47 CFR 90.689 - Field strength limits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false Field strength limits. 90.689 Section 90.689...-824/851-869 Mhz Band § 90.689 Field strength limits. (a) For purposes of implementing §§ 90.689... or measured field strength at any location on the border of the EA-based service area for EA...

47 CFR 90.689 - Field strength limits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 5 2010-10-01 2010-10-01 false Field strength limits. 90.689 Section 90.689...-824/851-869 Mhz Band § 90.689 Field strength limits. (a) For purposes of implementing §§ 90.689... or measured field strength at any location on the border of the EA-based service area for EA...

[Methodological aspects of functional neuroimaging at high field strength: a critical review].

PubMed

Scheef, L; Landsberg, M W; Boecker, H

2007-09-01

The last few years have proven that high field magnetic resonance imaging (MRI) is superior in nearly every way to conventional equipment up to 1.5 tesla (T). Following the global success of 3T-scanners in research institutes and medical practices, a new generation of MRI devices with field strengths of 7T and higher is now on the horizon. The introduction of ultra high fields has brought MRI technology closer to the physical limitations and increasingly greater costs are required to achieve this goal. This article provides a critical overview of the advantages and problems of functional neuroimaging using ultra high field strengths. This review is principally limited to T2*-based functional imaging techniques not dependent on contrast agents. The main issues include the significance of high field technology with respect to SNR, CNR, resolution, and sequences, as well as artifacts, noise exposure, and SAR. Of great relevance is the discussion of parallel imaging, which will presumably determine the further development of high and ultra high field strengths. Finally, the importance of high field strengths for functional neuroimaging is explained by selected publications.

Brownian motion of electrons in time-dependent magnetic fields.

NASA Technical Reports Server (NTRS)

Iverson, G. J.; Williams, R. M.

1973-01-01

The behavior of a weakly ionized plasma in slowly varying time-dependent magnetic fields is studied through an extension of Williamson's stochastic theory. In particular, attention is focused on the properties of electron diffusion in the plane perpendicular to the direction of the magnetic field, when the field strength is large. It is shown that, in the strong field limit, the classical 1/B-squared dependence of the perpendicular diffusion coefficient is obtained for two models in which the field B(t) is monotonic in t and for two models in which B(t) possesses at least one turning point.

Sunspot rotation. II. Effects of varying the field strength and twist of an emerging flux tube

NASA Astrophysics Data System (ADS)

Sturrock, Z.; Hood, A. W.

2016-09-01

Context. Observations of flux emergence indicate that rotational velocities may develop within sunspots. However, the dependence of this rotation on sub-photospheric field strength and twist remains largely unknown. Aims: We investigate the effects of varying the initial field strength and twist of an emerging sub-photospheric magnetic flux tube on the rotation of the sunspots at the photosphere. Methods: We consider a simple model of a stratified domain with a sub-photospheric interior layer and three overlying atmospheric layers. A twisted arched flux tube is inserted in the interior and is allowed to rise into the atmosphere. To achieve this, the magnetohydrodynamic equations are solved using the Lagrangian-remap code, Lare3d. We perform a parameter study by independently varying the sub-photospheric magnetic field strength and twist. Results: Altering the initial magnetic field strength and twist of the flux tube significantly affects the tube's evolution and the rotational motions that develop at the photosphere. The rotation angle, vorticity, and current show a direct dependence on the initial field strength. We find that an increase in field strength increases the angle through which the fieldlines rotate, the length of the fieldlines extending into the atmosphere, and the magnetic energy transported to the atmosphere. This also affects the amount of residual twist in the interior. The length of the fieldlines is crucial as we predict the twist per unit length equilibrates to a lower value on longer fieldlines. No such direct dependence is found when we modify the twist of the magnetic field owing to the complex effect this has on the tension force acting on the tube. However, there is still a clear ordering in quantities such as the rotation angle, helicity, and free energy with higher initial twist cases being related to sunspots that rotate more rapidly, transporting more helicity and magnetic energy to the atmosphere.

47 CFR 18.305 - Field strength limits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 1 2011-10-01 2011-10-01 false Field strength limits. 18.305 Section 18.305... Standards § 18.305 Field strength limits. (a) ISM equipment operating on a frequency specified in § 18.301... strength levels of emissions which lie outside the bands specified in § 18.301, unless otherwise indicated...

AC-electric field dependent electroformation of giant lipid vesicles.

PubMed

Politano, Timothy J; Froude, Victoria E; Jing, Benxin; Zhu, Yingxi

2010-08-01

Giant vesicles of larger than 5 microm, which have been of intense interest for their potential as drug delivery vehicles and as a model system for cell membranes, can be rapidly formed from a spin-coated lipid thin film under an electric field. In this work, we explore the AC-field dependent electroformation of giant lipid vesicles in aqueous media over a wide range of AC-frequency from 1 Hz to 1 MHz and peak-to-peak field strength from 0.212 V/mm to 40 V/mm between two parallel conducting electrode surfaces. By using fluorescence microscopy, we perform in-situ microscopic observations of the structural evolution of giant vesicles formed from spin-coated lipid films under varied uniform AC-electric fields. The real-time observation of bilayer bulging from the lipid film, vesicle growth and fusing further examine the critical role of AC-induced electroosmotic flow of surrounding fluids for giant vesicle formation. A rich AC-frequency and field strength phase diagram is obtained experimentally to predict the AC-electroformation of giant unilamellar vesicles (GUVs) of l-alpha-phosphatidylcholine, where a weak dependence of vesicle size on AC-frequency is observed at low AC-field voltages, showing decreased vesicle size with a narrowed size distribution with increased AC-frequency. Formation of vesicles was shown to be constrained by an upper field strength of 10 V/mm and an upper AC-frequency of 10 kHz. Within these parameters, giant lipid vesicles were formed predominantly unilamellar and prevalent across the entire electrode surfaces. Copyright 2010 Elsevier B.V. All rights reserved.

47 CFR 73.686 - Field strength measurements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... earth radius, of the largest available scale. (c) Collection of field strength data to determine... through the measurement area. (iii) Antenna elevation. When field strength is being measured for a one....686 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO...

47 CFR 73.686 - Field strength measurements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... earth radius, of the largest available scale. (c) Collection of field strength data to determine... through the measurement area. (iii) Antenna elevation. When field strength is being measured for a one....686 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO...

47 CFR 73.686 - Field strength measurements.

Code of Federal Regulations, 2011 CFR

2011-10-01

... earth radius, of the largest available scale. (c) Collection of field strength data to determine... through the measurement area. (iii) Antenna elevation. When field strength is being measured for a one....686 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO...

47 CFR 73.686 - Field strength measurements.

Code of Federal Regulations, 2012 CFR

2012-10-01

... earth radius, of the largest available scale. (c) Collection of field strength data to determine... through the measurement area. (iii) Antenna elevation. When field strength is being measured for a one....686 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO...

Field dependent magnetic anisotropy of Ga0.2Fe0.8 thin films

NASA Astrophysics Data System (ADS)

Resnick, Damon A.; McClure, A.; Kuster, C. M.; Rugheimer, P.; Idzerda, Y. U.

2011-04-01

Using longitudinal MOKE in combination with a variable strength rotating magnetic field, called the rotational MOKE (ROTMOKE) method, we show that the magnetic anisotropy for a Ga0.2Fe0.8 single crystal film with a thickness of 17 nm, grown on GaAs (001) with a thick ZnSe buffer layer, depends linearly on the strength of the applied magnetic field. The torque moment curves generated using ROTMOKE are well fit with a model that accounts for the uniaxial, cubic, or fourfold anisotropy, as well as additional terms with a linear dependence on the applied magnetic field. The uniaxial and cubic anisotropy fields, taken from both the hard and the easy axis scans, are seen to remain field independent. The field dependent terms are evidence of a large affect of the magnetostriction and its contribution to the effective magnetic anisotropy in GaxFe1-x thin films.

Spin-dependent polarizabilities of hydrogenic atoms in magnetic fields of arbitrary strength

NASA Astrophysics Data System (ADS)

Castner, T. G.; Dexter, D. L.; Druger, S. D.

1981-12-01

Utilizing the magnetic field-dependent spin-orbit interaction, the relativistic correction to the Zeeman energy, and the usual diamagnetic interaction, we have calculated spin-dependent electrical polarizabilities of hydrogenic atoms using the Hassé variational approach. The polarizabilities α(↑) and α(↓) for the two spin directions have been obtained for the electric field both parallel and perpendicular to the magnetic field Hz in the weak-field (γ<<1), intermediate-field (γ~1), and strong-field (γ>>1) limits, where γ=(ɛ2ℏ3Hzm*2e3c), with ɛ a static dielectric constant and m* an isotropic effective mass. The results for hydrogen atoms (ɛ=1 and m*=m) in the weak-field limit yield [α(↓)-α(↑)]α(0)~2.31α2fsγ (αfs=1137) with a negligible anisotropy. In the strong-field limit [α⊥(↓)-α⊥(↑)] falls precipitously while [α∥(↓)-α∥(↑)] continues to increase up to at least γ=104, but more slowly than linearly with γ. The spin-independent quantities [α∥(↓)+α∥(↑)] and [α⊥(↓)+α⊥(↑)] are discussed in the intermediate- and high-field limits and represent an extension of the earlier low-field results obtained by Dexter. The implications of these results for shallow-donor impurity atoms in semiconductors and for hydrogen-atom atmospheres of magnetic white dwarfs and neutron stars are briefly considered. The effects of the dramatic shrinkage of the electron's wave function on the spin Zeeman energy and the electron-proton hyperfine interaction are also discussed.

Similarity of SABRE field dependence in chemically different substrates

NASA Astrophysics Data System (ADS)

Dücker, Eibe B.; Kuhn, Lars T.; Münnemann, Kerstin; Griesinger, Christian

2012-01-01

The Non-Hydrogenative Parahydrogen-Induced Polarization (NH-PHIP) technique, which is referred to as Signal Amplification by Reversible Exchange (SABRE), has been reported to be applicable to various substrates and catalysts. For more detailed studies, pyridine was mainly examined in the past. Here, we examined several pyrazole derivatives towards their amenability to this method using Crabtree's Catalyst, which is the polarization transfer catalyst that is best documented. Additionally, the dependence of the signal enhancement on the field strength, at which the polarization step takes place, was examined for pyridine and four different pyrazoles. To achieve this, the polarization step was performed at numerous previously determined magnetic fields in the stray field of the NMR spectrometer. The substrate dependence of the field dependence proved to be relatively small for the different pyrazoles and a strong correlation to the field dependence for pyridine was observed. Reducing the number of spins in the catalyst by deuteration leads to increased enhancement. This indicates that more work has to be invested in order to be able to reproduce the SABRE field dependence by simulations.

Rapid Transition of the Hole Rashba Effect from Strong Field Dependence to Saturation in Semiconductor Nanowires

NASA Astrophysics Data System (ADS)

Luo, Jun-Wei; Li, Shu-Shen; Zunger, Alex

2017-09-01

The electric field manipulation of the Rashba spin-orbit coupling effects provides a route to electrically control spins, constituting the foundation of the field of semiconductor spintronics. In general, the strength of the Rashba effects depends linearly on the applied electric field and is significant only for heavy-atom materials with large intrinsic spin-orbit interaction under high electric fields. Here, we illustrate in 1D semiconductor nanowires an anomalous field dependence of the hole (but not electron) Rashba effect (HRE). (i) At low fields, the strength of the HRE exhibits a steep increase with the field so that even low fields can be used for device switching. (ii) At higher fields, the HRE undergoes a rapid transition to saturation with a giant strength even for light-atom materials such as Si (exceeding 100 meV Å). (iii) The nanowire-size dependence of the saturation HRE is rather weak for light-atom Si, so size fluctuations would have a limited effect; this is a key requirement for scalability of Rashba-field-based spintronic devices. These three features offer Si nanowires as a promising platform for the realization of scalable complementary metal-oxide-semiconductor compatible spintronic devices.

47 CFR 18.305 - Field strength limits.

Code of Federal Regulations, 2010 CFR

2010-10-01

...) Field strength limit (uV/m) Distance (meters) Any type unless otherwise specified (miscellaneous) Any...Any 2515 300300 Ultrasonic Below 490 kHz Below 500500 or more 2,400/F(kHz)2,400/F(kHz)× SQRT(power/500... kHzOn or above 90 kHz AnyAny 1,500300 430 430 1 Field strength may not exceed 10 μV/m at 1600 meters...

Rapid Transition of the Hole Rashba Effect from Strong Field Dependence to Saturation in Semiconductor Nanowires.

PubMed

Luo, Jun-Wei; Li, Shu-Shen; Zunger, Alex

2017-09-22

The electric field manipulation of the Rashba spin-orbit coupling effects provides a route to electrically control spins, constituting the foundation of the field of semiconductor spintronics. In general, the strength of the Rashba effects depends linearly on the applied electric field and is significant only for heavy-atom materials with large intrinsic spin-orbit interaction under high electric fields. Here, we illustrate in 1D semiconductor nanowires an anomalous field dependence of the hole (but not electron) Rashba effect (HRE). (i) At low fields, the strength of the HRE exhibits a steep increase with the field so that even low fields can be used for device switching. (ii) At higher fields, the HRE undergoes a rapid transition to saturation with a giant strength even for light-atom materials such as Si (exceeding 100 meV Å). (iii) The nanowire-size dependence of the saturation HRE is rather weak for light-atom Si, so size fluctuations would have a limited effect; this is a key requirement for scalability of Rashba-field-based spintronic devices. These three features offer Si nanowires as a promising platform for the realization of scalable complementary metal-oxide-semiconductor compatible spintronic devices.

Delayed Ego Strength Development in Opioid Dependent Adolescents and Young Adults.

PubMed

Abramoff, Benjamin A; Lange, Hannah L H; Matson, Steven C; Cottrill, Casey B; Bridge, Jeffrey A; Abdel-Rasoul, Mahmoud; Bonny, Andrea E

2015-01-01

Objective. To evaluate ego strengths, in the context of Erikson's framework, among adolescents and young adults diagnosed with opioid dependence as compared to non-drug using youth. Methods. Opioid dependent (n = 51) and non-drug using control (n = 31) youth completed the self-administered Psychosocial Inventory of Ego Strengths (PIES). The PIES assesses development in the framework of Erikson's ego strength stages. Multivariate linear regression modeling assessed the independent association of the primary covariate (opioid dependent versus control) as well as potential confounding variables (e.g., psychiatric comorbidities, intelligence) with total PIES score. Results. Mean total PIES score was significantly lower in opioid dependent youth (231.65 ± 30.39 opioid dependent versus 270.67 ± 30.06 control; p < 0.01). Evaluation of the PIES subscores found significant (p < 0.05) delays in all ego strength areas (hope, will, purpose, competence, fidelity, love, care, and wisdom). When adjusting for potential confounders, opioid dependence remained a significant (p < 0.001) independent predictor of total PIES score. Conclusion. Adolescents with opioid dependence demonstrated significant delays in ego strength development. A treatment approach acknowledging this delay may be needed in the counseling and treatment of adolescents with opioid dependence.

Delayed Ego Strength Development in Opioid Dependent Adolescents and Young Adults

PubMed Central

Abramoff, Benjamin A.; Lange, Hannah L. H.; Matson, Steven C.; Cottrill, Casey B.; Bridge, Jeffrey A.; Abdel-Rasoul, Mahmoud; Bonny, Andrea E.

2015-01-01

Objective. To evaluate ego strengths, in the context of Erikson's framework, among adolescents and young adults diagnosed with opioid dependence as compared to non-drug using youth. Methods. Opioid dependent (n = 51) and non-drug using control (n = 31) youth completed the self-administered Psychosocial Inventory of Ego Strengths (PIES). The PIES assesses development in the framework of Erikson's ego strength stages. Multivariate linear regression modeling assessed the independent association of the primary covariate (opioid dependent versus control) as well as potential confounding variables (e.g., psychiatric comorbidities, intelligence) with total PIES score. Results. Mean total PIES score was significantly lower in opioid dependent youth (231.65 ± 30.39 opioid dependent versus 270.67 ± 30.06 control; p < 0.01). Evaluation of the PIES subscores found significant (p < 0.05) delays in all ego strength areas (hope, will, purpose, competence, fidelity, love, care, and wisdom). When adjusting for potential confounders, opioid dependence remained a significant (p < 0.001) independent predictor of total PIES score. Conclusion. Adolescents with opioid dependence demonstrated significant delays in ego strength development. A treatment approach acknowledging this delay may be needed in the counseling and treatment of adolescents with opioid dependence. PMID:26664819

Ionospheric Longitude Storm Dependence Upon the Magnitude of the Earth's Magnetic Field

NASA Astrophysics Data System (ADS)

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

2007-12-01

The Earth's magnetic field in the ionosphere is understood to be non-dipolar with significant deviations in magnitude and orientation across the globe. This study models the mid-latitude ionospheric response to a geomagnetic storm for different idealizations of the Earth's magnetic field strength. In so doing the study addresses the question whether or not a longitude dependence in ionospheric storm responses could exist due to the longitude dependence of the magnetic field [ Huang et al., 2005], and if so, how significant is the effect? The mechanism by which the magnetic field magnitude has a first order effect is through the E x B plasma drift that has a vertical components, i.e., usually described as a meridional plasma drift caused by the zonal electric field. This vertical drift is inversely proportional to the magnitude of the magnetic field. A vertical drift raises or lowers the F-region into regions of lesser or greater recombination rates respectively, hence, directly affecting the plasma density. The Utah State University (USU) Time Dependent Ionospheric Model (TDIM) uses a tilted dipole magnetic field model to represent the Earth's field. The magnitude of magnetic field is specified by the dipole moment, in fact, the magnetic field strength on the surface of the Earth at the magnetic equator. Changing this one parameter enables studies to be made under identical storm conditions of the effect of different magnetic field magnitudes. For this study the normal 0.31 Gauss surface magnetic field is replaced by 0.24 Gauss and 0.41 Gauss. These two numbers represent the magnitude of the minimum and maximum observed field strength around the Earth equatorial region. The TDIM results are shown for a storm simulation that occurred on 5-6 November 2001. For otherwise identical model conditions and drivers, the difference in magnetic field strength results in a factor of 2 difference in TEC, NmF2, etc. Since the magnetic field magnitude is weakest in the Atlantic

Electronegativity, charge transfer, crystal field strength, and the point charge model revisited.

PubMed

Tanner, Peter A; Ning, Lixin

2013-02-21

Although the optical spectra of LnCl(6)(3-) systems are complex, only two crystal field parameters, B(40) and B(60), are required to model the J-multiplet crystal field splittings in octahedral symmetry. It is found that these parameters exhibit R(-5) and R(-7) dependence, respectively, upon the ionic radius Ln(3+)(VI), but not upon the Ln-Cl distance. More generally, the crystal field strengths of LnX(6) systems (X = Br, Cl, F, O) exhibit linear relationships with ligand electronegativity, charge transfer energy, and fractional ionic character of the Ln-X bond.

Energy flux determines magnetic field strength of planets and stars.

PubMed

Christensen, Ulrich R; Holzwarth, Volkmar; Reiners, Ansgar

2009-01-08

The magnetic fields of Earth and Jupiter, along with those of rapidly rotating, low-mass stars, are generated by convection-driven dynamos that may operate similarly (the slowly rotating Sun generates its field through a different dynamo mechanism). The field strengths of planets and stars vary over three orders of magnitude, but the critical factor causing that variation has hitherto been unclear. Here we report an extension of a scaling law derived from geodynamo models to rapidly rotating stars that have strong density stratification. The unifying principle in the scaling law is that the energy flux available for generating the magnetic field sets the field strength. Our scaling law fits the observed field strengths of Earth, Jupiter, young contracting stars and rapidly rotating low-mass stars, despite vast differences in the physical conditions of the objects. We predict that the field strengths of rapidly rotating brown dwarfs and massive extrasolar planets are high enough to make them observable.

