Helical Strips Research Articles

Analysis of solar flat plate collector with straight and helical flow path heat tube using mathematical modeling and java based simulation

In this study, a Mathematical Model for solar flat plate collector having plain and helical flow path heat tubes is developed for a Java based simulator software to study the performance of SFPC. A software simulation is a proven tool for efficient and economic prediction of heat transfer process results. The mathematical model of a SFPC is developed to investigate the fluid mean temperatures, heat gain and collector recovery factor, edge loss, bottom loss and collector efficiency. The simulation results were verified with experimental results and found that the simulator has the ability to predict the performance of the solar flat plate collector accurately as proven by the comparison of experimental data with simulation. The difference between the predicted and experimental results is, at maximum, approximately 4% which is within the acceptable limit considering some uncertainties in the input parameter values. A parametric study was performed between plain heat tubes and helical strip inserted heat tubes and it was found that the outlet fluid temperature and the energy efficiency of the system are improved in the helical strip inserted heat tubes and also the mass flow rate has a significant effect on the efficiency of the system.

Innovative solution for strength enhancement of metallic like-composite tubular structures axially crushed used as energy dissipating devices

This work presents the milestones of the underlying of a patented work [1] (Abdul-Latif, 2014) which aims to enhance the plastic buckling resistance of thin-walled right-circular cylindrical mild steel tubes deformed axially under the quasi-static compressive load. The proposed concept can be described by producing a metal like-composite where a hard phase incorporates in these tubes made by case-hardening of 15% of tubes outer surface with different geometrical shapes and a constant depth along the tubes thickness. To study the effect of case-hardening configurations, several forms were designed, made and tested. They were four ring forms (with 2, 3, 4 and 5 rings), two vertical strip forms (2 and 3 strips) and, six helical strip forms with three tilt angles of 30°, 45° and 60° (2H30, 3H30, 2H45, 3H45, 2H60 and 3H60). The total energy absorption of conventional tubes could be increased up to 46%. The effects of the case-hardened zone, quasi-static strain rate and the crush force efficiency were investigated. Moreover, the deformation modes of these case-hardened tubes were analyzed. The effect of the case-hardened forms could be classified into three categories by the gain percentage (low, intermediate and high gains). Especially in the high gain category, the material behavior seems to be directed by complicated local strain induced by the metal like-composite tube, where a triaxial strain state was encouraged particularly within the tube wall of 3H30. For this reason, the collapse load became the function of case-hardened forms.

Asymptotic boundary conditions analysis of a conducting strips loaded chiral circular cylinder in chiral medium

An analytical solution to study the scattering of electromagnetic plane wave from an infinitely long circular cylinder loaded with conducting helical strips is presented. The region outside the cylinder is occupied by free space/chiral medium. The spacing between the strips is assumed to be negligibly small as compared to incident wavelength. Cylindrical vector wave functions are used to assume the solution in terms of unknowns coefficients. Asymptotic strip boundary conditions are imposed to incorporate the contribution of interface and strips, simultaneously. Numerical results for the scattering echo-width are presented to highlight the effects due to loading the strips on chiral circular cylinder. Reduction in scattering echo-width of strips loaded chiral circular cylinder is useful to reduce the visibility of object at the observation point. Occurrence of same values of co- and cross scattering echo-width of strips loaded chiral cylinder for multiple values of radius may also be considered useful for hiding of object information. Special cases are also discussed for the validation of results.

Analytical and numerical models to predict the behavior of unbonded flexible risers under torsion

This paper presents analytical and numerical models to predict the behavior of unbonded flexible risers under torsion. The analytical model takes local bending and torsion of tensile armor wires into consideration, and equilibrium equations of forces and displacements of layers are deduced. The numerical model includes lay angle, cross-sectional profiles of carcass, pressure armor layer and contact between layers. Abaqus/Explicit quasi-static simulation and mass scaling are adopted to avoid convergence problem and excessive computation time caused by geometric and contact nonlinearities. Results show that local bending and torsion of helical strips may have great influence on torsional stiffness, but stress related to bending and torsion is negligible; the presentation of anti-friction tapes may have great influence both on torsional stiffness and stress; hysteresis of torsion-twist relationship under cyclic loading is obtained by numerical model, which cannot be predicted by analytical model because of the ignorance of friction between layers.

