Decrease In Field Strength Research Articles

A Tribute to Dr. William G. Roll: A NeuroQuantology Pioneer

I first met William G. Roll during the late summer of 1972 at a Parapsychology Conference sponsored by the Beloffs at the University of Edinburgh. He was a captivating lecturer and conveyed the most complex information with clarity and humour. Over the decades Dr. Roll was instrumental in the modern discoveries of brain function, non-local phenomena and what is now more appropriately termed NeuroQuantal effects. He convinced two of the most outstanding exceptional people with unusual talents, Sean Harribance and the late Ingo Swann, to be tested in our laboratory. As a result we showed a quantitative relationship between the duration of unusual theta activity from the right temporooccipital region of Mr. Swann and the degree of his accuracy during remote viewing of places and hidden photographs. For Mr. Harribance, we measured the conservation of energy for the increased emissions of photons from his right hemisphere (the same area that had shown increased perfusion during SPECT measurements) while he reported the memories of the person proximal to him and the minute decrease in magnetic field strength of the earth within about 1 m.

On the Collective Magnetic Field Strength and Vector Structure of Dark Umbral Cores Measured by the Hinode Spectropolarimeter

We study 7530 sunspot umbrae and pores measured by the Hinode Spectropolarimeter (SP) between November 2006 and November 2012. We primarily seek confirmation of the long term secular decrease in the mean magnetic field strength of sunspot umbrae found by Penn and Livingston (IAU Symp. 273, 126, 2011) between 1998 and 2011. The excellent SP photometric properties and full vector magnetic field determinations from full-Stokes Milne–Eddington inversions are used to address the interrelated properties of the magnetic field strength and brightness temperature for all umbral cores. We find non-linear relationships between magnetic field strength and umbral temperature (and continuum contrast), as well as between umbral radius and magnetic field strength. Using disambiguated vector data, we find that the azimuths measured in the umbral cores reflect an organization weakly influenced by Joy’s law. The large selection of umbrae displays a log-normal size spectrum similar to earlier solar cycles. Influenced by the amplitude of the solar cycle and the non-linear relationship between umbral size and core magnetic field strength, the distribution of core magnetic field strengths, fit most effectively with a skew-normal distribution, shows a weak solar cycle dependence. Yet, the mean magnetic field strength does not show a significant long term trend.

Theoretical and experimental study of the influence of nitrogen admixture on characteristics of dc diffuse glow discharge in rare gases at intermediate pressures

An effect of nitrogen admixture on the electric field in positive column of diffuse glow discharge in various rare gases at intermediate pressures is studied both experimentally and theoretically. The discharge is maintained in a cylindrical glass tube. Earlier it was observed and reproduced in calculations that addition of N2 (1%) to Ar at pressure 40 Torr led to noticeable decrease in the electric field strength at a fixed discharge current. In the present work there are results for pure Ne and Ne + 1%N2 gas mixtures at pressure 40 Torr. It is found that the addition of N2 to Ne leads to the increase in the electric field strength; the observed effect is reproduced in calculations. The explanation of differences in the impact of N2 addition on the electric field strength in Ar and Ne discharges is given. On the basis of the performed analysis it is predicted that the addition of N2 to He leads to the increase in the electric field in the discharge and the addition of N2 to Xe leads to the decrease in the electric field. For the case of He, the prediction is experimentally confirmed in this work, while for the case of Xe, it is corroborated by literature data.

Effect of grain size on the electrical properties of high dense BPT nanocrystalline ferroelectric ceramics

Abstract Nanosized Ba0.8Pb0.2TiO3 powders obtained by high energy ball milling were compacted and sintered into nanocrystalline ferroelectric ceramics using spark plasma sintering (SPS). The prepared ceramic samples were characterized by field emission scanning electron microscopy, X-ray diffraction, and electrical property measurements. All the samples show a density over 97% of the theoretical value and an average grain size of ∼60–200 nm depending on the ball milling time. The dielectric data exhibit a ferroelectric–paraelectric phase transition and a maximum relative permittivity of 19,000 at 225 °C and 100 kHz at the average grain size of ∼60 nm. The values of the dielectric constants both at room temperature and at the phase transition temperature increase considerably as the average grain size decreases. The remanent polarization and coercive field strength decrease slightly as the average grain size decreases but remain at an acceptable level for ferroelectric applications.

