51,617 research outputs found
X ray microscope/telescope test and alignment
The tasks performed by the Center for Applied Optics (CAO) in support of the Normal Incidence Multilayer X-Ray Optics Program are detailed. The Multi-Spectral Solar Telescope Array (MSSTA) was launched on a Terrier-boosted Black Brant sounding rocket from White Sands Missile Range on 13 May 1991. High resolution images of the sun in the soft x ray to extreme ultraviolet (EUV) regime were obtained with normal-incidence Cassegrain, Ritchey-Chretien, and Herschelian telescopes mounted in the sounding rocket. MSSTA represents the first use of multilayer optics to study a very broad range of x ray and EUV solar emissions. Energy-selective properties of multilayer-coated optics allow distinct groups of emission lines to be isolated in the solar corona and transition region. Features of the near and far coronal structures including magnetic loops of plasmas, coronal plumes, coronal holes, faint structures, and cool prominences are visible in these images. MSSTA successfully obtained unprecedented information regarding the structure and dynamics of the solar atmosphere in the temperature range of 10(exp 4)-10(exp 7) K. The performance of the MSSTA has demonstrated a unique combination of ultra-high spatial resolution and spectral differentiation by use of multilayer optics
Electromagnetic Polarizabilities: Lattice QCD in Background Fields
Chiral perturbation theory makes definitive predictions for the extrinsic
behavior of hadrons in external electric and magnetic fields. Near the chiral
limit, the electric and magnetic polarizabilities of pions, kaons, and nucleons
are determined in terms of a few well-known parameters. In this limit, hadrons
become quantum mechanically diffuse as polarizabilities scale with the inverse
square-root of the quark mass. In some cases, however, such predictions from
chiral perturbation theory have not compared well with experimental data.
Ultimately we must turn to first principles numerical simulations of QCD to
determine properties of hadrons, and confront the predictions of chiral
perturbation theory. To address the electromagnetic polarizabilities, we
utilize the background field technique. Restricting our attention to
calculations in background electric fields, we demonstrate new techniques to
determine electric polarizabilities and baryon magnetic moments for both
charged and neutral states. As we can study the quark mass dependence of
observables with lattice QCD, the lattice will provide a crucial test of our
understanding of low-energy QCD, which will be timely in light of ongoing
experiments, such as at COMPASS and HI\gamma S.Comment: 3 pages, talk given by B. C. Tiburzi at PANIC 201
The numerical evaluation of the maximum-likelihood estimate of a subset of mixture proportions
Necessary and sufficient conditions are given for a maximum likelihood estimate of a subset of mixture proportions. From these conditions, likelihood equations are derived satisfied by the maximum-likelihood estimate and a successive-approximations procedure is discussed as suggested by equations for numerically evaluating the maximum-likelihood estimate. It is shown that, with probability one for large samples, this procedure converges locally to the maximum-likelihood estimate whenever a certain step-size lies between zero and two. Furthermore, optimal rates of local convergence are obtained for a step-size which is bounded below by a number between one and two
An iterative procedure for obtaining maximum-likelihood estimates of the parameters for a mixture of normal distributions
A general iterative procedure is given for determining the consistent maximum likelihood estimates of normal distributions. In addition, a local maximum of the log-likelihood function, Newtons's method, a method of scoring, and modifications of these procedures are discussed
An iterative procedure for obtaining maximum-likelihood estimates of the parameters for a mixture of normal distributions, Addendum
New results and insights concerning a previously published iterative procedure for obtaining maximum-likelihood estimates of the parameters for a mixture of normal distributions were discussed. It was shown that the procedure converges locally to the consistent maximum likelihood estimate as long as a specified parameter is bounded between two limits. Bound values were given to yield optimal local convergence
Contribution to the extragalactic X-ray background from clusters of galaxies
The contribution to the extragalactic background from clusters of galaxies in the 2-6 keV band was computed. Two different cluster luminosity functions and two different models for cluster evolution were considered and a cluster X-ray luminosity-temperature relationship of the type L alpha T sup alpha +1/2 was assumed. It is found that the overall contribution of clusters to the background is approximately 10% of the total observed X-ray extragalactic approximately 150 eV is superimposed on the observed background. This result is quite insensitive to the different set of assumptions made in the calculation
