Magnetic alignment of block copolymer microdomains by intrinsic chain anisotropy

DOE PAGES

Rokhlenko, Yekaterina; Yager, Kevin G.; Gopinadhan, Manesh; ...

2015-12-18

We examine the role of intrinsic chain susceptibility anisotropy in magnetic field directed self-assembly of a block copolymer using in situ x-ray scattering. Alignment of a lamellar mesophase is observed on cooling across the disorder-order transition with the resulting orientational order inversely proportional to the cooling rate. We discuss the origin of the susceptibility anisotropy, Δ χ, that drives alignment and calculate its magnitude using coarse-grained molecular dynamics to sample conformations of surface-tethered chains, finding Δ χ ≈ 2×10 –8. From field-dependent scattering data, we estimate that grains of ≈ 1.2 μm are present during alignment. Furthermore, these results demonstratemore » that intrinsic anisotropy is sufficient to support strong field-induced mesophase alignment and suggest a versatile strategy for field control of orientational order in block copolymers.« less

Magnetic alignment of block copolymer microdomains by intrinsic chain anisotropy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rokhlenko, Yekaterina; Yager, Kevin G.; Gopinadhan, Manesh

We examine the role of intrinsic chain susceptibility anisotropy in magnetic field directed self-assembly of a block copolymer using in situ x-ray scattering. Alignment of a lamellar mesophase is observed on cooling across the disorder-order transition with the resulting orientational order inversely proportional to the cooling rate. We discuss the origin of the susceptibility anisotropy, Δ χ, that drives alignment and calculate its magnitude using coarse-grained molecular dynamics to sample conformations of surface-tethered chains, finding Δ χ ≈ 2×10 –8. From field-dependent scattering data, we estimate that grains of ≈ 1.2 μm are present during alignment. Furthermore, these results demonstratemore » that intrinsic anisotropy is sufficient to support strong field-induced mesophase alignment and suggest a versatile strategy for field control of orientational order in block copolymers.« less

Reconstruction of interatomic vectors by principle component analysis of nuclear magnetic resonance data in multiple alignments

NASA Astrophysics Data System (ADS)

Hus, Jean-Christophe; Bruschweiler, Rafael

2002-07-01

A general method is presented for the reconstruction of interatomic vector orientations from nuclear magnetic resonance (NMR) spectroscopic data of tensor interactions of rank 2, such as dipolar coupling and chemical shielding anisotropy interactions, in solids and partially aligned liquid-state systems. The method, called PRIMA, is based on a principal component analysis of the covariance matrix of the NMR parameters collected for multiple alignments. The five nonzero eigenvalues and their eigenvectors efficiently allow the approximate reconstruction of the vector orientations of the underlying interactions. The method is demonstrated for an isotropic distribution of sample orientations as well as for finite sets of orientations and internuclear vectors encountered in protein systems.

Probing topology and dynamics of the second transmembrane domain (M2δ) of the acetyl choline receptor using magnetically aligned lipid bilayers (bicelles) and EPR spectroscopy.

PubMed

Sahu, Indra D; Mayo, Daniel J; Subbaraman, Nidhi; Inbaraj, Johnson J; McCarrick, Robert M; Lorigan, Gary A

2017-08-01

Characterizing membrane protein structure and dynamics in the lipid bilayer membrane is very important but experimentally challenging. EPR spectroscopy offers a unique set of techniques to investigate a membrane protein structure, dynamics, topology, and distance constraints in lipid bilayers. Previously our lab demonstrated the use of magnetically aligned phospholipid bilayers (bicelles) for probing topology and dynamics of the membrane peptide M2δ of the acetyl choline receptor (AchR) as a proof of concept. In this study, magnetically aligned phospholipid bilayers and rigid spin labels were further utilized to provide improved dynamic information and topology of M2δ peptide. Seven TOAC-labeled AchR M2δ peptides were synthesized to demonstrate the utility of a multi-labeling amino acid substitution alignment strategy. Our data revealed the helical tilts to be 11°, 17°, 9°, 17°, 16°, 11°, 9°±4° for residues I7TOAC, Q13TOAC, A14TOAC, V15TOAC, C16TOAC, L17TOAC, and L18TOAC, respectively. The average helical tilt of the M2δ peptide was determined to be ∼13°. This study also revealed that the TOAC labels were attached to the M2δ peptide with different dynamics suggesting that the sites towards the C-terminal end are more rigid when compared to the sites towards the N-terminus. The dynamics of the TOAC labeled sites were more resolved in the aligned samples when compared to the randomly disordered samples. This study highlights the use of magnetically aligned lipid bilayer EPR technique to determine a more accurate helical tilt and more resolved local dynamics of AchR M2δ peptide. Copyright © 2017 Elsevier B.V. All rights reserved.

Molecular engineering of lanthanide ion chelating phospholipids generating assemblies with a switched magnetic susceptibility.

PubMed

Isabettini, Stéphane; Massabni, Sarah; Hodzic, Arnel; Durovic, Dzana; Kohlbrecher, Joachim; Ishikawa, Takashi; Fischer, Peter; Windhab, Erich J; Walde, Peter; Kuster, Simon

2017-08-09

Lanthanide ion (Ln 3+ ) chelating amphiphiles are powerful molecules for tailoring the magnetic response of polymolecular assemblies. Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA) complexed to Ln 3+ deliver highly magnetically responsive bicelles. Their magnetic properties are readily tuned by changing the bicellar size or the magnetic susceptibility Δχ of the bilayer lipids. The former technique is intrinsically bound to the region of the phase diagram guarantying the formation of bicelles. Methods aiming towards manipulating the Δχ of the bilayer are comparatively more robust, flexible and lacking. Herein, we synthesized a new Ln 3+ chelating phospholipid using glutamic acid as a backbone: DMPE-Glu-DTPA. The chelate polyhedron was specifically engineered to alter the Δχ, whilst remaining geometrically similar to DMPE-DTPA. Planar asymmetric assemblies hundreds of nanometers in size were achieved presenting unprecedented magnetic alignments. The DMPE-Glu-DTPA/Ln 3+ complex switched the Δχ, achieving perpendicular alignment of assemblies containing Dy 3+ and parallel alignment of those containing Tm 3+ . Moreover, samples with chelated Yb 3+ were more alignable than the Tm 3+ chelating counterparts. Such a possibility has never been demonstrated for planar Ln 3+ chelating polymolecular assemblies. The physico-chemical properties of these novel assemblies were further studied by monitoring the alignment behavior at different temperatures and by including 16 mol% of cholesterol (Chol-OH) in the phospholipid bilayer. The DMPE-Glu-DTPA/Ln 3+ complex and the resulting assemblies are promising candidates for applications in numerous fields including pharmaceutical technologies, structural characterization of membrane biomolecules by NMR spectroscopy, as contrasting agents for magnetic resonance imaging, and for the development of smart optical gels.

Quantifying selective alignment of ensemble nitrogen-vacancy centers in (111) diamond

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tahara, Kosuke; Ozawa, Hayato; Iwasaki, Takayuki

2015-11-09

Selective alignment of nitrogen-vacancy (NV) centers in diamond is an important technique towards its applications. Quantification of the alignment ratio is necessary to design the optimized diamond samples. However, this is not a straightforward problem for dense ensemble of the NV centers. We estimate the alignment ratio of ensemble NV centers along the [111] direction in (111) diamond by optically detected magnetic resonance measurements. Diamond films deposited by N{sub 2} doped chemical vapor deposition have NV center densities over 1 × 10{sup 15 }cm{sup −3} and alignment ratios over 75%. Although spin coherence time (T{sub 2}) is limited to a few μs bymore » electron spins of nitrogen impurities, the combination of the selective alignment and the high density can be a possible way to optimize NV-containing diamond samples for the sensing applications.« less

Magnetization reversal of in-plane uniaxial Co films and its dependence on epitaxial alignment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Idigoras, O., E-mail: o.idigoras@nanogune.eu; Suszka, A. K.; Berger, A.

2014-02-28

This work studies the influence of crystallographic alignment onto magnetization reversal in partially epitaxial Co films. A reproducible growth sequence was devised that allows for the continuous tuning of grain orientation disorder in Co films with uniaxial in-plane anisotropy by the controlled partial suppression of epitaxy. While all stable or meta-stable magnetization states occurring during a magnetic field cycle exhibit a uniform magnetization for fully epitaxial samples, non-uniform states appear for samples with sufficiently high grain orientation disorder. Simultaneously with the occurrence of stable domain states during the magnetization reversal, we observe a qualitative change of the applied field anglemore » dependence of the coercive field. Upon increasing the grain orientation disorder, we observe a disappearance of transient domain wall propagation as the dominating reversal process, which is characterized by an increase of the coercive field for applied field angles away from the easy axis for well-ordered epitaxial samples. Upon reaching a certain disorder threshold level, we also find an anomalous magnetization reversal, which is characterized by a non-monotonic behavior of the remanent magnetization and coercive field as a function of the applied field angle in the vicinity of the nominal hard axis. This anomaly is a collective reversal mode that is caused by disorder-induced frustration and it can be qualitatively and even quantitatively explained by means of a two Stoner-Wohlfarth particle model. Its predictions are furthermore corroborated by Kerr microscopy and by Brillouin light scattering measurements.« less

Effect of grain-alignment on the levitation force of melt-processed YBCO bulk superconductors

NASA Astrophysics Data System (ADS)

Yang, Wan-min; Zhou, Lian; Feng, Yong; Zhang, Ping-xiang; Wu, Min-zhi; Wu, Xiao-zu; Gawalek, W.

1999-07-01

Single-domain YBCO bulk superconductors have been fabricated by Top Seeded Melt Slow Cooling Growth(TSSCG) process. Two typical YBCO cylinder samples with differential grain-alignment were selected for the investigation of the relationship between the grain-alignment and the levitation force under the same testing condition at liquid nitrogen temperature. It is found that the levitation force values is much different for the two samples, the levitation force of the sample with H par c-axis is more than two times higher than that of the samples with H ⊥ c-axis. So it is necessary to take account of this anisotropy in practical applications. The relationship between a magnet and a superconductor can be well described with a double exponential function. All the results are discussed in details.

Magnetic Alignment of γ-Fe2O3 Nanoparticles in Polymer Nanocomposites

NASA Astrophysics Data System (ADS)

Jimenez, Andrew; Kumar, Sanat K.; Jestin, Jacques

Recent work in nanocomposites has been heavily focused on controlling the dispersion state of filler particles. The use of internal self-assembly based on matrix properties provides a limited solution to the desire for specified organizations. By introducing a magnetic field during the casting of a polymer solution it has been shown that particles can be oriented to form anisotropic structures - commonly sought after for improved mechanical properties. Here, magnetic nanoparticles were cast in two different polymer matrices to study the effect of various forces that lead to this highly desired alignment. The addition of the magnetic field as an external trigger was shown to not necessarily force the clustering, but rather orient the agglomerates already available in solution. This demonstrates the importance of other dominant forces introduced into the system by characteristics of the polymers themselves. While this magnetic field provides a direction for the sample, the key forces lie in the interactions between the polymers and nanoparticles (as well as their solvent). The study shows a dependence of anisotropy on the particle loading, matrix, and casting time, from which continued work hopes to quantify the clustering necessary to optimize alignment in the composite.

Spontaneous magnetic alignment behaviour in free-living lizards.

PubMed

Diego-Rasilla, Francisco J; Pérez-Mellado, Valentín; Pérez-Cembranos, Ana

2017-04-01

Several species of vertebrates exhibit spontaneous longitudinal body axis alignment relative to the Earth's magnetic field (i.e., magnetic alignment) while they are performing different behavioural tasks. Since magnetoreception is still not fully understood, studying magnetic alignment provides evidence for magnetoreception and broadens current knowledge of magnetic sense in animals. Furthermore, magnetic alignment widens the roles of magnetic sensitivity in animals and may contribute to shed new light on magnetoreception. In this context, spontaneous alignment in two species of lacertid lizards (Podarcis muralis and Podarcis lilfordi) during basking periods was monitored. Alignments in 255 P. muralis and 456 P. lilfordi were measured over a 5-year period. The possible influence of the sun's position (i.e., altitude and azimuth) and geomagnetic field values corresponding to the moment in which a particular lizard was observed on lizards' body axis orientation was evaluated. Both species exhibited a highly significant bimodal orientation along the north-northeast and south-southwest magnetic axis. The evidence from this study suggests that free-living lacertid lizards exhibit magnetic alignment behaviour, since their body alignments cannot be explained by an effect of the sun's position. On the contrary, lizard orientations were significantly correlated with geomagnetic field values at the time of each observation. We suggest that this behaviour might provide lizards with a constant directional reference while they are sun basking. This directional reference might improve their mental map of space to accomplish efficient escape behaviour. This study is the first to provide spontaneous magnetic alignment behaviour in free-living reptiles.

Spontaneous magnetic alignment behaviour in free-living lizards

NASA Astrophysics Data System (ADS)

Diego-Rasilla, Francisco J.; Pérez-Mellado, Valentín; Pérez-Cembranos, Ana

2017-04-01

Several species of vertebrates exhibit spontaneous longitudinal body axis alignment relative to the Earth's magnetic field (i.e., magnetic alignment) while they are performing different behavioural tasks. Since magnetoreception is still not fully understood, studying magnetic alignment provides evidence for magnetoreception and broadens current knowledge of magnetic sense in animals. Furthermore, magnetic alignment widens the roles of magnetic sensitivity in animals and may contribute to shed new light on magnetoreception. In this context, spontaneous alignment in two species of lacertid lizards ( Podarcis muralis and Podarcis lilfordi) during basking periods was monitored. Alignments in 255 P. muralis and 456 P. lilfordi were measured over a 5-year period. The possible influence of the sun's position (i.e., altitude and azimuth) and geomagnetic field values corresponding to the moment in which a particular lizard was observed on lizards' body axis orientation was evaluated. Both species exhibited a highly significant bimodal orientation along the north-northeast and south-southwest magnetic axis. The evidence from this study suggests that free-living lacertid lizards exhibit magnetic alignment behaviour, since their body alignments cannot be explained by an effect of the sun's position. On the contrary, lizard orientations were significantly correlated with geomagnetic field values at the time of each observation. We suggest that this behaviour might provide lizards with a constant directional reference while they are sun basking. This directional reference might improve their mental map of space to accomplish efficient escape behaviour. This study is the first to provide spontaneous magnetic alignment behaviour in free-living reptiles.

Magnetically aligned phospholipid bilayers in weak magnetic fields: optimization, mechanism, and advantages for X-band EPR studies.

PubMed

Cardon, Thomas B; Tiburu, Elvis K; Lorigan, Gary A

2003-03-01

Our lab is developing a spin-labeled EPR spectroscopic technique complementary to solid-state NMR studies to study the structure, orientation, and dynamics of uniaxially aligned integral membrane proteins inserted into magnetically aligned discotic phospholipid bilayers, or bicelles. The focus of this study is to optimize and understand the mechanisms involved in the magnetic alignment process of bicelle disks in weak magnetic fields. Developing experimental conditions for optimized magnetic alignment of bicelles in low magnetic fields may prove useful to study the dynamics of membrane proteins and its interactions with lipids, drugs, steroids, signaling events, other proteins, etc. In weak magnetic fields, the magnetic alignment of Tm(3+)-doped bicelle disks was thermodynamically and kinetically very sensitive to experimental conditions. Tm(3+)-doped bicelles were magnetically aligned using the following optimized procedure: the temperature was slowly raised at a rate of 1.9K/min from an initial temperature being between 298 and 307K to a final temperature of 318K in the presence of a static magnetic field of 6300G. The spin probe 3beta-doxyl-5alpha-cholestane (cholestane) was inserted into the bicelle disks and utilized to monitor bicelle alignment by analyzing the anisotropic hyperfine splitting for the corresponding EPR spectra. The phases of the bicelles were determined using solid-state 2H NMR spectroscopy and compared with the corresponding EPR spectra. Macroscopic alignment commenced in the liquid crystalline nematic phase (307K), continued to increase upon slowly raising the temperature, and was well-aligned in the liquid crystalline lamellar smectic phase (318K).

Magnetic field effect for cellulose nanofiber alignment

NASA Astrophysics Data System (ADS)

Kim, Jaehwan; Chen, Yi; Kang, Kwang-Sun; Park, Young-Bin; Schwartz, Mark

2008-11-01

Regenerated cellulose formed into cellulose nanofibers under strong magnetic field and aligned perpendicularly to the magnetic field. Well-aligned microfibrils were found as the exposure time of the magnetic field increased. Better alignment and more crystalline structure of the cellulose resulted in the increased decomposition temperature of the material. X-ray crystallograms showed that crystallinity index of the cellulose increased as the exposure time of the magnetic field increased.

Evaluation, development, and characterization of superconducting materials for space applications

NASA Technical Reports Server (NTRS)

Thorpe, Arthur N.

1990-01-01

The anisotropic electromagnetic features of a grain-aligned YBa2Cu3O(x) bulk sample derived from a process of long-time partial melt growth were investigated by the measurements of direct current magnetization (at 77 K) and alternating current susceptibility as a function of temperature, with the fields applied parallel and perpendicular to the c axis, respectively. The extended Bean model was further studied and applied to explain the experimental results. Upon comparison of the grain-aligned sample with pure single crystal materials, it is concluded that because of the existence of more effective pinning sites in the grain-aligned sample, not only its critical current density perpendicular to the c axis is improved, but the one parallel to the c axis is improved even more significantly. The anisotropy in the critical current densities in the grain-aligned sample at 77 K is at least one to two orders of magnitude smaller than in the pure single crystal. The measurement of anisotropy of alternating current susceptibility as a function of temperature, especially its imaginary part, shows that there are still some residues of interlayer weak links in the grain-aligned samples, but they are quite different from and far less serious than the weak links in the sintered sample.

Method for alignment of microwires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beardslee, Joseph A.; Lewis, Nathan S.; Sadtler, Bryce

2017-01-24

A method of aligning microwires includes modifying the microwires so they are more responsive to a magnetic field. The method also includes using a magnetic field so as to magnetically align the microwires. The method can further include capturing the microwires in a solid support structure that retains the longitudinal alignment of the microwires when the magnetic field is not applied to the microwires.

Alignment of Iron Nanoparticles in a Magnetic Field Due to Shape Anisotropy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radhakrishnan, Balasubramaniam; Nicholson, Don M; Eisenbach, Markus

2015-07-09

During high magnetic field processing there is evidence for alignment of non-spherical metallic particles above the Curie temperature in alloys with negligible magneto-crystalline anisotropy. The main driving force for alignment is the magnetic shape anisotropy. Current understanding of the phenomenon is not adequate to quantify the effect of particle size, aspect ratio, temperature and the magnetic field on particle alignment. We demonstrate a Monte Carlo approach coupled with size scaling to show the conditions under which alignment is possible.

Dogs are sensitive to small variations of the Earth’s magnetic field

PubMed Central

2013-01-01

Introduction Several mammalian species spontaneously align their body axis with respect to the Earth’s magnetic field (MF) lines in diverse behavioral contexts. Magnetic alignment is a suitable paradigm to scan for the occurrence of magnetosensitivity across animal taxa with the heuristic potential to contribute to the understanding of the mechanism of magnetoreception and identify further functions of magnetosensation apart from navigation. With this in mind we searched for signs of magnetic alignment in dogs. We measured the direction of the body axis in 70 dogs of 37 breeds during defecation (1,893 observations) and urination (5,582 observations) over a two-year period. After complete sampling, we sorted the data according to the geomagnetic conditions prevailing during the respective sampling periods. Relative declination and intensity changes of the MF during the respective dog walks were calculated from daily magnetograms. Directional preferences of dogs under different MF conditions were analyzed and tested by means of circular statistics. Results Dogs preferred to excrete with the body being aligned along the North–South axis under calm MF conditions. This directional behavior was abolished under unstable MF. The best predictor of the behavioral switch was the rate of change in declination, i.e., polar orientation of the MF. Conclusions It is for the first time that (a) magnetic sensitivity was proved in dogs, (b) a measurable, predictable behavioral reaction upon natural MF fluctuations could be unambiguously proven in a mammal, and (c) high sensitivity to small changes in polarity, rather than in intensity, of MF was identified as biologically meaningful. Our findings open new horizons in magnetoreception research. Since the MF is calm in only about 20% of the daylight period, our findings might provide an explanation why many magnetoreception experiments were hardly replicable and why directional values of records in diverse observations are frequently compromised by scatter. PMID:24370002

A UNIFIED MODEL OF GRAIN ALIGNMENT: RADIATIVE ALIGNMENT OF INTERSTELLAR GRAINS WITH MAGNETIC INCLUSIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoang, Thiem; Lazarian, A.

The radiative torque (RAT) alignment of interstellar grains with ordinary paramagnetic susceptibilities has been supported by earlier studies. The alignment of such grains depends on the so-called RAT parameter q {sup max}, which is determined by the grain shape. In this paper, we elaborate on our model of RAT alignment for grains with enhanced magnetic susceptibility due to iron inclusions, such that RAT alignment is magnetically enhanced, which we term the MRAT mechanism. Such grains can be aligned with high angular momentum at the so-called high- J attractor points, achieving a high degree of alignment. Using our analytical model ofmore » RATs, we derive the critical value of the magnetic relaxation parameter δ {sub m} to produce high- J attractor points as functions of q {sup max} and the anisotropic radiation angle relative to the magnetic field ψ . We find that if about 10% of the total iron abundance present in silicate grains is forming iron clusters, this is sufficient to produce high- J attractor points for all reasonable values of q {sup max}. To calculate the degree of grain alignment, we carry out numerical simulations of MRAT alignment by including stochastic excitations from gas collisions and magnetic fluctuations. We show that large grains can achieve perfect alignment when the high- J attractor point is present, regardless of the values of q {sup max}. Our obtained results pave the way for the physical modeling of polarized thermal dust emission as well as magnetic dipole emission. We also find that millimeter-sized grains in accretion disks may be aligned with the magnetic field if they are incorporated with iron nanoparticles.« less

Changes in collection efficiency in nylon net filter media through magnetic alignment of elongated aerosol particles.

PubMed

Lam, Christopher O; Finlay, W H

2009-10-01

Fiber aerosols tend to align parallel to surrounding fluid streamlines in shear flows, making their filtration more difficult. However, previous research indicates that composite particles made from cromoglycic acid fibers coated with small nanoscaled magnetite particles can align with an applied magnetic field. The present research explored the effect of magnetically aligning these fibers to increase their filtration. Nylon net filters were challenged with the aerosol fibers, and efficiency tests were performed with and without a magnetic field applied perpendicular to the flow direction. We investigated the effects of varying face velocities, the amount of magnetite material on the aerosol particles, and magnetic field strengths. Findings from the experiments, matched by supporting single-fiber theories, showed significant efficiency increases at the low face velocity of 1.5 cm s(-1) at all magnetite compositions, with efficiencies more than doubling due to magnetic field alignment in certain cases. At a higher face velocity of 5.12 cm s(-1), filtration efficiencies were less affected by the magnetic field alignment being, at most, 43% higher for magnetite weight compositions up to 30%, while at a face velocity of 10.23 cm s(-1) alignment effects were insignificant. In most cases, efficiencies became independent of magnetic field strength above 50 mT, suggesting full alignment of the fibers. The present data suggest that fiber alignment in a magnetic field may warrant applications in the filtration and detection of fibers, such as asbestos.

Cooperative ordering and kinetics of cellulose nanocrystal alignment in a magnetic field

DOE PAGES

De France, Kevin J.; Yager, Kevin G.; Hoare, Todd; ...

2016-07-13

Cellulose nanocrystals (CNCs) are emerging nanomaterials that form chiral nematic liquid crystals above a critical concentration (C*) and additionally orient within electromagnetic fields. The control over CNC alignment is significant for materials processing and end use; to date, magnetic alignment has been demonstrated using only strong fields over extended or arbitrary time scales. This work investigates the effects of comparatively weak magnetic fields (0–1.2 T) and CNC concentration (1.65–8.25 wt %) on the kinetics and degree of CNC ordering using small-angle X-ray scattering. Interparticle spacing, correlation length, and orientation order parameters (η and S) increased with time and field strengthmore » following a sigmoidal profile. In a 1.2 T magnetic field for CNC suspensions above C*, partial alignment occurred in under 2 min followed by slower cooperative ordering to achieve nearly perfect alignment in under 200 min (S = –0.499 where S = –0.5 indicates perfect antialignment). At 0.56 T, nearly perfect alignment was also achieved, yet the ordering was 36% slower. Outside of a magnetic field, the order parameter plateaued at 52% alignment (S = –0.26) after 5 h, showcasing the drastic effects of relatively weak magnetic fields on CNC alignment. For suspensions below C*, no magnetic alignment was detected.« less

Magnetostructural transition in Fe{sub 5}SiB{sub 2} observed with neutron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cedervall, Johan, E-mail: johan.cedervall@kemi.uu.se; Kontos, Sofia; Hansen, Thomas C.

2016-03-15

The crystal and magnetic structure of Fe{sub 5}SiB{sub 2} has been studied by a combination of X-ray and neutron diffraction. Also, the magnetocrystalline anisotropy energy constant has been estimated from magnetisation measurements. High quality samples have been prepared using high temperature synthesis and subsequent heat treatment protocols. The crystal structure is tetragonal within the space group I4/mcm and the compound behaves ferromagnetically with a Curie temperature of 760 K. At 172 K a spin reorientation occurs in the compound and the magnetic moments go from aligning along the c-axis (high T) down to the ab-plane (low T). The magnetocrystalline anisotropymore » energy constant has been estimated to 0.3 MJ/m{sup 3} at 300 K. - Highlights: • The crystal and magnetic structure of Fe{sub 5}SiB{sub 2} has been studied by diffraction. • At 172 K a spin reorientation occurs in the compound. • The magnetic moments are aligned along the c-axis at high T. • The magnetic moments are aligned in the ab-plane at low T. • The magnetocrystalline anisotropy energy constant has been estimated to 0.3 MJ/m{sup 3}.« less

Magnetic Cellulose Nanocrystal Based Anisotropic Polylactic Acid Nanocomposite Films: Influence on Electrical, Magnetic, Thermal, and Mechanical Properties.

PubMed

Dhar, Prodyut; Kumar, Amit; Katiyar, Vimal

2016-07-20

This paper reports a single-step co-precipitation method for the fabrication of magnetic cellulose nanocrystals (MGCNCs) with high iron oxide nanoparticle content (∼51 wt % loading) adsorbed onto cellulose nanocrystals (CNCs). X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman spectroscopic studies confirmed that the hydroxyl groups on the surface of CNCs (derived from the bamboo pulp) acted as anchor points for the adsorption of Fe3O4 nanoparticles. The fabricated MGCNCs have a high magnetic moment, which is utilized to orient the magnetoresponsive nanofillers in parallel or perpendicular orientations inside the polylactic acid (PLA) matrix. Magnetic-field-assisted directional alignment of MGCNCs led to the incorporation of anisotropic mechanical, thermal, and electrical properties in the fabricated PLA-MGCNC nanocomposites. Thermomechanical studies showed significant improvement in the elastic modulus and glass-transition temperature for the magnetically oriented samples. Differential scanning calorimetry (DSC) and XRD studies confirmed that the alignment of MGCNCs led to the improvement in the percentage crystallinity and, with the absence of the cold-crystallization phenomenon, finds a potential application in polymer processing in the presence of magnetic field. The tensile strength and percentage elongation for the parallel-oriented samples improved by ∼70 and 240%, respectively, and for perpendicular-oriented samples, by ∼58 and 172%, respectively, in comparison to the unoriented samples. Furthermore, its anisotropically induced electrical and magnetic properties are desirable for fabricating self-biased electronics products. We also demonstrate that the fabricated anisotropic PLA-MGCNC nanocomposites could be laminated into films with the incorporation of directionally tunable mechanical properties. Therefore, the current study provides a novel noninvasive approach of orienting nontoxic bioderived CNCs in the presence of low magnetic fields, with potential applications in the manufacturing of three-dimensional composites with microstructural features comparable to biological materials for high-performance engineering applications.

Thermal characterization of magnetically aligned carbonyl iron/agar composites.

PubMed

Diaz-Bleis, D; Vales-Pinzón, C; Freile-Pelegrín, Y; Alvarado-Gil, J J

2014-01-01

Composites of magnetic particles into polymeric matrices have received increasing research interest due to their capacity to respond to external magnetic or electromagnetic fields. In this study, agar from Gelidium robustum has been chosen as natural biocompatible polymer to build the matrix of the magnetic carbonyl iron particles (CIP) for their uses in biomedical fields. Heat transfer behavior of the CIP-agar composites containing different concentrations (5, 10, 15, 20, 25 and 30% w/w) of magnetically aligned and non-aligned CIP in the agar matrix was studied using photothermal radiometry (PTR) in the back-propagation emission configuration. The morphology of the CIP-agar composites with aligned and non-aligned CIP under magnetic field was also evaluated by scanning electron microscopy (SEM). The results revealed a dominant effect of CIP concentration over the alignment patterns induced by the magnetic field, which agrees with the behavior of the thermal diffusivity and thermal conductivity. Agar served as a perfect matrix to be used with CIP, and CIP-agar composites magnetically aligned at 20% CIP concentration can be considered as promising 'smart' material for hyperthermia treatments in the biomedical field. Copyright © 2013 Elsevier Ltd. All rights reserved.

Macroscopic Magnetization Control by Symmetry Breaking of Photoinduced Spin Reorientation with Intense Terahertz Magnetic Near Field

NASA Astrophysics Data System (ADS)

Kurihara, Takayuki; Watanabe, Hiroshi; Nakajima, Makoto; Karube, Shutaro; Oto, Kenichi; Otani, YoshiChika; Suemoto, Tohru

2018-03-01

We exploit an intense terahertz magnetic near field combined with femtosecond laser excitation to break the symmetry of photoinduced spin reorientation paths in ErFeO3 . We succeed in aligning macroscopic magnetization reaching up to 80% of total magnetization in the sample to selectable orientations by adjusting the time delay between terahertz and optical pump pulses. The spin dynamics are well reproduced by equations of motion, including time-dependent magnetic potential. We show that the direction of the generated magnetization is determined by the transient direction of spin tilting and the magnetic field at the moment of photoexcitation.

Processing, Fabrication, Characterization and Device Demonstration of High Temperature Superconducting Ceramics

DTIC Science & Technology

1994-07-30

optimize processes for grain alignment in bulk and tape samples; and (4) provide a technology base for utilization of flux-trap magnets . SUXIARY a) A...of the vortices in the bulk material. Neutron scattering experiments can be performed in a magnetic field range of -0.05 T up to several teslas, a...uncorrected for demagnetization ) was then taken as the field associated with the first nonzero value of magnetization -difference, AM; 3ee Figs.5&6

Progress in ETA-II magnetic field alignment using stretched wire and low energy electron beam techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deadrick, F.J.; Griffith, L.V.

1990-08-17

Flux line alignment of the solenoidal focus magnets used on the ETA-II linear induction accelerator is a key element leading to a reduction of beam corkscrew motion. Two techniques have been used on the ETA-II accelerator to measure and establish magnet alignment. A low energy electron beam has been used to directly map magnetic field lines, and recent work has utilized a pulsed stretched wire technique to measure magnet tilts and offsets with respect to a reference axis. This paper reports on the techniques used in the ETA-II accelerator alignment, and presents results from those measurements which show that acceleratormore » is magnetically aligned to within {approximately}{plus minus}200 microns. 3 refs., 8 figs.« less

Angular dependence of coercivity derived from alignment dependence of coercivity in Nd-Fe-B sintered magnets

NASA Astrophysics Data System (ADS)

Matsuura, Yutaka; Nakamura, Tetsuya; Sumitani, Kazushi; Kajiwara, Kentaro; Tamura, Ryuji; Osamura, Kozo

2018-01-01

Experimental results of the alignment dependence of the coercivity in Nd-Fe-B sintered magnets showed that the angle of magnetization reversal for anisotropically aligned magnets was bigger than that obtained from the theoretical results calculated using the postulation that every grain independently reverses its magnetization direction following the 1/cos θ law. The angles of reversed magnetization (θ1) for Nd13.48Co0.55B5.76Febal. with alignment α=0.95 and for Nd12.75Dy0.84B5.81Co0.55Febal. with α=0.96 were 30° and 36°, respectively, which were very similar to that of an ideal magnet with a Gaussian distribution (σ=31° and 44°, respectively) of the grain alignment. In this model, we postulated that every grain independently reversed according to the 1/cos θ law. The calculation results for the angular dependence of the coercivity using the values θ1=ω1(0°)=30°, σ=31° and θ1=ω1(0°)=36°, σ=44° could qualitatively and convincingly explain the observed angular dependence of the coercivity of Nd14.2B6.2Co1.0Febal. and Nd14.2Dy0.3B6.2Co1.0Febal.. It is speculated that the magnetic domain wall is pinned at grains tilted away from the easy magnetization direction, and when the magnetic domain wall de-pins from the tilted grains, the magnetic domain wall jumps through several grains. We suggest that the coercive force of the aligned magnet behaves like a low-aligned magnet owing to the magnetization reversal of the crust of the grains induced by the pinning and subsequent jumping of the magnetic domain wall.

New alnico magnets fabricated from pre-alloyed gas-atomized powder through diverse consolidation techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, W.; Zhou, L.; Kassen, A. G.

2015-05-25

Fine Alnico 8 spherical powder produced by gas atomization was consolidated through hot pressing (HP), hot isostatic pressing (HIP), and compression molding and subsequent sintering (CMS) techniques. The effects of different fabrication techniques and processing parameters on microstructure and magnetic properties were analyzed and compared. The HP, HIP, and CMS magnets exhibited different features in microstructures and magnetic properties. Magnetically annealed at 840°C for 10 min and subsequently tempered at 650°C for 5h and 580°C for 15h, the HIP sample achieved the best coercivity (H cj =1845 Oe) due to spinodally decomposed (SD) phases with uniform and well-faceted mosaic morphology.more » As a result, the CMS sample had a lower Hcj than HIP and HP samples, but a higher remanence and thus the best energy product (6.5 MGOe) due to preferential grain alignment induced by abnormal grain growth.« less

Polarization of Magnetic Dipole Emission and Spinning Dust Emission from Magnetic Nanoparticles

NASA Astrophysics Data System (ADS)

Hoang, Thiem; Lazarian, Alex

2016-04-01

Magnetic dipole emission (MDE) from interstellar magnetic nanoparticles is potentially an important Galactic foreground in the microwave frequencies, and its polarization level may pose great challenges for achieving reliable measurements of cosmic microwave background B-mode signal. To obtain realistic predictions for the polarization of MDE, we first compute the degree of alignment of big silicate grains incorporated with magnetic inclusions. We find that thermally rotating big grains with magnetic inclusions are weakly aligned and can achieve alignment saturation when the magnetic alignment rate becomes much faster than the rotational damping rate. We then compute the degree of alignment for free-flying magnetic nanoparticles, taking into account various interaction processes of grains with the ambient gas and radiation field, including neutral collisions, ion collisions, and infrared emission. We find that the rotational damping by infrared emission can significantly decrease the degree of alignment of small particles from the saturation level, whereas the excitation by ion collisions can enhance the alignment of ultrasmall particles. Using the computed degrees of alignment, we predict the polarization level of MDE from free-flying magnetic nanoparticles to be rather low. Such a polarization level is within the upper limits measured for anomalous microwave emission (AME), which indicates that MDE from free-flying iron particles may not be ruled out as a source of AME. We also quantify rotational emission from free-flying iron nanoparticles with permanent magnetic moments and find that its emissivity is about one order of magnitude lower than that from spinning polycyclic aromatic hydrocarbons.

POLARIZATION OF MAGNETIC DIPOLE EMISSION AND SPINNING DUST EMISSION FROM MAGNETIC NANOPARTICLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoang, Thiem; Lazarian, Alex

2016-04-20

Magnetic dipole emission (MDE) from interstellar magnetic nanoparticles is potentially an important Galactic foreground in the microwave frequencies, and its polarization level may pose great challenges for achieving reliable measurements of cosmic microwave background B-mode signal. To obtain realistic predictions for the polarization of MDE, we first compute the degree of alignment of big silicate grains incorporated with magnetic inclusions. We find that thermally rotating big grains with magnetic inclusions are weakly aligned and can achieve alignment saturation when the magnetic alignment rate becomes much faster than the rotational damping rate. We then compute the degree of alignment for free-flyingmore » magnetic nanoparticles, taking into account various interaction processes of grains with the ambient gas and radiation field, including neutral collisions, ion collisions, and infrared emission. We find that the rotational damping by infrared emission can significantly decrease the degree of alignment of small particles from the saturation level, whereas the excitation by ion collisions can enhance the alignment of ultrasmall particles. Using the computed degrees of alignment, we predict the polarization level of MDE from free-flying magnetic nanoparticles to be rather low. Such a polarization level is within the upper limits measured for anomalous microwave emission (AME), which indicates that MDE from free-flying iron particles may not be ruled out as a source of AME. We also quantify rotational emission from free-flying iron nanoparticles with permanent magnetic moments and find that its emissivity is about one order of magnitude lower than that from spinning polycyclic aromatic hydrocarbons.« less

Magnetic Measurements of Storage Ring Magnets for the APS Upgrade Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doose, C.; Dejus, R.; Jaski, M.

2017-06-01

Extensive prototyping of storage ring magnets is ongoing at the Advanced Photon Source (APS) in support of the APS Multi-Bend Achromat (MBA) upgrade project (APS-U) [1]. As part of the R&D activities four quadrupole magnets with slightly different geometries and pole tip materials, and one sextupole magnet with vanadium permendur (VP) pole tips were designed, built and tested. Magnets were measured individually using a rotating coil and a Hall probe for detailed mapping of the magnetic field. Magnets were then assembled and aligned relative to each other on a steel support plate and concrete plinth using precision machined surfaces tomore » gain experience with the alignment method chosen for the APS-U storage ring magnets. The required alignment of magnets on a common support structure is 30 μm rms. Measurements of magnetic field quality, strength and magnet alignment after subjecting the magnets and assemblies to different tests are presented.« less

Evolution of ferromagnetism in charge ordered manganite: An effect of external pressure

NASA Astrophysics Data System (ADS)

Dash, S.; Pradhan, M. K.; Rao, T. Lakshmana

2018-05-01

Detailed magnetic measurements of the Pr0.75Na0.25MnO3 polycrystalline sample have been carried out under external hydrostatic pressure upto 10kbar. Pressure strongly suppresses the first order magnetic transition, while thermal hysteresis narrows down progressively and then disappears with increase in pressure. The significant enhancement of the field cooled magnetization value at different pressures is due to the antiferromagnetic to ferromagnetic transformation, while ruling out any contribution from the domain alignment within the ferromagnetic phase.

Formation of the Sun-aligned arc region and the void (polar slot) under the null-separator structure

NASA Astrophysics Data System (ADS)

Tanaka, T.; Obara, T.; Watanabe, M.; Fujita, S.; Ebihara, Y.; Kataoka, R.

2017-04-01

From the global magnetosphere-ionosphere coupling simulation, we examined the formation of the Sun-aligned arc region and the void (polar slot) under the northward interplanetary magnetic field (IMF) with negative By condition. In the magnetospheric null-separator structure, the separatrices generated from two null points and two separators divide the entire space into four types of magnetic region, i.e., the IMF, the northern open magnetic field, the southern open magnetic field, and the closed magnetic field. In the ionosphere, the Sun-aligned arc region and the void are reproduced in the distributions of simulated plasma pressure and field-aligned current. The outermost closed magnetic field lines on the boundary (separatrix) between the northern open magnetic field and the closed magnetic field are projected to the northern ionosphere at the boundary between the Sun-aligned arc region and the void, both on the morning and evening sides. The magnetic field lines at the plasma sheet inner edge are projected to the equatorward boundary of the oval. Therefore, the Sun-aligned arc region is on the closed magnetic field lines of the plasma sheet. In the plasma sheet, an inflated structure (bulge) is generated at the junction of the tilted plasma sheet in the far-to-middle tail and nontilted plasma sheet in the ring current region. In the Northern Hemisphere, the bulge is on the evening side wrapped by the outermost closed magnetic field lines that are connected to the northern evening ionosphere. This inflated structure (bulge) is associated with shear flows that cause the Sun-aligned arc.

Vertical Si nanowire arrays fabricated by magnetically guided metal-assisted chemical etching

NASA Astrophysics Data System (ADS)

Chun, Dong Won; Kim, Tae Kyoung; Choi, Duyoung; Caldwell, Elizabeth; Kim, Young Jin; Paik, Jae Cheol; Jin, Sungho; Chen, Renkun

2016-11-01

In this work, vertically aligned Si nanowire arrays were fabricated by magnetically guided metal-assisted directional chemical etching. Using an anodized aluminum oxide template as a shadow mask, nanoscale Ni dot arrays were fabricated on an Si wafer to serve as a mask to protect the Si during the etching. For the magnetically guided chemical etching, we deposited a tri-layer metal catalyst (Au/Fe/Au) in a Swiss-cheese configuration and etched the sample under the magnetic field to improve the directionality of the Si nanowire etching and increase the etching rate along the vertical direction. After the etching, the nanowires were dried with minimal surface-tension-induced aggregation by utilizing a supercritical CO2 drying procedure. High-resolution transmission electron microscopy (HR-TEM) analysis confirmed the formation of single-crystal Si nanowires. The method developed here for producing vertically aligned Si nanowire arrays could find a wide range of applications in electrochemical and electronic devices.

Selective and directional actuation of elastomer films using chained magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Mishra, Sumeet R.; Dickey, Michael D.; Velev, Orlin D.; Tracy, Joseph B.

2016-01-01

We report selective and directional actuation of elastomer films utilizing magnetic anisotropy introduced by chains of Fe3O4 magnetic nanoparticles (MNPs). Under uniform magnetic fields or field gradients, dipolar interactions between the MNPs favor magnetization along the chain direction and cause selective lifting. This mechanism is described using a simple model.We report selective and directional actuation of elastomer films utilizing magnetic anisotropy introduced by chains of Fe3O4 magnetic nanoparticles (MNPs). Under uniform magnetic fields or field gradients, dipolar interactions between the MNPs favor magnetization along the chain direction and cause selective lifting. This mechanism is described using a simple model. Electronic supplementary information (ESI) available: Two videos for actuation while rotating the sample, experimental details of nanoparticle synthesis, polymer composite preparation, and alignment and bending studies, details of the theoretical model of actuation, and supplemental figures for understanding the behavior of rotating samples and results from modelling. See DOI: 10.1039/c5nr07410j

Ultrasonic alignment of bio-functionalized magnetic beads and live cells in PDMS micro-fluidic channel.

PubMed

Islam, Afroja T; Siddique, Ariful H; Ramulu, T S; Reddy, Venu; Eu, Young-Jae; Cho, Seung Hyun; Kim, CheolGi

2012-12-01

In this work, we demonstrated the alignment of polystyrene latex microspheres (diameter of 1 ~45 μm), bio-functionalized superparamagnetic beads (diameter 2.8 μm), and live cells (average diameter 1 ~2 μm) using an ultrasonic standing wave (USW) in a PDMS microfluidic channel (330 μm width) attached on a Si substrate for bio-medical applications. To generate a standing wave inside the channel, ultrasound of 2.25 MHz resonance frequency (for the channel width) was applied by two ultrasound transducers installed at both sides of the channel which caused the radiation force to concentrate the micro-particles at the single pressure nodal plane of USW. By increasing the frequency to the next resonance condition of the channel, the particles were concentrated in dual nodal planes. Migration time of the micro-particles towards the single nodal plane was recorded as 108 s, 17 s, and 115 s for polystyrene particles of 2 μm diameter, bio-functionalized magnetic beads, and live cells, respectively. These successful alignments of the bio-functionalized magnetic beads along the desired part of the channel can enhance the performance of a sensor which is applicable for the bio-hybrid system and the alignment of live cells without any damage can be used for sample pre-treatment for the application of lab-on-a-chip type bioassays.

Can primordial magnetic fields seeded by electroweak strings cause an alignment of quasar axes on cosmological scales?

PubMed

Poltis, Robert; Stojkovic, Dejan

2010-10-15

The decay of nontopological electroweak strings may leave an observable imprint in the Universe today in the form of primordial magnetic fields. Protogalaxies preferentially tend to form with their axis of rotation parallel to an external magnetic field, and, moreover, an external magnetic field produces torque which tends to align the galaxy axis with the magnetic field. We demonstrate that the shape of a magnetic field left over from two looped electroweak strings can explain the observed nontrivial alignment of quasar polarization vectors and make predictions for future observations.

Stiff, porous scaffolds from magnetized alumina particles aligned by magnetic freeze casting.

PubMed

Frank, Michael B; Naleway, Steven E; Haroush, Tsuk; Liu, Chin-Hung; Siu, Sze Hei; Ng, Jerry; Torres, Ivan; Ismail, Ali; Karandikar, Keyur; Porter, Michael M; Graeve, Olivia A; McKittrick, Joanna

2017-08-01

Bone consists of a hard mineral phase and a compliant biopolymer phase resulting in a composite material that is both lightweight and strong. Osteoporosis that degrades spongy bone preferentially over time leads to bone brittleness in the elderly. A porous ceramic material that can mimic spongy bone for a one-time implant provides a potential solution for the future needs of an aging population. Scaffolds made by magnetic freeze casting resemble the aligned porosity of spongy bone. A magnetic field applied throughout freezing induces particle chaining and alignment of lamellae structures between growing ice crystals. After freeze drying to extract the ice and sintering to strengthen the scaffold, cubes from the scaffold center are mechanically compressed along longitudinal (z-axis, ice growth direction) and transverse (y-axis, magnetic field direction) axes. The best alignment of lamellar walls in the scaffold center occurs when applying magnetic freeze casting with the largest particles (350nm) at an intermediate magnetic field strength (75mT), which also agrees with stiffness enhancement results in both z and y-axes. Magnetic moments of different sized magnetized alumina particles help determine the ideal magnetic field strength needed to induce alignment in the scaffold center rather than just at the poles. Copyright © 2017 Elsevier B.V. All rights reserved.

Microwave conductance properties of aligned multiwall carbon nanotube textile sheets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Brian L.; Martinez, Patricia; Zakhidov, Anvar A.

2015-07-06

Understanding the conductance properties of multi-walled carbon nanotube (MWNT) textile sheets in the microwave regime is essential for their potential use in high-speed and high-frequency applications. To expand current knowledge, complex high-frequency conductance measurements from 0.01 to 50 GHz and across temperatures from 4.2 K to 300 K and magnetic fields up to 2 T were made on textile sheets of highly aligned MWNTs with strand alignment oriented both parallel and perpendicular to the microwave electric field polarization. Sheets were drawn from 329 and 520 μm high MWNT forests that resulted in different DC resistance anisotropy. For all samples, themore » microwave conductance can be modeled approximately by a shunt capacitance in parallel with a frequency-independent conductance, but with no inductive contribution. Finally, this is consistent with diffusive Drude conduction as the primary transport mechanism up to 50 GHz. Further, it is found that the microwave conductance is essentially independent of both temperature and magnetic field.« less

Controllable growth of vertically aligned graphene on C-face SiC

DOE PAGES

Liu, Yu; Chen, Lianlian; Hilliard, Donovan; ...

2016-10-06

We investigated how to control the growth of vertically aligned graphene on C-face SiC by varying the processing conditions. It is found that, the growth rate scales with the annealing temperature and the graphene height is proportional to the annealing time. Temperature gradient and crystalline quality of the SiC substrates influence their vaporization. The partial vapor pressure is crucial as it can interfere with further vaporization. A growth mechanism is proposed in terms of physical vapor transport. The monolayer character of vertically aligned graphene is verified by Raman and X-ray absorption spectroscopy. With the processed samples, d 0 magnetism ismore » realized and negative magnetoresistance is observed after Cu implantation. We also prove that multiple carriers exist in vertically aligned graphene.« less

Controllable growth of vertically aligned graphene on C-face SiC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yu; Chen, Lianlian; Hilliard, Donovan

We investigated how to control the growth of vertically aligned graphene on C-face SiC by varying the processing conditions. It is found that, the growth rate scales with the annealing temperature and the graphene height is proportional to the annealing time. Temperature gradient and crystalline quality of the SiC substrates influence their vaporization. The partial vapor pressure is crucial as it can interfere with further vaporization. A growth mechanism is proposed in terms of physical vapor transport. The monolayer character of vertically aligned graphene is verified by Raman and X-ray absorption spectroscopy. With the processed samples, d 0 magnetism ismore » realized and negative magnetoresistance is observed after Cu implantation. We also prove that multiple carriers exist in vertically aligned graphene.« less

Resonant spin tunneling in randomly oriented nanospheres of Mn 12 acetate

DOE PAGES

Lendínez, S.; Zarzuela, R.; Tejada, J.; ...

2015-01-06

We report measurements and theoretical analysis of resonant spin tunneling in randomly oriented nanospheres of a molecular magnet. Amorphous nanospheres of Mn₁₂ acetate have been fabricated and characterized by chemical, infrared, TEM, X-ray, and magnetic methods. Magnetic measurements have revealed sharp tunneling peaks in the field derivative of the magnetization that occur at the typical resonant field values for the Mn₁₂ acetate crystal in the field parallel to the easy axis.Theoretical analysis is provided that explains these observations. We argue that resonant spin tunneling in a molecular magnet can be established in a powder sample, without the need for amore » single crystal and without aligning the easy magnetization axes of the molecules. This is confirmed by re-analyzing the old data on a powdered sample of non-oriented micron-size crystals of Mn₁₂ acetate. In conclusion, our findings can greatly simplify the selection of candidates for quantum spin tunneling among newly synthesized molecular magnets.« less

Resonant spin tunneling in randomly oriented nanospheres of Mn 12 acetate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lendínez, S.; Zarzuela, R.; Tejada, J.

We report measurements and theoretical analysis of resonant spin tunneling in randomly oriented nanospheres of a molecular magnet. Amorphous nanospheres of Mn₁₂ acetate have been fabricated and characterized by chemical, infrared, TEM, X-ray, and magnetic methods. Magnetic measurements have revealed sharp tunneling peaks in the field derivative of the magnetization that occur at the typical resonant field values for the Mn₁₂ acetate crystal in the field parallel to the easy axis.Theoretical analysis is provided that explains these observations. We argue that resonant spin tunneling in a molecular magnet can be established in a powder sample, without the need for amore » single crystal and without aligning the easy magnetization axes of the molecules. This is confirmed by re-analyzing the old data on a powdered sample of non-oriented micron-size crystals of Mn₁₂ acetate. In conclusion, our findings can greatly simplify the selection of candidates for quantum spin tunneling among newly synthesized molecular magnets.« less

Compaction and sintering behaviors of a Nd-Fe-B permanent magnet alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chin, T.; Hung, M.; Tsai, D.

1988-11-15

Extensive x-ray diffraction (XRD) and magnetic measurements were done on Nd/sub 15/ Fe/sub 77/ B/sub 8/ magnet alloy green compacts after cold isostatic pressing following a pulsed 2-T field (CIP) and die-pressing under a static 1.2-T perpendicular field (DP1) or parallel field (DP2), and on those after sintering. An alignment factor F, through the calculation of the integrated diffraction intensity ratio of the XRD patterns, was adopted as the effectiveness of magnetic alignment. At the green compact state, DP1 has the best alignment while CIP the worst. However, after sintering the alignment factor was such that CIP>DPI>DP2, the same ordermore » as the magnetic properties. Three mechanisms were proposed for the evolution of the alignment factor at different stages of sintering, i.e., that both the appearance of a liquid phase at low temperatures and preferred grain growth at high temperatures enhance F, while recrystallization at intermediate temperatures deteriorates F. CIP results in less-defect green compact, hence less recrystallization, leading to better resultant alignment« less

Collimator with attachment mechanism and system

DOEpatents

Kross, Brian J [Yorktown, VA; McKisson, John [Hampton, VA; Stolin, Aleksandr [Morgantown, WV; Weisenberger, Andrew G [Yorktown, VA; Zorn, Carl [Yorktown, VA

2012-07-10

A self-aligning collimator for a radiation imaging device that is secured and aligned through the use of a plurality of small magnets. The collimator allows for the rapid exchange, removal, or addition of collimators for the radiation imaging device without the need for tools. The accompanying method discloses the use of magnets and accompanying magnetic fields to align and secure collimators in a radiation imaging assembly.

Multistage Magnetic Separator of Cells and Proteins

NASA Technical Reports Server (NTRS)

Barton, Ken; Ainsworth, Mark; Daily, Bruce; Dunn, Scott; Metz, Bill; Vellinger, John; Taylor, Brock; Meador, Bruce

2005-01-01

The multistage electromagnetic separator for purifying cells and magnetic particles (MAGSEP) is a laboratory apparatus for separating and/or purifying particles (especially biological cells) on the basis of their magnetic susceptibility and magnetophoretic mobility. Whereas a typical prior apparatus based on similar principles offers only a single stage of separation, the MAGSEP, as its full name indicates, offers multiple stages of separation; this makes it possible to refine a sample population of particles to a higher level of purity or to categorize multiple portions of the sample on the basis of magnetic susceptibility and/or magnetophoretic mobility. The MAGSEP includes a processing unit and an electronic unit coupled to a personal computer. The processing unit includes upper and lower plates, a plate-rotation system, an electromagnet, an electromagnet-translation system, and a capture-magnet assembly. The plates are bolted together through a roller bearing that allows the plates to rotate with respect to each other. An interface between the plates acts as a seal for separating fluids. A lower cuvette can be aligned with as many as 15 upper cuvette stations for fraction collection during processing. A two-phase stepping motor drives the rotation system, causing the upper plate to rotate for the collection of each fraction of the sample material. The electromagnet generates a magnetic field across the lower cuvette, while the translation system translates the electromagnet upward along the lower cuvette. The current supplied to the electromagnet, and thus the magnetic flux density at the pole face of the electromagnet, can be set at a programmed value between 0 and 1,400 gauss (0.14 T). The rate of translation can be programmed between 5 and 2,000 m/s so as to align all sample particles in the same position in the cuvette. The capture magnet can be a permanent magnet. It is mounted on an arm connected to a stepping motor. The stepping motor rotates the arm to position the capture magnet above the upper cuvette into which a fraction of the sample is collected. The electronic unit includes a power switch, power-supply circuitry that accepts 110-Vac input power, an RS-232 interface, and status lights. The personal computer runs the MAGSEP software and controls the operation of the MAGSEP through the RS-232 interface. The status of the power, the translating electromagnet, the capture magnet, and the rotation of the upper plate are indicated in a graphical user interface on the computer screen.

Cluster glass induced exchange biaslike effect in the perovskite cobaltites

NASA Astrophysics Data System (ADS)

Luo, Wanju; Wang, Fangwei

2007-04-01

Exchange biaslike phenomenon is observed in the Ba doped perovskite polycrystalline LaCoO3. The magnetic hysteresis loop shifts in both horizontal and vertical directions at 5K when the samples are cooled down to 5K in a magnetic field. The nature of this magnetic anisotropy is ascribed to the freezing properties of the local anisotropy in the cluster glass system. The magnetic shifts in horizontal and vertical directions can be derived directly under the principle that the spins of a cluster are frozen in random orientations and aligned to the field direction upon zero field and field cooling, respectively.

Anisotropic Mechanical Properties of Magnetically Aligned Fibrin Gels Measured by Magnetic Resonance Elastography

PubMed Central

Namani, Ravi; Wood, Matthew D.; Sakiyama-Elbert, Shelly E.; Bayly, Philip V.

2009-01-01

The anisotropic mechanical properties of magnetically aligned fibrin gels were measured by magnetic resonance elastography (MRE) and by a standard mechanical test: unconfined compression. Soft anisotropic biomaterials are notoriously difficult to characterize, especially in vivo. MRE is well-suited for efficient, non-invasive, and nondestructive assessment of shear modulus. Direction-dependent differences in shear modulus were found to be statistically significant for gels polymerized at magnetic fields of 11.7T and 4.7T compared to control gels. Mechanical anisotropy was greater in the gels polymerized at the higher magnetic field. These observations were consistent with results from unconfined compression tests. Analysis of confocal microscopy images of gels showed measurable alignment of fibrils in gels polymerized at 11.7T. This study provides direct, quantitative measurements of the anisotropy in mechanical properties that accompanies fibril alignment in fibrin gels. PMID:19656516

Successive Phase Transitions and Magnetic Fluctuation in a Double-Perovskite NdBaMn2O6 Single Crystal

NASA Astrophysics Data System (ADS)

Yamada, S.; Sagayama, H.; Sugimoto, K.; Arima, T.

2018-03-01

We have succeeded in growing large high-quality single crystals of double-perovskite NdBaMn2O6 with c-axis aligned. Curie-Weiss paramagnetism and metallic conduction are observed above 290 K (TMI ). The magnetic susceptibility suddenly drops at TMI accompanied by a metal-insulator transition. Pervious studies using polycrystalline samples proposed that this material undergoes a ferromagnetic phase transition near 300K, and that the magnetic anomaly at TMI should be ascribed to layered antiferromagnetic phase transition. However, single-crystalline samples do not show any anomaly that indicates the ferromagnetic phase transition above TMI . We assign the onset of magnetic anisotropy at 235 K as antiferromagnetic transition temperature TN . Though the magnetization just above TMI shows the ferromagnetic-like magnetic-field dependence, the magnetization does not saturate under 70kOe at 300K. The magnetization behavior implies ferromagnetic fluctuation in the paramagnetic phase. The ferromagnetic fluctuation are also observed just below TMI . Because a metamagnetic transition is observed at a higher magnetic field, the ferromagnetic fluctuation competes with antiferromagnetic fluctuation in this temperature range.

Positioning and aligning CNTs by external magnetic field to assist localised epoxy cure

NASA Astrophysics Data System (ADS)

Ariu, G.; Hamerton, I.; Ivanov, D.

2016-01-01

This work focuses on the generation of conductive networks through the localised alignment of nano fillers, such as multi-walled carbon nanotubes (MWCNTs). The feasibility of alignment and positioning of functionalised MWCNTs by external DC magnetic fields was investigated. The aim of this manipulation is to enhance resin curing through AC induction heating due to hysteresis losses from the nanotubes. Experimental analyses focused on in-depth assessment of the nanotube functionalisation, processing and characterisation of magnetic, rheological and cure kinetics properties of the MWCNT solution. The study has shown that an external magnetic field has great potential for positioning and alignment of CNTs. The study demonstrated potential for creating well-ordered architectures with an unprecedented level of control of network geometry. Magnetic characterisation indicated cobalt-plated nanotubes to be the most suitable candidate for magnetic alignment due to their high magnetic sensitivity. Epoxy/metal-plated CNT nanocomposite systems were validated by thermal analysis as induction heating mediums. The curing process could therefore be optimised by the use of dielectric resins. This study offers a first step towards the proof of concept of this technique as a novel repair technology.

Direct-write 3D printing of composite materials with magnetically aligned discontinuous reinforcement

NASA Astrophysics Data System (ADS)

Martin, Joshua J.; Caunter, Andrew; Dendulk, Amy; Goodrich, Scott; Pembroke, Ryan; Shores, Dan; Erb, Randall M.

2017-05-01

Three-dimensional (3D) printing of fiber reinforced composites represents an enabling technology that may bring toughness and specific strength to complex parts. Recently, direct-write 3D printing has been offered as a promising route to manufacturing fiber reinforced composites that show high specific strength. These approaches primarily rely on the use of shear-alignment during the extrusion process to align fibers along the printing direction. Shear alignment prevents fibers from being oriented along principle stress directions of the final designed part. This paper describes a new direct-write style 3D printing system that incorporates magnetic fields to actively control the orientation of reinforcing fibers during the printing of fiber reinforced composites. Such a manufacturing system is fraught with complications from the high shear dominated alignment experienced by the fibers during extrusion to the slow magnetic alignment dynamics of fibers in viscous media. Here we characterize these issues and suggest effective operating windows in which magnetic alignment is a viable approach to orienting reinforcing particles during direct-write 3D printing.

Magnetopause Erosion During the 17 March 2015 Magnetic Storm: Combined Field-Aligned Currents, Auroral Oval, and Magnetopause Observations

NASA Technical Reports Server (NTRS)

Le, G.; Luehr, H.; Anderson, B. J.; Strangeway, R. J.; Russell, C. T.; Singer, H.; Slavin, J. A.; Zhang, Y.; Huang, T.; Bromund, K.;

Mu2e Transport Solenoid Cold-Mass Alignment Issues

DOE PAGES

Lopes, M.; Ambrosio, G.; Badgley, K.; ...

2017-01-05

The Muon-to-electron conversion experiment (Mu2e) at Fermilab is designed to explore charged lepton flavor violation. It is composed of three large superconducting solenoids: the Production Solenoid (PS), the Transport Solenoid (TS) and the Detector Solenoid (DS). The TS is formed by two magnets: TS upstream (TSu) and downstream (TSd). Each has its own cryostat and power supply. Tolerance sensitivity studies of the position and angular alignment of each coil in this magnet system were performed in the past with the objective to demonstrate that the magnet design meets all the field requirements. Furthermore, the alignment of the cold-masses is criticalmore » to maximize the transmission of muons and to avoid possible backgrounds that would reduce the sensitivity of the experiment. Each TS magnet cold-mass can be individually aligned. Here, we discuss implications of the alignment of the TS cold-masses in terms of the displacement of the magnetic center. Consideration of the practical mechanical limits are also presented.« less

Magnet-assisted device-level alignment for the fabrication of membrane-sandwiched polydimethylsiloxane microfluidic devices

NASA Astrophysics Data System (ADS)

Lu, J.-C.; Liao, W.-H.; Tung, Y.-C.

2012-07-01

Polydimethylsiloxane (PDMS) microfluidic device is one of the most essential techniques that advance microfluidics research in recent decades. PDMS is broadly exploited to construct microfluidic devices due to its unique and advantageous material properties. To realize more functionalities, PDMS microfluidic devices with multi-layer architectures, especially those with sandwiched membranes, have been developed for various applications. However, existing alignment methods for device fabrication are mainly based on manual observations, which are time consuming, inaccurate and inconsistent. This paper develops a magnet-assisted alignment method to enhance device-level alignment accuracy and precision without complicated fabrication processes. In the developed alignment method, magnets are embedded into PDMS layers at the corners of the device. The paired magnets are arranged in symmetric positions at each PDMS layer, and the magnetic attraction force automatically pulls the PDMS layers into the aligned position during assembly. This paper also applies the method to construct a practical microfluidic device, a tunable chaotic micromixer. The results demonstrate the successful operation of the device without failure, which suggests the accurate alignment and reliable bonding achieved by the method. Consequently, the fabrication method developed in this paper is promising to be exploited to construct various membrane-sandwiched PDMS microfluidic devices with more integrated functionalities to advance microfluidics research.

Controlling orientational order in block copolymers using low-intensity magnetic fields

PubMed Central

Choo, Youngwoo; Kawabata, Kohsuke; Kaufman, Gilad; Feng, Xunda; Di, Xiaojun; Rokhlenko, Yekaterina; Mahajan, Lalit H.; Ndaya, Dennis; Kasi, Rajeswari M.

2017-01-01

The interaction of fields with condensed matter during phase transitions produces a rich variety of physical phenomena. Self-assembly of liquid crystalline block copolymers (LC BCPs) in the presence of a magnetic field, for example, can result in highly oriented microstructures due to the LC BCP’s anisotropic magnetic susceptibility. We show that such oriented mesophases can be produced using low-intensity fields (<0.5 T) that are accessible using permanent magnets, in contrast to the high fields (>4 T) and superconducting magnets required to date. Low-intensity field alignment is enabled by the addition of labile mesogens that coassemble with the system’s nematic and smectic A mesophases. The alignment saturation field strength and alignment kinetics have pronounced dependences on the free mesogen concentration. Highly aligned states with orientation distribution coefficients close to unity were obtained at fields as small as 0.2 T. This remarkable field response originates in an enhancement of alignment kinetics due to a reduction in viscosity, and increased magnetostatic energy due to increases in grain size, in the presence of labile mesogens. These developments provide routes for controlling structural order in BCPs, including the possibility of producing nontrivial textures and patterns of alignment by locally screening fields using magnetic nanoparticles. PMID:29078379

27 T ultra-high static magnetic field changes orientation and morphology of mitotic spindles in human cells

PubMed Central

Zhang, Lei; Hou, Yubin; Li, Zhiyuan; Ji, Xinmiao; Wang, Ze; Wang, Huizhen; Tian, Xiaofei; Yu, Fazhi; Yang, Zhenye; Pi, Li; Mitchison, Timothy J; Lu, Qingyou; Zhang, Xin

2017-01-01

Purified microtubules have been shown to align along the static magnetic field (SMF) in vitro because of their diamagnetic anisotropy. However, whether mitotic spindle in mammalian cells can be aligned by magnetic field has not been experimentally proved. In particular, the biological effects of SMF of above 20 T (Tesla) on mammalian cells have never been reported. Here we found that in both CNE-2Z and RPE1 human cells spindle orients in 27 T SMF. The direction of spindle alignment depended on the extent to which chromosomes were aligned to form a planar metaphase plate. Our results show that the magnetic torque acts on both microtubules and chromosomes, and the preferred direction of spindle alignment relative to the field depends more on chromosome alignment than microtubules. In addition, spindle morphology was also perturbed by 27 T SMF. This is the first reported study that investigated the mammalian cellular responses to ultra-high magnetic field of above 20 T. Our study not only found that ultra-high magnetic field can change the orientation and morphology of mitotic spindles, but also provided a tool to probe the role of spindle orientation and perturbation in developmental and cancer biology. DOI: http://dx.doi.org/10.7554/eLife.22911.001 PMID:28244368

Magnetic properties of carbon-coated, ferromagnetic nanoparticles produced by a carbon-arc method

NASA Astrophysics Data System (ADS)

Brunsman, E. M.; Sutton, R.; Bortz, E.; Kirkpatrick, S.; Midelfort, K.; Williams, J.; Smith, P.; McHenry, M. E.; Majetich, S. A.; Artman, J. O.; De Graef, M.; Staley, S. W.

1994-05-01

The Krätschmer-Huffman carbon-arc method of preparing fullerenes has been used to generate carbon-coated transition metal (TM) and TM-carbide nanocrystallites. The magnetic nanocrystallites were extracted from the soot with a magnetic gradient field technique. For TM=Co the majority of nanocrystals exist as nominally spherical particles, 0.5-5 nm in radius. Hysteretic and temperature-dependent magnetic response, in randomly and magnetically aligned powder samples frozen in epoxy, correspond to fine particle magnetism associated with monodomain TM particles. The magnetization exhibits a unique functional dependence on H/T, and hysteresis below a blocking temperature TB. Below TB, the temperature dependence of the coercivity can be expressed as Hc=Hc0[1-(T/TB)1/2], where Hc0 is the 0 K coercivity.

Direct spectroscopic evidence for competition between thermal molecular agitation and magnetic field in a tetrameric protein in aqueous solution

NASA Astrophysics Data System (ADS)

Calabrò, Emanuele; Magazù, Salvatore

2018-05-01

Samples of a typical tetrameric protein, the hemoglobin, at the concentration of 150 mg/ml in bidistilled water solution, were exposed to a uniform magnetic field at 200 mT at different temperatures of 15∘C, 40∘C and 65∘C. Fourier Transform Infrared Spectroscopy was used to analyze the response of the secondary structure of the protein to both stress agents, heating and static magnetic field. The most relevant result which was observed was the significant increasing in intensity of the Amide I band after exposure to the uniform magnetic field at the room temperature of 15∘C. This result can be explained assuming that protein's α-helices aligned along the direction of the applied magnetic field due to their large dipole moment, inducing the alignment of the entire protein. Increasing of temperature up to 40∘C and 65∘C induced a significant reduction of the increasing in intensity of the Amide I band. This effect may be easily explained assuming that Brownian motion of the protein in water solution caused by thermal molecular agitation increased with increasing of temperature, contrasting the effect of the torque of the magnetic field applied to the protein in water solution.

Tentative Identification of Interstellar Dust in the Magnetic Wall of the Heliosphere

NASA Astrophysics Data System (ADS)

Frisch, Priscilla C.

2005-10-01

Observations of the weak polarization of light from nearby stars, reported by Tinbergen, are consistent with polarization by small (radius <0.14 μm), interstellar dust grains entrained in the magnetic wall of the heliosphere. The region of maximum polarization is toward ecliptic coordinates (λ, β)~(295deg, 0deg), corresponding to (l, b) = (20°, -21°). The direction of maximum polarization is offset along the ecliptic longitude by ~35° from the nose of the heliosphere and extends to low ecliptic latitudes. An offset is also seen between the region with the best-aligned dust grains, λ~281deg-330deg, and the upwind direction of the undeflected large grains, λ~259deg, β~+8deg, which are observed by Ulysses and Galileo to be flowing into the heliosphere. In the aligned-grain region, the strength of polarization anticorrelates with ecliptic latitude, indicating that the magnetic wall is predominantly at negative ecliptic latitudes. An extension of the magnetic wall to β<0deg, formed by the interstellar magnetic field BIS draped over the heliosphere, is consistent with predictions by Linde (1998). A consistent interpretation follows if the maximum-polarization region traces the heliosphere magnetic wall in a direction approximately perpendicular to BIS, while the region of best-aligned dust samples the region where BIS drapes smoothly over the heliosphere with maximum compression. These data are consistent with BIS being tilted by 60° with respect to the ecliptic plane and parallel to the Galactic plane. Interstellar dust grains captured in the heliosheath may also introduce a weak, but important, large-scale contaminant for the cosmic microwave background signal with a symmetry consistent with the relative tilts of BIS and the ecliptic.

Electrostatic lower hybrid waves excited by electromagnetic whistler mode waves scattering from planar magnetic-field-aligned plasma density irregularities

NASA Technical Reports Server (NTRS)

Bell, T. F.; Ngo, H. D.

1990-01-01

This paper presents a theoretical model for electrostatic lower hybrid waves excited by electromagnetic whistler mode waves propagating in regions of the magnetosphere and the topside ionosphere, where small-scale magnetic-field-aligned plasma density irregularities are thought to exist. In this model, the electrostatic waves are excited by linear mode coupling as the incident electromagnetic whistler mode waves scatter from the magnetic-field-aligned plasma density irregularities. Results indicate that high-amplitude short-wavelength (5 to 100 m) quasi-electrostatic whistler mode waves can be excited when electromagnetic whistler mode waves scatter from small-scale planar magnetic-field-aligned plasma density irregularities in the topside ionosphere and magnetosphere.

Venus' nighttime horizontal plasma flow, 'magnetic congestion', and ionospheric hole production

NASA Technical Reports Server (NTRS)

Grebowsky, J. M.; Mayr, H. G.; Curtis, S. A.; Taylor, H. A., Jr.

1983-01-01

A simple rectilinear, two-dimensional MHD model is used to investigate the effects of field-aligned plasma loss and cooling on a dense plasma convecting across a weak magnetic field, in order to illumine the Venus nighttime phenomena of horizontal plasma flow, magnetic congestion and ionospheric hole production. By parameterizing field-aligned variations and explicitly solving for cross magnetic field variations, it is shown that the abrupt horizontal enhancements of the vertical magnetic field, as well as sudden decreases of the plasma density to very low values (which are characteristic of ionospheric holes), can be produced in the presence of field-aligned losses.

Composite Materials with Magnetically Aligned Carbon Nanoparticles and Methods of Preparation

NASA Technical Reports Server (NTRS)

Salem, David R. (Inventor); Hong, Haiping (Inventor); Peterson, G.P. (Bud) (Inventor)

2018-01-01

The present invention relates to magnetically aligned carbon nanoparticle composites and methods of preparing the same. The composites comprise carbon nanoparticles, host material, magnetically sensitive nanoparticles and surfactant. The composites may have enhanced mechanical, thermal, and/or electrical properties.

Fixture for aligning motor assembly

DOEpatents

Shervington, Roger M.; Vaghani, Vallabh V.; Vanek, Laurence D.; Christensen, Scott A.

2009-12-08

An alignment fixture includes a rotor fixture, a stator fixture and a sensor system which measures a rotational displacement therebetween. The fixture precisely measures rotation of a generator stator assembly away from a NULL position referenced by a unique reference spline on the rotor shaft. By providing an adjustable location of the stator assembly within the housing, the magnetic axes within each generator shall be aligned to a predetermined and controlled tolerance between the generator interface mounting pin and the reference spline on the rotor shaft. Once magnetically aligned, each generator is essentially a line replaceable unit which may be readily mounted to any input of a multi-generator gearbox assembly with the assurance that the magnetic alignment will be within a predetermined tolerance.

Orientational control of block copolymer microdomains by sub-tesla magnetic fields

NASA Astrophysics Data System (ADS)

Gopinadhan, Manesh; Choo, Youngwoo; Feng, Xunda; Kawabata, Kohsuke; di, Xiaojun; Osuji, Chinedum

Magnetic fields offer a versatile approach to controlling the orientation of block copolymer (BCP) microdomains during self-assembly. To date however, such control has required the imposition of large magnetic fields (>3T), necessitating the use of complex magnet systems - either superconducting or very large conventional resistive magnets. Here we demonstrate the ability to direct BCP self-assembly using considerably smaller fields (<1T) which are accessible using simple rare-earth permanent magnets. The low field alignment is enabled by the presence of small quantities of mesogenic species that are blended into, and co-assemble with the liquid crystalline (LC) mesophase of the side-chain LC BCP under study. In situ SAXS experiments reveal a pronounced dependence of the critical alignment field strength on the stoichiometry of the blend, and the ability to generate aligned microdomains with orientational distribution coefficients exceeding 0.95 at sub-1 T fields for appropriate stoichiometries. The alignment response overall can be rationalized in terms of increased mobility and grain size due to the presence of the mesogenic additive. We use a permanent magnet to fabricate films with aligned nanopores, and the utility of this approach to generate complex BCP microdomain patterns in thin films by local field screening are highlighted. NSF DMR-1410568 and DMR-0847534.