Dependence of streamer density on electric field strength on positive electrode

NASA Astrophysics Data System (ADS)

Koki, Nakamura; Takahumi, Okuyama; Wang, Douyan; Takao, N.; Hidenori, Akiyama; Kumamoto University Collaboration

2015-09-01

Pulsed streamer discharge plasma, a type of non-thermal plasma, is known as generation method of reactive radicals and ozone and treatment of exhausted gas. From our previous research, the distance between electrodes has been considered a very important parameter for applications using pulsed streamer discharge. However, how the distance between electrodes affects the pulsed discharge hasn't been clarified. In this research, the propagation process of pulsed streamer discharge in a wire-plate electrode was observed using an ICCD camera for 4 electrodes having different distance between electrodes. The distance between electrodes was changeable at 45 mm, 40 mm, 35 mm, and 30 mm. The results show that, when the distance between electrodes was shortened, applied voltage with a pulse duration of 100 ns decreased from 80 to 60.3 kV. Conversely, discharge current increased from 149 to 190 A. Streamer head velocity became faster. On the other hand, Streamer head density at onset time of streamer head propagation didn't change. This is considered due to the electric field strength of streamer head at that time, in result, it was about 14 kV/mm under each distance between electrodes.

Potential Measurements of Coronal Magnetic Field Strengths Using Line Ratios in EUV and X-ray Spectra

NASA Astrophysics Data System (ADS)

Beiersdorfer, Peter; Scofield, J. H.; Lepson, J. K.; Osten, R.; Smith, R. K.

2006-09-01

We will discuss a class of lines from highly charged ions that are sensitive to the strength of the ambient magnetic field. Calculations show that the magnitude of field strengths that can be measured ranges from a few hundred gauss to several tens of kilogauss depending on the particular ion emitting the line. These calculations have been verified in the laboratory by studying the spectra of S VII, Ar IX, and Fe XVII. As an example of the diagnostic utility, the possibility of using these lines to determine the coronal magnetic field strength of Prox Cen will be presented. This work was supported by NASA Astronomy and Physics Research and Analysis program work order NNH04AA751, and was performed under the auspices of the Department of Energy by the University of California Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.

47 CFR 27.804 - Field strength limits at WMTS facility.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 2 2010-10-01 2010-10-01 false Field strength limits at WMTS facility. 27.804... MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES 1.4 GHz Band § 27.804 Field strength limits at WMTS facility. For any operation in the 1392-1395 MHz band, the predicted or measured field strength—into the WMTS band...

47 CFR 27.804 - Field strength limits at WMTS facility.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 2 2011-10-01 2011-10-01 false Field strength limits at WMTS facility. 27.804... MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES 1.4 GHz Band § 27.804 Field strength limits at WMTS facility. For any operation in the 1392-1395 MHz band, the predicted or measured field strength—into the WMTS band...

Electrohydrodynamics in nanochannels coated by mixed polymer brushes: effects of electric field strength and solvent quality

NASA Astrophysics Data System (ADS)

Cao, Qianqian; Tian, Xiu; You, Hao

2018-04-01

We examine the electrohydrodynamics in mixed polymer brush-coated nanochannels and the conformational dynamics of grafted polymers using molecular dynamics simulations. Charged (A) and neutral polymers (B) are alternately grafted on the channel surfaces. The effects of the electric field strength and solvent quality are addressed in detail. The dependence of electroosmotic flow characteristics and polymer conformational behavior on the solvent quality is influenced due to the change of the electric field strength. The enhanced electric field induces a collapse of the neutral polymer chains which adopt a highly extended conformation along the flow direction. However, the thickness of the charged polymer layer is affected weakly by the electric field, and even a slight swelling is identified for the A-B attraction case, implying the conformational coupling between two polymer species. Furthermore, the charged polymer chains incline entirely towards the electric field direction oppositely to the flow direction. More importantly, unlike the neutral polymer chains, the shape factor of the charged polymer chains, which is used to describe the overall shape of polymer chains, is reduced significantly with increasing the electric field strength, corresponding to a more coiled structure.

Strength of Gamma Rhythm Depends on Normalization

PubMed Central

Ray, Supratim; Ni, Amy M.; Maunsell, John H. R.

2013-01-01

Neuronal assemblies often exhibit stimulus-induced rhythmic activity in the gamma range (30–80 Hz), whose magnitude depends on the attentional load. This has led to the suggestion that gamma rhythms form dynamic communication channels across cortical areas processing the features of behaviorally relevant stimuli. Recently, attention has been linked to a normalization mechanism, in which the response of a neuron is suppressed (normalized) by the overall activity of a large pool of neighboring neurons. In this model, attention increases the excitatory drive received by the neuron, which in turn also increases the strength of normalization, thereby changing the balance of excitation and inhibition. Recent studies have shown that gamma power also depends on such excitatory–inhibitory interactions. Could modulation in gamma power during an attention task be a reflection of the changes in the underlying excitation–inhibition interactions? By manipulating the normalization strength independent of attentional load in macaque monkeys, we show that gamma power increases with increasing normalization, even when the attentional load is fixed. Further, manipulations of attention that increase normalization increase gamma power, even when they decrease the firing rate. Thus, gamma rhythms could be a reflection of changes in the relative strengths of excitation and normalization rather than playing a functional role in communication or control. PMID:23393427

Rats avoid high magnetic fields: dependence on an intact vestibular system

PubMed Central

Houpt, Thomas A.; Cassell, Jennifer A.; Riccardi, Christina; DenBleyker, Megan D.; Hood, Alison; Smith, James C.

2009-01-01

Summary HOUPT, T.A., J.A. CASSELL, C. RICCARDI, M.D. DENBLEYKER, A. HOOD, AND J.C. SMITH. Rats avoid high magnetic fields: dependence on an intact vestibular system. PHYSIOL BEHAV 00(0)000-000, 2006. High strength static magnetic fields are thought to be benign and largely undetectable by mammals. As magnetic resonance imaging (MRI) machines increase in strength, however, potential aversive effects may become clinically relevant. Here we report that rats find entry into a 14.1 T magnet aversive, and that they can detect and avoid entry into the magnet at a point where the magnetic field is 2 T or lower. Rats were trained to climb a ladder through the bore of a 14.1 T superconducting magnet. After their first climb into 14.1 T, most rats refused to re-enter the magnet or climb past the 2 T field line. This result was confirmed in a resistive magnet in which the magnetic field was varied from 1 to 14 T. Detection and avoidance required the vestibular apparatus of the inner ear, because labyrinthectomized rats readily traversed the magnet. The inner ear is a novel site for magnetic field transduction in mammals, but perturbation of the vestibular apparatus would be consistent with human reports of vertigo and nausea around high strength MRI machines. PMID:17585969

Microchip Electrophoresis at Elevated Temperatures and High Separation Field Strengths

PubMed Central

Mitra, Indranil; Marczak, Steven P.; Jacobson, Stephen C.

2014-01-01

We report free-solution microchip electrophoresis performed at elevated temperatures and high separation field strengths. We used microfluidic devices with 11-cm long separation channels to conduct separations at temperatures between 22 (ambient) and 45 °C and field strengths from 100 to 1000 V/cm. To evaluate separation performance, N-glycans were used as a model system and labeled with 8-aminopyrene-1,3,6-trisulfonic acid to impart charge for electrophoresis and render them fluorescent. Typically, increased diffusivity at higher temperatures leads to increased axial dispersion and poor separation performance; however, we demonstrate that sufficiently high separation field strengths can be used to offset the impact of increased diffusivity in order to maintain separation efficiency. Efficiencies for these free-solution separations are the same at temperatures of 25, 35, and 45 °C with separation field strengths ≥500 V/cm. PMID:24114979

47 CFR 73.61 - AM directional antenna field strength measurements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 4 2014-10-01 2014-10-01 false AM directional antenna field strength... RADIO SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.61 AM directional antenna field strength measurements. (a) Each AM station using a directional antenna with monitoring point locations...

47 CFR 73.61 - AM directional antenna field strength measurements.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 4 2011-10-01 2011-10-01 false AM directional antenna field strength... RADIO SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.61 AM directional antenna field strength measurements. (a) Each AM station using a directional antenna with monitoring point locations...

47 CFR 73.61 - AM directional antenna field strength measurements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 4 2013-10-01 2013-10-01 false AM directional antenna field strength... RADIO SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.61 AM directional antenna field strength measurements. (a) Each AM station using a directional antenna with monitoring point locations...

47 CFR 73.61 - AM directional antenna field strength measurements.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 4 2012-10-01 2012-10-01 false AM directional antenna field strength... RADIO SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.61 AM directional antenna field strength measurements. (a) Each AM station using a directional antenna with monitoring point locations...

47 CFR 73.61 - AM directional antenna field strength measurements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false AM directional antenna field strength... RADIO SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.61 AM directional antenna field strength measurements. (a) Each AM station using a directional antenna with monitoring point locations...

47 CFR 90.359 - Field strength limits for EA-licensed LMS systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false Field strength limits for EA-licensed LMS... § 90.359 Field strength limits for EA-licensed LMS systems. EA-licensed multilateration systems shall limit the field strength of signals transmitted from their base stations to 47 dBuV/m at their EA...

Scale-dependent measurements of meteorite strength: Implications for asteroid fragmentation

NASA Astrophysics Data System (ADS)

Cotto-Figueroa, Desireé; Asphaug, Erik; Garvie, Laurence A. J.; Rai, Ashwin; Johnston, Joel; Borkowski, Luke; Datta, Siddhant; Chattopadhyay, Aditi; Morris, Melissa A.

2016-10-01

Measuring the strengths of asteroidal materials is important for developing mitigation strategies for potential Earth impactors and for understanding properties of in situ materials on asteroids during human and robotic exploration. Studies of asteroid disruption and fragmentation have typically used the strengths determined from terrestrial analog materials, although questions have been raised regarding the suitability of these materials. The few published measurements of meteorite strength are typically significantly greater than those estimated from the stratospheric breakup of meter-sized meteoroids. Given the paucity of relevant strength data, the scale-varying strength properties of meteoritic and asteroidal materials are poorly constrained. Based on our uniaxial failure studies of centimeter-sized cubes of a carbonaceous and ordinary chondrite, we develop the first Weibull failure distribution analysis of meteorites. This Weibull distribution projected to meter scales, overlaps the strengths determined from asteroidal airbursts and can be used to predict properties of to the 100 m scale. In addition, our analysis shows that meter-scale boulders on asteroids are significantly weaker than small pieces of meteorites, while large meteorites surviving on Earth are selected by attrition. Further, the common use of terrestrial analog materials to predict scale-dependent strength properties significantly overestimates the strength of meter-sized asteroidal materials and therefore is unlikely well suited for the modeling of asteroid disruption and fragmentation. Given the strength scale-dependence determined for carbonaceous and ordinary chondrite meteorites, our results suggest that boulders of similar composition on asteroids will have compressive strengths significantly less than typical terrestrial rocks.

47 CFR 90.771 - Field strength limits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Policies Governing the Licensing and Use of Phase II Ea, Regional and Nationwide Systems § 90.771 Field... transmit frequencies, of EA and Regional licensees may not exceed a predicted 38 dBu field strength at... required in paragraph (a) of this section if all affected, co-channel EA and Regional licensees agree to...

47 CFR 90.771 - Field strength limits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... Policies Governing the Licensing and Use of Phase II Ea, Regional and Nationwide Systems § 90.771 Field... transmit frequencies, of EA and Regional licensees may not exceed a predicted 38 dBu field strength at... required in paragraph (a) of this section if all affected, co-channel EA and Regional licensees agree to...

Optical Field-Strength Polarization of Two-Mode Single-Photon States

ERIC Educational Resources Information Center

Linares, J.; Nistal, M. C.; Barral, D.; Moreno, V.

2010-01-01

We present a quantum analysis of two-mode single-photon states based on the probability distributions of the optical field strength (or position quadrature) in order to describe their quantum polarization characteristics, where polarization is understood as a significative confinement of the optical field-strength values on determined regions of…

Effects of magnetic field strength and particle aggregation on relaxivity of ultra-small dual contrast iron oxide nanoparticles

NASA Astrophysics Data System (ADS)

Ta, Hang T.; Li, Zhen; Wu, Yuao; Cowin, Gary; Zhang, Shaohua; Yago, Anya; Whittaker, Andrew K.; Xu, Zhi Ping

2017-11-01

This study aims to compare the relaxivities of ultra-small dual positive and negative contrast iron oxide nanoparticles (DCION) at different magnetic field strengths ranging from 4.7 to 16.4 T at physiological temperatures; and to investigate the effect of particle aggregation on relaxivities. Relaxivities of DCIONs were determined by magnetic resonance imaging scanners at 4.7, 7, 9.4, and 16.4 T. Both longitudinal (T 1) and transverse relaxation times (T 2) were measured by appropriate spin-echo sequences. It has been found that both longitudinal and transverse relaxivities are significantly dependent on the magnetic field strength. Particle aggregation also strongly affects the relaxivities. Awareness of the field strength and particle colloid stability is crucial for the comparison and evaluation of relaxivity values of these ultra-small iron oxide nanoparticles, and also for their medical applications as contrast agents.

ELF Field Strength Measurements Made in Connecticut During 1974

DTIC Science & Technology

1975-10-01

Ionospheric Phenomena on Extremely Low Frequency ( ELF ) Propagation," IEEE Transactions on Communications , vol. COM-22, no. 4, 1974, pp. 484-492...34f" ""WW" I I W»*-«P ’^ AD-A016 795 ELF FIELD STRENGTH MEASUREMENTS MADE IN CONNECTICUT DURING 1974 Peter R. Bannister...Report 4927 CD rH O ELF Field Strength Measurements Made In Connecticut During 1974 PETER R. BANNISTER FREDERICK J. WILLIAMS Submarin

Relationship between magnetic field strength and magnetic-resonance-related acoustic noise levels.

PubMed

Moelker, Adriaan; Wielopolski, Piotr A; Pattynama, Peter M T

2003-02-01

The need for better signal-to-noise ratios and resolution has pushed magnetic resonance imaging (MRI) towards high-field MR-scanners for which only little data on MR-related acoustic noise production have been published. The purpose of this study was to validate the theoretical relationship of sound pressure level (SPL) and static magnetic field strength. This is relevant for allowing adequate comparisons of acoustic data of MR systems at various magnetic field strengths. Acoustic data were acquired during various pulse sequences at field strengths of 0.5, 1.0, 1.5 and 2.0 Tesla using the same MRI unit by means of a Helicon rampable magnet. Continuous-equivalent, i.e. time-averaged, linear SPLs and 1/3-octave band frequencies were recorded. Ramping from 0.5 to 1.0 Tesla and from 1.0 to 2.0 Tesla resulted in an SPL increase of 5.7 and 5.2 dB(L), respectively, when averaged over the various pulse sequences. Most of the acoustic energy was in the 1-kHz frequency band, irrespective of magnetic field strength. The relation between field strength and SPL was slightly non-linear, i.e. a slightly less increase at higher field strengths, presumably caused by the elastic properties of the gradient coil encasings.

[3 Tesla MRI: successful results with higher field strengths].

PubMed

Schmitt, F; Grosu, D; Mohr, C; Purdy, D; Salem, K; Scott, K T; Stoeckel, B

2004-01-01

pancreas. The ability to increase resolution for musculoskeletal imaging has provided previously unseen detail. Bone structure, cartilage, and tendons and ligaments can be clearly visualized and pathology more easily detected due to an increased image quality. As the increase in field strength continues, a push to look at 7T has begun. The design philosophy is to keep the system as similar as possible, while changing only the frequency-dependent components. To date, both animal and human imaging have been performed on a whole body 7T scanner. Results show promise for both detailed imaging and functional MRI, but the road ahead is too long to be able to predict where it will end. The move toward higher field strengths is an exciting adventure in which 3T plays the role of trailblazer.

47 CFR 2.1053 - Measurements required: Field strength of spurious radiation.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 1 2011-10-01 2011-10-01 false Measurements required: Field strength of spurious radiation. 2.1053 Section 2.1053 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL... Procedures Certification § 2.1053 Measurements required: Field strength of spurious radiation. (a...

47 CFR 2.1053 - Measurements required: Field strength of spurious radiation.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 1 2014-10-01 2014-10-01 false Measurements required: Field strength of spurious radiation. 2.1053 Section 2.1053 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL... Procedures Certification § 2.1053 Measurements required: Field strength of spurious radiation. (a...

47 CFR 2.1053 - Measurements required: Field strength of spurious radiation.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 1 2013-10-01 2013-10-01 false Measurements required: Field strength of spurious radiation. 2.1053 Section 2.1053 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL... Procedures Certification § 2.1053 Measurements required: Field strength of spurious radiation. (a...

Low-field one-dimensional and direction-dependent relaxation imaging of bovine articular cartilage

NASA Astrophysics Data System (ADS)

Rössler, Erik; Mattea, Carlos; Mollova, Ayret; Stapf, Siegfried

2011-12-01

The structure of articular cartilage is separated into three layers of differently oriented collagen fibers, which is accompanied by a gradient of increasing glycosaminoglycan (GAG) and decreasing water concentration from the top layer towards the bone interface. The combined effect of these structural variations results in a change of the longitudinal and transverse relaxation times as a function of the distance from the cartilage surface. In this paper, this dependence is investigated at a magnetic field strength of 0.27 T with a one-dimensional depth resolution of 50 μm on bovine hip and stifle joint articular cartilage. By employing this method, advantage is taken of the increasing contrast of the longitudinal relaxation rate found at lower magnetic field strengths. Furthermore, evidence for an orientational dependence of relaxation times with respect to an axis normal to the surface plane is given, an observation that has recently been reported using high-field MRI and that was explained by preferential orientations of collagen bundles in each of the three cartilage zones. In order to quantify the extent of a further contrast mechanism and to estimate spatially dependent glycosaminoglycan concentrations, the data are supplemented by proton relaxation times that were acquired in bovine articular cartilage that was soaked in a 0.8 mM aqueous Gd ++ solution.

Educational application for visualization and analysis of electric field strength in multiple electrode electroporation.

PubMed

Mahnič-Kalamiza, Samo; Kotnik, Tadej; Miklavčič, Damijan

2012-10-30

Electrochemotherapy is a local treatment that utilizes electric pulses in order to achieve local increase in cytotoxicity of some anticancer drugs. The success of this treatment is highly dependent on parameters such as tissue electrical properties, applied voltages and spatial relations in placement of electrodes that are used to establish a cell-permeabilizing electric field in target tissue. Non-thermal irreversible electroporation techniques for ablation of tissue depend similarly on these parameters. In the treatment planning stage, if oversimplified approximations for evaluation of electric field are used, such as U/d (voltage-to-distance ratio), sufficient field strength may not be reached within the entire target (tumor) area, potentially resulting in treatment failure. In order to provide an aid in education of medical personnel performing electrochemotherapy and non-thermal irreversible electroporation for tissue ablation, assist in visualizing the electric field in needle electrode electroporation and the effects of changes in electrode placement, an application has been developed both as a desktop- and a web-based solution. It enables users to position up to twelve electrodes in a plane of adjustable dimensions representing a two-dimensional slice of tissue. By means of manipulation of electrode placement, i.e. repositioning, and the changes in electrical parameters, the users interact with the system and observe the resulting electrical field strength established by the inserted electrodes in real time. The field strength is calculated and visualized online and instantaneously reflects the desired changes, dramatically improving the user friendliness and educational value, especially compared to approaches utilizing general-purpose numerical modeling software, such as finite element modeling packages. In this paper we outline the need and offer a solution in medical education in the field of electroporation-based treatments, e.g. primarily

Technique for Predicting the RF Field Strength Inside an Enclosure

NASA Technical Reports Server (NTRS)

Hallett, M.; Reddell, J.

1998-01-01

This Memorandum presents a simple analytical technique for predicting the RF electric field strength inside an enclosed volume in which radio frequency radiation occurs. The technique was developed to predict the radio frequency (RF) field strength within a launch vehicle's fairing from payloads launched with their telemetry transmitters radiating and to the impact of the radiation on the vehicle and payload. The RF field strength is shown to be a function of the surface materials and surface areas. The method accounts for RF energy losses within exposed surfaces, through RF windows, and within multiple layers of dielectric materials which may cover the surfaces. This Memorandum includes the rigorous derivation of all equations and presents examples and data to support the validity of the technique.

