Pressure Anisotropy

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Jump conditions for pressure anisotropy and comparison with the Earth’s bow shock

Jump conditions for pressure anisotropy and comparison with the Earth’s bow shock

Rankine Hugoniot equations. It is important to note that their calculations are applicable for a wide range of plasma betas, various pressure anisotropy rates, and different shock geome- tries upstream of the fast shock wave. Furthermore, Erkaev et al. (2000) used the criteria of the fire-hose and mirror instability as additional equations to determine the pressure anisotropy downstream of the shock. These two threshold conditions give some additional restrictions to the behaviour of the plasma upstream and downstream of the shock wave and therefore, the anisotropy rate cannot be outside of the in- terval determined by the threshold of these two plasma insta- bilities. Since the Rankine Hugoniot equations can only be applied to regions close to the shock wave, the use of these plasma instabilities, which are identified by spacecraft mis- sions (e.g. Hill et al., 1995; Phan et al., 1996), gives some boundaries for the pressure anisotropy for either side of the shock. Different pressure anisotropy rates in the solar wind were examined by Biernat et al. (2000), Kiendl et al. (2000) and Vogl et al. (2000).

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Simultaneous Measurement of Plasma Pressure Anisotropy with a Double-Pass Thomson Scattering Diagnostic System on the TST-2

Simultaneous Measurement of Plasma Pressure Anisotropy with a Double-Pass Thomson Scattering Diagnostic System on the TST-2

We developed a double-pass Thomson scattering di- agnostic system on the TST-2, evaluated the systematic and random errors, and found the measurement error to be around 5 - 10% for plasmas with a density of 2 × 10 19 m − 3 . We observed a finite difference between pressures perpen- dicular and parallel to the magnetic field. The co-directed (i.e., the direction of electron acceleration) parallel pres- sure was almost always higher than the perpendicular pres- sure, and the counter-directed parallel pressure was al- most always lower than the others. There was a pressure anisotropy of around 30% at the plasma center, while at the plasma edge it was around 100%. This represents the

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Turbulence in collisionless plasmas : statistical analysis from numerical simulations with pressure anisotropy

Turbulence in collisionless plasmas : statistical analysis from numerical simulations with pressure anisotropy

Abstract. In recent years, we have experienced increasing interest in the understanding of the physical properties of collisionless plasmas, mostly because of the large number of astrophysical environments (e.g. the intracluster medium (ICM)) containing magnetic fields that are strong enough to be coupled with the ionized gas and characterized by densities sufficiently low to prevent the pressure isotropization with respect to the magnetic line direction. Under these conditions, a new class of kinetic instabilities arises, such as firehose and mirror instabilities, which have been studied extensively in the literature. Their role in the turbulence evolution and cascade process in the presence of pressure anisotropy, however, is still unclear. In this work, we present the first statistical analysis of turbulence in collisionless plasmas using three-dimensional numerical simulations and solving double-isothermal magnetohydrodynamic equations with the Chew–Goldberger–Low laws closure (CGL-MHD). We study models with different initial conditions to account for the firehose and mirror instabilities and to obtain different turbulent regimes. We found that the CGL- MHD subsonic and supersonic turbulences show small differences compared

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Nonlinear equilibrium structure of thin currents sheets: influence of electron pressure anisotropy

Nonlinear equilibrium structure of thin currents sheets: influence of electron pressure anisotropy

The results of our model show that there exists a class of equilibrium solutions of 1D self-consistent TCS configura- tion where anisotropic electrons provide a very characteris- tic contribution to the overall current structure. It has been shown earlier that the electrons may carry a significant part of the cross-tail current and lead to a bifurcated structure of the current density profile (Asano, 2001, 2003). In a more general case of electrons with anisotropic pressure, the TCS structure exhibits another characteristic feature. In the case of isotropic electrons, the magnetic field profile is flattened in the center of the sheet (Zelenyi et al., 2004), whereas in the anisotropic case it is steeper in this region. Important that anisotropy becomes a key word for the physics of such sheets and this physic is very different from that one meets dealing with isotropic Harris-type sheets. Interesting that even the very early pioneering work by Coppy and Rosenbluth (1968) empasized the critical role anisotropy could play in destabi- lization of such systems.