Spontaneous liquid crystal and ferromagnetic ordering of colloidal magnetic nanoplates

PubMed Central

Shuai, M.; Klittnick, A.; Shen, Y.; Smith, G. P.; Tuchband, M. R.; Zhu, C.; Petschek, R. G.; Mertelj, A.; Lisjak, D.; Čopič, M.; Maclennan, J. E.; Glaser, M. A.; Clark, N. A.

2016-01-01

Ferrofluids are familiar as colloidal suspensions of ferromagnetic nanoparticles in aqueous or organic solvents. The dispersed particles are randomly oriented but their moments become aligned if a magnetic field is applied, producing a variety of exotic and useful magnetomechanical effects. A longstanding interest and challenge has been to make such suspensions macroscopically ferromagnetic, that is having uniform magnetic alignment in the absence of a field. Here we report a fluid suspension of magnetic nanoplates that spontaneously aligns into an equilibrium nematic liquid crystal phase that is also macroscopically ferromagnetic. Its zero-field magnetization produces distinctive magnetic self-interaction effects, including liquid crystal textures of fluid block domains arranged in closed flux loops, and makes this phase highly sensitive, with it dramatically changing shape even in the Earth's magnetic field. PMID:26817823

Magnetically tunable control of light reflection in an unusual optical protein of squid

NASA Astrophysics Data System (ADS)

Iwasaka, M.; Tagawa, K.; Kikuchi, Y.

2017-05-01

In this study, we focused on the magnetically tunable changes in the reflectivity of the protein reflectin, which is generated by squid and used to control their body surface color for camouflage in seawater. A cellular organelle called an iridosome was separated from the skin of the dorsal part of a squid (cuttlefish; Sepia esculenta), and the light reflection dynamics of iridosomes containing reflectin were measured with and without exposure to a magnetic field of 500 mT. The magnetic field induced both steady and transient increases of reflection by the iridosomes, suggesting that a reversible conformational change occurred inside the iridosomes when the magnetic field was switched on and off. The intensity of light scattering perpendicular to the direction of the magnetic field increased when the magnetic field was applied. This kind of behavior (Type I) occurred in the majority (60%) of the measured samples. Another kind of reflection change (Type II) was a transient increase in light reflection. It is speculated that the wave-shaped structure of the lipid membrane connected to reflectin proteins changed to enhance the light reflection of reflectin by altering the diamagnetic orientation of the lipid layer in the bent part of the membrane under the applied magnetic field. Overall, our results suggest that the mesoscale lipid layers changed their alignment diamagnetically and the length between iridescent layers was modified by the magnetic field, even though no obvious change in alignment occurred at the microscale.

Composite Materials with Magnetically Aligned Carbon Nanoparticles Having Enhanced Electrical Properties and Methods of Preparation

NASA Technical Reports Server (NTRS)

Peterson, G.P. (Bud) (Inventor); Hong, Haiping (Inventor); Salem, David R. (Inventor)

2016-01-01

Magnetically aligned carbon nanoparticle composites have enhanced electrical properties. The composites comprise carbon nanoparticles, a host material, magnetically sensitive nanoparticles and a surfactant. In addition to enhanced electrical properties, the composites can have enhanced mechanical and thermal properties.

A torque balance measurement of anisotropy of the magnetic susceptibility in white matter.

PubMed

van Gelderen, Peter; Mandelkow, Hendrik; de Zwart, Jacco A; Duyn, Jeff H

2015-11-01

Recent MRI studies have suggested that the magnetic susceptibility of white matter (WM) in the human brain is anisotropic, providing a new contrast mechanism for the visualization of fiber bundles and allowing the extraction of cellular compartment-specific information. This study provides an independent confirmation and quantification of this anisotropy. Anisotropic magnetic susceptibility results in a torque exerted on WM when placed in a uniform magnetic field, tending to align the WM fibers with the field. To quantify the effect, excised spinal cord samples were placed in a torque balance inside the magnet of a 7 T MRI system and the magnetic torque was measured as function of orientation. All tissue samples (n = 5) showed orienting effects, confirming the presence of anisotropic susceptibility. Analysis of the magnetic torque resulted in reproducible values for the WM volume anisotropy that ranged from 13.6 to 19.2 ppb. The independently determined anisotropy values confirm estimates inferred from MRI experiments and validate the use of anisotropy to extract novel information about brain fiber structure and myelination. © 2014 Wiley Periodicals, Inc.

Alignment of SWNTs by protein-ligand interaction of functionalized magnetic particles under low magnetic fields.

PubMed

Park, Tae Jung; Park, Jong Pil; Lee, Seok Jae; Jung, Dae-Hwan; Ko, Young Koan; Jung, Hee-Tae; Lee, Sang Yup

2011-05-01

Carbon nanotubes (CNTs) have attracted considerable attention for applications using their superior mechanical, thermal and electrical properties. A simple method to controllably align single-walled CNTs (SWNTs) by using magnetic particles embedded with superparamagnetic iron oxide as an accelerator under the magnetic field was developed. The functionalization of SWNTs using biotin, interacted with streptavidin-coupled magnetic particles (micro-to-nano in diameter), and layer-by-layer assembly were performed for the alignment of a particular direction onto the clean silicon and the gold substrate at very low magnetic forces (0.02-0.89 T) at room temperature. The successful alignment of the SWNTs with multi-layer film was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). By changing the orientation and location of the substrates, crossed-networks of SWNTs-magnetic particle complex could easily be fabricated. We suggest that this approach, which consists of a combination of biological interaction among streptavidin-biotin and magnetite particles, should be useful for lateral orientation of individual SWNTs with controllable direction.

NMR of (133)Cs(+) in stretched hydrogels: One-dimensional, z- and NOESY spectra, and probing the ion's environment in erythrocytes.

PubMed

Kuchel, Philip W; Shishmarev, Dmitry; Puckeridge, Max; Levitt, Malcolm H; Naumann, Christoph; Chapman, Bogdan E

2015-12-01

(133)Cs nuclear magnetic resonance (NMR) spectroscopy was conducted on (133)Cs(+) in gelatin hydrogels that were either relaxed or stretched. Stretching generated a septet from this spin-7/2 nucleus, and its nuclear magnetic relaxation was studied via z-spectra, and two-dimensional nuclear Overhauser (NOESY) spectroscopy. Various spectral features were well simulated by using Mathematica and the software package SpinDynamica. Spectra of CsCl in suspensions of human erythrocytes embedded in gelatin gel showed separation of the resonances from the cation inside and outside the cells. Upon stretching the sample, the extracellular (133)Cs(+) signal split into a septet, while the intracellular peak was unchanged, revealing different alignment/ordering properties of the environment inside and around the cells. Differential interference contrast light microscopy confirmed that the cells were stretched when the overall sample was elongated. Analysis of the various spectral features of (133)Cs(+) reported here opens up applications of this K(+) congener for studies of cation-handling by metabolically-active cells and tissues in aligned states. Copyright © 2015 Elsevier Inc. All rights reserved.

Diagnosing the Role of Alfvén Waves in Magnetosphere-Ionosphere Coupling: Swarm Observations of Large Amplitude Nonstationary Magnetic Perturbations During an Interval of Northward IMF

NASA Astrophysics Data System (ADS)

Pakhotin, I. P.; Mann, I. R.; Lysak, R. L.; Knudsen, D. J.; Gjerloev, J. W.; Rae, I. J.; Forsyth, C.; Murphy, K. R.; Miles, D. M.; Ozeke, L. G.; Balasis, G.

2018-01-01

High-resolution multispacecraft Swarm data are used to examine magnetosphere-ionosphere coupling during a period of northward interplanetary magnetic field (IMF) on 31 May 2014. The observations reveal a prevalence of unexpectedly large amplitude (>100 nT) and time-varying magnetic perturbations during the polar passes, with especially large amplitude magnetic perturbations being associated with large-scale downward field-aligned currents. Differences between the magnetic field measurements sampled at 50 Hz from Swarm A and C, approximately 10 s apart along track, and the correspondence between the observed electric and magnetic fields at 16 samples per second, provide significant evidence for an important role for Alfvén waves in magnetosphere-ionosphere coupling even during northward IMF conditions. Spectral comparison between the wave E- and B-fields reveals a frequency-dependent phase difference and amplitude ratio consistent with interference between incident and reflected Alfvén waves. At low frequencies, the E/B ratio is in phase with an amplitude determined by the Pedersen conductance. At higher frequencies, the amplitude and phase change as a function of frequency in good agreement with an ionospheric Alfvén resonator model including Pedersen conductance effects. Indeed, within this Alfvén wave incidence, reflection, and interference paradigm, even quasi-static field-aligned currents might be reasonably interpreted as very low frequency (ω → 0) Alfvén waves. Overall, our results not only indicate the importance of Alfvén waves for magnetosphere-ionosphere coupling but also demonstrate a method for using Swarm data for the innovative experimental diagnosis of Pedersen conductance from low-Earth orbit satellite measurements.

What band rocks the MTB? (Invited)

NASA Astrophysics Data System (ADS)

Kind, J.; García-Rubio, I.; Gehring, A. U.

2013-12-01

Magnetotactic bacteria (MTB) are a polyphyletic group of bacteria that have been found in marine and lacustrine environments and soils [e.g. 1]. The hallmark of MTB is their intracellular formation of magnetosomes, single-domain ferrimagnetic particles that are aligned in chains. The chain configuration generates a strong magnetic dipole, which is used as magnetic compass to move the MTB into their favorable habit. The term band corresponds to a frequency window of microwaves in the gigahertz (GHz) range. Ferromagnetic resonance (FMR) spectroscopy uses the microwave absorption in a magnetic field to analyze the anisotropy properties and the domain state of magnetic materials. Specific microwave frequency causes absorption in a characteristic magnetic field range. For the investigation of MTB we use S-band (4.02 GHz), X-band (9.47 GHz), and Q-band (34.16 GHz). Experiments on cultured MTB and on sediment samples of Holocene age showed that absorption in X- and Q-band occurs when the sample is in a saturated or nearly saturated state [2, 3]. By contrast, absorption in the S-band appears in lower magnetic fields, where the sample is far from saturation. All FMR spectra show two distinct low-field features that can be assigned to magnetite particles in chains, aligned parallel and perpendicular to the external magnetic field. The detailed separation of the parallel and perpendicular components in the bulk samples is hampered, because of the random orientation of the chains in the sample. The comparison of S-, X-, and Q-band shows that the lower the frequency the better the separation of the components. In the S-band FMR spectroscopy, the separation of chains parallel to the external magnetic field is supported by the internal field of the sample. This field is caused by the remanence that contributes to the external magnetic field to fulfill the resonance condition [3,4]. Considering the different FMR responses, it can be postulated that a lower microwave frequency generally leads to a better resolution of the chain configuration. Finally, for the investigation of geological samples, the application of S-band can be a powerful tool to complement the commonly used X-band FMR spectroscopy, i.e. multiple band rock the MTB. [1] Blakemore R.P., 1975, Magnetotactic bacteria, Science, 190, 377-379 [2] Mastogiacomo G., Fischer H., Garcia-Rubio I., and Gehring A. U., 2010, Ferromagnetic resonance spectroscopic response of magnetic chains in a biological matrix, J. Magn. Magn. Matter, 322, 661-663, doi: 10.1016/j.jmmm.2009.10.035 [3] Gehring A. U., Kind. J., Charilaou M., Garcia-Rubio I., 2011, S-band ferromagnetic resonance spectroscopy and the detection of magnetofossils, J. R. Soc. Interface, 10(80), doi: 10.1098/rsif.2012.0790 [4] Kind J., van Raden U., Garcia-Rubio I., and Gehring A. U., 2012, Rock magnetic techniques complemented by ferromagnetic resonance spectroscopy to analyse a sediment record, Geophys. J. Int., 191, 51-61, doi: 10.1111/j.1365-246X.2012.05620.x

Magnetic Field Alignment of PS-P4VP: a Non-Liquid Crystalline Coil-Coil Block Copolymer

NASA Astrophysics Data System (ADS)

Rokhlenko, Yekaterina; Zhang, Kai; Larson, Steven; Gopalan, Padma; O'Hern, Corey; Osuji, Chinedum

2015-03-01

Magnetic fields provide the ability to control alignment of self-assembled soft materials such as block copolymers. Most prior work in this area has relied on the presence of ordered assemblies of anisotropic liquid crystalline species to ensure sufficient magnetic anisotropy to drive alignment. Recent experiments with poly(styrene-b-4-vinylpyridine), a non-liquid crystalline BCP, however, show field-induced alignment of a lamellar microstructure during cooling across the order-disorder transition. Using in situ x-ray scattering, we examine the roles of field strength and cooling rate on the alignment response of this low MW coil-coil BCP. Alignment is first observed at field strengths as low as 1 Tesla and improves markedly with both increasing field strength and slower cooling. We present a geometric argument to illustrate the origin of a finite, non-trivial magnetic susceptibility anisotropy for highly stretched surface-tethered polymer chains and corroborate this using coarse-grained molecular dynamics simulations. We rationalize the magnetic field response of the system in terms of the mobility afforded by the absence of entanglements, the intrinsic anisotropy resulting from the stretched polymer chains and sterically constrained conjugated rings, and the large grain size in these low molecular weight materials.

Spontaneous liquid crystal and ferromagnetic ordering of colloidal magnetic nanoplates

DOE PAGES

Shuai, M.; Klittnick, A.; Shen, Y.; ...

2016-01-28

Ferrofluids are familiar as colloidal suspensions of ferromagnetic nanoparticles in aqueous or organic solvents. The dispersed particles are randomly oriented but their moments become aligned if a magnetic field is applied, producing a variety of exotic and useful magnetomechanical effects. A longstanding interest and challenge has been to make such suspensions macroscopically ferromagnetic, that is having uniform magnetic alignment in the absence of a field. Here we report a fluid suspension of magnetic nanoplates that spontaneously aligns into an equilibrium nematic liquid crystal phase that is also macroscopically ferromagnetic. We find Its zero-field magnetization produces distinctive magnetic self-interaction effects, includingmore » liquid crystal textures of fluid block domains arranged in closed flux loops, and makes this phase highly sensitive, with it dramatically changing shape even in the Earth’s magnetic field.« less

Effect of grain alignment distribution on magnetic properties in (MM, Nd)-Fe-B sintered magnets

NASA Astrophysics Data System (ADS)

Yu, Xiaoqiang; Yue, Ming; Zhu, Minggang; Liu, Weiqiang; Li, Yuqing; Xi, Longlong; Li, Jiajie; Zhang, Jiuxing; Li, Wei

2018-03-01

H cj of (MM x Nd1-x )-Fe-B sintered magnets decreases distinctly with x increasing when misch metal (MM) content (x) ranges from 0.3 to 1. Practical application is taken into consideration so that the (MM0.6Nd0.4)-Fe-B components are chosen to analyze the changes in behavior of the magnetic properties. Both Magnet II and Magnet III belong to (MM0.6Nd0.4)-Fe-B sintered magnets, however, it should be noted that Magnet II is prepared by the single alloying method (SAM) and Magnet III is prepared by the double main phase alloy method (DMPAM). Core-shell structures of the magnets prepared by DMPAM can result in the higher H cj and lower knee-point coercivity (H k) compared with that by SAM. Furthermore, for Magnet II, the abnormal grain growth contributes to a better grain alignment and smaller distribution coefficient (σ) defined as the degree of grain alignment, which will enforce a higher tendency of the H cj decreasing and H k increasing. The expression of their normalized coercivity h(σ) is deduced by combining Gao’s starting field model with Kronmüller’s nucleation mechanism. Based on the overall h(σ) ~ σ curve, the best desirable h(σ) value is calculated when σ  =  0.09. Theoretically, for Magnet III, the resultant larger σ should be attributed to the more uniform grain alignment. In addition, the deviations of grain size distributions on the c-plane become more remarkable with more MM concentrates, which can be presented by SEM images. Meanwhile, by means of the pole figures, it is also verified that the grain alignment distribution becomes much more diverse with x increasing. Therefore, it can be predicted whether the grain alignment distribution is significant for H k and H cj of (MM x Nd1-x )-Fe-B sintered magnets (x  ≠  0.6) prepared by SAM/DMPAM or not.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruland, Robert

The Visible-Infrared SASE Amplifier (VISA) undulator consists of four 99cm long segments. Each undulator segment is set up on a pulsed-wire bench, to characterize the magnetic properties and to locate the magnetic axis of the FODO array. Subsequently, the location of the magnetic axis, as defined by the wire, is referenced to tooling balls on each magnet segment by means of a straightness interferometer. After installation in the vacuum chamber, the four magnet segments are aligned with respect to themselves and globally to the beam line reference laser. A specially designed alignment fixture is used to mount one straightness interferometermore » each in the horizontal and vertical plane of the beam. The goal of these procedures is to keep the combined rms trajectory error, due to magnetic and alignment errors, to 50{micro}m.« less

Magnetic Alignment of Pulsed Solenoids Using the Pulsed Wire Method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arbelaez, D.; Madur, A.; Lipton, T.M.

2011-04-01

A unique application of the pulsed-wire measurement method has been implemented for alignment of 2.5 T pulsed solenoid magnets. The magnetic axis measurement has been shown to have a resolution of better than 25 {micro}m. The accuracy of the technique allows for the identification of inherent field errors due to, for example, the winding layer transitions and the current leads. The alignment system is developed for the induction accelerator NDCX-II under construction at LBNL, an upgraded Neutralized Drift Compression experiment for research on warm dense matter and heavy ion fusion. Precise alignment is essential for NDCX-II, since the ion beammore » has a large energy spread associated with the rapid pulse compression such that misalignments lead to corkscrew deformation of the beam and reduced intensity at focus. The ability to align the magnetic axis of the pulsed solenoids to within 100 pm of the induction cell axis has been demonstrated.« less

Generating mixed morphology BaZrO3 artificial pinning centers for strong and isotropic pinning in BaZrO3-Y2O3 double-doped YBCO thin films

NASA Astrophysics Data System (ADS)

Chen, Shihong; Sebastian, Mary Ann; Gautam, Bibek; Wilt, Jamie; Chen, Yanbin; Sun, Lei; Xing, Zhongwen; Haugan, Timothy; Wu, Judy

2017-12-01

High concentration artificial pinning centers (APCs), such as BaZrO3 nanorods (BZO 1D APCs) aligned along the c-axis of the high temperature superconductor YBa2Cu3O7 (YBCO) can provide strong pinning of magnetic vortices and are desirable for applications in high magnetic fields. Unfortunately, in YBCO films with single-doping (SD) of BZO 1D APCs, a monotonic decreasing superconducting T c and critical current density J c(H) with BZO doping has been observed due to strain field overlap at high-concentration perfectly c-axis aligned BZO 1D APCs. In order to resolve this issue, double-doping (DD) of 2-6 vol% BZO 1D APCs and 3.0 vol% Y2O3 nanoparticles (Y2O3-NPs) in YBCO films has been explored to promote BZO-NR orientation misalignment from the c-axis. Remarkably, a monotonic increasing J c(H) with BZO 1D APCs concentration has been obtained in the BZO DD samples. Such a microstructure change is evidenced in the much smaller c-lattice parameter expansion of 0.103% in the DD samples as opposed to 0.511% in the SD counterparts and reduced c-axis alignment of the BZO 1D APCs as revealed in TEM. This yields a mixed 1D + 2D + 3D APC morphology and enhanced isotropic pinning with respect to the orientation of the H-field in the BZO DD samples.

Synthesis and orientation of barium hexaferrite ceramics by magnetic alignment

NASA Astrophysics Data System (ADS)

Autissier, Denis

1990-01-01

Particles of Ba 2Mn xZn 2- xFe 12O 22 with planar structure were prepared by chemical precipitation. They were processed by sleep casting in presence of a magnetic field. The degree of alignment was improved by a special sintering treatment. By this procedure an alignment as high as 99.9% is obtained.

CALUTRON

DOEpatents

Parkins, W.E.

1959-06-16

A calutron target arrangement is described which follows the shifting focus of the beam. Four magnets attached to the face of the receiver are arranged so that they are in magnetic equilibrium when the beam focus is properly aligned. Twisting of the beam causes heating of some of the magnets disturbing the equilibrium by permeability changes. The magnets restore equilibrium by moving the receiver face to proper alignment. (T.R.H.)

Compression Molding and Novel Sintering Treatments for Alnico Type-8 Permanent Magnets in Near-Final Shape with Preferred Orientation

NASA Astrophysics Data System (ADS)

Kassen, Aaron G.; White, Emma M. H.; Tang, Wei; Hu, Liangfa; Palasyuk, Andriy; Zhou, Lin; Anderson, Iver E.

2017-09-01

Economic uncertainty in the rare earth (RE) permanent magnet marketplace, as well as in an expanding electric drive vehicle market that favors permanent magnet alternating current synchronous drive motors, motivated renewed research in RE-free permanent magnets like "alnico," an Al-Ni-Co-Fe alloy. Thus, high-pressure, gas-atomized isotropic type-8H pre-alloyed alnico powder was compression molded with a clean burn- out binder to near-final shape and sintered to density >99% of cast alnico 8 (full density of 7.3 g/cm3). To produce aligned sintered alnico magnets for improved energy product and magnetic remanence, uniaxial stress was attempted to promote controlled grain growth, avoiding directional solidification that provides alignment in alnico 9. Successful development of solid-state powder processing may enable anisotropically aligned alnico magnets with enhanced energy density to be mass-produced.

Field gradients can control the alignment of nanorods.

PubMed

Ooi, Chinchun; Yellen, Benjamin B

2008-08-19

This work is motivated by the unexpected experimental observation that field gradients can control the alignment of nonmagnetic nanorods immersed inside magnetic fluids. In the presence of local field gradients, nanorods were observed to align perpendicular to the external field at low field strengths, but parallel to the external field at high field strengths. The switching behavior results from the competition between a preference to align with the external field (orientational potential energy) and preference to move into regions of minimum magnetic field (positional potential energy). A theoretical model is developed to explain this experimental behavior by investigating the statistics of nanorod alignment as a function of both the external uniform magnetic field strength and the local magnetic field variation above a periodic array of micromagnets. Computational phase diagrams are developed which indicate that the relative population of nanorods in parallel and perpendicular states can be adjusted through several control parameters. However, an energy barrier to rotation was discovered to influence the rate kinetics and restrict the utility of this assembly technique to nanorods which are slightly shorter than the micromagnet length. Experimental results concerning the orientation of nanorods inside magnetic fluid are also presented and shown to be in strong agreement with the theoretical work.

MSP-Tool: a VBA-based software tool for the analysis of multispecimen paleointensity data

NASA Astrophysics Data System (ADS)

Monster, Marilyn; de Groot, Lennart; Dekkers, Mark

2015-12-01

The multispecimen protocol (MSP) is a method to estimate the Earth's magnetic field's past strength from volcanic rocks or archeological materials. By reducing the amount of heating steps and aligning the specimens parallel to the applied field, thermochemical alteration and multi-domain effects are minimized. We present a new software tool, written for Microsoft Excel 2010 in Visual Basic for Applications (VBA), that evaluates paleointensity data acquired using this protocol. In addition to the three ratios (standard, fraction-corrected and domain-state-corrected) calculated following Dekkers and Böhnel (2006) and Fabian and Leonhardt (2010) and a number of other parameters proposed by Fabian and Leonhardt (2010), it also provides several reliability criteria. These include an alteration criterion, whether or not the linear regression intersects the y axis within the theoretically prescribed range, and two directional checks. Overprints and misalignment are detected by isolating the remaining natural remanent magnetization (NRM) and the partial thermoremanent magnetization (pTRM) gained and comparing their declinations and inclinations. The NRM remaining and pTRM gained are then used to calculate alignment-corrected multispecimen plots. Data are analyzed using bootstrap statistics. The program was tested on lava samples that were given a full TRM and that acquired their pTRMs at angles of 0, 15, 30 and 90° with respect to their NRMs. MSP-Tool adequately detected and largely corrected these artificial alignment errors.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kassen, Aaron G.; White, Emma M. H.; Tang, Wei

We present economic uncertainty in the rare earth (RE) permanent magnet marketplace, as well as in an expanding electric drive vehicle market that favors permanent magnet alternating current synchronous drive motors, motivated renewed research in RE-free permanent magnets like “alnico,” an Al-Ni-Co-Fe alloy. Thus, high-pressure, gas-atomized isotropic type-8H pre-alloyed alnico powder was compression molded with a clean burn-out binder to near-final shape and sintered to density >99% of cast alnico 8 (full density of 7.3 g/cm 3). To produce aligned sintered alnico magnets for improved energy product and magnetic remanence, uniaxial stress was attempted to promote controlled grain growth, avoidingmore » directional solidification that provides alignment in alnico 9. Lastly, successful development of solid-state powder processing may enable anisotropically aligned alnico magnets with enhanced energy density to be mass-produced.« less

90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer spin valve component investigated by polarized neutron reflectometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Callori, S. J., E-mail: sara.callori@ansto.gov.au; Bertinshaw, J.; Bragg Institute, Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234

2014-07-21

We have observed 90° magnetic coupling in a NiFe/FeMn/biased NiFe multilayer system using polarized neutron reflectometry. Magnetometry results show magnetic switching for both the biased and free NiFe layers, the latter of which reverses at low applied fields. As these measurements are only capable of providing information about the total magnetization within a sample, polarized neutron reflectometry was used to investigate the reversal behavior of the NiFe layers individually. Both the non-spin-flip and spin-flip neutron reflectometry signals were tracked around the free NiFe layer hysteresis loop and were used to detail the evolution of the magnetization during reversal. At lowmore » magnetic fields near the free NiFe coercive field, a large spin-flip signal was observed, indicating magnetization aligned perpendicular to both the applied field and pinned layer.« less

Detection of bacteria in suspension using a superconducting Quantum interference device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grossman, H.L.; Myers, W.R.; Vreeland, V.J.

2003-06-09

We demonstrate a technique for detecting magnetically-labeled Listeria monocytogenes and for measuring the binding rate between antibody-linked magnetic particles and bacteria. This assay, which is both sensitive and straightforward to perform, can quantify specific bacteria in a sample without the need to immobilize the bacteria or wash away unbound magnetic particles. In the measurement, we add 50 nm diameter superparamagnetic particles, coated with antibodies, to a liquid sample containing L. monocytogenes. We apply a pulsed magnetic field to align the magnetic dipole moments and use a high transition temperature Superconducting Quantum Interference Device (SQUID), an extremely sensitive detector of magneticmore » flux, to measure the magnetic relaxation signal when the field is turned off. Unbound particles randomize direction by Brownian rotation too quickly to be detected. In contrast, particles bound to L. monocytogenes are effectively immobilized and relax in about 1 s by rotation of the internal dipole moment. This Neel relaxation process is detected by the SQUID. The measurements indicate a detection limit of (5.6 {+-} 1.1) x 10{sup 6} L. monocytogenes for a 20 {micro}L sample volume. If the sample volume were reduced to 1 nL, we estimate that the detection limit could be improved to 230 {+-} 40 L. monocytogenes cells. Time-resolved measurements yield the binding rate between the particles and bacteria.« less

Structural, microstructural and magnetic evolution in cryo milled carbon doped MnAl.

PubMed

Fang, Hailiang; Cedervall, Johan; Hedlund, Daniel; Shafeie, Samrand; Deledda, Stefano; Olsson, Fredrik; von Fieandt, Linus; Bednarcik, Jozef; Svedlindh, Peter; Gunnarsson, Klas; Sahlberg, Martin

2018-02-06

The low cost, rare earth free τ-phase of MnAl has high potential to partially replace bonded Nd 2 Fe 14 B rare earth permanent magnets. However, the τ-phase is metastable and it is experimentally difficult to obtain powders suitable for the permanent magnet alignment process, which requires the fine powders to have an appropriate microstructure and high τ-phase purity. In this work, a new method to make high purity τ-phase fine powders is presented. A high purity τ-phase Mn 0.55 Al 0.45 C 0.02 alloy was synthesized by the drop synthesis method. The drop synthesized material was subjected to cryo milling and  followed by a flash heating process. The crystal structure and microstructure of the drop synthesized, cryo milled and flash heated samples were studied by X-ray in situ powder diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy and electron backscatter diffraction. Magnetic properties and magnetic structure of the drop synthesized, cryo milled, flash heated  samples were characterized by magnetometry and neutron powder diffraction, respectively. The results reveal that the 2 and 4 hours cryo milled and flash heated samples both exhibit high τ-phase purity and micron-sized round particle shapes. Moreover, the flash heated samples display high saturation magnetization as well as increased coercivity.

SYNTHETIC OBSERVATIONS OF MAGNETIC FIELDS IN PROTOSTELLAR CORES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Joyce W. Y.; Hull, Charles L. H.; Offner, Stella S. R., E-mail: chat.hull@cfa.harvard.edu, E-mail: jwyl1g12@soton.ac.uk

The role of magnetic fields in the early stages of star formation is not well constrained. In order to discriminate between different star formation models, we analyze 3D magnetohydrodynamic simulations of low-mass cores and explore the correlation between magnetic field orientation and outflow orientation over time. We produce synthetic observations of dust polarization at resolutions comparable to millimeter-wave dust polarization maps observed by the Combined Array for Research in Millimeter-wave Astronomy and compare these with 2D visualizations of projected magnetic field and column density. Cumulative distribution functions of the projected angle between the magnetic field and outflow show different degreesmore » of alignment in simulations with differing mass-to-flux ratios. The distribution function for the less magnetized core agrees with observations finding random alignment between outflow and field orientations, while the more magnetized core exhibits stronger alignment. We find that fractional polarization increases when the system is viewed such that the magnetic field is close to the plane of the sky, and the values of fractional polarization are consistent with observational measurements. The simulation outflow, which reflects the underlying angular momentum of the accreted gas, changes direction significantly over over the first ∼0.1 Myr of evolution. This movement could lead to the observed random alignment between outflows and the magnetic fields in protostellar cores.« less

Fast 3-T MR-guided transrectal prostate biopsy using an in-room tablet device for needle guide alignment: a feasibility study.

PubMed

Overduin, Christiaan G; Heidkamp, Jan; Rothgang, Eva; Barentsz, Jelle O; de Lange, Frank; Fütterer, Jurgen J

2018-05-22

To assess the feasibility of adding a tablet device inside the scanner room to assist needle-guide alignment during magnetic resonance (MR)-guided transrectal prostate biopsy. Twenty patients with one cancer-suspicious region (CSR) with PI-RADS score ≥ 4 on diagnostic multiparametric MRI were prospectively enrolled. Two orthogonal scan planes of an MR fluoroscopy sequence (~3 images/s) were aligned to the CSR and needle-guide pivoting point. Targeting was achieved by manipulating the needle-guide under MR fluoroscopy feedback on the in-room tablet device. Technical feasibility and targeting success were assessed. Complications and biopsy procedure times were also recorded. Needle-guide alignment with the in-room tablet device was technically successful in all patients and allowed sampling after a single alignment step in 19/20 (95%) CSRs (median size 14 mm, range: 4-45). Biopsy cores contained cancer in 18/20 patients. There were no per-procedural or post-biopsy complications. Using the tablet device, the mean time to first biopsy was 5.8 ± 1.0 min and the mean total procedure time was 23.7 ± 4.1 min. Use of an in-room tablet device to assist needle-guide alignment was feasible and safe during MR-guided transrectal prostate biopsy. Initial experience indicates potential for procedure time reduction. • Performing MR-guided prostate biopsy using an in-room tablet device is feasible. • CSRs could be sampled after a single alignment step in 19/20 patients. • The mean procedure time for biopsy with the tablet device was 23.7 min.

First evidence of anisotropy of GPS phase slips caused by the mid-latitude field-aligned ionospheric irregularities

NASA Astrophysics Data System (ADS)

Afraimovich, E. L.; Ishin, A. B.; Tinin, M. V.; Yasyukevich, Yu. V.; Jin, S. G.

2011-05-01

The mid-latitude field-aligned irregularity (FAI) along the magnetic field line is a common phenomenon in the ionosphere. However, few data reveal the field-aligned ionospheric irregularities. They are insufficient to identify FAIs effects so far, particularly effect on global positioning system (GPS) signals. In this paper, the mid-latitude FAIs by line-of-sight angular scanning relative to the local magnetic field vector are investigated using the denser GPS network observations in Japan. It has been the first found that total GPS L2 phase slips over Japan, during the recovery phase of the 12 Feb 2000 geomagnetic storm were caused by GPS signal scattering on FAIs both for the lines-of-sight aligned to the magnetic field line (the field of aligned scattering, FALS) and across the magnetic field line (the field of across scattering, FACS). The FALS results are also in a good agreement with the data of the magnetic field orientation control of GPS occultation observations of equatorial scintillation during thorough low earth orbit (LEO) satellites measurements, e.g. Challenging Minisatellite Payload (CHAMP) and Satellite de Aplicaciones Cientificas-C (SAC-C). The role of large-angle scattering almost along the normal to the magnetic field line in GPS scintillation is determined by attenuation of the irregularity anisotropy factor as compared with the other factors.

Torsional stress impedance and magneto-impedance in (Co0.95Fe0.05)72.5 Si12.5B15 amorphous wire with helical induced anisotropy

NASA Astrophysics Data System (ADS)

Blanco, J. M.; Zhukov, A. P.; González, J.

1999-12-01

The magneto-impedance effect icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/ZH = [Z(H)-Z(Hmax)]/Z(Hmax) has been measured in (Fe0.95Co0.05)72.5B15Si12.5 wire under torsion stress, icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/> (torsion angle per unit length) with axial magnetic field (H) as parameter. Without stress (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)H(H) dependence has a non-monotonous shape with first an increase of total impedance Z and then a decrease, i.e. shows a maximum at certain axial magnetic field Hm. It was found that the torsion stress dependence of electrical impedance (torsion impedance), (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> = [Z(icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/>)-Z(icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/>max)]/Z(icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/>max), has asymmetric character with a clear maximum at torsion angle, icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/> around 7icons/Journals/Common/pi" ALT="pi" ALIGN="TOP"/> rad m-1 in as-cast wire, while (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> reaches a maximum around 170%. Thermal treatments under torsion stress (without and with a previous annealing stage) develop a helical anisotropy on the amorphous wire, which drastically modifies the (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> response. Such treatments were carried out by using current annealing which resulted in a drastic increase of the maximum (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> up to 225%, and a change of torsion dependence of icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z with a tendency to a finally symmetric dependence of (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/>(icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/>). The maximum (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="MIDDLE"/> ratio, (icons/Journals/Common/Delta" ALT="Delta" ALIGN="TOP"/> Z/Z)icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/> m, was obtained under torsion stress of icons/Journals/Common/xi" ALT="xi" ALIGN="TOP"/> = 20icons/Journals/Common/pi" ALT="pi" ALIGN="TOP"/> rad m-1 (in a torsion annealed sample) and = 11 rad m-1 (with pre-annealing and torsion annealing). Observed dependences were explained taking into account the frozen-in magneto-elastic anisotropy owing to the internal stress distribution during the fabrication process, the helical anisotropies induced by the torsion strain and that developed by thermal treatment under torsion stress (torsion annealing). The differences in the shape and intensity of the maximum ( Z/Z) m between the torsion annealed and pre-annealed and torsion annealed samples should be ascribed to the visco-elastic character of the helical anisotropy induced by torsion stress.

Stability estimate for the aligned magnetic field in a periodic quantum waveguide from Dirichlet-to-Neumann map

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mejri, Youssef, E-mail: josef-bizert@hotmail.fr; Dép. des Mathématiques, Faculté des Sciences de Bizerte, 7021 Jarzouna; Laboratoire de Modélisation Mathématique et Numérique dans les Sciences de l’Ingénieur, ENIT BP 37, Le Belvedere, 1002 Tunis

In this article, we study the boundary inverse problem of determining the aligned magnetic field appearing in the magnetic Schrödinger equation in a periodic quantum cylindrical waveguide, by knowledge of the Dirichlet-to-Neumann map. We prove a Hölder stability estimate with respect to the Dirichlet-to-Neumann map, by means of the geometrical optics solutions of the magnetic Schrödinger equation.

Effect of angular momentum alignment and strong magnetic fields on the formation of protostellar discs

NASA Astrophysics Data System (ADS)

Gray, William J.; McKee, Christopher F.; Klein, Richard I.

2018-01-01

Star-forming molecular clouds are observed to be both highly magnetized and turbulent. Consequently, the formation of protostellar discs is largely dependent on the complex interaction between gravity, magnetic fields, and turbulence. Studies of non-turbulent protostellar disc formation with realistic magnetic fields have shown that these fields are efficient in removing angular momentum from the forming discs, preventing their formation. However, once turbulence is included, discs can form in even highly magnetized clouds, although the precise mechanism remains uncertain. Here, we present several high-resolution simulations of turbulent, realistically magnetized, high-mass molecular clouds with both aligned and random turbulence to study the role that turbulence, misalignment, and magnetic fields have on the formation of protostellar discs. We find that when the turbulence is artificially aligned so that the angular momentum is parallel to the initial uniform field, no rotationally supported discs are formed, regardless of the initial turbulent energy. We conclude that turbulence and the associated misalignment between the angular momentum and the magnetic field are crucial in the formation of protostellar discs in the presence of realistic magnetic fields.

BATMAN--an R package for the automated quantification of metabolites from nuclear magnetic resonance spectra using a Bayesian model.

PubMed

Hao, Jie; Astle, William; De Iorio, Maria; Ebbels, Timothy M D

2012-08-01

Nuclear Magnetic Resonance (NMR) spectra are widely used in metabolomics to obtain metabolite profiles in complex biological mixtures. Common methods used to assign and estimate concentrations of metabolites involve either an expert manual peak fitting or extra pre-processing steps, such as peak alignment and binning. Peak fitting is very time consuming and is subject to human error. Conversely, alignment and binning can introduce artefacts and limit immediate biological interpretation of models. We present the Bayesian automated metabolite analyser for NMR spectra (BATMAN), an R package that deconvolutes peaks from one-dimensional NMR spectra, automatically assigns them to specific metabolites from a target list and obtains concentration estimates. The Bayesian model incorporates information on characteristic peak patterns of metabolites and is able to account for shifts in the position of peaks commonly seen in NMR spectra of biological samples. It applies a Markov chain Monte Carlo algorithm to sample from a joint posterior distribution of the model parameters and obtains concentration estimates with reduced error compared with conventional numerical integration and comparable to manual deconvolution by experienced spectroscopists. http://www1.imperial.ac.uk/medicine/people/t.ebbels/ t.ebbels@imperial.ac.uk.

Cholesterol-diethylenetriaminepentaacetate complexed with thulium ions integrated into bicelles to increase their magnetic alignability.

PubMed

Liebi, Marianne; Kuster, Simon; Kohlbrecher, Joachim; Ishikawa, Takashi; Fischer, Peter; Walde, Peter; Windhab, Erich J

2013-11-27

Lanthanides have been used for several decades to increase the magnetic alignability of bicelles. DMPE-DTPA (1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylenetriaminepentaacetate) is commonly applied to anchor the lanthanides into the bicelles. However, because DMPE-DTPA has the tendency to accumulate at the highly curved edge region of the bicelles and if located there does not contribute to the magnetic orientation energy, we have tested cholesterol-DTPA complexed with thulium ions (Tm(3+)) as an alternative chelator to increase the magnetic alignability. Differential scanning calorimetric (DSC) measurements indicate the successful integration of cholesterol-DTPA into a DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) bilayer. Cryo transmission electron microscopy and small-angle neutron scattering (SANS) measurements show that the disklike structure, that is, bicelles, is maintained if cholesterol-DTPA·Tm(3+) is integrated into a mixture of DMPC, cholesterol, and DMPE-DTPA·Tm(3+). The size of the bicelles is increased compared to the size of the bicelles obtained from mixtures without cholesterol-DTPA·Tm(3+). Magnetic-field-induced birefringence and SANS measurements in a magnetic field show that with addition of cholesterol-DTPA·Tm(3+) the magnetic alignability of these bicelles is significantly increased compared to bicelles composed of DMPC, cholesterol, and DMPE-DTPA·Tm(3+) only.

Studies of isolated and interacting ferromagnetic gapped nanorings

NASA Astrophysics Data System (ADS)

Li, Jie; Zhang, Sheng; Bartell, Jason; Grigas, Chris; Nisoli, Cristiano; Lammert, Paul; Crespi, Vincent; Schiffer, Peter

2011-03-01

We have used micromagnetic simulation and magnetic force microscopy (MFM) to study isolated and interacting permalloy nanorings that are lithographically fabricated with gaps that prevent a rotationally symmetric magnetic state. The gapped nanorings have inner and outer radii of 200 and 300 nm respectively, and the gap has a subtended width of ~ 20 degrees. The nanorings generate a strong magnetic field only in the gap, and thus the magnetization states of gapped nanorings are much more accessible to MFM imaging than complete rings. We have investigated the properties of these gapped nanorings, including the anisotropy in their coercive field and the relative alignment of the magnetic polarization in coupled pairs. We acknowledge the financial support from DOE and Army Research Office.We are grateful to Professor Chris Leighton and Mike Erickson for assistance with sample preparation.

Understanding the multiferroicity in TmMn2O5 by a magnetically induced ferrielectric model

PubMed Central

Yang, L.; Li, X.; Liu, M. F.; Li, P. L.; Yan, Z. B.; Zeng, M.; Qin, M. H.; Gao, X. S.; Liu, J.-M.

2016-01-01

The magnetically induced electric polarization behaviors in multiferroic TmMn2O5 in response to varying temperature and magnetic field are carefully investigated by means of a series of characterizations including the high precision pyroelectric current technique. Here polycrystalline rather than single crystal samples are used for avoiding the strong electrically self-polarized effect in single crystals, and various parallel experiments on excluding the thermally excited current contributions are performed. The temperature-dependent electric polarization flop as a major character is identified for different measuring paths. The magneto-current measurements indicate that the electric polarization in the low temperature magnetic phase region has different origin from that in the high temperature magnetic phase. It is suggested that the electric polarization does have multiple components which align along different orientations, including the Mn3+-Mn4+-Mn3+ exchange striction induced polarization PMM, the Tm3+-Mn4+-Tm3+ exchange striction induced polarization PTM, and the low temperature polarization PLT probably associated with the Tm3+ commensurate phase. The observed electric polarization flop can be reasonably explained by the ferrielectric model proposed earlier for DyMn2O5, where PMM and PTM are the two antiparallel components both along the b-axis and PLT may align along the a-axis. Finally, several issues on the unusual temperature dependence of ferroelectric polarizations are discussed. PMID:27713482

Compression Molding and Novel Sintering Treatments for Alnico Type-8 Permanent Magnets in Near-Final Shape with Preferred Orientation

DOE PAGES

Kassen, Aaron G.; White, Emma M. H.; Tang, Wei; ...

2017-07-14

We present economic uncertainty in the rare earth (RE) permanent magnet marketplace, as well as in an expanding electric drive vehicle market that favors permanent magnet alternating current synchronous drive motors, motivated renewed research in RE-free permanent magnets like “alnico,” an Al-Ni-Co-Fe alloy. Thus, high-pressure, gas-atomized isotropic type-8H pre-alloyed alnico powder was compression molded with a clean burn-out binder to near-final shape and sintered to density >99% of cast alnico 8 (full density of 7.3 g/cm 3). To produce aligned sintered alnico magnets for improved energy product and magnetic remanence, uniaxial stress was attempted to promote controlled grain growth, avoidingmore » directional solidification that provides alignment in alnico 9. Lastly, successful development of solid-state powder processing may enable anisotropically aligned alnico magnets with enhanced energy density to be mass-produced.« less

Ultrafast giant magnetic cooling effect in ferromagnetic Co/Pt multilayers.

PubMed

Shim, Je-Ho; Ali Syed, Akbar; Kim, Chul-Hoon; Lee, Kyung Min; Park, Seung-Young; Jeong, Jong-Ryul; Kim, Dong-Hyun; Eon Kim, Dong

2017-10-06

The magnetic cooling effect originates from a large change in entropy by the forced magnetization alignment, which has long been considered to be utilized as an alternative environment-friendly cooling technology compared to conventional refrigeration. However, an ultimate timescale of the magnetic cooling effect has never been studied yet. Here, we report that a giant magnetic cooling (up to 200 K) phenomenon exists in the Co/Pt nano-multilayers on a femtosecond timescale during the photoinduced demagnetization and remagnetization, where the disordered spins are more rapidly aligned, and thus magnetically cooled, by the external magnetic field via the lattice-spin interaction in the multilayer system. These findings were obtained by the extensive analysis of time-resolved magneto-optical responses with systematic variation of laser fluence as well as external field strength and direction. Ultrafast giant magnetic cooling observed in the present study can enable a new avenue to the realization of ultrafast magnetic devices.The forced alignment of magnetic moments leads to a large change in entropy, which can be used to reduce the temperature of a material. Here, the authors show that this magnetic cooling effect occurs on a femtosecond time scale in cobalt-platinum nano-multilayers.

Magnetic tearing of plasma discharges due to nonuniform resistivity

NASA Technical Reports Server (NTRS)

Hassam, A. B.

1988-01-01

The rearrangement of current in a plasma discharge in response to resistivity nonuniformities within a magnetic surface is studied. It is shown that macroscopic magnetic islands develop about those surfaces where the nonuniformity is aligned with the magnetic field. If the nonuniformity and the field are not aligned anywhere, there is no current rearrangement; instead, relatively large plasma flows are set up. Such resistivity inhomogeneities can obtain in solar coronal loops and, in some circumstances, in tokamak discharges.

Detection of immunomagnetically captured 4',6-diamidino-2-phenyl-indole (DAPI)-labeled Escherichia coli 0157:H7 by fluorescent microscopic imaging

NASA Astrophysics Data System (ADS)

Tu, Shu-I.; Uknalis, Joseph; Patterson, Deidre; Gehring, Andrew G.

1999-01-01

Live cells of E. coliO157:H7 were captured by goat anti-E. coliO157 serum coated on the surface of polystyrene based immunomagnetic beads (IMB). The captured bacteria were labeled by 4',6-diamidino-2-phenylindole (DAPI), a nucleic acid stain, for observation by epifluorescent microscopy. The beads with captured bacteria were then concentrated by magnetic separators. The efficiency of this magnetic concentration step was less than that of using high speed centrifugation. The antibody-captured and IMB-immobilized bacteria were then applied on HF-treated, bovine serum albumin (BSA)-coated microscope slides mounted on an automated stage, and magnetically aligned before fluorescence distribution was measured by a cooled CCD attached to an inverted microscope. Since the beads were concentrated and linearly aligned along the edge of the magnetic field, image capture along the edge for a few field widths was sufficient to account for most of captured bacteria. We applied this approach to determine the bacterial counts in spiked beef hamburger patties. The results showed that after a 6-hour enrichment, sufficient number of the bacteria could be detected from the samples spiked with 1 CFU of E. coliO157:H7 per gram of the hamburger.

Development of Smart Optical Gels with Highly Magnetically Responsive Bicelles.

PubMed

Isabettini, Stéphane; Stucki, Sandro; Massabni, Sarah; Baumgartner, Mirjam E; Reckey, Pernille Q; Kohlbrecher, Joachim; Ishikawa, Takashi; Windhab, Erich J; Fischer, Peter; Kuster, Simon

2018-03-14

Hydrogels delivering on-demand tailorable optical properties are formidable smart materials with promising perspectives in numerous fields, including the development of modern sensors and switches, the essential quality criterion being a defined and readily measured response to environmental changes. Lanthanide ion (Ln 3+ )-chelating bicelles are interesting building blocks for such materials because of their magnetic responsive nature. Imbedding these phospholipid-based nanodiscs in a magnetically aligned state in gelatin permits an orientation-dependent retardation of polarized light. The resulting tailorable anisotropy gives the gel a well-defined optical signature observed as a birefringence signal. These phenomena were only reported for a single bicelle-gelatin pair and required high magnetic field strengths of 8 T. Herein, we demonstrate the versatility and enhance the viability of this technology with a new generation of aminocholesterol (Chol-NH 2 )-doped bicelles imbedded in two different types of gelatin. The highly magnetically responsive nature of the bicelles allowed to gel the anisotropy at commercially viable magnetic field strengths between 1 and 3 T. Thermoreversible gels with a unique optical signature were generated by exposing the system to various temperature conditions and external magnetic field strengths. The resulting optical properties were a signature of the gel's environmental history, effectively acting as a sensor. Solutions containing the bicelles simultaneously aligning parallel and perpendicular to the magnetic field directions were obtained by mixing samples chelating Tm 3+ and Dy 3+ . These systems were successfully gelled, providing a material with two distinct temperature-dependent optical characteristics. The high degree of tunability in the magnetic response of the bicelles enables encryption of the gel's optical properties. The proposed gels are viable candidates for temperature tracking of sensitive goods and provide numerous perspectives for future development of tomorrow's smart materials and technologies.

Measurement of L X-Ray Intensity Ratios for 92U and 90Th Elements Using Photoionization in an External Magnetic Field

NASA Astrophysics Data System (ADS)

Demir, D.; Sahin, Y.

2007-03-01

L x-ray intensity ratios Lell/Lγ, Lα/Lγ and Lβ/Lγ for 92U and 90Th are measured by using 59.5 keV incident photon energy at 110° and 125° scattering angles. The samples are located in the external magnetic field of intensities ±0.15T, ±0.30T, ±0.45T, ±0.60T and ±0.75T. The experimental results obtained for B = 0 are compared with the theoretical values calculated using Scofield's tables based on the Hartree-Slater theory. The contribution to the alignment of the external magnetic field is discussed. It is observed that the L x-ray intensity ratios decrease with the increasing magnetic field intensity.

Synergistic structures from magnetic freeze casting with surface magnetized alumina particles and platelets.

PubMed

Frank, Michael B; Hei Siu, Sze; Karandikar, Keyur; Liu, Chin-Hung; Naleway, Steven E; Porter, Michael M; Graeve, Olivia A; McKittrick, Joanna

2017-12-01

Magnetic freeze casting utilizes the freezing of water, a low magnetic field and surface magnetized materials to make multi-axis strengthened porous scaffolds. A much greater magnetic moment was measured for larger magnetized alumina platelets compared with smaller particles, which indicated that more platelet aggregation occurred within slurries. This led to more lamellar wall alignment along the magnetic field direction during magnetic freeze casting at 75 mT. Slurries with varying ratios of magnetized particles to platelets (0:1, 1:3, 1:1, 3:1, 7:1, 1:0) produced porous scaffolds with different structural features and degrees of lamellar wall alignment. The greatest mechanical enhancement in the magnetic field direction was identified in the synergistic condition with the highest particle to platelet ratio (7:1). Magnetic freeze casting with varying ratios of magnetized anisotropic and isotropic alumina provided insights about how heterogeneous morphologies aggregate within lamellar walls that impact mechanical properties. Fabrication of strengthened scaffolds with multi-axis aligned porosity was achieved without introducing different solid materials, freezing agents or additives. Resemblance of 7:1 particle to platelet scaffold microstructure to wood light-frame house construction is framed in the context of assembly inspiration being derived from both natural and synthetic sources. Copyright © 2017 Elsevier Ltd. All rights reserved.

Magnetic phase separation and unusual scenario of its temperature evolution in porous carbon-based nanomaterials doped with Au and Co

NASA Astrophysics Data System (ADS)

Ryzhov, V. A.; Lashkul, A. V.; Matveev, V. V.; Molkanov, P. L.; Kurbakov, A. I.; Kiselev, I. A.; Lisunov, K. G.; Galimov, D.; Lähderanta, E.

2018-01-01

Two porous glassy carbon-based samples doped with Au and Co were investigated. The magnetization study as well as measurements of the nonlinear longitudinal response to a weak ac field (NLR) and electron magnetic resonance give evidences for a presence of magnetic nanoparticles (MNPs) embedded in paramagnetic/ferromagnetic matrix respectively, both samples being in magnetically phase-separated state at temperatures above 300 K. Matrix, forming by paramagnetic centers located in matrix outside the MNPs, reveals exchange interactions providing its ferromagnetic (FM) ordering below TC ≈ 210 K in Au-doped sample and well above 350 K in Co-doped one. For the former, NLR data suggest a percolation character of the matrix long-range FM order, which is mainly caused by a porous amorphous sample structure. Temperature dependence of the magnetization in the Au-doped sample evidences presence of antiferromagnetic (AF) interactions of MNPs with surrounding matrix centers. At magnetic ordering below TC these interactions promote origination of "domains" involving matrix fragment and surrounding MNPs with near opposite orientation of their moments that decreases the magnetostatic energy. On further cooling, the domains exhibit AF ordering below Tcr ∼ 140 K < TC, resulting in formation of a peculiar "ferrimagnet". The porous amorphous structure leads to absence of translational and other symmetry features through the samples that allows canted ordering of magnetic moments in domains and in whole sample providing "canted ferrimagnetism". At low temperatures Ttr ∼ 3 K, "order-oder" transition, evidencing the non-Heisenberg character of this magnetic material, occurs from ordering like "canted ferrimagnet" to FM alignment, which is stimulated by external magnetic field. The data for Co-doped sample imply the similar evolution of magnetic state but at higher temperatures above 350 K. This state exhibits more homogeneous arrangement of the FM nanoparticles and the FM matrix. Order-order transition occurs in it at higher Ttr ∼ 10-15 K as well and followed by formation of long-range FM ordering found earlier by neutron diffraction. Doping of carbon-based nanomaterials by magnetic metals provides advantages for their possible practical applications as Co-doped sample with higher TC (>350 K) and larger remanent magnetization evidences.

Mechanical alignment of particles for use in fabricating superconducting and permanent magnetic materials

DOEpatents

Nellis, William J.; Maple, M. Brian

1992-01-01

A method for mechanically aligning oriented superconducting or permanently magnetic materials for further processing into constructs. This pretreatment optimizes the final crystallographic orientation and, thus, properties in these constructs. Such materials as superconducting fibers, needles and platelets are utilized.

TMRG studies on spin alignment in molecule-based ferrimagnetics [rapid communication

NASA Astrophysics Data System (ADS)

Liu, Q. M.; Yao, K. L.; Liu, Z. L.

2005-05-01

A physical picture of spin alignment in organic molecule-based ferrimagnets is presented from studying the thermal effective magnetic moment of the sublattice by use of the transfer matrix renormalization group. We conclude that the classical antiparallel spin alignment is not the most stable state. The three-spin system tends to parallel alignment when the exchange interaction between the biradical and the monoradical molecules is much weaker than that within the biradical, which can result in the decrease of the effective magnetic moment upon lowering the temperature. More importantly, we give the theoretical evidence that even the antiparallel spin alignment in the biradical monoradical alternating chain does not necessarily lead to ferrimagnetic spin ordering due to the formation of the spin singlet pairs, which suppresses the ferrimagnetic spin alignment.

Spontaneous Magnetic Alignment by Yearling Snapping Turtles: Rapid Association of Radio Frequency Dependent Pattern of Magnetic Input with Novel Surroundings

PubMed Central

Landler, Lukas; Painter, Michael S.; Youmans, Paul W.; Hopkins, William A.; Phillips, John B.

2015-01-01

We investigated spontaneous magnetic alignment (SMA) by juvenile snapping turtles using exposure to low-level radio frequency (RF) fields at the Larmor frequency to help characterize the underlying sensory mechanism. Turtles, first introduced to the testing environment without the presence of RF aligned consistently towards magnetic north when subsequent magnetic testing conditions were also free of RF (‘RF off → RF off’), but were disoriented when subsequently exposed to RF (‘RF off → RF on’). In contrast, animals initially introduced to the testing environment with RF present were disoriented when tested without RF (‘RF on → RF off’), but aligned towards magnetic south when tested with RF (‘RF on → RF on’). Sensitivity of the SMA response of yearling turtles to RF is consistent with the involvement of a radical pair mechanism. Furthermore, the effect of RF appears to result from a change in the pattern of magnetic input, rather than elimination of magnetic input altogether, as proposed to explain similar effects in other systems/organisms. The findings show that turtles first exposed to a novel environment form a lasting association between the pattern of magnetic input and their surroundings. However, under natural conditions turtles would never experience a change in the pattern of magnetic input. Therefore, if turtles form a similar association of magnetic cues with the surroundings each time they encounter unfamiliar habitat, as seems likely, the same pattern of magnetic input would be associated with multiple sites/localities. This would be expected from a sensory input that functions as a global reference frame, helping to place multiple locales (i.e., multiple local landmark arrays) into register to form a global map of familiar space. PMID:25978736

Spontaneous magnetic alignment by yearling snapping turtles: rapid association of radio frequency dependent pattern of magnetic input with novel surroundings.

PubMed

Landler, Lukas; Painter, Michael S; Youmans, Paul W; Hopkins, William A; Phillips, John B

2015-01-01

We investigated spontaneous magnetic alignment (SMA) by juvenile snapping turtles using exposure to low-level radio frequency (RF) fields at the Larmor frequency to help characterize the underlying sensory mechanism. Turtles, first introduced to the testing environment without the presence of RF aligned consistently towards magnetic north when subsequent magnetic testing conditions were also free of RF ('RF off → RF off'), but were disoriented when subsequently exposed to RF ('RF off → RF on'). In contrast, animals initially introduced to the testing environment with RF present were disoriented when tested without RF ('RF on → RF off'), but aligned towards magnetic south when tested with RF ('RF on → RF on'). Sensitivity of the SMA response of yearling turtles to RF is consistent with the involvement of a radical pair mechanism. Furthermore, the effect of RF appears to result from a change in the pattern of magnetic input, rather than elimination of magnetic input altogether, as proposed to explain similar effects in other systems/organisms. The findings show that turtles first exposed to a novel environment form a lasting association between the pattern of magnetic input and their surroundings. However, under natural conditions turtles would never experience a change in the pattern of magnetic input. Therefore, if turtles form a similar association of magnetic cues with the surroundings each time they encounter unfamiliar habitat, as seems likely, the same pattern of magnetic input would be associated with multiple sites/localities. This would be expected from a sensory input that functions as a global reference frame, helping to place multiple locales (i.e., multiple local landmark arrays) into register to form a global map of familiar space.

Collective alignment of nanorods in thin Newtonian films

NASA Astrophysics Data System (ADS)

Gu, Yu; Burtovyy, Ruslan; Townsend, James; Owens, Jeffery; Luzinov, Igor; Kornev, Konstantin

2013-11-01

We provide a complete analytical description of the alignment kinetics of magnetic nanorods in magnetic field. Nickel nanorods were formed by template electrochemical deposition in alumina membranes from a dispersion in a water-glycerol mixture. To ensure uniformity of the dispersion, the surface of the nickel nanorods was covered with polyvinylpyrrolidone (PVP). A 40-70 nm coating prevented aggregation of nanoroda. These modifications allowed us to control alignment of the nanorods in a magnetic field and test the proposed theory. An orientational distribution function of nanorods was introduced. We demonstrated that the 0.04% volume fraction of nanorods in the glycerol-water mixture behaves as a system of non-interacting particles. However, the kinetics of alignment of a nanorod assembly does not follow the predictions of the single-nanorod theory. The distribution function theory explains the kinetics of alignment of a nanorod assembly and shows the significance of the initial distribution of nanorods in the film. It can be used to develop an experimental protocol for controlled ordering of magnetic nanorods in thin films. This work was supported by the Air Force Office of Scientific Research, Grant numbers FA9550-12-1-0459 and FA8650-09-D-507 5900.

Developments in Scanning Hall Probe Microscopy

NASA Astrophysics Data System (ADS)

Chouinard, Taras; Chu, Ricky; David, Nigel; Broun, David

2009-05-01

Low temperature scanning Hall probe microscopy is a sensitive means of imaging magnetic structures with high spatial resolution and magnetic flux sensitivity approaching that of a Superconducting Quantum Interference Device. We have developed a scanning Hall probe microscope with novel features, including highly reliable coarse positioning, in situ optimization of sensor-sample alignment and capacitive transducers for linear, long range positioning measurement. This has been motivated by the need to reposition accurately above fabricated nanostructures such as small superconducting rings. Details of the design and performance will be presented as well as recent progress towards time-resolved measurements with sub nanosecond resolution.

Fantastic Striations and Where to Find Them: The Origin of Magnetically Aligned Striations in Interstellar Clouds

NASA Astrophysics Data System (ADS)

Chen, Che-Yu; Li, Zhi-Yun; King, Patrick K.; Fissel, Laura M.

2017-10-01

Thin, magnetically aligned striations of relatively moderate contrast with the background are commonly observed in both atomic and molecular clouds. They are also prominent in MHD simulations with turbulent converging shocks. The simulated striations develop within a dense, stagnated sheet in the midplane of the post-shock region where magnetically induced converging flows collide. We show analytically that the secondary flows are an inevitable consequence of the jump conditions of oblique MHD shocks. They produce the stagnated, sheet-like sub-layer through a secondary shock when, roughly speaking, the Alfvénic speed in the primary converging flows is supersonic, a condition that is relatively easy to satisfy in interstellar clouds. The dense sub-layer is naturally threaded by a strong magnetic field that lies close to the plane of the sub-layer. The substantial magnetic field makes the sheet highly anisotropic, which is the key to the striation formation. Specifically, perturbations of the primary inflow that vary spatially perpendicular to the magnetic field can easily roll up the sheet around the field lines without bending them, creating corrugations that appear as magnetically aligned striations in column density maps. On the other hand, perturbations that vary spatially along the field lines curve the sub-layer and alter its orientation relative to the magnetic field locally, seeding special locations that become slanted overdense filaments and prestellar cores through enhanced mass accumulation along field lines. In our scenario, the dense sub-layer, which is unique to magnetized oblique shocks, is the birthplace for both magnetically aligned diffuse striations and massive star-forming structures.

Fabrication Procedures and Birefringence Measurements for Designing Magnetically Responsive Lanthanide Ion Chelating Phospholipid Assemblies.

PubMed

Isabettini, Stéphane; Baumgartner, Mirjam E; Fischer, Peter; Windhab, Erich J; Liebi, Marianne; Kuster, Simon

2018-01-03

Bicelles are tunable disk-like polymolecular assemblies formed from a large variety of lipid mixtures. Applications range from membrane protein structural studies by nuclear magnetic resonance (NMR) to nanotechnological developments including the formation of optically active and magnetically switchable gels. Such technologies require high control of the assembly size, magnetic response and thermal resistance. Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and its lanthanide ion (Ln 3+ ) chelating phospholipid conjugate, 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA), assemble into highly magnetically responsive assemblies such as DMPC/DMPE-DTPA/Ln 3+ (molar ratio 4:1:1) bicelles. Introduction of cholesterol (Chol-OH) and steroid derivatives in the bilayer results in another set of assemblies offering unique physico-chemical properties. For a given lipid composition, the magnetic alignability is proportional to the bicelle size. The complexation of Ln 3+ results in unprecedented magnetic responses in terms of both magnitude and alignment direction. The thermo-reversible collapse of the disk-like structures into vesicles upon heating allows tailoring of the assemblies' dimensions by extrusion through membrane filters with defined pore sizes. The magnetically alignable bicelles are regenerated by cooling to 5 °C, resulting in assembly dimensions defined by the vesicle precursors. Herein, this fabrication procedure is explained and the magnetic alignability of the assemblies is quantified by birefringence measurements under a 5.5 T magnetic field. The birefringence signal, originating from the phospholipid bilayer, further enables monitoring of polymolecular changes occurring in the bilayer. This simple technique is complementary to NMR experiments that are commonly employed to characterize bicelles.

Magnetic Control of MOF Crystal Orientation and Alignment.

PubMed

Cheng, Fei; Marshall, Ellis S; Young, Adam J; Robinson, Peter J; Bouillard, Jean-Sebastien G; Adawi, Ali M; Vermeulen, Nicolaas A; Farha, Omar K; Reithofer, Michael R; Chin, Jia Min

2017-11-07

Most metal-organic frameworks (MOFs) possess anisotropic properties, the full exploitation of which necessitates a general strategy for the controllable orientation of such MOF crystals. Current methods largely rely upon layer-by-layer MOF epitaxy or tuning of MOF crystal growth on appropriate substrates, yielding MOFs with fixed crystal orientations. Here, the dynamic magnetic alignment of different MOF crystals (NH 2 -MIL-53(Al) and NU-1000) is shown. The MOFs were magnetized by electrostatic adsorption of iron oxide nanoparticles, dispersed in curable polymer resins (Formlabs 1+ clear resin/ Sylgard 184), magnetically oriented, and fixed by resin curing. The importance of crystal orientation on MOF functionality was demonstrated whereby magnetically aligned NU-1000/Sylgard 184 composite was excited with linearly polarized 405 nm light, affording an anisotropic fluorescence response dependent on the polarization angle of the excitation beam relative to NU-1000 crystal orientation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

An experimental approach in revisiting the magnetic orientation of cattle.

PubMed

Weijers, Debby; Hemerik, Lia; Heitkönig, Ignas M A

2018-01-01

In response to the increasing number of observational studies on an apparent south-north orientation in non-homing, non-migrating terrestrial mammals, we experimentally tested the alignment hypothesis using strong neodymium magnets on the resting orientation of individual cattle in Portugal. Contrary to the hypothesis, the 34 cows in the experiment showed no directional preference, neither with, nor without a strong neodymium magnet fixed to their collar. The concurrently performed 2,428 daytime observations-excluding the hottest part of the day-of 659 resting individual cattle did not show a south-north alignment when at rest either. The preferred compass orientation of these cows was on average 130 degrees from the magnetic north (i.e., south east). Cow compass orientation correlated significantly with sun direction, but not with wind direction. In as far as we can determine, this is the first experimental test on magnetic orientation in larger, non-homing, non-migrating mammals. These experimental and observational findings do not support previously published suggestions on the magnetic south-north alignment in these mammals.

Magnetic field alignment of coil-coil diblock copolymers and blends via intrinsic chain anisotropy

NASA Astrophysics Data System (ADS)

Rokhlenko, Yekaterina; Majewski, Pawel; Larson, Steven; Yager, Kevin; Gopalan, Padma; Avgeropoulos, Apostolos; Chan, Edwin; Osuji, Chinedum

Magnetic fields can control alignment of self-assembled soft materials such as block copolymers provided there is a suitably large magnetic susceptibility anisotropy present in the system. Recent results have highlighted the existence of a non-trivial intrinsic anisotropy in coil-coil diblock copolymers, specifically in lamellar-forming PS-b-P4VP, which enables alignment at field strengths of a few tesla in systems lacking mesogenic components. Alignment is predicated on correlation in the orientation of end-end vectors implied by the localization of block junctions at the microdomain interface and is observed on cooling across the order-disorder transition in the presence of the field. For appropriate combinations of field strength and grain size, we can leverage intrinsic chain anisotropy to magnetically direct self-assembly of many non-mesogenic systems, including other coil-coil BCPs like PS-b-PDMS and PS-b-PMMA, blends of BCPs of disparate morphologies and MWs, and blends of BCPs with homopolymers. This is noteworthy as blends of PS-b-P4VP with PEO provide a route to form functional materials such as nanoporous films by dissolution of PEO, or aligned ion conduction materials. We survey these various systems using TEM and in-situ X-ray scattering to study the phase behavior and temperature-, time- and field- dependent dynamics of alignment.

Iron Atoms in Cr-Mn Antiferromagnetic Matrix

NASA Astrophysics Data System (ADS)

Szymański, K.; Satuła, D.; Dobrzyński, L.; Biernacka, M.; Perzyńska, K.; Zaleski, P.

2002-06-01

The results of the Mössbauer effect measurements on bcc Cr rich Cr-Fe-Mn alloys in temperature range 12-296 K in zero- and in applied magnetic fields are reported. Monochromatic, circularly polarized radiation was used for investigation of iron moments alignment. Strong enhancement of internal hyperfine magnetic field induced by the applied magnetic field was detected and explained as due to dynamical effects. At high temperatures alignment of iron moments in antiferromagnetic phase is weakly magnetic field-dependent. At low temperatures the average hyperfine magnetic field is antiparallel to the net magnetization showing that iron moments are partly ordered by the applied field.

Superparamagnetism in carbon-coated Co particles produced by the Kratschmer carbon arc process

NASA Astrophysics Data System (ADS)

McHenry, M. E.; Majetich, S. A.; Artman, J. O.; Degraef, M.; Staley, S. W.

1994-04-01

A process based on the Kratschmer-Huffman carbon arc method of preparing fullerenes has been used to generate carbon-coated cobalt and cobalt carbide nanocrystallites. Magnetic nanocrystallites are extracted from the soot with a gradient field technique. For Co/C composites, structural characterization by x-ray diffraction and high-resolution transmission electron microscopy reveals the presence of a fcc Co phase, graphite, and a minority Co2C phase. The majority of Co nanocrystals exists as nominally spherical particles, 0.5-5 nm in radius. Hysteretic and temperature-dependent magnetic response, in randomly and magnetically aligned powder samples frozen in epoxy reveals fine-particle magnetism associated with monodomain Co particles. The magnetization exhibits a unique functional dependence on H/T, and hysteresis below a blocking temperature, TB~=160 K. Below TB, the temperature dependence of the coercivity is given by Hc=Hci[1-(T/TB)1/2], with Hci~=450 Oe.

Investigation of Anisotropic Bonded Magnets in Permanent Magnet Machine Applications

NASA Astrophysics Data System (ADS)

Khazdozian, H. A.; McCall, S. K.; Kramer, M. J.; Paranthaman, M. P.; Nlebedim, I. C.

Rare earth elements (REE) provide the high energy product necessary for permanent magnets, such as sintered Nd2Fe14B, in many applications like wind energy generators. However, REEs are considered critical materials due to risk in their supply. To reduce the use of critical materials in permanent magnet machines, the performance of anisotropic bonded NdFeB magnets, aligned under varying magnetic field strength, was simulated using 3D finite element analysis in a 3MW direct-drive permanent magnet generator (DDPMG), with sintered N42 magnets used as a baseline for comparison. For direct substitution of the anisotropic bonded magnets, approximately 85% of the efficiency of the baseline model was achieved, irrespective of the alignment field. The torque and power generation of the DDPMG was not found to vary significantly with increase in the alignment field. Finally, design changes were studied to allow for the achievement of rated torque and power with the use of anisotropic bonded magnets, demonstrating the potential for reduction of critical materials in permanent magnets for renewable energy applications. This work was supported by the Critical Materials Institute, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office.

Paramagnetic alignment of small grains: A novel method for measuring interstellar magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoang, Thiem; Martin, P. G.; Lazarian, A.

2014-07-20

We present a novel method to measure the strength of interstellar magnetic fields using ultraviolet (UV) polarization of starlight that is in part produced by weakly aligned, small dust grains. We begin with calculating the degrees of the paramagnetic alignment of small (size a ∼ 0.01 μm) and very small (a ∼ 0.001 μm) grains in the interstellar magnetic field due to the Davis-Greenstein relaxation and resonance relaxation. To calculate the degrees of paramagnetic alignment, we use Langevin equations and take into account various interaction processes essential for the rotational dynamics of small grains. We find that the alignment ofmore » small grains is necessary to reproduce the observed polarization in the UV, although the polarization arising from these small grains is negligible at the optical and infrared (IR) wavelengths. Based on fitting theoretical models to observed extinction and polarization curves, we find that the best-fit model for the case with the peak wavelength of polarization λ{sub max} < 0.55 μm requires a higher degree of alignment of small grains than for the typical case with λ{sub max} = 0.55 μm. We interpret the correlation between the systematic increase of the UV polarization relative to maximum polarization (i.e., of p(6 μm{sup –1})/p{sub max}) with λ{sub max}{sup −1} for cases of low λ{sub max} by appealing to the higher degree of alignment of small grains. We utilize the correlation of the paramagnetic alignment of small grains with the magnetic field strength B to suggest a new way to measure B using the observable parameters λ{sub max} and p(6 μm{sup –1})/p{sub max}.« less

Anisotropic Properties of Single-Crystalline CeNiGe2

NASA Astrophysics Data System (ADS)

Jung, M. H.; Harrison, N.; Lacerda, A. H.; Pagliuso, P. G.; Sarrao, J. L.; Thompson, J. D.

2002-07-01

The anisotropic properties of CeNiGe2 with a layered crystal structure have been studied by measurements of electrical resistivity, magnetic susceptibility and magnetization. It is confirmed that CeNiGe2 undergoes two-step antiferromagnetic transition at TNI = 4 K and TNII = 3 K as reported earlier on polycrystalline samples. CeNiGe2 is found to exhibit highly anisotropic properties with an easy magnetization axis along the longest crystallographic b direction. The magnetization ratio M(H//b)/M(H⊥b) is estimated to be about 15 at 5 T. The in-plane resistivity ρ⊥b(T) shows double maxima typical of that expected when an interplay of crystal-field and Kondo effects plays a role. The low-T maximum at 4 K in ρ⊥b(T) is strongly suppressed with increasing magnetic field. This negative magnetoresistance is a result of the strong reduction of magnetic scattering by the ferromagnetic alignment of Ce magnetic moments.

