Weak Field Strength Research Articles

MAGNETIC FIELDS OF AN ACTIVE REGION FILAMENT FROM FULL STOKES ANALYSIS OF Si I 1082.7 nm AND He I 1083.0 nm

Vector magnetic fields of an active region filament in the photosphere and upper chromosphere are obtained from spectro-polarimetric observations recorded with the Tenerife Infrared Polarimeter (TIP II) at the German Vacuum Tower Telescope (VTT). We apply Milne-Eddington inversions on full Stokes vectors of the photospheric Si I 1082.7 nm and the upper chromospheric He I triplet at 1083.0 nm to obtain magnetic field vector and velocity maps in two atmosphere layers. We find that: (1)A complete filament was already present in H$\alpha$ at the beginning of the TIP II data acquisition. Only a partially formed one, composed of multiple small threads, was present in He I. (2) The AR filament comprises two sections. One shows strong magnetic field intensities, about 600 - 800 G in the upper chromosphere and 800 - 1000 G in the photosphere. The other exhibits only comparatively weak magnetic field strengths in both layers. (3) The Stokes V signal is indicative of a dip in the magnetic field strength close to the chromospheric PIL. (3) In the chromosphere consistent upflows are found along the PIL flanked by downflows. (4) The transversal magnetic field is nearly parallel to the PIL in the photosphere and inclined by 20 - 30 degree in the chromosphere. (5) The chromospheric magnetic field around the filament is found to be in normal configuration, while the photospheric field presents a concave magnetic topology. The observations are consistent with the emergence of a flux rope with a subsequent formation of a filament.

325 MHz VERY LARGE ARRAY OBSERVATIONS OF ULTRACOOL DWARFS TVLM 513-46546 AND 2MASS J0036+1821104

We present 325 MHz (90 cm wavelength) radio observations of ultracool dwarfs TVLM 513-46546 and 2MASS J0036+1821104 using the Very Large Array (VLA) in June 2007. Ultracool dwarfs are expected to be undetectable at radio frequencies, yet observations at 8.5 GHz (3.5 cm) and 4.9 GHz (6 cm) of have revealed sources with > 100 {\mu}Jy quiescent radio flux and > 1 mJy pulses coincident with stellar rotation. The anomalous emission is likely a combination of gyrosynchrotron and cyclotron maser processes in a long-duration, large-scale magnetic field. Since the characteristic frequency for each process scales directly with the magnetic field magnitude, emission at lower frequencies may be detectable from regions with weaker field strength. We detect no significant radio emission at 325 MHz from TVLM 513-46546 or 2MASS J0036+1821104 over multiple stellar rotations, establishing 2.5{\sigma} total flux limits of 795 {\mu}Jy and 942 {\mu}Jy respectively. Analysis of an archival VLA 1.4 GHz observation of 2MASS J0036+1821104 from January 2005 also yields a non-detection at the level of < 130 {\mu}Jy . The combined radio observation history (0.3 GHz to 8.5 GHz) for these sources suggests a continuum emission spectrum for ultracool dwarfs which is either flat or inverted below 2-3 GHz. Further, if the cyclotron maser instability is responsible for the pulsed radio emission observed on some ultracool dwarfs, our low-frequency non-detections suggest that the active region responsible for the high-frequency bursts is confined within 2 stellar radii and driven by electron beams with energies less than 5 keV.

