Stearoyl-CoA desaturase-1 (SCD1) is a key player in lipid metabolism. SCD1 catalyzes the synthesis of monounsaturated fatty acids (MUFA). MUFA are then incorporated into triacylglycerols and ...phospholipids. Previous studies have shown that
deficiency in mice induces metabolic changes in the liver characterized by a decrease in de novo lipogenesis and an increase in β-oxidation. Interestingly,
-deficient mice show a decrease in the expression and maturation of the principal lipogenic transcription factor sterol receptor element binding protein-1 (SREBP-1). The mechanisms mediating this effect on de novo lipogenesis and β-oxidation have not been fully elucidated. We evaluated the role of
on de novo lipogenesis and β-oxidation in HepG2 cells. We also used
-deficient mice and two strains of transgenic mice that produce either oleate (GLS5) or palmitoleate (GLS3) in a liver-specific manner. We demonstrate that the expression of β-oxidation markers increases in
-deficient hepatocytes and suggest that this is due to an increase in cellular polyunsaturated fatty acid content. We also show that the changes in the level of SREBP-1 expression, for both the precursor and the mature forms, are mainly due to the lack of oleate in
-deficient hepatocytes. Indeed, oleate treatment of cultured HepG2 cells or hepatic oleate production in chow-fed GLS5 mice can restore SREBP-1 expression and increase hepatic de novo lipogenesis. Finally, we show that oleate specifically increases SREBP-1 nuclear accumulation, suggesting a central role for oleate in SREBP-1 signaling activity.
•Fluorine, silicon atoms and SiF molecule adsorption process on Si(001)-p(2 × 2) surface have been studied.•The minimum energy paths for F diffusion and SiF decomposition on the silicon surface are ...explored using the nudged elastic band (NEB) method.•Our results show that the dissociative adsorption of the SiF molecule is energetically the most favorable.•We have found that it is energetically easier for the fluorine atom to diffuse from the SiF molecule towards the surface than the diffusion from a surface site to another.
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The adsorption of the F and Si atoms as well as the SiF molecule on the Si(001)-p(2×2) surface is studied using first-principle calculations. Our results show that the fluorine atom saturates the dangling bond of the surface while the silicon adatom forms two bonds with the surface atoms. For the adsorption of the SiF molecule, we obtained one dissociative state which is the most stable one and seven non-dissociative states. The minimum energy paths for F diffusion and SiF decomposition on the silicon surface are explored using the nudged elastic band (NEB) method. Our study reveals that it is energetically favorable for the fluorine atom to diffuse from the SiF molecule to a surface site than the diffusion from surface site to another one.
In this study, we have harvested natural oleaster (wild olive) fibers, processed and characterized in terms of physicochemical performance as well as mechanical properties. The main constituents of ...oleaster fibers with their weight proportions are cellulose (38.11%), lignin (19.4%), and ash (3.1%). The specific density of the oleaster fiber is measured to (1.40256 g cm
−3
). The average elastic modulus, tensile strength, and elongation at the break of composites made from polymer resin and oleaster fibers (untreated and treated with 20% acetic anhydride) have undergone an improvement in mechanical properties, respectively, an elastic modulus of 8.39 MPa for a deformation of 0.48334% against for the treated composite with the deformation of 3.95%for an elastic modulus of 55.53 MPa. Their Young moduli are 41.029 GPa for the untreated fiber composite and 93.19 GPa for the acetic anhydride treated fiber composite, respectively. We have also studied the effects of acetic anhydride treatment on the mechanical properties and structure of the fibers. When treated with 20% acetic anhydride for 2 h, the tensile strength of oleaster fibers had increased significantly. A longer treatment time did not show any appreciable improvement. However, the tensile strength remained higher than the tensile strength for untreated fibers.
Abstract
In this study, an optical filter based on a plasmonic metal-insulator-metal (MIM) coupled waveguide resonator is simulated and investigated. Using the proposed structure leads to realizing a ...filter function between targeted wavelengths by manipulating the appropriate geometrical parameters of the resonators. Two-dimensional FDTD-based simulation is implemented to analyze the filter properties. The filter proposed proves to be a potential candidate for highly integrated optical circuit applications.
Stearoyl-CoA desaturase 1 (SCD1) is a delta-9 fatty acid desaturase that catalyzes the synthesis of mono-unsaturated fatty acids (MUFA). SCD1 is a critical control point regulating hepatic lipid ...synthesis and β-oxidation. Scd1 KO mice are resistant to the development of diet-induced non-alcoholic fatty liver disease (NAFLD). Using a chronic-binge protocol of ethanol-mediated liver injury, we aimed to determine if these KO mice are also resistant to the development of alcoholic fatty liver disease (AFLD).