Optical imaging using spatial grating effects in ferrofluids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dave, Vishakha; Virpura, Hiral; Patel, Rajesh, E-mail: rjp@mkbhavuni.edu.in

2015-06-24

Under the effect of magnetic field the magnetic nanoparticles of the ferrofluid tend to align in the direction of the magnetic field. This alignment of the magnetic nanoparticles behaves as a spatial grating and diffract light, when light is propagating perpendicular to the direction of the applied magnetic field. The chains of the magnetic nanoparticles represents a linear series of fringes like those observed in a grating/wire. Under applied magnetic field the circular beam of light transforms into a prominent diffraction line in the direction perpendicular to the applied magnetic field. This diffracted light illuminates larger area on the screen.more » This behavior can be used as magneto controlled illumination of the object and image analysis.« less

Aligning flaky FeSiAl particles with a two-dimensional rotating magnetic field to improve microwave-absorbing and shielding properties of composites

NASA Astrophysics Data System (ADS)

Liu, Chang; Cai, Jun; Duan, Yubing; Li, Xinghao; Zhang, Deyuan

2018-07-01

In order to enhance the microwave-absorbing and shielding properties of the composites, the flaky FeSiAl particles embedded in an epoxy polymer were aligned with a two-dimensional rotating magnetic field. The morphologies, electromagnetic (EM) characteristics, and microwave-absorbing and shielding properties of the unaligned and aligned FeSiAl/epoxy composites were investigated. The results showed that after alignment treatment, the flaky FeSiAl particles tend to orient uniformly in the rotating magnetic field, and the permittivity and permeability of the aligned composites were increased in the frequency range of 1-18 GHz compared with that of randomly distributed composites. The calculated microwave-absorbing properties indicated that the peak value of the return loss (RL) of the aligned composites can reach 8.8 dB, compared with 5.8 dB of the unaligned composites of 2.5 mm in thickness (60 wt%); and the bandwidth with RL value more than 6 dB is in a wider frequency range from 1 to 2.8 GHz. And the calculated shielding effectiveness (SE) of the aligned composites is 1.1-3 times higher than that of unaligned one in every thickness, and the maximum SE of the aligned one is 31.8 dB at 18 GHz with a thickness of 2.5 mm.

Magnetism on a Boron-doped Si(111)-√ 3 × √ 3 Surface

NASA Astrophysics Data System (ADS)

Moon, Chang-Youn; Eom, Daejin; Koo, Ja-Yong

2018-03-01

We perform first-principles calculation to investigate the possible magnetism on the Si(111)-√ 3 × √ 3 surface, which is stabilized for highly boron-doped samples. When the silicon adatom on top of a boron atom is removed to form a defect structure, three silicon dangling bonds are exposed, generating half-filled doubly degenerate energy levels in the band gap, which stabilizes a local magnetic moment of 2 μ B . When many such defect structures are adjacent to one another, they are found to align antiferromagnetically. However, we demonstrate that the ferromagnetism can be stabilized by adjusting the number of electrons in the defects, suggesting a possibility towards spintronic applications for this unique silicon surface structure.

Direct Observations of ULF and Whistler-Mode Chorus Modulation of 500eV EDI Electrons by MMS

NASA Astrophysics Data System (ADS)

Paulson, K. W.; Argall, M. R.; Ahmadi, N.; Torbert, R. B.; Le Contel, O.; Ergun, R.; Khotyaintsev, Y. V.; Strangeway, R. J.; Magnes, W.; Russell, C. T.

2016-12-01

We present here direct observations of chorus-wave modulated field-aligned 500 eV electrons using the Electron Drift Instrument (EDI) on board the Magnetospheric Multiscale mission. These periods of wave activity were additionally observed to be modulated by Pc5-frequency magnetic perturbations, some of which have been identified as drifting mirror-mode structures. The spacecraft encountered these mirror-mode structures just inside of the duskside magnetopause. Using the high sampling rate provided by EDI in burst sampling mode, we are able to observe the individual count fluctuations of field-aligned electrons in this region up to 512 Hz. We use the multiple look directions of EDI to generate both pitch angle and gyrophase plots of the fluctuating counts. Our observations often show unidirectional flow of these modulated electrons along the background field, and in some cases demonstrate gyrophase bunching in the wave region.

Electroconductive PET/SWNT Films by Solution Casting

NASA Technical Reports Server (NTRS)

Steinert, Brian W.; Dean, Derrick R.

2008-01-01

The market for electrically conductive polymers is rapidly growing, and an emerging pathway for attaining these materials is via polymer-carbon nanotube (CNT) nanocomposites, because of the superior properties of CNTs. Due to their excellent electrical properties and anisotropic magnetic susceptibility, we expect CNTs could be easily aligned to maximize their effectiveness in imparting electrical conductivity to the polymer matrix. Single-walled carbon nanotubes (SWNT) were dispersed in a polyethylene terephthalate (PET) matrix by solution blending then cast onto a glass substrate to create thin, flexible films. Various SWNT loading concentrations were implemented (0.5, 1.0, and 3.0 wt.%) to study the effect of additive density. The processing method was repeated to produce films in the presence of magnetic fields (3 and 9.4 Tesla). The SWNTs showed a high susceptibility to the magnetic field and were effectively aligned in the PET matrix. The alignment was characterized with Raman spectroscopy. Impedance spectroscopy was utilized to study the electrical behavior of the films. Concentration and dispersion seemed to play very important roles in improving electrical conductivity, while alignment played a secondary and less significant role. The most interesting result proved to be the effect of a magnetic field during processing. It appears that a magnetic field may improve dispersion of unmodified SWNTs, which seems to be more important than alignment. It was concluded that SWNTs offer a good option as conductive, nucleating filler for electroconductive polymer applications, and the utilization of a magnetic field may prove to be a novel method for CNT dispersion that could lead to improved nanocomposite materials.

Rapid learning of magnetic compass direction by C57BL/6 mice in a 4-armed 'plus' water maze.

PubMed

Phillips, John B; Youmans, Paul W; Muheim, Rachel; Sloan, Kelly A; Landler, Lukas; Painter, Michael S; Anderson, Christopher R

2013-01-01

Magnetoreception has been demonstrated in all five vertebrate classes. In rodents, nest building experiments have shown the use of magnetic cues by two families of molerats, Siberian hamsters and C57BL/6 mice. However, assays widely used to study rodent spatial cognition (e.g. water maze, radial arm maze) have failed to provide evidence for the use of magnetic cues. Here we show that C57BL/6 mice can learn the magnetic direction of a submerged platform in a 4-armed (plus) water maze. Naïve mice were given two brief training trials. In each trial, a mouse was confined to one arm of the maze with the submerged platform at the outer end in a predetermined alignment relative to magnetic north. Between trials, the training arm and magnetic field were rotated by 180(°) so that the mouse had to swim in the same magnetic direction to reach the submerged platform. The directional preference of each mouse was tested once in one of four magnetic field alignments by releasing it at the center of the maze with access to all four arms. Equal numbers of responses were obtained from mice tested in the four symmetrical magnetic field alignments. Findings show that two training trials are sufficient for mice to learn the magnetic direction of the submerged platform in a plus water maze. The success of these experiments may be explained by: (1) absence of alternative directional cues (2), rotation of magnetic field alignment, and (3) electromagnetic shielding to minimize radio frequency interference that has been shown to interfere with magnetic compass orientation of birds. These findings confirm that mice have a well-developed magnetic compass, and give further impetus to the question of whether epigeic rodents (e.g., mice and rats) have a photoreceptor-based magnetic compass similar to that found in amphibians and migratory birds.

Rapid Learning of Magnetic Compass Direction by C57BL/6 Mice in a 4-Armed ‘Plus’ Water Maze

PubMed Central

Phillips, John B.; Youmans, Paul W.; Muheim, Rachel; Sloan, Kelly A.; Landler, Lukas; Painter, Michael S.; Anderson, Christopher R.

2013-01-01

Magnetoreception has been demonstrated in all five vertebrate classes. In rodents, nest building experiments have shown the use of magnetic cues by two families of molerats, Siberian hamsters and C57BL/6 mice. However, assays widely used to study rodent spatial cognition (e.g. water maze, radial arm maze) have failed to provide evidence for the use of magnetic cues. Here we show that C57BL/6 mice can learn the magnetic direction of a submerged platform in a 4-armed (plus) water maze. Naïve mice were given two brief training trials. In each trial, a mouse was confined to one arm of the maze with the submerged platform at the outer end in a predetermined alignment relative to magnetic north. Between trials, the training arm and magnetic field were rotated by 180° so that the mouse had to swim in the same magnetic direction to reach the submerged platform. The directional preference of each mouse was tested once in one of four magnetic field alignments by releasing it at the center of the maze with access to all four arms. Equal numbers of responses were obtained from mice tested in the four symmetrical magnetic field alignments. Findings show that two training trials are sufficient for mice to learn the magnetic direction of the submerged platform in a plus water maze. The success of these experiments may be explained by: (1) absence of alternative directional cues (2), rotation of magnetic field alignment, and (3) electromagnetic shielding to minimize radio frequency interference that has been shown to interfere with magnetic compass orientation of birds. These findings confirm that mice have a well-developed magnetic compass, and give further impetus to the question of whether epigeic rodents (e.g., mice and rats) have a photoreceptor-based magnetic compass similar to that found in amphibians and migratory birds. PMID:24023673

Correlation between magnetic and electric field perturbations in the field-aligned current regions deduced from DE 2 observations

NASA Technical Reports Server (NTRS)

Ishii, M.; Sugiura, M.; Iyemori, T.; Slavin, J. A.

1992-01-01

The satellite-observed high correlations between magnetic and electric field perturbations in the high-latitude field-aligned current regions are investigated by examining the dependence of the relationship between Delta-B and E on spatial scale, using the electric and magnetic field data obtained by DE 2 in the polar regions. The results are compared with the Pedersen conductivity inferred from the international reference ionosphere model and the Alfven wave velocity calculated from the in situ ion density and magnetic field measurements.

Fantastic Striations and Where to Find Them: The Origin of Magnetically Aligned Striations in Interstellar Clouds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Che-Yu; Li, Zhi-Yun; King, Patrick K.

2017-10-01

Thin, magnetically aligned striations of relatively moderate contrast with the background are commonly observed in both atomic and molecular clouds. They are also prominent in MHD simulations with turbulent converging shocks. The simulated striations develop within a dense, stagnated sheet in the midplane of the post-shock region where magnetically induced converging flows collide. We show analytically that the secondary flows are an inevitable consequence of the jump conditions of oblique MHD shocks. They produce the stagnated, sheet-like sub-layer through a secondary shock when, roughly speaking, the Alfvénic speed in the primary converging flows is supersonic, a condition that is relativelymore » easy to satisfy in interstellar clouds. The dense sub-layer is naturally threaded by a strong magnetic field that lies close to the plane of the sub-layer. The substantial magnetic field makes the sheet highly anisotropic, which is the key to the striation formation. Specifically, perturbations of the primary inflow that vary spatially perpendicular to the magnetic field can easily roll up the sheet around the field lines without bending them, creating corrugations that appear as magnetically aligned striations in column density maps. On the other hand, perturbations that vary spatially along the field lines curve the sub-layer and alter its orientation relative to the magnetic field locally, seeding special locations that become slanted overdense filaments and prestellar cores through enhanced mass accumulation along field lines. In our scenario, the dense sub-layer, which is unique to magnetized oblique shocks, is the birthplace for both magnetically aligned diffuse striations and massive star-forming structures.« less

Directed Magnetic Particle Transport above Artificial Magnetic Domains Due to Dynamic Magnetic Potential Energy Landscape Transformation.

PubMed

Holzinger, Dennis; Koch, Iris; Burgard, Stefan; Ehresmann, Arno

2015-07-28

An approach for a remotely controllable transport of magnetic micro- and/or nanoparticles above a topographically flat exchange-bias (EB) thin film system, magnetically patterned into parallel stripe domains, is presented where the particle manipulation is achieved by sub-mT external magnetic field pulses. Superparamagnetic core-shell particles are moved stepwise by the dynamic transformation of the particles' magnetic potential energy landscape due to the external magnetic field pulses without affecting the magnetic state of the thin film system. The magnetic particle velocity is adjustable in the range of 1-100 μm/s by the design of the substrate's magnetic field landscape (MFL), the particle-substrate distance, and the magnitude of the applied external magnetic field pulses. The agglomeration of magnetic particles is avoided by the intrinsic magnetostatic repulsion of particles due to the parallel alignment of the particles' magnetic moments perpendicular to the transport direction and parallel to the surface normal of the substrate during the particle motion. The transport mechanism is modeled by a quantitative theory based on the precise knowledge of the sample's MFL and the particle-substrate distance.

The Polar Plasma Wave Instrument

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Persoon, A. M.; Randall, R. F.; Odem, D. L.; Remington, S. L.; Averkamp, T. F.; Debower, M. M.; Hospodarsky, G. B.; Huff, R. L.; Kirchner, D. L.

1995-01-01

The Plasma Wave Instrument on the Polar spacecraft is designed to provide measurements of plasma waves in the Earth's polar regions over the frequency range from 0.1 Hz to 800 kHz. Three orthogonal electric dipole antennas are used to detect electric fields, two in the spin plane and one aligned along the spacecraft spin axis. A magnetic loop antenna and a triaxial magnetic search coil antenna are used to detect magnetic fields. Signals from these antennas are processed by five receiver systems: a wideband receiver, a high-frequency waveform receiver, a low-frequency waveform receiver, two multichannel analyzers; and a pair of sweep frequency receivers. Compared to previous plasma wave instruments, the Polar plasma wave instrument has several new capabilities. These include (1) an expanded frequency range to improve coverage of both low- and high-frequency wave phenomena, (2) the ability to simultaneously capture signals from six orthogonal electric and magnetic field sensors, and (3) a digital wideband receiver with up to 8-bit resolution and sample rates as high as 249k samples s(exp -1).

Magnetic field sensing with nitrogen-vacancy color centers in diamond

NASA Astrophysics Data System (ADS)

Pham, Linh My

In recent years, the nitrogen-vacancy (NV) center has emerged as a promising magnetic sensor capable of measuring magnetic fields with high sensitivity and spatial resolution under ambient conditions. This combination of characteristics allows NV magnetometers to probe magnetic structures and systems that were previously inaccessible with alternative magnetic sensing technologies This dissertation presents and discusses a number of the initial efforts to demonstrate and improve NV magnetometry. In particular, a wide-field CCD based NV magnetic field imager capable of micron-scale spatial resolution is demonstrated; and magnetic field alignment, preferential NV orientation, and multipulse dynamical decoupling techniques are explored for enhancing magnetic sensitivity. The further application of dynamical decoupling control sequences as a spectral probe to extract information about the dynamics of the NV spin environment is also discussed; such information may be useful for determining optimal diamond sample parameters for different applications. Finally, several proposed and recently demonstrated applications which take advantage of NV magnetometers' sensitivity and spatial resolution at room temperature are presented, with particular focus on bio-magnetic field imaging.

Dynamical formation of spatially localized arrays of aligned nanowires in plastic films with magnetic anisotropy.

PubMed

Fragouli, Despina; Buonsanti, Raffaella; Bertoni, Giovanni; Sangregorio, Claudio; Innocenti, Claudia; Falqui, Andrea; Gatteschi, Dante; Cozzoli, Pantaleo Davide; Athanassiou, Athanassia; Cingolani, Roberto

2010-04-27

We present a simple technique for magnetic-field-induced formation, assembling, and positioning of magnetic nanowires in a polymer film. Starting from a polymer/iron oxide nanoparticle casted solution that is allowed to dry along with the application of a weak magnetic field, nanocomposite films incorporating aligned nanocrystal-built nanowire arrays are obtained. The control of the dimensions of the nanowires and of their localization across the polymer matrix is achieved by varying the duration of the applied magnetic field, in combination with the evaporation dynamics. These multifunctional anisotropic free-standing nanocomposite films, which demonstrate high magnetic anisotropy, can be used in a wide field of technological applications, ranging from sensors to microfluidics and magnetic devices.

Vector magnetometry of Fe/Cr/Fe trilayers with biquadratic coupling

NASA Astrophysics Data System (ADS)

Mansell, R.; Petit, D.; Fernández-Pacheco, A.; Lee, J. H.; Chin, S.-L.; Lavrijsen, R.; Cowburn, R. P.

2017-05-01

The magnetic reversal of epitaxial Fe/Cr/Fe trilayer samples grown on GaAs is studied. In wedged samples both long and short period coupling oscillations associated with Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling in Cr are seen in the easy axis saturation fields. By using vector vibrating sample magnetometry and both longitudinal and transverse magneto-optical Kerr effect magnetometry we are able to determine the exact reversal path of both the magnetic layers. Changes in the reversal behavior are seen with sub-monolayer changes of the thickness of the Cr interlayer. The two main reversal paths are described in terms of whether the reversal is dominated by bilinear RKKY coupling, which leads to an antiparallel state at remanence or by biquadratic coupling which leads to a 90 degree alignment of layers at remanence. The changing reversal behaviour is discussed with respect to the possibility of using such systems for multilayer memory applications and, in particular, the limits on the required accuracy of the sample growth.

Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron Antiferromagnet Ca 1 - x Sr x Co 2 - y As 2

DOE PAGES

Sangeetha, N. S.; Smetana, V.; Mudring, A. -V.; ...

2017-12-20

We report the inference of Ying et al. [Europhys. Lett. 104, 67005 (2013)] of a composition-induced change from c-axis ordered-moment alignment in a collinear A-type antiferromagnetic (AFM) structure at small x to ab-plane alignment in an unknown AFM structure at larger x in Ca 1-xSr xCo 2-yAs 2 with the body-centered tetragonal ThCr 2Si 2 structure is confirmed. Our major finding is an anomalous magnetic behavior in the crossover region 0.2 ≲ x ≲ 0.3 between these two phases. Also, in this region the magnetic susceptibility vs temperature χ ab(T) measured with magnetic fields H applied in the ab planemore » exhibit typical AFM behaviors with cusps at the Néel temperatures of ~ 65 K, whereas χ c(T) and the low-temperature isothermal magnetization M c(H) with H aligned along the c axis exhibit extremely soft ferromagneticlike behaviors.« less

Anomalous Composition-Induced Crossover in the Magnetic Properties of the Itinerant-Electron Antiferromagnet Ca 1 - x Sr x Co 2 - y As 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sangeetha, N. S.; Smetana, V.; Mudring, A. -V.

We report the inference of Ying et al. [Europhys. Lett. 104, 67005 (2013)] of a composition-induced change from c-axis ordered-moment alignment in a collinear A-type antiferromagnetic (AFM) structure at small x to ab-plane alignment in an unknown AFM structure at larger x in Ca 1-xSr xCo 2-yAs 2 with the body-centered tetragonal ThCr 2Si 2 structure is confirmed. Our major finding is an anomalous magnetic behavior in the crossover region 0.2 ≲ x ≲ 0.3 between these two phases. Also, in this region the magnetic susceptibility vs temperature χ ab(T) measured with magnetic fields H applied in the ab planemore » exhibit typical AFM behaviors with cusps at the Néel temperatures of ~ 65 K, whereas χ c(T) and the low-temperature isothermal magnetization M c(H) with H aligned along the c axis exhibit extremely soft ferromagneticlike behaviors.« less

Magnetic orientation of nontronite clay in aqueous dispersions and its effect on water diffusion.

PubMed

Abrahamsson, Christoffer; Nordstierna, Lars; Nordin, Matias; Dvinskikh, Sergey V; Nydén, Magnus

2015-01-01

The diffusion rate of water in dilute clay dispersions depends on particle concentration, size, shape, aggregation and water-particle interactions. As nontronite clay particles magnetically align parallel to the magnetic field, directional self-diffusion anisotropy can be created within such dispersion. Here we study water diffusion in exfoliated nontronite clay dispersions by diffusion NMR and time-dependant 1H-NMR-imaging profiles. The dispersion clay concentration was varied between 0.3 and 0.7 vol%. After magnetic alignment of the clay particles in these dispersions a maximum difference of 20% was measured between the parallel and perpendicular self-diffusion coefficients in the dispersion with 0.7 vol% clay. A method was developed to measure water diffusion within the dispersion in the absence of a magnetic field (random clay orientation) as this is not possible with standard diffusion NMR. However, no significant difference in self-diffusion coefficient between random and aligned dispersions could be observed. Copyright © 2014 Elsevier Inc. All rights reserved.

In situ SAXS study on cationic and non-ionic surfactant liquid crystals using synchrotron radiation.

PubMed

Fritscher, C; Hüsing, N; Bernstorff, S; Brandhuber, D; Koch, T; Seidler, S; Lichtenegger, H C

2005-11-01

In situ synchrotron small-angle X-ray scattering was used to investigate various surfactant/water systems with hexagonal and lamellar structures regarding their structural behaviour upon heating and cooling. Measurements of the non-ionic surfactant Triton X-45 (polyethylene glycol 4-tert-octylphenyl ether) at different surfactant concentrations show an alignment of the lamellar liquid-crystalline structure close to the wall of the glass capillaries and also a decrease in d-spacing following subsequent heating/cooling cycles. Additionally, samples were subjected to a weak magnetic field (0.3-0.7 T) during heating and cooling, but no influence of the magnetic field was observed.

An experimental approach in revisiting the magnetic orientation of cattle

PubMed Central

Weijers, Debby; Hemerik, Lia; Heitkönig, Ignas M. A.

2018-01-01

In response to the increasing number of observational studies on an apparent south-north orientation in non-homing, non-migrating terrestrial mammals, we experimentally tested the alignment hypothesis using strong neodymium magnets on the resting orientation of individual cattle in Portugal. Contrary to the hypothesis, the 34 cows in the experiment showed no directional preference, neither with, nor without a strong neodymium magnet fixed to their collar. The concurrently performed 2,428 daytime observations—excluding the hottest part of the day—of 659 resting individual cattle did not show a south-north alignment when at rest either. The preferred compass orientation of these cows was on average 130 degrees from the magnetic north (i.e., south east). Cow compass orientation correlated significantly with sun direction, but not with wind direction. In as far as we can determine, this is the first experimental test on magnetic orientation in larger, non-homing, non-migrating mammals. These experimental and observational findings do not support previously published suggestions on the magnetic south-north alignment in these mammals. PMID:29641517

FAST/Polar Conjunction Study of Field-Aligned Auroral Acceleration and Corresponding Magnetotail Drivers

NASA Technical Reports Server (NTRS)

Schriver, D.; Ashour-Abdalla, M.; Strangeway, R. J.; Richard, R. L.; Klezting, C.; Dotan, Y.; Wygant, J.

2003-01-01

The discrete aurora results when energized electrons bombard the Earth's atmosphere at high latitudes. This paper examines the physical processes that can cause field-aligned acceleration of plasma particles in the auroral region. A data and theoretical study has been carried out to examine the acceleration mechanisms that operate in the auroral zone and to identi@ the magnetospheric drivers of these acceleration mechanisms. The observations used in the study were collected by the Fast Auroral Snapshot (FAST) and Polar satellites when the two satellites were in approximate magnetic conjunction in the auroral region. During these events FAST was in the middle of the auroral zone and Polar was above the auroral zone in the near-Earth plasma sheet. Polar data were used to determine the conditions in the magnetotail at the time field-aligned acceleration was measured by FAST in the auroral zone. For each of the magnetotail drivers identified in the data study, the physics of field-aligned acceleration in the auroral region was examined using existing theoretical efforts and/or a long-system particle in cell simulation to model the magnetically connected region between the two satellites. Results from the study indicate that there are three main drivers of auroral acceleration: (1) field-aligned currents that lead to quasistatic parallel potential drops (parallel electric fields), (2) earthward flow of high-energy plasma beams from the magnetotail into the auroral zone that lead to quasistatic parallel potential drops, and (3) large-amplitude Alfven waves that propagate into the auroral region from the magnetotail. The events examined thus far confm the previously established invariant latitudinal dependence of the drivers and show a strong dependence on magnetic activity. Alfven waves tend to occur primarily at the poleward edge of the auroral region during more magnetically active times and are correlated with intense electron precipitation. At lower latitudes away from the poleward edge of the auroral zone is the primary field-aligned current region which results in the classical field- aligned acceleration associated with the auroral zone (electrons earthward and ion beams tailward). During times of high magnetic activity, high-energy ion beams originating from the magnetotail are observed within, and overlapping, the regions of primary and return field-aligned current. Along the field lines where the high-energy magnetotail ion beams are located, field-aligned acceleration can occur in the auroral zone leading to precipitating electrons and upwelling ionospheric ion beams. Field-aligned currents are present during both quiet and active times, while the Alfven waves and magnetotail ion beams were observed only during more magnetically active events.

Guided flows in coronal magnetic flux tubes

NASA Astrophysics Data System (ADS)

Petralia, A.; Reale, F.; Testa, P.

2018-01-01

Context. There is evidence that coronal plasma flows break down into fragments and become laminar. Aims: We investigate this effect by modelling flows confined along magnetic channels. Methods: We consider a full magnetohydrodynamic (MHD) model of a solar atmosphere box with a dipole magnetic field. We compare the propagation of a cylindrical flow perfectly aligned with the field to that of another flow with a slight misalignment. We assume a flow speed of 200 km s-1 and an ambient magnetic field of 30 G. Results: We find that although the aligned flow maintains its cylindrical symmetry while it travels along the magnetic tube, the misaligned one is rapidly squashed on one side, becoming laminar and eventually fragmented because of the interaction and back-reaction of the magnetic field. This model could explain an observation made by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory of erupted fragments that fall back onto the solar surface as thin and elongated strands and end up in a hedge-like configuration. Conclusions: The initial alignment of plasma flow plays an important role in determining the possible laminar structure and fragmentation of flows while they travel along magnetic channels. Movies are available in electronic form at http://www.aanda.org

Electronic and magnetic properties of bare armchair BC2N nanoribbons

NASA Astrophysics Data System (ADS)

Li, Hong; Xiao, Xiang; Tie, Jun; Lu, Jing

2017-03-01

We present the electronic and magnetic properties of bare armchair BC2N nanoribbons (ABC2NNRs) in the view of density functional calculations. We consider three types of edge terminations with a width of 0.75 2.10 nm. All the investigated ribbons exhibit magnetic ground states with the magnetic moments mainly located on the edge C atoms. Room temperature accessible magnetic stabilities are obtained for ABC2NNRs with NC-NC and NC-BC edge alignments. We find the ABC2NNRs have various electronic structures, where half-metal, metal, and semiconductor are all acquired depend on the edge alignment and magnetic coupling state. The results show the ABC2NNRs can be a promising candidate material in nanoelectronics and nanospintronics.

Magnetic Field Strengths and Grain Alignment Variations in the Local Bubble Wall

NASA Astrophysics Data System (ADS)

Medan, Ilija; Andersson, B.-G.

2018-01-01

Optical and infrared continuum polarization is known to be due to irregular dust grains aligned with the magnetic field. This provides an important tool to probe the geometry and strength of those fields, particularly if the variations in the grain alignment efficiencies can be understood. Here, we examine polarization variations observed throughout the Local Bubble for b>30○, using a large polarization survey of the North Galactic cap from Berdyugin et al. (2014). These data are supported by archival photometric and spectroscopic data along with the mapping of the Local Bubble by Lallement et al. (2003). We can accurately model the observational data assuming that the grain alignment variations are due to the radiation from the OB associations within 1 kpc of the sun. This strongly supports radiatively driven grain alignment. We also probe the relative strength of the magnetic field in the wall of the Local Bubble using the Davis-Chandrasekhar-Fermi method. We find evidence for a bimodal field strength distribution, where the variations in the field are correlated with the variations in grain alignment efficiency, indicating that the higher strength regions might represent a compression of the wall by the interaction of the outflow in the Local Bubble and the opposing flows by the surrounding OB associations.

Microstructure evaluation for Dy-free Nd-Fe-B sintered magnets with high coercivity

NASA Astrophysics Data System (ADS)

Goto, R.; Matsuura, M.; Sugimoto, S.; Tezuka, N.; Une, Y.; Sagawa, M.

2012-04-01

Nd-Fe-B sintered magnets are used for motors of hybrid or electric vehicles due to their high energy products. Dy is added to Nd-Fe-B sintered magnets to work in a high temperature environment. Although the addition of Dy decreases the magnetization of Nd-Fe-B magnets, it increases coercivity; a decrease in the amount of Dy is strongly required. Recently, Nd-Fe-B sintered magnets with a grain size of 1 μm achieved high coercivity of ˜20 kOe without the addition of Dy or other heavy rare earth elements. In this paper, the microstructure of their magnets was observed and compared to magnets with a grain size of ˜3 μm. The coercivity of magnets consisting of larger particles was 17 kOe. Microstructures were observed by the scanning electron microscope and the shapes of grains and the distribution of the Nd-rich phase were evaluated. The observation was promoted in two directions. One direction is the plane perpendicular to the magnetically aligned direction (c plane side) and the other is the side parallel to the magnetically aligned direction (c axis side). For magnets consisting of smaller particles, the shapes of grains are isotropic for the c plane side and elongated for the c axis side. The angle of minor axis prefers to be parallel to magnetically aligned direction. The distribution of the Nd-rich phase for magnets was also evaluated for both magnets. The distribution of the Nd-rich phase at triple junctions for the magnets with smaller particles becomes homogeneous compared to that for magnets with larger particles. It is considered that Dy-free magnets with high coercivity were realized by the achievement of homogeneous distribution of Nd-rich phase besides decreasing grain size.

Magnetic quenching of photonic activity in Fe3O4-elastomer composite

NASA Astrophysics Data System (ADS)

Ma, Danhao; Hess, Dustin T.; Shetty, Pralav P.; Adu, Kofi W.; Bell, Richard C.; Terrones, Mauricio

2016-01-01

We report a quenching phenomenon within the visible region of the electromagnetic spectrum in the photonic response of a passive Fe3O4-silicone elastomer composite film due to magnetically aligned Fe3O4 nanoparticles. We performed systematic studies of the polarization dependence, the effect of particle size, and an in- and out-of-plane particle alignment on the optical response of the Fe3O4-silicone elastomer composites using a UV/vis/NIR spectrometer. We observed systematic redshifts in the response of the out-of-plane composite films with increasing particle alignment and weight that are attributed to dipole-induced effects. There were no observable shifts in the spectra of the in-plane films, suggesting the orientation of the magnetic dipole and the induced electric dipole play a crucial role in the optical response. A dramatic suppression to near quenching of the photonic response occurred in films containing moderate concentrations of the aligned nanoparticles. This is attributed to the interplay between the intra- and the interparticle dipoles. This occurred even when low magnetic fields were used during the curing process, suggesting that particle alignment and particle size limitation are critical in the manipulation of the photonic properties. A dipole approximation model is used to explain the quenching phenomenon. An active system of such a composite has a potential application in magneto-optic switches.

Sequential magnetic switching in Fe/MgO(001) superlattices

NASA Astrophysics Data System (ADS)

Magnus, F.; Warnatz, T.; Palsson, G. K.; Devishvili, A.; Ukleev, V.; Palisaitis, J.; Persson, P. O. Å.; Hjörvarsson, B.

2018-05-01

Polarized neutron reflectometry is used to determine the sequence of magnetic switching in interlayer exchange coupled Fe/MgO(001) superlattices in an applied magnetic field. For 19.6 Å thick MgO layers we obtain a 90∘ periodic magnetic alignment between adjacent Fe layers at remanence. In an increasing applied field the top layer switches first followed by its second-nearest neighbor. For 16.4 Å MgO layers, a 180∘ periodic alignment is obtained at remanence and with increasing applied field the layer switching starts from the two outermost layers and proceeds inwards. This sequential tuneable switching opens up the possibility of designing three-dimensional magnetic structures with a predefined discrete switching sequence.

Engineering survey planning for the alignment of a particle accelerator: part I. Proposition of an assessment method

NASA Astrophysics Data System (ADS)

Junqueira Leão, Rodrigo; Raffaelo Baldo, Crhistian; Collucci da Costa Reis, Maria Luisa; Alves Trabanco, Jorge Luiz

2018-03-01

The performance of particle accelerators depends highly on the relative alignment between their components. The position and orientation of the magnetic lenses that form the trajectory of the charged beam is kept to micrometric tolerances in a range of hundreds of meters of the length of the machines. Therefore, the alignment problem is fundamentally of a dimensional metrology nature. There is no common way of expressing these tolerances in terms of terminology and alignment concept. The alignment needs for a certain machine is normally given in terms of deviations between the position of any magnet in the accelerator and the fitted line that relates the actual position of the magnets’ assembly. Root mean square errors and standard deviations are normally used interchangeably and measurement uncertainty is often neglected. Although some solutions have been employed successfully in several accelerators, there is no off-the-shelf solution to perform the alignment. Also, each alignment campaign makes use of different measuring instruments to achieve the desired results, which makes the alignment process a complex measurement chain. This paper explores these issues by reviewing the tolerances specified for the alignment of particle accelerators, and proposes a metric to assess the quality of the alignment. The metric has the advantage of fully integrating the measurement uncertainty in the process.

Methods used to identify seafloor spreading magnetic anomalies and to establish their relationship with the top of the basement topography in the Argentine continental margin between 35° S and 48° S

NASA Astrophysics Data System (ADS)

Abraham, D. A.; Ghidella, M. E.; Tassone, A.; Paterlini, M.; Ancarola, M.

2013-05-01

This paper discusses some methods for better identification of the spreading seafloor magnetic anomalies in the region between 35° S and 48° S at the outer edge of the continental margin of Argentina. In the area of Rio de la Plata craton and Patagonia Argentina, there is an extensional volcanic passive margin. This segment of the Atlantic continental margin is characterized by the existence of seismic reflectors sequences that lean toward the sea (seaward dipping reflectors - SDRs). These sequences of seismic reflectors, located in the transitional-continental basement wedge, are portrayed in seismic profiles as an interference pattern interpreted as basalt flows intercalated with sedimentary layers, and its origin is ascribed to volcanism occurred during the Early Cretaceous. The magnetic response of SDRs is in the area of the magnetic anomaly G (Rabinowitz and LaBrecque, 1979). Magnetic alignments are highlighted on a map by superimposing total field anomaly semitransparent layer of calculated numerical curvature. This method allows a regional identification of the most prominent alignments. It is convenient to calculate the curvature in the direction perpendicular to the magnetic alignments. The identification of seafloor spreading magnetic anomalies located in the eastern margin helps in the knowledge of the history of the Atlantic Ocean opening. M series magnetic alignments: M5n, M3n M0r (between 132 and 120 Ma) were identified in the analyzed area. The roughness of the top of the oceanic basement presents a contrast of amplitudes, in a wavelength range between about 4 km and 6 km, with the corresponding amplitudes in the area of the transitional crust. This contrast of amplitudes can be detected using spectral methods, especially short Fourier transform. The quantitative evaluation of the spectral energy density allowed the identification of wave numbers characterizing oceanic basement area and thus perform subsequent filtering of the signal with wavelengths found with the spectral method. The top of basement roughness was quantified using the root mean square (RMS), in sections of about 2 km, of residues between the depth of the basement top and first-degree polynomial that best fitted the sections. The spreading seafloor magnetic alignments are on oceanic crust area identified by the point of view of the roughness analysis. The combined use of the methods that we have developed on the magnetic surveys in the study area, allowed us to improve the layout of the magnetic alignments and identify the transition between oceanic and continental crust.

High-Field Magnetization Study of R_{2} {Fe}_{17} {N}_{2} R 2 Fe 17 N 2 ( R = {Ho} R = Ho and Er) Nitrides

NASA Astrophysics Data System (ADS)

Tereshina, I. S.; Tereshina-Chitrova, E. A.; Pelevin, I. A.; Doerr, M.; Law, J. M.; Verbetski, V. N.; Salamova, A. A.

2018-03-01

The structure and magnetic properties of the nitrided compounds R2Fe_{17}N2 (R = Ho and Er) are studied. The type of crystal structure Th2Ni_{17} is preserved upon nitrogenation, and the relative unit cell volume Δ V{/}V increase exceeds 6%. Magnetic studies are performed in fields up to 60 T at 4.2 K on aligned powder samples. Field-induced spin-reorientation (SR) transitions are observed in the M( H) curves of R2Fe_{17}N2. Unlike the parent R2Fe_{17} compounds, where the magnetization increases in steps as the field grows stronger, R2Fe_{17}N2 demonstrate a gradual increase in magnetization. It is indicative of the change of the SR transition from first to the second type. Extrapolation of magnetization curves to the theoretical value of magnetization in the forced ferromagnetic state yields the coefficient of the inter-sublattice R-Fe exchange interaction. The inter-sublattice exchange is found to decrease upon nitrogenation.

Magnetic polarons in antiferromagnetic CaMnO3-x (x<0.01) probed by O17 NMR

NASA Astrophysics Data System (ADS)

Trokiner, A.; Verkhovskii, S.; Yakubovskii, A.; Gerashenko, A.; Monod, P.; Kumagai, K.; Mikhalev, K.; Buzlukov, A.; Litvinova, Z.; Gorbenko, O.; Kaul, A.; Kartavtzeva, M.

2009-06-01

We study with O17 NMR and bulk magnetization a lightly electron doped CaMnO3-x (x<0.01) polycrystalline sample in the G -type antiferromagnetic state. The O17 NMR spectra show two lines with very different intensities corresponding to oxygen sites with very different local magnetic environments. The more intense unshifted line is due to the antiferromagnetic (AF) matrix. The thermal dependence of the magnetic moment of the AF sublattice deduced from the O17 linewidth is typical of insulating three-dimensional Heisenberg antiferromagnets. The less intense, strongly shifted line directly evidences the existence of ferromagnetic (FM) domains embedded in the AF spin lattice. The extremely narrow line in zero magnetic field indicates a nearly perfect alignment of the manganese spins in the FM domains which also display an unusually weak temperature dependence of their magnetic moment. We show that these FM entities start to move above 40 K in a slow-diffusion regime. These static and dynamic properties bear a strong similarity with those of a small size self-trapped magnetic polaron.

Magnetic field structure around cores with very low luminosity objects

NASA Astrophysics Data System (ADS)

Soam, A.; Maheswar, G.; Lee, Chang Won; Dib, Sami; Bhatt, H. C.; Tamura, Motohide; Kim, Gwanjeong

2015-01-01

Aims: We carried out optical polarimetry of five dense cores, (IRAM 04191, L1521F, L328, L673-7, and L1014) which are found to harbour very low luminosity objects (VeLLOs; Lint ≲ 0.1 L⊙). This study was conducted mainly to understand the role played by the magnetic field in the formation of very low and substellar mass range objects. Methods: Light from the stars, while passing through the dust grains that are aligned with their short axis parallel to an external magnetic field, becomes linearly polarised. The polarisation position angles measured for the stars can provide the plane-of-the sky magnetic field orientation. Because the light in the optical wavelength range is most efficiently polarised by the dust grains typically found at the outer layers of the molecular clouds, optical polarimetry mostly traces the magnetic field orientation of the core envelope. Results: The polarisation observations of stars projected on IRAM 04191, L328, L673-7, and L1014 were obtained in the R-band and those of L1521F were obtained in the V-band. The angular offsets between the envelope magnetic field direction (inferred from optical polarisation measurements) and the outflow position angles from the VeLLOs in IRAM 04191, L1521F, L328, L673-7, and L1014 are found to be 84°, 53°, 24°, 08°, and 15°, respectively. The mean value of the offsets for all the five clouds is ~ 37°. If we exclude IRAM 04191, the mean value reduces to become ~ 25°. In IRAM 04191, the offset between the projected envelope and the inner magnetic field (inferred from the submillimetre data obtained using SCUBA-POL) is found to be ~ 68°. The inner magnetic field, however, is found to be nearly aligned with the projected position angles of the minor axis, the rotation axis of the cloud, and the outflow from the IRAM 04191-IRS. We discuss a possible explanation for the nearly perpendicular orientation between the envelope and core scale magnetic fields in IRAM 04191. The angular offset between the envelope magnetic field direction and the minor axis of IRAM 04191, L1521F, L673-7, and L1014 are 82°, 60°, 47°, and 55°, respectively. The mean value of the offsets between the envelope magnetic field and the minor axis position angles for the four cores is found to be ~ 60°. Conclusions: The results obtained from our study on the limited sample of five cores with VeLLOs show that the outflows in three of them tend to nearly align with the envelope magnetic field. Table 4 is available in electronic form at http://www.aanda.org

A 4 K cryogenic probe for use in magnetic resonance force microscopy experiments

NASA Astrophysics Data System (ADS)

Smith, Doran D.; Alexson, Dimitri A.; Garbini, Joseph L.

2013-09-01

The detailed design of a mechanically detected nuclear magnetic resonance probe using the SPAM (Springiness Preservation by Aligning Magnetization) geometry, operating at 4 K, in vacuum, and a several-Tesla magnetic field is described. The probe head is vibration-isolated well enough from the environment by a three-spring suspension system that the cantilever achieves thermal equilibrium with the environment without the aid of eddy current damping. The probe uses an ultra-soft Si cantilever with a Ni sphere attached to its tip, and magnetic resonance is registered as a change in the resonant frequency of the driven cantilever. The RF system uses frequency sweeps for adiabatic rapid passage using a 500 μm diameter RF coil wound around a sapphire rod. The RF coil and optical fiber of the interferometer used to sense the cantilever's position are both located with respect to the cantilever using a Garbini micropositioner, and the sample stage is mounted on an Attocube nanopositioner.

Growth of carbon nanofibers on tipless cantilevers: process development and applications in scanning probe microscopy

NASA Astrophysics Data System (ADS)

Cui, Hongtao; Kalinin, Sergei; Yang, Xiaojing; Lowndes, Douglas

2005-03-01

Carbon nanofibers (CNFs) are grown on tipless cantilevers as probe tips for scanning probe microscopy. A catalyst dot pattern is formed on the surface of the tipless cantilever using electron beam lithography and CNF growth is performed in a direct-current plasma enhanced chemical vapor deposition reactor. Because the CNF is aligned with the electric field near the edge of the cantilever during growth, it is tilted with respect to the cantilever surface, which compensates partially for the probe tilt introduced when used in scanning probe microscopy. CNFs with different shapes and tip radii can be produced by variation of experimental conditions. The tip geometries of the CNF probes are defined by their catalyst particles, whose magnetic nature also imparts a capability for imaging magnetic samples. We have demonstrated their use in both atomic force and magnetic force surface imaging. These probe tips may provide information on magnetic phenomena at the nanometer scale in connection with the drive for ever-increasing storage density of magnetic hard disks.

Highly anisotropic magneto-transport and field orientation dependent oscillations in aligned carbon nanotube/epoxy composites

NASA Astrophysics Data System (ADS)

Wells, Brian; Kumar, Raj; Reynolds, C. Lewis; Peters, Kara; Bradford, Philip D.

2017-12-01

Carbon nanotubes (CNTs) have been widely investigated as additive materials for composites with potential applications in electronic devices due to their extremely large electrical conductivity and current density. Here, highly aligned CNT composite films were created using a sequential layering fabrication technique. The degree of CNT alignment leads to anisotropic resistance values which varies >400× in orthogonal directions. Similarly, the magnetoresistance (MR) of the CNT composite differs depending upon the relative direction of current and the applied magnetic field. A suppression of negative to positive MR crossover was also observed. More importantly, an overall positive magnetoresistance behavior with localized +/- oscillations was discovered at low fields which persists up to room temperature when the current (I) and in-plane magnetic field (B) were parallel to the axis of CNT (B∥I∥CNT), which is consistent with Aharonov-Bohm oscillations in our CNT/epoxy composites. When the current, applied magnetic field, and nanotube axis are aligned, the in-plane MR is positive instead of negative as observed for all other field, current, and tube orientations. Here, we provide in-depth analysis of the conduction mechanism and anisotropy in the magneto-transport properties of these aligned CNT-epoxy composites.

Radiative Grain Alignment in Protoplanetary Disks: Implications for Polarimetric Observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tazaki, Ryo; Lazarian, Alexandre; Nomura, Hideko, E-mail: rtazaki@kusastro.kyoto-u.ac.jp

2017-04-10

We apply the theory of radiative torque (RAT) alignment for studying protoplanetary disks around a T-Tauri star and perform 3D radiative transfer calculations to provide the expected maps of polarized radiation to be compared with observations, such as with ALMA. We revisit the issue of grain alignment for large grains expected in the protoplanetary disks and find that mm-sized grains at the midplane do not align with the magnetic field since the Larmor precession timescale for such large grains becomes longer than the gaseous damping timescale. Hence, for these grains the RAT theory predicts that the alignment axis is determinedmore » by the grain precession with respect to the radiative flux. As a result, we expect that the polarization will be in the azimuthal direction for a face-on disk. It is also shown that if dust grains have superparamagnetic inclusions, magnetic field alignment is possible for (sub-)micron grains at the surface layer of disks, and this can be tested by mid-infrared polarimetric observations.« less

Label-Free Alignment of Nonmagnetic Particles in a Small Uniform Magnetic Field.

PubMed

Wang, Zhaomeng; Wang, Ying; Wu, Rui Ge; Wang, Z P; Ramanujan, R V

2018-01-01

Label-free manipulation of biological entities can minimize damage, increase viability and improve efficiency of subsequent analysis. Understanding the mechanism of interaction between magnetic and nonmagnetic particles in an inverse ferrofluid can provide a mechanism of label-free manipulation of such entities in a uniform magnetic field. The magnetic force, induced by relative magnetic susceptibility difference between nonmagnetic particles and surrounding magnetic particles as well as particle-particle interaction were studied. Label-free alignment of nonmagnetic particles can be achieved by higher magnetic field strength (Ba), smaller particle spacing (R), larger particle size (rp1), and higher relative magnetic permeability difference between particle and the surrounding fluid (Rμr). Rμr can be used to predict the direction of the magnetic force between both magnetic and nonmagnetic particles. A sandwich structure, containing alternate layers of magnetic and nonmagnetic particle chains, was studied. This work can be used for manipulation of nonmagnetic particles in lab-on-a-chip applications.

Elliptically polarizing adjustable phase insertion device

DOEpatents

Carr, Roger

1995-01-01

An insertion device for extracting polarized electromagnetic energy from a beam of particles is disclosed. The insertion device includes four linear arrays of magnets which are aligned with the particle beam. The magnetic field strength to which the particles are subjected is adjusted by altering the relative alignment of the arrays in a direction parallel to that of the particle beam. Both the energy and polarization of the extracted energy may be varied by moving the relevant arrays parallel to the beam direction. The present invention requires a substantially simpler and more economical superstructure than insertion devices in which the magnetic field strength is altered by changing the gap between arrays of magnets.

Relationships between field-aligned currents, electric fields, and particle precipitation as observed by Dynamics Explorer-2

NASA Technical Reports Server (NTRS)

Sugiura, M.; Iyemori, T.; Hoffman, R. A.; Maynard, N. C.; Burch, J. L.; Winningham, J. D.

1984-01-01

The relationships between field-aligned currents, electric fields, and particle fluxes are determined using observations from the polar orbiting low-altitude satellite Dynamics Explorer-2. It is shown that the north-south electric field and the east-west magnetic field components are usually highly correlated in the field-aligned current regions. This proportionality observationally proves that the field-aligned current equals the divergence of the height-integrated ionospheric Pedersen current in the meridional plane to a high degree of approximation. As a general rule, in the evening sector the upward field-aligned currents flow in the boundary plasma sheet region and the downward currents flow in the central plasma sheet region. The current densities determined independently from the plasma and magnetic field measurements are compared. Although the current densities deduced from the two methods are in general agreement, the degree and extent of the agreement vary in individual cases.

Relationships between field-aligned currents, electric fields and particle precipitation as observed by dynamics Explorer-2

NASA Technical Reports Server (NTRS)

Sugiura, M.; Iyemori, T.; Hoffman, R. A.; Maynard, N. C.; Burch, J. L.; Winningham, J. D.

1983-01-01

The relationships between field-aligned currents, electric fields, and particle fluxes are determined using observations from the polar orbiting low-altitude satellite Dynamics Explorer-2. It is shown that the north-south electric field and the east-west magnetic field components are usually highly correlated in the field-aligned current regions. This proportionality observationally proves that the field-aligned current equals the divergence of the height-integrated ionospheric Pedersen current in the meridional plane to a high degree of approximation. As a general rule, in the evening sector the upward field-aligned currents flow in the boundary plasma sheet region and the downward currents flow in the central plasma sheet region. The current densities determined independently from the plasma and magnetic field measurements are compared. Although the current densities deduced from the two methods are in general agreement, the degree and extent of the agreement vary in individual cases.

Anisotropic Light Scattering from Ferrofluids

NASA Astrophysics Data System (ADS)

Rablau, Corneliu; Vaishnava, Prem; Naik, Ratna; Lawes, Gavin; Tackett, Ron; Sudakar, C.

2008-03-01

We have investigated the light scattering in DC magnetic fields from aqueous suspensions of Fe3O4 nanoparticles coated with tetra methyl ammonium hydroxide and γ-Fe2O3 nanoparticles embedded in alginate hydrogel. For Fe3O4 ferrofluid, anomalous light scattering behavior was observed when light propagated both parallel and perpendicular to the magnetic fields. This behavior is attributed to the alignment and aggregation of the nanoparticles in chain-like structures. A very different light scattering behavior was observed for γ-Fe2O3 alginate sample where, under the similar conditions, the application of the magnetic field produced no structured change in scattering. We attribute this difference to the absence of chain-like structures and constrained mobility of iron nanoparticles in the alginate sample. The observation is in agreement with our relaxation and dissipative heating results^1 where both samples exhibited Neel relaxation but only the Fe3O4 ferrofluid showed Brownian relaxation. The results suggest that Brownian relaxation and nanoparticle mobility are important for producing non-linear light scattering in such systems. ^1P.P. Vaishnava, R. Tackett, A. Dixit, C. Sudakar, R. Naik, and G. Lawes, J. Appl. Phys. 102, 063914 (2007).

Electrical-current-induced magnetic hysteresis in self-assembled vertically aligned L a 2 / 3 S r 1 / 3 Mn O 3 : ZnO nanopillar composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, W.; Lu, P.; Ihlefeld, J. F.

Magnetoresistive random-access memory (MRAM) is poised to become a next-generation information storage device. Yet, many materials challenges remain unsolved before it can become a widely used memory storage solution. Among them, an urgent need is to identify a material system that is suitable for downscaling and is compatible with low-power logic applications. Self-assembled, vertically aligned La 2/3Sr 1/3MnO 3: ZnO nanocomposites, in which La 2/3Sr 1/3MnO 3 (LSMO) matrix and ZnO nanopillars form an intertwined structure with coincident-site-matched growth occurring between the LSMO and ZnO vertical interfaces, may offer new MRAM applications by combining their superior electric, magnetic ( Bmore » ), and optical properties. Here, in this Rapid Communication, we show the results of electrical current induced magnetic hysteresis in magnetoresistance measurements in these nanopillar composites. We observe that when the current level is low, for example, 1 µA, the magnetoresistance displays a linear, negative, nonhysteretic B field dependence. Surprisingly, when a large current is used, I > 10 µA, a hysteretic behavior is observed when the B field is swept in the up and down directions. This hysteresis weakens as the sample temperature is increased. Finally, a possible spin-valve mechanism related to this electrical current induced magnetic hysteresis is proposed and discussed.« less

Electrical-current-induced magnetic hysteresis in self-assembled vertically aligned L a 2 / 3 S r 1 / 3 Mn O 3 : ZnO nanopillar composites

DOE PAGES

Pan, W.; Lu, P.; Ihlefeld, J. F.; ...

2018-02-22

Magnetoresistive random-access memory (MRAM) is poised to become a next-generation information storage device. Yet, many materials challenges remain unsolved before it can become a widely used memory storage solution. Among them, an urgent need is to identify a material system that is suitable for downscaling and is compatible with low-power logic applications. Self-assembled, vertically aligned La 2/3Sr 1/3MnO 3: ZnO nanocomposites, in which La 2/3Sr 1/3MnO 3 (LSMO) matrix and ZnO nanopillars form an intertwined structure with coincident-site-matched growth occurring between the LSMO and ZnO vertical interfaces, may offer new MRAM applications by combining their superior electric, magnetic ( Bmore » ), and optical properties. Here, in this Rapid Communication, we show the results of electrical current induced magnetic hysteresis in magnetoresistance measurements in these nanopillar composites. We observe that when the current level is low, for example, 1 µA, the magnetoresistance displays a linear, negative, nonhysteretic B field dependence. Surprisingly, when a large current is used, I > 10 µA, a hysteretic behavior is observed when the B field is swept in the up and down directions. This hysteresis weakens as the sample temperature is increased. Finally, a possible spin-valve mechanism related to this electrical current induced magnetic hysteresis is proposed and discussed.« less

SPAR X Technical Report for Experiment 76-22 Directional Solidification of Magnetic Composites

NASA Technical Reports Server (NTRS)

Bethin, J.

1984-01-01

The effects of gravity on Bridgman-Stockbarger directional solidification of off-eutectic Bi/MnBi were studied in reduced gravity aboard the SPAR X flight and compared to normal-gravity investigations and previous eutectic Bi/MnBi SPAR flight experiments. The directional solidification of off-eutectic Bi/MnBi results in either a dendritic structure connected with local cooperative growth or a coupled low volume fraction faceted/non faceted aligned rod eutectic whose Mn macrosegregation, MnBi rod size, interrod spacing, and thermal and magnetic properties are sensitive functions of the solidification processing conditions. Two hypoeutectic and two hypereutectic samples were solidified during 605 sec of furnace travel, with an initial 265 sec low-gravity interval. Comparison Earth-gravity samples were solidified in the same furance assembly under identical processing conditions. Macrosegregation in the low-g samples was consistent with a metastable increase in Mn solubility in the Bi matrix, in partial agreement with previous Bi/MnBi SPAR findings of MnBi volume reduction.

Current distribution and ac susceptibility response of a thin superconducting disc in an axial field: a theoretical approach

NASA Astrophysics Data System (ADS)

Aruna, S. A.; Zhang, P.; Lin, F. Y.; Ding, S. Y.; Yao, X. X.

2000-04-01

Within the framework of the thermally activated process of the flux line or flux line bundles, and by time integration of the 1D equation of motion of the circulating current density icons/Journals/Common/vecJ" ALT="vecJ" ALIGN="TOP"/> (icons/Journals/Common/rho" ALT="rho" ALIGN="TOP"/> ,t ), which is suitable for thin superconducting films (R >>d ,icons/Journals/Common/le" ALT="le" ALIGN="TOP"/> icons/Journals/Common/lambda" ALT="lambda" ALIGN="TOP"/> ), we present numerical calculations of the current profiles, magnetization hysteresis loops and ac susceptibility icons/Journals/Common/chi" ALT="chi" ALIGN="TOP"/> n = icons/Journals/Common/chi" ALT="chi" ALIGN="TOP"/> ´n +iicons/Journals/Common/chi" ALT="chi" ALIGN="TOP"/> ´´n for n = 1, 3 and 5 of a thin disc immersed in an axial time-dependent external magnetic field Ba (t ) = Bdc +Bac cos(2icons/Journals/Common/pi" ALT="pi" ALIGN="TOP"/> icons/Journals/Common/nu" ALT="nu" ALIGN="TOP"/> t ). Our calculated results are compared with those of the critical state model (CSM) and found to prove the approximate validity of the CSM below the irreversibility field. The differences between our computed results and those of the CSM are also discussed.

Magnetic Fabric Associated with Faulting of Poorly Consolidated Basin Sediments of the Rio Grande Rift, New Mexico, USA

NASA Astrophysics Data System (ADS)

Hudson, M. R.; Minor, S. A.; Caine, J. S.

2015-12-01

Permanent strain in sediments associated with shallow fault zones can be difficult to characterize. Anisotropy of magnetic susceptibility (AMS) data were obtained from 120 samples at 6 sites to assess the nature of fault-related AMS fabrics for 4 faults cutting Miocene-Pliocene basin fill sediments of the Rio Grande rift of north-central New Mexico. The San Ysidro (3 sites), Sand Hill, and West Paradise faults within the northern Albuquerque basin have normal offset whereas an unnamed fault near Buckman in the western Española basin has oblique strike-slip offset. Previous studies have shown that detrital magnetite controls magnetic susceptibility in rift sandstones, and in a 50-m-long hanging wall traverse of the San Ysidro fault, non-gouge samples have typical sedimentary AMS fabrics with Kmax and Kint axes (defining magnetic foliation) scattered within bedding. For the 5 normal-fault sites, samples from fault cores or adjacent mixed zones that lie within 1 m of the principal slip surface developed common deformation fabrics with (1) magnetic foliation inclined in the same azimuth but more shallowly dipping than the fault plane, and (2) magnetic lineation plunging down foliation dip with nearly the same trend as the fault striae, although nearer for sand versus clay gouge samples. These relations suggest that the sampled fault materials deformed by particulate flow with alignment of magnetite grains in the plane of maximum shortening. For a 2-m-long traverse at the Buckman site, horizontal sedimentary AMS foliation persists to < 15 cm to the fault slip surface, wherein foliation in sand and clay gouge rotates toward the steeply dipping fault plane in a sense consistent with sinistral offset. Collectively these data suggest permanent deformation fabrics were localized within < 1 m of fault surfaces and that AMS fabrics from gouge samples can provide kinematic information for faults in unconsolidated sediments which may lack associated slickenlines.

Golden-ratio rotated stack-of-stars acquisition for improved volumetric MRI.

PubMed

Zhou, Ziwu; Han, Fei; Yan, Lirong; Wang, Danny J J; Hu, Peng

2017-12-01

To develop and evaluate an improved stack-of-stars radial sampling strategy for reducing streaking artifacts. The conventional stack-of-stars sampling strategy collects the same radial angle for every partition (slice) encoding. In an undersampled acquisition, such an aligned acquisition generates coherent aliasing patterns and introduces strong streaking artifacts. We show that by rotating the radial spokes in a golden-angle manner along the partition-encoding direction, the aliasing pattern is modified, resulting in improved image quality for gridding and more advanced reconstruction methods. Computer simulations were performed and phantom as well as in vivo images for three different applications were acquired. Simulation, phantom, and in vivo experiments confirmed that the proposed method was able to generate images with less streaking artifact and sharper structures based on undersampled acquisitions in comparison with the conventional aligned approach at the same acceleration factors. By combining parallel imaging and compressed sensing in the reconstruction, streaking artifacts were mostly removed with improved delineation of fine structures using the proposed strategy. We present a simple method to reduce streaking artifacts and improve image quality in 3D stack-of-stars acquisitions by re-arranging the radial spoke angles in the 3D partition direction, which can be used for rapid volumetric imaging. Magn Reson Med 78:2290-2298, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Registration of 3D fetal neurosonography and MRI☆

PubMed Central

Kuklisova-Murgasova, Maria; Cifor, Amalia; Napolitano, Raffaele; Papageorghiou, Aris; Quaghebeur, Gerardine; Rutherford, Mary A.; Hajnal, Joseph V.; Noble, J. Alison; Schnabel, Julia A.

2013-01-01

We propose a method for registration of 3D fetal brain ultrasound with a reconstructed magnetic resonance fetal brain volume. This method, for the first time, allows the alignment of models of the fetal brain built from magnetic resonance images with 3D fetal brain ultrasound, opening possibilities to develop new, prior information based image analysis methods for 3D fetal neurosonography. The reconstructed magnetic resonance volume is first segmented using a probabilistic atlas and a pseudo ultrasound image volume is simulated from the segmentation. This pseudo ultrasound image is then affinely aligned with clinical ultrasound fetal brain volumes using a robust block-matching approach that can deal with intensity artefacts and missing features in the ultrasound images. A qualitative and quantitative evaluation demonstrates good performance of the method for our application, in comparison with other tested approaches. The intensity average of 27 ultrasound images co-aligned with the pseudo ultrasound template shows good correlation with anatomy of the fetal brain as seen in the reconstructed magnetic resonance image. PMID:23969169

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nuhn, Heinz-Dieter.

The Visual to Infrared SASE Amplifier (VISA) [1] FEL is designed to achieve saturation at radiation wavelengths between 800 and 600 nm with a 4-m pure permanent magnet undulator. The undulator comprises four 99-cm segments each of which has four FODO focusing cells superposed on the beam by means of permanent magnets in the gap alongside the beam. Each segment will also have two beam position monitors and two sets of x-y dipole correctors. The trajectory walk-off in each segment will be reduced to a value smaller than the rms beam radius by means of magnet sorting, precise fabrication, andmore » post-fabrication shimming and trim magnets. However, this leaves possible inter-segment alignment errors. A trajectory analysis code has been used in combination with the FRED3D [2] FEL code to simulate the effect of the shimming procedure and segment alignment errors on the electron beam trajectory and to determine the sensitivity of the FEL gain process to trajectory errors. The paper describes the technique used to establish tolerances for the segment alignment.« less

Low temperature superconductor and aligned high temperature superconductor magnetic dipole system and method for producing high magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, Ramesh; Scanlan, Ronald; Ghosh, Arup K.

A dipole-magnet system and method for producing high-magnetic-fields, including an open-region located in a radially-central-region to allow particle-beam transport and other uses, low-temperature-superconducting-coils comprised of low-temperature-superconducting-wire located in radially-outward-regions to generate high magnetic-fields, high-temperature-superconducting-coils comprised of high-temperature-superconducting-tape located in radially-inward-regions to generate even higher magnetic-fields and to reduce erroneous fields, support-structures to support the coils against large Lorentz-forces, a liquid-helium-system to cool the coils, and electrical-contacts to allow electric-current into and out of the coils. The high-temperature-superconducting-tape may be comprised of bismuth-strontium-calcium-copper-oxide or rare-earth-metal, barium-copper-oxide (ReBCO) where the rare-earth-metal may be yttrium, samarium, neodymium, or gadolinium. Advantageously, alignment of themore » large-dimension of the rectangular-cross-section or curved-cross-section of the high-temperature-superconducting-tape with the high-magnetic-field minimizes unwanted erroneous magnetic fields. Alignment may be accomplished by proper positioning, tilting the high-temperature-superconducting-coils, forming the high-temperature-superconducting-coils into a curved-cross-section, placing nonconducting wedge-shaped-material between windings, placing nonconducting curved-and-wedge-shaped-material between windings, or by a combination of these techniques.« less

A FAR-INFRARED OBSERVATIONAL TEST OF THE DIRECTIONAL DEPENDENCE IN RADIATIVE GRAIN ALIGNMENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vaillancourt, John E.; Andersson, B.-G., E-mail: jvaillancourt@sofia.usra.edu, E-mail: bg@sofia.usra.edu

The alignment of interstellar dust grains with magnetic fields provides a key method for measuring the strength and morphology of the fields. In turn, this provides a means to study the role of magnetic fields from diffuse gas to dense star-forming regions. The physical mechanism for aligning the grains has been a long-term subject of study and debate. The theory of radiative torques, in which an anisotropic radiation field imparts sufficient torques to align the grains while simultaneously spinning them to high rotational velocities, has passed a number of observational tests. Here we use archival polarization data in dense regionsmore » of the Orion molecular cloud (OMC-1) at 100, 350, and 850 μm to test the prediction that the alignment efficiency is dependent upon the relative orientations of the magnetic field and radiation anisotropy. We find that the expected polarization signal, with a 180-degree period, exists at all wavelengths out to radii of 1.5 arcmin centered on the Becklin–Neugebauer Kleinmann-Low (BNKL) object in OMC-1. The probabilities that these signals would occur due to random noise are low (≲1%), and are lowest toward BNKL compared to the rest of the cloud. Additionally, the relative magnetic field to radiation anisotropy directions accord with theoretical predictions in that they agree to better than 15° at 100 μm and 4° at 350 μm.« less

Aligning Plasma-Arc Welding Oscillations

NASA Technical Reports Server (NTRS)

Norris, Jeff; Fairley, Mike

1989-01-01

Tool aids in alignment of oscillator probe on variable-polarity plasma-arc welding torch. Probe magnetically pulls arc from side to side as it moves along joint. Tensile strength of joint depends on alignment of weld bead and on alignment of probe. Operator installs new tool on front of torch body, levels it with built-in bubble glass, inserts probe in slot on tool, and locks probe in place. Procedure faster and easier and resulting alignment more accurate and repeatable.

Alignment of Irregular Grains by Mechanical Torques

NASA Astrophysics Data System (ADS)

Hoang, Thiem; Cho, Jungyeon; Lazarian, A.

2018-01-01

We study the alignment of irregular dust grains by mechanical torques due to the drift of grains through the ambient gas. We first calculate mechanical alignment torques (MATs) resulting from specular reflection of gas atoms for seven irregular shapes: one shape of mirror symmetry, three highly irregular shapes (HIS), and three weakly irregular shapes (WIS). We find that the grain with mirror symmetry experiences negligible MATs due to its mirror-symmetry geometry. Three HIS can produce strong MATs, which exhibit some generic properties as radiative torques (RATs), while three WIS produce less efficient MATs. We then study grain alignment by MATs for the different angles between the drift velocity and the ambient magnetic field, for paramagnetic and superparamagnetic grains assuming efficient internal relaxation. We find that for HIS grains, MATs can align subsonically drifting grains in the same way as RATs, with low-J and high-J attractors. For supersonic drift, MATs can align grains with low-J and high-J attractors, analogous to RAT alignment by anisotropic radiation. We also show that the joint action of MATs and magnetic torques in grains with iron inclusions can lead to perfect MAT alignment. Our results point out the potential importance of MAT alignment for HIS grains predicted by the analytical model of Lazarian & Hoang, although more theoretical and observational studies are required due to uncertainty in the shape of interstellar grains. We outline astrophysical environments where MAT alignment is potentially important.

Relaxation dynamics of magnetization transitions in synthetic antiferromagnet with perpendicular anisotropy

NASA Astrophysics Data System (ADS)

Talantsev, A.; Lu, Y.; Fache, T.; Lavanant, M.; Hamadeh, A.; Aristov, A.; Koplak, O.; Morgunov, R.; Mangin, S.

2018-04-01

Two synthetic antiferromagnet bilayer systems with strong perpendicular anisotropy CoFeB/Ta/CoFeB and Pt/Co/Ir/Co/Pt have been grown using sputtering techniques. For both systems two types of magnetization transitions have been studied. The first one concerns transitions from a state where magnetizations of the two magnetic layers are parallel (P state) to a state where magnetizations of the two layers are aligned antiparallel (AP state). The second one concerns transitions between the two possible antiparallel alignments (AP+  to AP-). For both systems and both transitions after-effect measurements can be understood in the frame of nucleation—propagation model. Time derivative analysis of magnetic relaxation curves and mapping of the first order reversal curves at different temperature allowed us to demonstrate the presence of different pinning centers, which number can be controlled by magnetic field and temperature.

Tracing Magnetic Fields With The Polarization Of Submillimeter Lines

NASA Astrophysics Data System (ADS)

Zhang, Heshou; Yan, Huirong

2017-10-01

Magnetic fields play important roles in many astrophysical processes. However, there is no universal diagnostic for the magnetic fields in the interstellar medium (ISM) and each magnetic tracer has its limitation. Any new detection method is thus valuable. Theoretical studies have shown that submillimeter fine-structure lines are polarized due to atomic alignment by Ultraviolet (UV) photon-excitation, which opens up a new avenue to probe interstellar magnetic fields. The method is applicable to all radiative-excitation dominant region, e.g., H II Regions, PDRs. The polarization of the submillimeter fine-structure lines induced by atomic alignment could be substantial and the applicability of using the spectro-polarimetry of atomic lines to trace magnetic fields has been supported by synthetic observations of simulated ISM in our recent paper. Our results demonstrate that the polarization of submillimeter atomic lines is a powerful magnetic tracer and add great value to the observational studies of the submilimeter astronomy.

Enhancing Mechanical and Thermal Properties of Epoxy Nanocomposites via Alignment of Magnetized SiC Whiskers.

PubMed

Townsend, James; Burtovyy, Ruslan; Aprelev, Pavel; Kornev, Konstantin G; Luzinov, Igor

2017-07-12

This research is focused on the fabrication and properties of epoxy nanocomposites containing magnetized SiC whiskers (MSiCWs). To this end, we report an original strategy for fabrication of magnetically active SiCWs by decorating the whiskers with magnetic (iron oxide) nanoparticles via polymer-polymer (poly(acrylic acid)/poly(2-vinyl pyridine)) complexation. The obtained whiskers demonstrated a substantial magnetic response in the polymerizing epoxy resin, with application of only a 20 mT (200 G) magnetic field. We also found that the whiskers chemically reacted with the epoxy resin, causing formation of an extended interphase near the boundary of the whiskers. The SiC whiskers oriented with the magnetic field demonstrated positive effects on the behavior of epoxy-based nanocomposites. Namely, the aligned MSiCWs enhanced the thermomechanical properties of the materials significantly above that of the neat epoxy and epoxy nanocomposite, with randomly oriented whiskers.

Making Macroscopic Assemblies of Aligned Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Smalley, Richard E.; Colbert, Daniel T.; Smith, Ken A.; Walters, Deron A.; Casavant, Michael J.; Qin, Xiaochuan; Yakobson, Boris; Hauge, Robert H.; Saini, Rajesh Kumar; Chiung, Wan-Ting;

Role of the antiferromagnetic pinning layer on spin wave properties in IrMn/NiFe based spin-valves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gubbiotti, G., E-mail: gubbiotti@fisica.unipg.it; Tacchi, S.; Del Bianco, L.

2015-05-07

Brillouin light scattering (BLS) was exploited to study the spin wave properties of spin-valve (SV) type samples basically consisting of two 5 nm-thick NiFe layers (separated by a Cu spacer of 5 nm), differently biased through the interface exchange coupling with an antiferromagnetic IrMn layer. Three samples were investigated: a reference SV sample, without IrMn (reference); one sample with an IrMn underlayer (10 nm thick) coupled to the bottom NiFe film; one sample with IrMn underlayer and overlayer of different thickness (10 nm and 6 nm), coupled to the bottom and top NiFe film, respectively. The exchange coupling with the IrMn, causing the insurgence ofmore » the exchange bias effect, allowed the relative orientation of the NiFe magnetization vectors to be controlled by an external magnetic field, as assessed through hysteresis loop measurements by magneto-optic magnetometry. Thus, BLS spectra were acquired by sweeping the magnetic field so as to encompass both the parallel and antiparallel alignment of the NiFe layers. The BLS results, well reproduced by the presented theoretical model, clearly revealed the combined effects on the spin dynamic properties of the dipolar interaction between the two NiFe films and of the interface IrMn/NiFe exchange coupling.« less

Nanocalorimeter platform for in situ specific heat measurements and x-ray diffraction at low temperature

NASA Astrophysics Data System (ADS)

Willa, K.; Diao, Z.; Campanini, D.; Welp, U.; Divan, R.; Hudl, M.; Islam, Z.; Kwok, W.-K.; Rydh, A.

2017-12-01

Recent advances in electronics and nanofabrication have enabled membrane-based nanocalorimetry for measurements of the specific heat of microgram-sized samples. We have integrated a nanocalorimeter platform into a 4.5 T split-pair vertical-field magnet to allow for the simultaneous measurement of the specific heat and x-ray scattering in magnetic fields and at temperatures as low as 4 K. This multi-modal approach empowers researchers to directly correlate scattering experiments with insights from thermodynamic properties including structural, electronic, orbital, and magnetic phase transitions. The use of a nanocalorimeter sample platform enables numerous technical advantages: precise measurement and control of the sample temperature, quantification of beam heating effects, fast and precise positioning of the sample in the x-ray beam, and fast acquisition of x-ray scans over a wide temperature range without the need for time-consuming re-centering and re-alignment. Furthermore, on an YBa2Cu3O7-δ crystal and a copper foil, we demonstrate a novel approach to x-ray absorption spectroscopy by monitoring the change in sample temperature as a function of incident photon energy. Finally, we illustrate the new insights that can be gained from in situ structural and thermodynamic measurements by investigating the superheated state occurring at the first-order magneto-elastic phase transition of Fe2P, a material that is of interest for magnetocaloric applications.

icoshift: A versatile tool for the rapid alignment of 1D NMR spectra

NASA Astrophysics Data System (ADS)

Savorani, F.; Tomasi, G.; Engelsen, S. B.

2010-02-01

The increasing scientific and industrial interest towards metabonomics takes advantage from the high qualitative and quantitative information level of nuclear magnetic resonance (NMR) spectroscopy. However, several chemical and physical factors can affect the absolute and the relative position of an NMR signal and it is not always possible or desirable to eliminate these effects a priori. To remove misalignment of NMR signals a posteriori, several algorithms have been proposed in the literature. The icoshift program presented here is an open source and highly efficient program designed for solving signal alignment problems in metabonomic NMR data analysis. The icoshift algorithm is based on correlation shifting of spectral intervals and employs an FFT engine that aligns all spectra simultaneously. The algorithm is demonstrated to be faster than similar methods found in the literature making full-resolution alignment of large datasets feasible and thus avoiding down-sampling steps such as binning. The algorithm uses missing values as a filling alternative in order to avoid spectral artifacts at the segment boundaries. The algorithm is made open source and the Matlab code including documentation can be downloaded from www.models.life.ku.dk.

