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Critical velocity

Kathryn L Havens, Tatri Mukherjee, James M Finley
The ability to control the body's center of mass (CoM) is critical for preventing falls, which are a major health concern in aging populations. Control of the CoM has been assessed by characterizing dynamic margins of stability (MoS) which capture the dynamic relationship between the CoM and the base of support. Accurate estimation of CoM dynamics is best accomplished using a full-body marker set. However, a number of simplified estimates have been used throughout literature. Here, we determined the biases and sources of bias when computing MoS using four simplified CoM models, and we characterized how these biases varied in straight walking versus turning...
October 5, 2017: Gait & Posture
Timothy J Wright, Ravi Agrawal, Siby Samuel, Yuhua Wang, Shlomo Zilberstein, Donald L Fisher
OBJECTIVE: During conditional automated driving, a transition from the automated driving suite to manual control requires the driver to take over control at a moment's notice. Thus, it is critical that a driver be made situationally aware as quickly as possible in those conditions where he or she may not be paying full attention. Recent research suggests that specific cues about upcoming hazards (e.g., "crosswalk ahead") can increase the drivers' situation awareness during these safety-critical take-over situations when compared with a general cue ("take over control")...
October 11, 2017: Accident; Analysis and Prevention
Pei-Chi Ting, An-Hsun Chou, Chia-Chih Liao, Victor Chien-Chia Wu, Feng-Chun Tsai, Jaw-Ji Chu, Min-Wen Yang, Shi-Chuan Chang
BACKGROUND: The relationship between perioperative right ventricular (RV) performance and hemodynamic instability after cardiac surgery seemed less portrayed. Therefore, we sought to elucidate this relationship and compare the accuracy of different RV systolic indices in predicting outcome of cardiac surgery. METHODS: This study enrolled consecutive patients referred for cardiac surgeries. Exclusion criteria were non-sinus rhythm or contraindications to transesophageal echocardiography (TEE)...
October 10, 2017: Journal of the Chinese Medical Association: JCMA
Friederike M C Benning, Yusuke Sakiyama, Adam Mazur, Habib S T Bukhari, Roderick Y H Lim, Timm Maier
Multienzymes, such as the protein metazoan fatty acid synthase (FAS), are giant and highly dynamic molecular machines for critical biosynthetic processes. The molecular architecture of FAS was elucidated by static high-resolution crystallographic analysis, while electron microscopy revealed large-scale conformational variability in FAS with some correlation to functional states in catalysis. However, little is known about time scales of conformational dynamics, the trajectory of motions in individual FAS molecules and the extent of coupling between catalysis and structural changes...
October 12, 2017: ACS Nano
Abdul Jalil, Yiping Li, Wei Du, Wencai Wang, Jianwei Wang, Xiaomeng Gao, Hafiz Osama Sarwar Khan, Baozhu Pan, Kumud Acharya
Wind induced flow velocity patterns and associated thermal destratification can drive to hypoxia reduction in large shallow lakes. The effects of wind induced hydrodynamic changes on destratification and hypoxia reduction were investigated at the Meiling bay (N 31° 22' 56.4″, E 120° 9' 38.3″) of Lake Taihu, China. Vertical flow velocity profile analysis showed surface flow velocities consistency with the wind field and lower flow velocity profiles were also consistent (but with delay response time) when the wind speed was higher than 6...
October 8, 2017: Environmental Pollution
Mario Marcello Miglietta, Jordi Mazon, Vincenzo Motola, Antonello Pasini
Extreme events represent a topic of paramount importance and a challenge for modelling investigations. Due to the need of high-resolution models, the study of severe localized convective phenomena is even more critical, especially in relation to changes in forcing factors, such as sea surface temperatures (SSTs), in future climate scenarios. Here, we analyze the effect of changes in SSTs on the intensity of a tornadic supercell in the Mediterranean through modelling investigations. We show dramatic (nonlinear) changes for updraft helicity and vertical velocity, which measure the intensity of the supercell, even for variations of SST only of + /-1 K...
October 9, 2017: Scientific Reports
Judith Maria Dimphena van den Brule, Roeland Stolk, Elisabeth Janine Vinke, Lex Maxim van Loon, Peter Pickkers, Johannes Gerardus van der Hoeven, Matthijs Kox, Cornelia Wilhelmina Elisabeth Hoedemaekers
AIM: The aim of this study was to investigate the effects of different vasopressors on the cerebral vasculature during experimental human endotoxemia and sepsis. We used the critical closing pressure (CrCP) as a measure of cerebral vascular tone. METHODS: We performed a prospective pilot study, at the intensive care department (ICU) of a tertiary care university hospital in the Netherlands, in 40 healthy male subjects during experimental human endotoxemia (administration of bacterial lipopolysaccharide [LPS]) and in 10 patients with severe sepsis or septic shock...
