18,709 research outputs found
Volatility post Black Monday, myth or reality?
No full textPopular opinion argues that since the crash of 1987 markets worldwide have become increasingly volatile. Steve Thomas and Ray O'Brien approach the topic using different empirical data, with surprising results
Other title: Trial brief of intervenor plaintiffs Senator Jeff King, Senator Steve Abrams and Senator Ray Merrick.
No full textThis document is part of a collection of publications provided for information on Redistricting in Kansas.; application/pdf"Come Now Plaintiff Intervenors Senator Jeff King, Senator Steve Abrams, and Senator Ray Merrick, by and through counsel of record, and state that the senatorial map For the People 13(b) best satisfies federal and state constitutional, statutory requisites and guidelines issued by the Kansas legislature for senatorial redistricting.
Interactive ray shading of FRep objects
No full textIn this paper we present a method for interactive rendering general procedurally defined functionally represented (FRep) objects using the acceleration with graphics hardware, namely Graphics Processing Units (GPU). We obtain interactive rates by using GPU acceleration for all computations in rendering algorithm, such as ray-surface intersection, function evaluation and normal computations. We compute primary rays as well as secondary rays for shadows, reflection and refraction for obtaining high quality of the output visualization and further extension to ray-tracing of FRep objects. The algorithm is well-suited for modern GPUs and provides acceptable interactive rates with good quality of the results. A wide range of objects can be rendered including traditional skeletal implicit surfaces, constructive solids, and purely procedural objects such as 3D fractals
Magnetic X-ray Reflectivity
No full textThe scope of the thesis is to demonstrate the feasibility to examine magnetization profiles of
thin films and multilayer systems via magnetic soft and hard x-ray reflectivity. The focus here
is on 3d transition metals, which are used mainly for development of numerous noval magnetic
devices, that are both technologically and scientifically interesting. Complementary to Neutron
diffraction, which is the standard tool for the examination of magnetic structures in matter,
magnetic x-ray diffraction permits to study small samples and exhibits better Qz-resolution due
its small and only slightly divergent beam. The biggest advantage is its element specificity,
which enables one to probe different magnetic sites separately. The method of magnetic x-ray
reflectivity combines the strong magnetic circular dichroism (MCD) effect, significantly
enhancing the magnetic sensitivity of x-rays, with the technique of conventional specular
reflectivity, a well established tool for the structural studies of the chemical makeup of thin
films and artificial multilayer systems. The theory of resonant magnetic scattering within
dipole approximation combined with the specular reflectivity condition suggests that the
strongest effects are in the lower incident angle regime using circularly polarized x-rays. By
using soft and hard x-rays structures on a scale of a few to several hundreds of Å are probed,
which is the dimensions of the thicknesses of the layers of most thin film and multilayers
systems.
In order to retrieve quantitative information from the measured magnetic reflectivity curves, an
approach for visible light magneto-optical effects based on known dielectric tensors of the
sample has been adopted and applied for soft and hard x-ray resonant scattering. Sample
absorption and polarization changes in the sample are accounted for. Besides the structural
composition, the thickness of the individual layers and the index of refraction, also the
magnetic spin configuration can be chosen with arbitrary moment direction and magnitude by
modifying the off-diagonal terms in the dielectric tensor. The magnetic optical constants,
which determine the magnitude of the magnetic moments, are experimentally determined via
MCD absorption measurements and then retrieving the real part through the Kramers-Kronig
transformation of the measured imaginary part. This is shown in this work for several 3d
transition metals and edges. The simulations are sensitive to a variety of different spin
configurations: spiral spin structures, magnetic dead layers and of collinear alignment.
Experimentally the magnetic reflectivity of 3d transition metals has to distinguish between the
two available possible absorbtion edges, L and K, lying in different x-ray regions. The L-edges
are situated in the soft x-ray region and exhibit large enhancements of the magnetic cross
section, while the K-edges lie in the hard x-ray regime and show much smaller effects. In spite
of this handicap, the latter can be important due to the much larger penetration depth and better
Qz-resolution. The X13 beamline at the NSLS at Brookhaven National Laboratory consisting
of two branches for soft and hard-x ray operations, respectively, uses an elliptical polarized
wiggler (EPW), which produces circularly polarized x-rays in the orbit plane and allows fast
switching between left and right circular polarization. Lock-in detection is used to improve the
signal-to-noise ratio at the soft x-ray branch and single photon detection at the hard x-ray
branch to measure the magnetic signal. The EPW and the experimental setup was
commissioned to demonstrate the feasibility of magnetic x-ray experiments. Especially at the
hard x-ray beamline branch the small magnetic effects, less than 0.1% of the charge scattering,
were possible to detect. In order to satisfy the need for high flux the CMC-CAT beamline at the
APS in Argonne was used for magnetic hard x-ray reflectivity, providing an undulator
beamline where the high flux of linear polarized photons was converted into circular
polarization via a diamond phase plate, delivering much higher flux and better circular
polarization.
