25,448 research outputs found
Leaf stripe resistance of spring barley cultivars
Results of six years of screening trials clearly indicate that effective resistance against barley leaf stripe is available, also in modern cultivars. Among the spring barley cultivars that are currently most widely grown in Denmark, Cabaret, Troon, Sebastian, Justina and Brazil appear most resistant, but only Brazil combines a favourable resistance performance (= low mean and standard deviation of environment-adjusted leaf stripe incidence) with a high number of observations (= years of testing). However, the cultivars appearing most resistant over the years are relatively old ones such as Vada, Alabama, Odin and particularly Scarlett, which has been resistant in all years in which it was tested. Amongst the new cultivars, Marigold, Native and SW Immer appear to have the most promising resistance properties so far. However, they have only been tested in two years of which only one had reasonably high infection levels. The results furthermore indicate huge year-to-year variation in infection levels, presumably due to variation in environmental conditions related to leaf stripe infection
Distance growth of quantum states due to initial system--environment correlations
Intriguing features of the distance between two arbitrary states of an open
quantum system are identified that are induced by initial system-environment
correlations. As an example, we analyze a qubit dephasingly coupled to a
bosonic environment. Within tailored parameter regimes, initial correlations
are shown to substantially increase a distance between two qubit states
evolving to long-time limit states according to exact non-Markovian dynamics.
It exemplifies the breakdown of the distance contractivity of the reduced
dynamics.Comment: 4 pages, 3 figure
High damage potential of seed-borne spot blotch in organically grown spring barley in Denmark
Spot blotch of barley (Bipolaris sorokiniana, perfect state: Cochliobolus sativus) occurs wherever barley is grown but is normally not considered a major problem in Danish barley production. It is therefore not included in routine disease surveys or official variety testing in Denmark. However, recommended seed contamination thresholds are 30% for spring barley and 15% for winter barley. Several spring barley varieties were grown under organic (no seed dressing, mechanical weeding) and conventional (seed dressing with fungicides, herbicide application) production conditions at three sites in Denmark in 2003. The harvested seeds were analysed for contamination levels of seed-borne B. sorokiniana using a blotter method. The percentage of seeds contaminated with B. sorokiniana ranged from about 5 to 95 % and was highly depending on the site, production system and variety. Contamination levels of organically cultivated plots were about twice as high as those of plots receiving conventional treatments. The germinating ability of seeds was highly affected by the level of B. sorokiniana contamination and declined drastically at contamination levels above 60%. This effect appeared to differ among varieties. The 1000-grain weight was not affected by the level of spot blotch contamination of seeds. The results indicate that the importance of spot blotch may be underrated, especially in organic barley production and that the role of varietal resistance should be investigated. More results are expected from ongoing seed analyses
Optimal multiqubit operations for Josephson charge qubits
We introduce a method for finding the required control parameters for a
quantum computer that yields the desired quantum algorithm without invoking
elementary gates. We concentrate on the Josephson charge-qubit model, but the
scenario is readily extended to other physical realizations. Our strategy is to
numerically find any desired double- or triple-qubit gate. The motivation is
the need to significantly accelerate quantum algorithms in order to fight
decoherence.Comment: 4 pages, 5 figure
Option Pricing in Multivariate Stochastic Volatility Models of OU Type
We present a multivariate stochastic volatility model with leverage, which is
flexible enough to recapture the individual dynamics as well as the
interdependencies between several assets while still being highly analytically
tractable.
First we derive the characteristic function and give conditions that ensure
its analyticity and absolute integrability in some open complex strip around
zero. Therefore we can use Fourier methods to compute the prices of multi-asset
options efficiently. To show the applicability of our results, we propose a
concrete specification, the OU-Wishart model, where the dynamics of each
individual asset coincide with the popular Gamma-OU BNS model. This model can
be well calibrated to market prices, which we illustrate with an example using
options on the exchange rates of some major currencies. Finally, we show that
covariance swaps can also be priced in closed form.Comment: 28 pages, 5 figures, to appear in SIAM Journal on Financial
Mathematic
Correlations in Free Fermionic States
We study correlations in a bipartite, Fermionic, free state in terms of
perturbations induced by one party on the other. In particular, we show that
all so conditioned free states can be modelled by an auxiliary Fermionic system
and a suitable completely positive map.Comment: 17 pages, no figure
Classical Concepts in Quantum Programming
The rapid progress of computer technology has been accompanied by a
corresponding evolution of software development, from hardwired components and
binary machine code to high level programming languages, which allowed to
master the increasing hardware complexity and fully exploit its potential.
This paper investigates, how classical concepts like hardware abstraction,
hierarchical programs, data types, memory management, flow of control and
structured programming can be used in quantum computing. The experimental
language QCL will be introduced as an example, how elements like irreversible
functions, local variables and conditional branching, which have no direct
quantum counterparts, can be implemented, and how non-classical features like
the reversibility of unitary transformation or the non-observability of quantum
states can be accounted for within the framework of a procedural programming
language.Comment: 11 pages, 4 figures, software available from
http://tph.tuwien.ac.at/~oemer/qcl.html, submitted for QS2002 proceeding
Intermediate quantum maps for quantum computation
We study quantum maps displaying spectral statistics intermediate between
Poisson and Wigner-Dyson. It is shown that they can be simulated on a quantum
computer with a small number of gates, and efficiently yield information about
fidelity decay or spectral statistics. We study their matrix elements and
entanglement production, and show that they converge with time to distributions
which differ from random matrix predictions. A randomized version of these maps
can be implemented even more economically, and yields pseudorandom operators
with original properties, enabling for example to produce fractal random
vectors. These algorithms are within reach of present-day quantum computers.Comment: 4 pages, 4 figures, research done at
http://www.quantware.ups-tlse.fr
Rolling moments in a trailing vortex flow field
Pressure distributions are presented which were measured on a wing in close proximity to a tip vortex of known structure generated by a larger, upstream semispan wing. Overall loads calculated by integration of these pressures are checked by independent measurements made with an identical model mounted on a force balance. Several conventional methods of wing analysis are used to predict the loads on the following wing. Strip theory is shown to give uniformly poor results for loading distribution, although predictions of overall lift and rolling moment are sometimes acceptable. Good results are obtained for overall coefficients and loading distribution by using linearized pressures in vortex-lattice theory in conjunction with a rectilinear vortex. The equivalent relation from reverse-flow theory that can be used to give economic predictions for overall loads is presented
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