Stationary cylindrical vortex in a viscous electrically conducting fluid

An exact solution of the magnetohydrodynamic equations is constructed which describes steady vortex flow in a stationary cylinder on the axis of which a conductor carrying a known current is located. The solution is obtained under the assumption that the fluid is viscous and has finite electrical conductivity and that the magnetic field has only the axial and azimuthal components in a cylindrical coordinate system. It is found that the action of the Lorentz force is compensated by changing the pressure. Fluid flow occurs from the periphery to the axis of the cylinder under a pressure gradient, with flow rotation and swirling. The fluid flow causes a concentration of the magnetic lines near the axis of the cylinder, providing an exponential decrease in the magnetic field strength with distance from the axis. This flow can be considered as a model of a local increase in the magnetic field strength due to the transfer of its force lines by the flow of the electrically conducting fluid.

Evolution of helical cosmic magnetic fields as predicted by magnetohydrodynamic closure theory

We extend our recent derivation of the time evolution equations for the energy content of magnetic fields and turbulent motions for incompressible, homogeneous, and isotropic turbulence to include the case of nonvanishing helicity. These equations are subsequently numerically integrated in order to predict the present day primordial magnetic field strength and correlation length, depending on its initial helicity and magnetic energy density. We find that all prior analytic predictions for helical magnetic fields, such as the epoch when they become maximally helical and their subsequent growth of correlation length L ~ a^{1/3} and decrease of magnetic field strength B ~ a^{-1/3} with scale factor a, are well confirmed by the simulations. An initially fully helical primordial magnetic field is a factor 4 10^4 stronger at the present epoch then its nonhelical counterpart when generated during the electroweak epoch.

A Statistical Study on the Reconnection in Boundary Layers of Small-scale Magnetic Flux Tubes in Solar Winds

With the data from WIND satellite in 1995—2005, the small-scale magnetic flux tubes determined with two methods, i.e., the artificial recognition and program selection respectively, are compared. It is found that there are magnetic reconnections in the boundary layers of 41% small-scale magnetic flux tubes determined with the program selection method, which is similar to the re- sult of small-scale magnetic flux tubes determined with the method of artificial recognition. The features of magnetic reconnections, such as the magnetic shear angle, magnetic field strength, and duration of the dissipation region of recon- nection at the small-scale flux tubes’ boundaries determined from both methods have the same statistical tendency. This shows that there is no essential differ- ence in the properties of reconnections in the boundary layers of the small-scale magnetic flux tubes determined with the two methods. Hence the data yielded by both methods can be used as the samples for statistically studying the events of reconnection in the front and back boundary layers of small-scale flux ropes. There are totally 71 magnetic reconnection events selected in this paper. Our statistical result shows that in 50 events (70%) the decrease of magnetic field strength in the dissipation region of reconnection is larger than 20%, and in 47 events (66%) the magnetic shear angle is larger than 90 degrees. These indicate that the magnetic reconnections in boundaries of the small-scale magnetic flux tubes are more likely to be anti-parallel. The statistics has been performed sep- arately in the reconnections of the front and back boundary layers of small-scale magnetic flux tubes. The results show that the features of reconnections in the front and back boundaries are similar to each other, which is different from the various properties in the front and back boundaries of the magnetic clouds, and this means that the expansion in the large-scale magnetic flux tubes, such as magnetic clouds, does not happen in the small-scale magnetic flux tubes.

RESOLVING THE INTERNAL MAGNETIC STRUCTURE OF THE SOLAR NETWORK

We analyze the spectral asymmetry of Stokes V (circularly polarized) profiles of an individual network patch in the quiet Sun observed by Sunrise/IMaX. At a spatial resolution of 0.15"-0.18", the network elements contain substructure which is revealed by the spatial distribution of Stokes V asymmetries. The area asymmetry between the red and blue lobes of Stokes V increases from nearly zero at the core of the structure to values close to unity at its edges (one-lobed profiles). Such a distribution of the area asymmetry is consistent with magnetic fields expanding with height, i.e., an expanding magnetic canopy (which is required to fulfill pressure balance and flux conservation in the solar atmosphere). Inversion of the Stokes I and V profiles of the patch confirms this picture, revealing a decreasing field strength and increasing height of the canopy base from the core to the periphery of the network patch. However, the non-roundish shape of the structure and the presence of negative area and amplitude asymmetries reveal that the scenario is more complex than a canonical flux tube expanding with height surrounded by downflows.

ARE DECAYING MAGNETIC FIELDS ABOVE ACTIVE REGIONS RELATED TO CORONAL MASS EJECTION ONSET?

