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Bluetongue (BT) is a disease of ruminants caused by the bluetongue virus (BTV) transmitted by bites of Culicoides midges. Bluetongue has a worldwide prevalence and mortality in sheep varies from 0 to 30%. There are at least 27 BTV serotypes showing no or little cross protection. In 2006, BTV has been reported in north-western Europe for the first time, and has caused a huge outbreak with large economic losses. BTV (family Reoviridae, genus Orbivirus) is a non-enveloped virus with a ten-segmented dsRNA genome encoding seven viral proteins (VP1-7) and four non-structural (NS1-4) proteins. VP2 is the outer capsid protein, and is the serotype specific target for neutralizing antibodies. NS3 and its N-terminal truncated form NS3a (Seg-10) enable virus release from infected cells. Currently, live-attenuated and inactivated BT vaccines have been marketed, but these have several shortcomings. Therefore there is a need for next-generation types of BT vaccines with improved vaccine profile. Here, such a novel vaccine platform based on BTV without NS3/NS3a expression is described. BTV based on lab adapted strain BTV1, vaccine related BTV6, and virulent BTV8 were equipped with a deletion in Seg-10 abolishing NS3/NS3a expression and with Seg-2 encoding serotype determining VP2 from serotype 8. All three vaccine candidates were not virulent in sheep and did not show viremia, whereas seroconversion was dependent on replication of vaccine virus. This suggests that BTV without NS3/NS3a replicates only locally. Sheep were completely protected against infection of virulent BTV8. In a second efficacy experiment in sheep, complete serotype specific protection was demonstrated at nine weeks after booster vaccination. A competitive ELISA based on NS3 antibodies enables the differentiation of infected from vaccinated animals (DIVA). Uptake of the NS3/NS3a knockout vaccine candidate by midges is highly unlikely, due to the absence of viremia after vaccination. This vaccine candidate has therefore been named the Disabled Infectious, Single Animal (DISA) vaccine. Additionally, replication of BT DISA vaccine in midges is abolished as shown after injection of Culicoides sonorensis midges. The BT DISA vaccine platform was also adapted for other BTV serotypes by exchange of Seg-2 (VP2) or by use of chimeric Seg-2 originating from two different serotypes. The latter showed a broader application of the vaccine platform and neutralizing responses against both ancestor serotypes. In conclusion, BT DISA vaccine is effective, safe, enables DIVA, and can be used for many serotypes by exchange of VP2
On narrowing coated conductor film: emergence of granularity-induced field hysteresis of transport critical current
Critical current density Jc in polycrystalline or granular superconducting
material is known to be hysteretic with applied field H due to the focusing of
field within the boundary between adjacent grains. This is of concern in the
so-called coated conductors wherein superconducting film is grown on a
granular, but textured surface of a metal substrate. While previous work has
mainly been on Jc determined using induced or magnetization currents, the
present work utilizes transport current via an applied potential in strip
geometry. It is observed that the effect is not as pronounced using transport
current, probably due to a large difference in criterion voltage between the
two types of measurements. However, when the films are narrowed by patterning
into 200-, 100-, or 80-micron, the hysteresis is clearly seen, because of the
forcing of percolation across higher-angle grain boundaries. This effect is
compared for films grown on ion-beam-assisted-deposited (IBAD) YSZ substrate
and those grown on rolling-assisted-biaxially-textures substrates (RABiTS)
which have grains that are about ten times larger. The hysteresis is more
pronounced for the latter, which is more likely to have a weak grain boundary
spanning the width of the microbridge. This is also of concern to applications
in which coated conductors will be striated in order to reduce of AC losses.Comment: text-only: 10 pages, plus 5 figures on 5 page
Statistical mechanics of the international trade network
Analyzing real data on international trade covering the time interval
1950-2000, we show that in each year over the analyzed period the network is a
typical representative of the ensemble of maximally random weighted networks,
whose directed connections (bilateral trade volumes) are only characterized by
the product of the trading countries' GDPs. It means that time evolution of
this network may be considered as a continuous sequence of equilibrium states,
i.e. quasi-static process. This, in turn, allows one to apply the linear
response theory to make (and also verify) simple predictions about the network.
