bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of the cerebral pressure‐flow relationship using psychological stress to manipulate blood pressure
Authors: Brindle Ryan C. , Ginty Annie T. , Whittaker Anna C. , Carroll Douglas , Lucas Samuel J. E. 
Published: July 2018

AbstractRecent evidence indicates that cerebral autoregulation (CA) might be more pressure passive than previously thought. That is, cerebral blood flow, traditionally thought to be regulated independently of prevailing mean arterial pressure (MAP), might fluctuate, to some extent, as a function of MAP. However, due to limitations associated with experimental usage of pharmaceuticals to manipulate MAP and inconsistent control of arterial carbon dioxide, questions remain regarding the MAP‐cerebral blood flow relationship, especially during typical daily activities that alter MAP. Therefore, the current study aimed to assess CA using a nonpharmacological acute psychological stress task to augment MAP, while at the same time controlling for end‐tidal carbon dioxide (PETCO2). Twenty‐five healthy young adults completed a stressful task while continuous measures of MAP, middle cerebral artery blood flow velocity (MCAv), and PETCO2 were recorded. Slope values obtained from hierarchical linear regression were used to assess the strength of the MAP‐MCAv relationship and control for PETCO2. The stress task significantly increased MAP (p < 0.001) and MCAv (p < 0.001), and decreased PETCO2 (p = 0.05). For every 10 mmHg task‐induced increase in MAP, MCAv increased by ≈3.5%; task‐induced changes in PETCO2 did not appreciably change the MAP‐MCAv relationship. Greater task‐induced MAP responses were significantly related to decreased MAP‐MCAv slope values, consistent with CA. These data support the hypothesis that CA is more pressure passive than previously thought and provide initial evidence indicating that a pressure‐passive MAP‐MCAv relationship may play a role in the observed associations between MAP stress responses, stroke, and cerebrovascular disease.
The Correlated Pseudomarginal Method
Authors: Deligiannidis George , Doucet Arnaud , Pitt Michael K. 
Published: July 2018

SummaryThe pseudomarginal algorithm is a Metropolis–Hastings-type scheme which samples asymptotically from a target probability density when we can only estimate unbiasedly an unnormalized version of it. In a Bayesian context, it is a state of the art posterior simulation technique when the likelihood function is intractable but can be estimated unbiasedly by using Monte Carlo samples. However, for the performance of this scheme not to degrade as the number T of data points increases, it is typically necessary for the number N of Monte Carlo samples to be proportional to T to control the relative variance of the likelihood ratio estimator appearing in the acceptance probability of this algorithm. The correlated pseudomarginal method is a modification of the pseudomarginal method using a likelihood ratio estimator computed by using two correlated likelihood estimators. For random-effects models, we show under regularity conditions that the parameters of this scheme can be selected such that the relative variance of this likelihood ratio estimator is controlled when N increases sublinearly with T and we provide guidelines on how to optimize the algorithm on the basis of a non-standard weak convergence analysis. The efficiency of computations for Bayesian inference relative to the pseudomarginal method empirically increases with T and exceeds two orders of magnitude in some examples.
HIV‐1 drug resistance testing at second‐line regimen failure in Arua, Uganda: avoiding unnecessary switch to an empiric third‐line
Authors: Fily F. , Ayikobua E. , Ssemwanga D. , Nicholas S. , Kaleebu P. , Delaugerre C. , Pasquier E. , Amoros Quiles I. , Balkan S. , Schramm B. 
Published: July 2018

AbstractObjectivesThe number of patients on second‐line antiretroviral therapy is growing, but data on HIV drug resistance patterns at failure in resource‐constrained settings are scarce. We aimed to describe drug resistance and investigate the factors associated with extensive resistance to nucleoside/nucleotide reverse transcriptase inhibitors (NRTI), in patients failing second‐line therapy in the HIV outpatient clinic at Arua Regional Referral Hospital, Uganda.MethodsWe included patients who failed on second‐line therapy (two consecutive viral loads ≥1000 copies/mm3 by SAMBA‐1 point‐of‐care test) and who had a drug resistance test performed between September 2014 and March 2017. Logistic regression was used to investigate factors associated with NRTI genotypic sensitivity score (GSS) ≤1.ResultsSeventy‐eight patients were included: 42% female, median age 31 years and median time of 29 months on second‐line therapy. Among 70 cases with drug resistance test results, predominant subtypes were A (47%) and D (40%); 18.5% had ≥1 major protease inhibitor mutation; 82.8% had ≥1 NRTI mutation and 38.5% had extensive NRTI resistance (NRTI GSS ≤1). A nadir CD4 count ≤100/ml was associated with NRTI GSS ≤1 (OR 4.2, 95% CI [1.3–15.1]). Thirty (42.8%) patients were switched to third‐line therapy, composed of integrase inhibitor and protease inhibitor (60% darunavir/r) +/− NRTI. A follow‐up viral load was available for 19 third‐line patients at 12 months: 84.2% were undetectable.ConclusionsOur study highlights the need for access to drug resistance tests to avoid unnecessary switches to third‐line therapy, but also for access to third‐line drugs, in particular integrase inhibitors. Low nadir CD4 count might be an indicator of third‐line drug requirement for patients failing second‐line therapy.
Cost‐effectiveness analysis of a multi‐dimensional intervention to reduce inappropriate antibiotic prescribing for children with upper respiratory tract infections in China
Authors: Zhang Zhitong , Dawkins Bryony , Hicks Joseph P. , Walley John D. , Hulme Claire , Elsey Helen , Deng Simin , Lin Mei , Zeng Jun , Wei Xiaolin 
Published: July 2018

