Mean Turnover Time Research Articles

Threshold transient growth as a criterion for turbulent mean profiles

Lozano-Duran et al. (J. Fluid Mech., vol. 914, 2021, p. A8) have recently identified the ability of streamwise-averaged turbulent streak fields ${\mathcal {U}}(y,z,t)\hat {\boldsymbol {x}}$ in minimal channels to produce short-term transient growth as the key linear mechanism needed to sustain turbulence at $Re_{\tau }=180$ . Here, in an attempt to extend this result to larger domains and higher $Re_{\tau }$ , we model this streak transient growth as a two-stage linear process by first selecting the dominant streak structure expected to emerge over the eddy turnover time on the turbulent mean profile $U(y)\hat {\boldsymbol {x}}$ , and then examining the secondary growth on this (frozen) streak field ${\mathcal {U}}(y,z)\hat {\boldsymbol {x}}$ . Choosing the mean streak amplitude and eddy turnover time consistent with simulations captures the growth thresholds found by Lozano-Duran et al. (2021) for sustained turbulence. In a larger domain at $Re_{\tau }=180$ , the most energetic near-wall streaks observed in simulations are close to the predicted optimal streaks. This most energetic streak spacing, approaches the optimal streak at $Re_{\tau }=550$ where the secondary growth possible on each also comes together. A key prediction from the model is that the threshold transient growth required to sustain turbulence decreases with increasing $Re_{\tau }$ . More fundamentally, the work of Lozano-Duran et al. (2021) and our results suggest a subtle but significant revision of Malkus's (J. Fluid Mech., vol. 1, 1956, pp. 521–539) classic hypothesis concerning realisable turbulent mean profiles. The key property for a realisable turbulent mean profile could be the ability to generate sufficient short-term transient growth rather than dependence on its (long-term) linear stability characteristics, which was Malkus's original idea.

Isotopic labeling evidence shows faster carbon release from microbial residues than plant litter

Abstract Carbon (C) release from plant and microbial residues is a primary pathway of energy flow from photosynthetic and metabolic biomass to carbon dioxide (CO2) in terrestrial ecosystems. Traditional view show that microbial residue C is more resistant to decompose than plant litter because their smaller particle sizes could be preferentially occluded in microaggregates with less microbial accessibility. However, we still lack a quantitative assessment (i.e. isotopic C labeling) to isolate the progressive release of C fractions from both plant and microbial residues. Here we used a global data set of 117 decomposition experiments that traced the 13C or 14C release of isotopically labeled plant and microbial residues to estimate the C release rates and turnover times by using a first-order exponential kinetics model. The average C release rates of crop, grass and tree litter were 7.78, 3.79 and 2.11 yr−1, which were significantly lower than microbial residues (13.07 yr−1). Although C release rates of both plant and microbial residues were positively correlated with site temperature, the mean turnover time of microbial residues was 2–6 times lower than plant litter. We suggest that a constraint in microbial and plant residues leads to a predictable pattern of C release during terrestrial decomposition, which could be included in Earth system models.

First Reported Series of Cerebral Angiography Performed at an Outpatient Center: Safety and Satisfaction Results.