Coronal mass ejections (CMEs) are powered by magnetic energy stored in electric currents in coronal magnetic fields, with the pre-CME field in balance between outward magnetic pressure of the proto-ejecta and inward magnetic tension from confining overlying fields. In studies of global, current-free coronal magnetic field models --- Potential-Field Source-Surface (PFSS) models --- it has been reported that model field strengths above flare sites tend to be weaker in when CMEs occur than when eruptions fail to occur. This suggests that potential field models might usefully quantify magnetic confinement. An implication of this idea is that a decrease in model field strength overlying a possible eruption site should correspond to diminished confinement, implying an eruption is more likely. We have searched for such an effect by {\em post facto} investigation of the time evolution of model field strengths above a sample of 10 eruption sites, which included both slow and fast CMEs. In most events we study, we find no statistically significant evolution in either: (i) the rate of magnetic field decay with height; (ii) the strength of overlying magnetic fields near 50 Mm; (iii) or the ratio of fluxes at low and high altitudes (below 1.1$R_{\odot}$, and between 1.1--1.5$R_{\odot}$, respectively). Instead, we found that overlying field strengths and overlying flux tend to increase slightly, and their rates of decay with height become slightly more gradual, consistent with increased confinement. Since CMEs occur regardless of whether the parameters we use to quantify confinement are increasing or decreasing, either: (i) these parameters do not accurately characterize confinement in CME source regions; or (ii) systematic evolution in the large-scale magnetic environment of CME source regions is not, by itself, a necessary condition for CMEs to occur; or both.

Bending and Position Hysteresis of Magnetic Microfibers in Nonuniform Magnetic Fields

Magnetic microfibers are fibers that behave as a flexible paramagnetic body, for example, polymer fibers filled with superparamagnetic particles. A cantilevered magnetic microfiber will bend in response to an applied magnetic field. In a nonuniform field, generated for example by a single electromagnet or by a magnetic dipole, a magnetic microfiber displays position hysteresis as the field strength increases and decreases. This paper presents a model for determining stable shapes of a cantilevered magnetic microfiber in a nonuniform magnetic field. The model determines stable shapes by finding local minima of the potential energy using a Rayleigh-Ritz method. The model predicts the position hysteresis behavior observed in magnetic microfibers. Experimental data ware collected using two electromagnets with different geometries. The model simulation and experimental data compare well both qualitatively and quantitatively. The model will be useful for designing actuators based on magnetic microfibers and for characterizing the magnetic properties of fabricated fibers. A rigid bar model is also introduced, which captures the qualitative behavior of the fiber and illustrates the source of the position hysteresis behavior.

Variation in sunspot properties between 1999 and 2011 as observed with the Tenerife Infrared Polarimeter

We study the variation in the magnetic field strength and the umbral intensity of sunspots during the declining phase of the solar cycle no.23 and in the beginning of cycle no.24. We analyze a sample of 183 sunspots observed from 1999 until 2011 with the Tenerife Infrared Polarimeter at the German Vacuum Tower Telescope. The magnetic field strength is derived from the Zeeman splitting of the Stokes-V signal in one near-infrared spectral line, either Fe I 1564.8 nm, Fe I 1089.6 nm, or Si I 1082.7 nm. This avoids the effects of the unpolarized stray light from the field-free quiet Sun surroundings. The minimum umbral continuum intensity and umbral area are also measured. We find that there is a systematic trend for sunspots in the late stage of the solar cycle no.23 to be weaker, i.e., to have a smaller maximum magnetic field strength than those at the start of the cycle. The decrease in the field strength with time of about 94 G/yr is well beyond the statistical fluctuations that would be expected because of the larger number of sunspots close to cycle maximum (14 G/yr). In the same time interval, the continuum intensity of the umbra increases with a rate of 1.3 (+- 0.4)% of Ic/yr, while the umbral area does not show any trend above the statistical variance. Sunspots in the new cycle no.24 show higher field strengths and lower continuum intensities than those at the end of cycle no.23, interrupting the trend. Sunspots have an intrinsically weaker field strength and brighter umbrae at the late stages of solar cycles compared to their initial stages, without any significant change in their area. The abrupt increase in field strength in sunspots of the new cycle suggests that the cyclic variations are dominating over any long-term trend that continues across cycles. We find a slight decrease in field strength and an increase in intensity as a long-term trend across the cycles.

