•Formulated parsimonious, continuous model for optimizing the design of hybrid transit networks fed by shared bikes.•Significant cost savings were found in some cases over transit networks accessed ...on foot only and those accessed by feeder buses.•Jointly optimized transit and shared-bike systems can reduce costs for both patrons and the transit agency.•Revenue accrued from system-optimal pricing for shared bikes can often cover their cost, with or without subsidy.
Transit systems are designed in which access and egress can occur via a shared-bike service. Patrons may walk to shared-bike docking stations nearest their origins, and then cycle to their nearest transit stations where they deposit the bikes. The travel pattern is reversed when patrons cycle from their final transit stations on to their destinations. Patrons choose between this option and that of solely walking to or from transit stations. Shared bikes are priced to achieve the system-optimal assignment of the two feeder options.
Transit trunk-line networks are laid-out in hybrid fashion, as proposed in Daganzo (2010). Transit lines thus form square grids inside city centers, and radiate outward in the peripheries. As in Daganzo (2010) and other studies, a set of simplifying assumptions are adopted that pertain primarily to the nature of travel demand. These enable the formulation of a parsimonious, continuous model. The model produces designs that minimize total travel costs, and is ideally suited for high-level (i.e., strategic) planning. A similar model is developed for systems in which access or egress to or from transit can occur solely by walking, or by walking and riding fixed-route feeder buses in combination. The shared-bike and feeder-bus models both complement Daganzo's original model in which access and egress occur solely by walking.
Comparisons of these feeder options are drawn through numerical analyses. These are performed in parametric fashion by varying city size, travel demand, and economic conditions; and for trunk services that are provided either by ordinary buses, Bus Rapid Transit, or metro rail. Designs are produced for cases in which shared-bike and feeder-bus services are made to fit pre-existing and unchangeable trunk-line networks; and for cases in which trunk and feeder services are optimized jointly.
Outcomes reveal that shared-bike feeder systems can often reduce costs over walking alone, with cost savings as high as 7%, even when the shared bikes are made to fit a pre-existing transit network. Shared-biking often outperforms feeder-bus service as well. We further find that the joint optimization of trunk and shared-bike feeder services can reduce costs not only to users, but also to the transit agency that operates these services. Savings to the agency can be used to subsidize shared-bike services. We show that with or without this subsidy, shared-bike systems can always break even when they are suitably priced, and jointly optimized with trunk service.
Human acetylcholinesterase (AChE) is a significant target for therapeutic drugs. Here we present high resolution crystal structures of human AChE, alone and in complexes with drug ligands; donepezil, ...an Alzheimer’s disease drug, binds differently to human AChE than it does to Torpedo AChE. These crystals of human AChE provide a more accurate platform for further drug development than previously available.
IMPORTANCE Postoperative pulmonary complications can be a devastating consequence of surgery. Validated strategies to reduce these adverse outcomes are needed. OBJECTIVES To design, implement, and ...determine the efficacy of a suite of interventions for reducing postoperative pulmonary complications. DESIGN A before-after trial comparing our National Surgical Quality Improvement Program (NSQIP) pulmonary outcomes before and after implementing I COUGH, a multidisciplinary pulmonary care program. SETTING An urban, academic, safety-net hospital. PARTICIPANTS All patients who underwent general or vascular surgery at our institution during a 1-year period before and after implementation of I COUGH. INTERVENTIONS A multidisciplinary team developed a strategy to reduce pulmonary complications based on comprehensive patient and family education and a set of standardized electronic physician orders to specify early postoperative mobilization and pulmonary care. Designated by the acronym I COUGH, the program emphasizes incentive spirometry, coughing and deep breathing, oral care (brushing teeth and using mouthwash twice daily), understanding (patient and family education), getting out of bed at least 3 times daily, and head-of-bed elevation. Nursing and physician education promoted a culture of mobilization and I COUGH interventions. I COUGH was implemented for all general surgery and vascular surgery patients at our institution in August 2010. MAIN OUTCOMES AND MEASURES The NSQIP-reported incidence and risk-adjusted ratios of postoperative pneumonia and unplanned intubation, which NSQIP reports as observed-expected (OE) ratios for the 1-year period before implementing I COUGH and as odds ratios (ORs, statistically comparable to OE ratios) for the period after its implementation. RESULTS Before implementation of I COUGH, our incidence of postoperative pneumonia was 2.6%, falling to 1.6% after its implementation, and risk-adjusted outcomes fell from an OE ratio of 2.13 to an OR of 1.58. The incidence of unplanned intubations was 2.0% before I COUGH and 1.2% after I COUGH, with risk-adjusted outcomes decreasing from an OE ratio of 2.10 to an OR of 1.31. CONCLUSIONS AND RELEVANCE I COUGH, a standardized postoperative care program emphasizing patient education, early mobilization, and pulmonary interventions, reduced the incidence of postoperative pneumonia and unplanned intubation among our patients.
