28,191 research outputs found
VR/Urban: SMSlingshot
In this paper we describe the concept and design objectives of VR/Urban's media intervention tool SMSlingshot, which was presented at the Riga White Night Arts Festival 2009 for the first time
Scanning probe microscopy imaging of metallic nanocontacts
We show scanning probe microscopy measurements of metallic nanocontacts
between controlled electromigration cycles. The nanowires used for the thinning
process are fabricated by shadow evaporation. The highest resolution obtained
using scanning force microscopy is about 3 nm. During the first few
electromigration cycles the overall slit structure of the nanocontact is
formed. The slit first passes along grain boundaries and then at a later stage
vertically splits grains in the course of consuming them. We find that first
the whole wire is heated and later during the thinning process as the slit
forms the current runs over several smaller contacts which needs less power.Comment: 4 pages, 4 figure
A system for production of defective interfering particles in the absence of infectious influenza A virus
<div><p>Influenza A virus (IAV) infection poses a serious health threat and novel antiviral strategies are needed. Defective interfering particles (DIPs) can be generated in IAV infected cells due to errors of the viral polymerase and may suppress spread of wild type (wt) virus. The antiviral activity of DIPs is exerted by a DI genomic RNA segment that usually contains a large deletion and suppresses amplification of wt segments, potentially by competing for cellular and viral resources. DI-244 is a naturally occurring prototypic segment 1-derived DI RNA in which most of the PB2 open reading frame has been deleted and which is currently developed for antiviral therapy. At present, coinfection with wt virus is required for production of DI-244 particles which raises concerns regarding biosafety and may complicate interpretation of research results. Here, we show that cocultures of 293T and MDCK cell lines stably expressing codon optimized PB2 allow production of DI-244 particles solely from plasmids and in the absence of helper virus. Moreover, we demonstrate that infectivity of these particles can be quantified using MDCK-PB2 cells. Finally, we report that the DI-244 particles produced in this novel system exert potent antiviral activity against H1N1 and H3N2 IAV but not against the unrelated vesicular stomatitis virus. This is the first report of DIP production in the absence of infectious IAV and may spur efforts to develop DIPs for antiviral therapy.</p></div
Spiral vortices traveling between two rotating defects in the Taylor-Couette system
Numerical calculations of vortex flows in Taylor-Couette systems with counter
rotating cylinders are presented. The full, time dependent Navier-Stokes
equations are solved with a combination of a finite difference and a Galerkin
method. Annular gaps of radius ratio and of several heights are
simulated. They are closed by nonrotating lids that produce localized Ekman
vortices in their vicinity and that prevent axial phase propagation of spiral
vortices. Existence and spatio temporal properties of rotating defects, of
modulated Ekman vortices, and of the spiral vortex structures in the bulk are
elucidated in quantitative detail.Comment: 9 pages, 9 figure
Impact of elasticity on the piezoresponse of adjacent ferroelectric domains investigated by scanning force microscopy
As a consequence of elasticity, mechanical deformations of crystals occur on
a length scale comparable to their thickness. This is exemplified by applying a
homogeneous electric field to a multi-domain ferroelectric crystal: as one
domain is expanding the adjacent ones are contracting, leading to clamping at
the domain boundaries. The piezomechanically driven surface corrugation of
micron-sized domain patterns in thick crystals using large-area top electrodes
is thus drastically suppressed, barely accessible by means of piezoresponse
force microscopy
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Electronic state spectroscopy of C<sub>2</sub>Cl<sub>4</sub>
The VUV spectrum of C2Cl4 is reported in the energy range 3.8-10.8 eV (325-115 nm). Several photoabsorption features are observed for the first time, including a very weak low-lying band which is provisionally attributed to a π → π* triplet transition. Recent ab initio calculations of the molecule’s electronic transitions [Arulmozhiraja et al. J. Chem. Phys. 129 (2008) 174506] provide the basis for the present assignments below 8.5 eV. An extended ndπ series is proposed to account for several higher-energy Rydberg bands. The identification of vibrational structure, dominated by symmetric C=C and CCl2 stretching in excitations from the HOMO, largely agrees with previous spectroscopic studies. The present absolute photoabsorption cross sections cover a wider energy range than the previous measurements and are used to calculate UV photolysis lifetimes of this aeronomic molecule at altitudes between 20 and 50 km
Antiskyrmions stabilized at interfaces by anisotropic Dzyaloshinskii-Moriya interaction
Chiral magnets are an emerging class of topological matter harbouring
localized and topologically protected vortex-like magnetic textures called
skyrmions, which are currently under intense scrutiny as a new entity for
information storage and processing. Here, on the level of micromagnetics we
rigorously show that chiral magnets cannot only host skyrmions but also
antiskyrmions as least-energy configurations over all non-trivial homotopy
classes. We derive practical criteria for their occurrence and coexistence with
skyrmions that can be fulfilled by (110)-oriented interfaces in dependence on
the electronic structure. Relating the electronic structure to an atomistic
spin-lattice model by means of density-functional calculations and minimizing
the energy on a mesoscopic scale applying spin-relaxation methods, we propose a
double layer of Fe grown on a W(110) substrate as a practical example. We
conjecture that ultrathin magnetic films grown on semiconductor or heavy metal
substrates with symmetry are prototype classes of materials hosting
magnetic antiskyrmions.Comment: 20 pages (11 pages + 9 pages supplementary material
CENP-A Is Dispensable for Mitotic Centromere Function after Initial Centromere/Kinetochore Assembly
Human centromeres are defined by chromatin containing the histone H3 variant CENP-A assembled onto repetitive alphoid DNA sequences. By inducing rapid, complete degradation of endogenous CENP-A, we now demonstrate that once the first steps of centromere assembly have been completed in G1/S, continued CENP-A binding is not required for maintaining kinetochore attachment to centromeres or for centromere function in the next mitosis. Degradation of CENP-A prior to kinetochore assembly is found to block deposition of CENP-C and CENP-N, but not CENP-T, thereby producing defective kinetochores and failure of chromosome segregation. Without the continuing presence of CENP-A, CENP-B binding to alphoid DNA sequences becomes essential to preserve anchoring of CENP-C and the kinetochore to each centromere. Thus, there is a reciprocal interdependency of CENP-A chromatin and the underlying repetitive centromere DNA sequences bound by CENP-B in the maintenance of human chromosome segregation
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