900 research outputs found
Luminescence quenching of the triplet excimer state by air traces in gaseous argon
While developing a liquid argon detector for dark matter searches we
investigate the influence of air contamination on the VUV scintillation yield
in gaseous argon at atmospheric pressure. We determine with a radioactive
alpha-source the photon yield for various partial air pressures and different
reflectors and wavelength shifters. We find for the fast scintillation
component a time constant tau1= 11.3 +- 2.8 ns, independent of gas purity.
However, the decay time of the slow component depends on gas purity and is a
good indicator for the total VUV light yield. This dependence is attributed to
impurities destroying the long-lived argon excimer states. The population ratio
between the slowly and the fast decaying excimer states is determined for
alpha-particles to be 5.5 +-0.6 in argon gas at 1100 mbar and room temperature.
The measured mean life of the slow component is tau2 = 3.140 +- 0.067 microsec
at a partial air pressure of 2 x 10-6 mbar.Comment: 7 pages submitted to NIM
Supersolid phase with cold polar molecules on a triangular lattice
We study a system of heteronuclear molecules on a triangular lattice and
analyze the potential of this system for the experimental realization of a
supersolid phase. The ground state phase diagram contains superfluid, solid and
supersolid phases. At finite temperatures and strong interactions there is an
additional emulsion region, in contrast to similar models with short-range
interactions. We derive the maximal critical temperature and the
corresponding entropy for supersolidity and find feasible
experimental conditions for its realization.Comment: 4 pages, 4 figure
Standard surgical treatment in pancreatic cancer
Pancreatic cancer is the third leading neoplasm of the gastrointestinal system and has a dismal prognosis. The majority of patients are no more suitable for resection at time of diagnosis due to early development of distant metastases or major infiltrations of adjacent structures. However, due to the resistance of pancreatic cancers against chemoradiation, curative resection represents the only therapy with a potential for cure. For the surgical treatment of pancreatic head cancer, the classical Whipple operation is still the standard procedure but during the last two decades, pylorus-preserving duodenopancreatectomy has been evolved as a more conservative procedure in order to omit the consequences of partial gastrectomy. For cancer of the pancreatic body and tail, distal pancreatectomy or total pancreatectomy represent the current standard treatment. More radical methods like regional pancreatectomy and resection with extended lymph node dissection have failed so far to demonstrate any improvements in long-term survival compared to the standard types of resection. To further improve the treatment of pancreatic cancer, prospectively randomised trials are needed to compare these extended surgical procedures with the standard types of resectio
The Impact of the Introduction of Total Mesorectal Excision on Local Recurrence Rate and Survival in Rectal Cancer: Long-Term Results
Purpose: To investigate the influence of the introduction of total mesorectal excision (TME) on local recurrence rate and survival in patients with rectal cancer. Methods: A total of 171 consecutive patients underwent anterior or abdominoperineal resection for primary rectal cancer. When the TME technique was introduced, the clinical setting, including the surgeons, remained the same. Group 1 (1993-95, n=53) underwent conventional surgery and group 2 (1995-2001, n=118) underwent TME. All patients were followed for 7years or until death. Results: Between the two groups, no statistically significant differences were present with regards to patient-, treatment-, or tumor-related characteristics apart from the time point of radiotherapy. The total local recurrence rates were 11 of 53 (20.8%) in group 1 and 7 of 118 (5.9%) in group 2, and the rates of isolated local recurrences were 6 of 53 (11.3%) in group 1 and 2 of 118 (1.7%) in group 2. Both differences were highly statistically significant. The disease-free survival in groups 1 and 2 was 60.4 and 65.3% at 5years, and 58.5 and 65.3% at 7years, respectively. Excluding patients with synchronous or metachronous distant metastasis from the analysis, both the disease-free survival and the cancer-specific survival were statistically significantly better in group 2 than in group 1. No statistically significant difference between the two groups was detected regarding the overall survival. Conclusions: The introduction of TME led to an impressive reduction of the local recurrence rate. Survival is mainly determined by the occurrence of distant metastasis, but TME seems to improve survival in patients without systemic diseas
