Finite-precision measurement does not nullify the Kochen-Specker theorem

It is proven that any hidden variable theory of the type proposed by Meyer [Phys. Rev. Lett. {\bf 83}, 3751 (1999)], Kent [{\em ibid.} {\bf 83}, 3755 (1999)], and Clifton and Kent [Proc. R. Soc. London, Ser. A {\bf 456}, 2101 (2000)] leads to experimentally testable predictions that are in contradiction with those of quantum mechanics. Therefore, it is argued that the existence of dense Kochen-Specker-colorable sets must not be interpreted as a nullification of the physical impact of the Kochen-Specker theorem once the finite precision of real measurements is taken into account.Comment: REVTeX4, 5 page

Variation of the height of centreline of a heliostat and influence on the wind loading

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.Mostly located in desert areas, heliostat fields are subjected to various wind conditions. An ANSYS Fluent CFD model of a single heliostat in some worst-case positions is produced using numerical simulations with the realizable k-ε model. The intent of this paper is to show the possible effect that the clearance gap has on the force and moment coefficients of the heliostat. The incoming flow modeled is an ABL profile that has already been generated in a wind tunnel. For a wind angle of 0° and heliostat elevation angles of 90° and 30°, the HCL is varied and the force and moment coefficients are computed. It is shown that the coefficients are sensitive to the clearance gap. More specifically, there is a compromise between lift and drag, and a specific HCL is beneficial to minimize the hinge moment.cf201

Transient simulation of an atmospheric boundary layer flow past a heliostat using the Scale-Adaptive Simulation turbulence model

Heliostat fields are exposed to changing climatic conditions as they are mostly erected in open environments where the wind naturally features a high unsteadiness at low altitude due to the ground effects. Much of the computational fluid dynamics (CFD) content in the open literature is focused on Reynolds–averaged-Navier–Stokes (RANS) simulations, which can only predict mean loads. This paper considers an isolated heliostat in worst-case orientation. The drag force is numerically modelled by means of a Scale-Resolving Simulation (SRS) in ANSYS v19. This paper firstly deals with two different methods that generate perturbations at the inlet boundary: the spectral synthesiser and the vortex method. In an empty domain, an atmospheric boundary layer (ABL) profile is modelled based on a wind tunnel experiment. Secondly, the wind tunnel test of a single heliostat model in upright orientation is replicated, aiming to model the mean and peak drag forces. Applicable for highly separated flows, the Scale-Adaptive Simulation (SAS) turbulence model is employed as it is computationally more affordable than a Detached Eddy Simulation (DES) approach. The latter would require a higher grid resolution and a reduced time step size. The SAS showed little but acceptable decay of the inlet profiles whilst achieving lateral homogeneity. The mean and root-mean-square error of the drag force signal showed a deviation with the experiment of 0.04% and 5.8%, respectively, whereas the error on the peak drag forces was around 18%, possibly mostly due to the under-prediction of the turbulent integral length scale at the model location.The University of Pretoria, South Africa and the South African National Research Foundation.http://www.elsevier.com/locate/jweiahj2022Mechanical and Aeronautical Engineerin

Tilt order parameters, polarity and inversion phenomena in smectic liquid crystals

The order parameters for the phenomenological description of the smectic-{\it A} to smectic-{\it C} phase transition are formulated on the basis of molecular symmetry and structure. It is shown that, unless the long molecular axis is an axis of two-fold or higher rotational symmetry, the ordering of the molecules in the smectic-{\it C} phase gives rise to more than one tilt order parameter and to one or more polar order parameters. The latter describe the indigenous polarity of the smectic-{\it C} phase, which is not related to molecular chirality but underlies the appearance of spontaneous polarisation in chiral smectics. A phenomenological theory of the phase transition is formulated by means of a Landau expansion in two tilt order parameters (primary and secondary) and an indigenous polarity order parameter. The coupling among these order parameters determines the possibility of sign inversions in the temperature dependence of the spontaneous polarisation and of the helical pitch observed experimentally for some chiral smectic-{\it $C^{\ast}$} materials. The molecular interpretation of the inversion phenomena is examined in the light of the new formulation.Comment: 12 pages, 5 figures, RevTe

The Importance of Time Congruity in the Organisation.

