A pressure-gradient mechanism for vortex shedding in constricted channels.
Ontology highlight
ABSTRACT:
SUBMITTER: Boghosian ME
PROVIDER: S-EPMC3880383 | biostudies-other | 2013 Dec
REPOSITORIES: biostudies-other
Similar Datasets
Project description:This numerical investigation deals with study of flow past seven square cylinders arranged in staggered configuration. Simulations to the underlying problem are carried out by using the single relaxation time lattice Boltzmann method. The gap spacing between the staggered rows is varied in streamwise direction from 0.25 to 2 and for three transverse spacing i.e. T* = 1, 1.5 and 2. The complex vortex shedding mechanism is visualized for different streamwise and transverse gap spacings. Furthermore, the vortex shedding mechanisms in the wake of downstream row of cylinders are debated by using vorticity snapshots, time-trace plots of drag and lift coefficients and power spectra visualization of lift coefficient. It is also observed that the secondary cylinder interaction frequency contributes significantly to the hydrodynamic forces experienced by the cylinders. The physical parameters, such as Strouhal number, the drag and lift coefficients and their root-mean-square values have also been discussed in detail.
| S-EPMC6378353 | biostudies-literature
Project description:Blood damage and platelet activation are inherent problems with present day bi-leaflet mechanical heart valve designs. Passive flow control through different arrangements of vortex generators (VG) as means of improving pressure gradients and reducing turbulence are investigated. Rectangular VG arrays were mounted on the downstream surfaces of a 23 mm 3D printed mechanical valve. The effect of VGs on the resulting flow structures were assessed under pulsatile physiological flow conditions where high resolution particle image velocimetry measurement was performed. The co-rotating VGs showed lower Reynolds shear stresses and improved pressure gradients (PG) compared with the counter-rotating ones and the no-VG control one (that showed higher turbulence). RSS was found 38.13 ± 0.89, 12.95 ± 0.32, 15.75 ± 0.71, 24.54 ± 0.84 and 16.33 ± 0.58 Pa for the control, co-rotating VGs, 8 counter-rotating VGs, 4 far-spaced VGs and 4 closely-spaced VGs, respectively. PG of 10.45 ± 0.94 mmHg was obtained with co-rotating VGs and the difference was significant compared with the other configurations (control 14.88 ± 0.4 mmHg; 8 counter-rotating VGs 13.76 ± 0.51 mmHg; 4 far-spaced VGs 13.84 ± 0.09 mmHg; and 4 closely-spaced VGs 15.37 ± 0.16 mmHg). Co-rotating VGs for this application induce a more delayed flow separation and a more homogenized and streamlined transition of flow compared with the counter-rotating VGs. Passive flow control techniques deployed on BHMVs is potentially beneficial as significant control of flow at small length scales without inducing large-scale design modifications of the valve.
| S-EPMC6408289 | biostudies-literature
Project description:The Lagrangian vortex method has the advantage of producing highly detailed simulations of fluids such as turbulent smoke. However, this method has two problems: the construction of the velocity field from the vorticity field is inefficient, and handling the boundary condition is difficult. We present a pure Lagrangian vortex method, including a nested grid to accelerate the construction of the velocity field, and a novel boundary treatment method for the vorticity field. Based on a tree structure, the nested grid algorithm considerably improves the efficiency of the velocity computation while producing visual results that are comparable with the original flow. Based on the vortex-generating method, the least square method is used to compute the vorticity strength of the new vortex elements. Further, we consider the mutual influence between the generated vortex particles. We demonstrate our method’s benefits by using a vortex ring and various examples of interaction between the smoke and obstacles.
| S-EPMC9202895 | biostudies-literature
Project description:The canonical mechanistic model explaining potassium channel gating is of a conformational change that alternately dilates and constricts a collar-like intracellular entrance to the pore. It is based on the premise that K+ ions maintain a complete hydration shell while passing between the transmembrane cavity and cytosol, which must be accommodated. To put the canonical model to the test, we locked the conformation of a Kir K+ channel to prevent widening of the narrow collar. Unexpectedly, conduction was unimpaired in the locked channels. In parallel, we employed all-atom molecular dynamics to simulate K+ ions moving along the conduction pathway between the lower cavity and cytosol. During simulations, the constriction did not significantly widen. Instead, transient loss of some water molecules facilitated K+ permeation through the collar. The low free energy barrier to partial dehydration in the absence of conformational change indicates Kir channels are not gated by the canonical mechanism.
