Computer simulation-based nanothermal field and tissue damage analysis for cardiac tumor ablation.

Radiofrequency ablation is a nominally invasive technique to eradicate cancerous or non-cancerous cells by heating. However, it is still hampered to acquire a successful cell destruction process due to inappropriate RF intensities that will not entirely obliterate tumorous tissues, causing in treatment failure. In this study, we are acquainted with a nanoassisted RF ablation procedure of cardiac tumor to provide better outcomes for long-term survival rate without any recurrences. A three-dimensional thermo-electric energy model is employed to investigate nanothermal field and ablation efficiency into the left atrium tumor. The cell death model is adopted to quantify the degree of tissue injury while injecting the Fe3O4 nanoparticles concentrations up to 20% into the target tissue. The results reveal that when nanothermal field extents as a function of tissue depth (10 mm) from the electrode tip, the increasing thermal rates were approximately 0.54362%, 3.17039%, and 7.27397% for the particle concentration levels of 7%, 10%, and 15% compared with no-particle case. In the 7% Fe3O4 nanoparticles, 100% fractional damage index is achieved after ablation time of 18 s whereas tissue annihilation approach proceeds longer to complete for no-particle case. The outcomes indicate that injecting nanoparticles may lessen ablation time in surgeries and prevent damage to adjacent healthy tissue.

Numerical computation of pulsatile hemodynamics and diagnostic concern of coronary bifurcated artery flow for Newtonian and non-Newtonian fluid.

Atherosclerotic with the high occurrence of plaque formation due to stenosis has attracted wide attention among researchers. The left coronary artery has been studied in two-dimensional and in three-dimensional (3D) bifurcation as the models of blood flow through Newtonian and non-Newtonian fluids to better understand the physical mechanism. The computational Fluid Dynamics (CFD) technique is incorporated in COMSOL Multiphysics and then it is justified by satisfactory validation. It is found that the Newtonian model shows larger recirculation zones than non-Newtonian does. The present study also focuses on the evaluations of the lesion of diagnostic and the coefficient of pressure drop assessments on the basis of the diagnostic parameter's critical values affected by the rheological model. Nevertheless, the leading concentration of the subsisting investigation works is confined to the change of importance factor (IFc) affected by arterial blockage. But the IFc of non-Newtonian fluid for 3D left coronary artery bifurcation model decreases with increasing bifurcation angle and the time-averaged inlet pressure is the least for smaller bifurcation angles. The current research further concentrates that the flow separation length reduces with developing bifurcation angle in bifurcated geometry. It is significant to mention that non-Newtonian blood flow model incorporating hemodynamic and diagnostic parameters has great impacts on instantaneous flow systems.

Wall shear stress indicators influence the regular hemodynamic conditions in coronary main arterial diseases: cardiovascular abnormalities.

Computational hemodynamic (CH) characteristics play a central role in the onset and expansion of atherosclerotic plaques in the coronary main arteries. This study has explored the effects of hemodynamic properties especially coronary arterial wall tangential stresses on various healthy and diseased patient-based coronary artery models based on coronary computed tomography angiography (CCTA) imaging. The key components of the work are the CCTA image acquisition, accurate three-dimensional (3 D) model segmentation, reconstruction, appropriate grid generation, CH simulations, and analysis of the results by using open-source techniques. The CH simulation results have produced hemodynamic variables, including velocity magnitude (VM), mean arterial pressure difference, wall shear stress (WSS), time-averaged WSS (TAWSS), oscillatory shear index (OSI), relative residence time (RRT), and finally, computational fractional flow reserve (cFFR), that allow the pathophysiological conditions in patient-based coronary models. The VM, mean pressure difference, and WSS indices have yielded consistent simulation results for predicting the severity conditions of coronary diseases. We have compared our cFFR results with the published results and observed that the WSS indices were a good alternative approach for measuring the severity of coronary lesions. The CH results allow a medical expert to estimate the severity of a lumen area and stenosis physiological blood flow conditions in a non-invasive way.

Effects of non-Darcy mixed convection over a horizontal cone with different convective boundary conditions incorporating gyrotactic microorganisms on dispersion.