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Modeling Anisotropic Charged Neutron Star in Isotropic Coordinates

Modeling Anisotropic Charged Neutron Star in Isotropic Coordinates

In the formulism of realistic model of super dense stars, it is also important to include the pressure anisotropy. Bowers and Liang [4] extensively discuss the effect of pressure anisotropy in general relativity. At a density of the order of 10 / , nuclear matter may be anisotropic when its interactions need to be treated relativistically [5]. If there is existence of solid stellar core or presence of a type-3A super- fluid, one can also include pressure anisotropy [6]. Sokolov [7] suggest that a different kind of phase transition may lead to pressure anisotropy or pion condensation can generate anisotropy [8]. Since the neutron star has immense magnetic field, this also generate anisotropic pressure inside a compact star [9]. Usov [10] suggest that strong electric field may also cause pressure anisotropy.

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Komarov, Sergey
  

(2016):


	Thermal conduction in hot gas of galaxy clusters.


Dissertation, LMU München: Fakultät für Physik

Komarov, Sergey (2016): Thermal conduction in hot gas of galaxy clusters. Dissertation, LMU München: Fakultät für Physik

In this work, we assumed a static magnetic field taken from a region of a plasma where the field lines are stretched by a linear shear. Though at a given location in the ICM plasma, the field lines are not constantly stretched, the turbulent dynamo produces a magnetic-field-line configuration that consists of long folds (regions of amplified field) and short reversals (regions of decreasing/weak field). This means that mirror fluctuations may develop almost everywhere along the field lines in a turbulent ICM (see Rincon et al. 2016 for the first numerical evidence of this). We note that it is not yet known how the mirror and firehose instabilities evolve over multiple correlation times of a turbulent velocity field. However, the recent results by Melville et al. (2016) indicate that at the values of β typical for the ICM, the relaxation of pressure anisotropy in a changing macroscale velocity shear is almost insantaneous compared to the shear time. This may therefore suggest that the mirror instability does not have time to ever reach the saturated state (at St ≳ 2 according to Kunz et al. 2014), because the turbulent shear decorrelates earlier (at St ∼ 1). Thus, secularly growing mirrors are expected to be more common. In any case, since the results for both phases are similar up to a factor of order unity, we do not expect large deviations from the described above behavior. We may then argue that the amount of suppression found using the shearing-box simulations is characteristic for the ICM or any other turbulent weakly collisional high-β plasma.

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High Redshift Galaxies As Probes Of The Epoch Of Reionization

High Redshift Galaxies As Probes Of The Epoch Of Reionization

Here we develop an alternative approach for separating-out interloper contamination at the power spectrum level. Our starting point is to note that the mappings between ob- served wavelength/frequency and angle on the sky to co-moving length scales/wavenumbers are redshift dependent. If we assume the target redshift in converting between the ob- served frequencies and angles and co-moving coordinates, the interloper fluctuations will be mapped to the wrong wavenumbers. Since the remapping is different for the line of sight and transverse wavenumbers, the interloper contribution to the observed power spectrum will have a distinctive anisotropy. This is analogous to the Alcock-Paczynski (AP) effect (Alcock and Paczynski 1979; Ballinger et al. 1996), except in the case of the AP test a warping arises from assuming the wrong cosmology, while here the distortion results from adopting the incorrect redshift. We will show that this transfer of power and warping can be used to separate out the interloper contamination. This basic idea is men- tioned in previous work by Visbal and Loeb (2010) and Gong et al. (2014), but we develop the technique further here and apply it to quantify the prospects for cleaning interloper lines from future z ∼ 7 [CII] surveys. Although we focus on the illustrative example of IM with the [CII] line, our approach should be broadly applicable to IM surveys in other lines such as Lyα and CO transitions, and may also be of interest for traditional surveys detecting line-emitting galaxies.

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Investigation of the Use of Micro-Mechanical Testing to Analyze the Mechanical Anisotropy of the Zr-2.5%Nb Pressure Tube Alloy

Investigation of the Use of Micro-Mechanical Testing to Analyze the Mechanical Anisotropy of the Zr-2.5%Nb Pressure Tube Alloy

The latest fuel channels have been designed to have a lifespan of over 30 years. These channels, and in particular the pressure tube, are considered to have reached their end of service life when they can no longer meet their design and service demands. The combination of neutron flux, high temperature and pressure induced stresses over time results in a degradation of the properties of the pressure tubes. To an extent, the pressure tubes have been designed to accommodate extreme working conditions, but cracking have seldom occurred during operation [4-6]. Although the current CANDU reactor design has the capacity to withstand the consequences of a rupture of the pressure tube, researchers continue to strive to minimize the possibility of a fracture. The cost penalties of an unscheduled shutdown in operation in order to carry out repairs associated with any rupture and determine their cause has huge economic implications on the plant. Also, if such ruptures began to occur frequently, there would be an increase in the risk of them escalating to a more serious accident.

