Dielectric coupler for general purpose Q-band EPR cavity

Here, we report on a robust and efficient mechanism for tuning the microwave coupling of a Q-band (34 GHz), general purpose, cylindrical EPR cavity operating in the TE011 mode. This novel mechanism allows for both the adjustment of the cavity’s coupling over a wide frequency range, as well as its bandwidth from that of a high-Q cavity (about 10 MHz), to a broadband cavity (above 1 GHz). The coupling element consists of a dielectric plate fixed onto a movable waveguide short that allows for two modes of operation. In the first mode, the dielectric plate does not influence the resonance properties of the coupling iris and allows for precise, critical coupling of the high-Q cavity. In the second mode, the dielectric plate is positioned in front of the coupling iris, varying the iris’ resonance properties and allowing very strong overcoupling to be achieved. This mechanism can be generalized for other types of EPR cavities, in particular at high microwave frequencies

Electron-hole recombination properties of In0.5Ga0.5As/GaAs quantum dot solar cells and the influence on the open circuit voltage

We report on a detailed analysis of the temperature dependent electrical properties of In0.5Ga0.5As/GaAsquantum dotsolar cells. The effects leading to a reduction in the open circuit voltage are found to be the thermal injection of carriers from the n and p-type layers into the depletion region where they recombine with carriers occupying quantum dot states due to a thermal distribution. The departure of the device studied here from an ideal intermediate band solar cell is discussed.Thanks are due to the Australian Research Council for the financial support of this research and the Australian National Fabrication Facility for access to the facilities used in this work

Plasmonic quantum dot solar cells for enhanced infrared response

Enhanced near infrared photoresponse in plasmonic InGaAs/GaAs quantum dotsolar cells (QDSC) is demonstrated. Long wavelength light absorption in the wetting-layer and quantum-dot region of the quantum dotsolar cell is enhanced through scattering of light by silver nanoparticles deposited on the solar cellsurface.Plasmonic light trapping results in simultaneous increase in short-circuit current density by 5.3% and open circuit voltage by 0.9% in the QDSC, leading to an overall efficiency enhancement of 7.6%.This work was supported by the Australian Research Council (Grant No. DP1096361)

Temperature dependence of dark current properties of InGaAs/GaAs quantum dot solar cells

Self-assembledIn₀.₅Ga₀.₅As/GaAsquantum dotsolar cell (QDSC) was grown by metal organic chemical vapor deposition. Systematic measurements of dark current versus voltage (I-V) characteristics were carried out from 30 to 310 K. Compared with the reference GaAssolar cell, the QDSC exhibits larger dark current however its ideality factor (n) was smaller, which cannot be straightly interpreted by the conventional diode models. These results are important for the fundamental understanding of QDSC properties and further implementation of new solar cell designs for improved efficiency.The authors would like to acknowledge financial support from the Australian Research Council and facility support from the Australian National Fabrication Facility ACT node

Analytical expression for the quantum dot contribution to the quasistatic capacitance for conduction band characterization

This paper demonstrates an analytical expression for the quasistatic capacitance of a quantum dot layer embedded in a junction, where the reverse bias is used to discharge the initially occupied energy levels. This analysis can be used to determine the position and the Gaussian homogeneous broadening of the energy levels in the conduction band, and is applied for an InGaAs/GaAs quantum dot structure grown by metal organic chemical vapor deposition. It is shown that the Gaussian broadening of the conduction band levels is significantly larger than the broadening of the interband photoluminescence (PL) transitions involving both conduction and hole states. The analysis also reveals a contribution from the wetting layer both in PL and modeled C-V profiles which is much stronger than in typical molecular beam epitaxy grown dots. The presence of a built-in local field oriented from the apex of the dot toward its base, contrary to the direction expected for a strained dot with uniform composition (negative dipole), is also derived from fitting of the C-V experimental data

Common Carp Disrupt Ecosystem Structure and Function Through Middle-out Effects

Middle-out effects or a combination of top-down and bottom-up processes create many theoretical and empirical challenges in the realm of trophic ecology. We propose using specific autecology or species trait (i.e. behavioural) information to help explain and understand trophic dynamics that may involve complicated and nonunidirectional trophic interactions. The common carp (Cyprinus carpio) served as our model species for whole-lake observational and experimental studies; four trophic levels were measured to assess common carp-mediated middle-out effects across multiple lakes. We hypothesised that common carp could influence aquatic ecosystems through multiple pathways (i.e. abiotic and biotic foraging, early life feeding, nutrient). Both studies revealed most trophic levels were affected by common carp, highlighting strong middle-out effects likely caused by common carp foraging activities and abiotic influence (i.e. sediment resuspension). The loss of water transparency, submersed vegetation and a shift in zooplankton dynamics were the strongest effects. Trophic levels furthest from direct pathway effects were also affected (fish life history traits). The present study demonstrates that common carp can exert substantial effects on ecosystem structure and function. Species capable of middle-out effects can greatly modify communities through a variety of available pathways and are not confined to traditional top-down or bottom-up processes