John H. Dillon Medal Lecture: Magnetic Field Directed Self-Assembly of Block Copolymers and Surfactant Mesophases

NASA Astrophysics Data System (ADS)

Osuji, Chinedum

2015-03-01

Molecular self-assembly of block copolymers and small molecule surfactants gives rise to a rich phase behavior as a function of temperature, composition, and other variables. We consider the directed self-assembly of such soft mesophases using magnetic fields, principally through the use of in situ x-ray scattering studies. Field alignment is predicated on a sufficiently large product of magnetic anisotropy and grain size to produce magnetostatic interactions which are substantive relative to thermal forces. We examine the role of field strength on the phase behavior and alignment dynamics of a series of soft mesophases, outlining the possibility to readily create highly ordered functional materials over macroscopic length scales. We show that magnetic fields as large as 10 T have little discernable impact on the stability of block copolymer systems considered, with shifts in order-disorder transition temperatures of roughly 5 mK or smaller. Consequently, directed self-assembly in these systems proceeds by nucleation of randomly aligned grains which thereafter rotate into registry with the field. We highlight the tradeoff between decreasing mobility and increasing anisotropic field interaction that dictates alignment kinetics while transiting from a high temperature disordered state to an ordered system at lower temperatures. NSF support through DMR-0847534 is gratefully acknowledged.

Nanorobotic System iTRo for Controllable 1D Micro/nano Material Twisting Test.

PubMed

Lu, Haojian; Shang, Wanfeng; Wei, Xueyong; Yang, Zhan; Fukuda, Toshio; Shen, Yajing

2017-06-08

In-situ micro/nano characterization is an indispensable methodology for material research. However, the precise in-situ SEM twisting of 1D material with large range is still challenge for current techniques, mainly due to the testing device's large size and the misalignment between specimen and the rotation axis. Herein, we propose an in-situ twist test robot (iTRo) to address the above challenges and realize the precise in-situ SEM twisting test for the first time. Firstly, we developed the iTRo and designed a series of control strategies, including assembly error initialization, triple-image alignment (TIA) method for rotation axis alignment, deformation-based contact detection (DCD) method for sample assembly, and switch control for robots cooperation. After that, we chose three typical 1D material, i.e., magnetic microwire Fe 74 B 13 Si 11 C 2 , glass fiber, and human hair, for twisting test and characterized their properties. The results showed that our approach is able to align the sample to the twisting axis accurately, and it can provide large twisting range, heavy load and high controllability. This work fills the blank of current in-situ mechanical characterization methodologies, which is expected to give significant impact in the fundamental nanomaterial research and practical micro/nano characterization.

Elliptically polarizing adjustable phase insertion device

DOEpatents

Carr, R.

1995-01-17

An insertion device for extracting polarized electromagnetic energy from a beam of particles is disclosed. The insertion device includes four linear arrays of magnets which are aligned with the particle beam. The magnetic field strength to which the particles are subjected is adjusted by altering the relative alignment of the arrays in a direction parallel to that of the particle beam. Both the energy and polarization of the extracted energy may be varied by moving the relevant arrays parallel to the beam direction. The present invention requires a substantially simpler and more economical superstructure than insertion devices in which the magnetic field strength is altered by changing the gap between arrays of magnets. 3 figures.

Resonant optical alignment and orientation of Mn2+ spins in CdMnTe crystals

NASA Astrophysics Data System (ADS)

Baryshnikov, K. A.; Langer, L.; Akimov, I. A.; Korenev, V. L.; Kusrayev, Yu. G.; Averkiev, N. S.; Yakovlev, D. R.; Bayer, M.

2015-11-01

We report on spin orientation and alignment of Mn2 + ions in (Cd,Mn)Te diluted magnetic semiconductor crystals using resonant intracenter excitation with circular- and linear-polarized light. The resulting polarized emission of the magnetic ions is observed at low temperatures when the spin relaxation time of the Mn2 + ions is in the order of 1 ms , which considerably exceeds the photoluminescence decay time of 23 μ s . We demonstrate that the experimental data on optical orientation and alignment of Mn2 + ions can be explained using a phenomenological model that is based on the approximation of isolated centers.

Fracture Toughness Evaluation of a Ni2MnGa Alloy Through Micro Indentation Under Magneto-Mechanical Loading

NASA Astrophysics Data System (ADS)

Goanţă, Viorel; Ciocanel, Constantin

2017-12-01

Ni2MnGa is a ferromagnetic alloy that exhibits the shape memory effect either induced by an externally applied magnetic field or mechanical stress. Due to the former, the alloy is commonly called magnetic shape memory alloy or MSMA. The microstructure of the MSMA consists of tetragonal martensite variants (three in the most general case) that are characterized by a magnetization vector which is aligned with the short side of the tetragonal unit cell. Exposing the MSMA to a magnetic field causes the magnetization vector to rotate and align with the external field, eventually leading to variant reorientation. The variant reorientation is observed macroscopically in the form of recoverable strain of up to 6% [1, 2]. As the magnetic field induced reorientation happens instantaneously [1, 3], MSMAs are suitable for fast actuation, sensing, or power harvesting applications. However, actuation applications are limited by the maximum actuation stress of the material that is about 3.5MPa at approximately 2 to 3% reorientation strain. During MSMA fatigue magneto-mechanical characterization studies [4, 5] it was observed that cracks nucleate and grow on the surface of material samples, after a relatively small number of cycles, leading to loss in material performance. This triggered the need for understanding the mechanisms that govern crack nucleation and growth in MSMAs, as well as the nature of the material, i.e. ductile or brittle. The experimental study reported in this paper was carried out to determine material's fracture toughness, the predominant crack growth directions, and the orientation of the cracks relative to the mechanical loading direction and to the material's microstructure. A fixture has been developed to allow Vickers micro indentation of 3mm by 3mm by 20mm Ni2MnGa samples exposed to different levels of magnetic field and/or mechanical stress. Using the measured characteristics of the impression generated during micro indentation, the lengths of propagated cracks, and appropriate equations (introduced in the paper), and the fracture toughness was evaluated as a function of the magneto-mechanical loading experienced by the material. The influence of the magneto-mechanical loading on the growth of already nucleated cracks has also been evaluated.

Correlation of ICME Magnetic Fields at Radially Aligned Spacecraft

NASA Astrophysics Data System (ADS)

Good, S. W.; Forsyth, R. J.; Eastwood, J. P.; Möstl, C.

2018-03-01

The magnetic field structures of two interplanetary coronal mass ejections (ICMEs), each observed by a pair of spacecraft close to radial alignment, have been analysed. The ICMEs were observed in situ by MESSENGER and STEREO-B in November 2010 and November 2011, while the spacecraft were separated by more than 0.6 AU in heliocentric distance, less than 4° in heliographic longitude, and less than 7° in heliographic latitude. Both ICMEs took approximately two days to travel between the spacecraft. The ICME magnetic field profiles observed at MESSENGER have been mapped to the heliocentric distance of STEREO-B and compared directly to the profiles observed by STEREO-B. Figures that result from this mapping allow for easy qualitative assessment of similarity in the profiles. Macroscale features in the profiles that varied on timescales of one hour, and which corresponded to the underlying flux rope structure of the ICMEs, were well correlated in the solar east-west and north-south directed components, with Pearson's correlation coefficients of approximately 0.85 and 0.95, respectively; microscale features with timescales of one minute were uncorrelated. Overall correlation values in the profiles of one ICME were increased when an apparent change in the flux rope axis direction between the observing spacecraft was taken into account. The high degree of similarity seen in the magnetic field profiles may be interpreted in two ways. If the spacecraft sampled the same region of each ICME ( i.e. if the spacecraft angular separations are neglected), the similarity indicates that there was little evolution in the underlying structure of the sampled region during propagation. Alternatively, if the spacecraft observed different, nearby regions within the ICMEs, it indicates that there was spatial homogeneity across those different regions. The field structure similarity observed in these ICMEs points to the value of placing in situ space weather monitors well upstream of the Earth.

Self-propelled in-tube shuttle and control system for automated measurements of magnetic field alignment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boroski, W.N.; Nicol, T.H.; Pidcoe, S.V.

1990-03-01

A magnetic field alignment gauge is used to measure the field angle as a function of axial position in each of the magnets for the Superconducting Super Collider (SSC). Present measurements are made by manually pushing the through the magnet bore tube and stopping at intervals to record field measurements. Gauge location is controlled through graduation marks and alignment pins on the push rods. Field measurements are recorded on a logging multimeter with tape output. Described is a computerized control system being developed to replace the manual procedure for field alignment measurements. The automated system employs a pneumatic walking devicemore » to move the measurement gauge through the bore tube. Movement of the device, called the Self-Propelled In-Tube Shuttle (SPITS), is accomplished through an integral, gas driven, double-acting cylinder. The motion of the SPITS is transferred to the bore tube by means of a pair of controlled, retractable support feet. Control of the SPITS is accomplished through an RS-422 interface from an IBM-compatible computer to a series of solenoid-actuated air valves. Direction of SPITS travel is determined by the air-valve sequence, and is managed through the control software. Precise axial position of the gauge within the magnet is returned to the control system through an optically-encoded digital position transducer attached to the shuttle. Discussed is the performance of the transport device and control system during preliminary testing of the first prototype shuttle. 1 ref., 7 figs.« less

The mechanical life of magnetotactic bacteria inside sediments: implications for paleo- and environmental magnetism

NASA Astrophysics Data System (ADS)

Egli, Ramon; Mao, Xuegang

2015-04-01

Magnetotactic bacteria (MTB) are responsible for up to almost 100% of the magnetic signature of certain sediments through fossil reminders called magnetofossils. Besides being stable carriers of useful paleomagnetic signals, magnetofossils provide interesting environmental proxies that reflect MTB abundance variations due to nutrient supply and/or dilution by detrital/aeolian inputs. Unfortunately factors affecting MTB abundances in sediment are poorly known and based at best on extrapolations of observations on pure cultures. For example, MTB displacement models have been always based on the assumption that full alignment with the Earth magnetic field is possible, as observed in water. However, we recently found that the alignment of living MTB does not exceed few % inside sediments. This observation raises questions on the true nature of the biologic advantage of such bacteria over other motile organisms, and, ultimatively, on what is controlling their abundance in sediment. Here we report experiments that demonstrate the role of the Earth magnetic field in directing MTB to optimal living depths with the observed poor magnetic alignment. These exerments explain the apparent useless abundance of magnetosomes in certain MTB strains (e.g. M. Bavaricum) and reveal unexpected differences between strains with respect to their ability to cope with chemical signals and absent or reversed magnetic fields.

Aligning the magnetic field of a linear induction accelerator with a low-energy electron beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, J.C.; Deadrick, F.J.; Kallman, J.S.

1989-03-10

The Experimental Test Accelerator II (ETA-II) linear induction accelerator at Lawrence Livermore National Laboratory uses a solenoid magnet in each acceleration cell to focus and transport an electron beam over the length of the accelerator. To control growth of the corkscrew mode the magnetic field must be precisely aligned over the full length of the accelerate. Concentric with each solenoid magnet is sine/cosmic-wound correction coil to steer the beam and correct field errors. A low-energy electron probe traces the central flux line through the accelerator referenced to a mechanical axis that is defined by a copropagating laser beam. Correction coilsmore » are activated to force the central flux line to cross the mechanical axis at the end of each acceleration cell. The ratios of correction coil currents determined by the low-energy electron probe are then kept fixed to correct for field errors during normal operation with an accelerated beam. We describe the construction of the low-energy electron probe and report the results of experiments we conducted to measure magnetic alignment with and without the correction coils activated. 5 refs., 3 figs.« less

Broadband hybrid electromagnetic and piezoelectric energy harvesting from ambient vibrations and pneumatic vortices induced by running subway trains.

DOT National Transportation Integrated Search

2017-05-01

The airfoil-based electromagnetic energy harvester containing parallel array motion between moving coil and : trajectory matching multi-pole magnets was investigated. The magnets were aligned in an alternatively : magnetized formation of 6 magnets to...

Theory of fluorescence polarization in magnetically oriented photosynthetic systems.

PubMed Central

Knox, R S; Davidovich, M A

1978-01-01

Many cells and cell fragments are known to assume specific alignments with respect to an applied magnetic field. One indicator of this alignment is a difference between the intensities of fluorescence observed in polarizations parallel and perpendicular to the magnetic filed. We calculate these two intensities using a model that assumes axially symmetric membranes and that covers a wide variety of shapes from flat disk to right cylinder. The fluorescence is assumed to originate at chromophores randomly exicted but nonrandomly oriented in the membranes. The membrane alignment is assumed to be due to the net torque on a nonrandom distribution of diamagnetically anisotropic molecules. The predicted results are consistent with most magnetoorientation data from green cells, but we are able to show that Chlorella data are not consistent with the hypothesis that the membranes have, and maintain, a cuplike configuration. Images FIGURE 4 FIGURE 5 PMID:737283

Field-aligned particle currents near an auroral arc.

NASA Technical Reports Server (NTRS)

Choy, L. W.; Arnoldy, R. L.; Potter, W.; Kintner, P.; Cahill, L. J., Jr.

1971-01-01

A Nike-Tomahawk rocket equipped to measure electric and magnetic fields and charged particles from a few eV to several hundred keV energy was flown into an auroral band on April 11, 1970. The purpose of this flight was to obtain evidence of the low-energy electrons and protons that constitute a field-aligned sheet current, and also to obtain the magnetic signature of such a current and the electric field in and near the auroral-arc electric current system. Particular attention was given to a sudden increase in the field-aligned current associated with a prior sudden increase in the electric field and a sudden change in the magnetic field, all occurring near the edge of a visual auroral arc. Data obtained are discussed and analyzed; they present an important contribution to the problem of mapping of atmospheric auroral phenomena to the magnetospheric equatorial plane.

Simulation of plasma double-layer structures

NASA Technical Reports Server (NTRS)

Borovsky, J. E.; Joyce, G.

1982-01-01

Electrostatic plasma double layers are numerically simulated by means of a magnetized 2 1/2 dimensional particle in cell method. The investigation of planar double layers indicates that these one dimensional potential structures are susceptible to periodic disruption by instabilities in the low potential plasmas. Only a slight increase in the double layer thickness with an increase in its obliqueness to the magnetic field is observed. Weak magnetization results in the double layer electric field alignment of accelerated particles and strong magnetization results in their magnetic field alignment. The numerical simulations of spatially periodic two dimensional double layers also exhibit cyclical instability. A morphological invariance in two dimensional double layers with respect to the degree of magnetization implies that the potential structures scale with Debye lengths rather than with gyroradii. Electron beam excited electrostatic electron cyclotron waves and (ion beam driven) solitary waves are present in the plasmas adjacent to the double layers.

Planck intermediate results: XXXII. The relative orientation between the magnetic field and structures traced by interstellar dust

DOE PAGES

Adam, R.; Ade, P. A. R.; Aghanim, N.; ...

2016-02-09

The role of the magnetic field in the formation of the filamentary structures observed in the interstellar medium (ISM) is a debated topic owing to the paucity of relevant observations needed to test existing models. The Planck all-sky maps of linearly polarized emission from dust at 353 GHz provide the required combination of imaging and statistics to study the correlation between the structures of the Galactic magnetic field and of interstellar matter over the whole sky, both in the diffuse ISM and in molecular clouds. The data reveal that structures, or ridges, in the intensity map have counterparts in themore » Stokes Q and/or U maps. In this paper, we focus our study on structures at intermediate and high Galactic latitudes, which cover two orders of magnitude in column density, from 10 20 to 10 22 cm -2. We measure the magnetic field orientation on the plane ofthe sky from the polarization data, and present an algorithm to estimate the orientation of the ridges from the dust intensity map. We use analytical models to account for projection effects. Comparing polarization angles on and off the structures, we estimate the mean ratio between the strengths of the turbulent and mean components of the magnetic field to be between 0.6 and 1.0, with a preferred value of 0.8. We find that the ridges are usually aligned with the magnetic field measured on the structures. This statistical trend becomes more striking for increasing polarization fraction and decreasing column density. There is no alignment for the highest column density ridges. We interpret the increase in alignment with polarization fraction as a consequence of projection effects. We present maps to show that the decrease in alignment for high column density is not due to a loss of correlation between the distribution of matter and the geometry of the magnetic field. In molecular complexes, we also observe structures perpendicular to the magnetic field, which, statistically, cannot be accounted for by projection effects. This first statistical study of the relative orientation between the matter structures and the magnetic field in the ISM points out that, at the angular scales probed by Planck, the field geometry projected on the plane of the sky is correlated with the distribution of matter. In the diffuse ISM, the structures of matter are usually aligned with the magnetic field, while perpendicular structures appear in molecular clouds. Finally, we discuss our results in the context of models and MHD simulations, which attempt to describe the respective roles of turbulence, magnetic field, and self-gravity in the formation of structures in the magnetized ISM.« less

Planck intermediate results. XXXII. The relative orientation between the magnetic field and structures traced by interstellar dust

NASA Astrophysics Data System (ADS)

Planck Collaboration; Adam, R.; Ade, P. A. R.; Aghanim, N.; Alves, M. I. R.; Arnaud, M.; Arzoumanian, D.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bracco, A.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Chamballu, A.; Chiang, H. C.; Christensen, P. R.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Ferrière, K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Ghosh, T.; Giard, M.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Guillet, V.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Natoli, P.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oppermann, N.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ristorcelli, I.; Rocha, G.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Soler, J. D.; Spencer, L. D.; Stolyarov, V.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Wiesemeyer, H.; Yvon, D.; Zacchei, A.; Zonca, A.

2016-02-01

The role of the magnetic field in the formation of the filamentary structures observed in the interstellar medium (ISM) is a debated topic owing to the paucity of relevant observations needed to test existing models. The Planck all-sky maps of linearly polarized emission from dust at 353 GHz provide the required combination of imaging and statistics to study the correlation between the structures of the Galactic magnetic field and of interstellar matter over the whole sky, both in the diffuse ISM and in molecular clouds. The data reveal that structures, or ridges, in the intensity map have counterparts in the Stokes Q and/or U maps. We focus our study on structures at intermediate and high Galactic latitudes, which cover two orders of magnitude in column density, from 1020 to 1022 cm-2. We measure the magnetic field orientation on the plane ofthe sky from the polarization data, and present an algorithm to estimate the orientation of the ridges from the dust intensity map. We use analytical models to account for projection effects. Comparing polarization angles on and off the structures, we estimate the mean ratio between the strengths of the turbulent and mean components of the magnetic field to be between 0.6 and 1.0, with a preferred value of 0.8. We find that the ridges are usually aligned with the magnetic field measured on the structures. This statistical trend becomes more striking for increasing polarization fraction and decreasing column density. There is no alignment for the highest column density ridges. We interpret the increase in alignment with polarization fraction as a consequence of projection effects. We present maps to show that the decrease in alignment for high column density is not due to a loss of correlation between the distribution of matter and the geometry of the magnetic field. In molecular complexes, we also observe structures perpendicular to the magnetic field, which, statistically, cannot be accounted for by projection effects. This first statistical study of the relative orientation between the matter structures and the magnetic field in the ISM points out that, at the angular scales probed by Planck, the field geometry projected on the plane of the sky is correlated with the distribution of matter. In the diffuse ISM, the structures of matter are usually aligned with the magnetic field, while perpendicular structures appear in molecular clouds. We discuss our results in the context of models and MHD simulations, which attempt to describe the respective roles of turbulence, magnetic field, and self-gravity in the formation of structures in the magnetized ISM.

Planck intermediate results: XXXII. The relative orientation between the magnetic field and structures traced by interstellar dust

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adam, R.; Ade, P. A. R.; Aghanim, N.

The role of the magnetic field in the formation of the filamentary structures observed in the interstellar medium (ISM) is a debated topic owing to the paucity of relevant observations needed to test existing models. The Planck all-sky maps of linearly polarized emission from dust at 353 GHz provide the required combination of imaging and statistics to study the correlation between the structures of the Galactic magnetic field and of interstellar matter over the whole sky, both in the diffuse ISM and in molecular clouds. The data reveal that structures, or ridges, in the intensity map have counterparts in themore » Stokes Q and/or U maps. In this paper, we focus our study on structures at intermediate and high Galactic latitudes, which cover two orders of magnitude in column density, from 10 20 to 10 22 cm -2. We measure the magnetic field orientation on the plane ofthe sky from the polarization data, and present an algorithm to estimate the orientation of the ridges from the dust intensity map. We use analytical models to account for projection effects. Comparing polarization angles on and off the structures, we estimate the mean ratio between the strengths of the turbulent and mean components of the magnetic field to be between 0.6 and 1.0, with a preferred value of 0.8. We find that the ridges are usually aligned with the magnetic field measured on the structures. This statistical trend becomes more striking for increasing polarization fraction and decreasing column density. There is no alignment for the highest column density ridges. We interpret the increase in alignment with polarization fraction as a consequence of projection effects. We present maps to show that the decrease in alignment for high column density is not due to a loss of correlation between the distribution of matter and the geometry of the magnetic field. In molecular complexes, we also observe structures perpendicular to the magnetic field, which, statistically, cannot be accounted for by projection effects. This first statistical study of the relative orientation between the matter structures and the magnetic field in the ISM points out that, at the angular scales probed by Planck, the field geometry projected on the plane of the sky is correlated with the distribution of matter. In the diffuse ISM, the structures of matter are usually aligned with the magnetic field, while perpendicular structures appear in molecular clouds. Finally, we discuss our results in the context of models and MHD simulations, which attempt to describe the respective roles of turbulence, magnetic field, and self-gravity in the formation of structures in the magnetized ISM.« less

Mesohysteresis model for ferromagnetic materials by minimization of the micromagnetic free energy

NASA Astrophysics Data System (ADS)

van den Berg, A.; Dupré, L.; Van de Wiele, B.; Crevecoeur, G.

2009-04-01

To study the connection between macroscopic hysteretic behavior and the microstructural properties, this paper presents and validates a new material dependent three-dimensional mesoscopic magnetic hysteresis model. In the presented mesoscopic description, the different micromagnetic energy terms are reformulated on the space scale of the magnetic domains. The sample is discretized in cubic cells, each with a local stress state, local bcc crystallographic axes, etc. The magnetization is assumed to align with one of the three crystallographic axes, in positive or negative sense, defining six volume fractions within each cell. The micromagnetic Gibbs free energy is described in terms of these volume fractions. Hysteresis loops are computed by minimizing the mesoscopic Gibbs free energy using a modified gradient search for a sequence of external applied fields. To validate the mesohysteresis model, we studied the magnetic memory properties. Numerical experiments reveal that (1) minor hysteresis loops are indeed closed and (2) the closed minor loops are erased from the memory.

Template Synthesis and Magnetic Manipulation of Nickel Nanowires

ERIC Educational Resources Information Center

Bentley, Anne K.; Crone, Wendy C.; Farhoud, Mohammed; Ellis, Arthur B.; Lisensky, George C.; Nickel, Anne-Marie L.

2005-01-01

An experiment that highlights the role electrochemistry plays in the fabrication of nanoscale structures is presented. The movement and alignment of the nickel nanowires were observed, when manipulated using magnetic fields through the lens of an optical microscope using common magnets to alter the applied magnetic field.

Passive Magnetic Bearing

NASA Technical Reports Server (NTRS)

Studer, P. A.

1983-01-01

Magnetic bearing for limited rotation devices requires no feedback control system to sense and correct shaft position. Passive Magnetic Torsion Bearing requires no power supply and has no rubbing parts. Torsion wire restrains against axial instability. Magnetic flux geometry chosen to assure lateral stability with radial restoring force that maintains alignment.

Quantitative modeling and optimization of magnetic tweezers.

PubMed

Lipfert, Jan; Hao, Xiaomin; Dekker, Nynke H

2009-06-17

Magnetic tweezers are a powerful tool to manipulate single DNA or RNA molecules and to study nucleic acid-protein interactions in real time. Here, we have modeled the magnetic fields of permanent magnets in magnetic tweezers and computed the forces exerted on superparamagnetic beads from first principles. For simple, symmetric geometries the magnetic fields can be calculated semianalytically using the Biot-Savart law. For complicated geometries and in the presence of an iron yoke, we employ a finite-element three-dimensional PDE solver to numerically solve the magnetostatic problem. The theoretical predictions are in quantitative agreement with direct Hall-probe measurements of the magnetic field and with measurements of the force exerted on DNA-tethered beads. Using these predictive theories, we systematically explore the effects of magnet alignment, magnet spacing, magnet size, and of adding an iron yoke to the magnets on the forces that can be exerted on tethered particles. We find that the optimal configuration for maximal stretching forces is a vertically aligned pair of magnets, with a minimal gap between the magnets and minimal flow cell thickness. Following these principles, we present a configuration that allows one to apply > or = 40 pN stretching forces on approximately 1-microm tethered beads.

Quantitative Modeling and Optimization of Magnetic Tweezers

PubMed Central

Lipfert, Jan; Hao, Xiaomin; Dekker, Nynke H.

2009-01-01

Abstract Magnetic tweezers are a powerful tool to manipulate single DNA or RNA molecules and to study nucleic acid-protein interactions in real time. Here, we have modeled the magnetic fields of permanent magnets in magnetic tweezers and computed the forces exerted on superparamagnetic beads from first principles. For simple, symmetric geometries the magnetic fields can be calculated semianalytically using the Biot-Savart law. For complicated geometries and in the presence of an iron yoke, we employ a finite-element three-dimensional PDE solver to numerically solve the magnetostatic problem. The theoretical predictions are in quantitative agreement with direct Hall-probe measurements of the magnetic field and with measurements of the force exerted on DNA-tethered beads. Using these predictive theories, we systematically explore the effects of magnet alignment, magnet spacing, magnet size, and of adding an iron yoke to the magnets on the forces that can be exerted on tethered particles. We find that the optimal configuration for maximal stretching forces is a vertically aligned pair of magnets, with a minimal gap between the magnets and minimal flow cell thickness. Following these principles, we present a configuration that allows one to apply ≥40 pN stretching forces on ≈1-μm tethered beads. PMID:19527664

Magnetic anisotropy of Silurian organic-rich shale rocks and calcareous concretions from Northern Poland

NASA Astrophysics Data System (ADS)

Niezabitowska, Dominika; Szaniawski, Rafał

2017-04-01

The research has been performed on Wenlockian shales of Pelplin formation from the Pomerania region located in Northern Poland. These organic-rich marine shales were deposited on the western shelf of the Baltica paleo-continent and currently they constitute the cover of East European Platform. The studied shales lie almost completely flat without signs of tectonic deformations. Rock magnetic studies were carried out with the aim of recognizing ferro- and paramagnetic minerals in shales and thus fully understanding the origin of the magnetic anisotropy. The typical dark shales and spherical calcareous concretions from two boreholes were sampled. Based on deflection of shales beds bordered with a concretions, we deduce that such concretions were formed in the early stage of diagenesis, before the final compaction and lithification of surrounding shales. We obtained similar rockmagnetic results for both of rock types. The results of thermal variation of magnetic susceptibility and hysteresis loops show that the magnetic susceptibility is mainly controlled by paramagnetic minerals, due to domination of phyllosilicate minerals, with a smaller impact of ferromagnetic phase. The results of the hysteresis studies documented the domination of low coercivity ferromagnetic minerals, that is magnetite and pyrrhotite. The deposition alignment of flocculated phyllosilicates and further compaction determine distinct bedding parallel foliation of the AMS (Anisotropy of Magnetic Susceptibility) in the both drill cores. In one of the drill core the maximal AMS axes are almost randomly distributed in the bedding plane and show only a weak tendency for grouping. In the second drill core the magnetic lineation is better defined. In the case of concretions the bedding parallel magnetic foliation is also evident but it is much weaker than in shales. In turn, the magnetic lineation in the both drill cores is well developed and the maximal AMS axes are well grouped. In both of the cores the orientation of lineation from concretions complies with site mean lineation from shale rocks. To summarize, the results imply that the phyllosilicate minerals from shales are typically well aligned in the bedding plane by compaction processes. In the case of calcareous concretions the foliation is less developed due to their earlier cementation of flocculated phyllosicates in the calcareous matrix, which occurred before the end of sediments compaction. A good grouping of the maximal AMS axes within the early cemented concretions suggest that the magnetic lineation is rather sedimentary than tectonic in origin. We suggest that the magnetic lineation is probably related to the orientation of flocculated phyllosilicates due to transportation. This work has been funded by the Polish National Centre for Research and Development within the Blue Gas project (No BG2/SHALEMECH/14). Samples were provided by the PGNiG SA.

Field line twist and field-aligned currents in an axially symmetric equilibrium magnetosphere. [of Uranus

NASA Technical Reports Server (NTRS)

Voigt, Gerd-Hannes

1986-01-01

Field-aligned Birkeland currents and the angle of the magnetic line twist were calculated for an axially symmetric pole-on magnetosphere (assumed to be in MHD equilibrium). The angle of the field line twist was shown to have a strong radial dependence on the axisymmetric magnetotail as well as on the ionospheric conductivity and the amount of thermal plasma contained in closed magnetotail flux tubes. The field line twist results from the planetary rotation, which leads to the development of a toroidal magnetic B-sub-phi component and to differentially rotating magnetic field lines. It was shown that the time development of the toroidal magnetic B-sub-phi component and the rotation frequency are related through an induction equation.

FEL Trajectory Analysis for the VISA Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nuhn, Heinz-Dieter

1998-10-06

The Visual to Infrared SASE Amplifier (VISA) [1] FEL is designed to achieve saturation at radiation wavelengths between 800 and 600 nm with a 4-m pure permanent magnet undulator. The undulator comprises four 99-cm segments each of which has four FODO focusing cells superposed on the beam by means of permanent magnets in the gap alongside the beam. Each segment will also have two beam position monitors and two sets of x-y dipole correctors. The trajectory walk-off in each segment will be reduced to a value smaller than the rms beam radius by means of magnet sorting, precise fabrication, andmore » post-fabrication shimming and trim magnets. However, this leaves possible inter-segment alignment errors. A trajectory analysis code has been used in combination with the FRED3D [2] FEL code to simulate the effect of the shimming procedure and segment alignment errors on the electron beam trajectory and to determine the sensitivity of the FEL gain process to trajectory errors. The paper describes the technique used to establish tolerances for the segment alignment.« less

C/NOFS Observations of Electromagnetic Coupling Between Magnetically Conjugate MSTID Structures

NASA Technical Reports Server (NTRS)

Burke, W. J.; Martinis, C. R.; Lai, P. C.; Gentile, L. C.; Sullivan, C.; Pfaff, Robert F.

2016-01-01

This report demonstrates empirically that couplings between magnetically conjugate medium-scale traveling ionospheric disturbances (MSTIDs) are electromagnetic in nature. This is accomplished by comparing plasma density, electric, and magnetic perturbations sampled simultaneously by sensors on the Communication Navigation Outage Forecasting System (CNOFS) satellite. During the period of interest on 17 February 2010, CNOFS made three consecutive orbits while magnetically conjugate to the field of view of an all-sky imager located at El Leoncito, Argentina (31.8degS, 69.3degW). Imaged 630.0 nm airglow was characterized by alternating bands of relatively bright and dark emissions that were aligned from northeast to southwest and propagated toward the northwest, characteristic of MSTIDs in the southern hemisphere. Measurable Poynting fluxes flow along the Earths magnetic field (S) from generator to load hemispheres. While S was predominantly away from the ionosphere above El Leoncito, interhemispheric energy flows were not one-way streets. Measured Poynting flux intensities diminished with time over the three CNOFS passes, suggesting that source mechanisms of MSTIDs were absent or that initial impedance mismatches between the two hemispheres approached an equilibrium status.

C/NOFS observations of electromagnetic coupling between magnetically conjugate MSTID structures

NASA Astrophysics Data System (ADS)

Burke, W. J.; Martinis, C. R.; Lai, P. C.; Gentile, L. C.; Sullivan, C.; Pfaff, R. F.

2016-03-01

This report demonstrates empirically that couplings between magnetically conjugate medium-scale traveling ionospheric disturbances (MSTIDs) are electromagnetic in nature. This is accomplished by comparing plasma density, electric, and magnetic perturbations sampled simultaneously by sensors on the Communication/Navigation Outage Forecasting System (C/NOFS) satellite. During the period of interest on 17 February 2010, C/NOFS made three consecutive orbits while magnetically conjugate to the field of view of an all-sky imager located at El Leoncito, Argentina (31.8°S, 69.3°W). Imaged 630.0 nm airglow was characterized by alternating bands of relatively bright and dark emissions that were aligned from northeast to southwest and propagated toward the northwest, characteristic of MSTIDs in the southern hemisphere. Measurable Poynting fluxes flow along the Earth's magnetic field (S||) from "generator" to "load" hemispheres. While S|| was predominantly away from the ionosphere above El Leoncito, interhemispheric energy flows were not one-way streets. Measured Poynting flux intensities diminished with time over the three C/NOFS passes, suggesting that source mechanisms of MSTIDs were absent or that initial impedance mismatches between the two hemispheres approached an equilibrium status.

Magnetic structure and phase stability of the van der Waals bonded ferromagnet Fe 3-xGeTe 2

DOE PAGES

May, Andrew F.; Calder, Stuart A.; Cantoni, Claudia; ...

2016-01-08

The magnetic structure and phase diagram of the layered ferromagnetic compound Fe 3GeTe 2 have been investigated by a combination of synthesis, x-ray and neutron diffraction, high-resolution microscopy, and magnetization measurements. Single crystals were synthesized by self-flux reactions, and single-crystal neutron diffraction finds ferromagnetic order with moments of 1.11(5)μ B/Fe aligned along the c axis at 4 K. These flux-grown crystals have a lower Curie temperature T c ≈ 150 K than crystals previously grown by vapor transport (T c = 220 K). The difference is a reduced Fe content in the flux-grown crystals, as illustrated by the behavior observedmore » in a series of polycrystalline samples. As Fe content decreases, so do the Curie temperature, magnetic anisotropy, and net magnetization. Furthermore, Hall-effect and thermoelectric measurements on flux-grown crystals suggest that multiple carrier types contribute to electrical transport in Fe 3–xGeTe 2 and structurally similar Ni 3–xGeTe 2.« less

Fabrication of aligned magnetic nanoparticles using tobamoviruses.

PubMed

Kobayashi, Mime; Seki, Munetoshi; Tabata, Hitoshi; Watanabe, Yuichiro; Yamashita, Ichiro

2010-03-10

We used genetically modified tube-shaped tobamoviruses to produce 3 nm aligned magnetic nanoparticles. Amino acid residues facing the central channel of the virus were modified to increase the number of nucleation sites. Energy dispersive X-ray spectroscopy and superconducting quantum interference device analysis suggest that the particles consisted of Co-Pt alloy. The use of tobamovirus mutants is a promising approach to making a variety of components that can be applied to fabricate nanometer-scaled electronic devices.

A concise approach for building the s-T diagram for Mn-Fe-P-Si hysteretic magnetocaloric material

NASA Astrophysics Data System (ADS)

Christiaanse, T. V.; Campbell, O.; Trevizoli, P. V.; Misra, S.; van Asten, D.; Zhang, L.; Govindappa, P.; Niknia, I.; Teyber, R.; Rowe, A.

2017-09-01

The use of first order magnetocaloric materials (FOM’s) in magnetic cycles is of interest for the development of efficient magnetic heat pumps. FOM’s present promising magnetocaloric properties; however, hysteresis reduces the reversible adiabatic temperature change (Δ Tad ) of these materials, and consequently, impacts performance. The present paper evaluates the reversible Δ Tad in a FOM. Six samples of the Mn-Fe-P-Si material with different transition temperatures are examined. The samples are measured for heat capacity, magnetization, and adiabatic temperature change using heating and cooling protocols to characterize hysteresis. After correcting demagnetizing fields, the entropy-temperature (s-T ) diagrams are constructed and used to calculate adiabatic temperature change using four different thermal paths. The post-calculated Δ Tad is compared with experimental data from direct Δ Tad measurements. Most of the samples of Mn-Fe-P-Si show that post-calculated Δ Tad resulting from the heating zero field and cooling in-field entropy curves align best with the Δ Tad measurements. The impact of the demagnetizing field is shown in terms of absolute variation to the post-calculated Δ Tad . A functional representation is used to explain observed data sensitivities in the post-calculated Δ Tad .

CHANGE OF MAGNETIC FIELD-GAS ALIGNMENT AT THE GRAVITY-DRIVEN ALFVÉNIC TRANSITION IN MOLECULAR CLOUDS: IMPLICATIONS FOR DUST POLARIZATION OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Che-Yu; King, Patrick K.; Li, Zhi-Yun

Diffuse striations in molecular clouds are preferentially aligned with local magnetic fields, whereas dense filaments tend to be perpendicular to them. When and why this transition occurs remain uncertain. To explore the physics behind this transition, we compute the histogram of relative orientation (HRO) between the density gradient and the magnetic field in three-dimensional magnetohydrodynamic (MHD) simulations of prestellar core formation in shock-compressed regions within giant molecular clouds. We find that, in the magnetically dominated (sub-Alfvénic) post-shock region, the gas structure is preferentially aligned with the local magnetic field. For overdense sub-regions with super-Alfvénic gas, their elongation becomes preferentially perpendicularmore » to the local magnetic field. The transition occurs when self-gravitating gas gains enough kinetic energy from the gravitational acceleration to overcome the magnetic support against the cross-field contraction, which results in a power-law increase of the field strength with density. Similar results can be drawn from HROs in projected two-dimensional maps with integrated column densities and synthetic polarized dust emission. We quantitatively analyze our simulated polarization properties, and interpret the reduced polarization fraction at high column densities as the result of increased distortion of magnetic field directions in trans- or super-Alfvénic gas. Furthermore, we introduce measures of the inclination and tangledness of the magnetic field along the line of sight as the controlling factors of the polarization fraction. Observations of the polarization fraction and angle dispersion can therefore be utilized in studying local magnetic field morphology in star-forming regions.« less

Anion vacancy-mediated ferromagnetism in atomic-thick Ni3N nanosheets

NASA Astrophysics Data System (ADS)

Xia, Baorui; Wang, Tongtong; Chi, Xiao; Yu, Xiaojiang; Liu, Peitao; Zhang, Jingyan; Xi, Shibo; Du, Yonghua; Gao, Daqiang

2017-12-01

Realizing spin and electronic behavior of two-dimensional ultrathin nanosheets is significant to construct next generation nanoelectronics. Here, atomic-thick Ni3N nanosheets with clear room temperature ferromagnetism and high saturation magnetization (1.2 emu/g) are reported. X-ray magnetic circular dichroism and first-principles calculation results give the evidence that the observed intrinsic ferromagnetism in Ni3N nanosheets originates from the surface N-deficiency, where alignments of localized large magnetic moments of Ni in the vicinity of the N defect can be aligned parallel to activate macroscopic ferromagnetism. These ultrathin Ni3N nanosheets show great potential application in next-generation electron devices.

The evolution from long-range magnetic order to spin-glass behaviour in PrAu2(Si1- xGex)2

NASA Astrophysics Data System (ADS)

Krimmel, A.; Hemberger, J.; Kegler, C.; Nicklas, M.; Engelmayer, A.; Knebel, G.; Fritsch, V.; Reehuis, M.; Brando, M.; Loidl, A.

1999-09-01

We have studied the magnetic behaviour of PrAu2(Si1-xGex)2 by means of magnetic susceptibility, resistivity, and heat capacity measurements, and x-ray and neutron powder diffraction. All compounds are isostructural and crystallize in the well known ThCr2Si2-type structure. PrAu2Si2 shows the characteristic features of a canonical spin glass with a freezing temperature of TF = 3 K. Completely unexpectedly, on introducing/increasing the atomic disorder by alloying with Ge, the spin-glass transition is suppressed as is first evident from a slight decrease of the freezing temperature TF up to x = 0.10. Long-range magnetic order sets in for xicons/Journals/Common/ge" ALT="ge" ALIGN="TOP"/>0.12. Within the range 0.15icons/Journals/Common/le" ALT="le" ALIGN="TOP"/> xicons/Journals/Common/le" ALT="le" ALIGN="TOP"/>1, all compounds show the same simple AF-I-type antiferromagnetic structure with a monotonic increase of both the Néel temperature and the ordered magnetic moment for increasing Ge concentration. The magnetic phase diagram of PrAu2(Si1-xGex)2 is explained by the presence of weak disorder at a constant level at the Au sites. Clear indications of crystal-field effects have been observed.

High performance magnetic bearing systems using high temperature superconductors

DOEpatents

Abboud, Robert G.

1998-01-01

A magnetic bearing apparatus and a method for providing at least one stabilizing force in a magnetic bearing structure with a superconducting magnetic assembly and a magnetic assembly, by providing a superconducting magnetic member in the superconducting magnetic assembly with a plurality of domains and arranging said superconducting magnetic member such that at least one domain has a domain C-axis vector alignment angularly disposed relative to a reference axis of the magnetic member in the magnetic assembly.

Nanocalorimeter platform for in situ specific heat measurements and x-ray diffraction at low temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Willa, K.; Diao, Z.; Campanini, D.

Recent advances in electronics and nanofabrication have enabled membrane-based nanocalorimetry for measurements of the specific heat of microgram-sized samples. We have integrated a nanocalorimeter platform into a 4.5 T split-pair vertical-field magnet to allow for the simultaneous measurement of the specific heat and x-ray scattering in magnetic fields and at temperatures as low as 4 K. This multi-modal approach empowers researchers to directly correlate scattering experiments with insights from thermodynamic properties including structural, electronic, orbital, and magnetic phase transitions. The use of a nanocalorimeter sample platform enables numerous technical advantages: precise measurement and control of the sample temperature, quantification ofmore » beam heating effects, fast and precise positioning of the sample in the x-ray beam, and fast acquisition of x-ray scans over a wide temperature range without the need for time-consuming re-centering and re-alignment. Furthermore, on an YBa2Cu3O7-delta crystal and a copper foil, we demonstrate a novel approach to x-ray absorption spectroscopy by monitoring the change in sample temperature as a function of incident photon energy. Finally, we illustrate the new insights that can be gained from in situ structural and thermodynamic measurements by investigating the superheated state occurring at the first-order magneto-elastic phase transition of Fe2P, a material that is of interest for magnetocaloric applications.« less

Disruption of sheet-like structures in Alfvénic turbulence by magnetic reconnection

NASA Astrophysics Data System (ADS)

Mallet, A.; Schekochihin, A. A.; Chandran, B. D. G.

2017-07-01

We propose a mechanism whereby the intense, sheet-like structures naturally formed by dynamically aligning Alfvénic turbulence are destroyed by magnetic reconnection at a scale \\hat{λ }_D, larger than the dissipation scale predicted by models of intermittent, dynamically aligning turbulence. The reconnection process proceeds in several stages: first, a linear tearing mode with N magnetic islands grows and saturates, and then the X-points between these islands collapse into secondary current sheets, which then reconnect until the original structure is destroyed. This effectively imposes an upper limit on the anisotropy of the structures within the perpendicular plane, which means that at scale \\hat{λ }_D the turbulent dynamics change: at scales larger than \\hat{λ }_D, the turbulence exhibits scale-dependent dynamic alignment and a spectral index approximately equal to -3/2, while at scales smaller than \\hat{λ }_D, the turbulent structures undergo a succession of disruptions due to reconnection, limiting dynamic alignment, steepening the effective spectral index and changing the final dissipation scale. The scaling of \\hat{λ }_D with the Lundquist (magnetic Reynolds) number S_{L_\\perp } depends on the order of the statistics being considered, and on the specific model of intermittency; the transition between the two regimes in the energy spectrum is predicted at approximately \\hat{λ }_D˜ S_{L_\\perp }^{-0.6}. The spectral index below \\hat{λ }_D is bounded between -5/3 and -2.3. The final dissipation scale is at \\hat{λ }_{η ,∞}˜ S_{L_\\perp }^{-3/4}, the same as the Kolmogorov scale arising in theories of turbulence that do not involve scale-dependent dynamic alignment.

Convection in a nematic liquid crystal with homeotropic alignment and heated from below

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahlers, G.

Experimental results for convection in a thin horizontal layer of a homeotropically aligned nematic liquid crystal heated from below and in a vertical magnetic field are presented. A subcritical Hopf bifurcation leads to the convecting state. There is quantitative agreement between the measured and the predicted bifurcation line as a function of magnetic field. The nonlinear state near the bifurcation is one of spatio-temporal chaos which seems to be the result of a zig-zag instability of the straight-roll state.

Orientational alignment in solids from bidimensional isotropic-anisotropic nuclear magnetic resonance spectroscopy: applications to the analysis of aramide fibers.

PubMed

Sachleben, J R; Frydman, L

1997-02-01

The use of two-dimensional isotropic-anisotropic correlation spectroscopy for the analysis of orientational alignment in solids is presented. The theoretical background and advantages of this natural-abundance 13C NMR method of measurement are discussed, and demonstrated with a series of powder and single-crystal variable-angle correlation spectroscopy (VACSY) experiments on model systems. The technique is subsequently employed to analyze the orientational distributions of three polymer fibers: Kevlar 29, Kevlar 49 and Kevlar 149. Using complementary two-dimensional NMR data recorded on synthetic samples of poly(p-phenyleneterephthalamide), the precursor of Kevlar, it was found that these commercial fibers possess molecules distributed over a very narrow orientational range with respect to the macroscopic director. The widths measured for these director distribution arrangements were (12 +/- 1.5) degrees for Kevlar 29, (15 +/- 1.5) degrees for Kevlar 49, and (8 +/- 1.5) degrees for Kevlar 149. These figures compare well with previous results obtained for non-commercial fiber samples derived from the same polymer.

Effects of flow on the dynamics of a ferromagnetic nematic liquid crystal

NASA Astrophysics Data System (ADS)

Potisk, Tilen; Pleiner, Harald; Svenšek, Daniel; Brand, Helmut R.

2018-04-01

We investigate the effects of flow on the dynamics of ferromagnetic nematic liquid crystals. As a model, we study the coupled dynamics of the magnetization, M , the director field, n , associated with the liquid crystalline orientational order, and the velocity field, v . We evaluate how simple shear flow in a ferromagnetic nematic is modified in the presence of small external magnetic fields, and we make experimentally testable predictions for the resulting effective shear viscosity: an increase by a factor of 2 in a magnetic field of about 20 mT. Flow alignment, a characteristic feature of classical uniaxial nematic liquid crystals, is analyzed for ferromagnetic nematics for the two cases of magnetization in or perpendicular to the shear plane. In the former case, we find that small in-plane magnetic fields are sufficient to suppress tumbling and thus that the boundary between flow alignment and tumbling can be controlled easily. In the latter case, we furthermore find a possibility of flow alignment in a regime for which one obtains tumbling for the pure nematic component. We derive the analogs of the three Miesowicz viscosities well-known from usual nematic liquid crystals, corresponding to nine different configurations. Combinations of these can be used to determine several dynamic coefficients experimentally.

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

As part of the R and D program towards a fourth generation light source, a Self-Amplified Spontaneous Emission (SASE) demonstration is being prepared. The Visible-Infrared SASE Amplifier (VISA) undulator will be installed at Brookhaven National Laboratory by the end of the year. The VISA undulator is an in-vacuum, 4-meter long, 1.8 cm period, pure-permanent magnet device, with a novel, strong focusing, permanent magnet FODO array included within the fixed, 6 mm undulator gap. The undulator is constructed of 99 cm long segments. To attain maximum SASE gain requires establishing overlap of electron and photon beams to within 50 {micro}m rms.more » This imposes challenging tolerances on mechanical fabrication and magnetic field quality, and necessitates use of laser straightness interferometry for calibration and alignment of the magnetic axes of the undulator segments. This paper describes the magnetic centerline determination, and the fiducialization and alignment processes which were performed to meet the tolerance goal.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruland, Robert E.

As part of the R and D program towards a fourth generation light source, a Self-Amplified Spontaneous Emission (SASE) demonstration is being prepared. The Visible-Infrared SASE Amplifier (VISA) undulator is being installed at Brookhaven National Laboratory. The VISA undulator is an in-vacuum, 4-meter long, 1.8 cm period, pure-permanent magnet device, with a novel, strong focusing, permanent magnet FODO array included within the fixed, 6 mm undulator gap. The undulator is constructed of 99 cm long segments. To attain maximum SASE gain requires establishing overlap of electron and photon beams to within 50 pm rms. This imposes challenging tolerances on mechanicalmore » fabrication and magnetic field quality, and necessitates use of laser straightness interferometry for calibration and alignment of the magnetic axes of the undulator segments. This paper describes the magnetic centerline determination, and the fiducialization and alignment processes, which were performed to meet the tolerance goal.« less

Microbially assisted recording of the Earth's magnetic field in sediment.

PubMed

Zhao, Xiangyu; Egli, Ramon; Gilder, Stuart A; Müller, Sebastian

2016-02-11

Sediments continuously record variations of the Earth's magnetic field and thus provide an important archive for studying the geodynamo. The recording process occurs as magnetic grains partially align with the geomagnetic field during and after sediment deposition, generating a depositional remanent magnetization (DRM) or post-DRM (PDRM). (P)DRM acquisition mechanisms have been investigated for over 50 years, yet many aspects remain unclear. A key issue concerns the controversial role of bioturbation, that is, the mechanical disturbance of sediment by benthic organisms, during PDRM acquisition. A recent theory on bioturbation-driven PDRM appears to solve many inconsistencies between laboratory experiments and palaeomagnetic records, yet it lacks experimental proof. Here we fill this gap by documenting the important role of bioturbation-induced rotational diffusion for (P)DRM acquisition, including the control exerted on the recorded inclination and intensity, as determined by the equilibrium between aligning and perturbing torques acting on magnetic particles.

High performance magnetic bearing systems using high temperature superconductors

DOEpatents

Abboud, R.G.

1998-05-05

Disclosed are a magnetic bearing apparatus and a method for providing at least one stabilizing force in a magnetic bearing structure with a superconducting magnetic assembly and a magnetic assembly, by providing a superconducting magnetic member in the superconducting magnetic assembly with a plurality of domains and arranging said superconducting magnetic member such that at least one domain has a domain C-axis vector alignment angularly disposed relative to a reference axis of the magnetic member in the magnetic assembly. 7 figs.

Droplet-based magnetic bead immunoassay using microchannel-connected multiwell plates (μCHAMPs) for the detection of amyloid beta oligomers.

PubMed

Park, Min Cheol; Kim, Moojong; Lim, Gun Taek; Kang, Sung Min; An, Seong Soo A; Kim, Tae Song; Kang, Ji Yoon

2016-06-21

Multiwell plates are regularly used in analytical research and clinical diagnosis but often require laborious washing steps and large sample or reagent volumes (typically, 100 μL per well). To overcome such drawbacks in the conventional multiwell plate, we present a novel microchannel-connected multiwell plate (μCHAMP) that can be used for automated disease biomarker detection in a small sample volume by performing droplet-based magnetic bead immunoassay inside the plate. In this μCHAMP-based immunoassay platform, small volumes (30-50 μL) of aqueous-phase working droplets are stably confined within each well by the simple microchannel structure (200-300 μm in height and 0.5-1 mm in width), and magnetic beads are exclusively transported into an adjacent droplet through the oil-filled microchannels assisted by a magnet array aligned beneath and controlled by a XY-motorized stage. Using this μCHAMP-based platform, we were able to perform parallel detection of synthetic amyloid beta (Aβ) oligomers as a model analyte for the early diagnosis of Alzheimer's disease (AD). This platform easily simplified the laborious and consumptive immunoassay procedure by achieving automated parallel immunoassay (32 assays per operation in 3-well connected 96-well plate) within 1 hour and at low sample consumption (less than 10 μL per assay) with no cumbersome manual washing step. Moreover, it could detect synthetic Aβ oligomers even below 10 pg mL(-1) concentration with a calculated detection limit of ∼3 pg mL(-1). Therefore, the μCHAMP and droplet-based magnetic bead immunoassay, with the combination of XY-motorized magnet array, would be a useful platform in the diagnosis of human disease, including AD, which requires low consumption of the patient's body fluid sample and automation of the entire immunoassay procedure for high processing capacity.

Coherent radar estimates of high latitude field-aligned currents: the importance of conductance gradients

NASA Astrophysics Data System (ADS)

Kosch, M.; Nielsen, E.

Two bi-static VHF radar systems STARE and SABRE have been employed to estimate ionospheric electric field distributions in the geomagnetic latitude range 61 1 - 69 3 degrees over Scandinavia corresponding to the global Region 2 current system 173 days of data from all four radars have been analysed during the period 1982 to 1986 The average magnetic field-aligned currents have been computed as a function of the Kp and Ae indices using an empirical model of ionospheric Pedersen and Hall conductance taking into account conductance gradients The divergence of horizontal Pedersen currents and Hall conductance gradients have approximately the same importance for generating the Region 2 field-aligned currents Pedersen conductance gradients have a significant modifying effect A case study of field-aligned currents has been performed using the STARE radar system to obtain the instantaneous ionospheric electric field distribution in the vicinity of an auroral arc The instantaneous Hall conductance was estimated from the Scandinavian Magnetometer Array This study clearly shows that even for quiet steady state geomagnetic conditions conductance gradients are important modifiers of magnetic field-aligned currents

Epitaxial Ni-Mn-Ga-Co thin films on PMN-PT substrates for multicaloric applications

NASA Astrophysics Data System (ADS)

Schleicher, B.; Niemann, R.; Diestel, A.; Hühne, R.; Schultz, L.; Fähler, S.

2015-08-01

Multicaloric stacks consisting of a magnetocaloric film on a piezoelectric substrate promise improved caloric properties as the transition temperature can be controlled by both magnetic and electric fields. We present epitaxially grown magnetocaloric Ni-Mn-Ga-Co thin films on ferroelectric Pb(Mg1/3Nb2/3)0.72Ti0.28O3 substrates. Structure and microstructure of two samples, being in the austenitic and martensitic state at room temperature, are investigated by X-ray diffraction in two- and four-circle geometry and by atomic force microscopy. In addition, high temperature magnetometry was performed on the latter sample. The combination of these methods allows separating the influence of epitaxial growth and martensitic transformation. A preferential alignment of twin boundaries is observed already in the as-deposited state, which indicates the presence of prestress, without applying an electric field to the substrate. A temperature-magnetic field phase diagram is presented, which demonstrates the inverse magnetocaloric effect of the epitaxial Ni-Mn-Ga-Co film.

Driven magnetic reconnection in three dimensions - Energy conversion and field-aligned current generation

NASA Technical Reports Server (NTRS)

Sato, T.; Walker, R. J.; Ashour-Abdalla, M.

1984-01-01

The energy conversion processes occurring in three-dimensional driven reconnection is analyzed. In particular, the energy conversion processes during localized reconnection in a taillike magnetic configuration are studied. It is found that three-dimensional driven reconnection is a powerful energy converter which transforms magnetic energy into plasma bulk flow and thermal energy. Three-dimensional driven reconnection is an even more powerful energy converter than two-dimensional reconnection, because in the three-dimensional case, plasmas were drawn into the reconnection region from the sides as well as from the top and bottom. Field-aligned currents are generated by three-dimensional driven reconnection. The physical mechanism responsible for these currents which flow from the tail toward the ionosphere on the dawnside of the reconnection region and from the ionosphere toward the tail on the duskside is identified. The field-aligned currents form as the neutral sheet current is diverted through the slow shocks which form on the outer edge of the reconnected field lines (outer edge of the plasma sheet).

Parametric Transformation Analysis

NASA Technical Reports Server (NTRS)

Gary, G. Allan

2003-01-01

Because twisted coronal features are important proxies for predicting solar eruptive events, and, yet not clearly understood, we present new results to resolve the complex, non-potential magnetic field configurations of active regions. This research uses free-form deformation mathematics to generate the associated coronal magnetic field. We use a parametric representation of the magnetic field lines such that the field lines can be manipulated to match the structure of EUV and SXR coronal loops. The objective is to derive sigmoidal magnetic field solutions which allows the beta greater than 1 regions to be included, aligned and non-aligned electric currents to be calculated, and the Lorentz force to be determined. The advantage of our technique is that the solution is independent of the unknown upper and side boundary conditions, allows non-vanishing magnetic forces, and provides a global magnetic field solution, which contains high- and low-beta regimes and is consistent with all the coronal images of the region. We show that the mathematical description is unique and physical.

Neutron diffraction study of Tb0.5Ho0.5Mn2Si2

NASA Astrophysics Data System (ADS)

Pandey, Swati; Siruguri, Vasudeva; Rawat, Rajeev

2018-02-01

The magnetic properties of tetragonal polycrystalline intermetallic compound Tb0.5Ho0.5Mn2Si2 have been investigated using temperature dependent dc magnetic susceptibility and neutron powder diffraction studies. Results of high temperature susceptibility data shows anomaly at TN = 510 K while low temperature susceptibility data indicate two successive anomalies at T1 = 11 K and T2 = 25 K. Metamagnetic transition is observed in magnetization versus field curves. Our neutron diffraction results indicate three different magnetic regions with different magnetic structures. Neutron diffraction data shows that below T2, the intensities of some of the nuclear peaks get enhanced indicating ferromagnetic ordering, while additional magnetic reflections are observed below T1, indicating antiferromagnetic order. Ordering of rare earth sublattice at low temperature rearranges the ordering of Mn sublattice and results in reorientation of Mn spins at T1. At 2 K Tb/Ho moments are aligned along c-axis while Mn moments are aligned perpendicular to c-axis.

Saturn's Magnetic Field from the Cassini Grand Finale orbits

NASA Astrophysics Data System (ADS)

Dougherty, M. K.; Cao, H.; Khurana, K. K.; Hunt, G. J.; Provan, G.; Kellock, S.; Burton, M. E.; Burk, T. A.

2017-12-01

The fundamental aims of the Cassini magnetometer investigation during the Cassini Grand Finale orbits were determination of Saturn's internal planetary magnetic field and the rotation rate of the deep interior. The unique geometry of the orbits provided an unprecedented opportunity to measure the intrinsic magnetic field at close distances never before encountered. The surprising close alignment of Saturn's magnetic axis with its spin axis, known about since the days of Pioneer 11, has been a focus of the team's analysis since Cassini Saturn Orbit Insertion. However, the varying northern and southern magnetospheric planetary period oscillations, which fill the magnetosphere, has been a factor in masking the field signals from the interior. Here we describe an overview of the magnetometer results from the Grand Finale orbits, including confirmation of the extreme axisymmetric nature of the planetary magnetic field, implications for knowledge of the rotation rate and the behaviour of external magnetic fields (arising from the ring current, field aligned currents both at high and low latitudes and the modulating effect of the planetary period oscillations).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilbur, Jeffrey D.; Gomez, Enrique D.; Ellsworth, Mark W.

A procedure for creating samples that can be repeatedly cycled between weakly aligned and strongly aligned states is described. Poly(styrene-b-isoprene) block copolymer samples were first shear-aligned and then cross-linked using a high energy electron beam. Samples with more than 1.0 cross-links per chain on average showed almost complete recovery of their initial alignment state even after 20 cycles of heating above the order–disorder transition temperature of the un-cross-linked block copolymer. Samples with 1.1 cross-links per chain, which showed over 90% loss of alignment on heating and almost 100% recovery of alignment on cooling, provided the best example of a reversiblemore » aligned-to-unaligned transition. Samples with lower cross-linking densities exhibited irreversible loss of alignment upon heating, while those with higher cross-linking densities exhibited less than 90% loss of alignment upon heating. Alignment was quantified by a technique that we call two color depolarized light scattering (TCDLS), an extension of the traditional depolarized light scattering experiment used to determine the state of order in block copolymers. Qualitative confirmation of our interpretation of TCDLS data was obtained by small-angle X-ray scattering and transmission electron microscopy.« less

Magnetic fields from domestic appliances in the UK

NASA Astrophysics Data System (ADS)

Preece, A. W.; Kaune, W.; Grainger, P.; Preece, S.; Golding, J.

1997-01-01

In a survey of 50 UK homes the 50 Hz fundamental and harmonic magnetic fields generated by 806 domestic appliances found in the homes, and used regularly by mothers, were measured. Measurements were made in the direction of most likely access, and from the surface of the appliances. Mothers completed a questionnaire on the use of appliances and were monitored for 24 h so that acquired exposure could be compared with the measured ambient fields in the home. Appliances were measured at standard distances and an algorithm was used to calculate fields at 100 and 50 cm to remove room background contributions. A few appliances generated fields in excess of at 1 m: microwave cookers ; washing machines ; dishwashers ; some electric showers and can openers . Of continuously operating devices, only central heating pumps (), central heating boilers () and fish-tank air pumps () produced significant fields at 0.5 m. There were no obvious ways to group different types of appliances as high- or low-strength sources. Mothers spent on average about 4.5 h per day in the kitchen, where the strongest sources of magnetic field were located.

The interhemispheric and F region dynamo currents revisited with the Swarm constellation

NASA Astrophysics Data System (ADS)

Lühr, Hermann; Kervalishvili, Guram; Michaelis, Ingo; Rauberg, Jan; Ritter, Patricia; Park, Jaeheung; Merayo, Jose M. G.; Brauer, Peter

2015-05-01

Based on magnetic field data sampled by the Swarm satellite constellation it is possible for the first time to determine uniquely F region currents at low latitudes. Initial results are presented from the first 200 days of formation flight (17 April to 5 November 2014). Detailed results have been obtained for interhemispheric field-aligned currents connecting the solar quiet day magnetic variation (Sq) current systems in the two hemispheres. We obtain prominent currents from the Southern (winter) Hemisphere to the Northern around noon. Weaker currents in opposite direction are observed during morning and evening hours. Furthermore, we could confirm the existence of vertical currents above the dip equator, downward around noon and upward around sunset. For both current systems we present and discuss longitudinal variations.

Electromagnetically Induced Transparency Experiments for the Advanced Undergraduate Laboratory: Suppression of Polarization Impurity and Stray Magnetic Fields

NASA Astrophysics Data System (ADS)

Campbell, Kaleb; Jackson, Richard; van Vleet, Matthew; Kuhnash, Kodi; Worth, Bradley; Day, Amanda; Bali, Samir

2014-05-01

We investigate electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) in rubidium vapor using a single laser beam and a scanning magnetic field co-aligned with the laser propagation direction. We show that polarization impurity, stray magnetic fields and imperfect optical alignments cause broadening of the EIT/EIA signal and other spurious effects. We describe a systematic approach to minimizing these undesired effects, which produces EIT/EIA signals nearly two orders of magnitude narrower than the natural linewidth. We gratefully acknowledge funding from the American Chemical Society Petroleum Research Fund and Miami University. We also acknowledge the Miami University Instrumentation Laboratory for their invaluable contributions.

Radio-Optical Alignments in a Low Radio Luminosity Sample

NASA Technical Reports Server (NTRS)

Lacy, Mark; Ridgway, Susan E.; Wold, Margrethe; Lilje, Per B.; Rawlings, Steve

1999-01-01

We present an optically-based study of the alignment between the radio axes and the optical major axes of eight z approximately 0.7 radio galaxies in a 7C sample. The radio galaxies in this sample are approximately 20-times less radio luminous than 3C galaxies at the same redshift, and are significantly less radio-luminous than any other well-defined samples studied to date. Using Nordic Optical Telescope images taken in good seeing conditions at rest-frame wavelengths just longward of the 4000A break, we find a statistically significant alignment effect in the 7C sample. Furthermore, in two cases where the aligned components are well separated from the host we have been able to confirm spectroscopically that they are indeed at the same redshift as the radio galaxy. However, a quantitative analysis of the alignment in this sample and in a corresponding 3C sample from HST (Hubble Space Telescope) archival data indicates that the percentage of aligned flux may be lower and of smaller spatial scale in the 7C sample. Our study suggests that alignments on the 50-kpc scale are probably closely related to the radio luminosity, whereas those on the 15 kpc scale are not. We discuss these results in the context of popular models for the alignment effect.

Modification of crystal anisotropy and enhancement of magnetic moment of Co-doped SnO2 thin films annealed under magnetic field

PubMed Central

2014-01-01

Co-doped SnO2 thin films were grown by sputtering technique on SiO2/Si(001) substrates at room temperature, and then, thermal treatments with and without an applied magnetic field (HTT) were performed in vacuum at 600°C for 20 min. HTT was applied parallel and perpendicular to the substrate surface. Magnetic M(H) measurements reveal the coexistence of a strong antiferromagnetic (AFM) signal and a ferromagnetic (FM) component. The AFM component has a Néel temperature higher than room temperature, the spin axis lies parallel to the substrate surface, and the highest magnetic moment m =7 μB/Co at. is obtained when HTT is applied parallel to the substrate surface. Our results show an enhancement of FM moment per Co+2 from 0.06 to 0.42 μB/Co at. for the sample on which HTT was applied perpendicular to the surface. The FM order is attributed to the coupling of Co+2 ions through electrons trapped at the site of oxygen vacancies, as described by the bound magnetic polaron model. Our results suggest that FM order is aligned along [101] direction of Co-doped SnO2 nanocrystals, which is proposed to be the easy magnetization axis. PMID:25489286

Bunker probe: A plasma potential probe almost insensitive to its orientation with the magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costea, S., E-mail: stefan.costea@uibk.ac.at; Schneider, B. S.; Schrittwieser, R.

Due to their ability to suppress a large part of the electron current and thus measuring directly the plasma potential, ion sensitive probes have begun to be widely tested and used in fusion devices. For these probes to work, almost perfect alignment with the total magnetic field is necessary. This condition cannot always be fulfilled due to the curvature of magnetic fields, complex magnetic structure, or magnetic field reconnection. In this perspective, we have developed a plasma potential probe (named Bunker probe) based on the principle of the ion sensitive probe but almost insensitive to its orientation with the totalmore » magnetic field. Therefore it can be used to measure the plasma potential inside fusion devices, especially in regions with complex magnetic field topology. Experimental results are presented and compared with Ball-Pen probe measurements taken under identical conditions. We have observed that the floating potential of the Bunker probe is indeed little affected by its orientation with the magnetic field for angles ranging from 90° to 30°, in contrast to the Ball-Pen probe whose floating potential decreases towards that of a Langmuir probe if not properly aligned with the magnetic field.« less

Spin-stabilized magnetic levitation without vertical axis of rotation

DOEpatents

Romero, Louis [Albuquerque, NM; Christenson, Todd [Albuquerque, NM; Aaronson, Gene [Albuquerque, NM

2009-06-09

The symmetry properties of a magnetic levitation arrangement are exploited to produce spin-stabilized magnetic levitation without aligning the rotational axis of the rotor with the direction of the force of gravity. The rotation of the rotor stabilizes perturbations directed parallel to the rotational axis.

Avoiding Tokamak Disruptions by Applying Static Magnetic Fields That Align Locked Modes with Stabilizing Wave-Driven Currents [Avoiding Tokamak Disruptions by Magnetically Aligning Locked Modes with Stabilizing Wave-Driven Currents

DOE PAGES

Volpe, F. A.; Hyatt, Alan; La Haye, Robert J.; ...

2015-10-19

The international ITER tokamak has the objective of demonstrating the scientific feasibility of magnetic confinement fusion as a source of energy. A concern towards the achievement of this goal is represented by major disruptions: complete losses of confinement often initiated by a non-rotating ('locked') magnetic island created by magnetic reconnection. During disruptions, energy and particles accumulated in the plasma volume over many seconds are lost in a few milliseconds and released on the plasma-facing materials. In addition, multi-MA level currents flowing in the tokamak plasma for its sustainment and confinement are lost, also in milliseconds, thus terminating the plasma dischargemore » and causing electromagnetic stresses that, if unmitigated, could lead to excessive device wear. Moreover it is shown that magnetic perturbations can be used to avoid disruptions by "guiding" the magnetic island to lock in a position where it is accessible to millimetre wave beams that fully stabilize it.« less

Tailoring Staircase-like Hysteresis Loops in Electrodeposited Trisegmented Magnetic Nanowires: a Strategy toward Minimization of Interwire Interactions.

PubMed

Zhang, Jin; Agramunt-Puig, Sebastià; Del-Valle, Núria; Navau, Carles; Baró, Maria D; Estradé, Sònia; Peiró, Francesca; Pané, Salvador; Nelson, Bradley J; Sanchez, Alvaro; Nogués, Josep; Pellicer, Eva; Sort, Jordi

2016-02-17

A new strategy to minimize magnetic interactions between nanowires (NWs) dispersed in a fluid is proposed. Such a strategy consists of preparing trisegmented NWs containing two antiparallel ferromagnetic segments with dissimilar coercivity separated by a nonmagnetic spacer. The trisegmented NWs exhibit a staircase-like hysteresis loop with tunable shape that depends on the relative length of the soft- and hard-magnetic segments and the respective values of saturation magnetization. Such NWs are prepared by electrodepositing CoPt/Cu/Ni in a polycarbonate (PC) membrane. The antiparallel alignment is set by applying suitable magnetic fields while the NWs are still embedded in the PC membrane. Analytic calculations are used to demonstrate that the interaction magnetic energy from fully compensated trisegmented NWs with antiparallel alignment is reduced compared to a single-component NW with the same length or the trisegmented NWs with the two ferromagnetic counterparts parallel to each other. The proposed approach is appealing for the use of magnetic NWs in certain biological or catalytic applications where the aggregation of NWs is detrimental for optimized performance.

Simulation study of spheroidal dust gains charging: Applicable to dust grain alignment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zahed, H.; Sobhanian, S.; Mahmoodi, J.

2006-09-15

The charging process of nonspherical dust grains in an unmagnetized plasma as well as in the presence of a magnetic field is studied. It is shown that unlike the spherical dust grain, due to nonhomogeneity of charge distribution on the spheroidal dust surface, the resultant electric forces on electrons and ions are different. This process produces some surface charge density gradient on the nonspherical grain surface. Effects of a magnetic field and other plasma parameters on the properties of the dust particulate are studied. It has been shown that the alignment direction could be changed or even reversed with themore » magnetic field and plasma parameters. Finally, the charge distribution on the spheroidal grain surface is studied for different ambient parameters including plasma temperature, neutral collision frequency, and the magnitude of the magnetic field.« less

Optical and Magnetic Properties of ZnO Nanoparticles Doped with Co, Ni and Mn and Synthesized at Low Temperature.

PubMed

Hancock, Jared M; Rankin, William M; Hammad, Talaat M; Salem, Jamil S; Chesnel, Karine; Harrison, Roger G

2015-05-01

Zinc oxide nanomaterials were synthesized with small amounts of magnetic ions to create dilute magnetic semiconductors (DMS), by using a low temperature sol-gel method. Conditions were controlled such that a range of amounts of Co, Ni and Mn were incorporated. The incorporation could be tracked by color changes in the powders to blue for Co, green for Ni and yellow for Mn. XRD measurements showed the ZnO has the wurtzite structure with crystallites 8-12 nm in diameter. Nanoparticles were observed by SEM and TEM and TEM showed that the lattice fringes of different nanoparticles align. Nanoparticle alignment was disrupted when high concentrations of metal dopants were incorporated. Magnetic measurements showed a change in behavior from diamagnetic to paramagnetic with increasing concentration of metal dopants.

New perspectives on the supernova remnant Puppis A based on a radio polarization study

NASA Astrophysics Data System (ADS)

Reynoso, E. M.; Velázquez, P. F.; Cichowolski, S.

2018-06-01

We present a polarization study towards the supernova remnant (SNR) Puppis A based on original observations performed with the Australia Telescope Compact Array. Based on the analysis of a feature detected outside the SNR shell (called `the tail' throughout the paper), it was possible to disentangle the emission with origin in Puppis A itself from that coming from the foreground Vela SNR. We found a very low polarization fraction, of about 3 per cent on average. The upper limit of the magnetic field component parallel to the line of sight is estimated to be B∥ ˜ 20 μG. The statistical behaviour of the magnetic vectors shows two preferential directions, almost perpendicular to each other, which are approximately aligned with the flat edges of Puppis A. A third, narrow peak oriented perpendicular to the Galactic plane suggests the existence of an interstellar magnetic field locally aligned in this direction. There is evidence that the magnetic vectors along the shell are aligned with the shock front direction. The low polarization fraction and the statistical behaviour of the magnetic vectors are compatible with a scenario where the SNR evolves inside a stellar wind bubble with a box-like morphology, produced by the interaction of the different stellar winds, one of them magnetized, launched by the SN progenitor. This scenario can furthermore explain the morphology of Puppis A, rendering little support to the previously accepted picture which involved strong density gradients to explain the flat, eastern edge of the shell.

High Latitude Precipitating Energy Flux and Joule Heating During Geomagnetic Storms Determined from AMPERE Field-aligned Currents

NASA Astrophysics Data System (ADS)

Robinson, R. M.; Zanetti, L. J.; Anderson, B. J.; Korth, H.; Samara, M.; Michell, R.; Grubbs, G. A., II; Hampton, D. L.; Dropulic, A.

2016-12-01

A high latitude conductivity model based on field-aligned currents measured by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) provides the means for complete specification of electric fields and currents at high latitudes. Based on coordinated measurements made by AMPERE and the Poker Flat Incoherent Scatter Radar, the model determines the most likely value of the ionospheric conductance from the direction, magnitude, and magnetic local time of the field-aligned current. A conductance model driven by field-aligned currents ensures spatial and temporal consistency between the calculated electrodynamic parameters. To validate the results, the Pedersen and Hall conductances were used to calculate the energy flux associated with the energetic particle precipitation. When integrated over the entire hemisphere, the total energy flux compares well with the Hemispheric Power Index derived from the OVATION-PRIME model. The conductances were also combined with the field-aligned currents to calculate the self-consistent electric field, which was then used to compute horizontal currents and Joule heating. The magnetic perturbations derived from the currents replicate most of the variations observed in ground-based magnetograms. The model was used to study high latitude particle precipitation, currents, and Joule heating for 24 magnetic storms. In most cases, the total energy input from precipitating particles and Joule heating exhibits a sharply-peaked maximum at the times of local minima in Dst, suggesting a close coupling between the ring current and the high latitude currents driven by the Region 2 field-aligned currents. The rapid increase and decrease of the high latitude energy deposition suggests an explosive transfer of energy from the magnetosphere to the ionosphere just prior to storm recovery.

