Evidence for the use of magnetic cues in mound construction by the termite Amitermes meridionalis (Isoptera : Termitinae)

2002 ◽  
Vol 50 (4) ◽  
pp. 357 ◽  
Author(s):  
P. M. Jacklyn ◽  
U. Munro
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Cross Sections ◽  
Applied Magnetic Field ◽  
Geomagnetic Field ◽  
Horizontal Component ◽  
Mound Construction ◽  
Amitermes Meridionalis ◽  
Mound Architecture

The termite Amitermes meridionalis builds meridionally elongated mounds. We removed the tops of such mounds and then allowed the termites to repair their mounds in the natural geomagnetic field and in artificial magnetic fields with different magnetic declinations. Cross-sections of repaired mounds were taken and the arrangement of the small, elongated cells that form the basis of mound architecture was assessed. The results suggest that the termites align mound cells along the existing axis of the mound and the cardinal axes of the horizontal component of the applied magnetic field.

Effects of Electromagnetic Fields on the Quantum Yield of Free Radicals in Cryptochrome

2019 ◽  
Vol 953 ◽  
pp. 127-132
Author(s):  
Yu Ling Chen ◽  
Du Yan Geng ◽  
Chuan Fang Chen
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Free Radicals ◽  
Free Radical ◽  
Quantum Yield ◽  
Electromagnetic Fields ◽  
Applied Magnetic Field ◽  
Geomagnetic Field ◽  
Quantum Biology ◽  
The Magnetic Field

In this paper, the effects of the quantum yield of free radicals in cryptochrome exposed to different electromagnetic fields were studied through the quantum biology. The results showed that the spikes characteristics was produced in the free radicals in cryptochrome, when it exposed to the applied magnetic field (ω = 50 Hz, B0 = 50 μT). The spikes produced by the electromagnetic field was independent of the changes of polar θ. When the frequency of the magnetic field increased, the spikes characteristics produced in unit time also increased. These results showed that the environmental electromagnetic field could affect the response of organisms to the geomagnetic field by influencing the quantum yield in the mechanism of free radical pair.It provided a basis for studying the influence of environmental electromagnetic field on biology, especially the navigation of biological magnetism.

scholarly journals A magnetometer for the measurement of the Earth's vertical magnetic intensity in C. G. S. measure

1928 ◽  
Vol 117 (777) ◽  
pp. 434-458 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Vertical Component ◽  
Field Measurements ◽  
Horizontal Component ◽  
Magnetic Intensity ◽  
Earth’S Magnetic Field ◽  
Simple Operation ◽  
Horizontal Field ◽  
Earth's Magnetic Field

The measurement of the vertical component of the earth’s magnetic field is a less simple operation than that of the horizontal component. The horizontal field measurements are on a satisfactory basis, whether made by the swinging magnet method, or by the more recently developed electric magnetometers, in which known magnetic fields may be provided by means of known currents flowing through coils of known dimensions.

scholarly journals Пылевая плазма в тлеющем разряде в магнитном поле до 3000 G

2018 ◽  
Vol 44 (19) ◽  
pp. 66
Author(s):  
Е.С. Дзлиева ◽  
Л.А. Новиков ◽  
С.И. Павлов ◽  
В.Ю. Карасев
Keyword(s):  
Magnetic Field ◽  
Angular Velocity ◽  
Glow Discharge ◽  
Magnetic Fields ◽  
Dusty Plasma ◽  
Drag Force ◽  
Applied Magnetic Field ◽  
Magnetic Trap ◽  
Current Channel ◽  
Angular Velocities

AbstractA glow discharge dusty plasma in a magnetic trap in which the current channel narrows is obtained in moderate magnetic fields up to 3000 G. The results of initial experiments are reported. The formation of stable dusty plasma structures rotating at record-high angular velocities up to 15 rad/s is observed. The dependence of the angular velocity on the strength of the applied magnetic field is measured experimentally. We interpret it quantitatively on the basis of the ion drag force.

scholarly journals Quantifying the Benefit of a Dedicated “Magnetoskeleton” in Bacterial Magnetotaxis by Live-Cell Motility Tracking and Soft Agar Swimming Assay

2019 ◽  
Vol 86 (3) ◽  
Author(s):  
Daniel Pfeiffer ◽  
Dirk Schüler
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Strength ◽  
Cell Motility ◽  
Magnetic Field Strength ◽  
Geomagnetic Field ◽  
Soft Agar ◽  
Content Type ◽  
Magnetospirillum Gryphiswaldense ◽  
Weak Magnetic Fields