Application of Quantitative MRI for Brain Tissue Segmentation at 1.5 T and 3.0 T Field Strengths

PubMed Central

West, Janne; Blystad, Ida; Engström, Maria; Warntjes, Jan B. M.; Lundberg, Peter

2013-01-01

Background Brain tissue segmentation of white matter (WM), grey matter (GM), and cerebrospinal fluid (CSF) are important in neuroradiological applications. Quantitative Mri (qMRI) allows segmentation based on physical tissue properties, and the dependencies on MR scanner settings are removed. Brain tissue groups into clusters in the three dimensional space formed by the qMRI parameters R1, R2 and PD, and partial volume voxels are intermediate in this space. The qMRI parameters, however, depend on the main magnetic field strength. Therefore, longitudinal studies can be seriously limited by system upgrades. The aim of this work was to apply one recently described brain tissue segmentation method, based on qMRI, at both 1.5 T and 3.0 T field strengths, and to investigate similarities and differences. Methods In vivo qMRI measurements were performed on 10 healthy subjects using both 1.5 T and 3.0 T MR scanners. The brain tissue segmentation method was applied for both 1.5 T and 3.0 T and volumes of WM, GM, CSF and brain parenchymal fraction (BPF) were calculated on both field strengths. Repeatability was calculated for each scanner and a General Linear Model was used to examine the effect of field strength. Voxel-wise t-tests were also performed to evaluate regional differences. Results Statistically significant differences were found between 1.5 T and 3.0 T for WM, GM, CSF and BPF (p<0.001). Analyses of main effects showed that WM was underestimated, while GM and CSF were overestimated on 1.5 T compared to 3.0 T. The mean differences between 1.5 T and 3.0 T were -66 mL WM, 40 mL GM, 29 mL CSF and -1.99% BPF. Voxel-wise t-tests revealed regional differences of WM and GM in deep brain structures, cerebellum and brain stem. Conclusions Most of the brain was identically classified at the two field strengths, although some regional differences were observed. PMID:24066153

Time-Dependent Behavior of High-Strength Kevlar and Vectran Webbing

NASA Technical Reports Server (NTRS)

Jones, Thomas C.; Doggett, William R.

2014-01-01

High-strength Kevlar and Vectran webbings are currently being used by both NASA and industry as the primary load-bearing structure in inflatable space habitation modules. The time-dependent behavior of high-strength webbing architectures is a vital area of research that is providing critical material data to guide a more robust design process for this class of structures. This paper details the results of a series of time-dependent tests on 1-inch wide webbing including an initial set of comparative tests between specimens that underwent realtime and accelerated creep at 65 and 70% of their ultimate tensile strength. Variability in the ultimate tensile strength of the webbings is investigated and compared with variability in the creep life response. Additional testing studied the effects of load and displacement rate, specimen length and the time-dependent effects of preconditioning the webbings. The creep test facilities, instrumentation and test procedures are also detailed. The accelerated creep tests display consistently longer times to failure than their real-time counterparts; however, several factors were identified that may contribute to the observed disparity. Test setup and instrumentation, grip type, loading scheme, thermal environment and accelerated test postprocessing along with material variability are among these factors. Their effects are discussed and future work is detailed for the exploration and elimination of some of these factors in order to achieve a higher fidelity comparison.

47 CFR 73.686 - Field strength measurements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... earth radius, of the largest available scale. (c) Collection of field strength data to determine... measurements in inclement weather or when major weather fronts are moving through the measurement area. (iii....686 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO...

Small static electric field strength promotes aggregation-prone structures in amyloid-β(29-42)

NASA Astrophysics Data System (ADS)

Lu, Yan; Shi, Xiao-Feng; Salsbury, Freddie R.; Derreumaux, Philippe

2017-04-01

The formation of senile plaques in central neural system resulting from the aggregation of the amyloid β (Aβ) of 40 and 42 residues is one of the two hallmarks of Alzheimer's disease. Numerous experiments and computational studies have shown that the aggregation of Aβ peptides in vitro is very complex and depends on many factors such as pH, agitation, temperature, and peptide concentration. The impact of a static electric field (EF) on amyloid peptide aggregation has been much less studied, although EFs may have some applications to treat Parkinson's disease symptoms. Here, we study the influence of an EF strength of 20 mV/nm, present in the human brains, on the conformation of the Aβ29-42 dimer. Our 7 μs non-equilibrium atomistic simulations in aqueous solution show that this field-strength promotes substantially the formation of β-hairpins, believed to be a very important intermediate state during aggregation. This work also suggests that structural biology experiments conducted under appropriate EF strengths may help reduce the conformational heterogeneity of Aβ1-40/Aβ1-42 dimers and provide significant insights into their structures that may be disease-causing.

Initial Intervention Outcomes of the Dependable Strengths Project.

ERIC Educational Resources Information Center

McMurrer, James E., Jr.

Dependable Strengths Articulation Process (DSAP) is a self-development process designed to facilitate positive self-constructions and improved personal functioning. This study examined the effectiveness of DSAP interventions. Participants (N=30) were college graduates who had expressed a desire to improve their educational and career planning and…

47 CFR 73.184 - Groundwave field strength graphs.

Code of Federal Regulations, 2010 CFR

2010-10-01

... function of groundwave conductivity and distance from the source of radiation. The groundwave field... Propagation of Radio Waves Over the Surface of the Earth and in the Upper Atmosphere,” Part II, by Mr. K.A... relative values of groundwave field strength over a plane earth as a function of the numerical distance p...

Estimating the Magnetic Field Strength in Hot Jupiters

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

Yadav, Rakesh K.; Thorngren, Daniel P., E-mail: rakesh_yadav@fas.harvard.edu

A large fraction of known Jupiter-like exoplanets are inflated as compared to Jupiter. These “hot” Jupiters orbit close to their parent star and are bombarded with intense starlight. Many theories have been proposed to explain their radius inflation and several suggest that a small fraction of the incident starlight is injected into the planetary interior, which helps to puff up the planet. How will such energy injection affect the planetary dynamo? In this Letter, we estimate the surface magnetic field strength of hot Jupiters using scaling arguments that relate energy available in planetary interiors to the dynamo-generated magnetic fields. Wemore » find that if we take into account the energy injected in the planetary interior that is sufficient to inflate hot Jupiters to observed radii, then the resulting dynamo should be able generate magnetic fields that are more than an order of magnitude stronger than the Jovian values. Our analysis highlights the potential fundamental role of the stellar light in setting the field strength in hot Jupiters.« less

Pressure Dependence of Magnesite Flow Strength

NASA Astrophysics Data System (ADS)

Millard, J. W.; Holyoke, C. W., III; McDaniel, C.; Raterron, P.; Kronenberg, A. K.; Tokle, L.

2017-12-01

Recent experiments by Holyoke et al. (2014) indicate that magnesite is weak compared with olivine, leading to strain localization into magnesite-bearing horizons of downgoing subducting slabs, potentially leading to intermediate (200-400 km) deep focus earthquakes DFEs. Flow strengths (σ) of magnesite were determined as functions of strain rate and temperature (T), but not of pressure (P). In order to determine the pressure dependence of magnesite deforming by dislocation creep and low temperature plasticity (LTP), we performed triaxial deformation experiments on natural, coarse-grained (80 μm) magnesite aggregates at T = 900oC, strain rate of 2*10-5/s and P from 3.2 to 7.9 GPa in the D-DIA at Beamline 6-BMB at the Advanced Photon Source at Argonne National Lab. Strengths of magnesite aggregates increase as a function of pressure, from σ=0.85 GPa (at P = 3.2 GPa) to 1.69 GPa (at P = 7.9 GPa). Microstructures developed at P ≤ 6.2 GPa include grain flattening and sweeping undulatory extinction, and dynamic recrystallization at grain boundaries (by bulge nucleation), consistent with dislocation creep. Microstructures generated at P ≥ 6.7 GPa include some twins and kink bands, grain flattening and patchy undulatory extinction, and bulging recrystallization at grain boundaries. These microstructures indicate contributions to strain of both LTP and dislocation creep mechanisms. The pressure dependence can be described by a thermally activated enthalpy, where s increases with P by way of an activation volume V*. Based on both D-DIA and Griggs apparatus results (of Holyoke et al., 2014), V* = 8.5 (± 0.5) × 10-6 m3 mol-1. This value is comparable to V* determined for creep of olivine (9.5 (± 7) × 10-6 m3 mol-1 Durham et al., 2009), indicating that the strength difference between magnesite and olivine will continue to be significant at high pressures, and lead to strain localization at all subduction zone depths.

Electrokinetic transport of aerobic microorganisms under low-strength electric fields.

PubMed

Maillacheruvu, Krishnanand Y; Chinchoud, Preethi R

2011-01-01

To investigate the feasibility of utilizing low strength electric fields to transport commonly available mixed cultures such as those from an activated sludge process, bench scale batch reactor studies were conducted in sand and sandy loam soils. A readily biodegradable substrate, dextrose, was used to test the activity of the transported microorganisms. Electric field strengths of 7V, 10.5V, and 14V were used. Results from this investigation showed that an electric field strength of 0.46 Volts per cm was sufficient to transport activated sludge microorganisms across a sandy loam soil across a distance of about 8 cm in 72 h. More importantly, the electrokinetically transported microbial culture remained active and viable after the transport process and was biodegrade 44% of the dextrose in the soil medium. Electrokinetic treatment without microorganisms resulted in removal of 37% and the absence of any treatment yielded a removal of about 15%.

Spectral characterization of plastic scintillation detector response as a function of magnetic field strength

NASA Astrophysics Data System (ADS)

Simiele, E.; Kapsch, R.-P.; Ankerhold, U.; Culberson, W.; DeWerd, L.

2018-04-01

The purpose of this work was to characterize intensity and spectral response changes in a plastic scintillation detector (PSD) as a function of magnetic field strength. Spectra measurements as a function of magnetic field strength were performed using an optical spectrometer. The response of both a PSD and PMMA fiber were investigated to isolate the changes in response from the scintillator and the noise signal as a function of magnetic field strength. All irradiations were performed in water at a photon beam energy of 6 MV. Magnetic field strengths of (0, ±0.35, ±0.70, ±1.05, and  ±1.40) T were investigated. Four noise subtraction techniques were investigated to evaluate the impact on the resulting noise-subtracted scintillator response with magnetic field strength. The noise subtraction methods included direct spectral subtraction, the spectral method, and variants thereof. The PMMA fiber exhibited changes in response of up to 50% with magnetic field strength due to the directional light emission from \\breve{C} erenkov radiation. The PSD showed increases in response of up to 10% when not corrected for the noise signal, which agrees with previous investigations of scintillator response in magnetic fields. Decreases in the \\breve{C} erenkov light ratio with negative field strength were observed with a maximum change at  ‑1.40 T of 3.2% compared to 0 T. The change in the noise-subtracted PSD response as a function of magnetic field strength varied with the noise subtraction technique used. Even after noise subtraction, the PSD exhibited changes in response of up to 5.5% over the four noise subtraction methods investigated.

Electric field strength determination in filamentary DBDs by CARS-based four-wave mixing

NASA Astrophysics Data System (ADS)

Boehm, Patrick; Kettlitz, Manfred; Brandenburg, Ronny; Hoeft, Hans; Czarnetzki, Uwe

2016-09-01

The electric field strength is a basic parameter of non-thermal plasmas. Therefore, a profound knowledge of the electric field distribution is crucial. In this contribution a four wave mixing technique based on Coherent Anti-Stokes Raman spectroscopy (CARS) is used to measure electric field strengths in filamentary dielectric barrier discharges (DBDs). The discharges are operated with a pulsed voltage in nitrogen at atmospheric pressure. Small amounts hydrogen (10 vol%) are admixed as tracer gas to evaluate the electric field strength in the 1 mm discharge gap. Absolute values of the electric field strength are determined by calibration of the CARS setup with high voltage amplitudes below the ignition threshold of the arrangement. Alteration of the electric field strength has been observed during the internal polarity reversal and the breakdown process. In this case the major advantage over emission based methods is that this technique can be used independently from emission, e.g. in the pre-phase and in between two consecutive, opposite discharge pulses where no emission occurs at all. This work was supported by the Deutsche Forschungsgemeinschaft, Forschergruppe FOR 1123 and Sonderforschungsbereich TRR 24 ``Fundamentals of complex plasmas''.

A field like today's? The strength of the geomagnetic field 1.1 billion years ago

NASA Astrophysics Data System (ADS)

Sprain, Courtney J.; Swanson-Hysell, Nicholas L.; Fairchild, Luke M.; Gaastra, Kevin

2018-06-01

Palaeomagnetic data from ancient rocks are one of the few types of observational data that can be brought to bear on the long-term evolution of Earth's core. A recent compilation of palaeointensity estimates from throughout Earth history has been interpreted to indicate that Earth's magnetic field strength increased in the Mesoproterozoic (between 1.5 and 1.0 billion years ago), with this increase taken to mark the onset of inner core nucleation. However, much of the data within the Precambrian palaeointensity database are from Thellier-style experiments with non-ideal behaviour that manifests in results such as double-slope Arai plots. Choices made when interpreting these data may significantly change conclusions about long-term trends in the intensity of Earth's geomagnetic field. In this study, we present new palaeointensity results from volcanics of the ˜1.1-billion-year-old North American Midcontinent Rift. While most of the results exhibit non-ideal double-slope or sagging behaviour in Arai plots, some flows have more ideal single-slope behaviour leading to palaeointensity estimates that may be some of the best constraints on the strength of Earth's field for this time. Taken together, new and previously published palaeointensity data from the Midcontinent Rift yield a median field strength estimate of 56.0 ZAm2—very similar to the median for the past 300 Myr. These field strength estimates are distinctly higher than those for the preceding billion years (Ga) after excluding ca. 1.3 Ga data that may be biased by non-ideal behaviour—consistent with an increase in field strength in the late Mesoproterozoic. However, given that ˜90 per cent of palaeointensity estimates from 1.1 to 0.5 Ga come from the Midcontinent Rift, it is difficult to evaluate whether these high values relative to those estimated for the preceding billion years are the result of a stepwise, sustained increase in dipole moment. Regardless, palaeointensity estimates from the Midcontinent

A field like today's? The strength of the geomagnetic field 1.1 billion years ago

NASA Astrophysics Data System (ADS)

Sprain, Courtney J.; Swanson-Hysell, Nicholas L.; Fairchild, Luke M.; Gaastra, Kevin

2018-02-01

Paleomagnetic data from ancient rocks are one of the few types of observational data that can be brought to be bear on the long-term evolution of Earth's core. A recent compilation of paleointensity estimates from throughout Earth history has been interpreted to indicate that Earth's magnetic field strength increased in the Mesoproterozoic (between 1.5 and 1.0 billion years ago), with this increase taken to mark the onset of inner core nucleation. However, much of the data within the Precambrian paleointensity database are from Thellier-style experiments with non-ideal behavior that manifests in results such as double-slope Arai plots. Choices made when interpreting these data may significantly change conclusions about long-term trends in the intensity of Earth's geomagnetic field. In this study, we present new paleointensity results from volcanics of the ˜1.1 billion-year-old North American Midcontinent Rift. While most of the results exhibit non-ideal double-slope or sagging behavior in Arai plots, some flows have more ideal single-slope behavior leading to paleointensity estimates that may be some of the best constraints on the strength of Earth's field for this time. Taken together, new and previously published paleointensity data from the Midcontinent Rift yield a median field strength estimate of 56.0 ZAm2—very similar to the median for the past 300 million years. These field strength estimates are distinctly higher than those for the preceding billion years after excluding ca. 1.3 Ga data that may be biased by non-ideal behavior—consistent with an increase in field strength in the late Mesoproterozoic. However, given that ˜90 per cent of paleointensity estimates from 1.1 to 0.5 Ga come from the Midcontinent Rift, it is difficult to evaluate whether these high values relative to those estimated for the preceding billion years are the result of a stepwise, sustained increase in dipole moment. Regardless, paleointensity estimates from the Midcontinent

47 CFR 73.153 - Field strength measurements in support of applications or evidence at hearings.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 4 2011-10-01 2011-10-01 false Field strength measurements in support of... (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.153 Field strength..., groundwave field strength measurements will take precedence over theoretical values, provided such...

47 CFR 73.153 - Field strength measurements in support of applications or evidence at hearings.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false Field strength measurements in support of... (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.153 Field strength..., groundwave field strength measurements will take precedence over theoretical values, provided such...

47 CFR 5.87 - Frequencies for field strength surveys or equipment demonstrations.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 1 2012-10-01 2012-10-01 false Frequencies for field strength surveys or... EXPERIMENTAL RADIO SERVICE (OTHER THAN BROADCAST) Applications and Licenses § 5.87 Frequencies for field strength surveys or equipment demonstrations. (a) Authorizations issued under §§ 5.3 (e) and (f) of this...

47 CFR 5.87 - Frequencies for field strength surveys or equipment demonstrations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false Frequencies for field strength surveys or... EXPERIMENTAL RADIO SERVICE (OTHER THAN BROADCAST) Applications and Licenses § 5.87 Frequencies for field strength surveys or equipment demonstrations. (a) Authorizations issued under §§ 5.3 (e) and (f) of this...

47 CFR 5.87 - Frequencies for field strength surveys or equipment demonstrations.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 1 2011-10-01 2011-10-01 false Frequencies for field strength surveys or... EXPERIMENTAL RADIO SERVICE (OTHER THAN BROADCAST) Applications and Licenses § 5.87 Frequencies for field strength surveys or equipment demonstrations. (a) Authorizations issued under §§ 5.3 (e) and (f) of this...

Lower-extremity strength ratios of professional soccer players according to field position.

PubMed

Ruas, Cassio V; Minozzo, Felipe; Pinto, Matheus D; Brown, Lee E; Pinto, Ronei S

2015-05-01

Previous investigators have proposed that knee strength, hamstrings to quadriceps, and side-to-side asymmetries may vary according to soccer field positions. However, different results have been found in these variables, and a generalization of this topic could lead to data misinterpretation by coaches and soccer clubs. Thus, the aim of this study was to measure knee strength and asymmetry in soccer players across different field positions. One hundred and two male professional soccer players performed maximal concentric and eccentric isokinetic knee actions on the preferred and nonpreferred legs at a velocity of 60° · s. Players were divided into their field positions for analysis: goalkeepers, side backs, central backs, central defender midfielders, central attacking midfielders, and forwards. Results demonstrated that only goalkeepers (GK) differed from most other field positions on players' characteristics, and concentric peak torque across muscles. Although all players presented functional ratios of the preferred (0.79 ± 0.14) and nonpreferred (0.75 ± 0.13) legs below accepted normative values, there were no differences between positions for conventional or functional strength ratios or side-to-side asymmetry. The same comparisons were made only between field players, without inclusion of the GK, and no differences were found between positions. Therefore, the hamstrings to quadriceps and side-to-side asymmetries found here may reflect knee strength functional balance required for soccer skills performance and game demands across field positions. These results also suggest that isokinetic strength profiles should be considered differently in GK compared with other field positions due to their specific physiological and training characteristics.

47 CFR 90.359 - Field strength limits for EA-licensed LMS systems.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 5 2010-10-01 2010-10-01 false Field strength limits for EA-licensed LMS systems. 90.359 Section 90.359 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Intelligent Transportation Systems Radio Service § 90.359 Field strength limits for...

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.

Temperature Dependence of Molecular Line Strengths and Fei 1565 nm Zeeman Splitting in a Sunspot

NASA Astrophysics Data System (ADS)

Penn, M. J.; Walton, S.; Chapman, G.; Ceja, J.; Plick, W.

2003-03-01

Spectroscopic observations at 1565 nm were made in the eastern half of the main umbra of NOAA 9885 on 1 April 2002 using the National Solar Observatory McMath-Pierce Telescope at Kitt Peak with a tip-tilt image stabilization system and the California State University Northridge-National Solar Observatory infrared camera. The line depth of the OH blend at 1565.1 nm varies with the observed continuum temperature; the variation fits previous observations except that the continuum temperature is lower by 600 K. The equivalent width of the OH absorption line at 1565.2 nm shows a temperature dependence similar to previously published umbral molecular observations at 640 nm. A simple model of expected OH abundance based upon an ionization analogy to molecular dissociation is produced and agrees well with the temperature variation of the line equivalent width. A CN absorption line at 1564.6 nm shows a very different temperature dependence, likely due to complicated formation and destruction processes. Nonetheless a numerical fit of the temperature variation of the CN equivalent width is presented. Finally a comparison of the Zeeman splitting of the Fei 1564.8 nm line with the sunspot temperature derived from the continuum intensity shows an umbra somewhat cooler for a given magnetic field strength than previous comparisons using this infrared 1564.8 nm line, but consistent with these previous infrared measurements the umbra is hotter for a given magnetic field strength than magnetic and temperature measurements at 630.2 nm would suggest. Differences between the 630.2 nm and 1564.8 nm umbral temperature and magnetic field relations are explained with the different heights of formation of the lines and continua at these wavelengths.

