14,525 research outputs found
Far-field optical microscope with nanometer-scale resolution based on in-plane surface plasmon imaging
A new far-field optical microscopy technique capable of reaching
nanometer-scale resolution has been developed recently using the in-plane image
magnification by surface plasmon polaritons. This microscopy is based on the
optical properties of a metal-dielectric interface that may, in principle,
provide extremely large values of the effective refractive index n up to
100-1000 as seen by the surface plasmons. Thus, the theoretical diffraction
limit on resolution becomes lambda/2n, and falls into the nanometer-scale
range. The experimental realization of the microscope has demonstrated the
optical resolution better than 50 nm for 502 nm illumination wavelength.
However, the theory of such surface plasmon-based far-field microscope
presented so far gives an oversimplified picture of its operation. For example,
the imaginary part of the metal dielectric constant severely limits the
surface-plasmon propagation and the shortest attainable wavelength in most
cases, which in turn limits the microscope magnification. Here I describe how
this limitation has been overcome in the experiment, and analyze the practical
limits on the surface plasmon microscope resolution. In addition, I present
more experimental results, which strongly support the conclusion of extremely
high spatial resolution of the surface plasmon microscope.Comment: 23 pages, 9 figures, will be published in the topical issue on
Nanostructured Optical Metamaterials of the Journal of Optics A: Pure and
Applied Optics, Manuscript revised in response to referees comment
Factors Affecting Yield and Quality of Oats.
End of Project ReportQuality evaluation of oats relies primarily on hectolitre weight and, while it is an
important characteristic, work carried out at Oak Park and elsewhere has shown
that it does not accurately measure grain quality. Consequently, the selection of
oat lots and varieties which have a high milling value has been limited, as present
techniques fail to accurately determine the characteristics most closely related to
milling quality. In this regard the kernel content and the ease of husk removal,
termed the hullability, are the most important. This study has developed a new
test for assessing oat kernel content, which is more rapid and cheaper than
techniques currently available. Despite its obvious importance, oat hullability has
not been assessed to date in quality evaluation due to the absence of a test
procedure. However, this obstacle has now been overcome. The results of this
work also provide a much better understanding of how hullability of individual
varieties can be assessed, as well as investigating how this could be manipulated
at field level. Using the methods developed, the selection of varieties with
enhanced processing characteristics can now be carried out more precisely for
Irish conditions. The field trials conducted to evaluate the effect of agronomic
practices on quality indicated that the effect of factors such as nitrogen rate and
seed rate was small in comparison to variety, which had the largest and most
consistent effect. The variation in quality could not be completely explained by
variation in the panicle characteristics studied. Increasing the nitrogen rate
increased yield with the optimum being 160 kg N/ha in 1998 and 1999. However,
lodging became a very significant factor at nitrogen rates above 100 kg N/ha in
1998, although it did not occur in 1999. This work supports the current Teagasc
nitrogen recommendations for oats where levels of 110-140 kg N/ha (Soil Index
1) are advised
Nutrition Strategies for Triathlon
Contemporary sports nutrition guidelines recommend that each athlete develop a personalised, periodised and practical approach to eating that allows him or her to train hard, recover and adapt optimally, stay free of illness and injury and compete at their best at peak races. Competitive triathletes undertake a heavy training programme to prepare for three different sports while undertaking races varying in duration from 20 min to 10 h. The everyday diet should be adequate in energy availability, provide CHO in varying amounts and timing around workouts according to the benefits of training with low or high CHO availability and spread high-quality protein over the day to maximise the adaptive response to each session. Race nutrition requires a targeted and well-practised plan that maintains fuel and hydration goals over the duration of the specific event, according to the opportunities provided by the race and other challenges, such as a hot environment. Supplements and sports foods can make a small contribution to a sports nutrition plan, when medical supplements are used under supervision to prevent/treat nutrient deficiencies (e.g. iron or vitamin D) or when sports foods provide a convenient source of nutrients when it is impractical to eat whole foods. Finally, a few evidence-based performance supplements may contribute to optimal race performance when used according to best practice protocols to suit the triathlete’s goals and individual responsiveness
Geometrothermodynamics
We present the fundamentals of geometrothermodynamics, an approach to study
the properties of thermodynamic systems in terms of differential geometric
concepts. It is based, on the one hand, upon the well-known contact structure
of the thermodynamic phase space and, on the other hand, on the metric
structure of the space of thermodynamic equilibrium states. In order to make
these two structures compatible we introduce a Legendre invariant set of
metrics in the phase space, and demand that their pullback generates metrics on
the space of equilibrium states. We show that Weinhold's metric, which was
