11351 research outputs found
Sort by
Qualitative results on mixed problem of micropolar bodies with microtemperatures
Get PDFThe aim of our study is to transform the mixed initial boundary value problem considered in the context of micropolar thermoelastic bodies whose micro-particles possess microtemperatures in a temporal evolutionary equation on a Hilbert space. Then, with the help of some results from the theory of semigroups, the existence and the uniqueness of the solution for this equation is proved. Finally, we approach the continuous dependence of the solution upon initial data and loads, also with the help of the semigroup
Fractional Order Thermoelastic Deflection in a Thin Circular Plate
Get PDFIn this work, a quasi-static uncoupled theory of thermoelasticity based on time fractional heat conduction equation is used to model a thin circular plate, whose lower surface is maintained at zero temperature whereas the upper surface is insulated. The edge of the circular plate is fixed and clamped. Integral transform technique is used to derive the analytical solutions in the physi-cal domain. The numerical results for temperature distributions and thermal deflection are com-puted and represented graphically for Copper material
Interactions of Thermoelastic Beam in Modified Couple Stress Theory
Get PDFThis paper is concerned with the study of thermoelastic beam in modified couple stress theory. The governing equations of motion for modified couple stress theory and heat conduction equation for non-Fourier (non-classical process) are investigated to model the vibrations in a homogeneous isotropic thin beam in a closed form by employing the Euler Bernoulli beam theory. The generalized theories of thermoelasticity with one and two relaxation times are used to model the problem. Both ends of the beam are simply supported. The Laplace transform technique applied to solve the system of equations which are written in dimensionless form. A general algorithm of the inverse Laplace transform is developed. The thermal moment is approximated as the difference between the upper and the lower surfaces of the beam. The analytical results have been analyzed numerically with the help of MATLAB software. The lateral deflection, thermal moment, axial stress average due to normal heat flux in the beam are derived and computed numerically. Numerical inversion technique has been applied to recover the results in a physical domain. The effect of couple stress on the resulting quantities are depicted graphically for a specific model. Comparisons are made with the results of different theories in the absence and presence of couple stress parameter. Particular cases of interest are also derived. The present study may find applications in medical science, engineering, accelerometers, sensors, resonators etc. The study of lateral deflection, thermal moment and axial stress average is a significant problem of continuum mechanics
Applications of Planar Newtonian Four-body Problem to the Central Configurations
Get PDFThe present study deals with the applications of the planar Newtonian four-body problem to the different central configurations. The basic concept of central configuration is that the vector force must be in the direction of the position vector so that the origin may be taken at the centre of mass of the four bodies and the force towards the position vector multiplied by corresponding inverse mass is directly proportional to the position vector relative to the centre of mass. For applying the Newtonian four body problem to the central configuration, the equations of motion of four bodies have been established in inertial frame. By the methods of previous authors, some mathematical tools of the planar problem have been developed and by using them, the Newtonian four-body problem have been reduced to central configuration. All the previously generated mathematical models depend upon the directed areas, weighted directed areas and position vectors of the centre of the bodies. With the help of these models some conditions have been established, which show that the origin is located at the centre of mass of the system. Finally these conditions have been used to some particular cases of concave configuration, convex configuration and symmetric configuration to generate some tools which will be helpful for further researches of this field
Origin of the Regioselectivity in the Aldol Condensation between Hydroxymethylfurfural and Levulinic Acid: A DFT Investigation