National counter-terrorism (C-T) policies and challenges to human rights and civil liberties: Case study of United Kingdom
In the UK the rise post-2005 in “home-grown” terrorism, relying to a significant extent on strikes on soft targets by “self-starters,” means that the search for effective preventive measures remains a continuing concern. Below a number of the preventive counter-terror measures adopted post-9/11, and incrementally strengthened in response to the current threat, are found to fall into three categories and represent interventions at the stages in the path toward attacks. This chapter focuses on selected examples of these preventive measures. In terms of three key stages, firstly, there is the attempt to prevent radicalization, under the “Prevent” strategy. A second strategy relies on taking certain measures to control the activities of those considered likely – on the balance of probabilities – to engage in terrorist-related activity. A third preventive strategy relies on the special terrorism offences under the Terrorism Acts 2000 and 2006, as amended, intended to allow for intervention at a very early stage in terrorist plots and in preparing or instigating terrorist acts (“precursor” offences)
Extracting Electric Polarizabilities from Lattice QCD
Charged and neutral, pion and kaon electric polarizabilities are extracted
from lattice QCD using an ensemble of anisotropic gauge configurations with
dynamical clover fermions. We utilize classical background fields to access the
polarizabilities from two-point correlation functions. Uniform background
fields are achieved by quantizing the electric field strength with the proper
treatment of boundary flux. These external fields, however, are implemented
only in the valence quark sector. A novel method to extract charge particle
polarizabilities is successfully demonstrated for the first time.Comment: 17 pages, 6 figures, a few clarifications added, published versio
Pathways to apprenticeships and traineeships for people from culturally and linguistically diverse backgrounds
Western Australia is experiencing a substantial shortage of skilled labour.
The State Government is committed to increasing participation in the workforce across the board, through schemes such as the Plans 4 Jobs, especially because of the current severe skills shortage in the economy.
The State Government is also committed, through the four principles of civic values, fairness, equality, and participation enshrined in the WA Charter of Multiculturalism, to promoting the full participation of all groups in all aspects of our community – social, economic, and civil – and to removing any systemic barriers to full participation. This commitment is also embodied in the multi‐departmental Policy Framework for Substantive Equality.
Aside from equity, denying equal opportunity also engenders resentment and hostility within our community, diminishes human value, and denies the state the full benefits of all its members’ talents. The cost of discrimination accrues to those who are denied opportunity and to the society which tolerates discrimination.
Members of Culturally and Linguistically Diverse (CaLD) communities in this state, in particular those from new and emerging communities, do not currently participate in apprenticeships and traineeships in significant numbers; this is regrettable and it is recommended that measures be taken to remedy this.
The Western Australian Department of Education and Training (DET) commissioned this report to investigate barriers to apprenticeships and traineeships confronting people from CaLD backgrounds, and to recommend strategies to improve their participation in apprenticeships and traineeships. The project was undertaken by the Australian Academy of Race Relations (AARR) at Murdoch University, for DET, during the period July – November 2005.
DET has many good programmes to promote apprenticeships and traineeships, including to members of CaLD communities. However, the array and complexity of these can be daunting, resulting in a lack of awareness of all the programmes available
The relative abundance of neon and magnesium in the solar corona
A technique is proposed for specifically determining the relative solar coronal abundance of neon and magnesium. The relative abundance is calculated directly from the relative intensity of the resonance lines of Ne X (12.134A) and Mg XI (9.169A) without the need for the development of a detailed model of the thermal structure of the corona. Moderate resolution Bragg crystal spectrometer results from the OVI-10 satellite were used to determine a coronal neon to magnesium relative abundance of 1.47 + or - 0.38. The application of this technique to a recent higher resolution rocket observation gave an abundance ratio of approximately 0.93 + or - 0.15
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