An adaptive grid algorithm for one-dimensional nonlinear equations

Richards' equation, which models the flow of liquid through unsaturated porous media, is highly nonlinear and difficult to solve. Step gradients in the field variables require the use of fine grids and small time step sizes. The numerical instabilities caused by the nonlinearities often require the use of iterative methods such as Picard or Newton interation. These difficulties result in large CPU requirements in solving Richards equation. With this in mind, adaptive and multigrid methods are investigated for use with nonlinear equations such as Richards' equation. Attention is focused on one-dimensional transient problems. To investigate the use of multigrid and adaptive grid methods, a series of problems are studied. First, a multigrid program is developed and used to solve an ordinary differential equation, demonstrating the efficiency with which low and high frequency errors are smoothed out. The multigrid algorithm and an adaptive grid algorithm is used to solve one-dimensional transient partial differential equations, such as the diffusive and convective-diffusion equations. The performance of these programs are compared to that of the Gauss-Seidel and tridiagonal methods. The adaptive and multigrid schemes outperformed the Gauss-Seidel algorithm, but were not as fast as the tridiagonal method. The adaptive grid scheme solved the problems slightly faster than the multigrid method. To solve nonlinear problems, Picard iterations are introduced into the adaptive grid and tridiagonal methods. Burgers' equation is used as a test problem for the two algorithms. Both methods obtain solutions of comparable accuracy for similar time increments. For the Burgers' equation, the adaptive grid method finds the solution approximately three times faster than the tridiagonal method. Finally, both schemes are used to solve the water content formulation of the Richards' equation. For this problem, the adaptive grid method obtains a more accurate solution in fewer work units and less computation time than required by the tridiagonal method. The performance of the adaptive grid method tends to degrade as the solution process proceeds in time, but still remains faster than the tridiagonal scheme

The eSMA: description and first results

The eSMA ("extended SMA") combines the SMA, JCMT and CSO into a single facility, providing enhanced sensitivity and spatial resolution owing to the increased collecting area at the longest baselines. Until ALMA early science observing (2011), the eSMA will be the facility capable of the highest angular resolution observations at 345 GHz. The gain in sensitivity and resolution will bring new insights in a variety of fields, such as protoplanetary/transition disks, high-mass star formation, solar system bodies, nearby and high-z galaxies. Therefore the eSMA is an important facility to prepare the grounds for ALMA and train scientists in the techniques. Over the last two years, and especially since November 2006, there has been substantial progress toward making the eSMA into a working interferometer. In particular, (i) new 345-GHz receivers, that match the capabilities of the SMA system, were installed at the JCMT and CSO; (ii) numerous tests have been performed for receiver, correlator and baseline calibrations in order to determine and take into account the effects arising from the differences between the three types of antennas; (iii) first fringes at 345 GHz were obtained on August 30 2007, and the array has entered the science-verification stage. We report on the characteristics of the eSMA and its measured performance at 230 GHz and that expected at 345 GHz. We also present the results of the commissioning and some initial science-verification observations, including the first absorption measurement of the C/CO ratio in a galaxy at z=0.89, located along the line of sight to the lensed quasar PKS1830-211, and on the imaging of the vibrationally excited HCN line towards IRC+10216.Comment: 12 pages, 7 figures, paper number 7012-12, to appear in Proceedings of SPIE vol. 7012: "Ground-based and Airborne Telescopes II", SPIE conference on Astronomical Instrumentation, Marseille, 23-28 June 200

Holographic surface measurement system for the Fred Young Submillimeter Telescope

