On-line measurement of heat of combustion

An experimental method for an on-line measurement of heat of combustion of a gaseous hydrocarbon fuel mixture of unknown composition is developed. It involves combustion of a test gas with a known quantity of air to achieve a predetermined oxygen concentration level in the combustion products. This is accomplished by a feedback controller which maintains the gas volumetric flow rate at a level consistent with the desired oxygen concentration in the products. The heat of combustion is determined from a known correlation with the gas volumetric flow rate. An on-line microcomputer accesses the gas volumetric flow data, and displays the heat of combustion values at desired time intervals

Lack of direct evidence for a functional role of voltage-operated calcium channels in juxtaglomerular cells

In this study we have examined the role of voltage-gated calcium channels in the regulation of calcium in juxtaglomerular cells. Using a combination of patch-clamp and single-cell calcium measurement we obtained evidence neither for voltage-operated calcium currents nor for changes of the intracellular calcium concentration upon acute depolarizations of the cell membrane. Increases of the extracellular concentration of potassium to 80 mmol/l depolarized the juxtaglomerular cells close to the potassium equilibrium potential, but did not alter the intracellular calcium concentration neither in patch-clamped nor in intact Furaester-loaded cells. Moreover, basal renin secretion from a preparation enriched in mouse juxtaglomerular cells and from rat glomeruli with attached juxtaglomerular cells was not inhibited when extracellular potassium was isoosmotically increased to 56 mmol/l. In mouse kidney slices, however, depolarizing potassium concentrations caused a delayed inhibition at 56 mmol/l and a delayed stimulation of renin secretion at 110 mmol/l. Taken together, our study does not provide direct evidence for a role of voltage-activated calcium channels in the regulation of calcium and renin secretion in renal juxtaglomerular cells

The correlation of microstructure and mechanical properties of in-situ Al-Mg2Si cast composite processed by equal channel angular pressing

In this paper, the effect of equal channel angular pressing (ECAP) on microstructure and mechanical properties of hypereutectic Al-20%Mg2Si and Al-15%Mg2Si, as well as hypoeutectic Al-10%Mg2Si composites has been investigated. After fabricating the composites by in-situ casting, the composites were processed using the ECAP process up to two passes at room temperature. Microstructural studies have been carried out using a field emission scanning electron microscopy equipped with an energy dispersive X-ray spectrometer. Mechanical properties were also documented using Vickers microhardness and shear punch tests. In the hypereutectic composites, a decrease in the average size of pro-eutectic Mg2Si (Mg2Sip) particles, breakages in eutectic networks, and lengthening of the Al (α) phase in direction of shear bands were observed after the ECAP process. For instance, the average size of Mg2Sip Particles in Al-20%Mg2Si composite reduced from 40 to 17 μm after 2 passes of ECAP. Furthermore, a uniform distribution of Mg2Sip particles was developed in the matrix. In hypoeutectic composite, the ECAP process caused a uniform distribution of eutectic Mg2Si (Mg2SiE) in the matrix that considered a favorable microstructure. Microhardness measurements and shear punch results showed an ascending trend after each pass of ECAP for all specimens. For example, microhardness and shear strength of Al-20%Mg2Si increased from 88 HV and 109 MPa to 119 HV and 249 MPa after two passes indicating 35% and 34% increments, respectively. Density and porosity calculations by Archimedes principle revealed that the density of the composites increased after two passes of ECAP due to the reduction of porosity

Marine energy extraction of waves and tidal currents in Chabahar Bay

Development of modern energies is one of the most important issues that all countries have focused on and have tried to find a new model in that respect. This study investigates various methods of estimating energies that are produced by wave and then it concludes that the best method is spectrum analysis using Fourier analysis. Using available data of year 1998 in Chabahar and applying a program which is produced in MATLAB environment, rate of producible energy in year 1998 is equal to 6.9 Kwh/m² and producible power of waves has been estimated to be 3.9 Kw/m² with the lowest rate of energy observed in winter and the highest rate of wave energy in summer. Probable cause of this phenomenon could be seasonal winds that blow in summer. According to the flowmetry report done by Ports and Maritime Organization in Chabahar, in Aw1 Station has divided its 9-meter distance below water surface into 7 cells, therefore, with considering 1×1m channels and assuming that flow in each channel has been changed steadily, tide flow energy has been estimated and average energy of Chabahar station has been obtained equal to 0.12 w/m^2 within two weeks. In the second way, using program written in MATLAB environment and calculating the surface under the chart, tide energy has been calculated equal to 0.19w/ m^2. According to the obtained results, producible energy of tidal current in Chabahar Gulf is very low and it is not economical

Solving two-dimensional coupled Burgers equations via a stable hybridized discontinuous Galerkin method

The purpose of this paper is to design a fully discrete hybridized discon-tinuous Galerkin (HDG) method for solving a system of two-dimensional (2D) coupled Burgers equations over a specified spatial domain. The semi-discrete HDG method is designed for a nonlinear variational formulation on the spatial domain. By exploiting broken Sobolev approximation spaces in the HDG scheme, numerical fluxes are defined properly. It is shown that the proposed method is stable under specific mild conditions on the stabi-lization parameters to solve a well-posed (in the sense of energy method) 2D coupled Burgers equations, which is imposed by Dirichlet boundary conditions. The fully discrete HDG scheme is designed by exploiting the Crank–Nicolson method for time discretization. Also, the Newton–Raphson method that has the order of at least two is nominated for solving the obtained nonlinear system of coupled Burgers equations over the rect-angular domain. To reduce the complexity of the proposed method and the size of the linear system, we exploit the Schur complement idea. Numerical results declare that the best possible rates of convergence are achieved for approximate solutions of the 2D coupled Burgers equations and their first-order derivatives. Moreover, the proposed HDG method is examined for two other types of systems, that is, a system with high Reynolds numbers and a system with an unavailable exact solution. The acceptable results of examples show the flexibility of the proposed method in solving various problems