THE EFFECT OF ACTIVITY-RELATED MERIDIONAL FLOW MODULATION ON THE STRENGTH OF THE SOLAR POLAR MAGNETIC FIELD

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

Jiang, J.; Cameron, R. H.; Schmitt, D.

We studied the effect of the perturbation of the meridional flow in the activity belts detected by local helioseismology on the development and strength of the surface magnetic field at the polar caps. We carried out simulations of synthetic solar cycles with a flux transport model, which follows the cyclic evolution of the surface field determined by flux emergence and advective transport by near-surface flows. In each hemisphere, an axisymmetric band of latitudinal flows converging toward the central latitude of the activity belt was superposed onto the background poleward meridional flow. The overall effect of the flow perturbation is tomore » reduce the latitudinal separation of the magnetic polarities of a bipolar magnetic region and thus diminish its contribution to the polar field. As a result, the polar field maximum reached around cycle activity minimum is weakened by the presence of the meridional flow perturbation. For a flow perturbation consistent with helioseismic observations, the polar field is reduced by about 18% compared to the case without inflows. If the amplitude of the flow perturbation depends on the cycle strength, its effect on the polar field provides a nonlinearity that could contribute to limiting the amplitude of a Babcock-Leighton type dynamo.« less

47 CFR 2.1053 - Measurements required: Field strength of spurious radiation.

Code of Federal Regulations, 2010 CFR

2010-10-01

.... For equipment operating on frequencies below 890 MHz, an open field test is normally required, with... either impractical or impossible to make open field measurements (e.g. a broadcast transmitter installed... 47 Telecommunication 1 2010-10-01 2010-10-01 false Measurements required: Field strength of...

Alignments of Dark Matter Halos with Large-scale Tidal Fields: Mass and Redshift Dependence

NASA Astrophysics Data System (ADS)

Chen, Sijie; Wang, Huiyuan; Mo, H. J.; Shi, Jingjing

2016-07-01

Large-scale tidal fields estimated directly from the distribution of dark matter halos are used to investigate how halo shapes and spin vectors are aligned with the cosmic web. The major, intermediate, and minor axes of halos are aligned with the corresponding tidal axes, and halo spin axes tend to be parallel with the intermediate axes and perpendicular to the major axes of the tidal field. The strengths of these alignments generally increase with halo mass and redshift, but the dependence is only on the peak height, ν \\equiv {δ }{{c}}/σ ({M}{{h}},z). The scaling relations of the alignment strengths with the value of ν indicate that the alignment strengths remain roughly constant when the structures within which the halos reside are still in a quasi-linear regime, but decreases as nonlinear evolution becomes more important. We also calculate the alignments in projection so that our results can be compared directly with observations. Finally, we investigate the alignments of tidal tensors on large scales, and use the results to understand alignments of halo pairs separated at various distances. Our results suggest that the coherent structure of the tidal field is the underlying reason for the alignments of halos and galaxies seen in numerical simulations and in observations.

Temperature-dependent residual shear strength characteristics of smectite-bearing landslide soils

NASA Astrophysics Data System (ADS)

Shibasaki, Tatsuya; Matsuura, Sumio; Hasegawa, Yoichi

2017-02-01

This paper presents experimental investigations regarding the effect of temperature on the residual strength of landslide soils at slow-to-moderate shearing velocities. We performed ring-shear tests on 23 soil samples at temperatures of 6-29°C. The test results show that the shear strength of smectite-rich soils decreased when temperatures were relatively low. These positive temperature effects (strength losses at lower temperatures) observed for smectite-bearing soils are typical under relatively slow shearing rates. In contrast, under relatively high shearing rates, strength was gained as temperature decreased. As rheological properties of smectite suspensions are sensitive to environmental factors, such as temperature, pH, and dissolved ions, we inferred that temperature-dependent residual strengths of smectitic soils are also attributed to their specific rheological properties. Visual and scanning electron microscope observations of Ca-bentonite suggest that slickensided shear surfaces at slow shearing rates are very shiny and smooth, whereas those at moderate shearing rates are not glossy and are slightly turbulent, indicating that platy smectite particles are strongly orientated at slow velocities. The positive temperature effect is probably due to temperature-dependent microfriction that is mobilized in the parallel directions of the sheet structure of hydrous smectite particles. On the contrary, the influence of microviscous resistance, which appears in the vertical directions of the lamination, is assumed to increase at faster velocities. Our results imply that if slip-surface soils contain high fractions of smectite, decreases in ground temperature can lead to lowered shear resistance of the slip surface and trigger slow landslide movement.

Modelling and assessment of the electric field strength caused by mobile phone to the human head.

PubMed

Buckus, Raimondas; Strukcinskiene, Birute; Raistenskis, Juozas; Stukas, Rimantas

2016-06-01

Electromagnetic field exposure is the one of the most important physical agents that actively affects live organisms and environment. Active use of mobile phones influences the increase of electromagnetic field radiation. The aim of the study was to measure and assess the electric field strength caused by mobile phones to the human head. In this paper the software "COMSOL Multiphysics" was used to establish the electric field strength created by mobile phones around the head. The second generation (2G) Global System for Mobile (GSM) phones that operate in the frequency band of 900 MHz and reach the power of 2 W have a stronger electric field than (2G) GSM mobile phones that operate in the higher frequency band of 1,800 MHz and reach the power up to 1 W during conversation. The third generation of (3G) UMTS smart phones that effectively use high (2,100 MHz) radio frequency band emit the smallest electric field strength values during conversation. The highest electric field strength created by mobile phones is around the ear, i.e. the mobile phone location. The strength of mobile phone electric field on the phantom head decreases exponentially while moving sidewards from the center of the effect zone (the ear), and constitutes 1-12% of the artificial head's surface. The highest electric field strength values of mobile phones are associated with their higher power, bigger specific energy absorption rate (SAR) and lower frequency of mobile phone. The stronger electric field emitted by the more powerful mobile phones takes a higher percentage of the head surface. The highest electric field strength created by mobile phones is distributed over the user's ear.

Field-dependence of AC susceptibility in titanomagnetites

USGS Publications Warehouse

Jackson, M.; Moskowitz, B.; Rosenbaum, J.; Kissel, Catherie

1998-01-01

AC susceptibility measurements as a function of field amplitude Hac and of frequency show a strong field dependence for a set of synthetic titanomagnetites (Fe3-xTixO4) and for certain basalts from the SOH-1 Hawaiian drill hole and from Iceland. In-phase susceptibility is constant below fields of about 10-100 A/m, and then increases by as much as a factor of two as Hsc is increased to 2000 A/m. Both the initial field-independent susceptibilities and field-dependence of susceptibility are systematically related to composition: initial susceptibility is 3 SI for a single-crystal sphere of TMO (x = 0) and decreases with increasing titanium content; field-dependence is nearly zero for TM0 and increases systematically to a maximum near TM60 (x = 0.6). This field dependence can in some cases be mistaken for frequency dependence, and leaf to incorrect interpretations of magnetic grain size and composition when titanomagnetite is present.

Temperature- and field-dependent characterization of a conductor on round core cable

NASA Astrophysics Data System (ADS)

Barth, C.; van der Laan, D. C.; Bagrets, N.; Bayer, C. M.; Weiss, K.-P.; Lange, C.

2015-06-01

The conductor on round core (CORC) cable is one of the major high temperature superconductor cable concepts combining scalability, flexibility, mechanical strength, ease of fabrication and high current density; making it a possible candidate as conductor for large, high field magnets. To simulate the boundary conditions of such magnets as well as the temperature dependence of CORC cables a 1.16 m long sample consisting of 15, 4 mm wide SuperPower REBCO tapes was characterized using the ‘FBI’ (force—field—current) superconductor test facility of the Institute for Technical Physics of the Karlsruhe Institute of Technology. In a five step investigation, the CORC cable’s performance was determined at different transverse mechanical loads, magnetic background fields and temperatures as well as its response to swift current changes. In the first step, the sample’s 77 K, self-field current was measured in a liquid nitrogen bath. In the second step, the temperature dependence was measured at self-field condition and compared with extrapolated single tape data. In the third step, the magnetic background field was repeatedly cycled while measuring the current carrying capabilities to determine the impact of transverse Lorentz forces on the CORC cable sample’s performance. In the fourth step, the sample’s current carrying capabilities were measured at different background fields (2-12 T) and surface temperatures (4.2-51.5 K). Through finite element method simulations, the surface temperatures are converted into average sample temperatures and the gained field- and temperature dependence is compared with extrapolated single tape data. In the fifth step, the response of the CORC cable sample to rapid current changes (8.3 kA s-1) was observed with a fast data acquisition system. During these tests, the sample performance remains constant, no degradation is observed. The sample’s measured current carrying capabilities correlate to those of single tapes assuming

Field strengths and dissipated powers in microwave-excited high-pressure sulphur discharges

NASA Astrophysics Data System (ADS)

van Dongen, Menno; Körber, Achim; van der Heijden, Harm; Jonkers, Jeroen; Scholl, Robert; van der Mullen, Joost

1998-11-01

A method which makes it is possible to measure the electric field strength in microwave discharges is presented. A condition for this method is that the plasma has such a low conductivity that the associated skin depth is larger than the discharge radius. It is found that the field strength in high-pressure sulphur lamps is around 400 V 0022-3727/31/21/015/img10. Furthermore, this method allows the determination of the power absorbed in the resonator's wall and in the plasma and the estimation of the effective electric conductivity in the discharge.

47 CFR 73.189 - Minimum antenna heights or field strength requirements.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 4 2012-10-01 2012-10-01 false Minimum antenna heights or field strength... RADIO SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.189 Minimum antenna heights or field..., frequency, or transmitter location must also request authority to install a new antenna system or to make...

47 CFR 73.189 - Minimum antenna heights or field strength requirements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 4 2014-10-01 2014-10-01 false Minimum antenna heights or field strength... RADIO SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.189 Minimum antenna heights or field..., frequency, or transmitter location must also request authority to install a new antenna system or to make...

47 CFR 73.189 - Minimum antenna heights or field strength requirements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false Minimum antenna heights or field strength... RADIO SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.189 Minimum antenna heights or field..., frequency, or transmitter location must also request authority to install a new antenna system or to make...

47 CFR 73.189 - Minimum antenna heights or field strength requirements.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 4 2011-10-01 2011-10-01 false Minimum antenna heights or field strength... RADIO SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.189 Minimum antenna heights or field..., frequency, or transmitter location must also request authority to install a new antenna system or to make...

47 CFR 73.189 - Minimum antenna heights or field strength requirements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 4 2013-10-01 2013-10-01 false Minimum antenna heights or field strength... RADIO SERVICES RADIO BROADCAST SERVICES AM Broadcast Stations § 73.189 Minimum antenna heights or field..., frequency, or transmitter location must also request authority to install a new antenna system or to make...

Temperature dependent and applied field strength dependent magnetic study of cobalt nickel ferrite nano particles: Synthesized by an environmentally benign method

NASA Astrophysics Data System (ADS)

Sontu, Uday Bhasker; G, Narsinga Rao; Chou, F. C.; M, V. Ramana Reddy

2018-04-01

Spinel ferrites have come a long way in their versatile applications. The ever growing applications of these materials demand detailed study of material properties and environmental considerations in their synthesis. In this article, we report the effect of temperature and applied magnetic field strength on the magnetic behavior of the cobalt nickel ferrite nano powder samples. Basic structural properties of spinel ferrite nano particles, that are synthesized by an environmentally benign method of auto combustion, are characterized through XRD, TEM, RAMAN spectroscopy. Diffuse Reflectance Spectroscopy (DRS) is done to understand the nickel substitution effect on the optical properties of cobalt ferrite nano particles. Thermo magnetic studies using SQUID in the temperature range 5 K to 400 K and room temperature (300 K) VSM studies are performed on these samples. Fields of 0Oe (no applied field: ZF), 1 kOe (for ZFC and FC curves), 5 kOe (0.5 T), 50 kOe (5T) (for M-H loop study) are used to study the magnetic behavior of these nano particles. The XRD,TEM analysis suggest 40 nm crystallites that show changes in the cation distribution and phase changes in the spinel structure with nickel substitution. Raman micrographs support phase purity changes and cation redistributions with nickel substitution. Diffuse reflectance study on powder samples suggests two band gap values for nickel rich compounds. The Magnetic study of these sample nano particles show varied magnetic properties from that of hard magnetic, positive multi axial anisotropy and single-magnetic-domain structures at 5 K temperature to soft magnetic core shell like structures at 300 K temperature. Nickel substitution effect is non monotonous. Blocking temperature of all the samples is found to be higher than the values suggested in the literature.

Nanoscale Roughness of Natural Fault Surfaces Controlled by Scale-Dependent Yield Strength

NASA Astrophysics Data System (ADS)

Thom, C. A.; Brodsky, E. E.; Carpick, R. W.; Pharr, G. M.; Oliver, W. C.; Goldsby, D. L.

2017-09-01

Many natural fault surfaces exhibit remarkably similar scale-dependent roughness, which may reflect the scale-dependent yield strength of rocks. Using atomic force microscopy (AFM), we show that a sample of the Corona Heights Fault exhibits isotropic surface roughness well-described by a power law, with a Hurst exponent of 0.75 +/- 0.05 at all wavelengths from 60 nm to 10 μm. The roughness data and a recently proposed theoretical framework predict that yield strength varies with length scale as λ-0.25+/-0.05. Nanoindentation tests on the Corona Heights sample and another fault sample whose topography was previously measured with AFM (the Yair Fault) reveal a scale-dependent yield stress with power-law exponents of -0.12 +/- 0.06 and -0.18 +/- 0.08, respectively. These values are within one to two standard deviations of the predicted value, and provide experimental evidence that fault roughness is controlled by intrinsic material properties, which produces a characteristic surface geometry.

Utilization of the Boltzmann tail of TED for the calculation of the ``absolute'' work function and local field strength in FEM

NASA Astrophysics Data System (ADS)

Wysocki, J. K.

1984-02-01

The idea of Young and Clark of independent evaluation of the work function φ and electric field strength F in FEM [R.D. Young and H.E. Clark, Phys. Rev. Letters 17 (1966) 351] has been extended to the energy region above the Fermi level. The estimation of slowly varying elliptic functions, necessary to compute φ and F, using only experimental data is presented. Calculations for the W(111) plane using the field electron energy distribution and the integral field-emission current dependence on retarding voltage have been performed.

Region of Interest Correction Factors Improve Reliability of Diffusion Imaging Measures Within and Across Scanners and Field Strengths

PubMed Central

Venkatraman, Vijay K; Gonzalez, Christopher E.; Landman, Bennett; Goh, Joshua; Reiter, David A.; An, Yang; Resnick, Susan M.

2017-01-01

Diffusion tensor imaging (DTI) measures are commonly used as imaging markers to investigate individual differences in relation to behavioral and health-related characteristics. However, the ability to detect reliable associations in cross-sectional or longitudinal studies is limited by the reliability of the diffusion measures. Several studies have examined reliability of diffusion measures within (i.e. intra-site) and across (i.e. inter-site) scanners with mixed results. Our study compares the test-retest reliability of diffusion measures within and across scanners and field strengths in cognitively normal older adults with a follow-up interval less than 2.25 years. Intra-class correlation (ICC) and coefficient of variation (CoV) of fractional anisotropy (FA) and mean diffusivity (MD) were evaluated in sixteen white matter and twenty-six gray matter bilateral regions. The ICC for intra-site reliability (0.32 to 0.96 for FA and 0.18 to 0.95 for MD in white matter regions; 0.27 to 0.89 for MD and 0.03 to 0.79 for FA in gray matter regions) and inter-site reliability (0.28 to 0.95 for FA in white matter regions, 0.02 to 0.86 for MD in gray matter regions) with longer follow-up intervals were similar to earlier studies using shorter follow-up intervals. The reliability of across field strengths comparisons was lower than intra- and inter-site reliability. Within and across scanner comparisons showed that diffusion measures were more stable in larger white matter regions (> 1500 mm3). For gray matter regions, the MD measure showed stability in specific regions and was not dependent on region size. Linear correction factor estimated from cross-sectional or longitudinal data improved the reliability across field strengths. Our findings indicate that investigations relating diffusion measures to external variables must consider variable reliability across the distinct regions of interest and that correction factors can be used to improve consistency of measurement across

Contribution of Field Strength Gradients to the Net Vertical Current of Active Regions

NASA Astrophysics Data System (ADS)

Vemareddy, P.

2017-12-01

We examined the contribution of field strength gradients for the degree of net vertical current (NVC) neutralization in active regions (ARs). We used photospheric vector magnetic field observations of AR 11158 obtained by Helioseismic and Magnetic Imager on board SDO and Hinode. The vertical component of the electric current is decomposed into twist and shear terms. The NVC exhibits systematic evolution owing to the presence of the sheared polarity inversion line between rotating and shearing magnetic regions. We found that the sign of shear current distribution is opposite in dominant pixels (60%–65%) to that of twist current distribution, and its time profile bears no systematic trend. This result indicates that the gradient of magnetic field strength contributes to an opposite signed, though smaller in magnitude, current to that contributed by the magnetic field direction in the vertical component of the current. Consequently, the net value of the shear current is negative in both polarity regions, which when added to the net twist current reduces the direct current value in the north (B z > 0) polarity, resulting in a higher degree of NVC neutralization. We conjecture that the observed opposite signs of shear and twist currents are an indication, according to Parker, that the direct volume currents of flux tubes are canceled by their return currents, which are contributed by field strength gradients. Furthermore, with the increase of spatial resolution, we found higher values of twist, shear current distributions. However, the resolution effect is more useful in resolving the field strength gradients, and therefore suggests more contribution from shear current for the degree of NVC neutralization.

Strength and deformation of shocked diamond single crystals: Orientation dependence

DOE PAGES

Lang, John Michael Jr.; Winey, J. M.; Gupta, Y. M.

2018-03-01

Understanding and quantifying the strength or elastic limit of diamond single crystals is of considerable scientific and technological importance, and has been a subject of long standing theoretical and experimental interest. To examine the effect of crystalline anisotropy on strength and deformation of shocked diamond single crystals, plate impact experiments were conducted to measure wave profiles at various elastic impact stresses up to ~120 GPa along [110] and [111] crystal orientations. Using laser interferometry, particle velocity histories and shock velocities in the diamond samples were measured and were compared with similar measurements published previously for shock compression along the [100]more » direction. Wave profiles for all three orientations showed large elastic wave amplitudes followed by time-dependent inelastic deformation. From the measured wave profiles, the elastic limits were determined under well characterized uniaxial strain loading conditions. The measured elastic wave amplitudes for the [110] and [111] orientations were lower for higher elastic impact stress (stress attained for an elastic diamond response), consistent with the result reported previously for [100] diamond. The maximum resolved shear stress (MRSS) on the {111}<110> slip systems was determined for each orientation, revealing significant orientation dependence. The MRSS values for the [100] and [110] orientations (~33 GPa) are 25-30% of theoretical estimates; the MRSS value for the [111] orientation is significantly lower (~23 GPa). Our results demonstrate that the MRSS depends strongly on the stress component normal to the {111} planes or the resolved normal stress (RNS), suggesting that the RNS plays a key role in inhibiting the onset of inelastic deformation. Lower elastic wave amplitudes at higher peak stress and the effect of the RNS are inconsistent with typical dislocation slip mechanisms of inelastic deformation, suggesting instead an inelastic response

Strength and deformation of shocked diamond single crystals: Orientation dependence

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

Lang, John Michael Jr.; Winey, J. M.; Gupta, Y. M.

