Transit Time Effects Research Articles

Real-time fMRI neurofeedback of the anterior insula using arterial spin labelling.

Arterial spin labelling (ASL) is the only non-invasive technique that allows absolute quantification of perfusion and is increasingly used in brain activation studies. Contrary to the blood oxygen level-dependent (BOLD) effect ASL measures the cerebral blood flow (CBF) directly. However, the ASL signal has a lower signal-to-noise ratio (SNR), than the BOLD signal, which constrains its utilization in neurofeedback studies. If successful, ASL neurofeedback can be used to aid in the rehabilitation of health conditions with impaired blood flow, for example, stroke. We provide the first ASL-based neurofeedback study incorporating a double-blind, sham-controlled design. A pseudo-continuous ASL (pCASL) approach with background suppression and 3D GRASE readout was combined with a real-time post-processing pipeline. The real-time pipeline allows to monitor the ASL signal and provides real-time feedback on the neural activity to the subject. In total 41 healthy adults (19-56 years) divided into three groups underwent a neurofeedback-based emotion imagery training of the left anterior insula. Two groups differing only in the explicitness level of instruction received real training and a third group received sham feedback. Only those participants receiving real feedback with explicit instruction showed significantly higher absolute CBF values in the trained region during neurofeedback than participants receiving sham feedback. However, responder analyses of percent signal change values show no differences in activation between the three groups. Persisting limitations, such as the lower SNR, confounding effects of arterial transit time and partial volume effects still impact negatively the implementation of ASL neurofeedback.

Recommendations for quantitative cerebral perfusion MRI using multi-timepoint arterial spin labeling: Acquisition, quantification, and clinical applications.

Accurate assessment of cerebral perfusion is vital for understanding the hemodynamic processes involved in various neurological disorders and guiding clinical decision-making. This guidelines article provides a comprehensive overview of quantitative perfusion imaging of the brain using multi-timepoint arterial spin labeling (ASL), along with recommendations for its acquisition and quantification. A major benefit of acquiring ASL data with multiple label durations and/or post-labeling delays (PLDs) is being able to account for the effect of variable arterial transit time (ATT) on quantitative perfusion values and additionally visualize the spatial pattern of ATT itself, providing valuable clinical insights. Although multi-timepoint data can be acquired in the same scan time as single-PLD data with comparable perfusion measurement precision, its acquisition and postprocessing presents challenges beyond single-PLD ASL, impeding widespread adoption. Building upon the 2015 ASL consensus article, this work highlights the protocol distinctions specific to multi-timepoint ASL and provides robust recommendations for acquiring high-quality data. Additionally, we propose an extended quantification model based on the 2015 consensus model and discuss relevant postprocessing options to enhance the analysis of multi-timepoint ASL data. Furthermore, we review the potential clinical applications where multi-timepoint ASL is expected to offer significant benefits. This article is part of a series published by the International Society for Magnetic Resonance in Medicine (ISMRM) Perfusion Study Group, aiming to guide and inspire the advancement and utilization of ASL beyond the scope of the 2015 consensus article.

Assessment of the Effect of Transit Time between Harvesting and Processing on the Physicochemical Quality Parameters of Preharvest Burnt Sugarcane

Aim: This study was aimed at assessing the effect of time interval between harvesting and processing on the physical and chemical quality parameters of pre-harvest burnt sugarcane
 Study Design: An experimental research design was carried out that involve random selection of samples and sent to laboratory for analysis
 Place and Duration of Study: The study was carried out on July from 26th to 30th 2023 in Kilombero Valley located in the eastern part of Tanzania, between latitude 7 0 42'42'S and longitude 37 0 00'00'E. 
 Methodology: The NCO 376 variety of sugarcane was used, that were cut below ground level, the tops removed, stalks tightened in bundles. The sample size was 15. each sample constituted of 30 burnt sugarcane stalks samples that were randomly collected and sent to laboratory for analysis after 24 ,72 and 120 hours of storage. On every respective storage time, the samples were scratched with knife to remove external contaminants, the stalks were then milled using two roller machines to extract juice. The juice was filled and sealed in sterilized and labelled bottles ready for laboratory analysis. The laboratory analysis data collected were coded and entered in excel sheet and analysed using Statistical Package for Social Science (SPSS) version 25.
 Results: The result shows the means values for pH, brix , pol, purity and weight decreased with increase in storage time whereas the means values for dextran, yeast and Leuconostoc increased with increase storage time The results revealed that purity values were satisfactory in all storage time levels as compared to SASTA standard purity values (97.0 – 98.0% ), whereas mean values for brix and pol stored for 120 hours of storage time was not satisfactory.as compared to SASTA standard values for brix ( 18 – 23%) and pol (14 – 21%) .Dextran concentration was high as compared to South African Sugar Terminals (SAST) that maximum requirement for dextran is 150 mg/kg, dextran level as the measure of microbial deterioration was high in 72 and 120 storage hours indicating microbial contamination.
 Conclusion: Farmers and processors should be well informed about the consequence of delayed processing burned sugarcane to avoid economic loss for farmers and processors.