SummaryBackgroundWe developed a multifaceted intervention to reduce antibiotic prescription rate for children with upper respiratory tract infections (URTIs) among primary care doctors in township hospitals in China. The intervention achieved a 29% (95% CI 16–42) absolute risk reduction in antibiotic prescribing. This study was to assess the cost‐effectiveness of our intervention at reducing antibiotic prescribing in rural primary care facilities as measured by the intervention's effect on the antibiotic prescription rates for childhood URTIs.MethodsWe took a healthcare provider perspective, measuring costs of consultation (time cost of doctor), prescription monitoring process and peer‐review meetings (time cost of participants) and medication costs. Costs on provider side were collected through a bespoke questionnaire from all 25 township hospitals in December 2016, while medication costs were collected prospectively in the trial. Incremental cost‐effectiveness ratios were calculated by dividing the mean difference in cost of the two trial arms by the mean difference in antibiotic prescribing rate.ResultsThis showed an incremental cost of $0.03 per percentage point reduction in antibiotic prescribing. In addition to this incremental cost, the cost of implementing the intervention, including training and materials delivered by township hospitals, was $390.65 (SD $145.68) per healthcare facility.ConclusionsThis study shows that a multifaceted intervention programme, when embedded into routine practice, is very cost‐effective at reducing antibiotic prescribing in primary care facilities and has the potential of scale up in similar resource limited settings.
Effect of Deflected Inflow on Flows in a Strongly-Curved 90 Degree Elbow
Authors: Iwamoto Yukiharu , Kusuzaki Ryo , Sogo Motosuke , Yasuda Kazunori , Yamano Hidemasa , Tanaka Masaaki 
Published: July 2018

Wall pressure measurements and flow visualization were conducted for a 90 degree elbow with an axis curvature radius the same as its inner diameter (125 mm, Rc/D = 1). Reynolds numbers 320,000 and 500,000, based on the inner diameter and bulk velocity, were examined. A deflected inflow, having an almost constant velocity slope, was introduced in the present study. The velocity at the inside was 20% faster than the bulk velocity in the plane one diameter upstream of the elbow inlet.
Ensemble averaged pressure distributions showed that no difference of normalized pressure could be found in cases of Reynolds numbers of 320,000 and 500,000. Comparisons with a uniform inlet flow case [1] proved that a low-pressure region at the intrados of the elbow was weakened and that a high-pressure region outside strengthened in the deflected inflow case. The present case had a characteristic pressure distribution that the pressure downstream of the elbow increased at the inside until two diameters downstream from the elbow exit. Flow visualization concluded that the corresponding pressure increase was caused by a collision of a strengthened secondary flow convected from the extrados.
The unsteady pressure distribution in the present case showed that a circumferential extent of a strongly fluctuating region in the inside and downstream of the elbow decreased, comparing with the uniform inlet flow case.[1] Power spectral density functions of pressures exhibited that the fluctuation having the Strouhal number (based on the inner diameter and bulk velocity) of 0.6 existed in the downstream region of the elbow, which is 0.1 larger than that of the uniform inflow case.
A Hydraulic Design Procedure of Axial-Flow Pump
Authors: Shen Zhenhua , Rasmussen Svend , Ma Xiaofen , Jacobsen Christian Brix 
Published: July 2018

A radical decrease of the product development time has been achieved by implementation of simulation driven development on axial-flow pump design. A new automatic hydraulic design procedure of axial-flow pumps was developed. It consists of in-house developed parametric design template, Visual Basic macro, OpenFOAM and an in-house developed pump performance plot tool. In this procedure the parametric template includes propeller design and guide vane design. A mesh is generated by using OpenFOAM snappyHexMesh utility. Visual Basic macro is used to link the parametric template and OpenFOAM.
In order to validate the accuracy of predicting the hydraulic performance from this procedure, a high specific speed axial-flow pump was designed by using this procedure and an in-house optimization tool. Finally an aluminum scaled prototype was made by CNC machining. The CFD results show that BEP efficiency is equal to 83.5%, and testing shown BEP efficiency of 85%. It indicates that the hydraulic design from this procedure is both reliable and able to produce high efficiency designs.
Investigation on Rotor-Stator Interaction in a Low Specific Speed Centrifugal Pump
Authors: Zhang Ning , Yang Minguan , Gao Bo , Li Zhong , Ni Dan 
Published: July 2018