No full textOur previous work demonstrated that hydroxide ion (OH-) was able to catalyze aldol condensation reaction at room temperature between 5-hydroxymethylfurfural (HMF) and levulinic acid (LA). This work identified three primary reaction steps in this condensation reaction using density functional theory (DFT): (1) deprotonation of LA to generate LA ions, (2) LA ions addition at hydroxymethyl site of HMF, and (3) internal dehydration to form the condensation product. The reaction pathway through the C5 of LA forms a linear product that is favored with respect to both energy and configuration in all three elementary reaction steps. This is qualitatively consistent with the phenomenon observed in our previous experiment where the linear form is a main product. Further confirmation comes from the frontier orbital analysis of the transition states in the linear reaction route and explains the regioselectivity of product formation. (Chemical Equation Presented)
Microbiota, metabolome, and immune alterations in obese mice fed a high-fat diet containing type 2 resistant starch
No full textScope: We examined the intestinal and systemic responses to incorporating a type 2 resistant starch (RS) into a high fat diet fed to obese mice. Methods and results: Diet-induced obese, C57BL/6J male mice were fed an HF diet without or with 20% (by weight) high-amylose maize resistant starch (HF-RS) for 6 weeks. Serum adiponectin levels were higher with RS consumption, but there were no differences in weight gain and adiposity. With HF-RS, the expression levels of ileal TLR2 and Reg3g and cecal occludin, TLR2, TLR4, NOD1 and NOD2 were induced; whereas colonic concentrations of the inflammatory cytokine IL-17A declined. The intestinal, serum, liver, and urinary metabolomes were also altered. HF-RS resulted in lower amino acid concentrations, including lower serum branched chain amino acids, and increased quantities of urinary di/trimethylamine, 3-indoxylsulfate, and phenylacetylglycine. Corresponding to these changes were enrichments in Bacteroidetes (S24-7 family) and certain Firmicutes taxa (Lactobacillales and Erysipelotrichaceae) with the HF-RS diet. Parabacteroides and S24-7 positively associated with cecal maltose concentrations. These taxa and Erysipelotrichaceae, Allobaculum, and Bifidobacterium were directly correlated with uremic metabolites. Conclusion: Consumption of RS modified the intestinal microbiota, stimulated intestinal immunity and endocrine-responses, and modified systemic metabolomes in obese mice consuming an otherwise obesogenic diet
Biotechnological induction of shikimate-based antioxidant accumulation in Phyla dulcis
No full textBackground: Medicinal phytochemicals have been used as dietary supplements in Asia and Africa for thousands of years. Biologically active antioxidants are very diverse and low in their chemical compositions thereby limiting their efficacies. The present study focuses on the enhanced accumulation of closely related dietary antioxidants: shikimate, quinate, salicylate and tocopherol in Phyla dulcis, the Central American herb known for its anti-inflammatory medicinal properties; but its polyphenolic antioxidants had not been studied. Methods: Phyla dulcis stem cuttings were planted in the greenhouse, and in field plots and treated with solutions of stoichiometric mixes of mineral salts known to double crop biomass and yield. Controls were treated with water. At maturity, P. dulcis shoots and flowers were harvested per treatment, immediately frozen in liquid nitrogen, and submitted to metabolomic analyses by gas chromatography-time-of-flight mass spectrometry. Results: Field plot P. dulcis treated with KKS-mineral salts combination induced increased shikimate accumulation of 1.59 g per 100 g from the 0.799 g per 100 g in the untreated control. Similarly salicylate, quinate, and tocopherols increased in accumulation by many orders of magnitude in the stoichiometric mixes of mineral salts-treated P. dulcis compared with the untreated controls. Conclusion: The accumulated polyphenolic antioxidants permitted the deduction of the unique biosynthetic pathway of the shikimate, with a massive inhibition at the enzyme steps of dehydroquinate dehydratase and shikimate dehydrogenase
Strategic adaptation of nitrogen management for El Niño Southern Oscillation-induced winter wheat system
