bluuebunny/crossref_metadata_2025 huggingface dataset:
The critical closing pressure contribution to dynamic cerebral autoregulation in humans: influence of arterial partial pressure of CO2
Authors: Panerai Ronney B. , Minhas Jatinder S. , Llwyd Osian , Salinet Angela S. M. , Katsogridakis Emmanuel , Maggio Paola , Robinson Thompson G
Published: September 2020

Key points

Dynamic cerebral autoregulation (CA) is often expressed by the mean arterial blood pressure (MAP)–cerebral blood flow (CBF) relationship, with little attention given to the dynamic relationship between MAP and cerebrovascular resistance (CVR).

In CBF velocity (CBFV) recordings with transcranial Doppler, evidence demonstrates that CVR should be replaced by a combination of a resistance–area product (RAP) with a critical closing pressure (CrCP) parameter, the blood pressure value where CBFV reaches zero due to vessels collapsing.

Transfer function analysis of the MAP–CBFV relationship can be extended to the MAP–RAP and MAP–CrCP relationships, to assess their contribution to the dynamic CA response.

During normocapnia, both RAP and CrCP make a significant contribution to explaining the MAP–CBFV relationship.

Hypercapnia, a surrogate state of depressed CA, leads to marked changes in dynamic CA, that are entirely explained by the CrCP response, without further contribution from RAP in comparison with normocapnia.

Dynamic cerebral autoregulation (CA) is manifested by changes in the diameter of intra‐cerebral vessels, which control cerebrovascular resistance (CVR). We investigated the contribution of critical closing pressure (CrCP), an important determinant of CVR, to explain the cerebral blood flow (CBF) response to a sudden change in mean arterial blood pressure (MAP). In 76 healthy subjects (age range 21–70 years, 36 women), recordings of MAP (Finometer), CBF velocity (CBFV; transcranial Doppler ultrasound), end‐tidal CO2 (capnography) and heart rate (ECG) were performed for 5 min at rest (normocapnia) and during hypercapnia induced by breathing 5% CO2 in air. CrCP and the resistance–area product (RAP) were obtained for each cardiac cycle and their dynamic response to a step change in MAP was calculated by means of transfer function analysis. The recovery of the CBFV response, following a step change in MAP, was mainly due to the contribution of RAP during both breathing conditions. However, CrCP made a highly significant contribution during normocapnia (P < 0.0001) and was the sole determinant of changes in the CBFV response, resulting from hypercapnia, which led to a reduction in the autoregulation index from 5.70 ± 1.58 (normocapnia) to 4.14 ± 2.05 (hypercapnia; P < 0.0001). In conclusion, CrCP makes a very significant contribution to the dynamic CBFV response to changes in MAP and plays a major role in explaining the deterioration of dynamic CA induced by hypercapnia. Further studies are needed to assess the relevance of CrCP contribution in physiological and clinical studies.
Boundary Layer Flashback Model for Hydrogen Flames in Confined Geometries Including the Effect of Adverse Pressure Gradient
Authors: Björnsson Ólafur H. , Klein Sikke A. , Tober Joeri
Published: September 2020

The combustion properties of hydrogen make premixed hydrogen-air flames very prone to boundary layer flashback. This paper describes the improvement and extension of a boundary layer flashback model from Hoferichter et al. (2017, “Prediction of Confined Flame Flashback Limits Using Boundary Layer Separation Theory,” ASME J. Eng. Gas Turbines Power, 139(2), p. 021505) for flames confined in burner ducts. The original model did not perform well at higher preheat temperatures and overpredicted the backpressure of the flame at flashback by 4–5×. By simplifying the Lewis number-dependent flame speed computation and by applying a generalized version of Stratford's flow separation criterion (Stratford, 1959, “The Prediction of Separation of the Turbulent Boundary Layer,” J. Fluid Mech., 5(1), p. 1), the prediction accuracy is improved significantly. The effect of adverse pressure gradient flow on the flashback limits in 2 deg and 4 deg diffusers is also captured adequately by coupling the model to flow simulations and taking into account the increased flow separation tendency in diffuser flow. Future research will focus on further experimental validation and direct numerical simulations to gain better insight into the role of the quenching distance and turbulence statistics.
Thermal Properties Measurement of Particulate Fouling Samples of Air-Cooled Heat Exchangers Using Laser Flash Method
Authors: Sharma Arjun , Islam M. D. , Hajri Ebrahim Al
Published: September 2020

