Portion Of Track Research Articles

The effect of mandatory post-call relief on sleep and wellness in ophthalmology residents

BackgroundMultiple duty hour reforms have been implemented to optimize resident wellness through increasing opportunities for sleep recovery, but few studies have recorded objectively measured sleep or shown direct sleep and wellness benefits from such interventions. This study seeks to determine whether mandatory post-call relief policies with a partial night float system improved resident sleep, activity, and burnout among ophthalmology residents taking home call.MethodsWe conducted a two group cohort study of ophthalmology residents at the University Washington comparing post graduate year-2 (PGY-2) resident sleep, activity, and burnout between the optional post-call relief group from July 1, 2017 to June 30, 2019 to the mandatory post-call relief group from July 1, 2019 to June 30, 2021.ResultsOf twenty total residents participating in the survey portion, 18 residents participated in the sleep and activity tracking portion of the study, 9 in in the optional post-call relief cohort, and 9 in the mandatory post-call relief cohort. The mandatory post-call relief group recorded longer total sleep on call than the optional post-call relief group (p < 0.001). There was no difference in overnight sleep recorded on call (median 3.4 h), but residents recorded more time napping in the mandatory post-call relief cohort (p < 0.001). There was no significant difference between cohorts in amount of sleep while not on call. Residents in the mandatory post-call relief cohort recorded higher average daily steps, higher exercise time, and lower sedentary time than residents in the optional post-call relief cohort (p < 0.001). They also recorded lower median emotional exhaustion on the Maslach Burnout Inventory and lower stress in the Depression and Anxiety Stress Scale in the mandatory post-call relief cohort (p = 0.008).ConclusionsImplementation of mandatory post-call relief policies with a partial night-float system among PGY-2 residents was associated with more post-call naps with more overall physical activity, lower emotional exhaustion scores, and lower stress scores, despite no changes to overnight sleep on call or total sleep. Although sample size limits interpretation of data, implementation of mandatory post call relief could be considered to improve post-call sleep in programs with home call.

End-to-End Joint Multi-Object Detection and Tracking for Intelligent Transportation Systems

Environment perception is one of the most critical technology of intelligent transportation systems (ITS). Motion interaction between multiple vehicles in ITS makes it important to perform multi-object tracking (MOT). However, most existing MOT algorithms follow the tracking-by-detection framework, which separates detection and tracking into two independent segments and limit the global efficiency. Recently, a few algorithms have combined feature extraction into one network; however, the tracking portion continues to rely on data association, and requires complex post-processing for life cycle management. Those methods do not combine detection and tracking efficiently. This paper presents a novel network to realize joint multi-object detection and tracking in an end-to-end manner for ITS, named as global correlation network (GCNet). Unlike most object detection methods, GCNet introduces a global correlation layer for regression of absolute size and coordinates of bounding boxes, instead of offsetting predictions. The pipeline of detection and tracking in GCNet is conceptually simple, and does not require complicated tracking strategies such as non-maximum suppression and data association. GCNet was evaluated on a multi-vehicle tracking dataset, UA-DETRAC, demonstrating promising performance compared to state-of-the-art detectors and trackers.

The along-track etching structure of fission tracks in apatite: Observations and implications

Interpretation of apatite fission-track length data rests on the assumptions that etching fully reveals latent tracks, and that laboratory annealing of induced tracks constitutes a good proxy for geological annealing of spontaneous tracks. Recent work using improved step-etching procedures questions both of these assumptions. Step etching experiments interrogating the etching structure of tracks near and beyond their tips have shown that tracks are often not etched to their full extent of latent track damage in a standard single-step, 20-s etch, and that the etching structure in this outer region differs between fossil and induced tracks. In this study, we develop a more complete picture of track revelation for fossil and unannealed and annealed induced tracks in Durango apatite. Using first steps as early as 10 s after the beginning of etching, we discern differences in etching structure between various track types, and document a gradual fall-off in etching velocity from the track interior toward its tips. When effective etching time is constrained by selecting earlier-etching confined tracks for later analysis, mean lengths are longer, but length dispersion is not diminished. Although some proportion of unannealed tracks are under-etched after 20 s of etching, with increased levels of annealing the probability of an induced track being fully etched increases. We use an etch-anneal-etch procedure, consisting of partially etching tracks, annealing the apatite grains, and then continuing etching, to establish bulk etching rates at track tips. Bulk etching is effectively isotropic, as is etching velocity in the central portions of tracks, away from their tips. We use our data to compare two end-member possibilities for along-track etching structure, which provides a first step toward a deeper understanding of annealing and development of a more robust standard etching protocol.