Understanding and quantifying the strength or elastic limit of diamond single crystals is of considerable scientific and technological importance, and has been a subject of long standing theoretical and experimental interest. To examine the effect of crystalline anisotropy on strength and deformation of shocked diamond single crystals, plate impact experiments were conducted to measure wave profiles at various elastic impact stresses up to ~120 GPa along [110] and [111] crystal orientations. Using laser interferometry, particle velocity histories and shock velocities in the diamond samples were measured and were compared with similar measurements published previously for shock compression along the [100]more » direction. Wave profiles for all three orientations showed large elastic wave amplitudes followed by time-dependent inelastic deformation. From the measured wave profiles, the elastic limits were determined under well characterized uniaxial strain loading conditions. The measured elastic wave amplitudes for the [110] and [111] orientations were lower for higher elastic impact stress (stress attained for an elastic diamond response), consistent with the result reported previously for [100] diamond. The maximum resolved shear stress (MRSS) on the {111}<110> slip systems was determined for each orientation, revealing significant orientation dependence. The MRSS values for the [100] and [110] orientations (~33 GPa) are 25-30% of theoretical estimates; the MRSS value for the [111] orientation is significantly lower (~23 GPa). Our results demonstrate that the MRSS depends strongly on the stress component normal to the {111} planes or the resolved normal stress (RNS), suggesting that the RNS plays a key role in inhibiting the onset of inelastic deformation. Lower elastic wave amplitudes at higher peak stress and the effect of the RNS are inconsistent with typical dislocation slip mechanisms of inelastic deformation, suggesting instead an inelastic response

Strength and deformation of shocked diamond single crystals: Orientation dependence

NASA Astrophysics Data System (ADS)

Lang, J. M.; Winey, J. M.; Gupta, Y. M.

2018-03-01

Understanding and quantifying the strength or elastic limit of diamond single crystals is of considerable scientific and technological importance, and has been a subject of long standing theoretical and experimental interest. To examine the effect of crystalline anisotropy on strength and deformation of shocked diamond single crystals, plate impact experiments were conducted to measure wave profiles at various elastic impact stresses up to ˜120 GPa along [110] and [111] crystal orientations. Using laser interferometry, particle velocity histories and shock velocities in the diamond samples were measured and were compared with similar measurements published previously for shock compression along the [100] direction. Wave profiles for all three orientations showed large elastic wave amplitudes followed by time-dependent inelastic deformation. From the measured wave profiles, the elastic limits were determined under well characterized uniaxial strain loading conditions. The measured elastic wave amplitudes for the [110] and [111] orientations were lower for higher elastic impact stress (stress attained for an elastic diamond response), consistent with the result reported previously for [100] diamond. The maximum resolved shear stress (MRSS) on the {111}⟨110⟩ slip systems was determined for each orientation, revealing significant orientation dependence. The MRSS values for the [100] and [110] orientations (˜33 GPa) are 25%-30% of theoretical estimates; the MRSS value for the [111] orientation is significantly lower (˜23 GPa). Our results demonstrate that the MRSS depends strongly on the stress component normal to the {111} planes or the resolved normal stress (RNS), suggesting that the RNS plays a key role in inhibiting the onset of inelastic deformation. Lower elastic wave amplitudes at higher peak stress and the effect of the RNS are inconsistent with typical dislocation slip mechanisms of inelastic deformation, suggesting instead an inelastic response

Covalent character and electric field dependence of H2-AgX (X = F - I).

PubMed

Li, Xinying

2018-06-16

Mechanisms of Ag-X and Ag…H 2 interactions and stabilities of T-shaped H 2 -AgX (X = F - I) series were investigated at the CCSD(T) level. The "no-density" bond with smaller positive Laplacian and ELF values in interaction regions, as well as considerable delocalization index values, suggest weak covalent "charge-shift" character for the Ag…H 2 interaction. Structure and stability dependence on the electric field were investigated at the MP2 level. Relative total energy curves show obvious parabolic character, and the plots can be fitted by quadratic polynomials as functions of electric field strength.

47 CFR 1.544 - Application for broadcast station to conduct field strength measurements and for experimental...

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false Application for broadcast station to conduct field strength measurements and for experimental operation. 1.544 Section 1.544 Telecommunication... General Filing Requirements § 1.544 Application for broadcast station to conduct field strength...

Fracture strength of the particulate-reinforced ultra-high temperature ceramics based on a temperature dependent fracture toughness model

NASA Astrophysics Data System (ADS)

Wang, Ruzhuan; Li, Weiguo; Ji, Baohua; Fang, Daining

2017-10-01

The particulate-reinforced ultra-high temperature ceramics (pUHTCs) have been particularly developed for fabricating the leading edge and nose cap of hypersonic vehicles. They have drawn intensive attention of scientific community for their superior fracture strength at high temperatures. However, there is no proper model for predicting the fracture strength of the ceramic composites and its dependency on temperature. In order to account for the effect of temperature on the fracture strength, we proposed a concept called energy storage capacity, by which we derived a new model for depicting the temperature dependent fracture toughness of the composites. This model gives a quantitative relationship between the fracture toughness and temperature. Based on this temperature dependent fracture toughness model and Griffith criterion, we developed a new fracture strength model for predicting the temperature dependent fracture strength of pUHTCs at different temperatures. The model takes into account the effects of temperature, flaw size and residual stress without any fitting parameters. The predictions of the fracture strength of pUHTCs in argon or air agreed well with the experimental measurements. Additionally, our model offers a mechanism of monitoring the strength of materials at different temperatures by testing the change of flaw size. This study provides a quantitative tool for design, evaluation and monitoring of the fracture properties of pUHTCs at high temperatures.

Temperature dependence of elastic and strength properties of T300/5208 graphite-epoxy

NASA Technical Reports Server (NTRS)

Milkovich, S. M.; Herakovich, C. T.

1984-01-01

Experimental results are presented for the elastic and strength properties of T300/5208 graphite-epoxy at room temperature, 116K (-250 F), and 394K (+250 F). Results are presented for unidirectional 0, 90, and 45 degree laminates, and + or - 30, + or - 45, and + or - 60 degree angle-ply laminates. The stress-strain behavior of the 0 and 90 degree laminates is essentially linear for all three temperatures and that the stress-strain behavior of all other laminates is linear at 116K. A second-order curve provides the best fit for the temperature is linear at 116K. A second-order curve provides the best fit for the temperature dependence of the elastic modulus of all laminates and for the principal shear modulus. Poisson's ratio appears to vary linearly with temperature. all moduli decrease with increasing temperature except for E (sub 1) which exhibits a small increase. The strength temperature dependence is also quadratic for all laminates except the 0 degree - laminate which exhibits linear temperature dependence. In many cases the temperature dependence of properties is nearly linear.

Technique for Predicting the Radio Frequency Field Strength Inside an Enclosure

NASA Technical Reports Server (NTRS)

Hallett, Michael P.; Reddell, Jerry P.

1997-01-01

This technical memo represents a simple analytical technique for predicting the Radio Frequency (RF) field inside an enclosed volume in which radio frequency occurs. The technique was developed to predict the RF field strength within a launch vehicle fairing in which some payloads desire to launch with their telemetry transmitter radiating. This technique considers both the launch vehicle and the payload aspects.

Explicit role of ionic strength in retention behavior of polystyrene latex particles in sedimentation field-flow fractionation: Slip boundary model.

PubMed

Rah, Kyunil; Han, Sujeong; Choi, Jaeyeong; Eum, Chul Hun; Lee, Seungho

2017-12-15

We investigate an explicit role of the ionic strength in the retention behaviors of polystyrene (PS) latex particles in sedimentation field-flow fractionation (SdFFF) by hinging upon the retention theory recently developed [1] asR=(R o +v b * )/(1+v b * ). Here R is an experimental retention ratio, and R o is the analytical expression of the standard retention theory based on the parabolic flow velocity. The reduced boundary velocityv b * is expressed in terms of the ionic strength I of the carrier liquid as v b * =v b,o * /(1+εI), where v b,o * =0.070and ε=60 mM -1 for all the PS latex systems under investigation. We then apply this to study the explicit ionic strength effect on the retention behaviors of PS beads of 200, 300, 400, and 500nm, respectively. As a primary result, the strong dependence of the retention ratio on the ionic strength can be quantitatively accounted for in an excellent accuracy: The slip effect at the channel surface is significant, particularly when I≲0.5mM, without showing any distinguishable dependence on the specific additives to control I, such as FL-70, SDS, NaNO 3 , and NaN 3 . Based on the present study, we put forward an experimental means to estimate the ionic strength of an aqueous solution using an FFF technique. Copyright © 2017. Published by Elsevier B.V.

An Information Processing View of Field Dependence-Independence.

ERIC Educational Resources Information Center

Davis, J. Kent; Cochran, Kathryn F.

1989-01-01

Discusses field dependence-independence from an information processing perspective. Topics discussed include field dependence theory, stages of information processing, developmental issues and implications, and future directions. The information reviewed indicates that field-independent individuals are more efficient than field-dependent…

Dependency of Shear Strength on Test Rate in SiC/BSAS Ceramic Matrix Composite at Elevated Temperature

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Bansal, Narottam P.; Gyekenyesi, John P.

2003-01-01

Both interlaminar and in-plane shear strengths of a unidirectional Hi-Nicalon(TM) fiber-reinforced barium strontium aluminosilicate (SiC/BSAS) composite were determined at 1100 C in air as a function of test rate using double notch shear test specimens. The composite exhibited a significant effect of test rate on shear strength, regardless of orientation which was either in interlaminar or in in-plane direction, resulting in an appreciable shear-strength degradation of about 50 percent as test rate decreased from 3.3 10(exp -1) mm/s to 3.3 10(exp -5) mm/s. The rate dependency of composite's shear strength was very similar to that of ultimate tensile strength at 1100 C observed in a similar composite (2-D SiC/BSAS) in which tensile strength decreased by about 60 percent when test rate varied from the highest (5 MPa/s) to the lowest (0.005 MPa/s). A phenomenological, power-law slow crack growth formulation was proposed and formulated to account for the rate dependency of shear strength of the composite.

Shear-rate-dependent strength control on the dynamics of rainfall-triggered landslides, Tokushima Prefecture, Japan

USGS Publications Warehouse

Wang, G.; Suemine, A.; Schulz, W.H.

2010-01-01

A typhoon (Typhoon No. 10) attacked Shikoku Island and the Tyugoku area of Japan in 2004. This typhoon produced a new daily precipitation record of 1317 mm on Shikoku Island and triggered hundreds of landslides in Tokushima Prefecture. One catastrophic landslide was triggered in the Shiraishi area of Kisawa village, and destroyed more than 10 houses while also leaving an unstable block high on the slope. The unstable block kept moving after the event, showing accelerating and decelerating movement during and after rainfall and reaching a displacement of several meters before countermeasures were put into place. To examine the mechanism for this landsliding characteristic, samples (weathered serpentinite) were taken from the field, and their shear behaviours examined using ring shear tests. The test results revealed that the residual shear strength of the samples is positively dependent on the shear rate, which may provide an explanation for the continuous acceleratingdecelerating process of the landsliding. The roughness of the shear surface and the microstructure of the shear zone were measured and observed by laser microscope and SEM techniques in an attempt to clarify the mechanism of shear rate effect on the residual shear strength. Copyright ?? 2010 John Wiley & Sons, Ltd.

Consistency of field dependence in treated alcoholics.

PubMed

Danahy, S; Kahn, M W

1981-10-01

In accounting for the consistent finding that alcoholics are more field dependent than other groups, research generally supports the predisposition rather than the consequence hypothesis. In this study 32 alcoholics were tested for field dependence with Embedded Figures on admission to and at discharge from a 60-d treatment program. A large and significant drop in the field dependence measure was found, supporting the consequence hypothesis. The pre-posttime period not controlled in other studies, allowing for clearing acute effects and improved nutrition, health, and test motivation, amy account for this change.

Visualizing the optical field strengths in Au/dielectric nanostructures and its correlation to SERS enhancements

NASA Astrophysics Data System (ADS)

Rajesh, Y.; Sangani, L. D. Varma; Shaik, Ummar Pasha; Gaur, Anshu; Mohiddon, Md Ahamad; Krishna, M. Ghanashyam

2017-05-01

The role of dielectric surrounding over the Au nanostructure for surface plasmon resonance (SPR) behavior is investigated by scanning near field optical microscopy (SNOM). The observed optical field strengths are correlated with the surface enhanced Raman scattering (SERS) enhancement recorded for R6G molecule. Discontinuous nanostructured Au thin films are deposited by RF magnatron sputtering at very low rate on to three different dielectric substrates, ZnO, TiO2 and SiO2. These three Au/dielectric nanostructures are investigated using SNOM by illuminating it in near field and collecting in transmission far field configuration. The observed optical near field images of the three different nanostructures are discussed by taking their dielectric constant into the account. The SERS enhancements are correlated with the optical field strengths derived from the near field optical imaging.

A new estimate of average dipole field strength for the last five million years

NASA Astrophysics Data System (ADS)

Cromwell, G.; Tauxe, L.; Halldorsson, S. A.

2013-12-01

The Earth's ancient magnetic field can be approximated by a geocentric axial dipole (GAD) where the average field intensity is twice as strong at the poles than at the equator. The present day geomagnetic field, and some global paleointensity datasets, support the GAD hypothesis with a virtual axial dipole moment (VADM) of about 80 ZAm2. Significant departures from GAD for 0-5 Ma are found in Antarctica and Iceland where paleointensity experiments on massive flows (Antarctica) (1) and volcanic glasses (Iceland) produce average VADM estimates of 41.4 ZAm2 and 59.5 ZAm2, respectively. These combined intensities are much closer to a lower estimate for long-term dipole field strength, 50 ZAm2 (2), and some other estimates of average VADM based on paleointensities strictly from volcanic glasses. Proposed explanations for the observed non-GAD behavior, from otherwise high-quality paleointensity results, include incomplete temporal sampling, effects from the tangent cylinder, and hemispheric asymmetry. Differences in estimates of average magnetic field strength likely arise from inconsistent selection protocols and experiment methodologies. We address these possible biases and estimate the average dipole field strength for the last five million years by compiling measurement level data of IZZI-modified paleointensity experiments from lava flows around the globe (including new results from Iceland and the HSDP-2 Hawaii drill core). We use the Thellier Gui paleointensity interpreter (3) in order to apply objective criteria to all specimens, ensuring consistency between sites. Specimen level selection criteria are determined from a recent paleointensity investigation of modern Hawaiian lava flows where the expected magnetic field strength was accurately recovered when following certain selection parameters. Our new estimate of average dipole field strength for the last five million years incorporates multiple paleointensity studies on lava flows with diverse global and

RIEGER-TYPE PERIODICITY DURING SOLAR CYCLES 14–24: ESTIMATION OF DYNAMO MAGNETIC FIELD STRENGTH IN THE SOLAR INTERIOR

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

Gurgenashvili, Eka; Zaqarashvili, Teimuraz V.; Kukhianidze, Vasil

2016-07-20

Solar activity undergoes a variation over timescales of several months known as Rieger-type periodicity, which usually occurs near maxima of sunspot cycles. An early analysis showed that the periodicity appears only in some cycles and is absent in other cycles. But the appearance/absence during different cycles has not been explained. We performed a wavelet analysis of sunspot data from the Greenwich Royal Observatory and the Royal Observatory of Belgium during cycles 14–24. We found that the Rieger-type periods occur in all cycles, but they are cycle dependent: shorter periods occur during stronger cycles. Our analysis revealed a periodicity of 185–195more » days during the weak cycles 14–15 and 24 and a periodicity of 155–165 days during the stronger cycles 16–23. We derived the dispersion relation of the spherical harmonics of the magnetic Rossby waves in the presence of differential rotation and a toroidal magnetic field in the dynamo layer near the base of the convection zone. This showed that the harmonics of fast Rossby waves with m = 1 and n = 4, where m ( n ) indicates the toroidal (poloidal) wavenumbers, perfectly fit with the observed periodicity. The variation of the toroidal field strength from weaker to stronger cycles may lead to the different periods found in those cycles, which explains the observed enigmatic feature of the Rieger-type periodicity. Finally, we used the observed periodicity to estimate the dynamo field strength during cycles 14–24. Our estimations suggest a field strength of ∼40 kG for the stronger cycles and ∼20 kG for the weaker cycles.« less

Magnetic field dependence of the atomic collapse state in graphene

NASA Astrophysics Data System (ADS)

Moldovan, D.; Ramezani Masir, M.; Peeters, F. M.

2018-01-01

Quantum electrodynamics predicts that heavy atoms (Z > Zc ≈ 170 ) will undergo the process of atomic collapse where electrons sink into the positron continuum and a new family of so-called collapsing states emerges. The relativistic electrons in graphene exhibit the same physics but at a much lower critical charge (Zc ≈ 1 ) which has made it possible to confirm this phenomenon experimentally. However, there exist conflicting predictions on the effect of a magnetic field on atomic collapse. These theoretical predictions are based on the continuum Dirac-Weyl equation, which does not have an exact analytical solution for the interplay of a supercritical Coulomb potential and the magnetic field. Approximative solutions have been proposed, but because the two effects compete on similar energy scales, the theoretical treatment varies depending on the regime which is being considered. These limitations are overcome here by starting from a tight-binding approach and computing exact numerical results. By avoiding special limit cases, we found a smooth evolution between the different regimes. We predict that the atomic collapse effect persists even after the magnetic field is activated and that the critical charge remains unchanged. We show that the atomic collapse regime is characterized: (1) by a series of Landau level anticrossings and (2) by the absence of \\sqrt{B} scaling of the Landau levels with regard to magnetic field strength.

On the importance of body posture and skin modelling with respect to in situ electric field strengths in magnetic field exposure scenarios

NASA Astrophysics Data System (ADS)

Schmid, Gernot; Hirtl, Rene

2016-06-01

The reference levels and maximum permissible exposure values for magnetic fields that are currently used have been derived from basic restrictions under the assumption of upright standing body models in a standard posture, i.e. with arms laterally down and without contact with metallic objects. Moreover, if anatomical modelling of the body was used at all, the skin was represented as a single homogeneous tissue layer. In the present paper we addressed the possible impacts of posture and skin modelling in scenarios of exposure to a 50 Hz uniform magnetic field on the in situ electric field strength in peripheral tissues, which must be limited in order to avoid peripheral nerve stimulation. We considered different body postures including situations where body parts form large induction loops (e.g. clasped hands) with skin-to-skin and skin-to-metal contact spots and compared the results obtained with a homogeneous single-layer skin model to results obtained with a more realistic two-layer skin representation consisting of a low-conductivity stratum corneum layer on top of a combined layer for the cellular epidermis and dermis. Our results clearly indicated that postures with loops formed of body parts may lead to substantially higher maximum values of induced in situ electric field strengths than in the case of standard postures due to a highly concentrated current density and in situ electric field strength in the skin-to-skin and skin-to-metal contact regions. With a homogeneous single-layer skin, as is used for even the most recent anatomical body models in exposure assessment, the in situ electric field strength may exceed the basic restrictions in such situations, even when the reference levels and maximum permissible exposure values are not exceeded. However, when using the more realistic two-layer skin model the obtained in situ electric field strengths were substantially lower and no violations of the basic restrictions occurred, which can be explained by the

The tensile strength of ice and dust aggregates and its dependence on particle properties

NASA Astrophysics Data System (ADS)

Gundlach, B.; Schmidt, K. P.; Kreuzig, C.; Bischoff, D.; Rezaei, F.; Kothe, S.; Blum, J.; Grzesik, B.; Stoll, E.

2018-06-01

The knowledge of the tensile strength of astrophysical dust and ice aggregates is of major importance to understand the early stages of planet formation in our solar system and cometary activity. In this letter we report on an experimental setup, developed to measure the tensile strength of granular, astrophysical relevant materials, such as water ice and silica aggregates. We found that the tensile strength of aggregates composed of monodisperse silica particles depends on the grain size of the used material and is in a good agreement with the predictions of earlier works. For aggregates consisting of polydisperse water-ice particles, the measured tensile strength is very low compared to the theoretical prediction, which indicates that the specific surface energy of water ice at low temperatures is lower than previously assumed.

Regulatory Perspectives on Strength-Dependent Dissolution Profiles and Biowaiver Approaches for Immediate Release (IR) Oral Tablets in New Drug Applications.

PubMed

Suarez-Sharp, Sandra; Delvadia, Poonam R; Dorantes, Angelica; Duan, John; Externbrink, Anna; Gao, Zongming; Ghosh, Tapash; Miksinski, Sarah Pope; Seo, Paul

2016-05-01

Dissolution profile comparisons are used by the pharmaceutical industry to assess the similarity in the dissolution characteristics of two formulations to decide whether the implemented changes, usually minor/moderate in nature, will have an impact on the in vitro/in vivo performance of the drug product. When similarity testing is applied to support the approval of lower strengths of the same formulation, the traditional approach for dissolution profile comparison is not always applicable for drug products exhibiting strength-dependent dissolution and may lead to incorrect conclusions about product performance. The objective of this article is to describe reasonable biopharmaceutic approaches for developing a biowaiver strategy for low solubility, proportionally similar/non-proportionally similar in composition immediate release drug products that exhibit strength-dependent dissolution profiles. The paths highlighted in the article include (1) approaches to address biowaiver requests, such as the use of multi-unit dissolution testing to account for sink condition differences between the higher and lower strengths; (2) the use of a single- vs. strength-dependent dissolution method; and (3) the use of single- vs. strength-dependent dissolution acceptance criteria. These approaches are cost- and time-effective and can avoid unnecessary bioequivalence studies.