Fouling is one of the major factors that drastically affects heat exchanger performance. Especially in Middle East where most of the heat exchangers are air cooled due to scarcity of water. As these heat exchangers are placed in a harsh climate, they are at high risk of low performance due to dusty/sticky particulate fouling. In order to identify possible active/passive methods to control or ideally eliminate particulate fouling, it is desirable to know exact thermophysical properties of such particulate fouling. This study presents thermophysical property characterization of selected fouling samples from eight different fin fan heat exchangers installed in an oil & gas facility in the Middle East. Laser flash Analysis (LFA) method is a well-known technique for measurement of the thermophysical properties: thermal diffusivity, specific heat and thermal conductivity of materials. A new technique was developed to prepare powder particulate fouling samples to make them as disc shaped samples while maintaining the range of ± 12 mm diameter and ± 2 mm thickness. The LFA measurements was conducted using LFA 447 Nano Flash Netzsch over the temperature range from 25 °C to 125°C. The thermal diffusivity was measured with an accuracy of ± 3% and the specific heat capacity with an accuracy of ± 5%. As the thermal conductivity is a product of these two measured values, is calculated with an accuracy of ± 5.8% and the measurement repeatability was within 2%.
Comparison of Sweeping Gas and Direct Contact Membrane Distillation: Module Length Effect
Authors: Alqsair Umar F. , Alshwairekh Ahmed M. , Alwatban Anas M. , Krysko Robert , Oztekin Alparslan
Published: September 2020

Computational fluid dynamics simulations are conducted to compare the effect of module length in sweeping gas and direct contact membrane distillation systems for seawater desalination processes. In this work, the effect of temperature and concentration on the flux performance and temperature and concentration polarization characteristics are studied. CFD simulations are conducted in a three-dimensional module to characterize the steady-state velocity, temperature, and concentration field in the feed and permeate channel. The Reynolds number for the feed and the permeate stream is set to 500 and 1500, and thus the laminar flow model is adapted for each channel. The membrane properties are fixed in all cases considered. It is revealed that the local variation of the vapor flux, TPC, and CPC varies with module length in SGMD systems. However, the average values along the membrane in both module lengths do not vary much. Remedies for mitigating temperature polarization should be considered for future studies.
Study on Design Optimization of Fire Smoke Control Modes for Subway Transfer Channel With Ceiling Beams
Authors: Tian Xiangliang , Liu Chang , Zhong Maohua
Published: September 2020

In order to study the optimization modes of smoke control in the case of fire in metro transfer channel, a full-scale numerical station model with a single transfer channel is established. In case of fire, the influencing of ceiling beam, vent size on smoke control effect are analyzed. The ceiling temperature profile, CO concentration, visibility and smoke layer height under different conditions were studied to evaluate the smoke control effect of transfer channel and station hall. Based on this, the optimization suggestions of ventilation and smoke exhaust system design and smoke control modes for transfer channel are put forward. The results show that, the ceiling beams can effectively delay the speed of smoke diffusion and gain time for personnel escape and emergency rescue. The vent size has a great influence on the ventilation and smoke exhaust effect under the condition of meeting the designed ventilation capacity. Among the three common vent sizes listed in this research, the smaller the size is, the better the smoke control effect is. The length and width of vent with best smoke control effect are 1.2 m and 0.8m respectively.
Performance Improvement of Mass Transfer Through Membrane Using Ultrasound for HVAC Application
Authors: Gurubalan A. , Geoghegan Patrick J. , Maiya M. P. , Simonson Carey J.
Published: September 2020

Liquid desiccant dehumidification is one of the energy-efficient alternatives to conventional air conditioning systems for humidity control. Membrane dehumidifier is preferred to avoid the desiccant carryover, which occurs in a conventional packed bed dehumidifier. However, its mass transfer performance is lesser than that of the packed bed dehumidifier. This is due to additional mass transfer resistance of the membrane between the air and desiccant. It is found that the resistance by the boundary layer formed at the membrane-air interface accounts for a significant portion of the overall mass transfer resistance. Breaking of such boundary layer using ultrasound is an attractive technique to reduce the resistance. The present study experimentally investigates the influence of ultrasound on the mass transfer performance of a membrane humidifier. Subsequently, with the experimental results of the humidifier, the effect of ultrasound on the performance of the membrane dehumidifier is numerically studied. The performances of humidifier and dehumidifier are presented in terms of moisture addition or removal rate and latent effectiveness. It is found that the vibration due to ultrasound enhances the performance of the membrane dehumidifier by 1.5 times.
Analytical Model of the Soil Temperature Distribution Based on Weather Data
Authors: Reda M. Naser , Spinnler Markus , Mahamud Rajib , Sattelmayer Thomas
Published: September 2020

The measurement of soil temperature profiles for different locations or climates is essential for calculating the thermal performance of applications connected with the soil, e.g., underground heat storage systems. Estimating soil temperature profiles is identified as crucial knowledge for plant and crop growth as well as for germination in all agricultural tasks. The ground temperature depends on weather conditions (ambient temperature, solar irradiation, wind velocity, sky radiation, etc.) that contribute to the resulting temperature distribution within the soil close to the surface. In literature, several approaches have been discussed to predict soil temperature in different climates and locations, such as data-driven models, wavelet transform artificial neural networks, statistical models, etc. However, these models require extensive data sets from literature and high computational efforts. In the present study, a one-dimensional analytical model will be presented, which is based on the Green’s Function (GF) method. The model can estimate the daily and annual variation of the soil temperature distribution at different depths from real-time weather data sets. The model was experimentally validated with an accuracy of more than 96%. The significant advantage of the presented analytical method is the low computational cost, which is lower than that of numerical models by approximately two orders of magnitude.
Study of Hybrid Wet/Dry Cooling With Different Surface Morphology: Analyses on Pressure Drop and Thermal Performances
Authors: Saha Sudipta , Khan Jamil , Farouk Tanvir
Published: September 2020