This paper investigates the influence of dispersion impact on mixed convection flow over a horizontal cone within a non-Darcy porous medium. Multiple convective boundary conditions are applied to address the heat, mass and motile microorganism transfer phenomena. This paper incorporates the dispersion effect for gyrotactic microorganisms due to biological and environmental applications. By imposing appropriate similarity transformations, the nonlinear partial differential equations governing flow, temperature, concentration, and microbe fields are reduced to a system of ordinary differential equations & then solved using the MATLAB BVP4C function. The computation of grid independence test is analyzed for different flow profiles to show the precision of the points. In a few instances, our present numerical data is compared with previously published works, leading to excellent agreement. The non-Darcy effect, as well as mixed convection values from 0.1 to 0.9 and buoyancy parameters from 0.2 to 0.8, all significantly affects the velocity profile. The reduction in the microorganism profile is brought on by the increase in the bioconvection Lewis parameter and bio convection peclet number between 0.3 and 1. In the absence of dispersion, the variation of Biot numbers between 0.5 and 2, favor heat, mass, and motile microorganism transfer the most in the range of mixed convection parameter 0.5 to pure forced convection 1. Thermal, solutal and microorganism dispersion coefficients a, b, c that lie between [Formula: see text] and [Formula: see text] and higher values of modified peclet number ranges from 2 to 10 cause increased dispersion effects which lower flow transfer rates mostly in forced convection regime.

Thermal cooling performance of convective non-Newtonian nanofluid flowing with variant power-index across moving extending surface.

This communication focuses on assessing the effectiveness of nanoparticles, and a power-law variation fluid on a moving stretching surface is analyzed. Newtonian fluids for different nanomaterials are considered due to its industrial demand. The partial differential equations describing the flow are transformed to ordinary differential equations by employing local similarity transformations and then solved numerically by an effective numerical approach, namely, the local nonsimilarity method (LNS). The numerical solution is computed for different parameters by using the computational software MATLAB. Different types of nanoparticles are considered, and the impact of those nanoparticles as well as the impact of different pertaining parameters on velocity, temperature, missing velocity slope, and missing temperature slope are presented graphically. Comparisons are made with the available results in the open literature. Our investigation conveys a better impact on [Formula: see text] nanoparticles due to their higher thermal conductivity. Furthermore, an increase in the free stream velocity, missing temperature slope and velocity slope is enhanced, but after a point of separation, the missing temperature slope decays.

Dual solution for double-diffusive mixed convection opposing flow through a vertical cylinder saturated in a Darcy porous media containing gyrotactic microorganisms.

The steady mixed convection flow towards an isothermal permeable vertical cylinder nested in a fluid-saturated porous medium is studied. The Darcy model is applied to observe bioconvection through porous media. The suspension of gyrotactic microorganisms is considered for various applications in bioconvection. Appropriate similarity variables are opted to attain the dimensionless form of governing equations. The resulting momentum, energy, concentration, and motile microorganism density equations are then solved numerically. The resulting dual solutions are graphically visualized and physically analyzed. The results indicate that depending on the systems' parameters, dual solutions exist in opposing flow beyond a critical point where both solutions are connected. Our results were also compared with existing literature.

Effects of thermal slip and chemical reaction on free convective nanofluid from a horizontal plate embedded in a porous media.

We consider a two-dimensional, uniform, incompressible and free convection flow of a nano-fluid along a plane. The plate is located facing upward about the porous medium. Throughout the investigation, thermal slip, chemical reaction, heat emission/absorption is considered. In the modeling of nano-fluid we have considered the dynamic effect along with the Brownian and thermophoresis. In obtaining the governing equations, including the boundary conditions, an appropriate scaling is applied. The governing momentum equations, including thermal energy and nanoparticles equations are translated into a group of nonlinear ODEs by using Lie symmetry group transformation. The transformed equations are then solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order. The numerical results of velocity, temperature, and nanoparticle volume fraction profiles for varied physical parameters will be discussed and analyzed at the end. The discussion also includes the local Nusselt and the local Sherwood numbers against several of the systems' physical parameters. It is found that the velocity and temperature decrease with thermal slip and heat absorption whilst it increases by increasing heat generation and chemical reaction order. Our present results will be compared with similar existing literature results.

Numerical study of nano-biofilm stagnation flow from a nonlinear stretching/shrinking surface with variable nanofluid and bioconvection transport properties.