Electromagnetic-field dependence of the internal excited state of the polaron and the qubit in quantum dot with thickness

NASA Astrophysics Data System (ADS)

Bai, Xu-Fang; Xin, Wei; Yin, Hong-Wu; Eerdunchaolu

2017-06-01

The electromagnetic-field dependence of the ground and the first excited-state (GFES) energy eigenvalues and eigenfunctions of the strong-coupling polaron in a quantum dot (QD) was studied for various QD thicknesses by using the variational method of the Pekar type (VMPT). On this basis, we construct a qubit in the quantum dot (QQD) by taking a two-level structure of the polaron as the carrier. The results of numerical calculations indicate that the oscillation period of the qubit, {itT}{in0}, increases with increasing the thickness of the quantum dot (TQD) {itL}, but decreases with increasing the cyclotron frequency of the magnetic field (CFMF) ω{in{itc}}, electric-field strength {itF}, and electron-phonon coupling strength (EPCS) α. The probability density of the qubit |Ψ({itρ}, {itz}, {itt})|{su2} presents a normal distribution of the electronic transverse coordinate ρ, significantly influenced by the TQD and effective radius of the quantum dot (ERQD) {itR}{in0}, and shows a periodic oscillation with variations in the electronic longitudinal coordinate {itz}, polar angle φ and time {itt}. The decoherence time τ and the quality factor {itQ} of the free rotation increase with increasing the CFMF ω{in{itc}}, dispersion coefficient η, and EPCS α, but decrease with increasing the electric-field strength {itF}, TQD {itL}, and ERQD {itR}{in0}. The TQD is an important parameter of the qubit. Theoretically, the target, which is to regulate the oscillation period, decoherence time and quality factor of the free rotation of the qubit, can be achieved by designing different TQDs and regulating the strength of the electromagnetic field.

Observations of magnetic fields on solar-type stars

NASA Technical Reports Server (NTRS)

Marcy, G. W.

1982-01-01

Magnetic-field observations were carried out for 29 G and K main-sequence stars. The area covering-factors of magnetic regions tends to be greater in the K dwarfs than in the G dwarfs. However, no spectral-type dependence is found for the field strengths, contrary to predictions that pressure equilibrium with the ambient photospheric gas pressure would determine the surface field strengths. Coronal soft X-ray fluxes from the G and K dwarfs correlate well with the fraction of the stellar surface covered by magnetic regions. The dependence of coronal soft X-ray fluxes on photospheric field strengths is consistent with Stein's predicted generation-rates for Alfven waves. These dependences are inconsistent with the one dynamo model for which a specific prediction is offered. Finally, time variability of magnetic fields is seen on the two active stars that have been extensively monitored. Significant changes in magnetic fields are seen to occur on timescales as short as one day.

The effect of changing the magnetic field strength on HiPIMS deposition rates

NASA Astrophysics Data System (ADS)

Bradley, J. W.; Mishra, A.; Kelly, P. J.

2015-06-01

The marked difference in behaviour between HiPIMS and conventional dc or pulsed-dc magnetron sputtering discharges with changing magnetic field strengths is demonstrated through measurements of deposition rate. To provide a comparison between techniques the same circular magnetron was operated in the three excitation modes at a fixed average power of 680 W and a pressure of 0.54 Pa in the non-reactive sputtering of titanium. The total magnetic field strength B at the cathode surface in the middle of the racetrack was varied from 195 to 380 G. DC and pulsed-dc discharges show the expected behaviour that deposition rates fall with decreasing B (here by ~25-40%), however the opposite trend is observed in HiPIMS with deposition rates rising by a factor of 2 over the same decrease in B. These observations are understood from the stand point of the different composition and transport processes of the depositing metal flux between the techniques. In HiPIMS, this flux is largely ionic and slow post-ionized sputtered particles are subject to strong back attraction to the target by a retarding plasma potential structure ahead of them. The height of this potential barrier is known to increase with increasing B. From a simple phenomenological model of the sputtered particles fluxes, and using the measured deposition rates from the different techniques as inputs, the combined probabilities of ionization, α, and back attraction, β, of the metal species in HiPIMS has been calculated. There is a clear fall in αβ (from ~0.9 to ~0.7) with decreasing B-field strengths, we argue primarily due to a weakening of electrostatic ion back attraction, so leading to higher deposition rates. The results indicate that careful design of magnetron field strengths should be considered to optimise HiPIMS deposition rates.

Scale-dependent Normalized Amplitude and Weak Spectral Anisotropy of Magnetic Field Fluctuations in the Solar Wind Turbulence

NASA Astrophysics Data System (ADS)

Wang, Xin; Tu, Chuanyi; Marsch, Eckart; He, Jiansen; Wang, Linghua

2016-01-01

Turbulence in the solar wind was recently reported to be anisotropic, with the average power spectral index close to -2 when sampling parallel to the local mean magnetic field B0 and close to -5/3 when sampling perpendicular to the local B0. This result was widely considered to be observational evidence for the critical balance theory (CBT), which is derived by making the assumption that the turbulence strength is close to one. However, this basic assumption has not yet been checked carefully with observational data. Here we present for the first time the scale-dependent magnetic-field fluctuation amplitude, which is normalized by the local B0 and evaluated for both parallel and perpendicular sampling directions, using two 30-day intervals of Ulysses data. From our results, the turbulence strength is evaluated as much less than one at small scales in the parallel direction. An even stricter criterion is imposed when selecting the wavelet coefficients for a given sampling direction, so that the time stationarity of the local B0 is better ensured during the local sampling interval. The spectral index for the parallel direction is then found to be -1.75, whereas the spectral index in the perpendicular direction remains close to -1.65. These two new results, namely that the value of the turbulence strength is much less than one in the parallel direction and that the angle dependence of the spectral index is weak, cannot be explained by existing turbulence theories, like CBT, and thus will require new theoretical considerations and promote further observations of solar-wind turbulence.

Critical Magnetic Field Strengths for Unipolar Solar Coronal Plumes In Quiet Regions and Coronal Holes?

NASA Technical Reports Server (NTRS)

Avallone, Ellis; Tiwari, Sanjiv K.; Panesar, Navdeep K.; Moore, Ronald L.; Winebarger, Amy

2017-01-01

Coronal plumes are bright magnetic funnels that are found in quiet regions and coronal holes that extend high into the solar corona whose lifetimes can last from hours to days. The heating processes that make plumes bright involve the magnetic field at the base of the plume, but their intricacies remain mysterious. Raouafi et al. (2014) infer from observation that plume heating is a consequence of magnetic reconnection at the base, whereas Wang et al. (2016) infer that plume heating is a result of convergence of the magnetic flux at the plume's base, or base flux. Both papers suggest that the base flux in their plumes is of mixed polarity, but do not quantitatively measure the base flux or consider whether a critical magnetic field strength is required for plume production. To investigate the magnetic origins of plume heating, we track plume luminosity in the 171 Å wavelength as well as the abundance and strength of the base flux over the lifetimes of six unipolar coronal plumes. Of these, three are in coronal holes and three are in quiet regions. For this sample, we find that plume heating is triggered when convergence of the base flux surpasses a field strength of approximately 300 - 500 Gauss, and that the luminosity of both quiet region and coronal hole plumes respond similarly to the strength of the magnetic field in the base.

Chameleons with field-dependent couplings

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

Brax, Philippe; Bruck, Carsten van de; Mota, David F.

2010-10-15

Certain scalar-tensor theories exhibit the so-called chameleon mechanism, whereby observational signatures of scalar fields are hidden by a combination of self-interactions and interactions with ambient matter. Not all scalar-tensor theories exhibit such a chameleon mechanism, which has been originally found in models with inverse power runaway potentials and field-independent couplings to matter. In this paper we investigate field theories with field-dependent couplings and a power-law potential for the scalar field. We show that the theory indeed is a chameleon field theory. We find the thin-shell solution for a spherical body and investigate the consequences for Eoet-Wash experiments, fifth-force searches andmore » Casimir-force experiments. Requiring that the scalar field evades gravitational tests, we find that the coupling is sensitive to a mass scale which is of order of the Hubble scale today.« less

CNR considerations for rapid real-time MRI tumor tracking in radiotherapy hybrid devices: Effects of B{sub 0} field strength

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

Wachowicz, K., E-mail: keith.wachowicz@albertaheal

2016-08-15

Purpose: This work examines the subject of contrast-to-noise ratio (CNR), specifically between tumor and tissue background, and its dependence on the MRI field strength, B{sub 0}. This examination is motivated by the recent interest and developments in MRI/radiotherapy hybrids where real-time imaging can be used to guide treatment beams. The ability to distinguish a tumor from background tissue is of primary importance in this field, and this work seeks to elucidate the complex relationship between the CNR and B{sub 0} that is too often assumed to be purely linear. Methods: Experimentally based models of B{sub 0}-dependant relaxation for various tumormore » and normal tissues from the literature were used in conjunction with signal equations for MR sequences suitable for rapid real-time imaging to develop field-dependent predictions for CNR. These CNR models were developed for liver, lung, breast, glioma, and kidney tumors for spoiled gradient-echo, balanced steady-state free precession (bSSFP), and single-shot half-Fourier fast spin echo sequences. Results: Due to the pattern in which the relaxation properties of tissues are found to vary over B{sub 0} field (specifically the T{sub 1} time), there was always an improved CNR at lower fields compared to linear dependency. Further, in some tumor sites, the CNR at lower fields was found to be comparable to, or sometimes higher than those at higher fields (i.e., bSSFP CNR for glioma, kidney, and liver tumors). Conclusions: In terms of CNR, lower B{sub 0} fields have been shown to perform as well or better than higher fields for some tumor sites due to superior T{sub 1} contrast. In other sites this effect was less pronounced, reversing the CNR advantage. This complex relationship between CNR and B{sub 0} reveals both low and high magnetic fields as viable options for tumor tracking in MRI/radiotherapy hybrids.« less

H:q ratios and bilateral leg strength in college field and court sports players.

PubMed

Cheung, Roy T H; Smith, Andrew W; Wong, Del P

2012-06-01

One of the key components in sports injury prevention is the identification of imbalances in leg muscle strength. However, different leg muscle characteristics may occur in large playing area (field) sports and small playing area (court) sports, which should be considered in regular injury prevention assessment. This study examined the isokinetic hamstrings-to-quadriceps (H:Q) ratio and bilateral leg strength balance in 40 male college (age: 23.4 ± 2.5 yrs) team sport players (field sport = 23, soccer players; court sport = 17, volleyball and basketball players). Five repetitions of maximal knee concentric flexion and concentric extension were performed on an isokinetic dynamometer at two speeds (slow: 60°·s(-1) and fast: 300°·s(-1)) with 3 minutes rest between tests. Both legs were measured in counterbalanced order with the dominant leg being determined as the leg used to kick a ball. The highest concentric peak torque values (Nm) of the hamstrings and quadriceps of each leg were analyzed after body mass normalization (Nm·kg(-1)). Court sport players showed significantly weaker dominant leg hamstrings muscles at both contraction speeds (P < 0.05). The H:Q ratio was significantly larger in field players in their dominant leg at 60°·s(-1) (P < 0.001), and their non-dominant leg at 300°·s(-1) (P < 0.001) respectively. Sport-specific leg muscle strength was evident in college players from field and court sports. These results suggest the need for different muscle strength training and rehabilitation protocols for college players according to the musculature requirements in their respective sports.

Relative scale and the strength and deformability of rock masses

NASA Astrophysics Data System (ADS)

Schultz, Richard A.

1996-09-01

The strength and deformation of rocks depend strongly on the degree of fracturing, which can be assessed in the field and related systematically to these properties. Appropriate Mohr envelopes obtained from the Rock Mass Rating (RMR) classification system and the Hoek-Brown criterion for outcrops and other large-scale exposures of fractured rocks show that rock-mass cohesive strength, tensile strength, and unconfined compressive strength can be reduced by as much as a factor often relative to values for the unfractured material. The rock-mass deformation modulus is also reduced relative to Young's modulus. A "cook-book" example illustrates the use of RMR in field applications. The smaller values of rock-mass strength and deformability imply that there is a particular scale of observation whose identification is critical to applying laboratory measurements and associated failure criteria to geologic structures.

An overview of strength training injuries: acute and chronic.

PubMed

Lavallee, Mark E; Balam, Tucker

2010-01-01

This article introduces the history of strength training, explains the many different styles of strength training, and discusses common injuries specific to each style. Strength training is broken down into five disciplines: basic strength or resistance training, bodybuilding, power lifting, style-dependant strength sports (e.g., strongman competitions, Highland games, field events such as shot put, discus, hammer throw, and javelin), and Olympic-style weightlifting. Each style has its own principal injuries, both acute and chronic, related to the individual technique. Acute injuries should be further categorized as emergent or nonemergent. Specific age-related populations (i.e., the very young and the aging athlete) carry additional considerations.

Complete magnetic field dependence of SABRE-derived polarization.

PubMed

Kiryutin, Alexey S; Yurkovskaya, Alexandra V; Zimmermann, Herbert; Vieth, Hans-Martin; Ivanov, Konstantin L

2018-07-01

Signal amplification by reversible exchange (SABRE) is a promising hyperpolarization technique, which makes use of spin-order transfer from parahydrogen (the H 2 molecule in its singlet spin state) to a to-be-polarized substrate in a transient organometallic complex, termed the SABRE complex. In this work, we present an experimental method for measuring the magnetic field dependence of the SABRE effect over an ultrawide field range, namely, from 10 nT to 10 T. This approach gives a way to determine the complete magnetic field dependence of SABRE-derived polarization. Here, we focus on SABRE polarization of spin-1/2 hetero-nuclei, such as 13 C and 15 N and measure their polarization in the entire accessible field range; experimental studies are supported by calculations of polarization. Features of the field dependence of polarization can be attributed to level anticrossings in the spin system of the SABRE complex. Features at magnetic fields of the order of 100 nT-1 μT correspond to "strong coupling" of protons and hetero-nuclei, whereas features found in the mT field range stem from "strong coupling" of the proton system. Our approach gives a way to measuring and analyzing the complete SABRE field dependence, to probing NMR parameters of SABRE complexes and to optimizing the polarization value. Copyright © 2017 John Wiley & Sons, Ltd.

Rate dependent strengths of some solder joints

NASA Astrophysics Data System (ADS)

Williamson, D. M.; Field, J. E.; Palmer, S. J. P.; Siviour, C. R.

2007-08-01

The shear strengths of three lead-free solder joints have been measured over the range of loading rates 10-3 to ~105 mm min-1. Binary (SnAg), ternary (SnAgCu) and quaternary (Castin: SnAgCuSb) alloys have been compared to a conventional binary SnPb solder alloy. Results show that at loading rates from 10-3 to 102 mm min-1, all four materials exhibit a linear relationship between the shear strength and the loading rate when the data are plotted on a log-log plot. At the highest loading rate of 105 mm min-1, the strengths of the binary alloys were in agreement with extrapolations made from the lower loading rate data. In contrast, the strengths of the higher order alloys were found to be significantly lower than those predicted by extrapolation. This is explained by a change in failure mechanism on the part of the higher order alloys. Similar behaviour was found in measurements of the tensile strengths of solder joints using a novel high-rate loading tensile test. Optical and electron microscopy were used to examine the microstructures of interest in conjunction with energy dispersive x-ray analysis for elemental identification. The effect of artificial aging and reflow of the solder joints is also reported.

Developments in deep brain stimulation using time dependent magnetic fields

NASA Astrophysics Data System (ADS)

Crowther, L. J.; Nlebedim, I. C.; Jiles, D. C.

2012-04-01

The effect of head model complexity upon the strength of field in different brain regions for transcranial magnetic stimulation (TMS) has been investigated. Experimental measurements were used to verify the validity of magnetic field calculations and induced electric field calculations for three 3D human head models of varying complexity. Results show the inability for simplified head models to accurately determine the site of high fields that lead to neuronal stimulation and highlight the necessity for realistic head modeling for TMS applications.

Developments in deep brain stimulation using time dependent magnetic fields

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

Crowther, L.J.; Nlebedim, I.C.; Jiles, D.C.

2012-03-07

The effect of head model complexity upon the strength of field in different brain regions for transcranial magnetic stimulation (TMS) has been investigated. Experimental measurements were used to verify the validity of magnetic field calculations and induced electric field calculations for three 3D human head models of varying complexity. Results show the inability for simplified head models to accurately determine the site of high fields that lead to neuronal stimulation and highlight the necessity for realistic head modeling for TMS applications.

Imaging shear strength along subduction faults

USGS Publications Warehouse

Bletery, Quentin; Thomas, Amanda M.; Rempel, Alan W.; Hardebeck, Jeanne L.

2017-01-01

Subduction faults accumulate stress during long periods of time and release this stress suddenly, during earthquakes, when it reaches a threshold. This threshold, the shear strength, controls the occurrence and magnitude of earthquakes. We consider a 3-D model to derive an analytical expression for how the shear strength depends on the fault geometry, the convergence obliquity, frictional properties, and the stress field orientation. We then use estimates of these different parameters in Japan to infer the distribution of shear strength along a subduction fault. We show that the 2011 Mw9.0 Tohoku earthquake ruptured a fault portion characterized by unusually small variations in static shear strength. This observation is consistent with the hypothesis that large earthquakes preferentially rupture regions with relatively homogeneous shear strength. With increasing constraints on the different parameters at play, our approach could, in the future, help identify favorable locations for large earthquakes.

Mass and Magnetic Field Dependence of Electrostatic Particle Transport and Turbulence in LAPD-U

NASA Astrophysics Data System (ADS)

Crocker, N. A.; Gilmore, M.; Peebles, W. A.; Will, S.; Nguyen, X. V.; Carter, T. A.

2003-10-01

The scaling of particle transport with ion mass and magnetic field strength remains an open question in plasma research. Direct comparison of experiment with theory is often complicated by inability to significantly vary critical parameters such as ion mass, pressure gradient, ion gyro-radius, etc. The LAPD-U magnetized, linear plasma at UCLA provides the ideal platform for such studies, allowing large parameter variation. The magnetic field in LAPD-U can be varied over a range of 500 - 1500 G, while ion species can be varied to change mass by a factor of at least 10. In addition, ion gyro-radii are small compared to the plasma diameter ( 1 m). Cross-field transport in LAPD-U is thought to be caused by electrostatic turbulence, also a leading candidate for transport in fusion plasmas. It is planned, therefore, to investigate turbulence and transport characteristics as a function of parameter space. In particular, measurement of the mass and magnetic field dependence of electrostatic particle transport and turbulence characteristics in LAPD-U will be presented.

Energy Levels and Spectral Lines of Li Atoms in White Dwarf Strength Magnetic Fields

NASA Astrophysics Data System (ADS)

Zhao, L. B.

2018-04-01

A theoretical approach based on B-splines has been developed to calculate atomic structures and discrete spectra of Li atoms in a strong magnetic field typical of magnetic white dwarf stars. Energy levels are presented for 20 electronic states with the symmetries 20+, 20‑, 2(‑1)+, 2(‑1)‑, and 2(‑2)+. The magnetic field strengths involved range from 0 to 2350 MG. The wavelengths and oscillator strengths for the electric dipole transitions relevant to these magnetized atomic states are reported. The current results are compared to the limited theoretical data in the literature. A good agreement has been found for the lower energy levels, but a significant discrepancy is clearly visible for the higher energy levels. The existing discrepancies of the wavelengths and oscillator strengths are also discussed. Our investigation shows that the spectrum data of magnetized Li atoms previously published are obviously far from meeting requirements of analyzing discrete atomic spectra of magnetic white dwarfs with lithium atmospheres.

