118 research outputs found
Holographic model for dilepton production in p-p collisions
We propose a holographic model for dilepton production in proton-proton
collisions based on the exchange of vector mesons. The holographic hard wall
model is used to describe the dynamics and interactions of vector mesons and
baryons. We estimate the parameters lambda, mu, nu that characterize the
angular distribution of the produced dileptons in a region of q_T^2 << Q^2,
where perturbative QCD presents an effective strong coupling due to large
logarithm corrections.Comment: Revision: V4 In this version we modified the dimension of the
fermionic operator to match the canonical dimension of a baryonic operator.
This modification affected slightly our results with respect to v3. 25 pages,
3 Latex figures + 6 eps figures, 5 tables. To appear in Nucl. Phys.
Molecular characterization and phylogeny of Shiga toxin–producing Escherichia coli isolates obtained from two Dutch regions using whole genome sequencing
AbstractShiga toxin–producing Escherichia coli (STEC) is one of the major causes of human gastrointestinal disease and has been implicated in sporadic cases and outbreaks of diarrhoea, haemorrhagic colitis and haemolytic uremic syndrome worldwide. In this study, we determined the molecular characteristics and phylogenetic relationship of STEC isolates, and their genetic diversity was compared to that of other E. coli populations. Whole genome sequencing was performed on 132 clinical STEC isolates obtained from the faeces of 129 Dutch patients with gastrointestinal complaints. STEC isolates of this study belonged to 44 different sequence types (STs), 42 serogenotypes and 14 stx subtype combinations. Antibiotic resistance genes were more frequently present in stx1-positive isolates compared to stx2 and stx1 + stx2–positive isolates. The iha, mchB, mchC, mchF, subA, ireA, senB, saa and sigA genes were significantly more frequently present in eae-negative than in eae-positive STEC isolates. Presence of virulence genes encoding type III secretion proteins and adhesins was associated with isolates obtained from patients with bloody diarrhoea. Core genome phylogenetic analysis showed that isolates clustered according to their ST or serogenotypes irrespective of stx subtypes. Isolates obtained from patients with bloody diarrhoea were from diverse phylogenetic backgrounds. Some STEC isolates shared common ancestors with non-STEC isolates. Whole genome sequencing is a powerful tool for clinical microbiology, allowing high-resolution molecular typing, population structure analysis and detailed molecular characterization of strains. STEC isolates of a substantial genetic diversity and of distinct phylogenetic groups were observed in this study
The Position of High Frequency Waves with Respect to the Granulation Pattern
High frequency velocity oscillations were observed in the spectral lines Fe I
543.45nm and 543.29nm, using 2D spectroscopy with a Fabry- Perot and speckle
reconstruction, at the VTT in Tenerife. We investigate the radial component of
waves with frequencies in the range 8 - 22mHz in the internetwork, network and
a pore. We find that the occurrence of waves do not show any preference on
location and are equally distributed over down-flows and up-flows, regardless
of the activity of the observed area in the line of Fe I 543.45nm. The waves
observed in the lower formed line of Fe I 543.29nm seem to appear
preferentially over down-flows.Comment: Article has 12 pages and 7 images. It is accepted in Solar Physics
Journa
Pathologic features of prostate cancer found at population-based screening with a four-year interval
BACKGROUND: The currently recommended frequency for prostate-specific
antigen (PSA) screening tests for prostate cancer is 1 year, but the
optimal screening interval is not known. Our goal was to determine if a
longer interval would compromise the detection of curable prostate cancer.
METHODS: A cohort of 4491 men aged 55-75 years, all participants in the
Rotterdam section of the European Randomized Study of (population-based)
Screening for Prostate Cancer, were invited to participate in an initial
PSA screening. Men who received that screening were invited for a second
screen 4 years later. Pathology findings from needle biopsy cores were
compared for men in both rounds. Statistical tests were two-sided.
