4,790 research outputs found
Lifetimes of ultralong-range strontium Rydberg molecules in a dense BEC
The lifetimes and decay channels of ultralong-range Rydberg molecules created
in a dense BEC are examined by monitoring the time evolution of the Rydberg
population using field ionization. Studies of molecules with values of
principal quantum number, , in the range to that contain tens
to hundreds of ground state atoms within the Rydberg electron orbit show that
their presence leads to marked changes in the field ionization characteristics.
The Rydberg molecules have lifetimes of s, their destruction
being attributed to two main processes: formation of Sr ions through
associative ionization, and dissociation induced through -changing
collisions. The observed loss rates are consistent with a reaction model that
emphasizes the interaction between the Rydberg core ion and its nearest
neighbor ground-state atom. The measured lifetimes place strict limits on the
time scales over which studies involving Rydberg species in cold, dense atomic
gases can be undertaken and limit the coherence times for such measurements.Comment: 9 pages, 8 figure
Access for Laparoendoscopic Single Site Surgery
Laparoscopic surgery is the standard of care for many abdominal and pelvic operations and is widely applied today. LESS (Laparo-Endoscopic Single Site) surgery, originally attempted in the 1990s, is an advanced minimally invasive approach that allows laparoscopic operations to be undertaken through a small (<15âmm) incision in the umbilicus, a preexisting scar. The presence of a preexisting scar allows LESS surgery to be essentially scarless, which is the key benefit to LESS operations. Herein, we review our experience with over 500 LESS operations and discuss the key techniques to establishing access to the peritoneal cavity. We review the options for obtaining access, available instrumentation, common challenges and solutions for access. We conclude that LESS surgery is safe and provides outcomes with superior cosmesis relative to conventional laparoscopy. LESS surgery should be embraced, as patient demand is rapidly increasing
Probing Nonlocal Spatial Correlations in Quantum Gases with Ultra-long-range Rydberg Molecules
We present photo-excitation of ultra-long-range Rydberg molecules as a probe
of spatial correlations in quantum gases. Rydberg molecules can be created with
well-defined internuclear spacing, set by the radius of the outer lobe of the
Rydberg electron wavefunction . By varying the principal quantum number
of the target Rydberg state, the molecular excitation rate can be used to
map the pair-correlation function of the trapped gas . We
demonstrate this with ultracold Sr gases and probe pair-separation length
scales ranging from , which are on the order of the
thermal de Broglie wavelength for temperatures around 1 K. We observe
bunching for a single-component Bose gas of Sr and anti-bunching due to
Pauli exclusion at short distances for a polarized Fermi gas of Sr,
revealing the effects of quantum statistics.Comment: 6 pages, 5 figure
Theory of excitation of Rydberg polarons in an atomic quantum gas
We present a quantum many-body description of the excitation spectrum of
Rydberg polarons in a Bose gas. The many-body Hamiltonian is solved with
functional determinant theory, and we extend this technique to describe Rydberg
polarons of finite mass. Mean-field and classical descriptions of the spectrum
are derived as approximations of the many-body theory. The various approaches
are applied to experimental observations of polarons created by excitation of
Rydberg atoms in a strontium Bose-Einstein condensate.Comment: 14 pages, 9 figures. arXiv admin note: substantial text overlap with
arXiv:1706.0371
Creation of Rydberg Polarons in a Bose Gas
We report spectroscopic observation of Rydberg polarons in an atomic Bose
gas. Polarons are created by excitation of Rydberg atoms as impurities in a
strontium Bose-Einstein condensate. They are distinguished from previously
studied polarons by macroscopic occupation of bound molecular states that arise
from scattering of the weakly bound Rydberg electron from ground-state atoms.
The absence of a -wave resonance in the low-energy electron-atom scattering
in Sr introduces a universal behavior in the Rydberg spectral lineshape and in
scaling of the spectral width (narrowing) with the Rydberg principal quantum
number, . Spectral features are described with a functional determinant
approach (FDA) that solves an extended Fr\"{o}hlich Hamiltonian for a mobile
impurity in a Bose gas. Excited states of polyatomic Rydberg molecules
(trimers, tetrameters, and pentamers) are experimentally resolved and
accurately reproduced with FDA.Comment: 5 pages, 3 figure
Synthesising interprocedural bit-precise termination proofs
Proving program termination is key to guaranteeing absence of undesirable behaviour, such as hanging programs and even security vulnerabilities such as denial-of-service attacks. To make termination checks scale to large systems, interprocedural termination analysis seems essential, which is a largely unexplored area of research in termination analysis, where most effort has focussed on difficult single-procedure problems. We present a modular termination analysis for C programs using template-based interprocedural summarisation. Our analysis combines a context-sensitive, over-approximating forward analysis with the inference of under-approximating preconditions for termination. Bit-precise termination arguments are synthesised over lexicographic linear ranking function templates. Our experimental results show that our tool 2LS outperforms state-of-the-art alternatives, and demonstrate the clear advantage of interprocedural reasoning over monolithic analysis in terms of efficiency, while retaining comparable precision
Determination of circulating Mycobacterium tuberculosis strains and transmission patterns among pulmonary TB patients in Kawempe municipality, Uganda, using MIRU-VNTR
<p>Abstract</p> <p>Background</p> <p>Mycobacterial interspersed repetitive units - variable number of tandem repeats (MIRU-VNTR) genotyping is a powerful tool for unraveling clonally complex <it>Mycobacterium tuberculosis </it>(MTB) strains and detection of transmission patterns. Using MIRU-VNTR, MTB genotypes and their transmission patterns among patients with new and active pulmonary tuberculosis (PTB) in Kawempe municipality in Kampala, Uganda was determined.</p> <p>Results</p> <p>MIRU-VNTR genotyping was performed by PCR-amplification of 15 MTB-MIRU loci from 113 cultured specimens from 113 PTB patients (one culture sample per patient). To determine lineages, the genotypes were entered into the MIRU-VNTR<it>plus </it>database [<url>http://www.miru-vntrplus.org/</url>] as numerical codes corresponding to the number of alleles at each locus. Ten different lineages were obtained: Uganda II (40% of specimens), Uganda I (14%), LAM (6%), Delhi/CAS (3%), Haarlem (3%), Beijing (3%), Cameroon (3%), EAI (2%), TUR (2%) and S (1%). Uganda I and Uganda II were the most predominant genotypes. Genotypes for 29 isolates (26%) did not match any strain in the database and were considered unique. There was high diversity of MIRU-VNTR genotypes, with a total of 94 distinct patterns. Thirty four isolates grouped into 15 distinct clusters each with two to four isolates. Eight households had similar MTB strains for both index and contact cases, indicating possible transmission.</p> <p>Conclusion</p> <p>MIRU-VNTR genotyping revealed high MTB strain diversity with low clustering in Kawempe municipality. The technique has a high discriminatory power for genotyping MTB strains in Uganda.</p
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