Components, impacts and costs of dementia home support: a research programme including the DESCANT RCT

BackgroundOver half of people with dementia live at home. We know little about what home support could be clinically effective or cost-effective in enabling them to live well.ObjectivesWe aimed to (1) review evidence for components of home support, identify their presence in the literature and in services in England, and develop an appropriate economic model; (2) develop and test a practical memory support package in early-stage dementia, test the clinical effectiveness and cost-effectiveness of routine home support in later-stage dementia and design a toolkit based on this evidence; and (3) elicit the preferences of staff, carers and people with dementia for home support inputs and packages, and evaluate the cost-effectiveness of these approaches in early- and later-stage dementia.DesignWe undertook (1) an evidence synthesis, national surveys on the NHS and social care and an economic review; (2) a multicentre pragmatic randomised trial [Dementia Early Stage Cognitive Aids New Trial (DESCANT)] to estimate the clinical effectiveness and cost-effectiveness of providing memory aids and guidance to people with early-stage dementia (the DESCANT intervention), alongside process evaluation and qualitative analysis, an observational study of existing care packages in later-stage dementia along with qualitative analysis, and toolkit development to summarise this evidence; and (3) consultation with experts, staff and carers to explore the balance between informal and paid home support using case vignettes, discrete choice experiments to explore the preferences of people with dementia and carers between home support packages in early- and later-stage dementia, and cost–utility analysis building on trial and observational study.SettingThe national surveys described Community Mental Health Teams, memory clinics and social care services across England. Recruitment to the trial was through memory services in nine NHS trusts in England and one health board in Wales. Recruitment to the observational study was through social services in 17 local authorities in England. Recruitment for the vignette and preference studies was through memory services, community centres and carers’ organisations.ParticipantsPeople aged > 50 years with dementia within 1 year of first attendance at a memory clinic were eligible for the trial. People aged > 60 years with later-stage dementia within 3 months of a review of care needs were eligible for the observational study. We recruited staff, carers and people with dementia for the vignette and preference studies. All participants had to give written informed consent.Main outcome measuresThe trial and observational study used the Bristol Activities of Daily Living Scale as the primary outcome and also measured quality of life, capability, cognition, general psychological health and carers’ sense of competence.MethodsOwing to the heterogeneity of interventions, methods and outcome measures, our evidence and economic reviews both used narrative synthesis. The main source of economic studies was the NHS Economic Evaluation Database. We analysed the trial and observational study by linear mixed models. We analysed the trial by ‘treatment allocated’ and used propensity scores to minimise confounding in the observational study.ResultsOur reviews and surveys identified several home support approaches of potential benefit. In early-stage dementia, the DESCANT trial had 468 randomised participants (234 intervention participants and 234 control participants), with 347 participants analysed. We found no significant effect at the primary end point of 6 months of the DESCANT intervention on any of several participant outcome measures. The primary outcome was the Bristol Activities of Daily Living Scale, for which scores range from 0 to 60, with higher scores showing greater dependence. After adjustment for differences at baseline, the mean difference was 0.38, slightly but not significantly favouring the comparator group receiving treatment as usual. The 95% confidence interval ran from –0.89 to 1.65 (p = 0.56). There was no evidence that more intensive care packages in later-stage dementia were more effective than basic care. However, formal home care appeared to help keep people at home. Staff recommended informal care that cost 88% of formal care, but for informal carers this ratio was only 62%. People with dementia preferred social and recreational activities, and carers preferred respite care and regular home care. The DESCANT intervention is probably not cost-effective in early-stage dementia, and intensive care packages are probably not cost-effective in later-stage dementia. From the perspective of the third sector, intermediate intensity packages were cheaper but less effective. Certain elements may be driving these results, notably reduced use of carers’ groups.LimitationsOur chosen outcome measures may not reflect subtle outcomes valued by people with dementia.ConclusionsSeveral approaches preferred by people with dementia and their carers have potential. However, memory aids aiming to affect daily living activities in early-stage dementia or intensive packages compared with basic care in later-stage dementia were not clinically effective or cost-effective.Future workFurther work needs to identify what people with dementia and their carers prefer and develop more sensitive outcome measures.Study registrationCurrent Controlled Trials ISRCTN12591717. The evidence synthesis is registered as PROSPERO CRD42014008890.FundingThis project was funded by the National Institute for Health Research (NIHR) Programme Grants for Applied Research programme and will be published in full in Programme Grants for Applied Research; Vol. 9, No. 6. See the NIHR Journals Library website for further project information

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead