11351 research outputs found
Sort by
Relationship of serum Vitamin D concentrations with Adipokines and Cardiometabolic risk among non-Hispanic black type 2 diabetic and non-diabetic subjects: A cross-sectional study
No full textBackground: To report the association of serum 25-hydroxyvitamin D [25(OH)D] and its association with adipokines and cardiometabolic risk factors in Haitian Americans (HA) and African Americans (AA) by ethnicity and type 2 diabetes (T2D) status. Methods: A cross-sectional study in 197 HA (92 with T2D and 102 without T2D) and 200 AA (97 with T2D and 103 without T2D) recruited in South Florida. Serum 25(OH)D concentrations and adipokines were analyzed by ELISA and cardiometabolic risk factors were indexed by obesity, glycemic control, insulin sensitivity, lipid profile, and blood pressure. Results: Controlling for age, BMI, energy intake, smoking status and HOMA2-IR in multivariate linear regression analyses, serum 25(OH)D concentrations were significantly associated with WC (R2 = 0.760, B = - 0.092, P = 0.027), HbA1C (R2 = 0.142, B = - 0.012, P = 0.010), and TG (R2 = 0.159, B = - 1.192, P = 0.003) in only HA without T2D. While serum 25(OH)D concentrations were significantly associated with TC (R2 = 0.168, B = - 0.329, P = 0.040), log leptin (R2 = 0.544, B = - 0.007, P = 0.021), and adiponectin (R2 = 0.144, B = 0.111, P = 0.033), but slightly associated with LDL-c (R2 = 0.133, B = - 0.278, P = 0.064) in only AA without T2D. Among individuals with T2D, serum 25(OH)D concentrations were marginally associated with IL-6 (R2 = 0.109, B = 0.076, P = 0.085) in HA with T2D, and there was a trend toward significance with log leptin (R2 = 0.393, B = - 0.006, P = 0.075) in AA with T2D in regression analysis. Conclusions: The findings that the associations of serum 25(OH)D concentrations with adipokines and cardiometabolic factors differ between HA and AA has clinical and public implications to guide design of T2D preventive strategies that are culturally specific even within the same ethnicity
Carbon dioxide emission in relation with irrigation and organic amendments from a sweet corn field
No full textSoil moisture and organic matter level affects soil respiration and microbial activities, which in turn impact greenhouse gas (GHG) emissions. This study was conducted to evaluate the effect of irrigation levels (75% [deficit], 100% [full], and 125% [excess] of reference crop evapotranspiration requirements), and organic amendments (OA) type (chicken manure [CM] and bone meal [BM]) and OA application rates (0,168, 336 and 672 kg total N ha−1) on (i) soil physical properties (bulk density, organic matter content and soil moisture content) and (ii) soil carbon dioxide (CO2) emissions from a highly weathered tropical Hawai\u27ian soil. Carbon dioxide readings were consistently taken once or twice a week for the duration of the cropping season. A drip irrigation system was used to apply the appropriate amount of irrigation water to the treatment plots. Treatments were randomly selected and corresponding organic amendments were manually incorporated into the soil. Plots were cultivated with sweet corn (Zea mays ‘SS-16’). Soil moisture content within and below the rootzone was monitored using a TDR 300 soil moisture sensor (Spectrum Technologies, Inc., Plainfield, IL, USA) connected with 12 cm long prongs. Soil bulk density and organic matter content were determined at the end of the cropping season. Analysis of variance results revealed that OA type, rate, and their interaction had significant effect on soil CO2 flux (P \u3c 0.05). Among the OA rates, all CM mostly resulted in significantly higher soil CO2 fluxes compared to BM and control treatment (p \u3c 0.05). The two highest rates of BM treatment were not significantly different from the control with regard to soil CO2 flux. In addition, organic amendments affected soil moisture dynamics during the crop growing season and organic matter content measured after the crop harvest. While additional studies are needed to further investigate the effect of irrigation levels on soil CO2 flux, it is recommended that in order to minimize soil CO2 emissions, BM soil amendments could be a potential option to reduce soil CO2 fluxes from agricultural fields similar to the one used in this study
Renewable polymers: Synthesis and characterization of poly(4-ketopimelic acid-glycerol)
No full textCondensation polymerization of renewable resources-based monomers, 4-ketopimelic acid and glycerol, were studied using two different catalysts; p-toluenesulfonic acid and Sb2O3. The highest polymer yield of 96% was achieved by using a 3:4 mole ratio mixture of 4-ketopimelic acid and glycerol, with Sb2O3 (0.5 mol% relative to 4-ketopimelic acid) as catalyst and heating at 23-210°C, under N2 for 1 h; then 210°C, vacuum, 12 h. The poly(4-ketopimelic acid-glycerol) formed is insoluble in all common organic solvents and is shown to contain a branched polymeric structure with ketal and ester links by using FT-IR, 1H and 13C NMR spectroscopy
Carbon dioxide emission in relation with irrigation and organic amendments from a sweet corn field
No full textSoil moisture and organic matter level affects soil respiration and microbial activities, which in turn impact greenhouse gas (GHG) emissions. This study was conducted to evaluate the effect of irrigation levels (75% [deficit], 100% [full], and 125% [excess] of reference crop evapotranspiration requirements), and organic amendments (OA) type (chicken manure [CM] and bone meal [BM]) and OA application rates (0,168, 336 and 672 kg total N ha−1) on (i) soil physical properties (bulk density, organic matter content and soil moisture content) and (ii) soil carbon dioxide (CO2) emissions from a highly weathered tropical Hawai\u27ian soil. Carbon dioxide readings were consistently taken once or twice a week for the duration of the cropping season. A drip irrigation system was used to apply the appropriate amount of irrigation water to the treatment plots. Treatments were randomly selected and corresponding organic amendments were manually incorporated into the soil. Plots were cultivated with sweet corn (Zea mays ‘SS-16’). Soil moisture content within and below the rootzone was monitored using a TDR 300 soil moisture sensor (Spectrum Technologies, Inc., Plainfield, IL, USA) connected with 12 cm long prongs. Soil bulk density and organic matter content were determined at the end of the cropping season. Analysis of variance results revealed that OA type, rate, and their interaction had significant effect on soil CO2 flux (P \u3c 0.05). Among the OA rates, all CM mostly resulted in significantly higher soil CO2 fluxes compared to BM and control treatment (p \u3c 0.05). The two highest rates of BM treatment were not significantly different from the control with regard to soil CO2 flux. In addition, organic amendments affected soil moisture dynamics during the crop growing season and organic matter content measured after the crop harvest. While additional studies are needed to further investigate the effect of irrigation levels on soil CO2 flux, it is recommended that in order to minimize soil CO2 emissions, BM soil amendments could be a potential option to reduce soil CO2 fluxes from agricultural fields similar to the one used in this study
