2,153 research outputs found
An optical nanocavity incorporating a fluorescent organic dye having a high quality factor
We have fabricated an L3 optical nanocavity operating at visible wavelengths that is coated with a thin-film of a fluorescent molecular-dye. The cavity was directly fabricated into a pre-etched, free-standing silicon-nitride (SIN) membrane and had a quality factor of Q = 2650. This relatively high Q-factor approaches the theoretical limit that can be expected from an L3 nanocavity using silicon nitride as a dielectric material and is achieved as a result of the solvent-free cavity-fabrication protocol that we have developed. We show that the fluorescence from a red-emitting fluorescent dye coated onto the cavity surface undergoes strong emission intensity enhancement at a series of discrete wavelengths corresponding to the cavity modes. Three dimensional finite difference time domain (FDTD) calculations are used to predict the mode structure of the cavities with excellent agreement demonstrated between theory and experiment
Do soil depth and plant community composition interact to modify the resistance and resilience of grassland ecosystem functioning to drought?
While the effect of drought on plant communities and their associated ecosystem functions is well studied, little research has considered how responses are modified by soil depth and depth heterogeneity. We conducted a mesocosm study comprising shallow and deep soils, and variable and uniform soil depths, and two levels of plant community composition, and exposed them to a simulated drought to test for interactive effects of these treatments on the resilience of carbon dioxide fluxes, plant functional traits, and soil chemical properties. We tested the hypotheses that: 1) shallow and variable depth soils lead to increased resistance and resilience of ecosystem functions to drought due to more exploitative plant trait strategies; 2) plant communities associated with intensively managed high fertility soils, will have more exploitative root traits than extensively managed, lower fertility plant communities. These traits will be associated with higher resistance and resilience to drought and may interact with soil depth and depth heterogeneity to amplify the effects on ecosystem functions.Our results showed that while there were strong soil depth/heterogeneity effects on plant driven carbon fluxes, it did not affect resistance or resilience to drought, and there were no treatment effects on plant available carbon or nitrogen. We did observe a significant increase in exploitative root traits in shallow and variable soils relative to deep and uniform, which may have resulted in a compensation effect which led to the similar drought responses.Plant community compositions representative of intensive management were more drought resilient than more diverse âextensiveâ communities irrespective of soil depth or soil depth heterogeneity. In intensively managed plant communities, root traits were more representative of exploitative strategies. Taken together our results suggest that reorganisation of root traits in response to soil depth could buffer drought effects on ecosystem functions.<br/
The Ministry of Works and the Development of Souvenir Guides from 1955
The first formal guidebooks for historic sites placed in state guardianship in the United Kingdom appeared in 1917. There was an expansion of the series in the 1930s and 1950s. However, from the late 1950s the Ministry of Works, and later the Ministry of Public Buildings and Works, started to produce an additional series of illustrated souvenir guides. One distinct group covered Royal Palaces: the Tower of London, Hampton Court Palace, Queen Victoria's residence of Osborne House on the Isle of Wight, and Holyroodhouse in Edin-burgh. This was followed by guides for archaeological sites such as Stone-henge and Avebury, the Neolithic flint mines at Grime's Graves, the Roman villa at Lullingstone, and Hadrian's Wall. In 1961, a series of guides, with covers designed by Kyffin Williams, was produced for the English castles constructed in North Wales. These illustrated guides, some with colour, prepared the way for the fully designed guides now produced by English Heritage, Cadw, and Historic Environment Scotland
Gravitino constraints on models of neutrino masses and leptogenesis
In the supersymmetric extensions of the standard model, neutrino masses and
leptogenesis requires existence of new particles. We point out that if these
particles with lepton number violating interactions have standard model gauge
interactions, then they may not be created after reheating because of the
gravitino problem. This will rule out all existing models of neutrino masses
and leptogenesis, except the one with right-handed singlet neutrinos.Comment: 12 pages latex file with one postscript figur
Preterm birth a long distance from home and its significant social and financial stress
The present paper reports a retrospective cohort of preterm infants admitted to our hospital who delivered outside the normal geographical catchment area of the mother's local level three neonatal nursery. Nineteen mothers had 21 preterm infants (23.1-34.9 weeks, 500-2330 g born) where 14 infants required ventilation (median 57 h, range 3-428). Eighteen survivors had a median length of stay of 41 days (range 3-91). Twelve of 19 mothers were interviewed: all described isolation, loneliness, poor social support and significant financial hardship related to getting their infants back to a local hospital or home. To avoid these problems, we recommend confining travel to within a short distance from home or local maternity unit after 22 weeks
