Large Integrated Absorption Enhancement in Plasmonic Solar Cells by Combining Metallic Gratings and Antireflection Coatings

We describe an ultrathin solar cell architecture that combines the benefits of both plasmonic photovoltaics and traditional antireflection coatings. Spatially resolved electron generation rates are used to determine the total integrated current improvement under AM1.5G solar illumination, which can reach a factor of 1.8. The frequency-dependent absorption is found to strongly correlate with the occupation of optical modes within the structure, and the improved absorption is mainly attributed to improved coupling to guided modes rather than localized resonant modes

Solar Cell Light Trapping beyond the Ray Optic Limit

In 1982, Yablonovitch proposed a thermodynamic limit on light trapping within homogeneous semiconductor slabs, which implied a minimum thickness needed to fully absorb the solar spectrum. However, this limit is valid for geometrical optics but not for a new generation of subwavelength solar absorbers such as ultrathin or inhomogeneously structured cells, wire-based cells, photonic crystal-based cells, and plasmonic cells. Here we show that the key to exceeding the conventional ray optic or so-called ergodic light trapping limit is in designing an elevated local density of optical states (LDOS) for the absorber. Moreover, for any semiconductor we show that it is always possible to exceed the ray optic light trapping limit and use these principles to design a number of new solar absorbers with the key feature of having an elevated LDOS within the absorbing region of the device, opening new avenues for solar cell design and cost reduction

Light trapping beyond the 4n^2 limit in thin waveguides

We describe a method for determining the maximum absorption enhancement in thin film waveguides based on optical dispersion relations. For thin film structures that support one, well-confined guided mode, we find that the absorption enhancement can surpass the traditional limit of 4n^2 when the propagation constant is large and/or the modal group velocity is small compared to the bulk value. We use this relationship as a guide to predicting structures that can exceed the 4n^2 light trapping limit, such as plasmonic and slot waveguides. Finally, we calculate the overall absorption for both single and multimode waveguides, and show examples of absorption enhancements in excess of 4n^2 for both cases

Role of Schizosaccharomyces pombe RecQ homolog recombination and checkpoint genes in UV Damage tolerance

The cellular responses to DNA damage are complex and include direct DNA repair pathways that remove the damage and indirect damage responses which allow cells to survive DNA damage that has not been, or cannot be, removed. We have identified the gene mutated in the rad12.502 strain as a Schizosaccharomyces pombe recQ homolog. The same gene (designated rqh1) is also mutated in the hus2.22 mutant. We show that Rqh1 is involved in a DNA damage survival mechanism which prevents cell death when UV-induced DNA damage cannot be removed. This pathway also requires the correct functioning of the recombination machinery and the six checkpoint tad gene products plus the Cds1 kinase. Our data suggest that Rqh1 operates during S phase as part of a mechanism which prevents DNA damage causing cell lethality. This process may involve the bypass of DNA damage sites by the replication fork. Finally, in contrast with the reported literature, we do not find that rqh1 (rad12) mutant cells are defective in UV dimer endonuclease activity

The Richard commission and the financing of devolved government : the economics of devolution in Wales: Briefing No. 8

If the Barnett formula is rigorously applied to determine the budget of the Welsh Assembly Government, this will ultimately adversely affect the economy of Wales by limiting the growth in aggregate demand. This effect is reinforced now that population weights determining rises in expenditure in Wales (and Scotland and Northern Ireland) are regularly up-dated. There is some controversy in Wales about whether some form of needs-assessment exercise would favour Wales relative to its current position. What is clear is that the outcome of a rigorous, long term application of the Barnett formula would be a share of UK public expenditures in Wales (and Scotland and Northern Ireland) that was almost certainly below the level that would be dictated by any conventional understanding of 'needs'. The impact of the tax-varying power favoured by the Richard Commission is ambiguous, with the direction of effects dependent on the reaction of the current labour force and potential migrants. If workers insist on full compensation for loss of income to tax through a rise in gross wages a tax rise would lead to an economic contraction. However, if workers value the additional public services financed by the tax rise as equal to their loss of disposable income, this effect can be avoided. Much in other words would depend on how the proceeds of the tax rise were spen

Blogging Beyond Blackboard for Deeper Learning

Presentation by Marie Hulme and Pilar Munday at the Fairfield University Center for Academic Excellence Annual Conference on Innovative Pedagogy & Course Redesign May 29-30, 2014

Precision measurement of the Casimir-Lifshitz force in a fluid

The Casimir force, which results from the confinement of the quantum mechanical zero-point fluctuations of the electromagnetic fields, has received significant attention in recent years for its effect on micro- and nano-scale mechanical systems. With few exceptions, experimental observations have been limited to conductive bodies interacting separated by vacuum or air. However, interesting phenomena including repulsive forces are expected to exist in certain circumstances between metals and dielectrics when the intervening medium is not vacuum. In order to better understand the effect of the Casimir force in such situations and to test the robustness of the generalized Casimir-Lifshitz theory, we have performed the first precision measurements of the Casimir force between two metals immersed in a fluid. For this situation, the measured force is attractive and is approximately 80% smaller than the force predicted by Casimir for ideal metals in vacuum. We present experimental results and find them to be consistent with Lifshitz's theory.Comment: 6 pages, 3 figures. (version before final publication

Investigations into the Toxicology of Spirolides, a Group of Marine Phycotoxins

Spirolides are marine phycotoxins produced by the dinoflagellates Alexandrium ostenfeldii and A. peruvianum. Here we report that 13-desmethyl spirolide C shows little cytotoxicity when incubated with various cultured mammalian cell lines. When administered to mice by intraperitoneal (ip) injection, however, this substance was highly toxic, with an LD50 value of 6.9 µg/kg body weight (BW), showing that such in vitro cytotoxicity tests are not appropriate for predicting the in vivo toxicity of this toxin. Four other spirolides, A, B, C, and 20-methyl spirolide G, were also toxic to mice by ip injection, with LD50 values of 37, 99, 8.0 and 8.0 µg/kg BW respectively. However, the acute toxicities of these compounds were lower by at least an order of magnitude when administration by gavage and their toxic effects were further diminished when administered with food. These results have implications for future studies of the toxicology of these marine toxins and the risk assessment of human exposure

Integrating Interactive Technology to Promote Learner Autonomy: Challenges and Rewards

In an increasingly complex and interconnected world, students and faculty must understand and harness the power of technology to synthesize, analyze, and communicate ideas and information. A multi-modal, multidisciplinary approach of teaching and learning is critical. This presentation will examine how to best leverage the technological strengths of 21st century learners in an interdisciplinary networked community, utilizing on-line tools such as Twitter and e-portfolios. This will be anchored within a context of a larger discussion of current education theories, including cognitive, social constructivism, and connectivism. Four presenters will address recent research on the impact of technology tools on teaching and learning . Section one will describe the dynamic process in which pedagogy, content, and technologies influence each other when designing online experiences. Section two we will discuss the pedagogical benefits of the University\u27s new on-line, interdisciplinary networked community of learners, the Virtual Public Square project. Section three will show how Twitter has been used in a foreign language course to promote learner autonomy. The final section will discuss the high-impact practice of utilizing e-portfolios for both faculty and student assessment in a freshman course. Each of the four sections will address the wide range of student responses in terms of habits of mind and the gap between faculty and student perceptions in defining the characteristics of 21st century digital illiteracies