Formation of rectifier with gold nanoclusters

Gold nanoclusters encapsulated with organic molecules are of great interest for its possible applications in the fields of molecular electronics, catalysis and medical science. Here we demonstrate that monolayer and bilayer films of thiol-capped gold nanoclusters can exhibit diode-like properties provided controlled spatial asymmetry exist between two tunnel junctions used to connect a thiol capped gold nanoclusters. Current-voltage characteristics of this rectifier were obtained from conducting probe atomic force microscopy measurements and also from conventional two probe resistance measurements. Systematic x-ray reflectivity and atomic force microscopy measurements were carried out to characterize the spatial asymmetry introduced by a monolayer of fatty acid salt gadolinium stearate used to deposit thiol-capped gold nanocluster molecules on hydrophilic SiO2-Si(001) substrate by Langmuir Blodgett technique. This information was used to explain prominent rectification observed in these nano-structured films.Comment: 13 pages, 3 figure

What does it mean for urban life to see livestock grazing in post-industrial American cities?

Until the nineteenth century, American urban dwellers cohabited with livestock and cities formed ecologically diverse spaces. In the late nineteenth century, a series of urban livestock policies coupled with industrial agricultural transformations displaced livestock to urban fringes and rural areas. These developments radically altered human–animal relationships in the urban context, limited economic opportunity and over time have shaped contemporary issues of food access and food justice within cities. Post-industrial cities in the United States, such as Detroit, are characterised by patterns of urban shrinkage and high levels of vacancy. Within this context, urban farming has emerged as a framework and movement to stabilise communities, address local food access and leverage vacancy towards new models of occupation. In 2013, the City of Detroit Urban Agricultural Ordinance was passed to formalise decades of community-driven urban agricultural practices. The ordinance provides guidelines for urban farms and gardens and for managing allied resources. Deliberation on urban agriculture and livestock ordinances continues today. While existing policies provide a framework for food-based development of neighbourhoods, they remain focused on the incremental scale of existing single-family housing and adjacent vacant plots versus larger assemblages that may participate in the production of new urban collectives and assemblages. Detroit’s current context presents opportunities to scale operations via new urban design typologies and socially integrated models that leverage vacancy to construct alternate, collective models of urban life. A speculative urban design proposition for Riverbend Farming Cooperative is presented and proposes a courtyard-based cooperative farming development incorporating permaculture and animal husbandry within a formerly residential superblock as an alternative model of urban development. Through this design speculation, the article reflects upon the social, economic and ecological potentials for cohabiting with livestock and illustrates opportunities and challenges for new models of community development balancing social, environmental and economic interests through new models of agri-urbanism

Viability of Noether symmetry of F(R) theory of gravity

Canonization of F(R) theory of gravity to explore Noether symmetry is performed treating R - 6(\frac{\ddot a}{a} + \frac{\dot a^2}{a^2} + \frac{k}{a^2}) = 0 as a constraint of the theory in Robertson-Walker space-time, which implies that R is taken as an auxiliary variable. Although it yields correct field equations, Noether symmetry does not allow linear term in the action, and as such does not produce a viable cosmological model. Here, we show that this technique of exploring Noether symmetry does not allow even a non-linear form of F(R), if the configuration space is enlarged by including a scalar field in addition, or taking anisotropic models into account. Surprisingly enough, it does not reproduce the symmetry that already exists in the literature (A. K. Sanyal, B. Modak, C. Rubano and E. Piedipalumbo, Gen.Relativ.Grav.37, 407 (2005), arXiv:astro-ph/0310610) for scalar tensor theory of gravity in the presence of R^2 term. Thus, R can not be treated as an auxiliary variable and hence Noether symmetry of arbitrary form of F(R) theory of gravity remains obscure. However, there exists in general, a conserved current for F(R) theory of gravity in the presence of a non-minimally coupled scalar-tensor theory (A. K. Sanyal, Phys.Lett.B624, 81 (2005), arXiv:hep-th/0504021 and Mod.Phys.Lett.A25, 2667 (2010), arXiv:0910.2385 [astro-ph.CO]). Here, we briefly expatiate the non-Noether conserved current and cite an example to reveal its importance in finding cosmological solution for such an action, taking F(R) \propto R^{3/2}.Comment: 16 pages, 1 figure. appears in Int J Theoretical Phys (2012

A FP-LAPW Study of Structural, Electronic, Elastic and Mechanical Properties of CePd3 Intermetallic Compound

A theoretical study of structural, electronic, elastic and mechanical properties of CePd3 intermetallic compound has been investigated systematically using first principles density functional theory. The calculations are carried out within LSDA for the exchange correlation potential. The ground state properties such as lattice parameter (a0), bulk modulus (B) and its pressure derivative (B′) are calculated and obtained lattice parameter of this compound shows well agreement with the experimental results. We have calculated the elastic constants (C11, C12 and C44), which has not been calculated and measured yet. From energy dispersion curves, it is found that the studied compound is metallic in nature. Ductility of this compound is analyzed using Pugh’s criteria and Cauchy’s pressure (C11- C12). The mechanical properties such as Young’s modulus, shear modulus, anisotropic ratio, Poison’s ratio have been calculated for the first time using the Voigt–Reuss–Hill (VRH) averaging scheme. The average sound velocities (vm), density (ρ) and Debye temperature (θD) of this compound are also estimated from the elastic constants. Keywords: Pugh’scriteria; Density functional theory; Elastic constants; Ductility. 

Magnetic properties of 3d-impurities substituted in GaAs

We have calculated the magnetic properties of substituted 3d-impurities (Cr-Ni) in a GaAs host by means of first principles electronic structure calculations. We provide a novel model explaining the ferromagnetic long rang order of III-V dilute magnetic semiconductors. The origin of the ferromagnetism is shown to be due to delocalized spin-uncompensated As dangling bond electrons. Besides the quantitative prediction of the magnetic moments, our model provides an understanding of the halfmetallicity, and the raise of the critical temperature with the impurity concentration