This work conducts a multiphase multi-physics numerical study on this mixed mode cooling system, where evaporation of a liquid water film augments the convective cooling by evaporative heat and mass transfer. The mathematical framework consists of coupled mass, momentum, energy equation with species transport of air and evaporated water in the gas phase. Author’s prior works on perfectly flat surface predicted a minimum 500% increase of heat transfer coefficient in presence of a dual mode heat transfer. Current effort conducts a parametric study based on the different surface roughness structures over a broad range of Reynolds number condition. Array of circular, squared and triangular shaped grooves have been introduced along the surface exposed to the evaporating liquid. The cooling performances have been analyzed for different surface roughness structures and then compared against the flat film configuration. Furthermore, pressure drop across the liquid-gas interface has also been analyzed to predict the pumping power of the system. Model predicts that triangular shaped grooves exhibits a maximum ∼22% decrease in thermal resistance with a minimum pressure drop (∼5.5 times) across the interface. The square shaped surface morphology achieves 18% reduction in thermal resistance, with a penalty of pressure drop increase by a factor of ∼8. In comparison, circular grooves exhibit similar thermal performance but with a slightly a lower pressure drop (∼7 times). The numerical predictions have been compared with similar experimental findings and qualitative agreement was observed.
Thermal and Electrical Conductance of Pressure Tube/Calandria Tube Interface
Authors: Azih Chukwudi , MacCoy Reilly , Mazhar Hazem , Fraser Chris
Published: September 2020

In some engineered systems, the interface thermal conductance is a key parameter that governs the heat transfer behaviour of components in solid-solid contact. For example, in certain postulated accident scenarios for CANDU reactors, the pressure tube (PT) may deform into contact with the calandria tube (CT) to form a more direct path for heat transfer from the fuel to the moderator. There have been no direct measurements of interface thermal conductance in integrated “Contact boiling” experiments designed to mimic this Loss-of-coolant accident (LOCA) scenario due to the geometrical limits of the test components and the cumbersome nature of the instrumentation required to extract contact conductance data. It has been noted that the modelling of the contact conductance is one of the main sources of uncertainty in predicting the outcome of the contact boiling experiments that mimic LOCA scenarios. The present study demonstrated an analogy between the electrical and thermal contact conductance for PT/CT interfaces. The range of interface pressure and interface temperatures studies are selected to match the expected range of conditions during a CANDU LOCA scenario. The experiment setup consists of two sets of specimen representing PT and CT material. The specimen are instrumented with four K-type thermocouples in sequence to capture the temperature gradient imposed via a three-chamber oven. Within a range of interface pressures from 2 to 7 MPa and a temperature range from 510 to 720°C, the analogy is independent of the interface pressure or the load applied. This demonstrates the measurement of the electrical conductance between the PT and CT in contact boiling as a promising technique for obtaining in-situ information on the thermal contact conductance during integrated experiments.
Exploration of ZnO Nanostructure Growth on Various Metal Substrates for Enhancement of Surface Wettability and Evaporation Processes
Authors: Cabrera Samuel , Carey Van P.
Published: September 2020

Recent studies have indicated that ZnO superhydrophilic surfaces on copper and aluminum substrates enhance surface wettability and evaporation processes in droplet evaporation and pool boiling experiments. At slightly superheated surface temperatures, droplet evaporation on a nanoporous superhydrophilic surface exhibits onset of nucleation and nucleate boiling effects found in pool boiling processes. This study explores water droplet evaporation and quenching experiments conducted on nanostructured surfaces of a 45° downward facing pyramid copper, aluminum, and 304 stainless steel substrate. The nanostructured surfaces were used to conduct adiabatic droplet deposition, droplet evaporation, and quenching experiments. Through the three experiments and through surface characterization, by means of scanning electron microscopy, the underlying heat transfer performance and mechanism of droplet evaporation and pool boiling on various host metal substrates can be understood. The six surfaces tested were the following: bare copper, aluminum, and 304 stainless steel surfaces; and ZnO nanostructured surfaces on copper, aluminum, and 304 stainless steel. The experimental variables in this study were temperature and time. Through temperature and time measurements, the mean heat flux at varying superheats could be determined. Experimental results indicate the ZnO nanostructure enhances wettability and water evaporation on a variety of metal substrates. The presence of the ZnO nanostructure increases the mean heat flux and critical heat flux (CHF) in comparison to the bare metal surfaces. These results provide insight into the potential of enhancing spray cooling systems by growing a ZnO nanostructure on a heat exchanger fabricated of various metals.
Numerical Investigation of the Capture Efficiency of a Domestic Range Hood
Authors: Benchikh Le Hocine Alla Eddine , Poncet Sébastien , Fellouah Hachimi
Published: September 2020

