Repeatability and comparison of clinical techniques for anterior chamber angle assessment

Purpose To assess the repeatability of gonioscopy, van Herick method and anterior segment Optical Coherence Tomography (AS-OCT) and determine the agreement between these techniques within a community optometry setting. Methods Gonioscopy, van Herick method and AS-OCT imaging were performed by an optometrist on two occasions, 1 month apart, on 80 subjects aged over 40 years recruited from community optometry practices. Anterior segment images were captured with a spectral domain OCT (Topcon 3D OCT-2000; wavelength 840 nm) set to the Anterior Segment (AS) mode. Eyes were graded as open or occludable for each method. AS-OCT images from both visits were graded by a second optometrist masked to the gonioscopy and van Herick method results, and the visit on which the images were acquired. Cohen's kappa (κ) was used to describe the intra-observer repeatability. Likelihood ratios, sensitivity and specificity of van Herick method and AS-OCT were calculated, using gonioscopy as the reference standard. Results Measurements were obtained from 80 eyes of 80 subjects. In four cases, AS-OCT images were un-gradable due to difficulty in locating the scleral spur. The repeatability of gonioscopy was fair κ = 0.29, while that of the van Herick method (κ = 0.54) and AS-OCT (κ = 0.47) were somewhat better. The van Herick method showed good sensitivity (visit 1: 75%, visit 2: 69%) and high specificity (visit 1: 88%, visit 2: 96%). The sensitivity of AS-OCT was fair (visit 1: 46%, visit 2: 25%), but specificity was high (visit 1: 87%. visit 2: 89%). Conclusion Intra-observer repeatability was better for van Herick method and for AS-OCT than for gonioscopy, despite the latter being considered the gold standard method. The van Herick method appeared to be more sensitive than AS-OCT when identifying eyes at risk of angle closure. A standalone anterior segment OCT with a longer wavelength laser could afford better visualisation of the angle, and might therefore be expected to enable the examiner to make more precise classifications. These instruments are not widely used by optometrists in clinical practice in the UK at present

A Novel Passive Defrost System for a Frozen Retail Display Cabinet with a Low Evaporator

An energy efficient thermo-siphon method of defrosting the air coils on a commercial half glass door (HGD)/well retail display cabinet has been developed (FrigescoTM) and the performance compared with the existing electric defrost system under EN ISO 23953 test room conditions. Previous work by (Foster et al, 2013) used a passive thermo-siphon to defrost the top evaporator inside the top (glass door) section and a pump assisted thermo-siphon to defrost the well section. This was due to the head being too low to adequately defrost the well evaporator with a passive thermo-siphon. This work describes a passive thermo-siphon with no pump. To enable the thermo-siphon to operate efficiently the design of the evaporator was optimised. The thermo-siphon heated quicker and melted water faster than the electric defrost. The thermo-siphon used less electrical heat and had an added benefit of free sub-cooling

An Exhaustive Symmetry Approach to Structure Determination: Phase Transitions in Bi2Sn2O7

The exploitable properties of many materials are intimately linked to symmetry-lowering structural phase transitions. We present an automated and exhaustive symmetry-mode method for systematically exploring and solving such structures which will be widely applicable to a range of functional materials. We exemplify the method with an investigation of the Bi2Sn2O7 pyrochlore, which has been shown to undergo transitions from a parent γ cubic phase to β and α structures on cooling. The results include the first reliable structural model for β-Bi2Sn2O7 (orthorhombic Aba2, a = 7.571833(8), b = 21.41262(2), and c = 15.132459(14) Å) and a much simpler description of α-Bi2Sn2O7 (monoclinic Cc, a = 13.15493(6), b = 7.54118(4), and c = 15.07672(7) Å, β = 125.0120(3)°) than has been presented previously. We use the symmetry-mode basis to describe the phase transition in terms of coupled rotations of the Bi2O′ anti-cristobalite framework, which allow Bi atoms to adopt low-symmetry coordination environments favored by lone-pair cations

Testing for rational speculative bubbles in the Brazilian residential real-estate market

Speculative bubbles have been occurring periodically in local or global real estate markets and are considered a potential cause of economic crises. In this context, the detection of explosive behaviors in the financial market and the implementation of early warning diagnosis tests are of critical importance. The recent increase in Brazilian housing prices has risen concerns that the Brazilian economy may have a speculative housing bubble. In the present paper, we employ a recently proposed recursive unit root test in order to identify possible speculative bubbles in data from the Brazilian residential real-estate market. The empirical results show evidence for speculative price bubbles both in Rio de Janeiro and Sao Paulo, the two main Brazilian cities