Background Data revealed that our urban, academic, safety net medical center was a high outlier for postoperative venous thromboembolism (VTE). Our goal was to implement and determine the efficacy of ...a standardized intervention for reducing postoperative VTE complications. Study Design We developed a strategy to decrease VTE complications, based on standardized electronic physician orders that specify early postoperative mobilization and mandatory VTE risk stratification for every patient, using the “Caprini” grading system. The derived scores dictate the nature and duration of VTE prophylaxis, including on an outpatient basis. Electronic reminders about appropriate VTE prophylaxis are automatically generated before and after operations, and on discharge. Both mechanical (pneumatic compression boots) and pharmacologic prophylaxis (unfractionated or low molecular weight heparin) are used, as indicated by risk level. We conducted a before-and-after trial, comparing National Surgical Quality Improvement Program (NSQIP) VTE outcomes (deep vein thromboses and pulmonary emboli) before and after implementing the standardized risk-stratified protocol combined with a postoperative mobilization program. Measured outcomes included NSQIP-reported raw and risk-adjusted VTE outcomes during 2 years before and after implementing the VTE prevention program. Results The incidence of deep venous thromboses decreased by 84%, from 1.9% to 0.3% (p < 0.01), with implementation of VTE prevention efforts; the pulmonary emboli incidence fell by 55%, from 1.1% to 0.5% (p < 0.01). Risk-adjusted VTE outcomes steadily declined from an odds ratio of 3.41 to 0.94 (p < 0.05). Conclusions A patient care program, emphasizing early postoperative mobilization along with mandatory VTE risk stratification and commensurate electronic prophylaxis recommendations, significantly reduced the likelihood of VTE complications among our patients.
An agent-based, multichannel simulation of a downtown area reveals the impacts of both time-shifting traffic demand with congestion pricing, and supplying extra capacity by banning left turns. The ...downtown street network was idealized, and loosely resembles central Los Angeles. On the demand-side, prices were set based on time-of-day and distance traveled. On the supply side, left-turn maneuvers were prohibited at all intersections on the network.
Although both traffic management measures reduced travel costs when used alone, the left-turn ban was much less effective than pricing. When combined with pricing under congested conditions, however, the left-turn ban’s effectiveness increased considerably—it more than doubled in some cases. Furthermore, the two measures combined reduced travel costs in synergistic fashion. In some cases, this synergistic effect was responsible for 30% of the cost reduction. This strong synergy suggests that turning bans should be considered as an added option when contemplating congestion pricing.
Purpose
While previously thought to be clinically indolent, recent data suggest significant late metastatic capacity of solitary fibrous tumors (SFTs). We define prognostic factors for recurrence and ...disease-specific death (DSD) in resected primary SFTs.
Methods
Resected primary SFTs from 1982 to 2015 were identified from a prospective, single institutional database. Risk factors for local (LR) and distant recurrence (DR), and DSD were assessed using competing risk analysis.