In centrifugal pump, due to intense rotor-stator interaction, high amplitude pressure pulsating would be induced, and it has a crucial influence on the stable operating of the pump. In this paper, a low specific speed centrifugal pump is investigated to illustrate unsteady flow within the centrifugal pump. Pressure pulsation signals are attained by mounting 20 monitoring points along the spiral volute, covering all the interested region of the model pump. FFT (Fast Fourier Transform algorithm) is applied to analyze the time-domain pressure signals.
Results show that in pressure spectra, evident peaks at blade passing frequency fBPF together with its high harmonics can be identified, and the amplitudes are closely associated with operating conditions of the model pump and the positions of the monitoring points. At nominal flow rate, four vortical regions with high amplitude are captured inside the model pump. And the unsteady vortical structure at the near tongue region is related to the relative position of the impeller with respect to the tongue, and the upstream effect of the volute tongue significantly affects the vorticity distribution on the blade pressure side.
At off-design conditions, the interaction pattern between the vortical structure and the volute tongue is significantly affected compared with that at the rated condition, as to the upstream effect of the tongue. At high flow rate, partial vortex would separate from the main vortex, but at low flow rate, the cutting and impingement effects of the tongue are much weaker due to almost all the vortex moving to the narrow side of the tongue.
Based on the analysis of rotor-stator interaction in the model pump, some conclusions could be obtained. Pressure amplitudes at fBPF are associated with the positions of monitoring points and operating conditions of the model pump. Vorticity magnitude at blade exit increases as the impeller passes the volute tongue. And the fluid-dynamic blade-volute interaction is dominated by the vorticity shedding from blade trailing edge and their impingement on the volute tongue with subsequent cutting and distortion. And high pressure amplitude is generated with the corresponding high vorticity magnitude observed. So the intense interaction between flow structures (jet-wake pattern) and volute tongue is crucial to unsteady pressure pulsation. Thus, to lower pressure pulsation amplitude and fluid dynamic forces, controlling the vortical structure at blade trailing edge is an effective method.
Numerical Simulation of Partial Slip Contact Using a Semi-Analytical Method
Authors: Armand J. , Salles L. , Schwingshackl C. W. 
Published: July 2018

Almost all mechanical structures consist of an assembly of components that are linked together with joints. If such a structure experiences vibration during operation, micro-sliding can occur in the joint, resulting in fretting wear. Fretting wear affects the mechanical properties of the joints over their lifetime and as a result impacts the non-linear dynamic response of the system. For accurate prediction of the non-linear dynamic response over the lifetime of the structure, fretting wear should be considered in the analysis.
Fretting wear studies require an accurate assessment of the stresses and strains in the contacting surfaces of the joints. To provide this information, a contact solver based on the semi-analytical method has been implemented in this study. By solving the normal and tangential contact problems between two elastic semi-infinite bodies, the contact solver allows an accurate calculation of the pressure and shear distributions as well as the relative slips in the contact area. The computed results for a smooth spherical contact between similar elastic materials are presented and validated against analytical solutions. The results are also compared with those obtained from finite element simulations to demonstrate the accuracy and computational benefits of the semi-analytical method. Its capabilities are further illustrated in a new test case of a cylinder with rounded edges on a flat surface, which is a more realistic contact representation of an industrial joint.
Dynamic Behaviour of Ox Tibial and Femoral Bones: A Comparison With Human Bones
Authors: Hoursan Hesam , Ahmadian Mohammad Taghi 
Published: July 2018

Finite element models have been widely employed in an effort to quantify the stress and strain distribution around human bones as well as implanted prostheses and to explore the influence of these distributions on their long-term stability. In order to provide meaningful predictions, such models must contain an appropriate reflection of mechanical properties. Detailed geometrical and density information is now readily available from CT scanning. However, there are still many complications regarding patient-specific geometrical differences and bone dynamic behavior in-vivo. Experimental studies on animal bones, due to their convenience and accessibility, have always played a key role in simulating human bone behavior. In current study, a modal experiment has been done on an ox femoral and tibial bones and the results have been compared with those reported from human bones. Results have been obtained in terms of natural frequencies of medio-lateral bending mode shapes and damping ratios, and compared with those obtained by some previous studies. The results suggest similar pattern in modal behavior, but considerable difference between natural frequencies due to geometrical differences. To consider structural damping ratios, due to existence of moisture and marrow in bone in-vivo, samples have been obtained few hours post-mortem and the ratio has been extracted for each natural frequency.
Finally, conclusions have been made on the similarity of the models and how to improve the FE models of human tibial and femoral components.
Real Time Dynamic System Stochastic Identification in Video Capture for Data Compression, Image Interpolation, Prediction, and Augmented Reality
Authors: Goeller Adrien , Dion Jean-Luc , Soriano Thierry , Roux Bernard 
Published: July 2018