October 4, 2017: Shock
Chengcheng Feng, Shihong Xu, Yifan Liu, Yanfeng Wang, Wenqi Wang, Jingkun Yang, Chunyan Zhao, Qinghua Liu, Jun Li
In teleost, sex steroid hormones are critical for reproduction. Progestin is known to promote spermiation. To further understand the functions of progestin via its receptors during the annual reproductive cycle in male turbot (Scophthalmus maximus), we observed testicular development, quantified several sex steroid hormones, detected the expression of progestin receptors, and measured various sperm parameters. Results showed that the turbot testicular structure was of the lobular type. During breeding season, a number of spermatocytes (stage III) developed into spermatids (stage IV), then differentiated into sperm during spermiogenesis (stage V), and finally regressed to spermatocytes (stage VI)...
October 6, 2017: Fish Physiology and Biochemistry
Siying Lin, Tanfis I Alam, Vishal I Kottadiel, Carl J VanGessel, Wei-Chun Tang, Yann R Chemla, Venigalla B Rao
The speed at which a molecular motor operates is critically important for the survival of a virus or an organism but very little is known about the underlying mechanisms. Tailed bacteriophage T4 employs one of the fastest and most powerful packaging motors, a pentamer of gp17 that translocates DNA at a rate of up to ∼2000-bp/s. We hypothesize, guided by structural and genetic analyses, that a unique hydrophobic environment in the catalytic space of gp17-adenosine triphosphatase (ATPase) determines the rate at which the 'lytic water' molecule is activated and OH- nucleophile is generated, in turn determining the speed of the motor...
September 13, 2017: Nucleic Acids Research
Emmanuel Katsogridakis, David M Simpson, Glen Bush, Lingke Fan, Anthony A Birch, Robert Allen, John F Potter, Ronney B Panerai
Previous studies on cerebral autoregulation have shown the existence of hemispheric symmetry, which may be altered in stroke and traumatic brain injury. There is a paucity of data however on whether the response is symmetrical between those disturbances that cause cerebral hyperperfusion, to those that cause hypoperfusion. Our aim was to investigate whether the responses of cerebral autoregulation to haemodynamic stimuli of different directions are symmetrical. Approach: Using a previously described assessment method, we employed coherent averaging of the cerebral blood flow velocity (CBFV) responses to thigh cuff inflation and deflation, as driven by pseudorandom binary sequences, whilst simultaneously altering the inspired CO2...
October 3, 2017: Physiological Measurement
Michael J Lanspa, Benjamin J Briggs, Eliotte L Hirshberg, Cristina M Pratt, Colin K Grissom, Samuel M Brown
OBJECTIVE: The accuracy of various techniques to predict response to volume expansion in shock has been studied, but less well known is how feasible these techniques are in the ICU. METHODS: This is a prospective observation single-center study of inpatients from a mixed profile ICU who received volume expansion. At time of volume expansion, we determined whether a particular technique to predict response was feasible, according to rules developed from available literature and nurse assessment...
July 2017: International Journal of Critical Illness and Injury Science
Peifang Wang, Xun Wang, Chao Wang, Lingzhan Miao, Jun Hou, Qiusheng Yuan
River systems have critical roles in the natural water environment and the transportation of nutrients. Anthropogenic activities, including wastewater discharge and river damming, raise adverse impacts on ecosystem and continuum of rivers. An increasing amount of attention has been paid to riverine bacterioplankton as they make vital contributions to biogeochemical nutrient cycle. A comprehensive study was conducted on the bacterioplankton community along the Yarlung Tsangpo River, which is the longest plateau river in China and is suffering from various anthropogenic impacts...
October 2, 2017: Scientific Reports
Arezoo Tavakoli, Ainon Hamzah
BACKGROUND: Benzaldehyde dehydrogenase (BZDH) is encoded by the xylC that catalyzes the conversion of benzaldehyde into benzoate in many pathways such as toluene degradation. OBJECTIVES: In this study, the xylC gene from Rhodococcus ruber UKMP-5M was expressed in Escherichia coli, purified, and characterized. MATERIALS AND METHODS: The xylC was amplified and cloned in E. coli. The recombinant plasmid pGEMT-xylC was digested by NdeI and HindIII to construct plasmid pET28b-xylC and transformed in E...
