316 research outputs found
Non-equilibrium steady state of sparse systems
A resistor-network picture of transitions is appropriate for the study of
energy absorption by weakly chaotic or weakly interacting driven systems. Such
"sparse" systems reach a novel non-equilibrium steady state (NESS) once coupled
to a bath. In the stochastic case there is an analogy to the physics of
percolating glassy systems, and an extension of the fluctuation-dissipation
phenomenology is proposed. In the mesoscopic case the quantum NESS might differ
enormously from the stochastic NESS, with saturation temperature determined by
the sparsity. A toy model where the sparsity of the system is modeled using a
log-normal random ensemble is analyzed.Comment: 6 pages, 6 figures, EPL accepted versio
Quantum response of weakly chaotic systems
Chaotic systems, that have a small Lyapunov exponent, do not obey the common
random matrix theory predictions within a wide "weak quantum chaos" regime.
This leads to a novel prediction for the rate of heating for cold atoms in
optical billiards with vibrating walls. The Hamiltonian matrix of the driven
system does not look like one from a Gaussian ensemble, but rather it is very
sparse. This sparsity can be characterized by parameters and that
reflect the percentage of large elements, and their connectivity respectively.
For we use a resistor network calculation that has direct relation to the
semi-linear response characteristics of the system.Comment: 7 pages, 5 figures, expanded improved versio
Resistive Switching Assisted by Noise
We extend results by Stotland and Di Ventra on the phenomenon of resistive
switching aided by noise. We further the analysis of the mechanism underlying
the beneficial role of noise and study the EPIR (Electrical Pulse Induced
Resistance) ratio dependence with noise power. In the case of internal noise we
find an optimal range where the EPIR ratio is both maximized and independent of
the preceding resistive state. However, when external noise is considered no
beneficial effect is observed.Comment: To be published in "Theory and Applications of Nonlinear Dynamics:
Model and Design of Complex Systems", Proceedings of ICAND 2012 (Springer,
2013
Energy absorption by "sparse" systems: beyond linear response theory
The analysis of the response to driving in the case of weakly chaotic or
weakly interacting systems should go beyond linear response theory. Due to the
"sparsity" of the perturbation matrix, a resistor network picture of
transitions between energy levels is essential. The Kubo formula is modified,
replacing the "algebraic" average over the squared matrix elements by a
"resistor network" average. Consequently the response becomes semi-linear
rather than linear. Some novel results have been obtained in the context of two
prototype problems: the heating rate of particles in Billiards with vibrating
walls; and the Ohmic Joule conductance of mesoscopic rings driven by
electromotive force. Respectively, the obtained results are contrasted with the
"Wall formula" and the "Drude formula".Comment: 8 pages, 7 figures, short pedagogical review. Proceedings of FQMT
conference (Prague, 2011). Ref correcte
The information entropy of quantum mechanical states
It is well known that a Shannon based definition of information entropy leads
in the classical case to the Boltzmann entropy. It is tempting to regard the
Von Neumann entropy as the corresponding quantum mechanical definition. But the
latter is problematic from quantum information point of view. Consequently we
introduce a new definition of entropy that reflects the inherent uncertainty of
quantum mechanical states. We derive for it an explicit expression, and discuss
some of its general properties. We distinguish between the minimum uncertainty
entropy of pure states, and the excess statistical entropy of mixtures.Comment: 7 pages, 1 figur
Applying the COM-B model to creation of an IT-enabled health coaching and resource linkage program for low-income Latina moms with recent gestational diabetes: the STAR MAMA program.
