A Symplectic Dynamics Proof of the Degree–Genus Formula

We classify global surfaces of section for the Reeb flow of the standard contact form on the 3-sphere (defining the Hopf fibration), with boundaries oriented positively by the flow. As an application, we prove the degree-genus formula for complex projective curves, using an elementary degeneration process inspired by the language of holomorphic buildings in symplectic field theory.

378. Descriptive Analysis of SARS-CoV-2 Infections Among Health System and University Employees

Background We aimed to describe SARS-CoV-2 (COVID-19) infections among employees in a large, academic institution. Table 1. COVID-19 Attribution Definitions Table 2. Description of 3,140 COVID 19 Infections in Employees from 3/2020 to 4/2021 Methods We prospectively tracked and traced COVID-19 infections among employees across our health system and university. Each employee with a confirmed positive test and 3 presumed positive cases were interviewed with a standard contact tracing template that included descriptive variables such as high-risk behaviors and contacts, dates worked while infectious, and initial symptoms. Using this information, the most likely location of infection acquisition was adjudicated (Table 1). We compared behavior frequency between community and unknown, likely community and community and unknown cases using descriptive statistics. Table 3. Risk Factors for Community, Likely Community, and Unknown Cases Number of SARS-CoV-2 cases among employees between 3/2020 and 4/2021 by month and stratified according to clinical employee working in the healthcare system, non-clinical employee employed by the healthcare system, and university employee Results From 3/2020 to 4/2021 we identified 3,140 COVID-19 infections in 3,119 employees out of a total of 34,562 employees (9.0%) (Figure 1). Of those 3,119 employees 1,685 (54.0%) were clinical employees working in the health system, 916 (29.4%) were non-clinical employees working in the health system, and 518 (16.6%) were university employees. Descriptive characteristics for the COVID-19 infections and adjudications are outlined in Table 2. Severe disease among employees was significantly less frequent compared to patients in the health system (15.3% vs 2.2%, p< 0.01). The frequency of travel within 14 days, masked gatherings and unmasked gatherings/activities was not significantly different between the community and unknown, likely community groups or the community and unknown groups (Table 3). Conclusion The majority of COVID-19 infections were linked to acquisition in the community, and few were attributed to workplace exposures. Employees with unknown sources of COVID-19 participated in higher-risk activities at approximately the same frequency as employees with community sources of COVID-19. The most frequently reported initial symptoms were mild and non-specific and rarely included fever. Despite a comprehensive testing and benefit program, a large proportion of COVID-positive employees worked with symptoms, highlighting ongoing challenges with presenteeism in healthcare. Disclosures Rebekah W. Moehring, MD, MPH, UpToDate, Inc. (Other Financial or Material Support, Author Royalties)

Empirical evidence on the efficiency of bidirectional contact tracing in COVID-19

Despite ubiquitous rollout of contact tracing to counteract the spread of COVID-19, few countries have been spared from widespread community transmission, highlighting the need for more effective tracing strategies1,2. Standard contact tracing practice identifies, quarantines and tests persons exposed to an infected person during the contagious period, assumed to start two days before symptom onset or diagnosis3,4. Backward contact tracing intends to identify the source of the infection and persons infected by the same source, either by extending the contact tracing window or investigating suspected source events. These approaches have shown promise in modelling studies, but lack empirical data supporting their efficiency5–7. In the first large cohort study on backward contact tracing for COVID-19, we found that extending the contact tracing window backward by 5 days increased the number of identified contacts by 49.2%. The risk of infection amongst these additional contacts was similar to contacts exposed during the standard tracing window and significantly higher than symptomatic individuals in a control group, leading to an increase of 42.0% in cases identified through contact tracing. The risk was not limited to attendees of suspected source events. Our results imply an urgent need to implement backward contact tracing globally.

Stable Knots and Links in Electromagnetic Fields

Persistent topological structures in physical systems have become increasingly important over the last years. Electromagnetic fields with knotted field lines play a special role among these, since they can be used to transfer their knottedness to other systems like plasmas and quantum fluids. In null electromagnetic fields the electric and the magnetic field lines evolve like unbreakable elastic filaments in a fluid flow. In particular, their topology is preserved for all time, so that all knotted closed field lines maintain their knot type. We use an approach due to Bateman to prove that for every link L there is such an electromagnetic field that satisfies Maxwell’s equations in free space and that has closed electric and magnetic field lines in the shape of L for all time. The knotted and linked field lines turn out to be projections of real analytic Legendrian links with respect to the standard contact structure on the 3-sphere.

ASSESSMENT OF KNOWLEDGE AND AWARENESS OF COVID-19 PROTOCOLS IN DENTAL CLINIC BY THE PARENTS; A SURVEY-BASED STUDY AMONG THE PARENTS ATTENDING REU CLINICS

Introduction: Patients visiting a dental facility expect the dentists to adhere to standard, contact, and airborne safety measures involving the proper use of personal protective gear and hand hygiene habits. Materials and Methods: This is a cross sectional study conducted among the parents of pediatric patients using an online survey. 519 parents were contacted in the two campuses of REU. Results: 45.3% participants felt that a visit to dental clinic is more dangerous than public places, 11% were not worried about contracting virus from dental clinic, fathers were more positive since the beginning of COVID-19 pandemic (24.9%). Conclusion: The overall level of knowledge and awareness regarding dental clinics infection protocol among the study participants is satisfactory. Keywords: Parental knowledge, dental treatment, COVID-19, infection control.