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Diffusion Anisotropy of the Internal Capsule and the Corona Radiata in Association with Stroke and Tumors as Measured by Diffusion weighted MR Imaging

Diffusion Anisotropy of the Internal Capsule and the Corona Radiata in Association with Stroke and Tumors as Measured by Diffusion weighted MR Imaging

There have been some reports regarding the re- lationship between wallerian degeneration and clin- ical findings. Wallerian degeneration of the pyra- midal tracts was often found in patients with capsular infarction, especially when associated with motor deficit (31). Orita et al (32) measured an area of wallerian degeneration in the pons on T2- weighted coronal images in patients with cerebro- vascular disease of the internal capsule and con- cluded that the area of wallerian degeneration was related to the severity of the motor deficit. Watan- abe and Tashiro (33) and Sawlani et al (34) com- pared the functional prognosis between patients with and without wallerian degeneration and found that the presence of wallerian degeneration corre- lated well with persistent functional disability. Therefore, the measurement of the diffusion an- isotropy might help to predict the functional prog- nosis of patients earlier in the acute stage of in- farction. Igarashi et al (17) evaluated the change in diffusion anisotropy associated with wallerian de- generation of the pyramidal tracts in patients with supratentorial cerebrovascular accidents by use of 3D anisotropy contrast MR images. Patients ex- amined during the acute stage who later recovered from hemiparesis had no visible changes on the 3D anisotropy contrast images, whereas patients who

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Anisotropy and Empirical Relations for the Estimation of Anisotropy Parameters in Niger Delta Depobelts

Anisotropy and Empirical Relations for the Estimation of Anisotropy Parameters in Niger Delta Depobelts

It is also worthy to note that when a sand contains large amounts of authigenic clays, it may become intrinsi- cally anisotropic (Wang, 2002) [9]. This accounts for the behaviour of sand in Figure 4 and Figure 6 where the sand bodies in Well A (Central Swamp depobelt) shows some traces of anisotropy in γ/ε plots and in δ/ŋ plots respectively. The alternating sequences of sands and shales in the Niger Delta geologically is possibly responsi- ble for this behaviour.

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Magnetic resonance of the NiFe2O4 nanoparticles in the gigahertz range

Magnetic resonance of the NiFe2O4 nanoparticles in the gigahertz range

prepared by a sol – gel process. X-ray diffraction and scanning electron microscopy results indicate that the samples are polycrystalline nanoparticles, and the size of the particles increases obviously with the thermal treatment temperature. The consequence of the surface composition suggests that the oxygen defects are present in the nanoparticle surface, and this surface magnetic state can show a strong surface anisotropy. With decreasing size of the particle, the surface magnetic effect is predominant, resulting in an increase of resonance frequency for NiFe 2 O 4 nanoparticles. This finding

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Dynamics of a geomagnetic storm on 7–10 September 2015 as observed by TWINS and simulated by CIMI

Dynamics of a geomagnetic storm on 7–10 September 2015 as observed by TWINS and simulated by CIMI

To understand how the electric shielding works to affect the paths of the injected particles, we note that the convec- tion electric field from the solar wind is mapped into the magnetosphere along open field lines into the polar iono- sphere. It is then shielded from penetrating to lower latitudes and therefore further into the inner magnetosphere by the Birkeland Region 2 currents driven by pressure gradients in the ring current. During geomagnetic storms when there is a sharp turn in the z-component of the interplanetary magnetic field (IMF) from negative to positive (see row 2 of Fig. 1), the accompanying electric field in the ionosphere associated with the Region 2 currents can produce what is referred to as over- shielding. See for example Jaggi and Wolf (1973). There are also neutral disturbance dynamo electric fields in the iono- sphere that affect electric shielding. Localized and short time injections may contribute to the complexity of these effects.