A mathematical model is developed for stagnation point flow toward a stretching or shrinking sheet of liquid nano-biofilm containing spherical nano-particles and bioconvecting gyrotactic micro-organisms. Variable transport properties of the liquid (viscosity, thermal conductivity, nano-particle species diffusivity) and micro-organisms (species diffusivity) are considered. Buongiorno's two-component nanoscale model is deployed and spherical nanoparticles in a dilute nanofluid considered. Using a similarity transformation, the nonlinear systems of partial differential equations is converted into nonlinear ordinary differential equations. These resulting equations are solved numerically using a central space finite difference method in the CodeBlocks Fortran platform. Graphical plots for the distribution of reduced skin friction coefficient, reduced Nusselt number, reduced Sherwood number and the reduced local density of the motile microorganisms as well as the velocity, temperature, nanoparticle volume fraction and the density of motile microorganisms are presented for the influence of wall velocity power-law index (m), viscosity parameter [Formula: see text], thermal conductivity parameter (c4), nano-particle mass diffusivity (c6), micro-organism species diffusivity (c8), thermophoresis parameter [Formula: see text], Brownian motion parameter [Formula: see text], Lewis number [Formula: see text], bioconvection Schmidt number [Formula: see text], bioconvection constant (σ) and bioconvection Péclet number [Formula: see text]. Validation of the solutions via comparison related to previous simpler models is included. Further verification of the general model is conducted with the Adomian decomposition method (ADM). Extensive interpretation of the physics is included. Skin friction is elevated with viscosity parameter ([Formula: see text] whereas it is suppressed with greater Lewis number and thermophoresis parameter. Temperatures are elevated with increasing thermal conductivity parameter ([Formula: see text] whereas Nusselt numbers are reduced. Nano-particle volume fraction (concentration) is enhanced with increasing nano-particle mass diffusivity parameter ([Formula: see text]) whereas it is markedly reduced with greater Lewis number (Le) and Brownian motion parameter (Nb). With increasing stretching/shrinking velocity power-law exponent ([Formula: see text] skin friction is decreased whereas Nusselt number and Sherwood number are both elevated. Motile microorganism density is boosted strongly with increasing micro-organism diffusivity parameter ([Formula: see text]) and Brownian motion parameter (Nb) but reduced considerably with greater bioconvection Schmidt number (Sc) and bioconvection Péclet number (Pe). The simulations find applications in deposition processes in nano-bio-coating manufacturing processes.

Stability theory of nano-fluid over an exponentially stretching cylindrical surface containing microorganisms.

This research is emphasized to describe the stability analysis in the form of dual solution of the flow and heat analysis on nanofluid over an exponential stretching cylindrical surface containing microorganisms. The research is also implemented to manifest the dual profiles of velocity, temperature and nanoparticle concentration in the effect of velocity ratio parameter ([Formula: see text]). Living microorganisms' cell are mixed into the nanofluid to neglect the unstable condition of nano type particles. The governing equations are transformed to non-linear ordinary differential equations with respect to pertinent boundary conditions by using similarity transformation. The significant differential equations are solved using build in function bvp4c in MATLAB. It is seen that the solution is not unique for vertical stretching sheet. This research is reached to excellent argument when found results are compared with available result. It is noticed that dual results are obtained demanding on critical value ([Formula: see text]), the meanings are indicated at these critical values both solutions are connected and behind these critical value boundary layer separates thus the solution are not stable.

The effect of hemodynamic parameters in patient-based coronary artery models with serial stenoses: normal and hypertension cases.

The purpose of this study is to investigate the hemodynamic significance of various degrees of coronary area of stenosis (AS) and multiple sequential stenoses (MSS) in normal and hypertension pressure conditions. MSS in a single branch coronary artery pose challenges to determine the physiological assessment in the prevalent invasive intervention. The hemodynamic parameters of each stenosis are influenced by other stenoses in the single branch of MSS coronary artery. In this study, we entirely use open source tools and techniques for coronary computed tomography angiography (CCTA) image segmentation, 3D reconstruction, grid generation and hemodynamic simulations. The results yield different hemodynamic parameters such as velocity magnitude, mean arterial pressure difference, flow-pressure linear relation, wall shear stress (WSS) and eventually virtual fractional flow reserve (vFFR) allowing for the prediction and the assessment of lumen area severity conditions in MSS coronaries.