Ambulatory surgery centers (ASCs) are increasingly common venues for same-day neurosurgical procedures, allowing for cost-effective, high-quality patient care. We present the first and largest series of patients undergoing diagnostic cerebral angiography at an ASC to demonstrate the effectiveness, safety, and efficiency of outpatient endovascular care. We retrospectively reviewed data for consecutive patients who underwent diagnostic cerebral angiography at our ASC between January 1, 2024, and May 29, 2024. Data collected included vascular access approach, procedural duration, turnover time, and periprocedural complications. Using a standardized 2-week postprocedural survey, patients were asked to provide comments and rate their subjective satisfaction from a 1 to 5 scale, with "5" being completely satisfied. All cases were performed with a physician team comprising 1 attending neuroendovascular neurosurgery and 1 neuroendovascular fellow present. Fentanyl and midazolam were administered for conscious sedation in all cases. Among the 67 patients included in this series, the mean procedural duration was 29.4 ± 8.6 minutes. The mean turnover time was 13.7 ± 3.6 minutes. Between transradial (46 of 67 [68.7%]) and transfemoral (21 of 67 [31.3%]) access site approaches, there were no statistically significant differences in mean procedural duration (29.4 ± 8.0 vs 29.2 ± 9.9 minutes, respectively; P = .72) or turnover time (14.0 ± 3.9 vs 12.9 ± 2.8 minutes, respectively; P = .4). No complications occurred periprocedurally or within the 2-week follow-up period. A total of 48 (71.6%) of 67 patients responded to the postprocedural survey, all of whom unanimously reported a score of "5." We found that diagnostic cerebral angiography performed at our ASC was safe and effective for patient care. In addition, all survey respondents (71.6% of those provided the survey) reported highest levels of satisfaction. The integration of neuroendovascular procedures into ASCs potentially offers a cost-effective and highly efficient option in an evolving economic landscape.

Boosting efficiency in the endoscopy suite: integrating team workflows improves productivity and minimizes cost

Inefficiencies in the endoscopy suite cause frustration for physicians, hospital administrators, staff, and patients. Turnover time (TOT), the time between one case ending and another beginning, is subjectively disproportionate between various team members. We aimed to define perceptions of TOT and target steps within the process to improve efficiency. This was a prospective cohort study at a tertiary center outpatient endoscopy unit. Phase I aimed to identify the TOT process components based on time stamps in the electronic medical record (N= 686). We defined gastroenterologist perceived TOT (pTOT), anesthesia pTOT, and standard TOT (sTOT). TOT length was calculated for each subgroup. Patient transport was identified as an intervenable target. In Phase II, the task of patient transport moved from the anesthesiology team to endoscopy nurses. Mean TOT and proportion of cases with sTOT<15 minutes' preintervention (n= 2192) and postintervention (n= 292) were compared. Seven key TOT components were identified that explain variations in pTOT. Average anesthesia pTOT was 15 minutes, whereas average gastroenterologist pTOT was 34 minutes (25.9% vs 57.2% of case length; P= .0007). In Phase II, mean sTOT improved from 18.51 to 14.25 minutes (P< .0001), and proportion of sTOT within 15 minutes improved from 41.79% to 58.90% (P< .0001). This intervention saved 45 minutes per room per day, allowing for a revenue potential of more than $300,000 per year per procedure room. This study defines variations in TOT and shows that finding imbalances and sharing the workload significantly cuts costs and improves the overall efficiency of the different subgroups in the turnover process.

Optimising operating theatre (OT) efficiency while maintaining the standardised patient care in adolescent idiopathic scoliosis (AIS) surgery with the dedicated spine team approach: a specialised spine unit experience.

To report the efficiency of OT utilisation and perioperative outcomes with a dedicated spine team approach in AIS patients who underwent posterior spinal fusion (PSF) surgeries in a consecutive case operation list. Three AIS patients operated in a day (8:00AM-8:00PM) by a dedicated spine team were recruited between 2021 and 2022. The dedicated team comprised of three senior spine consultants who operated using a dual attending surgeon strategy, an anaesthetic consultant, dedicated surgical scrub nurses, anaesthesiology nurses, radiographers, and neuromonitoring technicians. Patients were categorised according to the sequence of operation list of the day (Case 1, Case 2, and Case 3). OT efficiency was represented by OT time in five stages (preoperative time, operative time, postoperative time, total OT time, and turnover time). OT time and perioperative outcomes were compared. 102 cases were analysed. On average, Case 1 began at 8:38AM whereas Case 3 ended by 5:54PM. OT efficiency was consistent throughout the day of operation with comparable OT time in all five stages between groups (p > 0.05). The mean turnover time was 15.1 ± 13.5min and themean operative time was 123.0 ± 28.1min. Intraoperative arterial blood gas (ABG) parameters were maintained in an optimal range. Thecomplication rate was 2.0% (N = 2/102). Consistent OT efficiency was demonstrated with a dedicated spine team approach. Despite performing three AIS cases in a consecutive case operation list, patients' safety was not compromised as perioperative outcomes between groups were comparable.

