Generation of zonal flows by kinetic Alfvén waves

The generation of zonal flows by kinetic Alfvén waves is analyzed. It is noted that the basic approach underlying the existing theory of this phenomenon is too simplified because it attributes the generation of zonal flows to instabilities of an individual monochromatic wave packet of kinetic Alfvén waves. It is shown that, when a monochromatic wave packet is stable, it is necessary to analyze a more complicated situation with a double-peak packet (or, in the simplest case, with two pump waves). It is found that, for a double-peak packet of kinetic Alfvén waves, there is a new class of instabilities of zonal flows and that these instabilities are analogous to two-stream instabilities in linear theory. The main types of such instabilities are investigated.     

Generation of Alfvén waves by a plasma inhomogeneity moving in the Earth’s magnetosphere

The generation of an Alfvén wave by an azimuthally drifting cloud of high-energy particles injected in the Earth’s magnetosphere is studied analytically. In contrast to the previous studies where the generation mechanisms associated with the resonant wave-particle interaction were considered, a nonresonant mechanism is investigated in which the wave is excited by the alternating current produced by drifting particles. It is shown that, at a point with a given azimuthal coordinate, a poloidally polarized wave, in which the magnetic field lines oscillate predominantly in the radial direction, is excited immediately after the passage of the particle cloud through this point. As the cloud moves away from that point, the wave polarization becomes toroidal (the magnetic field lines oscillate predominantly in the azimuthal direction). The azimuthal wavenumber m is defined as the ratio of the wave eigenfrequency to the angular velocity of the cloud (the drift velocity of the particles). It is shown that the amplitudes of the waves so generated are close to those obtained under realistic assumptions about the density and energy of the particles.     

No evidence of cellular alterations by MilliTesla-level static and 50 Hz magnetic fields on S. cerevisiae

In an attempt to determine whether magnetic field (MF) exposures might induce cellular alterations, S. cerevisiae yeast cells were exposed to static or sinusoidal 50?Hz homogeneous MF (0.35?mT, 1.4?mT, and 2.45?mT) for 1?h and 72?h. Unsynchronized cells grown exponentially while exposed to MF, containing cells in all stages of the mitotic cell cycle. MF was generated by a pair of Helmholtz coils (40?cm in diameter, coaxial, separated by 20?cm). Survival, cell cycle distribution, colony forming ability, and mutation frequency were assayed. No differences in the above-mentioned parameters were observed in MF exposed samples in relation to unexposed controls, suggesting that homogeneous MF at these intensities do not produce appreciable cellular alterations in this organism under typical in vitro growth conditions.     

Magnetic induction for the sensing of magnetic fields by animals—An analysis

Magnetic induction is analyzed as a possible mechanism for the detection of weak magnetic fields by animals. The range of parameters possible for a system which provides a signal greater than thermal noise and meets other constraints is determined. It is concluded that an organ millimeters in size is required to sense the Earth's field by induction. The labyrinth of the inner ear is discussed in these terms.     

Resistive drift-alfvén turbulence in a tokamak edge plasma

The behavior of turbulent fluxes in the vicinity of a resonant point m/n = q(x _res) in a plane edge plasma layer in a tokamak is studied by numerically analyzing the nonlinear MHD equations in a five-field electromagnetic model. Simulations show that the heat and electron turbulent fluxes decrease with increasing ion temperature at the plasma edge. It is shown that these fluxes are suppressed due to the stabilization mechanism associated with an increase in the shear of the E × B drift velocity, which in turn increases with increasing ion pressure gradient. The effect of the zonal magnetic field on turbulent transport is also investigated. It is shown that an increase in this field stabilizes edge plasma turbulence.     

Cyclotron resonance as a cause of biological effects of weak electric and magnetic fields?

Even weak electric and magnetic fields have been found to cause interaction effects in vitro only within small frequency ranges. The existence of such "frequency windows" may be explained by a cyclotron resonance model which also takes the influence of the earth's magnetic field into consideration. In this paper analytical relations are developed which permit the determination of energy uptake and motion curve diameter. On the basis of this calculations it can be concluded that, giving consideration to interparticle interactions and the limitations of motion curve dimensions due to the limited dimensions of cells and cellular interspaces, energy uptake in vivo is many orders of magnitude below thermal energy, and can therefore be neglected.     