Behavior of Concrete Cylinder Confined with Helical Composites Strips

This paper presents theexperimental investigations on the behavior of a short concrete cylinder confined with helical FRP strip under axial compressive load,the results show that the compressive strength increases with increase in the width of the FRP and the decrease in pitch of the helix that follows the FRP on the side surface of the concrete cylinder. The numerical analysis conducted to describe the behavior of confined cylinders confirmed the experimental stress-strain curves and the numerical ones are recorded. A new method for predicting the ultimate compressive strength is also presented. The model is quite simple and can be adapted to the concrete cylinders confined with other types of FRP, for different widths and different values of the pitch of the helix, and for different values of the compressive strength of reference concrete. The mathematical optimization, of the function that describes the ultimate strength of confined cylinder is adjustable. It allows predicting the optimal values of various parameters: the confinement strength, the width of the FRP, the pitch of the helix, and the compressive strength of concrete, for different expected strength gain rates and for different intervals containing the studied variables.

Design and Fabrication of Bench-Scale Flash Pyrolysis Reactor for Bio-Fuel Production

The purpose of this paper is to present the construction and testing of a bench-scale flash pyrolysis reactor for bio fuel production from local biomasses such as empty fruit bunches (EFB) and rice husk. The reactor is intended for a mobile application where it can be brought into the fields. The design is based on ablative reactor technology so that larger feed size can be processed. The moving rotor is equipped with helical strips to create optimum centrifugal and mechanical force inside the system. In order to provide a sustainable heat source, the resulting syngas is burned and recycled back into the reactor. This reactor will operate with reactor temperature ranges from 450 to 600 °C, 300 - 1,000 °C/s heating rates and 5 - 20 g/min biomass processing capacity. This study can provide an important basis in designing a mobile fast pyrolysis reactor for Malaysia’s biomass which in general consists of higher cellulose content

Oxidized Low Density Lipoprotein (OX-LDL) Induced Arterial Muscle Contraction Signaling Mechanisms

Oxidized low-density lipoprotein cholesterol (OX-LDL), a reactive oxidant, forms when reactive oxygen species interact with LDL. Elevated OX-LDL may contribute to high blood pressure associated with diseases such as diabetes and obesity. The current study objective was to determine if OX-LDL is a vasoconstrictor acting through the OX-LDL receptor (LOX1) on arterial smooth muscle and elucidate the intracellular signaling mechanism. Arteries were extracted from Sprague-Dawley rats (SD) and obese F1 offspring (ZS) of Zucker diabetic fatty rats (ZDF) x spontaneously hypertensive heart failure rats (SHHF). Pulmonary arterial and aortic rings and caudal arterial helical strips were attached to force transducers in muscle baths. Arterial preparations were contracted with high KCl to establish maximum force development in response to membrane depolarization (Po). Addition of OX-LDL caused contractions of varying strength dependent on the arterial type. OX-LDL contractions were normalized to % Po. Caudal artery was more reactive to OX-LDL than aorta or pulmonary artery. Interestingly, LOX1 density varied with arterial type in proportion to the magnitude of the contractile response to OX-LDL. OX-LDL contractions in the absence of calcium generated about 50% as much force as in normal calcium. Experiments with myosin light chain kinase and Rho kinase inhibitors, ML-9 and Y-27632, suggest OX-LDL induced contraction is mediated by additive effects of two distinct signaling pathways activated concomitantly in the presence of calcium. Results may impact development of new therapeutic agents to control hypertension associated with disorders in which circulating LDL levels are high in a high oxidizing environment.

