22 research outputs found
Chemotaxis When Bacteria Remember: Drift versus Diffusion
{\sl Escherichia coli} ({\sl E. coli}) bacteria govern their trajectories by
switching between running and tumbling modes as a function of the nutrient
concentration they experienced in the past. At short time one observes a drift
of the bacterial population, while at long time one observes accumulation in
high-nutrient regions. Recent work has viewed chemotaxis as a compromise
between drift toward favorable regions and accumulation in favorable regions. A
number of earlier studies assume that a bacterium resets its memory at tumbles
-- a fact not borne out by experiment -- and make use of approximate
coarse-grained descriptions. Here, we revisit the problem of chemotaxis without
resorting to any memory resets. We find that when bacteria respond to the
environment in a non-adaptive manner, chemotaxis is generally dominated by
diffusion, whereas when bacteria respond in an adaptive manner, chemotaxis is
dominated by a bias in the motion. In the adaptive case, favorable drift occurs
together with favorable accumulation. We derive our results from detailed
simulations and a variety of analytical arguments. In particular, we introduce
a new coarse-grained description of chemotaxis as biased diffusion, and we
discuss the way it departs from older coarse-grained descriptions.Comment: Revised version, journal reference adde
2011 ASA/ACCF/AHA/AANN/AANS/ACR/ASNR/CNS/SAIP/SCAI/SIR/SNIS/SVM/SVS Guideline on the Management of Patients With Extracranial Carotid and Vertebral Artery Disease: Executive Summary A Report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines, and the American Stroke Association, American Association of Neuroscience Nurses, American Association of Neurological Surgeons, American College of Radiology, American Society of Neuroradiology, Congress of Neurological Surgeons, Society of Atherosclerosis Imaging and Prevention, Society for Cardiovascular Angiography and Interventions, Society of Interventional Radiology, Society of NeuroInterventional Surgery, Society for Vascular Medicine, and Society for Vascular Surgery Developed in Collaboration With the American Academy of Neurology and Society of Cardiovascular Computed Tomography
Evidence for perinatal and child health care guidelines in crisis settings: can Cochrane help?
<p>Abstract</p> <p>Background</p> <p>It is important that healthcare provided in crisis settings is based on the best available research evidence. We reviewed guidelines for child and perinatal health care in crisis situations to determine whether they were based on research evidence, whether Cochrane systematic reviews were available in the clinical areas addressed by these guidelines and whether summaries of these reviews were provided in Evidence Aid.</p> <p>Methods</p> <p>Broad internet searches were undertaken to identify relevant guidelines. Guidelines were appraised using AGREE and the clinical areas that were relevant to perinatal or child health were extracted. We searched The Cochrane Database of Systematic Reviews to identify potentially relevant reviews. For each review we determined how many trials were included, and how many were conducted in resource-limited settings.</p> <p>Results</p> <p>Six guidelines met selection criteria. None of the included guidelines were clearly based on research evidence. 198 Cochrane reviews were potentially relevant to the guidelines. These reviews predominantly addressed nutrient supplementation, breastfeeding, malaria, maternal hypertension, premature labour and prevention of HIV transmission. Most reviews included studies from developing settings. However for large portions of the guidelines, particularly health services delivery, there were no relevant reviews. Only 18 (9.1%) reviews have summaries in Evidence Aid.</p> <p>Conclusions</p> <p>We did not identify any evidence-based guidelines for perinatal and child health care in disaster settings. We found many Cochrane reviews that could contribute to the evidence-base supporting future guidelines. However there are important issues to be addressed in terms of the relevance of the available reviews and increasing the number of reviews addressing health care delivery.</p
Strong Interaction Physics at the Luminosity Frontier with 22 GeV Electrons at Jefferson Lab
This document presents the initial scientific case for upgrading the
Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab)
to 22 GeV. It is the result of a community effort, incorporating insights from
a series of workshops conducted between March 2022 and April 2023. With a track
record of over 25 years in delivering the world's most intense and precise
multi-GeV electron beams, CEBAF's potential for a higher energy upgrade
presents a unique opportunity for an innovative nuclear physics program, which
seamlessly integrates a rich historical background with a promising future. The
proposed physics program encompass a diverse range of investigations centered
around the nonperturbative dynamics inherent in hadron structure and the
exploration of strongly interacting systems. It builds upon the exceptional
capabilities of CEBAF in high-luminosity operations, the availability of
existing or planned Hall equipment, and recent advancements in accelerator
technology. The proposed program cover various scientific topics, including
Hadron Spectroscopy, Partonic Structure and Spin, Hadronization and Transverse
Momentum, Spatial Structure, Mechanical Properties, Form Factors and Emergent
Hadron Mass, Hadron-Quark Transition, and Nuclear Dynamics at Extreme
Conditions, as well as QCD Confinement and Fundamental Symmetries. Each topic
highlights the key measurements achievable at a 22 GeV CEBAF accelerator.