Scheduling and Vendor Consistency Improves Turnover Time Efficiency in Total Joint Arthroplasty

BackgroundMaximizing operative room (OR) efficiency is important for hospital efficiency, patient care, and positive surgeon and staff morale. Reducing turnover time (TOT) has become a popular focus to improve OR efficiency. The present study evaluated if TOT is influenced by changing case type, implant vendor, and/or laterality. MethodsIn total, 444 turnovers from January to July 2023 were retrospectively analyzed. All turnovers were same-surgeon turnovers between primary arthroplasty cases in dedicated, overlapping rooms. Single linear regression models tested the predictability of TOT based on case type, vendor, and laterality. A multivariate multiple regression and 1-way Analyses of Variance analyzed variables against each other. Independent sample t-tests evaluated TOTs when all variables were the same or different. ResultsChanging versus keeping the same case type increased TOT by 2.4 minutes (95% confidence interval [CI] = 0.7, 4.0; P = .004). Changing vendors increased TOT by 2.9 minutes (95% CI = 1.1, 4.7; P = .002). Laterality did not affect TOT, with a change of 0.9 minutes (95% CI = −0.6, 2.5; P = .229). Vendor (P = .030) independently predicted TOT when analyzed as a covariate with case type (P = .410). The TOT with same case type and vendor (mean 38.2 minutes; range, 22 to 62) was less than that of different case types and vendors (mean 41.4 minutes; range, 26 to 73) (P = .017). Mean TOT differed by 5.5 minutes when keeping all variables the same versus all different (P = .018). ConclusionsMaintaining a consistent case type, vendor, and laterality had a synergistic effect in reducing TOT in arthroplasty ORs with the same primary surgeon running 2 overlapping rooms. Changing vendor representatives was found to independently predict TOT increases, which is likely attributed to a disruption in workflow and collaboration of the multidisciplinary OR team. Level of EvidenceLevel III.

Biotic and Abiotic Factors Controlling Spatial Variation of Mean Carbon Turnover Time in Forest Soil

AbstractSoil carbon persistence in forests plays a pivotal role in regulating terrestrial feedback to climate change. However, the relative contributions of biotic and abiotic factors in controlling geographic variation of forest soil carbon turnover time (τsoc) remains unclear. Here, we first sampled soils from 12 permanent forest plots across eastern China and detected higher radiocarbon‐derived mean turnover time of soil organic carbon in the deep (30–100 cm; 2,087 ± 246 years) than the surface (0–30 cm; 249 ± 80 years) layer. Further analyses based on the partial Mantel test and structural equation model illustrated that the interactions of climate, vegetation, and soil factors are more complex in deep than surface soils. Then, we established a global database of radiocarbon‐derived τsoc from 1897 forest soil samples. On the global scale, τsoc was significantly higher in the deep (3,081 ± 398 years) than the surface (332 ± 56 years) layer. Soil depth alone explained 11.7% of the spatial variation in τsoc, and the interactions between climate, stand age, and soil depth account for 68.6% of the variation. These findings highlight the joint control of climate, vegetation, and soil depth in the spatial variation of soil carbon persistence in global forests.