Mice fed a low-fat diet (especially low in MUFA) containing 5% ethanol for 10days, followed by a single ethanol (5g/kg) gavage, developed severe liver injury manifesting as hepatic steatosis. This was associated with an increase in de novo lipogenesis and inflammation. Using this model, we show that Scd1 KO mice are resistant to the development of AFLD. Scd1 KO mice do not show accumulation of hepatic triglycerides, activation of de novo lipogenesis nor elevation of cytokines or other pro-inflammatory markers. Incubating HepG2 cells with a SCD1 inhibitor induced a similar resistance to the effect of ethanol, confirming a role for SCD1 activity in mediating ethanol-induced hepatic injury.
Taken together, our study shows that SCD1 is a key player in the development of AFLD and associated deleterious effects, and suggests SCD1 inhibition as a therapeutic option for the treatment of this hepatic disease.
•Chronic+binge protocol of ethanol abuse in low fat and low MUFA diet induces liver injury.•SCD1 deficiency protects mice against ethanol-induced liver injury.•SCD1 KO mice do not develop alcoholic hepatic steatosis or inflammation.•SCD1 inhibitor shows a similar effect on cultured hepatocytes.•Inhibition of SCD1 activity could represent a therapeutic target for alcoholic steatosis.
This paper presents the bending and buckling analyses of simply supported nanowires using various classical and nonclassical higher-order shear deformation theories (HSDTs). A one-dimensional ...structure is modeled with including the surface effects based on the Gurtin–Murdoch surface elasticity theory (nonclassical beam theory) and the small-scale effect based on the Eringen nonlocal theory (nonlocal beam theory); the transverse displacement is divided into two bending and shear components. A system of governing equations is derived with the help of the minimum total potential energy principle and resolved via Navier’s solutions. Several numerical results are presented and compared with those given in the literature. The results showed that the influence of the surface effects on the bending and buckling load of nanowires is more pronounced than that of the nonlocal parameter.
► The APEX model provided adequate simulations for the annual volume of irrigation return flows and its N loads. ► APEX simulated that irrigation improvement was the best management option to reduce ...N loads in the IRF of the three watersheds. ► APEX simulations properly identified the main soil and crop N polluters within the watersheds.
One of the main constraints of irrigated agriculture is off-site N pollution due to export of nitrate in irrigation return flows (IRF). Models capable of simulating the growth of crops and the N loads in IRF as affected by irrigation and N fertilization may be valuable tools in watershed studies. The Agricultural Policy Environmental eXtender (APEX) model was used to assess best management practices for reducing off-site N loads in the IRF of three Mediterranean irrigated watersheds (Akarsu in Turkey, La Violada in Spain and Sidi Rached in Algeria). The watersheds (ranging from 4013 to 10,971
ha) were monitored along three hydrological years to determine the volume of IRF and the NO
3-N concentrations and loads in IRF. APEX was calibrated with the data of the first two years and validated with the last year's data. APEX adequately simulated crop evapotranspiration and the volume of IRF and N loads in the IRF (errors
<
20%). Simulated annual values were in general more accurate than simulated monthly values. APEX predicted that improving irrigation management (change of irrigation system and/or scheduling) will decrease N loads in IRF over current values by 45% (Akarsu), 40% (La Violada), and 8% (Sidi Rached). However, improved N fertilization only will reduce N loads in IRF by 17% (Akarsu) or below 5% (La Violada and Sidi Rached). Improving irrigation management will increase IRF NO
3-N concentrations by 19% in La Violada and will decrease or will remain the same in the other two watersheds. APEX simulations identified the main soils (shallow and low water holding capacity soils) and crops (heavily fertilized or shallow-root crops) N polluters within the studied watersheds. Overall, APEX simulated that the improvement of irrigation performance was the best management strategy to decrease off-site N pollution while maintaining or increasing crop yields in the three studied Mediterranean watersheds.
The present work deals with the valorization of the lignin. The lignin is a by-product of the black liquor of the paper industry, which has a very complex composition structure. In this study, this ...lignin is obtained from the Alfa grass (Stipa Tenacissima L, also named Esparto grass). A composite material with polymer matrix (unsaturated polyester) reinforced with the lignin at various proportions has been elaborated and a comparison of its mechanical and physico-chemical characteristics to another type of composite material constituted of polymer matrix (unsaturated polyester) reinforced with Alfa fibers has been achieved. The characterization of these composites materials is based on tensile as well as thermal degradation tests under isothermal conditions. In order to explain the deviation from the linear profile (weight losses), a mathematical model has been used to show that the degradation energy is the same for all temperature ranges. This model allowed us to calculate the activation energy (48 kJ/mole.K), which corresponds to the process of off-gassing, break of macromolecular chains and weight loss.
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