Comfort criteria in building are increasing continuously. Multiple studies tend to use CFD approaches in order to predict and optimize the flow conditions accurately. One of the most relevant problematic is the extraction of the CO2 by kitchen hoods. In the present work, a new solver, based on a buoyancy Boussinesq solver and a turbulent passive scalar transport equation, is developed in OpenFoam to model the heated CO2 extraction by a rotating fan using the Multiple reference frame (MRF) approach. The new solver is first validated successfully against experimental results of a heated cavity and CO2 diffusion. An improvement of 30% in the capture efficiency is reached by increasing the extraction flow rate of the fan from 100 to 300 cfm. An extraction efficiency of 100% is observed for flow rates above 330 cfm. The novelty of this study is to present a new open-source solver able to model the rotation of the whole fan, CO2 transport and heat exchange simultaneously in steady state.
On-Machine Diamond Tool Shaping to Realize Highly Efficient Ultraprecision Machining System
Authors: Xu Meng , Yokoyama Naoyo , Nakamoto Keiichi , Takeuchi Yoshimi
Published: September 2020

Tool wear is one of the critical issues which deteriorate machining accuracy in ultraprecision machining. However, tool setting errors caused by the change of worn tool during a machining operation should be carefully compensated by identifying the gaps between the ideal tool center point and the actual tool center point, which inevitably lead to low machining efficiency. Because of the long consumption time of actual tool center point detection, this study aims at achieving on-machine shaping of a diamond tool which is commonly used in ultraprecision machining. In the previous study, shaping conditions without tool chipping are investigated by using various shaping materials. Then, in order to create a flank face that is necessary to realize preferable cutting, a pin gauge made of cemented carbide is adopted as the shaper. From the conducted experiments, it is found that the proposed on-machine shaping can create a specific cutting edge and a flank face on an ultraprecision machine tool.
A Conflict-Free Routing Method for Automated Guided Vehicles Using Reinforcement Learning
Authors: Chujo Taichi , Nishida Kosei , Nishi Tatsushi
Published: September 2020

In a modern large-scale fabrication, hundreds of vehicles are used for transportation. Since traffic conditions are changing rapidly, the routing of automated guided vehicles (AGV) needs to be changed according to the change in traffic conditions. We propose a conflict-free routing method for AGVs using reinforcement learning in dynamic transportation. An advantage of the proposed method is that a change in the state can be obtained as an evaluation function. Therefore, the action can be selected according to the states. A deadlock avoidance method in bidirectional transport systems is developed using reinforcement learning. The effectiveness of the proposed method is demonstrated by comparing the performance with the conventional Q learning algorithm from computational results.
An Automated Image Analysis and Cell Identification System Using Machine Learning Methods
Authors: Itano Keiko , Ochiai Koji , Takahashi Koichi , Matsushima Takahide , Asahara Hiroshi
Published: September 2020

In many biological laboratories, biologists analyze images and identify cell or organ states manually. There are some problems: lack of human resource and high experimental costs, among others. Identification results vary according to the person. To solve these problems, the process automation of biologists’ operations and quantitative identification are needed. Here, a cell-foci-phenotype identification system is developed by applying image processing and machine learning methods to fluorescent cell images. With this system, cell-foci-phenotype with high accuracy can be predicted and biologists’ efforts in doing image analysis can be reduced.
Fractional-Order Variable-Gain Super-Twisting Control With Application to Wafer Stages of Photolithography Systems
Authors: Kuang Zhian , Sun Liting , Gao Huijun , Tomizuka Masayoshi
Published: September 2020

In this paper, a novel fractional-order variable-gain super-twisting control (FVSTC) scheme is proposed and applied to improve the tracking performance of wafer stages in the photolithography systems. The FVSTC overcomes the drawbacks of the super-twisting control (STC) such as slow response speed and incomplete compensation to disturbances. First, to improve the dynamics of the states on the sliding surface, a fractional-order sliding surface is designed. Moreover, to improve the dynamics of the sliding mode variable, an equivalent-control-based method is utilized, and a switching controller based on a variable-gain super-twisting algorithm is deployed. Via such designed schemes, the proposed controller is robust against external disturbances and model uncertainties. Stability proof of the closed-loop system is provided. Numerical simulations to track a sinusoidal signal and experiments on a wafer stage testbed are conducted. The results show that the proposed FVSTC scheme can achieve much better tracking performance than conventional methods.
Strain Transfer Analysis for Surface Bonded Fiber Sensor Considering Temperature Influence
Authors: Hu Xiaochen , Fan Zhaoyan
Published: September 2020

