Effect Of Weak Magnetic Field Research Articles

Phase diagram of am iron-nitride magnetic fluid: effects of temperature and weak magnetic field

The phase diagram is studied for a magnetic fluid with uniform iron-nitride particles. The magnetic properties were measured at various temperatures in weak magnetic fields. The results show a temperature-induced transition. Weak magnetic fields stabilize the state observed at the higher temperatures.

Effect of Synthesis Process and Substrate on Electrical and Thermal Transport Properties of Bi-2212

Resistivity, thermoelectric power, and thermal conductivity have been measured for a Bi-2212 system synthesized from a glassy precursor, either with a commercially Al2O3 substrate or with a homemade BaZrO3 substrate. Those measurements show that the BaZrO3 substrate gives better superconducting properties to the Bi-2212 than the Al2O3 substrate. The effect of (1.0 T) weak magnetic field has been searched for. The thermal magnetoconductivity and the contributions of the magnetic field to the thermoelectrical power are studied and compared through fine measurements. An electronic contribution seems to appear already well above the critical temperature and to exist up to 200°K. The onset temperature is thus deduced.

Theoretical Limits on the Threshold for the Response of Long Cells to Weak Extremely Low Frequency Electric Fields Due to Ionic and Molecular Flux Rectification

Understanding exposure thresholds for the response of biological systems to extremely low frequency (ELF) electric and magnetic fields is a fundamental problem of long-standing interest. We consider a two-state model for voltage-gated channels in the membrane of an isolated elongated cell ( L cell = 1 mm; r cell = 25 μm) and use a previously described process of ionic and molecular flux rectification to set lower bounds for a threshold exposure. A key assumption is that it is the ability of weak physical fields to alter biochemistry that is limiting, not the ability of a small number of molecules to alter biological systems. Moreover, molecular shot noise, not thermal voltage noise, is the basis of threshold estimates. Models with and without stochastic resonance are used, with a long exposure time, t exp = 10 4 s. We also determined the dependence of the threshold on the basal transport rate. By considering both spherical and elongated cells, we find that the lowest bound for the threshold is E min ≈ 9 × 10 −3 V m −1 (9 × 10 −5 V cm −1). Using a conservative value for the loop radius r loop = 0.3 m for induced current, the corresponding lower bound in the human body for a magnetic field exposure is B min ≈ 6 × 10 −4 T (6 G). Unless large, organized, and electrically amplifying multicellular systems such as the ampullae of Lorenzini of elasmobranch fish are involved, these results strongly suggest that the biophysical mechanism of voltage-gated macromolecules in the membranes of cells can be ruled out as a basis of possible effects of weak ELF electric and magnetic fields in humans.

Effects of weak magnetic fields on free radical recombination reactions

The radical pair mechanism is used to elucidate how applied magnetic fields that are weaker in strength than typical hyperfine interactions can influence the yields and kinetics of recombination reactions of free radicals in solution. The so-called low field effect is shown to arise from coherent superpositions of degenerate electron-nuclear spin states in a spin-correlated radical pair in zero field. A weak applied magnetic field causes these (zero-quantum) coherences to oscillate, leading to coherent interconversion of singlet and triplet electronic states of the radical pair and hence changes in the yields of recombination products and of the free radicals that escape into solution. For singlet geminate radical pairs, the low field effect leads to a boost in the concentration of free radicals, which may be relevant in the context of in vivo biological effects of electromagnetic fields. Using analytical approaches in limiting cases, the maximum possible low field effects are calculated for a variety of radical pairs. Sizeable changes in reaction yields (∽20%) are found for almost any radical pair provided the spin-correlation persists long enough for significant evolution of the electron spins under the influence of the weak applied field. The conditions necessary for observing effects as large as ∽20% are discussed.

Effects of weak magnetic fields on free radical recombination reactions

Effects of weak magnetic fields on free radical recombination reactions

Effects of weak low-frequency magnetic fields on spruce seed germination under acid conditions

We studied the effects of weak and extremely low frequency magnetic fields on the growth and germination of spruce seedlings (Picea abies (L.) Karst.) that were exposed simultaneously to different pH levels. The experiments showed that a weak, sinusoidal magnetic field (50 Hz, 26 and 105 µT, stimulation 12 h/day), which was computer controlled and generated by a system of Helmholtz-like coils, slightly reduced the length of the seedlings and delayed germination at low pH levels. A 26- µT magnetic field at 50 Hz slightly reduced the length of the seedlings at pH 2, delayed germination between pH 2 and 3, and caused no effects or were even stimulatory at pH 6 and 7. At a higher magnetic flux density (105 µT) the length, fresh weight, and germination were reduced mostly at pH 2 and 3 and with a higher statistical significance than at 26 µT. Germination was influenced during the first days of germination, and later the effect diminished rapidly. A 10- µT magnetic field at 46 Hz stimulated only the length of the seedlings. This phenomenon corresponds to the observations made by some other authors, namely that biological systems during various phases of intensive growth and (or) in suboptimal environmental conditions (physiological stress) are prone to exhibit greater sensitivity to extremely low frequency fields.