Electrostatic ion instabilities in the presence of parallel currents and transverse electric fields

NASA Technical Reports Server (NTRS)

Ganguli, G.; Palmadesso, P. J.

1988-01-01

The electrostatic ion instabilities are studied for oblique propagation in the presence of magnetic field-aligned currents and transverse localized electric fields in a weakly collisional plasma. The presence of transverse electric fields result in mode excitation for magnetic field aligned current values that are otherwise stable. The electron collisions enhance the growth while ion collisions have a damping effect. These results are discussed in the context of observations of low frequency ion modes in the auroral ionosphere by radar and rocket experiments.

Engineering survey planning for the alignment of a particle accelerator: part II. Design of a reference network and measurement strategy

NASA Astrophysics Data System (ADS)

Junqueira Leão, Rodrigo; Raffaelo Baldo, Crhistian; Collucci da Costa Reis, Maria Luisa; Alves Trabanco, Jorge Luiz

2018-03-01

The building blocks of particle accelerators are magnets responsible for keeping beams of charged particles at a desired trajectory. Magnets are commonly grouped in support structures named girders, which are mounted on vertical and horizontal stages. The performance of this type of machine is highly dependent on the relative alignment between its main components. The length of particle accelerators ranges from small machines to large-scale national or international facilities, with typical lengths of hundreds of meters to a few kilometers. This relatively large volume together with micrometric positioning tolerances make the alignment activity a classical large-scale dimensional metrology problem. The alignment concept relies on networks of fixed monuments installed on the building structure to which all accelerator components are referred. In this work, the Sirius accelerator is taken as a case study, and an alignment network is optimized via computational methods in terms of geometry, densification, and surveying procedure. Laser trackers are employed to guide the installation and measure the girders’ positions, using the optimized network as a reference and applying the metric developed in part I of this paper. Simulations demonstrate the feasibility of aligning the 220 girders of the Sirius synchrotron to better than 0.080 mm, at a coverage probability of 95%.

Injectable Anisotropic Nanocomposite Hydrogels Direct in Situ Growth and Alignment of Myotubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

De France, Kevin J.; Yager, Kevin G.; Chan, Katelyn J. W.

Here, while injectable in situ cross-linking hydrogels have attracted increasing attention as minimally invasive tissue scaffolds and controlled delivery systems, their inherently disorganized and isotropic network structure limits their utility in engineering oriented biological tissues. Traditional methods to prepare anisotropic hydrogels are not easily translatable to injectable systems given the need for external equipment to direct anisotropic gel fabrication and/or the required use of temperatures or solvents incompatible with biological systems. Herein, we report a new class of injectable nanocomposite hydrogels based on hydrazone cross-linked poly(oligoethylene glycol methacrylate) and magnetically aligned cellulose nanocrystals (CNCs) capable of encapsulating skeletal muscle myoblastsmore » and promoting their differentiation into highly oriented myotubes in situ. CNC alignment occurs on the same time scale as network gelation and remains fixed after the removal of the magnetic field, enabling concurrent CNC orientation and hydrogel injection. The aligned hydrogels show mechanical and swelling profiles that can be rationally modulated by the degree of CNC alignment and can direct myotube alignment both in two- and three-dimensions following coinjection of the myoblasts with the gel precursor components. As such, these hydrogels represent a critical advancement in anisotropic biomimetic scaffolds that can be generated noninvasively in vivo following simple injection.« less

Injectable Anisotropic Nanocomposite Hydrogels Direct in Situ Growth and Alignment of Myotubes

DOE PAGES

De France, Kevin J.; Yager, Kevin G.; Chan, Katelyn J. W.; ...

2017-09-28

Here, while injectable in situ cross-linking hydrogels have attracted increasing attention as minimally invasive tissue scaffolds and controlled delivery systems, their inherently disorganized and isotropic network structure limits their utility in engineering oriented biological tissues. Traditional methods to prepare anisotropic hydrogels are not easily translatable to injectable systems given the need for external equipment to direct anisotropic gel fabrication and/or the required use of temperatures or solvents incompatible with biological systems. Herein, we report a new class of injectable nanocomposite hydrogels based on hydrazone cross-linked poly(oligoethylene glycol methacrylate) and magnetically aligned cellulose nanocrystals (CNCs) capable of encapsulating skeletal muscle myoblastsmore » and promoting their differentiation into highly oriented myotubes in situ. CNC alignment occurs on the same time scale as network gelation and remains fixed after the removal of the magnetic field, enabling concurrent CNC orientation and hydrogel injection. The aligned hydrogels show mechanical and swelling profiles that can be rationally modulated by the degree of CNC alignment and can direct myotube alignment both in two- and three-dimensions following coinjection of the myoblasts with the gel precursor components. As such, these hydrogels represent a critical advancement in anisotropic biomimetic scaffolds that can be generated noninvasively in vivo following simple injection.« less

Assessing Students' Conceptual Knowledge of Electricity and Magnetism

ERIC Educational Resources Information Center

McColgan, Michele W.; Finn, Rose A.; Broder, Darren L.; Hassel, George E.

2017-01-01

We present the Electricity and Magnetism Conceptual Assessment (EMCA), a new assessment aligned with second-semester introductory physics courses. Topics covered include electrostatics, electric fields, circuits, magnetism, and induction. We have two motives for writing a new assessment. First, we find other assessments such as the Brief…

Interacting Compasses

ERIC Educational Resources Information Center

Riveros, Hector G.; Betancourt, Julian

2009-01-01

The use of multiple compasses to map and visualize magnetic fields is well-known. The magnetic field exerts a torque on the compasses aligning them along the lines of force. Some science museums show the field of a magnet using a table with many compasses in a closely packed arrangement. However, the very interesting interactions that occur…

Field demonstration of magnetic tomography technology for determination of dowel bar position in concrete pavement.

DOT National Transportation Integrated Search

2006-01-01

The purpose of this study was to demonstrate and evaluate the use of magnetic tomography technology through the use of Magnetic Imaging Tools' (MIT) MIT Scan-2. The main objective was to measure the alignment of dowel bars in a few jointed plain conc...

Final Report: Nanoscale Dynamical Heterogeneity in Complex Magnetic Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kevan, Stephen

2016-05-27

A magnetic object can be demagnetized by dropping it on a hard surface, but what does ‘demagnetized’ actually mean? In 1919 Heinrich Barkhausen proved the existence of magnetic domains, which are regions of uniform magnetization that are much larger than atoms but much smaller than a macroscopic object. A material is fully magnetized when domain magnetizations are aligned, while it is demagnetized when the domain magnetizations are randomly oriented and the net magnetization is zero. The heterogeneity of a demagnetized object leads to interesting questions. Magnets are unstable when their poles align, and stable when their poles anti-align, so whymore » is the magnetized state ever stable? What do domains look like? What is the structure of a domain wall? How does the magnetized state transform to the demagnetized state? How do domains appear and disappear? What are the statistical properties of domains and how do these vary as the domain pattern evolves? Some of these questions remain the focus of intense study nearly a century after Barkhausen’s discovery. For example, just a few years ago a new kind of magnetic texture called a skyrmion was discovered. A skyrmion is a magnetic domain that is a nanometer-scale, topologically protected vortex. ‘Topologically protected’ means that skyrmions are hard to destroy and so are stable for extended periods. Skyrmions are characterized by integral quantum numbers and are observed to move with little dissipation and so could store and process information with very low power input. Our research project uses soft x-rays, which offer very high magnetic contrast, to probe magnetic heterogeneity and to measure how it evolves in time under external influences. We will condition a soft x-ray beam so that the wave fronts will be coherent, that is, they will be smooth and well-defined. When coherent soft x-ray beam interacts with a magnetic material, the magnetic heterogeneity is imprinted onto the wave fronts and projected into a diffraction pattern. These patterns will be analyzed to understand the structure, motion, and statistical properties of magnetic textures and their boundaries. Over the period covered by this grant we will study a) the structure, phase behaviors, and motion of skyrmions in various thin film materials, and 2) the statistical properties of Barkhausen cascades, which are a key factor in how magnetization varies.« less

Body MR Imaging: Artifacts, k-Space, and Solutions

PubMed Central

Seethamraju, Ravi T.; Patel, Pritesh; Hahn, Peter F.; Kirsch, John E.; Guimaraes, Alexander R.

2015-01-01

Body magnetic resonance (MR) imaging is challenging because of the complex interaction of multiple factors, including motion arising from respiration and bowel peristalsis, susceptibility effects secondary to bowel gas, and the need to cover a large field of view. The combination of these factors makes body MR imaging more prone to artifacts, compared with imaging of other anatomic regions. Understanding the basic MR physics underlying artifacts is crucial to recognizing the trade-offs involved in mitigating artifacts and improving image quality. Artifacts can be classified into three main groups: (a) artifacts related to magnetic field imperfections, including the static magnetic field, the radiofrequency (RF) field, and gradient fields; (b) artifacts related to motion; and (c) artifacts arising from methods used to sample the MR signal. Static magnetic field homogeneity is essential for many MR techniques, such as fat saturation and balanced steady-state free precession. Susceptibility effects become more pronounced at higher field strengths and can be ameliorated by using spin-echo sequences when possible, increasing the receiver bandwidth, and aligning the phase-encoding gradient with the strongest susceptibility gradients, among other strategies. Nonuniformities in the RF transmit field, including dielectric effects, can be minimized by applying dielectric pads or imaging at lower field strength. Motion artifacts can be overcome through respiratory synchronization, alternative k-space sampling schemes, and parallel imaging. Aliasing and truncation artifacts derive from limitations in digital sampling of the MR signal and can be rectified by adjusting the sampling parameters. Understanding the causes of artifacts and their possible solutions will enable practitioners of body MR imaging to meet the challenges of novel pulse sequence design, parallel imaging, and increasing field strength. ©RSNA, 2015 PMID:26207581

Magnetization measurements reveal the local shear stiffness of hydrogels probed by ferromagnetic nanorods

NASA Astrophysics Data System (ADS)

Bender, P.; Tschöpe, A.; Birringer, R.

2014-12-01

The local mechanical coupling of ferromagnetic nanorods in hydrogels was characterized by magnetization measurements. Nickel nanorods were synthesized by the AAO-template method and embedded in gelatine hydrogels with mechanically soft or hard matrix properties determined by the gelatine weight fraction. By applying a homogeneous magnetic field during gelation the nanorods were aligned along the field resulting in uniaxially textured ferrogels. The magnetization curves of the soft ferrogel exhibited not only important similarities but also characteristic differences as compared to the hard ferrogel. The hystereses measured in a field parallel to the texture axis were almost identical for both samples indicating effective coupling of the nanorods with the polymer network. By contrast, measurements in a magnetic field perpendicular to the texture axis revealed a much higher initial susceptibility of the soft as compared to the hard ferrogel. This difference was attributed to the additional rotation of the nanorods allowed by the reduced shear modulus in the soft ferrogel matrix. Two methods for data analysis were presented which enabled us to determine the shear modulus of the gelatine matrix which was interpreted as a local rather than macroscopic quantity in consideration of the nanoscale of the probe particles.

Effective cell trapping using PDMS microspheres in an acoustofluidic chip.

PubMed

Yin, Di; Xu, Gangwei; Wang, Mengyuan; Shen, Mingwu; Xu, Tiegang; Zhu, Xiaoyue; Shi, Xiangyang

2017-09-01

We present a facile particle-based cell manipulation method using acoustic radiation forces. In this work, we selected several representative particles including poly(lactic-co-glycolic acid) (PLGA) microspheres, silica-coated magnetic microbeads, polydimethylsiloxane (PDMS) microspheres and investigated the responses of these particle systems to ultrasonic standing waves (USWs) in a microfluidic chip. We show that depending on the nature (positive or negative acoustic contrast factors) of the particles, these particle systems display different alignment behaviors along the microfluidic channel under USWs. Specifically, PLGA microspheres and silica-coated magnetic microbeads are able to be aligned in the middle of the microfluidic channel, while PDMS microspheres are translocated to the side walls of the channel, which is beneficial for cell trapping and manipulation. Further results demonstrate that the functional PDMS microspheres with a negative acoustic contrast factor can be used to trap cells to the pressure antinodes in the acoustofluidic chip. Cell viability tests reveal that the ultrasonic manipulation does not exert any harmful effect to the cells. This acoustic-based particle and cell manipulation technique may hold a great promise for the development of rapid, noninvasive, continuous assays for detecting of cells and separation of biological samples. Copyright © 2017 Elsevier B.V. All rights reserved.

Magnetically actuated tissue engineered scaffold: insights into mechanism of physical stimulation

NASA Astrophysics Data System (ADS)

Sapir-Lekhovitser, Yulia; Rotenberg, Menahem Y.; Jopp, Juergen; Friedman, Gary; Polyak, Boris; Cohen, Smadar

2016-02-01

Providing the right stimulatory conditions resulting in efficient tissue promoting microenvironment in vitro and in vivo is one of the ultimate goals in tissue development for regenerative medicine. It has been shown that in addition to molecular signals (e.g. growth factors) physical cues are also required for generation of functional cell constructs. These cues are particularly relevant to engineering of biological tissues, within which mechanical stress activates mechano-sensitive receptors, initiating biochemical pathways which lead to the production of functionally mature tissue. Uniform magnetic fields coupled with magnetizable nanoparticles embedded within three dimensional (3D) scaffold structures remotely create transient physical forces that can be transferrable to cells present in close proximity to the nanoparticles. This study investigated the hypothesis that magnetically responsive alginate scaffold can undergo reversible shape deformation due to alignment of scaffold's walls in a uniform magnetic field. Using custom made Helmholtz coil setup adapted to an Atomic Force Microscope we monitored changes in matrix dimensions in situ as a function of applied magnetic field, concentration of magnetic particles within the scaffold wall structure and rigidity of the matrix. Our results show that magnetically responsive scaffolds exposed to an externally applied time-varying uniform magnetic field undergo a reversible shape deformation. This indicates on possibility of generating bending/stretching forces that may exert a mechanical effect on cells due to alternating pattern of scaffold wall alignment and relaxation. We suggest that the matrix structure deformation is produced by immobilized magnetic nanoparticles within the matrix walls resulting in a collective alignment of scaffold walls upon magnetization. The estimated mechanical force that can be imparted on cells grown on the scaffold wall at experimental conditions is in the order of 1 pN, which correlates well with reported threshold to induce mechanotransduction effects on cellular level. This work is our next step in understanding of how to accurately create proper stimulatory microenvironment for promotion of cellular organization to form mature tissue engineered constructs.

Hall Effect–Mediated Magnetic Flux Transport in Protoplanetary Disks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bai, Xue-Ning; Stone, James M.

2017-02-10

The global evolution of protoplanetary disks (PPDs) has recently been shown to be largely controlled by the amount of poloidal magnetic flux threading the disk. The amount of magnetic flux must also coevolve with the disk, as a result of magnetic flux transport, a process that is poorly understood. In weakly ionized gas as in PPDs, magnetic flux is largely frozen in the electron fluid, except when resistivity is large. When the disk is largely laminar, we show that the relative drift between the electrons and ions (the Hall drift), and the ions and neutral fluids (ambipolar drift) can playmore » a dominant role on the transport of magnetic flux. Using two-dimensional simulations that incorporate the Hall effect and ambipolar diffusion (AD) with prescribed diffusivities, we show that when large-scale poloidal field is aligned with disk rotation, the Hall effect rapidly drags magnetic flux inward at the midplane region, while it slowly pushes flux outward above/below the midplane. This leads to a highly radially elongated field configuration as a global manifestation of the Hall-shear instability. This field configuration further promotes rapid outward flux transport by AD at the midplane, leading to instability saturation. In quasi-steady state, magnetic flux is transported outward at approximately the same rate at all heights, and the rate is comparable to the Hall-free case. For anti-aligned field polarity, the Hall effect consistently transports magnetic flux outward, leading to a largely vertical field configuration in the midplane region. The field lines in the upper layer first bend radially inward and then outward to launch a disk wind. Overall, the net rate of outward flux transport is about twice as fast as that of the aligned case. In addition, the rate of flux transport increases with increasing disk magnetization. The absolute rate of transport is sensitive to disk microphysics, which remains to be explored in future studies.« less

Magnetically actuated tissue engineered scaffold: insights into mechanism of physical stimulation

PubMed Central

Sapir-Lekhovitser, Yulia; Rotenberg, Menahem Y.; Jopp, Juergen; Friedman, Gary; Polyak, Boris; Cohen, Smadar

2016-01-01

Providing the right stimulatory conditions resulting in efficient tissue promoting microenvironment in vitro and in vivo is one of the ultimate goals in tissue development for regenerative medicine. It has been shown that in addition to molecular signals (e.g. growth factors) physical cues are also required for generation of functional cell constructs. These cues are particularly relevant to engineering of biological tissues, within which mechanical stress activates mechano-sensitive receptors, initiating biochemical pathways which lead to the production of functionally mature tissue. Uniform magnetic fields coupled with magnetizable nanoparticles embedded within three dimensional (3D) scaffold structures remotely create transient physical forces that can be transferrable to cells present in close proximity to the nanoparticles. This study investigated the hypothesis that magnetically responsive alginate scaffold can undergo reversible shape deformation due to alignment of scaffold’s walls in a uniform magnetic field. Using custom made Helmholtz coil setup adapted to an Atomic Force Microscope we monitored changes in matrix dimensions in situ as a function of applied magnetic field, concentration of magnetic particles within the scaffold wall structure and rigidity of the matrix. Our results show that magnetically responsive scaffolds exposed to an externally applied time-varying uniform magnetic field undergo a reversible shape deformation. This indicates on possibility of generating bending/stretching forces that may exert a mechanical effect on cells due to alternating pattern of scaffold wall alignment and relaxation. We suggest that the matrix structure deformation is produced by immobilized magnetic nanoparticles within the matrix walls resulting in a collective alignment of scaffold walls upon magnetization. The estimated mechanical force that can be imparted on cells grown on the scaffold wall at experimental conditions is in the order of 1 pN, which correlates well with reported threshold to induce mechanotransduction effects on cellular level. This work is our next step in understanding of how to accurately create proper stimulatory microenvironment for promotion of cellular organization to form mature tissue engineered constructs. PMID:26790538

A theoretical study of the global F region for June solstice, solar maximum, and low magnetic activity

NASA Technical Reports Server (NTRS)

Sojka, J. J.; Schunk, R. W.

1985-01-01

A time-dependent, three-dimensional, multi-ion model of the ionospheric F region at 120-800 km altitude is presented. Account is taken of field-aligned diffusion, cross-field electrodynamic drifts in equatorial and high latitude regions, interhemispheric flow, thermospheric winds, polar wind escape, energy-dependent chemical reactions and neutral composition changes. Attention is also given to the effects of ion production by solar EUV radiation and auroral precipitation, thermal conduction, diffusion-thermal heat flow, local heating and cooling processes, offsets between the geomagnetic and geographic poles, and bending of field lines near the magnetic equator. The model incorporates all phenomena described by previous models and can be applied to tracing magnetic storm and substorm disturbances from high to low latitudes on a global scale. Sample results are provided for ionospheric features during a June solstice, the solar maximum and in a period of low geomagnetic activity. The model will eventually be used to study coupled ionosphere-thermosphere activity.

Currents and Associated Electron Scattering and Bouncing Near the Diffusion Region at Earth's Magnetopause

NASA Technical Reports Server (NTRS)

Lavraud, B.; Zhang, Y. C.; Vernisse, Y.; Gershman, D. J.; Dorelli, J.; Cassak, P. A.; Dargent, J.; Pollock, C.; Giles, B.; Aunai, N.;

Magnetic Properties of Restacked 2D Spin 1/2 honeycomb RuCl3 Nanosheets.

PubMed

Weber, Daniel; Schoop, Leslie M; Duppel, Viola; Lippmann, Judith M; Nuss, Jürgen; Lotsch, Bettina V

2016-06-08

Spin 1/2 honeycomb materials have gained substantial interest due to their exotic magnetism and possible application in quantum computing. However, in all current materials out-of-plane interactions are interfering with the in-plane order, hence a true 2D magnetic honeycomb system is still in demand. Here, we report the exfoliation of the magnetic semiconductor α-RuCl3 into the first halide monolayers and the magnetic characterization of the spin 1/2 honeycomb arrangement of turbostratically stacked RuCl3 monolayers. The exfoliation is based on a reductive lithiation/hydration approach, which gives rise to a loss of cooperative magnetism due to the disruption of the spin 1/2 state by electron injection into the layers. The restacked, macroscopic pellets of RuCl3 layers lack symmetry along the stacking direction. After an oxidative treatment, cooperative magnetism similar to the bulk is restored. The oxidized pellets of restacked single layers feature a magnetic transition at TN = 7 K if the field is aligned parallel to the ab-plane, while the magnetic properties differ from bulk α-RuCl3 if the field is aligned perpendicular to the ab-plane. The deliberate introduction of turbostratic disorder to manipulate the magnetic properties of RuCl3 is of interest for research in frustrated magnetism and complex magnetic order as predicted by the Kitaev-Heisenberg model.

Alignment of Carbon Nanotubes Comprising Magnetically Sensitive Metal Oxides in Nanofluids

NASA Technical Reports Server (NTRS)

Hong, Haiping (Inventor); Peterson, G. P. " Bud" (Inventor)

2016-01-01

The present invention is a nanoparticle mixture or suspension or nanofluid comprising nonmagnetically sensitive nanoparticles, magnetically sensitive nanoparticles, and surfactant(s). The present invention also relates to methods of preparing and using the same.

Alignment of Carbon Nanotubes Comprising Magnetically Sensitive Metal Oxides in Nanofluids

NASA Technical Reports Server (NTRS)

Peterson, G. P. 'Bud' (Inventor); Hong, Haiping (Inventor)

2014-01-01

The present invention is a nanoparticle mixture or suspension or nanofluid comprising nonmagnetically sensitive nanoparticles, magnetically sensitive nanoparticles, and surfactant(s). The present invention also relates to methods of preparing and using the same.

Search for signatures of magnetically-induced alignment in the arrival directions measured by the Pierre Auger Observatory

NASA Astrophysics Data System (ADS)

Pierre Auger Collaboration; Abreu, P.; Aglietta, M.; Ahn, E. J.; Albuquerque, I. F. M.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Antičić, T.; Anzalone, A.; Aramo, C.; Arganda, E.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Bäcker, T.; Balzer, M.; Barber, K. B.; Barbosa, A. F.; Bardenet, R.; Barroso, S. L. C.; Baughman, B.; Bäuml, J.; Beatty, J. J.; Becker, B. R.; Becker, K. H.; Bellétoile, A.; Bellido, J. A.; Benzvi, S.; Berat, C.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, F.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brogueira, P.; Brown, W. C.; Bruijn, R.; Buchholz, P.; Bueno, A.; Burton, R. E.; Caballero-Mora, K. S.; Caramete, L.; Caruso, R.; Castellina, A.; Catalano, O.; Cataldi, G.; Cazon, L.; Cester, R.; Chauvin, J.; Cheng, S. H.; Chiavassa, A.; Chinellato, J. A.; Chou, A.; Chudoba, J.; Clay, R. W.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cook, H.; Cooper, M. J.; Coppens, J.; Cordier, A.; Coutu, S.; Covault, C. E.; Creusot, A.; Criss, A.; Cronin, J.; Curutiu, A.; Dagoret-Campagne, S.; Dallier, R.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; de Domenico, M.; de Donato, C.; de Jong, S. J.; de La Vega, G.; de Mello Junior, W. J. M.; de Mello Neto, J. R. T.; de Mitri, I.; de Souza, V.; de Vries, K. D.; Decerprit, G.; Del Peral, L.; Del Río, M.; Deligny, O.; Dembinski, H.; Dhital, N.; di Giulio, C.; Diaz, J. C.; Díaz Castro, M. L.; Diep, P. N.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; Dos Anjos, J. C.; Dova, M. T.; D'Urso, D.; Dutan, I.; Ebr, J.; Engel, R.; Erdmann, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Fajardo Tapia, I.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Ferrero, A.; Fick, B.; Filevich, A.; Filipčič, A.; Fliescher, S.; Fracchiolla, C. E.; Fraenkel, E. D.; Fröhlich, U.; Fuchs, B.; Gaior, R.; Gamarra, R. F.; Gambetta, S.; García, B.; García Gámez, D.; Garcia-Pinto, D.; Gascon, A.; Gemmeke, H.; Gesterling, K.; Ghia, P. L.; Giaccari, U.; Giller, M.; Glass, H.; Gold, M. S.; Golup, G.; Gomez Albarracin, F.; Gómez Berisso, M.; Gonçalves, P.; Gonzalez, D.; Gonzalez, J. G.; Gookin, B.; Góra, D.; Gorgi, A.; Gouffon, P.; Gozzini, S. R.; Grashorn, E.; Grebe, S.; Griffith, N.; Grigat, M.; Grillo, A. F.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Guzman, A.; Hague, J. D.; Hansen, P.; Harari, D.; Harmsma, S.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Herve, A. E.; Hojvat, C.; Hollon, N.; Holmes, V. C.; Homola, P.; Hörandel, J. R.; Horneffer, A.; Hrabovský, M.; Huege, T.; Insolia, A.; Ionita, F.; Italiano, A.; Jarne, C.; Jiraskova, S.; Josebachuili, M.; Kadija, K.; Kampert, K. H.; Karhan, P.; Kasper, P.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kelley, J. L.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapp, J.; Koang, D.-H.; Kotera, K.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuehn, F.; Kuempel, D.; Kulbartz, J. K.; Kunka, N.; La Rosa, G.; Lachaud, C.; Lautridou, P.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Lemiere, A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Lopez Agüera, A.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Lyberis, H.; Maccarone, M. C.; Macolino, C.; Maldera, S.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, J.; Marin, V.; Maris, I. C.; Marquez Falcon, H. R.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurizio, D.; Mazur, P. O.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Mertsch, P.; Meurer, C.; Mićanović, S.; Micheletti, M. I.; Miller, W.; Miramonti, L.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morales, B.; Morello, C.; Moreno, E.; Moreno, J. C.; Morris, C.; Mostafá, M.; Moura, C. A.; Mueller, S.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navarro, J. L.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Nhung, P. T.; Niemietz, L.; Nierstenhoefer, N.; Nitz, D.; Nosek, D.; Nožka, L.; Nyklicek, M.; Oehlschläger, J.; Olinto, A.; Oliva, P.; Olmos-Gilbaja, V. M.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Parente, G.; Parizot, E.; Parra, A.; Parsons, R. D.; Pastor, S.; Paul, T.; Pech, M.; PeĶala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Petrera, S.; Petrinca, P.; Petrolini, A.; Petrov, Y.; Petrovic, J.; Pfendner, C.; Phan, N.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Ponce, V. H.; Pontz, M.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rivera, H.; Rizi, V.; Roberts, J.; Robledo, C.; Rodrigues de Carvalho, W.; Rodriguez, G.; Rodriguez Martino, J.; Rodriguez Rojo, J.; Rodriguez-Cabo, I.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Rouillé-D'Orfeuil, B.; Roulet, E.; Rovero, A. C.; Rühle, C.; Salamida, F.; Salazar, H.; Salina, G.; Sánchez, F.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarkar, S.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Schmidt, A.; Schmidt, F.; Scholten, O.; Schoorlemmer, H.; Schovancova, J.; Schovánek, P.; Schröder, F.; Schulte, S.; Schuster, D.; Sciutto, S. J.; Scuderi, M.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Silva Lopez, H. H.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Spinka, H.; Squartini, R.; Stanic, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Strazzeri, E.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Šuša, T.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Tamashiro, A.; Tapia, A.; Tartare, M.; Taşcău, O.; Tavera Ruiz, C. G.; Tcaciuc, R.; Tegolo, D.; Thao, N. T.; Thomas, D.; Tiffenberg, J.; Timmermans, C.; Tiwari, D. K.; Tkaczyk, W.; Todero Peixoto, C. J.; Tomé, B.; Tonachini, A.; Travnicek, P.; Tridapalli, D. B.; Tristram, G.; Trovato, E.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van den Berg, A. M.; Varela, E.; Vargas Cárdenas, B.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villaseñor, L.; Wahlberg, H.; Wahrlich, P.; Wainberg, O.; Walz, D.; Warner, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Westerhoff, S.; Whelan, B. J.; Wieczorek, G.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Will, M.; Williams, C.; Winchen, T.; Winnick, M. G.; Wommer, M.; Wundheiler, B.; Yamamoto, T.; Yapici, T.; Younk, P.; Yuan, G.; Yushkov, A.; Zamorano, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zaw, I.; Zepeda, A.; Zimbres Silva, M.; Ziolkowski, M.

2012-01-01

We present the results of an analysis of data recorded at the Pierre Auger Observatory in which we search for groups of directionally-aligned events (or 'multiplets') which exhibit a correlation between arrival direction and the inverse of the energy. These signatures are expected from sets of events coming from the same source after having been deflected by intervening coherent magnetic fields. The observation of several events from the same source would open the possibility to accurately reconstruct the position of the source and also measure the integral of the component of the magnetic field orthogonal to the trajectory of the cosmic rays. We describe the largest multiplets found and compute the probability that they appeared by chance from an isotropic distribution. We find no statistically significant evidence for the presence of multiplets arising from magnetic deflections in the present data.

Search for signatures of magnetically-induced alignment in the arrival directions measured by the Pierre Auger Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abreu, P.; /Lisbon, IST; Aglietta, M.

2011-11-01

We present the results of an analysis of data recorded at the Pierre Auger Observatory in which we search for groups of directionally-aligned events (or ''multiplets'') which exhibit a correlation between arrival direction and the inverse of the energy. These signatures are expected from sets of events coming from the same source after having been deflected by intervening coherent magnetic fields. The observation of several events from the same source would open the possibility to accurately reconstruct the position of the source and also measure the integral of the component of the magnetic field orthogonal to the trajectory of themore » cosmic rays. We describe the largest multiplets found and compute the probability that they appeared by chance from an isotropic distribution. We find no statistically significant evidence for the presence of multiplets arising from magnetic deflections in the present data.« less

The alignment of molecular cloud magnetic fields with the spiral arms in M33.

PubMed

Li, Hua-bai; Henning, Thomas

2011-11-16

The formation of molecular clouds, which serve as stellar nurseries in galaxies, is poorly understood. A class of cloud formation models suggests that a large-scale galactic magnetic field is irrelevant at the scale of individual clouds, because the turbulence and rotation of a cloud may randomize the orientation of its magnetic field. Alternatively, galactic fields could be strong enough to impose their direction upon individual clouds, thereby regulating cloud accumulation and fragmentation, and affecting the rate and efficiency of star formation. Our location in the disk of the Galaxy makes an assessment of the situation difficult. Here we report observations of the magnetic field orientation of six giant molecular cloud complexes in the nearby, almost face-on, galaxy M33. The fields are aligned with the spiral arms, suggesting that the large-scale field in M33 anchors the clouds. ©2011 Macmillan Publishers Limited. All rights reserved

Auroral particle acceleration: An example of a universal plasma process

NASA Astrophysics Data System (ADS)

Haerendel, G.

1980-06-01

The occurrence of discrete and narrow auroral arcs is attributed to a sudden release of magnetic tensions set up in a magnetospheric-ionospheric current circuit of high strength. At altitudes of several 1000 km the condition of frozen in magnetic fields can be broken temporarily in thin regions corresponding to the observed width of auroral arcs. This implies magnetic field-aligned potential drops of several kilovolts supported by certain anomalous transport processes which can only be maintained in a quasi-stationary fashion if the current density exceeds a critical limit. The region of field aligned potential drops is structured by two pairs of standing waves which are generalized Alfven waves of large amplitude across which the parallel electric field has a finite jump. The waves are emitted from the leading edge of the acceleration region which propagates slowly into the stressed magnetic field.

Eliminating crystals in non-oxide optical fiber preforms and optical fibers

NASA Technical Reports Server (NTRS)

LaPointe, Michael R. (Inventor); Tucker, Dennis S. (Inventor)

2010-01-01

A method is provided for eliminating crystals in non-oxide optical fiber preforms as well as optical fibers drawn therefrom. The optical-fiber-drawing axis of the preform is aligned with the force of gravity. A magnetic field is applied to the preform as it is heated to at least a melting temperature thereof. The magnetic field is applied in a direction that is parallel to the preform's optical-fiber-drawing axis. The preform is then cooled to a temperature that is less than a glass transition temperature of the preform while the preform is maintained in the magnetic field. When the processed preform is to have an optical fiber drawn therefrom, the preform's optical-fiber-drawing axis is again aligned with the force of gravity and a magnetic field is again applied along the axis as the optical fiber is drawn from the preform.

A Hands-On Approach to Maglev for Gifted Students.

ERIC Educational Resources Information Center

Budd, Raymond T.

2003-01-01

This article discusses how Magnetic Levitation (Maglev) can be taught to gifted students in grades 4-9 using hands-on activities that align to the National Science Standards. Principles of magnetic levitation, advantages of magnetic levitation, construction of a Maglev project, testing and evaluation of vehicles, and presentation of the unit are…

Relaxation processes in a low-order three-dimensional magnetohydrodynamics model

NASA Technical Reports Server (NTRS)

Stribling, Troy; Matthaeus, William H.

1991-01-01

The time asymptotic behavior of a Galerkin model of 3D magnetohydrodynamics (MHD) has been interpreted using the selective decay and dynamic alignment relaxation theories. A large number of simulations has been performed that scan a parameter space defined by the rugged ideal invariants, including energy, cross helicity, and magnetic helicity. It is concluded that time asymptotic state can be interpreted as a relaxation to minimum energy. A simple decay model, based on absolute equilibrium theory, is found to predict a mapping of initial onto time asymptotic states, and to accurately describe the long time behavior of the runs when magnetic helicity is present. Attention is also given to two processes, operating on time scales shorter than selective decay and dynamic alignment, in which the ratio of kinetic to magnetic energy relaxes to values 0(1). The faster of the two processes takes states initially dominant in magnetic energy to a state of near-equipartition between kinetic and magnetic energy through power law growth of kinetic energy. The other process takes states initially dominant in kinetic energy to the near-equipartitioned state through exponential growth of magnetic energy.

Anisotropic thermal property of magnetically oriented carbon nanotube polymer composites

NASA Astrophysics Data System (ADS)

Li, Bin; Dong, Shuai; Wang, Caiping; Wang, Xiaojie; Fang, Jun

2016-04-01

This paper proposes a method for preparing multi-walled carbon nanotubea/polydimethylsiloxane (MWCNTs/PDMS) composites with enhanced thermal properties by using a high magnetic field (up to 10T). The MWCNT are oriented magnetically inside a silicone by in-situ polymerization method. The anisotropic structure would be expected to produce directional thermal conductivity. This study will provide a new approach to the development of anisotropic thermal-conductive polymer composites. Systematic studies with the preparation of silicone/graphene composites corresponding to their thermal and mechanical properties are carried out under various conditions: intensity of magnetic field, time, temperature, fillings. The effect of MWCNT/graphene content and preparation procedures on thermal conductivity of composites is investigated. Dynamic mechanical analysis (DMA) is used to reveal the mechanical properties of the composites in terms of the filling contents and magnetic field strength. The scanning electron microscope (SEM) is used to observe the micro-structure of the MWCNT composites. The alignment of MWCNTs in PDMS matrix is also studied by Raman spectroscopy. The thermal conductivity measurements show that the magnetically aligned CNT-composites feature high anisotropy in thermal conductivity.

Effect of the carbonyl iron particles on acoustic absorption properties of magnetic polyurethane foam

NASA Astrophysics Data System (ADS)

Geng, Jialu; Wang, Caiping; Zhu, Honglang; Wang, Xiaojie

2018-03-01

Elastomeric matrix embedded with magnetic micro-sized particles has magnetically controllable properties, which has been investigated extensively in the last decades. In this study we develop a new magnetically controllable elastomeric material for acoustic applications at lower frequencies. The soft polyurethane foam is used as matrix material due to its extraordinary elastic and acoustic absorption properties. One-step method is used to synthesize polyurethane foam, in which all components including polyether polyols 330N, MDI, deionized water, silicone oil, carbonyl iron particle (CIP) and catalyst are put into one container for curing. Changing any component can induce the change of polyurethane foam's properties, such as physical and acoustic properties. The effect of the content of MDI on acoustic absorption is studied. The CIPs are aligned under extra magnetic field during the foaming process. And the property of polyurethane foam with aligned CIPs is also investigated. Scanning electron microscope (SEM) is used to observe the structure of pore and particle-chain. The two-microphone impedance tube and the transfer function method are used to test acoustic absorption property of the magnetic foams.

Improvement of wireless power transmission efficiency of implantable subcutaneous devices by closed magnetic circuit mechanism.

PubMed

Jo, Sung-Eun; Joung, Sanghoon; Suh, Jun-Kyo Francis; Kim, Yong-Jun

2012-09-01

Induction coils were fabricated based on flexible printed circuit board for inductive transcutaneous power transmission. The coil had closed magnetic circuit (CMC) structure consisting of inner and outer magnetic core. The power transmission efficiency of the fabricated device was measured in the air and in vivo condition. It was confirmed that the CMC coil had higher transmission efficiency than typical air-core coil. The power transmission efficiency during a misalignment between primary coil and implanted secondary coil was also evaluated. The decrease of mutual inductance between the two coils caused by the misalignment led to a low efficiency of the inductive link. Therefore, it is important to properly align the primary coil and implanted secondary coil for effective power transmission. To align the coils, a feedback coil was proposed. This was integrated on the backside of the primary coil and enabled the detection of a misalignment of the primary and secondary coils. As a result of using the feedback coil, the primary and secondary coils could be aligned without knowledge of the position of the implanted secondary coil.

Retention time alignment of LC/MS data by a divide-and-conquer algorithm.

PubMed

Zhang, Zhongqi

2012-04-01

Liquid chromatography-mass spectrometry (LC/MS) has become the method of choice for characterizing complex mixtures. These analyses often involve quantitative comparison of components in multiple samples. To achieve automated sample comparison, the components of interest must be detected and identified, and their retention times aligned and peak areas calculated. This article describes a simple pairwise iterative retention time alignment algorithm, based on the divide-and-conquer approach, for alignment of ion features detected in LC/MS experiments. In this iterative algorithm, ion features in the sample run are first aligned with features in the reference run by applying a single constant shift of retention time. The sample chromatogram is then divided into two shorter chromatograms, which are aligned to the reference chromatogram the same way. Each shorter chromatogram is further divided into even shorter chromatograms. This process continues until each chromatogram is sufficiently narrow so that ion features within it have a similar retention time shift. In six pairwise LC/MS alignment examples containing a total of 6507 confirmed true corresponding feature pairs with retention time shifts up to five peak widths, the algorithm successfully aligned these features with an error rate of 0.2%. The alignment algorithm is demonstrated to be fast, robust, fully automatic, and superior to other algorithms. After alignment and gap-filling of detected ion features, their abundances can be tabulated for direct comparison between samples.

Microtesla SABRE enables 10% nitrogen-15 nuclear spin polarization.

PubMed

Theis, Thomas; Truong, Milton L; Coffey, Aaron M; Shchepin, Roman V; Waddell, Kevin W; Shi, Fan; Goodson, Boyd M; Warren, Warren S; Chekmenev, Eduard Y

2015-02-04

Parahydrogen is demonstrated to efficiently transfer its nuclear spin hyperpolarization to nitrogen-15 in pyridine and nicotinamide (vitamin B(3) amide) by conducting "signal amplification by reversible exchange" (SABRE) at microtesla fields within a magnetic shield. Following transfer of the sample from the magnetic shield chamber to a conventional NMR spectrometer, the (15)N NMR signals for these molecules are enhanced by ∼30,000- and ∼20,000-fold at 9.4 T, corresponding to ∼10% and ∼7% nuclear spin polarization, respectively. This method, dubbed "SABRE in shield enables alignment transfer to heteronuclei" or "SABRE-SHEATH", promises to be a simple, cost-effective way to hyperpolarize heteronuclei. It may be particularly useful for in vivo applications because of longer hyperpolarization lifetimes, lack of background signal, and facile chemical-shift discrimination of different species.

Microtesla SABRE Enables 10% Nitrogen-15 Nuclear Spin Polarization

PubMed Central

2016-01-01

Parahydrogen is demonstrated to efficiently transfer its nuclear spin hyperpolarization to nitrogen-15 in pyridine and nicotinamide (vitamin B3 amide) by conducting “signal amplification by reversible exchange” (SABRE) at microtesla fields within a magnetic shield. Following transfer of the sample from the magnetic shield chamber to a conventional NMR spectrometer, the 15N NMR signals for these molecules are enhanced by ∼30,000- and ∼20,000-fold at 9.4 T, corresponding to ∼10% and ∼7% nuclear spin polarization, respectively. This method, dubbed “SABRE in shield enables alignment transfer to heteronuclei” or “SABRE-SHEATH”, promises to be a simple, cost-effective way to hyperpolarize heteronuclei. It may be particularly useful for in vivo applications because of longer hyperpolarization lifetimes, lack of background signal, and facile chemical-shift discrimination of different species. PMID:25583142

Formation of precessing jets by tilted black hole discs in 3D general relativistic MHD simulations

NASA Astrophysics Data System (ADS)

Liska, M.; Hesp, C.; Tchekhovskoy, A.; Ingram, A.; van der Klis, M.; Markoff, S.

2018-02-01

Gas falling into a black hole (BH) from large distances is unaware of BH spin direction, and misalignment between the accretion disc and BH spin is expected to be common. However, the physics of tilted discs (e.g. angular momentum transport and jet formation) is poorly understood. Using our new GPU-accelerated code H-AMR, we performed 3D general relativistic magnetohydrodynamic simulations of tilted thick accretion discs around rapidly spinning BHs, at the highest resolution to date. We explored the limit where disc thermal pressure dominates magnetic pressure, and showed for the first time that, for different magnetic field strengths on the BH, these flows launch magnetized relativistic jets propagating along the rotation axis of the tilted disc (rather than of the BH). If strong large-scale magnetic flux reaches the BH, it bends the inner few gravitational radii of the disc and jets into partial alignment with the BH spin. On longer time-scales, the simulated disc-jet system as a whole undergoes Lense-Thirring precession and approaches alignment, demonstrating for the first time that jets can be used as probes of disc precession. When the disc turbulence is well resolved, our isolated discs spread out, causing both the alignment and precession to slow down.

Self-organization and stability of magnetosome chains—A simulation study

PubMed Central

Faivre, Damien; Klumpp, Stefan

2018-01-01

Magnetotactic bacteria orient in magnetic fields with the help of their magnetosome chain, a linear structure of membrane enclosed magnetic nanoparticles (magnetosomes) anchored to a cytoskeletal filament. Here, we use simulations to study the assembly and the stability of magnetosome chains. We introduce a computational model describing the attachment of the magnetosomes to the filament and their magnetic interactions. We show that the filamentous backbone is crucial for the robust assembly of the magnetic particles into a linear chain, which in turn is key for the functionality of the chain in cellular orientation and magnetically directed swimming. In addition, we simulate the response to an external magnetic field that is rotated away from the axis of the filament, an experimental method used to probe the mechanical stability of the chain. The competition between alignment along the filament and alignment with the external fields leads to the rupture of a chain if the applied field exceeeds a threshold value. These observations are in agreement with previous experiments at the population level. Beyond that, our simulations provide a detailed picture of chain rupture at the single cell level, which is found to happen through two abrupt events, which both depend on the field strength and orientation. The re-formation of the chain structure after such rupture is found to be strongly sped up in the presence of a magnetic field parallel to the filament, an observation that may also be of interest for the design of self-healing materials. Our simulations underline the dynamic nature of the magnetosome chain. More generally, they show the rich complexity of self-assembly in systems with competing driving forces for alignment. PMID:29315342

Auroral field-aligned current observations during the Cassini F-ring and Proximal orbits

NASA Astrophysics Data System (ADS)

Hunt, G. J.; Bunce, E. J.; Cao, H.; Cowley, S.; Dougherty, M. K.; Khurana, K. K.; Provan, G.; Southwood, D. J.

2017-12-01

Cassini's F-ring and Proximal orbits have provided a fantastic opportunity to examine Saturn's magnetic field closer to the planet than ever before. It is critical to understand external contributions to the azimuthal field component, as it can provide information on any asymmetry of the internal field. However, signatures of the auroral field-aligned currents are also present in this field component. Here we will identify and discuss these current signatures in the dawn and dusk sections in the northern and southern hemispheres, respectively. Previous results from observations during 2008 showed that in southern hemisphere these currents were strongly modulated by the southern planetary period oscillation (PPO) system. While the northern hemisphere data was modulated by both northern and southern PPOs, thus giving the first direct evidence of inter-hemispheric PPO currents. In both hemispheres, the PPO currents that give rise to the 10.7 h magnetic field oscillations observed throughout Saturn's magnetosphere, were separated from the PPO-independent (e.g. subcorotation) currents. These results provide a framework to which the Grand Finale orbits can be examined within. Here, we will assess how the field-aligned currents have evolved in comparison to the 2008 dataset. We will show that for the most part the observed field-aligned currents agree with the theoretical expectations. However, we will discuss the differences in terms of the PPO modulation, seasonal, and local time changes between the two datasets. Finally, we will discuss the implications of the azimuthal magnetic field contributions of these field-aligned currents on the data from the Proximal orbits.

Simulation of enhanced deposition due to magnetic field alignment of ellipsoidal particles in a lung bifurcation.

PubMed

Martinez, R C; Roshchenko, A; Minev, P; Finlay, W H

2013-02-01

Aerosolized chemotherapy has been recognized as a potential treatment for lung cancer. The challenge of providing sufficient therapeutic effects without reaching dose-limiting toxicity levels hinders the development of aerosolized chemotherapy. This could be mitigated by increasing drug-delivery efficiency with a noninvasive drug-targeting delivery method. The purpose of this study is to use direct numerical simulations to study the resulting local enhancement of deposition due to magnetic field alignment of high aspect ratio particles. High aspect ratio particles were approximated by a rigid ellipsoid with a minor diameter of 0.5 μm and fluid particle density ratio of 1,000. Particle trajectories were calculated by solving the coupled fluid particle equations using an in-house micro-macro grid finite element algorithm based on a previously developed fictitious domain approach. Particle trajectories were simulated in a morphologically realistic geometry modeling a symmetrical terminal bronchiole bifurcation. Flow conditions were steady inspiratory air flow due to typical breathing at 18 L/min. Deposition efficiency was estimated for two different cases: [1] particles aligned with the streamlines and [2] particles with fixed angular orientation simulating the magnetic field alignment of our previous in vitro study. The local enhancement factor defined as the ratio between deposition efficiency of Case [1] and Case [2] was found to be 1.43 and 3.46 for particles with an aspect ratio of 6 and 20, respectively. Results indicate that externally forcing local alignment of high aspect ratio particles can increase local deposition considerably.

Experimental Estimation of CLASP Spatial Resolution: Results of the Instrument's Optical Alignment

NASA Technical Reports Server (NTRS)

Giono, Gabrial; Katsukawa, Yukio; Ishikawa, Ryoko; Narukage, Noriyuki; Bando, Takamasa; Kano, Ryohei; Suematsu, Yoshinori; Kobayashi, Ken; Winebarger, Amy; Auchere, Frederic

2015-01-01

The Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) is a sounding-rocket experiment currently being built at the National Astronomical Observatory of Japan. This instrument aims to probe for the first time the magnetic field strength and orientation in the solar upper-chromosphere and lower-transition region. CLASP will measure the polarization of the Lyman-Alpha line (121.6nm) with an unprecedented accuracy, and derive the magnetic field information through the Hanle effect. Although polarization accuracy and spectral resolution are crucial for the Hanle effect detection, spatial resolution is also important to get reliable context image via the slit-jaw camera. As spatial resolution is directly related with the alignment of optics, it is also a good way of ensuring the alignment of the instrument to meet the scientific requirement. This poster will detail the experiments carried out to align CLASP's optics (telescope and spectrograph), as both part of the instrument were aligned separately. The telescope was aligned in double-pass mode, and a laser interferometer (He-Ne) was used to measure the telescope's wavefront error (WFE). The secondary mirror tilt and position were adjusted to remove comas and defocus aberrations from the WFE. Effect of gravity on the WFE measurement was estimated and the final WFE derived in zero-g condition for CLASP telescope will be presented. In addition, an estimation of the spot shape and size derived from the final WFE will also be shown. The spectrograph was aligned with a custom procedure: because Ly-??light is absorbed by air, the spectrograph's off-axis parabolic mirrors were aligned in Visible Light (VL) using a custom-made VL grating instead of the flight Ly-? grating. Results of the alignment in Visible Light will be shown and the spot shape recorded with CCDs at various position along the slit will be displayed. Results from both alignment experiment will be compared to the design requirement, and will be combined in order to estimate CLASP spatial resolution after its alignment in visible light.

Double-spiral magnetic structure of the Fe/Cr multilayer revealed by nuclear resonance reflectivity

NASA Astrophysics Data System (ADS)

Andreeva, M. A.; Baulin, R. A.; Chumakov, A. I.; Rüffer, R.; Smirnov, G. V.; Babanov, Y. A.; Devyaterikov, D. I.; Milyaev, M. A.; Ponomarev, D. A.; Romashev, L. N.; Ustinov, V. V.

2018-01-01

We have studied the magnetization depth profiles in a [57Fe (dFe) /Cr (dCr) ]30 multilayer with ultrathin Fe layers and nominal thickness of the chromium spacers dCr≈2.0 nm using nuclear resonance scattering of synchrotron radiation. The presence of a broad pure-magnetic half-order (1/2) Bragg reflection has been detected at zero external field. The joint fit of the reflectivity curves and Mössbauer spectra of reflectivity measured near the critical angle and at the "magnetic" peak reveals that the magnetic structure of the multilayer is formed by two spirals, one in the odd and another one in the even iron layers, with the opposite signs of rotation. The double-spiral structure starts from the surface with the almost-antiferromagnetic alignment of the adjacent Fe layers. The rotation of the two spirals leads to nearly ferromagnetic alignment of the two magnetic subsystems at some depth, where the sudden turn of the magnetic vectors by ˜180∘ (spin flop) appears, and both spirals start to rotate in opposite directions. The observation of this unusual double-spiral magnetic structure suggests that the unique properties of giant magnetoresistance devices can be further tailored using ultrathin magnetic layers.

Force sensor using changes in magnetic flux

NASA Technical Reports Server (NTRS)

Pickens, Herman L. (Inventor); Richard, James A. (Inventor)

2012-01-01

A force sensor includes a magnetostrictive material and a magnetic field generator positioned in proximity thereto. A magnetic field is induced in and surrounding the magnetostrictive material such that lines of magnetic flux pass through the magnetostrictive material. A sensor positioned in the vicinity of the magnetostrictive material measures changes in one of flux angle and flux density when the magnetostrictive material experiences an applied force that is aligned with the lines of magnetic flux.

Developing a Magnetic Circular Dichroism Apparatus Equipped with Neodymium Magnet for Students to Investigate the Electronic Structures of Transition Metals and Lanthanoids

ERIC Educational Resources Information Center

Yakubu, Abdallah; Suzuki, Takayoshi; Kita, Masakazu

2017-01-01

This paper describes the development of a simple magnetic circular dichroism (MCD) apparatus from a wood base and neodymium magnets and its configuration in the Faraday alignment. The applicability and effectiveness of the apparatus for MCD spectra measurements have been examined. The apparatus was used by undergraduate students to conduct MCD…

Clustering of Magnetic Swimmers in a Poiseuille Flow

NASA Astrophysics Data System (ADS)

Meng, Fanlong; Matsunaga, Daiki; Golestanian, Ramin

2018-05-01

We investigate the collective behavior of magnetic swimmers, which are suspended in a Poiseuille flow and placed under an external magnetic field, using analytical techniques and Brownian dynamics simulations. We find that the interplay between intrinsic activity, external alignment, and magnetic dipole-dipole interactions leads to longitudinal structure formation. Our work sheds light on a recent experimental observation of a clustering instability in this system.

Search for the elusive magnetic state of hexagonal iron: The antiferromagnetic Fe71Ru29 hcp alloy

NASA Astrophysics Data System (ADS)

Petrillo, C.; Postorino, P.; Orecchini, A.; Sacchetti, F.

2018-03-01

The magnetic states of iron and their dependence on crystal structure represent an important case study for the physics of magnetism and its role in fundamental and applied science, including geophysical sciences. hcp iron is the most elusive structure as it exists only at high pressure but, at the same time, it is expected to be stable up to very high temperature. Exploring the magnetic state of pure Fe at high pressure is difficult and no conclusive results have been obtained. Simple binary alloys where the hexagonal phase of Fe is stabilized, offer a more controllable alternative to investigate iron magnetism. We carried out a neutron diffraction experiment on hcp Fe71Ru29 disordered alloy as a function of temperature. Fe in the hexagonal lattice of this specific alloy results to be antiferromagnetically aligned with a rather complex structure and a small magnetic moment. The temperature dependence suggests a Néel temperature TN = 124 ± 10 K, a value consistent with the low magnetic moment of 1.04 ± 0.10 μB obtained from the diffraction data that also suggest a non-commensurate magnetic structure with magnetic moments probably aligned along the c axis. The present data provide evidence for magnetic ordering in hcp Fe and support the theoretical description of magnetism of pure Fe at high pressure.

Effect of horizontal strong static magnetic field on swimming behaviour of Paramecium caudatum

NASA Astrophysics Data System (ADS)

Fujiwara, Yoshihisa; Tomishige, Masahiko; Itoh, Yasuhiro; Fujiwara, Masao; Shibata, Naho; Kosaka, Toshikazu; Hosoya, Hiroshi; Tanimoto, Yoshifumi

2006-05-01

Effect of horizontal strong static magnetic field on swimming behaviour of Paramecium caudatum was studied by using a superconducting magnet. Around a centre of a round vessel, random swimming at 0 T and aligned swimming parallel to the magnetic field (MF) of 8 T were observed. Near a wall of the vessel, however, swimming round and round along the wall at 0 T and aligned swimming of turning at right angles upon collision with the wall, which was remarkable around 1-4 T, were detected. It was experimentally revealed that the former MF-induced parallel swimming at the vessel centre was caused physicochemically by the parallel magnetic orientation of the cell itself. From magnetic field dependence of the extent of the orientation, the magnetic susceptibility anisotropy (χ ∥-χ ⊥) was first obtained to be 3.4× 10-23 emu cell-1 at 298 K for Paramecium caudatum. The orientation of the cell was considered to result from the magnetic orientation of the cell membrane. On the other hand, although mechanisms of the latter swimming near the vessel wall regardless of the absence and presence of the magnetic field are unclear at present, these experimental results indicate that whether the cell exists near the wall alters the magnetic field effect on the swimming in the horizontal magnetic field.

Studying internal and external magnetic fields in Japan using MAGSAT data

NASA Technical Reports Server (NTRS)

Fukushima, N. (Principal Investigator); Maeda, H.; Yukutake, T.; Tanaka, M.; Oshima, S.; Ogawa, K.; Kawamura, M.; Miyazaki, Y.; Uyeda, S.; Kobayashi, K.

1980-01-01

Examination of the total intensity data of CHRONIT on a few paths over Japan and its neighboring sea shows MAGSAT is extremely useful for studying the local magnetic anomaly. In high latitudes, the signatures of field aligned currents are clearly recognized. These include (1) the persistent basic pattern of current flow; (2) the more intense currents in the summer hemisphere than in the winter hemisphere; (3) more fluctuations in current intensities in summer dawn hours; and (4) apparent dawn-dusk asymmetry in the field-aligned current intensity between the north and south polar regions.

High-temperature interlayer magnetoresistance in La5Mo4O16

NASA Astrophysics Data System (ADS)

Kobayashi, K.; Katsufuji, T.

2011-03-01

We found that La5Mo4O16 with Mo4+ and Mo5+ ions (S=1 and S=1/2 spins) on a quasisquare lattice exhibits a distinct magnetoresistance for the current perpendicular to the square-lattice layers below the antiferromagnetic ordering temperature TAF=190 K. This magnetoresistance occurs well below 1 T, and can be attributed to a metamagnetic transition from antiferromagnetically aligned moments between the layers to ferromagnetically aligned ones. The magnetoresistance changes its characteristic with the change of the magnetic state below TF=70 K, where spontaneous magnetization appears.

Anisotropy of magnetic susceptibility used to detect coring-induced sediment disturbance and filter palaeomagnetic secular variation data: IODP sites M0061 and M0062 (Baltic Sea)

NASA Astrophysics Data System (ADS)

Snowball, Ian; Almqvist, Bjarne; Lougheed, Bryan; Svensson, Anna; Wiers, Steffen; Herrero-Bervera, Emilio

2017-04-01

Inspired by palaeomagnetic data obtained from two sites (M0061 and M0062) cored during IODP Expedition 347 - Baltic Sea Paleoenvironment we studied the Hemsön Alloformation, which is a series of brackish water muds consisting of horizontal planar and parallel laminated (varved) silty clays free from bioturbation. We determined the anisotropy of magnetic susceptibility (AMS) and characteristic remanence (ChRM) directions of a total of 1,102 discrete samples cut from (i) IODP cores recovered by an Advanced Piston corer and (ii) a series of six sediment cores recovered from the same sites by a Kullenberg piston corer. Systematic core splitting, sub-sampling methods and measurements were applied to all sub-samples. We experimentally tested for field-impressed AMS of these muds, in which titanomagnetite carries magnetic remanence and this test was negative. The AMS is likely determined by paramagnetic minerals. As expected for horizontally bedded sediments, the vast majority of the K1 (maximum) and K2 (intermediate) axes had inclinations close to 0 degrees and the AMS shape parameter (T) indicates an oblate fabric. The declinations of the K1 and K2 directions of the sub-samples taken from Kullenberg cores showed a wide distribution around the bedding plane, with no preferred alignment along any specimen axis. Exceptions are samples from the upper 1.5 m of some of these cores, in which the K1 and K2 directions were vertical, the K3 (minimum) axis shallow and T became prolate. We conclude that the Kullenberg corer, which penetrated the top sediments with a pressure of approximately 15 bar, occasionally under-sampled during penetration and vertically stretched the top sediments. Sub-samples from the upper sections of Kullenberg cores had relatively steep ChRM inclinations and we rejected samples that had a prolate, vertically oriented AMS ellipsoid. Surprisingly, the declinations of the K1 axis of all sub-samples taken from IODP APC core sections, which were not oriented relative to each other with respect to azimuth, clustered tightly within the 90-270 degree specimen axis (K2 is within the 0-180 degree axis). This axis is the direction across each cores' split surface (i.e. perpendicular to the "push" direction of the sub-sampling boxes). The APC cores were characterized by various degrees of downwards bending of the planar varves towards the inner surface of the core liner. We conclude that the initial hydraulic pressure applied by the APC, which was consistently above 50 bar during Expedition 347, was needlessly high and created a conical sediment structure and the distinct alignment of the magnetic susceptibility axes along specimen axes. APC core sections with marked disturbances were characterized by ChRM inclinations below 65 degrees, which is a lower limit predicted by time varying geomagnetic field models for the duration of the Hemsö Alloformation (the most recent 6000 years). We rejected samples for palaeomagnetic purposes if the K1 inclination was steeper than 10 degrees. Our study highlights the added value of measuring AMS of discrete sub-samples as an independent control of the suitability of sediments as a source of palaeomagnetic data.

An MHD simulation of By-dependent magnetospheric convection and field-aligned currents during northward IMF

NASA Technical Reports Server (NTRS)

Ogino, T.; Walker, R. J.; Ashour-Abdalla, M.; Dawson, J. M.

1985-01-01

A three-dimensional MHD simulation code is used to model the magnetospheric configuration when the IMF has both a northward B(z) component and a B(y) component in the east-west direction. Projections of the plasma pressure, the field-aligned velocity, the field-aligned vorticity, and the field-aligned current along the magnetic field lines into the northern ionosphere are shown and discussed. Cross-sectional patterns of these parameters are shown. The results demonstrate that the B(y) component of the IMF strongly influences the plasma sheet configuration and the magnetospheric convection pattern.

Neutron and X-ray single-crystal diffraction from protein microcrystals via magnetically oriented microcrystal arrays in gels.

PubMed

Tsukui, Shu; Kimura, Fumiko; Kusaka, Katsuhiro; Baba, Seiki; Mizuno, Nobuhiro; Kimura, Tsunehisa

2016-07-01

Protein microcrystals magnetically aligned in D2O hydrogels were subjected to neutron diffraction measurements, and reflections were observed for the first time to a resolution of 3.4 Å from lysozyme microcrystals (∼10 × 10 × 50 µm). This result demonstrated the possibility that magnetically oriented microcrystals consolidated in D2O gels may provide a promising means to obtain single-crystal neutron diffraction from proteins that do not crystallize at the sizes required for neutron diffraction structure determination. In addition, lysozyme microcrystals aligned in H2O hydrogels allowed structure determination at a resolution of 1.76 Å at room temperature by X-ray diffraction. The use of gels has advantages since the microcrystals are measured under hydrated conditions.

Impact of Electro-Magneto Concave Collector on the Characterizations of Electrospun Nanofibers

NASA Astrophysics Data System (ADS)

Shehata, Nader; Abdelkader, Mohamed

2018-05-01

We introduce a modified approach to produce aligned nanofibers through electro-magneto concave collectors. Both electric and magnetic fields distributions are simulated with COMSOL Multiphysics for different collectors including conventional, concave and modified concave collectors by adding magnetic discs in the back. Orientation matrices are evaluated for each collector in the study, and the highest degree of alignment is found to be with the modified concave collector with a percentage of 68%, followed by the concave collector with a percentage of 57%, which shows an improvement of the proposed method by adding a magnetic field. The generated nanofiber mats from the electro-magneto concave collector show improvements in both mechanical (Young's modulus = 117.66 MPa) and thermal properties compared to both concave and conventional collectors.

The Magnetohydrodynamic Kelvin-Helmholtz Instability: A Two-dimensional Numerical Study

NASA Astrophysics Data System (ADS)

Frank, Adam; Jones, T. W.; Ryu, Dongsu; Gaalaas, Joseph B.

1996-04-01

We have carried out two-dimensional simulations of the nonlinear evolution of unstable sheared magnetohydrodynamic flows. These calculations extend the earlier work of Miura (1984) and consider periodic sections of flows containing aligned magnetic fields. Two equal density, compressible fluids are separated by a shear layer with a hyperbolic tangent velocity profile. We considered two cases: a strong magnetic field (Alfvén Mach number, MA = 2.5) and a weak field (MA = 5). Each flow rapidly evolves until it reaches a nearly steady condition, which is fundamentally different from the analogous gas- dynamic state. Both MHD flows relax to a stable, laminar flow on timescales less than or of the order of 15 linear growth times, measured from saturation of the instability. That timescale is several orders of magnitude less than the nominal dissipation time for these simulated flows, so this condition represents an quasi-steady relaxed state analogous to the long-lived single vortex, known as "Kelvin's Cat's Eye," formed in two-dimensional nearly ideal gasdynamic simulations of a vortex sheet. The strong magnetic field case reaches saturation as magnetic tension in the displaced flow boundary becomes sufficient to stabilize it. That flow then relaxes in a straightforward way to the steady, laminar flow condition. The weak magnetic field case, on the other hand, begins development of the vortex expected for gasdynamics, but that vortex is destroyed by magnetic stresses that locally become strong. Magnetic topologies lead to reconnection and dynamical alignment between magnetic and velocity fields. Together these processes produce a sequence of intermittent vortices and subsequent relaxation to a nearly laminar flow condition in which the magnetic cross helicity is nearly maximized. Remaining irregularities show several interesting properties. A pair of magnetic flux tubes are formed that straddle the boundary between the oppositely moving fluids. Velocity and magnetic fluctuations within those features are closely aligned, representing Alfvén waves propagating locally downstream. The flux tubes surround a low-density channel of hot gas that contains most of the excess entropy generated through the relaxation process.

An integrated workflow for robust alignment and simplified quantitative analysis of NMR spectrometry data.

PubMed

Vu, Trung N; Valkenborg, Dirk; Smets, Koen; Verwaest, Kim A; Dommisse, Roger; Lemière, Filip; Verschoren, Alain; Goethals, Bart; Laukens, Kris

2011-10-20

Nuclear magnetic resonance spectroscopy (NMR) is a powerful technique to reveal and compare quantitative metabolic profiles of biological tissues. However, chemical and physical sample variations make the analysis of the data challenging, and typically require the application of a number of preprocessing steps prior to data interpretation. For example, noise reduction, normalization, baseline correction, peak picking, spectrum alignment and statistical analysis are indispensable components in any NMR analysis pipeline. We introduce a novel suite of informatics tools for the quantitative analysis of NMR metabolomic profile data. The core of the processing cascade is a novel peak alignment algorithm, called hierarchical Cluster-based Peak Alignment (CluPA). The algorithm aligns a target spectrum to the reference spectrum in a top-down fashion by building a hierarchical cluster tree from peak lists of reference and target spectra and then dividing the spectra into smaller segments based on the most distant clusters of the tree. To reduce the computational time to estimate the spectral misalignment, the method makes use of Fast Fourier Transformation (FFT) cross-correlation. Since the method returns a high-quality alignment, we can propose a simple methodology to study the variability of the NMR spectra. For each aligned NMR data point the ratio of the between-group and within-group sum of squares (BW-ratio) is calculated to quantify the difference in variability between and within predefined groups of NMR spectra. This differential analysis is related to the calculation of the F-statistic or a one-way ANOVA, but without distributional assumptions. Statistical inference based on the BW-ratio is achieved by bootstrapping the null distribution from the experimental data. The workflow performance was evaluated using a previously published dataset. Correlation maps, spectral and grey scale plots show clear improvements in comparison to other methods, and the down-to-earth quantitative analysis works well for the CluPA-aligned spectra. The whole workflow is embedded into a modular and statistically sound framework that is implemented as an R package called "speaq" ("spectrum alignment and quantitation"), which is freely available from http://code.google.com/p/speaq/.

Epitaxial Ni-Mn-Ga-Co thin films on PMN-PT substrates for multicaloric applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schleicher, B., E-mail: b.schleicher@ifw-dresden.de; Niemann, R.; Schultz, L.

2015-08-07

Multicaloric stacks consisting of a magnetocaloric film on a piezoelectric substrate promise improved caloric properties as the transition temperature can be controlled by both magnetic and electric fields. We present epitaxially grown magnetocaloric Ni-Mn-Ga-Co thin films on ferroelectric Pb(Mg{sub 1/3}Nb{sub 2/3}){sub 0.72}Ti{sub 0.28}O{sub 3} substrates. Structure and microstructure of two samples, being in the austenitic and martensitic state at room temperature, are investigated by X-ray diffraction in two- and four-circle geometry and by atomic force microscopy. In addition, high temperature magnetometry was performed on the latter sample. The combination of these methods allows separating the influence of epitaxial growth andmore » martensitic transformation. A preferential alignment of twin boundaries is observed already in the as-deposited state, which indicates the presence of prestress, without applying an electric field to the substrate. A temperature-magnetic field phase diagram is presented, which demonstrates the inverse magnetocaloric effect of the epitaxial Ni-Mn-Ga-Co film.« less

Method and system for controlling a permanent magnet machine

DOEpatents

Walters, James E.

2003-05-20

Method and system for controlling the start of a permanent magnet machine are provided. The method allows to assign a parameter value indicative of an estimated initial rotor position of the machine. The method further allows to energize the machine with a level of current being sufficiently high to start rotor motion in a desired direction in the event the initial rotor position estimate is sufficiently close to the actual rotor position of the machine. A sensing action allows to sense whether any incremental changes in rotor position occur in response to the energizing action. In the event no changes in rotor position are sensed, the method allows to incrementally adjust the estimated rotor position by a first set of angular values until changes in rotor position are sensed. In the event changes in rotor position are sensed, the method allows to provide a rotor alignment signal as rotor motion continues. The alignment signal allows to align the estimated rotor position relative to the actual rotor position. This alignment action allows for operating the machine over a wide speed range.

Magnetic Compton scattering study of Laves phase ZrFe2 and Sc doped ZrFe2: Experiment and Green function based relativistic calculations

NASA Astrophysics Data System (ADS)

Bhatt, Samir; Mund, H. S.; Kumar, Kishor; Bapna, Komal; Dashora, Alpa; Itou, M.; Sakurai, Y.; Ahuja, B. L.

2018-05-01

Spin momentum densities of ferromagnetic ZrFe2 and Zr0.8Sc0.2Fe2 have been measured using magnetic Compton scattering with 182.65 keV circularly polarized synchrotron radiations. Site specific spin moments, which are responsible for the formation of total spin moment, have been deduced from Compton line shapes. At room temperature, the computed spin moment of ZrFe2 is found to be slightly higher than that of Sc doped ZrFe2 which is in consensus with the magnetization data. To compare the experimental data, we have also computed magnetic Compton profiles (MCPs), total and partial spin projected density of states (DOS) and the site specific spin moments using spin-polarized relativistic Korringa-Kohn-Rostoker method. It is observed that the spin moment at Fe site is aligned antiparallel to that of Zr site in both ZrFe2 and Zr0.8Sc0.2Fe2. The MCP results when compared with vibrating sample magnetometer based magnetization data, show a very small contribution of orbital moment in the formation of total magnetic moments in both the compounds. The DOS of ferromagnetic ground state of ZrFe2 and Zr0.8Sc0.2Fe2 are interpreted on the basis of a covalent magnetic model beyond the Stoner rigid band model. It appears that on alloying between a magnetic and a non-magnetic partner (with low valence), a polarization develops on the non-magnetic atom which is anti-parallel to that of the magnetic atom.

Note: A simple sample transfer alignment for ultra-high vacuum systems.

PubMed

Tamtögl, A; Carter, E A; Ward, D J; Avidor, N; Kole, P R; Jardine, A P; Allison, W

2016-06-01

The alignment of ultra-high-vacuum sample transfer systems can be problematic when there is no direct line of sight to assist the user. We present the design of a simple and cheap system which greatly simplifies the alignment of sample transfer devices. Our method is based on the adaptation of a commercial digital camera which provides live views from within the vacuum chamber. The images of the camera are further processed using an image recognition and processing code which determines any misalignments and reports them to the user. Installation has proven to be extremely useful in order to align the sample with respect to the transfer mechanism. Furthermore, the alignment software can be easily adapted for other systems.

Near-infrared polarimetric adaptive optics observations of NGC 1068: a torus created by a hydromagnetic outflow wind

NASA Astrophysics Data System (ADS)

Lopez-Rodriguez, E.; Packham, C.; Jones, T. J.; Nikutta, R.; McMaster, L.; Mason, R. E.; Elvis, M.; Shenoy, D.; Alonso-Herrero, A.; Ramírez, E.; González Martín, O.; Hönig, S. F.; Levenson, N. A.; Ramos Almeida, C.; Perlman, E.

2015-09-01

We present J' and K' imaging linear polarimetric adaptive optics observations of NGC 1068 using MMT-Pol on the 6.5-m MMT. These observations allow us to study the torus from a magnetohydrodynamical (MHD) framework. In a 0.5 arcsec (30 pc) aperture at K', we find that polarization arising from the passage of radiation from the inner edge of the torus through magnetically aligned dust grains in the clumps is the dominant polarization mechanism, with an intrinsic polarization of 7.0 ± 2.2 per cent. This result yields a torus magnetic field strength in the range of 4-82 mG through paramagnetic alignment, and 139^{+11}_{-20} mG through the Chandrasekhar-Fermi method. The measured position angle (P.A.) of polarization at K' is found to be similar to the P.A. of the obscuring dusty component at few parsec scales using infrared interferometric techniques. We show that the constant component of the magnetic field is responsible for the alignment of the dust grains, and aligned with the torus axis on to the plane of the sky. Adopting this magnetic field configuration and the physical conditions of the clumps in the MHD outflow wind model, we estimate a mass outflow rate ≤0.17 M⊙ yr-1 at 0.4 pc from the central engine for those clumps showing near-infrared dichroism. The models used were able to create the torus in a time-scale of ≥105 yr with a rotational velocity of ≤1228 km s-1 at 0.4 pc. We conclude that the evolution, morphology and kinematics of the torus in NGC 1068 can be explained within a MHD framework.

Modelling the Auroral Magnetosphere-Ionosphere Coupling System at Jupiter

NASA Astrophysics Data System (ADS)

Bunce, E. J.; Cowley, S.; Provan, G.

2016-12-01

The magnetosphere-ionosphere coupling system at Jupiter is a topic of central significance in understanding the fundamental properties of its large-scale plasma environment. Theoretical discussion of this topic typically considers the properties of the field-aligned current systems that form part of a large-scale magnetosphere-ionosphere coupling current system associated with momentum exchange between the ionosphere and the magnetosphere, communicated via the magnetic field. The current system associated with the main oval is believed to be related to centrifugally-driven outward radial transport of iogenic plasma that leads to sub-corotation in the middle magnetosphere. In addition to the magnetosphere-ionosphere coupling current system, upward-directed field-aligned currents may flow at the open-closed field line boundary due to the shear between outer closed field lines and open field lines, which may relate to emission poleward of the main oval. An axi-symmetric model of the plasma flow in the jovian system, the related coupling currents, and the consequent auroral precipitation based on these combined ideas was initially devised to represent typical steady-state conditions for the system and later extended to consider auroral effects resulting from sudden compressions of the magnetosphere. More recently, the model has been extended along model magnetic field lines into the magnetosphere in order to relate them to in situ observations from the NASA Juno spacecraft at Jupiter. The field-aligned coupling currents associated with the modelled current systems produce a readily-observable azimuthal field signature that bends the field lines out of magnetic meridians. Here we show the computed azimuthal fields produced by our model auroral current system throughout the region between the ionosphere and the magnetic equator, and illustrate the results by evaluation of various model parameters (e.g. field-aligned current density, accelerating voltages, accelerated energy flux) along the Juno orbits.