나선형 블룸라인 PFL을 이용한 50 ns 펄스폭의 고전압 펄스 발생

A high voltage pulse generator based on the Blumlein pulse forming line (PFL) was fabricated to produce a voltage pulse whose peak value is ∼300 kV and pulse duration is ∼50 ns. Three cylindrical electrodes, such as inner, middle, and outer electrodes, are concentrically placed to make a compact PFL. To increase the pulse duration of the output pulse without any change of the size of the generator, the middle electrode is replaced by a helical strip electrode. To determine the radius of the helical electrode, the impedance of the helical Blumlein PFL is calculated using an approximate formula where the dispersive property of the helical Blumlein PFL is not considered. The dependence of the impedance on the frequency is computed by a commercial program. The number of turns in the helical electrode is decided to provide a demanded pulse duration. The experimental result shows that the helical Blumlein PFL is capable of making a high voltage pulse of ∼50 ns pulse duration.

Smooth muscle-selective CPI-17 expression increases vascular smooth muscle contraction and blood pressure

Recent data revealed that protein kinase C-potentiated myosin phosphatase inhibitor of 17 kDa (CPI-17), a myosin phosphatase inhibitory protein preferentially expressed in smooth muscle, is upregulated/activated in several diseases but whether this CPI-17 increase plays a causal role in pathologically enhanced vascular smooth muscle contractility and blood pressure remains unclear. To address this possibility, we generated a smooth muscle-specific CPI-17 transgenic mouse model (CPI-17-Tg) and demonstrated that the CPI-17 transgene was selectively expressed in smooth muscle-enriched tissues, including mesenteric arteries. The isometric contractions in the isolated second-order branch of mesenteric artery helical strips from CPI-17-Tg mice were significantly enhanced compared with controls in response to phenylephrine, U-46619, serotonin, ANG II, high potassium, and calcium. The perfusion pressure increases in isolated perfused mesenteric vascular beds in response to norepinephrine were also enhanced in CPI-17-Tg mice. The hypercontractility was associated with increased phosphorylation of CPI-17 and 20-kDa myosin light chain under basal and stimulated conditions. Surprisingly, the protein levels of rho kinase 2 and protein kinase Cα/δ were significantly increased in CPI-17-Tg mouse mesenteric arteries. Radiotelemetry measurements demonstrated that blood pressure was significantly increased in CPI-17-Tg mice. However, no vascular remodeling was detected by morphometric analysis. Taken together, our results demonstrate that increased CPI-17 expression in smooth muscle promotes vascular smooth muscle contractility and increases blood pressure, implicating a pathological significant role of CPI-17 upregulation.

Analysis of Structural Parameters for Unbonded Flexible Pipes

Due to the complex structure and nonuniform material of unbonded flexible pipes, an elastic thin-walled cylinder model and a helical steel strip model were established respectively to simulate different layers based on the specific structure form and parameters. Quasi-static incremental load was adopted to identify the structural parameters which had significant effects on the axial, radial and bending behavior of the pipes during the complex deformation. Sensitivity of these parameters were also analysed. The conclusion in this paper could provide guaidance for the design of unbonded flexible pipe.

Abstract 509: Essential Role of Vascular Smooth Muscle Bmal1 in Diurnal Variations of Contraction and Blood Pressure

Bmal1 is an obligatory core clock gene that is ubiquitously expressed but has been demonstrated to have tissue specific functions. However, the vascular smooth muscle specific function of bmal1 is unknown. We generated a smooth muscle specific bmal1 knockout mouse model (SM-bmal1-ko) and investigated the role of bmal1 in vascular smooth muscle contraction and blood pressure regulation. Isometric contractions were measured in isolated right renal artery and 2 nd order branch of mesenteric artery helical strips. Blood pressure was monitored in conscious free-moving mice using radiotelemetry. We demonstrated that bmal1 was selectively deleted in smooth muscle enriched tissues like mesenteric arteries. Moreover, the diurnal variations of bmal1 target genes per1/2 were abolished in mesenteric arteries. The isometric contractions in response to alpha1 agonist phenylephrine and to 5-HT were significantly diminished in vascular helical strips isolated from SM-bmal1-ko mice compared to that from control flox mice. The contractile diurnal variations detected in the renal arteries isolated from control flox mice were significantly diminished in samples isolated from SM-bmal1-ko mice. Moreover, in vivo , the diurnal variations in the instantaneous pressor responses to intravenous phenylephrine injection were significantly diminished in SM-bmal1-ko mice compared to control flox mice. Twenty four hour mean arterial blood pressure was significantly decreased under 12:12 light:dark, constant light or constant dark conditions. Importantly, the amplitude of blood pressure diurnal variations was significantly diminished in SM-bmal1-ko mice. Importantly, neither the level nor the diurnal variations of locomotor activity was affected by bmal1 deletion. This indicates that the central SCN clock function is not affected in the SM-bmal1-ko mice and the blood pressure alterations in SM-bmal1-ko mice is not a consequence of changed locomotor activity. Taken together, our results demonstrate an essential role of bmal1 in the diurnal variations of vascular smooth muscle contraction and blood pressure.

