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Critical velocity

Alessia Gloria, Augusto Carluccio, Laura Wegher, Domenico Robbe, Claudio Valorz, Alberto Contri
Background: Semen evaluation is used to estimate the testicular function. In bulls, the spermatozoa present in the ejaculate are the result of a process that begun more than 2 mo earlier, bequeathing a delayed depiction of the actual function of the testis. Since testis vascularization might be critical for the gonad function, selected pulse wave Doppler ultrasound parameters were assessed in this study, for instance the peak systolic velocity, the end diastolic velocity and the resistive index of the testicular artery along the spermatic cord, the marginal portion of the testicular artery and the intratesticular branches of the testicular artery both in healthy adult and young bulls...
2018: Journal of Animal Science and Biotechnology
Kenneth R Beyerlein
Diffraction imaging of nonequilibrium dynamics at atomic resolution is becoming possible with X-ray free-electron lasers. However, there are unresolved problems with applying this method to objects that are confined in only one dimension. Here I show that reliable one-dimensional coherent diffraction imaging is possible by splicing together images recovered from different time delays in an optical pump X-ray probe experiment. The time and space evolution of antiferromagnetic order in a vibrationally excited complex oxide heterostructure is recovered from time-resolved measurements of a resonant soft X-ray diffraction peak...
February 13, 2018: Proceedings of the National Academy of Sciences of the United States of America
Taylor B Lawson, Devon E Scott-Drechsel, Venkat Keshav Chivukula, Sandra Rugonyi, Kent L Thornburg, Monica T Hinds
Congenital heart defects (CHDs) represent the most common form of human birth defects; approximately one-third of heart defects involve malformations of the outflow tract (OFT). Maternal diabetes increases the risk of CHD by 3-5 fold. During heart organogenesis, little is known about the effects of hyperglycemia on hemodynamics, which are critical to normal heart development. Heart development prior to septation in the chick embryo was studied under hyperglycemic conditions. Sustained hyperglycemic conditions were induced, raising the average plasma glucose concentration from 70 mg/dL to 180 mg/dL, akin to the fasting plasma glucose of a patient with diabetes...
February 12, 2018: Journal of Cardiovascular Development and Disease
James S Hogg, James G Hopker, Sarah L Coakley, Alexis R Mauger
PURPOSE: The self-paced maximal oxygen uptake test (SPV) may offer effective training prescription metrics for athletes. This study aimed to examine whether SPV-derived data could be used for training prescription. METHODS: Twenty-four recreationally active male and female runners were randomly assigned between two training groups: (1) Standardised (STND) and (2) Self-Paced (S-P). Participants completed 4 running sessions a week using a global positioning system-enabled (GPS) watch: 2 × interval sessions; 1 × recovery run; and 1 × tempo run...
February 12, 2018: European Journal of Applied Physiology
S Das, T Sahoo, M H Meylan
The propagation of flexural gravity waves, routinely used to model wave interaction with sea ice, is studied, including the effect of compression and current. A number of significant and surprising properties are shown to exist. The occurrence of blocking above a critical value of compression is illustrated. This is analogous to propagation of surface gravity waves in the presence of opposing current and light wave propagation in the curved space-time near a black hole, therefore providing a novel system for studying analogue gravity...
January 2018: Proceedings. Mathematical, Physical, and Engineering Sciences
Alberto Otero-Cacho, María Aymerich, M Teresa Flores-Arias, Miguel Abal, Ezequiel Álvarez, Vicente Pérez-Muñuzuri, Alberto P Muñuzuri
Understanding hemodynamics in blood circulation is crucial in order to unveil the mechanisms underlying the formation of stenosis and atherosclerosis. In fact, there are experimental evidences pointing out to the existence of some given vessel configurations that are more likely to develop the above mentioned pathologies. Along this manuscript, we performed an exhaustive investigation in a simplified model aiming to characterize by means of physical quantities those regions and configurations in vessel bifurcations that are more likely to develop such pathologies...