An Infinite Dimensional Symmetry Algebra in String Theory

Symmetry transformations of the space-time fields of string theory are generated by certain similarity transformations of the stress-tensor of the associated conformal field theories. This observation is complicated by the fact that, as we explain, many of the operators we habitually use in string theory (such as vertices and currents) have ill-defined commutators. However, we identify an infinite-dimensional subalgebra whose commutators are not singular, and explicitly calculate its structure constants. This constitutes a subalgebra of the gauge symmetry of string theory, although it may act on auxiliary as well as propagating fields. We term this object a {\it weighted tensor algebra}, and, while it appears to be a distant cousin of the $W$-algebras, it has not, to our knowledge, appeared in the literature before.Comment: 14 pages, Plain TeX, report RU93-8, CTP-TAMU-2/94, CERN-TH.7022/9

Salivary free light chains as a new biomarker to measure psychological stress: the impact of a university exam period on salivary immunoglobulins, cortisol, DHEA and symptoms of infection:the impact of a university exam period on salivary immunoglobulins, cortisol, DHEA and symptoms of infection

Introduction: Measurement of immunoglobulin free light chains (FLCs) in saliva can serve as a non-invasive biomarker in health and behavioural research. FLCs have been explored in relation to physiological stress but FLC responses to psychological stress and their relationship with infections remain unknown. This study aimed to investigate the impact of exam period stress on salivary FLCs alongside other established biomarkers of stress and whether FLCs relate to symptoms of infection. Methods: 58 healthy adults studying at university completed saliva samples and questionnaires in a period without exams (baseline), and again prior to the start of an exam period. Saliva samples were assessed for FLCs, IgA, cortisol and dehydroepiandrosterone (DHEA). Measures of life events stress, perceived stress, anxiety and depression were completed. Students also reported incidence and severity of symptoms of infection and rated general well-being at baseline, prior to, during and after the exam period. Exercise, sleep and alcohol consumption were also assessed at both timepoints. Results: FLCs secretion rates were significantly lower at the exam period compared to baseline (p &lt;.01), with reductions of 26% and 25% for κ FLC and λ FLC, respectively. In agreement, salivary IgA secretion rate was lower at exams (non-significant trend, p =.07). Cortisol concentration significantly increased at exams (p &lt;.05) while DHEA did not change, leading to an increase in the cortisol:DHEA ratio (p =.06). Depression (p &lt;.05) and anxiety increased from baseline to exams and life stress reported in the build up to the exam period was higher compared with baseline (p &lt;.001). Well-being significantly decreased from baseline to exams (p &lt;.01). The proportion of participants reporting infection symptoms (70%) was unchanged between baseline and prior to exams. No significant relationships were found between FLCs or other saliva parameters and infection symptoms, well-being or stress/psychological measures. Changes in saliva parameters between timepoints were independent of health behaviours. Conclusions: Salivary FLCs are responsive to life events stress and corroborate with IgA. This preliminary study highlights the potential utility of FLCs as a new salivary biomarker in stress research.</p

Reasons People Living with HIV Might Prefer Oral Daily Antiretroviral Therapy, Long-Acting Formulations or Future HIV Remission Options

A growing body of research is beginning to elucidate reasons people living with HIV (PLWHIV) might prefer oral daily antiretroviral treatment (ART) compared with emerging long-acting ART (LA-ART) or HIV remission strategies under investigation. Our objective is to provide qualitative insights into the reasons why PLWHIV might prefer one of these HIV control therapies over others. From May to August 2018, we implemented a semistructured cross-sectional survey of PLWHIV in the United States to better understand patient preferences around various HIV treatment and remission options. Using free text, respondents were asked to explain why they preferred one HIV control option over the other two. We analyzed responses to the open-ended survey questions on reasons for preferring oral daily ART versus LA-ART versus HIV remission strategies using conventional content analysis. The results showed that PLWHIV preferred oral daily ART because of its familiarity and known safety and efficacy profile, whereas those who preferred LA-ART would value the convenience it offers. Finally, HIV remission strategies would be preferred to avoid taking ART altogether. The qualitative results provide insights into reasons why PLWHIV in the United States might prefer oral daily ART versus novel therapies. More importantly, they provide information to better align HIV virological control strategies with end-user perspectives. To make informed choices around evolving HIV therapeutics, PLWHIV and HIV care providers would benefit from decision tools to better assess options and trade-offs. More research is needed on how best to effectively support PLWHIV and HIV care providers in shared decision-making

A Model for Twin Kilohertz Quasi-Periodic Oscillations in Neutron Star Low-Mass X-Ray Binaries

We suggest a plausible interpretation for the twin kiloHertz quasi-periodic oscillations (kHz QPOs) in neutron star low-mass X-ray binaries. We identify the upper kHz QPO frequencies to be the rotational frequency and the lower kHz QPOs the standing kink modes of loop oscillations at the inner edge of the accretion disk, respectively. Taking into account the interaction between the neutron star magnetic field and the disk, this model naturally relates the twin QPO frequencies with the star's spin frequencies. We have applied the model to four X-ray sources with kHz QPOs detected simultaneously and known spin frequencies.Comment: 12 pages including 3 figures, accepted for publication in ApJ