Increase In Maximal Velocity Research Articles

Effects of Race Car's Speed on the Aerodynamic Aspect Using Computational Fluid Dynamics Analysis

This research employs Computational Fluid Dynamics (CFD) methods to investigate the intricate relationship between race car speed and external aerodynamics during high-performance racing competitions. The primary objectives encompass the application of CFD in pre-processing and analyzing external aerodynamic aspects, coupled with a comprehensive examination of the external flow around a race car for a nuanced understanding of its aerodynamic performance. Various car speeds were considered with the RANS (k-ω SST) turbulent model. The results unveiled a direct correlation between inlet velocity and the maximum velocity attained by the race car. The aerodynamic design intricately directs the airflow, leading to higher velocities predominantly along the upper part of the car body. Noteworthy is the revelation that the highest recorded maximum velocity of 231.06 m/s coincides with a peak inlet velocity of 200 m/s, suggesting a consistent increase in maximum velocity with rising inlet velocity. This research emphasizes the pivotal role of inlet velocity in achieving peak car speed performance. It sheds light on the significance of turbulent model selection in capturing the complexities of external flow dynamics. This knowledge contributes to optimizing the external aerodynamics of race car body design, ultimately enhancing performance and competitiveness in the dynamic world of Formula 1 racing.

Electroosmotic flow in graphene nanochannels considering steric effects

Graphene nanochannels are excellent channels for electroosmotic flow (EOF) due to their larger slip length. In this study, the fully developed EOF in graphene nanochannels is investigated numerically, where the influence of surface charge mobility on the Navier-slip boundary conditions and the influence of steric effect on the electric potential distribution are considered. In addition, an analytical solution is provided for the scenario with low zeta potential. Detailed investigations are conducted on the impact of slip length, surface charge density, surface charge mobility, effective ion size, solution concentration, and channel height on velocity profiles. The findings indicate that the velocity increases with slip length, surface charge density, and effective ion size. Yet, accounting for surface charge mobility (αs = 0.815) leads to a reduction in slip velocity. It is noteworthy that our investigation focuses on quantifying the velocity decline due to surface charge mobility, as well as the velocity enhancement resulting from the steric effect. By adjusting parameters, such as channel height, bare slip length, and solution concentration, we achieve a maximum velocity increase of approximately 48%. These insights are valuable for optimizing the design of efficient electro-osmotic pumping systems.

Improved hydrodynamic properties and enhanced resistance to particle deposition and membrane fouling by millimeter-scale patterned membranes

Membrane fouling is considered a persistent challenge in membrane technology for water and wastewater treatment. Membrane surface patterning is a chemical-free means of controlling membrane fouling. Previous studies mainly focused on nano- and micro-scale patterns, with little attention paid on millimeter-scale patterns on the membrane surface. In this study, the millimeter-scale patterned microfiltration membranes with different pattern heights (PM50, PM55 and PM60) were fabricated, the performances in resisting particle deposition and membrane fouling with synthetic wastewater were examined compared with flat-sheet membrane (FM), and the underlying hydrodynamic mechanism was unveiled using computational fluid dynamics (CFD). CFD simulation results reveal that compared to micro- and nano-scale patterns, millimeter-scale patterns exert a notable increase in maximum velocity, average shear stress and maximum shear stress. All the three millimeter-scale patterned membranes exhibit superior resistance to both particle deposition and membrane fouling than FM, owing to the improvement of hydrodynamic properties instead of enlarged membrane area. PM55 shows the lowest flux decline ratios and least particle/foulant deposition among the three millimeter-scale patterned membranes in both particle deposition and membrane fouling experiments. Pattern height plays a crucial role, as small pattern height cannot generate significant vortices, while high pattern height leads to flow separation. For PM55, the vortices form in the valley regions and locate close to bulk flow, which help transport the deposited particles or foulants back to the bulk flow. The design of pattern configuration is suggested to be tailored based on particle size. Future research can focus on the pilot testing of millimeter-scale patterned membranes, as well as the long-term stability with actual influent.

Aortic valve calcification is promoted by interleukin-8 and restricted through antagonizing CXCR2.

