12,935 research outputs found
Visibility Fringe Reduction Due to Noise-Induced Effects: Microscopic Approach to Interference Experiments
Decoherence is the main process behind the quantum to classical transition.
It is a purely quantum mechanical effect by which the system looses its ability
to exhibit coherent behavior. The recent experimental observation of
diffraction and interference patterns for large molecules raises some
interesting questions. In this context, we identify possible agents of
decoherence to take into account when modeling these experiments and study
theirs visible (or not) effects on the interference pattern. Thereby, we
present an analysis of matter wave interferometry in the presence of a dynamic
quantum environment and study how much the visibility fringe is reduced and in
which timescale the decoherence effects destroy the interference of massive
objects. Finally, we apply our results to the experimental data reported on
fullerenes and cold neutrons.Comment: 14 pages, 5 figures. Version to appear in Mod. Phys.
Keck IR Spectroscopy of WZ Sge: Detection of Molecular Emission from the Accretion Disk
Time-resolved IR spectroscopy of WZ Sge was obtained using NIRSPEC on Keck
II. We detect CO and H emission from the accretion disk placing WZ
Sge into a rarefied class of astronomical objects including YSOs and high
luminosity early-type stars. During the eclipse phase, the molecular emission
greatly weakens but no firm evidence for the secondary star is seen allowing
new limits on its luminosity to be determined. The detection of molecular
emission provides physical properties within the outer disk of T=3000K and
N cm. Such a cool, dense region, not associated with areas
of H I and He I emission, provides the first observational confirmation of
predictions made by accretion disk models.Comment: 10 pages, 3 figures. Accepted for publication in ApJ Letter
A consistent scalar-tensor cosmology for inflation, dark energy and the Hubble parameter
The authors are grateful for financial support to the Cruickshank Trust (CW), EPSRC/GG-Top (CW, JR), Omani Government (MA), Science Without Borders programme, CNPq, Brazil (DR), and STFC/CfFP (CW, AM, RB, JM). CW and AM acknowledge the hospitality of CERN, where this work was started. The University of Aberdeen and University of Edinburgh are charitable bodies registered in Scotland, with respective registration numbers SC013683 and SC005336.Peer reviewedPostprin
Dark/Visible Parallel Universes and Big Bang Nucleosynthesis
We develop a model for visible matter-dark matter interaction based on the
exchange of a massive gray boson called herein the Mulato. Our model hinges on
the assumption that all known particles in the visible matter have their
counterparts in the dark matter. We postulate six families of particles five of
which are dark. This leads to the unavoidable postulation of six parallel
worlds, the visible one and five invisible worlds. A close study of big bang
nucleosynthesis (BBN), baryon asymmetries, cosmic microwave background (CMB)
bounds, galaxy dynamics, together with the Standard Model assumptions, help us
to set a limit on the mass and width of the new gauge boson. Modification of
the statistics underlying the kinetic energy distribution of particles during
the BBN is also discussed. The changes in reaction rates during the BBN due to
a departure from the Debye-Hueckel electron screening model is also
investigated.Comment: Invited talk at the Workshops "CompStar: the physics and astrophysics
of compact stars", Tahiti, June 4-8, 2012, "New Directions in Nuclear
Astrophysics", Castiglion Fiorentino, Italy, June 18-22, 2012, and
"Carpathian Summer School of Physics", Sinaia, Romania, June 24 - July 7,
2012. To be published in AIP Proceeding
Enrollment in YFV Vaccine Trial: An Evaluation of Recruitment Outcomes Associated with a Randomized Controlled Double-Blind Trial of a Live Attenuated Yellow Fever Vaccine
This investigation evaluated several factors associated with diverse participant enrollment of a clinical trial assessing safety, immunogenicity, and comparative viremia associated with administration of 17-D live, attenuated yellow fever vaccine given alone or in combination with human immune globulin. We obtained baseline participant information (e.g., sociodemographic, medical) and followed recruitment outcomes from 2005 to 2007. Of 355 potential Yellow Fever vaccine study participants, 231 cases were analyzed. Strong interest in study participation was observed among racial and ethnically diverse persons with 36.34% eligible following initial study screening, resulting in 18.75% enrollment. The percentage of white participants increased from 63.66% (prescreened sample) to 81.25% (enrollment group). The regression model was significant with white race as a predictor of enrollment (OR=2.744, 95% CI=1.415-5.320, p=0.003).In addition, persons were more likely to enroll via direct outreach and referral mechanisms compared to mass advertising (OR=2.433, 95% CI=1.102-5.369). The findings indicate that racially diverse populations can be recruited to vaccine clinical trials, yet actual enrollment may not reflect that diversit
Solving Problems by Analogy: The Benefits and Detriments of Hints and Depressed Moods
In Experiment 1, mildly depressed (dysphoric) and nondysphoric subjects tried to solve logic, problems that were analogous to subsequent target problems; then they attempted target solutions with or wit hour hints in the form of the analogues\u27 themes. Target solutions were impaired by the hints in the nondysphoric group alone. Experiment 2A was a no-training control to verify that transfer did indeed occur. In Experiment 2B, all subjects received hints in the transfer phase; the training phase was either problem oriented (as in Experiment 1) or memory oriented. Again, nondysphoric subjects solved fewerproblems following problem-oriented training than did both dysphoric subjects in that condition and nondysphoric subjects with memory-oriented training. Experiment 3 replicated the previous results in thenondysphoric samples. We, interpret these findings within the, transfer- appropriate processing framework
Emotionality in Free Recall: Language Specificity in Bilingual Memory
Bilingual subjects (Spanish English) who had acquired fluency in their second language after 8 years of age rated 18 emotional and 18 neutral words for ease of pronunciation, implied activity, or emotionality; half of each type was presented in Spanish and half in English. During a subsequent, unexpected test of free recall subjects recalled more emotional than neutral words, but only for words that had been presented in the native language. This finding applied across native-language groups and suggests that emotion provides a basis for language specificity in bilingual memory
Training the Forgetting of Negative Material: The Role of Active Suppression and the Relation to Stress Reactivity
In this study, the authors investigated whether training participants to use cognitive strategies can aid forgetting in depression. Participants diagnosed with major depressive disorder (MDD) and never-depressed participants learned to associate neutral cue words with a positive or negative target word and were then instructed not to think about the negative targets when shown their cues. The authors compared 3 different conditions: an unaided condition, a positive-substitute condition, and a negative-substitute condition. In the substitute conditions, participants were instructed to use new targets to keep from thinking about the original targets. After the trainingphase, participants were instructed to recall all targets when presented with the cues. MDD participants, in contrast with control participants, did not exhibit forgetting of negative words in the unaided condition. In both the negative and positive substitute conditions, however, MDD participants showed successful forgetting of negative words and a clear practice effect. In contrast, negative substitute words did not aid forgetting by the control participants. These findings suggest that training depressed individuals to use cognitive strategies can increase forgetting of negative words
Hadrons in AdS/QCD models
We discuss applications of gauge/gravity duality to describe the spectrum of
light hadrons. We compare two particular 5-dimensional approaches: a model with
an infrared deformed Anti-de Sitter metric and another one based on a dynamical
AdS/QCD framework with back-reacted geometry in a dilaton/gravity background.
The models break softly the scale invariance in the infrared region and allow
mass gap for the field excitations in the gravity description, while keeping
the conformal property of the metric close to the four-dimensional boundary.
The models provide linear Regge trajectories for light mesons, associated with
specially designed infrared gravity properties. We also review the results for
the decay widths of the f0's into two pions, as overlap integrals between
mesonic string amplitudes, which are in qualitative agreement with data
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