Photodetachment dynamics in a time-dependent oscillating electric field

NASA Astrophysics Data System (ADS)

Wang, De-hua; Xu, Qin-feng; Du, Jie

2017-03-01

Using the time-dependent form of closed orbit theory, as developed by Haggerty and Delos [M.R. Haggerty, J.B. Delos, Phys. Rev. A 61, 053406 (2000)], and by Yang and Robicheaux [B.C. Yang, F. Robicheaux, Phys. Rev. A 93, 053413 (2016)], we study the photodetachment dynamics of a hydrogen negative ion in a time-dependent oscillating electric field. Compared to the photodetachment in a static electric field, the photodetachment dynamics of a negative ion in the time-dependent oscillating electric field become much more complicated but more interesting. Since the applied electric field is oscillating with time, the photodetachment cross section of the negative ion in the oscillating electric field is time-dependent. In a time-dependent framework, we put forward an analytical formula for calculating the instantaneous photodetachment cross section of this system. Our study suggests that the instantaneous photodetachment cross section exhibits oscillatory structure, which depends sensitively on the frequency of the oscillating electric field. With increasing frequency of the oscillating electric field, the number of closed orbits increases and the oscillatory structure in the photodetachment cross section becomes much more complicated. The connection between the detached electron's closed orbit with the oscillating cross section is analyzed quantitatively. This study provides a clear and intuitive picture for the photodetachment processes of a negative ion in the presence of an oscillating electric field. We hope that our work will be useful in guiding future experimental research.

Magnetic field strength of a neutron-star-powered ultraluminous X-ray source

NASA Astrophysics Data System (ADS)

Brightman, M.; Harrison, F. A.; Fürst, F.; Middleton, M. J.; Walton, D. J.; Stern, D.; Fabian, A. C.; Heida, M.; Barret, D.; Bachetti, M.

2018-04-01

Ultraluminous X-ray sources (ULXs) are bright X-ray sources in nearby galaxies not associated with the central supermassive black hole. Their luminosities imply they are powered by either an extreme accretion rate onto a compact stellar remnant, or an intermediate mass ( 100-105M⊙) black hole1. Recently detected coherent pulsations coming from three bright ULXs2-5 demonstrate that some of these sources are powered by accretion onto a neutron star, implying accretion rates significantly in excess of the Eddington limit, a high degree of geometric beaming, or both. The physical challenges associated with the high implied accretion rates can be mitigated if the neutron star surface field is very high (1014 G)6, since this suppresses the electron scattering cross-section, reducing the radiation pressure that chokes off accretion for high luminosities. Surface magnetic field strengths can be determined through cyclotron resonance scattering features7,8 produced by the transition of charged particles between quantized Landau levels. Here, we present the detection at a significance of 3.8σ of an absorption line at 4.5 keV in the Chandra spectrum of a ULX in M51. This feature is likely to be a cyclotron resonance scattering feature produced by the strong magnetic field of a neutron star. Assuming scattering off electrons, the magnetic field strength is implied to be 1011 G, while protons would imply a magnetic field of B 1015 G.

Using coronal seismology to estimate the magnetic field strength in a realistic coronal model

NASA Astrophysics Data System (ADS)

Chen, F.; Peter, H.

2015-09-01

Aims: Coronal seismology is used extensively to estimate properties of the corona, e.g. the coronal magnetic field strength is derived from oscillations observed in coronal loops. We present a three-dimensional coronal simulation, including a realistic energy balance in which we observe oscillations of a loop in synthesised coronal emission. We use these results to test the inversions based on coronal seismology. Methods: From the simulation of the corona above an active region, we synthesise extreme ultraviolet emission from the model corona. From this, we derive maps of line intensity and Doppler shift providing synthetic data in the same format as obtained from observations. We fit the (Doppler) oscillation of the loop in the same fashion as done for observations to derive the oscillation period and damping time. Results: The loop oscillation seen in our model is similar to imaging and spectroscopic observations of the Sun. The velocity disturbance of the kink oscillation shows an oscillation period of 52.5 s and a damping time of 125 s, which are both consistent with the ranges of periods and damping times found in observations. Using standard coronal seismology techniques, we find an average magnetic field strength of Bkink = 79 G for our loop in the simulation, while in the loop the field strength drops from roughly 300 G at the coronal base to 50 G at the apex. Using the data from our simulation, we can infer what the average magnetic field derived from coronal seismology actually means. It is close to the magnetic field strength in a constant cross-section flux tube, which would give the same wave travel time through the loop. Conclusions: Our model produced a realistic looking loop-dominated corona, and provides realistic information on the oscillation properties that can be used to calibrate and better understand the result from coronal seismology. A movie associated with Fig. 1 is available in electronic form at http://www.aanda.org

Doxycycline shows dose-dependent changes in hernia repair strength after mesh repair.

PubMed

Tharappel, Job C; Harris, Jennifer W; Zwischenberger, Brittany A; Levy, Salomon M; Puleo, David A; Roth, J Scott

2016-05-01

Ventral hernia is a commonly occurring surgical problem. Our earlier studies have shown that a 30 mg/kg dose of doxycycline can significantly impact the strength of polypropylene (PP) mesh in a rat hernia repair model at 6 and 12 weeks. The objective of the present study was to investigate the dose dependence of doxycycline treatment on hernia repair strengths in rats. Fifty-six Sprague-Dawley rats underwent hernia repair with either PP mesh (n = 28) or sutures only (primary; n = 28); both groups were further divided into four doxycycline groups of seven animals each: control (0 mg/kg), low (3 mg/kg), medium (10 mg/kg), and high (30 mg/kg). One day before hernia repair surgery, animals received doxycycline doses by gavage and continued receiving daily until euthanasia. After 8 weeks, rats were euthanized and tissue samples from hernia repaired area were collected and analyzed for tensile strength using a tensiometer (Instron, Canton, MA, USA), while MMPs 2, 3, and 9, and collagen type 1 and 3 were analyzed by western blotting. In mesh-repaired animals, medium and high doxycycline dose repaired mesh fascia interface (MFI) showed significant increase in tensile strength when compared to control. In the primary repaired animals, there was no significant difference in MFI tensile strength in any dose group. In medium-dose MFI, there was a significant reduction in MMPs 2, 3, and 9. In this animal group, MFI showed significant increase in collagen 1 and significant reduction in collagen type 3 when compared to control. It is possible to improve the strength of mesh-repaired tissue by administering a significantly lower dose of the drug, which has implications for translation of the findings.

A compact high-speed mechanical sample shuttle for field-dependent high-resolution solution NMR

NASA Astrophysics Data System (ADS)

Chou, Ching-Yu; Chu, Minglee; Chang, Chi-Fon; Huang, Tai-huang

2012-01-01

Analysis of NMR relaxation data has provided significant insight on molecular dynamic, leading to a more comprehensive understanding of macromolecular functions. However, traditional methodology allows relaxation measurements performed only at a few fixed high fields, thus severely restricting their potential for extracting more complete dynamic information. Here we report the design and performance of a compact high-speed servo-mechanical shuttle assembly adapted to a commercial 600 MHz high-field superconducting magnet. The assembly is capable of shuttling the sample in a regular NMR tube from the center of the magnet to the top (fringe field ˜0.01 T) in 100 ms with no loss of sensitivity other than that due to intrinsic relaxation. The shuttle device can be installed by a single experienced user in 30 min. Excellent 2D- 15N-HSQC spectra of (u- 13C, 15N)-ubiquitin with relaxation at low fields (3.77 T) and detection at 14.1 T were obtained to illustrate its utility in R 1 measurements of macromolecules at low fields. Field-dependent 13C-R 1 data of (3,3,3-d)-alanine at various field strengths were determined and analyzed to assess CSA and 1H- 13C dipolar contributions to the carboxyl 13C-R 1.

Time-Dependent Stress Rupture Strength Degradation of Hi-Nicalon Fiber-Reinforced Silicon Carbide Composites at Intermediate Temperatures

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.

2016-01-01

The stress rupture strength of silicon carbide fiber-reinforced silicon carbide composites with a boron nitride fiber coating decreases with time within the intermediate temperature range of 700 to 950 degree Celsius. Various theories have been proposed to explain the cause of the time-dependent stress rupture strength. The objective of this paper is to investigate the relative significance of the various theories for the time-dependent strength of silicon carbide fiber-reinforced silicon carbide composites. This is achieved through the development of a numerically based progressive failure analysis routine and through the application of the routine to simulate the composite stress rupture tests. The progressive failure routine is a time-marching routine with an iterative loop between a probability of fiber survival equation and a force equilibrium equation within each time step. Failure of the composite is assumed to initiate near a matrix crack and the progression of fiber failures occurs by global load sharing. The probability of survival equation is derived from consideration of the strength of ceramic fibers with randomly occurring and slow growing flaws as well as the mechanical interaction between the fibers and matrix near a matrix crack. The force equilibrium equation follows from the global load sharing presumption. The results of progressive failure analyses of the composite tests suggest that the relationship between time and stress-rupture strength is attributed almost entirely to the slow flaw growth within the fibers. Although other mechanisms may be present, they appear to have only a minor influence on the observed time-dependent behavior.

Airborne field strength monitoring

NASA Astrophysics Data System (ADS)

Bredemeyer, J.; Kleine-Ostmann, T.; Schrader, T.; Münter, K.; Ritter, J.

2007-06-01

In civil and military aviation, ground based navigation aids (NAVAIDS) are still crucial for flight guidance even though the acceptance of satellite based systems (GNSS) increases. Part of the calibration process for NAVAIDS (ILS, DME, VOR) is to perform a flight inspection according to specified methods as stated in a document (DOC8071, 2000) by the International Civil Aviation Organization (ICAO). One major task is to determine the coverage, or, in other words, the true signal-in-space field strength of a ground transmitter. This has always been a challenge to flight inspection up to now, since, especially in the L-band (DME, 1GHz), the antenna installed performance was known with an uncertainty of 10 dB or even more. In order to meet ICAO's required accuracy of ±3 dB it is necessary to have a precise 3-D antenna factor of the receiving antenna operating on the airborne platform including all losses and impedance mismatching. Introducing precise, effective antenna factors to flight inspection to achieve the required accuracy is new and not published in relevant papers yet. The authors try to establish a new balanced procedure between simulation and validation by airborne and ground measurements. This involves the interpretation of measured scattering parameters gained both on the ground and airborne in comparison with numerical results obtained by the multilevel fast multipole algorithm (MLFMA) accelerated method of moments (MoM) using a complex geometric model of the aircraft. First results will be presented in this paper.

Research on breakdown characteristics of oil-paper insulation in compound field at different temperatures

NASA Astrophysics Data System (ADS)

Li, L.; Chen, M. Y.; Zhu, X. C.; Gao, Z. W.; Zhang, H. D.; Li, G. X.; Zhang, J.; Yu, C. L.; Feng, Y. M.

2018-01-01

The breakdown characteristics of oil-paper insulation in AC, DC and compound field at different temperatures were studied. The breakdown mechanism of oil-paper insulation at different temperatures and in AC and DC electric fields was analyzed. The breakdown characteristic mechanisms of the oil-paper insulation in the compound field at different temperatures were obtained: the dielectric strength of oil-paper compound insulation is changed gradually from dependence on oil dielectric strength to dependence on paperboard dielectric strength at low temperature. The dielectric strength of oil-paper compound insulation is always related to the oil dielectric strength closely at high temperature with decrease of AC content.

Molecular Dynamics in Physiological Solutions: Force Fields, Alkali Metal Ions, and Ionic Strength.

PubMed

Zhang, Chao; Raugei, Simone; Eisenberg, Bob; Carloni, Paolo

2010-07-13

The monovalent ions Na(+) and K(+) and Cl(-) are present in any living organism. The fundamental thermodynamic properties of solutions containing such ions is given as the excess (electro-)chemical potential differences of single ions at finite ionic strength. This quantity is key for many biological processes, including ion permeation in membrane ion channels and DNA-protein interaction. It is given by a chemical contribution, related to the ion activity, and an electric contribution, related to the Galvani potential of the water/air interface. Here we investigate molecular dynamics based predictions of these quantities by using a variety of ion/water force fields commonly used in biological simulation, namely the AMBER (the newly developed), CHARMM, OPLS, Dang95 with TIP3P, and SPC/E water. Comparison with experiment is made with the corresponding values for salts, for which data are available. The calculations based on the newly developed AMBER force field with TIP3P water agrees well with experiment for both KCl and NaCl electrolytes in water solutions, as previously reported. The simulations based on the CHARMM-TIP3P and Dang95-SPC/E force fields agree well for the KCl and NaCl solutions, respectively. The other models are not as accurate. Single cations excess (electro-)chemical potential differences turn out to be similar for all the force fields considered here. In the case of KCl, the calculated electric contribution is consistent with higher level calculations. Instead, such agreement is not found with NaCl. Finally, we found that the calculated activities for single Cl(-) ions turn out to depend clearly on the type of counterion used, with all the force fields investigated. The implications of these findings for biomolecular systems are discussed.

Stimulus augmenting and field dependence in children of alcoholic fathers.

PubMed

Hennecke, L

1984-11-01

The relationship between paternal alcoholism and two perceptual characteristics, stimulus augmenting and field dependence, was tested in boys and girls aged 10-12. Thirty children of alcoholic fathers, presumed at high risk for the disease because of its familial-genetic component, were compared with 30 children of nonalcoholic parents. Stimulus augmenting was measured by the Kinesthetic Figural After-Effect (KFA) test and field dependence by the Embedded Figures Test (EFT). It was reasoned that the consistent findings of field dependence in alcoholics could be a manifestation of brain damage and the consequent cognitive deficits often found in alcoholics. Thus it was proposed that field dependence would not differentiate the children of alcoholic fathers from those of nonalcoholics. No difference in field dependence was found between the groups, which supports other evidence that alcoholism can lead to field dependence. Since KFA scores revealed a significantly higher incidence of stimulus augmenters in the children of alcoholic fathers, it is proposed that stimulus augmenting is premorbid to alcoholism. It remains unclear, however, whether this phenomenon is due to an environmental or genetic factor.

Critical Magnetic Field Strengths for Unipolar Solar Coronal Plumes in Quiet Regions and Coronal Holes?

NASA Astrophysics Data System (ADS)

Avallone, E. A.; Tiwari, S. K.; Panesar, N. K.; Moore, R. L.

2017-12-01

Coronal plumes are sporadic fountain-like structures that are bright in coronal emission. Each is a magnetic funnel rooted in a strong patch of dominant-polarity photospheric magnetic flux surrounded by a predominantly-unipolar magnetic network, either in a quiet region or a coronal hole. The heating processes that make plumes bright evidently involve the magnetic field in the base of the plume, but remain mysterious. Raouafi et al. (2014) inferred from observations that plume heating is a consequence of magnetic reconnection in the base, whereas Wang et al. (2016) showed that plume heating turns on/off from convection-driven convergence/divergence of the base flux. While both papers suggest that the base magnetic flux in their plumes is of mixed polarity, these papers provide no measurements of the abundance and strength of the evolving base flux or consider whether a critical magnetic field strength is required for a plume to become noticeably bright. To address plume production and evolution, we track the plume luminosity and the abundance and strength of the base magnetic flux over the lifetimes of six coronal plumes, using Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) 171 Å images and SDO/Helioseismic and Magnetic Imager (HMI) line-of-sight magnetograms. Three of these plumes are in coronal holes, three are in quiet regions, and each plume exhibits a unipolar base flux. We track the base magnetic flux over each plume's lifetime to affirm that its convergence and divergence respectively coincide with the appearance and disappearance of the plume in 171 Å images. We tentatively find that plume formation requires enough convergence of the base flux to surpass a field strength of ˜300-500 Gauss, and that quiet Sun and coronal-hole plumes both exhibit the same behavior in the response of their luminosity in 171 Å to the strength of the magnetic field in the base.

Characterisation of cationic potato starch by asymmetrical flow field-flow fractionation. Influence of ionic strength and degree of substitution.

PubMed

Santacruz, Stalin

2014-06-15

The properties of a paper sheet depend on the absorption together with the physico-chemical properties of additives used in the paper processing. The effect of ionic strength and degree of substitution of cationic potato starch on the elution pattern of asymmetrical flow field-flow fractionation was analysed. The effect of starch derivatisation, in either dry or wet phase, was also investigated. Average molar mass showed no difference between the starches obtained from the two derivatisation processes. Apparent densities showed that dry cationic starch had higher density than wet cationic starch for a hydrodynamic radius between 50 and 100 nm. Elution times of native and three cationic starches increased when the ionic strength increased from 50 to 100mM. No differences in the molar mass among cationic starches with different degree of substitution suggested no degradation due to a derivatisation process. Large sample loads can be used at 100mM without overloading. Copyright © 2014 Elsevier Ltd. All rights reserved.

In situ rock strength and far field stress in the Nankai accretionary complex: Integration of downhole data from multiple wells

NASA Astrophysics Data System (ADS)

Huffman, K. A.; Saffer, D. M.

2014-12-01

Knowing the magnitude of tectonic stress and rock strength at seismically active margins is important towards understanding fault strength and failure mechanics, yet both are difficult to measure in situ. Recent work at subduction margins, including Integrated Ocean Drilling Program (IODP) Nankai Trough Subduction Zone Experiment (NanTroSEIZE) drillsites, uses the width of compressional wellbore breakouts (BO), which depends on far field stress conditions, rock strength, and borehole annular pressure (APRS), to estimate the magnitude of horizontal principal stresses (SHmax and Shmin); estimates are problematic due to uncertainty in rock strength (unconfined compressive strength/UCS- for which direct measurements are scarce) and rheology that govern stress distribution at the wellbore. We conduct a novel case study at IODP Site C0002, where a hole was drilled twice with different boundary conditions, providing an opportunity to define in situ stress and strength from field data. Site C0002 is the main deep riser borehole for NanTroSEIZE, located near the seaward edge of the Kumano Basin above the seismogenic plate boundary, ~30 km from the trench. Several boreholes were drilled at the site. During IODP Expedition 314 in 2007, Hole C0002A was drilled with a suite of logging while drilling (LWD) tools to 1401 mbsf in a riserless mode. Hole C0002F, ~70 m away, was drilled to 862 mbsf in riserless mode during Exp. 326 in 2010 and deepened to 2005 mbsf in a riser mode during Expedition 338 in 2012-2013. Increased APRS achieved by riser drilling stabilizes the borehole and suppresses BO, consistent with resistivity imaging data from Exp. 314 that document well-developed, continuous BO throughout the borehole, and data from Expedition 338 indicating few BO. We use a semi-Newtonian approach to solve for stress and UCS consistent with the observed BO width and measured APRS in the two holes over the interval from 862-2005 mbsf. Effective SHmax ranges from ~10-30 MPa and

The performance of interventional loopless MRI antennae at higher magnetic field strengths

PubMed Central

El-Sharkawy, AbdEl-Monem M.; Qian, Di; Bottomley, Paul A.

