1,599 research outputs found
The control of PVY in Dutch seed potato culture
Over the recent years Potato virus Y presents a growing problem in Dutch seed potato culture. In recent years a significant % of seed potato lots was de-classified due to PVY infections. This apparent increase in PVY infections was unexpected since no increase in field symptoms were observed and the numbers of aphids caught in the yellow water traps and high suction traps showed a clear decline over the last 10 years http://www.aab.org.uk/images/VIRO_CONF_PROG.pd
Ephemeral properties and the illusion of microscopic particles
Founding our analysis on the Geneva-Brussels approach to quantum mechanics,
we use conventional macroscopic objects as guiding examples to clarify the
content of two important results of the beginning of twentieth century:
Einstein-Podolsky-Rosen's reality criterion and Heisenberg's uncertainty
principle. We then use them in combination to show that our widespread belief
in the existence of microscopic particles is only the result of a cognitive
illusion, as microscopic particles are not particles, but are instead the
ephemeral spatial and local manifestations of non-spatial and non-local
entities
An active feedback recovery technique from disruption events induced by m=2 n=1 tearing modes in ohmically heated tokamak plasmas
We present experimental results of magnetic feedback control on the m=2, n=1
tearing mode in RFX-mod operated as a circular ohmically heated tokamak. The
feedback suppression of the non-resonant m=2, n=1 Resistive Wall Mode (RWM) in
q(a)<2 plasmas is a well-established result of RFX-mod. The control of the
tearing counterpart, which develops in q(a)>2 equilibrium, is instead a more
difficult issue. In fact, the disruption induced by a growing amplitude m=2,
n=1 tearing mode can be prevented by feedback only when the resonant surface
q=2 is close to the plasma edge, namely 2<q(a)<2.5, and the electron density
does not exceed approximately half of the Greenwald limit. A combined technique
of tearing mode and q(a) control has been therefore developed to recover the
discharge from the most critical conditions: the potentially disruptive tearing
mode is converted into the relatively benign RWM by suddenly decreasing q(a)
below 2. The experiments demonstrate the concept with 100% of successful cases.
The q(a) control has been performed through the plasma current, given the
capability of the toroidal loop-voltage power supply of RFX-mod. We also
propose a path for controlling q(a) by acting on the plasma shape, which could
be applied to medium size elongated tokamaks
Measurement Theory in Lax-Phillips Formalism
It is shown that the application of Lax-Phillips scattering theory to quantum
mechanics provides a natural framework for the realization of the ideas of the
Many-Hilbert-Space theory of Machida and Namiki to describe the development of
decoherence in the process of measurement. We show that if the quantum
mechanical evolution is pointwise in time, then decoherence occurs only if the
Hamiltonian is time-dependent. If the evolution is not pointwise in time (as in
Liouville space), then the decoherence may occur even for closed systems. These
conclusions apply as well to the general problem of mixing of states.Comment: 14 pages, IASSNS-HEP 93/6
Constraints on Lorentz Invariance Violation from Fermi-Large Area Telescope Observations of Gamma-Ray Bursts
We analyze the MeV/GeV emission from four bright Gamma-Ray Bursts (GRBs)
observed by the Fermi-Large Area Telescope to produce robust, stringent
constraints on a dependence of the speed of light in vacuo on the photon energy
(vacuum dispersion), a form of Lorentz invariance violation (LIV) allowed by
some Quantum Gravity (QG) theories. First, we use three different and
complementary techniques to constrain the total degree of dispersion observed
in the data. Additionally, using a maximally conservative set of assumptions on
possible source-intrinsic spectral-evolution effects, we constrain any vacuum
dispersion solely attributed to LIV. We then derive limits on the "QG energy
scale" (the energy scale that LIV-inducing QG effects become important, E_QG)
and the coefficients of the Standard Model Extension. For the subluminal case
(where high energy photons propagate more slowly than lower energy photons) and
without taking into account any source-intrinsic dispersion, our most stringent
limits (at 95% CL) are obtained from GRB090510 and are E_{QG,1}>7.6 times the
Planck energy (E_Pl) and E_{QG,2}>1.3 x 10^11 GeV for linear and quadratic
leading order LIV-induced vacuum dispersion, respectively. These limits improve
the latest constraints by Fermi and H.E.S.S. by a factor of ~2. Our results
disfavor any class of models requiring E_{QG,1} \lesssim E_Pl.Comment: Accepted for publication by Physical Review
Agrotechnologies towards Ecotechnologies the three pillars for developing Eco-design
International audienceTo boost agrotechnologies towards ecotechnologies ("environmental technologies" according to ETAP programme of EU, or "more ecologically productive technologies" in the context of agriculture), we need to strengthen a "triple bottom" system: -To take into account, in "Life Cycle Analysis" methodologies, the natural variability in time and space of these applications in land use. - To develop an overall approach for realistic machinery qualification, in order to feed the environmental burdens accurately through relevant data bases collected on agrotechnologies in real action. - To work on Eco-innovation processes, by deepening specific innovation tools and methods, for implementation of innovative solutions chosen according to LCA results. This paper presents the concept, develops the methods and illustrates them by examples of results on organic spreading technologies
How Events Come Into Being: EEQT, Particle Tracks, Quantum Chaos, and Tunneling Time
In sections 1 and 2 we review Event Enhanced Quantum Theory (EEQT). In
section 3 we discuss applications of EEQT to tunneling time, and compare its
quantitative predictions with other approaches, in particular with
B\"uttiker-Larmor and Bohm trajectory approach. In section 4 we discuss quantum
chaos and quantum fractals resulting from simultaneous continuous monitoring of
several non-commuting observables. In particular we show self-similar,
non-linear, iterated function system-type, patterns arising from quantum jumps
and from the associated Markov operator. Concluding remarks pointing to
possible future development of EEQT are given in section 5.Comment: latex, 27 pages, 7 postscript figures. Paper submitted to Proc.
Conference "Mysteries, Puzzles And Paradoxes In Quantum Mechanics, Workshop
on Entanglement And Decoherence, Palazzo Feltrinelli, Gargnano, Garda Lake,
Italy, 20-25 September, 199
The role of infrared divergence for decoherence
Continuous and discrete superselection rules induced by the interaction with
the environment are investigated for a class of exactly soluble Hamiltonian
models. The environment is given by a Boson field. Stable superselection
sectors emerge if and only if the low frequences dominate and the ground state
of the Boson field disappears due to infrared divergence. The models allow
uniform estimates of all transition matrix elements between different
superselection sectors.Comment: 11 pages, extended and simplified proo
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