625 research outputs found
Controlling the quantum number distribution and yield of Rydberg states via the duration of the laser pulse
We show that the distribution of quantum numbers of Rydberg states does not
only depend on the field strength and wavelength of the laser which the atom is
exposed to, but that it also changes significantly with the duration of the
laser pulse. We provide an intuitive explanation for the underlying mechanism
and derive a scaling law for the position of the peak in the quantum number
distribution on the pulse duration. The new analytic description for the
electron's movement in the superposed laser and Coulomb field (applied in the
study of quantum numbers) is then used to explain the decrease of the Rydberg
yield with longer pulse durations. This description stands in contrast to the
concepts that explained the decrease so far and also reveals that
approximations which neglect Coulomb effects during propagation are not
sufficient in cases such as this.Comment: 8 pages, 8 figure
Magnetoresistance in Disordered Graphene: The Role of Pseudospin and Dimensionality Effects Unraveled
We report a theoretical low-field magnetotransport study unveiling the effect
of pseudospin in realistic models of weakly disordered graphene-based
materials. Using an efficient Kubo computational method, and simulating the
effect of charges trapped in the oxide, different magnetoconductance
fingerprints are numerically obtained in system sizes as large as 0.3
micronmeter squared, containing tens of millions of carbon atoms. In
two-dimensional graphene, a strong valley mixing is found to irreparably yield
a positive magnetoconductance (weak localization), whereas crossovers from
positive to a negative magnetoconductance (weak antilocalization) are obtained
by reducing disorder strength down to the ballistic limit. In sharp contrast,
graphene nanoribbons with lateral size as large as 10nm show no sign of weak
antilocalization, even for very small disorder strength. Our results
rationalize the emergence of a complex phase diagram of magnetoconductance
fingerprints, shedding some new light on the microscopical origin of pseudospin
effects.Comment: 8 pages, 5 figure
Instantaneous ionization rate as a functional derivative
We describe an approach defining instantaneous ionization rate (IIR) as a
functional derivative of the total ionization probability. The definition is
based on physical quantities which are directly measurable, such as the total
ionization probability and the waveform of the pulse. The definition is,
therefore, unambiguous and does not suffer from gauge non-invariance. We
compute IIR by solving numerically the time-dependent Schrodinger equation for
the hydrogen atom in a strong laser field. We find that the IIR lags behind the
electric field, but this lag is entirely due to the long tail effect of the
Coulomb field. In agreement with the previous results using attoclock
methodology, therefore, the IIR we define does not show measurable delay in
strong field tunnel ionization
Long-term course and outcome of obsessive-compulsive patientsafter cognitive-behavioral therapy in combination with eitherfluvoxamine or placebo: A 7-year follow-up of a randomized double-blind trial
Longitudinal studies with very long follow-up periods of patients with obsessive-compulsive disorder (OCD) who have received adequate treatment are rare. In the current study, 30 of 37 inpatients (81%) with severe OCD were followed up 6-8 years after treatment with cognitive-behavioral therapy (CBT) in combination with either fluvoxamine or placebo in a randomized design. The significant improvements (with large effectsizes) in obsessive-compulsive symptoms from pre- to post-treatment (41% reduction on the Y-BOCS) remained stable at follow-up (45 %). Responder rates, defined as ≥35% reduction on the Y-BOCS, were 67% and 60%, respectively. Depressive symptoms decreased significantly not only from pre- to post-treatment but also during follow-up. Re-hospitalization, which occurred in 11 patients (37 %), was associated with more severe depressive symptoms at pre-treatment and living without a partner. Full symptom remission at follow-up, defined as both Y-BOCS total score ≤ 7 and no longer meeting diagnostic criteria for OCD, was achieved by 8 patients (27 %). Patients without full remission at follow-up had a significantly longer history of OCD, assessed at pretreatment, compared to remitted patients. The shortterm treatment outcome had no predictive value for the long-term course. Throughout the naturalistic follow-up, nearly all patients (29 patients) received additional psychotherapy and/or medication. This might indicate that such chronic OCD patients usually need additional therapeutic support after effective inpatient treatment to maintain their improvements over long period
European Society of Gastrointestinal Endoscopy, European Society of Gastroenterology and Endoscopy Nurses and Associates, and the European Society of Anaesthesiology Guideline: Non-anesthesiologist administration of propofol for GI endoscopy
Biology and conservation of freshwater bivalves : past, present and future perspectives
Freshwater bivalves have been highly
threatened by human activities, and recently their
global decline has been causing conservational and
social concern. In this paper, we review the most
important research events in freshwater bivalve biology
calling attention to the main scientific achievements.
A great bias exists in the research effort, with
much more information available for bivalve species
belonging to the Unionida in comparison to other
groups. The same is true for the origin of these studies,
since the publishing pattern does not always correspond
to the hotspots of biodiversity but is concentrated in the northern hemisphere mainly in
North America, Europe and Russia, with regions such
as Africa and Southeast Asia being quite understudied.