introduced {\it ad hoc}, is not contained within this invariant set. We propose
alternative metrics which allow us to redefine the concept of thermodynamic
length in an invariant manner and to study phase transitions in terms of
curvature singularities.Comment: Revised version, to be published in Jour. Math. Phy
Combining Passive Thermography and Acoustic Emission for Large Area Fatigue Damage Growth Assessment of a Composite Structure
Passive thermography and acoustic emission data were obtained for improved real time damage detection during fatigue loading. A strong positive correlation was demonstrated between acoustic energy event location and thermal heating, especially if the structure under load was nearing ultimate failure. An image processing routine was developed to map the acoustic emission data onto the thermal imagery. This required removing optical barrel distortion and angular rotation from the thermal data. The acoustic emission data were then mapped onto thermal data, revealing the cluster of acoustic emission event locations around the thermal signatures of interest. By combining both techniques, progression of damage growth is confirmed and areas of failure are identified. This technology provides improved real time inspections of advanced composite structures during fatigue testing.Keywords: Thermal nondestructive evaluation, fatigue damage detection, aerospace composite inspection, acoustic emission, passive thermograph
Ecosystem carbon & nitrogen cycling across a precipitation gradient of the central Great Plains
The SGS-LTER research site was established in 1980 by researchers at Colorado State University as part of a network of long-term research sites within the US LTER Network, supported by the National Science Foundation. Scientists within the Natural Resource Ecology Lab, Department of Forest and Rangeland Stewardship, Department of Soil and Crop Sciences, and Biology Department at CSU, California State Fullerton, USDA Agricultural Research Service, University of Northern Colorado, and the University of Wyoming, among others, have contributed to our understanding of the structure and functions of the shortgrass steppe and other diverse ecosystems across the network while maintaining a common mission and sharing expertise, data and infrastructure.Regional analyses have shown that ecosystem pools of carbon (C) and nitrogen (N) increase as precipitation increases from the semi-arid shortgrass steppe to the tallgrass prairie of the Central Great Plains. Models based on our functional understanding of biogeochemical processes predict that ecosystem C and N fluxes also increase across this community gradient; however, few field flux data exist to evaluate these predictions. We measured decomposition rates, soil respiration, and in situ net nitrogen mineralization at five sites across a precipitation gradient in the Great Plains region. Soil respiration (SResp) and the decomposition constant, k, for common substrate litter bags were significantly higher in the sub-humid mixed and tallgrass prairie (growing season average mid-day SResp = 7.20 ÎĽmol CO2 m-2 sec-1, k = 0.66 yr-1) than the semi-arid shortgrass steppe (SResp = 4.55 ÎĽmol CO2 m-2 sec-1, k = 0.32 yr-1). In contrast, in situ net nitrogen mineralization was not significantly different across sites. The C flux data concur with predictions from current biogeochemical models; however, the in situ net nitrogen mineralization results do not. We hypothesize that this discrepancy results from the difficulties associated with measuring in situ net nitrogen mineralization in soils with vastly different immobilization potentials
Theoretical Examination of the Lithium Depletion Boundary
We explore the sensitivity in open cluster ages obtained by the lithium
depletion boundary (LDB) technique to the stellar model input physics. The LDB
age technique is limited to open clusters with ages ranging from 20 to 200 Myr.
Effective 1-sig errors in the LDB technique due to uncertain input physics are
roughly 3% at the oldest age increasing to 8% at the youngest age. Bolometric
correction uncertainties add an additional 10 to 6% error to the LDB age
technique for old and young clusters, respectively. Rotation rates matching the
observed fastest rotators in the Pleiades affect LDB ages by less than 2%. The
range of rotation rates in an open cluster are expected to ``smear'' the LDB
location by only 0.02 mag for a Pleiades age cluster increasing to 0.06 mag for
a 20 Myr cluster. Thus, the observational error of locating the LDB (~7-10%)
and the bolometric correction uncertainty currently dominate the error in LDB
ages. For our base case, we formally derive a LDB age of 148 +- 19 Myr for the
Pleiades, where the error includes 8, 3, and 9% contributions from
observational, theoretical, and bolometric correction sources, respectively. A
maximally plausible 0.3 magnitude shift in the I-band bolometric correction to
reconcile main sequence isochrone fits with the observed (V-I) color for the
low mass Pleiades members results in an age of 126 +- 11 Myr, where the error
includes observational and theoretical errors only. Upper main-sequence-fitting
ages that do not include convective core overshoot for the Pleiades (~75 Myr)
are ruled out by the LDB age technique.Comment: 35 pages, 9 figures, accepted Ap
The Hilbert-Schmidt Theorem Formulation of the R-Matrix Theory
Using the Hilbert-Schmidt theorem, we reformulate the R-matrix theory in
terms of a uniformly and absolutely convergent expansion. Term by term
differentiation is possible with this expansion in the neighborhood of the
surface. Methods for improving the convergence are discussed when the
R-function series is truncated for practical applications.Comment: 16 pages, Late
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