Electrophysiological properties of heteromeric TRPV4–C1 channels

We previously reported that TRPV4 and TRPC1 can co-assemble to form heteromeric TRPV4–C1 channels [12]. In the present study, we characterized some basic electrophysiological properties of heteromeric TRPV4–C1 channels. 4α-Phorbol 12,13-didecanoate (4α-PDD, a TRPV4 agonist) activated a single channel current in HEK293 cells co-expressing TRPV4 and TRPC1. The activity of the channels was abrogated by a TRPC1-targeting blocking antibody T1E3. Conductance of the channels was ~95pS for outward currents and ~83pS for inward currents. The channels with similar conductance were also recorded in cells expressing TRPV4–C1 concatamers, in which assembled channels were expected to be mostly 2V4:2C1. Fluorescence Resonance Energy Transfer (FRET) experiments confirmed the formation of a protein complex with 2V4:2C1 stoichiometry while suggesting an unlikeliness of 3V4:1C1 or 1V4:3C1 stoichiometry. Monovalent cation permeability profiles were compared between heteromeric TRPV4–C1 and homomeric TRPV4 channels. For heteromeric TRPV4–C1 channels, their permeation profile was found to fit to Eisenman sequence VI, indicative of a strong field strength cation binding site, whereas for homomeric TRPV4 channels, their permeation profile corresponded to Eisenman sequence IV for a weak field strength binding site. Compared to homomeric TRPV4 channels, heteromeric TRPV4–C1 channels were slightly more permeable to Ca2+ and had a reduced sensitivity to extracellular Ca2+ inhibition. In summary, we found that, when TRPV4 and TRPC1 were co-expressed in HEK293 cells, the predominate assembly type was 2V4:2C1. The heteromeric TRPV4–C1 channels display distinct electrophysiological properties different from those of homomeric TRPV4 channels.

Electromagnetic Navigation System for CT-Guided Biopsy of Small Lesions

The purpose of this study was to evaluate an electromagnetic navigation system for CT-guided biopsy of small lesions. Standardized CT anthropomorphic phantoms were biopsied by two attending radiologists. CT scans of the phantom and surface electromagnetic fiducial markers were imported into the memory of the 3D electromagnetic navigation system. Each radiologist assessed the accuracy of biopsy using electromagnetic navigation alone by targeting sets of nine lesions (size range, 8-14 mm; skin to target distance, 5.7-12.8 cm) under eight different conditions of detector field strength and orientation (n = 117). As a control, each radiologist also biopsied two sets of five targets using conventional CT-guided technique. Biopsy accuracy, number of needle passes, procedure time, and radiation dose were compared. Under optimal conditions (phantom perpendicular to the electromagnetic receiver at highest possible field strength), phantom accuracy to the center of the lesion was 2.6 ± 1.1 mm. This translated into hitting 84.4% (38/45) of targets in a single pass (1.1 ± 0.4 CT confirmations), which was significantly fewer than the 3.6 ± 1.3 CT checks required for conventional technique (p < 0.001). The mean targeting time was 38.8 ± 18.2 seconds per lesion. Including procedural planning (∼5.5 minutes) and final CT confirmation of placement (∼3.5 minutes), the full electromagnetic tracking procedure required significantly less time (551.6 ± 87.4 seconds [∼9 minutes]) than conventional CT (833.3 ± 283.8 seconds [∼14 minutes]) for successful targeting (p < 0.001). Less favorable conditions, including nonperpendicular relation between the axis of the machine and weaker field strength, resulted in statistically significant lower accuracy (3.7 ± 1 mm, p < 0.001). Nevertheless, first-pass biopsy accuracy was 58.3% (21/36) and second-pass (35/36) accuracy was 97.2%. Lesions farther from the skin than 20-25 cm were out of range for successful electromagnetic tracking. Virtual electromagnetic tracking appears to have high accuracy in needle placement, potentially reducing time and radiation exposure compared with those of conventional CT techniques in the biopsy of small lesions.

Effects of magnetic fields on photoionized pillars and globules

The effects of initially uniform magnetic fields on the formation and evolution of dense pillars and cometary globules at the boundaries of H II regions are investigated using 3D radiation-magnetohydrodynamics simulations. It is shown, in agreement with previous work, that a strong initial magnetic field is required to significantly alter the non-magnetised dynamics because the energy input from photoionisation is so large that it remains the dominant driver of the dynamics in most situations. Additionally it is found that for weak and medium field strengths an initially perpendicular field is swept into alignment with the pillar during its dynamical evolution, matching magnetic field observations of the `Pillars of Creation' in M16 and also some cometary globules. A strong perpendicular magnetic field remains in its initial configuration and also confines the photoevaporation flow into a bar-shaped dense ionised ribbon which partially shields the ionisation front and would be readily observable in recombination lines. A simple analytic model is presented to explain the properties of this bright linear structure. These results show that magnetic field strengths in star-forming regions can in principle be significantly constrained by the morphology of structures which form at the borders of H II regions.

Permeation Properties of CALHM1

Department of Physiology, University of Pennsylvania, Philadelphia, PA 19104Recently, CALHM1, a gene of previously unknown function, was identified as a risk factor for late-onset Alzheimer‘s disease (AD). It was suggested that CALHM1 might be an ion channel or ion channel regulator. We used two-electrode voltage clamp (TEV) to measure CALHM1-induced ionic conductances in the plasma membrane of Xenopus oocytes. To investigate which ions permeate the CALHM1-induced conductance, we employed instantaneous current/voltage protocols to measure reversal potentials (Erev) in various solutions. In the absence of extracellular divalent cations, CALHM1 is weakly cation selective, with PNa : PK : PCl = 1 : 1.11 : 0.52. In CALHM1 injected oocytes, the relative permeability among monovalent cations (with respect to Na+) is PRb = PCs = PK > PNa > PLi > PNMDG, indicating that CALHM1-induced permeability is relatively nonselective for monovalent cations. CALHM1 induced currents are divalent cation selective, with PNa : PCa : PBa : PMg = 1 : 13.8 : 8.6 : 3.1. This selectivity sequence represents a Sherry III/IV sequence, consistent with a weak-field strength site in the permeation pore. The presence of extracellular divalent cations strongly alters the gating properties of CALHM1 induced currents. However, the presence of extracellular divalent cations only slightly alters the relative permeability of K+ and Cl- (PNa : PK : PCl = 1 : 1.46 : 0.88). Using large organic cations and a volume exclusion model, we estimated the radius of the CALHM1 associated ion channel pore in the absence of divalent cations to be 6.9 to 8.7 A. (Supported by NIH GM/DK56328 and a pilot project from the University Pennsylvania AD Core Center.)

Signal of quark deconfinement in thermal evolution neutron stars with deconfinement heating

Abstract As neutron stars spin-down and contract, the deconfinement phase transition can continue to occur, resulting in energy release (so-called deconfinement heating) in case of the first-order phase transition. The thermal evolution of neutron stars is investigated to combine phase transition and the related energy release self-consistently. We find that the appearance of deconfinement heating during spin-down result in not only the cooling delay but also the increase of surface temperature of stars. For stars characterized by intermediate and weak magnetic field strength, a period of increasing surface temperature could exist. Especially, a sharp jump in surface temperature can be produced as soon as quark matter appears in the core of stars with a weak magnetic field. We think that this may serve as evidence for the existence of deconfinement quark matter. The results show that deconfinement heating facilitates the emergence of such characteristic signature during the thermal evolution process of neutron stars.

A STUDY OF MAGNETIC BRIGHT POINTS IN THE Na I D 1 LINE

High cadence, multiwavelength, optical observations of solar magnetic bright points, captured at disk center using the ROSA and IBIS imaging systems on the Dunn Solar Telescope, are presented. Magnetic bright points manifesting in the Na I D1 core are found to preferentially exist in regions containing strong downflows, in addition to co-spatial underlying photospheric magnetic field concentrations. Downdrafts within Na I D1 bright points exhibit speeds of up to 7km/s, with preferred structural symmetry in intensity, magnetic field and velocity profiles about the bright point center. Excess intensities associated with G-band and Ca II K observations of magnetic bright points reveal a power-law trend when plotted as a function of magnetic flux density. However, Na I D1 observations of the same magnetic features indicate an intensity plateau at weak magnetic field strengths below ~150G, suggesting the presence of a two-component heating process; one which is primarily acoustic, the other predominantly magnetic. We suggest that this finding is related to the physical expansion of magnetic flux tubes, with weak field strengths (~50G) expanding by ~76%, compared to a ~44% expansion when higher field strengths (~150G) are present. These observations provide the first experimental evidence of rapid downdrafts in Na I D1 magnetic bright points, and reveal the nature of a previously unresolved intensity plateau associated with these structures.

Translocation of compact polymer chains through a nanopore

We perform dynamical Monte Carlo simulation to study the forced translocation of compact polymer chains in three-dimensional lattices. The chains are driven through a nanopore connecting two infinite channels by an external field. The scaling properties of average translocation time τ and translocation time distribution (TTD) are studied. The effects of contact energy (ɛC), electric field strength (E), and nanopore width (L) on the scaling exponent (α) of average translocation time τ∼Nα and the TTD are investigated. For the scaling behavior of τ∼Nα, we have found that there is no crossover behavior with weak field strength when the nanopore width is one lattice spacing, which is less than average bond length, while crossover behaviors are observed for larger nanopore widths. The scaling exponent α also depends on contact energy ɛC and electric field strength E. For the TTD, it shifts from the Gaussian to a right-skew distribution with the electric field E increasing for short chains; while for long chains, multi-peak distributions are observed. As a primary and simple model, compact polymer chains are extensively used to capture the structure and thermodynamic properties of proteins, therefore we can investigate the protein translocation by simulating compact chain translocation, and this study will be useful for exploring the complex translocation behaviors of proteins.

QED effective action in a constant electromagnetic field under conditions of possible Lorentz invariance violation in the Dirac equation

This paper is devoted to the calculation of corrections to QED effective action associated with the axial-vector condensate bμ, which violate the Lorentz invariance. It was shown that the linear in bμ contribution to the 1-loop effective action (Chern-Simons term) is absent in the case of a constant electromagnetic field. The contribution, which is quadratic in bμ, was calculated for the cases of both constant magnetic and electric fields. Asymptotic estimates of the quadratic in bμ term for strong and weak field strengths were obtained.

Signal of quark deconfinement in thermal evolution neutron stars with deconfinement heating

As neutron stars spin-down and contract, the deconfinement phase transition can continue to occur, resulting in energy release (so-called deconfinement heating) in case of the first-order phase transition. The thermal evolution of neutron stars is investigated to combine phase transition and the related energy release self-consistently. We find that the appearance of deconfinement heating during spin-down result in not only the cooling delay but also the increase of surface temperature of stars. For stars characterized by intermediate and weak magnetic field strength, a period of increasing surface temperature could exist. Especially, a sharp jump in surface temperature can be produced as soon as quark matter appears in the core of stars with a weak magnetic field. We think that this may serve as evidence for the existence of deconfinement quark matter. The results show that deconfinement heating facilitates the emergence of such characteristic signature during the thermal evolution process of neutron stars.

A high resolution Mirnov array for the Mega Ampere Spherical Tokamak

Over the past two decades, the increase in neutral-beam heating and alpha particle production in magnetically confined fusion plasmas has led to an increase in energetic particle driven mode activity, much of which has an electromagnetic signature which can be detected by the use of external Mirnov coils. Typically, the frequency and spatial wave number band of such oscillations increase with increasing injection energy, offering new challenges for diagnostic design. In particular, as the frequency approaches the megahertz range, care must be taken to model the stray capacitance of the coil, which limits the resonant frequency of the probe; model transmission line effects in the system, which if unchecked can produce system resonances; and minimize coil conductive shielding, so as to minimize skin currents which limit the frequency response of the coil. As well as optimizing the frequency response, the coils should also be positioned to confidently identify oscillations over a wide wave number band. This work, which draws on new techniques in stray capacitance modeling and coil positioning, is a case study of the outboard Mirnov array for high-frequency acquisition in the Mega Ampere Spherical Tokamak, and is intended as a roadmap for the design of high frequency, weak field strength magnetic diagnostics.

58kHz 대역 미약 전계강도 무선기기 기술 기준에 관한 연구

This paper compared the output limits value of the Korean weak electric field strength wireless device in the 58kHz band with the standard values of foreign countries. Through this, the study confirmed that the Korean regulation was lower by about 50dB than those of the USA or Europe. In order to prove this, the study measured outputs by entrusting the 58kHz EAS system to two measuring companies. As a result of these measurements, electric field strengths were shown to be and respectively, and these values were confirmed to exceed the current Korean standard of . Accordingly, it is deemed necessary to review the specifications of the Korean standard in the 58kHz band.

Global non-axisymmetric perturbation configurations in a composite disc system with an isopedic magnetic field: relation between dark matter halo and magnetic field

We study global non-axisymmetric stationary perturbations of aligned and unaligned logarithmic spiral configurations in an axisymmetric composite differentially rotating disc system of scale-free stellar and isopedically magnetized gas discs coupled by gravity. The infinitely thin gas disc is threaded across by a vertical magnetic field Bz with a constant dimensionless isopedic ratio of surface gas mass density Σ(g) to Bz with G being the gravitational constant. Our exploration focuses on the relation between the isopedic ratio λ and the dark matter amount represented by a gravitational potential ratio in order to sustain stationary perturbation configurations, where is the gravitational potential of a presumed axisymmetric halo of dark matter and Φ is the gravitational potential of the composite disc matter. For typical disc galaxies, we explore relevant parameter ranges numerically. High and low λ values correspond to relatively weak and strong magnetic fields given the same gas surface mass density, respectively. The main goal of our model analysis is to reveal the relation between isopedic magnetic fields and dark matter halo in spiral galaxies with globally stationary perturbation configurations. Our results show that for stationary perturbation configurations, fairly strong yet realistic magnetic fields require a considerably larger amount of dark matter in aligned and unaligned cases than weak or moderate magnetic field strengths. We discuss astrophysical and cosmological implications of our findings. For examples, patterns and pattern speeds of galaxies may change during the course of galactic evolution. Multiple-armed galaxies may be more numerous in the early Universe. Flocculent galaxies may represent the transitional phase of pattern variations in galaxies.

Cavities of weak magnetic field strength in the wake of FTEs: Results from global magnetospheric MHD simulations

We use the global magnetohydrodynamic (MHD) code BATS‐R‐US to model multipoint observations of Flux Transfer Event (FTE) signatures. Simulations with high spatial and temporal resolution predict that cavities of weak magnetic field strength protruding into the magnetosphere trail FTEs. These predictions are consistent with recently reported multi‐point Cluster observations of traveling magnetopause erosion regions (TMERs).

Dynamic Properties of the TRPML3 Pore and their Modification by the Varitint-Waddler Phenotype

TRPML3 is a Ca2+ channel expressed in intracellular vesicular compartments and is regulated by H+ that interact with the large intravesicular loop between transmembrane domains 1 and 2. The A419P mutation in TRPML3 causes the varitint-waddler phenotype as a result of gain-of-function (GOF). The mechanism by which the A419P mutation leads to GOF is unknown. Here, we show that the TRPML3 pore is dynamic and expands when conducting Ca2+ to change its permeability and selectivity from a strong to a weak field strength site. Pore expansion appears to be regulated by trapping Ca2+, probably within the pore. Expansion of the pore can be reversed only by conducting Na+ through the pore. The A419P mutation, which locks the channel in an open state results in permanently expanded pore. Notably, the TRPML3(H283A) mutation that eliminates regulation of TRPML3 by H+ and locks the channel in an open state shows the same pore properties as wild-type TRPML3. On the other hand, the pore mutation E449A also locks the channel in an open state and permanently expanded pore. Interestingly, the TRPML3 large intravesicular loop interacts with the pore domain composed of transmembranes 5 and 6. Although this interaction is enhanced by the A419P and E449A mutations, it is not affected by the loop mutation H283A, suggesting that pore expansion together with enhanced loop-pore communication is responsible for the GOF. These findings provide a molecular mechanism for GOF by the TRPML3(A419P) mutation to account for the varitint-waddler disease phenotype.

