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"Jones, Richard"
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Ultrafast exciton transport at early times in quantum dot solids
Quantum dot (QD) solids are an emerging platform for developing a range of optoelectronic devices. Thus, understanding exciton dynamics is essential towards developing and optimizing QD devices. Here, using transient absorption microscopy, we reveal the initial exciton dynamics in QDs with femtosecond timescales. We observe high exciton diffusivity (~10
2
cm
2
s
–1
) in lead chalcogenide QDs within the first few hundred femtoseconds after photoexcitation followed by a transition to a slower regime (~10
–1
–1 cm
2
s
–1
). QD solids with larger interdot distances exhibit higher initial diffusivity and a delayed transition to the slower regime, while higher QD packing density and heterogeneity accelerate this transition. The fast transport regime occurs only in materials with exciton Bohr radii much larger than the QD sizes, suggesting the transport of delocalized excitons in this regime and a transition to slower transport governed by exciton localization. These findings suggest routes to control the optoelectronic properties of QD solids.
Understanding exciton dynamics in quantum dots is important for realizing their potential in optoelectronics. Here, the authors use femtosecond transient absorption microscopy to reveal ultrafast exciton transport, enhanced at larger interdot distance and taking place within hundreds of femtoseconds after generation.
Journal Article
An Introduction to the Study of Mysticism
2022 CHOICE Outstanding Academic Title
The purpose of this book is to fill a gap in contemporary mystical
studies: an overview of the basic ways to approach mystical
experiences and mysticism. It discusses the problem of definitions
of \"mystical experiences\" and \"mysticism\" and advances
characterizations of \"mystical experiences\" in terms of certain
altered states of consciousness and \"mysticism\" in terms of
encompassing ways of life centered on such experiences and states.
Types of mystical experiences, enlightened states, paths, and
doctrines are discussed, as is the relation of mystical experiences
and mysticism to religions and cultures. The approaches of
constructivism, contextualism, essentialism, and perennialism are
presented. Themes in the history of the world's major mystical
traditions are set forth. Approaches to mystical phenomena in
sociology, psychology, gender studies, and neuroscience are
introduced. Basic philosophical issues related to whether mystical
experiences are veridical and mystical claims valid, mystics'
problems of language, art, and morality are laid out. Older and
newer comparative approaches in religious studies and in Christian
theology are discussed, along with postmodernist objections. The
intended audience is undergraduates and the general public
interested in the general issues related to mysticism.
eBook
What can we know about future precipitation in Africa? Robustness, significance and added value of projections from a large ensemble of regional climate models
We employ a large ensemble of Regional Climate Models (RCMs) from the COordinated Regional-climate Downscaling EXperiment to explore two questions: (1) what can we know about the future precipitation characteristics over Africa? and (2) does this information differ from that derived from the driving Global Climate Models (GCMs)? By taking into account both the statistical significance of the change and the models’ agreement on its sign, we identify regions where the projected climate change signal is robust, suggesting confidence that the precipitation characteristics will change, and those where changes in the precipitation statistics are non-significant. Results show that, when spatially averaged, the RCMs median change is usually in agreement with that of the GCMs ensemble: even though the change in seasonal mean precipitation may differ, in some cases, other precipitation characteristics (e.g., intensity, frequency, and duration of dry and wet spells) show the same tendency. When the robust change (i.e., the value of the change averaged only over the land points where it is robust) is compared between the GCMs and RCMs, similarities are striking, indicating that, although with some uncertainty on the geographical extent, GCMs and RCMs project a consistent future. Potential added value of downscaling future climate projections (i.e., non-negligible fine-scale information that is absent in the lower resolution simulations) is found for instance over the Ethiopian highlands, where the RCM ensemble shows a robust decrease in mean precipitation in contrast with the GCMs results. This discrepancy may be associated with the better representation of topographical details that are missing in the large scale GCMs. The impact of the heterogeneity of the GCM–RCM matrix on the results has been also investigated; we found that, for most regions and indices, where results are robust or non-significant, they are so independently on the choice of the RCM or GCM. However, there are cases, especially over Central Africa and parts of West Africa, where results are uncertain, i.e. most of the RCMs project a statistically significant change but they do not agree on its sign. In these cases, especially where results are clearly clustered according to the RCM, there is not a simple way of subsampling the model ensemble in order to reduce the uncertainty or to infer a more robust result.
Journal Article
Post-Transplantation Cyclophosphamide-Based Graft-versus-Host Disease Prophylaxis
In this trial, 1-year GVHD-free, relapse-free survival after stem-cell transplantation was 52.7% in the cyclophosphamide–tacrolimus–mycophenolate mofetil group and 34.9% in the tacrolimus–methotrexate group.
Journal Article
Low Dose Organochlorine Pesticides and Polychlorinated Biphenyls Predict Obesity, Dyslipidemia, and Insulin Resistance among People Free of Diabetes
There is emerging evidence that background exposure to persistent organic pollutants (POPs) are important in the development of conditions predisposing to diabetes as well as of type 2 diabetes itself. We recently reported that low dose POPs predicted incident type 2 diabetes in a nested case-control study. The current study examined if low dose POPs predicted future adiposity, dyslipidemia, and insulin resistance among controls without diabetes in that study.
The 90 controls were diabetes-free during 20 years follow-up. They were a stratified random sample, enriched with overweight and obese persons. POPs measured in 1987-88 (year 2) sera included 8 organochlorine (OC) pesticides, 22 polychlorinated biphenyls (PCBs), and 1 polybrominated biphenyl (PBB). Body mass index (BMI), triglycerides, HDL-cholesterol, LDL-cholesterol, and homeostasis model assessment value for insulin resistance (HOMA-IR) were study outcomes at 2005-06 (year 20). The evolution of study outcomes during 18 years by categories of serum concentrations of POPs at year 2 was evaluated by adjusting for the baseline values of outcomes plus potential confounders. Parallel to prediction of type 2 diabetes, many statistically significant associations of POPs with dysmetabolic conditions appeared at low dose, forming inverted U-shaped dose-response relations. Among OC pesticides, p,p'-DDE most consistently predicted higher BMI, triglycerides, and HOMA-IR and lower HDL-cholesterol at year 20 after adjusting for baseline values. Oxychlordane, trans-nonachlor, and hexachlorobenzene also significantly predicted higher triglycerides. Persistent PCBs with ≥7 chlorides predicted higher BMI, triglycerides, and HOMA-IR and lower HDL-cholesterol at year 20 with similar dose-response curves.
Simultaneous exposure to various POPs in the general population may contribute to development of obesity, dyslipidemia, and insulin resistance, common precursors of type 2 diabetes and cardiovascular diseases. Although obesity is a primary cause of these metabolic abnormalities, POPs exposure may contribute to excess adiposity and other features of dysmetabolism.
Journal Article