In particular, we show that bilateral trade fulfills fluctuation-response
theorem, which states that the average relative change in import (export)
between two countries is a sum of relative changes in their GDPs. Yearly
changes in trade volumes prove that the theorem is valid.Comment: 6 pages, 2 figure
Microwave Near-Field Imaging of Electric Fields in a Superconducting Microstrip Resonator
We describe the use of a cryogenic near-field scanning microwave microscope
to image microwave electric fields from superconducting and normal-metal
microstrip resonators. The microscope employs an open-ended coaxial probe and
operates from 77 to 300 K in the 0.01-20 GHz frequency range with a spatial
resolution of about 200 mm. We describe the operation of the system and present
microwave images of Cu and Tl2Ba2CaCu2O8 microstrip resonators, showing
standing wave patterns at the fundamental and second harmonic frequencies.Comment: 9 pages, 3 eps figure
Low Power Superconducting Microwave Applications and Microwave Microscopy
We briefly review some non-accelerator high-frequency applications of
superconductors. These include the use of high-Tc superconductors in front-end
band-pass filters in cellular telephone base stations, the High Temperature
Superconductor Space Experiment, and high-speed digital electronics. We also
present an overview of our work on a novel form of near-field scanning
microscopy at microwave frequencies. This form of microscopy can be used to
investigate the microwave properties of metals and dielectrics on length scales
as small as 1 mm. With this microscope we have demonstrated quantitative
imaging of sheet resistance and topography at microwave frequencies. An
examination of the local microwave response of the surface of a heat-treated
bulk Nb sample is also presented.Comment: 11 pages, including 6 figures. Presented at the Eight Workshop on RF
Superconductivity. To appear in Particle Accelerator
Near-Field Scanning Microwave Microscopy: Measuring Local Microwave Properties and Electric Field Distributions
We describe the near-field microwave microscopy of microwave devices on a
length scale much smaller than the wavelength used for imaging. Our microscope
can be operated in two possible configurations, allowing a quantitative study
of either material properties or local electric fields.Comment: 4 pages, 8 figures, minor corrections to text and 2 figure
Near-Field Microwave Microscopy of Materials Properties
Near-field microwave microscopy has created the opportunity for a new class
of electrodynamics experiments of materials. Freed from the constraints of
traditional microwave optics, experiments can be carried out at high spatial
resolution over a broad frequency range. In addition, the measurements can be
done quantitatively so that images of microwave materials properties can be
created. We review the five major types of near-field microwave microscopes and
discuss our own form of microscopy in detail. Quantitative images of microwave
sheet resistance, dielectric constant, and dielectric tunability are presented
and discussed. Future prospects for near-field measurements of microwave
electrodynamic properties are also presented.Comment: 31 pages, 9 figures, lecture given at the 1999 NATO ASI on Microwave
Superconductivity Changes suggested by editor, including full reference
Frequency Following Imaging of Electric Fields from Resonant Superconducting Devices using a Scanning Near-Field Microwave Microscope
We have developed a scanning near-field microwave microscope that operates at
cryogenic temperatures. Our system uses an open-ended coaxial probe with a 200
mm inner conductor diameter and operates from 77 to 300 K in the 0.01-20 GHz
frequency range. In this paper, we present microwave images of the electric
field distribution above a Tl2Ba2CaCu2O8 microstrip resonator at 77 K, measured
at several heights. In addition, we describe the use of a frequency-following
circuit to study the influence of the probe on the resonant frequency of the
device.Comment: 4 pages, postscript file with 6 figures conference proceeding for the
Applied Superconductivity Conference 199
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