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Critical velocity

Behrooz Ferdowsi, Carlos P Ortiz, Douglas J Jerolmack
Soil creeps imperceptibly downhill, but also fails catastrophically to create landslides. Despite the importance of these processes as hazards and in sculpting landscapes, there is no agreed-upon model that captures the full range of behavior. Here we examine the granular origins of hillslope soil transport by discrete element method simulations and reanalysis of measurements in natural landscapes. We find creep for slopes below a critical gradient, where average particle velocity (sediment flux) increases exponentially with friction coefficient (gradient)...
April 23, 2018: Proceedings of the National Academy of Sciences of the United States of America
Jing Jin, Chin Hong Ooi, Dzung Viet Dao, Nam-Trung Nguyen
The coalescence process of liquid marbles is vital to their promising roles as reactors or mixers in digital microfluidics. However, the underlying mechanisms and critical conditions of liquid marble coalescence are not well understood. This paper studies the coalescence process of two equally-sized liquid marbles via vertical collision aided by dielectrophoretic handling. A liquid marble was picked up using the dielectrophoretic force and then dropped vertically onto another liquid marble resting on a hydrophobic powder bed...
April 23, 2018: Soft Matter
A Goswami, S Barbot
Slow-slip events are earthquake-like events only with much lower slip rates. While peak coseismic velocities can reach tens of meters per second, slow-slip is on the order of 10-7±2 m/s and may last for days to weeks. Under the rate-and-state model of fault friction, slow-slip is produced only when the asperity size is commensurate with the critical nucleation size, a function of frictional properties. However, it is unlikely that all subduction zones embody the same frictional properties. In addition to friction, plastic flow of antigorite-rich serpentinite may significantly influence the dynamics of fault slip near the mantle wedge corner...
April 18, 2018: Scientific Reports
Kanchan Kulkarni, Xueyi Xie, Ezequiel Marron Fernandez de Velasco, Allison Anderson, Kirill A Martemyanov, Kevin Wickman, Elena G Tolkacheva
A large body of work has established the prominent roles of the atrial M2R-IKACh signaling pathway, and the negative regulatory protein RGS6, in modulating critical aspects of parasympathetic influence on cardiac function, including pace-making, heart rate (HR) variability (HRV), and atrial arrhythmogenesis. Despite increasing evidence of its innervation of the ventricles, and the expression of M2R, IKACh channel subunits, and RGS6 in ventricle, the effects of parasympathetic modulation on ventricular electrophysiology are less clear...
2018: PloS One
Xinghao Hu, Sri Ramulu Torati, Jonghwan Yoon, Byeonghwa Lim, Kunwoo Kim, CheolGi Kim
We demonstrate an efficient approach for quantifying frictional forces (sub-pN) at nano-bio interfaces by controlled magnetic forces, which is based on simultaneous measurements of critical frequencies for streptavidin-coupled magnetic particles. The maximum phase angle, being corresponded with the critical frequency, is formulated in terms of magnetic, frictional and viscous forces of the particles on DNA and SiO2 functionalized micromagnet arrays. The streptavidin/DNA interface shows lower friction as an enhanced lubrication than the streptavidin/SiO2 interface, which is indicated by the lower transition field of quasi-static motion, the larger ratio of dynamic particles, and also the higher velocity of the particles...
April 18, 2018: ACS Applied Materials & Interfaces
Y Hou, L Cai, X Wang, X Chen, D Zhu, D Johnson, X Shi
A series of stepped velocity tests were carried out in a Brett-type swimming respirometer and the overall range in swimming performance for twelve Schizothoracinae species was measured. The relative critical swimming speed Ucrit and burst speed Uburst decreased with body length, while absolute Ucrit and Uburst increased with body length. Ucrit increased with temperature up to approximately 15o C and then decreased. Species with a high Ucrit also displayed a higher Uburst .
April 16, 2018: Journal of Fish Biology
Neeral R Patel, Elizabeth Dick, Nicola Batrick, Michael Jenkins, Elika Kashef
Blunt thoracic aortic injury (TAI) occurs most frequently as a sequelae of high impact deceleration such as high velocity road traffic accidents and falls from height. The burden of mortality and morbidity is high, however advances in pre-hospital care, diagnostic imaging and endovascular therapies have improved outcomes in this group of patients. Emergent treatment depends on accurate, early diagnosis by the radiologist. It is therefore of paramount importance that radiologists are familiar with both the direct (intimal flap, pseudoaneurysm, aortic contour irregularity and contrast extravasation) and indirect (periaortic haematoma) imaging findings of TAI...