A Cognitive Anycast Routing Method for Delay-Tolerant Networks

A cognitive networking approach to the anycast routing problem for delay-tolerant networking (DTN) is proposed. The method is suitable for the space–ground and other domains where communications are recurrently challenged by diverse link impairments, including long propagation delays, communication asymmetry, and lengthy disruptions. The proposed method delivers data bundles achieving low delays by avoiding, whenever possible, link congestion and long wait times for contacts to become active, and without the need of duplicating data bundles. Network gateways use a spiking neural network (SNN) to decide the optimal outbound link for each bundle. The SNN is regularly updated to reflect the expected cost of the routing decisions, which helps to fine-tune future decisions. The method is decentralized and selects both the anycast group member to be used as the sink and the path to reach that node. A series of experiments were carried out on a network testbed to evaluate the method. The results demonstrate its performance advantage over unicast routing, as anycast routing is not yet supported by the current DTN standard (Contact Graph Routing). The proposed approach yields improved performance for space applications that require as-fast-as-possible data returns.

The cost-effectiveness of accelerated partner therapy (APT) compared to standard contact tracing for people with chlamydia: an economic evaluation based on the LUSTRUM population-based chlamydia transmission model

Objective: To investigate the cost-effectiveness of accelerated partner therapy (APT) compared with standard contact tracing for people with sexually transmitted chlamydia infection in the United Kingdom Design: Economic evaluation using a model consisting of two components: a population-based chlamydia transmission component, to estimate the impact of APT on chlamydia prevalence, and an economic component, to estimate the impact of APT on healthcare costs and health outcomes. Setting: United Kingdom Participants: Hypothetical heterosexual population of 50,000 men and 50,000 women aged 16-34 years. Main Outcome Measures: Cost-effectiveness based on quality-adjusted life years (QALYs) gained and major outcomes averted (MOA), defined as mild pelvic inflammatory disease (PID), severe PID, chronic pelvic pain, ectopic pregnancy, tubal factor infertility and epididymitis. Results: For a model population of 50,000 men and 50,000 women and an APT intervention lasting 5 years, the intervention cost of APT (&pound135,201) is greater than the intervention cost of standard contact tracing (&pound116,334). When the costs of complications arising from chlamydia are considered, the total cost of APT (&pound370,657) is lower than standard contact tracing (&pound379,597). Thus, APT yields a total cost saving of approximately &pound9000 and leads to 73 fewer major outcomes and 21 fewer QALYs lost. Hence, APT is the dominant PN strategy. APT remained cost-effective across the full range of sensitivity analyses. Conclusions: Based on cost-effectiveness grounds APT is likely to be recommended as an alternative to standard contact tracing for chlamydia infection in the United Kingdom

Contact Pneumatic Ureterolithotripsy Using LMA StoneBreaker Lithotriptor and Search for Opportunities to Increase Effectiveness

The objective: to evaluate the effectiveness of portable pneumatic contact lithotripter LMA StoneBreaker in endoscopic contact ureterolithotripsy of ureteral stones of different localization depending on their density and search for opportunities to increase it. Materials and methods. Contact pneumatic ureterolithotripsy was performed in 89 patients (49 men, 40 women), 39 (43.8%) patients (I group) underwent standard contact pneumoureterolithotripsy, and 50 (56.2%) patients (11 group) – modified (with prior fixation of the stone in the ureter loop Dormia), which allowed urethrolithotripsy in situ and prevented the migration of stones and their fragments proximally. The number of strokes required to initiate fragmentation, complete fragmentation, and total ureterolithotripcy time for stones of different localization and density were determined. The integrity of the stones was determined by computed tomography in units of Haunsfield (HU). The mineral composition of stone fragments after their removal was diagnosed by X-ray diffraction analysis. The effectiveness of the applied methods was evaluated in groups of patients by complete (100%) removal of stone fragments from the ureter and by the number of cases of retrograde migration of stones into the renal cavity. Results. No intraoperative complications were observed. The number of strokes for the initial and complete disintegration of the stone, regardless of the method of ureterolithotripsy and their localization, depended on their density, ie its mineral composition. The minimum number of strokes for start and complete fragmentation of the stone was recorded in patients with a stone density of 480+54 HU and diagnosed as phosphates. Oxalate and uric acid stones, as well as their combinations (density 1310–1580 HU) required the maximum number of blows. Stone migration was noted in 8 (8.99%) patients. Thanks to intraoperative stone fixation was able to reduce the average time of lithotripsy (from 15,65±6.9 min to 12.3±6,15 min) and reduce the frequency of retrograde stone migration from 15.4% (in 6 patients of group 1) to 4% (2 patients of ІI group). The dependence of lithotripsy efficiency on stone localization is established. It was highest in patients with stones of the lower third of the ureter (95% in patients of group 1 and 100% of patients in group II) and with low density (480–840 HU). The lowest efficacy was observed in patients whose stones were localized in the upper third of the ureter (66.3% in group I and 90% in group II) and had a high density (more than 1200 HU). Due to the fixation of the stone with modified pneumoureterolithotripsy, the overall effectiveness of the method increased from 84.6% to 96%. Conclusions. Traneurethral contact pneumoureterolithotrysis using a portable pneumatic lithotripter LMA Stonebreaker – is effective, safe, minimally costly and easy to use. The effectiveness of contact pneumatic ureterolithotripsy depends on the location and density of the stone. The number of strokes required for the initial and complete fragmentation of the stone directly depends on the density of the stone and does not depend on its location and method of performing pneumoureterolithotripsy. The use of a modified technique with fixation of the stone in the ureter during the process of lithotripsy reduces the time of the operation and increases its effectiveness.