Conversion of a linear to a circular plasmid in the relapsing fever agent Borrelia hermsii.

Spirochetes of the genus Borrelia have genomes composed of both linear and circular replicons. We characterized the genomic organization of B. burgdorferi, B. hermsii, B. turicatae, and B. anserina with pulsed-field gel electrophoresis. All four species contained a linear chromosome approximately 1 Mb in size and multiple linear plasmids in the 16- to 200-kb size range. Plasmids 180 and 170 kb in size, present in the relapsing fever agents B. hermsii and B. turicatae but not in the other two species, behaved as linear duplex DNA molecules under different electrophoretic conditions. A variant of strain HSI of B. hermsii had a 180-kb circular instead of linear plasmid. There were no detectable differences in the growth rates or in the expression of cellular proteins between cells bearing linear forms and those bearing circular forms of the plasmid. The conversion to a circular conformation of monomeric length was demonstrated by the introduction of strand breaks with irradiation, restriction endonuclease analysis, and direct observation of the DNA molecules by fluorescent microscopy. Consideration of different models for the replication of linear DNA suggests that circular intermediates may be involved in the replication of linear replicons in Borrelia spp.

High- and low-infectivity phenotypes of clonal populations of in vitro-cultured Borrelia burgdorferi.

Borrelias that cause Lyme disease lose the ability to infect and cause disease in laboratory animals following 10 to 16 passages of in vitro culture. In this study, clonal populations of the Sh-2-82 (Sh2) and B31 strains of Borrelia burgdorferi were isolated by subsurface plating on BSK-II agar plates and examined for infectivity in the C3H/HeN mouse model. Mice were injected intradermally with 10(5) B. burgdorferi organisms, and the tibiotarsal joint, heart, and bladder were cultured 2 to 4 weeks postinfection to determine whether viable organisms were present. Clones exhibited either a high-infectivity phenotype, in which cultures were consistently positive at all organ sites, or a low-infectivity phenotype, in which a low proportion of cultures were positive (5 of 40 in a representative experiment). In an Sh2 population that had undergone five in vitro passages, 7 of 10 clones were of the high-infectivity phenotype, and the remaining clones were of the low-infectivity phenotype. The proportion of high-infectivity clones decreased with continued in vitro passage, with only 1 of 10 clones exhibiting the high-infectivity phenotype after 10 passages and 0 of 10 clones yielding positive cultures after 20 passages. Representative high- and low-infectivity clones from passage 5 Sh2 cultures had 50% infectious doses of 1.8 x 10(2) and 1 x 10(5), respectively. Subclones consistently reflected the same infectivity phenotypes as those of the parent clones. The protein profiles and plasmid contents of the high- and low-infectivity clones were compared and exhibited few discernible differences. On the basis of these results, the loss of infectivity during in vitro culture results from the outgrowth of low-infectivity clones and begins to occur within the first five in vitro passages. Further examination of clonal populations may lead to the identification of genetic and protein factors important in the virulence and pathogenicity of Lyme disease borrelias.

The cryptic ospC gene of Borrelia burgdorferi B31 is located on a circular plasmid.

Borrelia burgdorferi B31 cells lacking all linear plasmids or all but the 49-kb linear plasmid expressed the otherwise silent gene for the outer membrane protein OspC. In the first demonstration of a function for a circular plasmid of Borrelia spp., ospC was located on a 27-kb circular plasmid of B31.

Megabase-sized linear DNA in the bacterium Borrelia burgdorferi, the Lyme disease agent.

Using pulsed-field gel electrophoresis we examined the genome of Borrelia burgdorferi, a eubacterium of the spirochete phylum and the agent of Lyme disease. A population of this species' cells was lysed in situ in agarose blocks. An abundant DNA form that behaved as a linear duplex molecule under different electrophoretic conditions was found. The estimated size of the molecule was 950 kilobases. DNA from two other genera of spirochetes did not enter the gel under these conditions. These studies indicate that Borrelia spirochetes, perhaps uniquely among prokaryotic organisms, have linear chromosomes.