On the possibility of reflection of Alfvén waves in a curvilinear magnetic field

The propagation of Alfvén waves in a plasma immersed in a curvilinear magnetic field is investigated by using a 2D model. The waves are described by a 1D equation that formally coincides with the equation for the case of a quasi-uniform straight magnetic field with a modified Alfvén velocity that takes into account the longitudinal dependence of the Lame coefficients. It is shown that toroidal and poloidal Alfvén modes depend differently on the magnetic-field geometry. In the case of a 2D plane-parallel configuration of the magnetic field, poloidal modes are efficiently reflected from regions where the magnetic field lines sharply converge or diverge. This effect can result in the formation of open-field-line Alfvén quasi-resonators.     

Renegotiating gender and class in the berry fields of Michoacán,Mexico

This article examines the renegotiation of gender and class in a rural Mexican community where economic crisis in the sugar industry led foreign agribusinesses to promote blackberry and raspberry production for export and hire primarily women as berry pickers. Analysis focuses on the transition from a sugar economy where mostly men worked in the cane fields to non-traditional agricultural exports when women entered agricultural waged labor in unprecedented numbers. This restructuring of the regional economy raises important questions regarding the marginalization of differentiated subaltern groups and the nature of new sets of power relations between transnational agribusinesses, berry growers, and waged workers. I analyze the contradictions of this changing social field that connects Northern consumers, transnational company executives, berry growers, and waged laborers in a web of differential power relations as they reverberate along the commodity chain from campesino households to the global market.     

Anomalous Zemplén deacylation reactions of alpha- and beta-D-mannopyranoside derivatives

Reaction of mono-, di-, and trisaccharide derivatives of methyl beta-D- and octyl beta-D-mannopyranosides bearing ester groups at isolated and non-isolated positions on the same molecule, under Zemplén conditions (catalytic amount of sodium methoxide in methanol) gave partially deacylated compounds, in which the O-acyl groups were retained at isolated sites. In the case of one disaccharide, all the benzoyl groups remained intact at the reducing end, while all the acetyl functions were removable from the nonreducing end. In another case, both isolated ester groups at positions 2 and 4 were retained at the reducing end. The isolated 2-O-acyl groups on methyl alpha-D-mannopyranoside compounds were more labile than on the corresponding beta-mannosides under the same conditions. The mechanism of the reaction may be different for ester groups at isolated or non-isolated positions. In the latter case, acyl migration may take place and carry acyl groups into a less hindered position.     

Tissue-culture cell fractionation. Fractionation of cellular membranes from 125I/lactoperoxidase-labelled Lettrée cells homogenized by bicarbonate-induced lysis: resolution of membranes by zonal centrifugation and in sucrose and metrizamide gradients.

1. Lettrée cells were grown intraperitoneally in MF-1 mice and labelled extrinsically by the 125I/lactoperoxidase technique. 2. The cells were swollen in 1 mM-NaHCO3 and disrupted in a Dounce homogenizer. 3. Crude fractions of endoplasmic reticulum, plasma membrane and mitochondria were separated from a post-nuclear supernatant by sedimentation-rate gradient centrifugation in a BXIV zonal rotor. 4. Further resolution of these membranes was carried out in isopycnic sucrose gradients. 5. Bands of material from the latter were subfractionated in gradients of metrizamide. Some very pure subfractions of plasma membrane and endoplasmic reticulum were obtained. In addition, one subfraction containing 125I and NADPH-cytochrome c reductase but no Na++K+-stimulated adenosine triphosphatase and another containing these two enzymes but no 125I were resolved.     

