2,840 research outputs found
FReD: The floral reflectance spectra database
Floral reflectance measurements are of great value to researchers who need consider the real colour of flowers, for example in the context of how the flowers appear to their pollinators. We have thus developed the Floral Reflectance Database (FReD) to assist these researchers, gathering together floral reflectance data in a publicly available, searchable online database. The first version of the database is now available online at "http://www.reflectance.co.uk":http://www.reflectance.co.uk. We anticipate that this resource will be of interest to researchers working on flower colour and animal vision
Turnstile behaviour of the Cooper-pair pump
We have experimentally studied the behaviour of the so-called Cooper pair
pump (CPP) with three Josephson junctions, in the limit of small Josephson
coupling EJ < EC. These experiments show that the CPP can be operated as a
traditional turnstile device yielding a gate-induced current 2ef in the
direction of the bias voltage, by applying an RF-signal with frequency f to the
two gates in phase, while residing at the degeneracy node of the gate plane.
Accuracy of the CPP during this kind of operation was about 3% and the
fundamental Landau-Zener limit was observed to lie above 20 MHz. We have also
measured the current pumped through the array by rotating around the degeneracy
node in the gate plane. We show that this reproduces the turnstile-kind of
behavior. To overcome the contradiction between the obtained e-periodic
DC-modulation and a pure 2e-behaviour in the RF-measurements, we base our
observations on a general principle that the system always minimises its
energy. It suggests that if the excess quasiparticles in the system have a
freedom to tunnel, they will organize themselves to the configuration yielding
the highest current.Comment: 29 pages, 16 figures, uses REVTeX and graphicx-packag
A Latent Variable Approach to Multivariate Quantitative Trait Loci
A novel approach based on latent variable modelling is presented for the analysis of multivariate quantitative and qualitative trait loci. The approach is general in the sense that it enables the joint analysis of many kinds of quantitative and qualitative traits (including count data and censored traits) in a single modelling framework. In the framework, the observations are modelled as functions of latent variables, which are then affected by quantitative trait loci. Separating the analysis in this way means that measurement errors in the phenotypic observations can be included easily in the model, providing robust inferences. The performance of the method is illustrated using two real multivariate datasets, from barley and Scots pine
Exposure to glycols and their renal effects in motor servicing workers
Ten car mechanics frequently exposed to glycol-based cooling liquids were followed during a workshift. Airborne ethylene and propylene glycol concentrations in the car mechanics' environment were measured. The car mechanics gave urine samples after the workshift and their excretion of ethylene glycol, propylene glycol, oxalic acid, calcium and ammonia was analysed and compared to that of unexposed office workers. Urinary succinate dehydrogenase activity and glycosaminoglycans were also measured in both groups. Airborne ethylene and propylene glycol concentrations in the car mechanics' environment were negligible. Urinary ethylene glycol excretion in exposed workers was significantly higher than that in unexposed workers, but propylene glycol excretion was at the same level as in controls. In the exposed group, the excretion of the end metabolite of ethylene glycol, oxalic acid (47 ± 11 mmol/mol creatinine, mean ± SD, n= 10) differed slightly from that of controls (36 ± 14 mmol/mol creatinine, mean ± SD, n= 10). Urinary excretion of ammonia was higher among exposed workers than office workers. The excretion of calcium did not differ from that of controls. A marginally decreased urinary succinate dehydrogenase activity was found in the exposed men. The excretion of glycosaminoglycans was significantly lower in exposed workers. Therefore, it seems that ethylene glycol is absorbed by skin contact. The internal body burden is associated with oxaluria and increased ammoniagenesis typical of chronic acidosi
Causal connection in parsec-scale relativistic jets: results from the MOJAVE VLBI survey
We report that active galactic nucleus (AGN) jets are causally connected on
parsec scales, based on 15 GHz Very Long Baseline Array (VLBA) data from a
sample of 133 AGN jets. This result is achieved through a new method for
measuring the product of the jet Lorentz factor and the intrinsic opening angle
Gamma*theta_j from measured apparent opening angles in flux density limited
samples of AGN jets. The Gamma*theta_j parameter is important for jet physics
because it is related to the jet-frame sidewise expansion speed and causal
connection between the jet edges and its symmetry axis. Most importantly, the
standard model of jet production requires that the jet be causally connected
with its symmetry axis, implying that Gamma*theta_j < 1. When we apply our
method to the MOJAVE flux density limited sample of radio loud objects, we find
Gamma*theta_j = 0.2, implying that AGN jets are causally connected. We also
find evidence that AGN jets viewed very close to the line of sight effectively
have smaller intrinsic opening angles compared with jets viewed more off-axis,
which is consistent with Doppler beaming and a fast inner spine/slow outer
sheath velocity field. Notably, gamma-ray burst (GRB) jets have a typical
Gamma*theta_j that is two orders of magnitude higher, suggesting that different
physical mechanisms are at work in GRB jets compared to AGN jets. A useful
application of our result is that a jet's beaming parameters can be derived.
Assuming Gamma*theta_j is approximately constant in the AGN jet population, an
individual jet's Doppler factor and Lorentz factor (and therefore also its
viewing angle) can be determined using two observable quantities: apparent jet
opening angle and the apparent speed of jet components.Comment: 9 pages, 4 figure
Same-sex sociosexual behaviour is widespread and heritable in male rhesus macaques
Numerous reports have documented the occurrence of same-sex sociosexual behaviour (SSB) across animal species. However, the distribution of the behaviour within a species is needed to test the theories describing its evolution and maintenance, in particular whether the behaviour is heritable and can therefore evolve by natural selection. Here, we collected detailed observations across three years of social and mounting behaviour of 236 male semi-wild rhesus macaques, which we combined with a pedigree dating back to 1938, to show that SSB was both repeatable (19.35%) and heritable (6.4%). Demographic factors (age and group structure) explained SSB variation only marginally. Furthermore, we found a positive genetic correlation between same-sex mounter and mountee activities, indicating a common basis to different forms of SSB. Finally, we found no evidence of fitness costs to SSB, but show instead that the behaviour mediated coalitionary partnerships that have been linked with improved reproductive success. Together, our results demonstrate that SSB is frequent in rhesus macaques, can evolve, and is not costly, indicating that SSB may be a common feature of primate reproductive ecology
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