Pravastatin normalizes ET-1-induced contraction in the aorta of type 2 diabetic OLETF rats by suppressing the KSR1/ERK complex

Endothelin (ET)-1 is a likely candidate for a key role in diabetic vascular complications. In the present study, we hypothesized that treatment with pravastatin (an inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase) would normalize the ET-1-induced contraction in aortas isolated from type 2 diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats. Contractile responses were examined by measuring isometric force in endothelium-denuded aortic helical strips from four groups: Long-Evans Tokushima Otsuka (LETO; genetic control), OLETF (type 2 diabetic), pravastatin-treated LETO, and pravastatin-treated OLETF rats. Both immunoblot analysis and immunoprecipitation assays were used to examine Src, protein phosphatase (PP)2A, kinase suppressor of Ras (KSR)1, and ERK signaling pathway protein levels and activities. In endothelium-denuded aortas isolated from OLETF rats at the chronic stage of diabetes (56-60 wk) (vs. those from age-matched LETO rats), we found the following: 1) ET-1-induced contraction was enhanced, 2) ERK1/2 phosphorylation was increased, 3) phosphorylations of KSR1 and PP2A were reduced (i.e., enhancement of the kinase active state), 4) ERK1/2-KSR1 complexes were increased, and 5) Src tyrosine kinase activity was diminished. Endothelium-denuded aortas isolated from OLETF rats treated with pravastatin (10 mg/kg po, daily for 4 wk) exhibited normalized ET-1-induced contractions and suppressed ET-1-stimulated ERK phosphorylation, with the associated phosphorylated KSR1 and phosphorylated PP2A levels being increased toward normal levels. These results suggest that in type 2 diabetic rats, pravastatin normalizes ET-1-induced contraction in aortic smooth muscle via a suppression of PP2A/KSR1/ERK activities after an enhancement of Src kinase activity.

Multiple Effects of Gymnopilin on Circulatory System of the Rat

Gymnopilin is one of the substances produced by the hallucinogenic mushroom, Gymnopilus junonius. In this study, we examined effects of gymnopilins purified from wild fruiting bodies of G. junonius on contractile activity of aorta preparations and blood pressure in rats. Gymnopilins at lower concentrations than 5 mg/mL did not evoke contraction of helical strips of the thoracic aorta. In contrast, gymnopilins (5 mg/mL) applied to the aorta strips pre-contracted by norepinephrine (100 nM) caused relaxation. This relaxing action did not depend on the activity of the endothelium cells. The relaxing effect of 5-mg/mL gymnopilins was observed in aorta strips contracted by angiotensin II (10 nM) and the high K+ solution (60 mM). Moreover, the adenylyl cyclase inhibitor, SQ-22536, significantly inhibited the relaxing effect of gymnopilins at 1 mg/mL on the norepinephrine-contracted strips. These results suggested that gymnopilins acted directly on smooth muscle cells of the aorta and activated the cAMP-dependent cascade to cause the vasodilation. Paradoxically, gymnopilins injection into the jugular vein transiently increased blood pressure without affecting the heart rate. This result suggests that gymnopilins increase cardiac output and/or tension of the artery through the excitation of the vasomotor nerve that overcame the direct relaxing effect on the vascular smooth muscle.