Strain transfer ratio is one of the key characteristics to determine the accuracy of sensors for strain measurement and structural health monitoring. This paper presented a theoretical study on the strain transfer ratio of optical fiber sensors, which is generally bonded on the surface of target structure by adhesives to measure strain or stress. Compared to the prior efforts where only one type of loads, either mechanical or thermal, is considered, this paper included both of them in the modeling of strain transfer ratio and derived a general analytical expression for their relationships. It has been found that the strain transfer ratio is not a constant in some cases but varies with the strain being measured. The work studied the characteristics of fiber optic sensor in two consecutive approaches: 1) A simplified 2-dimentional multi-layer analytical model was built to derive the expression of strain transfer ratio as a function of the structural and material properties; 2) a numerical model that considers the realistic 3-dimentional structure of the sensor installation scenario was established for validating the analytical model in different case studies. Simulation results have shown that the analytical model matches well with the behavior of strain transfer ratio estimated by the numerical model, with an error less than 1.35%. Based on the validated analytical model, the discussion was further extended to derive the lower limit of the bonding length of optical fiber sensors to satisfy the requirement of measurement accuracy.
Active Interlayer Heating for Sustainable Selective Laser Sintering With Reclaimed Polyamide 12 Powders
Authors: Yang Feifei , Jiang Tianyu , Chen Xu , Lalier Greg , Bartolone John
Published: September 2020

Selective laser sintering (SLS) technology produces a substantial amount of un-sintered polyamide 12 powders after the manufacturing process. Failure to recycle and reuse these aged powders not only leads to economic losses but also is environmentally unfriendly. This is particularly problematic for powder particles close to the heat-affected zones that go through severe thermal degradations during the laser sintering processes. Limited procedures exist for systematically reusing such extremely aged powders. This work proposes a systematic method to maximize reusability of aged and extremely aged polyamide 12 powders. Building on a previously untapped interlayer heating, pre-processing, and a systematic mixing of powder materials, we show how reclaimed polyamide 12 powders can be consistently reprinted into functional samples, with mechanical properties even superior to current industrial norms. In particular, the proposed method can yield printed samples with 18.04% higher tensile strength and 55.29% larger elongation at break using as much as 30% of extremely aged powders compared to the benchmark sample.
Identification of a Kinematic Model of a 6DOF Industrial Manipulator With Angular Positioning Deviation “Error Map” of Rotary Axes
Authors: Alam Md Moktadir , Ibaraki Soichi , Fukuda Koki , Morita Sho , Usuki Hiroshi
Published: September 2020

To improve the overall “absolute” positioning accuracy for the industrial manipulator, it is indispensable to calibrate its kinematic parameters. In conventional studies, researchers have focused on Denavit–Hartenberg (D-H) parameters. However, until now, for industrial manipulators, the absolute accuracy is significantly poor than its repeatability. In this study, we propose a new kinematic model of a 6DOF (degrees of freedom) industrial manipulator with the angular positioning deviation “error map” of each rotary axis. The angular positioning deviation is modeled as a function of command angular positions, as well as the rotation direction to model the influence of backlash. We also propose a method to identify the angular positioning deviation of all the rotary axes by using a laser tracker.
A Real-Time Receding Horizon Sequence Planner for Disassembly in a Human-Robot Collaboration Setting
Authors: Lee Meng-Lun , Behdad Sara , Liang Xiao , Zheng Minghui
Published: September 2020

Product disassembly is a labor-intensive process and is far from being automated. Typically, disassembly is not robust enough to handle product varieties from different shapes, models, and physical uncertainties due to component imperfections, damage throughout component usage, or insufficient product information. To overcome these difficulties and to automate the disassembly procedure through human-robot collaboration without excessive computational cost, this paper proposes a real-time receding horizon sequence planner that distributes tasks between robot and human operator while taking real-time human motion into consideration. The sequence planner aims to address several issues in the disassembly line, such as varying orientations, safety constraints of human operators, uncertainty of human operation, and the computational cost of large number of disassembly tasks. The proposed disassembly sequence planner identifies both the positions and orientations of the to-be-disassembled items, as well as the locations of human operator, and obtains an optimal disassembly sequence that follows disassembly rules and safety constraints for human operation. Experimental tests have been conducted to validate the proposed planner: the robot can locate and disassemble the components following the optimal sequence, and consider explicitly human operator’s real-time motion, and collaborate with the human operator without violating safety constraints.
Lumbar Intervertebral Kinematics During an Unstable Sitting Task and Its Association With Standing-Induced Low Back Pain
Authors: Viggiani Daniel , Mannen Erin M. , Nelson-Wong Erika , Wong Alexander , Ghiselli Gary , Shelburne Kevin B. , Davidson Bradley S. , Callaghan Jack P.
Published: September 2020

