2H NMR Spectra for D2O Adsorbed on Oriented Cellulose Fibers

1996 ◽  
Vol 50 (12) ◽  
pp. 1512-1518 ◽  
Author(s):  
Tie-Qiang Li
Keyword(s):  
Magnetic Field ◽  
Nmr Spectra ◽  
Lateral Diffusion ◽  
Cellulose Fibers ◽  
Exchange Model ◽  
Average Lifetime ◽  
Band Shape ◽  
Mutual Exchange ◽  
Oriented Parallel ◽  
The Magnetic Field

2H NMR spectra for D2O adsorbed on cellulose fibers which are macroscopically oriented demonstrate that the axis of cellulose fibers can be regarded as the director of the average molecular motion of the adsorbed D2O. The spectra for samples prepared from fiber sheets depend on the orientation of the sheets with respect to the magnetic field as well as the fiber orientation in the sheets. When the sheets are oriented perpendicular to the magnetic field, all the fibers in the sheets are perpendicular to the field irrespective of the fiber orientations in the sheets, and a partially overlapped quadrupole splitting is observed. When the sheets are oriented parallel to the magnetic field, the observed spectra deviate significantly from the expected 2D powder patterns, and the distribution of fiber orientations in the sheets has a significant influence on the observed band shape. An N-site mutual exchange model was used to account for the lateral diffusion of water molecules from one fiber to another. In a comparison of the simulated spectra based on the N-site mutual exchange model with the experimentally recorded spectra, the average lifetime for the adsorbed D2O molecules to reside on cellulose fibrils was estimated to be about 1.5 ms.

Anisotropic Magnetic Fibers Produced via a Magnetic Drawing Process

MRS Advances ◽  
2017 ◽  
Vol 2 (16) ◽  
pp. 921-926
Author(s):  
Corey Breznak ◽  
Paris von Lockette
Keyword(s):  
Magnetic Field ◽  
Magnetic Material ◽  
Barium Hexaferrite ◽  
Magnetic Domains ◽  
Squareness Ratio ◽  
High Anisotropy ◽  
Field Lines ◽  
Von Mises ◽  
Oriented Parallel ◽  
The Magnetic Field

ABSTRACTThis work aims to develop magnetic fibers whose magnetic properties improve upon fibers produced using existing techniques. The goal of this work is to develop magnetic fibers that are magnetically anisotropic, with high squareness ratios when the fibers are oriented parallel to the applied magnetic field, and lower square ratios when the fibers are oriented perpendicular to the field. In this work, barium hexaferrite particles were embedded in a Sylgard elastomer matrix. The magnetic material was placed on a sheet of acrylic with spacers on opposite ends. A top sheet of acrylic was placed on the spacers. A 0.5 T permanent magnet was placed on top of the upper piece of acrylic. Magnetic fibers were drawn as the material aligned itself with the magnetic field lines of the magnet. After the fibers cured they were tested on a vibrating sample magnetometer at angles parallel and perpendicular to the field. The results showed that the fibers were highly anisotropic, with an average squareness ratio of 0.82 in the easy axis and an average squareness ratio of 0.34 in the hard axis. Although, the fibers were anisotropic, there was a high variability in the magnetization when normalized by the total volume of the fiber. This indicates that the magnetic content varies within each fiber, likely due to the variation in the strength of the magnetic field lines of the external magnet. This research demonstrated that magnetic fibers with high anisotropy can be fabricated, but the amount of magnetic material in each fiber from the same batch needs to be tuned to decrease variability. Fitting this experimentally found squareness ratio to a von Mises distribution, the concentration parameter was calculated to be 0.14. This indicates the magnetic domains within each fiber are highly aligned with the externally applied field.

scholarly journals The Galactic Halo in Hydrostatic Equilibrium

1997 ◽  
Vol 166 ◽  
pp. 475-478
Author(s):  
P.M.W. Kalberla ◽  
J. Pietz ◽  
J. Kerp
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Large Scale ◽  
Galactic Halo ◽  
Galactic Plane ◽  
High Energy ◽  
Scale Height ◽  
Hydrostatic Equilibrium ◽  
Oriented Parallel ◽  
The Magnetic Field

AbstractThe large scale distribution of gas, magnetic field and cosmic rays in the Galaxy is explored. We analyze recent all-sky surveys of HI gas (Leiden/Dwingeloo survey), soft X-ray radiation (ROSAT) and high energy gamma-rays (EGRET > 100 MeV) in combination with the 408 MHz survey. Prom these observations we derive a Galactic halo model consistent with hydrostatic equilibrium conditions.The large scale equilibrium configuration consists of two separate domains with different properties and scale sizes: 1)The gaseous halo consists of collisionally ionized gas at T=106.2K as well as HI and has an exponential scale height hz ~ 4.4 kpc. The radial distribution is characterized by the galactocentric scale length A1 ~ 15 kpc. All components of the halo – gas, magnetic field and cosmic rays – contribute equally to the pressure. The magnetic field in the halo is oriented parallel to the Galactic plane.2)The disk extends up to a scale height of hz ~ 1 kpc and is associated with irregular magnetic fields. Here the pressure of the magnetic field is only ⅓ of the gas pressure. The cosmic rays are only weakly coupled to the disk.