An evaluation of topsoil carbon storage in Chinese deserts

Deserts are important components of the terrestrial ecosystem, and significantly affect the terrestrial carbon cycle. However, their carbon storage is poorly understood. To evaluate the topsoil carbon storage in Chinese deserts, we systematically collected topsoil samples (to a depth of 10 cm) from 12 deserts in northern China and analyzed their organic carbon storage. We used partial correlation and boosted regression tree (BRT) analysis to analyze the factors influencing the spatial distribution of soil organic carbon density based on climate, vegetation, soil grain-size distribution, and element geochemistry. The total organic carbon pool of Chinese deserts was 4.83 × 108 t, the mean soil organic carbon density was 1.37 ± 0.18 kg C m−2, and the mean turnover time was 16.50 ± 2.66 yr. With the largest area, the Taklimakan Desert had the highest topsoil organic carbon storage (1.77 × 108 t). The organic carbon density was high in the east and low in the west, whereas the turnover time showed the opposite trend. The soil organic carbon density was >2 kg C m−2 in the four sandy lands in the eastern region, and was greater than the values for the eight deserts (0.72 to 1.22 kg C m−2). Grain-size (i.e., the silt and clay contents) had the strongest influence on the organic carbon density in Chinese deserts, followed by element geochemistry. Precipitation was the main climatic factor that affected the distribution of organic carbon density in the deserts. Based on climate and vegetation cover trends during the past 20 years, Chinese deserts have a high potential for future organic carbon sequestration.

Consecutive Surgeon and Anesthesia Team Improve Turnover Time in the Operating Room.

Efficient management of the operating room (OR) contributes to much of today's healthcare expenditure and plays a critical role in generating revenue for most healthcare systems. Scheduling of OR cases with the same team and surgeon have been reported to improve turnover time between cases which in turn, improves efficiency and resource utilization. We aim to assess different operating room procedures within multiple subspecialties and explore the factors that positively and negatively influence turnover time (TOT) in the operating room. We conducted a retrospective review of cases that were completed on weekdays between 0600 and 2359 from July 2017 through March 2018. Cases between 0000 and 0559 were excluded from this study. Of the total 2,714 cases included in our study, transplant surgery had the highest mean TOT (71 ± 48min) with orthopedic surgery cases without robots having the lowest mean TOT. OR cases in rooms with the same specialty had significantly less mean TOT compared to rooms switching between different subspecialties (70 vs. 117min; p < 0.0001). Similarly, cases with the same surgeon and anesthesia team had a significant lower TOT (p < 0.0001). Consecutive specialty, surgeon, anesthesiologist, and prior procedure ending before 15:00 were all independent predictors of lower TOT (p < 0.0001). Our study shows scheduling cases with the same OR team for elective cases can decrease TOT and potentially increase operating room efficiency during the day. Further studies may be needed to assess the long-term effects of such variables affecting OR TOT on healthcare expenditure.

Triple-isotope mass balance of mid-latitude, groundwater controlled lake

Lakes constitute an important part of the hydrological cycle on continents. Recent developments in high-resolution laser spectroscopy made feasible triple-isotope, high-precision analyses of water samples (δ2H, δ18O and δ17O). We conducted in-depth, comprehensive assessment of the potential and usefulness of the triple-isotope mass balance approach to quantify water budget of lakes and surface water bodies. A small, groundwater-controlled lake located in the vicinity of Krakow, southern Poland, was selected for this purpose. Approximately 30% higher incoming and outgoing groundwater fluxes derived from 2H-based budget, when compared to 18O- and 17O-based budgets, were obtained when isotopic composition of ambient moisture interacting with the lake was assumed to be in isotopic equilibrium with the local precipitation. Since the ambient moisture interacting with a given lake is in fact a mixture of the vapour released by the evaporating surface water body and the free-atmosphere water vapour, we proposed the procedure to calculate the isotopic composition of this mixture. This approach led to fully consistent triple-isotope mass balance of the studied lake. The underground water fluxes derived separately for the three isotope tracers in use (2H, 18O and 17O) turned out to be identical within the quoted uncertainties, thus supporting internal consistency of the obtained results. The magnitude of the calculated fluxes was in the order of 3200 mm year−1 for the incoming groundwater flux and 3100 mm year−1 for underground losses of lake water through seepage to the local aquifer. The calculated mean turnover time of water in the studied lake is only ca. 16 months, which guarantees a good quality of lake water, a critical parameter in the light of intensive exploitation of this lake as a popular recreational destination during summer.