In situ measurement of the electron elastic reflection coefficient at a plasma-exposed silicon dioxide surface

Plasma simulations require accurate input data that describe the interactions of electrons with plasma-exposed surfaces. One important, rarely studied interaction is elastic reflection. This article presents measurements of the elastic reflection coefficient made in situ, i.e. during plasma exposure, in an inductively coupled plasma (icp) reactor that has an azimuthally asymmetric, rf-biased substrate electrode. The rf current and voltage across the sheath adjacent to this electrode were measured, along with the ion current density and electron temperature, for argon plasmas at 0.67 and 1.33 Pa. Using the measurements and a numerical sheath model, the currents contributed by electrons that are emitted from the rf-biased electrode are determined. Some emitted electrons are elastically reflected from the opposing surface, the fused quartz window below the icp source. Deflection of these electrons by 13.56 MHz electric and magnetic fields in the plasma can prevent them from returning to the rf-biased electrode, producing a second-harmonic current at 27.12 MHz. The transport of the emitted electrons is simulated by a plasma model that includes electric and magnetic effects, transit-time effects, elastic reflection at the electrode as well as the window, and multiple passes through the plasma. From the plasma model and the measured 27.12 MHz current, the elastic reflection coefficient at the quartz window was determined, for electron energies from 25 eV to 1.2 keV. The measured reflection coefficient was higher than literature values for clean Si, but it had a similar energy-dependence. An approximate analytical form for its energy-dependence is presented, as well as an uncertainty analysis.

Pharmacodynamic Age Structured Population Model For Cell Trafficking

ObjectivesCell trafficking encompasses movement of the immune system cells (e.g., granulocytes, lymphocytes) between the blood and the extravascular tissues (e.g., lymph nodes). Corticosteroids are known to suppress cell trafficking. The age-structured cell population models introduce the transit time as a structure that allows one to quantify the distribution of times the immune cells spend in the blood and the extravascular tissues. The objective of this work is to develop an age-structured cell population model describing drug effects on cell trafficking and to implement the model in pharmacometric software to enable parameter estimation and simulations. MethodsWe adopted the well-known McKendrick age-structured population model to describe the age distributions in two cell populations: blood cells and cells in the extravascular space. The hazard of cell recirculation from the extravascular tissues was age dependent and described by the Weibull function with the shape ν and scale β parameters. The drug effect on cell trafficking was modeled as the product of the Emax function of the drug plasma concentration and the Weibull hazard. The model was implemented in NONMEM 7.5.1. The model was applied to the basophil data in 34 healthy subjects who received a single intramuscular or oral dose of 6 mg dexamethasone (DEX). A recently published pharmacokinetic model was applied to describe DEX plasma concentration. Typical values of parameter estimates were further used to simulate the DEX effect of the basophil mean transit time in the extravascular tissues. ResultsSimulations of basophil time courses for varying ν demonstrated that the rebound in the blood count data following drug administration is only possible for ν >1. The estimates of model parameters were ν = 3.02, β = 0.00863 1/h, and IC50 = 7.47 ng/mL. The calculated baseline mean transit times of basophils in the blood 7.2 h and extravascular tissues 104.9 h agree with the values reported in the literature. ConclusionsWe introduced an age-structured population model to describe cell trafficking between the blood and extravascular tissues. The model was adopted to account for the inhibitory drug effect on the cell recirculation. We showed that the age structure is essential to explain the rebound observed in the blood count response to a single dose drug administration. The model was validated using the basophil responses to DEX treatment in healthy subjects.

Small Bowel Capsule Endoscopy: Benefits of Rereading Rather than Repeating—A Single Blinded Randomized Study

Abstract Objectives Small bowel capsule endoscopy (SBCE) technology detects small bowel lesions. Many factors affect its sensitivity. SBCE is also costly, and patients might not be able to repeat the test when results are equivocal. Instead of repeating the test, reading the results by two endoscopists might provide a better or a cheaper option in the right settings. We studied the sensitivity of SBCE when read by two different physicians and checked if, rather than repeating the examination, rereading the results improved its sensitivity. Furthermore, we studied the effect of small bowel transit time (SBTT) on the diagnostic yield. Materials and Methods A retrospective cohort study on capsule endoscopies was conducted between 2018 and 2019 in a tertiary care center in Lebanon. A total of 42 patients with anemia or obscure gastrointestinal bleed were included for SBCE after a negative evaluation with upper and lower gastrointestinal (GI) endoscopy. Two specialists read the results. The second physician was blinded from the first reader's results. We compared the sensitivity of the two readings. SBTT correlation with the diagnostic yield was calculated. Results Out of 42 patients, 18 tested positive in the first reading and 31 in the second reading. The diagnostic yield increased from 43 to 74% (p = 0.0043). Among the 33 patients who had a documented SBTT, longer SBTT correlated with a higher diagnostic yield (odds ratio [OR] > 1), but no statistical significance was demonstrated. Conclusion Within the limitations of this study, we found that rereading capsule endoscopy can be more cost-effective than repeating the test.

Effects of Pulse Transit Time and Pulse Arrival Time on Cuff-less Blood Pressure Estimation: A Comparison Study with Multiple Experimental Interventions.

Pulse transit time (PTT) has shown a correlation with blood pressure (BP), and it is considered as a potential marker for cuff-less BP estimation. However, pulse arrival time (PAT) including pre-ejection period (PEP) has been utilized more widely because of its convenience to acquisition and calculation. In spite of this, whether PAT can surrogate PTT has been a controversial topic for many years. In this study, we designed an experiment on 55 subjects with multiple interventions, those may cause the changes in BP and PEP. We analyzed the linear and nonlinear correlations between BP and PTT/PAT, and also assessed the performances of PTT-based and PAT-based models on tracking the BP variation. Five typical BP estimation models were used for comparison. We found that PEP could change rapidly in response to the interventions related with physical stress. Although PTT had a better linear correlation with BP, most of the PAT-based models showed more accuracy than PTT-based models in all of the interventions, especially for the calibrated models. It is suggested that PAT has the potential to predict BP, and the inclusion of PEP in the measurement of PAT is necessary.

Second-harmonic currents in rf-biased, inductively coupled discharges

Capacitively-coupled plasmas generate strong current or voltage signals at harmonics of their driving frequencies. Inductively coupled plasma (icp) systems generally do not, unless they are equipped with capacitively-coupled rf bias, which generates strong signals at harmonics of its driving frequency. Recently, however, at an asymmetric, rf-biased electrode, a current component was detected at the second harmonic of the inductive source frequency, not the rf-bias frequency. The origin of this current is here investigated (in argon discharges at 1.3 Pa) by comparison with measurements made at a symmetric electrode and predictions made by two numerical models. The first simulates the sheath at the rf-biased electrode; the second models the plasma. Because capacitive coupling from the inductive source was minimized by a Faraday shield, the nonlinearity of the sheath contributes negligible second-harmonic current. Modulation of the photon flux in the plasma, however, produces a second-harmonic current photoemitted from the rf-biased electrode. The external circuitry and nonlinear inductive coupling produce a second-harmonic sheath voltage, which in turn generates second-harmonic current both directly and through a transit-time effect. The second model simulates how electrons emitted from the electrode—and then reflected at the quartz dielectric window of the inductive source—are deflected by the electric and magnetic fields in the plasma. It also gives predictions for the transit-time effect. Magnetic deflections and the transit-time effect usually dominate the electric deflection. Together these three mechanisms produce a second-harmonic current that has a Fourier amplitude approximately half the current that is elastically reflected at the icp window. These results suggest it may be possible to use the second-harmonic current to determine the elastic reflection coefficient at the window.

An assessment of the downstream implications of blood culture collection and transit.