People developing transient low back pain during standing have altered control of their spine and hips during standing tasks, but the transfer of these responses to other tasks has not been assessed. This study used video fluoroscopy to assess lumbar spine intervertebral kinematics of people who do and do not develop standing-induced low back pain during a seated chair-tilting task. A total of 9 females and 8 males were categorized as pain developers (5 females and 3 males) or nonpain developers (4 females and 5 males) using a 2-hour standing exposure; pain developers reported transient low back pain and nonpain developers did not. Participants were imaged with sagittal plane fluoroscopy at 25 Hz while cyclically tilting their pelvises anteriorly and posteriorly on an unstable chair. Intervertebral angles, relative contributions, and anterior–posterior translations were measured for the L3/L4, L4/L5, and L5/S1 joints and compared between sexes, pain groups, joints, and tilting directions. Female pain developers experienced more extension in their L5/S1 joints in both tilting directions compared with female nonpain developers, a finding not present in males. The specificity in intervertebral kinematics to sex-pain group combinations suggests that these subgroups of pain developers and nonpain developers may implement different control strategies.
Using SHAPE-MaP To Model RNA Secondary Structure and Identify 3′UTR Variation in Chikungunya Virus
Authors: Madden Emily A. , Plante Kenneth S. , Morrison Clayton R. , Kutchko Katrina M. , Sanders Wes , Long Kristin M. , Taft-Benz Sharon , Cruz Cisneros Marta C. , White Ashlyn Morgan , Sarkar Sanjay , Reynolds Grace , Vincent Heather A. , Laederach Alain , Moorman Nathanial J. , Heise Mark T.
Published: September 2020

Chikungunya virus (CHIKV) is a mosquito-borne RNA virus that causes febrile illness and debilitating arthralgia in humans. CHIKV causes explosive outbreaks but there are no approved therapies to treat or prevent CHIKV infection. The CHIKV genome contains functional RNA secondary structures that are essential for proper virus replication. Since RNA secondary structures have only been defined for a small portion of the CHIKV genome, we used a chemical probing method to define the RNA secondary structures of CHIKV genomic RNA. We identified 23 highly specific structured regions of the genome, and confirmed the functional importance of one structure using mutagenesis. Furthermore, we defined the RNA secondary structure of three CHIKV 3′UTR variants that differ in their ability to replicate in mosquito cells. Our study highlights the complexity of the CHIKV genome and describes new systems for designing compensatory mutations to test the functional relevance of viral RNA secondary structures.
Pediatric emergency department utilisation during Ramadan: a retrospective cross-sectional study
Authors: Sawaya Rasha D , Wakil Cynthia , Shayya Sami , Al Hariri Moustafa , Dakessian Alik , Wazir Adonis , Makki Maha , Jamali Sarah , Tamim Hani
Published: September 2020

Objective

To investigate the impact of Ramadan on patient characteristics, diagnoses and metrics in the paediatric emergency department (PED).

Design

Retrospective cross-sectional study.

Setting

PED of a tertiary care centre in Lebanon.

Patients

All paediatric patients.

Exposure

Ramadan (June 2016 and 2017) versus the months before and after Ramadan (non-Ramadan).

Main outcome measures

Patient and illness characteristics and PED metrics including peak patient load; presentation timings; length of stay; and times to order tests, receive samples and report results.

Results

We included 5711 patients with mean age of 6.1±5.3 years and 55.4% males. The number of daily visits was 28.3±6.5 during Ramadan versus 31.5±7.3 during non-Ramadan (p=0.004). The peak time of visits ranged from 18:00 to 22:00 during non-Ramadan versus from 22:00 to 02:00 during Ramadan. During Ramadan, there were significantly more gastrointestinal (GI) and trauma-related complaints (39.0% vs 35.4%, p=0.01 and 2.9% vs 1.8%, p=0.005). The Ramadan group had faster work efficiency measures such as times to order tests (21.1±21.3 vs 24.3±28.1 min, p<0.0001) and to collect samples (50.7±44.5 vs 54.8±42.6 min, p=0.03).

Conclusions

Ramadan changes presentation patterns, with fewer daily visits and a later peak time of visits. Ramadan also affects illness presentation patterns with more GI and trauma cases. Fasting times during Ramadan did not affect staff work efficiency. These findings could help EDs structure their staffing to optimise resource allocation during Ramadan.
Exploring the health and service utilisation of general practice patients with a history of adverse childhood experiences (ACEs): an observational study using electronic health records
Authors: Hardcastle Katie , Bellis Mark A , Sharp Catherine A , Hughes Karen
Published: September 2020

Objectives

To examine the relationships between adverse childhood experiences (ACEs), chronic health and health service utilisation among a sample of general practice patients.

Design

Cross-sectional observational study using anonymised data from electronic health records for 763 patients.

Setting

Four general practices in northwest England and North Wales.

Outcome measures

Patient demographic data (age, gender); body mass index; self-reported smoking status; self-reported ACEs; diagnosis of chronic health conditions; current mental health problems; total number of service contacts and repeat medication use in the previous 6 months.

Results

A history of ACEs (experiencing abuse or neglect as a child, and/or growing up in a household characterised by violence, substance use, mental health problems or criminal behaviour) was strongly independently associated with current mental health problems, smoking and chronic obstructive pulmonary disease, showing a dose–response relationship with level of ACE exposure. Medication use and contact were significantly greater among patients with high ACE exposure (≥4 ACEs), compared with those with no ACEs. However, contrary to findings from population studies, health service utilisation was not significantly different for patients with increased ACE exposure (1–3 ACEs) and their ACE-free counterparts.