Altered clock gene expression and vascular smooth muscle diurnal contractile variations in type 2 diabeticdb/dbmice

This study was designed to determine whether the 24-h rhythms of clock gene expression and vascular smooth muscle (VSM) contractile responses are altered in type 2 diabetic db/db mice. Control and db/db mice were euthanized at 6-h intervals throughout the day. The aorta, mesenteric arteries, heart, kidney, and brain were isolated. Clock and target gene mRNA levels were determined by either real-time PCR or in situ hybridization. Isometric contractions were measured in isolated aortic helical strips, and pressor responses to an intravenous injection of vasoconstrictors were determined in vivo using radiotelemetry. We found that the 24-h mRNA rhythms of the following genes were suppressed in db/db mice compared with control mice: the clock genes period homolog 1/2 (Per1/2) and cryptochrome 1/2 (Cry1/2) and their target genes D site albumin promoter-binding protein (Dbp) and peroxisome proliferator-activated receptor-γ (Pparg) in the aorta and mesenteric arteries; Dbp in the heart; Per1, nuclear receptor subfamily 1, group D, member 1 (Rev-erba), and Dbp in the kidney; and Per1 in the suprachiasmatic nucleus. The 24-h contractile variations in response to phenylephrine (α(1)-agonist), ANG II, and high K(+) were significantly altered in the aortas from db/db mice compared with control mice. The diurnal variations of the in vivo pressor responses to phenylephrine and ANG II were lost in db/db mice. Moreover, the 24-h mRNA rhythms of the contraction-related proteins Rho kinase 1/2, PKC-potentiated phosphatase inhibitory protein of 17 kDa, calponin-3, tropomyosin-1/2, and smooth muscle protein 22-α were suppressed in db/db mice compared with control mice. Together, our data demonstrated that the 24-h rhythms of clock gene mRNA, mRNA levels of several contraction-related proteins, and VSM contraction were disrupted in db/db mice, which may contribute to the disruption of their blood pressure circadian rhythm.

Comparison of inboard and outboard magnetic footprints from topological noise and field errors in the DIII-D

Any canonical transformation of Hamiltonian equations is symplectic, and any area-preserving transformation in 2D is a symplectomorphism. Based on these, a discrete symplectic map and its continuous symplectic analog are derived for forward magnetic field line trajectories in natural canonical coordinates. The unperturbed axisymmetric Hamiltonian for magnetic field lines is constructed from the experimental data in the DIII-D. The equilibrium Hamiltonian is a highly accurate, analytic, and realistic representation of the magnetic geometry of the DIII-D. These symplectic mathematical maps are used to calculate the trajectories of magnetic field lines in the DIII-D. Internal statistical topological noise and field errors are irreducible and ubiquitous in magnetic confinement schemes for fusion. It is important to know the stochasticity and magnetic footprint from noise and error fields. The estimates of the spectrum and mode amplitudes of the spatial topological noise and magnetic errors in the DIII-D are used as magnetic perturbation. The discrete and continuous symplectic maps are used to calculate the magnetic footprint on the inboard and outboard collector plates of the DIII-D by inverting the natural coordinates to physical coordinates. Radial variation of magnetic perturbation and the response of plasma to perturbation are not included. The footprints are in the form of toroidally winding helical strips. The area of footprint scales linearly with amplitude. The outboard footprint has higher transverse extent, higher area, and higher fractal dimension. The field diffusion near the X-point for backward lines is higher than that for forward lines. Diffusion for lines that strike the plate is about three to four orders of magnitude higher than for lines that do not strike. Line loss and flux loss show a drop when the amplitude of perturbation is about 18–19 × 10−6, indicating the possible presence of a barrier. The physical parameters such as toroidal angle, length, and poloidal angle covered before striking and the safety factor all have a fractal structure.