The implications of the variables within the pre-analytical phase of blood culture processing are poorly understood. This study aims to explore the effect of transit times (TT) and culture volume, on time to microbiological diagnosis and patient outcomes. Blood cultures received between 1st March and 31st July 2020/21 were identified. TT, time in incubator (TII), and for positive samples, request to positivity times (RPT) were calculated. Demographic details were recorded for all samples, and culture volume, length of stay (LoS), and 30-day mortality for patients with positive samples. Statistical analysis examined how culture volume and TT effected culture positivity and outcome; in the context of the 4-h national TT target. Totally, 14,375 blood culture bottles were received from 7367 patients; 988 (13.4%) were positive for organisms. There was no significant difference between TT of negative and positive samples. The RPT was significantly lower for samples with TT < 4h (p < 0.001). Culture bottle volume did not affect RPT (p = 0.482) or TII (p = 0.367). A prolonged TT was associated with a longer length-of-stay in those with a bacteraemia with a significant organism (p = 0.001). We found shorter blood culture transportation time was associated with a significantly faster time of positive culture reporting, while optimal blood culture volume did not make a significant impact. Delays in reporting for significant organisms correspond to a prolonged LoS. Laboratory centralisation makes achieving the 4-h target a logistical challenge; however, this data suggests such targets have significant microbiological and clinical impacts.

Effect of small bowel transit time on accuracy of video capsule endoscopy in evaluating suspected small bowel bleeding.

Obscure small bowel bleeding is defined as gastrointestinal bleeding (GIB) that is unidentifiable with esophagogastroduodenoscopy and a colonoscopy with video capsule endoscopy (VCE) being the next gold standard step for evaluation. Small bowel transit time (SBTT) is a metric of a VCE study that is defined as the time the capsule takes to travel through the small intestine. To determine if SBTT within the VCE study, correlates to overall detection of obscure small bowel bleeds. Furthermore, we attempted to identify any existing correlation between SBTT and re-bleeding after a negative VCE study. This is a single center retrospective analysis of VCE studies performed for overt and occult GIB at Einstein Medical Center, Philadelphia, between 2015 and 2019. Inclusion criteria primarily consisted of patients 18 years or older who had a VCE study done as part of the workup for a GIB. Patients with incomplete VCEs, poor preparation, or with less than 6 mo of follow up were excluded. A re-bleeding event was defined either as overt or occult within a 6-mo timeframe. Overt re-bleeding was defined as Visible melena or hematochezia with > 2 gm/dL drop in hemoglobin defined an overt re-bleeding event; whereas an unexplained > 2 gm/dL drop in hemoglobin with no visible bleeding defined an occult re-bleed. Results indicated that there was a significant and positive point biserial correlation between SBTT of 220 min and detection of a bleeding focus with a statistically significant p value of 0.008. However, the area under the curve was negligible when trying to identify a threshold time for SBTT to discriminate between risk of re-bleeding events after a negative VCE. In terms of SBTT and association with accuracy of VCE finding a bleeding focus, 220 min was found to be adequate transit time to accurately find a bleeding focus, when present. It was found that no threshold SBTT could be identified to help predict re-bleeding after a negative VCE.

Intensity Dependent Transient Response of Amorphous Photodiode and Solar Cell

The study of amorphous semiconductors is of great interest because they find important applications in many electronic devices, like large area solar cells and photosensors. We have developed a methodology for the analysis of transient response of amorphous photodiodes when switched off from steady-state and when they are exposed to a δ pulse of light. For this purpose continuity equations and the transit time effect have been calculated. For the p-i-n photodiodes, characteristics of photo current decay have been analyzed for an ideal case in which the diode is assumed to have a unit current gain. It is found that characteristics either due to decay from steady-state or due to light pulse excitation is transit time dominated. The short-circuit performance of solar cells resembles to a p-i-n diode because a solar cell is essentially a p-i-n diode which is used as an energy converter. Thus short circuit current decay of solar cells behaves similar to the photocurrent decay of the diode and the same method of analysis can be applied.

Process-based modelling of microbial community dynamics in the human colon

The human colon contains a dynamic microbial community whose composition has important implications for human health. In this work, we build a process-based model of the colonic microbial ecosystem and compare with general empirical observations and the results of in vivo experiments. Our model comprises a complex microbial ecosystem along with absorption of short chain fatty acids (SCFA) and water by the host through the gut wall, variations in incoming dietary substrates (in the form of ‘meals’ whose composition varies in time), bowel movements, feedback on microbial growth from changes in pH resulting from SCFA production and multiple compartments to represent the proximal, transverse and distal colon. We verify our model against a number of observed criteria, e.g. total SCFA concentrations, SCFA ratios, mass of bowel movements, pH and water absorption over the transit time; and then run simulations investigating the effect of colonic transit time, and the composition and amount of indigestible carbohydrate in the host diet, which we compare with in vivo studies. The code is available as an R package (microPopGut) to aid future research.