Conclusions

Findings highlight the contribution ACEs make to unequal distributions of risk to health and well-being and patterns of health service use in the UK.
Cadaveric simulation versus standard training for postgraduate trauma and orthopaedic surgical trainees: protocol for the CAD:TRAUMA study multicentre randomised controlled educational trial
Authors: James Hannah K , Pattison Giles T R , Fisher Joanne D , Griffin Damian
Published: September 2020

Introduction

The quantity and quality of surgical training in the UK has been negatively affected by reduced working hours and National Health Service (NHS) financial pressures. Traditionally surgical training has occurred by the master-apprentice model involving a process of graduated responsibility, but a modern alternative is to use simulation for the early stages of training. It is not known if simulation training for junior trainees can safeguard patients and improve clinical outcomes. This paper details the protocol for a multicentre randomised controlled educational trial of a cadaveric simulation training intervention versus standard training for junior postgraduate orthopaedic surgeons-in-training. This is the first study to assess the effect of cadaveric simulation training for open surgery on patient outcome. The feasibility of delivering cadaveric training, use of radiographic and clinical outcome measures to assess impact and the challenges of upscaling provision will be explored.

Methods and analysis

We will recruit postgraduate orthopaedic surgeons-in-training in the first 3 years (of 8) of the specialist training programme. Participants will be block randomised and allocated to either cadaveric simulation or standard ‘on-the-job’ training, learning three common orthopaedic procedures, each of which is a substudy within the trial. The procedures are (1) dynamic hip screw, (2) hemiarthroplasty and (3) ankle fracture fixation. These procedures have been selected as they are very common procedures which are routinely performed by junior surgeons-in-training. A pragmatic approach to sample size is taken in lieu of a formal power calculation as this is novel exploratory work with no a priori estimate of effect size to reference. The primary outcome measure is the technical success of the surgery performed on patients by the participating surgeons-in-training during the follow-up period for the three substudy procedures, as measured by the implant position on the postoperative radiograph. The secondary outcome measures are procedure time, postoperative complication rate and patient health state at 4 months postoperation (EQ-5D—substudies 1 and 2 only).

Ethics, registration and dissemination

National research ethics approval was granted for this study by the NHS Research Authority South Birmingham Research Ethics Committee (15/WM/0464). Confidentiality Advisory Group approval was granted for accessing radiographic and outcome data without patient consent on 27 February 2017 (16/CAG/0125). The results of this trial will be submitted to a peer-reviewed journal and will inform educational and clinical practice.

Trial registration number

ISRCTN20431944
Inequalities in complete childhood immunisation in Nepal: results from a population-based cross-sectional study
Authors: Song In Han , Palley Elizabeth , Atteraya Madhu Sudhan
Published: September 2020

Objective

To investigate the effect of different aspects of inequality on childhood immunisation rates in Nepal. The study hypothesised that social inequality factors (eg, gender of a child, age of mother, caste/ethnic affiliation, mother’s socioeconomic status, place of residence and other structural barrier factors such as living in extreme poverty and distance to health facility) affect the likelihood of children being immunised.

Design

Using gender of a child, age of mother, caste/ethnic affiliation, mother’s socioeconomic status, place of residence and other structural barrier factors such as living in extreme poverty and distance to health facility as independent variables, we performed bivariate and multivariate logistic regression analyses.

Setting

This study used data from the most recent nationally representative cross-sectional Nepal Demographic and Health Survey in 2016.

Participants

The analysis reviewed data from 1025 children aged 12–23 months old.

Outcome measures

The main outcome variable was childhood immunisation.

Results

Only 79.2% of children were fully immunised. The complete vaccination rate of ethnic/caste subpopulations ranged from 66.4% to 85.2%. Similarly, multivariate analysis revealed that children from the previously untouchable caste (OR 0.58; CI 0.33 to 0.99) and the Terai caste (OR 0.54; CI 0.29 to 0.99) were less likely to be fully immunised than children from the high Hindu caste.

Conclusion

Given Nepal’s limited resources, we suggest that programmes that target the families of children who are least likely to be fully immunised, specifically those who are not only poor but also in financial crises and ‘underprivileged’ caste families, might be an effective strategy to improve Nepal’s childhood immunisation rates.
Cohort profile: the PHARMO Perinatal Research Network (PPRN) in the Netherlands: a population-based mother–child linked cohort
Authors: Houben E. , Broeders L. , Steegers E.A.P. , Herings R.M.C.
Published: September 2020

Purpose

Observational population-based research is a very suitable non-invasive method for studies in the vulnerable populations of pregnant women and children. Therefore, the PHARMO Perinatal Research Network (PPRN) was set up as a resource for life course perinatal and paediatric research by linking population-based data from existing registrations.

Participants

From 1999 to 2017, the PPRN captures approximately 542 900 pregnancies of 387 100 mothers (‘Pregnancy Cohort’). Additionally, mother–child linkage is currently available for a quarter of these pregnancies (‘Child Cohort’). The PPRN contains preconceptional information on maternal healthcare, as well as detailed pregnancy and neonatal data, extending into long-term follow-up and outcomes after birth for both mother and child up to nearly 20 years. It includes linked data from different primary and secondary healthcare settings.

