30,292 research outputs found
Spheromak Experiment Using Separate Guns For Formation And Sustainment
An experiment is described that incorporates the use of separate magnetized plasma guns for formation and sustainment of a spheromak. It is shown that energy coupling efficiency approaches unity if the gun and spheromak are of comparable size. A large gun should be able to operate at lower current and therefore lower voltage. In addition, it is expected that a gun matched to the size of the spheromak will cause less perturbation to the equilibrium. It is proposed to use a smaller gun for spheromak formation and a large, efficient gun for sustainment. The theoretical basis for the experiment is developed, and the details of the experiment are described. A prediction of the equilibrium magnetic flux surfaces using the EFIT code is presented
PRICE VERSUS QUOTA REDUCTIONS: U.S. FLUE-CURED TOBACCO POLICY
Declining domestic cigarette consumption, increased global competition, and loss of import restrictions indicate decreased demand for U.S. flue-cured tobacco. The effects of 10% declines in domestic and export demand are evaluated under a policy of reducing quota to maintain price versus a policy of allowing price to fall to maintain quota. Changes in prices, quantities, revenues, and economic rents are simulated. Losses to nonfarming quota owners are minimized under a policy of price maintenance, while losses in revenues to tobacco-producing areas are minimized by a policy of quota maintenance. Aggregate losses to tobacco growers are greater under a policy of quota maintenance.Flue-cured, Policy, Price reduction, Quota, Tobacco, Agricultural and Food Policy,
The role and effects of teaching assistants in English primary schools (Years 4 to 6) 2000-2003. Results from the Class Size and Pupil-Adult Ratios (CSPAR) KS2 Project
It is widely assumed that increasing the number of Teaching Assistants (TAs) in the classroom will be beneficial to children, and this is one important aim of the recently implemented Workforce Agreement. But there are still significant gaps in knowledge about many aspects of their deployment and impact. The Class Size and Pupil-Adult Ratio (CSPAR) KS2 study built on earlier findings when the pupils were in reception and KS1 and investigated: 1. the deployment of TAs in classrooms and how key parties involved perceived this; 2. the effect of TAs on interactions involving pupils and teachers in the same classrooms, and on pupil attainments. The study had a longitudinal, mixed method and multi-informant design. There were 202 schools, 332 classes and 8728 pupils in Y4. Methods of data collection included: for the whole sample) questionnaires completed by TAs, teachers and head teachers, assessments of pupil attainments in mathematics, English and science, data on pupil background, and (for a sub-sample) case studies and a systematic observation study. This study found that the TA’s role in KS2 is predominantly a direct one, in the sense of face-to-face interactions supporting certain pupils. There was no evidence that the presence of TAs, or any characteristic of TAs, had a measurable effect on pupil attainment. However, results were clear in showing that TAs had an indirect effect on teaching, e.g., pupils had a more active form of interaction with the teacher and there was more individualised teacher attention. This supported teachers’ views that TAs are effective in supporting them in this way. We conclude that more attention needs to be paid to what we call the pedagogical role of TAs so that they can be used effectively to help teachers and pupils, particularly in the context of the enhanced roles for TAs being introduced as part of the Government’s remodeling agenda
Texas Natural Resources Inventory and Monitoring System (TNRIMS), Applications System Verification and Transfer (ASVT), Remote Sensing Information Subsystem (RSIS): Acceptance test procedures
There are no author-identified significant results in this report
Stars that Move Together Were Born Together
It is challenging to reliably identify stars that were born together outside
of actively star-forming regions and bound stellar systems. However, co-natal
stars should be present throughout the Galaxy, and their demographics can shed
light on the clustered nature of star formation and the dynamical state of the
disk. In previous work we presented a set of simulations of the Galactic disk
that followed the clustered formation and dynamical evolution of 4 billion
individual stars over the last 5 Gyr. The simulations predict that a high
fraction of co-moving stars with physical and 3D velocity separation of pc and km s are co-natal. In this
\textit{Letter}, we use \textit{Gaia} DR2 and LAMOST DR4 data to identify and
study co-moving pairs. We find that the distribution of relative velocities and
separations of pairs in the data is in good agreement with the predictions from
the simulation. We identify 111 co-moving pairs in the Solar neighborhood with
reliable astrometric and spectroscopic measurements. These pairs show a strong
preference for having similar metallicities when compared to random field
pairs. We therefore conclude that these pairs were very likely born together.