Cell density dependent response ofE. Coli cells to weak ELF magnetic fields

The effects of weak magnetic fields of extremely low frequency (ELF) on E. coli K12 AB1157 cells were studied by the method of anomalous viscosity time dependencies (AVTD). E. coli cells at different densities within a range of 5 x 10(5)-10(9) cell/ml were exposed to ELF (sinusoidal, 30 microT peak, 15 min) at a frequency of 9 Hz. A transient effect with maximum 40-120 min after exposure was observed. Kinetics of the per-cell-normalised ELF effects fitted well to a Gaussian distribution for all densities during exposure. A maximum value of these kinetics and a time for this maximum were strongly dependent on the cell density during exposure. These data suggest a cell-to-cell interaction during response to ELF. Both dependencies had three regions close to a plateau within the ranges of 3 x 10(5) - 2 x 10(7) cell/ml, 4 x 10(7) - 2 x 10(8) cell/ml and 4 x 10(8)-10(9) cell/ml and two rather sharp transitions between these plateaus. The effect reached a maximum value at a density of 4 x 10(8) cell/ml. Practically no effect was observed at the lowest density of 3 x 10(5) cell/ml. The data suggested that the ELF effect was mainly caused by a secondary rather than a primary reaction. The filtrates from exposed cells neither induced significant AVTD changes in unexposed cells nor increased the ELF effect when were added to cells before exposure. The data did not provide evidence for significant contribution of stable chemical messengers, but some unstable compounds such as radicals could be involved in the mechanism of cell-to-cell interaction during response to ELF. The results obtained were also in accordance with a model based on an re-emission of secondary photons during resonance fluorescence.

Effects of weak low-frequency magnetic fields on spruce seed germination under acid conditions

We studied the effects of weak and extremely low frequency magnetic fields on the growth and germination of spruce seedlings (Picea abies (L.) Karst.) that were exposed simultaneously to different pH levels. The experiments showed that a weak, sinusoidal magnetic field (50 Hz, 26 and 105 µT, stimulation 12 h/day), which was computer controlled and generated by a system of Helmholtz-like coils, slightly reduced the length of the seedlings and delayed germination at low pH levels. A 26- µT magnetic field at 50 Hz slightly reduced the length of the seedlings at pH 2, delayed germination between pH 2 and 3, and caused no effects or were even stimulatory at pH 6 and 7. At a higher magnetic flux density (105 µT) the length, fresh weight, and germination were reduced mostly at pH 2 and 3 and with a higher statistical significance than at 26 µT. Germination was influenced during the first days of germination, and later the effect diminished rapidly. A 10- µT magnetic field at 46 Hz stimulated only the length of the seedlings. This phenomenon corresponds to the observations made by some other authors, namely that biological systems during various phases of intensive growth and (or) in suboptimal environmental conditions (physiological stress) are prone to exhibit greater sensitivity to extremely low frequency fields.

P VII.21 - P VII.21 Effects of weak ELF magnetic fields and nalidixic acid on induction of recA-lacZ fusion in E. coli cells

P VII.21 - P VII.21 Effects of weak ELF magnetic fields and nalidixic acid on induction of recA-lacZ fusion in E. coli cells

Metaphors for the effects of weak, sequentially complex magnetic fields.

Metaphors to explain the effects of weak, complex magnetic fields upon the neuromatrices of organisms are suggested. The ratio of the amplitude of the time-varying components to steady-state components for complex magnetic field for effective biological responses may display Weber values that are similar to those for the electrical activity of the brain, the detection of changes in sound pressure by the ear and for more classical sensory thresholds. The nonlinear, suprathreshold characteristic of weak magnetic field effects would be similar to the effective narrow windows of concentrations of ligands values for receptor subtypes with different affinities. Signals composed of trains of between 100 and 1000 successive, fast (1 to 3 msec.) transients, which would contain the most biological information, would require low amplitudes to which the substrates could respond and with which the neuromatrix could resonate.