Direct and indirect costs in the conservative management of undisplaced scaphoid fractures
The scaphoid is the most commonly fractured carpal bone, and preferable treatment of undisplaced fractures is controversial. In order to assess the socio-economic impact of treatment modalities, we analysed the cost of conservative management of 54 undisplaced scaphoid fractures. Global costs amounted to 14.077 Swiss francs (9385 euros) per patient. Direct costs represent only 10% of global costs. No significant correlation was found between costs and timing of diagnosis, hand dominance or complications. Thirty-four percent of patients were able to resume their job with the wrist immobilised without complication, but at an obvious impact on indirect and global costs. If early resumption of professional activities during conservative treatment of undisplaced scaphoid fractures does not impair successful fracture healing, patients should be encouraged to return to work as early as possible, as is routinely done after percutaneous fracture fixation. This will contribute to massively reducing the cost of conservative treatmen
Memory-augmented Dense Predictive Coding for Video Representation Learning
The objective of this paper is self-supervised learning from video, in
particular for representations for action recognition. We make the following
contributions: (i) We propose a new architecture and learning framework
Memory-augmented Dense Predictive Coding (MemDPC) for the task. It is trained
with a predictive attention mechanism over the set of compressed memories, such
that any future states can always be constructed by a convex combination of the
condense representations, allowing to make multiple hypotheses efficiently.
(ii) We investigate visual-only self-supervised video representation learning
from RGB frames, or from unsupervised optical flow, or both. (iii) We
thoroughly evaluate the quality of learnt representation on four different
downstream tasks: action recognition, video retrieval, learning with scarce
annotations, and unintentional action classification. In all cases, we
demonstrate state-of-the-art or comparable performance over other approaches
with orders of magnitude fewer training data.Comment: ECCV2020, Spotligh
Vortex Lattice Locking in Rotating Two-Component Bose-Einstein Condensates
The vortex density of a rotating superfluid, divided by its particle mass,
dictates the superfluid's angular velocity through the Feynman relation. To
find how the Feynman relation applies to superfluid mixtures, we investigate a
rotating two-component Bose-Einstein condensate, composed of bosons with
different masses. We find that in the case of sufficiently strong interspecies
attraction, the vortex lattices of the two condensates lock and rotate at the
drive frequency, while the superfluids themselves rotate at two different
velocities, whose ratio is the ratio between the particle mass of the two
species. In this paper, we characterize the vortex-locked state, establish its
regime of stability, and find that it surives within a disk smaller than a
critical radius, beyond which vortices become unbound, and the two Bose-gas
rings rotate together at the frequency of the external drive.Comment: 6 pages, 2 figure
Broad-Range 16S rRNA Gene Polymerase Chain Reaction for Diagnosis of Culture-Negative Bacterial Infections
This study defines the role of 16S ribosomal RNA (rRNA) gene polymerase chain reaction (PCR) for diagnosis of culture-negative bacterial infections. Our data show that 16S rRNA PCR is particularly valuable for identification of pathogens in patients pretreated with antibiotic
Pseudoscalar meson photoproduction: from known to undiscovered resonances
The role of dynamics in spin observables for pseudoscalar meson
photoproduction is investigated using a density matrix approach in a multipole
truncated framework. Extraction of novel rules for and reactions based on resonance dominance, and on
other broad and reasonable dynamical assumptions, are discussed. Observables
that are particularly sensitive to missing nucleonic resonances predicted by
quark-based approaches, are singled out.Comment: 22 pages, latex, 3 figure
Finite temperature quantum simulation of stabilizer Hamiltonians
We present a scheme for robust finite temperature quantum simulation of
stabilizer Hamiltonians. The scheme is designed for realization in a physical
system consisting of a finite set of neutral atoms trapped in an addressable
optical lattice that are controllable via 1- and 2-body operations together
with dissipative 1-body operations such as optical pumping. We show that these
minimal physical constraints suffice for design of a quantum simulation scheme
for any stabilizer Hamiltonian at either finite or zero temperature. We
demonstrate the approach with application to the abelian and non-abelian toric
codes.Comment: 13 pages, 2 figure
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