The simulations predict that co-natal pairs originate preferentially from
high-mass and relatively young ( Gyr) star clusters. \textit{Gaia} will
eventually deliver well-determined metallicities for the brightest stars,
enabling the identification of thousands of co-natal pairs due to disrupting
star clusters in the solar neighborhood.Comment: 6 pages, 4 figures, 1 table. Submitted to ApJL. Catalog here:
http://harshilkamdar.github.io/2019/04/03/pairs.htm
The Impact of Rotation on the Evolution of Low-Mass Stars
High precision photometry and spectroscopy of low-mass stars reveal a variety
of properties standard stellar evolution cannot predict. Rotation, an essential
ingredient of stellar evolution, is a step towards resolving the discrepancy
between model predictions and observations. The first rotating stellar model,
continuously tracing a low-mass star from the pre-main sequence onto the
horizontal branch, is presented. The predicted luminosity functions of globular
clusters and surface rotation velocities on the horizontal branch are
discussed.Comment: 5 pages, 6 figures, to be published in the Proceedings of the
Conference 'Unsolved Problems in Stellar Physics', Cambridge, 2-6 July 200
3D Monte Carlo radiation transfer modelling of photodynamic therapy
We acknowledge the support of the UK Engineering and Physics Sciences Research Council (EPSRC) for funding through a studentship for C L Campbell as well as the Alfred Stewart Trust.The effects of ageing and skin type on Photodynamic Therapy (PDT) for different treatment methods have been theoretically investigated. A multilayered Monte Carlo Radiation Transfer model is presented where both daylight activated PDT and conventional PDT are compared. It was found that light penetrates deeper through older skin with a lighter complexion, which translates into a deeper effective treatment depth. The effect of ageing was found to be larger for darker skin types. The investigation further strengthens the usage of daylight as a potential light source for PDT where effective treatment depths of about 2 mm can be achieved.Publisher PD
Antikaon Production in Proton-Nucleus Reactions and the properties in nuclear matter
We calculate the momentum-dependent potentials for and mesons in
a dispersion approach at nuclear density using the information from
the vacuum and scattering amplitudes, however, leaving out the
resonance contributions for the in-medium analysis. Whereas the potential
is found to be repulsive ( + 30 MeV) and to show only a moderate
momentum dependence, the selfenergy at normal nuclear matter density
turns out to be - 200 MeV at zero momentum in line with kaon atomic
data, however, decreases rapidly in magnitude for higher momenta. The antikaon
production in p + A reactions is calculated within a coupled transport approach
and compared to the data at KEK including different assumptions for the
antikaon potentials. Furthermore, detailed predictions are made for and reactions at 2.5 GeV in order to determine the
momentum dependent antikaon potential experimentally.Comment: 27 pages, LaTeX, including 14 ps-figures, UGI-98-1
The Weak Clustering of Gas-Rich Galaxies
We examine the clustering properties of HI-selected galaxies through an
analysis of the HI Parkes All-Sky Survey Catalogue (HICAT) two-point
correlation function. Various sub-samples are extracted from this catalogue to
study the overall clustering of HI-rich galaxies and its dependence on
luminosity, HI gas mass and rotational velocity. These samples cover the entire
southern sky Dec < 0 deg, containing up to 4,174 galaxies over the radial
velocity range 300-12,700 km/s. A scale length of r_0 = 3.45 +/- 0.25 Mpc/h and
slope of gamma = 1.47 +/- 0.08 is obtained for the HI-rich galaxy real-space
correlation function, making gas-rich galaxies among the most weakly clustered
objects known. HI-selected galaxies also exhibit weaker clustering than
optically selected galaxies of comparable luminosities. Good agreement is found
between our results and those of synthetic HI-rich galaxy catalogues generated
from the Millennium Run CDM simulation. Bisecting HICAT using different
parameter cuts, clustering is found to depend most strongly on rotational
velocity and luminosity, while the dependency on HI mass is marginal. Splitting
the sample around v_rot = 108 km/s, a scale length of r_0 = 2.86 +/- 0.46 Mpc/h
is found for galaxies with low rotational velocities compared to r_0 = 3.96 +/-
0.33 Mpc/h for the high rotational velocity sample.Comment: Accepted for publication in the Astrophysical Journa
- …