Improved efficiency of microcrystalline silicon thin film solar cells with wide band-gap CdS buffer layer

In this paper, we have reported a new structure based upon an optical simulation of maximum light trapping and management in microcrystalline silicon thin film solar cells by using multi texture schemes and introducing an n-type cadmium sulphide (CdS) buffer layer with the goal of extreme light coupling and absorption in silicon absorber layer. Photon absorption was improved by optimising the front and back texturing of transparent conductive oxide (TCO) layers and variation in buffer layer thickness. We have demonstrated that light trapping can be improved with proposed geometry of 1μm thick crystalline silicon absorber layer below a thin layer of wide band gap material. We have improved the short circuit current densities by 1.35mA/cm2 resulting in a total short circuit current of 25 mA/cm2 and conversion efficiency of 9% with the addition of CdS buffer layer and multi textures, under global AM1.5 conditions. In this study, we have used 2 Dimensional Full Vectorial Finite Element (2DFVFEM) to design and optimize the proposed light propagation in solar cell structure configuration. Our simulation results show that interface morphology of CdS layer thickness and textures with different aspect and ratios have the most prominent influence on solar cell performance in terms of both short circuit current and quantum efficiency

Chiral Lagrangians at finite density

The effective SU(2) chiral Lagrangian with external sources is given in the presence of non-vanishing nucleon densities by calculating the in-medium contributions of the chiral pion-nucleon Lagrangian. As a by product, a relativistic quantum field theory for Fermi many-particle systems at zero temperature is directly derived from relativistic quantum field theory with functional methods.Comment: 6 Pages, 3 figures, REVTeX. Extended version. Explicit Feynman rules are give

Does Entrepreneurship Reduce Unemployment?

The relationship between unemployment and entrepreneurship has been shrouded with ambiguity. There is assumed to be a two-way causation between changes in the level of entrepreneurship and that of unemployment-- a "Schumpeter" effect of entrepreneurship reducing unemployment and a "refugee" or "shopkeeper" effect of unemployment stimulating entrepreneurship. The purpose of this paper is to try to reconcile the ambiguities found in the relationship between unemployment and entrepreneurship. We do this by introducing a two equation model where changes in unemployment and in the number of business owners are linked to subsequent changes in those variables for a panel of 23 OECD countries over the period 1974-1998. The existence of two distinct and separate relationships between unemployment and entrepreneurship is identified including significant "Schumpeter" and "refugee" effects

Survival in equilibrium step fluctuations

We report the results of analytic and numerical investigations of the time scale of survival or non-zero-crossing probability $S(t)$ in equilibrium step fluctuations described by Langevin equations appropriate for attachment/detachment and edge-diffusion limited kinetics. An exact relation between long-time behaviors of the survival probability and the autocorrelation function is established and numerically verified. $S(t)$ is shown to exhibit simple scaling behavior as a function of system size and sampling time. Our theoretical results are in agreement with those obtained from an analysis of experimental dynamical STM data on step fluctuations on Al/Si(111) and Ag(111) surfaces.Comment: RevTeX, 4 pages, 3 figure

Impeded Industrial Restructuring: the growth penalty

This paper documents that a process of industrial restructuring has been transforming the developed economies, where large corporations are accounting for less economic activity and small firms are accounting for a greater share of economic activity. Not all countries, however, are experiencing the same shift in their industrial structures. Very little is known about the cost of resisting this restructuring process. The goal of this paper is to identify whether there is a cost, measured in terms of forgone growth, of an impeded restructuring process. The cost is measured by linking growth rates of European countries to deviations from the optimal industrial structure. The empirical evidence suggests that countries impeding the restructuring process pay a penalty in terms of forgone growth

Choosing more mathematics : happiness through work?