Citrinin-producing capacity of Monascus purpureus in response to low −frequency magnetic fields

Citrinin is a type of mycotoxin that negatively affects Monascus products. Application of a low-frequency magnetic field (LF-MF) decreased citrinin production by M. purpureus in liquid-state fermentation during shake flask culture. Under 30 °C incubation, six different magnetic field induction intensity (MF-II), four different exposure times and five exposure time periods were tested to discover optimal treatment conditions. The cultures were exposure to a MF-II of 1.6 mT from 0 to 2 d of incubation time. With LF-MF treatment, peak citrinin production decreased by 46.7% while yellow, red, orange pigments and monacolin K production increased by 31.3%, 40.3%, 41.7% and 29.3%, respectively, compared with control groups at 12 d of incubation. Moreover, the relative expression levels of the citrinin biosynthesis genes pksCT and ctnA were 0.46 and 0.43 times lower, respectively, than the control values relative to the GAPDH reference gene. This study provides evidence that LF-MF is a preferable way to alter M. purpureus metabolism to reduce citrinin production and to increase pigments and monacolin K production without affecting cell growth. Therefore, LF-MF may be used as a tool to process Monascus products to obtain important functional food additive while reducing the adverse effects of citrinin.     

Photosynthesis of plant régénérants. Specificity ofin vitro conditions and plantlet response

Regenerants from tobacco(Nicotiana tabacum L. cv. White Burley) leaf segments cultivatedin vitro in vessels with solid agar medium under usual conditions (plantlets) grew under very low irradiance (I = 40 μxmol m?2 s?1), very high relative humidity (more than 90%) and decreased CO₂ concentration (c_a) during light period. In comparison with seedlings of a similar number of leaves and similar total leaf area grown in sand and nutrient solution, the plantlets had lower dry mass of shoots and roots per plant and thinner leaves almost without trichomes and epicuticular waxes. Due to a low transpiration rate under high relative humidity the water potential of plantlet leaves was higher than that of seedling leaves and the difference in water potential between leaves and medium was lowei. The rate of water loss from leaves detached from plantlets was considerably faster than that from seedlings under the same conditions (I = 110 μrnol m^?2; s^?1, temperature 30 °C, relative humidity 50 %). Net photosynthetie rates (P_n) of leaves of plantlets and seedlings measured under saturating I, natural ca and the leaf temperature 20 °C were similar, nevertheless the shape of curves relating Pn to c» indicated some differences in photosynthetie parameters(e.g. saturation of Pn under lower ca> higher CO2 compensation concentration in plantlets than in seedlings). Similarly compensation and saturating I were lower in plantlets than in seedlings. The shape of transpiration curves as well as the expressive linear phases of P_N(ca) and P_N(I) curves of plantlet leaves indicated ineffective stomatal control of gas exchance. These results were confirmed by microscopic observations of stomatal movementsin situ     

Improved cell growth and Taxol production of suspension-cultured Taxus chinensis var. mairei in alternating and direct current magnetic fields

The growth of suspension cultures of Taxus chinensis var. mairei and Taxol production were promoted both by a sinusoidal alternating current magnetic field (50 Hz, 3.5 mT) and by a direct current magnetic field (3.5 mT). Taxol production increased rapidly from the 4th d with the direct current magnetic field but most slowly with the alternating current magnetic field. The maximal yield of Taxol was 490 microg l(-1) with the direct current magnetic field and 425 microg l(-1) with the alternating current magnetic field after 8 d of culture, which were, respectively, 1.4-fold and 1.2-fold of that without exposure to a magnetic field.     

Generation of artificial channels by multimerization of β-strands from natural porin

General diffusion porins are passive transmembrane channels. We have explored the possibility to create artificial nanopores starting from natural β-barrel structures. Structural elements of bacterial porins were used to build a series of artificial nanopores. The basic module was selected by multi-alignment of general diffusion porins. The sequence corresponded to a highly conserved motif containing two β-strands, which was obtained from Escherichia coli OmpF. Dimeric to octameric repeats were obtained through cDNA recombinant technology. The hexameric repeat was used to test its properties. This protein was expressed, purified and reconstituted in the planar bilayer membranes. It was able to form channels in membranes with a conductance of 300 pS in 150 mm KCl and did not show any relevant voltage-dependence.     