Findings to date

Through record linkage of the Netherlands Perinatal Registry and the PHARMO Database Network, we have established a large population-based research network including data on demographics, medication use, medical conditions and details concerning labour, birth and neonatal outcomes. Here, we provide an overview of record types available from the PPRN, available database follow-up and pregnancy characteristics of the PPRN cohorts. The PPRN has been used for a number of different pharmacoepidemiological studies, for example, to confirm that preterm-born infants were more likely than full-term infants to be hospitalised or use medication. Similar long-term comparisons showed that children born following spontaneous preterm labour were at increased risk of neurodevelopmental and respiratory conditions. Most recently, the PPRN provided important evidence on the trends in use of potentially harmful medication during pregnancy.

Future plans

The PPRN provides a unique and rich data set facilitating large-scale observational pharmacoepidemiological perinatal research. The patient-level linkage of many different healthcare data sources allows for long-term follow-up of mother and child, with ongoing annual updates.
Clinical risk score to predict in-hospital mortality in COVID-19 patients: a retrospective cohort study
Authors: Fumagalli Carlo , Rozzini Renzo , Vannini Matteo , Coccia Flaminia , Cesaroni Giulia , Mazzeo Francesca , Cola Maria , Bartoloni Alessandro , Fontanari Paolo , Lavorini Federico , Marcucci Rossella , Morettini Alessandro , Nozzoli Carlo , Peris Adriano , Pieralli Filippo , Pini Riccardo , Poggesi Loredana , Ungar Andrea , Fumagalli Stefano , Marchionni Niccolò
Published: September 2020

Objectives

Several physiological abnormalities that develop during COVID-19 are associated with increased mortality. In the present study, we aimed to develop a clinical risk score to predict the in-hospital mortality in COVID-19 patients, based on a set of variables available soon after the hospitalisation triage.

Setting

Retrospective cohort study of 516 patients consecutively admitted for COVID-19 to two Italian tertiary hospitals located in Northern and Central Italy were collected from 22 February 2020 (date of first admission) to 10 April 2020.

Participants

Consecutive patients≥18 years admitted for COVID-19.

Main outcome measures

Simple clinical and laboratory findings readily available after triage were compared by patients’ survival status (‘dead’ vs ‘alive’), with the objective of identifying baseline variables associated with mortality. These were used to build a COVID-19 in-hospital mortality risk score (COVID-19MRS).

Results

Mean age was 67±13 years (mean±SD), and 66.9% were male. Using Cox regression analysis, tertiles of increasing age (≥75, upper vs <62 years, lower: HR 7.92; p<0.001) and number of chronic diseases (≥4 vs 0–1: HR 2.09; p=0.007), respiratory rate (HR 1.04 per unit increase; p=0.001), PaO2/FiO2 (HR 0.995 per unit increase; p<0.001), serum creatinine (HR 1.34 per unit increase; p<0.001) and platelet count (HR 0.995 per unit increase; p=0.001) were predictors of mortality. All six predictors were used to build the COVID-19MRS (Area Under the Curve 0.90, 95% CI 0.87 to 0.93), which proved to be highly accurate in stratifying patients at low, intermediate and high risk of in-hospital death (p<0.001).

Conclusions

The COVID-19MRS is a rapid, operator-independent and inexpensive clinical tool that objectively predicts mortality in patients with COVID-19. The score could be helpful from triage to guide earlier assignment of COVID-19 patients to the most appropriate level of care.
Craniectomy for acute disseminated encephalomyelitis
Authors: Bourke David , Woon Kelvin
Published: September 2020

A 17-year-old girl underwent emergency bifrontal craniectomy for severely raised intracranial pressure with brainstem compression, having developed acute disseminated encephalomyelitis (ADEM) following Epstein-Barr virus infection. We discuss the current evidence for craniectomy in both ADEM and infective encephalitis and propose an approach to management.
Dissimilar biodiversity data sets yield congruent patterns and inference in lichens
Authors: Lendemer James C. , Coyle Jessica R.
Published: September 2020

Large-scale efforts to aggregate and promote the re-use of biodiversity data are leading to novel insights into biogeography and macroecology. However, secondary analyses must account for the tradeoffs and limitations of the original studies. Studies of speciose and taxonomically complex groups often utilize morphospecies or functional subsets as proxies, potentially complicating data re-use. We evaluated whether lichen biodiversity patterns are robust to differences in sampling methodology, utilizing parallel analyses to compare species richness, regional species pool variation, species probabilities of occurrence, and correlation of those three with environmental variables in data sets that cover the same geographic region. Our analyses revealed that, although individual species distributions sometimes differed in idiosyncratic ways, inference based on the aggregated response of multiple species was generally robust across the two datasets, despite differences in observer expertise and functional and taxonomic scope. This suggests that biodiversity data assembled from disparate sources could be used to evaluate biogeographical and macroecological hypotheses in understudied groups such as lichens, particularly at larger spatial scales.