scholarly journals Can disordered radical pair systems provide a basis for a magnetic compass in animals?

2009 ◽  
Vol 7 (suppl_2) ◽  
Author(s):  
Erin Hill ◽  
Thorsten Ritz
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Radical Pair ◽  
Magnetic Compass ◽  
Magnetic Field Direction ◽  
Chemical Signal ◽  
Radical Pairs ◽  
Directional Information ◽  
Minimum Number ◽  
Signal Production

A proposed mechanism for magnetic compasses in animals is that systems of radical pairs transduce magnetic field information to the nervous system. One can show that perfectly ordered arrays of radical pairs are sensitive to the direction of the external magnetic field and can thus operate, in principle, as a magnetic compass. Here, we investigate how disorder, inherent in biological cells, affects the ability of radical pair systems to provide directional information. We consider biologically inspired geometrical arrangements of ensembles of radical pairs with increasing amounts of disorder and calculate the effect of changing the direction of the external magnetic field on the rate of chemical signal production by radical pair systems. Using a previously established signal transduction model, we estimate the minimum number of receptors necessary to allow for detection of the change in chemical signal owing to changes in magnetic field direction. We quantify the required increase in the number of receptors to compensate for the signal attenuation through increased disorder. We find radical-pair-based compass systems to be relatively robust against disorder, suggesting several scenarios as to how a compass structure can be realized in a biological cell.

scholarly journals Light-dependent magnetoreception in birds: the crucial step occurs in the dark

2016 ◽  
Vol 13 (118) ◽  
pp. 20151010 ◽  
Author(s):  
Roswitha Wiltschko ◽  
Margaret Ahmad ◽  
Christine Nießner ◽  
Dennis Gehring ◽  
Wolfgang Wiltschko
Keyword(s):  
Magnetic Field ◽  
Flavin Adenine Dinucleotide ◽  
Radical Pair ◽  
Magnetic Compass ◽  
Radical Pairs ◽  
Intermittent Light ◽  
Pair Model ◽  
Dark Interval ◽  
Behavioural Experiments ◽  
The Magnetic Field

The Radical Pair Model proposes that the avian magnetic compass is based on spin-chemical processes: since the ratio between the two spin states singlet and triplet of radical pairs depends on their alignment in the magnetic field, it can provide information on magnetic directions. Cryptochromes, blue light-absorbing flavoproteins, with flavin adenine dinucleotide as chromophore, are suggested as molecules forming the radical pairs underlying magnetoreception. When activated by light, cryptochromes undergo a redox cycle, in the course of which radical pairs are generated during photo-reduction as well as during light-independent re-oxidation. This raised the question as to which radical pair is crucial for mediating magnetic directions. Here, we present the results from behavioural experiments with intermittent light and magnetic field pulses that clearly show that magnetoreception is possible in the dark interval, pointing to the radical pair formed during flavin re-oxidation. This differs from the mechanism considered for cryptochrome signalling the presence of light and rules out most current models of an avian magnetic compass based on the radical pair generated during photo-reduction. Using the radical pair formed during re-oxidation may represent a specific adaptation of the avian magnetic compass.

Theoretical Modeling and Exact Solution for Extreme Bending Deformation of Hard-Magnetic Soft Beams

2020 ◽  
Vol 87 (4) ◽  
Author(s):  
Wei Chen ◽  
Lin Wang
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Exact Solutions ◽  
Flexible Electronics ◽  
Soft Materials ◽  
Theoretical Modeling ◽  
Magnetic Field Direction ◽  
Magnetic Actuation ◽  
Governing Equations ◽  
Analysis And Design

Abstract Hard-magnetic soft materials (HMSMs) manufactured by embedding hard-magnetic particles in soft materials belong to a new type of soft active materials. The abilities of fast and complicated transformations of hard-magnetic soft structures provide a promising technology for soft robotics, flexible electronics, and biomedical devices. It is significant to investigate the mechanical behaviors of hard-magnetic soft structures for their better applications. In this work, a hard-magnetic soft beam under an external magnetic field is theoretically modeled and the exact solutions for its mechanical responses are presented. First, the governing equations and boundary conditions are derived based on the principle of minimum potential energy. To solve the derived governing equations analytically, a new polynomial fitting model for hyperelastic materials is proposed for the hard-magnetic soft beam. Then, the exact solutions of a cantilevered hard-magnetic soft beam actuated by a uniform magnetic field in any direction are obtained. The newly derived exact solutions are further verified by comparing current results with those from recent simulations and experiments. For large bending angles up to 90 deg and extreme bending angle up to 180 deg, quite consistent agreement among exact solutions, numerical simulations, and experimental observations can be achieved. Finally, using our theoretical model, the deformation of the hard-magnetic soft beam actuated by magnetic fields in an arbitrary direction with non-zero magnetic declination is explored. When the magnetic actuation is increased from a small level gradually, the hard-magnetic soft beam deflects and it would undergo small, large, and extreme bending deformations in sequence. It is very interesting that, when the magnetic actuation is sufficiently large, the hard-magnetic soft beam is stretched and its centerline tends to align with the external magnetic field direction, implying that the hard-magnetic soft beam undergoes a uniaxial tension. The theoretical modeling and exact solutions for hard-magnetic soft beams are expected to be useful in the analysis and design of soft materials and structures.