Losartan improves aortic endothelium-dependent relaxation via proline-rich tyrosine kinase 2/Src/Akt pathway in type 2 diabetic Goto-Kakizaki rats

In diabetic states, endothelial dysfunction is related to vascular complications. We hypothesized that insulin-induced relaxation and the associated proline-rich tyrosine kinase 2 (Pyk2)/Src/Akt pathway would be abnormal in aortas from the Goto-Kakizaki (GK) type 2 diabetic rat, which exhibits hyperglycemia/insulin resistance, and that losartan treatment of such rats (25 mg·kg(-1)·day(-1) for 2 wk) would correct these abnormalities. Endothelium-dependent relaxation was by measuring isometric force in helical strips of aortas from four groups, each of 30 rats: normal Wistar (control), GK (diabetic), losartan-treated normal, and losartan-treated GK. Pyk2, Src, and Akt/endothelial nitric oxide synthase (eNOS) signaling-pathway protein levels and activities were assayed mainly by Western blotting and partly by immunohistochemistry. In GK (vs. age-matched control) aortas, various insulin-stimulated levels [nitric oxide production and the phosphorylations of eNOS at Ser(1177), of Akt at Thr(308), of phosphoinositide-dependent kinase-1 (PDK1) at Ser(241), of Src at Tyr(416), and of Pyk2 at Tyr(579)] were all significantly decreased and unaffected by either Src inhibitor (PP2) or Pyk2 inhibitor (AG17), while the insulin-stimulated levels of insulin receptor substrate (IRS)-1 phosphorylation at Ser(307), total-eNOS, and total-Akt were significantly increased. Losartan treatment normalized these altered levels. The insulin-stimulated phosphorylation levels of Src/PDK1/Akt/eNOS, but not of Pyk2, were decreased by PP2 in control and losartan-treated GK, but not in GK, aortas. These results suggest that in the GK diabetic aorta increased phospho-IRS-1 (at Ser(307)) and decreased Pyk2/Src activity inhibit insulin-induced stimulation of the PDK/Akt/eNOS pathway. The observed increase in phospho-IRS-1 (at Ser(307)) may result from increased angiotensin II activity.

Symplectic calculation of the outboard magnetic footprint from noise and error fields in the DIII-D

AbstractThe backward symplectic DIII-D map and continuous symplectic analog of the map for magnetic field line trajectories in the DIII-D [10] (Luxon, J. L. and Davis, L. E. 1985 Fusion Technol.8, 441) in natural canonical coordinates are used to calculate the magnetic footprint on the outboard collector plate of the DIII-D tokamak from the field errors and internal topological noise. The equilibrium generating function for the DIII-D used in the map very accurately represents the magnetic geometry of the DIII-D. The step-size of the map is kept considerably small so that the magnetic perturbation added from symplectic discretization of the Hamiltonian equations of the magnetic field line trajectories is very small. The natural canonical coordinates allow inverting to the real physical space. The combination of highly accurate equilibrium generating function, natural canonical coordinates, symplecticity, and small step-size then together gives a very accurate calculation of magnetic footprint. Radial variation of magnetic perturbation and the response of plasma to perturbation are not included. The footprint is in the form of toroidally winding helical strips. The area of footprint scales as 1st power of amplitude. The physical parameters as toroidal angle, length, and poloidal angle covered before striking, and the safety factor all have fractal structure. The average field diffusion near X-point for lines that strike and that do not strike differs by about four orders of magnitude. The flux loss decreases for high values of amplitude of perturbation.

Analysis of Mechanical Properties of Pipes with Helical Reinforcement under Axial Tension

Flexible pipes with helical reinforcement are widely used in the marine engineering and tissue engineering because of their low bending stiffness. Through appropriate design, they could also meet the strength requirement. All studies on this kind of structures regard the pitch angle of helical wires, strips or fibers as a vital parameter influencing the mechanical properties. In this study, we compare the tensile property of pipes with helical reinforcements braided in different initial pitch angles. Contact pressure is taken into consideration and eliminated by using deformation compatibility equation. The pitch angle changes under axial tension which induces the geometric nonlinearity. It is noted that when the pitch angle is larger than a critical value, even if there is no internal or external pressure, helixes will contact with the core under axial tension. But the initial pitch angle can not be too large since the contact pressure will induce partial buckling of the flexible pipe.

