1,042 research outputs found
Effect of spacing and size of planting material on growth and yield of turmeric grown in coconut plantation
Effect of spacing and seed rhizome size on growth and yield of ginger grown as intercrop in coconut plantation in West Bengal
Spin-selective reactions of radical pairs act as quantum measurements
Since the 1970s, spin-selective reactions of radical pairs have been modelled
theoretically by adding phenomenological rate equations to the quantum
mechanical equation of motion of the radical pair spin density matrix. Here,
using a quantum measurement approach, we derive an alternative set of rate
expressions which predict a faster decay of coherent superpositions of the
singlet and triplet radical pair states. The difference between the two
results, however, is not dramatic and would probably be difficult to
distinguish experimentally from decoherence arising from other sources.Comment: Chemical Physics Letters, in press. 17 pages including 2 figues; pdf
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Reaction operators for spin-selective chemical reactions of radical pairs
Spin-selective reactions of radical pairs have traditionally been modelled
theoretically by adding phenomenological rate equations to the quantum
mechanical equation of motion of the radical pair spin density matrix. More
recently an alternative set of rate expressions, based on a quantum measurement
approach, has been suggested. Here we show how these two reaction operators can
be seen as limiting cases of a more general reaction scheme.Comment: 10 pages, pdf from MS Word. Chem. Phys. Lett. (in press
Time evolution of spin state of radical ion pair in microwave field: An analytical solution
The paper reports an exact solution for the problem of spin evolution of
radical ion pair in static magnetic and resonant microwave field taking into
account Zeeman and hyperfine interactions and spin relaxation. The values of
parameters that provide one of the four possible types of solution are
analysed. It is demonstrated that in the absence of spin relaxation, besides
the zero field invariant an invariant at large amplitudes of the resonant
microwave field can be found. The two invariants open the possibility for
simple calculation of microwave pulses to control quantum state of the radical
pair. The effect of relaxation on the invariants is analysed and it is shown
that changes in the high field invariant are induced by phase relaxation.Comment: 18 pages, 7 figure
Condensation of charged bosons in plasma physics and cosmology
The screening of impurities in plasma with Bose-Einstein condensate of
electrically charged bosons is considered. It is shown that the screened
potential is drastically different from the usual Debye one. The polarization
operator of photons in plasma acquires infrared singular terms at small photon
momentum and the screened potential drops down as a power of distance and even
has an oscillating behavior, similar to the Friedel oscillations in plasma with
degenerate fermions. The magnetic properties of the cosmological plasma with
condensed W-bosons are also discussed. It is shown that W-bosons condense in
the ferromagnetic state. It could lead to spontaneous magnetization of the
primeval plasma. The created magnetic fields may seed galactic and
intergalactic magnetic fields observed in the present-day universe.Comment: 9 pages, invited talk at the International Seminar "Quarks 2010",
Kolomna, Russia, June, 6-12, 201
Electron spin relaxation can enhance the performance of a cryptochrome-based magnetic compass sensor
The radical pair model of the avian magnetoreceptor relies on longâlived electron spin coherence. Dephasing, resulting from interactions of the spins with their fluctuating environment, is generally assumed to degrade the sensitivity of this compass to the direction of the Earth's magnetic field. Here we argue that certain spin relaxation mechanisms can enhance its performance. We focus on the flavinâtryptophan radical pair in cryptochrome, currently the only candidate magnetoreceptor molecule. Correlation functions for fluctuations in the distance between the two radicals in Arabidopsis thaliana cryptochrome 1 were obtained from molecular dynamics simulations and used to calculate the spin relaxation caused by modulation of the exchange and dipolar interactions. We find that intermediate spin relaxation rates afford substantial enhancements in the sensitivity of the reaction yields to an Earthâstrength magnetic field. Supported by calculations using toy radical pair models, we argue that these enhancements could be consistent with the molecular dynamics and magnetic interactions in avian cryptochromes
Implementation of NMR quantum computation with para-hydrogen derived high purity quantum states
We demonstrate the first implementation of a quantum algorithm on a liquid
state nuclear magnetic resonance (NMR) quantum computer using almost pure
states. This was achieved using a two qubit device where the initial state is
an almost pure singlet nuclear spin state of a pair of 1H nuclei arising from a
chemical reaction involving para-hydrogen. We have implemented Deutsch's
algorithm for distinguishing between constant and balanced functions with a
single query.Comment: 7 pages RevTex including 6 figures. Figures 4-6 are low quality to
save space. Submitted to Phys Rev
Fluorescence-detected magnetic field effects on radical pair reactions from femtolitre volumes
We show that the effects of applied magnetic fields on radical pair reactions can be sensitively measured from sample volumes as low as ~100 femtolitres using total internal reflection fluorescence microscopy. Development of a fluorescence-based microscope method is likely to be a key step in further miniaturisation that will allow detection of magnetic field effects on single molecules
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