining
the results with those obtained from direct measurements in flavor physics and
determine the preferred range for the top-quark decay width within different
scenarios.Comment: 36 pages, 17 figure
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