3,133 research outputs found
Fast algorithms for min independent dominating set
We first devise a branching algorithm that computes a minimum independent
dominating set on any graph with running time O*(2^0.424n) and polynomial
space. This improves the O*(2^0.441n) result by (S. Gaspers and M. Liedloff, A
branch-and-reduce algorithm for finding a minimum independent dominating set in
graphs, Proc. WG'06). We then show that, for every r>3, it is possible to
compute an r-((r-1)/r)log_2(r)-approximate solution for min independent
dominating set within time O*(2^(nlog_2(r)/r))
PRM76 Stated time-allocation, adherence, and health-outcome tradeoff preferences in cystic fibrosis households
Generating socially appropriate tutorial dialog
Analysis of student-tutor coaching dialogs suggest that good human tutors attend to and attempt to influence the motivational state of learners. Moreover, they are sensitive to the social face of the learner, and seek to mitigate the potential face threat of their comments. This paper describes a dialog generator for pedagogical agents that takes motivation and face threat factors into account. This enables the agent to interact with learners in a socially appropriate fashion, and foster intrinsic motivation on the part of the learner, which in turn may lead to more positive learner affective states
Superconductivity from D3/D7: Holographic Pion Superfluid
We show that a D3/D7 system (at zero quark mass limit) at finite isospin
chemical potential goes through a superconductor (superfluid) like phase
transition. This is similar to a flavored superfluid phase studied in QCD
literature, where mesonic operators condensate. We have studied the frequency
dependent conductivity of the condensate and found a delta function pole in the
zero frequency limit. This is an example of superconductivity in a string
theory context. Consequently we have found a superfluid/supercurrent type
solution and studied the associated phase diagram. The superconducting
transition changes from second order to first order at a critical superfluid
velocity. We have studied various properties of the superconducting system like
superfluid density, energy gap, second sound etc. We investigate the
possibility of the isospin chemical potential modifying the embedding of the
flavor branes by checking whether the transverse scalars also condense at low
temperature. This however does not seem to be the case.Comment: 18 pages, 8 figures, revtex
Methylene blue: an alternative, multi-purpose stain for detection, analysis and isolation of nucleic acids
A series of experiments was performed utilizing Methylene Blue (MeB) in place of the intercalating dyes ethidium bromide (EtBr) and acridine orange (AO) to stain, visualize, and isolate DNA and RNA. MeB proved to be superior to the other dyes for several purposes: 1) visualization of glyoxalated (chemically denatured) RNA in agarose gels, 2) staining of nucleic acids that are to be used in subsequent hybridization experiments, and 3) isolation and purification of plasmid DNA by CsCl ultracentrifugation. MeB was found to perform at least as well as EtBr or AO for visualization of DNA in agarose of acrylamide gels, and DNA stained with MeB can be purified from agarose gel slices by the Gene Clean protocol. These results indicate that MeB is a very effective nucleic acid stain. Its safety versus conventional intercalating dyes will be discussed.Здійснено серію експериментів з використання метиленового синього (МС) замість інтеркалюючих барвників бромистого етидію (ЕВ) та. акридинового оранжевого (АО) для забарвлення, візуалізації та виділення ДНК і РНК. Показано, що МС переважає інші барвники у використанні для декількох цілей: 1) візуалізації гліоксильовано'і (хімічно денатурованої) РНК в агарозних гелях; 2) забарвлювання нуклеїнових кислот, які в подальшому будуть використані в експериментах з гібридизації; 3) виділення та очистки плазмідної ДНК ультрацентрифугуванням в CsCl. Знайдено, що за допомогою МС ДНК так само добре виявляється в гелях агарози або акриламіду, як і з використанням ЕВ і АО, а ДНК, забарвлена МС, може бути очищена із зрізів гелей агарози по протоколу «Gene Clean». Ці результати вказують на те, що МС є дуже ефективним барвником нуклеїнових кислот. Обговорюється його безпека іюрівняно з загальноприйнятними інтеркалюючими барвниками.Проведена серия экспериментов по использованию метиленового синего (МС) вместо интеркалирующих красителей бромистого этидия (ЭВ) и акридинового оранжевого (АО) для окрашивания, визуализации и выделения ДНК и РНК. Показано, что МС превосходит другие красители в использовании для нескольких целей: 1) визуализации глиоксилированной (химически денатурированной) РНК в агарозных гелях; 2) окрашивания нуклеиновых кислот, которые впоследствии будут использоваться в экспериментах по гибридизации; 3) выделения и очистки плазмидной ДНК ультрацентрифугированием в CsCl. Обнаружено, что МС так же пригоден для визуализации ДНК в гелях агарозы или акриламида, как ЭВ или АО, а ДНК, окрашенная МС, может быть очищена из срезов гелей агарозы по протоколу «Gene Clean». Эти результаты указывают на то, что МС – очень эффективный краситель нуклеиновых кислот. Обсуждается его безопасность по сравнению с общепринятыми интеркалирующими красителями
Use of variability in national and regional data to estimate the prevalence of lymphangioleiomyomatosis
