Applied molecular quantum electrodynamics: geometric aspects of the efficiency of photonic interactions

This thesis presents applications of molecular quantum electrodynamics (MQED) to the analysis of resonance energy transfer (RET), molecular absorption and emission, and light scattering by molecules. An MQED framework describes such processes as a series of microscopic photonic interaction events. Multi-interaction processes entail intermediate states of the system’s evolution remaining unspecified, requiring careful interpretation. RET, as modified by coupling with the nearest molecule of the surrounding refractive medium, is investigated. Special attention is given to a system geometry where unmodified RET is impossible, so coupling with the third chromophore is essential. Two distinct treatments are given to emission by a multi-chromophore system, distinguished by different ways of framing the quantum system: Either all photons are virtual and chromophores share excitation, or real photons interact with a single unspecified chromophore. Anomalously high fluorescence-anisotropy is explainable with the latter analysis. Off-resonant light is known to modify the absorption behaviour of molecules: This weak-interaction is analysed with an MQED formulation modified by field dressing, modelling advanced media effects in the condensed phase. Within the electric-dipole approximation, hyper-Rayleigh scattering (HRS) is considered forbidden for centrosymmetric molecules: By including higher-multipole interactions, mechanisms enabling conventionally-forbidden HRS are discovered. For each process analysed, the main results are predictions for the efficiency or observable rate. The relative positions and orientations of the molecules and fields are the key variables, so the rate equations are typically complicated functions thereof. Where rate equations depend on molecular orientation, it is often appropriate to calculate the average value over all orientations, giving results applicable to the fluid phase. System geometry may exert very fine control – a process forbidden in one case may become allowed by a minor change of one chromophore’s alignment. This thesis contributes to understanding the precise requirements of molecular geometry that must inform the design of energy-transfer systems

Kinetics of heterogeneous nucleation for low mean cluster populations

The process of nucleation is normally described using rate equations for the mean populations of molecular clusters. This approach can be justified for cases where these mean populations are large. However, it may be unsuitable in the case of heterogeneous nucleation on small particles if the mean populations are of the order of unity or less. In such a case, considering the average populations might be erroneous since the statistical fluctuations in the molecular populations should be taken into account. Here a stochastic treatment of heterogeneous nucleation kinetics is presented that is described by a set of master equations, and a modified expression for the nucleation rate has been deduced. Furthermore, a numerical method for solving the stochastic system has been examined, and the results show that the rate of nucleation can differ greatly from that obtained with the traditional kinetics. (C) 2003 American Institute of Physics

A systems network approach for climate change vulnerability assessment

Vulnerability to climate change is a product of biophysical and social dynamics. Assessments of community or regional vulnerability, however, often focus on quantitative infrastructure and environmental assessments, or qualitative assessments of a community's social dynamics and livelihood activities. A dearth of integrated quantitative assessments is a major barrier for decision makers who require quantitative outputs and indicators, which can measure where vulnerability is most severe and can be linked to climate projections. Our framework and analysis helps address such gaps by identifying variables to build climate change vulnerability indices, which we pilot here focusing on Inuit communities in the Canadian Arctic. We start with a systematic literature review of community-based vulnerability studies and assess relationships among 58 social and biophysical variables. We then use multiplex network analysis to determine how social and environmental variables interact among and within the key component of vulnerability: exposure, sensitivity, and adaptive capacity. We identify several structurally important variables that interact within and across the three dimensions of vulnerability. This method is transferable as an integrative means of understanding not only the direct causes of vulnerability, but also relations that are less tangible. The approach of multiplex network analysis can be a building block to ongoing development of vulnerability indices within the human dimensions of climate change field

Neglect of Medical Evidence of Torture in Guantánamo Bay: A Case Series

Vincent Iacopino and Stephen Xenakis review case records of nine individuals imprisoned at Guantánamo Bay which indicate that medical personnel assigned to the US Department of Defense neglected and/or concealed medical evidence of torture

An assessment of road-verge grass as a feedstock for farm-fed anaerobic digestion plants

Cuttings from road-verge grass could provide biomass for energy generation, but currently this potential is not exploited. This research assessed the technical, practical and financial feasibility of using grass harvested from road verges as a feedstock in farm-fed anaerobic digestion (AD) plants. The methane potential (191 mL CH4 gDM−1) and digestion characteristics of verge grass were similar to those of current farm feedstocks; indicating suitability for AD. Ensiling had no significant impact on the biomethane generated. Testing co-digestions of verge grass with current farm feedstocks showed enhanced methane yields, suggesting that verge grass could be a valuable addition to AD feedstock mixes. In a case study of the UK county of Lincolnshire, potential volumes and locations of verge grass biomass were estimated, with capacities and locations of existing AD plants, to assess the potential to supply practical grass volumes. Grass harvesting costs were modelled and compared with other feedstock costs. Finally, the attitudes of AD operators to using verge grass were investigated to understand whether a market for verge grass exists. In a small survey all operators were willing to use it as a feedstock and most were prepared to pay over the estimated harvesting cost. If verge grass was legally recognised as a waste product it could be attractive to AD operators especially where financial incentives to use waste feedstocks are in place. In rural areas, verge grass could be harvested and co-digested by existing farm-fed AD plants, potentially reducing the cost of road verge maintenance and increasing biodiversity

Jacobi-Predictor-Corrector Approach for the Fractional Ordinary Differential Equations

We present a novel numerical method, called {\tt Jacobi-predictor-corrector approach}, for the numerical solution of fractional ordinary differential equations based on the polynomial interpolation and the Gauss-Lobatto quadrature w.r.t. the Jacobi-weight function $\omega(s)=(1-s)^{\alpha-1}(1+s)^0$. This method has the computational cost O(N) and the convergent order $IN$, where $N$ and $IN$ are, respectively, the total computational steps and the number of used interpolating points. The detailed error analysis is performed, and the extensive numerical experiments confirm the theoretical results and show the robustness of this method.Comment: 24 pages, 5 figure

High prevalence of irritable bowel syndrome-type symptoms in microscopic colitis: implications for treatment.