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Can Diffusion Tensor Imaging Noninvasively Detect IDH1 Gene Mutations in Astrogliomas? A Retrospective Study of 112 Cases

Can Diffusion Tensor Imaging Noninvasively Detect IDH1 Gene Mutations in Astrogliomas? A Retrospective Study of 112 Cases

According to the DTI data, the workstation automatically gener- ated the fractional anisotropy (FA) and ADC mapping. All of the FA and ADC maps were retrospectively interpreted by 2 experi- enced neuroradiologists (W. Tan and W. Huang, with 10 and 6 years of brain MR imaging experience, respectively) who did not know the pathologic results. The maximal FA was measured by manually placing ROIs in the most solid and highest signal-inten- sity part of the tumoral regions on the FA mapping by visual inspection. The size of every ROI was between 15–20 pixels. The mean value of small ROIs drawn to encompass the voxels with maximal FA values was recorded. Each neuroradiologist drew 3 ROIs to obtain the maximal FA, according to the gray-scale map. The maximal FA value among these values was chosen as the result. An average of the results of 2 neuroradiologists was used as the patient’s maximal FA. If the value for one reader varied by ⬎ 20% from the second reader, 18 a third reader, a neuroradiolo-

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Anisotropy and nonlinearity in superlattices

Anisotropy and nonlinearity in superlattices

However, with increasing anisotropy, the z-direction electron and hole masses become to different, with a much larger increase in hole mass. When the upper and lower (average) curvatures or equivalently, the average effective masses are too different the total chemical potential is relatively smaller (see Fig. 3b) and so is the inversion factor tanh ½ b ð hx l Þ=2 of Eq. (6), thus reducing the gain in Fig. 1. This influence of different electron and hole masses on the inversion is fully consistent with the detailed analysis for isolated quantum wells seen e.g. in Chow et al. (1992). Note that the method presented here can be used for a large number of other materials and superlattices as long as tunneling between adjacent

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Prediction of Neutron Emission Anisotropy for Validation of an Analysis Model for Neutron Spectra in Beam-Injected LHD Deuterium Plasmas

Prediction of Neutron Emission Anisotropy for Validation of an Analysis Model for Neutron Spectra in Beam-Injected LHD Deuterium Plasmas

emitted in the directions χ = 0 ◦ and 180 ◦ are increased, and those emitted in the direction χ = 90 ◦ are decreased, as shown in Fig. 4. Therefore, in this case, the fraction of the neutron flux at θ = 0 ◦ increases and that at θ = 180 ◦ decreases compared to the case of isotropic emission at both poloidal planes φ = 0 ◦ and 18 ◦ . In the same man- ner, for NB#5, the fraction of the flux at θ = 0 ◦ decreases, whereas that at θ = 180 ◦ ought to increase compared to the isotropic case, because of neutron emission anisotropy shown in Fig. 4. However, in the plane of φ = 0 ◦ , the normalized flux at θ = 180 ◦ is smaller than the case with isotropic emission. In this poloidal plane, the profile of the energetic deuteron has a peak far from the equatorial plane (the plane Z = 0 in Fig. 1) when the perpendicular NB is injected [22]. This energetic-deuteron profile, correspond- ing to the neutron emission profile, determines the fraction of the flux at θ = 180 ◦ and φ = 0 ◦ rather than neutron emission anisotropy. The locations of the irradiation ends at the 2.5-L and the 8-O ports almost correspond to the po- sition θ = 281 ◦ and φ = 0 ◦ and the position θ = 14 ◦ and φ = 18 ◦ , respectively. Hence, the ratio of neutron rates observed at the two foils provides an indication of neutron emission anisotropy.

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Estimation of the Effect of Anisotropy on Young’s Moduli and Poisson’s Ratios of Sedimentary Rocks Using Core Samples in Western and Central Part of Tripura, India

Estimation of the Effect of Anisotropy on Young’s Moduli and Poisson’s Ratios of Sedimentary Rocks Using Core Samples in Western and Central Part of Tripura, India

across the open ones. The sands and sandstone are intrin- sically isotropic unless they are fractured, finely layered or clay bearing. Wang shows that the brine-saturated Africa reservoir sands, which are essentially clay free, have very little anisotropy (average P-anisotropy and S- anisotropy are probably within the measurement uncer- tainties) [17]. For the brine saturated tight sands, the anisotropy is 5.0% for the P-wave and 3.3% for the S-wave when averaged over all samples at all pressures. At the net reservoir pressure of 7500 psi (51.7 MPa), anisotropy is slightly lower, averaging 4.6% and 3.2% for P-and S-waves, respectively. Gas-saturated tight sands and shaly sands show some degrees of anisotropy, ranging from 0% to 36% for P-waves and 0.3% to 19.5% for S-waves. When averaged at all pressures, the anisot- ropy is 9.9% for the P-wave and 5.5% for the S-wave.

