57 research outputs found
Optimizing immunoslot blot assays and application to low DNA adduct levels using an amplification approach
Immunoslot blot assays have been used for the analysis of many DNA adducts, but problems are frequently encountered in achieving reproducible results. Each step of the assay was examined systematically, and it was found that the major problems are in the DNA fragmentation step and the use of the manifold apparatus. Optimization was performed on both the malondialdehydeâdeoxyguanosine (M1dG) adduct and the O6-carboxymethylâdeoxyguanosine (O6CMdG) adduct to demonstrate the applicability to other DNA adducts. Blood samples from the European Prospective Investigation on Cancer(EPIC) study (n = 162) were analyzed for M1dG adducts, and the data showed no correlation with adduct levels in other tissues, indicating that the EPIC blood samples were not useful for studying M1dG adducts. Blood samples from a processed meat versus vegetarian diet intervention (n = 6) were analyzed for O6CMdG, and many were below the limit of detection. The reduction of background adduct levels in standard DNA was investigated using chemical and whole genome amplification approaches. The latter gave a sensitivity improvement of 2.6 adducts per 107 nucleotides for the analysis of O6CMdG. Subsequentreanalysis for O6CMdG showed a weakly significant increase in O6CMdG on the processed meat diet compared with the vegetarian diet, demonstrating that further studies are warranted. 2010 Elsevier Inc. All rights reserved
Performance and durability of broadband antireflection coatings for thin film CdTe solar cells
Light reflection from the glass surface of a photovoltaic (PV) module is a significant source of energy
loss for all types of PV devices. The reflection at the glass and air interface accounts for 4% of the total
energy. Single layer antireflection coatings with sufficiently low refractive index have been used, such as
those using magnesium fluoride or porous silica, but these are only effective over a narrow range of
wavelengths. In this paper, the authors report on the design, deposition, and testing of multilayer
broadband antireflection coatings. These coatings reduce the weighted average reflection over the
wavelength range used by thin film CdTe devices to just 1.22%, resulting in a 3.6% relative increase in
device efficiency. The authors have used multilayer stacks consisting of silica and zirconia layers
deposited using reactive magnetron sputtering. Details of the stack design, sputter deposition process
parameters, and the optical and microstructural properties of the layers are provided. Antireflection
coatings on glass exposed to the outdoors must not degrade over the lifetime of the module. A
comprehensive set of accelerated environmental durability tests has been carried out in accordance with
IEC 61646 PV qualification tests. The durability tests confirmed no damage to the coatings or
performance drop as a result of thermal cycling or damp heat. All attempts to perform pull tests resulted
in either adhesive or substrate failure, with no damage to the coating itself. The coatings also passed acid
attack tests. Scratch resistance, abrasion resistance, and adhesion tests have also been conducted. The
optical performance of the coatings was monitored during these tests, and the coatings were visually
inspected for any sign of mechanical failure. These tests provide confidence that broadband
antireflection coatings are highly durable and will maintain their performance over the lifetime of the
solar module. All dielectric metal-oxide multilayer coatings have better optical performance and superior
durability compared with alternative single layer porous solâgel coatings. Thin film CdTe devices are
particularly problematic because the antireflection coating is applied to one side of the glass, while
device layers are deposited directly on to the opposite glass surface in the superstrate configuration. In
thin film CdTe production, the glass is exposed to high temperature processes during the absorber deposition
and the cadmium chloride activation treatment. If glass precoated with a broadband antireflection
coating is to be used, then the coating must withstand temperatures of up to 550 C. Surprisingly, our
studies have shown that multilayer silica/zirconia antireflection coatings on soda lime glass remain unaffected
by temperatures reaching 600 C, at which point mild crazing is observed. This is an important
observation, demonstrating that low cost glass, which is preprocessed with a broadband antireflection
coating, is directly useable in thin film CdTe module production
The Performance of Private Equity Funds: Does Diversification Matter?
This paper is the first systematic analysis of the impact of diversification on the performance of private equity funds. A unique data set allows the exact evaluation of diversification across the dimensions financing stages, industries, and countries. Very different levels of diversification can be observed across sample funds. While some funds are highly specialized others are highly diversified. The empirical results show that the rate of return of private equity funds declines with diversification across financing stages, but increases with diversification across industries. Accordingly, the fraction of portfolio companies which have a negative return or return nothing at all, increase with diversification across financing stages. Diversification across countries has no systematic effect on the performance of private equity funds
Changes of solar cell parameters during damp-heat exposure
The degradation of PV modules during damp-heat exposure is investigated. Power degradation is analysed in dependence of temperature and humidity during exposure. The moduleâs equivalent circuit parameters are calculated from I-V characteristics measured during ageing. A dose function is developed and degradations of power as well as equivalent circuit parameters can be analysed against the dose, which provides a better understanding of the module ageing behaviour. EL images of modules before and after ageing support the changes of solar cell parameters
A European proficiency test on thin film tandem photovoltaic devices
A round robin proficiency test RR PT on thin film multi junction MJ photovoltaic PV cells was run between 13 laboratories within the European project CHEETAH. Five encapsulated PV cells were circulated to participants for being tested at Standard Test Conditions STC . Three cells were a Si amp; 956;c Si tandem PV devices, each of which had a different short circuit current ratio between the top junction and the bottom one; the remaining two cells were single junction PV devices made with material representative of the individual junctions in the MJ cells. The RR PT s main purpose was to assess the capability of the participating laboratories, in terms of employed facilities and procedures, to test MJ PV devices. Therefore, participant
Means versus ends in opaque institutional fields: Trading off compliance and achievement in sustainability standard adoption
__Abstract__
The long-standing discussion on decoupling has recently moved from adopters not implementing the agreed-upon policies to compliant adopters not achieving the goals intended by institutional entrepreneurs. This âmeans-ends decouplingâ prevails especially in highly opaque fields, where practices, causality, and performance are hard to understand and chart. I conceptualize the conditions under which the adoption of institutions in relatively opaque fields leads to the achievement of the envisaged goals. Voluntary sustainability standards governing socioenvironmental issues illustrate these arguments. I argue that the lack of field transparency drives institutional entrepreneurs to create and maintain concrete and uniform rules, apply strong incentives, and disseminate âbest practicesâ to ensure substantive adopter compliance. However, such rigid institutions are ill-equipped to deal with the causal complexity and practice multiplicity underlying opacity while they smother adopter agency. The ensuing tension between substantive compliance and goal achievement leads to an inherent trade-off: institutional entrepreneurs who remedy the policy-practice decoupling may enhance the disparity between means and ends, and vice versa. While sustainability standards and other institutions in highly opaque fields can, therefore, not fully achieve the envisaged goals, the trade-off can be reduced through systemically designed institutions that promote goal internalization and contain niche institutions
Interest alignment rents and competitive advantage
This paper articulates a theory of the conditions under which the alignment between individual and collective interests generates sustainable competitive advantage. The theory is based on the influence of tacitness, context specificity, and causal ambiguity in the determinants of different types of motivation (extrinsic, normative intrinsic, and hedonic instinsic) under varying conditions of environmental dynamism. The analysis indicates the need to consider motivational processes as a complement to current resource- and competence-based approaches in a comprehensive theory of competitive advantage
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