11,348 research outputs found
A chain rule for the expected suprema of Gaussian processes
The expected supremum of a Gaussian process indexed by the image of an index
set under a function class is bounded in terms of separate properties of the
index set and the function class. The bound is relevant to the estimation of
nonlinear transformations or the analysis of learning algorithms whenever
hypotheses are chosen from composite classes, as is the case for multi-layer
models
Vortex pinning by cylindrical defects in type-II superconductors: Numerical solutions to the Ginzburg-Landau equations
We numerically integrate the one-dimensional, cylindrically symmetric Ginzburg-Landau equations to calculate the spatial variation of the order parameter and supercurrents for a vortex trapped by a cylindrical defect. We use the resulting field distributions to estimate the pinning energy, and make use of the vortex/two-dimensional boson analogy to calculate the depinning temperature. The microscopic behavior oi the fields depends on the size, and the conductivity of the cylindrical defect appears to be important for the pinning
Using Sideband Transitions for Two-Qubit Operations in Superconducting Circuits
We demonstrate time resolved driving of two-photon blue sideband transitions
between superconducting qubits and a transmission line resonator. Using the
sidebands, we implement a pulse sequence that first entangles one qubit with
the resonator, and subsequently distributes the entanglement between two
qubits. We show generation of 75% fidelity Bell states by this method. The full
density matrix of the two qubit system is extracted using joint measurement and
quantum state tomography, and shows close agreement with numerical simulation.
The scheme is potentially extendable to a scalable universal gate for quantum
computation.Comment: 4 pages, 5 figures, version with high resolution figures available at
http://qudev.ethz.ch/content/science/PubsPapers.htm
Characteristic velocities of stripped-envelope core-collapse supernova cores
The velocity of the inner ejecta of stripped-envelope core-collapse
supernovae (CC-SNe) is studied by means of an analysis of their nebular
spectra. Stripped-envelope CC-SNe are the result of the explosion of bare cores
of massive stars ( M), and their late-time spectra are
typically dominated by a strong [O {\sc i}] 6300, 6363 emission
line produced by the innermost, slow-moving ejecta which are not visible at
earlier times as they are located below the photosphere. A characteristic
velocity of the inner ejecta is obtained for a sample of 56 stripped-envelope
CC-SNe of different spectral types (IIb, Ib, Ic) using direct measurements of
the line width as well as spectral fitting. For most SNe, this value shows a
small scatter around 4500 km s. Observations ( days) of
stripped-envelope CC-SNe have revealed a subclass of very energetic SNe, termed
broad-lined SNe (BL-SNe) or hypernovae, which are characterised by broad
absorption lines in the early-time spectra, indicative of outer ejecta moving
at very high velocity (). SNe identified as BL in the early phase
show large variations of core velocities at late phases, with some having much
higher and some having similar velocities with respect to regular CC-SNe. This
might indicate asphericity of the inner ejecta of BL-SNe, a possibility we
investigate using synthetic three-dimensional nebular spectra.Comment: 14 pages, 10 figures, MNRAS accepte
Sainfoin – New Data on Anthelmintic Effects and Production in Sheep and Goats
Gastrointestinal nematodes (GIN) are one of the most important problems affecting health and therefore performance and welfare in small ruminant husbandry. The control of these parasites in the past strongly relied on the repeated use of anthelmintic drugs. This has led to nematode populations which are resistant to most of the currently available anthelmintics. Furthermore customer’s demands for organic and residue free animal products are increasing. The aforementioned problems have given a strong impetus for the development of new non-chemical strategies to control GIN. Previous research has pointed out the anthelmintic potential of sainfoin (Onobrychis viciifolia) and other tanniferous (CT) feed sources in goats and lambs infected with GIN. A recent Swiss experiment focussed on the use of sainfoin and field bean (Vicia faba, cv. Scirocco) as single CT sources as well as in combination for additional synergic effects, to reduce periparturient GIN egg rise of ewes in late gestation and early lactation. Another experiment with Alpine goats concentrated on the influence of sainfoin on milk performance and cheese quality. The results of these experiments will be presented and discussed in connection with previous knowledge on (i) anthelmintic effects of sainfoin and (ii) the influence of sainfoin administration on performance
Nesting behaviour influences species-specific gas exchange across avian eggshells
Carefully controlled gas exchange across the eggshell is essential for the development of the avian embryo. Water vapour conductance (GH2O) across the shell, typically measured as mass loss during incubation, has been demonstrated to optimally ensure the healthy development of the embryo while avoiding desiccation. Accordingly, eggs exposed to sub-optimal gas exchange have reduced hatching success. We tested the association between eggshell GH2O and putative life-history correlates of adult birds, ecological nest parameters and physical characteristics of the egg itself to investigate how variation in GH2O has evolved to maintain optimal water loss across a diverse set of nest environments. We measured gas exchange through eggshell fragments in 151 British breeding bird species and fitted phylogenetically controlled, general linear models to test the relationship between GH2O and potential predictor parameters of each species. Of our 17 life-history traits, only two were retained in the final model: wet-incubating parent and nest type. Eggs of species where the parent habitually returned to the nest with wet plumage had significantly higher GH2O than those of parents that returned to the nest with dry plumage. Eggs of species nesting in ground burrows, cliffs and arboreal cups had significantly higher GH2O than those of species nesting on the ground in open nests or cups, in tree cavities and in shallow arboreal nests. Phylogenetic signal (measured as Pagel's λ) was intermediate in magnitude, suggesting that differences observed in the GH2O are dependent upon a combination of shared ancestry and species-specific life history and ecological traits. Although these data are correlational by nature, they are consistent with the hypothesis that parents constrained to return to the nest with wet plumage will increase the humidity of the nest environment, and the eggs of these species have evolved a higher GH2O to overcome this constraint and still achieve optimal water loss during incubation. We also suggest that eggs laid in cup nests and burrows may require a higher GH2O to overcome the increased humidity as a result from the confined nest microclimate lacking air movements through the nest. Taken together, these comparative data imply that species-specific levels of gas exchange across avian eggshells are variable and evolve in response to ecological and physical variation resulting from parental and nesting behaviours
Locking of accessible information and implications for the security of quantum cryptography
The unconditional security of a quantum key distribution protocol is often
defined in terms of the accessible information, that is, the maximum mutual
information between the distributed key S and the outcome of an optimal
measurement on the adversary's (quantum) system. We show that, even if this
quantity is small, certain parts of the key S might still be completely
insecure when S is used in applications, such as for one-time pad encryption.
This flaw is due to a locking property of the accessible information: one
additional (physical) bit of information might increase the accessible
information by more than one bit.Comment: 5 pages; minor change
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