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Value of Diffusion Weighted Imaging and Apparent Diffusion Coefficient in Recent Cerebral Infarctions: A Correlative Study with Contrast Enhanced T1 Weighted Imaging

Value of Diffusion Weighted Imaging and Apparent Diffusion Coefficient in Recent Cerebral Infarctions: A Correlative Study with Contrast Enhanced T1 Weighted Imaging

anisotropy. A higher relative signal intensity in subacute thrombotic infarcts than in embolic in- farcts may be largely attributed to diffusion an- isotropy. Twelve of 20 ROIs of thrombotic infarcts were located in the centrum semiovale, the corona radiata, the internal capsule, the pons, and the me- dulla oblongata; where the neuronal fibers had a tendency to run suprainferiorly, they were nearly parallel to the orientation of diffusion-encoding gradient pairs, resulting in a high ADC and a low signal intensity on diffusion-weighted images in the contralateral brain tissue. Meanwhile, only four of 21 ROIs of embolic infarcts were placed in these regions. The relative ADC of subacute thrombotic infarcts to the contralateral normal brain tissue (0.77 6 0.35 mm 2 /s) was significantly lower than

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Diffusion Anisotropy in the Corpus Callosum

Diffusion Anisotropy in the Corpus Callosum

that allow the rapid and rotationally invariant imaging of water diffusion in vivo, imaging of the diffusion characteristics of water within the human brain is now possible. Specifically, by calculating the diffusion ten- sor, both the magnitude and directionality of water diffusion in major white-matter tracts can be character- ized (12–15). This knowledge leads to insights regarding the microscopic architecture of the white-matter tracts (13, 16). The purpose of this investigation was to deter- mine the regional diffusion characteristics in the normal human adult corpus callosum. We hypothesized that no significant regional variation in diffusion anisotropy within the corpus callosum is present and that diffusion anisotropy is constant regardless of the age or sex of the patient.

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Principal Component Analysis of Diffusion Tensor Images to Determine White Matter Injury Patterns Underlying Postconcussive Headache

Principal Component Analysis of Diffusion Tensor Images to Determine White Matter Injury Patterns Underlying Postconcussive Headache

BACKGROUND AND PURPOSE: Principal component analysis, a data-reduction algorithm, generates a set of principal components that are independent, linear combinations of the original dataset. Our study sought to use principal component analysis of fractional anisot- ropy maps to identify white matter injury patterns that correlate with posttraumatic headache after mild traumatic brain injury. MATERIALS AND METHODS: Diffusion tensor imaging and neurocognitive testing with the Immediate Post-Concussion Assessment and Cognitive Test were performed in 40 patients with mild traumatic brain injury and 24 without posttraumatic headache. Principal compo- nent analysis of coregistered fractional anisotropy maps was performed. Regression analysis of the major principal components was used to identify those correlated with posttraumatic headache. Finally, each principal component that correlated with posttraumatic headache was screened against other postconcussive symptoms and demographic factors.

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TA Anisotropy Summary

TA Anisotropy Summary

The main di ffi culty in identifying the origin of UHE- CRs is the loss of directional information due to magnetic field induced deflection. The deflection angle of a 60 EeV proton over a distance of 50 Mpc is estimated to be a few degrees assuming models with an intergalactic mag- netic field (IGMF) strength of 1 nG. Meanwhile, the esti- mated deflection by the galactic magnetic field (GMF) is between a few degrees and ten degrees, depending on the direction in the sky. If the highest-energy cosmic rays are protons coming from matter in the local universe such as the nearby galaxies, then the maximum amplitude of the cosmic-ray anisotropy above ∼ 60 EeV is expected to be detectable by the latest UHECR detectors [2].

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