Visual pathways evaluation in Kearns Sayre syndrome: a diffusion tensor imaging study.

Kearns Sayre syndrome (KSS) is a mitochondrial disorder characterized by development of visual impairment. Electroretinogram (ERG) and visual evoked potentials are not able to provide topographical information of optic damage. The purpose of this study was to explore retrochiasmatic optic pathway alteration in KSS with diffusion tractographic analysis and to compare it with different tracts. DTI from 8 KSS subjects (14.7 years) and 10 healthy controls (HC) were acquired on a 3T scanner. Optic radiations (OR), optic tracts (OT), inferior frontooccipital fasciculus (IFOF) and corticospinal tract (CST) were reconstructed with probabilistic tractography. Fractional anisotropy (FA), apparent diffusion coefficient (ADC), radial (RD), and axial diffusivity (AD) were calculated, evaluating group differences. T test on diffusion parameters identified significantly different track portions among cohorts. All patients had optic pathway alterations at electrophysiological examination. Significant lower FA were found in OT, IFOF, and CST of KSS group. RD was significantly higher in bilateral OR, IFOF, CST, and right OT, while ADC was higher in bilateral OR and CST. RD values were higher in the proximal and distal portion of OR bilaterally and in the distal portion of right OT, while widespread differences were found in IFOF and CST. No significant differences were found for AD. FA profiles analysis demonstrated significant differences between groups in several regions of OT, IFOF, and CST, while ADC assessment revealed spread differences in OR and CST. DTI evaluation of retrochiasmatic tracks may represent a useful tool to topographically investigate retrochiasmatic visual impairment in KSS.

Temporal dependence of shifts in mu opioid receptor mobility at the cell surface after agonist binding observed by single-particle tracking

Agonist binding to the mu opioid receptor (MOR) results in conformational changes that allow recruitment of G-proteins, activation of downstream effectors and eventual desensitization and internalization, all of which could affect receptor mobility. The present study employed single particle tracking (SPT) of quantum dot labeled FLAG-tagged MORs to examine shifts in MOR mobility after agonist binding. FLAG-MORs on the plasma membrane were in both mobile and immobile states under basal conditions. Activation of FLAG-MORs with DAMGO caused an acute increase in the fraction of mobile MORs, and free portions of mobile tracks were partially dependent on interactions with G-proteins. In contrast, 10-minute exposure to DAMGO or morphine increased the fraction of immobile FLAG-MORs. While the decrease in mobility with prolonged DAMGO exposure corresponded to an increase in colocalization with clathrin, the increase in colocalization was present in both mobile and immobile FLAG-MORs. Thus, no single mobility state of the receptor accounted for colocalization with clathrin. These findings demonstrate that SPT can be used to track agonist-dependent changes in MOR mobility over time, but that the mobility states observed likely arise from a diverse set of interactions and will be most informative when examined in concert with particular downstream effectors.