Lean approach to the management of patients undergoing intravitreal injections during COVID-19 pandemic.

Background:To introduce Lean approach principles in the management of patients undergoing intravitreal injections (IVIs) for wet age-related macular degeneration.Methods:Retrospective single-centre cohort study. Services location, IVIs scheduling, utilization of staff, data recording methods, ophthalmic examination and surgical procedures were analysed; a new Intravitreal Injection Centre (IVIC) was developed according to Lean principles. Mean number of daily IVIs performed, mean time between registration and discharge, mean turnover time in between patients, percentages of performed IVIs on the monthly scheduled IVIs and of patients rating their experience ⩾8/10 via standardized feedback questionnaires were retrospectively analysed.Results:The mean IVIs number per day increased from 20 ± 4.08 to 50 ± 7.07, and the mean time between registration and discharge of a patient decreased from 240 ± 14.14 to 60 ± 8.16 min (p = 0.00057 and p < 0.00001, respectively). Mean turnover time in between patients decreased from 10 ± 1.41 to 8 ± 2 min (p = 0.055). The percentage of monthly IVIs performed on the total of scheduled IVIs increased from 60% to 100%, and the percentage of satisfied patients who rated IVIC ⩾8/10 increased from 45% to 95% (p = 0.0177 and p < 0.00105, respectively).Conclusion:The IVIC improved the quality, efficiency, speed of the overall procedures and clinical capacity of the IVI service through a fast one-way route for patients, limiting time wasted and total distance travelled. This model facilitates the creation of a one-stop clinic through the just-in-time management principle and may be relevant to other ophthalmology services.

Kinetics of Allosteric Inhibition of Single Enzyme by Product Molecules.

Single-molecule experiment probed the catalytic conversions of Amplex Red to resorufin by horseradish peroxidase in which the product molecules were found to act as the allosteric inhibitor for the individual enzyme. While broad distributions of the initial reaction velocities and the number of product molecules required to cease the reaction unraveled the underlying dynamic disorder in the reaction pathway, bulk experimental measurements established the particularity of noncompetitive inhibition of the enzyme species. In this work, to rationalize the observed phenomena, we present a stochastic kinetic model of the enzymatic reaction taking into account the inhibitions of the enzyme and enzyme-substrate complex in the circumstance of their structural fluctuations. Starting from a chemical master equation that can further be reduced into a set of ordinary differential equations for the case of single-enzyme kinetics, we derived an analytical expression for the turnover time distribution, the first moment of which yielded the mean turnover time. The inverse of the latter showed excellent agreement with the bulk data of the initial enzymatic velocities measured in the presence of varying inhibitor concentrations. This supports the observed nature of inhibition which we further confirmed by constructing double-reciprocal plots for the inhibited kinetics. In addition, we successfully recovered ensemble data from another experiment that redesigned the aforesaid single-molecule catalysis to investigate the effects of molecular crowders on reaction velocity; the latter was greatly alleviated with increasing the molecular weight of the crowders. On the other hand, the calculated randomness parameter, determined from the higher moment of the turnover time distribution, clearly inferred dynamic disorder in the catalytic turnovers. Our work under a unified framework provides a robust theoretical description for the experimental kinetic study and eradicates the necessity of assuming an alternative mode of inhibition in analyzing the data, not consistent with the experiments, considered earlier.

Impact of a Preoperative Safety Checklist on Perioperative Quality Outcomes and Operative Efficiency.

