III-V Semiconductor Quantum Nano-Photonic Circuits

This thesis describes the optical spectroscopic measurements of III-V nano-photonic circuit elements with integrated self-assembled quantum dot single-photon sources, as a step towards achieving an on-chip quantum optical circuit. An electrically controllable optical router consisting of an embedded quantum dot within a photonic crystal cavity which is selectively coupled to separate waveguides is presented. By tuning the voltage, the quantum dot emission can be directed into either waveguide. This is experimentally demonstrated with spatially resolved microphotoluminescence measurements. An electrically driven single-photon source monolithically integrated with nano-photonic circuitry is investigated. In this device, lectroluminescent emission from a single quantum dot is channelled through a suspended nanobeam waveguide. The emission is shown to be highly coherent with coherence properties which are sufficient to observe non-classical interference. Correlation and cross-correlation measurements are used to confirm the single-photon nature of the source and the propagation of the single photons. A detailed investigation of the on-chip two-photon interference of two dissimilar sources is presented. Photons emitted by a quantum dot embedded in one arm of a directional coupler are combined with photons originating from an external laser. The occurrence of Hong-Ou-Mandel interference is confirmed with cross-correlation measurements

NS2 is dispensable for efficient assembly of hepatitis C virus-like particles in a bipartite trans-encapsidation system.

Infectious hepatitis C virus (HCV) particle production in the genotype 2a JFH-1-based cell culture system involves non-structural proteins in addition to canonical virion components. NS2 has been proposed to act as a protein adaptor, co-ordinating the early stages of virion assembly. However, other studies have identified late-acting roles for this protein, making its precise involvement in infectious particle production unclear. Using a robust, bipartite trans-encapsidation system based upon baculovirus expression of HCV structural proteins, we have generated HCV-like particles (HCV-LP) in the absence of NS2 with overt similarity to wild-type virions. HCV-LP could transduce naive cells with trans-encapsidated subgenomic replicon RNAs and shared similar biochemical and biophysical properties with JFH-1 HCV. Both genotype 1b and JFH-1 intracellular HCV-LP were produced in the absence of NS2, whereas restoring NS2 to the JFH-1 system dramatically enhanced secreted infectivity, consistent with a late-acting role. Our system recapitulated authentic HCV particle assembly via trans-complementation of bicistronic, NS2-deleted, chimeric HCV, which is otherwise deficient in particle production. This closely resembled replicon-mediated NS2 trans-complementation, confirming that baculovirus expression of HCV proteins did not unduly affect particle production. Furthermore, this suggests that separation of structural protein expression from replicating HCV RNAs that are destined to be packaged alleviates an early stage requirement for NS2 during particle formation. This highlights our current lack of understanding of how NS2 mediates assembly, yet comparison of full-length and bipartite systems may provide further insight into this process

On-chip interference of single photons from an embedded quantum dot and an external laser

In this work, we demonstrate the on-chip two-photon interference between single photons emitted by a single self-assembled InGaAs quantum dot and an external laser. The quantum dot is embedded within one arm of an air-clad directional coupler which acts as a beam-splitter for incoming light. Photons originating from an attenuated external laser are coupled to the second arm of the beam-splitter and then combined with the quantum dot photons, giving rise to two-photon quantum interference between dissimilar sources. We verify the occurrence of on-chip Hong-Ou-Mandel interference by cross-correlating the optical signal from the separate output ports of the directional coupler. This experimental approach allows us to use classical light source (laser) to assess in a single step the overall device performance in the quantum regime and probe quantum dot photon indistinguishability on application realistic time scales.Comment: 5 pages, 3 figure

Degeneration of basal and limbic networks is a core feature of behavioural variant frontotemporal dementia

Acknowledgment We would like to acknowledge the support of the Maxwell Computer Cluster funded by the University of Aberdeen. We also gratefully acknowledge study investigators and the generosity of study participants. Funding This study was sponsored entirely by TauRx Therapeutics Ltd (PAR1577). The Maxwell Computer Cluster is funded by the University of Aberdeen.Peer reviewedPublisher PD

Isolation and Identification of Pyrene Mineralizing Mycobacterium spp. from Contaminated and Uncontaminated Sources

Copyright © 2011 Christopher W. M. Lease et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Mycobacterium isolates obtained from PAH-contaminated and uncontaminated matrices were evaluated for their ability to degrade three-, four- and five-ring PAHs. PAH enrichment studies were prepared using pyrene and inocula obtained from manufacturing gas plant (MGP) soil, uncontaminated agricultural soil, and faeces from Macropus fuliginosus (Western Grey Kangaroo). Three pyrene-degrading microorganisms isolated from the corresponding enrichment cultures had broad substrate ranges, however, isolates could be differentiated based on surfactant, phenol, hydrocarbon and PAH utilisation. 16S rRNA analysis identified all three isolates as Mycobacterium sp. The Mycobacterium spp. could rapidly degrade phenanthrene and pyrene, however, no strain had the capacity to utilise fluorene or benzo[a]pyrene. When pyrene mineralisation experiments were performed, 70–79% of added 14C was evolved as 14CO2 after 10 days. The present study demonstrates that PAH degrading microorganisms may be isolated from a diverse range of environmental matrices. The present study demonstrates that prior exposure to PAHs was not a prerequisite for PAH catabolic activity for two of these Mycobacterium isolates

Association Between Myopia, Ultraviolet B Radiation Exposure, Serum Vitamin D Concentrations, and Genetic Polymorphisms in Vitamin D Metabolic Pathways in a Multicountry European Study.