Limitation of finite element analysis of poroelastic behavior of biological tissues undergoing rapid loading

The finite element method is used in biomechanics to provide numerical solutions to simulations of structures having complex geometry and spatially differing material properties. Time-varying load deformation behaviors can result from solid viscoelasticity as well as viscous fluid flow through porous materials. Finite element poroelastic analysis of rapidly loaded slow-draining materials may be ill-conditioned, but this problem is not widely known in the biomechanics field. It appears as instabilities in the calculation of interstitial fluid pressures, especially near boundaries and between different materials. Accurate solutions can require impractical compromises between mesh size and time steps. This article investigates the constraints imposed by this problem on tissues representative of the intervertebral disc, subjected to moderate physiological rates of deformation. Two test cylindrical structures were found to require over 10(4) linear displacement-constant pressure elements to avoid serious oscillations in calculated fluid pressure. Fewer Taylor–Hood (quadratic displacement–linear pressure elements) were required, but with complementary increases in computational costs. The Vermeer–Verruijt criterion for 1D mesh size provided guidelines for 3D mesh sizes for given time steps. Pressure instabilities may impose limitations on the use of the finite element method for simulating fluid transport behaviors of biological soft tissues at moderately rapid physiological loading rates

Cloning, expression, purification and CD analysis of recombinant human betatrophin

Betatrophin is a member of the angiopoietin-like (ANGPTL) family that has been implicated in both triglyceride and glucose metabolism. The physiological functions and molecular targets of this protein remain largely unknown; hence, a purified available protein would aid study of the exact role of betatrophin in lipid or glucose metabolism. In this study, we cloned the full-length cDNA of betatrophin from a human liver cDNA library. Betatrophin was expressed in the pET-21b-E. coli Bl21 (DE3) system and purified by immobilized metal-affinity chromatography and ion-exchange chromatography. Circular dichroism spectroscopy revealed α-helix as the major regular secondary structure in recombinant betatrophin. The production method is based on commonly available resources; therefore, it can be readily implemented

Cloning, expression, purification and CD analysis of recombinant human betatrophin

Betatrophin is a member of the angiopoietin-like (ANGPTL) family that has been implicated in both triglyceride and glucose metabolism. The physiological functions and molecular targets of this protein remain largely unknown; hence, a purified available protein would aid study of the exact role of betatrophin in lipid or glucose metabolism. In this study, we cloned the full-length cDNA of betatrophin from a human liver cDNA library. Betatrophin was expressed in the pET-21b-E. coli Bl21 (DE3) system and purified by immobilized metal-affinity chromatography and ion-exchange chromatography. Circular dichroism spectroscopy revealed α-helix as the major regular secondary structure in recombinant betatrophin. The production method is based on commonly available resources; therefore, it can be readily implemented

Complications of transcatheter closure in patent ductus arteriosus patients

Background: Published studies have shown excellent success rates and also low rates of life-threatening complications with trans-catheter closure of patent ductus arteriosus (PDA). However, most studies to date have been conducted in developed nations and reports from developing countries such as Iran are lacking. Objectives: To report our experience with trans-catheter closure of patent ductus arteriosus (PDA) and compare two devices and complications. Patients and Methods: From 2007 to 2011, 72 consecutive PDA cases were prospectively enrolled. For PDAs � 2 mm, the coiling method was employed whereas patients with PDA > 2 mm received Amplatzer duct occlusion (ADO). Success was defined as trivial residual shunt (< 1 mm) in the echocardiography performed 30 minutes after the procedure. After the procedure, the patients were admitted to the pediatric cardiology ward and observed for 72 hours during which the occurrence of major and minor complications was monitored. Major complications included cardiac arrest, displacement and/or embolization of the device and patient needing blood transfusion due to severe hemorrhage. Sampling was based on convenience method and the patients who had significant pulmonary artery hypertension were excluded from our study. Statistical analyses were done using SPSS software version 23 (IBM corp., New York, United States). Continuous variables are presented as mea

Seamless integration of the coastal ocean in global marine carbon cycle modeling

We present the first global ocean-biogeochemistry model that uses a telescoping high resolution for an improved representation of coastal carbon dynamics: ICON-Coast. Based on the unstructured triangular grid topology of the model, we globally apply a grid refinement in the land-ocean transition zone to better resolve the complex circulation of shallow shelves and marginal seas as well as ocean-shelf exchange. Moreover, we incorporate tidal currents including bottom drag effects, and extend the parameterizations of the model's biogeochemistry component to account explicitly for key shelf-specific carbon transformation processes. These comprise sediment resuspension, temperature-dependent remineralization in the water column and sediment, riverine matter fluxes from land including terrestrial organic carbon, and variable sinking speed of aggregated particulate matter. The combination of regional grid refinement and enhanced process representation enables for the first time a seamless incorporation of the global coastal ocean in model-based Earth system research. In particular, ICON-Coast encompasses all coastal areas around the globe within a single, consistent ocean-biogeochemistry model, thus naturally accounting for two-way coupling of ocean-shelf feedback mechanisms at the global scale. The high quality of the model results as well as the efficiency in computational cost and storage requirements proves this strategy a pioneering approach for global high-resolution modeling. We conclude that ICON-Coast represents a new tool to deepen our mechanistic understanding of the role of the land-ocean transition zone in the global carbon cycle, and to narrow related uncertainties in global future projections