Additional preoperative safety checklist requirements at Penn State Health were recently implemented on the morning of surgery. We evaluate whether this added safety policy impacted reported adverse patient safety events and institutional operating room performance indicators. Key operating room performance indicators from fiscal years 2016 through 2019 quarter 2 were reviewed. Additional attestation requirements by the attending surgeon were implemented at start of fiscal year 2018 (July 1, 2017). All reported perioperative patient safety events during this time were reviewed with events classified into one of 8 select categories. Total operative case volume was 49,894 cases in fiscal years 2016 and 2017, and 36,533 in fiscal years 2018 and 2019 through quarter 2 (p <0.10). Mean operating room use was 81% in both groups (p <0.46). First case on time start rates decreased from 79.5% to 58%, respectively (p <0.0001). Mean turnover time between cases also increased from 35 minutes to 40 minutes, respectively (p <0.0001). There were 252 patient events (0.51%) in fiscal years 2016 and 2017 compared to 94 (0.26%) events in fiscal years 2018 and 2019 through quarter 2 following implementation of the surgical safety checklist (p <0.0001). The number of incomplete preoperative checklists (39 vs 14, p=0.008) and missing/incomplete patient identification bands (15 vs 2, p=0.004) were also decreased between fiscal years 2016 and 2017, and fiscal years 2018 and 2019 through quarter 2, respectively. A day-of-surgery safety checklist decreased the number of reported patient safety events but with a negative impact on standard metrics of operating room productivity for 18 months following implementation. Further study is necessary to determine if these effects persist over time.

Analysis of operating room efficiency between a hospital-owned ambulatory surgical center and hospital outpatient department

BackgroundAmbulatory surgery centers (ASCs) are frequently utilized; however some ambulatory procedures may be performed in hospital outpatient departments (HOPs). Our aim was to compare operating room efficiency between our ASC and HOP. MethodsWe reviewed outpatient general surgery procedures performed at our ASC and HOP. Total case time was divided into five components: ancillary time, procedure time, exit time, turnover time, and nonoperative time. ResultsOverall, 220 procedures were included (114 ASC, 106 HOP). Expressed in minutes, the mean turnover time (29.8 ± 9.6 vs. 24.5 ± 12.7; p < 0.01), ancillary time (32.2 ± 7.0 vs. 22.2 ± 4.5; p < 0.01), procedure time (77.4 ± 44.9 vs. 56.2 ± 23.0 p < 0.01), exit time (11.8 ± 4.4 vs. 8.5 ± 4.3; p < 0.01), and nonoperative time (62.9 ± 21.9 vs. 48.7 ± 15.0; p < 0.01) were longer at the HOP than at the ASC. ConclusionASC outpatient procedures are more efficient than those performed at our HOP. A system evaluation of our HOP operating room efficiency is necessary.

Smoke radiocarbon measurements from Indonesian fires provide evidence for burning of millennia-aged peat

In response to a strong El Niño, fires in Indonesia during September and October 2015 released a large amount of carbon dioxide and created a massive regional smoke cloud that severely degraded air quality in many urban centers across Southeast Asia. Although several lines of evidence indicate that peat burning was a dominant contributor to emissions in the region, El Niño-induced drought is also known to increase deforestation fires and agricultural waste burning in plantations. As a result, uncertainties remain with respect to partitioning emissions among different ecosystem and fire types. Here we measured the radiocarbon content (14C) of carbonaceous aerosol samples collected in Singapore from September 2014 through October 2015, with the aim of identifying the age and origin of fire-emitted fine particulate matter (particulate matter with an aerodynamic diameter less than or equal to 2.5 μm). The Δ14C of fire-emitted aerosol was -76 ± 51‰, corresponding to a carbon pool of combusted organic matter with a mean turnover time of 800 ± 420 y. Our observations indicated that smoke plumes reaching Singapore originated primarily from peat burning (∼85%), and not from deforestation fires or waste burning. Atmospheric transport modeling confirmed that fires in Sumatra and Borneo were dominant contributors to elevated PM2.5 in Singapore during the fire season. The mean age of the carbonaceous aerosol, which predates the Industrial Revolution, highlights the importance of improving peatland fire management during future El Niño events for meeting climate mitigation and air quality commitments.