Background: Understanding the true prevalence of lymphangioleiomyomatosis (LAM) is important in estimating disease burden and targeting specific interventions. As with all rare diseases, obtaining reliable epidemiological data is difficult and requires innovative approaches. Aim: To determine the prevalence and incidence of LAM using data from patient organizations in seven countries, and to use the extent to which the prevalence of LAM varies regionally and nationally to determine whether prevalence estimates are related to health-care provision. Methods: Numbers of women with LAM were obtained from patient groups and national databases from seven countries (n = 1001). Prevalence was calculated for regions within countries using female population figures from census data. Incidence estimates were calculated for the USA, UK and Switzerland. Regional variation in prevalence and changes in incidence over time were analysed using Poisson regression and linear regression. Results: Prevalence of LAM in the seven countries ranged from 3.4 to 7.8/million women with significant variation, both between countries and between states in the USA. This variation did not relate to the number of pulmonary specialists in the region nor the percentage of population with health insurance, but suggests a large number of patients remain undiagnosed. The incidence of LAM from 2004 to 2008 ranged from 0.23 to 0.31/million women/per year in the USA, UK and Switzerland. Conclusions: Using this method, we have found that the prevalence of LAM is higher than that previously recorded and that many patients with LAM are undiagnose
Bubbling Orientifolds
We investigate a class of 1/2-BPS bubbling geometries associated to
orientifolds of type IIB string theory and thereby to excited states of the
SO(N)/Sp(N) N=4 supersymmetric Yang-Mills theory. The geometries are in
correspondence with free fermions moving in a harmonic oscillator potential on
the half-line. Branes wrapped on torsion cycles of these geometries are
identified in the fermi fluid description. Besides being of intrinsic interest,
these solutions may also occur as local geometries in flux compactifications
where orientifold planes are present to ensure global charge cancellation. We
comment on the extension of this procedure to M-theory orientifolds.Comment: 25 pages, 11 figures. v2: few references adde
Killing spectroscopy of closed timelike curves
We analyse the existence of closed timelike curves in spacetimes which
possess an isometry. In particular we check which discrete quotients of such
spaces lead to closed timelike curves. As a by-product of our analysis, we
prove that the notion of existence or non-existence of closed timelike curves
is a T-duality invariant notion, whenever the direction along which we apply
such transformations is everywhere spacelike. Our formalism is
straightforwardly applied to supersymmetric theories. We provide some new
examples in the context of D-branes and generalized pp-waves.Comment: 1+35 pages, no figures; v2, new references added. Final version to
appear in JHE
Nonequilibrium excitations in Ferromagnetic Nanoparticles
In recent measurements of tunneling transport through individual
ferromagnetic Co nanograins, Deshmukh, Gu\'eron, Ralph et al.
\cite{mandar,gueron} (DGR) observed a tunneling spectrum with discrete
resonances, whose spacing was much smaller than what one would expect from
naive independent-electron estimates. In a previous publication,
\cite{prl_kleff} we had suggested that this was a consequence of nonequilibrium
excitations, and had proposed a ``minimal model'' for ferromagnetism in
nanograins with a discrete excitation spectrum as a framework for analyzing the
experimental data. In the present paper, we provide a detailed analysis of the
properties of this model: We delineate which many-body electron states must be
considered when constructing the tunneling spectrum, discuss various
nonequilibrium scenarios and compare their results with the experimental data
of Refs. \cite{mandar,gueron}. We show that a combination of nonequilibrium
spin- and single-particle excitations can account for most of the observed
features, in particular the abundance of resonances, the resonance spacing and
the absence of Zeeman splitting.Comment: 13 pages, 10 figure
PSD95 and nNOS interaction as a novel molecular target to modulate conditioned fear: relevance to PTSD
Stimulation of N-methyl-D-aspartic acid receptors (NMDARs) and the resulting increase of nitric oxide (NO) production are critical for fear memory formation. Following NMDAR activation, efficient production of NO requires linking the 95 kDa postsynaptic density protein (PSD95), a scaffolding protein to neuronal nitric oxide synthase (nNOS). A variety of previously studied NMDAR antagonists and NOS inhibitors can disrupt fear conditioning, but they also affect many other CNS functions such as motor activity, anxiety, and learning. We hypothesized that disrupting nNOS and PSD95 interaction in the amygdala, a critical site for fear memory formation, will reduce conditioned fear. Our results show that systemic treatment with ZL006, a compound that disrupts PSD95/nNOS binding, attenuates fear memory compared to its inactive isomer ZL007. Co-immunoprecipitation after fear conditioning showed a robust increase in the amygdala PSD95/nNOS binding, which was blocked by systemic pre-administration of ZL006. Treatment of amygdala slices with ZL006 also impaired long-term potentiation (LTP), a cellular signature of synaptic plasticity. Direct intra-amygdala infusion of ZL006 also attenuated conditioned fear. Finally, unlike NMDAR antagonist MK-801, ZL006 does not affect locomotion, social interaction, object recognition memory, and spatial memory. These findings support the hypothesis that disrupting the PSD95/nNOS interaction downstream of NMDARs selectively reduces fear memory, and highlights PSD95/nNOS interaction as a novel target for fear-related disorders, such as posttraumatic stress disorder
- …