| S-EPMC7295778 | biostudies-literature
Project description:Wave fields with orbital angular momentum (OAM) have been widely investigated in metasurfaces. By engineering acoustic metasurfaces with phase gradient elements, phase twisting is commonly used to obtain acoustic OAM. However, it has limited ability to manipulate sound vortices, and a more powerful mechanism for sound vortex manipulation is strongly desired. Here, we propose the diffraction mechanism to manipulate sound vortices in a cylindrical waveguide with phase gradient metagratings (PGMs). A sound vortex diffraction law is theoretically revealed based on the generalized conservation principle of topological charge. This diffraction law can explain and predict the complicated diffraction phenomena of sound vortices, as confirmed by numerical simulations. To exemplify our findings, we designed and experimentally verified a PGM based on Helmholtz resonators that support asymmetric transmission of sound vortices. Our work provides previously unidentified opportunities for manipulating sound vortices, which can advance more versatile design for OAM-based devices.
| S-EPMC7852395 | biostudies-literature
Project description:Intracellular delivery of functional macromolecules, such as DNA and RNA, across the cell membrane and into the cytosol, is a critical process in both biology and medicine. Herein, we develop and use microfluidic chips containing post arrays to induce microfluidic vortex shedding, or μVS, for cell membrane poration that permits delivery of mRNA into primary human T lymphocytes. We demonstrate transfection with μVS by delivery of a 996-nucleotide mRNA construct encoding enhanced green fluorescent protein (EGFP) and assessed transfection efficiencies by quantifying levels of EGFP protein expression. We achieved high transfection efficiency (63.6 ± 3.44% EGFP + viable cells) with high cell viability (77.3 ± 0.58%) and recovery (88.7 ± 3.21%) in CD3 + T cells 19 hrs after μVS processing. Importantly, we show that processing cells via μVS does not negatively affect cell growth rates or alter cell states. We also demonstrate processing speeds of greater than 2.0 × 106 cells s-1 at volumes ranging from 0.1 to 1.5 milliliters. Altogether, these results highlight the use of μVS as a rapid and gentle delivery method with promising potential to engineer primary human cells for research and clinical applications.
| S-EPMC6397276 | biostudies-literature
Project description:Microfluidic vortex shedding (µVS) can rapidly deliver mRNA to T cells with high yield and minimal perturbation of the cell state. The mechanistic underpinning of µVS intracellular delivery remains undefined and µVS-Cas9 genome editing requires further studies. Herein, we evaluated a series of µVS devices containing splitter plates to attenuate vortex shedding and understand the contribution of computed force and frequency on efficiency and viability. We then selected a µVS design to knockout the expression of the endogenous T cell receptor in primary human T cells via delivery of Cas9 ribonucleoprotein (RNP) with and without brief exposure to an electric field (eµVS). µVS alone resulted in an equivalent yield of genome-edited T cells relative to electroporation with improved cell quality. A 1.8-fold increase in editing efficiency was demonstrated with eµVS with negligible impact on cell viability. Herein, we demonstrate efficient processing of 5 × 106 cells suspend in 100 µl of cGMP OptiMEM in under 5 s, with the capacity of a single device to process between 106 to 108 in 1 to 30 s. Cumulatively, these results demonstrate the rapid and robust utility of µVS and eµVS for genome editing human primary T cells with Cas9 RNPs.