Building up the soil carbon pool via the cultivation of green manure crops in the Loess Plateau of China

The growth of summer legumes as green manures (GM) may influence the soil C pool, thereby affecting soil quality and productivity in a traditional cropping system. However, there is a lack of research on whether the inclusion of GM crops enhances the C economy under semiarid conditions. An ongoing field experiment was conducted on Cumulic Haplustoll in the northwest region of China to (i) quantify the biomass C release patterns of three GM legumes; (ii) evaluate the effect of the GM legumes on the soil organic carbon (SOC) stock (0–20 cm depth), and (iii) estimate the soil C dynamics for the GM systems under semiarid conditions in more detail. The results showed that the percentages of the remaining GM C in the soil after one year of decomposition averaged 26% and 33% for the above-ground and below-ground residues, respectively. Thus, the 5-yr growth of GM legumes continuously significantly improved the SOC and easily oxidized organic carbon (EOOC) concentrations, as well as the corresponding stocks (except for soybean) (P < 0.01), compared with the original soil at the 0–20 cm depth. We estimated the annual decomposition rate of SOC as 1%, and the C added by the crops that remained in the SOC as 23% each year using the one-compartment model. The mean turnover time of the SOC at equilibrium was estimated to be 22 years, indicating that the loess soil was not C saturated and still had the potential for C sequestration. In general, Huai bean performed better on biomass production, C accumulation, and soil C sequestration than mung bean and soybean under the dryland conditions during the 5-yr period of this study. Consequently, the cultivation of leguminous GM during the summer is a better option than bare fallow to improve the soil fertility and environmental sustainability not only in the Loess Plateau of China but also in other similar dryland regions.

Tardiness of starts of surgical cases is not substantively greater when the preceding surgeon in an operating room is of a different versus the same specialty

Study objectiveSwitching from one specialty to another increases mean turnover times (i.e., interval between the exit and entrance of consecutive patients in an operating room [OR]). We estimate the effect on the mean tardiness of to-follow surgeons from following another surgeon of a different versus same specialty. Tardiness of a case's start time refers to the number of minutes the patient enters the OR later than scheduled; tardiness is 0 min if the patient enters early. Tardiness cause surgeon waiting. There are multiple causes of tardiness, but, most often, the preceding case(s) took longer than estimated. Design10-year historical cohort study with all surgical cases performed during regular workdays. SettingLarge teaching hospital. MeasurementsEstimated OR end times were calculated using a Bayesian method. Because tardiness is influenced by the estimated case start time (i.e., later starting cases have greater tardiness), tardiness values were adjusted to a 12 noon start time for the 2nd surgeon. Main resultsThe cases of to-follow surgeons in ORs had mean tardiness of 45.1 (SE 0.6) min. When the to-follow surgeon in the OR was of a different versus the same specialty from the first surgeon, the mean turnover time was 7.3 (0.4) min longer (P < 0.00001). However, the mean tardiness was not significantly affected (0.1 min, 95% confidence interval [CI] −2.7 to 3.0 min; P = 0.93). In comparison, if one or more of the preceding cases in an OR was an add-on case, the increase in mean tardiness was 35 min (95% CI 28 to 43 min; P < 0.00001). ConclusionsOR managers can assure surgeons with afternoon starts that following a surgeon of a different specialty generally will not increase their waiting time. Case scheduling should focus on reducing over-utilized OR time and thus the hours that anesthesiologists and nurses work late.