External magnetic field dependent influence of lanthanide ions on the chemistry of radical pairs in micelles

1985 ◽  
Vol 120 (4-5) ◽  
pp. 397-400 ◽  
Author(s):  
Nicholas J. Turro ◽  
Xuegong Lei ◽  
Ian R. Gould ◽  
Matthew B. Zimmt
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Lanthanide Ions ◽  
Radical Pairs ◽  
Field Dependent

scholarly journals Flux tubes in Nf = 2 + 1 QCD with external magnetic fields

2018 ◽  
Vol 175 ◽  
pp. 12008 ◽  
Author(s):  
Claudio Bonati ◽  
Salvatore Calì ◽  
Massimo D’Elia ◽  
Michele Mesiti ◽  
Francesco Negro ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Tree Level ◽  
Magnetic Field Direction ◽  
Physical Point ◽  
Flux Tubes ◽  
Gauge Action ◽  
Uniform External Magnetic Field ◽  
Static Quark ◽  
The Magnetic Field

We study the behavior of the confining flux tube in Nf = 2 + 1 QCD at the physical point, discretized with the stout smearing improved staggered quark action and the tree level Symazik gauge action. We discuss how it depends on a uniform external magnetic field, showing how it displays anisotropies with respect to the magnetic field direction. Moreover, we compare the observed anisotropy pattern with that of the static quark-antiquark (QQ̅) potential we obtained in [1, 2].

Time-resolved studies of radical pairs

2009 ◽  
Vol 37 (2) ◽  
pp. 358-362 ◽  
Author(s):  
Jonathan R. Woodward ◽  
Timothy J. Foster ◽  
Alex R. Jones ◽  
Adrian T. Salaoru ◽  
Nigel S. Scrutton
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Chemical Reactions ◽  
Radical Pair ◽  
Radical Pair Mechanism ◽  
Magnetic Field Effects ◽  
Radical Pairs ◽  
Time Resolved ◽  
Field Effects ◽  
Field Sensitivity

The effect of magnetic fields on chemical reactions through the RP (radical pair) mechanism is well established, but there are few examples, in the literature, of biological reactions that proceed through RP intermediates and show magnetic field-sensitivity. The present and future relevance of magnetic field effects in biological reactions is discussed.

scholarly journals Radical pairs may play a role in microtubule reorganization

2021 ◽  
Author(s):  
Hadi ZADEH-HAGHIGHI ◽  
Christoph Simon
Keyword(s):  
Magnetic Field ◽  
Radical Pair ◽  
Spin Dynamics ◽  
Radical Pair Mechanism ◽  
Magnetic Field Effects ◽  
Radical Pairs ◽  
Quantum Theories ◽  
Mechanism Model ◽  
Field Effects ◽  
Isotopic Dependence

The exact mechanism behind general anesthesia remains an open question in neuroscience. It has been proposed that anesthetics selectively prevent consciousness and memory via acting on microtubules (MTs). It is known that the magnetic field modulates MT organization. A recent study shows that a radical pair model can explain the isotope effect in xenon-induced anesthesia and predicts magnetic field effects on anesthetic potency. Further, reactive oxygen species are also implicated in MT stability and anesthesia. Based on a simple radical pair mechanism model and a simple mathematical model of MT organization, we show that magnetic fields can modulate spin dynamics of naturally occurring radical pairs in MT. We show that the spin dynamics influence a rate in the reaction cycle, which translates into a change in the MT density. We can reproduce magnetic field effects on the MT concentration that have been observed. Our model also predicts additional effects at slightly higher fields. Our model further predicts that the effect of zinc on the MT density exhibits isotopic dependence. The findings of this work make a connection between microtubule-based and radical pair-based quantum theories of consciousness.

scholarly journals Upper bound on the biological effects of 50/60 Hz magnetic fields mediated by radical pairs

2018 ◽  
Author(s):  
P. J. Hore
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Upper Bound ◽  
Prolonged Exposure ◽  
Radical Pair ◽  
Biological Effects ◽  
Radical Pair Mechanism ◽  
Childhood Leukaemia ◽  
Radical Pairs ◽  
Increased Risk

AbstractProlonged exposure to weak (~1 μT) extremely-low-frequency (ELF, 50/60 Hz) magnetic fields has been associated with an increased risk of childhood leukaemia. One of the few biophysical mechanisms that might account for this link involves short-lived chemical reaction intermediates known as radical pairs. In this report, we use spin dynamics simulations to derive an upper bound of 10 parts per million on the effect of a 1 μT ELF magnetic field on the yield of a radical pair reaction. By comparing this figure with the corresponding effects of changes in the strength of the Earth’s magnetic field, we conclude that if exposure to such weak 50/60 Hz magnetic fields has any effect on human biology, and results from a radical pair mechanism, then the risk should be no greater than travelling a few kilometres towards or away from the geomagnetic north or south pole.

Characteristics of Ultrasound Propagation in a Magnetic Fluid Under Uniform Magnetic Field

2003 ◽  
Author(s):  
Masaaki Motozawa ◽  
Tatsuo Sawada
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetic Fluid ◽  
Uniform Magnetic Field ◽  
Colloidal Particles ◽  
Magnetic Field Intensity ◽  
Magnetic Field Direction ◽  
Ultrasound Propagation ◽  
Ultrasonic Propagation ◽  
The Magnetic Field

When an external magnetic field is applied to a magnetic fluid, some of the colloidal particles coagulate and form chain-like clusters. Properties of ultrasonic propagation wave are changed by these chain-like clusters. We carried out measurement of the ultrasonic propagation velocity in a magnetic fluid. Measurement were made by changing the magnetic field intensity from 0 mT to 570 mT, and the angle between the magnetic field direction and direction of the ultrasound propagation from 0° to 180°. The ultrasound frequencies were 1 MHz, 2 MHz and 4 MHz. Some of experimental results for the characteristics of ultrasound propagation in a magnetic fluid under a uniform magnetic field were reported.

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