Sharp-pointed susceptibility of ferromagnetic films with magnetic anisotropy inhomogeneous in thickness

2018 ◽  
Vol 32 (17) ◽  
pp. 1840034 ◽  
Author(s):  
Yu. I. Dzhezherya ◽  
A. O. Khrebtov ◽  
D. P. Azarkh ◽  
S. P. Kruchinin
Keyword(s):  
Magnetic Field ◽  
Interphase Boundary ◽  
Film Plane ◽  
Magnetic Susceptibility Tensor ◽  
Ferromagnetic Films ◽  
Highly Sensitive ◽  
Sensitive Sensor ◽  
Oriented Parallel ◽  
The Magnetic Field ◽  
Frequency Dependences

It is shown that in ferromagnetic films with anisotropy inhomogeneous in thickness, an interphase boundary can be formed for certain values and directions of the magnetic field. This boundary has a stable magnetic configuration. It is oriented parallel to the film plane and separates the regions with different orientations of the magnetization. In an alternating magnetic field, the interphase boundary oscillates, which may be accompanied by a resonance. The field and frequency dependences of the components of the magnetic susceptibility tensor are determined. It is shown that the susceptibility coefficients at a resonance are extremely sensitive to the direction of the external magnetic field which can underlie the development of a highly sensitive sensor.

Chemisch induzierte Kernpolarisation von Phenylhalogeniden bei der Photolyse von Aroylperoxiden

1969 ◽  
Vol 24 (11) ◽  
pp. 1771-1778 ◽  
Author(s):  
M. Lehnig ◽  
H. Fischer
Keyword(s):  
Magnetic Field ◽  
Field Dependence ◽  
Dynamic Nuclear Polarization ◽  
Nmr Spectra ◽  
Magnetic Field Dependence ◽  
Nuclear Polarization ◽  
Radical Reactions ◽  
Chemically Induced ◽  
Polarization Mechanism ◽  
The Magnetic Field

Abstract By a flow technique chemically induced nuclear polarization is observed in the NMR-spectra of phenylhalides formed during photolysis of aroylperoxides in solution. The main features of the polarization are quantitatively explained by dynamic nuclear polarization (CIDNP) of protons in the intermediate phenyl radicals. Some details however indicate that a second polarization mechanism is also present. This mechanism leads to a multiplet-effect type polarization and operates presumably during bond fromation in the radical reactions. Some results on the magnetic field dependence of the nuclear polarizations are given.

Deuteron NMR Lineshapes in the Antiferroelectric Liquid Crystalline Phase of MHPOBC

2000 ◽  
Vol 55 (1-2) ◽  
pp. 298-300
Author(s):  
R. Blinc ◽  
A. Gregorovič ◽  
B. Zalar
Keyword(s):  
Magnetic Field ◽  
Crystalline Phase ◽  
Nmr Spectra ◽  
Liquid Crystalline ◽  
Translational Diffusion ◽  
Liquid Crystalline Phase ◽  
Magnetic Field Direction ◽  
Liquid Crystalline Phases ◽  
The Magnetic Field ◽  
Deuteron Nmr

The deuteron NMR lineshapes in the tilted antiferroeelectric smectic liquid crystalline phases are evaluated for: i) the case of a discrete short pitch modulation P1 = N • d where N = 2,3,4, ii) for a superposition of two modulations p1 and p0 where p0 ≫p1 as well as iii) for the case where in addition rapid molecular exchange between adjacent layers takes place due to translational diffusion. The results are compared with the experimental deuteron NMR spectra of α-CD2 deuterated MHPOBC in the Sm C*A phase measured at different angles between the magnetic field direction and the normals to the smectic layers. The alternating tilt structure of the Sm C*A phase is confirmed

Magnetic resonance studies of (ReO 4 ) 2- in calcium tungstate

1975 ◽  
Vol 346 (1647) ◽  
pp. 497-513 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Resonance ◽  
Single Electron ◽  
Spin Hamiltonian ◽  
Calcium Tungstate ◽  
Magnetic Resonance Studies ◽  
Tetragonal Form ◽  
Oriented Parallel ◽  
Hamiltonian Parameters ◽  
The Magnetic Field

The e. p. r. spectrum of (ReO 4 ) 2– in CaWO 4 has been measured in the temperature 4–120 K as a function of orientation. The spectrum including many forbidden lines may be fitted to the spin Hamiltonian H = μ B B· g· S· + I· ÷ S. + I· P̃. I· in tetragonal form with S = ½ and I =5/2. At 4.2 K, endor measurements for the magnetic field oriented parallel to the unique axis, taken in con­junction with the e. p. r. spectrum, yield spin Hamiltonian parameters g ǁ = 1.8549 ± 0.0002, g ⊥ = 1.7164 ± 0.0002, A ǁ = ( ± )(42 ± 2) x 10 -4 cm -1 , A ⊥ = (±) (32 ± 2) x 10 -4 cm -1 and P ǁ = (∓) (5 ± 3) x 10 -4 cm -1 , with g N = ( ± ) 1.27 for the 187 Re nuclide. These parameters are consistent with the single electron occupying the |3 z 2 — r 2 > orbital of a 5d 1 ion. The e. p. r. linewidth, which is strongly sensitive to both orientation and temperature, has been examined in detail. Preliminary studies of the relaxation proper­ties of the centre are discussed in qualitative terms.

Observing the galactic magnetic field

1967 ◽  
Vol 31 ◽  
pp. 375-380
Author(s):  
H. C. van de Hulst
Keyword(s):  
Magnetic Field ◽  
Fair Agreement ◽  
Solar Neighbourhood ◽  
Galactic Magnetic Field ◽  
The Magnetic Field

Various methods of observing the galactic magnetic field are reviewed, and their results summarized. There is fair agreement about the direction of the magnetic field in the solar neighbourhood:l= 50° to 80°; the strength of the field in the disk is of the order of 10-5gauss.

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