12,202 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
Red blood cells and other non-spherical capsules in shear flow: oscillatory dynamics and the tank-treading-to-tumbling transition
We consider the motion of red blood cells and other non-spherical
microcapsules dilutely suspended in a simple shear flow. Our analysis indicates
that depending on the viscosity, membrane elasticity, geometry and shear rate,
the particle exhibits either tumbling, tank-treading of the membrane about the
viscous interior with periodic oscillations of the orientation angle, or
intermittent behavior in which the two modes occur alternately. For red blood
cells, we compute the complete phase diagram and identify a novel
tank-treading-to-tumbling transition at low shear rates. Observations of such
motions coupled with our theoretical framework may provide a sensitive means of
assessing capsule properties.Comment: 11 pages, 4 figure
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
On the Key-Uncertainty of Quantum Ciphers and the Computational Security of One-way Quantum Transmission
We consider the scenario where Alice wants to send a secret (classical)
-bit message to Bob using a classical key, and where only one-way
transmission from Alice to Bob is possible. In this case, quantum communication
cannot help to obtain perfect secrecy with key length smaller then . We
study the question of whether there might still be fundamental differences
between the case where quantum as opposed to classical communication is used.
In this direction, we show that there exist ciphers with perfect security
producing quantum ciphertext where, even if an adversary knows the plaintext
and applies an optimal measurement on the ciphertext, his Shannon uncertainty
about the key used is almost maximal. This is in contrast to the classical case
where the adversary always learns bits of information on the key in a known
plaintext attack. We also show that there is a limit to how different the
classical and quantum cases can be: the most probable key, given matching
plain- and ciphertexts, has the same probability in both the quantum and the
classical cases. We suggest an application of our results in the case where
only a short secret key is available and the message is much longer.Comment: 19 pages, 2 figures. This is a revised version of an earlier version
that appeared in the proc. of Eucrocrypt'04:LNCS3027, 200
Close to Uniform Prime Number Generation With Fewer Random Bits
In this paper, we analyze several variants of a simple method for generating
prime numbers with fewer random bits. To generate a prime less than ,
the basic idea is to fix a constant , pick a
uniformly random coprime to , and choose of the form ,
where only is updated if the primality test fails. We prove that variants
of this approach provide prime generation algorithms requiring few random bits
and whose output distribution is close to uniform, under less and less
expensive assumptions: first a relatively strong conjecture by H.L. Montgomery,
made precise by Friedlander and Granville; then the Extended Riemann
Hypothesis; and finally fully unconditionally using the
Barban-Davenport-Halberstam theorem. We argue that this approach has a number
of desirable properties compared to previous algorithms.Comment: Full version of ICALP 2014 paper. Alternate version of IACR ePrint
Report 2011/48
Scattering properties of Venus' surface
Radar backscatter functions Sigma-(carat)(sub 0)(phi) for incidence angles between 0 less than or equal to phi less than or equal to 4-10 deg were derived from Magellan altimetry radar echoes. The procedure includes constrained solution of a system of simultaneous equations for which the echo-spectrum and echo time profile are inputs. A practical and workable set of constraints was applied; optimization and improved results are expected as the analysis matures. The scattering functions yield information on small-scale surface structures (tens of centimeters to tens of meters) but averaged over hundreds of sq km. RMS surface slopes derived from fits of analytic functions to the Sigma-(carat)(sub 0)(phi) results were converted to map form and show patterns similar to those reported using other techniques. While all three forms are found on Venus, fit residuals imply that an exponential scattering function matches data better than either the Hagfors or Gaussian form in most areas, although the Hagfors function may be a better descriptor at some sites. Limited study of image data indicates that average backscatter cross section, and possibly its slope, can be derived at oblique angles (17 deg less than or equal to phi less than or equal to 45 deg). Offsets of the echo peak in altimetry spectra are surprisingly common and are loosely correlated with Venus topography, but no cause for this phenomenon was identified
Optical determination and identification of organic shells around nanoparticles: application to silver nanoparticles
We present a simple method to prove the presence of an organic shell around
silver nanoparticles. This method is based on the comparison between optical
extinction measurements of isolated nanoparticles and Mie calculations
predicting the expected wavelength of the Localized Surface Plasmon Resonance
of the nanoparticles with and without the presence of an organic layer. This
method was applied to silver nanoparticles which seemed to be well protected
from oxidation. Further experimental characterization via Surface Enhanced
Raman Spectroscopy (SERS) measurements allowed to identify this protective
shell as ethylene glycol. Combining LSPR and SERS measurements could thus give
proof of both presence and identification for other plasmonic nanoparticles
surrounded by organic shells
Control methods for Dermanyssus gallinae in systems for laying hens: results of an international seminar
This paper reports the results of a seminar on poultry red mite (PRM), Dermanyssus gallinae. Eighteen researchers from eight European countries discussed life cycle issues of the mite, effects of mites on hens and egg production, and monitoring and control methods for PRM in poultry facilities. It was determined that PRM probably causes more damage than envisaged, with the cost in The Netherlands alone reaching 11 million euro per annum. However a great deal is still unknown about PRM (e.g. reproduction, survival methods, etc.) and that PRM monitoring is an important instrument in recognising and admitting the problem and in taking timely measures. Currently, the most promising control method combines heating the hen house in combination with chemical treatments. Future areas of development which show promise include the use of entomopathogenic fungi, vaccination and predatory mites. The final aim is to solve the problem of D. gallinae in housing systems for laying hens
NASA follow-on to the Bangladesh Agro-Climatic Environmental Monitoring Project
The NASA responsibility and activities for the follow-on to the original Agro-Climatic Environmental Monitoring Project (ACEMP) which was completed during 1987 is described. Five training sessions which comprise the NASA ACEMP follow-on are: Agrometeorology, Meteorology of Severe Storms Using GEMPAK, Satellite Oceanography, Hydrology, and Meteorology with TOVS. The objective of the follow-on is to train Bangladesh Government staff in the use of satellite data for remote sensing applications. This activity also encourages the scientific connection between NASA/Goddard Space Flight Center and The Bangladesh Space and Remote Sensing Organization (SPARRSO)
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