Cl-/base exchange in rat mesangial cells: regulation of intracellular pH.

The present study was designed to determine whether rat glomerular mesangial cells possess Cl- -dependent intracellular pH (pHi) regulatory processes. Rat glomerular mesangial cells were grown to confluence on glass coverslips. Intracellular pH (pHi) was measured with BCECF. Steady state pHi in HCO3- containing solutions was 7.08 +/- 0.03 (N = 13). When extracellular Cl- was acutely removed, pHi increased at a rate of 0.57 +/- 0.03 pH/min units (N = 8), P less than 0.001. DIDS (0.5 mM) significantly decreased the rate of increase in pHi to 0.34 +/- 0.04 pH/min, P less than 0.01. Na+ removal and amiloride (1 mM) did not alter the increase in pHi induced by Cl- removal. Steady state pHi in the absence of Cl- was significantly increased above control, 7.39 +/- 0.02 (N = 7), P less than 0.001. Following the acute alkalinization of pHi by CO2 removal, pHi recovered at a rate of 0.07 +/- 0.01 pH/min (N = 9). In the absence of Cl-, the pHi recovery rate was significantly decreased to 0.01 +/- 0.008 pH/min (N = 5), P less than 0.01. DIDS (0.5 mM) significantly decreased the rate of pHi recovery to 0.02 +/- 0.01 pH/min (N = 5), P less than 0.01. Na+ removal and amiloride (1 mM) had no effect on the rate of pHi recovery following acute alkaline loading.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of cellular Ca++ in phosphorylation of 21 K and 19 K polypeptides in cultured thyroid cells: effects of phorbol ester, trifluoperazine, and 8-diethylamino-octyl-3,4,5-trimethoxybenzoate hydrochloride.

Cultured dog thyroid cells contain 21 and 19 kilodalton (K) phosphoproteins which by several criteria have been identified as light chains of myosin (MLC). TSH causes a reduction in the phosphorylation state of the 21 K-19 K proteins, at least in part through activating adenylate cyclase and increasing cAMP levels. We now report that 12-O-tetradecanoyl-phorbol-13-acetate (TPA) also decreases the 21 K-19 K protein phosphorylation state, but in contrast to that due to TSH, the TPA-induced decrease is not associated with elevated cAMP levels. The effect of TPA was not additive to that of TSH. Because Ca++ is a major factor regulating MLC kinase and TPA-stimulated protein kinase C in other systems, the role of Ca++ in the phosphorylation of the 21 and 19 K polypeptides in dog thyroid was examined. In intact cells, both (8-diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8) (1 X 10(-4) M) and trifluoperazine (TFP) (4 X 10(-5) M) increase basal 21 K-19 K protein phosphorylation and inhibit the decrease in phosphorylation caused by TSH and TPA without affecting cAMP levels. Ionophore A23187 (5 X 10(-6) M) counteracts TMB-8- and TFP-stimulated phosphorylation as well as TMB-8 and TFP inhibition of TSH- and TPA-reduced 21 K-19 K phosphorylation. Incubation of 32PO4-labeled dog thyroid cells in the absence of extracellular Ca++ or with verapamil does not significantly affect basally phosphorylated 21 K-19 K proteins or the decreased 21 K-19 K phosphorylation state caused by TSH. These results strongly suggest that the phosphorylation state of the 21 and 19 K proteins is affected more significantly by intracellular Ca++ pools than by extracellular Ca++, and implicate a kinase(s) other than Ca++-calmodulin-dependent MLC kinase in the phosphorylation of MLC in the dog thyroid.

Effects of phorbol esters on metabolic variables in the thyroid.

Since 12-O-tetradecanoyl-phorbol-13-acetate (TPA) reproduced some of the effects of TSH on phosphorylation of polypeptides in the thyroid, its effects on several thyroid metabolic variables were investigated. Like TSH, TPA stimulated glucose oxidation, iodide organification, and 32P incorporation into phospholipids in thyroid slices. However, in contrast to TSH, it did not augment cAMP accumulation. An inactive phorbol ester, 4 alpha-phorbol, did not reproduce any of the effects of TPA. An initial incubation of thyroid slices with TPA decreased the stimulation of cAMP, glucose oxidation, and colloid droplet formation induced by TSH. However, an initial incubation with TPA did not modify the subsequent stimulation of glucose oxidation induced by (Bu)2 cAMP. TPA potentiated the ability of TSH to desensitize the adenylate cyclase system. Although both TPA and TSH increased 32P incorporation into phospholipids, the patterns were different when individual phospholipids were examined. These results indicate another regulatory mechanism for thyroid cell functions independent of cAMP.