Furthermore, this document outlines the significant physics outcomes and unique
aspects of these programs that distinguish them from other existing or planned
facilities. In summary, this document provides an exciting rationale for the
energy upgrade of CEBAF to 22 GeV, outlining the transformative scientific
potential that lies within reach, and the remarkable opportunities it offers
for advancing our understanding of hadron physics and related fundamental
phenomena.Comment: Updates to the list of authors; Preprint number changed from theory
to experiment; Updates to sections 4 and 6, including additional figure
Prognostic model to predict postoperative acute kidney injury in patients undergoing major gastrointestinal surgery based on a national prospective observational cohort study.
Background: Acute illness, existing co-morbidities and surgical stress response can all contribute to postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery. The aim of this study was prospectively to develop a pragmatic prognostic model to stratify patients according to risk of developing AKI after major gastrointestinal surgery. Methods: This prospective multicentre cohort study included consecutive adults undergoing elective or emergency gastrointestinal resection, liver resection or stoma reversal in 2-week blocks over a continuous 3-month period. The primary outcome was the rate of AKI within 7 days of surgery. Bootstrap stability was used to select clinically plausible risk factors into the model. Internal model validation was carried out by bootstrap validation. Results: A total of 4544 patients were included across 173 centres in the UK and Ireland. The overall rate of AKI was 14·2 per cent (646 of 4544) and the 30-day mortality rate was 1·8 per cent (84 of 4544). Stage 1 AKI was significantly associated with 30-day mortality (unadjusted odds ratio 7·61, 95 per cent c.i. 4·49 to 12·90; P < 0·001), with increasing odds of death with each AKI stage. Six variables were selected for inclusion in the prognostic model: age, sex, ASA grade, preoperative estimated glomerular filtration rate, planned open surgery and preoperative use of either an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. Internal validation demonstrated good model discrimination (c-statistic 0·65). Discussion: Following major gastrointestinal surgery, AKI occurred in one in seven patients. This preoperative prognostic model identified patients at high risk of postoperative AKI. Validation in an independent data set is required to ensure generalizability
Safety and efficacy of a novel device for treatment of thrombotic and atherosclerotic lesions in native coronary arteries and saphenous vein grafts: results from the multicenter X-Sizer for treatment of thrombus and atherosclerosis in coronary applications trial (X-TRACT) study.
Intervention in thrombotic lesions and diseased saphenous vein grafts frequently results in thromboembolic complications, including no-reflow, distal branch occlusion, periprocedural MI, and death. The utility of a novel thromboatherectomy device, the X-Sizer, was tested in 50 consecutive patients at nine U.S. centers. A total of 61 lesions were treated in 31 vein grafts and 19 native coronary arteries; thrombus was present in 78% of lesions, and TIMI 0-1 flow in 21%. TIMI 3 flow improved from 57% at baseline to 94% postprocedure. No patient developed visible distal thromboemboli, side-branch occlusion, or reduced antegrade flow. Thirty-day events included one death (2.0%), Q- or non-Q-wave MI in 4.0%, TVR in 6.0%, and any MACE in 6.0%. We conclude that the use of the X-Sizer prior to percutaneous intervention is safe in high-risk vein grafts and thrombotic lesions and results in a low rate of adverse events compared to historical controls