March 2017: Iranian journal of biotechnology
Yang Yang, David Burghoff, John Reno, Qing Hu
Frequency combs based on quantum cascade lasers (QCLs) are finding promising applications in high-speed broadband spectroscopy in the terahertz regime, where many molecules have their "fingerprints." To form stable combs in QCLs, an effective control of group velocity dispersion plays a critical role. The dispersion of the QCL cavity has two main parts: a static part from the material and a dynamic part from the intersubband transitions. Unlike the gain, which is clamped to a fixed value above the lasing threshold, dispersion associated with the intersubband transitions changes with bias, even above the threshold, and this reduces the dynamic range of comb formation...
October 1, 2017: Optics Letters
Tao Liu, Rainer H Müller, Jan P Möschwitzer
Objective Drug nanosuspension is one of the established methods to improve the bioavailability of poorly soluble drugs. Drug physical properties aspect (morphology, solid state, starting size et al) is a critical parameter determining the production efficiency. Some drug modification approaches such as spray-drying were proved to improve the millability of drug powders. However, the mechanism behind those improved performances is unclear. This study is to systematically investigate the influence of those physical properties...
September 28, 2017: Drug Development and Industrial Pharmacy
Elisa Passini, Oliver J Britton, Hua Rong Lu, Jutta Rohrbacher, An N Hermans, David J Gallacher, Robert J H Greig, Alfonso Bueno-Orovio, Blanca Rodriguez
Early prediction of cardiotoxicity is critical for drug development. Current animal models raise ethical and translational questions, and have limited accuracy in clinical risk prediction. Human-based computer models constitute a fast, cheap and potentially effective alternative to experimental assays, also facilitating translation to human. Key challenges include consideration of inter-cellular variability in drug responses and integration of computational and experimental methods in safety pharmacology. Our aim is to evaluate the ability of in silico drug trials in populations of human action potential (AP) models to predict clinical risk of drug-induced arrhythmias based on ion channel information, and to compare simulation results against experimental assays commonly used for drug testing...
2017: Frontiers in Physiology
Marco Cardis, Maura Casadio, Rajiv Ranganathan
Motor variability plays an important role in motor learning, although the exact mechanisms of how variability affects learning is not well understood. Recent evidence suggests that motor variability may have different effects on learning in redundant tasks, depending on whether it is present in the task space (where it affects task performance), or in the null space (where it has no effect on task performance). Here we examined the effect of directly introducing null and task space variability using a manipulandum during the learning of a motor task...
September 27, 2017: Journal of Neurophysiology
Yong Zhang, Kuiling Li, Jun Wang, Deyin Hou, Huijuan Liu
To understand the mass transfer behaviors in hollow fiber membrane contactors, ozone fluxes affected by various conditions and membranes were investigated. For physical absorption, mass transfer rate increased with liquid velocity and the ozone concentration in the gas. Gas flow rate was little affected when the velocity was larger than the critical value, which was 6.1 × 10(-3)m/s in this study. For chemical absorption, the flux was determined by the reaction rate between ozone and the absorbent. Therefore, concentration, species, and pH affected the mass transfer process markedly...
September 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
Raz Halifa Levi, Yacov Kantor
We use Newtonian and overdamped Langevin dynamics to study long flexible polymers dragged by an external force at a constant velocity v. The work W performed by that force depends on the initial state of the polymer and the details of the process. The Jarzynski equality can be used to relate the nonequilibrium work distribution P(W) obtained from repeated experiments to the equilibrium free energy difference ΔF between the initial and final states. We use the power law dependence of the geometrical and dynamical characteristics of the polymer on the number of monomers N to suggest the existence of a critical velocity v_{c}(N), such that for v<v_{c} the reconstruction of ΔF is an easy task, while for v significantly exceeding v_{c} it becomes practically impossible...
August 2017: Physical Review. E
Yang Zhang, Yong-Xiang Huang, Nan Jiang, Yu-Lu Liu, Zhi-Ming Lu, Xiang Qiu, Quan Zhou
We investigate fluctuations of the velocity and temperature fields in two-dimensional (2D) Rayleigh-Bénard (RB) convection by means of direct numerical simulations (DNS) over the Rayleigh number range 10^{6}≤Ra≤10^{10} and for a fixed Prandtl number Pr=5.3 and aspect ratio Γ=1. Our results show that there exists a counter-gradient turbulent transport of energy from fluctuations to the mean flow both locally and globally, implying that the Reynolds stress is one of the driving mechanisms of the large-scale circulation in 2D turbulent RB convection besides the buoyancy of thermal plumes...
August 2017: Physical Review. E
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