February 12, 2018: Scientific Reports
R Blancas, Ó Martínez-González, D Ballesteros, A Núñez, J Luján, D Rodríguez-Serrano, A Hernández, C Martínez-Díaz, C M Parra, B L Matamala, M A Alonso, M Chana
OBJECTIVE: To assess the correlation between left ventricular outflow tract velocity time integral (LVOT VTI) and stroke volume index (SVI) calculated by thermodilution methods in ventilated critically ill patients. DESIGN: A prospective, descriptive, multicenter study was performed. SETTING: Five intensive care units from university hospitals. PATIENTS: Patients older than 17 years needing mechanical ventilation and invasive hemodynamic monitoring were included...
February 7, 2018: Medicina Intensiva
T Dvir, F Massee, L Attias, M Khodas, M Aprili, C H L Quay, H Steinberg
Tunnel junctions, an established platform for high resolution spectroscopy of superconductors, require defect-free insulating barriers; however, oxides, the most common barrier, can only grow on a limited selection of materials. We show that van der Waals tunnel barriers, fabricated by exfoliation and transfer of layered semiconductors, sustain stable currents with strong suppression of sub-gap tunneling. This allows us to measure the spectra of bulk (20 nm) and ultrathin (3- and 4-layer) NbSe2 devices at 70 mK...
February 9, 2018: Nature Communications
Tara D Edwards, Erich D Bain, Shawn T Cole, Reygan M Freeney, Virginia A Halls, Juliana Ivancik, Joseph L Lenhart, Eugene Napadensky, Jian H Yu, James Q Zheng, Randy A Mrozek
This paper describes a new witness material for quantifying the back face deformation (BFD) resulting from high rate impact of ballistic protective equipment. Accurate BFD quantification is critical for the assessment and certification of personal protective equipment, such as body armor and helmets, and ballistic evaluation. A common witness material is ballistic clay, specifically, Roma Plastilina No. 1 (RP1). RP1 must be heated to nearly 38°C to pass calibration, and used within a limited time frame to remain in calibration...
January 31, 2018: Forensic Science International
Muralikrishna Raju, Pavan B Govindaraju, Adri C T van Duin, Matthias Ihme
Recent theoretical and experimental studies reported ultra-high water permeability and salt rejection in nanoporous single-layer graphene. However, creating and controlling the size and distribution of nanometer-scale pores pose significant challenges to application of these membranes for water desalination. Graphyne and hydrogenated graphyne have tremendous potential as ultra-permeable membranes for desalination and wastewater reclamation due to their uniform pore-distribution, atomic thickness and mechano-chemical stability...
February 9, 2018: Nanoscale
Haoxun Wang, Chenchang Liu, Guofeng You
Human organic anion transporter-3 (hOAT3) is richly expressed in the kidney, where it plays critical roles in the secretion, from the blood to urine, of clinically important drugs, such as anti-viral therapeutics, anti-cancer drugs, antibiotics, antihypertensives, and anti-inflammatories. In the current study, we examined the role of dexamethasone in hOAT3 transport activity in the kidney HEK293 cells. Cis-inhibition study showed that dexamethasone exhibited a concentration-dependent inhibition of hOAT3-mediated uptake of estrone sulfate, a prototypical substrate for the transporter, with IC50 value of 49...
February 2, 2018: Journal of Pharmacological Sciences
Luis G Egea, Rocío Jiménez-Ramos, Ignacio Hernández, Tjeerd J Bouma, Fernando G Brun
Global change has been acknowledged as one of the main threats to the biosphere and its provision of ecosystem services, especially in marine ecosystems. Seagrasses play a critical ecological role in coastal ecosystems, but their responses to ocean acidification (OA) and climate change are not well understood. There have been previous studies focused on the effects of OA, but the outcome of interactions with co-factors predicted to alter during climate change still needs to be addressed. For example, the impact of higher CO2 and different hydrodynamic regimes on seagrass performance remains unknown...
2018: PloS One
Man Y Lam, Victoria J Haunton, Thompson G Robinson, Ronney B Panerai
We studied cerebral blood velocity (CBV), and associated hemodynamic parameters during gradual changes in head positioning in a nonstroke group. CBV (transcranial Doppler ultrasound), beat-to-beat blood pressure (BP, Finometer), and end-tidal carbon dioxide (ETCO2 , capnography) were recorded between lying flat (0°) and sitting up (30°) head positions, in 18 volunteers (10 female, mean age, 57 ± 16 years), at two visits (12 ± 8 days). A significant reduction was found between 5-min FLAT (0°) and 5-min SIT (30°) positions in CBV (visit 1: 4...