In 1991 Kaufman, Lane, and Lindquist proposed that time congruity in terms of an individual's time preferences and the time use methods of an organisation would lead to satisfactory performance and enhancement of quality of work and general life. The research reported here presents a study which uses commensurate person and job measures of time personality in an organisational setting to assess the effects of time congruity on one aspect of work life, job-related affective well-being. Results show that time personality and time congruity were found to have direct effects on well-being and the influence of time congruity was found to be mediated through time personality, thus contributing to the person–job (P–J) fit literature which suggests that direct effects are often more important than indirect effects. The study also provides some practical examples of ways to address some of the previously cited methodological issues in P–J fit research

Understanding bias in relationships between the food environment and diet quality: The Coronary Artery Risk Development in Young Adults (CARDIA) study

Background The relationship between food environment exposures and diet behaviours is unclear, possibly because the majority of studies ignore potential residual confounding. Methods We used 20 years (1985-1986, 1992-1993 2005-2006) of data from the Coronary Artery Risk Development in Young Adults (CARDIA) study across four US cities (Birmingham, Alabama; Chicago, Illinois; Minneapolis, Minnesota; Oakland, California) and instrumental variables (IV) regression to obtain causal estimates of longitudinal associations between the percentage of neighbourhood food outlets (per total food outlets within 1 km network distance of respondent residence) and an a priori diet quality score, with higher scores indicating higher diet quality. To assess the presence and magnitude of bias related to residual confounding, we compared results from causal models (IV regression) to non-causal models, including ordinary least squares regression, which does not account for residual confounding at all and fixed-effects regression, which only controls for time-invariant unmeasured characteristics. Results The mean diet quality score across follow-up was 63.4 (SD=12.7). A 10% increase in fast food restaurants (relative to full-service restaurants) was associated with a lower diet quality score over time using IV regression (β=-1.01, 95% CI -1.99 to -0.04); estimates were attenuated using non-causal models. The percentage of neighbourhood convenience and grocery stores (relative to supermarkets) was not associated with diet quality in any model, but estimates from non-causal models were similarly attenuated compared with causal models. Conclusion Ignoring residual confounding may generate biased estimated effects of neighbourhood food outlets on diet outcomes and may have contributed to weak findings in the food environment literature

Does unmeasured confounding influence associations between the retail food environment and body mass index over time? The Coronary Artery Risk Development in Young Adults (CARDIA) study

Background: Findings in the observational retail food environment and obesity literature are inconsistent, potentially due to a lack of adjustment for residual confounding. Methods: Using data from the CARDIA study (n ¼ 12 174 person-observations; 6 examinations; 1985-2011) across four US cities (Birmingham, AL; Chicago, IL; Minneapolis, MN; Oakland, CA), we used instrumental-variables (IV) regression to obtain causal estimates of the longitudinal associations between the percentage of neighbourhood food stores or restaurants (per total food outlets within 1 km network distance of respondent residence) with body mass index (BMI), adjusting for individual-level socio-demographics, health behaviours, city, year, total food outlets and market-level prices. To determine the presence and extent of bias, we compared the magnitude and direction of results with ordinary least squares (OLS) and random effects (RE) regression, which do not control for residual confounding, and with fixed effects (FE) regression, which does not control for time-varying residual confounding. Results: Relative to neighbourhood supermarkets (which tend to be larger and have healthier options than grocery stores), a higher percentage of grocery stores [mean-¼ 53.4%; standard deviation (SD) ¼ 31.8%] was positively associated with BMI [b ¼ 0.05; 95% confidence interval (CI) ¼ 0.01, 0.10] using IV regression. However, associations were negligible or null using OLS (b ¼ 0.001; 95% CI ¼ 0.01, 0.01), RE (b ¼ 0.003; 95% CI ¼ 0.01, 0.0001) and FE (b ¼ 0.003; 95% CI ¼ 0.01, 0.0002) regression. Neighbourhood convenience stores and fast-food restaurants were not associated with BMI in any model. Conclusions: Longitudinal associations between neighbourhood food outlets and BMI were greater in magnitude using a causal model, suggesting that weak findings in the literature may be due to residual confounding