Effect of magnetic bead agglomeration on Cytomagnetometric measurements.

PubMed

Möller, Winfried; Nemoto, Iku; Heyder, Joachim

2003-12-01

Magnetic twisting cytometry (MTC) is a novel tool to measure cytoskeleton-associated cell functions by the use of ferromagnetic microbeads. Magnetic beads are either incorporated by living cells by phagocytic processes or attached to integrin receptors to the cell membrane. The magnetic beads are magnetized and aligned in a strong magnetic field pulse. The application of twisting forces allows to investigate mechanical properties (stiffness, viscoelasticity) of the cytoskeleton of living cells by analyzing the magnetic cell field. Incorporated magnetic beads undergo intracellular transport processes, which result in a loss of particle alignment and in a decay of the remanent magnetic cell field. This process, called relaxation, depends on the mechanical cytoskeletal properties and can directly visualize the intracellular energy of cellular transport processes. The preparation of spherical monodisperse ferromagnetic beads made it possible to understand the above-described processes using mathematical models. Experimental conditions with many magnetic particles per cell enhances the formation of aggregates because of the attractive forces between magnetic spheres, resulting in a change of magnetic properties and of hydrodynamic behavior. Due to mutual magnetization, the remanent magnetic moment of an aggregate is stronger compared to the same number of single particles. This implies a higher cell field. Additionally the relaxation is retarded because of the change in shape factor and in volume, which also implies a faulty estimation of intracellular transport energy. Magnetic particle twisting is less influenced. In summary, valuable cytomagnetometric measurements have to be done with less than one particle per macrophage to ensure low probability of multiple particles per cell.

Ionospheric electron heating, optical emissions, and striations induced by powerful HF radio waves at high latitudes: Aspect angle dependence

NASA Astrophysics Data System (ADS)

Rietveld, M. T.; Kosch, M. J.; Blagoveshchenskaya, N. F.; Kornienko, V. A.; Leyser, T. B.; Yeoman, T. K.

2003-04-01

In recent years, large electron temperature increases of 300% (3000 K above background) caused by powerful HF-radio wave injection have been observed during nighttime using the EISCAT incoherent scatter radar near Tromsø in northern Norway. In a case study we examine the spatial structure of the modified region. The electron heating is accompanied by ion heating of about 100 degrees and magnetic field-aligned measurements show ion outflows increasing with height up to 300 m s-1 at 582 km. The electron density decreases by up to 20%. When the radar antenna was scanned between three elevations from near field-aligned to vertical, the strongest heating effects were always obtained in the field-aligned position. When the HF-pump beam was scanned between the same three positions, the heating was still almost always strongest in the field-aligned direction. Simultaneous images of the 630 nm O(1D) line in the radio-induced aurora showed that the enhancement caused by the HF radio waves also remained localized near the field-aligned position. Coherent HF radar backscatter also appeared strongest when the pump beam was pointed field-aligned. These results are similar to some Langmuir turbulence phenomena which also show a strong preference for excitation by HF rays launched in the field-aligned direction. The correlation of the position of largest temperature enhancement with the position of the radio-induced aurora suggests that a common mechanism, upper-hybrid wave turbulence, is responsible for both effects. Why the strongest heating effects occur for HF rays directed along the magnetic field is still unclear, but self-focusing on field-aligned striations is a candidate mechanism, and possibly ionospheric tilts may be important.

Vertical Alignment of Single-Walled Carbon Nanotubes on Nanostructure Fabricated by Atomic Force Microscope

DTIC Science & Technology

2007-02-16

SWNT films by Langmuir - Blodgett methods,8 and chemical assembly of SWNTs on a large substrate.9 Al- though these methods provide a good way to control... Langmuir - Blodgett to Self-Assembly. Academic: New York, (1991). [10] Moon, J.H., Shin, J.W., Kim, S.Y., Park, J.W. Langmuir , 12, 4621, (1996...aligning CNTs in solu- tion by applying an electric field5 or a magnetic field,6 align- ing SWNTs by blending them with liquid crystal,7 assem- bling

The electrical resistivity and percolation threshold of MWCNTs/polymer composites filled with a few aligned carbonyl iron particles

NASA Astrophysics Data System (ADS)

Dong, Shuai; Wang, Xiaojie

2018-03-01

Conductive polymer composites (CPCs) consist of multi-walled carbon nanotubes (MWCNTs), a few carbonyl iron particles (CIPs) and polydimethylsiloxane (PDMS) are fabricated under a moderate magnetic field. The alignment of CIPs will change the structure of MWCNT network, and consequently the electrical properties of CPCs. The volume fraction of CIPs is fixed at 0.08 vol% at which CIPs will not directly participate in electric conduction. The electrical resistivity of CPCs and the changes of resistance versus strain are evaluated at various MWCNT volume fractions. The testing results show that a percolation threshold as low as 0.19 vol% is obtained due to the effect of aligned CIPs, comparing with 0.39 vol% of isotropic MWCNT/CIP/PDMS (prepared without magnetic field). Meanwhile, the anisotropic structure reduces the electrical resistivity by more than 80% when the MWCNT volume fractions is over the percolation threshold.

The auroral current circuit and field-aligned currents observed by FAST

NASA Astrophysics Data System (ADS)

Elphic, R. C.; Bonnell, J. W.; Strangeway, R. J.; Kepko, L.; Ergun, R. E.; McFadden, J. P.; Carlson, C. W.; Peria, W.; Cattell, C. A.; Klumpar, D.; Shelley, E.; Peterson, W.; Moebius, E.; Kistler, L.; Pfaff, R.

FAST observes signatures of small-scale downward-going current at the edges of the inverted-V regions where the primary (auroral) electrons are found. In the winter pre-midnight auroral zone these downward currents are carried by upward flowing low- and medium-energy (up to several keV) electron beams. FAST instrumentation shows agreement between the current densities inferred from both the electron distributions and gradients in the magnetic field. FAST data taken near apogee (˜4000-km altitude) commonly show downward current magnetic field deflections consistent with the observed upward flux of ˜109 electrons cm-2 s-1, or current densities of several µA m-2. The electron, field-aligned current and electric field signatures indicate the downward currents may be associated with “black aurora” and auroral ionospheric cavities. The field-aligned voltage-current relationship in the downward current region is nonlinear.

Relationship between PC index and magnetospheric field-aligned currents measured by Swarm satellites

NASA Astrophysics Data System (ADS)

Troshichev, O.; Sormakov, D.; Behlke, R.

2018-03-01

The relationship between the magnetospheric field-aligned currents (FAC) monitored by the Swarm satellites and the magnetic activity PC index (which is a proxy of the solar wind energy incoming into the magnetosphere) is examined. It is shown that current intensities measured in the R1 and R2 FAC layers at the poleward and equtorward boundaries of the auroral oval are well correlated, the R2 currents being evidently secondary in relation to R1 currents and correlation in the dawn and dusk oval sectors being better than in the noon and night sectors. There is evident relationship between the PC index and the intensity of field-aligned currents in the R1 dawn and dusk layers: increase of FAC intensity in the course of substorm development is accompanied by increasing the PC index values. Correlation between PC and FAC intensities in the R2 dawn and dusk layers is also observed, but it is much weaker. No correlation is observed between PC and field-aligned currents in the midnight as well as in the noon sectors ahead of the substorm expansion phase. The results are indicative of the R1 field-aligned currents as a driver of the polar cap magnetic activity (PC index) and currents in the R2 layer.

Electromagnetic versus Lense-Thirring alignment of black hole accretion discs

NASA Astrophysics Data System (ADS)

Polko, Peter; McKinney, Jonathan C.

2017-01-01

Accretion discs and black holes (BHs) have angular momenta that are generally misaligned, which can lead to warped discs and bends in any jets produced. We examine whether a disc that is misaligned at large radii can be aligned more efficiently by the torque of a Blandford-Znajek (BZ) jet than by Lense-Thirring (LT) precession. To obtain a strong result, we will assume that these torques maximally align the disc, rather than cause precession, or disc tearing. We consider several disc states that include radiatively inefficient thick discs, radiatively efficient thin discs, and super-Eddington accretion discs. The magnetic field strength of the BZ jet is chosen as either from standard equipartition arguments or from magnetically arrested disc (MAD) simulations. We show that standard thin accretion discs can reach spin-disc alignment out to large radii long before LT would play a role, due to the slow infall time that gives even a weak BZ jet time to align the disc. We show that geometrically thick radiatively inefficient discs and super-Eddington discs in the MAD state reach spin-disc alignment near the BH when density profiles are shallow as in magnetohydrodynamical simulations, while the BZ jet aligns discs with steep density profiles (as in advection-dominated accretion flows) out to larger radii. Our results imply that the BZ jet torque should affect the cosmological evolution of BH spin magnitude and direction, spin measurements in active galactic nuclei and X-ray binaries, and the interpretations for Event Horizon Telescope observations of discs or jets in strong-field gravity regimes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahamdioua, N., E-mail: mahamdioua.nabil@gmail.com; Amira, A.; Altintas, S.P.

We present structural, magnetic and electrical properties of the polycrystalline A-site-deficient yttrium doped double layered manganites La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7} (x=0.2, 0.3 and 0.4) prepared by a solid state reaction method. The samples crystallize in the tetragonal structure with the space group I4/mmm. Doping with Y decreases the cell parameters and causes a decrease of the metal-insulator transition temperature. The same evolution with doping is also seen for the deduced Curie temperature from susceptibility curves which present a clear paramagnetic-ferromagnetic transition. The significant positive intrinsic magnetoresistance, shown in all samples, reaches 85% at 122 K under 7more » T for 0.3 doped sample and can be attributed to the suppression of spin fluctuations via aligning the spins under external magnetic field, while the extrinsic one is attributed to the inter-grain spin-polarized tunneling across the grain boundaries. The simulation of the resistivity curves in the entire temperature range show that the percolation model is suitable to fit our results. The applied magnetic field increases the density of states near the Fermi level, which is in accordance with the observed decrease of resistivity. - Graphical abstract: Resistivity and magnetoresistance of La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7} (x=0.2, 0.3, 0.4). Solid lines correspond to the fitting results. Display Omitted.« less

Integrated crystal mounting and alignment system for high-throughput biological crystallography

DOEpatents

Nordmeyer, Robert A.; Snell, Gyorgy P.; Cornell, Earl W.; Kolbe, William F.; Yegian, Derek T.; Earnest, Thomas N.; Jaklevich, Joseph M.; Cork, Carl W.; Santarsiero, Bernard D.; Stevens, Raymond C.

2007-09-25

A method and apparatus for the transportation, remote and unattended mounting, and visual alignment and monitoring of protein crystals for synchrotron generated x-ray diffraction analysis. The protein samples are maintained at liquid nitrogen temperatures at all times: during shipment, before mounting, mounting, alignment, data acquisition and following removal. The samples must additionally be stably aligned to within a few microns at a point in space. The ability to accurately perform these tasks remotely and automatically leads to a significant increase in sample throughput and reliability for high-volume protein characterization efforts. Since the protein samples are placed in a shipping-compatible layered stack of sample cassettes each holding many samples, a large number of samples can be shipped in a single cryogenic shipping container.

Integrated crystal mounting and alignment system for high-throughput biological crystallography

DOEpatents

Nordmeyer, Robert A.; Snell, Gyorgy P.; Cornell, Earl W.; Kolbe, William; Yegian, Derek; Earnest, Thomas N.; Jaklevic, Joseph M.; Cork, Carl W.; Santarsiero, Bernard D.; Stevens, Raymond C.

2005-07-19

A method and apparatus for the transportation, remote and unattended mounting, and visual alignment and monitoring of protein crystals for synchrotron generated x-ray diffraction analysis. The protein samples are maintained at liquid nitrogen temperatures at all times: during shipment, before mounting, mounting, alignment, data acquisition and following removal. The samples must additionally be stably aligned to within a few microns at a point in space. The ability to accurately perform these tasks remotely and automatically leads to a significant increase in sample throughput and reliability for high-volume protein characterization efforts. Since the protein samples are placed in a shipping-compatible layered stack of sample cassettes each holding many samples, a large number of samples can be shipped in a single cryogenic shipping container.

A smart temperature and magnetic-responsive gating carbon nanotube membrane for ion and protein transportation

PubMed Central

Cong, Hailin; Xu, Xiaodan; Yu, Bing; Yang, Zhaohui; Zhang, Xiaoyan

2016-01-01

Carbon nanotube (CNT) nanoporous membranes based on pre-aligned CNTs have superior nano-transportation properties in biological science. Herein, we report a smart temperature- and temperature-magnetic-responsive CNT nanoporous membrane (CNM) by grafting thermal-sensitive poly(N-isopropylacrylamide) (PNIPAM) and Fe3O4 nanoparticles (Fe3O4-NPs) on the open ends of pre-aligned CNTs with a diameter around 15 nm via surface-initiated atom transfer radical polymerization (SI-ATRP) method. The inner cavity of the modified CNTs in the membrane is designed to be the only path for ion and protein transportation, and its effective diameter with a variation from ~5.7 nm to ~12.4 nm can be reversible tuned by temperature and magnetic field. The PNIPAM modified CNM (PNIPAM-CNM) and PNIPAM magnetic nanoparticles modified CNM (PNIPAM-MAG-CNM) exhibit excellent temperature- or temperature-magnetic-responsive gating property to separate proteins of different sizes. The PNIPAM-CNMs and PNIPAM-MAG-CNMs have potential applications in making artificial cells, biosensors, bioseparation and purification filters. PMID:27535103

Magnetic shuffling of coronal downdrafts

NASA Astrophysics Data System (ADS)

Petralia, A.; Reale, F.; Orlando, S.

2017-02-01

Context. Channelled fragmented downflows are ubiquitous in magnetized atmospheres, and have recently been addressed based on an observation after a solar eruption. Aims: We study the possible back-effect of the magnetic field on the propagation of confined flows. Methods: We compared two 3D magnetohydrodynamic simulations of dense supersonic plasma blobs that fall down along a coronal magnetic flux tube. In one, the blobs move strictly along the field lines; in the other, the initial velocity of the blobs is not perfectly aligned with the magnetic field and the field is weaker. Results: The aligned blobs remain compact while flowing along the tube, with the generated shocks. The misaligned blobs are disrupted and merge through the chaotic shuffling of the field lines. They are structured into thinner filaments. Alfvén wave fronts are generated together with shocks ahead of the dense moving front. Conclusions: Downflowing plasma fragments can be chaotically and efficiently mixed if their motion is misaligned with field lines, with broad implications for disk accretion in protostars, coronal eruptions, and rain, for example. Movies associated to Figs. 2 and 3 are available at http://www.aanda.org

Field-aligned structure of the storm time Pc 5 wave of November 14-15, 1979

NASA Astrophysics Data System (ADS)

Takahashi, K.; Higbie, P. R.; Fennell, J. F.; Amata, E.

1987-06-01

Magnetic field data from the four satellites SCATHA (P78-2), GOES 2, GOES 3, and GOES 2 have been analyzed to examine the magnetic field-aligned structure of a storm time Pc 5 wave that occurred on November 14-15, 1979. The wave had both transverse and compressional components. At a given instance, the compressional and the radial components oscillated in phase or 180 deg out of phase, and the compressional and the azimuthal components oscillated +90 deg or -90 deg out of phase. In addition, each component changed its amplitude with magnetic latitude: the compressional component had a minimum at the magnetic equator, whereas the transverse components had a maximum at the equator and minima several degrees off the equator. A 180 deg relative phase switching among the components occurred across the latitudes of amplitude minima. From these observations, the field line displacement of the wave is confirmed to have an antisymmetric standing structure about the magnetic equator with a parallel wave length of a few earth radii.

Two-stage Electron Acceleration by 3D Collisionless Guide-field Magnetic Reconnection

NASA Astrophysics Data System (ADS)

Buechner, J.; Munoz, P.

2017-12-01

We discuss a two-stage process of electron acceleration near X-lines of 3D collisionless guide-field magnetic reconnection. Non-relativistic electrons are first pre-accelerated by magnetic-field-aligned (parallel) electric fields. At the nonlinear stage of 3D guide-field magnetic reconnection electric and magnetic fields become filamentary structured due to streaming instabilities. This causes an additional curvature-driven electron acceleration in the guide-field direction. The resulting spectrum of the accelerated electrons follows a power law.

High-Curie-Temperature Ferromagnetism in (Sc,Fe)F3 Fluorides and its Dependence on Chemical Valence.

PubMed

Hu, Lei; Chen, Jun; Fan, Longlong; Ren, Yang; Huang, Qingzhen; Sanson, Andrea; Jiang, Zheng; Zhou, Mei; Rong, Yangchun; Wang, Yong; Deng, Jinxia; Xing, Xianran

2015-08-19

A magnetic metal-fluoride system is shown for the first time to have a high Curie temperature (≈545 K). The magnetism correlates intimately with the Fe(2+)/Fe(3+) ratio. As the ratio increases, the weak magnetism displayed by unordered magnetic moments intensifies, and these magnetic moments align in parallel. Simultaneously, a magneto-volume effect is also shown to increase the lattice volume. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ionospheric Scintillation Explorer (ISX)

NASA Astrophysics Data System (ADS)

Iuliano, J.; Bahcivan, H.

2015-12-01

NSF has recently selected Ionospheric Scintillation Explorer (ISX), a 3U Cubesat mission to explore the three-dimensional structure of scintillation-scale ionospheric irregularities associated with Equatorial Spread F (ESF). ISX is a collaborative effort between SRI International and Cal Poly. This project addresses the science question: To what distance along a flux tube does an irregularity of certain transverse-scale extend? It has been difficult to measure the magnetic field-alignment of scintillation-scale turbulent structures because of the difficulty of sampling a flux tube at multiple locations within a short time. This measurement is now possible due to the worldwide transition to DTV, which presents unique signals of opportunity for remote sensing of ionospheric irregularities from numerous vantage points. DTV spectra, in various formats, contain phase-stable, narrowband pilot carrier components that are transmitted simultaneously. A 4-channel radar receiver will simultaneously record up to 4 spatially separated transmissions from the ground. Correlations of amplitude and phase scintillation patterns corresponding to multiple points on the same flux tube will be a measure of the spatial extent of the structures along the magnetic field. A subset of geometries where two or more transmitters are aligned with the orbital path will be used to infer the temporal development of the structures. ISX has the following broad impact. Scintillation of space-based radio signals is a space weather problem that is intensively studied. ISX is a step toward a CubeSat constellation to monitor worldwide TEC variations and radio wave distortions on thousands of ionospheric paths. Furthermore, the rapid sampling along spacecraft orbits provides a unique dataset to deterministically reconstruct ionospheric irregularities at scintillation-scale resolution using diffraction radio tomography, a technique that enables prediction of scintillations at other radio frequencies, and potentially, mitigation of phase distortions.

A formalism for reference dosimetry in photon beams in the presence of a magnetic field

NASA Astrophysics Data System (ADS)

van Asselen, B.; Woodings, S. J.; Hackett, S. L.; van Soest, T. L.; Kok, J. G. M.; Raaymakers, B. W.; Wolthaus, J. W. H.

2018-06-01

A generic formalism is proposed for reference dosimetry in the presence of a magnetic field. Besides the regular correction factors from the conventional reference dosimetry formalisms, two factors are used to take into account magnetic field effects: (1) a dose conversion factor to correct for the change in local dose distribution and (2) a correction of the reading of the dosimeter used for the reference dosimetry measurements. The formalism was applied to the Elekta MRI-Linac, for which the 1.5 T magnetic field is orthogonal to the 7 MV photon beam. For this setup at reference conditions it was shown that the dose decreases with increasing magnetic field strength. The reduction in local dose for a 1.5 T transverse field, compared to no field is 0.51%  ±  0.03% at the reference point of 10 cm depth. The effect of the magnetic field on the reading of the dosimeter was measured for two waterproof ionization chambers types (PTW 30013 and IBA FC65-G) before and after multiple ramp-up and ramp-downs of the magnetic field. The chambers were aligned perpendicular and parallel to the magnetic field. The corrections of the readings of the perpendicularly aligned chambers were 0.967  ±  0.002 and 0.957  ±  0.002 for respectively the PTW and IBA ionization chambers. In the parallel alignment the corrections were small; 0.997  ±  0.001 and 1.002  ±  0.003 for the PTW and IBA chamber respectively. The change in reading due to the magnetic field can be measured by individual departments. The proposed formalism can be used to determine the correction factors needed to establish the absorbed dose in a magnetic field. It requires Monte Carlo simulations of the local dose and measurements of the response of the dosimeter. The formalism was successfully implemented for the MRI-Linac and is applicable for other field strengths and geometries.

A formalism for reference dosimetry in photon beams in the presence of a magnetic field.

PubMed

van Asselen, B; Woodings, S J; Hackett, S L; van Soest, T L; Kok, J G M; Raaymakers, B W; Wolthaus, J W H

2018-06-11

A generic formalism is proposed for reference dosimetry in the presence of a magnetic field. Besides the regular correction factors from the conventional reference dosimetry formalisms, two factors are used to take into account magnetic field effects: (1) a dose conversion factor to correct for the change in local dose distribution and (2) a correction of the reading of the dosimeter used for the reference dosimetry measurements. The formalism was applied to the Elekta MRI-Linac, for which the 1.5 T magnetic field is orthogonal to the 7 MV photon beam. For this setup at reference conditions it was shown that the dose decreases with increasing magnetic field strength. The reduction in local dose for a 1.5 T transverse field, compared to no field is 0.51%  ±  0.03% at the reference point of 10 cm depth. The effect of the magnetic field on the reading of the dosimeter was measured for two waterproof ionization chambers types (PTW 30013 and IBA FC65-G) before and after multiple ramp-up and ramp-downs of the magnetic field. The chambers were aligned perpendicular and parallel to the magnetic field. The corrections of the readings of the perpendicularly aligned chambers were 0.967  ±  0.002 and 0.957  ±  0.002 for respectively the PTW and IBA ionization chambers. In the parallel alignment the corrections were small; 0.997  ±  0.001 and 1.002  ±  0.003 for the PTW and IBA chamber respectively. The change in reading due to the magnetic field can be measured by individual departments. The proposed formalism can be used to determine the correction factors needed to establish the absorbed dose in a magnetic field. It requires Monte Carlo simulations of the local dose and measurements of the response of the dosimeter. The formalism was successfully implemented for the MRI-Linac and is applicable for other field strengths and geometries.

Magnetic properties and coercivity mechanism of Sm{sub 1-x}Pr{sub x}Co{sub 5} (x=0-0.6) nanoflakes prepared by surfactant-assisted ball milling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, M. L.; Yue, M., E-mail: yueming@bjut.edu.cn; Wu, Q.

2016-05-15

Sm{sub 1-x}Pr{sub x}Co{sub 5} (x=0-0.6) nanoflakes with CaCu{sub 5} structure were successfully prepared by surfactant-assisted high-energy ball milling (SAHEBM). The crystal structure and magnetic properties of Sm{sub 1-x}Pr{sub x}Co{sub 5} (x=0-0.6) nanoflakes were studied by X-ray diffraction and vibrating sample magnetometer. Effects of Pr addition on the structure, magnetic properties and coercivity mechanism of Sm{sub 1-x}Pr{sub x}Co{sub 5} nanoflakes were systematically investigated. XRD results show that all the nanoflakes have a hexagonal CaCu{sub 5}-type (Sm, Pr){sub 1}Co{sub 5} main phase and the (Sm, Pr){sub 2}Co{sub 7} impurity phase, and all of the samples exhibit a strong (00l) texture after magneticmore » alignment. As the Pr content increases, remanence firstly increases, then slightly reduced, while anisotropy field (H{sub A}) and H{sub ci} of decrease monotonically. Maximum energy product [(BH){sub max}] of the flakes increases first, peaks at 24.4 MGOe with Pr content of x = 0.4, then drops again. Magnetization behavior analysis indicate that the coercivity mechanism is mainly controlled by inhomogeneous domain wall pinning, and the pinning strength weakens with the increased Pr content, suggesting the great influence of H{sub A} on the coercivity of flakes.« less

Highly reproducible laser beam scanning device for an internal source laser desorption microprobe Fourier transform mass spectrometer

NASA Astrophysics Data System (ADS)

Scott, Jill R.; Tremblay, Paul L.

2002-03-01

Traditionally, mass spectrometry has relied on manipulating the sample target to provide scanning capabilities for laser desorption microprobes. This has been problematic for an internal source laser desorption Fourier transform mass spectrometer (LD-FTMS) because of the high magnetic field (7 Tesla) and geometric constraints of the superconducting magnet bore. To overcome these limitations, we have implemented a unique external laser scanning mechanism for an internal source LD-FTMS. This mechanism provides adjustable resolution enhancement so that the spatial resolution at the target is not limited to that of the stepper motors at the light source (˜5 μm/step). The spatial resolution is now limited by the practical optical diffraction limit of the final focusing lens. The scanning mechanism employs a virtual source that is wavelength independent up to the final focusing lens, which can be controlled remotely to account for focal length dependence on wavelength. A binary index provides an automatic alignment feature. The virtual source is located ˜9 ft from the sample; therefore, it is completely outside of the vacuum system and beyond the 50 G line of the fringing magnetic field. To eliminate reproducibility problems associated with vacuum pump vibrations, we have taken advantage of the magnetic field inherent to the FTMS to utilize Lenz's law for vibrational dampening. The LD-FTMS microprobe has exceptional reproducibility, which enables successive mapping sequences for depth-profiling studies.

Synthesis and optimization of the magnetic properties of aligned strontium ferrite nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ebrahimi, Fatemeh, E-mail: F.Ebrahimi@ma.iut.ac.ir; Bakhshi, Saeed Reza; Ashrafizadeh, Fakhreddin

Highlights: • Dip coating method was used to synthesize strontium ferrite nanowires in template. • Size of nanowires was controlled via anodization parameters. • Fe/Sr ratio was optimized in precursor. • Magnetic properties of nanowires and nanopowders were compared. - Abstract: High aspect ratio strontium hexaferrite nanowires were fabricated by dip coating in alumina template. Fe/Sr ratio was changed from 10 to 12 in precursor, and the samples were annealed at a range of temperatures 500–900 °C in order to optimize the magnetic properties of strontium ferrite in the form of nanowires. Field emission scanning electron microscope (FESEM) proved themore » formation of nanowires in the templates, while TEM images revealed a high degree of crystallinity. The ferrites were further characterized by X-ray diffraction (XRD) and energy dispersive X-ray spectrometer (EDS). Magnetic properties of the specimens were studied by a SQUID at 10–300 K. The results showed that the coercivity of packed density nanowires in the template was much less than that of the nanopowders. On the other hand, the coercivity of nanowires at ambient temperature was less than low temperature coercivity.« less

Directional preference in dogs: Laterality and "pull of the north"

PubMed Central

Adámková, Jana; Svoboda, Jan; Benediktová, Kateřina; Martini, Sabine; Nováková, Petra; Tůma, David; Kučerová, Michaela; Divišová, Michaela; Begall, Sabine; Hart, Vlastimil

2017-01-01

Laterality is a well described phenomenon in domestic dogs. It was shown that dogs, under calm Earth's magnetic field conditions, when marking their home ranges, tend to head about north- or southwards and display thus magnetic alignment. The question arises whether magnetic alignment might be affected or even compromised by laterality and vice versa. We tested the preference of dogs to choose between two dishes with snacks that were placed left and right, in different compass directions (north and east, east and south, south and west or west and north) in front of them. Some dogs were right-lateral, some left-lateral but most of them were ambilateral. There was a preference for the dish placed north compared to the one placed east of the dog ("pull of the north"). This effect was highly significant in small and medium-sized breeds but not in larger breeds, highly significant in females, in older dogs, in lateralized dogs but less significant or not significant in males, younger dogs, or ambilateral dogs. Laterality and “pull of the north” are phenomena which should be considered in diverse tasks and behavioral tests with which dogs or other animals might be confronted. The interaction and possible conflict between lateralization and "pull of the north" might be also considered as a reason for shifted magnetic alignment observed in different animal species in different contexts. PMID:28945773

Directional preference in dogs: Laterality and "pull of the north".

PubMed

Adámková, Jana; Svoboda, Jan; Benediktová, Kateřina; Martini, Sabine; Nováková, Petra; Tůma, David; Kučerová, Michaela; Divišová, Michaela; Begall, Sabine; Hart, Vlastimil; Burda, Hynek

2017-01-01

Laterality is a well described phenomenon in domestic dogs. It was shown that dogs, under calm Earth's magnetic field conditions, when marking their home ranges, tend to head about north- or southwards and display thus magnetic alignment. The question arises whether magnetic alignment might be affected or even compromised by laterality and vice versa. We tested the preference of dogs to choose between two dishes with snacks that were placed left and right, in different compass directions (north and east, east and south, south and west or west and north) in front of them. Some dogs were right-lateral, some left-lateral but most of them were ambilateral. There was a preference for the dish placed north compared to the one placed east of the dog ("pull of the north"). This effect was highly significant in small and medium-sized breeds but not in larger breeds, highly significant in females, in older dogs, in lateralized dogs but less significant or not significant in males, younger dogs, or ambilateral dogs. Laterality and "pull of the north" are phenomena which should be considered in diverse tasks and behavioral tests with which dogs or other animals might be confronted. The interaction and possible conflict between lateralization and "pull of the north" might be also considered as a reason for shifted magnetic alignment observed in different animal species in different contexts.

Ion irradiation effects on a magnetic Si/Ni/Si trilayer and lateral magnetic-nonmagnetic multistrip patterning by focused ion beam

NASA Astrophysics Data System (ADS)

Dev, B. N.; Banu, Nasrin; Fassbender, J.; Grenzer, J.; Schell, N.; Bischoff, L.; Groetzschel, R.; McCord, J.

2017-10-01

Fabrication of a multistrip magnetic/nonmagnetic structure in a thin sandwiched Ni layer [Si(5 nm)/Ni(15 nm)/Si] by a focused ion beam (FIB) irradiation has been attempted. A control experiment was initially performed by irradiation with a standard 30 keV Ga ion beam at various fluences. Analyses were carried out by Rutherford backscattering spectrometry, X-ray reflectivity, magnetooptical Kerr effect (MOKE) measurements and MOKE microscopy. With increasing ion fluence, the coercivity as well as Kerr rotation decreases. A threshold ion fluence has been identified, where ferromagnetism of the Ni layer is lost at room temperature and due to Si incorporation into the Ni layer, a Ni0.68Si0.32 alloy layer is formed. This fluence was used in FIB irradiation of parallel 50 nm wide stripes, leaving 1 µm wide unirradiated stripes in between. MOKE microscopy on this FIB-patterned sample has revealed interacting magnetic domains across several stripes. Considering shape anisotropy effects, which would favour an alignment of magnetization parallel to the stripe axis, the opposite behaviour is observed. Magneto-elastic effects introducing a stress-induced anisotropy component oriented perpendicular to the stripe axis are the most plausible explanation for the observed behaviour.

Designing an optimum pulsed magnetic field by a resistance/self-inductance/capacitance discharge system and alignment of carbon nanotubes embedded in polypyrrole matrix

NASA Astrophysics Data System (ADS)

Kazemikia, Kaveh; Bonabi, Fahimeh; Asadpoorchallo, Ali; Shokrzadeh, Majid

2015-02-01

In this work, an optimized pulsed magnetic field production apparatus is designed based on a RLC (Resistance/Self-inductance/Capacitance) discharge circuit. An algorithm for designing an optimum magnetic coil is presented. The coil is designed to work at room temperature. With a minor physical reinforcement, the magnetic flux density can be set up to 12 Tesla with 2 ms duration time. In our design process, the magnitude and the length of the magnetic pulse are the desired parameters. The magnetic field magnitude in the RLC circuit is maximized on the basis of the optimal design of the coil. The variables which are used in the optimization process are wire diameter and the number of coil layers. The coil design ensures the critically damped response of the RLC circuit. The electrical, mechanical, and thermal constraints are applied to the design process. A locus of probable magnetic flux density values versus wire diameter and coil layer is provided to locate the optimum coil parameters. Another locus of magnetic flux density values versus capacitance and initial voltage of the RLC circuit is extracted to locate the optimum circuit parameters. Finally, the application of high magnetic fields on carbon nanotube-PolyPyrrole (CNT-PPy) nano-composite is presented. Scanning probe microscopy technique is used to observe the orientation of CNTs after exposure to a magnetic field. The result shows alignment of CNTs in a 10.3 Tesla, 1.5 ms magnetic pulse.

Penetration of Magnetosheath Plasma into Dayside Magnetosphere. 2. ; Magnetic Field in Plasma Filaments

NASA Technical Reports Server (NTRS)

Lyatsky, Wladislaw; Pollock, Craig; Goldstein, Melvyn L.; Lyatskaya, Sonya Inna; Avanov, Levon Albert

2016-01-01

In this paper, we examined plasma structures (filaments), observed in the dayside magnetosphere but containing magnetosheath plasma. These filaments show the stable antisunward motion (while the ambient magnetospheric plasma moved in the opposite direction) and the existence of a strip of magnetospheric plasma, separating these filaments from the magnetosheath. These results, however, contradict both theoretical studies and simulations by Schindler (1979), Ma et al. (1991), Dai and Woodward (1994, 1998), and other researchers, who reported that the motion of such filaments through the magnetosphere is possible only when their magnetic field is directed very close to the ambient magnetic field, which is not the situation that is observed. In this study, we show that this seeming contradiction may be related to different events as the theoretical studies and simulations are related to the case when the filament magnetic field is about aligned with filament orientation, whereas the observations show that the magnetic field in these filaments may be rotating. In this case, the rotating magnetic field, changing incessantly its direction, drastically affects the penetration of plasma filaments into the magnetosphere. In this case, the filaments with rotating magnetic field, even if in each moment it is significantly inclined to the ambient magnetic field, may propagate through the magnetosphere, if their average (for the rotation period) magnetic field is aligned with the ambient magnetic field. This shows that neglecting the rotation of magnetic field in these filaments may lead to wrong results.

Measurement of untruncated nuclear spin interactions via zero- to ultralow-field nuclear magnetic resonance

NASA Astrophysics Data System (ADS)

Blanchard, J. W.; Sjolander, T. F.; King, J. P.; Ledbetter, M. P.; Levine, E. H.; Bajaj, V. S.; Budker, D.; Pines, A.

2015-12-01

Zero- to ultralow-field nuclear magnetic resonance (ZULF NMR) provides a new regime for the measurement of nuclear spin-spin interactions free from the effects of large magnetic fields, such as truncation of terms that do not commute with the Zeeman Hamiltonian. One such interaction, the magnetic dipole-dipole coupling, is a valuable source of spatial information in NMR, though many terms are unobservable in high-field NMR, and the coupling averages to zero under isotropic molecular tumbling. Under partial alignment, this information is retained in the form of so-called residual dipolar couplings. We report zero- to ultralow-field NMR measurements of residual dipolar couplings in acetonitrile-2-13C aligned in stretched polyvinyl acetate gels. This permits the investigation of dipolar couplings as a perturbation on the indirect spin-spin J coupling in the absence of an applied magnetic field. As a consequence of working at zero magnetic field, we observe terms of the dipole-dipole coupling Hamiltonian that are invisible in conventional high-field NMR. This technique expands the capabilities of zero- to ultralow-field NMR and has potential applications in precision measurement of subtle physical interactions, chemical analysis, and characterization of local mesoscale structure in materials.

Thin-Film Permanent Magnets for Integrated Electromagnetic Components.

DTIC Science & Technology

1992-06-01

crystallization growth temperature, the self demagnetization energy can be used to favor the growth of crystallites with the easy axes of magnetization ...due to the demagnetization energy. 5 Relatively thick films of Sm-Co based permanent magnet films have been deposited onto precoated sapphire and A12 0...of films with the easy axes of magnetization aligned onto the film plane. The self demagnetization field can only affect the film texture for systems

Latitudinal and longitudinal behavior of the geomagnetic field during a disturbed period: A case study using wavelet techniques

NASA Astrophysics Data System (ADS)

Klausner, Virginia; Domingues, Margarete Oliveira; Mendes, Odim; da Costa, Aracy Mendes; Papa, Andres Reinaldo Rodriguez; Gonzalez, Arian Ojeda

2016-11-01

Coronal mass ejections are the primary cause of the highly disturbed conditions observed in the magnetosphere. Momentum and energy from the solar wind are transferred to the Earth's magnetosphere mainly via magnetic reconnection which produces open field lines connecting the Earth magnetic field to the solar wind. Magnetospheric currents are coupled to the ionosphere through field-aligned currents. This particular characteristic of the magnetosphere-ionosphere interconnection is discussed here on the basis of the energy transfer from high (auroral currents) to low-latitudes (ring current). The objective of this work is to examine how the conditions during a magnetic storm can affect the global space and time configuration of the ring current, and, how these processes can affect the region of the South Atlantic Magnetic Anomaly. The H- or X-components of the Earth's magnetic field were examined using a set of six magnetometers approximately aligned around the geographic longitude at about 10 °, 140 ° and 295 ° from latitudes of 70 ° N to 70 ° S and aligned throughout the equatorial region, for the event of October 18-22, 1998. The investigation of simultaneous observations of data measured at different locations makes it possible to determine the effects of the magnetosphere-ionosphere coupling, and, it tries to establish some relationships among them. This work also compares the responses of the aligned magnetic observatories to the responses in the South Atlantic Magnetic Anomaly region. The major contribution of this paper is related to the applied methodology of the discrete wavelet transform. The wavelet coefficients are used as a filter to extract the information in high frequencies of the analyzed magnetogram. They also better represent information about the injections of energy and, consequently, the disturbances of the geomagnetic field measured on the ground. As a result, we present a better way to visualize the correlation between the X- or H-components. In the latitude range from ∼ 40 ° S to ∼ 60 ° N, the wavelet signatures do not show remarkable differences, except for the amplitudes of the wavelet coefficients. The sequence of transient field variations detected at auroral latitudes is probably associated to occurrences of substorms, while at lower latitudes, these variations are associated to the enhancement of the ring current.

Field-aligned currents observed in the vicinity of a moving auroral arc

NASA Technical Reports Server (NTRS)

Goertz, C. K.; Bruening, K.

1984-01-01

The sounding rocket Porcupine F4 was launched into an auroral arc and the field aligned currents were independently deduced from magnetic field measurements; the horizontal current deduced from the electric field measurements and height integrated conductivity calculations; and measurements of electron fluxes. Above the arc the different methods agree. The magnetosphere acts as generator and the ionosphere as load. North of the arc, the first two methods disagree, possibly due to an Alfven wave carrying the observed magnetic field perturbation. The energy flow is out of the ionosphere. Here the ionosphere acts as generator and the magnetosphere as load.

Net field-aligned currents observed by Triad

NASA Technical Reports Server (NTRS)

Sugiura, M.; Potemra, T. A.

1975-01-01

From the Triad magnetometer observation of a step-like level shift in the east-west component of the magnetic field at 800 km altitude, the existence of a net current flowing into or away from the ionosphere in a current layer was inferred. The current direction is toward the ionosphere on the morning side and away from it on the afternoon side. The field aligned currents observed by Triad are considered as being an important element in the electro-dynamical coupling between the distant magnetosphere and the ionosphere. The current density integrated over the thickness of the layer increases with increasing magnetic activity, but the relation between the current density and Kp in individual cases is not a simple linear relation. An extrapolation of the statistical relation to Kp = 0 indicates existence of a sheet current of order 0.1 amp/m even at extremely quiet times. During periods of higher magnetic activity an integrated current of approximately 1 amp/m and average current density of order 0.000001 amp/sq m are observed. The location and the latitudinal width of the field aligned current layer carrying the net current very roughly agree with those of the region of high electron intensities in the trapping boundary.

Low-energy ion distribution functions on a magnetically quiet day at geostationary altitude /L = 7/

NASA Technical Reports Server (NTRS)

Singh, N.; Raitt, W. J.; Yasuhara, F.

1982-01-01

Ion energy and pitch angle distribution functions are examined for a magnetically quiet day using averaged data from ATS 6. For both field-aligned and perpendicular fluxes, the populations have a mixture of characteristic energies, and the distribution functions can be fairly well approximated by Maxwellian distributions over three different energy bands in the range 3-600 eV. Pitch angle distributions varying with local time, and energy distributions are used to compute total ion density. Pitch angle scattering mechanisms responsible for the observed transformation of pitch angle distribution are examined, and it is found that a magnetic noise of a certain power spectral density belonging to the electromagnetic ion cyclotron mode near the ion cyclotron frequency can be effective in trapping the field aligned fluxes by pitch angle scattering.

Magnetically aligned nanodomains: application in high-performance ion conductive membranes.

PubMed

Hasani-Sadrabadi, Mohammad Mahdi; Majedi, Fatemeh Sadat; Coullerez, Géraldine; Dashtimoghadam, Erfan; VanDersarl, Jules John; Bertsch, Arnaud; Moaddel, Homayoun; Jacob, Karl I; Renaud, Philippe

2014-05-28

Polyelectrolyte-coated magnetic nanoparticles were prepared by decorating the surface of superparamagnetic iron oxide nanoparticles (SPIONs) with crosslinked chitosan oligopolysaccharide (CS). These positively charged particles (CS-SPIONs) were then added to a negatively charged polymer (Nafion), and cast into membranes under an applied magnetic field. TEM and SAXS measurements confirmed this process created aligned, cylindrical nanodomains in the membranes. This was also indirectly confirmed by proton conductivity values. The strong electrostatic interaction between chitosan and Nafion prevented oxygen permeability and water evaporation at elevated temperatures through the proton conductive channels. The resultant proton exchange membranes showed lower conduction dependency to relative humidity, which is highly desirable for hydrogen fuel cells. The fuel cell performance tests were performed on the designed polyelectrolyte membrane by hydrogen-oxygen single cells at elevated temperature (120 °C) and low relative humidity.

Enhancement of room temperature ferromagnetism in tin oxide nanocrystal using organic solvents

NASA Astrophysics Data System (ADS)

Sakthiraj, K.; Hema, M.; Balachandra Kumar, K.

2017-10-01

The effect of organic solvents (ethanol & ethylene glycol) on the room temperature ferromagnetism in nanocrystalline tin oxide has been studied. The samples were synthesized using sol-gel method with the mixture of water & organic liquid as solvent. It is found that pristine SnO2 nanocrystal contain two different types of paramagnetic centres over their surface:(i) surface chemisorbed oxygen species and (ii) Sn interstitial & oxygen vacancy defect pair. The magnetic moment induced in the as-prepared samples is mainly contributed by the alignment of local spin moments resulting from these defects. These surface defect states are highly activated by the usage of ethylene glycol solvent rather than ethylene in tin oxide nanostructure synthesis. Powder X-ray diffraction, transmission electron microscope imaging, energy dispersive spectrometry, Fourier transformed infrared spectroscopy, UV-vis absorption spectroscopy, photoluminescence spectroscopy, vibrating sample magnetometer measurement and electron spin resonance spectroscopy were employed to characterize the nanostructured tin oxide materials.

Magnetic resonance imaging of the long head of the biceps tendon: benefit of coplanar image.

PubMed

Lin, Anderson; Ting, Julius; Lee, Kwo-Whei

2007-01-01

To evaluate coplanar imaging of the long head of the biceps tendon. We retrospectively compared coronal oblique magnetic resonance images aligned with the principal supraspinatus tendon and with the intra-articular biceps tendon in 21 patients. Magnetic resonance images were analyzed for lesions depicted, including superior labral anteroposterior (SLAP) tears. Arthroscopic findings were reviewed. Coronal oblique images aligned with intra-articular biceps tendon depicted 18 (86%) of 21 coplanar intra-articular biceps tendons. Coplanar images identified 6 cases of tendinosis, 1 tear, 3 intra-articular ruptures, and 20 (95.2%) of 21 exact origins of the tendon. Arthroscopy revealed 18 SLAP tears. The detection of SLAP lesions between both coronal oblique magnetic resonance images was significantly different (P = 0.007). Advantages included imaging of the intra-articular biceps tendon with least partial-volume effects, definition of SLAP lesions and the tendinous origin at the supraglenoid tubercle, depiction of intra-articular bicipital ruptures, and increased sensitivity and specificity for intra-articular lesions.

Nighttime magnetic field fluctuations in the topside ionosphere at midlatitudes and their relation to medium-scale traveling ionospheric disturbances: The spatial structure and scale sizes

NASA Astrophysics Data System (ADS)

Park, Jaeheung; Lühr, Hermann; Kervalishvili, Guram; Rauberg, Jan; Michaelis, Ingo; Stolle, Claudia; Kwak, Young-Sil

2015-08-01

Previous studies suggested that electric and/or magnetic field fluctuations observed in the nighttime topside ionosphere at midlatitudes generally originate from quiet time nocturnal medium-scale traveling ionospheric disturbances (MSTIDs). However, decisive evidences for the connection between the two have been missing. In this study we make use of the multispacecraft observations of midlatitude magnetic fluctuations (MMFs) in the nighttime topside ionosphere by the Swarm constellation. The analysis results show that the area hosting MMFs is elongated in the NW-SE (NE-SW) direction in the Northern (Southern) Hemisphere. The elongation direction and the magnetic field polarization support that the area hosting MMFs is nearly field aligned. All these properties of MMFs suggest that they have close relationship with MSTIDs. Expectation values of root-mean-square field-aligned currents associated with MMFs are up to about 4 nA/m2. MMF coherency significantly drops for longitudinal distances of ≥1∘.

Investigation of the Possibility of Using Nuclear Magnetic Spin Alignment

NASA Technical Reports Server (NTRS)

Dent, William V., Jr.

1998-01-01

The goal of the program to investigate a "Gasdynamic fusion propulsion system for space exploration" is to develop a fusion propulsion system for a manned mission to the planet mars. A study using Deuterium and Tritium atoms are currently in progress. When these atoms under-go fusion, the resulting neutrons and alpha particles are emitted in random directions (isotropically). The probable direction of emission is equal for all directions, thus resulting in wasted energy, massive shielding and cooling requirements, and serious problems with the physics of achieving fusion. If the nuclear magnetic spin moments of the deuterium and tritium nuclei could be precisely aligned at the moment of fusion, the stream of emitted neutrons could be directed out the rear of the spacecraft for thrust and the alpha particles directed forward into an electromagnet ot produce electricity to continue operating the fusion engine. The following supporting topics are discussed: nuclear magnetic moments and spin precession in magnetic field, nuclear spin quantum mechanics, kinematics of nuclear reactions, and angular distribution of particles.

Disparate ultrafast dynamics of itinerant and localized magnetic moments in gadolinium metal

PubMed Central

Frietsch, B.; Bowlan, J.; Carley, R.; Teichmann, M.; Wienholdt, S.; Hinzke, D.; Nowak, U.; Carva, K.; Oppeneer, P. M.; Weinelt, M.

2015-01-01

The Heisenberg–Dirac intra-atomic exchange coupling is responsible for the formation of the atomic spin moment and thus the strongest interaction in magnetism. Therefore, it is generally assumed that intra-atomic exchange leads to a quasi-instantaneous aligning process in the magnetic moment dynamics of spins in separate, on-site atomic orbitals. Following ultrashort optical excitation of gadolinium metal, we concurrently record in photoemission the 4f magnetic linear dichroism and 5d exchange splitting. Their dynamics differ by one order of magnitude, with decay constants of 14 versus 0.8 ps, respectively. Spin dynamics simulations based on an orbital-resolved Heisenberg Hamiltonian combined with first-principles calculations explain the particular dynamics of 5d and 4f spin moments well, and corroborate that the 5d exchange splitting traces closely the 5d spin-moment dynamics. Thus gadolinium shows disparate dynamics of the localized 4f and the itinerant 5d spin moments, demonstrating a breakdown of their intra-atomic exchange alignment on a picosecond timescale. PMID:26355196

Comparison of Flux-Surface Aligned Curvilinear Coordinate Systems and Neoclassical Magnetic Field Predictions

NASA Astrophysics Data System (ADS)

Collart, T. G.; Stacey, W. M.

2015-11-01

Several methods are presented for extending the traditional analytic ``circular'' representation of flux-surface aligned curvilinear coordinate systems to more accurately describe equilibrium plasma geometry and magnetic fields in DIII-D. The formalism originally presented by Miller is extended to include different poloidal variations in the upper and lower hemispheres. A coordinate system based on separate Fourier expansions of major radius and vertical position greatly improves accuracy in edge plasma structure representation. Scale factors and basis vectors for a system formed by expanding the circular model minor radius can be represented using linear combinations of Fourier basis functions. A general method for coordinate system orthogonalization is presented and applied to all curvilinear models. A formalism for the magnetic field structure in these curvilinear models is presented, and the resulting magnetic field predictions are compared against calculations performed in a Cartesian system using an experimentally based EFIT prediction for the Grad-Shafranov equilibrium. Supported by: US DOE under DE-FG02-00ER54538.

Beam based alignment and its relevance in Indus-2.

PubMed

Jena, Saroj Kumar; Husain, Riyasat; Gandhi, M L; Agrawal, R K; Yadav, S; Ghodke, A D

2015-09-01

Initially in the Indus-2 storage ring, the closed orbit distortion (COD) could be best corrected to 1.3 mm rms in the horizontal and 0.43 mm rms in the vertical plane. The strength of the corrector magnets required high values for COD correction. This revealed that offsets in COD readout by the beam position monitors (BPMs) played a role in not achieving a rms COD lower than the above value. Thus, the offset between the electrical center of BPMs and the magnetic center of the nearest quadrupole magnet could be estimated using the beam based alignment (BBA) method. It prefers that the quadrupole magnet is able to be controlled individually and active shunt power supply (ASPS) system was designed for this purpose that works efficiently. This paper describes the methodology of BBA, topology of ASPS and its performance, and COD minimization using the measured BPM offsets. After BBA, the COD could be reduced to 0.45 mm rms and 0.2 mm rms in horizontal and vertical planes, respectively.

Beam based alignment and its relevance in Indus-2

NASA Astrophysics Data System (ADS)

Jena, Saroj Kumar; Husain, Riyasat; Gandhi, M. L.; Agrawal, R. K.; Yadav, S.; Ghodke, A. D.

2015-09-01

Initially in the Indus-2 storage ring, the closed orbit distortion (COD) could be best corrected to 1.3 mm rms in the horizontal and 0.43 mm rms in the vertical plane. The strength of the corrector magnets required high values for COD correction. This revealed that offsets in COD readout by the beam position monitors (BPMs) played a role in not achieving a rms COD lower than the above value. Thus, the offset between the electrical center of BPMs and the magnetic center of the nearest quadrupole magnet could be estimated using the beam based alignment (BBA) method. It prefers that the quadrupole magnet is able to be controlled individually and active shunt power supply (ASPS) system was designed for this purpose that works efficiently. This paper describes the methodology of BBA, topology of ASPS and its performance, and COD minimization using the measured BPM offsets. After BBA, the COD could be reduced to 0.45 mm rms and 0.2 mm rms in horizontal and vertical planes, respectively.

Physically motivated global alignment method for electron tomography

DOE PAGES

Sanders, Toby; Prange, Micah; Akatay, Cem; ...

2015-04-08

Electron tomography is widely used for nanoscale determination of 3-D structures in many areas of science. Determining the 3-D structure of a sample from electron tomography involves three major steps: acquisition of sequence of 2-D projection images of the sample with the electron microscope, alignment of the images to a common coordinate system, and 3-D reconstruction and segmentation of the sample from the aligned image data. The resolution of the 3-D reconstruction is directly influenced by the accuracy of the alignment, and therefore, it is crucial to have a robust and dependable alignment method. In this paper, we develop amore » new alignment method which avoids the use of markers and instead traces the computed paths of many identifiable ‘local’ center-of-mass points as the sample is rotated. Compared with traditional correlation schemes, the alignment method presented here is resistant to cumulative error observed from correlation techniques, has very rigorous mathematical justification, and is very robust since many points and paths are used, all of which inevitably improves the quality of the reconstruction and confidence in the scientific results.« less

Magnetically aligned H I fibers and the rolling hough transform

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, S. E.; Putman, M. E.; Peek, J. E. G.

2014-07-01

We present observations of a new group of structures in the diffuse Galactic interstellar medium (ISM): slender, linear H I features we dub 'fibers' that extend for many degrees at high Galactic latitude. To characterize and measure the extent and strength of these fibers, we present the Rolling Hough Transform, a new machine vision method for parameterizing the coherent linearity of structures in the image plane. With this powerful new tool we show that the fibers are oriented along the interstellar magnetic field as probed by starlight polarization. We find that these low column density (N{sub H} {sub I}≃5×10{sup 18}more » cm{sup –2}) fiber features are most likely a component of the local cavity wall, about 100 pc away. The H I data we use to demonstrate this alignment at high latitude are from the Galactic Arecibo L-Band Feed Array H I (GALFA-H I) Survey and the Parkes Galactic All Sky Survey. We find better alignment in the higher resolution GALFA-H I data, where the fibers are more visually evident. This trend continues in our investigation of magnetically aligned linear features in the Riegel-Crutcher H I cold cloud, detected in the Southern Galactic Plane Survey. We propose an application of the RHT for estimating the field strength in such a cloud, based on the Chandrasekhar-Fermi method. We conclude that data-driven, quantitative studies of ISM morphology can be very powerful predictors of underlying physical quantities.« less

Microstructural evolution and magnetic properties of ultrafine solute-atom particles formed in a Cu75-Ni20-Fe5 alloy on isothermal annealing

NASA Astrophysics Data System (ADS)

Kim, Jun-Seop; Takeda, Mahoto; Bae, Dong-Sik

2016-12-01

Microstructural features strongly affect magnetism in nano-granular magnetic materials. In the present work we have investigated the relationship between the magnetic properties and the self-organized microstructure formed in a Cu75-Ni20-Fe5 alloy comprising ferromagnetic elements and copper atoms. High resolution transmission electron microscopy (HRTEM) observations showed that on isothermal annealing at 873 K, nano-scale solute (Fe,Ni)-rich clusters initially formed with a random distribution in the Cu-rich matrix. Superconducting quantum interference device (SQUID) measurements revealed that these ultrafine solute clusters exhibited super-spinglass and superparamagnetic states. On further isothermal annealing the precipitates evolved to cubic or rectangular ferromagnetic particles and aligned along the <100> directions of the copper-rich matrix. Electron energy-band calculations based on the first-principle Korringa-Kohn-Rostocker (KKR) method were also implemented to investigate both the electronic structure and the magnetic properties of the alloy. Inputting compositions obtained experimentally by scanning transmission electron microscopy-electron dispersive X-ray spectroscopy (STEM-EDS) analysis, the KKR calculation confirmed that ferromagnetic precipitates (of moment 1.07μB per atom) formed after annealing for 2 × 104 min. Magneto-thermogravimetric (MTG) analysis determined with high sensitivity the Curie temperatures and magnetic susceptibility above room temperature of samples containing nano-scale ferromagnetic particles.

Tamper resistant magnetic stripes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naylor, R.B.; Sharp, D.J.

1999-11-09

This invention relates to a magnetic stripe comprising a medium in which magnetized particles are suspended and in which the encoded information is recorded by actual physical rotation or alignment of the previously magnetized particles within the flux reversals of the stripe which are 180{degree} opposed in their magnetic polarity. The magnetized particles are suspended in a medium which is solid, or physically rigid, at ambient temperatures but which at moderately elevated temperatures, such as 40 C, is thinable to a viscosity permissive of rotation of the particles therein under applications of moderate external magnetic field strengths within acceptable timemore » limits.« less

Tamper resistant magnetic stripes

DOEpatents

Naylor, Richard Brian; Sharp, Donald J.

1999-01-01

This invention relates to a magnetic stripe comprising a medium in which magnetized particles are suspended and in which the encoded information is recorded by actual physical rotation or alignment of the previously magnetized particles within the flux reversals of the stripe which are 180.degree. opposed in their magnetic polarity. The magnetized particles are suspended in a medium which is solid, or physically rigid, at ambient temperatures but which at moderately elevated temperatures, such as 40.degree. C., is thinable to a viscosity permissive of rotation of the particles therein under applications of moderate external magnetic field strengths within acceptable time limits.

Sample holder with optical features

DOEpatents

Milas, Mirko; Zhu, Yimei; Rameau, Jonathan David

2013-07-30

A sample holder for holding a sample to be observed for research purposes, particularly in a transmission electron microscope (TEM), generally includes an external alignment part for directing a light beam in a predetermined beam direction, a sample holder body in optical communication with the external alignment part and a sample support member disposed at a distal end of the sample holder body opposite the external alignment part for holding a sample to be analyzed. The sample holder body defines an internal conduit for the light beam and the sample support member includes a light beam positioner for directing the light beam between the sample holder body and the sample held by the sample support member.

Transmission electron microscope sample holder with optical features

DOEpatents

Milas, Mirko [Port Jefferson, NY; Zhu, Yimei [Stony Brook, NY; Rameau, Jonathan David [Coram, NY

2012-03-27

A sample holder for holding a sample to be observed for research purposes, particularly in a transmission electron microscope (TEM), generally includes an external alignment part for directing a light beam in a predetermined beam direction, a sample holder body in optical communication with the external alignment part and a sample support member disposed at a distal end of the sample holder body opposite the external alignment part for holding a sample to be analyzed. The sample holder body defines an internal conduit for the light beam and the sample support member includes a light beam positioner for directing the light beam between the sample holder body and the sample held by the sample support member.

Exploration of a possible cause of magnetic reconfiguration/reconnection due to generation, rather than annihilation, of magnetic field in a nun-uniform thin current sheet

NASA Astrophysics Data System (ADS)

Huang, Y. C.; Lyu, L. H.

2014-12-01

Magnetic reconfiguration/reconnection plays an important role on energy and plasma transport in the space plasma. It is known that magnetic field lines on two sides of a tangential discontinuity can connect to each other only at a neutral point, where the strength of the magnetic field is equal to zero. Thus, the standard reconnection picture with magnetic field lines intersecting at the neutral point is not applicable to the component reconnection events observed at the magnetopause and in the solar corona. In our early study (Yu, Lyu, & Wu, 2011), we have shown that annihilation of magnetic field near a thin current sheet can lead to the formation of normal magnetic field component (normal to the current sheet) to break the frozen-in condition and to accelerate the reconnected plasma flux, even without the presence of a neutral point. In this study, we examine whether or not a generation, rather than annihilation, of magnetic field in a nun-uniform thin current sheet can also lead to reconnection of plasma flux. Our results indicate that a non-uniform enhancement of electric current can yield formation of field-aligned currents. The normal-component magnetic field generated by the field-aligned currents can yield reconnection of plasma flux just outside the current-enhancement region. The particle motion that can lead to non-uniform enhancement of electric currents will be discussed.

Non-rigid alignment in electron tomography in materials science.

PubMed

Printemps, Tony; Bernier, Nicolas; Bleuet, Pierre; Mula, Guido; Hervé, Lionel

2016-09-01

Electron tomography is a key technique that enables the visualization of an object in three dimensions with a resolution of about a nanometre. High-quality 3D reconstruction is possible thanks to the latest compressed sensing algorithms and/or better alignment and preprocessing of the 2D projections. Rigid alignment of 2D projections is routine in electron tomography. However, it cannot correct misalignments induced by (i) deformations of the sample due to radiation damage or (ii) drifting of the sample during the acquisition of an image in scanning transmission electron microscope mode. In both cases, those misalignments can give rise to artefacts in the reconstruction. We propose a simple-to-implement non-rigid alignment technique to correct those artefacts. This technique is particularly suited for needle-shaped samples in materials science. It is initiated by a rigid alignment of the projections and it is then followed by several rigid alignments of different parts of the projections. Piecewise linear deformations are applied to each projection to force them to simultaneously satisfy the rigid alignments of the different parts. The efficiency of this technique is demonstrated on three samples, an intermetallic sample with deformation misalignments due to a high electron dose typical to spectroscopic electron tomography, a porous silicon sample with an extremely thin end particularly sensitive to electron beam and another porous silicon sample that was drifting during image acquisitions. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

Spectroscopic characterizations of a mixed surfactant mesophase and its application in materials synthesis

NASA Astrophysics Data System (ADS)

Liu, Limin

A viscous lyotropic crystalline mesophase containing bis (2-ethylhexyl) sodium sulfosuccinate (AOT), alpha-phosphatidylcholine (lecithin), with comparable volume fractions of isooctane and water was characterized by Fourier-transform 31P and 1H nuclear magnetic resonance (NMR) spectroscopy. Shear alignment on the reverse hexagonal mesophase was reflected through both 31P NMR and 1H NMR spectra. A complicated 31P spectrum was observed as a result of superposition of chemical shifts according to the distribution of crystalline domains prior to shear. The initially disordered samples with polydomain structures became macroscopically aligned after Couette shear and the alignment retained for a long period of time. 31P NMR chemical shift anisotropy characteristics were used to elucidate orientation of the hexagonal phase. Interestingly, 1H NMR of the water, methyl and methylene groups exhibited spectral changes upon shear alignment closely corresponding with that of 31P NMR spectra. A reverse hexagonal to lamellar phase transition was manifested as an expanding of the expressed 31P NMR chemical shift anisotropy and an apparent reversal of the powder pattern with increasing water content and/or temperature. Correspondingly, 1H NMR spectra also experienced a spectral pattern transition as the water content or temperature was increased. These observations complement the findings of mesophase alignment obtained using small angle neutron scattering (SANS) and imply that 31P and 1H NMR spectroscopy can be used as probes to define microstructure and monitor orientation changes in this binary surfactant system. This is especially beneficial if these mesophases are used as templates for materials synthesis. The mesophase retains its alignment for extended periods allowing materials synthesis to be decoupled from the application of shear. Highly aligned string-like silica nanostructures were obtained through templated synthesis in the columnar hexagonal structure of the viscous lyotropic crystalline mesophase. A two-step procedure was used to first shear-align the surfactant mesophase, and then conduct synthesis under quiescent conditions in the mesophase. Polystyrene was post-grafted to the silica surface without disturbing its nanostring morphology. The coupling of materials synthesis in surfactant mesophases with processing techniques (e.g. extrusion) may result in functional materials, such as new catalyst support and membrane nanoarchitectures.

In vitro three-dimensional aortic vasculature modeling based on sensor fusion between intravascular ultrasound and magnetic tracker.

PubMed

Shi, Chaoyang; Tercero, Carlos; Ikeda, Seiichi; Ooe, Katsutoshi; Fukuda, Toshio; Komori, Kimihiro; Yamamoto, Kiyohito

2012-09-01

It is desirable to reduce aortic stent graft installation time and the amount of contrast media used for this process. Guidance with augmented reality can achieve this by facilitating alignment of the stent graft with the renal and mesenteric arteries. For this purpose, a sensor fusion is proposed between intravascular ultrasound (IVUS) and magnetic trackers to construct three-dimensional virtual reality models of the blood vessels, as well as improvements to the gradient vector flow snake for boundary detection in ultrasound images. In vitro vasculature imaging experiments were done with hybrid probe and silicone models of the vasculature. The dispersion of samples for the magnetic tracker in the hybrid probe increased less than 1 mm when the IVUS was activated. Three-dimensional models of the descending thoracic aorta, with cross-section radius average error of 0.94 mm, were built from the data fusion. The development of this technology will enable reduction in the amount of contrast media required for in vivo and real-time three-dimensional blood vessel imaging. Copyright © 2012 John Wiley & Sons, Ltd.

Polarized light modulates light-dependent magnetic compass orientation in birds

PubMed Central

Muheim, Rachel; Sjöberg, Sissel; Pinzon-Rodriguez, Atticus

2016-01-01

Magnetoreception of the light-dependent magnetic compass in birds is suggested to be mediated by a radical-pair mechanism taking place in the avian retina. Biophysical models on magnetic field effects on radical pairs generally assume that the light activating the magnetoreceptor molecules is nondirectional and unpolarized, and that light absorption is isotropic. However, natural skylight enters the avian retina unidirectionally, through the cornea and the lens, and is often partially polarized. In addition, cryptochromes, the putative magnetoreceptor molecules, absorb light anisotropically, i.e., they preferentially absorb light of a specific direction and polarization, implying that the light-dependent magnetic compass is intrinsically polarization sensitive. To test putative interactions between the avian magnetic compass and polarized light, we developed a spatial orientation assay and trained zebra finches to magnetic and/or overhead polarized light cues in a four-arm “plus” maze. The birds did not use overhead polarized light near the zenith for sky compass orientation. Instead, overhead polarized light modulated light-dependent magnetic compass orientation, i.e., how the birds perceive the magnetic field. Birds were well oriented when tested with the polarized light axis aligned parallel to the magnetic field. When the polarized light axis was aligned perpendicular to the magnetic field, the birds became disoriented. These findings are the first behavioral evidence to our knowledge for a direct interaction between polarized light and the light-dependent magnetic compass in an animal. They reveal a fundamentally new property of the radical pair-based magnetoreceptor with key implications for how birds and other animals perceive the Earth’s magnetic field. PMID:26811473

Polarized light modulates light-dependent magnetic compass orientation in birds.

PubMed

Muheim, Rachel; Sjöberg, Sissel; Pinzon-Rodriguez, Atticus

2016-02-09

Magnetoreception of the light-dependent magnetic compass in birds is suggested to be mediated by a radical-pair mechanism taking place in the avian retina. Biophysical models on magnetic field effects on radical pairs generally assume that the light activating the magnetoreceptor molecules is nondirectional and unpolarized, and that light absorption is isotropic. However, natural skylight enters the avian retina unidirectionally, through the cornea and the lens, and is often partially polarized. In addition, cryptochromes, the putative magnetoreceptor molecules, absorb light anisotropically, i.e., they preferentially absorb light of a specific direction and polarization, implying that the light-dependent magnetic compass is intrinsically polarization sensitive. To test putative interactions between the avian magnetic compass and polarized light, we developed a spatial orientation assay and trained zebra finches to magnetic and/or overhead polarized light cues in a four-arm "plus" maze. The birds did not use overhead polarized light near the zenith for sky compass orientation. Instead, overhead polarized light modulated light-dependent magnetic compass orientation, i.e., how the birds perceive the magnetic field. Birds were well oriented when tested with the polarized light axis aligned parallel to the magnetic field. When the polarized light axis was aligned perpendicular to the magnetic field, the birds became disoriented. These findings are the first behavioral evidence to our knowledge for a direct interaction between polarized light and the light-dependent magnetic compass in an animal. They reveal a fundamentally new property of the radical pair-based magnetoreceptor with key implications for how birds and other animals perceive the Earth's magnetic field.

Efficient and robust model-to-image alignment using 3D scale-invariant features.

PubMed

Toews, Matthew; Wells, William M

2013-04-01

This paper presents feature-based alignment (FBA), a general method for efficient and robust model-to-image alignment. Volumetric images, e.g. CT scans of the human body, are modeled probabilistically as a collage of 3D scale-invariant image features within a normalized reference space. Features are incorporated as a latent random variable and marginalized out in computing a maximum a posteriori alignment solution. The model is learned from features extracted in pre-aligned training images, then fit to features extracted from a new image to identify a globally optimal locally linear alignment solution. Novel techniques are presented for determining local feature orientation and efficiently encoding feature intensity in 3D. Experiments involving difficult magnetic resonance (MR) images of the human brain demonstrate FBA achieves alignment accuracy similar to widely-used registration methods, while requiring a fraction of the memory and computation resources and offering a more robust, globally optimal solution. Experiments on CT human body scans demonstrate FBA as an effective system for automatic human body alignment where other alignment methods break down. Copyright © 2012 Elsevier B.V. All rights reserved.

Efficient and Robust Model-to-Image Alignment using 3D Scale-Invariant Features

PubMed Central

Toews, Matthew; Wells, William M.

2013-01-01

This paper presents feature-based alignment (FBA), a general method for efficient and robust model-to-image alignment. Volumetric images, e.g. CT scans of the human body, are modeled probabilistically as a collage of 3D scale-invariant image features within a normalized reference space. Features are incorporated as a latent random variable and marginalized out in computing a maximum a-posteriori alignment solution. The model is learned from features extracted in pre-aligned training images, then fit to features extracted from a new image to identify a globally optimal locally linear alignment solution. Novel techniques are presented for determining local feature orientation and efficiently encoding feature intensity in 3D. Experiments involving difficult magnetic resonance (MR) images of the human brain demonstrate FBA achieves alignment accuracy similar to widely-used registration methods, while requiring a fraction of the memory and computation resources and offering a more robust, globally optimal solution. Experiments on CT human body scans demonstrate FBA as an effective system for automatic human body alignment where other alignment methods break down. PMID:23265799

Suppression of ferromagnetic order by Ag-doping: A neutron scattering investigation on Ce₂(Pd_1-xAg_x)₂In (x = 0.20, 0.50).

PubMed

Martinelli, Alberto; Giovannini, Mauro; Sereni, Julian G; Ritter, Clemens

2018-05-24

The ground state magnetic behaviour of Ce2(Pd0.8Ag0.2)2In and Ce2(Pd0.5Ag0.5)2In, found in the ferromagnetic branch of Ce2Pd2In, has been investigated by neutron powder diffraction at low temperature. Ce2(Pd0.8Ag0.2)2In is characterized by a ferromagnetic structure with the Ce moments aligned along the c-axis and values of 0.96(2) μB. The compound retains the P4/mbm throughout the magnetic transition, although the magnetic ordering is accompanied by a significant decrease of the lattice strain along [00l], suggesting a magnetostructural contribution. The magnetic behaviour of Ce2(Pd0.5Ag0.5)2In is very different; this compound exhibits an extremely reduced magnetic scattering contribution in the diffraction pattern, that can be ascribed to a different kind of ferromagnetic ordering, with extremely reduced magnetic moments (~ 0.1 μB) aligned along [0l0]. These results point to a competition between different types of magnetic correlations induced by Ag-substitution, giving rise to a magnetically frustrated scenario in Ce2(Pd0.5Ag0.5)2In. © 2018 IOP Publishing Ltd.

Statistical properties of the polarized emission of Planck Galactic cold clumps

NASA Astrophysics Data System (ADS)

Ristorcelli, Isabelle; Planck Collaboration

2015-08-01

The Galactic magnetic fields are considered as one of the key components regulating star formation, but their actual role on the dense cores formation and evolution remains today an open question.Dust polarized continuum emission is particularly well suited to probe the dense and cold medium and study the magnetic field structure. Such observations also provide tight constraints to better understand the efficiency of the dust alignment along the magnetic field lines, which in turn relate on our grasp to properly interpret the B-field properties.With the Planck all-sky survey of dust submillimeter emission in intensity and polarization, we can investigate the intermediate scales, between that of molecular cloud and of prestellar cores, and perform a statistical analysis on the polarization properties of cold clumps.Combined with the IRAS map at 100microns, the Planck survey has allowed to build the first all-sky catalogue of Galactic Cold Clumps (PGCC, Planck 2015 results XXVIII 2015). The corresponding 13188 sources cover a broad range in physical properties, and correspond to different evolutionary stages, from cold and starless clumps, nearby cores, to young protostellar objects still embedded in their cold surrounding cloud.I will present the main results of our polarization analysis obtained on different samples of sources from the PGCC catalogue, based on the 353GHz polarized emission measured with Planck. The statistical properties are derived from a stacking method, using optimized estimators for the polarization fraction and angle parameters. These properties are determined and compared according to the nature of the sources (starless or YSOs), their size or density range. Finally, I will present a comparison of our results with predictions from MHD simulations of clumps including radiative transfer and the dust radiative torque alignment mechanism.

Polymeric variable optical attenuators based on magnetic sensitive stimuli materials

NASA Astrophysics Data System (ADS)

de Pedro, S.; Cadarso, V. J.; Ackermann, T. N.; Muñoz-Berbel, X.; Plaza, J. A.; Brugger, J.; Büttgenbach, S.; Llobera, A.

2014-12-01

Magnetically-actuable, polymer-based variable optical attenuators (VOA) are presented in this paper. The design comprises a cantilever which also plays the role of a waveguide and the input/output alignment elements for simple alignment, yet still rendering an efficient coupling. Magnetic properties have been conferred to these micro-opto-electromechanical systems (MOEMS) by implementing two different strategies: in the first case, a magnetic sensitive stimuli material (M-SSM) is obtained by a combination of polydimethylsiloxane (PDMS) and ferrofluid (FF) in ratios between 14.9 wt % and 29.9 wt %. An M-SSM strip under the waveguide-cantilever, defined with soft lithography (SLT), provides the required actuation capability. In the second case, specific volumes of FF are dispensed at the end of the cantilever tip (outside the waveguide) by means of inkjet printing (IJP), obtaining the required magnetic response while holding the optical transparency of the waveguide-cantilever. In the absence of a magnetic field, the waveguide-cantilever is aligned with the output fiber optics and thus the intrinsic optical losses can be obtained. Numerical simulations, validated experimentally, have shown that, for any cantilever length, the VOAs defined by IJP present lower intrinsic optical losses than their SLT counterparts. Under an applied magnetic field (Bapp), both VOA configurations experience a misalignment between the waveguide-cantilever and the output fiber optics. Thus, the proposed VOAs modulate the output power as a function of the cantilever displacement, which is proportional to Bapp. The experimental results for the three different waveguide-cantilever lengths and six different FF concentrations (three per technology) show maximum deflections of 220 µm at 29.9 wt % of FF for VOASLT and 250 µm at 22.3 wt % FF for VOAIJP, at 0.57 kG for both. These deflections provide maximum actuation losses of 16.1 dB and 18.9 dB for the VOASLT and VOAIJP, respectively.