We also summarize information about past, present
and future perspectives concerning the most important
research topics that include taxonomy, systematics,
anatomy, physiology, ecology and conservation of
freshwater bivalves. Finally, we introduce the articles
published in this Hydrobiologia special issue related
with the International Meeting on Biology and Conservation
of Freshwater Bivalves held in 2012 in
Braganc¸a, Portugal.We would like to express our gratitude to our sponsors and institutions, especially to the Polytechnic Institute of Braganca for all the logistic support. We acknowledge all keynote speakers, authors, session chairpersons and especially to all attendees whose contributions were fundamental for the success of this meeting. We would also like to thank all referees of this special issue and to Koen Martens, Editor-in-Chief of Hydrobiologia, for all the valuable comments and suggestions. The chronogram was built with the help of the expert opinion of fellow colleagues Rafael Araujo, Arthur Bogan, Kevin Cummings, Dan Graf, Wendell Haag, Karl-Otto Nagel and David Strayer to whom we are very grateful. The authors acknowledge the support provided by Portuguese Foundation for Science and Technology (FCT) and COMPETE funds-projects CONBI (Contract: PTDC/AAC-AMB/117688/2010) and ECO-IAS (Contract: PTDC/AAC-AMB/116685/2010), and by the European Regional Development Fund (ERDF) through the COMPETE, under the project "PEst-C/MAR/LA0015/2011"
First results from the CRESST-III low-mass dark matter program
The CRESST experiment is a direct dark matter search which aims to measure
interactions of potential dark matter particles in an earth-bound detector.
With the current stage, CRESST-III, we focus on a low energy threshold for
increased sensitivity towards light dark matter particles. In this manuscript
we describe the analysis of one detector operated in the first run of
CRESST-III (05/2016-02/2018) achieving a nuclear recoil threshold of 30.1eV.
This result was obtained with a 23.6g CaWO crystal operated as a cryogenic
scintillating calorimeter in the CRESST setup at the Laboratori Nazionali del
Gran Sasso (LNGS). Both the primary phonon/heat signal and the simultaneously
emitted scintillation light, which is absorbed in a separate
silicon-on-sapphire light absorber, are measured with highly sensitive
transition edge sensors operated at ~15mK. The unique combination of these
sensors with the light element oxygen present in our target yields sensitivity
to dark matter particle masses as low as 160MeV/c.Comment: 9 pages, 9 figure
Long-Term Follow-Up of the Intergroup Exemestane Study
Purpose: The Intergroup Exemestane Study, an investigator-led study of 4,724 postmenopausal patients with early breast cancer (clinical trial information: ISRCTN11883920), has previously demonstrated that a switch from adjuvant endocrine therapy after 2 to 3 years of tamoxifen to exemestane was associated with clinically relevant improvements in efficacy. Here, we report the final efficacy analyses of this cohort. Patients and Methods: Patients who remained disease free after 2 to 3 years of adjuvant tamoxifen were randomly assigned to continue tamoxifen or switch to exemestane to complete a total of 5 years of adjuvant endocrine therapy. Given the large number of non–breast cancer–related deaths now reported, breast cancer–free survival (BCFS), with censorship of intercurrent deaths, was the primary survival end point of interest. Analyses focus on patients with estrogen receptor-positive or unknown tumors (n = 4,599). Results: At the time of the data snapshot, median follow-up was 120 months. In the population that was estrogen receptor positive or had unknown estrogen receptor status, 1,111 BCFS events were observed with 508 (22.1%) of 2,294 patients in the exemestane group and 603 (26.2%) of 2,305 patients in the tamoxifen group. The data corresponded to an absolute difference (between exemestane and tamoxifen) at 10 years of 4.0% (95% CI, 1.2% to 6.7%), and the hazard ratio (HR) of 0.81 (95% CI, 0.72 to 0.92) favored exemestane. This difference remained in multivariable analysis that was adjusted for nodal status, prior use of hormone replacement therapy, and prior chemotherapy (HR, 0.80; 95% CI, 0.71 to 0.90; P < .001). A modest improvement in overall survival was seen with exemestane; the absolute difference (between exemestane and tamoxifen) at 10 years in the population that was estrogen receptor positive or had unknown estrogen receptor status was 2.1% (95% CI, −0.5% to 4.6%), and the HR was 0.89 (95% CI, 0.78 to 1.01; P = .08). For the intention-to-treat population, the absolute difference was 1.6% (95% CI, −0.9% to 4.1%); the HR was 0.91 (95% CI, 0.80 to 1.03, P = .15). No statistically significant difference was observed in the proportion of patients who reported a fracture event in the post-treatment period. Conclusion: The Intergroup Exemestane Study and contemporaneous studies have established that a strategy of switching to an aromatase inhibitor after 2 to 3 years of tamoxifen can lead to sustained benefits in terms of reduction of disease recurrence and breast cancer mortality
Graphite and Hexagonal Boron-Nitride Possess the Same Interlayer Distance. Why?
Graphite and hexagonal boron nitride (h-BN) are two prominent members of the
family of layered materials possessing a hexagonal lattice. While graphite has
non-polar homo-nuclear C-C intra-layer bonds, h-BN presents highly polar B-N
bonds resulting in different optimal stacking modes of the two materials in
bulk form. Furthermore, the static polarizabilities of the constituent atoms
considerably differ from each other suggesting large differences in the
dispersive component of the interlayer bonding. Despite these major differences
both materials present practically identical interlayer distances. To
understand this finding, a comparative study of the nature of the interlayer
bonding in both materials is presented. A full lattice sum of the interactions
between the partially charged atomic centers in h-BN results in vanishingly
small monopolar electrostatic contributions to the interlayer binding energy.
Higher order electrostatic multipoles, exchange, and short-range correlation
contributions are found to be very similar in both materials and to almost
completely cancel out by the Pauli repulsions at physically relevant interlayer
distances resulting in a marginal effective contribution to the interlayer
binding. Further analysis of the dispersive energy term reveals that despite
the large differences in the individual atomic polarizabilities the
hetero-atomic B-N C6 coefficient is very similar to the homo-atomic C-C
coefficient in the hexagonal bulk form resulting in very similar dispersive
contribution to the interlayer binding. The overall binding energy curves of
both materials are thus very similar predicting practically the same interlayer
distance and very similar binding energies.Comment: 18 pages, 5 figures, 2 table
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