Detecting and decomposing self-overlapping curves

AbstractA curve is self-overlapping if it can be divided by nontrivial line segments into simple curves. We show how to test whether a given curve is self-overlapping, and also how to construct sets of line segments that demonstrate that the curve is self-overlapping. We also describe several interesting topological properties of self-overlapping curves

A Queueing Analysis of Hashing With Lazy Deletion

Hashing with lazy deletion is a simple method for maintaining a dynamic dictionary: items are inserted and sought as usual in a separate-chaining hash table; however, items that no longer need to be in the data structure remain until a later insertion operation stumbles on them and removes them from the table. Because hashing with lazy deletion does not delete items as soon as possible, it keeps more items in the dictionary than methods that use more careful deletion strategies. On the other hand, its space overhead is much smaller than those more careful methods, so if the number of extra items is not too large, hashing with lazy deletion can be a practical algorithm when space is scarce. In this paper, we analyze the expected amount of excess space used by hashing with lazy deletion

Effectiveness of EDACS Versus ADAPT Accelerated Diagnostic Pathways for Chest Pain: A Pragmatic Randomized Controlled Trial Embedded Within Practice

Study objective A 2-hour accelerated diagnostic pathway based on the Thrombolysis in Myocardial Infarction score, ECG, and troponin measures (ADAPT-ADP) increased early discharge of patients with suspected acute myocardial infarction presenting to the emergency department compared with standard care (from 11% to 19.3%). Observational studies suggest that an accelerated diagnostic pathway using the Emergency Department Assessment of Chest Pain Score (EDACS-ADP) may further increase this proportion. This trial tests for the existence and size of any beneficial effect of using the EDACS-ADP in routine clinical care. Methods This was a pragmatic randomized controlled trial of adults with suspected acute myocardial infarction, comparing the ADAPT-ADP and the EDACS-ADP. The primary outcome was the proportion of patients discharged to outpatient care within 6 hours of attendance, without subsequent major adverse cardiac event within 30 days. Results Five hundred fifty-eight patients were recruited, 279 in each arm. Sixty-six patients (11.8%) had a major adverse cardiac event within 30 days (ADAPT-ADP 29; EDACS-ADP 37); 11.1% more patients (95% confidence interval 2.8% to 19.4%) were identified as low risk in EDACS-ADP (41.6%) than in ADAPT-ADP (30.5%). No low-risk patients had a major adverse cardiac event within 30 days (0.0% [0.0% to 1.9%]). There was no difference in the primary outcome of proportion discharged within 6 hours (EDACS-ADP 32.3%; ADAPT-ADP 34.4%; difference −2.1% [−10.3% to 6.0%], P=.65). Conclusion There was no difference in the proportion of patients discharged early despite more patients being classified as low risk by the EDACS-ADP than the ADAPT-ADP. Both accelerated diagnostic pathways are effective strategies for chest pain assessment and resulted in an increased rate of early discharges compared with previously reported rates

Trapping of Intermediates with Substrate Analog HBOCaA in the Polymerizations Catalyzer by Class III Polyhydroxybutyrate (PHB) Synthase from Allochromatium Vinosum

Polyhydroxybutyrate (PHB) synthases (PhaCs) catalyze the formation of biodegradable PHB polymers that are considered as an ideal alternative to petroleum-based plastics. To provide strong evidence for the preferred mechanistic model involving covalent and noncovalent intermediates, a substrate analog HBOCoA was synthesized chemoenzymatically. Substitution of sulfur in the native substrate HBCoA with an oxygen in HBOCoA enabled detection of (HB)nOCoA (n = 2–6) intermediates when the polymerization was catalyzed by wild-type (wt-)PhaECAv at 5.84 hr−1. This extremely slow rate is due to thermodynamically unfavorable steps that involve formation of enzyme-bound PHB species (thioesters) from corresponding CoA oxoesters. Synthesized standards (HB)nOCoA (n = 2–3) were found to undergo both reacylation and hydrolysis catalyzed by the synthase. Distribution of the hydrolysis products highlights the importance of the penultimate ester group as previously suggested. Importantly, the reaction between primed synthase [3H]-sT-PhaECAv and HBOCoA yielded [3H]-sTet-O-CoA at a rate constant faster than 17.4 s−1, which represents the first example that a substrate analog undergoes PHB chain elongation at a rate close to that of the native substrate (65.0 s−1). Therefore, for the first time with a wt-synthase, strong evidence was obtained to support our favored PHB chain elongation model

Multiwavelength Monitoring of the BL Lacertae Object PKS 2155-304 in May 1994. I. The Ground-Based Campaign

Optical, near-infrared, and radio observations of the BL Lac object PKS2155-304 were obtained simultaneously with a continuous UV/EUV/X-ray monitoring campaign in 1994 May. Further optical observations were gathered throughout most of 1994. The radio, millimeter, and near-infrared data show no strong correlations with the higher energies. The optical light curves exhibit flickering of 0.2-0.3 mag on timescales of 1-2 days, superimposed on longer timescale variations. Rapid variations of ~0.01 mag/min, which, if real, are the fastest seen to date for any BL Lac object. Small (0.2-0.3 mag) increases in the V and R bands occur simultaneously with a flare seen at higher energies. All optical wavebands (UBVRI) track each other well over the period of observation with no detectable delay. For most of the period the average colors remain relatively constant, although there is a tendency for the colors (in particular B-V) to vary more when the source fades. In polarized light, PKS 2155-304 showed strong color dependence and the highest optical polarization (U = 14.3%) ever observed for this source. The polarization variations trace the flares seen in the ultraviolet flux.Comment: 45 pages, latex file with encapsulated postscript, accepted to the Astrophysical Journa

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries