2,395 research outputs found
Residual strain in free-standing CdTe nanowires overgrown with HgTe
We investigate the crystal properties of CdTe nanowires overgrown with HgTe.
Scanning electron microscopy (SEM) and scanning transmission electron
microscopy (STEM) confirm, that the growth results in a high ensemble
uniformity and that the individual heterostructures are single-crystalline,
respectively. We use high-resolution X-ray diffraction (HRXRD) to investigate
strain, caused by the small lattice mismatch between the two materials. We find
that both CdTe and HgTe show changes in lattice constant compared to the
respective bulk lattice constants. The measurements reveal a complex strain
pattern with signatures of both uniaxial and shear strains present in the
overgrown nanowires
Multiqubit Spin
It is proposed that the state space of a quantum object with a complicated
discrete spectrum can be used as a basis for multiqubit recording and
processing of information in a quantum computer. As an example, nuclear spin
3/2 is considered. The possibilities of writing and reading two quantum bits of
information, preparation of the initial state, implementation of the "rotation"
and "controlled negation" operations, which are sufficient for constructing any
algorithms, are demonstrated.Comment: 7 pages, PostScript, no figures; translation of Pis'ma Zh. Eksp.
Teor. Fiz. 70, No. 1, pp. 59-63, 10 July 1999; (Submitted 29 April 1999;
resubmitted 2 June 1999
NMR Simulation of an Eight-State Quantum System
The propagation of excitation along a one-dimensional chain of atoms is
simulated by means of NMR. The physical system used as an analog quantum
computer is a nucleus of 133-Cs (spin 7/2) in a liquid crystalline matrix. The
Hamiltonian of migration is simulated by using a special 7-frequency pulse, and
the dynamics is monitored by following the transfer of population from one of
the 8 spin energy levels to the other.Comment: 10 pages, 3 figure
Epidemiology and integrated control of Potato Late Blight in Europe
Phytophthora infestans, the causal agent of late blight, is a major threat to potato production in northwestern Europe. Before 1980, the worldwide population of P. infestans outside Mexico appeared to be asexual and to consist of a single clonal lineage of A1 mating type characterized by a single genotype. It is widely believed that new strains migrated into Europe in 1976 and that this led to subsequent population changes including the introduction of the A2 mating type. The population characteristics of recently collected isolates in NW Europe show a diverse population including both mating types, sexual reproduction and oospores, although differences are observed between regions. Although it is difficult to find direct evidence that new strains are more aggressive, there are several indications from experiments and field epidemics that the aggressiveness of P. infestans has increased in the past 20 years. The relative importance of the different primary inoculum sources and specific measures for reducing their role, such as covering dumps with plastic and preventing seed tubers from becoming infected, is described for the different regions. In NW Europe, varieties with greater resistance tend not to be grown on a large scale. From the grower’s perspective, the savings in fungicide input that can be achieved with these varieties are not compensated by the higher (perceived) risk of blight. Fungicides play a crucial role in the integrated control of late blight. The spray strategies in NW Europe and a table of the specific attributes of the most important fungicides in Europe are presented. The development and use of decision support systems (DSSs) in NW Europe are described. In The Netherlands, it is estimated that almost 40% of potato growers use recommendations based on commercially available DSS. In the Nordic countries, a new DSS concept with a fixed 7-day spray interval and a variable dose rate is being tested. In the UK, commercially available DSSs are used for c. 8% of the area. The validity of Smith Periods for the new population of P. infestans in the UK is currently being evaluated
Path Integrals in Polar Field Variables in QFT
We show how to transform a -dimensional Euclidean path integral in terms
of two (Cartesian) fields to a path integral in terms of polar field variables.
First we present a conjecture that states how this transformation should be
done. Then we show that this conjecture is correct in the case of two toy
models. Finally the conjecture will be proven for a general QFT model with two
fields
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