Production and turnover of microbial organic matter in surface intertidal sediments

Benthic microorganisms play a significant role in the remineralization of sedimentary organic matter (OM). In order to constrain the growth rate, turnover and carbon metabolism of microbial communities in anoxic sandy sediments, we quantified the rate of inorganic carbon (IC) assimilation and of lipid production via a recently developed dual isotope-labelling assay that can differentiate autotrophic vs. heterotrophic production in a 22 cm sediment core from the Janssand tidal flat (Wadden Sea, Germany). Despite an extremely low concentration of total organic carbon (TOC) in the majority of samples (<0.3%), the concentration of total fatty acids (TFAs) was in the range 4.5 to 28.4 μg/mg TOC, suggestive of a high contribution of fresh microbial and algal biomass to the TOC pool. This was corroborated by a production rate of microbial FAs, which ranged from 0.3 to 4.7 μg TFAs/gdw/yr (where dw = dry wt) and the mean turnover time of microbial FAs was 6 ± 5 yr. The enhanced production rate of iso- and anteiso-branched FAs was consistent with the presence of an active population of sulfate reducing Deltaproteobacteria. The assimilation rate of IC into bacterial lipids was relatively low (0.16 ± 0.07 μg C/gdw/yr) in OM-lean sandy sediments (i.e. upper 17 cm), such that the IC assimilation to lipid production ratio values was typically <0.3, indicating that heterotrophic bacteria were dominant and dark IC fixation played a minor role at the study site. The measured rates of FA production converted to an anaerobic heterotrophic C demand of 0.4–1.8 µg C/gdw/d, assuming a bacterial growth efficiency of 10%. Such high biomass proportion, production rate and C demand suggested that dissolved OM must play a vital role in sustaining the active heterotrophic microbial populations in these sandy sediments.

Single-Molecule Kinetics of an Enzyme in the Presence of Multiple Substrates.

Herein, the catalytic activity of a single enzyme in the presence of multiple substrates is studied. Three different mechanisms of bisubstrate binding, namely, ordered sequential, random sequential and ping-pong nonsequential pathway, are broadly discussed. By means of the chemical master equation approach, exact expressions for the waiting-time distributions, the mean turnover time and the randomness parameter as a function of the substrate concentration, such that both concentrations are fixed, but one of them is changed quasi-statically are obtained. The randomness parameter is not equal to unity at intermediate to high substrate concentrations, which indicates the presence of multiple rate-limiting steps in the reaction pathway in all three modes of bisubstrate binding. This arises due to transitions between the free enzyme and the enzyme-substrate complexes that occur on comparable timescales. Such turnover statistics of the single enzyme can also distinguish between the different types of bisubstrate binding mechanisms.

A modified collaborative model to improve surgical flow health care processes in Veterans Affairs Medical Centers

The Veterans Health Administration (VHA) Office of Systems Redesign and Improvement, in collaboration with the VHA National Surgery Office and Veterans Affairs Center for Applied Systems Engineering (VA-CASE) - Veterans Engineering Resource Center (VERC), conducted a national process improvement initiative in Fiscal Year 2012 to promote more effective and efficient use of surgical unit resources. This improvement effort adopted a modified collaborative model with the incorporation of symposia and Rapid Process Improvement Workshops (RPIWs) to address concerns from collaborative teams for a more efficient surgical flow. Throughout the seven-month duration of the initiative, 20 teams participated and completed a total of 468 Plan-Do-Study-Act (PDSA) cycles to implement changes and improve performance levels in defined measures. At the conclusion, on average, teams were able to improve performance on the first case on-time start rate by 24%, mean turnover time by 14%, cancellation rate by 5%, and Operating Room (OR) utilization by 8%. The projected annual Cost Savings was estimated to be nearly $25 million. This modified improvement model overcame some of the challenges experienced in a traditional improvement collaborative model such as lack of clarity of clear roles and responsibilities of team members and clear and consistent aims. The operations in surgical flow were improved in multiple ways to achieve overall better performance. Future improvement initiatives have the potential to further enhance performance outcomes by focusing even more efforts on the preparation phase, increasing team participation and leadership buy-in, utilizing on-going reports that track team progress and focusing on sustain and spread.