Effect of Si-doped and undoped inter-layer transition time on the strain-compensated InGaAs/InAlAs QCL active region grown with MOVPE

In this study, we report the effect of the combination of Si-doped and undoped inter-layer transition time in the strain compensated In0.67Ga0.33As/In0.36Al0.64As quantum cascade laser (QCL) structure grown on InP substrate by Metal Organic Vapor Phase Epitaxy (MOVPE). In situ reflectance spectroscopy and high resolution X-ray diffraction (HRXRD) technique have been used for the analysis of growth steps and crystalline quality of QCL structures, respectively. In addition, since thickness accuracy is very important for QCLs, two different thickness calculation methods have been used in the Global Fit simulation program for detailed thickness accuracy of structures. As a result, optimum values for thickness accuracy have been obtained as 5 and 10 s between undoped and Si-doped layers, respectively, as verified by the two methods.

Resonant Plasmonic Terahertz Detection in Gated Graphene p - i - n Field-Effect Structures Enabled by Nonlinearity from Zener-Klein Tunneling

We propose and analyze the terahertz (THz) detectors based on a gated graphene p-i-n (GPIN) field-effect transistor (FET) structure. The reverse-biased i-region between the gates plays the role of the electrons and holes injectors exhibiting nonlinear $I-V$ characteristics due to the Zener-Klein tunneling. This region enables the THz signal rectification, which provides their detection. The gated regions serve as the electron and hole reservoirs and the THz resonant plasma cavities. The resonant excitation of the electron and hole plasmonic oscillations results in a substantial increase in the THz detector responsivity at the signal frequency close to the plasma frequency and its harmonics. Due to the specifics of the i-region AC conductance frequency dependence, associated with the transit-time effects, the GPIN-FET response at the frequency, corresponding to the excitation of a higher plasmonic mode, can be stronger than for the fundamental mode. The GPIN-FETs can exhibit fairly high responsivity at room temperatures. Lowering of the latter can result in its further enhancement due to weakening of the carrier momentum relaxation.

Breakdown Characteristics of Liquid Silicone Rubber in Needle-Plane Configuration Under Polarity Reversal

The results of breakdown voltages in liquid silicone rubber (LSiR) insulation under stepped polarity reversal voltages at a uniform temperature in a needle-plane electrode system are presented in this article. In the presence of defects such as sharp conductor projections or protrusions in the cable insulation stressed under polarity reversal direct current (dc) voltages, the electric field distribution is far more complex due to nonlinear insulation conductivity and time-dependent field distribution. The electric field distribution and space-charge accumulation are intricate functions of factors such as geometry and nonlinear conduction. In this article, a two-dimensional (2-D) axisymmetric model of a needle-plane geometry is developed using the finite-element method to compute the time-dependent field, space charge, and current density distribution under polarity reversal dc, which apparently did not get much attention until now. Interesting results on the effect of polarity transition time and applied polarity time step on the abovementioned distributions are addressed and presented. The pronounced effects of nonlinear conductivity on the time-dependent field distribution are also demonstrated. Furthermore, from the breakdown experiments conducted on tip-plane electrode system for different tip radii and applied time steps, the results put forward a rational and practical estimate of the breakdown field using the proposed model.

A Transient Analysis for Amorphous Photoconductors

The study has been carried out for the transient response of photosensors fabricated by amorphous semiconductors under variable levels of excitation when switched off from steady-state. The curves for the entire range of the transient have been plotted in the terms of photoconductivity and they can be converted to current decay curves by multiplying with the applied electric field and the cross-sectional area of the sample. For this purpose, in the calculations, the transit time effect is included. Also, the switching time and gain of the photoconductor have been calculated. It is found that the current gain of the device increases as the density of thermal equilibrium electrons is made higher, compared to that of holes by moving the Fermi level upward. However, this also increased the switching time and its performance, as a switch becomes poorer.

Analysis of temporal carrier build‐up in reconfigurable field‐effect transistor

Based on the analysis of the carrier density change of a symmetric gate reconfigurable field-effect transistor that can operate p- or n-type transistors in an integrated circuit (IC), its unique limiting factor, carrier build-up time, is quantitatively derived for operating speed in addition to conventional resistance and capacitance (RC) and transit time effect. Originating from the characteristic of carrier confinement in a channel between two Schottky potential barriers, the carrier build-up time for the operation could take up to ∼1000 times longer than the transit time across the channel.