No full textThe rainfall anomaly (RA) associated with El Niño-Southern Oscillation (ENSO) has various unwanted impacts on agricultural system globally. The loss of inorganic nitrogen (N) depending on extreme wet or dry conditions is a major concern. The main objective of this study was to adapt site-specific N strategies to mitigate the effects of ENSO on yields of winter wheat (Triticum aestivum L.; WW) system. After thorough calibration and evaluation, Decision Support Systems for Agrotechnology Transfer (DSSAT, version 4.5) model suite was adapted. Seasonal analysis was used to compare the variability in simulated leached-N, N uptake, and WW yields under long-term historical real-weather conditions. The site X climate interactions and impacts of weather factors on WW yields were assessed across 60 growing seasons in three phases of ENSO: El Niño (EN), La Niña (LN), and neutral (NT). Based on RA, the simulated yields were lower during LN than EN (11 %) and NT (12 %) on coastal sandy-loam soils and higher during LN than EN (13 %) and NT (8 %) on heavy silt loam soils at valley. N strategy with basal of 22 kg N ha−1 + a split of 112 kg N ha−1 at Feekes (F) 4 stage of WW was adapted for maximum yield and minimum N leaching during LN at valley and NT at coastal sites. However, basal of 22 kg N ha−1 + two equal splits of 56 kg N ha−1 at both F4 and F6 was found as the most adaptable N strategy during both EN and NT phases at valley and EN and LN at coastal sites
Biotechnological induction of shikimate-based antioxidant accumulation in Phyla dulcis
No full textBackground: Medicinal phytochemicals have been used as dietary supplements in Asia and Africa for thousands of years. Biologically active antioxidants are very diverse and low in their chemical compositions thereby limiting their efficacies. The present study focuses on the enhanced accumulation of closely related dietary antioxidants: shikimate, quinate, salicylate and tocopherol in Phyla dulcis, the Central American herb known for its anti-inflammatory medicinal properties; but its polyphenolic antioxidants had not been studied. Methods: Phyla dulcis stem cuttings were planted in the greenhouse, and in field plots and treated with solutions of stoichiometric mixes of mineral salts known to double crop biomass and yield. Controls were treated with water. At maturity, P. dulcis shoots and flowers were harvested per treatment, immediately frozen in liquid nitrogen, and submitted to metabolomic analyses by gas chromatography-time-of-flight mass spectrometry. Results: Field plot P. dulcis treated with KKS-mineral salts combination induced increased shikimate accumulation of 1.59 g per 100 g from the 0.799 g per 100 g in the untreated control. Similarly salicylate, quinate, and tocopherols increased in accumulation by many orders of magnitude in the stoichiometric mixes of mineral salts-treated P. dulcis compared with the untreated controls. Conclusion: The accumulated polyphenolic antioxidants permitted the deduction of the unique biosynthetic pathway of the shikimate, with a massive inhibition at the enzyme steps of dehydroquinate dehydratase and shikimate dehydrogenase
State of the Art of Water for Food Within the Nexus Framework
No full textPurpose of Review: The purpose of this study is to evaluate the state of knowledge regarding water for food within the water-energy-food (WEF) nexus framework. Three topics are considered: improved plant genetics; irrigation technology and practices; and urban agriculture. Recent Findings: Research in plant genetics has sought to understand plant mechanisms that produce higher-yielding crops, identify and map genetic loci regions responsible for desirable plant traits, and introduce new and safe methods of precision plant breeding. In addition, new discoveries in irrigation practices are crucial in sustaining and further increasing yields as a result of improved irrigation water use efficiency through near-real time spatio-temporal monitoring of soil moisture, evapotranspiration, and rainfall. Urban agriculture has been proliferating in recent years, and recent research demonstrates the possibility of non-traditional, urban farming methods to produce food in a water- and land-efficient way. Summary: Opportunities remain to increase water use efficiency and/or decrease water usage throughout the food supply chain. Food producers need to achieve greater value from the water used through enhanced management supported by new technology and guided by scientific findings evolving from multidisciplinary research. To achieve this, constant exchange is needed between regulatory agencies, farmers, food manufacturers, and researchers to ensure all stakeholders are up to date on the issues, policies, technologies, and discoveries related to water and food production sustainability