In computer vision, cameras more and more accurate, fast, 3D featured are used. These still evolutions generate more data, which is an issue for users to store it with standard compression for example for recording proof in case of products manufacture defective.
The aim of this work is to develop a specific solution adapted for vision systems which have a known scenario and can be described by dynamic models. In this framework, Kalman filters are used for data compression, observable variable prediction, and augmented reality. The developed concepts are tested with a scenario of a ruler on a table. The experiment aims to check the data compression level, the estimation of the friction forces coefficient of the ruler and the prediction of the stop position.
Heartbeat Energy Harvesting Using the Fan-Folded Piezoelectric Beam Geometry
Authors: Ansari M. H. , Karami M. Amin 
Published: July 2018

A three dimensional piezoelectric vibration energy harvester is designed to generate electricity from heartbeat vibrations. The device consists of several bimorph piezoelectric beams stacked on top of each other. These horizontal bimorph beams are connected to each other by rigid vertical beams making a fan-folded geometry. One end of the design is clamped and the other end is free.
One major problem in micro-scale piezoelectric energy harvesters is their high natural frequency. The same challenge is faced in development of a compact vibration energy harvester for the low frequency heartbeat vibrations. One way to decrease the natural frequency is to increase the length of the bimorph beam. This approach is not usually practical due to size limitations. By utilizing the fan-folded geometry, the natural frequency is decreased while the size constraints are observed. The required size limit of the energy harvester is 1 cm by 1 cm by 1 cm.
In this paper, the natural frequencies and mode shapes of fan-folded energy harvesters are analytically derived. The electro-mechanical coupling has been included in the model for the piezoelectric beam. The design criteria for the device are discussed.
Observed Rotordynamic Phenomena in Aircraft Gas Turbine Development
Authors: Ehrich Fredric F. 
Published: July 2018

Observations, analysis and understanding of out-of-the-ordinary rotordynamic phenomena (including several instabilities and nonlinear responses) observed in aircraft gas turbine engines and other high-speed rotating machinery over the course of the author’s career in the design and development of aircraft gas turbine engines are described. Some observed phenomena were already widely recognized in the rotordynamic community such as:
• Hysteretic whirl
• The tip clearance effect on stability of turbomachinery rotors
• Instability due to trapped liquids in the rotor
• Hysteresis in the resonant peak amplitude
• Effective suppression of rotor instability by anisotropy in the engine support structure
Other observations were fairly new to the field of rotordynamics at that time they were observed but were identified as being new manifestations of vibration phenomena already familiar to vibration technologists in fields other than high-speed rotordynamics such as:
• Sum-and-difference frequency response
• Relaxation oscillations
• Nonlinear effects of anisotropic clearance in roller and gas bearings
At that time these phenomena were observed, the pressure for remediation of the problems they represented in the context of ongoing aircraft engine development resulted in intense attention and analysis which, in turn, often resulted in new insights, useful diagnoses, and effective remedial actions.
Design and Development of a Soft Robotic Back Orthosis
Authors: Govin Deven , Saenz Luis , Athanasaki Grigoria , Snyder Laura , Polygerinos Panagiotis 
Published: July 2018

Chronic back pain is a disorder which affects a large portion of the American population at some time during their lifespan. There are many causes for lower back pain and usually can be an indicator of a serious medical condition. This problem plagues the nation and the world leading to an estimated annual cost for back pain treatment amounts to $50 billion. This problem isn’t isolated to just the United States either, the world at large suffers from back pain and unfortunately modern treatment methods are effective but the technology simply hasn’t progressed in decades. The main drawback appears to be the rigidity of the device, which limits flexibility and comfort. The soft pneumatic actuators of this newfound device have the potential to provide the appropriate applications chronic back pain suffers and post-surgery patients.
In this work, the design and development of a soft robotic back orthotic device that has the capability to relieve back pain by assisting patients to fully achieve the upright position and stabilize the lumbosacral spine, is presented. The soft robotic actuators of this device allow the support to be disabled when the patient is in a supported position. Unlike conventional robotic assistive devices, this pneumatically actuated back orthosis provides dynamic support while being lightweight, comfortable, and cost affordable. After testing the device in a laboratory environment, the data overall displays a trend decreasing in EMG activity of the Erector Spinae muscles. This reduced activity leads to a reduction in strain on the patient.