The sample used to demonstrate the feasibility of the method of magnetic reflectivity consists
of two multilayer structures of Fe/Cr on top of each other, where the iron spins of the upper are
ferromagnetically and of the lower antiferromagnetically coupled, representing an exchange
bias system. The sample was characterized with conventional x-ray reflectivity and MOKE
measurements in order to accurately determine the structural composition and magnetic
configuration (hysteresis loops), respectively. Magnetic reflectivity experiments on the L-edges
at the X13A beamline showed strong magnetic effects, which could be clearly identified as
ferromagnetic and antiferromagnetic Bragg peak contributions and simulation confirmed the
collinear alignment and full magnetization of the iron spins throughout the iron layers. Energyand
magnetic field dependent measurements complete the picture. By tuning the x-ray energy
to the chromium L-edge, a signal 20 times weaker compared with iron, demonstrates that the
weak magnetic moment in the chromium layers could be detected. Especially the AFM
contribution shows strong effects which could be qualitatively and quantitatively evaluated.
Simulation show clearly that the magnetic moment is concentrated at the interfaces and could
be approximated to a magnetic layer with an effective thickness of about 0.5 Å assuming a step
function in the magnetization profile.
Soft x-ray data usually suffer from strong absorption and the limited Qz-range and resolution
and therefore the use of hard x-rays seems desirable to probe the whole sample. Magnetic hard
x-ray reflectivity measurements on the Fe/Cr double multilayer carried out at the CMC
beamline by switching the magnetic field on the sample show clear magnetic Bragg reflection
at the ferromagnetic structural peaks. They are very well reproduced by simulations and thus
confirm the collinear alignment of the iron spins. In order to probe the AFM spin configuration
the helicity of the photon beam has to be switched with constant magnetic field. In spite of
complications in the reflectivity spectra it was possible to extract the relative orientation of the
AFM to FM spin configuration in the two multilayers.
In summary the work showed for the example of an Fe/Cr double multilayer that magnetic soft
and hard x-ray reflectivity can be applied to retrieve information about the magnetization
profile of thin magnetic films and multilayer, and can compliment polarized neutron scattering
Greetings Music Lovers
No full textThe premiere of Steve Urquhart's new audio documentary exploring the life and work of BBC Radio Lancashire broadcaster and Wire contributor Steve Barker.
May 2018 sees veteran Wire writer and dub/roots columnist Steve Barker celebrate 40 years at BBC Radio Lancashire, where his legendary freeform show On The Wire continues to promote underground and new music every Saturday night at midnight. This special audio portrait charts Steve’s influential (and occasionally turbulent) four decades on air. On The Wire was among the first to interview The Smiths and Depeche Mode; it played 808 State’s “Pacific State” and A Guy Called Gerald’s “Voodoo Ray” before anyone else; it even staged a free Fall gig at Clitheroe Castle. It’s been threatened by BBC cuts – twice – and both times saved with the help of its fiercely loyal listeners across Lancashire and worldwide.
Made by Steve Urquhart – producer of the recent BBC Radio 3 feature A Portrait Of Val Wilmer, chronicling another renowned Wire contributor – Greetings Music Lover features rare archive material plus new interviews from On-U Sound’s Adrian Sherwood, Lee ‘Scratch’ Perry, David Rodigan, Stuart Maconie, The Wire’s Tony Herrington and Derek Walmsley, plus various contributors to On The Wire over the years, and Steve Barker himself
[Letter from Alex Bradford to Lieutenant and Mrs. Ray Starner - November 4, 1940]
No full textLetter from Alex Bradford to Lieutenant and Mrs. Ray Starner describing the the current state of affairs that the author was experiencing, including: the London blitz, the moral of the troops on the ground, and the collective company of men opposing the Nazi regime
Cadastral survey crew, Ray Hancey, Val Schultz, and Steve Dodds
No full textCadastral survey crew, Ray Hancey, Val Schultz, and Steve Dodds
The student's guide to completing an author study
No full textThe 'Student's guide to completing an author study' emerged during the early development of the school library resource center program at Glen Stewart Elementary School in Stratford Canada on Prince Edward Island. This research process centered on an author study, with direct teaching and clear assignment. The resulting model has been adapted to various grade levels and subject areas in different schools.Source type: Electronic(1)http://proquest.umi.com/pqdweb?did=49237063&Fmt=7&clientId=65345&RQT=309&VName=PQ
Active X-ray optics for the next generation of X-ray space telescopes
No full textDescribed within is the design, manufacture, metrology and X-ray testing of an active X-ray
prototype intended for the next generation of X-ray telescopes. One of the challenges faced by
the X-ray telescope community is how to combine high resolution and high sensitivity into one
system, as weight limitations place constraints on the optics that can be launched. Therefore the
mandate of the active X-ray prototype is to provide high sensitivity through the ability of the optics
to be nested and to deliver high angular resolution through the active control of the optic’s form.
Piezoelectric unimorph actuators provide the active component: it is intended that they will correct
for figure errors within the optic and therefore increase the angular resolution capability.
The prototype’s design is based upon an ellipsoidal segment which provides point-to-point
focussing of an X-ray source. The prototype itself is composed of an electroformed nickel optic
where the non-reflective surface is populated with 30 piezoelectric actuators and it is the production
of the prototype that is the core of the presented research. Metrology of the actuators’ influence
functions is presented and highlight the prototype’s ability to deform its optic surface by microns.
In addition, the measured influence functions are compared against finite element models and a
distinct similarity between the functions is observed.
The prototype was tested at an X-ray beamline facility in November 2008 and the results
showed the prototype’s ability to correct the optic to achieve an improved angular resolution: from
0.786 arc-minutes to 0.686 arc-minutes in terms of full width half maximum. Finally, difficulties
in the manufacture of the prototype and X-ray testing shall be presented alongside future work in
conclusion to this thesis
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