Obtaining CKM Phase Information from B Penguin Decays
We discuss a method for extracting CP phases from pairs of B decays which are
related by flavor SU(3). One decay (B0 -> M1 M2) receives a significant bbar ->
dbar penguin contribution. The second (B' -> M1' M2') has a significant bbar ->
sbar penguin contribution, but is dominated by a single amplitude. CP phase
information is obtained using the fact that the B' -> M1' M2' amplitude is
related by SU(3) to a piece of the B0 -> M1 M2 amplitude. The leading-order
SU(3)-breaking effect (~25%) responsible for the main theoretical error can be
removed. For some decay pairs, it can be written in terms of known decay
constants. In other cases, it involves a ratio of form factors. However, this
form-factor ratio can either be measured experimentally, or eliminated by
considering a double ratio of amplitudes. In all cases, one is left only with a
second-order effect, ~5%. We find twelve pairs of B decays to which this method
can be applied. Depending on the decay pair, we estimate the total theoretical
error in relating the B' -> M1' M2' and B0 -> M1 M2 amplitudes to be between 5%
and 15%. The most promising decay pairs are Bd -> pi+ pi- and Bu+ -> K0 pi+,
and Bd -> D+ D- and Bd -> Ds+ D- or Bu+ -> Ds+ D0bar.Comment: 38 pages, JHEP format, no figures. Comments added to text regarding
most promising decay pairs; references added; conclusions unchange
The DiskMass Survey. II. Error Budget
We present a performance analysis of the DiskMass Survey. The survey uses
collisionless tracers in the form of disk stars to measure the surface-density
of spiral disks, to provide an absolute calibration of the stellar
mass-to-light ratio, and to yield robust estimates of the dark-matter halo
density profile in the inner regions of galaxies. We find a disk inclination
range of 25-35 degrees is optimal for our measurements, consistent with our
survey design to select nearly face-on galaxies. Uncertainties in disk
scale-heights are significant, but can be estimated from radial scale-lengths
to 25% now, and more precisely in the future. We detail the spectroscopic
analysis used to derive line-of-sight velocity dispersions, precise at low
surface-brightness, and accurate in the presence of composite stellar
populations. Our methods take full advantage of large-grasp integral-field
spectroscopy and an extensive library of observed stars. We show that the
baryon-to-total mass fraction (F_b) is not a well-defined observational
quantity because it is coupled to the halo mass model. This remains true even
when the disk mass is known and spatially-extended rotation curves are
available. In contrast, the fraction of the rotation speed supplied by the disk
at 2.2 scale lengths (disk maximality) is a robust observational indicator of
the baryonic disk contribution to the potential. We construct the error-budget
for the key quantities: dynamical disk mass surface-density, disk stellar
mass-to-light ratio, and disk maximality (V_disk / V_circular). Random and
systematic errors in these quantities for individual galaxies will be ~25%,
while survey precision for sample quartiles are reduced to 10%, largely devoid
of systematic errors outside of distance uncertainties.Comment: To appear in ApJ; 88 pages, 4 tables, 18 figures. High-resolution
version available at
http://www.astro.wisc.edu/~mab/publications/DMS_II_preprint.pd
Large Scale Pressure Fluctuations and Sunyaev-Zel'dovich Effect
The Sunyaev-Zel'dovich (SZ) effect associated with pressure fluctuations of
the large scale structure gas distribution will be probed with current and
upcoming wide-field small angular scale cosmic microwave background
experiments. We study the generation of pressure fluctuations by baryons which
are present in virialized dark matter halos and by baryons present in small
overdensities. For collapsed halos, assuming the gas distribution is in
hydrostatic equilibrium with matter density distribution, we predict the
pressure power spectrum and bispectrum associated with the large scale
structure gas distribution by extending the dark matter halo approach which
describes the density field in terms of correlations between and within halos.
The projected pressure power spectrum allows a determination of the resulting
SZ power spectrum due to virialized structures. The unshocked photoionized
baryons present in smaller overdensities trace the Jeans-scale smoothed dark
matter distribution. They provide a lower limit to the SZ effect due to large
scale structure in the absence of massive collapsed halos. We extend our
calculations to discuss higher order statistics, such as bispectrum and
skewness in SZ data. The SZ-weak lensing cross-correlation is suggested as a
probe of correlations between dark matter and baryon density fields, while the
probability distribution functions of peak statistics of SZ halos in wide field
CMB data can be used as a probe of cosmology and non-Gaussian evolution of
large scale structure pressure fluctuations.Comment: 16 pages, 9 figures; Revised with expanded discussions. Phys. Rev. D.
(in press
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