Catalase activity and susceptibility of grapevine callus culture (cv. Cabernet Sauvignon) to Botrytis cinerea infection: Effects of UV-B exposure

Research Note

Mechanical Response of Hollow Metallic Nanolattices: Combining Structural and Material Size Effects

Ordered cellular solids have higher compressive yield strength and stiffness compared to stochastic foams. The mechanical properties of cellular solids depend on their relative density and follow structural scaling laws. These scaling laws assume the mechanical properties of the constituent materials, like modulus and yield strength, to be constant and dictate that equivalent-density cellular solids made from the same material should have identical mechanical properties. We present the fabrication and mechanical properties of three-dimensional hollow gold nanolattices whose compressive responses demonstrate that strength and stiffness vary as a function of geometry and tube wall thickness. All nanolattices had octahedron geometry, a constant relative density, ρ ∼ 5%, a unit cell size of 5–20 μm, and a constant grain size in the Au film of 25–50 nm. Structural effects were explored by increasing the unit cell angle from 30 deg to 60 deg while keeping all other parameters constant; material size effects were probed by varying the tube wall thickness, t, from 200 nm to 635 nm, at a constant relative density and grain size. In situ uniaxial compression experiments revealed an order of magnitude increase in yield stress and modulus in nanolattices with greater lattice angles, and a 150% increase in the yield strength without a concomitant change in modulus in thicker-walled nanolattices for fixed lattice angles. These results imply that independent control of structural and material size effects enables tunability of mechanical properties of three-dimensional architected metamaterials and highlight the importance of material, geometric, and microstructural effects in small-scale mechanics

Determination of orbits of planetary artificial satellites and planetary gravitational fields

Orbit determination of planetary artificial satellites and planetary gravitational field

Formation of contacts between doped carbon nanotubes and aluminum electrodes

A theoretical study of the a semiconducting carbon nanotube (CNT) bonding to an aluminum electrode is presented using density functional theory to determine the electronic structure, and charge transport across the junction is studied using non-equilibrium Green's functions. The properties of CNT-metal junctions are of interest for optimizing metal-semiconductor junctions for Schottky barrier transistors and for the formation of Ohmic contacts for nanoelectronics. We first consider the properties of an undoped (16,0) CNT bonded to an aluminum electrode, including an analysis of metal induced gap states and examination of the surface dipole. The junction is then modified by introduction of substitutional dopants into the CNT using nitrogen and boron to form n- and p-type semiconductors, respectively, and the resulting impact of the doping on current transport across the junctions is calculated. As an alternative doping strategy, tetrathiafulvalene is introduced endohedrally and found to act as an n-type dopant in agreement with previous experimental studies. From electron transmission and current voltage characteristics, it is found that the doped junctions can be engineered to have much lower onset resistances relative to the undoped junction. It is found that the current-voltage characteristics display increased resistance for larger forward and reverse biases: For one polarity, the resistance increase is associated with the introduction of the CNT band gap into the voltage bias window, whereas for the opposing voltage polarity, the resistance increase is due to large charge carrier-substitutional dopant scattering. For the case of the endohedral doping scheme, it is found that the carrier-dopant scattering is effectively absent. (C) 2013 AIP Publishing LLC

Solution to the problem of the poor cyclic fatigue resistance of bulk metallic glasses

The recent development of metallic glass-matrix composites represents a particular milestone in engineering materials for structural applications owing to their remarkable combination of strength and toughness. However, metallic glasses are highly susceptible to cyclic fatigue damage, and previous attempts to solve this problem have been largely disappointing. Here, we propose and demonstrate a microstructural design strategy to overcome this limitation by matching the microstructural length scales (of the second phase) to mechanical crack-length scales. Specifically, semisolid processing is used to optimize the volume fraction, morphology, and size of second-phase dendrites to confine any initial deformation (shear banding) to the glassy regions separating dendrite arms having length scales of ≈2 μm, i.e., to less than the critical crack size for failure. Confinement of the damage to such interdendritic regions results in enhancement of fatigue lifetimes and increases the fatigue limit by an order of magnitude, making these “designed” composites as resistant to fatigue damage as high-strength steels and aluminum alloys. These design strategies can be universally applied to any other metallic glass systems

Effect of Banded Fertilizer on Manganese Toxicity of Burley Tobacco

Relatively large amounts (1500 to 3000 lbs per acre) of inorganic fertilizers are commonly broadcast preplant in the production of burley tobacco. Such high rates of fertilizer increase both the salt content of the soil solution and soil acidity, often causing reduced stands, manganese toxicity, plant molybdenum and calcium deficiencies, delayed growth and maturity, and reduced yield and quality of cured leaf. Manganese toxicity alone is thought to cost growers 30-40 million dollars each year from yield loss and the costs associated with growing extra acreage the following year to make up their quota¥ Improved fertilizer management systems are needed to increase early plant growth and fertilizer use efficiency. The objective of this study was to determine the effect of banding fertilizer 10 to 12 inches to the side of the row, as compared to preplant broadcast applications, on concentration of manganese and growth of burley tobacco during the early season

Insertion as an alternative to workfare: active labour-market schemes in the Parisian suburbs

Many governments have tightened the link between welfare and work by attaching conditionality to out-of-work benefits, extending these requirements to new client groups, and imposing market competition and greater managerial control in service delivery – principles typically characterised as ‘workfare’. Based on field research in Seine-Saint-Denis, we examine French ‘insertion’ schemes aimed at disadvantaged but potentially job-ready clients, characterized by weak conditionality, low marketization, strong professional autonomy, and local network control. We show that insertion systems have resisted policy attempts to expand workfare-derived principles, reflecting street-level actors’ belief in the key advantages of the former over the latter. In contrast with arguments stressing institutional and cultural stickiness, our explanation for this resistance thus highlights the decentralized network governance of front-line services and the limits to central government power

Policy instruments in the Common Agricultural Policy

Policy changes in the Common Agricultural Policy (CAP) can be explained in terms of the exhaustion and long-term contradictions of policy instruments. Changes in policy instruments have reoriented the policy without any change in formal Treaty goals. The social and economic efficacy of instruments in terms of evidence-based policy analysis was a key factor in whether they were delegitimized. The original policy instruments were generally dysfunctional, but reframing the policy in terms of a multifunctionality paradigm permitted the development of more efficacious instruments. A dynamic interaction takes place between the instruments and policy informed by the predominant discourses