204 research outputs found
Chains of Quasi-Classical Informations for Bipartite Correlations and the Role of Twin Observables
Having the quantum correlations in a general bipartite state in mind, the
information accessible by simultaneous measurement on both subsystems is shown
never to exceed the information accessible by measurement on one subsystem,
which, in turn is proved not to exceed the von Neumann mutual information. A
particular pair of (opposite- subsystem) observables are shown to be
responsible both for the amount of quasi-classical correlations and for that of
the purely quantum entanglement in the pure-state case: the former via
simultaneous subsystem measurements, and the latter through the entropy of
coherence or of incompatibility, which is defined for the general case. The
observables at issue are so-called twin observables. A general definition of
the latter is given in terms of their detailed properties.Comment: 7 pages, Latex2e, selected for the December 2002 issue of the Virtual
Journal of Quantum Informatio
Electronic friction and liquid-flow-induced voltage in nanotubes
A recent exciting experiment by Ghosh et al. reported that the flow of an
ion-containing liquid such as water through bundles of single-walled carbon
nanotubes induces a voltage in the nanotubes that grows logarithmically with
the flow velocity v0. We propose an explanation for this observation. Assuming
that the liquid molecules nearest the nanotube form a 2D solid-like monolayer
pinned through the adsorbed ions to the nanotubes, the monolayer sliding will
occur by elastic loading followed by local yield (stick-slip). The drifting
adsorbed ions produce a voltage in the nanotube through electronic friction
against free electrons inside the nanotube. Thermally excited jumps over
force-biased barriers, well-known in stick-slip, can explain the logarithmic
voltage growth with flow velocity. We estimate the short circuit current and
the internal resistance of the nanotube voltage generator.Comment: 8 pages, 3 figures; published on PRB
(http://link.aps.org/abstract/PRB/v69/e235410) and on the Virtual Journal of
Nanoscale Science and Technology (http://www.vjnano.org, July 14, 2002, Vol.
10, Iss. 2
Photometric reconstruction of a dynamic textured surface from just one color image acquisition
http://www.opticsinfobase.org/josaa/abstract.cfm?msid=85528 This article has been selected for inclusion in the Virtual Journal for Biomedical Optics (Vol. 3, Iss. 4)International audienceTextured surface analysis is essential for many applications. We present a three-dimensional recovery approach for real textured surfaces based on photometric stereo. The aim is to be able to measure the textured surfaces with a high degree of accuracy. For this, we use a color digital sensor and principles of color photometric stereo. This method uses a single color image, instead of a sequence of gray-scale images, to recover the surface of the three dimensions. It can thus be integrated into dynamic systems where there is significant relative motion between the object and the camera. To evaluate the performances of our method, we compare it on real textured surfaces to traditional photometric stereo using three images. We show thus that it is possible to have similar results with just one color image
Current Assisted, Thermally Activated Flux Liberation in Ultrathin Nanopatterned NbN Superconducting Meander Structures
We present results from an extensive study of fluctuation phenomena in
superconducting nanowires made from sputtered NbN. Nanoscale wires were
fabricated in form of a meander and operated at a constant temperature
T~0.4Tc(0). The superconducting state is driven close to the electronic phase
transition by a high bias current near the critical one. Fluctuations of
sufficient strength temporarily drive a section of the meander structure into
the normal conducting state, which can be registered as a voltage pulse of
nanosecond duration. We considered three different models (vortex-antivortex
pairs, vortex edge barriers and phase slip centers) to explain the experimental
data. Only thermally excited vortices, either via unbinding of
vortex-antivortex pairs or vortices overcoming the edge barrier, lead to a
satisfactory and consistent description for all measurements.Comment: 41 Pages, 5 Chapters, 7 Figures, 2 Tables, 30 Equations, 68
References; Selected for the January 15, 2010 Issue of the Virtual Journal of
Applications of Superconductivit
Radiative charge transfer lifetime of the excited state of (NaCa)
New experiments were proposed recently to investigate the regime of cold
atomic and molecular ion-atom collision processes in a special hybrid
neutral-atom--ion trap under high vacuum conditions. The collisional cooling of
laser pre-cooled Ca ions by ultracold Na atoms is being studied. Modeling
this process requires knowledge of the radiative lifetime of the excited
singlet A state of the (NaCa) molecular system. We calculate
the rate coefficient for radiative charge transfer using a semiclassical
approach. The dipole radial matrix elements between the ground and the excited
states, and the potential curves were calculated using Complete Active Space
Self-Consistent field and M\"oller-Plesset second order perturbation theory
(CASSCF/MP2) with an extended Gaussian basis, 6-311+G(3df). The semiclassical
charge transfer rate coefficient was averaged over a thermal Maxwellian
distribution. In addition we also present elastic collision cross sections and
the spin-exchange cross section. The rate coefficient for charge transfer was
found to be cm/sec, while those for the elastic and
spin-exchange cross sections were found to be several orders of magnitude
higher ( cm/sec and cm/sec,
respectively). This confirms our assumption that the milli-Kelvin regime of
collisional cooling of calcium ions by sodium atoms is favorable with the
respect to low loss of calcium ions due to the charge transfer.Comment: 4 pages, 5 figures; v.2 - conceptual change
Communitywide Database Designs for Tracking Innovation Impact: COMETS, STARS and Nanobank
Data availability is arguably the greatest impediment to advancing the science of science and innovation policy and practice (SciSIPP). This paper describes the contents, methodology and use of the public online COMETS (Connecting Outcome Measures in Entrepreneurship Technology and Science) database spanning all sciences, technologies, and high-tech industries; its parent COMETSandSTARS database which adds more data at organization and individual scientist-inventor-entrepreneur level restricted by vendor licenses to onsite use at NBER and/or UCLA; and their prototype Nanobank covering only nano-scale sciences and technologies. Some or all of these databases include or will include: US patents (granted and applications); NIH, NSF, SBIR, STTR Grants; Thomson Reuters Web of Knowledge; ISI Highly Cited; US doctoral dissertations; IPEDS/HEGIS universities; all firms and other organizations which ever publish in ISI listed journals beginning in 1981, are assigned US patents (from 1975), or are listed on a covered grant; additional nanotechnology firms based on web search. Ticker/CUSIP codes enable linking public firms to the major databases covering them. A major matching/disambiguation effort assigns unique identifiers for an organization or individual so that their appearances are linked within and across the constituent legacy databases. Extensive geographic coding enables analysis at country, region, state, county, or city levels. The databases provide very flexible sources of data for serious research on many issues in the study of organizations in innovation systems in the development and spread of knowledge, and the economics of science. Enabling the study of these topics, among others, COMETS contributes substantially to the science of science and technology.
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