Quantum cascade laser light propagation through hollow silica waveguides

In this paper, the transmission characteristics of hollow silica waveguides with bore diameters of 300 and 1000 μm are investigated using a 7.8-μm quantum cascade laser system. We show that the bore diameter, coiling and launch conditions have an impact on the number of supported modes in the waveguide. Experimental verification of theoretical predictions is achieved using a thermal imaging camera to monitor output intensity distributions from waveguides under a range of conditions. The thermal imaging camera allowed for more detailed images than could be obtained with a conventionally used beam profiler. The results show that quasi-single-mode transmission is achievable under certain conditions although guided single-mode transmission in coiled waveguides requires a smaller bore diameter-to-wavelength ratio than is currently available. Assessment of mode population is made by investigating the spatial frequency content of images recorded at the waveguide output using Fourier transform techniques

Photometric compliance of tablet screens and retro-illuminated acuity charts as visual acuity measurement devices

Mobile technology is increasingly used to measure visual acuity. Standards for chart-based acuity tests specify photometric requirements for luminance, optotype contrast and luminance uniformity. Manufacturers provide some photometric data but little is known about tablet performance for visual acuity testing. This study photometrically characterised seven tablet computers (iPad, Apple inc.) and three ETDRS (Early Treatment Diabetic Retinopathy Study) visual acuity charts with room lights on and off, and compared findings with visual acuity measurement standards. Tablet screen luminance and contrast were measured using nine points across a black and white checkerboard test screen at five arbitrary brightness levels. ETDRS optotypes and adjacent white background luminance and contrast were measured. All seven tablets (room lights off) exceeded the most stringent requirement for mean luminance (≥ 120 cd/m2) providing the nominal brightness setting was above 50%. All exceeded contrast requirement (Weber ≥ 90%) regardless of brightness setting, and five were marginally below the required luminance uniformity threshold (Lmin/Lmax ≥ 80%). Re-assessing three tablets with room lights on made little difference to mean luminance or contrast, and improved luminance uniformity to exceed the threshold. The three EDTRS charts (room lights off) had adequate mean luminance (≥ 120 cd/m2) and Weber contrast (≥ 90%), but all three charts failed to meet the luminance uniformity standard (Lmin/Lmax ≥ 80%). Two charts were operating beyond manufacturer’s recommended lamp replacement schedule. With room lights on, chart mean luminance and Weber contrast increased, but two charts still had inadequate luminance uniformity. Tablet computers showed less inter-device variability, higher contrast, and better luminance uniformity than charts in both lights-on and lights-off environments, providing brightness setting was >50%. Overall, iPad tablets matched or marginally out-performed ETDRS charts in terms of photometric compliance with high contrast acuity standards

All grown up? Market maturity and investment in London's purpose-built student accommodation sector

Purpose: The UK's purpose-built student accommodation (PBSA) sector has seen significant institutional investment in recent decades. This paper unpacks contemporary trends and perspectives on the sector. It questions whether PBSA has moved from being an “alternative” to “mainstream” residential asset class, framing the analysis through the lens of market maturity. / Design/methodology/approach: The methods triangulate perspectives drawn from literature on the evolution of PBSA as an asset class with illustrations of investment trends across the UK between 2005 and 2020 using data from Real Capital Analytics (RCA), combined with findings from 40 semi-structured interviews with investors and stakeholders in PBSA in the UK London is the focus of the work, whilst other regional cities are integrated for comparison. / Findings: The results demonstrate that London's PBSA market is ahead of trends currently being replicated in regional cities. However, the regions currently offer greater return potential and opportunities for risk taking compared to London, where yields are compressed, and the market is considered lower risk. The concept of maturity remains useful as a framework for evaluating markets, however a more granular analysis of sectors is necessary to further understand asset classes within sectors. PBSA continues to trade at a premium across the UK; it is considered the most mature residential asset class. / Practical implications: The emergence of PBSA as an asset class continues to play a developing role within the residential sector and UK investment market. Risk, value and local context remain key when integrating PBSA into institutional portfolios, and as the first to consider the UK market from a qualitative research approach, this research provides a snapshot of these influences in 2021. / Originality/value: Our approach offers original insight into investment trends across the UK and is the first to focus reflections on the London market specifically. The research highlights the role of PBSA as a vanguard asset class for investors into residential, situating its growth within the framework of market maturity and drawing out market nuances from interviews

Pulsar magnetic alignment and the pulsewidth-age relation

Using pulsewidth data for 872 isolated radio pulsars we test the hypothesis that pulsars evolve through a progressive narrowing of the emission cone combined with progressive alignment of the spin and magnetic axes. The new data provide strong evidence for the alignment over a time-scale of about 1 Myr with a log standard deviation of around 0.8 across the observed population. This time-scale is shorter than the time-scale of about 10 Myr found by previous authors, but the log standard deviation is larger. The results are inconsistent with models based on magnetic field decay alone or monotonic counter-alignment to orthogonal rotation. The best fits are obtained for a braking index parameter n_gamma approximately equal to 2.3, consistent the mean of the six measured values, but based on a much larger sample of young pulsars. The least-squares fitted models are used to predict the mean inclination angle between the spin and magnetic axes as a function of log characteristic age. Comparing these predictions to existing estimates it is found that the model in which pulsars are born with a random angle of inclination gives the best fit to the data. Plots of the mean beaming fraction as a function of characteristic age are presented using the best-fitting model parameters.Comment: 13 pages, 11 figures, Accepted for publication in MNRA