Hydrotherapy and its effects on chronic pain intensity, physical functionality and quality of life in the elderly

Chronic pain is often associated with impaired muscle strength and limited physical activity and performance, resulting in impaired physical functioning. This study aimed to determine whether voluntary participation in a structured 6-week hydrotherapy exercise programme would improve pain management, functionality and quality of life in an elderly population (n = 22; 77.7 ± 6.6 y)suffering from chronic pain and living in nursing homes in Tshwane. The experimental group (n= 13) attended hydrotherapy classes twice a week for six weeks, while the control group (n = 9)did not. Questionnaires were completed (Chronic Pain Grade, Functional Status Index, and the SF 36), and functional testing performed, in both groups at weeks 0, 3 and 6. The experimental group reported reduced pain intensity at week 3 (p = 0.051); reduced pain-induced disability at week 6 (p = 0.080); reduced assisted help required for activities of daily living (ADL) at week 3 (p = 0.040); reduced difficulty on performing ADL at week 3 (p = 0.012) and reduced pain experienced with ADL at week 3 (p = 0.007) and week 6 (p = 0.014). Improvements in upper body strength and agility were demonstrated. Improvements in sub-scales for quality of life were demonstrated at weeks 3 and 6. The control group showed no statistically significant changes in the above parameters. In conclusion, participation in structured hydrotherapy classes has been shown in this small study to be a beneficial intervention strategy for managing chronic pain in the elderly.http://www.ajol.info/journal_index.php?jid=153&ab=ajpherd2017-12-31am201

Hydrological (in)stability in Southern Siberia during the Younger Dryas and early Holocene

Southern Siberia is currently undergoing rapid warming, inducing changes in vegetation, loss of permafrost, and impacts on the hydrodynamics of lakes and rivers. Lake sediments are key archives of environmental change and contain a record of ecosystem variability, as well as providing proxy indicators of wider environmental and climatic change. Investigating how hydrological systems have responded to past shifts in climate can provide essential context for better understanding future ecosystem changes in Siberia. Oxygen isotope ratios within lacustrine records provide fundamental information on past variability in hydrological systems. Here we present a new oxygen isotope record from diatom silica (ẟ18Odiatom) at Lake Baunt (55°11′15″N, 113°01,45″E), in the southern part of eastern Siberia, and consider how the site has responded to climate changes between the Younger Dryas and Early to Mid Holocene (ca. 12.4 to 6.2 ka cal BP). Excursions in ẟ18Odiatom are influenced by air temperature and the seasonality, quantity, and source of atmospheric precipitation. These variables are a function of the strength of the Siberian High, which controls temperature, the proportion and quantity of winter versus summer precipitation, and the relative dominance of Atlantic versus Pacific air masses. A regional comparison with other Siberian ẟ18Odiatom records, from lakes Baikal and Kotokel, suggests that ẟ18Odiatom variations in southern Siberia reflect increased continentality during the Younger Dryas, delayed Early Holocene warming in the region, and substantial climate instability between ~10.5 to ~8.2 ka cal BP. Unstable conditions during the Early Holocene thermal optimum most likely reflect localised changes from glacial melting. Taking the profiles from three very different lakes together, highlight the influence of site specific factors on the individual records, and how one site is not indicative of the region as a whole. Overall, the study documents how sensitive this important region is to both internal and external forcing