We describe a system being developed for measuring the shapes of the mirrors of the Fred Young Submillimeter Telescope (FYST), now under construction for the CCAT Observatory. "Holographic" antenna-measuring techniques are an efficient and accurate way of measuring the surfaces of large millimeter-wave telescopes and they have the advantage of measuring the wave-front errors of the whole system under operational conditions, e.g. at night on an exposed site. Applying this to FYST, however, presents significant challenges because of the high accuracy needed, the fact that the telescope consists of two large off-axis mirrors, and a requirement that measurements can be made without personnel present. We use a high-frequency (~300GHz) source which is relatively close to the telescope aperture (<1/100th of the Fresnel distance) to minimize atmospheric effects. The main receiver is in the receiver cabin and can be moved under remote control to different positions, so that the wave-front errors in different parts of the focal plane can be measured. A second receiver placed on the yoke provides a phase reference. The signals are combined in a digital cross-correlation spectrometer. Scanning the telescope provides a map of the complex beam pattern. The surface errors are found by inference, i.e. we make models of the reflectors with errors and calculate the patterns expected, and then iterate to find the best match to the data. To do this we have developed a fast and accurate method for calculating the patterns using the Kirchhoff-Fresnel formulation. This paper presents details of the design and outlines the results from simulations of the measurement and inference process. These indicate that a measurement accuracy of ~3 microns rms is achievable.Comment: Proceedings Volume 11445, Ground-based and Airborne Telescopes VIII SPIE Astronomical Telescopes + Instrumentation, 2020, Online Only Conferenc

Does wage rank affect employees' well-being?

How do workers make wage comparisons? Both an experimental study and an analysis of 16,000 British employees are reported. Satisfaction and well-being levels are shown to depend on more than simple relative pay. They depend upon the ordinal rank of an individual's wage within a comparison group. “Rank” itself thus seems to matter to human beings. Moreover, consistent with psychological theory, quits in a workplace are correlated with pay distribution skewness

Prompt Optical Observations of Gamma-ray Bursts

The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs). A search for optical counterparts to six GRBs with localization errors of 1 square degree or better produced no detections. The earliest limiting sensitivity is m(ROTSE) > 13.1 at 10.85 seconds (5 second exposure) after the gamma-ray rise, and the best limit is m(ROTSE) > 16.0 at 62 minutes (897 second exposure). These are the most stringent limits obtained for GRB optical counterpart brightness in the first hour after the burst. Consideration of the gamma-ray fluence and peak flux for these bursts and for GRB990123 indicates that there is not a strong positive correlation between optical flux and gamma-ray emission.Comment: 4 pages, 3 figures, submitted to ApJ Letter

Are people who participate in cultural activities more satisfied with life?

The influence of various aspects of life on wellbeing has been extensively researched. However, despite little empirical evidence, participation in leisure activities has been assumed to increase subjective wellbeing. Leisure is important because it is more under personal control than other sources of life satisfaction. This study asked whether people who participate in cultural leisure activities have higher life satisfaction than people who do not, if different types of leisure have the same influence on life satisfaction and if satisfaction is dependent on the frequency of participation or the number of activities undertaken. It used data from UKHLS Survey to establish associations between type, number and frequency of participation in leisure activities and life satisfaction. Results showed an independent and positive association of participation in sport, heritage and active-creative leisure activities and life satisfaction but not for participation in popular entertainment, theatre hobbies and museum/galleries. The association of reading hobbies and sedentary-creative activities and life satisfaction was negative. High life satisfaction was associated with engaging in a number of different activities rather than the frequency of participation in each of them. The results have implications for policy makers and leisure services providers, in particular those associated with heritage recreation. Subjective wellbeing measures, such as life satisfaction, and not economic measures alone should be considered in the evaluation of services. The promotion of leisure activities which are active and promote social interaction should be considered in programmes aimed at improving the quality of life

Chemical and kinematical properties of BSSs and HB stars in NGC 6397

We used three sets of high-resolution spectra acquired with the multifiber facility FLAMES at the Very Large Telescope of the European Southern Observatory to investigate the chemical and kinematical properties of a sample of 42 horizontal branch (HB) stars, 18 Blue Straggler Stars (BSSs) and 86 main sequence turn-off and sub-giant branch stars in the nearby globular cluster NGC 6397. We measured rotational velocities and Fe, O and Mg abundances. All the unevolved stars in our sample turn out to have low rotational velocites (v sin i< 10\kms), while HB stars and BSSs show a broad distribution, with values ranging from 0 to 70 \kms. For HB stars with T<10500 K there is a clear temperature-oxygen anti-correlation, that can be understood if the star position along the HB is mainly determined by the He content. The hottest BSSs and HB stars (with temperatures T>8200 K and T> 10500 K, respectively) also show significant deviations in their iron abundance with respect to the cluster metallicity (as traced by the unevolved stars, [Fe/H]=-2.12). While similar chemical patterns have been already observed in other hot HB stars, this is the first evidence ever collected for BSSs. We interprete these abundance anomalies as due to the metal radiative levitation, occurring in stars with shallow or no convective envelopes