This paper examines how A-level students construct relationships between work and happiness in their accounts of choosing mathematics and further mathematics A-level. I develop a theoretical framework that positions work and happiness as opposed, managed and working on the self and use this to examine students' dual engagement with individual practices of the self and institutional practices of school mathematics. Interviews with students acknowledge four imperatives that they use as discursive resources to position themselves as successful/unsuccessful students: you have to work, you have to not work, you have to be happy, you have to work at being happy. Tensions in these positions lead students to rework their identities or drop further mathematics. I then identify the practices of mathematics teaching that students use to explain un/happiness in work, and show how dependable mathematics and working together are constructed as 'happy objects' for students, who develop strategies for claiming control over these shapers of happiness. © 2010 British Society for Research into Learning Mathematics

On being the right size as an animal with plastids

Plastids typically reside in plant or algal cells—with one notable exception. There is one group of multicellular animals, sea slugs in the order Sacoglossa, members of which feed on siphonaceous algae. The slugs sequester the ingested plastids in the cytosol of cells in their digestive gland, giving the animals the color of leaves. In a few species of slugs, including members of the genus Elysia, the stolen plastids (kleptoplasts) can remain morphologically intact for weeks and months, surrounded by the animal cytosol, which is separated from the plastid stroma by only the inner and outer plastid membranes. The kleptoplasts of the Sacoglossa are the only case described so far in nature where plastids interface directly with the metazoan cytosol. That makes them interesting in their own right, but it has also led to the idea that it might someday be possible to engineer photosynthetic animals. Is that really possible? And if so, how big would the photosynthetic organs of such animals need to be? Here we provide two sets of calculations: one based on a best case scenario assuming that animals with kleptoplasts can be, on a per cm2 basis, as efficient at CO2 fixation as maize leaves, and one based on14 CO2 fixation rates measured in plastid-bearing sea slugs. We also tabulate an overview of the literature going back to 1970 reporting direct measurements or indirect estimates of the CO2 fixing capabilities of Sacoglossan slugs with plastids

Quantum Mirrors and Crossing Symmetry as Heart of Ghost Imaging

In this paper it is proved that the key to understanding the ghost imaging mystery are the crossing symmetric photon reactions in the nonlinear media. Hence, the laws of the plane quantum mirror (QM) and that of spherical quantum mirror, observed in the ghost imaging experiments, are obtained as natural consequences of the energy-momentum conservation laws. So, it is shown that the ghost imaging laws depend only on the energy-momentum conservation and not on the photons entanglement. The extension of these results to the ghost imaging with other kind of light is discussed. Some fundamental experiments for a decisive tests of the [SPDC-DFG]-quantum mirror are suggested.Comment: 11 pages, 9 figure

Bottom Effect in Atomic Force Microscopy Nanomechanics

In this work, the influence of the rigid substrate on the determination of the sample Young''s modulus, the so-called bottom-effect artifact, is demonstrated by an atomic force microscopy force-spectroscopy experiment. The nanomechanical properties of a one-component supported lipid membrane (SLM) exhibiting areas of two different thicknesses are studied: While a standard contact mechanics model (Sneddon) provides two different elastic moduli for these two morphologies, it is shown that Garcia''s bottom-effect artifact correction yields a unique value, as expected for an intrinsic material property. Remarkably, it is demonstrated that the ratio between the contact radius (and not only the indentation) and the sample thickness is the key parameter addressing the relevance of the bottom-effect artifact. The experimental results are validated by finite element method simulations providing a solid support to Garcia''s theory. The amphiphilic nature of the investigated material is representative of several kinds of lipids, suggesting that the results have far reaching implications for determining the correct Young''s modulus of SLMs. The generality of Garcia''s bottom-effect artifact correction allows its application to every kind of supported soft film

A Perturbative Calculation of the Electromagnetic Form Factors of the Deuteron

Making use of the effective field theory expansion recently developed by the authors, we compute the electromagnetic form factors of the deuteron analytically to next-to-leading order (NLO). The computation is rather simple, and involves calculating several Feynman diagrams, using dimensional regularization. The results agree well with data and indicate that the expansion is converging. They do not suffer from any ambiguities arising from off-shell versus on-shell amplitudes.Comment: 22 pages, 8 figures. Discussion of effective range theory added, typos correcte