Beyond the poor man's implementation of unconditionally stable algorithms to solve the time-dependent Maxwell Equations

For the recently introduced algorithms to solve the time-dependent Maxwell equations (see Phys.Rev.E Vol.64 p.066705 (2001)), we construct a variable grid implementation and an improved spatial discretization implementation that preserve the property of the algorithms to be unconditionally stable by construction. We find that the performance and accuracy of the corresponding algorithms are significant and illustrate their practical relevance by simulating various physical model systems.Comment: 18 pages, 16 figure

Radial solitons in armchair carbon nanotubes

Radial solitons are investigated in armchair carbon nanotubes using a generalized Lennard-Jones potential. The radial solitons are found in terms of moving kink defects whose velocity obeys a dispersion relation. Effects of lattice discreteness on the shape of kink defects are examined by estimating the Peierls stress. Results suggest that the typical size for an unpinned kink phase is of the order of a lattice spacing.Comment: 11 pages, 3(eps) figure

Does stakeholder pressure influence corporate GHG emissions reporting? Empirical evidence from Europe

Purpose – The purpose of this paper is to seek to shed light on the practice of incomplete corporate disclosure of quantitative Greenhouse gas (GHG) emissions and investigates whether external stakeholder pressure influences the existence, and separately, the completeness of voluntary GHG emissions disclosures by 431 European companies. Design/methodology/approach – A classification of reporting completeness is developed with respect to the scope, type and reporting boundary of GHG emissions based on the guidelines of the GHG Protocol, Global Reporting Initiative and the Carbon Disclosure Project. Logistic regression analysis is applied to examine whether proxies for exposure to climate change concerns from different stakeholder groups influence the existence and/or completeness of quantitative GHG emissions disclosure. Findings – From 2005 to 2009, on average only 15 percent of companies that disclose GHG emissions report them in a manner that the authors consider complete. Results of regression analyses suggest that external stakeholder pressure is a determinant of the existence but not the completeness of emissions disclosure. Findings are consistent with stakeholder theory arguments that companies respond to external stakeholder pressure to report GHG emissions, but also with legitimacy theory claims that firms can use carbon disclosure, in this case the incomplete reporting of emissions, as a symbolic act to address legitimacy exposures. Practical implications – Bringing corporate GHG emissions disclosure in line with recommended guidelines will require either more direct stakeholder pressure or, perhaps, a mandated disclosure regime. In the meantime, users of the data will need to carefully consider the relevance of the reported data and develop the necessary competencies to detect and control for its incompleteness. A more troubling concern is that stakeholders may instead grow to accept less than complete disclosure. Originality/value – The paper represents the first large-scale empirical study into the completeness of companies’ disclosure of quantitative GHG emissions and is the first to analyze these disclosures in the context of stakeholder pressure and its relation to legitimation

Reshaping Global Change Science for the 21st Century: Young Scientists’ Perspectives

Humanity is facing unprecedented environmental, social, and economic challenges. We ask what the role of the global science community should be in tackling these challenges. Increased awareness of the social context in which science is being produced; acceptance of the importance of controversy; and reflection around normative assumptions underlying research are needed. To help solve humanity’s grand challenges scientists need to move towards a transdisciplinary view of science where knowledge emerges from a collaborative environment and where young scientists are trained to work across disciplinary boundaries and engage with policy communities

Climate change and asset prices: are corporate carbon disclosure and performance priced appropriately?

This paper empirically assesses the value relevance of information on corporate climate change disclosure and performance to asset prices, and discusses whether this information is priced appropriately. Findings indicate that corporate disclosures of quantitative GHG emissions and, to a lesser extent, carbon performance are value relevant. We use hand-collected information on quantitative greenhouse gas (GHG) emissions for 433 European companies and build portfolios based on GHG disclosure and performance. We regress portfolios on Carhart (1997) four factor models extended for industry effects over the years 2005 to 2009. Results show that investors achieved abnormal risk-adjusted returns of up to 13.05% annually by exploiting inefficiently priced positive effects of (complete) GHG emissions disclosure and good corporate climate change performance in terms of GHG efficiency. Results imply that, firstly, information costs involved in carbon disclosure and management do not present a burden on corporate financial resources. Secondly, investors should not neglect carbon disclosure and performance when making investment decisions. Thirdly, during the period analysed financial markets were inefficient in pricing publicly available information on carbon disclosure and performance. Mandatory and standardised information on carbon performance would consequently not only increase market efficiency but result in better allocation of capital within the real economy

Real-time image processing for label-free enrichment of Actinobacteria cultivated in picolitre droplets

The majority of today's antimicrobial therapeutics is derived from secondary metabolites produced by Actinobacteria. While it is generally assumed that less than 1% of Actinobacteria species from soil habitats have been cultivated so far, classic screening approaches fail to supply new substances, often due to limited throughput and frequent rediscovery of already known strains. To overcome these restrictions, we implement high-throughput cultivation of soil-derived Actinobacteria in microfluidic pL-droplets by generating more than 600000 pure cultures per hour from a spore suspension that can subsequently be incubated for days to weeks. Moreover, we introduce triggered imaging with real-time image-based droplet classification as a novel universal method for pL-droplet sorting. Growth-dependent droplet sorting at frequencies above 100 Hz is performed for label-free enrichment and extraction of microcultures. The combination of both cultivation of Actinobacteria in pL-droplets and real-time detection of growing Actinobacteria has great potential in screening for yet unknown species as well as their undiscovered natural products

Critical temperature and density of spin-flips in the anisotropic random field Ising model

We present analytical results for the strongly anisotropic random field Ising model, consisting of weakly interacting spin chains. We combine the mean-field treatment of interchain interactions with an analytical calculation of the average chain free energy (``chain mean-field'' approach). The free energy is found using a mapping on a Brownian motion model. We calculate the order parameter and give expressions for the critical random magnetic field strength below which the ground state exhibits long range order and for the critical temperature as a function of the random magnetic field strength. In the limit of vanishing interchain interactions, we obtain corrections to the zero-temperature estimate by Imry and Ma [Phys. Rev. Lett. 35, 1399 (1975)] of the ground state density of domain walls (spin-flips) in the one-dimensional random field Ising model. One of the problems to which our model has direct relevance is the lattice dimerization in disordered quasi-one-dimensional Peierls materials, such as the conjugated polymer trans-polyacetylene.Comment: 28 pages, revtex, 4 postscript figures, to appear in Phys. Rev.

Re-shaping Sustainability Science for the 21st Century: Young Scientists’ Perspectives

Humanity is facing unprecedented environmental, social and economic challenges. We ask what the role of the sustainability science community should be in tackling these challenges, focusing particularly on young scientists’ perspectives on the issue. On the basis of a questionnaire and a workshop with young scientists, we identify four major challenges facing humanity and develop three guidelines for sustainability science that seeks to address them. Results show that to help address humanity’s grand challenges, sustainability scientists need to move towards a trans-disciplinary system view of science and sustainability science problems. According to this view knowledge emerges from a collaborative and transdisciplinary environment and young scientists are trained to work across disciplinary boundaries and engage with policy communities