Dephosphorylation of 19K and 21K polypeptides in response to thyroid-stimulating hormone in cultured thyroid cells.

Cultured dog thyroid cells incubated with [32P] phosphate contain at least two phosphoproteins of 19 and 21 kDalton (K), as determined by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Myosin light chain appears to be a component of the 19K and 21K phosphoproteins by the following criteria: 1) coextraction with myosin heavy chain from Triton-insoluble cytoskeletons with KCl-ATP, 2) coisolation with myosin heavy chain by immunoprecipitation, and 3) purification of undenatured myosin with pyrophosphate-agarose gel electrophoresis. The phosphorylation state of these proteins is decreased by incubation of cells with TSH. In the basal state, the 19K and 21K proteins from Triton-insoluble cytoskeleton fractions contain 0.86 +/- 0.07 (+/- SE) mol phosphate/mol protein, which is reduced to 0.34 +/- 0.03 in TSH-treated cells. TSH-induced dephosphorylation occurs in 1 min with 2.5 mU/ml TSH and reaches a maximum at 15 min. This TSH effect appears to be mediated by cAMP, since it is mimicked by (Bu)2cAMP, forskolin, cholera toxin, and prostaglandin E1 and is potentiated by isobutylmethylxanthine. Carbamylcholine, ionophore A23187, and norepinephrine, which inhibit TSH stimulation of cAMP, have no effect on basal phosphorylation of the 19K and 21K proteins, but do inhibit the effect of TSH.

Morphological and biochemical responses of cultured thyroid cells to thyrotropin.

In the thyroid gland, TSH stimulates cAMP formation, exocytosis of precursor (noniodinated) thyroglobulin, endocytosis of thyroglobulin, and proteolytic processing of the thyroglobulin to form thyroid hormones. In this report we describe TSH effects on cAMP levels, microtubules, microfilaments, myosin fibrils, and the morphology of cultured thyroid follicle cells. The cells were normally cultured in the presence of 10 mU/ml TSH, and fresh TSH produced no stimulation when assayed for cAMP production in a 15-min assay. When such cells were cultured for up to 72 h in the absence of TSH and then assayed for cAMP production, the basal levels were much reduced, but fresh TSH stimulated cAMP levels half-maximally at 1 mU/ml and up to 50-fold at 20 mU/ml. Microtubules, myosin fibers, and microfilaments were demonstrated by indirect immunofluorescent staining. Fluorescent staining of fibers was observed in cells fixed before lysis and in cells lysed before fixation. In control cells grown without hormone, microtubules originated near the nucleus and extended to the cell periphery. Myosin-containing fibrils traversed the cell or radiated from foci. Microfilaments spanned the cell in a stress fiber pattern. After incubation with 20 mU/ml TSH and 4 mM isobutylmethylxanthine (IBMX) for 10-20 min, the microtubules in up to half of the cells appeared altered and more granular, and the cell periphery was scalloped. After 15-30 min with TSH and IBMX, normal myosin fibers were replaced with a fine lattice-work, peripheral staining disappeared, and the proportion of nonfibrous myosin increased. Stress fibers demonstrated with antibody to actin also disappeared, and the peripheral structures observed in normal cells became fragmented. Incubation with forskolin or TSH and IBMX for 2-3 h resulted in arborization of 30-60% of the cells that contained bundles of microtubules, myosin fibers, or microfilaments into dendrite-like processes and increased staining near the nucleus. At 5 h, more than 80% of the cells were arborized. These morphological changes were less pronounced with IBMX alone and minimal with TSH alone. The time course of cAMP levels observed basally or after TSH, forskolin, or TSH and IBMX was consistent with the relative effects of these agents on arborization. These studies are consistent with effects of cAMP on microtubules, myosin-containing fibrils, and microfilaments and may provide a basis for the morphological response to TSH.