Low-dose cyclophosphamide induces anti-tumor T-cell responses which associate with survival in metastatic colorectal cancer

Purpose: Anti-cancer T-cell responses can control tumors, but immune-suppressive mechanisms in vivo prevent their function. The role of regulatory T-cells (Tregs) in metastatic colorectal cancer (mCRC) is unclear. We have previously shown depletion of Tregs enhances CRC-specific effector T-cell responses. Low dose cyclophosphamide (CPM) targets Tregs in animal models and some human studies, however the effect of CPM in mCRC is unknown. Experimental Design: Fifty-five mCRC patients were enrolled onto a phase I/II trial and randomized to receive two week-long courses of low-dose (50mg twice-a-day) CPM or not. The absolute number, phenotype and anti-tumor function of peripheral blood-derived lymphocyte subsets were monitored throughout treatment, along with 18-month follow-up. Results: Initially CPM reduced proliferation in all lymphocyte subsets, however, a rapid mobilization of effector T-cells overcame this decrease, leading to increased absolute T-cell numbers. In contrast, a reduction in proportional and absolute Treg, B-cell and NK-cell numbers occurred. The expansion and subsequent activation of effector T-cells was focused on tumor-specific T-cells, producing both granzyme B and IFN-gamma. CPM-treated patients demonstrating the most enhanced IFN-gamma+ tumor-specific T-cell responses exhibited a significant delay in tumor progression (HR=0.29, 95% CI 0.12-0.69, P=0.0047), compared to non-responders and no-treatment controls. Conclusions: CPM-induced Treg-depletion is mirrored by a striking boost to anti-tumor immunity. This study provides the first direct evidence of the benefit of naturally primed T-cells in mCRC patients. Our results also support the concept that non-mutated self-antigens can act as useful targets for immunotherapies

Addition of the mammalian target of rapamycin inhibitor, Everolimus, to consolidation therapy in acute myeloid leukaemia: experience from the UK NCRI AML17 trial

As part of the UK NCRI AML17 trial, adult patients with acute myeloid leukemia in remission could be randomized to receive the mammalian target of rapamycin inhibitor everolimus, sequentially with post-induction chemotherapy. Three hundred and thirty-nine patients were randomised (2:1) to receive everolimus or not for a maximum of 84 days between chemotherapy courses. The primary endpoint was relapse-free survival. At 5 years there was no difference in relapse-free survival [29% versus 40%; odds ratio 1.19 (0.9-1.59) P=0.2], cumulative incidence of relapse [60% versus 54%: odds ratio 1.12 (0.82-1.52): P=0.5] or overall survival [45% versus 58%: odds ratio 1.3 (0.94-1.81): P=0.11]. The independent Data Monitoring Committee advised study termination after randomization of 339 of the intended 600 patients because of excess mortality in the everolimus arm without any evidence of beneficial disease control. The delivery of the everolimus dose was variable, but there was no evidence of clinical benefit in patients with adequate dose delivery compared with no treatment. This study suggests that the addition of mammalian target of rapamycin inhibition to chemotherapy provides no benefit

Evaluating drug treatments for Parkinson's disease: how good are the trials?

The prevalence of Parkinson's disease will increase as the population ages, making it important to identify reliably the most effective drug therapy Although many randomised controlled trials have evaluated the efficacy of different classes of drugs in both early and later Parkinson's disease, uncertainty about best treatment remains because of small numbers, inadequate follow up, and inappropriate end points Much larger trials are needed with long term follow up and end points of relevance to patients Large simple pragmatic trials have improved treatment of heart disease, stroke, and cancer and their methods should be applied to Parkinson's disease and other neurodegenerative disease