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Field Interaction (field + interaction)

Distribution by Scientific Domains

Physics and Astronomy	72%

Selected Abstracts

The origins and present status of the radio wave controversy in NMR

CONCEPTS IN MAGNETIC RESONANCE, Issue 4 2009
D.I. Hoult
Abstract The origins, history, and present status of the controversy surrounding a quantum description of the NMR signal as being due to radio waves are traced. With the Principle of Relativity and Coulomb's Law as formal starting points and the minimum of mathematics needed for understanding, the derivation of a classical electromagnetic theory of signal reception is first given. The agreement between that classical theory and a recent NMR experiment is then presented, leading to proof that, except for the highest field imaging experiments, there is no significant contribution of radio waves to the signal. Attention is drawn to the very different properties of the near and far energy, momenta, and fields inherent in the derivation. The role of the Correspondence Principle in formulating a quantum description is then emphasized and it is shown that the standard NMR interpretation of Dicke's theory of coherent spontaneous emission,that the latter is responsible for the NMR signal,cannot be correct. Finally, the author speculates on some of the intriguing relationships found in the classical electrodynamics of NMR signal reception and attempts to relate them to a common quantum electrodynamic precept of near field interaction: that the free induction decay voltage present at the terminals of an open-circuit receiving coil is based on an exchange of virtual photons between the nuclei in a sample and the free electrons in a receiving coil. © 2009 Crown in the right of Canada. Concepts Magn Reson Part A 34A: 193,216, 2009. [source]

Cover Picture: Fortschritte der Physik 11,12 / 2009

FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 11-12 2009
Article first published online: 9 NOV 200
The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source]

Cover Picture: Fortschritte der Physik 10 / 2009

FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 10 2009
Article first published online: 14 SEP 200
The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source]

Cover Picture: Fortschritte der Physik 9 / 2009

FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 9 2009
Article first published online: 21 AUG 200
The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source]

Cover Picture: Fortschritte der Physik 5,7 / 2009

FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 5-7 2009
Article first published online: 27 MAY 200
The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source]

Cover Picture: Fortschritte der Physik 3,4 /2009

FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 3-4 2009
Article first published online: 23 MAR 200
The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source]

Cover Picture: Fortschritte der Physik 1,2 /2009

FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 1-2 2009
Article first published online: 9 FEB 200
The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source]

ABSINTH: A new continuum solvation model for simulations of polypeptides in aqueous solutions

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 5 2009
Andreas Vitalis
Abstract A new implicit solvation model for use in Monte Carlo simulations of polypeptides is introduced. The model is termed ABSINTH for self- Assembly of Biomolecules Studied by an Implicit, Novel, and Tunable Hamiltonian. It is designed primarily for simulating conformational equilibria and oligomerization reactions of intrinsically disordered proteins in aqueous solutions. The paradigm for ABSINTH is conceptually similar to the EEF1 model of Lazaridis and Karplus (Proteins 1999, 35, 133). In ABSINTH, the transfer of a polypeptide solute from the gas phase into a continuum solvent is the sum of a direct mean field interaction (DMFI), and a term to model the screening of polar interactions. Polypeptide solutes are decomposed into a set of distinct solvation groups. The DMFI is a sum of contributions from each of the solvation groups, which are analogs of model compounds. Continuum-mediated screening of electrostatic interactions is achieved using a framework similar to the one used for the DMFI. Promising results are shown for a set of test cases. These include the calculation of NMR coupling constants for short peptides, the assessment of the thermal stability of two small proteins, reversible folding of both an ,-helix and a ,-hairpin forming peptide, and the polymeric properties of intrinsically disordered polyglutamine peptides of varying lengths. The tests reveal that the computational expense for simulations with the ABSINTH implicit solvation model increase by a factor that is in the range of 2.5,5.0 with respect to gas-phase calculations. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009 [source]

Modeling of ZnO nanorods for evanescent field optical sensors

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2007
Sandra Börner
Abstract The optical wave guiding properties of ZnO nanorods are simulated and studied in detail using a block-iterative frequency-domain method and the results of a finite difference method as reference data. The simulations are performed for different wavelengths in the infrared spectral region that are related to specific gas absorption lines. Here both single ZnO nanorods and nanorod arrays with varying period lengths are investigated. The evanescent field distributions and penetration depths into the surrounding media are analyzed and compared as a function of wavelength and rod diameter. Our results give a general overview on the size range where ZnO nanorods may be used for evanescent field interaction based sensors for the detection of gas molecules like CO, CO2 or O2. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Structural and magnetic properties in the ruthenate Bi2.67Pr0.33Ru3O11

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2006
S. Zouari
Abstract An unreported praseodymium substituted phase of the Bi-Ru-O system with formula Bi2.67Pr0.33Ru3O11was prepared. Its crystal structure and magnetic properties were investigated. Pr substituted occurs only on one of the two Bi sites. The magnetism of the compound is dominated by a Pr3+ contribution, that appears to interact antiferromagnetically. A non linear variation of the reciprocal magnetic susceptibility is observed that appears to account for crystal electric field interactions on the Pr3+ ions. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Comment: A biological guide for electromagnetic safety: the stress response

BIOELECTROMAGNETICS, Issue 8 2004
Martin Blank
Abstract Questions of safety of electromagnetic (EM) fields should be based on relevant biological properties, i.e., specific cellular reactions to potentially harmful stimuli. The stress response is a well documented protective reaction of plant and animal cells to a variety of environmental threats, and it is stimulated by both extremely low frequency (ELF) and radio frequency (RF) EM fields. It involves activation of DNA to initiate synthesis of stress proteins. Thermal and non-thermal stimuli affect different segments of DNA and utilize different biochemical pathways. However, both ELF and RF stimulate the same non-thermal pathway. Since the same biochemical reactions are stimulated in different frequency ranges with very different specific absorption rates (SARs), SAR level is not a valid basis for safety standards. Studies of EM field interactions with DNA and with model systems provide insight into a plausible mechanism that can be effective in ELF and RF ranges. Bioelectromagnetics 25:642,646, 2004. © 2004 Wiley-Liss, Inc. [source]