Reduction of laser-induced retinal injury applying the combination of the 3D variable electric and magnetic fields in “vivo”

Oscillating Low Frequency Electro-Magnetic Fields action on eye retina restoration in Rattus Norvegicus was studied in the present work. A beneficial effect of 3-Dimention Oscillating Low Frequency Electro-Magnetic Field was found for the specific values of Electro-Magnetic Field parameters. We found that eye retina damaged by radiation of the fundamental frequency harmonic of a YAG laser has recovered earlier and rehabilitated to the original 3D-state in the presence of OLFEMF, with the parameters listed below in the text. The results obtained were explained by the action of oscillating sub-macro-motions in the cells upon the metabolic processes in these cells.     

Swimming behaviour of the multicellular magnetotactic prokaryote ‘Candidatus Magnetoglobus multicellularis’ under applied magnetic fields and ultraviolet light

Magnetotactic bacteria move by rotating their flagella and concomitantly are aligned to magnetic fields because they present magnetosomes, which are intracellular organelles composed by membrane-bound magnetic crystals. This results in magnetotaxis, which is swimming along magnetic field lines. Magnetotactic bacteria are morphologically diverse, including cocci, rods, spirilla and multicellular forms known as magnetotactic multicellular prokaryotes (MMPs). ‘Candidatus Magnetoglobus multicellularis’ is presently the best known MMP. Here we describe the helical trajectories performed by these microorganisms as they swim forward, as well as their response to UV light. We measured the radius of the trajectory, time period and translational velocity (velocity along the helix axis), which enabled the calculation of other trajectory parameters such as pitch, tangential velocity (velocity along the helix path), angular frequency, and theta angle (the angle between the helix path and the helix axis). The data revealed that ‘Ca. M. multicellularis’ swims along elongated helical trajectories with diameters approaching the diameter of the microorganism. In addition, we observed that ‘Ca. M. multicellularis’ responds to UV laser pulses by swimming backwards, returning to forward swimming several seconds after the UV laser pulse. UV light from a fluorescence microscope showed a similar effect. Thus, phototaxis is used in addition to magnetotaxis in this microorganism.     

Power-frequency magnetic fields at 50 Hz do not affect fertility and development in rats and mice

In the present study, the effects of power-frequency magnetic fields (PF-MF) on fertility and development were investigated in rats and mice. Adult Sprague-Dawley rats and C57BL/6J mice were divided into four groups: a sham exposure group and 30-µT, 100-µT and 500-µT PF-MF exposure groups. The rats were exposed for 24 weeks, and the exposure time for mice ranged from 18 d to 12 weeks, dependent on the different investigated end points. The rats and mice were exposed for 20 h/d. Plasma hormone levels in rats and mice were analyzed. Furthermore, pregnancy rates and implanted embryos were recorded in pregnant mice. Finally, the neonatal growth of mice was evaluated. The results showed that none of the three intensities affected the body weight and paired ovary weight in female rats. Meanwhile, none of the three intensities affected the body weight, weights of paired testes, weights of paired epididymis and sperm count in male rats. Similarly, no significant differences were found in plasma sex hormone levels between the different PF-MF exposure groups and the sham exposure group. In addition, the pregnancy rates and implanted embryos were not significantly different between the four groups. Moreover, PF-MF exposures had no effects on either the number of fetuses in pregnant mice or the growth and development of neonatal mice.     

Generation of superoxide and singlet oxygen from α-tocopherolquinone and analogues

Three potential routes to generation of reactive oxygen species (ROS) from α-tocopherolquinone (α-TQ) have been identified. The quinone of the water-soluble vitamin E analogue Trolox C (Trol-Q) is reduced by hydrated electron and isopropanol α-hydroxyalkyl radical, and the resulting semiquinone reacts with molecular oxygen to form superoxide with a second order rate constant of 1.3 × 10⁸ dm³/mol/s, illustrating the potential for redox cycling. Illumination (UV-A, 355 nm) of the quinone of 2,2,5,7,8-pentamethyl-6-hydroxychromanol (PMHC-Q) leads to a reactive short-lived (ca. 10^{? 6} s) triplet state, able to oxidise tryptophan with a second order rate constant greater than 10⁹ dm³/mol/s. The triplet states of these quinones sensitize singlet oxygen formation with quantum yields of about 0.8. Such potentially damaging reactions of α-TQ may in part account for the recent findings that high levels of dietary vitamin E supplementation lack any beneficial effect and may lead to slightly enhanced levels of overall mortality.