4,100 research outputs found
Surfaces of Нigh-Tс Superconductors Studied by Means of the Scanning Tunneling Microscope
Observations of the natural surface of BiSrCaCu₂Oₓ sintered ceramics applying the
scanning tunneling microscope are reported. Measurements were performed in air at room
temperature. It can be deduced from the surface images, on which the growth steps are visible with
heights corresponding to the dimension of the unit cell along the c-axis or its multiples, that the bulk
orthorhombic structure extends to the surface. The surface investigated is rather clean, inert and
metallic in nature. It can be identified as the Bi-O layer.Zadanie pt. Digitalizacja i udostępnienie w Cyfrowym Repozytorium Uniwersytetu Łódzkiego kolekcji czasopism naukowych wydawanych przez Uniwersytet Łódzki nr 885/P-DUN/2014 zostało dofinansowane ze środków MNiSW w ramach działalności upowszechniającej naukę
Measurement of g-factor tensor in a quantum dot and disentanglement of exciton spins
We perform polarization-resolved magneto-optical measurements on single InAsP
quantum dots embedded in an InP nanowire. In order to determine all elements of
the electron and hole -factor tensors, we measure in magnetic field with
different orientations. The results of these measurements are in good agreement
with a model based on exchange terms and Zeeman interaction. In our experiment,
polarization analysis delivers a powerful tool that not only significantly
increases the precision of the measurements, but also enables us to probe the
exciton spin state evolution in magnetic fields. We propose a disentangling
scheme of heavy-hole exciton spins enabling a measurement of the electron spin
time
Numerical relativity in higher dimensions
We give a status report on our project targeted at performing numerical simulations of a head-on collision of non-spinning black holes in higher dimensional non-compact space-times. These simulations should help us understand black objects in higher dimensions and their stability properties. They are also relevant for the problem of black hole formation and evaporation in particle accelerators and cosmic rays. We use the symmetries of the system to reduce the problem to an effective 3+1 problem, allowing the use of existing numerical codes. As a simple application of the formalism, we present the results for the evolution of a five dimensional single black hole space-time. © 2010 IOP Publishing Ltd
Head-on collisions of unequal mass black holes in D=5 dimensions
We study head-on collisions of unequal mass black hole binaries in D=5
space-time dimensions, with mass ratios between 1:1 and 1:4. Information about
gravitational radiation is extracted by using the Kodama-Ishibashi
gauge-invariant formalism and details of the apparent horizon of the final
black hole. For the first time, we present waveforms, total integrated energy
and momentum for this process. Our results show surprisingly good agreement,
within 5% or less, with those extrapolated from linearized, point-particle
calculations. Our results also show that consistency with the area theorem
bound requires that the same process in a large number of spacetime dimensions
must display new features.Comment: 10 pages, 5 figures, RevTex4. v2: Published versio
Investigation of starch hydration by 2D time domain NMR
Proton exchange between spin groups of the solid matrix of hydrated granular potato starch and water was studied using the 2D time domain NMR. The proton spin-spin relaxation time T, and spin-lattice relaxation time T (selective and non-selective pulse sequences) were measured at room temperature. The observed spin relaxation results were analysed for exchange assuming a two-site exchange model (between water and solid matrix of starch). In this analysis we determined the intrinsic spin-lattice relaxation time for water protons (49 ms) and solid starch matrix protons (172 ms), as well as the water-starch magnetization exchange rate (86 s)
Numerical relativity for D dimensional axially symmetric space-times: formalism and code tests
The numerical evolution of Einstein's field equations in a generic background
has the potential to answer a variety of important questions in physics: from
applications to the gauge-gravity duality, to modelling black hole production
in TeV gravity scenarios, analysis of the stability of exact solutions and
tests of Cosmic Censorship. In order to investigate these questions, we extend
numerical relativity to more general space-times than those investigated
hitherto, by developing a framework to study the numerical evolution of D
dimensional vacuum space-times with an SO(D-2) isometry group for D\ge 5, or
SO(D-3) for D\ge 6.
Performing a dimensional reduction on a (D-4)-sphere, the D dimensional
vacuum Einstein equations are rewritten as a 3+1 dimensional system with source
terms, and presented in the Baumgarte, Shapiro, Shibata and Nakamura (BSSN)
formulation. This allows the use of existing 3+1 dimensional numerical codes
with small adaptations. Brill-Lindquist initial data are constructed in D
dimensions and a procedure to match them to our 3+1 dimensional evolution
equations is given. We have implemented our framework by adapting the LEAN code
and perform a variety of simulations of non-spinning black hole space-times.
Specifically, we present a modified moving puncture gauge which facilitates
long term stable simulations in D=5. We further demonstrate the internal
consistency of the code by studying convergence and comparing numerical versus
analytic results in the case of geodesic slicing for D=5,6.Comment: 31 pages, 6 figures; v2 Minor changes and added two references.
Matches the published version in PRD
Elevating crop disease resistance with cloned genes
Essentially all plant species exhibit heritable genetic variation for resistance to a variety of plant diseases caused by fungi, bacteria, oomycetes or viruses. Disease losses in crop monocultures are already significant, and would be greater but for applications of disease-controlling agrichemicals. For sustainable intensification of crop production, we argue that disease control should as far as possible be achieved using genetics rather than using costly recurrent chemical sprays. The latter imply CO2 emissions from diesel fuel and potential soil compaction from tractor journeys. Great progress has been made in the past 25 years in our understanding of the molecular basis of plant disease resistance mechanisms, and of how pathogens circumvent them. These insights can inform more sophisticated approaches to elevating disease resistance in crops that help us tip the evolutionary balance in favour of the crop and away from the pathogen. We illustrate this theme with an account of a genetically modified (GM) blight-resistant potato trial in Norwich, using the Rpi-vnt1.1 gene isolated from a wild relative of potato, Solanum venturii, and introduced by GM methods into the potato variety Desiree
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