| S-EPMC8175688 | biostudies-literature
Project description:AimsThe diastolic pressure gradient (DPG) has been proposed as a marker pulmonary vascular disease in the setting of left heart failure (HF). However, its diagnostic utility is compromised by the high prevalence of physiologically incompatible negative values (DPGNEG) and the contradictory evidence on its prognostic value. Pressure pulsatility impacts on DPG measurements, thus conceivably, pulmonary artery wedge pressure (PAWP) measurements insusceptible to the oscillatory effect of the V-wave might yield a more reliable DPG assessment. We set out to investigate how the instantaneous PAWP at the trough of the Y-descent (PAWPY) influences the prevalence of DPGNEG and the prognostic value of the resultant DPGY.MethodsHundred and fifty-three consecutive HF patients referred for right heart catheterisation were enrolled prospectively. DPG, as currently recommended, was calculated. Subsequently, PAWPY was measured and the corresponding DPGY was calculated.ResultsDPGY yielded higher values (median, IQR: 3.2, 0.6-5.7 mmHg) than DPG (median, IQR: 0.9, - 1.7-3.8 mmHg); p < 0.001. Conventional DPG was negative in 45% of the patients whereas DPGY in only 15%. During follow-up (22 ± 14 months) 58 patients have undergone heart-transplantation or died. The predictive ability of DPGY ≥ 6 mmHg for the above defined end-point events was significant [HR 2.1; p = 0.007] and independent of resting mean pulmonary artery pressure (PAPM). In contrast, conventional DPG did not comprise significant prognostic value following adjustment for PAPM.ConclusionInstantaneous pressures at the trough of Y-descent yield significantly fewer DPGNEG than conventional DPG and entail superior prognostic value in HF patients with and without PH.
| S-EPMC7588394 | biostudies-literature
Project description:During the multistep process of metastasis, cancer cells encounter various mechanical forces which make them deform drastically. Developing accurate in-silico models, capable of simulating the interactions between the mechanical forces and highly deformable cancer cells, can pave the way for the development of novel diagnostic and predictive methods for metastatic progression. Spring-network models of cancer cell, empowered by our recently proposed identification approach, promises a versatile numerical tool for developing experimentally validated models that can simulate complex interactions at cellular scale. Using this numerical tool, we presented spring-network models of breast cancer cells that can accurately replicate the experimental data of deformation behavior of the cells flowing in a fluidic domain and passing narrow constrictions comparable to microcapillary. First, using high-speed imaging, we experimentally studied the deformability of breast cancer cell lines with varying metastatic potential (MCF-7 (less invasive), SKBR-3 (medium-high invasive), and MDA-MB-231 (highly invasive)) in terms of their entry time to a constricted microfluidic channel. We observed that MDA-MB-231, that has the highest metastatic potential, is the most deformable cell among the three. Then, by focusing on this cell line, experimental measurements were expanded to two more constricted microchannel dimensions. The experimental deformability data in three constricted microchannel sizes for various cell sizes, enabled accurate identification of the unknown parameters of the spring-network model of the breast cancer cell line (MDA-MB-231). Our results show that the identified parameters depend on the cell size, suggesting the need for a systematic procedure for identifying the size-dependent parameters of spring-network models of cells. As the numerical results show, the presented cell models can simulate the entry process of the cell into constricted channels with very good agreements with the measured experimental data.
| S-EPMC10786721 | biostudies-literature
Project description:Adoptive chimeric antigen receptor T-cell (CAR-T) therapy is transformative and approved for hematologic malignancies. It is also being developed for the treatment of solid tumors, autoimmune disorders, heart disease, and aging. Despite unprecedented clinical outcomes, CAR-T and other engineered cell therapies face a variety of manufacturing and safety challenges. Traditional methods, such as lentivirus transduction and electroporation, result in random integration or cause significant cellular damage, which can limit the safety and efficacy of engineered cell therapies. We present hydroporation as a gentle and effective alternative for intracellular delivery. Hydroporation resulted in 1.7- to 2-fold higher CAR-T yields compared to electroporation with superior cell viability and recovery. Hydroporated cells exhibited rapid proliferation, robust target cell lysis, and increased pro-inflammatory and regulatory cytokine secretion in addition to improved CAR-T yield by day 5 post-transfection. We demonstrate that scaled-up hydroporation can process 5 x 108 cells in less than 10 s, showcasing the platform as a viable solution for high-yield CAR-T manufacturing with the potential for improved therapeutic outcomes.
| S-EPMC11230359 | biostudies-literature