Effect of Nonlinear Thermal Radiation on MHD Chemically Reacting Maxwell Fluid Flow Past a Linearly Stretching Sheet
Get PDFThis communication addresses the influence of nonlinear thermal radiation on magneto hydrodynamic Maxwell fluid flow past a linearly stretching surface with heat and mass transfer. The effects of heat generation/absorption and chemical reaction are taken into account. At first, we converted the governing partial differential equations into nonlinear ordinary differential equations with the help of suitable similarity transformations and solved by using Runge-Kutta based shooting technique. Further, the effects of various physical parameters on velocity, temperature and concentration fields were discussed thoroughly with the help of graphs obtained by using bvp5c MATLAB package. In view of many engineering applications we also computed the friction factor, heat and mass transfer coefficients and presented them in tables. Results indicate that an increase in thermal buoyancy parameter enhances the fluid velocity but suppresses the temperature. Deborah number have tendency to reduce the fluid velocity and mass transfer rate. It is also perceived that temperature ratio parameter has the propensity to enrich the fluid temperature
New structure for exact solutions of nonlinear time fractional Sharma-Tasso-Olver equation via conformable fractional derivative
Get PDFIn this paper new fractional derivative and direct algebraic method are used to construct exact solutions of the nonlinear time fractional Sharma-Tasso-Olver equation. As a result, three families of exact analytical solutions are obtained. The results reveal that the proposed method is very effective and simple for obtaining approximate solutions of nonlinear fractional partial differential equations
Numerical solution of linear time delay systems using Chebyshev-tau spectral method
Get PDFIn this paper, a hybrid method based on method of steps and a Chebyshev-tau spectral method for solving linear time delay systems of differential equations is proposed. The method first converts the time delay system to a system of ordinary dierential equations by the method of steps and then employs Chebyshev polynomials to construct an approx- imate solution for the system. In fact, the solution of the system is expanded in terms of orthogonal Chebyshev polynomials which reduces the solution of the system to the solution of a system of algebraic equations. Also, we transform the coefficient matrix of the algebraic system to a block quasi upper triangular matrix and the latter system can be solved more efficiently than the first one. Furthermore, using orthogonal Chebyshev polynomials enables us to apply fast Fourier transform for calculating matrix-vector multiplications which makes the proposed method to be more efficient. Consistency, stability and convergence analysis of the method are provided. Numerous numerical examples are given to demonstrate efficiency and accuracy of the method. Comparisons are made with available literature
Thermal stress analysis in a functionally graded hollow elliptic-cylinder subjected to uniform temperature distribution
Get PDFIn this paper, an analytical method of a thermoelastic problem for a medium with functionally graded material properties is developed in a theoretical manner for the elliptic-cylindrical coordinate system under the assumption that the material properties except for Poisson’s ratio and density are assumed to vary arbitrarily with the exponential law in the radial direction. An attempt has been made to reconsider the fundamental system of equations for functionally graded solids in a two-dimensional state under thermal and mechanical loads. The general solution of displacement formulation is obtained by the introduction of appropriate transformation and carried out the analysis by taking into account the variation of inhomogeneity parameters. Furthermore, the aforementioned problem degenerated into the problem of the circular region by applying limiting conditions, and the results are validated. Numerical computations are carried out for ceramic-metal-based functionally graded material, in which zirconia is selected as ceramic and aluminium as metal and are represented graphically
Analytical solutions for the Black-Scholes equation
Get PDFIn this paper, the Black-Sholes equation (BS) has been applied successfully with the Cauchy-Euler method and the method of separation of variables and new analytical solutions have been found. The linear partial differential equation (PDE) transformed to linear ordinary differential equation (ODE) as well. We acquired three types of solutions including hyperbolic, trigonometric and rational solutions. Descriptions of these methods are given and the obtained results reveal that three methods are tools for exploring partial differential models
Thermoelastic analysis of a nonhomogeneous hollow cylinder with internal heat generation
Get PDFIn the present paper, we have determined the heat conduction and thermal stresses of a hollow cylinder with inhomogeneous material properties and internal heat generation. All the material properties except Poisson’s ratio and density are assumed to be given by a simple power law in axial direction. We have obtained the solution of the two dimensional heat conduction equation in the transient state in terms of Bessel’s and trigonometric functions. The influence of inhomogeneity on the thermal and mechanical behavior is examined. Numerical computations are carried out for both homogeneous and nonhomogeneous cylinders and are represented graphically