ABSTRACT The alphaproteobacterium Magnetospirillum gryphiswaldense has the intriguing ability to navigate within magnetic fields, a behavior named magnetotaxis, governed by the formation of magnetosomes, intracellular membrane-enveloped crystals of magnetite. Magnetosomes are aligned in chains along the cell’s motility axis by a dedicated multipart cytoskeleton (“magnetoskeleton”); however, precise estimates of its significance for magnetotaxis have not been reported. Here, we estimated the alignment of strains deficient in various magnetoskeletal constituents by live-cell motility tracking within defined magnetic fields ranging from 50 μT (reflecting the geomagnetic field) up to 400 μT. Motility tracking revealed that ΔmamY and ΔmamK strains (which assemble mispositioned and fragmented chains, respectively) are partially impaired in magnetotaxis, with approximately equal contributions of both proteins. This impairment was reflected by a required magnetic field strength of 200 μT to achieve a similar degree of alignment as for the wild-type strain in a 50-μT magnetic field. In contrast, the ΔmamJ strain, which predominantly forms clusters of magnetosomes, was only weakly aligned under any of the tested field conditions and could barely be distinguished from a nonmagnetic mutant. Most findings were corroborated by a soft agar swimming assay to analyze magnetotaxis based on the degree of distortion of swim halos formed in magnetic fields. Motility tracking further revealed that swimming speeds of M. gryphiswaldense are highest within the field strength equaling the geomagnetic field. In conclusion, magnetic properties and intracellular positioning of magnetosomes by a dedicated magnetoskeleton are required and optimized for bacterial magnetotaxis and most efficient locomotion within the geomagnetic field. IMPORTANCE In Magnetospirillum gryphiswaldense, magnetosomes are aligned in quasi-linear chains in a helical cell by a complex cytoskeletal network, including the actin-like MamK and adapter MamJ for magnetosome chain concatenation and segregation and MamY to position magnetosome chains along the shortest cellular axis of motility. Magnetosome chain positioning is assumed to be required for efficient magnetic navigation; however, the significance and contribution of all key constituents have not been quantified within defined and weak magnetic fields reflecting the geomagnetic field. Employing two different motility-based methods to consider the flagellum-mediated propulsion of cells, we depict individual benefits of all magnetoskeletal constituents for magnetotaxis. Whereas lack of mamJ resulted almost in an inability to align cells in weak magnetic fields, an approximately 4-fold-increased magnetic field strength was required to compensate for the loss of mamK or mamY. In summary, the magnetoskeleton and optimal positioning of magnetosome chains are required for efficient magnetotaxis.

On Petschek's mechanism for dissipating interstellar magnetic fields

1967 ◽  
Vol 31 ◽  
pp. 131
Author(s):  
Donat G. Wentzel
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Geomagnetic Field ◽  
Stationary Flow ◽  
Absorption Lines ◽  
Galactic Magnetic Field ◽  
Hydromagnetic Flow ◽  
Gas Density ◽  
Interstellar Clouds ◽  
Density Distributions

Petschek's solution for the hydromagnetic flow at a magnetic neutral plane is applied to the interior of interstellar clouds. The stationary flow between the opposed magnetic fields involves a streaming speed of about 3 km/s and a gas density of roughly 102atoms/cm3. At most one-tenth of all the gas resides in these streams, but their low temperatures should make them observable in absorption at 21 cm; they may even dominate the interstellar absorption lines of Ca+and of Na, since the abundance of these absorbing ions, proportional to the recombination rate of the dominant ions with electrons, depends on the square of the gas density. Optical and 21-cm lines may, therefore, represent somewhat different samples of the interstellar velocity and density distributions.In analogy to the geomagnetic field, which is separated from the interplanetary field, interstellar clouds may be separated from the general galactic magnetic field. Such magnetic bubbles can move through the galactic field without twisting it, but they can maintain their identity only if they contain a twisted magnetic field. This field leads to the operation of Petschek's Mechanism and makes these clouds prominent in the optical absorption lines. A full evaluation of Petschek's Mechanism must involve some plasma instability to reconnect the lines of force.Details of this work have appeared elsewhere (Wentzel 1966).

The measurement of a weak alternating magnetic field in unshielded space

Metrologiya ◽  
2021 ◽  
pp. 46-59
Author(s):  
O. L. Sokol-Kutylovskii
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Induction ◽  
Geomagnetic Field ◽  
Gradient Methods ◽  
Alternating Magnetic Field ◽  
Geomagnetic Variations ◽  
Weak Magnetic Fields ◽  
Random Character

In connection with attempts to use various types of sensors for measuring weak magnetic fields in geophysics, magnetobiology, and medicine in an unshielded space, the problem of comparing the results of these measurements arose. The issues of measuring a weak alternating magnetic field by various magnetic induction sensors in an unshielded space in the absence of obvious geomagnetic variations are considered. It is shown that the amplitude of natural geomagnetic noise in a quiet geomagnetic field in the absence of geomagnetic variations has a random character; therefore, gradient methods for measuring a weak alternating magnetic field are limited from below by the level of natural geomagnetic noise. The influence of the size of sensors of a weak alternating magnetic field on the results of measurements of broadband random geomagnetic noise is noted.

