2,542 research outputs found
Experimental characterization of an uniaxial angle cut whispering gallery mode resonator
The usual configuration of uniaxial whispering gallery mode resonators is a
disk shaped geometry where the optic axis points along the symmetry axis, a so
called z-cut resonator. Recently x-cut resonators, where the optic axis lies in
the equatorial plane, became of interest as they enable extremely broadband
second harmonic generation. In this paper we report on the properties of a more
generalized system, the so called angle-cut resonator, where the optic axis
exhibits an arbitrary angle against the symmetry axis. We show experimentally
that the modal structure and quality factors are similar to common resonators
but that the polarization properties differ quite significantly: due to the
asymmetry the polarization depends on the equatorial position and is, in
general, elliptical
The third dimension in river restoration: how anthropogenic disturbance changes boundary conditions for ecological mitigation
The goals of the European Water Framework Directive changed the perspective on rivers from human to ecosystem-based river management. After decades of channelizing and damming rivers, restoration projects are applied with more or less successful outcomes. The anthropogenic influence put on rivers can change their physical parameters and result in a different morphological type of river. Using the Ammer River as an example, a comparison between applied systems of corridor determination based on historical maps and data; calculation of regime width; and the change in parameters and river typology are pointed out. The results showed (a) a change in stream power and morphology (b) great difference between the historical and the predicted river type and (c) that regulated rivers can have a near-natural morphology
Forward-backward correlations in nucleus-nucleus collisions: baseline contributions from geometrical fluctuations
We discuss the effects of initial collision geometry and centrality bin
definition on correlation and fluctuation observables in nucleus-nucleus
collisions. We focus on the forward-backward correlation coefficient recently
measured by the STAR Collaboration in Au+Au collisions at RHIC. Our study is
carried out within two models: the Glauber Monte Carlo code with a `toy'
wounded nucleon model and the hadron-string dynamics (HSD) transport approach.
We show that strong correlations can arise due to averaging over events in one
centrality bin. We, furthermore, argue that a study of the dependence of
correlations on the centrality bin definition as well as the bin size may
distinguish between these `trivial' correlations and correlations arising from
`new physics'.Comment: 12 pages, 6 figure
Enhanced Anandamide Plasma Levels in Patients with Complex Regional Pain Syndrome following Traumatic Injury: A Preliminary Report
The complex regional pain syndrome (CRPS) is a disabling neuropathic pain condition that may develop following injuries of the extremities. The pathogenesis of this syndrome is not clear; however, it includes complex interactions between the nervous and the immune system resulting in chronic inflammation, pain and trophic changes. This interaction may be mediated by chronic stress which is thought to activate the endogenous cannabinoid (endocannabinoid) system (ECS). We conducted an open, prospective, comparative clinical study to determine plasma level of the endocannabinoid anandamide by high-performance liquid chromatography and a tandem mass spectrometry system in 10 patients with CRPS type I versus 10 age- and sex-matched healthy controls. As compared to healthy controls, CRPS patients showed significantly higher plasma concentrations of anandamide. These results indicate that the peripheral ECS is activated in CRPS. Further studies are warranted to evaluate the role of the ECS in the limitation of inflammation and pain. Copyright (C) 2009 S. Karger AG, Base
Progesterone during the breeding season and pregnancy in female muskoxen on different dietary regimens
Previously, we documented lowered calving success in captive muskoxen raised for 6 years on a low nutritional plane. In an effort to identify causes of lowered calf production, we looked at serum progesterone during the breeding season in muskoxen raised on either a high (HP) or low (LP) nutritional plane. Complete cessation of estrous cycli-city in 2 parous cows was the only irregularity identified. Abortion and/or embryonic loss occurred in both HP and LP cows. We also compared progesterone during pregnancy between the 2 nutritional planes and lactating and non-lacta-ting cows. The timing of the rise and fall of the mid-pregnant progesterone peak was consistent with stage of gestation and apparently independent of time of breeding, diet or lactational status
Dynamics of Droplets Moving on Lubricated Polymer Brushes
Understanding the dynamics of drops on polymer-coated surfaces is crucial for
optimizing applications such as self-cleaning materials or microfluidic
devices. While the static and dynamic properties of deposited drops have been
well characterised, a microscopic understanding of the underlying dynamics is
missing. In particular, it is unclear how drop dynamics depends on the amount
of uncrosslinked chains in the brush, because experimental techniques fail to
quantify those. Here we use coarse-grained simulations to study droplets moving
on a lubricated polymer brush substrate under the influence of an external body
force. The simulation model is based on the many body dissipative particle
dynamics (mDPD) method and designed to mimic a system of water droplets on
polydimethylsiloxane (PDMS) brushes with chemically identical PDMS lubricant.
In agreement with experiments, we find a sublinear power law dependence between
the external force and the droplet velocity , with
; however, the exponents differ ( in
simulations versus in experiments). With increasing
velocity, the droplets elongate and the receding contact angle decreases,
whereas the advancing contact angle remains roughly constant. Analyzing the
flow profiles inside the droplet reveals that the droplets do not slide, but
roll, with vanishing slip at the substrate surface. Surprisingly, adding
lubricant has very little effect on the effective friction force between the
droplet and the substrate, even though it has a pronounced effect on the size
and structure of the wetting ridge, especially above the cloaking transition
Population structure and dynamics in captive muskoxen at the Large Animal Research Station, 1988-1994
The muskox colony at the Large Animal Research Station, started in 1979, totaled 22 individuals before calving in 1988. Between 1988 -1994 cows of breeding age have been maintained on either a high plane (HP) or low plane (LP) of nutrition, and as far as possible, female offspring are kept with their mother's group. During this time the population has increased from 22 to 43 animals (25 females and 18 males). Fifty-four calves were born with an overall sex ratio of 52:48 (male:female). When partitioned between the 2 nutritional planes the sex ratio was HP 45:55 and LP 62:38. The calf/cow ratio was 0.83 in 1988 and 0.86 in 1994. The LP group accounted for most of the variability in pregnancy rate, primarily through delayed puberty and breeding pauses. Calf mortality was due mainly to abortions, stillbirths and neonatal death (n=12), 7 deaths occurred between 2 weeks and 1 year of age. All stillbirths and abortions (n=4) and 6 of 8 neonatal deaths affected calves of HP cows. Thirteen adults died, 4 males were loaned to other facilities and 2 new calves were added
Concentração de N na decomposição foliar de espécies lenhosas em sistemas agroflorestais (alley cropping) em Morretes, PR.
Nos sistemas de alley cropping a decomposição e subseqüente liberação de nutrientes das folhas e ramos podem ter importante influência na matéria orgânica e na reserva de nutrientes do solo. Coleman e Crossley (1996) resumem que, em geral, a decomposição é resultado da ação da biota em substratos com diferentes composições, em contraste com o clima.1 CD-ROM
Multiplicity Fluctuations in Hadron-Resonance Gas
The charged hadron multiplicity fluctuations are considered in the canonical
ensemble. The microscopic correlator method is extended to include three
conserved charges: baryon number, electric charge and strangeness. The
analytical formulae are presented that allow to include resonance decay
contributions to correlations and fluctuations. We make the predictions for the
scaled variances of negative, positive and all charged hadrons in the most
central Pb+Pb (Au+Au) collisions for different collision energies from SIS and
AGS to SPS and RHIC.Comment: 19 pages, 4 figure
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