Effects of low frequency electromagnetic fields on the activity of ornithine decarboxylase in developing chicken embryos

In another paper we have reported the results of a study involving over 2500 chick embryos, in which time-varying magnetic fields (MFs) were shown to induce morphological abnormality. In an attempt to understand the mechanism by which these abnormalities arise, the present work explores the effects of weak magnetic fields (MFs) on the activity of the growth related enzyme ornithine decarboxylase (ODC) in chick embryos. The results presented here demonstrate that a 4 μT, 60 Hz sinusoidal magnetic field significantly enhances ODC activity during gastrulation, and diminishes ODC activity during neurulation. In another set of experiments, slightly older embryos were analyzed for gross morphology. The abnormality rate among MF-exposed embryos was approximately three times that of control embryos — with the vast majority of malformations being neural tube abnormalities. When embryos with morphological abnormalities were assayed separately from those which were morphologically normal, it was found that the ODC activity in the abnormal group was significantly less than that in the normal group. However, comparison of normal control embryos with normal MF exposed embryos showed no differences in ODC activity. Similarly comparison of abnormal control embryos with abnormal MF-exposed embryos showed no differences in the ODC activity. We speculate that MF-induced ODC alterations during neurulation may be related to the occurrence of MF-induced neural tube abnormalities at later stages of development.

Interference of Ion Quantum States Within a Protein Explains Weak Magnetic Field's Effect on Biosystems

A consistent physical model is proposed that explains weak ELF magnetic field effects on biological systems. An interference is described of quantum states of bound ions in protein cavities for the first time. The ion quantum dynamics is investigated at idealized case in the colinear static and alternating magnetic fields. There is taken into account a nuclear spin of ion and a nonlinear protein response on redistribution of the ion probability density. A formula is developed for the magnetic-dependent part of an ion-protein dissociation probability. Typical frequency and amplitude spectra are calculated for the interference in various magnetic conditions including the “magnetic vacuum” and compared with the known experimental data.

Magnetic field effects on photoluminescence in PPP. Investigation of the influence of chain length and degree of order

The effect of weak static magnetic fields on the photoluminescence quantum yield in poly(para-phenylene) films, which differ in chain length and degree of crystallinity, were investigated in the temperature range between 100 and 300 K. Applying a magnetic field enhances the photoluminescence quantum yield, the relative photoluminescence increase being about a factor 10 −4. On the basis of the magnetic field sensitivity, it is proposed that the emission of photoluminescence is partially due to geminate recombination of charge carriers. The formation of intermediate charge transfer states after photoexcitation is responsible for the appearance of the magnetic field effect. Properties of these states are investigated in terms of magnetic field effects, and the influence of the structure of the polymer films is discussed.

Novel effects of weak magnetic fields on post-implantation damage in semiconductors and superconducting ceramics

Novel experimentally verifiable and theoretically explained effects of weak static magnetic fields (WSMFs) acting during ion implantation of semiconductors and superconducting ceramics (SCC) at 300 K, moderate ion energies (e.g. 200–400 keV) and low dosage (e.g. 10 11–10 13 m −2) on the post-implantation radiation damage (PIRD) and material parameters are discussed. The WSMF of strength of H ≈ 1 kOe reduces, as previously reported, the PIRD in Hg 08Cd 02Te and InSb by factors of 2 and 1.54, respectively, and can increase the PIRD and change material parameters in SCCs. The WSMF effects on the radiation damage is a generic consequence of the kinetic electron-related theory of atomic rate processes in solids which shows that local electron transitions (LETs) in the nanometer vicinity of hopping atoms (defects) influence exponentially defect formation and migration rates. The magnetic field changing the LET number affects exponentially the rates of formation, migration and agglomeration of point defects and thus change the radiation damage.

A one-dimensional model of a negative ion source

A theoretical model is presented which uses one-dimensional plasma transport to describe a hydrogen discharge in which negative ions are formed. The model is based on discharges which are confined by a magnetic multipole field on the anode surface (multipole or `bucket' sources) and includes the effects of weak transverse magnetic fields within the plasma to cool the electron temperature in the discharge to a level at which dissociative attachment collisions allow significant fractional densities of ions to form. The transport equations are based on the moments of the Boltzmann equation and these are coupled with the plasma collision processes associated with ionization and negative ion production. The presence of negative ions in the plasma allows the electron transport across the magnetic fields to be anomalously high because each electron spends part of its time as a negative ion which is only weakly affected by the field. The model is tested on two multipole sources which have produced negative current densities up to around and have extensive measurements of the electron and ion densities, electron temperature and plasma potential as functions of position, arc current, voltage and pressure. The model uses the source geometry and arc parameters to calculate the plasma properties and obtains good agreement with experiment in both cases. In the companion paper the model is tested on a third source chamber with different diagnostics.

Effects of weak magnetic fields on post-implantation damage in superconducting oxides

Experimentally verifiable effects of weak permanent magnetic fields (PMF’s) acting during ion implantation in high-Tc superconducting (HTSC) materials at T ⋍ 300K on post-implantation damage (PID) and material parameters are considered. The presence of PMF’s of H ⋍ 103Oe during ion implantation can enlarge substantially the PID in HTSC materials implanted with ions of moderate energies (e.g. 200–400 keV) and dosage (1011-1012 cm-3) at room temperature. The PMF-induced increase in the radiation damage causes the corresponding enhancement in the material resistivity R and reduction in the critical current jcir (measured after the cooling of the HTSC material down to T(L) < Tc after the ion implantation). This is an extension of the PMF effects found experimentally (and explained theoretically) in semiconductors in our previous work [7]. The experimentally verifiable PMF effects on the defect (atomic) migration and radiation damage is a generic consequence of the kinetic electron-related theory of atomic rate processes in solids. The theory links the PMF effects with electron transitions occurring in the nanometer vicinity of atoms overcoming energy barriers which affect exponentially rates of atomic (defect) diffusion. The magnetic field can enhance the number of downward electron transitions that accompany atomic (defect) jumps over energy barriers and synchronize with the jumps. This enhances exponentially the rates of defect migration out of thermal spikes that prevents the defects from fast recombination, and thus, the PMF increases the PID and changes correspondingly R and jcir.

The Effect of Weak Permanent Magnetic Fields on the Electric Properties of Lipid-Bilayers

Abstract Black lipid membranes were prepared on a Teflon septum separating electrically the two chambers of a Teflon cuvette, using the technique of Mueller et al., (Nature 194. 979 (1962)). An external, static magnetic field was applied, whose intensity varied from 0 G to 100 G at the membrane location. Field applications higher than 10 G are effecting higher leakage currents, increased capacity and faster breakdown of the bilayer state, as compared to the absence of a magnetic field. If bilayers were doped with chlorophyll a, these effects were increased. Quantum mechanical and thermodynamical phenomena on membranes will be discussed as possible origins of these effects.

Studies of trapped strontium ions in low magnetic fields

The effect of weak magnetic fields (≤ 1 mT) on small clouds and single ions of strontium has been studied. The fluorescence rate and hence the cooling efficiency is sharply reduced for fields of less than around 0.2 mT. The magnetic field also splits the various levels involved through the Zeeman effect. In particular, the2S1/2−2D5/2 transition at 674 nm, which is the basis for a potential optical frequency standard, is split into a maximum of 10 components, depending upon the experimental geometry. This is studied for various configurations of the magnetic field and 674 nm laser polarization. The implication for frequency-standards work is that the standard will need to be operated in a small but highly stable field.

What is the etiology of human brain tumors?. A report on the first lebow conference

Although the conference could not provide a definitive etiologic explanation for the observed increase in incidence of human brain tumors, particularly among the elderly, nevertheless, this interdisciplinary gathering of prominent scientists and clinicians proved invaluable in identifying new avenues of research. Clearly, the puzzle of what causes brain tumors is highly complex, involving links to ionizing/electromagnetic radiation, familial, and dietary factors. The Lebow Conference provided an important scientific framework upon which to build further research studies, and its influence will be felt for years to come.

A detailed study of the effects of weak magnetic fields on the forward scattering of resonant laser light by sodium vapour

The effects of magnetic optical activity in the sodium D1 line are investigated in detail both theoretically and experimentally. Particular consideration is given to the ultra-narrow Hanle-type features that are produced by the crossing of ground state Zeeman sub-levels and which although strongly exhibited by the Fg=2 to Fe=1, 2 doublet, are apparently absent from the Fg=1 to Fe=1,2 doublet. We demonstrate, quantitatively for the first time, that these features are principally a manifestation of Delta M=2 (quadrupole) coherences and are therefore not evidence for the existence of Delta M=4 (hexadecapole) coherences as originally proposed by Gawlik and co-workers (1987). Indeed the latter is shown to have little influence on these features even at light field intensities for which significant power broadening is observed. We also show explicitly that the width of these narrow crossing features is, for the typical vapour pressures used to give an optically thin sample, a function of the average time of transit through the light field. Using a simple phenomenological model we predict numerically both the absolute width of these coherence features and the rate at which they power broaden. Finally a brief consideration of the same coherence effects within the D2 line is presented.