6,049 research outputs found
Ultrafast spatio-temporal dynamics of terahertz generation by ionizing two-color femtosecond pulses in gases
We present a combined theoretical and experimental study of spatio-temporal
propagation effects in terahertz (THz) generation in gases using two-color
ionizing laser pulses. The observed strong broadening of the THz spectra with
increasing gas pressure reveals the prominent role of spatio-temporal reshaping
and of a plasma-induced blue-shift of the pump pulses in the generation
process. Results obtained from (3+1)-dimensional simulations are in good
agreement with experimental findings and clarify the mechanisms responsible for
THz emission
Vortex ring refraction at large Froude numbers
We have experimentally studied the impact of an initially planar axisymmetric
vortex ring, incident at an oblique angle, upon a gravity-induced interface
separating two fluids of differing densities. After impact, the vortex ring was
found to exhibit a variety of subsequent trajectories, which we organize
according to both the incidence angle, , and the interface strength,
defined as the ratio of the Atwood and Froude numbers, . For grazing
incidence angles ( deg.) vortices either penetrate or
reflect from the interface, depending on whether the interface is weak or
strong. In some cases, reflected vortices execute damped oscillations before
finally disintegrating. For smaller incidence angles (
deg.) vortices penetrate the interface. When there is a strong interface, these
vortices are observed to curve back up toward the interface. When there is a
weak interface, these vortices are observed to refract downward, away from the
interface. The critical interface strength below which vortex ring refraction
is observed is given by .Comment: 26 pages, 11 figures; Submitted to Physical Review
Community as resource: crowdsourcing transcription of an historic newspaper.
Like many cultural heritage institutions, the Archives and Special Collections at the University of Louisville faces the dichotomy of material abundance and budgetary scarcity. Driven by the desire to make historical primary sources accessible online, this organization harnessed the power of the public to transcribe the Louisville Leader, an historic African American newspaper. The first sections of this article define crowdsourcing and describe how it was implemented at the University of Louisville, including the tools adopted and the process used. The latter sections outline the marketing strategy, the public response, and lessons learned from this ongoing project
Overcoming legacy processing in photographic collections through collaboration and digital technologies.
In the 1960s, a Louisville photography studio began donating its negatives, prints, and invoices to the University of Louisville Photographic Archives. The Caufield & Shook Collection remains a significant primary source for local history and a prime candidate for digitization. Unfortunately, on its receipt non-archivists processed the collection with little documentation of original order or organizational decision making. Additionally, workflow choices were determined largely by the desire to maximize student labor. In 2017, the Digital Initiatives Librarian worked with in-house application developers and archives staff to create a workflow that has significantly sped up the process of making this valuable photographic collection accessible online. This article describes how archivists recovered from the poor processing decisions, used technology to enhance the digitization workflow, and developed a list of best practices for future processing and digitization of large photographic collections
Pluto: A Monte Carlo Simulation Tool for Hadronic Physics
Pluto is a Monte-Carlo event generator designed for hadronic interactions
from Pion production threshold to intermediate energies of a few GeV per
nucleon, as well as for studies of heavy ion reactions. This report gives an
overview of the design of the package, the included models and the user
interface.Comment: XI International Workshop on Advanced Computing and Analysis
Techniques in Physics Research, April 23-27 2007, Amsterdam, the Netherland
Stellar Archaeology in the Galactic halo with the Ultra-Faint Dwarfs: VI. Ursa Major II
We present a B, V color-magnitude diagram (CMD) of the Milky Way dwarf
satellite Ursa Major II (UMa II), spanning the magnitude range from V ~ 15 to V
~ 23.5 mag and extending over a 18 {\times} 18 arcmin2 area centered on the
galaxy. Our photometry goes down to about 2 magnitudes below the galaxy's main
sequence turn-off, that we detected at V ~ 21.5 mag. We have discovered a
bona-fide RR Lyrae variable star in UMa II, which we use to estimate a
conservative dereddened distance modulus for the galaxy of (m-M)0 =
17.70{\pm}0.04{\pm}0.12 mag, where the first error accounts for the
uncertainties of the calibrated photometry, and the second reflects our lack of
information on the metallicity of the star. The corresponding distance to UMa
II is 34.7 {\pm} 0.6 ({\pm} 2.0) kpc. Our photometry shows evidence of a spread
in the galaxy subgiant branch, compatible with a spread in metal abundance in
the range between Z=0.0001 and Z=0.001. Based on our estimate of the distance,
a comparison of the fiducial lines of the Galactic globular clusters (GCs) M68
and M5 ([Fe/H]=-2.27 {\pm} 0.04 dex and -1.33 {\pm} 0.02 dex, respectively),
with the position on the CMD of spectroscopically confirmed galaxy members, may
suggest the existence of stellar populations of different metal abundance/age
in the central region of UMa II.Comment: To appear in Ap
The relationship between resting-state functional connectivity, antidepressant discontinuation and depression relapse
The risk of relapsing into depression after stopping antidepressants is high, but no established
predictors exist. Resting-state functional magnetic resonance imaging (rsfMRI) measures may help
predict relapse and identify the mechanisms by which relapses occur. rsfMRI data were acquired from
healthy controls and from patients with remitted major depressive disorder on antidepressants.