Inflammatory cytokines play a critical role in the progression of calcific aortic valve disease (CAVD), for which there is currently no pharmacological treatment. The aim of this study was to test the hypothesis that interleukin-8 (IL-8), known to be involved in arterial calcification, also promotes aortic valve calcification (AVC) and to evaluate whether pharmacologically blocking the IL-8 receptor, CXC motif chemokine receptor 2 (CXCR2), could be effective in preventing AVC progression. A cohort of 195 patients (median age 73, 74% men) diagnosed with aortic valve stenosis (severe in 16.9% of cases) were prospectively followed by CT for a median time of 2.6 years. A Cox proportional hazards regression analysis indicated that baseline IL-8 serum concentrations were associated with rapid progression of AVC, defined as an annualized change in the calcification score by CT ≥ 110 AU/year, after adjustment for age, gender, bicuspid anatomy and baseline disease severity. In vitro, exposure of primary human aortic valvular interstitial cells (hVICs) to 15 pg/ml IL-8 induced a two-fold increase in inorganic phosphate (Pi)-induced calcification. IL-8 promoted NFκB pathway activation, MMP-12 expression, and elastin degradation in hVICs exposed to Pi. These effects were prevented by SCH527123, an antagonist of CXCR2. The expression of CXCR2 was confirmed in hVICs and samples of aortic valves isolated from patients with CAVD, in which the receptor was mainly found in calcified areas, along with MMP-12 and a degraded form of elastin. Finally, in a rat model of chronic kidney disease-associated CAVD, SCH527123 treatment (1 mg/kg/day given orally for 11 weeks) limited the decrease in aortic cusp separation, the increase in maximal velocity of the transaortic jet, and the increase in aortic mean pressure gradient measured by echocardiography, effects that were associated with a reduction in hydroxyapatite deposition and MMP-12 expression in the aortic valves. Overall, these results highlight, for the first time, a significant role for IL-8 in the progression of CAVD by promoting calcification via a CXCR2-- and MMP-12-dependent mechanism that leads to elastin degradation, and identify CXCR2 as a promising therapeutic target for the treatment of CAVD.

Theoretical and Numerical Study on Dynamic Response of Propellant Actuator

In order to solve the complexity of the structure, assembly process, component contact state and working process of the propellant actuator by conventional methods, a novel design method based on theoretical and numerical analysis was proposed. The internal ballistic model of the propellant actuator was established based on the classical internal ballistic theory, and the pressure–time characteristic curve of the propellant gas was then obtained. According to the characteristic curve, the dynamic characteristics of the piston under different design conditions of the shear slice were calculated by numerical simulation. The results show that the pressure–time characteristics of the internal ballistic model were in good agreement with the experimental data, indicating that the the internal ballistic model of the propellant actuator is reasonable. Additionally, the structure optimization design and drop safety of the propellant actuator were carried out using the finite element method. It was found that with increasing the propellant charge, the movement time of the piston decreases and the maximum velocity increases. Moreover, the critical values of the propellant charge are 5 mg, 6 mg, 7 mg for the thickness of the shear slice of 0.2 mm, 0.3 mm and 0.4 mm, respectively.

Increase and Decrease in Velocity and Force During Exercise with a Hybrid Robotic-FES Rehabilitation System.

Early rehabilitation is beneficial for stroke patients, but it is often delayed since the patients are often bedbound due to their general condition. New robotic rehabilitation devices such as ROBERT® enable patients to exercise even while bedbound. During pilot testing of an automated FES-delivery system combined with ROBERT®, we observed both increased and decreased exerted velocity and interaction force during repetitive exercising with the system. The goal of the current study was thus to investigate the extent of both potentiation and fatigue, as assessed in the velocity and interaction force produced in response to repetitive robotic-FES exercising. Eight healthy subjects completed 50 repetitions of leg-press exercises using the hybrid robotic-FES system. For individual subjects, significant changes were found for both mean and maximal velocities and interaction forces exerted during the exercise. Roughly half of the subjects had an increase in maximal velocity and interaction force during the exercise, and half exhibited an increase in mean velocity, whereas three subjects had an increase in mean interaction force during the exercise. The changes in mean velocity were in the range of -40.6 to 30.9% and for the maximal velocity they were in the range of -21.9 to 22.0%. The changes for mean interaction force were in the range of -5.8 to 11.0%, while for the maximal interaction force, they were in the range of -7.8 to 14.4%. These changes might pose significant challenges for future developments of hybrid robotic-FES rehabilitation systems, as the system must be able to comply with the observed changes, and appropriately adapt to them in order to maintain efficacy and safety.