April 12, 2018: British Journal of Radiology
Nicolás Eduardo Muzzio, Marcos Carballido, Miguel Pasquale, Pedro Horacio González, Omar Azzaroni, Alejandro Jorge Arvia
The epidermal growth factor (EGF) plays a key role in physiological and pathological processes. This work reports on the influence of EGF concentration (<i>c</i><sub>EGF</sub>) on the modulation of individual cell phenotype and cell colony kinetics with the aim of perturbing the colony front roughness fluctuations. For this purpose, HeLa cell colonies that remain confluent along the whole expansion process with initial quasi-radial geometry and different initial cell populations, as well as colonies with initial quasi-linear geometry and large cell population, are employed...
April 6, 2018: Physical Biology
Long Qian, Hongwei Zhao, Yue Guo, Yuanshang Li, Mingxing Zhou, Liguo Yang, Zhiwei Wang, Yifan Sun
Knowledge of brain tissue mechanical properties may be critical for formulating hypotheses about some specific diseases mechanisms and its accurate simulations such as traumatic brain injury (TBI) and tumor growth. Compared to traditional tests (e.g. tensile and compression), indentation shows superiority by virtue of its pinpoint and nondestructive/quasi-nondestructive. As a viscoelastic material, the properties of brain tissue depend on the strain rate by definition. However most efforts focus on the aspect of velocity in the field of brain indentation, rather than strain rate...
March 28, 2018: Journal of the Mechanical Behavior of Biomedical Materials
Agnieszka Uryga, Magdalena Kasprowicz, Leanne Calviello, Rolf R Diehl, Katarzyna Kaczmarska, Marek Czosnyka
BACKGROUND: Prior methods evaluating the changes in cerebral arterial blood volume (∆Ca BV) assumed that brain blood transport distal to big cerebral arteries can be approximated with a non-pulsatile flow (CFF) model. In this study, a modified ∆Ca BV calculation that accounts for pulsatile blood flow forward (PFF) from large cerebral arteries to resistive arterioles was investigated. The aim was to assess cerebral hemodynamic indices estimated by both CFF and PFF models while changing arterial blood carbon dioxide concentration (EtCO2 ) in healthy volunteers...
April 4, 2018: Journal of Clinical Monitoring and Computing
Hojun Lim, Jay D Carroll, Corbett C Battaile, Shuh Rong Chen, Alexander P Moore, J Matthew D Lane
Deformation mechanisms in bcc metals, especially in dynamic regimes, show unusual complexity, which complicates their use in high-reliability applications. Here, we employ novel, high-velocity cylinder impact experiments to explore plastic anisotropy in single crystal specimens under high-rate loading. The bcc tantalum single crystals exhibit unusually high deformation localization and strong plastic anisotropy when compared to polycrystalline samples. Several impact orientations - [100], [110], [111] and [[Formula: see text]] - are characterized over a range of impact velocities to examine orientation-dependent mechanical behavior versus strain rate...
April 3, 2018: Scientific Reports
Kalle H Sipilä, Kati Drushinin, Pekka Rappu, Johanna Jokinen, Tiina A Salminen, Antti M Salo, Jarmo Käpylä, Johanna Myllyharju, Jyrki Heino
Collagens are the most abundant extracellular matrix proteins in vertebrates and have a characteristic triple-helix structure. Hydroxylation of proline residues is critical for helix stability, and diminished prolyl hydroxylase activity causes widespread defects in connective tissues. Still, the role of proline hydroxylation in the binding of collagen receptors such as integrins is unclear. Here, we isolated skin collagen from genetically modified mice having reduced prolyl 4-hydroxylase activity. At room temperature, the reduced proline hydroxylation did not affect interactions with the recombinant integrin α2I domain, but at 37°C, collagen hydroxylation correlated with the avidity of α2I domain binding...
April 3, 2018: Journal of Biological Chemistry
Wen-Pin Hsieh, Frédéric Deschamps, Takuo Okuchi, Jung-Fu Lin
Iron may critically influence the physical properties and thermochemical structures of Earth's lower mantle. Its effects on thermal conductivity, with possible consequences on heat transfer and mantle dynamics, however, remain largely unknown. We measured the lattice thermal conductivity of lower-mantle ferropericlase to 120 GPa using the ultrafast optical pump-probe technique in a diamond anvil cell. The thermal conductivity of ferropericlase with 56% iron significantly drops by a factor of 1.8 across the spin transition around 53 GPa, while that with 8-10% iron increases monotonically with pressure, causing an enhanced iron substitution effect in the low-spin state...