IMPORTANCE: Myopia is becoming increasingly common globally and is associated with potentially sight-threatening complications. Spending time outdoors is protective, but the mechanism underlying this association is poorly understood. OBJECTIVE: To examine the association of myopia with ultraviolet B radiation (UVB; directly associated with time outdoors and sunlight exposure), serum vitamin D concentrations, and vitamin D pathway genetic variants, adjusting for years in education. DESIGN, SETTING, AND PARTICIPANTS: A cross-sectional, population-based random sample of participants 65 years and older was chosen from 6 study centers from the European Eye Study between November 6, 2000, to November 15, 2002. Of 4187 participants, 4166 attended an eye examination including refraction, gave a blood sample, and were interviewed by trained fieldworkers using a structured questionnaire. Myopia was defined as a mean spherical equivalent of -0.75 diopters or less. Exclusion criteria included aphakia, pseudophakia, late age-related macular degeneration, and vision impairment due to cataract, resulting in 371 participants with myopia and 2797 without. EXPOSURES: Exposure to UVB estimated by combining meteorological and questionnaire data at different ages, single-nucleotide polymorphisms in vitamin D metabolic pathway genes, serum vitamin D3 concentrations, and years of education. MAIN OUTCOMES AND MEASURES: Odds ratios (ORs) of UVB, serum vitamin D3 concentrations, vitamin D single-nucleotide polymorphisms, and myopia estimated from logistic regression. RESULT: Of the included 3168 participants, the mean (SD) age was 72.4 (5) years, and 1456 (46.0%) were male. An SD increase in UVB exposure at age 14 to 19 years (OR, 0.81; 95% CI, 0.71-0.92) and 20 to 39 years (OR, 0.7; 95% CI, 0.62-0.93) was associated with a reduced adjusted OR of myopia; those in the highest tertile of years of education had twice the OR of myopia (OR, 2.08; 95% CI, 1.41-3.06). No independent associations between myopia and serum vitamin D3 concentrations nor variants in genes associated with vitamin D metabolism were found. An unexpected finding was that the highest quintile of plasma lutein concentrations was associated with a reduced OR of myopia (OR, 0.57; 95% CI, 0.46-0.72). CONCLUSIONS AND RELEVANCE: Increased UVB exposure was associated with reduced myopia, particularly in adolescence and young adulthood. The association was not altered by adjusting for education. We found no convincing evidence for a direct role of vitamin D in myopia risk. The relationship between high plasma lutein concentrations and a lower risk of myopia requires replication

Tropomyosin 1: multiple roles in the developing heart and in the formation of congenital heart defects

Tropomyosin 1 (TPM1) is an essential sarcomeric component, stabilising the thin filament and facilitating actin's interaction with myosin. A number of sarcomeric proteins, such as alpha myosin heavy chain, play crucial roles in cardiac development. Mutations in these genes have been linked to congenital heart defects (CHDs), occurring in approximately 1 in 145 live births. To date, TPM1 has not been associated with isolated CHDs. Analysis of 380 CHD cases revealed three novel mutations in the TPM1 gene; IVS1 + 2T > C, I130V, S229F and a polyadenylation signal site variant GATAAA/AATAAA. Analysis of IVS1 + 2T > C revealed aberrant pre-mRNA splicing. In addition, abnormal structural properties were found in hearts transfected with TPM1 carrying I130V and S229F mutations. Phenotypic analysis of TPM1 morpholino-treated embryos revealed roles for TPM1 in cardiac looping, atrial septation and ventricular trabeculae formation and increased apoptosis was seen within the heart. In addition, sarcomere assembly was affected and altered action potentials were exhibited. This study demonstrated that sarcomeric TPM1 plays vital roles in cardiogenesis and is a suitable candidate gene for screening individuals with isolated CHDs

Applying Recent Argumentation Methods to Some Ancient Examples of Plausible Reasoning

Plausible (eikotic) reasoning known from ancient Greek (late Academic) skeptical philosophy is shown to be a clear notion that can be analyzed by argu- mentation methods, and that is important for argumentation studies. It is shown how there is a continuous thread running from the Sophists to the skeptical philosopher Carneades, through remarks of Locke and Bentham on the subject, to recent research in artificial intelligence. Eleven characteristics of plausible reasoning are specified by analyzing key examples of it recognized as important in ancient Greek skeptical philosophy using an artificial intelligence model called the Carneades Argumentation System (CAS). By applying CAS to ancient examples it is shown how plausible reasoning is especially useful for gaining a better understanding of evidential reasoning in law, and argued that it can also be applied to everyday argumentation. Our analysis of the snake and rope example of Carneades is also used to point out some ways CAS needs to be extended if it is to more fully model the views of this ancient philosopher on argumentation

Diminishing benefits of urban living for children and adolescents’ growth and development

Optimal growth and development in childhood and adolescence is crucial for lifelong health and well-being1–6. Here we used data from 2,325 population-based studies, with measurements of height and weight from 71 million participants, to report the height and body-mass index (BMI) of children and adolescents aged 5–19 years on the basis of rural and urban place of residence in 200 countries and territories from 1990 to 2020. In 1990, children and adolescents residing in cities were taller than their rural counterparts in all but a few high-income countries. By 2020, the urban height advantage became smaller in most countries, and in many high-income western countries it reversed into a small urban-based disadvantage. The exception was for boys in most countries in sub-Saharan Africa and in some countries in Oceania, south Asia and the region of central Asia, Middle East and north Africa. In these countries, successive cohorts of boys from rural places either did not gain height or possibly became shorter, and hence fell further behind their urban peers. The difference between the age-standardized mean BMI of children in urban and rural areas was \u3c1.1 kg m–2 in the vast majority of countries. Within this small range, BMI increased slightly more in cities than in rural areas, except in south Asia, sub-Saharan Africa and some countries in central and eastern Europe. Our results show that in much of the world, the growth and developmental advantages of living in cities have diminished in the twenty-first century, whereas in much of sub-Saharan Africa they have amplified