Feeding home ranges of Pacific Coast Feeding Group gray whales

ABSTRACTThere is a lack of detailed information about the range and habitat use of gray whales (Eschrichtius robustus) during their seasonal occupation off the Pacific Northwest (PNW) coast from northern California to southeast Alaska, USA. These data are important for management because of anthropogenic pressures (e.g., indigenous harvesting, fishing gear entanglements, ship strikes, naval exercises, siting of marine renewable energy facilities). We applied satellite tags to 35 gray whales in the eastern north Pacific (ENP) off the coasts of Oregon and northern California from September to December 2009, 2012, and 2013. These whales are members of the Pacific Coast Feeding Group (PCFG), a subset of gray whales in the ENP that feed off the PNW, during summer and fall. Tracking periods for the satellite‐tagged whales in this study ranged from 3 days to 383 days. We applied a Bayesian switching state‐space model (SSSM) to locations for each whale track to provide a regularized track with 2 estimated locations per day and associated movement behavior (either transiting or area‐restricted searching [ARS]). We isolated the portion of the SSSM track in the feeding area for each whale by removing all southward and northward migration locations. We calculated home ranges (90% isopleths) and core areas (50% isopleths) for these non‐migrating, feeding‐area tracks with &gt;50 SSSM locations using local convex hull utilization distributions. Feeding‐area home ranges for the resulting 23 whales covered most of the near‐shore waters from northern California to Icy Bay, Alaska, and ranged in size from 81 km2to 13,634 km2. Core areas varied widely in size (11–3,976 km2) and location between individuals, with the highest‐use areas off Point St. George in northern California, the central coast of Oregon, and the southern coast of Washington, USA. Nearshore waters off Point St. George were a hot spot for whales in the PCFG in late fall, close to where most of the whales were tagged; 19 whales had overlapping home ranges and 15 whales had overlapping core areas there. One whale, a male tracked for 383 days, did not migrate, spending the entire winter off Point St. George and the California‐Oregon border. Residence times (portions of the track with a minimum of 3 successive locations in ARS behavioral mode) ranged from 1 day to 142.5 days; 19 whales had residencies &gt;30 days in some areas. Because most of the whales in this study were tagged in the fall in the southern portion of the feeding area, off northern California, results are weighted toward fall and winter movements. Although some whales were tracked into the spring and summer, additional tagging earlier in the year and in more northerly locations would provide an even clearer picture of gray whale use of feeding areas in the PNW. Nevertheless, these results constitute valuable information about high‐use areas for gray whales in this region, providing baseline home range data for future comparisons with regard to year‐to‐year variability, potential responses to climate change, and exposure to anthropogenic activities in the marine environment. © 2019 The Authors.Journal of Wildlife ManagementPublished by Wiley Periodicals, Inc. on behalf of The Wildlife Society.

A Method for Identifying Midlatitude Mesoscale Convective Systems in Radar Mosaics. Part II: Tracking

AbstractThis research is Part II of a two-part study that evaluates the ability of image-processing and select machine-learning algorithms to detect, classify, and track midlatitude mesoscale convective systems (MCSs) in radar-reflectivity images for the conterminous United States. This paper focuses on the tracking portion of this framework. Tracking is completed through a two-step process using slice (snapshots of instantaneous MCS intensity) data generated in Part I. The first step is to perform spatiotemporal matching, which associates slices through temporally adjacent radar-reflectivity images to generate swaths, or storm tracks. When multiple slices are found to be matches, a difference-minimization procedure is used to associate the most similar slice with the existing swath. Once this step is completed, a second step combines swaths that are spatiotemporally close. Tracking performance is assessed by calculating select metrics for all available swath-building perturbations to determine the optimal approach in tracking. Frequency maps and time series generated from the swaths suggest that the spatiotemporal occurrence of these swaths is reasonable as determined from previous work. Further, these events exhibit a diurnal cycle that is distinct from that of overall convection for the conterminous United States. Last, machine-learning predictions are found to limit areas of high MCS frequency to the central and eastern Great Plains.

On use of characteristic wavelengths of track irregularities to predict track portions with deteriorated wheel/rail forces

Abstract The dynamic performance of the railway vehicles and the guiding tracks is mainly governed by the wheel-rail interactions, particularly in cases of track irregularities. In this work, a united model was developed to investigate the track portions subject to violent wheel/rail forces triggered by track irregularities at middle-low frequencies. In the modeling procedures, a time-frequency unification method combining wavelet transform and Wigner-Ville distribution for characterizing time-frequency characteristics of track irregularities and a three-dimensional nonlinear model for describing vehicle-track interaction signatures were developed and coupled, based on which the method for predicting track portions subject to deteriorated wheel/rail forces was proposed. The theoretical models developed in this paper were comprehensively validated by numerical investigations. The significance of this present study mainly lies on offering a new path to establish correlation and realize mutual prediction between track irregularity and railway system dynamics.

Coalescence Prevention Algorithm for Level Set Method

An algorithm to prevent or delay bubble coalescence for the level set (LS) method is presented. This novel algorithm uses the LS method field to detect when bubbles are in close proximity, indicating a potential coalescence event, and applies a repellent force to simulate the unresolved liquid drainage force. The model is introduced by locally modifying the surface tension force near the liquid film drainage area. The algorithm can also simulate the liquid drainage time of the thin film by controlling the length of time the increased surface tension has been applied. Thus, a new method of modeling bubble coalescence has been developed. Several test cases were designed to demonstrate the capabilities of the algorithm. The simulations, including a mesh study, confirmed the abilities to identify and prevent coalescence as well as implement the time tracking portion, with an additional 10–25% computational cost. Ongoing tests aim to verify the algorithm's functionality for simulations with different flow conditions, a ranging number of bubbles, and both structured and unstructured computational mesh types. Specifically, a bubble rising toward a free surface provides a test of performance and demonstrates the ability to consistently prevent coalescence. In addition, a two bubble case and a seven bubble case provide a more complex demonstration of how the algorithm performs for larger simulations. These cases are compared to much more expensive simulations capable of resolving the liquid film drainage (through very high local mesh resolution) to investigate how the algorithm replicates the liquid film drainage process.

Quantification of the influence of the track geometry variability on the train dynamics

In a context of increasing interoperability, several high speed trains are likely to run on the same tracks, whereas they have been originally designed for specific railway networks. Due to different mechanical properties, the dynamic behaviors of the vehicles will be very different from one train to another. The track-vehicle system being strongly non-linear, the dynamic interaction between the vehicle and the railway track has moreover to be analyzed not only on a few track portions but on the whole realm of possibilities of running conditions that the train can be confronted to during its life cycle. The idea of this paper is therefore to show to what extent this influence of the track geometry variability on the train dynamics can be analyzed from the coupling of a deterministic multibody modeling of the train with a track geometry stochastic modeling, which has been identified and validated from experimental data.

Applications of situation-dependent intensity and intensity spread predictions based on a weighted analog technique

A version of our situation-dependent intensity prediction (SDIP) is proposed for operational application after three modifications: (i) Ten historical track analogs are matched with Joint Typhoon Warning Center (JTWC) official track forecasts rather than besttracks; (ii) Giving two times as much weight to the 72 h — 120 h portion of the track as to the 0–72 h portion to give higher rankings for analog tracks with similar landfall or recurvature positions and timing; and (iii) Weighting both the intensity prediction technique and a new intensity spread guidance product according to new rankings of the track analogs rather than assuming all track analogs are equally likely. These special matchings and weightings of the track analogs in this weighted-analog intensity (WANI) add skill in the 72–120 h forecast intervals in regions where landfalls occur. Viability as an operational technique is demonstrated as the WANI has only 1 kt larger mean absolute errors than the JTWC intensity errors from 12 h through 72 h, and the WANI is 5 kt (20%) better at 120 h. The WANI rank-weighted intensity spreads each 12 h among the 10 best historical track analogs are processed to reduce any intensity bias and calibrated to reduce (increase) the over-determined (under-determined) intensity spreads at early (later) forecast intervals. Thus, the situation-dependent intensity spread guidance is generated that will include about 68% of the verifying intensities at all forecast intervals. Four examples of the WANI intensity predictions and intensity spread guidance are presented to illustrate how the forecaster might use this information in potential landfall and intensity bifurcation situations.

Track irregularities stochastic modeling

High speed trains are currently meant to run faster and to carry heavier loads, while being less energy consuming and still respecting the security and comfort certification criteria. To face these challenges, a better understanding of the interaction between the dynamic train behavior and the track geometry is needed. As during its lifecycle, the train faces a great variability of track conditions, this dynamic behavior has indeed to be characterized on track portions sets that are representative of the whole railway network. This paper is thus devoted to the development of a stochastic modeling of the track geometry and its identification with experimental measurements. Based on a spatial and statistical decomposition, this model allows the spatial and statistical variability and dependency of the track geometry to be taken into account. Moreover, it allows the generation of realistic track geometries that are representative of a whole railway network. First, this paper describes a practical implementation of the proposed method and then applies this method to the modeling of a particular French high speed line, for which experimental data are available.

Domain decomposition with discrete element simulations using shared-memory parallel computing for railways applications

Numerical simulation with discrete elements leads to several issues for large-scale problems and long loading times, as for the granular dynamic simulations of the ballasted railway behaviour. To reduce computational costs, we study the use of two strategies: domain decomposition methods and shared-memory parallelisation with OpenMP. An example of a maintenance process, the tamping, on a portion of railway track with seven sleepers, is simulated.

Analysis and design of new floating slab track for special trackwork using finite element analysis.

This paper discusses the development of a new vibration isolation system for tunnel crossovers in a future rail line extension. The previous design included ballasted track on top of continuous concrete slabs on rubber vibration isolators. The goal of the new design was to replace the ballast and tie track with rails fastened directly to discrete slabs similar to the vibration isolation system utilized on running portions of track within existing tunnels. Finite element analysis (FEA) was used to evaluate the dynamic interaction between the vehicle, rails, resilient rail fasteners and the vibration isolation system. The results of the analyses guided the design in determining the size and thickness of the inertia slabs, the stiffness and design of the rubber vibration isolation pads, and the rail fastener selection.

Tribological characteristics of polyethylene bearings of knee prostheses

This paper deals with the problem of tribological failure of artificial knee prostheses. The clinical problem is introduced by analysis of worn knee bearings made of ultra-high molecular weight polyethylene. Three different failure mechanisms are described: subsurface-originated contact fatigue failure, surface-originated wear of the articulating surface, and surface-originated wear of the back (non-articulating) surface. The wear processes were simulated in a rolling/sliding wear tester built for this specific purpose. The influence of gamma-irradiation dose on wear and contact fatigue was determined. Wear was greatest at the portion of the wear track where the lubricating fluid film was thinnest and a boundary or mixed lubrication regime prevailed.

Three‐dimensional structures and elemental distributions of Stardust impact tracks using synchrotron microtomography and X‐ray fluorescence analysis

Abstract— Three‐dimensional structures and elemental abundances of four impact tracks in silica aerogel keystones of Stardust samples from comet 81P/Wild 2 (bulbous track 67 and carrot‐type tracks 46, 47, and 68) were examined non‐destructively by synchrotron radiation‐based microtomography and X‐ray fluorescence analysis. Track features, such as lengths, volumes and width as a function of track depth, were obtained quantitatively by tomography. A bulbous portion was present near the track entrance even in carrot‐type tracks. Each impact of a cometary dust particle results in the particle disaggregated into small pieces that were widely distributed on the track walls as well as at its terminal. Fe, S, Ca, Ni, and eight minor elements are concentrated in the bulbous portion of track 68 as well as in terminal grains. It was confirmed that bulbous portions and thin tracks were formed by disaggregation of very fine fragile materials and relatively coarse crystalline particles, respectively. The almost constant ratio of whole Fe mass to track volume indicates that the track volume is almost proportional to the impact kinetic energy. The size of the original impactor was estimated from the absolute Fe mass by assuming its Fe content (CI) and bulk density. Relations between the track sizes normalized by the impactor size and impact conditions are roughly consistent with those of previous hypervelocity impact experiments.