The Structure and Function of Horseradish Peroxidase (HRP) under the Influence of Faradarmani Consciousness Field

The study of biological enzymes with their unique properties, such as substrate interactions, conformational changes, and catalytic rates, is a key to basic and applied enzymology research. Among enzymes, horseradish peroxidase (HRP) has been widely used in studying the metabolism of biological systems. In this study, we measure changes in the activity and structure of horseradish peroxidase in both laboratory grade and isoforms extracted from the plant under the influence of Faradarmani Consciousness Field (FCF). Our objectives were first to test the effect of FCF on the structure and function of HRP and, secondly, to analyze whether or not changes in the maximum velocity and Michaelis constant were reproducible under the influence of FCF. We observed that the laboratory-grade HRP had a 5% decrease in maximum velocity and an 18% increase in Michaelis constant as a result of the FCF treatment when compared to the non-treated controls. On the other hand, the HRP extracted from the plant tissue showed a 6% and 40% increase in maximum velocity and Michaelis constant, respectively, under FCF. Additionally, changes in the fluorescence emission intensity spectrum suggest that both structural and functional changes in this enzyme result from the FCF treatment.

Normal Values and Patterns of Normality and Physiological Variability of Mitral and Tricuspid Inflow Pulsed Doppler in Healthy Children.

Background: While mitral (MV) and tricuspid valve (TV) pulsed Doppler velocities and derived gradients are commonly evaluated, data on normal pediatric values are limited. This study aimed to evaluate the normal values and physiological variability for MV and TV Doppler velocities and derived gradients in a large cohort of prospectively enrolled healthy children. Methods: The echocardiographic measurements included pulsed Doppler MV and TV E and A velocities, E deceleration times (EDT), maximal and mean gradients, and velocity time integral (VTI). Results: A total of 544 healthy subjects (median age 6.4 years, range 1 day–17.68 years) were included. MV and TV E velocity, E/A ratio, and E and A wave duration increased, while A velocity decreased with age (p < 0.001). Along with an increase in VTI, there occurred a progressive increase in maximum velocity and gradients and a decrease in mean velocities and gradients. E/A inversions were common, especially at the TV in neonates and infants. For MV, inversion in either one, two, or three consecutive beats occurred in 51.9% of neonates and 18.3% of infants, while it was rare at older ages (all p < 0.001). For TV, inversions in three consecutive beats occurred in 71.4% of neonates, while inversions in only one or two beats were more common in infants (27.3%). For TV, inversion in one or more beats, however, was not infrequent at all ages. Conclusions: We report normal values and patterns of normality and physiological variability for MV and TV inflow Doppler from a large population of healthy children.

Selenomethionine (Se-Met) Induces the Cystine/Glutamate Exchanger SLC7A11 in Cultured Human Retinal Pigment Epithelial (RPE) Cells: Implications for Antioxidant Therapy in Aging Retina.

Oxidative damage has been identified as a major causative factor in degenerative diseases of the retina; retinal pigment epithelial (RPE) cells are at high risk. Hence, identifying novel strategies for increasing the antioxidant capacity of RPE cells, the purpose of this study, is important. Specifically, we evaluated the influence of selenium in the form of selenomethionine (Se-Met) in cultured RPE cells on system xc- expression and functional activity and on cellular levels of glutathione, a major cellular antioxidant. ARPE-19 and mouse RPE cells were cultured with and without selenomethionine (Se-Met), the principal form of selenium in the diet. Promoter activity assay, uptake assay, RT-PCR, northern and western blots, and immunofluorescence were used to analyze the expression of xc-, Nrf2, and its target genes. Se-Met activated Nrf2 and induced the expression and function of xc- in RPE. Other target genes of Nrf2 were also induced. System xc- consists of two subunits, and Se-Met induced the subunit responsible for transport activity (SLC7A11). Selenocysteine also induced xc- but with less potency. The effect of Se-met on xc- was associated with an increase in maximal velocity and an increase in substrate affinity. Se-Met increased the cellular levels of glutathione in the control, an oxidatively stressed RPE. The Se-Met effect was selective; under identical conditions, taurine transport was not affected and Na+-coupled glutamate transport was inhibited. This study demonstrates that Se-Met enhances the antioxidant capacity of RPE by inducing the transporter xc- with a consequent increase in glutathione.

