18,343 research outputs found
Kidson's relation between sunspot number and the movement of high pressure systems in Australia
Kidson's relation is briefly described. It is concluded that if a relation is found between sunspots and weather, it is likely to appear in the march of high and low pressure systems around the poles
Analyticity of the SRB measure for a class of simple Anosov flows
We consider perturbations of the Hamiltonian flow associated with the
geodesic flow on a surface of constant negative curvature. We prove that, under
a small perturbation, not necessarely of Hamiltonian character, the SRB measure
associated to the flow exists and is analytic in the strength of the
perturbation. An explicit example of "thermostatted" dissipative dynamics is
constructed.Comment: 23 pages, corrected typo
Using Charge Asymmetries to Measure Single Top Quark Production at the LHC
Electroweak production of single top quarks is an as-yet-unverified
prediction of the Standard model, potentially sensitive to new physics. Two of
the single top quark productions channels have significant charge asymmetries
at the LHC, while the much larger background from is nearly
charge-symmetric. This can be used to reduce systematic uncertainties and make
precision measurements of single top quark production.Comment: 4 pages, 1 figur
The Relation between Approximation in Distribution and Shadowing in Molecular Dynamics
Molecular dynamics refers to the computer simulation of a material at the
atomic level. An open problem in numerical analysis is to explain the apparent
reliability of molecular dynamics simulations. The difficulty is that
individual trajectories computed in molecular dynamics are accurate for only
short time intervals, whereas apparently reliable information can be extracted
from very long-time simulations. It has been conjectured that long molecular
dynamics trajectories have low-dimensional statistical features that accurately
approximate those of the original system. Another conjecture is that numerical
trajectories satisfy the shadowing property: that they are close over long time
intervals to exact trajectories but with different initial conditions. We prove
that these two views are actually equivalent to each other, after we suitably
modify the concept of shadowing. A key ingredient of our result is a general
theorem that allows us to take random elements of a metric space that are close
in distribution and embed them in the same probability space so that they are
close in a strong sense. This result is similar to the Strassen-Dudley Theorem
except that a mapping is provided between the two random elements. Our results
on shadowing are motivated by molecular dynamics but apply to the approximation
of any dynamical system when initial conditions are selected according to a
probability measure.Comment: 21 pages, final version accepted in SIAM Dyn Sy
Direct observation of a highly spin-polarized organic spinterface at room temperature
The design of large-scale electronic circuits that are entirely
spintronics-driven requires a current source that is highly spin-polarised at
and beyond room temperature, cheap to build, efficient at the nanoscale and
straightforward to integrate with semiconductors. Yet despite research within
several subfields spanning nearly two decades, this key building block is still
lacking. We experimentally and theoretically show how the interface between Co
and phthalocyanine molecules constitutes a promising candidate. Spin-polarised
direct and inverse photoemission experiments reveal a high degree of spin
polarisation at room temperature at this interface. We measured a magnetic
moment on the molecules's nitrogen pi orbitals, which substantiates an
ab-initio theoretical description of highly spin-polarised charge conduction
across the interface due to differing spinterface formation mechanims in each
spin channel. We propose, through this example, a recipe to engineer simple
organic-inorganic interfaces with remarkable spintronic properties that can
endure well above room temperature
Institutionalizing health impact assessment in London as a public health tool for increasing synergy between policies in other areas
Objectives: To describe the background to the inclusion of health impact assessment (HIA) in the development process for the London mayoral strategies, the HIA processes developed, how these evolved, and the role of HIA in identifying synergies between and conflicting priorities of different strategies.Study design: Case series.Methods: Early HIAs had just a few weeks for the whole HIA process. A rapid appraisal approach was developed. Stages included: scoping, reviewing published evidence, a stakeholder workshop, drafting a report, review of the report by the London Health Commission, and submission of the final report to the Mayor. The process evolved as more assessments were conducted. More recently, an integrated impact assessment (IIA) method has been developed that fuses the key aspects of this HIA method with sustainability assessment, strategic environmental assessment and equalities assessment.Results: Whilst some of the early strategy drafts encompassed some elements of health, health was not a priority. Conducting HIAs was important both to ensure that the strategies reflected health concerns and to raise awareness about health and its determinants within the Greater London Authority (GLA). HIA recommendations were useful for identifying synergies and conflicts between strategies. HIA can be successfully integrated into other impact assessment processes.Conclusions: The HIAs ensured that health became more integral to the strategies and increased understanding of determinants of health and how the GLA impacts on health and health inequalities. Inclusion of HIA within IIA ensures that health and health inequalities impacts are considered robustly within statutory impact assessments. (C) 2010 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved
Ion yields and erosion rates for Si1−xGex(0x1) ultralow energy O2+ secondary ion mass spectrometry in the energy range of 0.25–1 keV
We report the SIMS parameters required for the quantitative analysis of Si1−xGex across the range of 0 ≤ x ≤ 1 when using low energy O2+ primary ions at normal incidence. These include the silicon and germanium secondary ion yield [i.e., the measured ion signal (ions/s)] and erosion rate [i.e., the speed at which the material sputters (nm/min)] as a function of x. We show that the ratio Rx of erosion rates, Si1−xGex/Si, at a given x is almost independent of beam energy, implying that the properties of the altered layer are dominated by the interaction of oxygen with silicon. Rx shows an exponential dependence on x. Unsurprisingly, the silicon and germanium secondary ion yields are found to depart somewhat from proportionality to (1−x) and x, respectively, although an approximate linear relationship could be used for quantification across around 30% of the range of x (i.e., a reference material containing Ge fraction x would give reasonably accurate quantification across the range of ±0.15x). Direct comparison of the useful (ion) yields [i.e., the ratio of ion yield to the total number of atoms sputtered for a particular species (ions/atom)] and the sputter yields [i.e., the total number of atoms sputtered per incident primary ion (atoms/ions)] reveals a moderate matrix effect where the former decrease monotonically with increasing x except at the lowest beam energy investigated (250 eV). Here, the useful yield of Ge is found to be invariant with x. At 250 eV, the germanium ion and sputter yields are proportional to x for all x
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