Investigation of structural and electrical properties of La{sub 0.7}(Ba{sub 1-x}Ca{sub x}){sub 0.3}MnO{sub 3} compounds by sol-gel method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winarsih, Suci; Kurniawan, Budhy, E-mail: bkuru07@gmail.com; Manaf, Azwar

2016-06-17

In this paper, we explored structural and electrical properties of La{sub 0.7}(Ba{sub 1-x}Ca{sub x}){sub 0.3}MnO{sub 3} (x = 0; 0.03; and 0.05) compounds. The general structure of perovskite manganites is AMnO{sub 3} (A= trivalent rare earth with divalent ion-doped). Average A-site cation size, external pressure, and the variance of the cation size σ{sup 2} are one of many factors that affected to magneto-transport properties of manganites as reported by others. In this work we focus only on the electrical properties in La{sub 0.7}Ba{sub 0.3}MnO{sub 3} Ca-doped compound which may influence crystal structure resulting resistivity phenomena under magnetic field influence. Allmore » samples were synthesized by sol-gel method from which fine powders were obtained. The X-ray powder diffraction pattern of powder materials shows that all samples are fully crystalline with a rhombohedral structure. Rietveld refinement shows that the presence of calcium has changed some crystal structural parameters such lattice parameter, Mn–O bond length, and Mn–O–Mn angles. The electrical resistivity of all synthesized materials investigated by four point probe method using Cryogenic Magnet in the temperature range of 50-300 K under influence a magnetic field shows resistivity temperature dependent. In fact presence of calcium has reduced the resistivity. It might occure because it has made an enhancement in the mobility of hopping electrons. The magnetic external field causes the resistivity decreased for all samples because host spin align by delocalizing the charge carries so electron itinerant through the lattice suggested by other authors. Both calcium dopant concentration and the applied external magnetic field shows strong correlation in reduction of resistivity.« less

Joint Inversion of 3d Mt/gravity/magnetic at Pisagua Fault.

NASA Astrophysics Data System (ADS)

Bascur, J.; Saez, P.; Tapia, R.; Humpire, M.

2017-12-01

This work shows the results of a joint inversion at Pisagua Fault using 3D Magnetotellurics (MT), gravity and regional magnetic data. The MT survey has a poor coverage of study area with only 21 stations; however, it allows to detect a low resistivity zone aligned with the Pisagua Fault trace that it is interpreted as a damage zone. The integration of gravity and magnetic data, which have more dense sampling and coverage, adds more detail and resolution to the detected low resistivity structure and helps to improve the structure interpretation using the resulted models (density, magnetic-susceptibility and electrical resistivity). The joint inversion process minimizes a multiple target function which includes the data misfit, model roughness and coupling norms (crossgradient and direct relations) for all geophysical methods considered (MT, gravity and magnetic). This process is solved iteratively using the Gauss-Newton method which updates the model of each geophysical method improving its individual data misfit, model roughness and the coupling with the other geophysical models. For solving the model updates of magnetic and gravity methods were developed dedicated 3D inversion software codes which include the coupling norms with additionals geophysical parameters. The model update of the 3D MT is calculated using an iterative method which sequentially filters the priority model and the output model of a single 3D MT inversion process for obtaining the resistivity model coupled solution with the gravity and magnetic methods.

Evidence of Ubiquitous Large-Amplitude Alfven waves in the Global Field-Aligned Current System

NASA Astrophysics Data System (ADS)

Pakhotin, I.; Mann, I.; Lysak, R. L.; Knudsen, D. J.; Burchill, J. K.; Gjerloev, J. W.; Rae, J.; Forsyth, C.; Murphy, K. R.; Miles, D.; Ozeke, L.; Balasis, G.

2017-12-01

Large-amplitude non-stationarities have been observed during an analysis of a quiescent field-aligned current system crossing using the multi-satellite Swarm constellation. Using simultaneous electric and magnetic field measurements it has been determined that these non-stationarities, reaching tens to hundreds of nanoteslas, are Alfvenic in nature. Evidence suggests that these large-amplitude Alfven waves are a ubiquitous, fundamentally inherent feature of and exist in a continuum with larger-scale field-aligned currents, and both can be explained using the same physical paradigm of reflected Alfven waves.

[Influence on flux density of intraoral dental magnets during 1.5 and 3.0 tesla MRI].

PubMed

Blankenstein, F H; Truong, B; Thomas, A; Boeckler, A; Peroz, I

2011-08-01

When using dental duo-magnet systems, a mini-magnet remains in the jaw after removal of the prosthesis. In some cases, implant-borne magnets may be removed, whereas tooth-borne magnets are irreversibly fixed on a natural tooth root. The goal of this paper is to identify the impacts of the duration and orientation of exposure on these magnets in a 1.5 or 3 Tesla MRI. For this study, 30 SmCo and 60 NdFeB magnets were used. During the first experiment, they were exposed with free orientation for 64 minutes. During the second experiment, the magnets were fixed in position and exposed at 1.5 and 3 Tesla while aligned in a parallel or antiparallel direction. While the duration of exposure in MRI is irrelevant, the orientation is not. The coercive field strength of these NdFeB and SmCo alloys is not sufficient to reliably withstand demagnetization in a 1.5 or 3 T MRI when aligned in an antiparallel direction. At 1.5 T neodymium magnets were reduced to approx. 34 % and samarium magnets to approx. 92 % of their initial values. At 3 T all magnets were reversed. As a precaution, the worst-case scenario, i. e. an antiparallel orientation, should be assumed when using a duo-magnet system. If an MRI can be postponed, the general dentist should remove implant-borne magnets. If there is a vital indication, irreversible damage to the magnets is acceptable in consultation with the patient since the replacement costs are irrelevant given the underlying disease. © Georg Thieme Verlag KG Stuttgart · New York.

DOES MAGNETIC-FIELD-ROTATION MISALIGNMENT SOLVE THE MAGNETIC BRAKING CATASTROPHE IN PROTOSTELLAR DISK FORMATION?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Zhiyun; Krasnopolsky, Ruben; Shang, Hsien

2013-09-01

Stars form in dense cores of molecular clouds that are observed to be significantly magnetized. In the simplest case of a laminar (non-turbulent) core with the magnetic field aligned with the rotation axis, both analytic considerations and numerical simulations have shown that the formation of a large, 10{sup 2} AU scale, rotationally supported protostellar disk is suppressed by magnetic braking in the ideal MHD limit for a realistic level of core magnetization. This theoretical difficulty in forming protostellar disks is termed the ''magnetic braking catastrophe''. A possible resolution to this problem, proposed by Hennebelle and Ciardi and Joos et al.,more » is that misalignment between the magnetic field and rotation axis may weaken the magnetic braking enough to enable disk formation. We evaluate this possibility quantitatively through numerical simulations. We confirm the basic result of Joos et al. that the misalignment is indeed conducive to disk formation. In relatively weakly magnetized cores with dimensionless mass-to-flux ratio {approx}> 4, it enabled the formation of rotationally supported disks that would otherwise be suppressed if the magnetic field and rotation axis are aligned. For more strongly magnetized cores, disk formation remains suppressed, however, even for the maximum tilt angle of 90 Degree-Sign . If dense cores are as strongly magnetized as indicated by OH Zeeman observations (with a mean dimensionless mass-to-flux ratio {approx}2), it would be difficult for the misalignment alone to enable disk formation in the majority of them. We conclude that, while beneficial to disk formation, especially for the relatively weak field case, misalignment does not completely solve the problem of catastrophic magnetic braking in general.« less

A dynamic programming approach for the alignment of signal peaks in multiple gas chromatography-mass spectrometry experiments.

PubMed

Robinson, Mark D; De Souza, David P; Keen, Woon Wai; Saunders, Eleanor C; McConville, Malcolm J; Speed, Terence P; Likić, Vladimir A

2007-10-29

Gas chromatography-mass spectrometry (GC-MS) is a robust platform for the profiling of certain classes of small molecules in biological samples. When multiple samples are profiled, including replicates of the same sample and/or different sample states, one needs to account for retention time drifts between experiments. This can be achieved either by the alignment of chromatographic profiles prior to peak detection, or by matching signal peaks after they have been extracted from chromatogram data matrices. Automated retention time correction is particularly important in non-targeted profiling studies. A new approach for matching signal peaks based on dynamic programming is presented. The proposed approach relies on both peak retention times and mass spectra. The alignment of more than two peak lists involves three steps: (1) all possible pairs of peak lists are aligned, and similarity of each pair of peak lists is estimated; (2) the guide tree is built based on the similarity between the peak lists; (3) peak lists are progressively aligned starting with the two most similar peak lists, following the guide tree until all peak lists are exhausted. When two or more experiments are performed on different sample states and each consisting of multiple replicates, peak lists within each set of replicate experiments are aligned first (within-state alignment), and subsequently the resulting alignments are aligned themselves (between-state alignment). When more than two sets of replicate experiments are present, the between-state alignment also employs the guide tree. We demonstrate the usefulness of this approach on GC-MS metabolic profiling experiments acquired on wild-type and mutant Leishmania mexicana parasites. We propose a progressive method to match signal peaks across multiple GC-MS experiments based on dynamic programming. A sensitive peak similarity function is proposed to balance peak retention time and peak mass spectra similarities. This approach can produce the optimal alignment between an arbitrary number of peak lists, and models explicitly within-state and between-state peak alignment. The accuracy of the proposed method was close to the accuracy of manually-curated peak matching, which required tens of man-hours for the analyzed data sets. The proposed approach may offer significant advantages for processing of high-throughput metabolomics data, especially when large numbers of experimental replicates and multiple sample states are analyzed.

Spatiotemporal alignment of in utero BOLD-MRI series.

PubMed

Turk, Esra Abaci; Luo, Jie; Gagoski, Borjan; Pascau, Javier; Bibbo, Carolina; Robinson, Julian N; Grant, P Ellen; Adalsteinsson, Elfar; Golland, Polina; Malpica, Norberto

2017-08-01

To present a method for spatiotemporal alignment of in-utero magnetic resonance imaging (MRI) time series acquired during maternal hyperoxia for enabling improved quantitative tracking of blood oxygen level-dependent (BOLD) signal changes that characterize oxygen transport through the placenta to fetal organs. The proposed pipeline for spatiotemporal alignment of images acquired with a single-shot gradient echo echo-planar imaging includes 1) signal nonuniformity correction, 2) intravolume motion correction based on nonrigid registration, 3) correction of motion and nonrigid deformations across volumes, and 4) detection of the outlier volumes to be discarded from subsequent analysis. BOLD MRI time series collected from 10 pregnant women during 3T scans were analyzed using this pipeline. To assess pipeline performance, signal fluctuations between consecutive timepoints were examined. In addition, volume overlap and distance between manual region of interest (ROI) delineations in a subset of frames and the delineations obtained through propagation of the ROIs from the reference frame were used to quantify alignment accuracy. A previously demonstrated rigid registration approach was used for comparison. The proposed pipeline improved anatomical alignment of placenta and fetal organs over the state-of-the-art rigid motion correction methods. In particular, unexpected temporal signal fluctuations during the first normoxia period were significantly decreased (P < 0.01) and volume overlap and distance between region boundaries measures were significantly improved (P < 0.01). The proposed approach to align MRI time series enables more accurate quantitative studies of placental function by improving spatiotemporal alignment across placenta and fetal organs. 1 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2017;46:403-412. © 2017 International Society for Magnetic Resonance in Medicine.

Space Technology 5 Multipoint Observations of Temporal and Spatial Variability of Field-Aligned Currents

NASA Technical Reports Server (NTRS)

Le, G.; Wang, Y.; Slavin, J. A.; Strangeway, R. L.

2009-01-01

Space Technology 5 (ST5) is a constellation mission consisting of three microsatellites. It provides the first multipoint magnetic field measurements in low Earth orbit, which enables us to separate spatial and temporal variations. In this paper, we present a study of the temporal variability of field-aligned currents using the ST5 data. We examine the field-aligned current observations during and after a geomagnetic storm and compare the magnetic field profiles at the three spacecraft. The multipoint data demonstrate that mesoscale current structures, commonly embedded within large-scale current sheets, are very dynamic with highly variable current density and/or polarity in approx.10 min time scales. On the other hand, the data also show that the time scales for the currents to be relatively stable are approx.1 min for mesoscale currents and approx.10 min for large-scale currents. These temporal features are very likely associated with dynamic variations of their charge carriers (mainly electrons) as they respond to the variations of the parallel electric field in auroral acceleration region. The characteristic time scales for the temporal variability of mesoscale field-aligned currents are found to be consistent with those of auroral parallel electric field.

FAST/Polar Conjunction Study of Field-Aligned Auroral Acceleration and Corresponding Magnetotail Drivers

NASA Technical Reports Server (NTRS)

Schriver, D.; Ashour-Abdalla, M.; Strangeway, R. J.; Richard, R. L.; Klezting, C.; Dotan, Y.; Wygant, J.

2002-01-01

The discrete aurora results when energized electrons bombard the Earth's atmosphere at high latitudes. This paper examines the physical processes that can cause field-aligned acceleration of plasma particles in the auroral region. A data and theoretical study has been carried out to examine the acceleration mechanisms that operate in the auroral zone and to identity the magnetospheric drivers of these acceleration mechanisms. The observations used in the study were collected by the Fast Auroral SnapshoT (FAST) and Polar satellites when the two satellites were in approximate magnetic conjunction in the auroral region. During these events FAST was in the middle of the auroral zone and Polar was above the auroral zone in the near-Earth plasma sheet. Polar data was used to determine the conditions in the magnetotail at the time field-aligned acceleration was measured by FAST in the auroral zone. For each of the magnetotail drivers identified in the data study, the physics of field-aligned acceleration in the auroral region was examined using existing theoretical efforts and a long-system particle-in-cell simulation to model the magnetically connected region between the two satellites.

Filamentary field-aligned currents at the polar cap region during northward interplanetary magnetic field derived with the Swarm constellation

PubMed Central

Lühr, Hermann; Huang, Tao; Wing, Simon; Kervalishvili, Guram; Rauberg, Jan; Korth, Haje

2017-01-01

ESA’s Swarm constellation mission makes it possible for the first time to determine field-aligned currents (FACs) in the ionosphere uniquely. In particular at high latitudes, the dual-satellite approach can reliably detect some FAC structures which are missed by the traditional single-satellite technique. These FAC events occur preferentially poleward of the auroral oval and during times of northward interplanetary magnetic field (IMF) orientation. Most events appear on the nightside. They are not related to the typical FAC structures poleward of the cusp, commonly termed NBZ. Simultaneously observed precipitating particle spectrograms and auroral images from Defense Meteorological Satellite Program (DMSP) satellites are consistent with the detected FACs and indicate that they occur on closed field lines mostly adjacent to the auroral oval. We suggest that the FACs are associated with Sun-aligned filamentary auroral arcs. Here we introduce in an initial study features of the high-latitude FAC structures which have been observed during the early phase of the Swarm mission. A more systematic survey over longer times is required to fully characterize the so far undetected field aligned currents. PMID:29056833

Archaeomagnetic Dating

ERIC Educational Resources Information Center

Linford, Paul

2004-01-01

Some naturally occurring minerals possess a permanent magnetization. Certain processes such as sedimentation or kiln-firing can cause the particles in structures made of such materials to align themselves with the direction of Earth's magnetic field at the time. This direction has varied over the last few thousand years in ways that can be traced…

Contribution of the polarization moments of different rank to the integral CPT signal

NASA Astrophysics Data System (ADS)

Taskova, E.; Alipieva, E.; Todorov, G.

2016-01-01

In the present work we investigate the relation of the polarization moments having different ranks with the tensor components which form the observable integral CPT signal, in the presence of a stray magnetic field. A numerical experiment with parameters close to the real ones is performed, using a program based on the irreducible tensor operator formalism1. The integral fluorescent signal is calculated for the non-polarized fluorescence at different laser power excitation. Detailed analysis of the numerical solutions for all tensor components which describe population and alignment allows visualizing the dynamics of their behavior in dependence on the experimental geometry and laboratory magnetic field B'. The dependence of population f00, longitudinal f02 and transverse f22 alignment in the presence of transverse magnetic field is investigated. The shape and sign of the resonance change with laser power.

Alignment effect of N2(A3Σu+) in the energy transfer reaction of aligned N2(A3Σu+) + NO(X2Π) → NO(A2Σ+) + N2(X1Σg+).

PubMed

Ohoyama, H; Maruyama, S

2012-06-28

Steric effect in the energy transfer reaction of N(2)(A(3)Σ(u)(+)) + NO(X(2)Π) → NO(A(2)Σ(+)) + N(2)(X(1)Σ(g)(+)) has been studied under crossed beam conditions at a collision energy of ~0.07 eV by using an aligned N(2)(A(3)Σ(u)(+)) beam prepared by a magnetic hexapole. The emission intensity of NO(A(2)Σ(+)) has been measured as a function of the magnetic orientation field direction (i.e., alignment of N(2)(A(3)Σ(u)(+))) in the collision frame. A significant alignment effect on the energy transfer probability is observed. The shape of the steric opacity function turns out to be most reactive at the oblique configuration of N(2)(A(3)Σ(u)(+)) with an orientation angle of γ(v(R)) ~ 45° with respect to the relative velocity vector (v(R)), which has a good correlation with the spatial distribution of the 2pπ(g)* molecular orbital of N(2)(A(3)Σ(u)(+)). We propose the electron exchange mechanism in which the energy transfer probability is dominantly controlled by the orbital overlap between N(2)(2pπ(g)*) and NO(6σ).

Japanese MAGSAT team

NASA Technical Reports Server (NTRS)

Fukushima, N.; Maeda, H.; Yukutake, T.; Tanaka, M.; Miyazaki, Y.; Oshima, S.; Ogawa, K.; Kawamura, M.; Uyeda, S.; Kobayashi, K.

1982-01-01

Construction of a model of the regional magnetic field and investigation of the local magnetic anomalies and their origin were approaches used in attempts to study the crustal structure near Japan and its Antarctic bases. Spatial properties of the regional magnetic field and comparison of the regional model with that derived from MAGSAT data are discussed. Possible causes of the magnetic anomalies, and results of aeromagnetic surveys incorporating gravity and seismic data are explored. Ionospheric and magnetospheric contributions to geomagnetic variations, field-aligned currents, magnetic geomagnetic pulsations, and hydromagnetic waves by analysis of MAGSAT data are also examined.

Self-alignment of plasmonic gold nanorods in reconfigurable anisotropic fluids for tunable bulk metamaterial applications.

PubMed

Liu, Qingkun; Cui, Yanxia; Gardner, Dennis; Li, Xin; He, Sailing; Smalyukh, Ivan I

2010-04-14

We demonstrate the bulk self-alignment of dispersed gold nanorods imposed by the intrinsic cylindrical micelle self-assembly in nematic and hexagonal liquid crystalline phases of anisotropic fluids. External magnetic field and shearing allow for alignment and realignment of the liquid crystal matrix with the ensuing long-range orientational order of well-dispersed plasmonic nanorods. This results in a switchable polarization-sensitive plasmon resonance exhibiting stark differences from that of the same nanorods in isotropic fluids. The device-scale bulk nanoparticle alignment may enable optical metamaterial mass production and control of properties arising from combining the switchable nanoscale structure of anisotropic fluids with the surface plasmon resonance properties of the plasmonic nanorods.

The effect of the earth's and stray magnetic fields on mobile mass spectrometer systems.

PubMed

Bell, Ryan J; Davey, Nicholas G; Martinsen, Morten; Short, R Timothy; Gill, Chris G; Krogh, Erik T

2015-02-01

Development of small, field-portable mass spectrometers has enabled a rapid growth of in-field measurements on mobile platforms. In such in-field measurements, unexpected signal variability has been observed by the authors in portable ion traps with internal electron ionization. The orientation of magnetic fields (such as the Earth's) relative to the ionization electron beam trajectory can significantly alter the electron flux into a quadrupole ion trap, resulting in significant changes in the instrumental sensitivity. Instrument simulations and experiments were performed relative to the earth's magnetic field to assess the importance of (1) nonpoint-source electron sources, (2) vertical versus horizontal electron beam orientation, and (3) secondary magnetic fields created by the instrument itself. Electron lens focus effects were explored by additional simulations, and were paralleled by experiments performed with a mass spectrometer mounted on a rotating platform. Additionally, magnetically permeable metals were used to shield (1) the entire instrument from the Earth's magnetic field, and (2) the electron beam from both the Earth's and instrument's magnetic fields. Both simulation and experimental results suggest the predominant influence on directionally dependent signal variability is the result of the summation of two magnetic vectors. As such, the most effective method for reducing this effect is the shielding of the electron beam from both magnetic vectors, thus improving electron beam alignment and removing any directional dependency. The improved ionizing electron beam alignment also allows for significant improvements in overall instrument sensitivity.

High magnetic field test of bismuth Hall sensors for ITER steady state magnetic diagnostic.

PubMed

Ďuran, I; Entler, S; Kohout, M; Kočan, M; Vayakis, G

2016-11-01

Performance of bismuth Hall sensors developed for the ITER steady state magnetic diagnostic was investigated for high magnetic fields in the range ±7 T. Response of the sensors to the magnetic field was found to be nonlinear particularly within the range ±1 T. Significant contribution of the planar Hall effect to the sensors output voltage causing undesirable cross field sensitivity was identified. It was demonstrated that this effect can be minimized by the optimization of the sensor geometry and alignment with the magnetic field and by the application of "current-spinning technique."

Tunable system for production of mirror and cusp configurations using chassis of permanent magnets

NASA Astrophysics Data System (ADS)

Hyde, Alexander; Bushmelov, Maxim; Batishchev, Oleg

2018-03-01

Compact arrays of permanent magnets have shown promise as replacements for electromagnets in applications requiring magnetic cusps and mirrors. An adjustable system capable of suspending and translating a pair of light, nonmagnetic chassis carrying such sources of magnetic field has been designed and constructed. Using this device to align two cylindrical chassis, strong solenoid-like domains of field, as well as classic biconic cusp and magnetic mirror topologies, are generated. Employing a pair of ring-shaped chassis instead, the superposition of their naturally-emitted cusps is demonstrated to produce sextupolar and octupolar magnetic fields.

Robustness of the filamentation instability for asymmetric plasma shells collision in arbitrarily oriented magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bret, A.

2013-10-15

The filamentation instability triggered when two counter streaming plasma shells overlap appears to be the main mechanism by which collisionless shocks are generated. It has been known for long that a flow aligned magnetic field can completely suppress this instability. In a recent paper [Phys. Plasmas 18, 080706 (2011)], it was demonstrated in two dimensions that for the case of two cold, symmetric, relativistically colliding shells, such cancellation cannot occur if the field is not perfectly aligned. Here, this result is extended to the case of two asymmetric shells. The filamentation instability appears therefore as an increasingly robust mechanism tomore » generate shocks.« less

Stable Fe nanomagnets encapsulated inside vertically-aligned carbon nanotubes.

PubMed

Bondino, Federica; Magnano, Elena; Ciancio, Regina; Castellarin Cudia, Carla; Barla, Alessandro; Carlino, Elvio; Yakhou-Harris, Flora; Rupesinghe, Nalin; Cepek, Cinzia

2017-12-06

Well-defined sized (5-10 nm) metallic iron nanoparticles (NPs) with body-centered cubic structure encapsulated inside the tip of millimeter-long vertically aligned carbon nanotubes (VACNTs) of uniform length have been investigated with high-resolution transmission electron microscopy and soft X-ray spectroscopy techniques. Surface-sensitive and chemically-selective measurements have been used to evaluate the magnetic properties of the encapsulated NPs. The encapsulated Fe NPs display magnetic remanence up to room temperature, low coercivity, high chemical stability and no significant anisotropy. Our surface-sensitive measurements combined with the specific morphology of the studied VACNTs allow us to pinpoint the contribution of the surface oxidized or hydroxidized iron catalysts present at the VACNT-substrate interface.

Alignment of a vector magnetometer to an optical prism

NASA Astrophysics Data System (ADS)

Dietrich, M. R.; Bailey, K. G.; O'Connor, T. P.

2017-05-01

A method for alignment of a vector magnetometer to a rigidly attached prism is presented. This enables optical comparison of the magnetometer axes to physical surfaces in the apparatus, and thus an absolute determination of the magnetic field direction in space. This is in contrast with more common techniques, which focus on precise determination of the relative angles between magnetometer axes, and so are more suited to measuring differences in the direction of magnetic fields. Here we demonstrate precision better than 500 μrad on a fluxgate magnetometer, which also gives the coil orthogonality errors to a similar precision. The relative sensitivity of the three axes is also determined, with a precision of about 5 ×10 -4 .

Note: A simple image processing based fiducial auto-alignment method for sample registration.

PubMed

Robertson, Wesley D; Porto, Lucas R; Ip, Candice J X; Nantel, Megan K T; Tellkamp, Friedjof; Lu, Yinfei; Miller, R J Dwayne

2015-08-01

A simple method for the location and auto-alignment of sample fiducials for sample registration using widely available MATLAB/LabVIEW software is demonstrated. The method is robust, easily implemented, and applicable to a wide variety of experiment types for improved reproducibility and increased setup speed. The software uses image processing to locate and measure the diameter and center point of circular fiducials for distance self-calibration and iterative alignment and can be used with most imaging systems. The method is demonstrated to be fast and reliable in locating and aligning sample fiducials, provided here by a nanofabricated array, with accuracy within the optical resolution of the imaging system. The software was further demonstrated to register, load, and sample the dynamically wetted array.

Thermal Conductivity of Polyimide/Carbon Nanofiller Blends

NASA Technical Reports Server (NTRS)

Delozier, D. M.; Watson, K. A.; Ghose, S.; Working, D. C.; Connell, J. W.; Smith, J. G.; Sun, Y. P.; Lin, Y.

2006-01-01

Ultem(TM) was mixed with three different carbon-based nanofillers in efforts to increase the thermal conductivity of the polymer. After initial mixing, the nanocomposites were extruded or processed via the Laboratory Mixing Molder (LMM) process. High resolution scanning electron microscopy (HRSEM) revealed significant alignment of the nanofillers in the extruded samples. Thermal conductivity measurements were made both in the direction and perpendicular to the direction of alignment of nanofillers as well as for unaligned samples. It was found that the largest improvement in thermal conductivity was achieved in the case of aligned samples when the measurement was performed in the direction of alignment. Unaligned samples also showed a significant improvement in thermal conductivity and may be useful in applications when it is not possible to align the nanofiller. However the improvements in thermal conductivity did not approach those expected based on a rule of mixtures. This is likely due to poor phonon transfer through the matrix.

Multiscale field-aligned current analyzer

NASA Astrophysics Data System (ADS)

Bunescu, C.; Marghitu, O.; Constantinescu, D.; Narita, Y.; Vogt, J.; Blǎgǎu, A.

2015-11-01

The magnetosphere-ionosphere coupling is achieved, essentially, by a superposition of quasi-stationary and time-dependent field-aligned currents (FACs), over a broad range of spatial and temporal scales. The planarity of the FAC structures observed by satellite data and the orientation of the planar FAC sheets can be investigated by the well-established minimum variance analysis (MVA) of the magnetic perturbation. However, such investigations are often constrained to a predefined time window, i.e., to a specific scale of the FAC. The multiscale field-aligned current analyzer, introduced here, relies on performing MVA continuously and over a range of scales by varying the width of the analyzing window, appropriate for the complexity of the magnetic field signatures above the auroral oval. The proposed technique provides multiscale information on the planarity and orientation of the observed FACs. A new approach, based on the derivative of the largest eigenvalue of the magnetic variance matrix with respect to the length of the analysis window, makes possible the inference of the current structures' location (center) and scale (thickness). The capabilities of the FAC analyzer are explored analytically for the magnetic field profile of the Harris sheet and tested on synthetic FAC structures with uniform current density and infinite or finite geometry in the cross-section plane of the FAC. The method is illustrated with data observed by the Cluster spacecraft on crossing the nightside auroral region, and the results are cross checked with the optical observations from the Time History of Events and Macroscale Interactions during Substorms ground network.

Importance of doping and frustration in itinerant Fe-doped Cr 2Al

DOE PAGES

Susner, M. A.; Parker, D. S.; Sefat, A. S.

2015-05-12

We performed an experimental and theoretical study comparing the effects of Fe-doping of Cr 2Al, an antiferromagnet with a N el temperature of 670 K, with known results on Fe-doping of antiferromagnetic bcc Cr. (Cr 1-xFe x) 2Al materials are found to exhibit a rapid suppression of antiferromagnetic order with the presence of Fe, decreasing T N to 170 K for x=0.10. Antiferromagnetic behavior disappears entirely at x≈0.125 after which point increasing paramagnetic behavior is exhibited. Moreover, this is unlike the effects of Fe doping of bcc antiferromagnetic Cr, in which T N gradually decreases followed by the appearance ofmore » a ferromagnetic state. Theoretical calculations explain that the Cr 2Al-Fe suppression of magnetic order originates from two effects: the first is band narrowing caused by doping of additional electrons from Fe substitution that weakens itinerant magnetism; the second is magnetic frustration of the Cr itinerant moments in Fe-substituted Cr 2Al. In pure-phase Cr 2Al, the Cr moments have an antiparallel alignment; however, these are destroyed through Fe substitution and the preference of Fe for parallel alignment with Cr. This is unlike bulk Fe-doped Cr alloys in which the Fe anti-aligns with the Cr atoms, and speaks to the importance of the Al atoms in the magnetic structure of Cr 2Al and Fe-doped Cr 2Al.« less

Spacecraft Observations of Oblique Electron Beams Breaking the Frozen-In Law During Asymmetric Reconnection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Egedal, J.; Le, Ari; Daughton, William

Fully kinetic simulations of asymmetric magnetic reconnection reveal the presence of magnetic-field-aligned beams of electrons flowing toward the topological magnetic x line. Within the ~ 6d e electron-diffusion region, the beams become oblique to the local magnetic field, providing a unique signature of the electron-diffusion region where the electron frozen-in law is broken. These numerical predictions are confirmed by in situ Magnetospheric Multiscale spacecraft observations during asymmetric reconnection at Earth’s dayside magnetopause.

Spacecraft Observations of Oblique Electron Beams Breaking the Frozen-In Law During Asymmetric Reconnection

DOE PAGES

Egedal, J.; Le, Ari; Daughton, William; ...

2018-01-29

Fully kinetic simulations of asymmetric magnetic reconnection reveal the presence of magnetic-field-aligned beams of electrons flowing toward the topological magnetic x line. Within the ~ 6d e electron-diffusion region, the beams become oblique to the local magnetic field, providing a unique signature of the electron-diffusion region where the electron frozen-in law is broken. These numerical predictions are confirmed by in situ Magnetospheric Multiscale spacecraft observations during asymmetric reconnection at Earth’s dayside magnetopause.

Revealing magnetic ordering and spin-phonon coupling in Y1-x Tb x MnO3 (0.1  ⩽  x  ⩽  0.3) compounds

NASA Astrophysics Data System (ADS)

Chakraborty, Keka R.; Paul, Barnita; Shukla, R.; Krishna, P. S. R.; Kumar, Amit; Mukadam, M. D.; Mandal, B. P.; Roy, Anushree; Tyagi, A. K.; Yusuf, S. M.

2017-04-01

The structural and magnetic properties of the Y1-x Tb x MnO3 (0.1  ⩽  x  ⩽  0.3) compounds were investigated. Neutron diffraction patterns for all three samples, recorded at room temperature (RT), were fitted to the nuclear structure confirming the paramagnetic nature of the compounds. At 2.8 K, for the x  =  0.1 sample magnetic moments of the Tb3+ ionic as well as Mn3+ ionic were ordered. At 5 K for the x  =  0.2 sample only the Mn3+ ionic magnetic moments were ordered. There were six sites for Mn atoms. Three on the z  =  0 plane and three on the z  =  0.5 plane (where z corresponds to  +c axis).The Mn3+ionic moments were confined to the a-b plane with a net magnitude of 2.78(3) µ B, and 2.90(3) µ B for the x  =  0.1 and the x  =  0.2 samples. The Tb3+ionic moments had a magnitude of 1.36(4) µ B at 2.8 K and were aligned antiferromagnetically along the crystallographic c-axis for the x  =  0.1 sample. The low moment in comparison with Mn3+ free ions has been attributed to crystalline electric fields similar to that found in the parent compound YMnO3 and also in another rare earth manganite viz HoMnO3. The x  =  0.3 sample was found to be a canonical spin glass. To investigate the role of the above spin ordering in Y1-x Tb x MnO3 in governing the phonon dynamics, temperature dependent Raman measurements were carried out. We observed the deviation of the phonon frequency near 685 cm-1 and its line-width from the expected anharmonic behaviour around magnetic ordering temperature for Tb substituted compounds with x  =  0.1 and 0.2. This was attributed to the spin-phonon coupling in these systems. The anomalous behaviour of this phonon mode in the canonical spin glass compound with x  =  0.3, indicated that the coupling sustained even in the presence of only local magnetic ordering.

Highly controlled orientation of CaBi4Ti4O15 using a strong magnetic field

NASA Astrophysics Data System (ADS)

Suzuki, Tohru S.; Kimura, Masahiko; Shiratsuyu, Kosuke; Ando, Akira; Sakka, Yoshio; Sakabe, Yukio

2006-09-01

The texture of feeble magnetic ceramics can be controlled by a strong magnetic field. When the magnetic susceptibility of the c axis is smaller than that of the other axes, the c axis aligns perpendicular to the magnetic field; however, the direction is randomly oriented on the plane perpendicular to the magnetic field. The authors demonstrate in this letter that a highly controlled texture in bismuth titanate, which has a c-axis susceptibility smaller than the other axes, can be achieved using a two-step magnetic field procedure. This highly controlled orientation is effective for improving the electromechanical coupling coefficient.

ChromAlign: A two-step algorithmic procedure for time alignment of three-dimensional LC-MS chromatographic surfaces.

PubMed

Sadygov, Rovshan G; Maroto, Fernando Martin; Hühmer, Andreas F R

2006-12-15

We present an algorithmic approach to align three-dimensional chromatographic surfaces of LC-MS data of complex mixture samples. The approach consists of two steps. In the first step, we prealign chromatographic profiles: two-dimensional projections of chromatographic surfaces. This is accomplished by correlation analysis using fast Fourier transforms. In this step, a temporal offset that maximizes the overlap and dot product between two chromatographic profiles is determined. In the second step, the algorithm generates correlation matrix elements between full mass scans of the reference and sample chromatographic surfaces. The temporal offset from the first step indicates a range of the mass scans that are possibly correlated, then the correlation matrix is calculated only for these mass scans. The correlation matrix carries information on highly correlated scans, but it does not itself determine the scan or time alignment. Alignment is determined as a path in the correlation matrix that maximizes the sum of the correlation matrix elements. The computational complexity of the optimal path generation problem is reduced by the use of dynamic programming. The program produces time-aligned surfaces. The use of the temporal offset from the first step in the second step reduces the computation time for generating the correlation matrix and speeds up the process. The algorithm has been implemented in a program, ChromAlign, developed in C++ language for the .NET2 environment in WINDOWS XP. In this work, we demonstrate the applications of ChromAlign to alignment of LC-MS surfaces of several datasets: a mixture of known proteins, samples from digests of surface proteins of T-cells, and samples prepared from digests of cerebrospinal fluid. ChromAlign accurately aligns the LC-MS surfaces we studied. In these examples, we discuss various aspects of the alignment by ChromAlign, such as constant time axis shifts and warping of chromatographic surfaces.

Conceptual design of the cryostat for the new high luminosity (HL-LHC) triplet magnets

NASA Astrophysics Data System (ADS)

Ramos, D.; Parma, V.; Moretti, M.; Eymin, C.; Todesco, E.; Van Weelderen, R.; Prin, H.; Berkowitz Zamora, D.

2017-12-01

The High Luminosity LHC (HL-LHC) is a project to upgrade the LHC collider after 2020-2025 to increase the integrated luminosity by about one order of magnitude and extend the physics production until 2035. An upgrade of the focusing triplets insertion system for the ATLAS and CMS experiments is foreseen using superconducting magnets operating in a pressurised superfluid helium bath at 1.9 K. This will require the design and construction of four continuous cryostats, each about sixty meters in length and one meter in diameter, for the final beam focusing quadrupoles, corrector magnets and beam separation dipoles. The design is constrained by the dimensions of the existing tunnel and accessibility restrictions imposing the integration of cryogenic piping inside the cryostat, thus resulting in a very compact integration. As the alignment and position stability of the magnets is crucial for the luminosity performance of the machine, the magnet support system must be carefully designed in order to cope with parasitic forces and thermo-mechanical load cycles. In this paper, we present the conceptual design of the cryostat and discuss the approach to address the stringent and often conflicting requirements of alignment, integration and thermal aspects.

In-plane/out-of-plane disorder influence on the magnetic anisotropy of Fe{sub 1−y}Mn{sub y}Pt-L1{sub 0} bulk alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cuadrado, R.; Catalan Institute of Nanoscience and Nanotechnology; Liu, Kai

2016-03-21

The random substitution of a non-magnetic species instead of Fe atoms in FePt-L1{sub 0} bulk alloy will permit to tune the magnetic anisotropy energy of this material. We have performed by means of first principles calculations a study of Fe{sub 1−y}Mn{sub y}Pt-L1{sub 0} (y = 0.0, 0.08, 0.12, 0.17, 0.22, and 0.25) bulk alloy for a fixed Pt concentration when the Mn species have ferro-/antiferromagnetic (FM,AFM) alignment at the same(different) atomic plane(s). This substitution will promote several in-plane lattice values for a fixed amount of Mn. Charge hybridization will change compared to the FePt-L1{sub 0} bulk due to this lattice variation leadingmore » to a site resolved magnetic moment modification. We demonstrate that this translates into a total magnetic anisotropy reduction for the AFM phase and an enhancement for the FM alignment. Several geometric configurations were taken into account for a fixed Mn concentration because of different possible Mn positions in the simulation cell.« less

Direct observation of the alignment of ferromagnetic spins by antiferromagnetic spins

NASA Astrophysics Data System (ADS)

Nolting, F.; Scholl, A.; Stöhr, J.; Seo, J. W.; Fompeyrine, J.; Siegwart, H.; Locquet, J.-P.; Anders, S.; Lüning, J.; Fullerton, E. E.; Toney, M. F.; Scheinfein, M. R.; Padmore, H. A.

2000-06-01

The arrangement of spins at interfaces in a layered magnetic material often has an important effect on the properties of the material. One example of this is the directional coupling between the spins in an antiferromagnet and those in an adjacent ferromagnet, an effect first discovered in 1956 and referred to as exchange bias. Because of its technological importance for the development of advanced devices such as magnetic read heads and magnetic memory cells, this phenomenon has received much attention. Despite extensive studies, however, exchange bias is still poorly understood, largely due to the lack of techniques capable of providing detailed information about the arrangement of magnetic moments near interfaces. Here we present polarization-dependent X-ray magnetic dichroism spectro-microscopy that reveals the micromagnetic structure on both sides of a ferromagnetic-antiferromagnetic interface. Images of thin ferromagnetic Co films grown on antiferromagnetic LaFeO3 show a direct link between the arrangement of spins in each material. Remanent hysteresis loops, recorded for individual ferromagnetic domains, show a local exchange bias. Our results imply that the alignment of the ferromagnetic spins is determined, domain by domain, by the spin directions in the underlying antiferromagnetic layer.

A general method for controlling and resolving rotational orientation of molecules in molecule-surface collisions

PubMed Central

Godsi, Oded; Corem, Gefen; Alkoby, Yosef; Cantin, Joshua T.; Krems, Roman V.; Somers, Mark F.; Meyer, Jörg; Kroes, Geert-Jan; Maniv, Tsofar; Alexandrowicz, Gil

2017-01-01

The outcome of molecule–surface collisions can be modified by pre-aligning the molecule; however, experiments accomplishing this are rare because of the difficulty of preparing molecules in aligned quantum states. Here we present a general solution to this problem based on magnetic manipulation of the rotational magnetic moment of the incident molecule. We apply the technique to the scattering of H2 from flat and stepped copper surfaces. We demonstrate control of the molecule's initial quantum state, allowing a direct comparison of differences in the stereodynamic scattering from the two surfaces. Our results show that a stepped surface exhibits a much larger dependence of the corrugation of the interaction on the alignment of the molecule than the low-index surface. We also demonstrate an extension of the technique that transforms the set-up into an interferometer, which is sensitive to molecular quantum states both before and after the scattering event. PMID:28480890

Enhanced antibacterial activity through the controlled alignment of graphene oxide nanosheets.

PubMed

Lu, Xinglin; Feng, Xunda; Werber, Jay R; Chu, Chiheng; Zucker, Ines; Kim, Jae-Hong; Osuji, Chinedum O; Elimelech, Menachem

2017-11-14

The cytotoxicity of 2D graphene-based nanomaterials (GBNs) is highly important for engineered applications and environmental health. However, the isotropic orientation of GBNs, most notably graphene oxide (GO), in previous experimental studies obscured the interpretation of cytotoxic contributions of nanosheet edges. Here, we investigate the orientation-dependent interaction of GBNs with bacteria using GO composite films. To produce the films, GO nanosheets are aligned in a magnetic field, immobilized by cross-linking of the surrounding matrix, and exposed on the surface through oxidative etching. Characterization by small-angle X-ray scattering and atomic force microscopy confirms that GO nanosheets align progressively well with increasing magnetic field strength and that the alignment is effectively preserved by cross-linking. When contacted with the model bacterium Escherichia coli , GO nanosheets with vertical orientation exhibit enhanced antibacterial activity compared with random and horizontal orientations. Further characterization is performed to explain the enhanced antibacterial activity of the film with vertically aligned GO. Using phospholipid vesicles as a model system, we observe that GO nanosheets induce physical disruption of the lipid bilayer. Additionally, we find substantial GO-induced oxidation of glutathione, a model intracellular antioxidant, paired with limited generation of reactive oxygen species, suggesting that oxidation occurs through a direct electron-transfer mechanism. These physical and chemical mechanisms both require nanosheet penetration of the cell membrane, suggesting that the enhanced antibacterial activity of the film with vertically aligned GO stems from an increased density of edges with a preferential orientation for membrane disruption. The importance of nanosheet penetration for cytotoxicity has direct implications for the design of engineering surfaces using GBNs.

Dust Polarization toward Embedded Protostars in Ophiuchus with ALMA. I. VLA 1623

NASA Astrophysics Data System (ADS)

Sadavoy, Sarah I.; Myers, Philip C.; Stephens, Ian W.; Tobin, John; Commerçon, Benoît; Henning, Thomas; Looney, Leslie; Kwon, Woojin; Segura-Cox, Dominique; Harris, Robert

2018-06-01

We present high-resolution (∼30 au) ALMA Band 6 dust polarization observations of VLA 1623. The VLA 1623 data resolve compact ∼40 au inner disks around the two protobinary sources, VLA 1623-A and VLA 1623-B, and also an extended ∼180 au ring of dust around VLA 1623-A. This dust ring was previously identified as a large disk in lower-resolution observations. We detect highly structured dust polarization toward the inner disks and the extended ring with typical polarization fractions ≈1.7% and ≈2.4%, respectively. The two components also show distinct polarization morphologies. The inner disks have uniform polarization angles aligned with their minor axes. This morphology is consistent with expectations from dust scattering. By contrast, the extended dust ring has an azimuthal polarization morphology not previously seen in lower-resolution observations. We find that our observations are well-fit by a static, oblate spheroid model with a flux-frozen, poloidal magnetic field. We propose that the polarization traces magnetic grain alignment likely from flux freezing on large scales and magnetic diffusion on small scales. Alternatively, the azimuthal polarization may be attributed to grain alignment by the anisotropic radiation field. If the grains are radiatively aligned, then our observations indicate that large (∼100 μm) dust grains grow quickly at large angular extents. Finally, we identify significant proper motion of VLA 1623 using our observations and those in the literature. This result indicates that the proper motion of nearby systems must be corrected for when combining ALMA data from different epochs.

Magnetism variations and susceptibility hysteresis at the metal-insulator phase transition temperature of VO2 in a composite film containing vanadium and tungsten oxides

NASA Astrophysics Data System (ADS)

Akande, Amos A.; Rammutla, Koena E.; Moyo, Thomas; Osman, Nadir S. E.; Nkosi, Steven S.; Jafta, Charl J.; Mwakikunga, Bonex W.

2015-02-01

We report on the magnetic property of 0.67-WO3+0.33-VOx mixture film deposit on the corning glass substrate using the chemical sol-gel and atmospheric pressure chemical vapor deposition (APCVD) methods. The XRD and Raman spectroscopy confirm species of both materials, and the morphological studies with FIB-SEM and TEM reveal segregation of W and V atoms. XPS reveals that V4+ from VO2 forms only 11% of the film; V3+ in the form of V2O3 form 1% of the film, 21% is V5+ from V2O5 and 67% is given to W6+ from WO3. The analysis of the ESR data shows some sharp changes in the magnetism near the metal-to-insulator (MIT), which could be theoretically interpreted as the ordering or alignment of electron spins from net moment nature to parallel alignment of magnetic moment. The derivatives of magnetic susceptibility established the thermally induced magnetic property: two distinct transitions of 339 K for heating data and 338 K for cooling data for 151.2 mT field were obtained. Similar results were also obtained for 308.7 mT field, 336 K for heating data and 335 K for cooling data. VSM results confirm a paramagnetic phase with a small amount of magnetically ordered phase.

Magnetically aligned dust and SiO maser polarisation in the envelope of the red supergiant VY Canis Majoris

NASA Astrophysics Data System (ADS)

Vlemmings, W. H. T.; Khouri, T.; Martí-Vidal, I.; Tafoya, D.; Baudry, A.; Etoka, S.; Humphreys, E. M. L.; Jones, T. J.; Kemball, A.; O'Gorman, E.; Pérez-Sánchez, A. F.; Richards, A. M. S.

2017-07-01

Aims: Polarisation observations of circumstellar dust and molecular (thermal and maser) lines provide unique information about dust properties and magnetic fields in circumstellar envelopes of evolved stars. Methods: We use Atacama Large Millimeter/submillimeter Array (ALMA) Band 5 science verification observations of the red supergiant VY CMa to study the polarisation of SiO thermal/maser lines and dust continuum at 1.7 mm wavelength. We analyse both linear and circular polarisation and derive the magnetic field strength and structure, assuming the polarisation of the lines originates from the Zeeman effect, and that of the dust originates from aligned dust grains. We also discuss other effects that could give rise to the observed polarisation. Results: We detect, for the first time, significant polarisation ( 3%) of the circumstellar dust emission at millimeter wavelengths. The polarisation is uniform with an electric vector position angle of 8°. Varying levels of linear polarisation are detected for the J = 4 - 328SiO v = 0, 1, 2, and 29SiO v = 0, 1 lines, with the strongest polarisation fraction of 30% found for the 29SiO v = 1 maser. The linear polarisation vectors rotate with velocity, consistent with earlier observations. We also find significant (up to 1%) circular polarisation in several lines, consistent with previous measurements. We conclude that the detection is robust against calibration and regular instrumental errors, although we cannot yet fully rule out non-standard instrumental effects. Conclusions: Emission from magnetically aligned grains is the most likely origin of the observed continuum polarisation. This implies that the dust is embedded in a magnetic field >13 mG. The maser line polarisation traces the magnetic field structure. The magnetic field in the gas and dust is consistent with an approximately toroidal field configuration, but only higher angular resolution observations will be able to reveal more detailed field structure. If the circular polarisation is due to Zeeman splitting, it indicates a magnetic field strength of 1-3 Gauss, consistent with previous maser observations.

Sudden motility reversal indicates sensing of magnetic field gradients in Magnetospirillum magneticum AMB-1 strain

PubMed Central

González, Lina M; Ruder, Warren C; Mitchell, Aaron P; Messner, William C; LeDuc, Philip R

2015-01-01

Many motile unicellular organisms have evolved specialized behaviors for detecting and responding to environmental cues such as chemical gradients (chemotaxis) and oxygen gradients (aerotaxis). Magnetotaxis is found in magnetotactic bacteria and it is defined as the passive alignment of these cells to the geomagnetic field along with active swimming. Herein we show that Magnetospirillum magneticum (AMB-1) show a unique set of responses that indicates they sense and respond not only to the direction of magnetic fields by aligning and swimming, but also to changes in the magnetic field or magnetic field gradients. We present data showing that AMB-1 cells exhibit sudden motility reversals when we impose them to local magnetic field gradients. Our system employs permalloy (Ni80Fe20) islands to curve and diverge the magnetic field lines emanating from our custom-designed Helmholtz coils in the vicinity of the islands (creating a drop in the field across the islands). The three distinct movements we have observed as they approach the permalloy islands are: unidirectional, single reverse and double reverse. Our findings indicate that these reverse movements occur in response to magnetic field gradients. In addition, using a permanent magnet we found further evidence that supports this claim. Motile AMB-1 cells swim away from the north and south poles of a permanent magnet when the magnet is positioned less than ∼30 mm from the droplet of cells. All together, these results indicate previously unknown response capabilities arising from the magnetic sensing systems of AMB-1 cells. These responses could enable them to cope with magnetic disturbances that could in turn potentially inhibit their efficient search for nutrients. PMID:25478682

Investigation of magnetic properties of Fe{sub 3}O{sub 4} nanoparticles using temperature dependent magnetic hyperthermia in ferrofluids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nemala, H.; Thakur, J. S.; Lawes, G.

2014-07-21

Rate of heat generated by magnetic nanoparticles in a ferrofluid is affected by their magnetic properties, temperature, and viscosity of the carrier liquid. We have investigated temperature dependent magnetic hyperthermia in ferrofluids, consisting of dextran coated superparamagnetic Fe{sub 3}O{sub 4} nanoparticles, subjected to external magnetic fields of various frequencies (188–375 kHz) and amplitudes (140–235 Oe). Transmission electron microscopy measurements show that the nanoparticles are polydispersed with a mean diameter of 13.8 ± 3.1 nm. The fitting of experimental dc magnetization data to a standard Langevin function incorporating particle size distribution yields a mean diameter of 10.6 ± 1.2 nm, and a reduced saturation magnetization (∼65 emu/g) comparedmore » to the bulk value of Fe{sub 3}O{sub 4} (∼95 emu/g). This is due to the presence of a finite surface layer (∼1 nm thickness) of non-aligned spins surrounding the ferromagnetically aligned Fe{sub 3}O{sub 4} core. We found the specific absorption rate, measured as power absorbed per gram of iron oxide nanoparticles, decreases monotonically with increasing temperature for all values of magnetic field and frequency. Using the size distribution of magnetic nanoparticles estimated from the magnetization measurements, we have fitted the specific absorption rate versus temperature data using a linear response theory and relaxation dissipation mechanisms to determine the value of magnetic anisotropy constant (28 ± 2 kJ/m{sup 3}) of Fe{sub 3}O{sub 4} nanoparticles.« less

Sudden motility reversal indicates sensing of magnetic field gradients in Magnetospirillum magneticum AMB-1 strain.

PubMed

González, Lina M; Ruder, Warren C; Mitchell, Aaron P; Messner, William C; LeDuc, Philip R

2015-06-01

Many motile unicellular organisms have evolved specialized behaviors for detecting and responding to environmental cues such as chemical gradients (chemotaxis) and oxygen gradients (aerotaxis). Magnetotaxis is found in magnetotactic bacteria and it is defined as the passive alignment of these cells to the geomagnetic field along with active swimming. Herein we show that Magnetospirillum magneticum (AMB-1) show a unique set of responses that indicates they sense and respond not only to the direction of magnetic fields by aligning and swimming, but also to changes in the magnetic field or magnetic field gradients. We present data showing that AMB-1 cells exhibit sudden motility reversals when we impose them to local magnetic field gradients. Our system employs permalloy (Ni(80)Fe(20)) islands to curve and diverge the magnetic field lines emanating from our custom-designed Helmholtz coils in the vicinity of the islands (creating a drop in the field across the islands). The three distinct movements we have observed as they approach the permalloy islands are: unidirectional, single reverse and double reverse. Our findings indicate that these reverse movements occur in response to magnetic field gradients. In addition, using a permanent magnet we found further evidence that supports this claim. Motile AMB-1 cells swim away from the north and south poles of a permanent magnet when the magnet is positioned less than ∼30 mm from the droplet of cells. All together, these results indicate previously unknown response capabilities arising from the magnetic sensing systems of AMB-1 cells. These responses could enable them to cope with magnetic disturbances that could in turn potentially inhibit their efficient search for nutrients.

The ties that bind: interorganizational linkages and physician-system alignment.

PubMed

Alexander, J A; Waters, T M; Burns, L R; Shortell, S M; Gillies, R R; Budetti, P P; Zuckerman, H S

2001-07-01

To examine the association between the degree of alignment between physicians and health care systems, and interorganizational linkages between physician groups and health care systems. The study used a cross sectional, comparative analysis using a sample of 1,279 physicians practicing in loosely affiliated arrangements and 1,781 physicians in 61 groups closely affiliated with 14 vertically integrated health systems. Measures of physician alignment were based on multiitem scales validated in previous studies and derived from surveys sent to individual physicians. Measures of interorganizational linkages were specified at the institutional, administrative, and technical core levels of the physician group and were developed from surveys sent to the administrator of each of the 61 physician groups in the sample. Two stage Heckman models with fixed effects adjustments in the second stage were used to correct for sample selection and clustering respectively. After accounting for sample selection, fixed effects, and group and individual controls, physicians in groups with more valued practice service linkages display consistently higher alignment with systems than physicians in groups that have fewer such linkages. Results also suggest that centralized administrative control lowers physician-system alignment for selected measures of alignment. Governance interlocks exhibited only weak associations with alignment. Our findings suggest that alignment generally follows resource exchanges that promote value-added contributions to physicians and physician groups while preserving control and authority within the group.

Europium III binding and the reorientation of magnetically aligned bicelles: insights from deuterium NMR spectroscopy.

PubMed Central

Crowell, K J; Macdonald, P M

2001-01-01

Solid-state deuterium ((2)H) NMR spectroscopy was used to study the reorientation of magnetically ordered bicelles in the presence of the paramagnetic lanthanide Eu(3+). Bicelles were composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) plus 1,2-dihexanoyl-sn-glycero-3-phosphocholine plus either the anionic lipid 1,2-dimyristoyl-sn-3-phosphoglycerol, or the cationic lipid 1,2-dimyristoyl-3-trimethyl ammonium propane. Alignment of the bicelles in the magnetic field produced (2)H NMR spectra consisting of a pair of quadrupole doublets, one from the alpha-deuterons and one from the beta-deuterons of DMPC-alpha,beta-d(4). Eu(3+) addition induced the appearance of a second set of quadrupole doublets, having approximately twice the quadrupolar splittings of the originals, and growing progressively in intensity with increasing Eu(3+), at the expense of the intensity of the originals. The new resonances were attributed to bicelles having a parallel alignment with respect to the magnetic field, as opposed to the perpendicular alignment preferred in the absence of Eu(3+). Therefore, the equilibrium degree and kinetics of reorientation could be evaluated from the (2)H NMR spectra. For more cationic initial surface charges, higher amounts of added Eu(3+) were required to induce a given degree of reorientation. However, the equilibrium degree of bicellar reorientation was found to depend solely on the amount of bound Eu(3+), regardless of the bicelle composition. The kinetics of reorientation were a function of lipid concentration. At high lipid concentration, a single fast rate of reorientation (minutes) described the approach to the equilibrium degree of orientation. At lower lipid concentrations, two rates processes were discernible: one fast (minutes) and one slow (hours). The data indicate, therefore, that bicelle reorientation is a phase transition made critical by bicelle-bicelle interactions. PMID:11423411

Micropole undulator

DOEpatents

Tatchyn, Roman O.; Csonka, Paul L.; Cremer, Jay T.

1990-12-11

Micropole undulators for use in the generation of x-rays from moving charged particles are disclosed. Two rows of spaced apart poles are arranged so that each pole produces a magnetic field aligned with all other similar fields. The poles are the ends of "C"-shaped magnets. In each row, adjacent poles are separated by spacers made of a superconducting material.

Cryo-tomography Tilt-series Alignment with Consideration of the Beam-induced Sample Motion

PubMed Central

Fernandez, Jose-Jesus; Li, Sam; Bharat, Tanmay A. M.; Agard, David A.

2018-01-01

Recent evidence suggests that the beam-induced motion of the sample during tilt-series acquisition is a major resolution-limiting factor in electron cryo-tomography (cryoET). It causes suboptimal tilt-series alignment and thus deterioration of the reconstruction quality. Here we present a novel approach to tilt-series alignment and tomographic reconstruction that considers the beam-induced sample motion through the tilt-series. It extends the standard fiducial-based alignment approach in cryoET by introducing quadratic polynomials to model the sample motion. The model can be used during reconstruction to yield a motion-compensated tomogram. We evaluated our method on various datasets with different sample sizes. The results demonstrate that our method could be a useful tool to improve the quality of tomograms and the resolution in cryoET. PMID:29410148

Artificial Aurora Generated by HAARP (Invited)

NASA Astrophysics Data System (ADS)

Streltsov, A. V.; Kendall, E. A.

2013-12-01

We present results from the ionospheric heating experiment conducted on March 12, 2013 at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska. During the experiment HAARP transmitted X-mode 4.57 MHz waves modulated with the frequency 0.9 mHz and pointed in the direction of the magnetic zenith. The beam was focused to ~20 km spot at the altitude 100 km. The heating produces two effects: First, it generates magnetic field-aligned currents producing D and H components of the magnetic field with frequency 0.9 mHz detected by fluxgate magnetometer in Gakona. Second, the heating produced bright luminous structures in the heated region detected with the SRI telescope in 427.8 nm, 557.7 nm, 630.0 nm wavelengths. We emphasize, that for the best of our knowledge, this is the first experiment where the heating of the ionosphere with X-mode produces luminous structures in the ionosphere. We classify this luminosity as an 'artificial aurora', because it correlate with the intensity of the magnetic field-aligned currents, and such correlation is constantly seen in the natural aurora.

Modelling gamma-ray light curves of phase-aligned millisecond pulsars

NASA Astrophysics Data System (ADS)

Chang, Shan; Zhang, Li; Li, Xiang; Jiang, Zejun

2018-04-01

Three gamma-ray millisecond pulsars (MSPs), PSR J1939+2134, PSR J1959+2048, and PSR J0034-0534, have been confirmed to have a common feature of phase-aligned in radio and gamma-ray bands. With a geometric (two-pole caustic) model and a physical outer gap model (revised 3D outer gap model) in a three dimensional (3D) retarded magnetic dipole with a perturbation magnetic field, the observed features of these MSPs are studied. In order to obtained the best-fitting model parameters, the Markov chain Monte Carlo technique is used and reasonable GeV band light curves for three MSPs are given. Our calculations indicate that MSPs emit high energy photons with smaller inclination angles (α ≈ 10°-50°), larger view angles (ζ ≈ 65°-100°), and smaller perturbation factor (ɛ ≈ -0.15-0.1). Note that the factor ɛ, describing the strength of the perturbed magnetic field, is all less than zero in these two models, so the magnetic field caused by current-induced play a leading role in the pulsed location of MSPs.

Modelling dust polarization observations of molecular clouds through MHD simulations

NASA Astrophysics Data System (ADS)

King, Patrick K.; Fissel, Laura M.; Chen, Che-Yu; Li, Zhi-Yun

2018-03-01

The BLASTPol observations of Vela C have provided the most detailed characterization of the polarization fraction p and dispersion in polarization angles S for a molecular cloud. We compare the observed distributions of p and S with those obtained in synthetic observations of simulations of molecular clouds, assuming homogeneous grain alignment. We find that the orientation of the mean magnetic field relative to the observer has a significant effect on the p and S distributions. These distributions for Vela C are most consistent with synthetic observations where the mean magnetic field is close to the line of sight. Our results point to apparent magnetic disorder in the Vela C molecular cloud, although it can be due to either an inclination effect (i.e. observing close to the mean field direction) or significant field tangling from strong turbulence/low magnetization. The joint correlations of p with column density and of S with column density for the synthetic observations generally agree poorly with the Vela C joint correlations, suggesting that understanding these correlations requires a more sophisticated treatment of grain alignment physics.

Beam based alignment and its relevance in Indus-2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jena, Saroj Kumar; Husain, Riyasat; Gandhi, M. L.

2015-09-15

Initially in the Indus-2 storage ring, the closed orbit distortion (COD) could be best corrected to 1.3 mm rms in the horizontal and 0.43 mm rms in the vertical plane. The strength of the corrector magnets required high values for COD correction. This revealed that offsets in COD readout by the beam position monitors (BPMs) played a role in not achieving a rms COD lower than the above value. Thus, the offset between the electrical center of BPMs and the magnetic center of the nearest quadrupole magnet could be estimated using the beam based alignment (BBA) method. It prefers thatmore » the quadrupole magnet is able to be controlled individually and active shunt power supply (ASPS) system was designed for this purpose that works efficiently. This paper describes the methodology of BBA, topology of ASPS and its performance, and COD minimization using the measured BPM offsets. After BBA, the COD could be reduced to 0.45 mm rms and 0.2 mm rms in horizontal and vertical planes, respectively.« less

Folded waveguide coupler

DOEpatents

Owens, Thomas L.

1988-03-01

A resonant cavity waveguide coupler for ICRH of a magnetically confined plasma. The coupler consists of a series of inter-leaved metallic vanes disposed withn an enclosure analogous to a very wide, simple rectangular waveguide that has been "folded" several times. At the mouth of the coupler, a polarizing plate is provided which has coupling apertures aligned with selected folds of the waveguide through which rf waves are launched with magnetic fields of the waves aligned in parallel with the magnetic fields confining the plasma being heated to provide coupling to the fast magnetosonic wave within the plasma in the frequency usage of from about 50-200 mHz. A shorting plate terminates the back of the cavity at a distance approximately equal to one-half the guide wavelength from the mouth of the coupler to ensure that the electric field of the waves launched through the polarizing plate apertures are small while the magnetic field is near a maximum. Power is fed into the coupler folded cavity by means of an input coaxial line feed arrangement at a point which provides an impedance match between the cavity and the coaxial input line.

On the synthesis and microstructure analysis of high performance MnBi

NASA Astrophysics Data System (ADS)

Chen, Yu-Chun; Sawatzki, Simon; Ener, Semih; Sepehri-Amin, Hossein; Leineweber, Andreas; Gregori, Giuliano; Qu, Fei; Muralidhar, Shreyas; Ohkubo, Tadakatsu; Hono, Kazuhiro; Gutfleisch, Oliver; Kronmüller, Helmut; Schütz, Gisela; Goering, Eberhard

2016-12-01

Highly anisotropic MnBi powder with over 90 wt% low-temperature phase can be prepared using conventional arc-melting and 2 hour-low energy ball milling (BM) followed by magnetic separation. After proper alignment, the purified Mn55Bi45(Mn45Bi55) powder show remarkable magnetic properties: mass remanence of 71(65) Am2/kg and coercivity of 1.23(1.18) T at 300 K. The nominal maximum energy product of 120 kJ/m3 is achieved in the purified 2h-BM Mn55Bi45 powder, close to theoretical value of 140.8 kJ/m3. The Mn55Bi45(Mn45Bi55) bulk magnets show the highest volume remanence of 0.68(0.57) T at 300 K, while they were consolidated at 573(523) K by a pressure of 200 MPa for 5 minutes using hot-compaction method. In addition to the observed grain size, the coercivity of the hot-compacted samples at 300 K was found to be strongly related to the amount of metallic Mn and Bi residue at the grain-boundary. Our study proves that the magnetic properties of the Mn45Bi55 bulk magnets are stable up to 500 K, and the nominal (BH)max values are still above 40 kJ/m3 at 500 K showing the potential ability for high-temperature applications.

Magnetic properties of hybrid elastomers with magnetically hard fillers: rotation of particles

NASA Astrophysics Data System (ADS)

Stepanov, G. V.; Borin, D. Yu; Bakhtiiarov, A. V.; Storozhenko, P. A.

2017-03-01

Hybrid magnetic elastomers belonging to the family of magnetorheological elastomers contain magnetically hard components and are of the utmost interest for the development of semiactive and active damping devices as well as actuators and sensors. The processes of magnetizing of such elastomers are accompanied by structural rearrangements inside the material. When magnetized, the elastomer gains its own magnetic moment resulting in changes of its magneto-mechanical properties, which remain permanent, even in the absence of external magnetic fields. Influenced by the magnetic field, magnetized particles move inside the matrix forming chain-like structures. In addition, the magnetically hard particles can rotate to align their magnetic moments with the new direction of the external field. Such an elastomer cannot be demagnetized by the application of a reverse field.

High magnetic susceptibility granodiorite as a source of surface magnetic anomalies in the King George Island, Antarctica

NASA Astrophysics Data System (ADS)

Kon, S.; Nakamura, N.; Funaki, M.; Sakanaka, S.

2012-12-01

Change in plate motion produces convergence of the two oceanic lithospheres and the formation of volcanic island arcs above the subducted older and thicker plate. The association of calc-alkaline diorites to tonalites and granodiorites (ACG) is typical plutonic rocks of the volcanic arcs. In the many island arcs that surround the Pacific Ocean, ACG generally forms shallow level plutons and is closely associated with volcanic rocks. The Japan Arc setting had occurred the emplacement of the highly magnetic granitoid along the fore-arc basin before back-arc spreading at middle Miocene, showing a linear positive magnetic anomaly. Similar magnetic anomalies have also been exhibited along the Circum-Pacific Belt. Along East Antarctica, it is well known that the South Shetland Islands have been formed by back-arc spreading related to the subduction along the South Shetland trench during the late Cretaceous and middle Miocene. Moreover, geology in the South Shetland Islands consists of lava flows with subordinate pyroclastic deposits, intrusive dykes-sills, granitic plutons, displaying a typical subduction-related calc-alkaline volcanic association. However, there is little report on the presence of fore-arc granitoid. Here we report the distribution and structure of the granitic plutons around Marian Cove in the King George Island, South Shetland, East Antarctica by surface geological survey and magnetic anisotropic studies. Then we compare the distribution of granitic plutons with surface magnetic anomalies through our ship-borne and foot-borne magnetic surveys. The granitic plutons are distributed only shallow around the Marian cove in the King George Island, and the plutons had been intruded in the Sejong formation with pyroclastic deposits and basaltic/rhyoritic lavas, suggesting the post back-arc spreading. We sampled 8 plutons, 12 basaltic lavas and 6 andestic dykes, all located within four kilometer radius from the Korean Antarctic research station (King Sejong station) in the western side of King George Island. The plutonic rocks of diorite and granodiorite show high values of bulk magnetic susceptibility of c.a. 0.01-0.4 SI, appearing to be the source of positive magnetic anomaly. We also revealed the preferred petrofabric lineation directions at the sites using anisotropy of magnetic susceptibility (AMS). The AMS showed the plutonic rocks represent the vertical intrusion from the deep seated magma. Our optical microscope observation verified the maximum AMS orientation is parallel to the preferred alignment of framework-forming plagioclase, suggesting the alignment of euhedral magnetite grains along the long-axes of plagioclases. Our ship-borne and foot-borne surveys of geomagnetic filed anomaly agree well with the distribution of the plutonic rocks, revealing the possible origin of surface magnetic anomaly. These suggests that the plutons in this area may be included ACG, and this magnetic surveys is proposed to infer the availability to find out the presence of granitoid.

Optical properties of orthodontic aligners--spectrophotometry analysis of three types before and after aging.

PubMed

Lombardo, Luca; Arreghini, Angela; Maccarrone, Roberta; Bianchi, Anna; Scalia, Santo; Siciliani, Giuseppe

2015-01-01

The aim was to assess and compare absorbance and transmittance values of three types of clear orthodontic aligners before and after two cycles of in vitro aging. Nine samples of orthodontic aligners from three different manufacturers (Invisalign, Align Technology, Santa Clara, CA, USA; All-In, Micerium, Avegno, GE, Italy; F22 Aligner, Sweden & Martina, Due Carrare, PD, Italy) were selected, and each sample was subjected to spectrophotometry analysis of both its transmittance and absorbance a total of 27 times. Samples were subsequently aged in vitro at a constant temperature in artificial saliva supplemented with food colouring for two cycles of 14 days each. The spectrophotometry protocol was then repeated, and the resulting data were analysed and compared by means of ANOVA (p < 0.05). All types of aligners tested yielded lower transmittance and higher absorbance values after aging, but the difference was not significant in any case. That being said, the F22 aligners were found to be most transparent, both before and after aging, followed by Invisalign and All-In, and these differences were statistically significant. Commercial aligners possess significantly different optical, and therefore aesthetic, properties, both as delivered and following aging.

Vortex Flipping in Superconductor-Ferromagnet Spin Valve Structures

NASA Astrophysics Data System (ADS)

Patino, Edgar J.; Aprili, Marco; Blamire, Mark; Maeno, Yoshiteru

2014-03-01

We report in plane magnetization measurements on Ni/Nb/Ni/CoO and Co/Nb/Co/CoO spin valve structures with one of the ferromagnetic layers pinned by an antiferromagnetic layer. In samples with Ni, below the superconducting transition Tc, our results show strong evidence of vortex flipping driven by the ferromagnets magnetization. This is a direct consequence of proximity effect that leads to vortex supercurrents leakage into the ferromagnets. Here the polarized electron spins are subject to vortices magnetic field occasioning vortex flipping. Such novel mechanism has been made possible for the first time by fabrication of the F/S/F/AF multilayered spin valves with a thin-enough S layer to barely confine vortices inside as well as thin-enough F layers to align and control the magnetization within the plane. When Co is used there is no observation of vortex flipping effect. This is attributed to Co shorter coherence length. Interestingly instead a reduction in pinning field of about 400 Oe is observed when the Nb layer is in superconducting state. This effect cannot be explained in terms of vortex fields. In view of these facts any explanation must be directly related to proximity effect and thus a remarkable phenomenon that deserves further investigation. Programa Nacional de Ciencias Basicas COLCIENCIAS (No. 120452128168).

Sol–gel auto-combustion synthesis of PVP/CoFe{sub 2}O{sub 4} nanocomposite and its magnetic characterization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurtan, U.; Topkaya, R., E-mail: rtopkaya@gyte.edu.tr; Baykal, A.

2013-11-15

Graphical abstract: - Highlights: • The Poly(vinyl pyrrolidone) (PVP) was used as a surface capping agent. • PVP/CoFe{sub 2}O{sub 4} nanocomposite was synthesized by a sol-gel auto-combustion method. • The existence of the spin-disordered surface layer was established. - Abstract: Poly(vinyl pyrrolidone)/CoFe{sub 2}O{sub 4} nanocomposite has been fabricated by a sol–gel auto-combustion method. Poly(vinyl pyrrolidone) was used as a reducing agent as well as a surface capping agent to prevent particle aggregation and stabilize the particles. The average crystallite size estimated from X-ray line profile fitting was found to be 20 ± 7 nm. The high field irreversibility and unsaturatedmore » magnetization behaviours indicate the presence of the core–shell structure in the sample. The exchange bias effect observed at 10 K suggests the existence of the magnetically aligned core surrounded by spin-disordered surface layer. The reduced remanent magnetization value of 0.6 at 10 K (higher than the theoretical value of 0.5) shows the PVP/CoFe{sub 2}O{sub 4} nanocomposite to have cubic magnetocrystalline anisotropy according to the Stoner–Wohlfarth model.« less

Magnetospheric convection during quiet or moderately disturbed times

NASA Technical Reports Server (NTRS)

Caudal, G.; Blanc, M.

1988-01-01

The processes which contribute to the large-scale plasma circulation in the earth's environment during quiet times, or during reasonable stable magnetic conditions are reviewed. The various sources of field-aligned current generation in the solar wind and the magnetosphere are presented. The generation of field-aligned currents on open field lines connected to either polar cap and the generation of closed field lines of the inner magnetosphere are examined. Consideration is given to the hypothesis of Caudal (1987) that loss processes of trapped particles are competing with adiabatic motions in the generation of field-aligned currents in the inner magnetosphere.

Robust algorithm for aligning two-dimensional chromatograms.

PubMed

Gros, Jonas; Nabi, Deedar; Dimitriou-Christidis, Petros; Rutler, Rebecca; Arey, J Samuel

2012-11-06

Comprehensive two-dimensional gas chromatography (GC × GC) chromatograms typically exhibit run-to-run retention time variability. Chromatogram alignment is often a desirable step prior to further analysis of the data, for example, in studies of environmental forensics or weathering of complex mixtures. We present a new algorithm for aligning whole GC × GC chromatograms. This technique is based on alignment points that have locations indicated by the user both in a target chromatogram and in a reference chromatogram. We applied the algorithm to two sets of samples. First, we aligned the chromatograms of twelve compositionally distinct oil spill samples, all analyzed using the same instrument parameters. Second, we applied the algorithm to two compositionally distinct wastewater extracts analyzed using two different instrument temperature programs, thus involving larger retention time shifts than the first sample set. For both sample sets, the new algorithm performed favorably compared to two other available alignment algorithms: that of Pierce, K. M.; Wood, Lianna F.; Wright, B. W.; Synovec, R. E. Anal. Chem.2005, 77, 7735-7743 and 2-D COW from Zhang, D.; Huang, X.; Regnier, F. E.; Zhang, M. Anal. Chem.2008, 80, 2664-2671. The new algorithm achieves the best matches of retention times for test analytes, avoids some artifacts which result from the other alignment algorithms, and incurs the least modification of quantitative signal information.