Patients with microscopic colitis (MC) often present with abdominal pain and diarrhoea, and previous data suggest that there may be overlap between MC and irritable bowel syndrome (IBS). We evaluated the prevalence of IBS-type symptoms in patients with MC, and assess the impact of these symptoms on psychological health and quality of life.We conducted a cross-sectional survey of individuals with a histological diagnosis of MC, collecting demographic data, Rome III IBS-type symptoms, and mood, somatization, and quality of life data.In total, 151 (31.6%) of 478 individuals with a new diagnosis of MC completed questionnaires, 52 (34.4%) of whom reported IBS-type symptoms. The commonest histological subtype was collagenous colitis (51.7%, n = 78), followed by lymphocytic colitis (39.1%, n = 59). Individuals with IBS-type symptoms had significantly higher levels of anxiety [Hospital Anxiety and Depression Scale (HADS) anxiety score 8.6 versus 5.1, p < 0.001], depression (HADS depression score 6.2 versus 3.6, p = 0.001), and somatoform-type behaviour (Patient Health Questionnaire 15 score 12.7 versus 8.0, p < 0.001) compared with individuals who did not. Those with IBS-type symptoms scored significantly worse across all domains of the 36-item Short Form questionnaire, except for physical functioning.More than one third of individuals with MC reported IBS-type symptoms, although whether this is due to ongoing inflammation is unclear. These individuals had higher levels of anxiety, depression, and somatization, and impaired quality of life. Identifying concomitant IBS in individuals with MC may have important implications for management decisions

An integrative climate change vulnerability index for Arctic aviation and marine transportation

Climate change vulnerability research methods are often divergent, drawing from siloed biophysical risk approaches or social-contextual frameworks, lacking methods for integrative approaches. This substantial gap has been noted by scientists, policymakers and communities, inhibiting decision-makers’ capacity to implement adaptation policies responsive to both physical risks and social sensitivities. Aiming to contribute to the growing literature on integrated vulnerability approaches, we conceptualize and translate new integrative theoretical insights of vulnerability research to a scalable quantitative method. Piloted through a climate change vulnerability index for aviation and marine sectors in the Canadian Arctic, this study demonstrates an avenue of applying vulnerability concepts to assess both biophysical and social components analyzing future changes with linked RCP climate projections. The iterative process we outline is transferable and adaptable across the circumpolar north, as well as other global regions and shows that transportation vulnerability varies across Inuit regions depending on modeled hazards and transportation infrastructures

Efficient and Fast Synthesis of Few-Layer Black Phosphorus via Microwave-Assisted Liquid-Phase Exfoliation

High‐quality, few‐layer black‐phosphorus (BP) flakes are prepared in a common organic solvent with very short processing times using microwave‐assisted liquid‐phase exfoliation. A comprehensive range of analysis, combined with density‐functional theory calculations, confirms that the product prepared using the microwave technique is few‐layer BP with small‐ and large‐area flakes. The suspended exfoliated BP sheets show excellent stability, while samples dispersed onto silicon from the suspensions exhibit low oxidation levels after several days in ambient conditions. This straightforward synthesis method is facile, efficient, and extremely fast, and does not involve use of any surfactant or ultrasonication steps and will facilitate future development of phosphorene research

The Cost of Simplifying Air Travel When Modeling Disease Spread

BACKGROUND: Air travel plays a key role in the spread of many pathogens. Modeling the long distance spread of infectious disease in these cases requires an air travel model. Highly detailed air transportation models can be over determined and computationally problematic. We compared the predictions of a simplified air transport model with those of a model of all routes and assessed the impact of differences on models of infectious disease. METHODOLOGY/PRINCIPAL FINDINGS: Using U.S. ticket data from 2007, we compared a simplified "pipe" model, in which individuals flow in and out of the air transport system based on the number of arrivals and departures from a given airport, to a fully saturated model where all routes are modeled individually. We also compared the pipe model to a "gravity" model where the probability of travel is scaled by physical distance; the gravity model did not differ significantly from the pipe model. The pipe model roughly approximated actual air travel, but tended to overestimate the number of trips between small airports and underestimate travel between major east and west coast airports. For most routes, the maximum number of false (or missed) introductions of disease is small (<1 per day) but for a few routes this rate is greatly underestimated by the pipe model. CONCLUSIONS/SIGNIFICANCE: If our interest is in large scale regional and national effects of disease, the simplified pipe model may be adequate. If we are interested in specific effects of interventions on particular air routes or the time for the disease to reach a particular location, a more complex point-to-point model will be more accurate. For many problems a hybrid model that independently models some frequently traveled routes may be the best choice. Regardless of the model used, the effect of simplifications and sensitivity to errors in parameter estimation should be analyzed