9,199 research outputs found
Evaluation of floor vibrations induced by walking in reinforced concrete buildings
Floor vibrations induced by human walking were investigated in a reinforced concrete structure. Six experimental floor structures were built in laboratories with the same dimensions and boundary conditions. Subjective tests were performed to assess the vibration serviceability of the floor structures. First, the subjects were asked to walk across a floor and then to rate the intensity of the vibrations, acceptability, and serviceability of the floors. In the second part of the tests, the subjects were seated on a chair placed in the middle of the floor and asked to rate floor vibrations when the walker passed the subjects. Floor vibrations induced by human walking were analyzed using peak acceleration, root mean square (r.m.s.) acceleration, and the vibration dose value (VDV), and four weighting functions (Wb, Wk, Wg, and Wm) were applied. Significant differences in the measured floor vibration were found across the floor structures, larger floor vibration lead to greater perceived vibration intensity, lower acceptability and serviceability. The Wb and Wk were found to be more applicable than Wg and Wm to explain perception of floor vibration. It was observed that the impact noise induced by walking did not influence the evaluation of floor vibratio
Quantum and super-quantum group related to the Alexander-Conway polynomial
We describe the quasitriangular structure (universal -matrix) on the
non-standard quantum group associated to the
Alexander-Conway matrix solution of the Yang-Baxter equation. We show that this
Hopf algebra is connected with the super-Hopf algebra by a general
process of superization.Comment: 8 pages, LaTex file, Talk given at the XXVIII Karpacz Winter School,
Karpacz, Poland, February 199
Atrial fibrillation after gastrointestinal surgery: incidence and associated risk factors
BACKGROUND: Atrial fibrillation (AF) is a common dysrhythmia that can occur after major physiological stress including surgery (postoperative AF). There are few data on postoperative AF after abdominal surgery. We set out to define the incidence of de novo postoperative AF after abdominal surgery and associated risk factors. METHODS: The Patient History Integrated Data store administrative database was interrogated for patients aged ≥65 y undergoing abdominal surgery from April 2012 to April 2014. Patients with pre-existing AF were excluded. The primary outcome was diagnosis of AF. RESULTS: Two thousand nine hundred and sixty-seven cases were included of whom 187 developed postoperative AF within 90 d (6.3%). The rate of postoperative AF varied by operation and was highest in small bowel resection (17.2%) and lowest in biliary surgery (4.8%). Median time to detection of postoperative AF was 32 d. Patients who developed postoperative AF were significantly older than those who did not develop AF (median age 75.3 y versus 72.4 y, P < 0.01). Logistic regression modeling found increasing age (odds ratio [OR] 1.03 [confidence interval {CI} 1.01-1.06], hypertension OR 1.73 [CI 1.19-2.51]), congestive cardiac failure (OR 3.04 [CI 1.88-4.92], and vascular disease OR 2.29 [CI 1.39-3.37]) were predictive of the development of postoperative AF within 30 d. The area under the curve for this model was 0.733. CONCLUSIONS: Postoperative AF affects a significant number of patients after abdominal surgery. Demographics such as history of cardiovascular disease might aid prediction of postoperative AF. Postoperative AF is mostly identified after discharge, suggesting the need for postoperative screening
Anyonic Bogomol'nyi Solitons in a Gauged O(3) Sigma Model
We introduce the self-dual abelian gauged sigma models where the
Maxwell and Chern-Simons terms constitute the kinetic terms for the gauge
field. These models have quite rich structures and various limits. Our models
are found to exhibit both symmetric and broken phases of the gauge group. We
discuss the pure Chern-Simons limit in some detail and study rotationally
symmetric solitons.Comment: 14 pages, 6 Postscript figures uuencoded, written in REVTe
Wave propagation, reflection and transmission in non-uniform one-dimensional structural waveguides
Comments on discrete time in quantum mechanics
The possibility that time can be regarded as a discrete parameter is
re-examined. We study the dynamics of the free particle and find in some cases
superluminal propagation
Risk factors for ischaemic colitis after surgery for abdominal aortic aneurysm: a systematic review and observational meta-analysis
BACKGROUND: Ischaemic colitis is an infrequent but serious complication following repair of abdominal aortic aneurysm (AAA), with high mortality rates. This systematic review set out to identify risk factors for the development of ischaemic colitis after AAA surgery. METHODS: A systematic search of the MEDLINE, EMBASE and CINAHL databases was performed. This search was limited to studies published in the English language after 1990. Abstracts were screened by two authors. Eligible studies were obtained as full text for further examination. Data was extracted by two authors, and any disputes were resolved via consensus. Extracted data was pooled using Mantel-Haenszel random effects models. Bias was assessed using two Cochrane-approved tools. Effect sizes are expressed as relative risk ratios alongside the 95 % confidence interval. Statistical significance was defined at the level of p < 0.05. RESULTS: From 388 studies identified in the initial search, 33 articles were included in the final synthesis and analysis. Risk factors were grouped into patient (female gender, disease severity) and operative factors (peri-procedural hypotension, operative modality). The risk of ischaemic colitis was significantly higher when undergoing emergency repair versus elective (risk ratio (RR) 7.36, 3.08 to 17.58, p < 0.001). Endovascular repair reduced the likelihood of ischaemic colitis (RR 0.22, 0.12 to 0.39, p < 0.001). DISCUSSION: The quality of published evidence on this subject is poor with many retrospective datasets and inconsistent reporting across studies. Despite this, emergency presentation and open repair should prompt close monitoring for the development of IC
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