Characterization of the Hydrodynamics in the USP Basket Apparatus Using Computational Fluid Dynamics

Computational fluid dynamics (CFD) has been extensively used for the USP paddle apparatus II, but limited CFD studies have been conducted on the USP basket apparatus I. We expanded on past CFD basket studies to consider the presence of a tablet inside the basket, compared predictions to in vivo conditions, and confirmed observations around the complexity of nonuniform hydrodynamics. Tablets near the basket perimeter experienced near 5-fold increase in maximum velocity and surface shear stress compared to tablets placed at the center of the basket. At higher basket speeds, the predicted velocities at the center of the basket were closer to in vivo predictions but the surface shear stress was about 2 orders of magnitude lesser. Simulations with a high viscosity fluid (1 Pa-s) showed a 10-fold increase in shear stress on a tablet but a decrease in strain rate compared to low-viscosity medium (0.001 Pa-s) which could impact dissolution rates. Also presented are the insights into turbulent energy dissipation rates that could help in a priori prediction of dissolution rates. Overall, the CFD analysis presented in this work reveals significant differences between the basket and in vivo conditions and will help inform relevant in vitro testing.

Numerical investigation of thermal creeping effect on a microsensor gas temperature and velocity distribution

ABSTRACT The study of fluid flow and heat transfer inside micromechanical systems is the focus of many researchers due to their importance in microchannels as small-scale devices. Reducing the size of channel has lead the scientist to concentrate on microsensor. Metal oxide gas microsensors, as a micromechanical device, are used to detect gases such as O3, SO2, CO2, NO, NH3, CH4, etc. The purpose of the current study is to numerically investigate the influence of three-dimensional diverging/converging microchannel on its gas inlet temperature while the flow of gas is due to thermal creeping. The coupled governing nonlinear differential equations, mass, momentum, energy, and species, are solved using an in-house code that is based on finite element. Maxwell equation for the slip boundary condition where the Knudsen number is between 0.01 and 0.1 is utilized. The result shows as channel width increases from 500 to 1300 µm the maximum increase in velocity is about 19% and the maximum decrease in temperature is about 1%, and the velocity and temperature stay constant after l = 1300 µm for all converging channels. From 500to 50 µm, the maximum decrease in velocity is about 30%, and the maximum decrease in temperature is about 1% that the maximum velocity changes take place at y = 1000 µm.

Acute Kinematic Effects of Sprinting With Motorized Assistance.

Clark, K, Cahill, M, Korfist, C, and Whitacre, T. Acute kinematic effects of sprinting with motorized assistance. J Strength Cond Res 35(7): 1856-1864, 2021-Although assisted sprinting has become popular for training maximum velocity, the acute effects are not fully understood. To examine this modality, 14 developmental male sprinters (age: 18.0 ± 2.5 years, 100-m personal best: 10.80 ± 0.31 seconds) performed maximal trials, both unassisted and assisted with a motorized towing device using a load of 7 kg (9.9 ± 0.9% body mass). Significant increases in maximum velocity (+9.4%, p ≤ 0.001, d = 3.28) occurred due to very large increases in stride length (+8.7%, p ≤ 0.001, d = 2.04) but not stride rate (+0.7%, p = 0.36, d = 0.11). Stride length increased due to small changes in distance traveled by the center of mass during ground contact (+3.7%, p ≤ 0.001, d = 0.40) combined with very large changes in distance traveled by the center of mass during flight (+13.1%, p ≤ 0.001, d = 2.62). Although stride rate did not demonstrate significant between-condition differences, the combination of contact and flight time was different. Compared to unassisted sprinting, assisted sprinting caused small but significant decreases in contact time (-5.2%, p ≤ 0.001, d = 0.49) and small but significant increases in flight time (+3.4%, p < 0.05, d = 0.58). Sprinting with motorized assistance elicited supramaximal velocities with decreased contact times, which may represent a neuromuscular stimulus for athletes attempting to enhance sprinting performance. Future research is needed to investigate the effects of this modality across various assistive loads and athletic populations, and to determine the longitudinal efficacy as a training method for improving maximum-velocity sprinting performance.