Optimization of plasmid electrotransformation into Escherichia coli using Taguchi statistical method

Electroporation is a mechanical method used to introduce polar molecules into a host cell through the cell membrane. In this procedure, a large electric pulse temporarily disturbs the phospholipid bilayer allowing molecules like DNA to pass into the cell. Application of statistical methods to determine the appropriate processes have been suggested for genetic engineering and biotechnology technique such as electroporation. This study explains the use of Taguchi statistical method to optimize the conditions for efficient plasmid transformation into Escherichia coli via electroporation. In order to improve electroporation, optical density of bacteria, recovery time and electrical parameter (field strength and capacitance) were optimized using the Taguchi statistical method. ANOVA of obtained data indicated that the optimal conditions of electrotransformation of pET-28a (+) plasmid into Escherichia coli BL21(DE3)pLysS was 0.7, 120 min, 12 kV/cm and 50 μF, for optical density of cell culture, recovery time, field strength and capacitance, respectively. The most significant alterations are decrease in field strength and increase in optical density in comparison with common electroporation protocol. The maximum level of plasmid transformation obtained under optimal condition was 8.7×108 transformants/μg DNA plasmid, which was 6.7 fold higher than the control condition. Keywords: Electroporation, Taguchi statistical method, Plasmid

PROBING HELICAL MAGNETIC FIELDS IN AGN BY ROTATION MEASURE GRADIENTS STUDIES

One of the tools that can provide evidence about the existence of helical magnetic fields in AGN is the observation of rotation measure gradients across the jet. Such observations have been previously made successfully, proving that such gradients are far from being rare, but common and typically persistent over several years, although some of them may show a reversal in the direction along the jet. Further studies of rotation measure gradients can help us in our understanding of the magnetic field properties and structure in the base of the jets. We studied Very Long Baseline Array (VLBA) polarimetric observations of 8 sources consistent of some quasars and BL Lacs at 12, 15, 22, 24 and 43 GHz and we find that all but two sources show indications of rotation measure gradients, either parallel or perpendicular to the jet. We interpret gradients perpendicular to the jet as indications of the change of the line of sight of the magnetic field due to its helicity, and gradients parallel to the jet as the decrease of magnetic field strength and/or electron density as we move along the jet. When comparing our results with the literature, we find temptative evidence of a rotation measure gradient flip, which can be explained as a change of the pitch angle or jet bending.

A novel method for investigating electrical breakdown enhancement by nm-sized features

Electrical transport studies across nm-thick dielectric films can be complicated, and datasets compromised, by local electrical breakdown enhanced by nm-sized features. To avoid this problem we need to know the minimal voltage that causes the enhanced electrical breakdown, a task that usually requires numerous measurements and simulation of which is not trivial. Here we describe and use a model system, using a "floating" gold pad to contact Au nanoparticles, NPs, to simultaneously measure numerous junctions with high aspect ratio NP contacts, with a dielectric film, thus revealing the lowest electrical breakdown voltage of a specific dielectric-nanocontact combination. For a 48 ± 1.5 Å SiO(2) layer and a ∼7 Å monolayer of organic molecules (to link the Au NPs) we show how the breakdown voltage decreases from 4.5 ± 0.4 V for a flat contact, to 2.4 ± 0.4 V if 5 nm Au NPs are introduced on the surface. The fact that larger Au NPs on the surface do not necessarily result in significantly higher breakdown voltages illustrates the need for combining experiments with model calculations. This combination shows two opposite effects of increasing the particle size, i.e., increase in defect density in the insulator and decrease in electric field strength. Understanding the process then explains why these systems are vulnerable to electrical breakdown as a result of spikes in regular electrical grids. Finally we use XPS-based chemically resolved electrical measurements to confirm that breakdown occurs indeed right below the nm-sized features.

Archeomagnetic studies of ceramics from the archeological monument in Ubeda, Spain

The archaeomagnetic study of the ceramics from the multilayered archeological monument Ubeda in Spain provided the data on the geomagnetic field strength in the period of accumulation of cultural deposits. According to the results obtained for the Ubeda monument of the Bronze Age and the La Motilla Del Azuer multilayer archaeological monument dated to the second millennium BC, the time interval of accumulation of the Ubeda cultural deposits likely spans from the last quarter of the 19th to 18th centuries BC. The sharp decrease in the geomagnetic field strength in the 19th century BC. established against the obtained data is consistent with the archaeomagnetic results for other Eurasian regions and can be used for correlating the ages of various archeological monuments and stages of culture.