April 2, 2018: Proceedings of the National Academy of Sciences of the United States of America
D S R Angrimani, G R Silvestrini, M M Brito, R A Abreu, L L Almeida, C I Vannucchi
Benign prostatic hyperplasia (BPH) is characterized by an enlargement of the prostate accompanied by an increase in prostatic blood perfusion and vascularization. The most indicated treatment is to perform orchiectomy, however, medical treatment with finasteride can be an option for breeding dogs or elderly animals with a critical health status. In dogs, the influence of medical treatment on prostatic hemodynamics is still unknown. Therefore, this study aimed to evaluate the effects of benign prostatic hyperplasia and finasteride therapy on hemodynamic and vascular features of the canine prostate...
March 27, 2018: Theriogenology
Qiaochu Li, Kuo-Fu Tseng, Stephen J King, Weihong Qiu, Jing Xu
Kinesin-1 (hereafter referred to as kinesin) is a major microtubule-based motor protein for plus-end-directed intracellular transport in live cells. While the single-molecule functions of kinesin are well characterized, the physiologically relevant transport of membranous cargos by small teams of kinesins remains poorly understood. A key experimental challenge remains in the quantitative control of the number of motors driving transport. Here we utilized "motile fraction" to overcome this challenge and experimentally accessed transport by a single kinesin through the physiologically relevant transport by a small team of kinesins...
March 28, 2018: Journal of Chemical Physics
Petrice M Cogswell, Jeroen C W Siero, Sarah K Lants, Spencer Waddle, L Taylor Davis, Guillaume Gilbert, Jeroen Hendrikse, Manus J Donahue
BACKGROUND: Flow suppression techniques have been developed for intracranial (IC) vessel wall imaging (VWI) and optimized using simulations; however, simulation results may not translate in vivo. PURPOSE: To evaluate experimentally how IC vessel wall and lumen measurements change in identical subjects when evaluated using the most commonly available blood and cerebrospinal fluid (CSF) flow suppression modules and VWI sequences. STUDY TYPE: Prospective...
March 31, 2018: Journal of Magnetic Resonance Imaging: JMRI
Timothy R Kent, Charles B Bott, Zhi-Wu Wang
In the wake of the success of aerobic granulation in sequential batch reactors (SBRs) for treating wastewater, attention is beginning to turn to continuous flow applications. This is a necessary step given the advantages of continuous flow treatment processes and the fact that the majority of full-scale wastewater treatment plants across the world are operated with aeration tanks and clarifiers in a continuous flow mode. As in SBRs, applying a selection pressure, based on differences in either settling velocity or the size of the biomass, is essential for successful granulation in continuous flow reactors (CFRs)...
March 26, 2018: Biotechnology Advances
Gary G Adams, Andrew Meal, Paul S Morgan, Qushmua E Alzahrani, Hanne Zobel, Ryan Lithgo, M Samil Kok, David T M Besong, Shahwar I Jiwani, Simon Ballance, Stephen E Harding, Naomi Chayen, Richard B Gillis
The structure and function of clinical dosage insulin and its analogues were assessed. This included 'native insulins' (human recombinant, bovine, porcine), 'fast-acting analogues' (aspart, glulisine, lispro) and 'slow-acting analogues' (glargine, detemir, degludec). Analytical ultracentrifugation, both sedimentation velocity and equilibrium experiments, were employed to yield distributions of both molar mass and sedimentation coefficient of all nine insulins. Size exclusion chromatography, coupled to multi-angle light scattering, was also used to explore the function of these analogues...
2018: PloS One
Jianling Yuan, Richard Lee, Kathryn Ellen Dusenbery, Chung K Lee, Damien C Mathew, Paul Wayne Sperduto, Yoichi Watanabe
Purpose: Repeat stereotactic radiosurgery (SRS) is an attractive alternative to whole brain radiation therapy (WBRT) for treatment of recurrent brain metastases (BM). The purpose of this study is to determine the cumulative doses to the brain and critical normal structures in patients who underwent repeat courses of Gamma Knife (GK) SRS. Materials and methods: We retrospectively identified ten patients who received at least three GK-SRS sessions for multiply recurrent BM at our institution from 2013 to 2016...
2018: Frontiers in Oncology
Vilas Saldanha, Nathan Tiedeken, Brandon Godfrey, Nichole Ingalls
Background: Since the start of the conflict in the Middle East in 2001, military orthopedic surgeons have faced complex orthopedic injuries including high-energy soft tissue wounds, traumatic amputations, and open fractures. Although orthopedic surgeons are well trained in the management of osseous injuries, the treatment of soft tissue injuries can be technically challenging and unfamiliar. Early washout, debridement of devitalized tissue, external fixation of bony injuries, and antibiotic therapy remain the foundation of early wound management...
March 26, 2018: Military Medicine
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