Semiconductor Crystal Growth by the Vertical Bridgman Process With Transverse Rotating Magnetic Fields

2006 ◽  
Vol 129 (2) ◽  
pp. 241-243 ◽  
Author(s):  
X. Wang ◽  
N. Ma
Keyword(s):  
Magnetic Field ◽  
Crystal Growth ◽  
Magnetic Fields ◽  
Applied Magnetic Field ◽  
Rotating Magnetic Field ◽  
Semiconductor Crystal ◽  
Rotating Magnetic Fields ◽  
Electrically Conducting ◽  
Vertical Bridgman ◽  
Bridgman Process

During the vertical Bridgman process, a single semiconductor crystal is grown by the solidification of an initially molten semiconductor contained in an ampoule. The motion of the electrically conducting molten semiconductor can be controlled with an externally applied magnetic field. This paper treats the flow of a molten semiconductor and the dopant transport during the vertical Bridgman process with a periodic transverse or rotating magnetic field. The frequency of the externally applied magnetic field is sufficiently low that this field penetrates throughout the molten semiconductor. Dopant distributions in the crystal are presented.

scholarly journals A Quantum Charged Particle under Sudden Jumps of the Magnetic Field and Shape of Non-Circular Solenoids

2019 ◽  
Vol 1 (2) ◽  
pp. 193-207 ◽  
Author(s):  
Viktor V. Dodonov ◽  
Matheus B. Horovits
Keyword(s):  
Magnetic Field ◽  
Charged Particle ◽  
Magnetic Fields ◽  
Electric Fields ◽  
Cross Sections ◽  
Magnetic Moment ◽  
Landau Gauge ◽  
Time Dependent ◽  
The Mean ◽  
The Magnetic Field

We consider a quantum charged particle moving in the x y plane under the action of a time-dependent magnetic field described by means of the linear vector potential of the form A = B ( t ) − y ( 1 + β ) , x ( 1 − β ) / 2 . Such potentials with β ≠ 0 exist inside infinite solenoids with non-circular cross sections. The systems with different values of β are not equivalent for nonstationary magnetic fields or time-dependent parameters β ( t ) , due to different structures of induced electric fields. Using the approximation of the stepwise variations of parameters, we obtain explicit formulas describing the change of the mean energy and magnetic moment. The generation of squeezing with respect to the relative and guiding center coordinates is also studied. The change of magnetic moment can be twice bigger for the Landau gauge than for the circular gauge, and this change can happen without any change of the angular momentum. A strong amplification of the magnetic moment can happen even for rapidly decreasing magnetic fields.

scholarly journals Modified Adiabatic Approximation for A Hydrogen Atom Moving in A Magnetic Field

1994 ◽  
Vol 147 ◽  
pp. 555-559
Author(s):  
V.G. Bezchastnov ◽  
A.Y. Potekhin
Keyword(s):  
Magnetic Field ◽  
Hydrogen Atom ◽  
Magnetic Fields ◽  
Density Distribution ◽  
Cross Sections ◽  
Electron Density Distribution ◽  
Adiabatic Approximation ◽  
Strong Magnetic Fields ◽  
Radiative Transitions ◽  
The Magnetic Field

AbstractMotion of a hydrogen atom across the magnetic field shifts center of electron density distribution. For strong magnetic fields, the radiative transitions can be considered in the modified adiabatic approximation in which the shifts are taken into account. The method is illustrated by calculating the photoionization cross sections.

Experimental Investigation of Magnetically-Induced Thermal Conductance Variations in a Ferromagnetic Nanofluid

2011 ◽  
Author(s):  
Alexander M. Gardner ◽  
Indira Seshadri ◽  
Ganpati Ramanath ◽  
Theodorian Borca-Tasciuc
Keyword(s):  
Magnetic Field ◽  
Thermal Conductivity ◽  
Experimental Investigation ◽  
Magnetic Fields ◽  
Thermal Resistance ◽  
Applied Magnetic Field ◽  
Thermal Conductance ◽  
Flow Characteristics ◽  
Test Apparatus ◽  
The Subject

Ferrofluids have been the subject of great interest in engineering because of their unique flow characteristics under magnetic fields (Rosensweig, 1987). However, there are limited experiments which show the potential of ferrofluids to undergo controlled changes in thermal conductivity (Philip et al., 2008) under magnetic fields. The purpose of this experiment is to investigate thermal transport in ferrofluids. A test apparatus was designed and the thermal resistance of a commercially available ferromagnetic fluid within a test cell was measured as a function of the applied magnetic field.

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