Flux transfer events: Motion and signatures

We present results from a 2.5 dimensional hybrid code simulation for the evolution of flux transfer events (FTEs) during intervals of due southward interplanetary magnetic field (IMF) orientation. The structures invariably form between pairs of reconnection lines, often remaining nearly stationary on the subsolar magnetopause before their motion begins. Although a few structures move sunward, ultimately coalescing with others, most eventually accelerate antisunward, reaching velocities many times greater than the sound speed in the magnetosheath but only about one Alfvén speed greater than the ambient magnetosheath flow. At these velocities, slow mode wakes (but not shocks) marked by density enhancements and magnetic field strength decreases extend outward from the structures into the magnetosheath. Upon encountering the cusps, the structures decelerate, undergo reconnection, and are destroyed.

Synthesis and Characterization of CaF2 Nanoparticles with Different Doping Concentrations of Er3+

Abstract The calcium fluoride nanoparticles with a variety of doping amounts of erbium ions were prepared by CTAB/C4H9OH/C7H16/H2O reverse micro-emulsion method. The nanoparticles were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), absorption and fluorescence spectra. The XRD patterns indicated a typical cubic fluorite structure and no other impurities. The TEM results showed one kind of particles with uniform grain size and without agglomeration were synthesized. The FTIR spectra revealed that there were some amounts of -OH, NO 3 − and organic groups absorbed on the surfaces of the particles before being annealed. The absorption spectra presented many absorption peaks and bands corresponding to the rich energy levels of erbium ion. The Red-Shift of absorption bands and Blue-Shift of fluorescence peak could attribute to the weakened energy level split as a result of the decrease in crystal field strength.

Sources for geomagnetism—a comparative study of models

The paper proposes—and argues in favor of an alternative model to account for the dipole geomagnetic field in which a hitherto unrecognized piezomagnetic effect is the actual cause. This model offers a plausible explanation for the observed field reversals, the westward drift, and the secularly decreasing field strength. It is consistent with recent satellite data, and capable of generalization to planets other than Earth. It also accounts for the fact that the dipole axis is displaced from the geographic axis, and that the center of the dipole is displaced from the geographic center.

Optimal design on wideband directional coupler

Combining the modified Bethe small holes coupling theory with McDonald thickness theory and field averaging correction factor, it is accurate to design the weak coupling waveguide directional coupler. While the coupling is tight, the decrease of the field strength in the main waveguide caused by aperture should not be neglected. For a −6 dB directional coupler is described in this article, the theoretical value of coupling is good agree to the simulation value, by simulated and optimized with the professional software computer simulation technology (CST). In the designed waveband, the error of coupling between theoretical value and simulating one is less than 0.25 dB. The error of coupling between simulation value and designed value is less than 0.5 dB. To improve the isolation, some spaces between two adjacent holes are turned from the traditional ¼ centre guided wavelength. The performance of isolation has 5 dB improvement, and length of the coupling area is only 51.06 mm.

TIME-DEPENDENT MODELS OF FLARES FROM SAGITTARIUS A*

The emission from Sgr A*, the supermassive black hole in the Galactic Center, shows order of magnitude variability ("flares") a few times a day that is particularly prominent in the near-infrared (NIR) and X-rays. We present a time-dependent model for these flares motivated by the hypothesis that dissipation of magnetic energy powers the flares. We show that episodic magnetic reconnection can occur near the last stable circular orbit in time-dependent magnetohydrodynamic simulations of black hole accretion - the timescales and energetics of these events are broadly consistent with the flares from Sgr A*. Motivated by these results, we present a spatially one-zone time-dependent model for the electron distribution function in flares, including energy loss due to synchrotron cooling and adiabatic expansion. Synchrotron emission from transiently accelerated particles can explain the NIR/X-ray lightcurves and spectra of a luminous flare observed 4 April 2007. A significant decrease in the magnetic field strength during the flare (coincident with the electron acceleration) is required to explain the simultaneity and symmetry of the simultaneous lightcurves. Our models predict that the NIR and X-ray spectral indices differ by 0.5 and that there is only modest variation in the spectral index during flares. We also explore implications of this model for longer wavelength (radio-submm) emission seemingly associated with X-ray and NIR flares; we argue that a few hour decrease in the submm emission is a more generic consequence of large-scale magnetic reconnection than delayed radio emission from adiabatic expansion.