Environmentally relevant concentrations of di(2-ethylhexyl)phthalate exposure alter larval growth and locomotion in medaka fish via multiple pathways

Di(2-ethylhexyl)phthalate (DEHP) is a commonly used plasticizer, with evidence of ubiquitous human exposure and widespread occurrence in the aquatic environment. It is an emerging environmental pollutant with regulatory priority; however, most studies have focused on the toxicity of DEHP related to endocrine disruption and reproduction in mammals. The ecotoxicological impact of phthalates (e.g., DEHP) on early life stages of fish under environmentally relevant concentrations of chronic exposure remains unclear. In this study, 7-day post-hatching fry of medaka fish (Oryzias latipes) underwent 21-day continuous exposure to DEHP solutions at 20, 100 and 200 μg/L to assess the effects on fish development and locomotion and related toxic mechanisms. Larval mortality was low with DEHP (20–200 μg/L) within 21 days, but such exposure significantly reduced fish body weight and length and altered swimming behavior. At 21 days, DEHP exposure resulted in specific patterns of larval locomotion (e.g., increased maximum velocity and absolute turn angle) and dose-dependently increased the mRNA expression of acetylcholinesterase (ache) but did not alter AChE activity. Transcriptional expression of antioxidants such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase and peroxisome proliferation-activated receptor and retinoid X receptor genes was significantly suppressed with 21-day DEHP exposure (20–200 μg/L), with marginal alteration in reactive oxygen species levels and antioxidant activities within the dosing period. As well, DEHP altered the mRNA expression of p53-regulated apoptosis pathways, such as upregulated p53, p21 and bcl-2 and downregulated caspase-3 expression, with increased enzymatic activity of caspase-3 in larvae. Our results suggest that toxic mechanisms of waterborne DEHP altered fish growth and locomotion likely via a combined effect of oxidative stress, neurotoxicity and apoptosis pathways.

Renal sympathetic denervation increases renal blood volume per cardiac cycle: a serial magnetic resonance imaging study in resistant hypertension

AimPreclinical studies have demonstrated improvements in renal blood flow after renal sympathetic denervation (RSDN); however, such effects are yet to be confirmed in patients with resistant hypertension. Herein, we assessed the effects of RSDN on renal artery blood flow and diameter at multiple time points post-RSDN.Methods and resultsPatients (n=11) with systolic blood pressures ≥160 mmHg despite taking three or more antihypertensive medications at maximum tolerated dose were recruited into this single-center, prospective, non-blinded study. Magnetic resonance imaging indices included renal blood flow and renal artery diameters at baseline, 1 month and 6 months. In addition to significant decreases in blood pressures (p<0.0001), total volume of blood flow per cardiac cycle increased by 20% from 6.9±2 mL at baseline to 8.4±2 mL (p=0.003) at 1 month and to 8.0±2 mL (p=0.04) 6 months post-procedure, with no changes in the renal blood flow. There was a significant decrease in renal artery diameters from 7±2 mm at baseline to 6±1 mm (p=0.03) at 1 month post-procedure. This decrease was associated with increases in maximum velocity of blood flow from 73±20 cm/s at baseline to 78±19 cm/s at 1 month post-procedure. Notably, both parameters reverted to 7±2 mm and 72±18 cm/s, respectively, 6 months after procedure.ConclusionRSDN improves renal physiology as evidenced by significant improvements in total volume of blood flow per cardiac cycle. Additionally, for the first time, we identified a transient decrease in renal artery diameters immediately after procedure potentially caused by edema and inflammation that reverted to baseline values 6 months post-procedure.