February 2018: Physiological Reports
Delphine Georges, Hugues de Courson, Romain Lanchon, Musa Sesay, Karine Nouette-Gaulain, Matthieu Biais
BACKGROUND: In mechanically ventilated patients, an increase in cardiac index during an end-expiratory-occlusion test predicts fluid responsiveness. To identify this rapid increase in cardiac index, continuous and instantaneous cardiac index monitoring is necessary, decreasing its feasibility at the bedside. Our study was designed to investigate whether changes in velocity time integral and in peak velocity obtained using transthoracic echocardiography during an end-expiratory-occlusion maneuver could predict fluid responsiveness...
February 8, 2018: Critical Care: the Official Journal of the Critical Care Forum
Florence H Sheehan, R Eugene Zierler
Healthcare providers who use peripheral vascular and cardiac ultrasound require specialized training to develop the technical and interpretive skills necessary to perform accurate diagnostic tests. Assessment of competence is a critical component of training that documents a learner's progress and is a requirement for competency-based medical education (CBME) as well as specialty certification or credentialing. The use of simulation for CBME in diagnostic ultrasound is particularly appealing since it incorporates both the psychomotor and cognitive domains while eliminating dependency on the availability of live patients with a range of pathology...
February 1, 2018: Vascular Medicine
Philip Brainin, Daria Frestad, Eva Prescott
AIMS: Coronary vascular dysfunction is linked with poor cardiovascular prognosis in patients without obstructive coronary artery disease (CAD) but a critical appraisal of the literature is lacking. METHODS AND RESULTS: We performed a systematic review and meta-analysis to quantify the cardiovascular risk associated with endothelial dependent and non-endothelial dependent coronary vascular dysfunction in patients with normal or non-obstructive CAD (epicardial stenosis <50%)...
March 1, 2018: International Journal of Cardiology
Haley C Bergstrom, M Travis Byrd, Brian J Wallace, Jody L Clasey
This study examined the acute effects of a multi-ingredient pre-workout supplement on: 1) total, lower, and upper body volume of resistance exercise; and 2) the subsequent lower body strength (isokinetic leg extension and flexion), lower (vertical jump [VJ] height), upper body power (bench-throw velocity [BTv]), and cycle ergometry performance (critical power [CP] and anaerobic work capacity [AWC]). Twelve men completed baseline strength and power measures prior to two experimental visits, supplement (SUP) and placebo (PL)...
February 1, 2018: Journal of Strength and Conditioning Research
Chensen Lin, Shuo Chen, Lanlan Xiao, Yang Liu
Controlling the motion of liquid drops on solid surface has broad technological implications. In this study, the many-body dissipative particle dynamics (MDPD) was employed to study the drop behaviors on chemical chessboard-patterned surfaces formed by square or triangular tiles. The scaling relationship of the model was established based on the surface tension, viscosity, and density of a real fluid, and an improved contact angle measurement technique was introduced to the MDPD system. For drops on a horizontal plane with different tile sizes, the equilibrium morphology was examined...
February 1, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Paul S Sung, Pamela Danial
Postural responses following slip perturbations are critical to fall prevention strategies. It is unclear how postural reactions with a handheld task can validly be transferred to treadmill-induced slip perturbations in subjects with recurrent low back pain (LBP). The purpose of this study was to investigate trunk reaction times and trunk flexion angle as well as velocity following the slips between subjects with and without LBP. There were 29 subjects with LBP and 40 control subjects who participated in the study...
January 25, 2018: Annals of Biomedical Engineering
Christian Rummel, Reto Basciani, Arto Nirkko, Gerhard Schroth, Monika Stucki, David Reineke, Balthasar Eberle, Heiko A Kaiser
Stroke due to hypoperfusion or emboli is a devastating adverse event of cardiac surgery, but early detection and treatment could protect patients from an unfavorable postoperative course. Hypoperfusion and emboli can be detected with transcranial Doppler of the middle cerebral artery (MCA). The measured blood flow velocity correlates with cerebral oxygenation determined clinically by near-infrared spectroscopy (NIRS) of the frontal cortex. We tested the potential advantage of a spatially extended NIRS in detecting critical events in three cardiac surgery patients with a whole-head fiber holder of the FOIRE-3000 continuous-wave NIRS system...
January 2018: Journal of Biomedical Optics
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