BACKGROUND:One of the fastest growing risk groups for early onset of diabetes is women with a recent pregnancy complicated by gestational diabetes, and for this group, Latinas are the largest at-risk group in the USA. Although evidence-based interventions, such as the Diabetes Prevention Program (DPP), which focuses on low-cost changes in eating, physical activity and weight management can lower diabetes risk and delay onset, these programs have yet to be tailored to postpartum Latina women. This study aims to tailor a IT-enabled health communication program to promote DPP-concordant behavior change among postpartum Latina women with recent gestational diabetes. The COM-B model (incorporating Capability, Opportunity, and Motivational behavioral barriers and enablers) and the Behavior Change Wheel (BCW) framework, convey a theoretically based approach for intervention development. We combined a health literacy-tailored health IT tool for reaching ethnic minority patients with diabetes with a BCW-based approach to develop a health coaching intervention targeted to postpartum Latina women with recent gestational diabetes. Current evidence, four focus groups (n = 22 participants), and input from a Regional Consortium of health care providers, diabetes experts, and health literacy practitioners informed the intervention development. Thematic analysis of focus group data used the COM-B model to determine content. Relevant cultural, theoretical, and technological components that underpin the design and development of the intervention were selected using the BCW framework. RESULTS:STAR MAMA delivers DPP content in Spanish and English using health communication strategies to: (1) validate the emotions and experiences postpartum women struggle with; (2) encourage integration of prevention strategies into family life through mothers becoming intergenerational custodians of health; and (3) increase social and material supports through referral to social networks, health coaches, and community resources. Feasibility, acceptability, and health-related outcomes (weight loss, physical activity, consumption of healthy foods, breastfeeding, and glucose screening) will be evaluated at 9 months postpartum using a randomized controlled trial design. CONCLUSIONS:STAR MAMA provides a DPP-based intervention that integrates theory-based design steps. Through systematic use of behavioral theory to inform intervention development, STAR MAMA may represent a strategy to develop health IT intervention tools to meet the needs of diverse populations. TRIAL REGISTRATION:ClinicalTrials.gov NCT02240420
Derivation of the Rules of Quantum Mechanics from Information-Theoretic Axioms
Conventional quantum mechanics with a complex Hilbert space and the Born Rule
is derived from five axioms describing properties of probability distributions
for the outcome of measurements. Axioms I,II,III are common to quantum
mechanics and hidden variable theories. Axiom IV recognizes a phenomenon, first
noted by Turing and von Neumann, in which the increase in entropy resulting
from a measurement is reduced by a suitable intermediate measurement. This is
shown to be impossible for local hidden variable theories. Axiom IV, together
with the first three, almost suffice to deduce the conventional rules but allow
some exotic, alternatives such as real or quaternionic quantum mechanics. Axiom
V recognizes a property of the distribution of outcomes of random measurements
on qubits which holds only in the complex Hilbert space model. It is then shown
that the five axioms also imply the conventional rules for all dimensions.Comment: 20 pages, 6 figure
Evolution of TNF-Induced Apoptosis Reveals 550 My of Functional Conservation
The Precambrian explosion led to the rapid appearance of most major animal phyla alive today. It has been argued that the complexity of life has steadily increased since that event. Here we challenge this hypothesis through the characterization of apoptosis in reef-building corals, representatives of some of the earliest animals. Bioinformatic analysis reveals that all of the major components of the death receptor pathway are present in coral with high-predicted structural conservation with Homo sapiens. The TNF receptor-ligand superfamilies (TNFRSF/TNFSF) are central mediators of the death receptor pathway, and the predicted proteome of Acropora digitifera contains more putative coral TNFRSF members than any organism described thus far, including humans. This high abundance of TNFRSF members, as well as the predicted structural conservation of other death receptor signaling proteins, led us to wonder what would happen if corals were exposed to a member of the human TNFSF (HuTNFα). HuTNFα was found to bind directly to coral cells, increase caspase activity, cause apoptotic blebbing and cell death, and finally induce coral bleaching. Next, immortalized human T cells (Jurkats) expressing a functional death receptor pathway (WT) and a corresponding Fas-associated death domain protein (FADD) KO cell line were exposed to a coral TNFSF member (AdTNF1) identified and purified here. AdTNF1 treatment resulted in significantly higher cell death (P \u3c 0.0001) in WT Jurkats compared with the corresponding FADD KO, demonstrating that coral AdTNF1 activates the H. sapiens death receptor pathway. Taken together, these data show remarkable conservation of the TNF-induced apoptotic response representing 550 My of functional conservation
Recent advances on information transmission and storage assisted by noise
The interplay between nonlinear dynamic systems and noise has proved to be of
great relevance in several application areas. In this presentation, we focus on
the areas of information transmission and storage. We review some recent
results on information transmission through nonlinear channels assisted by
noise. We also present recent proposals of memory devices in which noise plays
an essential role. Finally, we discuss new results on the influence of noise in
memristors.Comment: To be published in "Theory and Applications of Nonlinear Dynamics:
Model and Design of Complex Systems", Proceedings of ICAND 2012 (Springer,
2014
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