Higgs decays and brane gravi-vectors

Higgs boson decays in flexible brane world models with stable, massive gravi-vectors are considered. Such vectors couple bilinearly to the standard model fields through either the standard model energy-momentum tensor, the weak hypercharge field strength, or the Higgs scalar. The role of the coupling involving the extrinsic curvature is highlighted. It is found that within the presently allowed parameter space, the decay rate of the Higgs into two gravi-vectors (which would appear as an invisible Higgs decay) can be comparable to the rate for any of the standard model decay modes.

Three‐dimensional MHD simulations of Ganymede’s magnetosphere

Ganymede is unique among planetary moons because it has its own magnetic field strong enough to form a magnetosphere within Jupiter’s magnetospheric environment. Here we report on our three‐dimensional global magnetohydrodynamic (MHD) simulations that model the interaction between Ganymede’s magnetosphere and the corotating Jovian plasma. We use the measured field and particle properties to define our boundary conditions. Our simulations show that, in addition to the familiar structures such as the magnetopause and equatorial current sheet, Ganymede’s magnetosphere extends into an Alfvén wing that mediates the interaction of Ganymede with the plasma and ionosphere of Jupiter. The field‐aligned currents in the Alfvén wing close on themselves not only through the moon and its ionosphere. They also close through the magnetopause and tail current sheets. The pattern of the field‐aligned currents varies according to the orientation of the external magnetic field and asymmetries in the intensities of the parallel currents are organized by the clock angle of the ambient field in the plane perpendicular to the incident flow. The simulations reproduce quite closely the magnetic field structure measured by the Galileo magnetometer for all six close encounters. The magnetopause currents are well resolved in our high resolution simulations, producing sharp rotations in the field orientation consistent with the observations. However, the discrepancies between our model results and the data, such as the weaker field strength near closest approach in multiple simulated flybys, suggest the possibility that Ganymede’s intrinsic magnetic field may be stronger than the accepted value. The magnetosphere produced in our simulations can provide us with realistic estimates of the moon’s magnetic environment thereby enabling us to refine our determination of Ganymede’s internal magnetic field and to better understand the energetic particle behavior.

Crater FTEs: Simulation results and THEMIS observations

The BATS‐R‐US magnetohydrodynamic (MHD) model predicts flux transfer events (FTEs) with strong core magnetic fields embedded within a broadened current layer of weak magnetic field strengths on the equatorial dayside magnetopause during intervals of southward and duskward interplanetary magnetic field (IMF) orientation. Multipoint THEMIS observations at 2202 UT on June 20, 2007 of a southward‐moving FTE on the post‐noon magnetopause confirm the predictions of the model. THEMIS‐E and ‐A with large impact parameters simply observe enhanced magnetic field strengths in draped magnetosheath magnetic field lines, THEMIS‐B and ‐C with moderate impact parameters pass through the broadened current layer to observe crater FTEs with deep troughs bounding a strong core field, while THEMIS‐D with a very low impact parameter observes the core magnetic field strength enhancement embedded in the current layer.

Review: evidence does not support use of static magnets for pain

M H Pittler Dr M H Pittler, Peninsula Medical School, Exeter, UK; max.pittler@pms.ac.uk Are static magnets effective treatment for pain? ### Data sources: Medline, CINAHL, EMBASE/Excerpta Medica, Allied and Complementary...