56,348 research outputs found
The Theory of SNOM: A Novel Approach
In this paper we consider the application of electromagnetic theory to the
analysis of the Scanning Near-field Optical Microscope (SNOM) in order to
predict experimentally observable quantities such as the transmission or
reflection coefficients for a particular tip-surface configuration. In
particular we present the first application of a transfer matrix based
calculation to this challenging problem by using an adaptive co-ordinate
transformation to accurately model the shape of the SNOM tip.
We also investigate the possibility of increasing the transmitted light
through the SNOM tip by introducing a metal wire into the centre of the tip.
This converts the tip into a co-axial cable. We show that, in principle, this
can dramatically improve the transmission characteristics without having a
detrimental effect on the resolution.Comment: 19 pages, 11 figures. To be published in the Journal of Modern Optic
On the real zeroes of the Hurwitz zeta-function and Bernoulli polynomials
The behaviour of real zeroes of the Hurwitz zeta function is investigated. It is
shown that has no real zeroes in the region for large negative
. In the region the zeroes are
asymptotically located at the lines with integer . If
is the number of real zeroes of with given then
As a corollary we have a
simple proof of Inkeri's result that the number of real roots of the classical
Bernoulli polynomials for large is asymptotically equal to
.Comment: 9 pages, 2 figure
Replacement of fluid-filter elements without interruption of flow
Gatling-type filter assembly, preloaded with several filter elements enables filter replacement without breaking into the operative fluid system. When the filter element becomes contaminated, a unit inner subassembly is rotated 60 degrees to position a clean filter in the line
Pedestrian demand modelling of large cities: an applied example from London
This paper introduces a methodology for the development of city wide pedestrian demand models and shows its application to London. The approach used for modelling is Multiple Regression Analysis of independent variables against the dependent variable of observed pedestrian flows. The test samples were from manual observation studies of average total pedestrian flow per hour on 237 sample sites. The model will provide predicted flow values for all 7,526 street segments in the 25 square kilometres of Central London. It has been independently validated by Transport for London and is being tested against further observation data. The longer term aim is to extend the model to the entire greater London area and to incorporate additional policy levers for use as a transport planning and evaluation tool
Promoting Public Health In The Context Of The “Obesity Epidemic”: False Starts And Promising New Directions
In the battle to combat obesity rates in the United States, several misconceptions have dominated policy initiatives. We address those misconceptions, including the notion that restrictive diets lead to long-term weight loss, that stigmatizing obesity is an effective strategy for promoting weight reduction, and that weight and physical health should be considered synonymous with one another. In offering correctives to each of these points, we draw on psychological science to suggest new policies that could be enacted at both the local and national levels. Instead of policies that rely solely on individual willpower, which is susceptible to failure, we recommend those that make use of environmental changes to reduce the amount of willpower necessary to achieve healthy behavior. Ultimately, the most effective policies will promote health rather than any arbitrary level of weight
In search for a perfect shape of polyhedra: Buffon transformation
For an arbitrary polygon consider a new one by joining the centres of
consecutive edges. Iteration of this procedure leads to a shape which is affine
equivalent to a regular polygon. This regularisation effect is usually ascribed
to Count Buffon (1707-1788). We discuss a natural analogue of this procedure
for 3-dimensional polyhedra, which leads to a new notion of affine -regular
polyhedra. The main result is the proof of existence of star-shaped affine
-regular polyhedra with prescribed combinatorial structure, under partial
symmetry and simpliciality assumptions. The proof is based on deep results from
spectral graph theory due to Colin de Verdiere and Lovasz.Comment: Slightly revised version with added example of pentakis dodecahedro
Taking A Stand: The Effects Of Standing Desks On Task Performance And Engagement
Time spent sitting is associated with negative health outcomes, motivating some individuals to adopt standing desk workstations. This study represents the first investigation of the effects of standing desk use on reading comprehension and creativity. In a counterbalanced, within-subjects design, 96 participants completed reading comprehension and creativity tasks while both sitting and standing. Participants self-reported their mood during the tasks and also responded to measures of expended effort and task difficulty. In addition, participants indicated whether they expected that they would perform better on work-relevant tasks while sitting or standing. Despite participants’ beliefs that they would perform worse on most tasks while standing, body position did not affect reading comprehension or creativity performance, nor did it affect perceptions of effort or difficulty. Mood was also unaffected by position, with a few exceptions: Participants exhibited greater task engagement (i.e., interest, enthusiasm, and alertness) and less comfort while standing rather than sitting. In sum, performance and psychological experience as related to task completion were nearly entirely uninfluenced by acute (~30-min) standing desk use. View Full-Tex
Holographic photography of high velocity particles
Fourier transform hologram camera increases the velocity range for holography by a factor of 10 to 1000. Two different optical systems, using a triangular arrangement of beam splitters and a mirror to illuminate the object from two directions, are investigated
ROSAT observations of the dwarf starforming galaxy Holmerg II (UGC 4305)
We present ROSAT PSPC and HRI observations of the dwarf irregular galaxy
Holmberg II (UGC4305). This is one of the most luminous dwarf galaxies (Lx~
10^{40} erg s^{-1} cm^{-2}) detected in the ROSAT All-Sky Survey. The X-ray
emission comes from a single unresolved point source, coincident with a large
HII region which emits intense radio emission. The source is variable on both
year and day timescales, clearly favouring accretion into a compact object
rather than a supernova remnant or a superbubble interpretation for the origin
of the X-ray emission. However, its X-ray spectrum is well-fit by a a
Raymond-Smith spectrum with kT~0.8 keV, lower than the temperature of X-ray
binaries in nearby spiral galaxies.Comment: Accepted for publication in MNRA
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