RESULTS: A total of 4133 men were screened in the first round (the
prevalence screen), and 2385 were screened in the second round. The median
amount of cancer in needle biopsy sets was 7.0 mm (95% confidence interval
[CI] = 5.4 mm to 8.6 mm) in the first round and 4.1 mm (95% CI = 2.6 mm to
5.6 mm) in the second round (P =.001). Thirty-six percent of the
adenocarcinomas detected in the first round but only 16% of those detected
in the second round had a Gleason score of 7 or higher (mean difference =
20% [95% CI = 10% to 30%]; P<.001). Whereas 25% of the adenocarcinomas
detected in the first round had adverse prognostic features, only 6% of
those detected in the second round did (mean difference = 19% [95% CI =
11% to 26%]; P<.001). Baseline PSA values were predictive for the amount
of tumor in biopsies in men with cancer in the first round but not for
that in the second round. CONCLUSION: Most large prostate cancers with
high serum PSA levels were effectively detected in a prevalence screen. In
this population, a screening interval of 4 years appears to be short
enough to constrain the development of large tumors, although it is
inconclusive whether this will result in a survival benefit
Accessing transversity with interference fragmentation functions
We discuss in detail the option to access the transversity distribution
function by utilizing the analyzing power of interference
fragmentation functions in two-pion production inside the same current jet. The
transverse polarization of the fragmenting quark is related to the transverse
component of the relative momentum of the hadron pair via a new azimuthal
angle. As a specific example, we spell out thoroughly the way to extract
from a measured single spin asymmetry in two-pion inclusive
lepton-nucleon scattering. To estimate the sizes of observable effects we
employ a spectator model for the fragmentation functions. The resulting
asymmetry of our example is discussed as arising in different scenarios for the
transversity.Comment: 17 pages, 15 figures in .eps format included, typesetted in RevTeX
and epsfig.sty, submitted to Phys. Rev.
Lectures on conformal field theory and Kac-Moody algebras
This is an introduction to the basic ideas and to a few further selected
topics in conformal quantum field theory and in the theory of Kac-Moody
algebras.Comment: 59 pages, LaTeX2e, extended version of lectures given at the Graduate
Course on Conformal Field Theory and Integrable Models (Budapest, August
1996), to appear in Springer Lecture Notes in Physic
The ^4He trimer as an Efimov system
We review the results obtained in the last four decades which demonstrate the
Efimov nature of the He three-atomic system.Comment: Review article for a special issue of the Few-Body Systems journal
devoted to Efimov physic
Toward an internally consistent astronomical distance scale
Accurate astronomical distance determination is crucial for all fields in
astrophysics, from Galactic to cosmological scales. Despite, or perhaps because
of, significant efforts to determine accurate distances, using a wide range of
methods, tracers, and techniques, an internally consistent astronomical
distance framework has not yet been established. We review current efforts to
homogenize the Local Group's distance framework, with particular emphasis on
the potential of RR Lyrae stars as distance indicators, and attempt to extend
this in an internally consistent manner to cosmological distances. Calibration
based on Type Ia supernovae and distance determinations based on gravitational
lensing represent particularly promising approaches. We provide a positive
outlook to improvements to the status quo expected from future surveys,
missions, and facilities. Astronomical distance determination has clearly
reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press
(chapter 8 of a special collection resulting from the May 2016 ISSI-BJ
workshop on Astronomical Distance Determination in the Space Age
Implementation and outcome of robotic liver surgery in the Netherlands: a nationwide analysis
Objective:To determine the nationwide implementation and surgical outcome of minor and major robotic liver surgery (RLS) and assess the first phase of implementation of RLS during the learning curve. Background:RLS may be a valuable alternative to laparoscopic liver surgery. Nationwide population-based studies with data on implementation and outcome of RLS are lacking. Methods:Multicenter retrospective cohort study including consecutive patients who underwent RLS for all indications in 9 Dutch centers (August 2014-March 2021). Data on all liver resections were obtained from the mandatory nationwide Dutch Hepato Biliary Audit (DHBA) including data from all 27 centers for liver surgery in the Netherlands. Outcomes were stratified for minor, technically major, and anatomically major RLS. Learning curve effect was assessed using cumulative sum analysis for blood loss. Results:Of 9437 liver resections, 400 were RLS (4.2%) procedures including 207 minor (52.2%), 141 technically major (35.3%), and 52 anatomically major (13%). The nationwide use of RLS increased from 0.2% in 2014 to 11.9% in 2020. The proportion of RLS among all minimally invasive liver resections increased from 2% to 28%. Median blood loss was 150 mL (interquartile range 50-350 mL] and the conversion rate 6.3% (n=25). The rate of Clavien-Dindo grade >= III complications was 7.0% (n=27), median length of hospital stay 4 days (interquartile range 2-5) and 30-day/in-hospital mortality 0.8% (n=3). The R0 resection rate was 83.2% (n=263). Cumulative sum analysis for blood loss found a learning curve of at least 33 major RLS procedures. Conclusions:The nationwide use of RLS in the Netherlands has increased rapidly with currently one-tenth of all liver resections and one-fourth of all minimally invasive liver resections being performed robotically. Although surgical outcomes of RLS in selected patient seem favorable, future prospective studies should determine its added value.Surgical oncolog
Strategies and performance of the CMS silicon tracker alignment during LHC Run 2
The strategies for and the performance of the CMS silicon tracking system alignment during the 2015–2018 data-taking period of the LHC are described. The alignment procedures during and after data taking are explained. Alignment scenarios are also derived for use in the simulation of the detector response. Systematic effects, related to intrinsic symmetries of the alignment task or to external constraints, are discussed and illustrated for different scenarios
- …