Application of the Kalman-Levy Filter for Tracking Maneuvering Targets

Among target tracking algorithms using Kalman filtering-like approaches, the standard assumptions are Gaussian process and measurement noise models. Based on these assumptions, the Kalman filter is widely used in single or multiple filter versions (e.g., in an interacting multiple model (IMM) estimator). The oversimplification resulting from the above assumptions can cause degradation in tracking performance. In this paper we explore the application of Kalman-Levy filter to handle maneuvering targets. This filter assumes a heavy-tailed noise distribution known as the Levy distribution. Due to the heavy-tailed nature of the assumed distribution, the Kalman-Levy filter is more effective in the presence of large errors that can occur, for example, due to the onset of acceleration or deceleration. However, for the same reason, the performance of the Kalman-Levy filter in the nonmaneuvering portion of track is worse than that of a Kalman filter. For this reason, an IMM with one Kalman and one Kalman-Levy module is developed here. Also, the superiority of the IMM with Kalman-Levy module over only Kalman-filter-based IMM for realistic maneuvers is shown by simulation results.

Reliability analysis of track circuit of Indian railway signalling system

This paper deals with the reliability modelling of one of the vital subsystems of railway signalling, called track circuit. The track circuit, a complex repairable system, is used to identify the occupancy of a portion of railway track by a train. It is observed that operations of track circuit are affected by a number of problems in relation to its intensity of use, repair and maintenance and environmental stress. Keeping in view its operating efficiency to the effect of these problems, the recommended parametric model based on repairable system technique is applied to estimate the failure rate probability of the system. Two graphical methods, viz., Nelson−Aalen and Total Time on Test (TTT) plots, are used to analyse the trend of the failure time data for a set of representative track circuits in Kharagpur Division of Indian Railways. Finally, the intensity function of the track circuit is assessed and investigated.

Détermination expérimentale d'une loi de tassement du ballast des voies ferrées soumises à un chargement latéral

A one-third scale bench test representing a portion of railway track has permited to determine a lateral settlement law of the ballast. The experimentation uses a two-block sleeper with ballast and with elastomeric or wood representing the soil. A jack exerts the same signal as the train. Two similitudes have been tried with the bench test. The first one conserves the volumetric mass of the ballast and the stresses just under the blocks, and the second one conserves the volumetric mass of the ballast and the acceleration. Measured settlements are different in the two cases of similitude. From this it may be deduced that one phenomenon is responsible for the settlement: vibrations. We have identified two laws for the lateral settlement of the ballast: one for a few cycles and another one for a lot of cycles. The sum of these two laws can describe the whole behaviour of the ballast. These laws are in accordance with the measurements made on track.Key words: ballast, settlement, experimentation, reduced scale, railroad track.

In vivo three-dimensional patellar tracking on the femur.

In vivo three-dimensional patellar tracking under weightbearing conditions was investigated with the principal reference axes of the femur in the coronal and axial planes, using a biplanar image-matching technique. Three-dimensional knee models of eight healthy volunteers were constructed using computed tomography scanning. Projection images of the models were fitted onto anteroposterior and lateral radiographs of the knees at hyperextension and at every 15 degrees from 0 degrees to 120 degrees flexion. Knee motion then was reconstructed on a computer. Patellar tracking during knee flexion was described simply with a medial jerk shift of 8 mm in early flexion until 30 degrees and a linear tracking with minimal mediolateral translation. The linear tracking portion was located laterally 5 mm from the mediolateral center of the femoral condyles. On average, the direction of this linear tracking was almost perpendicular to the distal condylar line in the coronal plane and perpendicular to the posterior condylar axis in the axial plane. These results help improve the understanding of patellofemoral kinematics and provide useful information for the design and positioning of the prostheses used in total knee arthroplasty.