Severe Obesity Shifts Metabolic Thresholds but Does Not Attenuate Aerobic Training Adaptations in Zucker Rats.

Severe obesity affects metabolism with potential to influence the lactate and glycemic response to different exercise intensities in untrained and trained rats. Here we evaluated metabolic thresholds and maximal aerobic capacity in rats with severe obesity and lean counterparts at pre- and post-training. Zucker rats (obese: n = 10, lean: n = 10) were submitted to constant treadmill bouts, to determine the maximal lactate steady state, and an incremental treadmill test, to determine the lactate threshold, glycemic threshold and maximal velocity at pre and post 8 weeks of treadmill training. Velocities of the lactate threshold and glycemic threshold agreed with the maximal lactate steady state velocity on most comparisons. The maximal lactate steady state velocity occurred at higher percentage of the maximal velocity in Zucker rats at pre-training than the percentage commonly reported and used for training prescription for other rat strains (i.e., 60%) (obese = 78 ± 9% and lean = 68 ± 5%, P < 0.05 vs. 60%). The maximal lactate steady state velocity and maximal velocity were lower in the obese group at pre-training (P < 0.05 vs. lean), increased in both groups at post-training (P < 0.05 vs. pre), but were still lower in the obese group at post-training (P < 0.05 vs. lean). Training-induced increase in maximal lactate steady state, lactate threshold and glycemic threshold velocities was similar between groups (P > 0.05), whereas increase in maximal velocity was greater in the obese group (P < 0.05 vs. lean). In conclusion, lactate threshold, glycemic threshold and maximal lactate steady state occurred at similar exercise intensity in Zucker rats at pre- and post-training. Severe obesity shifted metabolic thresholds to higher exercise intensity at pre-training, but did not attenuate submaximal and maximal aerobic training adaptations.

Effect of a Six-Week Preparation Period on Acute Physiological Responses to a Simulated Combat in Young National-Level Taekwondo Athletes.

The aim of this study was to examine changes in physical attributes, physiological characteristics and responses that occurred in a simulated combat during a six-week preparatory period in young taekwondo athletes. Seven athletes (age 12.17 ± 1.11 years) were examined before (pre-intervention) and after (post-intervention) a preparatory period for physical fitness and physiological responses to a 2×90 s simulated bout with a 30 s rest period. The heart rate (HR) was monitored during the simulated combat, and handgrip muscle strength (HMS) along with the countermovement jump (CMJ) were recorded before and after the combat. When compared with pre-intervention values, in post-intervention we observed a decrease in body mass, body fat percentage, and the HR at rest and during recovery after a 3 min step test, and an increase in maximal velocity of the cycle ergometer force-velocity test, the CMJ and mean power during the 30 s continuous jumping test (p<0.05). Furthermore, HR responses to a simulated combat were lower in the post-intervention session (p<0.05). CMJ values increased after the bout in both pre and post-intervention, with higher absolute values in the latter case (p<0.05), whereas there was no difference in HMS. Based on these findings, it can be concluded that the acute physiological responses to a simulated taekwondo combat vary during a season, which might be explained by changes in physical fitness.

Analysis of flow characteristics around islands due to semi-diurnal currents in the Han River, Korea

In this study, an unsteady 2D depth-averaged flow model by Petrov-Galerkin stabilization was developed to investigate flow characteristics caused by semi-diurnal current at the tidal reach of the Han River. In order to analyze the velocity field around islands located in the mid-course of the Han River, simulations of the transient flow were conducted with principal lunar and solar semidiurnal constituent conditions. In addition, the influence of an artificial island construction located at the tributary confluence was quantitatively examined. The results show that, under normal flow condition, around Bam Island, main flow was inclined to the left half of the river span, and the velocity reversal was occurred during the flood tide which would result in the deposition sediment to form the Island. Under bank-full flood condition, velocities around No-deul Island were higher than those around Seon-yu Island reaching 3.5 m/s in maximum. The construction of the artificial island at the Jung-nang Stream confluence caused the significant reduction in the flood conveyance of the Han River and 90% increase in maximum velocity during the bank-full flood flow condition.