Public Support for University Funding: Trends and Determinants in Ontario, 1980-1990

This paper examines trends in public support for government funding of universities over the past decade, identifies significant social factors related to attitudes on university funding during this period, and briefly discusses possible future tendencies in public support for university funding. Growing public support for increased university funding in Ontario is documented. A variety of types of potential influences is assessed, including societal context, socio-economic status, demographic and political orientation factors. Age, educational attainment, and community size, as well as support for general government spending, are found to have significant individual-level effects on support for university funding. Multi-variate analyses suggest a growing isolation of older, less formally educated and rural people as opponents of increased university funding. The implications of these patterns in the context of an aging but increasingly educated population are then considered.Cet article examine les tendances du soutien public à l'égard des subventions gouvernementales accordées aux universités au cours des dix dernières années, identifie d'importants facteurs sociaux qui sont liés aux attitudes vis-à-vis l'attribution des fonds aux universités durant cette période, et discute brièvement des tendances éventuelles d'évolution du soutien public à l'égard des subventions accordées aux universités. On montre qu'il existe un soutienpopulaire croissant en faveur de l'augmentation des subventions accordées aux universités en Ontario. On évalue divers types d'influences possibles, y compris le contexte sociétal, le situation socio-économique, et les facteurs associés à l'orientation démographique et politique. L'âge, la scolarisation, la taille de la communauté dans laquelle on vit. ainsi que l'appui accordé aux dépenses publiques de façon générale semblent avoir des effets significatifs sur le niveau de soutien accordé au financement universitaire. Des analyses multi-variées suggèrent que les personnes plus âgés, moins scolarisées et vivant en milieux ruraux s'opposent davantage à l'augmentation des fonds accordés aux universités. On conclut en examinant les implications de ces constats dans le contexte d'une population vieillissante et de plus en plus scolarisée

Union Influence on Worker Education and Training in Canada in Tough Times

This research has focused on re-analyzing data from previous large-scale Canadian surveys that include information on education and training activities and union status, as well as other demographic and organizational factors, most prominently the 1993 and 1997 Adult Education and Training Surveys. In contrast to some recent studies, we find that union status has had consistent positive individual-level effects in Canada on participation in adult education courses and employer-sponsored courses in general, and especially for women union members. In addition, our analysis of data from the 1998 national survey on informal learning finds that in this much more extensive form of learning, unionized workers are significantly more likely than non-unionized workers to participate in more directly empowering forms of knowledge including learning about workers’ rights and political issues

Interest in unions and associations in a knowledge-base economy: Canadian evidence

oai:justlabour.journals.yorku.ca:article/1This study analyzes the results of a 2010 national survey of Canadian non-managerial employees' membership and interest in worker organizations. This is the first general survey to include associations as well as unions. Profiles of membership and interest in unions and associations are presented, then demographic, organizational and attitudinal factors related to interest in joining these worker organizations are examined. The findings suggest that, in spite of some recent decline in union density, most Canadian non-managerial workers who are interested in collective representation are members of at least one of these organizations. The strongest interest in joining is expressed by those who are highly educated, poorly paid and feel underemployed-even if allowed some workplace "voice". The limited prior focus on unions needs to be expanded to attend to both unions and associations as worker-controlled vehicles of representation, particularly to identify strategic alliances with the growing numbers of professional employees.

Using Student-Generated UV-Induced \u3cem\u3eEscherichia coli\u3c/em\u3e Mutants in a Directed Inquiry Undergraduate Genetics Laboratory

We report a thematic sequence of directed inquiry-based labs taking students from bacterial mutagenesis and phenotypic identification of their own self-created mutant, through identification of mutated genes by biochemical testing, to verification of mutant alleles by complementation, and finally to mutant allele characterization by DNA sequence analysis. The lab utilizes UV mutagenesis with wild-type Escherichia coli and a UV-sensitive isogenic derivative optimized for undergraduate use. The labs take advantage of the simplicity of E. coli in a realistic genetic investigation using safe UV irradiation methods for creation and characterization of novel mutants. Assessment data collected over three offerings of the course suggest that the labs, which combine original investigation in a scientifically realistic intellectual environment with learned techniques and concepts, were instrumental in improving students’ learning in a number of areas. These include the development of critical thinking skills and understanding of concepts and methods. Student responses also suggest the labs were helpful in improving students’understanding of the scientific process as a rational series of experimental investigations and awareness of the interdisciplinary nature of scientific inquiry