Validation of Splicing Events in Transcriptome Sequencing Data

PubMed Central

Kaisers, Wolfgang; Ptok, Johannes; Schwender, Holger; Schaal, Heiner

2017-01-01

Genomic alignments of sequenced cellular messenger RNA contain gapped alignments which are interpreted as consequence of intron removal. The resulting gap-sites, genomic locations of alignment gaps, are landmarks representing potential splice-sites. As alignment algorithms report gap-sites with a considerable false discovery rate, validations are required. We describe two quality scores, gap quality score (gqs) and weighted gap information score (wgis), developed for validation of putative splicing events: While gqs solely relies on alignment data wgis additionally considers information from the genomic sequence. FASTQ files obtained from 54 human dermal fibroblast samples were aligned against the human genome (GRCh38) using TopHat and STAR aligner. Statistical properties of gap-sites validated by gqs and wgis were evaluated by their sequence similarity to known exon-intron borders. Within the 54 samples, TopHat identifies 1,000,380 and STAR reports 6,487,577 gap-sites. Due to the lack of strand information, however, the percentage of identified GT-AG gap-sites is rather low. While gap-sites from TopHat contain ≈89% GT-AG, gap-sites from STAR only contain ≈42% GT-AG dinucleotide pairs in merged data from 54 fibroblast samples. Validation with gqs yields 156,251 gap-sites from TopHat alignments and 166,294 from STAR alignments. Validation with wgis yields 770,327 gap-sites from TopHat alignments and 1,065,596 from STAR alignments. Both alignment algorithms, TopHat and STAR, report gap-sites with considerable false discovery rate, which can drastically be reduced by validation with gqs and wgis. PMID:28545234

Small system for tritium accelerator mass spectrometry

DOEpatents

Roberts, M.L.; Davis, J.C.

1993-02-23

Apparatus for ionizing and accelerating a sample containing isotopes of hydrogen and detecting the ratios of hydrogen isotopes contained in the sample is disclosed. An ion source generates a substantially linear ion beam including ions of tritium from the sample. A radio-frequency quadrupole accelerator is directly coupled to and axially aligned with the source at an angle of substantially zero degrees. The accelerator accelerates species of the sample having different mass to different energy levels along the same axis as the ion beam. A spectrometer is used to detect the concentration of tritium ions in the sample. In one form of the invention, an energy loss spectrometer is used which includes a foil to block the passage of hydrogen, deuterium and [sup 3]He ions, and a surface barrier or scintillation detector to detect the concentration of tritium ions. In another form of the invention, a combined momentum/energy loss spectrometer is used which includes a magnet to separate the ion beams, with Faraday cups to measure the hydrogen and deuterium and a surface barrier or scintillation detector for the tritium ions.

Small system for tritium accelerator mass spectrometry

DOEpatents

Roberts, Mark L.; Davis, Jay C.

1993-01-01

Apparatus for ionizing and accelerating a sample containing isotopes of hydrogen and detecting the ratios of hydrogen isotopes contained in the sample is disclosed. An ion source generates a substantially linear ion beam including ions of tritium from the sample. A radio-frequency quadrupole accelerator is directly coupled to and axially aligned with the source at an angle of substantially zero degrees. The accelerator accelerates species of the sample having different mass to different energy levels along the same axis as the ion beam. A spectrometer is used to detect the concentration of tritium ions in the sample. In one form of the invention, an energy loss spectrometer is used which includes a foil to block the passage of hydrogen, deuterium and .sup.3 He ions, and a surface barrier or scintillation detector to detect the concentration of tritium ions. In another form of the invention, a combined momentum/energy loss spectrometer is used which includes a magnet to separate the ion beams, with Faraday cups to measure the hydrogen and deuterium and a surface barrier or scintillation detector for the tritium ions.

A fast cross-validation method for alignment of electron tomography images based on Beer-Lambert law.

PubMed

Yan, Rui; Edwards, Thomas J; Pankratz, Logan M; Kuhn, Richard J; Lanman, Jason K; Liu, Jun; Jiang, Wen

2015-11-01

In electron tomography, accurate alignment of tilt series is an essential step in attaining high-resolution 3D reconstructions. Nevertheless, quantitative assessment of alignment quality has remained a challenging issue, even though many alignment methods have been reported. Here, we report a fast and accurate method, tomoAlignEval, based on the Beer-Lambert law, for the evaluation of alignment quality. Our method is able to globally estimate the alignment accuracy by measuring the goodness of log-linear relationship of the beam intensity attenuations at different tilt angles. Extensive tests with experimental data demonstrated its robust performance with stained and cryo samples. Our method is not only significantly faster but also more sensitive than measurements of tomogram resolution using Fourier shell correlation method (FSCe/o). From these tests, we also conclude that while current alignment methods are sufficiently accurate for stained samples, inaccurate alignments remain a major limitation for high resolution cryo-electron tomography. Copyright © 2015 Elsevier Inc. All rights reserved.

A fast cross-validation method for alignment of electron tomography images based on Beer-Lambert law

PubMed Central

Yan, Rui; Edwards, Thomas J.; Pankratz, Logan M.; Kuhn, Richard J.; Lanman, Jason K.; Liu, Jun; Jiang, Wen

2015-01-01

In electron tomography, accurate alignment of tilt series is an essential step in attaining high-resolution 3D reconstructions. Nevertheless, quantitative assessment of alignment quality has remained a challenging issue, even though many alignment methods have been reported. Here, we report a fast and accurate method, tomoAlignEval, based on the Beer-Lambert law, for the evaluation of alignment quality. Our method is able to globally estimate the alignment accuracy by measuring the goodness of log-linear relationship of the beam intensity attenuations at different tilt angles. Extensive tests with experimental data demonstrated its robust performance with stained and cryo samples. Our method is not only significantly faster but also more sensitive than measurements of tomogram resolution using Fourier shell correlation method (FSCe/o). From these tests, we also conclude that while current alignment methods are sufficiently accurate for stained samples, inaccurate alignments remain a major limitation for high resolution cryo-electron tomography. PMID:26455556

Genes and proteins involved in bacterial magnetic particle formation.

PubMed

Matsunaga, Tadashi; Okamura, Yoshiko

2003-11-01

Magnetic bacteria synthesize intracellular magnetosomes that impart a cellular swimming behaviour referred to as magnetotaxis. The magnetic structures aligned in chains are postulated to function as biological compass needles allowing the bacterium to migrate along redox gradients through the Earth's geomagnetic field lines. Despite the discovery of this unique group of microorganisms 28 years ago, the mechanisms of magnetic crystal biomineralization have yet to be fully elucidated. This review describes the current knowledge of the genes and proteins involved in magnetite formation in magnetic bacteria and the biotechnological applications of biomagnetites in the interdisciplinary fields of nanobiotechnology, medicine and environmental management.

Investigation of antarctic crust and upper mantle using MAGSAT and other geophysical data. M.S. Thesis. Final Report, Sep. 1979 - Aug. 1983

NASA Technical Reports Server (NTRS)

Bentley, C. R.; Ritzwoller, M. H.

1983-01-01

Data selection and reduction procedures are described by which scalar and vector magnetic anomaly maps are constructed. The scalar and vertical magnetic anomalies are believed to be generated mainly in the Earth's crust. The horizontal anomalies are believed to be mainly due to short-period field-aligned currents. The correlation of scalar magnetic anomalies with known oceanic structure is remarkable -- magnetic highs are associated with oceanic ridges and magnetic lows with abyssal plains. The correlation between anomalies and continental geology is not so clear.

Energetic ion observations in the magnetic cloud of 14-15 January 1988 and their implications for the magnetic field topology

NASA Technical Reports Server (NTRS)

Richardson, I. G.; Farrugia, C. J.; Burlaga, L. F.

1991-01-01

On 14-15 January 1988, a magnetic cloud with a local field topology consistent with an east-west aligned cylindrical flux-rope and which formed the driver of an interplanetary shock passed the earth. Using 0.5-4 MeV/n ion data from the instrument on IMP 8, the paper addresses the question of whether or not magnetic field lines within the magnetic cloud were connected to the sun. An impulsive solar particle event was detected inside the magnetic cloud strongly suggesting that the field lines were rooted at the sun.

Magnetic domain pattern in hierarchically twinned epitaxial Ni-Mn-Ga films.

PubMed

Diestel, Anett; Neu, Volker; Backen, Anja; Schultz, Ludwig; Fähler, Sebastian

2013-07-03

Magnetic shape memory alloys exhibit a hierarchically twinned microstructure, which has been examined thoroughly in epitaxial Ni-Mn-Ga films. Here we analyze the consequences of this 'twin within twins' microstructure on the magnetic domain pattern. Atomic and magnetic force microscopy are used to probe the correlation between the martensitic microstructure and magnetic domains. We examine the consequences of different twin boundary orientations with respect to the substrate normal as well as variant boundaries between differently aligned twinned laminates. A detailed micromagnetic analysis is given which describes the influence of the finite film thickness on the formation of magnetic band domains in these multiferroic materials.

Role of dipolar interactions on morphologies and tunnel magnetoresistance in assemblies of magnetic nanoparticles

NASA Astrophysics Data System (ADS)

Anand, Manish; Carrey, Julian; Banerjee, Varsha

2018-05-01

We undertake comprehensive simulations of 2d arrays (Lx ×Ly) of magnetic nanoparticles (MNPs) with dipole-dipole interactions by solving LLG equations. Our primary interest is to understand the correspondence between equilibrium spin (ES) morphologies and tunnel magnetoresistance (TMR) as a function of Θ - the ratio of the dipolar to the anisotropy strength, sample size Lx , aspect ratio Ar =Ly /Lx and the direction of the applied field H → = HêH . The parameter Θ is varied by choosing three distinct particles: (i) α -Fe2O3 (Θ ≃ 0) , (ii) Co (Θ ≃ 0.37) and (iii) Fe3O4 (Θ ≃ 1.28) . Our main observations are as follows: (a) For weakly interacting spins (Θ ≃ 0) , the morphology has randomly oriented magnetic moments for all sample sizes and aspect ratios. The TMR exhibits a peak value of 50% at the coercive field Hc . It is robust with respect to Lx and Ar , and isotropic with respect to êH . (b) For strong interactions (Θ > 1) , the moments order in the plane of the sample. The ES morphology comprises of magnetically aligned regions interspersed with flux closure loops. For fields along x or y, the maximum TMR amplitude decrease to ∼30%. For êH = z ̂ , it drops to ∼3%. The TMR is robust with respect to Lx and Ar and isotropic in the x and y directions only. (c) In strongly interacting samples (Θ > 1) with Lx comparable to the size of a flux closure loop, increasing Ar creates ferromagnetic chains in the sample oriented along y or - y . Consequently, for êH = y ̂ , the TMR magnitude for Ar = 1 is ∼33% while that for Ar = 32 drops to ∼16%. For êH = x ̂ on the other hand, it is ∼30% and independent of Ar . The TMR of long ribbons of MNPs has a strong dependence on Ar and is anisotropic in all three directions.

Thermal Conductivity of Polyimide/Carbon Nanofiller Blends

NASA Technical Reports Server (NTRS)

Ghose, S.; Watson, K. A.; Delozier, D. M.; Working, D. C.; Connell, J. W.; Smith, J. G.; Sun, Y. P.; Lin, Y.

2007-01-01

In efforts to improve the thermal conductivity (TC) of Ultem(TM) 1000, it was compounded with three carbon based nano-fillers. Multiwalled carbon nanotubes (MWCNT), vapor grown carbon nanofibers (CNF) and expanded graphite (EG) were investigated. Ribbons were extruded to form samples in which the nano-fillers were aligned. Samples were also fabricated by compression molding in which the nano-fillers were randomly oriented. The thermal properties were evaluated by DSC and TGA, and the mechanical properties of the aligned samples were determined by tensile testing. The degree of dispersion and alignment of the nanoparticles were investigated with high-resolution scanning electron microscopy. The thermal conductivity of the samples was measured in both the direction of alignment as well as perpendicular to that direction using the Nanoflash technique. The results of this study will be presented.

Thermal Conductivity of Polyimide/Nanofiller Blends

NASA Technical Reports Server (NTRS)

Ghose, S.; Watson, K. A.; Delozier, D. M.; Working, D. c.; Connell, J. W.; Smith, J. G.; Sun, Y. P.; Lin, Y.

2006-01-01

In efforts to improve the thermal conductivity of Ultem(TM) 1000, it was compounded with three carbon based nano-fillers. Multiwalled carbon nanotubes (MWCNT), vapor grown carbon nanofibers (CNF) and expanded graphite (EG) were investigated. Ribbons were extruded to form samples in which the nano-fillers were aligned. Samples were also fabricated by compression molding in which the nano-fillers were randomly oriented. The thermal properties were evaluated by DSC and TGA, and the mechanical properties of the aligned samples were determined by tensile testing. The degree of dispersion and alignment of the nanoparticles were investigated with high-resolution scanning electron microscopy. The thermal conductivity of the samples was measured in both the direction of alignment as well as perpendicular to that direction using the Nanoflash technique. The results of this study will be presented.

Paleomagnetic and oxygen isotopic evidence for long term diagenesis in radiolarian chert, Pindos Mountains, Greece

NASA Astrophysics Data System (ADS)

Baltuck, Miriam

1987-02-01

Paleomagnetics was used in an attempt to improve chronostratigraphy in the Middle and Upper Jurassic radiolarian chert and siliceous mudstone of the Pindos Zone, Greece. Remanent magnetism studies showed strong magnetic intensity but scattered orientation. Orientation of some pressure solution features in the radiolarities indicates their formation under horizontal pressure, a condition which in Pindos geologic history would only have occurred during early Cretaceous or Cenozoic tectonics, indicating very late diagenesis in these parts of the section. From time of deposition to later time at which diagenesis can be documented, the Earth's magnetic field would have reversed many times. Remagnetization during solution-precipitation steps of silica diagenesis could complicate the rock magnetics. Oxygen isotopic and major element analyses of radiolarite lithologies show a systematic variation of rate of silica diagenesis in different host lithologies, thus solution-precipitation would occur at widely differing times throughout the section lithologies. If the dissolution of the silica cement were physically to free magnetic material from an earlier orientation, the result could be a partial shift toward alignment with the ambient magnetic field. Alternatively, complete reorientation of particles could have occurred at varying times in different parts of the section as a function of host lithology. During the northward movement and clockwise rotation of the Apulian subplate (including Pindos) these different lithologies could completely reorient during different stages of silica diagenesis, locking the orientation of iron magnetic moments into alignment with the ambient magnetic field at time of precipitation to result in a strong intensity but scattered orientation of Pindos rock magnetics.

Alignment of a vector magnetometer to an optical prism.

PubMed

Dietrich, M R; Bailey, K G; O'Connor, T P

2017-05-01

A method for alignment of a vector magnetometer to a rigidly attached prism is presented. This enables optical comparison of the magnetometer axes to physical surfaces in the apparatus, and thus an absolute determination of the magnetic field direction in space. This is in contrast with more common techniques, which focus on precise determination of the relative angles between magnetometer axes, and so are more suited to measuring differences in the direction of magnetic fields. Here we demonstrate precision better than 500 μrad on a fluxgate magnetometer, which also gives the coil orthogonality errors to a similar precision. The relative sensitivity of the three axes is also determined, with a precision of about 5 × 10 -4 .

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsuura, Yukihito, E-mail: matsuura@chem.nara-k.ac.jp

The tunneling magnetoresistance (TMR) of a silicon chain sandwiched between nickel electrodes was examined by using first-principles density functional theory. The relative orientation of the magnetization in a parallel-alignment (PA) configuration of two nickel electrodes enhanced the current with a bias less than 0.4 V compared with that in an antiparallel-alignment configuration. Consequently, the silicon chain-nickel electrodes yielded good TMR characteristics. In addition, there was polarized spin current in the PA configuration. The spin polarization of sulfur atoms functioning as a linking bridge between the chain and nickel electrode played an important role in the magnetic effects of the electric current.more » Moreover, the hybridization of the sulfur 3p orbital and σ-conjugated silicon 3p orbital contributed to increasing the total current.« less

Properties and behaviour of FAC currents in the inner magnetosphere

NASA Astrophysics Data System (ADS)

Yang, Junying; Dunlop, Malcolm; Yang, Yanyan; Xiong, Chao; Lühr, Hermann; Cao, Jinbin; Li, Liuyuan; Ma, Yuduan; Shen, Chao

2017-04-01

Cusp, region 1 and 2, and other large scale field-aligned currents (FACs), are sampled in situ by both the four Cluster spacecraft and by the three Swarm spacecraft at different altitudes, separated by a few to several Earth radii, and sometimes simultaneously. Here, the capability of Swarm-Cluster coordination for probing the behaviour of the field aligned currents (FACs) at medium and low orbits is explored. Joint signatures of R1 and R2 FACs (as well as cusp, R0 and NBZ currents) can be found and compared in terms of the magnetic signatures, using multi-spacecraft analysis where possible. Using the Swarm configuration, statistical correlation analysis of the local time variation of R1/R2 FACs can be shown and compared to standard MVA analysis. For context, we identify the associated auroral boundaries through application of a method to determine the FAC intensity gradients in order to interpret and resolve the R1 and R2 FACs. We also explore the relation of R2 FACs to the ring current properties measured in situ.

Rigid-body motion correction of the liver in image reconstruction for golden-angle stack-of-stars DCE MRI.

PubMed

Johansson, Adam; Balter, James; Cao, Yue

2018-03-01

Respiratory motion can affect pharmacokinetic perfusion parameters quantified from liver dynamic contrast-enhanced MRI. Image registration can be used to align dynamic images after reconstruction. However, intra-image motion blur remains after alignment and can alter the shape of contrast-agent uptake curves. We introduce a method to correct for inter- and intra-image motion during image reconstruction. Sixteen liver dynamic contrast-enhanced MRI examinations of nine subjects were performed using a golden-angle stack-of-stars sequence. For each examination, an image time series with high temporal resolution but severe streak artifacts was reconstructed. Images were aligned using region-limited rigid image registration within a region of interest covering the liver. The transformations resulting from alignment were used to correct raw data for motion by modulating and rotating acquired lines in k-space. The corrected data were then reconstructed using view sharing. Portal-venous input functions extracted from motion-corrected images had significantly greater peak signal enhancements (mean increase: 16%, t-test, P <  0.001) than those from images aligned using image registration after reconstruction. In addition, portal-venous perfusion maps estimated from motion-corrected images showed fewer artifacts close to the edge of the liver. Motion-corrected image reconstruction restores uptake curves distorted by motion. Motion correction also reduces motion artifacts in estimated perfusion parameter maps. Magn Reson Med 79:1345-1353, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

High-Altitude Closed Magnetic Loops at Mars Observed by MAVEN

NASA Astrophysics Data System (ADS)

Xu, Shaosui; Mitchell, David; Luhmann, Janet; Ma, Yingjuan; Fang, Xiaohua; Harada, Yuki; Hara, Takuya; Brain, David; Weber, Tristan; Mazelle, Christian; DiBraccio, Gina A.

2017-11-01

With electron and magnetic field data obtained by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we have identified closed magnetic field lines, with both foot points embedded in the dayside ionosphere, extending up to 6,200 km altitude into the Martian tail. This topology is deduced from photoelectrons produced in the dayside ionosphere being observed traveling both parallel and antiparallel to the magnetic field. At trapped-zone pitch angles (within a range centered on 90° where electrons magnetically reflect before interacting with the atmosphere), cases with either solar wind electrons or photoelectrons have been found, indicating different formation mechanisms for these closed loops. These large closed loops are present in MHD simulations. The case with field-aligned photoelectrons mixed with solar wind electrons having trapped-zone pitch angles is likely to be associated with reconnection, while the case with photoelectrons at all pitch angles is probably due to closed field lines being pulled tailward by the surrounding plasma flow. By utilizing an algorithm for distinguishing photoelectrons from solar wind electrons in pitch angle-resolved energy spectra, we systematically map the spatial distribution and occurrence rate of these closed magnetic loops over the region sampled by the MAVEN orbit. We find that the occurrence rate ranges from a few percent to a few tens of percent outside of the optical shadow and less than one percent within the shadow. These observations can be used to investigate the general magnetic topology in the tail, which is relevant to cold ion escape, reconnection, and flux ropes.

Exchange bias effect in L10-ordered FePt and FeCo-based bilayer structure: effect of increasing applied field

NASA Astrophysics Data System (ADS)

Singh, Sadhana; Kumar, Dileep; Bhagat, Babli; Choudhary, R. J.; Reddy, V. R.; Gupta, Ajay

2018-02-01

The applied magnetic field (H APP) dependence of the exchange bias (EB) is studied in an exchange-coupled thin-film bilayer composed of a hard ferromagnetic FePt layer in the proximity of a soft ferromagnetic FeCo layer. FePt/FeCo structure is deposited in an ultra-high vacuum chamber, where the FePt layer was first annealed at 823 K for 30 min and subsequently cooled to room temperature in the presence of an in-plane magnetic field, H MAX ~ 1.5 kOe to promote L10-ordered hard magnetic phase with magnetic moments aligned in one of the in-plane directions in the FePt layer. In-situ magneto-optical Kerr effect measurements during different stages of bilayer growth and detailed ex-situ superconducting quantum interference device-vibrating sample magnetometer measurements jointly revealed that due to the interplay between exchange coupling at the interface and dipolar energies of the saturated hard FePt layer, a hysteresis loop of FeCo layer shifts along the magnetic field axis. A clear dependence of EB field (H EB) on increasing maximum value of the H APP during the hysteresis loop measurement is understood in terms of the magnetic state of soft and hard magnetic layers, where EB increases with increasing H APP until the hard layer moment remains undisturbed in its remanence state. As soon as the field was sufficient to rotate the spins of the FePt layer, the loop became symmetric with respect to the field axis.

Understating Polarization in the Interstellar Medium Through the Theory of Radiative Torque Alignment

NASA Astrophysics Data System (ADS)

Caputo, Miranda; Andersson, B.-G.; Kulas, Kristin Rose

2018-06-01

Although it is known that the dust grains in the ISM align with magnetic fields, the alignment physics of these particles is still somewhat unclear. Utilizing direct observational data and Radiative Alignment Torque (RAT) theory, further constraints can be put onto this alignment. Due to the physics of this alignment, there is a linear relationship between the extinction of the light seen through a dust cloud (AV) and the wavelength of maximum polarization. A previous study, focusing on the Taurus cloud, found that there is a second, steeper relationship seen beyond an extinction of about four magnitudes, likely due to grain growth, in addition to the original linear relationship. We present early results from observations of low-to-medium extinction lines of sight in the starless cloud L183 (aka L134N), aimed at testing the Taurus results. We are currently extending the survey of stars behind L183 to higher extinctions to better probe the origins of the bifurcation seen in the Taurus results.

The Consequences of Alfven Waves and Parallel Potential Drops in the Auroral Zone

NASA Technical Reports Server (NTRS)

Schriver, David

2003-01-01

The goal of this research is to examine the causes of field-aligned plasma acceleration in the auroral zone using satellite data and numerical simulations. A primary question to be addressed is what causes the field-aligned acceleration of electrons (leading to precipitation) and ions (leading to upwelling ions) in the auroral zone. Data from the Fast Auroral SnapshoT (FAST) and Polar satellites is used when the two satellites are in approximate magnetic conjunction and are in the auroral region. FAST is at relatively low altitudes and samples plasma in the midst of the auroral acceleration region while Polar is at much higher altitudes and can measure plasmas and waves propagating towards the Earth. Polar can determine the sources of energy streaming earthward from the magnetotail, either in the form of field-aligned currents, electromagnetic waves or kinetic particle energy, that ultimately leads to the acceleration of plasma in the auroral zone. After identifying and examining several events, numerical simulations are run that bridges the spatial region between the two satellites. The code is a one-dimensional, long system length particle in cell simulation that has been developed to model the auroral region. A main goal of this research project is to include Alfven waves in the simulation to examine how these waves can accelerate plasma in the auroral zone.

Field-aligned current associated with a distorted two-cell convection pattern during northward interplanetary magnetic field

NASA Technical Reports Server (NTRS)

Zhu, L.; Schunk, R. W.; Sojka, J. J.

1991-01-01

The influence of the ionospheric conductance on the field-aligned current associated with a distorted two-cell convection pattern during northward IMF was investigated using the Heppner-Maynard (1987) convection model and the Utah State University conductivity model described by Rasmussen and Schunk (1987). Results show that the variation of the ionospheric conductivity distribution can significantly affect the features of the field-aligned current for northward IMF, where matching or mismatching between the conductance gradient and the convection electric field plays a key role. It was found that the increase of the field-aligned current in the polar cap observed during summer is mainly due to the increasing contribution from the Pedersen current, and that the increase of the field-aligned current in both the oval region and the evening-midnight sector during the active aurora period is mainly due to the increasing contribution from the Hall current.

Multi-subject Manifold Alignment of Functional Network Structures via Joint Diagonalization.

PubMed

Nenning, Karl-Heinz; Kollndorfer, Kathrin; Schöpf, Veronika; Prayer, Daniela; Langs, Georg

2015-01-01

Functional magnetic resonance imaging group studies rely on the ability to establish correspondence across individuals. This enables location specific comparison of functional brain characteristics. Registration is often based on morphology and does not take variability of functional localization into account. This can lead to a loss of specificity, or confounds when studying diseases. In this paper we propose multi-subject functional registration by manifold alignment via coupled joint diagonalization. The functional network structure of each subject is encoded in a diffusion map, where functional relationships are decoupled from spatial position. Two-step manifold alignment estimates initial correspondences between functionally equivalent regions. Then, coupled joint diagonalization establishes common eigenbases across all individuals, and refines the functional correspondences. We evaluate our approach on fMRI data acquired during a language paradigm. Experiments demonstrate the benefits in matching accuracy achieved by coupled joint diagonalization compared to previously proposed functional alignment approaches, or alignment based on structural correspondences.

Characterization of the IMF By-dependent field-aligned currents in the cleft region based on DE 2 observations

NASA Technical Reports Server (NTRS)

Taguchi, S.; Sugiura, M.; Winningham, J. D.; Slavin, J. A.

1993-01-01

The magnetic field and plasma data from 47 passes of DE-2 are used to study the IMF By-dependent distribution of field-aligned currents in the cleft region. It is proposed that the low-latitude cleft current (LCC) region is not an extension of the region 1 or region 2 current system and that a pair of LCCs and high-latitude cleft currents (HCCs) constitutes the cleft field-aligned current regime. The proposed pair of cleft field-aligned currents is explained with a qualitative model in which this pair of currents is generated on open field lines that have just been reconnected on the dayside magnetopause. The electric fields are transmitted along the field lines to the ionosphere, creating a poleward electric field and a pair of field-aligned currents when By is positive; the pair of field-aligned currents consists of a downward current at lower latitudes and an upward current at higher latitudes. In the By negative case, the model explains the reversal of the field-aligned current direction in the LCC and HCC regions.

r-Process nucleosynthesis from three-dimensional jet-driven core-collapse supernovae with magnetic misalignments

NASA Astrophysics Data System (ADS)

Halevi, Goni; Mösta, Philipp

2018-06-01

We investigate r-process nucleosynthesis in three-dimensional general relativistic magnetohydrodynamic simulations of jet-driven supernovae resulting from rapidly rotating, strongly magnetized core-collapse. We explore the effect of misaligning the pre-collapse magnetic field with respect to the rotation axis by performing four simulations: one aligned model and models with 15°, 30°, and 45° misalignments. The simulations we present employ a microphysical finite-temperature equation of state and a leakage scheme that captures the overall energetics and lepton number exchange due to post-bounce neutrino emission and absorption. We track the thermodynamic properties of the ejected material with Lagrangian tracer particles and analyse its composition with the nuclear reaction network SKYNET. By using different neutrino luminosities in post-processing the tracer data with SKYNET, we constrain the impact of uncertainties in neutrino luminosities. We find that, for the aligned model considered here, the use of an approximate leakage scheme results in neutrino luminosity uncertainties corresponding to a factor of 100-1000 uncertainty in the abundance of third peak r-process elements. Our results show that for misalignments of 30° or less, r-process elements are robustly produced as long as neutrino luminosities are reasonably low (≲ 5 × 1052 erg s-1). For a more extreme misalignment of 45°, we find the production of r-process elements beyond the second peak significantly reduced. We conclude that robust r-process nucleosynthesis in magnetorotational supernovae requires a progenitor stellar core with a large poloidal magnetic field component that is at least moderately (within ˜30°) aligned with the rotation axis.

ON THE MISALIGNMENT BETWEEN CHROMOSPHERIC FEATURES AND THE MAGNETIC FIELD ON THE SUN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martínez-Sykora, Juan; Pontieu, Bart De; Hansteen, Viggo

2016-11-01

Observations of the upper chromosphere show an enormous amount of intricate fine structure. Much of this comes in the form of linear features, which are most often assumed to be well aligned with the direction of the magnetic field in the low plasma β regime that is thought to dominate the upper chromosphere. We use advanced radiative magnetohydrodynamic simulations, including the effects of ion-neutral interactions (using the generalized Ohm’s law) in the partially ionized chromosphere, to show that the magnetic field is often not well aligned with chromospheric features. This occurs where the ambipolar diffusion is large, i.e., ions andmore » neutral populations decouple as the ion-neutral collision frequency drops, allowing the field to slip through the neutral population; where currents perpendicular to the field are strong; and where thermodynamic timescales are longer than or similar to those of ambipolar diffusion. We find this often happens in dynamic spicule or fibril-like features at the top of the chromosphere. This has important consequences for field extrapolation methods, which increasingly use such upper chromospheric features to help constrain the chromospheric magnetic field: our results invalidate the underlying assumption that these features are aligned with the field. In addition, our results cast doubt on results from 1D hydrodynamic models, which assume that plasma remains on the same field lines. Finally, our simulations show that ambipolar diffusion significantly alters the amount of free energy available in the coronal part of our simulated volume, which is likely to have consequences for studies of flare initiation.« less

Micropole undulator

DOEpatents

Tatchyn, R.O.; Csonka, P.L.; Cremer, J.T.

1990-12-11

Micropole undulators for use in the generation of x-rays from moving charged particles are disclosed. Two rows of spaced apart poles are arranged so that each pole produces a magnetic field aligned with all other similar fields. The poles are the ends of C''-shaped magnets. In each row, adjacent poles are separated by spacers made of a superconducting material. 11 figs.

Inertial Currents in Isotropic Plasma

NASA Technical Reports Server (NTRS)

Heinemann, M.; Erickson, G. M.; Pontius, D. H., Jr.

1993-01-01

The magnetospheric convection electric field contributes to Birkeland currents. The effects of the field are to polarize the plasma by displacing the bounce paths of the ions from those of electrons, to redistribute the pressure so that it is not constant along magnetic field lines, and to enhance the pressure gradient by the gradient of the bulk speed. Changes in the polarization charge during the convection of the plasma are neutralized by electrons in the form of field-aligned currents that close through the ionosphere. The pressure drives field-aligned currents through its gradient in the same manner as in quasi-static plasma, but with modifications that are important if the bulk speed is of the order of the ion thermal speed; the variations in the pressure along field lines are maintained by a weak parallel potential drop. These effects are described in terms of the field-aligned currents in steady state, isotropic, MED plasma. Solutions are developed by taking the MHD limit of two-fluid solutions and illustrated in the special case of Maxwellian plasma for which the temperature is constant along magnetic field lines. The expression for the Birkeland current density is a generalization of Vasyliunas' expression for the field-aligned current density in quasi-static plasma and provides a unifying expression when both pressure gradients and ion inertia operate simultaneously as sources of field-aligned currents. It contains a full account of different aspects of the ion flow (parallel and perpendicular velocity and vorticity) that contribute to the currents. Contributions of ion inertia to field-aligned currents will occur in regions of strong velocity shear, electric field reversal, or large gradients in the parallel velocity or number density, and may be important in the low-latitude boundary layer, plasma sheet boundary layer, and the inner edge region of the plasma sheet.

Inertial currents in isotropic plasma

NASA Technical Reports Server (NTRS)

Heinemann, M.; Erickson, G. M.; Pontius, D. H. JR.

1994-01-01

The magnetospheric convection electric field contributes to Birkeland currents. The effects of the field are to polarize the plasma by displacing the bounce paths of the ions from those of electrons, to redistribute the pressure so that it is not constant along magnetic field lines, and to enhance the pressure gradient by the gradient of the bulk speed. Changes in the polarization charge during the convection of the plasma are neutralized by electrons in the form of field-aligned currents that close through the ionosphere. The pressure drives field-aligned currents through its gradient in the same manner as in quasi-static plasma, but with modifications that are important if the bulk speed is of the order of the ion thermal speed; the variations in the pressure along field lines are maintained by a weak parallel potential drop. These effects are described in terms of the field-aligned currents in steady state, isotropic, magnetohyrodynamic (MHD) plasma. Solutions are developed by taking the MHD limit of two-fluid solutions and illustrated in the special case of Maxwellian plasma for which the temperature is constant along magnetic field lines. The expression for the Birkeland current density is a generalization of Vasyliunas' expression for the field-aligned current density in quasi-static plasma and provides a unifying expression when both pressure gradients and ion inertia operate simultaneously as sources of field-aligned currents. It contains a full account of different aspects of the ion flow (parallel and perpendicular velocity and vorticity) that contribute to the currents. Contributions of ion inertia to field-aligned currents will occur in regions of strong velocity shear, electric field reversal, or large gradients in the parallel velocity or number density, and may be important in the low-latitude boundary layer, plasma sheet boundary layer, and the inner edge region of the plasma sheet.

Inertial currents in isotropic plasma

NASA Technical Reports Server (NTRS)

Heinemann, M.; Erickson, G. M.; Pontius, D. H., Jr.

1994-01-01

The magnetospheric convection electric field contributes to Birkeland currents. The effects of the field are to polarize the plasma by displacing the bounce paths of the ions from those of electrons, to redistribute the pressure so that it is not constant along magnetic field lines, and to enhance the pressure gradient by the gradient of the bulk speed. Changes in the polarization charge during the convection of the plasma are neutralized by electrons in the form of field-aligned currents that close through the ionosphere. The pressure drives field-aligned currents through its gradient in the same manner as in quasi-static plasmas, but with modifications that are important if the bulk speed is of the order of the ion thermal speed; the variations in the pressure along field lines are maintained by a weak parallel potential drop. These effects are described in terms of the field-aligned currents in steady state, isotropic, MHD plasma. Solutions are developed by taking the MHD limit ot two-fluid solutions and illustrated in the special case of Maxwellian plasma for which the temperature is constant along magnetic field lines. The expression for the Birkeland current density is a generalization of Vasyliunas' expression for the field-aligned current density in quasi-static plasma and provides a unifying expression when both pressure gradients and ion inertia operate simultaneously as sources of field-aligned currents. It contains a full account of different aspects of the ion flow (parallel and perpendicular velocity and vorticity) that contribute to the currents. Contributions of ion inertia to field-aligned currents will occur in regions of strong velocity shear, electric field reversal, or large gradients in the parallel velocity or number density, and may be important in the low-latitude boundary layer, plasma sheet boundary layer, and the inner edge region of the plasma sheet.

Magnetic biosensor using a high transition temperature SQUID

NASA Astrophysics Data System (ADS)

Grossman, Helene Lila

A high transition temperature (Tc) Superconducting QUantum Interference Device (SQUID) is used to detect magnetically-labeled microorganisms. The targets are identified and quantified by means of magnetic relaxation measurements, with no need for unbound magnetic labels to be washed away. The binding rate between antibody-linked magnetic particles and targets can be measured with this technique. Installed in a "SQUID microscope," a YBa2Cu 3O7-delta SQUID is mounted on a sapphire rod thermally linked to a liquid nitrogen can; these components are enclosed in a fiberglass vacuum chamber. A thin window separates the vacuum chamber from the sample, which is at room temperature and atmospheric pressure. In one mode of the experiment, targets are immobilized on a substrate and immersed a suspension of ˜50 nm diameter superparamagnetic particles, coated with antibodies. A pulsed magnetic field aligns the magnetic dipole moments, and the SQUID measures the magnetic relaxation signal each time the field is turned off. Unbound particles relax within ˜50 mus by Brownian rotation, too fast for the SQUID system to measure. In contrast, particles bound to targets have their Brownian motion inhibited. These particles relax in ˜1 s by rotation of the internal dipole moment, and this Neel relaxation process is detected by the SQUID. This assay is demonstrated with a model system of liposomes carrying the FLAG epitope; the detection limit is (2.7 +/- 0.2) x 105 particles. The replacement of the SQUID with a gradiometer improves the detection limit to (7.0 +/- 0.7) x 103 particles. In an alternate mode of the experiment, freely suspended targets (larger than ˜1 mum diameter) are detected. Since the Brownian relaxation time of the targets is longer than the measurement time, particles bound to targets are effectively immobilized and exhibit Neel relaxation. Listeria monocytogenes are detected using this method; the sensitivity is (1.1 +/- 0.2) x 105 bacteria in 20 muL. For a 1 nL sample volume, the detection limit is expected to be 230 +/- 40 bacteria. Time-resolved measurements, which yield the binding rate between particles and bacteria, are reported. Also, potential improvements to the system and possible applications are discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

RAKOWKSY,G.; ASPENLEITER,J.; SOLOMON,L.

The Visible-Infrared SASE Amplifier (VISA) undulator is an in-vacuum, 4-meter long, 1.8 cm period, pure-permanent magnet device, with a novel, strong focusing, permanent magnet FODO array included within the fixed, 6 mm undulator gap. The undulator magnet is constructed of 99-cm long segments, joined into a continuous structure. To attain maximum SASE gain requites establishing overlap of electron and photon beams to within 50 microns rms. This imposes challenging tolerances on mechanical fabrication and magnetic field quality, and necessitates use of laser straightness interferometry for calibration and alignment of the magnetic axes of the undulator segments. This paper describes themore » computerized magnet sorting, pulsed-wire magnetic measurements, trajectory shimming and magnetic axis calibration performed to meet this goal.« less

Wave propagation characteristics of a magnetic granular chain

NASA Astrophysics Data System (ADS)

Leng, Dingxin; Liu, Guijie; Sun, Lingyu; Wang, Xiaojie

2017-10-01

We investigate the wave propagation characteristics of a horizontal alignment of magnetic grains under a non-uniform magnetic field. The magnetic force of each grain is obtained using Maxwell's principle. The contact interaction of grains is based on Hertz potential. The effects of magnetic field strength on the dynamic responses of a granular chain under strong, intermediate, and weak amplitudes of incident impulses in comparison with static precompression force are studied. Different wave propagation modes induced by the magnetic field are observed. The applied field strength demonstrably reinforces the granular-position-dependent behaviors of decreasing amplitude and increasing wave propagation velocity. The magnetic field-induced features of a magnetic granular chain have potential applications in adaptive structures for shock attenuation.

Elastic moduli of the distorted Kagome-lattice ferromagnet Nd3Ru4Al12

NASA Astrophysics Data System (ADS)

Suzuki, Takashi; Mizuno, Takuyou; Takezawa, Kohki; Kamikawa, Shuhei; Andreev, Alexander V.; Gorbunov, Denis I.; Henriques, Margarida S.; Ishii, Isao

2018-05-01

The distorted kagome-lattice compound Nd3Ru4Al12 has the hexagonal structure. This compound is reported as a ferromagnet in which spins are aligned along the c-axis with the Curie temperature TC = 39 K . The nature of localized f-electrons is expected in Nd3Ru4Al12, and magnetic anisotropy can be attributed to a crystal electric field (CEF) effect. We performed ultrasonic measurements on a Nd3Ru4Al12 single-crystalline sample in order to investigate the phase transition at TC and the CEF effect. All longitudinal and transverse elastic moduli increase monotonically with decreasing temperature, and no clear elastic softening due to a quadrupole interaction is detected under the hexagonal CEF. This result is in contrast to an isomorphic compound Dy3Ru4Al12 with a remarkable elastic softening of the transverse modulus C44. At the ferromagnetic phase transition, the moduli show obvious elastic anomalies, suggesting characteristic couplings between a strain and a magnetic order parameter.

A High-resolution Model of Field-aligned Currents Through Empirical Orthogonal Functions Analysis (MFACE)

NASA Technical Reports Server (NTRS)

He, Maosheng; Vogt, Joachim; Luehr, Hermann; Sorbalo, Eugen; Blagau, Adrian; Le, Guan; Lu, Gang

2012-01-01

Ten years of CHAMP magnetic field measurements are integrated into MFACE, a model of field-aligned currents (FACs) using empirical orthogonal functions (EOFs). EOF1 gives the basic Region-1/Region-2 pattern varying mainly with the interplanetary magnetic field Bz component. EOF2 captures separately the cusp current signature and By-related variability. Compared to existing models, MFACE yields significantly better spatial resolution, reproduces typically observed FAC thickness and intensity, improves on the magnetic local time (MLT) distribution, and gives the seasonal dependence of FAC latitudes and the NBZ current signature. MFACE further reveals systematic dependences on By, including 1) Region-1/Region-2 topology modifications around noon; 2) imbalance between upward and downward maximum current density; 3) MLT location of the Harang discontinuity. Furthermore, our procedure allows quantifying response times of FACs to solar wind driving at the bow shock nose: we obtain 20 minutes and 35-40 minutes lags for the FAC density and latitude, respectively.

Penetration of the Interplanetary Magnetic Field B(sub y) into Earth's Plasma Sheet

NASA Technical Reports Server (NTRS)

Hau, L.-N.; Erickson, G. M.

1995-01-01

There has been considerable recent interest in the relationship between the cross-tail magnetic field component B(sub y) and tail dynamics. The purpose of this paper is to give an overall description of the penetration of the interplanetary magnetic field (IMF) B(sub y) into the near-Earth plasma sheet. We show that plasma sheet B(sub y) may be generated by the differential shear motion of field lines and enhanced by flux tube compression. The latter mechanism leads to a B(sub y) analogue of the pressure-balance inconsistency as flux tubes move from the far tail toward the Earth. The growth of B(sub y), however, may be limited by the dawn-dusk asymmetry in the shear velocity as a result of plasma sheet tilting. B(sub y) penetration into the plasma sheet implies field-aligned currents flowing between hemispheres. These currents together with the IMF B(sub y) related mantle field-aligned currents effectively shield the lobe from the IMF B(sub y).

Magnetic preferential orientation of metal oxide superconducting materials

DOEpatents

Capone, D.W.; Dunlap, B.D.; Veal, B.W.

1990-07-17

A superconductor comprised of a polycrystalline metal oxide such as YBa[sub 2]Cu[sub 3]O[sub 7[minus]X] (where 0 < X < 0.5) exhibits superconducting properties and is capable of conducting very large current densities. By aligning the two-dimensional Cu-O layers which carry the current in the superconducting state in the a- and b-directions, i.e., within the basal plane, a high degree of crystalline axes alignment is provided between adjacent grains permitting the conduction of high current densities. The highly anisotropic diamagnetic susceptibility of the polycrystalline metal oxide material permits the use of an applied magnetic field to orient the individual crystals when in the superconducting state to substantially increase current transport between adjacent grains. In another embodiment, the anisotropic paramagnetic susceptibility of rare-earth ions substituted into the oxide material is made use of as an applied magnetic field orients the particles in a preferential direction. This latter operation can be performed with the material in the normal (non-superconducting) state. 4 figs.

Magnetic preferential orientation of metal oxide superconducting materials

DOEpatents

Capone, Donald W.; Dunlap, Bobby D.; Veal, Boyd W.

1990-01-01

A superconductor comprised of a polycrystalline metal oxide such as YBa.sub.2 Cu.sub.3 O.sub.7-X (where 0

Observations of a field-aligned ion/ion-beam instability in a magnetized laboratory plasma

NASA Astrophysics Data System (ADS)

Heuer, P. V.; Weidl, M. S.; Dorst, R. S.; Schaeffer, D. B.; Bondarenko, A. S.; Tripathi, S. K. P.; Van Compernolle, B.; Vincena, S.; Constantin, C. G.; Niemann, C.; Winske, D.

2018-03-01

Collisionless coupling between super Alfvénic ions and an ambient plasma parallel to a background magnetic field is mediated by a set of electromagnetic ion/ion-beam instabilities including the resonant right hand instability (RHI). To study this coupling and its role in parallel shock formation, a new experimental configuration at the University of California, Los Angeles utilizes high-energy and high-repetition-rate lasers to create a super-Alfvénic field-aligned debris plasma within an ambient plasma in the Large Plasma Device. We used a time-resolved fluorescence monochromator and an array of Langmuir probes to characterize the laser plasma velocity distribution and density. The debris ions were observed to be sufficiently super-Alfvénic and dense to excite the RHI. Measurements with magnetic flux probes exhibited a right-hand circularly polarized frequency chirp consistent with the excitation of the RHI near the laser target. We compared measurements to 2D hybrid simulations of the experiment.

Observations of a field-aligned ion/ion-beam instability in a magnetized laboratory plasma

DOE PAGES

Heuer, P. V.; Weidl, M. S.; Dorst, R. S.; ...

2018-03-01

Collisionless coupling between super Alfvénic ions and an ambient plasma parallel to a background magnetic field is mediated by a set of electromagnetic ion/ion-beam instabilities including the resonant right hand instability (RHI). To study this coupling and its role in parallel shock formation, a new experimental configuration at the University of California, Los Angeles utilizes high-energy and high-repetition-rate lasers to create a super-Alfvénic field-aligned debris plasma within an ambient plasma in the Large Plasma Device. We used a time-resolved fluorescence monochromator and an array of Langmuir probes to characterize the laser plasma velocity distribution and density. The debris ions weremore » observed to be sufficiently super-Alfvénic and dense to excite the RHI. Measurements with magnetic flux probes exhibited a right-hand circularly polarized frequency chirp consistent with the excitation of the RHI near the laser target. To conclude, we compared measurements to 2D hybrid simulations of the experiment.« less

An MHD simulation of the effects of the interplanetary magnetic field By component on the interaction of the solar wind with the earth's magnetosphere during southward interplanetary magnetic field

NASA Technical Reports Server (NTRS)

Ogino, T.; Walker, R. J.; Ashour-Abdalla, M.; Dawson, J. M.

1986-01-01

The interaction between the solar wind and the earth's magnetosphere has been studied by using a time-dependent three-dimensional MHD model in which the IMF pointed in several directions between dawnward and southward. When the IMF is dawnward, the dayside cusp and the tail lobes shift toward the morningside in the northern magnetosphere. The plasma sheet rotates toward the north on the dawnside of the tail and toward the south on the duskside. For an increasing southward IMF component, the plasma sheet becomes thinner and subsequently wavy because of patchy or localized tail reconnection. At the same time, the tail field-aligned currents have a filamentary layered structure. When projected onto the northern polar cap, the filamentary field-aligned currents are located in the same area as the region 1 currents, with a pattern similar to that associated with auroral surges. Magnetic reconnection also occurs on the dayside magnetopause for southward IMF.

Observations of a field-aligned ion/ion-beam instability in a magnetized laboratory plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heuer, P. V.; Weidl, M. S.; Dorst, R. S.

Collisionless coupling between super Alfvénic ions and an ambient plasma parallel to a background magnetic field is mediated by a set of electromagnetic ion/ion-beam instabilities including the resonant right hand instability (RHI). To study this coupling and its role in parallel shock formation, a new experimental configuration at the University of California, Los Angeles utilizes high-energy and high-repetition-rate lasers to create a super-Alfvénic field-aligned debris plasma within an ambient plasma in the Large Plasma Device. We used a time-resolved fluorescence monochromator and an array of Langmuir probes to characterize the laser plasma velocity distribution and density. The debris ions weremore » observed to be sufficiently super-Alfvénic and dense to excite the RHI. Measurements with magnetic flux probes exhibited a right-hand circularly polarized frequency chirp consistent with the excitation of the RHI near the laser target. To conclude, we compared measurements to 2D hybrid simulations of the experiment.« less

High levels of maternally transferred mercury disrupt magnetic responses of snapping turtle hatchlings (Chelydra serpentina).

PubMed

Landler, Lukas; Painter, Michael S; Coe, Brittney Hopkins; Youmans, Paul W; Hopkins, William A; Phillips, John B

2017-09-01

The Earth's magnetic field is involved in spatial behaviours ranging from long-distance migration to non-goal directed behaviours, such as spontaneous magnetic alignment (SMA). Mercury is a harmful pollutant most often generated from anthropogenic sources that can bio-accumulate in animal tissue over a lifetime. We compared SMA of hatchling snapping turtles from mothers captured at reference (i.e., low mercury) and mercury contaminated sites. Reference turtles showed radio frequency-dependent SMA along the north-south axis, consistent with previous studies of SMA, while turtles with high levels of maternally inherited mercury failed to show consistent magnetic alignment. In contrast, there was no difference between reference and mercury exposed turtles on standard performance measures. The magnetic field plays an important role in animal orientation behaviour and may also help to integrate spatial information from a variety of sensory modalities. As a consequence, mercury may compromise the performance of turtles in a wide variety of spatial tasks. Future research is needed to determine the threshold for mercury effects on snapping turtles, whether mercury exposure compromises spatial behaviour of adult turtles, and whether mercury has a direct effect on the magnetoreception mechanism(s) that mediate SMA or a more general effect on the nervous system. Copyright © 2017 Elsevier Ltd. All rights reserved.

3-D Localization Method for a Magnetically Actuated Soft Capsule Endoscope and Its Applications

PubMed Central

Yim, Sehyuk; Sitti, Metin

2014-01-01

In this paper, we present a 3-D localization method for a magnetically actuated soft capsule endoscope (MASCE). The proposed localization scheme consists of three steps. First, MASCE is oriented to be coaxially aligned with an external permanent magnet (EPM). Second, MASCE is axially contracted by the enhanced magnetic attraction of the approaching EPM. Third, MASCE recovers its initial shape by the retracting EPM as the magnetic attraction weakens. The combination of the estimated direction in the coaxial alignment step and the estimated distance in the shape deformation (recovery) step provides the position of MASCE in 3-D. It is experimentally shown that the proposed localization method could provide 2.0–3.7 mm of distance error in 3-D. This study also introduces two new applications of the proposed localization method. First, based on the trace of contact points between the MASCE and the surface of the stomach, the 3-D geometrical model of a synthetic stomach was reconstructed. Next, the relative tissue compliance at each local contact point in the stomach was characterized by measuring the local tissue deformation at each point due to the preloading force. Finally, the characterized relative tissue compliance parameter was mapped onto the geometrical model of the stomach toward future use in disease diagnosis. PMID:25383064

Controlled alignment of carbon nanofibers in a large-scale synthesis process

NASA Astrophysics Data System (ADS)

Merkulov, Vladimir I.; Melechko, A. V.; Guillorn, M. A.; Simpson, M. L.; Lowndes, D. H.; Whealton, J. H.; Raridon, R. J.

2002-06-01

Controlled alignment of catalytically grown carbon nanofibers (CNFs) at a variable angle to the substrate during a plasma-enhanced chemical vapor deposition process is achieved. The CNF alignment is controlled by the direction of the electric field lines during the synthesis process. Off normal CNF orientations are achieved by positioning the sample in the vicinity of geometrical features of the sample holder, where bending of the electric field lines occurs. The controlled growth of kinked CNFs that consist of two parts aligned at different angles to the substrate normal also is demonstrated.

Comparative Analysis of Mass Spectral Similarity Measures on Peak Alignment for Comprehensive Two-Dimensional Gas Chromatography Mass Spectrometry

PubMed Central

2013-01-01

Peak alignment is a critical procedure in mass spectrometry-based biomarker discovery in metabolomics. One of peak alignment approaches to comprehensive two-dimensional gas chromatography mass spectrometry (GC×GC-MS) data is peak matching-based alignment. A key to the peak matching-based alignment is the calculation of mass spectral similarity scores. Various mass spectral similarity measures have been developed mainly for compound identification, but the effect of these spectral similarity measures on the performance of peak matching-based alignment still remains unknown. Therefore, we selected five mass spectral similarity measures, cosine correlation, Pearson's correlation, Spearman's correlation, partial correlation, and part correlation, and examined their effects on peak alignment using two sets of experimental GC×GC-MS data. The results show that the spectral similarity measure does not affect the alignment accuracy significantly in analysis of data from less complex samples, while the partial correlation performs much better than other spectral similarity measures when analyzing experimental data acquired from complex biological samples. PMID:24151524

New results in the theory of dust grain alignment

NASA Technical Reports Server (NTRS)

Cugnon, Pierre

1989-01-01

Two complementary approaches are used in an attempt to propose an appropriate formulation of the solution to the problem of magnetic alignment of grains in the diffuse and/or the more denser clouds, whatever the mechanism of rotational excitation can be. The interest of such a unified formulation is mainly that the same theoretical expression for polarization can be used everywhere, allowing for easier comparisons between regions where the physical conditions are highly different. The first consists in applying a Monte-Carlo method to a limited number of representative cases, for which all the torques acting on the grain are taken into account: impulsive random torques due to direct collisions with gas atoms, to evaporation of atoms from the surface, and to exo-energetic recombinations forming hydrogen molecules, followed by violent ejections from peculiar sites; magnetic torques. Three characteristic times are associated with these torques: the collisional damping time, the time necessary to change completely the actual sites configuration narrowly bound to the correlation time of the suprathermal torque; and the magnetic damping time. The second approach starts from a heuristic point of view. It consists in a generalization of results (Cugnon, 1983; see also Purcell and Spitzer, 1971; Greenberg, 1978) obtained for thermal alignment to the suprathermal case. It appears indeed that in two extreme cases, the thermal formulation may be used after redefinition of involved times and temperatures.

An anisotropic hydrogel with electrostatic repulsion between cofacially aligned nanosheets

NASA Astrophysics Data System (ADS)

Liu, Mingjie; Ishida, Yasuhiro; Ebina, Yasuo; Sasaki, Takayoshi; Hikima, Takaaki; Takata, Masaki; Aida, Takuzo

2015-01-01

Machine technology frequently puts magnetic or electrostatic repulsive forces to practical use, as in maglev trains, vehicle suspensions or non-contact bearings. In contrast, materials design overwhelmingly focuses on attractive interactions, such as in the many advanced polymer-based composites, where inorganic fillers interact with a polymer matrix to improve mechanical properties. However, articular cartilage strikingly illustrates how electrostatic repulsion can be harnessed to achieve unparalleled functional efficiency: it permits virtually frictionless mechanical motion within joints, even under high compression. Here we describe a composite hydrogel with anisotropic mechanical properties dominated by electrostatic repulsion between negatively charged unilamellar titanate nanosheets embedded within it. Crucial to the behaviour of this hydrogel is the serendipitous discovery of cofacial nanosheet alignment in aqueous colloidal dispersions subjected to a strong magnetic field, which maximizes electrostatic repulsion and thereby induces a quasi-crystalline structural ordering over macroscopic length scales and with uniformly large face-to-face nanosheet separation. We fix this transiently induced structural order by transforming the dispersion into a hydrogel using light-triggered in situ vinyl polymerization. The resultant hydrogel, containing charged inorganic structures that align cofacially in a magnetic flux, deforms easily under shear forces applied parallel to the embedded nanosheets yet resists compressive forces applied orthogonally. We anticipate that the concept of embedding anisotropic repulsive electrostatics within a composite material, inspired by articular cartilage, will open up new possibilities for developing soft materials with unusual functions.

An anisotropic hydrogel with electrostatic repulsion between cofacially aligned nanosheets.

PubMed

Liu, Mingjie; Ishida, Yasuhiro; Ebina, Yasuo; Sasaki, Takayoshi; Hikima, Takaaki; Takata, Masaki; Aida, Takuzo

2015-01-01

Machine technology frequently puts magnetic or electrostatic repulsive forces to practical use, as in maglev trains, vehicle suspensions or non-contact bearings. In contrast, materials design overwhelmingly focuses on attractive interactions, such as in the many advanced polymer-based composites, where inorganic fillers interact with a polymer matrix to improve mechanical properties. However, articular cartilage strikingly illustrates how electrostatic repulsion can be harnessed to achieve unparalleled functional efficiency: it permits virtually frictionless mechanical motion within joints, even under high compression. Here we describe a composite hydrogel with anisotropic mechanical properties dominated by electrostatic repulsion between negatively charged unilamellar titanate nanosheets embedded within it. Crucial to the behaviour of this hydrogel is the serendipitous discovery of cofacial nanosheet alignment in aqueous colloidal dispersions subjected to a strong magnetic field, which maximizes electrostatic repulsion and thereby induces a quasi-crystalline structural ordering over macroscopic length scales and with uniformly large face-to-face nanosheet separation. We fix this transiently induced structural order by transforming the dispersion into a hydrogel using light-triggered in situ vinyl polymerization. The resultant hydrogel, containing charged inorganic structures that align cofacially in a magnetic flux, deforms easily under shear forces applied parallel to the embedded nanosheets yet resists compressive forces applied orthogonally. We anticipate that the concept of embedding anisotropic repulsive electrostatics within a composite material, inspired by articular cartilage, will open up new possibilities for developing soft materials with unusual functions.

The competition between magnetocrystalline and shape anisotropy on the magnetic and magneto-transport properties of crystallographically aligned CuCr2Se4 thin films

NASA Astrophysics Data System (ADS)

Edelman, I.; Esters, M.; Johnson, D. C.; Yurkin, G.; Tarasov, A.; Rautsky, M.; Volochaev, M.; Lyashchenko, S.; Ivantsov, R.; Petrov, D.; Solovyov, L. A.

2017-12-01

Crystallographically aligned nanocrystalline films of the ferromagnetic spinel CuCr2Se4 were successfully synthesized and their structure and alignment were confirmed by X-ray diffraction and high-resolution transmission electron microscopy. The average size of the crystallites is about 200-250 nm, and their (1 1 1) crystal planes are parallel to the film plane. A good match of the film's electronic structure to that of bulk CuCr2Se4 is confirmed by transverse Kerr effect measurements. Four easy 〈1 1 1〉 axes are present in the films. One of these axes is oriented perpendicular and three others are oriented at an angle of 19.5° relative to the film plane. The magnetic properties of the films are determined by a competition between the out-of-plane magnetocrystalline anisotropy and the in-plane shape anisotropy. Magnetic measurements show that the dominating type of anisotropy switches from shape to magnetocrystalline anisotropy near 160 K, which leads to a switch of the effective easy axis from inside the film plane at room temperature to perpendicular to the film plane as the temperature decreases. At last, a moderately large, negative value of the low-temperature magnetoresistance was observed for the first time in CuCr2Se4 films.

Rail-RNA: scalable analysis of RNA-seq splicing and coverage.

PubMed

Nellore, Abhinav; Collado-Torres, Leonardo; Jaffe, Andrew E; Alquicira-Hernández, José; Wilks, Christopher; Pritt, Jacob; Morton, James; Leek, Jeffrey T; Langmead, Ben

2017-12-15

RNA sequencing (RNA-seq) experiments now span hundreds to thousands of samples. Current spliced alignment software is designed to analyze each sample separately. Consequently, no information is gained from analyzing multiple samples together, and it requires extra work to obtain analysis products that incorporate data from across samples. We describe Rail-RNA, a cloud-enabled spliced aligner that analyzes many samples at once. Rail-RNA eliminates redundant work across samples, making it more efficient as samples are added. For many samples, Rail-RNA is more accurate than annotation-assisted aligners. We use Rail-RNA to align 667 RNA-seq samples from the GEUVADIS project on Amazon Web Services in under 16 h for US$0.91 per sample. Rail-RNA outputs alignments in SAM/BAM format; but it also outputs (i) base-level coverage bigWigs for each sample; (ii) coverage bigWigs encoding normalized mean and median coverages at each base across samples analyzed; and (iii) exon-exon splice junctions and indels (features) in columnar formats that juxtapose coverages in samples in which a given feature is found. Supplementary outputs are ready for use with downstream packages for reproducible statistical analysis. We use Rail-RNA to identify expressed regions in the GEUVADIS samples and show that both annotated and unannotated (novel) expressed regions exhibit consistent patterns of variation across populations and with respect to known confounding variables. Rail-RNA is open-source software available at http://rail.bio. anellore@gmail.com or langmea@cs.jhu.edu. Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

Structure of an energetic narrow discrete arc

NASA Technical Reports Server (NTRS)

Mcfadden, J. P.; Carlson, C. W.; Boehm, M. H.

1990-01-01

Particle distributions, waves, dc electric fields, and magnetic fields were measured by two sounding rockets at altitudes of 950 and 430 km through an energetic (greater than 5 keV) narrow (about 10 km) stable discrete arc. Although the payloads' magnetic footprints were separated by only 50 km, differences in the arc's structure were observed including the spatial width, peak energy, and characteristic spectra. The energetic electron precipitation included both slowly varying isotropic fluxes that formed an inverted-V energy-time signature and rapidly varying field-aligned fluxes at or below the isotropic spectral peak. The isotropic precipitation had a flux discontinuity inside the arc indicating the arc was present on a boundary between two different magnetospheric plasmas. Dispersive and nondispersive bursts of field-aligned electrons were measured throughout the arc, appearing over broad energy ranges or as monoenergetic beams. Dispersive bursts gave variable source distances less than 8000 km. Plateauing of some of the most intense bursts suggests that waves stabilized these electrons. During the lower altitude arc crossing, the field-aligned component formed a separate inverted-V energy-time signature whose peak energy was half the isotropic peak energy.

Space Technology 5 Multi-point Measurements of Near-Earth Magnetic Fields: Initial Results

NASA Technical Reports Server (NTRS)

Slavin, James A.; Le, G.; Strangeway, R. L.; Wang, Y.; Boardsen, S.A.; Moldwin, M. B.; Spence, H. E.

2007-01-01

The Space Technology 5 (ST-5) mission successfully placed three micro-satellites in a 300 x 4500 km dawn-dusk orbit on 22 March 2006. Each spacecraft carried a boom-mounted vector fluxgate magnetometer that returned highly sensitive and accurate measurements of the geomagnetic field. These data allow, for the first time, the separation of temporal and spatial variations in field-aligned current (FAC) perturbations measured in low-Earth orbit on time scales of approximately 10 sec to 10 min. The constellation measurements are used to directly determine field-aligned current sheet motion, thickness and current density. In doing so, we demonstrate two multi-point methods for the inference of FAC current density that have not previously been possible in low-Earth orbit; 1) the "standard method," based upon s/c velocity, but corrected for FAC current sheet motion, and 2) the "gradiometer method" which uses simultaneous magnetic field measurements at two points with known separation. Future studies will apply these methods to the entire ST-5 data set and expand to include geomagnetic field gradient analyses as well as field-aligned and ionospheric currents.

High volume production of nanostructured materials

DOEpatents

Ripley, Edward B [Knoxville, TN; Morrell, Jonathan S [Knoxville, TN; Seals, Roland D [Oak Ridge, TN; Ludtka, Gerard M [Oak Ridge, TN

2009-10-13

A system and method for high volume production of nanoparticles, nanotubes, and items incorporating nanoparticles and nanotubes. Microwave, radio frequency, or infrared energy vaporizes a metal catalyst which, as it condenses, is contacted by carbon or other elements such as silicon, germanium, or boron to form agglomerates. The agglomerates may be annealed to accelerate the production of nanotubes. Magnetic or electric fields may be used to align the nanotubes during their production. The nanotubes may be separated from the production byproducts in aligned or non-aligned configurations. The agglomerates may be formed directly into tools, optionally in compositions that incorporate other materials such as abrasives, binders, carbon-carbon composites, and cermets.

Methods for high volume production of nanostructured materials

DOEpatents

Ripley, Edward B [Knoxville, TN; Morrell, Jonathan S [Knoxville, TN; Seals, Roland D [Oak Ridge, TN; Ludtka, Gerald M [Oak Ridge, TN

2011-03-22

A system and method for high volume production of nanoparticles, nanotubes, and items incorporating nanoparticles and nanotubes. Microwave, radio frequency, or infrared energy vaporizes a metal catalyst which, as it condenses, is contacted by carbon or other elements such as silicon, germanium, or boron to form agglomerates. The agglomerates may be annealed to accelerate the production of nanotubes. Magnetic or electric fields may be used to align the nanotubes during their production. The nanotubes may be separated from the production byproducts in aligned or non-aligned configurations. The agglomerates may be formed directly into tools, optionally in compositions that incorporate other materials such as abrasives, binders, carbon-carbon composites, and cermets.

A Comprehensive Two-Dimensional Retention Time Alignment Algorithm To Enhance Chemometric Analysis of Comprehensive Two-Dimensional Separation Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pierce, Karisa M.; Wood, Lianna F.; Wright, Bob W.

2005-12-01

A comprehensive two-dimensional (2D) retention time alignment algorithm was developed using a novel indexing scheme. The algorithm is termed comprehensive because it functions to correct the entire chromatogram in both dimensions and it preserves the separation information in both dimensions. Although the algorithm is demonstrated by correcting comprehensive two-dimensional gas chromatography (GC x GC) data, the algorithm is designed to correct shifting in all forms of 2D separations, such as LC x LC, LC x CE, CE x CE, and LC x GC. This 2D alignment algorithm was applied to three different data sets composed of replicate GC x GCmore » separations of (1) three 22-component control mixtures, (2) three gasoline samples, and (3) three diesel samples. The three data sets were collected using slightly different temperature or pressure programs to engender significant retention time shifting in the raw data and then demonstrate subsequent corrections of that shifting upon comprehensive 2D alignment of the data sets. Thirty 12-min GC x GC separations from three 22-component control mixtures were used to evaluate the 2D alignment performance (10 runs/mixture). The average standard deviation of the first column retention time improved 5-fold from 0.020 min (before alignment) to 0.004 min (after alignment). Concurrently, the average standard deviation of second column retention time improved 4-fold from 3.5 ms (before alignment) to 0.8 ms (after alignment). Alignment of the 30 control mixture chromatograms took 20 min. The quantitative integrity of the GC x GC data following 2D alignment was also investigated. The mean integrated signal was determined for all components in the three 22-component mixtures for all 30 replicates. The average percent difference in the integrated signal for each component before and after alignment was 2.6%. Singular value decomposition (SVD) was applied to the 22-component control mixture data before and after alignment to show the restoration of trilinearity to the data, since trilinearity benefits chemometric analysis. By applying comprehensive 2D retention time alignment to all three data sets (control mixtures, gasoline samples, and diesel samples), classification by principal component analysis (PCA) substantially improved, resulting in 100% accurate scores clustering.« less

Exceptionally large magneto-optical response in dispersions of plate-like nanocrystallites and magnetic nanoparticles

NASA Astrophysics Data System (ADS)

May, Kathrin; Eremin, Alexey; Stannarius, Ralf; Szabó, Balázs; Börzsönyi, Tamás; Appel, Ingo; Behrens, Silke; Klein, Susanne

2017-06-01

We introduce a binary colloidal system with an exceptionally strong magneto-optical response. Its induced optical birefringence at even low magnetic fields (in the mT range) reaches a value with the same order of magnitude as that of nematic liquid crystals. This system is based on a binary mixture of plate-like, non-magnetic pigment nanoparticles and a small volume fraction (< 1 v %) of spherical magnetic nanoparticles. In the field-free state, the suspension is isotropic. Birefringence is caused by an alignment of the pigment platelets, commanded by shape-anisotropic agglomerates of the magnetic nanoparticles in an external magnetic field. We give a semiquantitative discussion about this.

Unveiling the Role of the Magnetic Field at the Smallest Scales of Star Formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hull, Charles L. H.; Mocz, Philip; Burkhart, Blakesley

We report Atacama Large Millimeter/submillimeter Array (ALMA) observations of polarized dust emission from the protostellar source Ser-emb 8 at a linear resolution of 140 au. Assuming models of dust-grain alignment hold, the observed polarization pattern gives a projected view of the magnetic field structure in this source. Contrary to expectations based on models of strongly magnetized star formation, the magnetic field in Ser-emb 8 does not exhibit an hourglass morphology. Combining the new ALMA data with previous observational studies, we can connect magnetic field structure from protostellar core (∼80,000 au) to disk (∼100 au) scales. We compare our observations withmore » four magnetohydrodynamic gravo-turbulence simulations made with the AREPO code that have initial conditions ranging from super-Alfvénic (weakly magnetized) to sub-Alfvénic (strongly magnetized). These simulations achieve the spatial dynamic range necessary to resolve the collapse of protostars from the parsec scale of star-forming clouds down to the ∼100 au scale probed by ALMA. Only in the very strongly magnetized simulation do we see both the preservation of the field direction from cloud to disk scales and an hourglass-shaped field at <1000 au scales. We conduct an analysis of the relative orientation of the magnetic field and the density structure in both the Ser-emb 8 ALMA observations and the synthetic observations of the four AREPO simulations. We conclude that the Ser-emb 8 data are most similar to the weakly magnetized simulations, which exhibit random alignment, in contrast to the strongly magnetized simulation, where the magnetic field plays a role in shaping the density structure in the source. In the weak-field case, it is turbulence—not the magnetic field—that shapes the material that forms the protostar, highlighting the dominant role that turbulence can play across many orders of magnitude in spatial scale.« less

Cross-tail magnetic flux ropes as observed by the GEOTAIL spacecraft

NASA Technical Reports Server (NTRS)

Lepping, R. P.; Fairfield, D. H.; Jones, J.; Frank, L. A.; Paterson, W. R.; Kokubun, S.; Yamamoto, T.

1995-01-01

Ten transient magnetic structures in Earth's magnetotail, as observed in GEOTAIL measurements, selected for early 1993 (at (-) X(sub GSM) = 90 - 130 Earth radii), are shown to have helical magnetic field configurations similar to those of interplanetary magnetic clouds at 1 AU but smaller in size by a factor of approximately = 700. Such structures are shown to be well approximated by a comprehensive magnetic force-free flux-rope model. For this limited set of 10 events the rope axes are seen to be typically aligned with the Y(sub GSM) axis and the average diameter of these structures is approximately = 15 Earth radii.

Studies on the Magnetic Center of the Mu2e Solenoid System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lopes, M. L.; Ambrosio, G.; Buehler, M.

2014-01-01

The definition of the magnetic center in the Mu2e solenoid system is not trivial given the S-shaped nature of the transport solenoid. Moreover, due to the fringe field of the larger bore adjacent magnets-production solenoid and the detector solenoid-the magnetic center does not coincide with the geometric center of the system. The reference magnetic center can be obtained by tracking a low-momentum charged particle through the whole system. This paper will discuss this method and will evaluate the deviations from the nominal magnetic center given the tolerances in the manufacturing and the alignment of the coils. Methods for the correctionmore » of the magnetic center will also be presented.« less

Magnetically induced orientation of mesochannels in mesoporous silica films at 30 tesla.

PubMed

Yamauchi, Yusuke; Sawada, Makoto; Komatsu, Masaki; Sugiyama, Atsushi; Osaka, Tetsuya; Hirota, Noriyuki; Sakka, Yoshio; Kuroda, Kazuyuki

2007-12-03

We demonstrate the magnetically induced orientation of mesochannels in mesoporous silica films prepared with low-molecular-weight surfactants under an extremely high magnetic field of 30 T. This process is principally applicable to any type of surfactant that has magnetic anisotropy because such a high magnetic field provides sufficient magnetic energy for smooth magnetic orientation. Hexadecyltrimethylammonium bromide (CTAB) and polyoxyethylene-10-cetyl ether (Brij 56) were used as cationic and nonionic surfactants, respectively. According to XRD and cross-sectional TEM, mesochannels aligned perpendicular to the substrates were observed in films prepared with low-molecular-weight surfactants, although the effect was incomplete. The evolution of these types of films should lead to future applications such as highly sensitive chemical sensors and selective separation.

Small-scale field-aligned currents caused by tropical cyclones as observed by the SWARM satellites above the ionosphere

NASA Astrophysics Data System (ADS)

Aoyama, T.; Iyemori, T.; Nakanishi, K.

2014-12-01

We present case studies of small-scale magnetic fluctuations above typhoons, hurricanes and cyclones as observed by the swarm constellation. It is reported lately that AGWs(atmospheric gravity waves) generated by meteorological phenomena in the troposphere such as typhoons and tornadoes, large earthquakes and volcanic eruptions propagate to the mesosphere and thermosphere. We observe them in various forms(e.g. airglows, ionospheric disturbances and TEC variations). We are proposing the following model. AGWs caused by atmospheric disturbances in the troposphere propagate to the ionospheric E-layer, drive dynamo action and generate field-aligned currents. The satellites observe magnetic fluctuations above the ionosphere. In this presentation, we focus on cases of tropical cyclone(hurricanes in North America, typhoons in North-West Pacific).

A Two-Dimensional Manganese Gallium Nitride Surface Structure Showing Ferromagnetism at Room Temperature.

PubMed

Ma, Yingqiao; Chinchore, Abhijit V; Smith, Arthur R; Barral, María Andrea; Ferrari, Valeria

2018-01-10

Practical applications of semiconductor spintronic devices necessitate ferromagnetic behavior at or above room temperature. In this paper, we demonstrate a two-dimensional manganese gallium nitride surface structure (MnGaN-2D) which is atomically thin and shows ferromagnetic domain structure at room temperature as measured by spin-resolved scanning tunneling microscopy and spectroscopy. Application of small magnetic fields proves that the observed magnetic domains follow a hysteretic behavior. Two initially oppositely oriented MnGaN-2D domains are rotated into alignment with only 120 mT and remain mostly in alignment at remanence. The measurements are further supported by first-principles theoretical calculations which reveal highly spin-polarized and spin-split surface states with spin polarization of up to 95% for manganese local density of states.