Results
A total of 219 patients with median follow-up of 6.1 (0.1–22) years were included. Five- and 10-year cumulative DSD was 9 and 11%, respectively. Size greater than the median 8 cm, gender, location, and complete gross resection were significantly associated with DSD (
p
< 0.05). Five- and 10-year cumulative risk (CR) of LR was 4 and 7%, whereas 5- and 10-year CR of DR was 13 and 16%, respectively. LR was associated with location (
p
= 0.02) and tumor size (
p
= 0.02), and DR was associated with size (
p
< 0.01). Histopathologic classification did not predict long-term behavior with both malignant and benign tumors demonstrating capacity for DR and associated death. Tumors in the thoracic cavity and abdomen/retroperitoneum presented the greatest risk of DR (16 and 27% 10-year CR). On multivariate analysis, size ≥ 8 cm (hazard ratio 2.89,
p
= 0.05) and tumor location in chest or abdominal/retroperitoneal cavity (hazard ratio 2.68,
p
= 0.01) significantly impacted DSD.
Conclusions
Recurrence is highly associated with DSD and events occur as late as 16 years after initial presentation, including in patients with initially considered benign tumors. Patients with large (≥ 8 cm) tumors in the chest or abdominal/retroperitoneal cavity are at greatest risk.
Measurements taken downstream of freeway/on-ramp merges have previously shown that discharge flow diminishes when a merge becomes an isolated bottleneck. By means of observation and experiment, we ...show here that metering an on-ramp can recover the higher discharge flow at a merge and thereby increase the merge capacity. Detailed observations were collected at a single merge using video. These data revealed that the reductions in discharge flow are triggered by a queue that forms near the merge in the freeway shoulder lane and then spreads laterally, as drivers change lanes to maneuver around slow traffic. Our experiments show that once restrictive metering mitigated this shoulder lane queue, high outflows often returned to the median lane. High merge outflows could be restored in all freeway lanes by then relaxing the metering rate so that inflows from the on-ramp increased. Although outflows recovered in this fashion were not sustained for periods greater than 13
min, the findings are the first real evidence that ramp metering can favorably affect the capacity of an isolated merge. Furthermore, these findings point to control strategies that might generate higher outflows for more prolonged periods and increase merge capacity even more. Finally, the findings uncover details of merge operation that are essential for developing realistic theories of merging traffic.
•Time-varying, but spatially-uniform metering rates generated via model predictive control are redistributed along cordons in spatially-varying fashion.•The redistribution is achieved using ...Reinforcement Learning (RL).•Street networks are conveniently and fully represented as directed graphs, which require adaptations to neural network architectures.•The result is an RL controller that can be trained on data from a single cordon, and thereafter deployed on other cordons elsewhere in a city sans additional learning.•Spatially-varying metering policies generated by the controller are shown to outperform spatially-uniform metering policies.
The work explores how Reinforcement Learning can be used to re-time traffic signals around cordoned neighborhoods. An RL-based controller is developed by representing traffic states as graph-structured data and customizing corresponding neural network architectures to handle those data. The customizations enable the controller to: (i) model neighborhood-wide traffic based on directed-graph representations; (ii) use the representations to identify patterns in real-time traffic measurements; and (iii) capture those patterns to a spatial representation needed for selecting optimal cordon-metering rates. Input to the selection process also includes a total inflow to be admitted through a cordon. The rate is optimized in a separate process that is not part of the present work. Our RL-controller distributes that separately-optimized rate across the signalized street links that feed traffic through the cordon. The resulting metering rates vary from one feeder link to the next. The selection process can reoccur at short time intervals in response to changing traffic patterns. Once trained on a few cordons, the RL-controller can be deployed on cordons elsewhere in a city without additional training.
This portability feature is confirmed via simulations of traffic on an idealized street network. The tests also indicate that the controller can reduce the network’s vehicle hours traveled well beyond what can be achieved via spatially-uniform cordon metering. The extra reductions in VHT are found to grow larger when traffic exhibits greater in-homogeneities over the network.
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