S3299 The Effect of Small Bowel Transit Time on the Accuracy of VCE in Evaluation of Suspected Small Bowel Bleeding: A Retrospective Analysis at Einstein Medical Center

S3299 The Effect of Small Bowel Transit Time on the Accuracy of VCE in Evaluation of Suspected Small Bowel Bleeding: A Retrospective Analysis at Einstein Medical Center

Arterial Transit Time-Based Multidelay Combination Strategy Improves Arterial Spin Labeling Cerebral Blood Flow Measurement Accuracy in Severe Steno-Occlusive Diseases.

Although perfusion imaging plays a key role in the management of steno-occlusive diseases, the clinical usefulness of arterial spin labeling (ASL) is limited by technical issues. To examine the effect of arterial transit time (ATT) prolongation on cerebral blood flow (CBF) measurement accuracy and identify the best CBF measurement protocol for steno-occlusive diseases. Prospective. Moyamoya (n=10) and atherosclerotic diseases (n= 8). A 3.0T/3DT1 -weighted and ASL. Hadamard-encoded multidelay ASL scans with/without vessel suppression (VS) and single-delay ASL scans with long-label duration (LD) and long postlabeling delay (PLD), referred to as long-label long-delay (LLLD), were acquired. CBF measurement accuracy and its ATT dependency, measured as the correlation between the relative CBF measurement difference (ASL-single-photon emission computed tomography [SPECT]) and ATT, were compared among 1) Combo (incorporating multidelay and LLLD data based on ATT), 2) standard (LD/PLD=1333/2333 msec), and 3) LLLD (LD/PLD=4000/4000 msec) protocols, using whole-brain voxel-wise correlation with reference standard SPECT CBF. The effect of VS on CBF measurement accuracy was also assessed. Pearson's correlation coefficient, repeated-measures analysis of variance, t-test. P< 0.05 was considered significant. Pearson's correlation coefficients between ASL and SPECT CBF measurements were as follows: Combo=0.55 ± 0.09; standard=0.52 ± 0.12; LLLD=0.41 ± 0.10. CBF measurement was least accurate in LLLD and most accurate in Combo. VS significantly improved overall CBF measurement accuracy in the standard protocol and in moyamoya patients for the Combo. ATT dependency analysis revealed that, compared with Combo, the standard and LLLD protocols showed significantly lower and negative and significantly higher and positive correlations, respectively (standard=-0.12 ± 0.04, Combo=-0.04 ± 0.03, LLLD=0.17 ± 0.03). By using ATT-corrected CBF derived from LD/PLD=1333/2333 msec as a base and by compensating underestimation in delayed regions using multidelay scans, the ATT-based Combo strategy improves CBF measurement accuracy compared with single-delay protocols in severe steno-occlusive diseases. 1 TECHNICAL EFFICACY: Stage 2.

The Impact of Facility Layout on Service Worker Behavior: An Empirical Study of Nurses in the Emergency Department

Problem definition: We study the impact of service facility layout on how service workers organize their tasks. We focus on the hospital emergency department (ED) as a service setting in which nurses (servers) have discretion over how they interact with patients (customers) in a facility that introduces significant heterogeneity in necessary walking distance. Academic/practical relevance: Prior studies on facility layout in operations have largely focused on the direct effect of transit times on reduced productivity. We extend this work to show how skilled service workers such as nurses adapt their work behavior to enhance their productivity in response to facility layout constraints. Methodology: To study this empirically, we utilize a unique data set consisting of infrared nurse location tracking data, patient electronic medical record data, bedside patient call data, and the architectural floor plan of a large academic ED. Results: Nurses working in a busy ED appear to reduce their walking distance by batching their tasks to distant patient rooms. Although the patients in these rooms receive the same amount of care time, this behavior results in longer wait times between nurse visits and more nurse call button activations, but it does not compromise the overall quality of care delivered. Nurse call button use is linked with poor patient satisfaction and interrupts nurse workflow. Managerial implications: These findings show that even in services, facility layout can lead to servers using task timing discretion in ways that help the server but lead to a additional waiting time for the customer. We propose countering the negative effects of distance-based task batching through proactive nurse rounding and operational transparency.