Patients were assessed a second time either before or after discontinuation of the antidepressant,
and followed up for six months to assess relapse. A seed-based functional connectivity analysis
was conducted focusing on the left subgenual anterior cingulate cortex and left posterior cingulate
cortex. Seeds in the amygdala and dorsolateral prefrontal cortex were explored. 44 healthy controls
(age: 33.8 (10.5), 73% female) and 84 patients (age: 34.23 (10.8), 80% female) were included in the
analysis. 29 patients went on to relapse and 38 remained well. The seed-based analysis showed
that discontinuation resulted in an increased functional connectivity between the right dorsolateral
prefrontal cortex and the parietal cortex in non-relapsers. In an exploratory analysis, this functional
connectivity predicted relapse risk with a balanced accuracy of 0.86. Further seed-based analyses,
however, failed to reveal diferences in functional connectivity between patients and controls,
between relapsers and non-relapsers before discontinuation and changes due to discontinuation
independent of relapse. In conclusion, changes in the connectivity between the dorsolateral prefrontal
cortex and the posterior default mode network were associated with and predictive of relapse after
open-label antidepressant discontinuation. This fnding requires replication in a larger dataset
The Clinical and Pathological Profile of BRCA1 Gene Methylated Breast Cancer Women. A Meta-Analysis
Background: DNA aberrant hypermethylation is the major cause of transcriptional silencing of the breast cancer gene 1 (BRCA1) gene in sporadic breast cancer patients. The aim of the present meta-analysis was to analyze all available studies reporting clinical characteristics of BRCA1 gene hypermethylated breast cancer in women, and to pool the results to provide a unique clinical profile of this cancer population. Methods: On September 2020, a systematic literature search was performed. Data were retrieved from PubMed, MEDLINE, and Scopus by searching the terms: “BRCA*” AND “methyl*” AND “breast”. All studies evaluating the association between BRCA1 methylation status and breast cancer patients’ clinicopathological features were considered for inclusion. Results: 465 studies were retrieved. Thirty (6.4%) studies including 3985 patients met all selection criteria. The pooled analysis data revealed a significant correlation between BRCA1 gene hypermethylation and advanced breast cancer disease stage (OR = 0.75: 95% CI: 0.58–0.97; p = 0.03, fixed effects model), lymph nodes involvement (OR = 1.22: 95% CI: 1.01–1.48; p = 0.04, fixed effects model), and pre-menopausal status (OR = 1.34: 95% CI: 1.08–1.66; p = 0.008, fixed effects model). No association could be found between BRCA1 hypermethylation and tumor histology (OR = 0.78: 95% CI: 0.59–1.03; p = 0.08, fixed effects model), tumor grading (OR = 0.78: 95% CI: 0.46–1.32; p = 0.36, fixed effects model), and breast cancer molecular classification (OR = 1.59: 95% CI: 0.68–3.72; p = 0.29, random effects model). Conclusions: hypermethylation of the BRCA1 gene significantly correlates with advanced breast cancer disease, lymph nodes involvement, and pre-menopausal cancer onset
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