An accurate symplectic calculation of the inboard magnetic footprint from statistical topological noise and field errors in the DIII-D

Any canonical transformation of Hamiltonian equations is symplectic, and any area-preserving transformation in 2D is a symplectomorphism. Based on these, a discrete symplectic map and its continuous symplectic analog are derived for forward magnetic field line trajectories in natural canonical coordinates. The unperturbed axisymmetric Hamiltonian for magnetic field lines is constructed from the experimental data in the DIII-D [J. L. Luxon and L. E. Davis, Fusion Technol. 8, 441 (1985)]. The equilibrium Hamiltonian is a highly accurate, analytic, and realistic representation of the magnetic geometry of the DIII-D. These symplectic mathematical maps are used to calculate the magnetic footprint on the inboard collector plate in the DIII-D. Internal statistical topological noise and field errors are irreducible and ubiquitous in magnetic confinement schemes for fusion. It is important to know the stochasticity and magnetic footprint from noise and error fields. The estimates of the spectrum and mode amplitudes of the spatial topological noise and magnetic errors in the DIII-D are used as magnetic perturbation. The discrete and continuous symplectic maps are used to calculate the magnetic footprint on the inboard collector plate of the DIII-D by inverting the natural coordinates to physical coordinates. The combination of highly accurate equilibrium generating function, natural canonical coordinates, symplecticity, and small step-size together gives a very accurate calculation of magnetic footprint. Radial variation of magnetic perturbation and the response of plasma to perturbation are not included. The inboard footprint from noise and errors are dominated by m=3, n=1 mode. The footprint is in the form of a toroidally winding helical strip. The width of stochastic layer scales as 12 power of amplitude. The area of footprint scales as first power of amplitude. The physical parameters such as toroidal angle, length, and poloidal angle covered before striking, and the safety factor all have fractal structure. The average field diffusion near the X-point for lines that strike and that do not strike differs by about three to four orders of magnitude. The magnetic footprint gives the maximal bounds on size and heat flux density on collector plate.

Activation of SUR2B/Kir6.1 Subtype of Adenosine Triphosphate-sensitive Potassium Channel Improves Pressure Overload-induced Cardiac Remodeling via Protecting Endothelial Function

We sought to explore new strategies targeting SUR2B/Kir6.1, a subtype of adenosine triphosphate (ATP)-sensitive potassium channels (KATP), against pressure overload-induced heart failure. The effects of natakalim, a SUR2B/Kir6.1 selective channel opener, on progression of cardiac remodeling were investigated. Pressure overload-induced heart failure was induced in Wistar rats by abdominal aortic banding. The effects of natakalim (1, 3, and 9 mg·kg⁻¹·d⁻¹ for 10 weeks) on myocardial hypertrophy and heart failure, cardiac histology, vasoactive compounds, and gene expression were assessed. Ten weeks after the onset of pressure overload, natakalim treatment potently inhibited cardiac hypertrophy and prevented heart failure. Natakalim remarkably inhibited the changes of left ventricular hemodynamic parameters and reversed the increase of heart mass index, left ventricular weight index, and lung weight index. Histological examination demonstrated that there was no significant hypertrophy or fibrosis in pressure-overloaded hearts of natakalim-treated rats. Ultrastructural examination of hearts revealed well-organized myofibrils with mitochondria grouped along the periphery of longitudinally oriented fibers in rats from the natakalim group. The content of serum nitric oxide and plasma prostacyclin was increased, whereas that of plasma endothelin-1 and cardiac tissue hydroxyproline and atrial and B-type natriuretic peptide messenger RNA was downregulated in natakalim-treated rats. Natakalim at 0.01-100 µM had no effects on isolated working hearts derived from Wistar rats; however, natakalim had endothelium-dependent vasodilatory effects on the isolated tail artery helical strips precontracted with norepinephrine. These results indicate that natakalim reduces heart failure caused by pressure overloading by activating the SUR2B/Kir6.1 KATP channel subtype and protecting against endothelial dysfunction.