A three-dimensional hydrodynamic model for aquaculture: a case study in the Bay of Fundy

Impacts of aquaculture on the local current field and the erosion of the bottom sedi- ment in the Bay of Fundy, Canada, have been investigated with a 3-dimensional hydrodynamic model. The model is evaluated against independent observations of the current. Model results show that the presence of fish cages restricts water flow and reduces the velocity in the surface layer occupied by the cages, but enhances the water velocity in the bottom layer beneath the cages. Sensitivity studies show that the change in the flow velocity beneath the cages is sensitive to variations in the drag coefficient and the height of the fish cages. As the drag coefficient increases, the bottom velocity also increases until a steady state value is reached. For the cage height, however, the tidal speed beneath the cages first increases with cage height and then sig- nificantly decreases with further increasing height. The maximum increase in velocity occurs when the cage height is about half the local water depth (H/H0 = 0.5, where H is the cage height and H0 is the water depth). The increase in bottom velocity significantly speeds up the erosion of the bottom sediment. The model results also indicate that there is an optimal drag coefficient and an optimal cage height for a specific farm site. By utilizing the optimal drag coefficient and height, it is possible to speed up sediment erosion beneath the cages and, thus, decrease the environ - mental problems caused by accumulated fish farm waste.

Engineering the allosteric properties of archaeal non-phosphorylating glyceraldehyde-3-phosphate dehydrogenases

The archaeal non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase (GAPN, EC 1.2.1.9) is a highly allosteric enzyme activated by glucose 1-phosphate (Glc1P). Recent kinetic analyses of two GAPN homologs from Sulfolobales show different allosteric behaviors toward the substrate glyceraldehyde-3-phosphate (GAP) and the allosteric effector Glc1P. In GAPN from Sulfolobus tokodaii (Sto-GAPN), Glc1P-induced activation follows an increase in affinity for GAP rather than an increase in maximum velocity, whereas in GAPN from Sulfolobus solfataricus (Sso-GAPN), Glc1P-induced activation follows an increase in maximum velocity rather than in affinity for GAP. To explore the molecular basis of this difference between Sto-GAPN and Sso-GAPN, we generated 14 mutants and 2 chimeras. The analyses of chimeric GAPNs generated from regions of Sto-GAPN and Sso-GAPN indicated that a 57-residue module located in the subunit interface was clearly involved in their allosteric behavior. Among the point mutations in this modular region, the Y139R variant of Sto-GAPN no longer displayed a sigmoidal K-type-like allostery, but instead had apparent V-type allostery similar to that of Sso-GAPN, suggesting that the residue located in the center of the homotetramer critically contributes to the allosteric behavior.

The effect of base roughness on the development of a dense granular flow down an inclined plane

The development of the flow of a granular material down an inclined plane starting from rest is studied as a function of the base roughness. In the simulations, the particles are rough frictional spheres interacting via the Hertz contact law. The rough base is made of a random configuration of fixed spheres with diameter different from the flowing particles, and the base roughness is decreased by decreasing the diameter of the base particles. The transition from an ordered to a disordered flowing state at a critical value of the base particle diameter, first reported by Kumaran and Maheshwari [Phys. Fluids 24, 053302 (2012)]10.1063/1.4710543 for particles with the linear contact model, is observed for the Hertzian contact model as well. The flow development for the ordered and disordered flows is very different. During the development of the disordered flow for the rougher base, there is shearing throughout the height. During the development of the ordered flow for the smoother base, there is a shear layer at the bottom and a plug region with no internal shearing above. In the shear layer, the particles are layered and hexagonally ordered in the plane parallel to the base, and the velocity profile is well approximated by Bagnold law. The flow develops in two phases. In the first phase, the thickness of the shear layer and the maximum velocity increase linearly in time till the shear front reaches the top. In the second phase, after the shear layer encompasses the entire flow, there is a much slower increase in the maximum velocity until the steady state is reached.