2008-01-01

Interventional, “loopless antenna” MRI detectors are currently limited to 1.5 T. This study investigates whether loopless antennae offer signal-to-noise ratio (SNR) and field-of-view (FOV) advantages at higher fields, and whether device heating can be controlled within safe limits. The absolute SNR performance of loopless antennae from 0.5 to 5 T is investigated both analytically, using electromagnetic (EM) dipole antenna theory, and numerically with the EM method of moments, and found to vary almost quadratically with field strength depending on the medium’s electrical properties, the noise being dominated by direct sample conduction losses. The prediction is confirmed by measurements of the absolute SNR of low-loss loopless antennae fabricated for 1.5, 3, and 4.7 T, immersed in physiologically comparable saline. Gains of 3.8±0.2- and 9.7±0.3-fold in SNR, and approximately 10- and 50-fold gains in the useful FOV area are observed at 3 and 4.7 T, respectively, compared to 1.5 T. Heat testing of a 3 T biocompatible nitinol-antenna fabricated with a redesigned decoupling circuit shows maximum heating of ∼1 °C for MRI operating at high MRI exposure levels. Experiments in the rabbit aorta confirm the SNR and FOV advantages of the 3 T antenna versus an equivalent commercial 1.5 T device in vivo. This work is the first to study the performance of experimental internal MRI detectors above 1.5 T. The large SNR and FOV gains realized present a major opportunity for high-resolution imaging of vascular pathology and MRI-guided intervention. PMID:18561676

Temperature-dependent residual shear strength characteristics of smectite-rich landslide soils

NASA Astrophysics Data System (ADS)

Shibasaki, Tatsuya; Matsuura, Sumio; Okamoto, Takashi

2015-04-01

On gentle clayey slopes in weathered argillaceous rock areas, there exist many landslides which repeatedly reactivate with slow movement. The slip surface soils of these landslides are sometimes composed dominantly of swelling clay mineral (smectite) which is well known to show extremely low residual friction angle. From field data monitored at landslide sites in Japan, it has become clear that some landslides with relatively shallow slip surface begin to move and become active in late autumn or early winter every year. In such cases, the triggering mechanisms of landslides have not been understood well enough, because landslide initiation and movement are not always clearly linked with rises in pore water pressures (ground water levels). In this study, we focus on the influence of seasonal variation in ground temperature on slope stability and have investigated the effect of temperature on the shear strength of slip surface soils. Undisturbed soil samples were collected by boring from the Busuno landslide in Japan. We performed box shear experiments on undisturbed slip surface soils at low temperature ranges (approximately 5-25 °C). XRD analysis revealed that these soils contain high fraction of smectite. Slickensided slip surface within test specimen was coincided with the shearing plane of the shear box and shear displacement was applied precisely along the localized slip surface. Experiments were performed under slow shearing rate condition (0.005mm/min) and the results showed that shear strength decreased with decreasing temperature. Temperature effect was rather significant on frictional angle than on cohesion. Ring shear experiments were also performed on normally-consolidated remoulded samples. Under residual strength condition, temperature-change experiments (cooling-event tests) ranging approximately from 5 to 25 °C were performed on smectite-rich landslide soils and commercial bentonites. As well as the results by box shear test, shear weakening

47 CFR 73.151 - Field strength measurements to establish performance of directional antennas.

Code of Federal Regulations, 2010 CFR

2010-10-01

... verified either by field strength measurement or by computer modeling and sampling system verification. (a... specifically identified by the Commission. (c) Computer modeling and sample system verification of modeled... performance verified by computer modeling and sample system verification. (1) A matrix of impedance...

Resolution Improvements in in Vivo1H NMR Spectra with Increased Magnetic Field Strength

NASA Astrophysics Data System (ADS)

Gruetter, Rolf; Weisdorf, Sally A.; Rajanayagan, Vasantham; Terpstra, Melissa; Merkle, Hellmut; Truwit, Charles L.; Garwood, Michael; Nyberg, Scott L.; Ugurbil, Kâmil

1998-11-01

The measurement of cerebral metabolites using highly homologous localization techniques and similar shimming methods was performed in the human brain at 1.5 and 4 T as well as in the dog and rat brain at 9.4 T. In rat brain, improved resolution was achieved by shimming all first- and second-order shim coils using a fully adiabatic FASTMAP sequence. The spectra showed a clear improvement in spectral resolution for all metabolite resonances with increased field strength. Changes in cerebral glutamine content were clearly observed at 4 T compared to 1.5 T in patients with hepatic encephalopathy. At 9.4 T, glutamine H4 at 2.46 ppm was fully resolved from glutamate H4 at 2.37 ppm, as was the potential resonance from γ-amino-butyric acid at 2.30 ppm and N-acetyl-aspartyl-glutamate at 2.05 ppm. Singlet linewidths were found to be as low as 6 Hz (0.015 ppm) at 9.4 T, indicating a substantial decrease in ppm linewidth with field strength. Furthermore, the methylene peak of creatine was partially resolved from phosphocreatine, indicating a close to 1:1 relationship in gray matter. We conclude that increasing the magnetic field strength increases spectral resolution also for1H NMR, which can lead to more than linear sensitivity gains.

Magnetic field evolution in white dwarfs: The hall effect and complexity of the field

NASA Technical Reports Server (NTRS)

Muslimov, A. G.; Van Horn, H. M.; Wood, M. A.

1995-01-01

We calculate the evolution of the magnetic fields in white dwarfs, taking into account the Hall effect. Because this effect depends nonlinearly upon the magnetic field strength B, the time dependences of the various multipole field components are coupled. The evolution of the field is thus significantly more complicated than has been indicated by previous investigations. Our calculations employ recent white dwarf evolutionary sequences computed for stars with masses 0.4, 0.6, 0.8, and 1.0 solar mass. We show that in the presence of a strong (up to approximately 10(exp 9) G) internal toroidal magnetic field; the evolution of even the lowest order poloidal modes can be substantially changed by the Hall effect. As an example, we compute the evolution of an initially weak quadrupole component, which we take arbitrarily to be approximately 0.1%-1% of the strength of a dominant dipole field. We find that coupling provided by the Hall effect can produce growth of the ratio of the quadrupole to the dipole component of the surface value of the magnetic field strength by more than a factor of 10 over the 10(exp 9) to 10(exp 10) year cooling lifetime of the white dwarf. Some consequences of these results for the process of magnetic-field evolution in white dwarfs are briefly discussed.

Specific absorption rate dependence on temperature in magnetic field hyperthermia measured by dynamic hysteresis losses (ac magnetometry)

NASA Astrophysics Data System (ADS)

Garaio, Eneko; Sandre, Olivier; Collantes, Juan-Mari; Garcia, Jose Angel; Mornet, Stéphane; Plazaola, Fernando

2015-01-01

Magnetic nanoparticles (NPs) are intensively studied for their potential use for magnetic hyperthermia, a treatment that has passed a phase II clinical trial against severe brain cancer (glioblastoma) at the end of 2011. Their heating power, characterized by the ‘specific absorption rate (SAR)’, is often considered temperature independent in the literature, mainly because of the difficulties that arise from the measurement methodology. Using a dynamic magnetometer presented in a recent paper, we measure here the thermal dependence of SAR for superparamagnetic iron oxide (maghemite) NPs of four different size-ranges corresponding to mean diameters around 12 nm, 14 nm, 15 nm and 16 nm. The article reports a parametrical study extending from 10 to 60 {}^\\circ C in temperature, from 75 to 1031 kHz in frequency, and from 2 to 24 kA m-1 in magnetic field strength. It was observed that SAR values of smaller NPs decrease with temperature whereas for the larger sample (16 nm) SAR values increase with temperature. The measured variation of SAR with temperature is frequency dependent. This behaviour is fully explained within the scope of linear response theory based on Néel and Brown relaxation processes, using independent magnetic measurements of the specific magnetization and the magnetic anisotropy constant. A good quantitative agreement between experimental values and theoretical values is confirmed in a tri-dimensional space that uses as coordinates the field strength, the frequency and the temperature.

Pulsar Emission Geometry and Accelerating Field Strength

NASA Technical Reports Server (NTRS)

DeCesar, Megan E.; Harding, Alice K.; Miller, M. Coleman; Kalapotharakos, Constantinos; Parent, Damien

2012-01-01

The high-quality Fermi LAT observations of gamma-ray pulsars have opened a new window to understanding the generation mechanisms of high-energy emission from these systems, The high statistics allow for careful modeling of the light curve features as well as for phase resolved spectral modeling. We modeled the LAT light curves of the Vela and CTA I pulsars with simulated high-energy light curves generated from geometrical representations of the outer gap and slot gap emission models. within the vacuum retarded dipole and force-free fields. A Markov Chain Monte Carlo maximum likelihood method was used to explore the phase space of the magnetic inclination angle, viewing angle. maximum emission radius, and gap width. We also used the measured spectral cutoff energies to estimate the accelerating parallel electric field dependence on radius. under the assumptions that the high-energy emission is dominated by curvature radiation and the geometry (radius of emission and minimum radius of curvature of the magnetic field lines) is determined by the best fitting light curves for each model. We find that light curves from the vacuum field more closely match the observed light curves and multiwavelength constraints, and that the calculated parallel electric field can place additional constraints on the emission geometry

A compact high-speed mechanical sample shuttle for field-dependent high-resolution solution NMR.

PubMed

Chou, Ching-Yu; Chu, Minglee; Chang, Chi-Fon; Huang, Tai-Huang

2012-01-01

Analysis of NMR relaxation data has provided significant insight on molecular dynamic, leading to a more comprehensive understanding of macromolecular functions. However, traditional methodology allows relaxation measurements performed only at a few fixed high fields, thus severely restricting their potential for extracting more complete dynamic information. Here we report the design and performance of a compact high-speed servo-mechanical shuttle assembly adapted to a commercial 600 MHz high-field superconducting magnet. The assembly is capable of shuttling the sample in a regular NMR tube from the center of the magnet to the top (fringe field ∼0.01 T) in 100 ms with no loss of sensitivity other than that due to intrinsic relaxation. The shuttle device can be installed by a single experienced user in 30 min. Excellent 2D-(15)N-HSQC spectra of (u-(13)C, (15)N)-ubiquitin with relaxation at low fields (3.77 T) and detection at 14.1T were obtained to illustrate its utility in R(1) measurements of macromolecules at low fields. Field-dependent (13)C-R(1) data of (3,3,3-d)-alanine at various field strengths were determined and analyzed to assess CSA and (1)H-(13)C dipolar contributions to the carboxyl (13)C-R(1). Copyright © 2011 Elsevier Inc. All rights reserved.

Temperature Dependence of the Upper Critical Field in Disordered Hubbard Model with Attraction

NASA Astrophysics Data System (ADS)

Kuchinskii, E. Z.; Kuleeva, N. A.; Sadovskii, M. V.

2017-12-01

We study disorder effects upon the temperature behavior of the upper critical magnetic field in an attractive Hubbard model within the generalized DMFT+Σ approach. We consider the wide range of attraction potentials U—from the weak coupling limit, where superconductivity is described by BCS model, up to the strong coupling limit, where superconducting transition is related to Bose-Einstein condensation (BEC) of compact Cooper pairs, formed at temperatures significantly higher than superconducting transition temperature, as well as the wide range of disorder—from weak to strong, when the system is in the vicinity of Anderson transition. The growth of coupling strength leads to the rapid growth of H c2( T), especially at low temperatures. In BEC limit and in the region of BCS-BEC crossover H c2( T), dependence becomes practically linear. Disordering also leads to the general growth of H c2( T). In BCS limit of weak coupling increasing disorder lead both to the growth of the slope of the upper critical field in the vicinity of the transition point and to the increase of H c2( T) in the low temperature region. In the limit of strong disorder in the vicinity of the Anderson transition localization corrections lead to the additional growth of H c2( T) at low temperatures, so that the H c2( T) dependence becomes concave. In BCS-BEC crossover region and in BEC limit disorder only slightly influences the slope of the upper critical field close to T c . However, in the low temperature region H c2 ( T may significantly grow with disorder in the vicinity of the Anderson transition, where localization corrections notably increase H c2 ( T = 0) also making H c2( T) dependence concave.

Magnetic nanoparticles with high specific absorption rate of electromagnetic energy at low field strength for hyperthermia therapy

PubMed Central

Stigliano, Robert; Baker, Ian

2015-01-01

Magnetic nanoparticles (MNPs), referred to as the Dartmouth MNPs, which exhibit high specific absorption rate at low applied field strength have been developed for hyperthermia therapy applications. The MNPs consist of small (2–5 nm) single crystals of gamma-Fe2O3 with saccharide chains implanted in their crystalline structure, forming 20–40 nm flower-like aggregates with a hydrodynamic diameter of 110–120 nm. The MNPs form stable (>12 months) colloidal solutions in water and exhibit no hysteresis under an applied quasistatic magnetic field, and produce a significant amount of heat at field strengths as low as 100 Oe at 99–164 kHz. The MNP heating mechanisms under an alternating magnetic field (AMF) are discussed and analyzed quantitatively based on (a) the calculated multi-scale MNP interactions obtained using a three dimensional numerical model called the method of auxiliary sources, (b) measured MNP frequency spectra, and (c) quantified MNP friction losses based on magneto-viscous theory. The frequency responses and hysteresis curves of the Dartmouth MNPs are measured and compared to the modeled data. The specific absorption rate of the particles is measured at various AMF strengths and frequencies, and compared to commercially available MNPs. The comparisons demonstrate the superior heating properties of the Dartmouth MNPs at low field strengths (<250 Oe). This may extend MNP hyperthermia therapy to deeper tumors that were previously non-viable targets, potentially enabling the treatment of some of the most difficult cancers, such as pancreatic and rectal cancers, without damaging normal tissue. PMID:25825545

Magnetic nanoparticles with high specific absorption rate of electromagnetic energy at low field strength for hyperthermia therapy

NASA Astrophysics Data System (ADS)

Shubitidze, Fridon; Kekalo, Katsiaryna; Stigliano, Robert; Baker, Ian

2015-03-01

Magnetic nanoparticles (MNPs), referred to as the Dartmouth MNPs, which exhibit high specific absorption rate at low applied field strength have been developed for hyperthermia therapy applications. The MNPs consist of small (2-5 nm) single crystals of gamma-Fe2O3 with saccharide chains implanted in their crystalline structure, forming 20-40 nm flower-like aggregates with a hydrodynamic diameter of 110-120 nm. The MNPs form stable (>12 months) colloidal solutions in water and exhibit no hysteresis under an applied quasistatic magnetic field, and produce a significant amount of heat at field strengths as low as 100 Oe at 99-164 kHz. The MNP heating mechanisms under an alternating magnetic field (AMF) are discussed and analyzed quantitatively based on (a) the calculated multi-scale MNP interactions obtained using a three dimensional numerical model called the method of auxiliary sources, (b) measured MNP frequency spectra, and (c) quantified MNP friction losses based on magneto-viscous theory. The frequency responses and hysteresis curves of the Dartmouth MNPs are measured and compared to the modeled data. The specific absorption rate of the particles is measured at various AMF strengths and frequencies, and compared to commercially available MNPs. The comparisons demonstrate the superior heating properties of the Dartmouth MNPs at low field strengths (<250 Oe). This may extend MNP hyperthermia therapy to deeper tumors that were previously non-viable targets, potentially enabling the treatment of some of the most difficult cancers, such as pancreatic and rectal cancers, without damaging normal tissue.

Magnetic nanoparticles with high specific absorption rate of electromagnetic energy at low field strength for hyperthermia therapy.

PubMed

Shubitidze, Fridon; Kekalo, Katsiaryna; Stigliano, Robert; Baker, Ian

2015-03-07

Magnetic nanoparticles (MNPs), referred to as the Dartmouth MNPs, which exhibit high specific absorption rate at low applied field strength have been developed for hyperthermia therapy applications. The MNPs consist of small (2-5 nm) single crystals of gamma-Fe 2 O 3 with saccharide chains implanted in their crystalline structure, forming 20-40 nm flower-like aggregates with a hydrodynamic diameter of 110-120 nm. The MNPs form stable (>12 months) colloidal solutions in water and exhibit no hysteresis under an applied quasistatic magnetic field, and produce a significant amount of heat at field strengths as low as 100 Oe at 99-164 kHz. The MNP heating mechanisms under an alternating magnetic field (AMF) are discussed and analyzed quantitatively based on (a) the calculated multi-scale MNP interactions obtained using a three dimensional numerical model called the method of auxiliary sources, (b) measured MNP frequency spectra, and (c) quantified MNP friction losses based on magneto-viscous theory. The frequency responses and hysteresis curves of the Dartmouth MNPs are measured and compared to the modeled data. The specific absorption rate of the particles is measured at various AMF strengths and frequencies, and compared to commercially available MNPs. The comparisons demonstrate the superior heating properties of the Dartmouth MNPs at low field strengths (<250 Oe). This may extend MNP hyperthermia therapy to deeper tumors that were previously non-viable targets, potentially enabling the treatment of some of the most difficult cancers, such as pancreatic and rectal cancers, without damaging normal tissue.

Control over Janus micromotors by the strength of a magnetic field

NASA Astrophysics Data System (ADS)

Baraban, Larysa; Makarov, Denys; Schmidt, Oliver G.; Cuniberti, Gianaurelio; Leiderer, Paul; Erbe, Artur

2013-01-01

For transportation of molecules or biological cells using artificial motors, the control over their motion, i.e. direction and speed of transfer, is important. Here, we demonstrate that modification of the velocity and orientation of a magnetic Janus particle can be efficiently controlled by tuning the strength of an applied homogeneous magnetic field. Interestingly, by keeping the same orientation of the magnetic field but changing its magnitude not only the velocity of capped particles can be altered but even their direction of motion can be reversed. We put forth a simple qualitative model, which allows us to explain this intriguing observation.For transportation of molecules or biological cells using artificial motors, the control over their motion, i.e. direction and speed of transfer, is important. Here, we demonstrate that modification of the velocity and orientation of a magnetic Janus particle can be efficiently controlled by tuning the strength of an applied homogeneous magnetic field. Interestingly, by keeping the same orientation of the magnetic field but changing its magnitude not only the velocity of capped particles can be altered but even their direction of motion can be reversed. We put forth a simple qualitative model, which allows us to explain this intriguing observation. Electronic supplementary information (ESI) available: Videos (1-3) describe the behavior of the magnetic Janus micromotors at different magnetic fields applied. The magnetic field is always applied along the positive direction of the y-axis. All the movies are recorded at the same frame rate of 21 images per second. Experiments were performed at 30 wt% of hydrogen peroxide in aqueous solution. Video 1 shows the motion of the Janus micromotors when a small magnetic field is applied (B = 0.2 mT). The particle is propelled in the direction ``opposite to the cap'' with a velocity of about 6 μm s-1. Video 2 displays the motion of the same Janus bead when an intermediately strong

The Relationship Between Perceptual Egocentrism and Field Dependence in Early Childhood

ERIC Educational Resources Information Center

Bowd, Alan D.

1975-01-01

Kindergarten children were administered tests of inductive reasoning and field dependence and a series of perceptual egocentrism tasks. Results confirm a positive relation between field dependence and perceptual egocentrism; they also question the validity of the field-dependence construct in early childhood. (GO)

The effects of magnetic field in plume region on the performance of multi-cusped field thruster

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

Hu, Peng, E-mail: hupengemail@126.com; Liu, Hui, E-mail: thruster@126.com; Yu, Daren

2015-10-15

The performance characteristics of a Multi-cusped Field Thruster depending on the magnetic field in the plume region were investigated. Five magnetic field shielding rings were separately mounted near the exit of discharge channel to decrease the strength of magnetic field in the plume region in different levels, while the magnetic field in the upstream was well maintained. The test results show that the electron current increases with the decrease of magnetic field strength in the plume region, which gives rise to higher propellant utilization and lower current utilization. On the other hand, the stronger magnetic field in the plume regionmore » improves the performance at low voltages (high current mode) while lower magnetic field improves the performance at high voltages (low current mode). This work can provide some optimal design ideas of the magnetic strength in the plume region to improve the performance of thruster.« less

Ionic strength dependence of the oxidation of SO2 by H2O2 in sodium chloride particles

NASA Astrophysics Data System (ADS)

Ali, H. M.; Iedema, M.; Yu, X.-Y.; Cowin, J. P.

2014-06-01

The reaction of sulfur dioxide and hydrogen peroxide in the presence of deliquesced (>75% RH) sodium chloride (brine) particles was studied by utilizing a cross flow mini-reactor. The reaction kinetics were followed by observing chloride depletion in particles by computer-controlled scanning electron microscope with energy dispersive X-ray analysis, namely CCSEM/EDX. The reactions take place in concentrated mixed salt brine aerosols, for which no complete kinetic equilibrium data previously existed. We measured the Henry's law solubility of H2O2 in brine solutions to close that gap. We also calculated the reaction rate as the particle transforms continuously from concentrated NaCl brine to, eventually, a mixed NaHSO4 plus H2SO4 brine solution. The reaction rate of the SO2 oxidation by H2O2 was found to be influenced by the change in ionic strength as the particle undergoes compositional transformation, following closely the dependence of the third order rate constant on ionic strength as predicted using established rate equations. This is the first study that has measured the ionic strength dependence of sulfate formation (in non-aqueous media) from oxidation of mixed salt brine aerosols in the presence of H2O2. It also gives the first report of the dependence of the Henry's law constant of H2O2 on ionic strength.

Ionic strength dependence of the oxidation of SO2 by H2O2 in sodium chloride particles

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

Ali, Hashim M.; Iedema, Martin J.; Yu, Xiao-Ying

The reaction of sulfur dioxide and hydrogen peroxide in the presence of deliquesced (>75% RH) sodium particles was studied by utilizing a crossflow-mini reactor. The reaction kinetics was followed by observing chloride depletion in particles by computer-controlled scanning electron microscope with energy dispersive X-ray analysis, namely SEM/EDX. The reactions take place in concentrated mixed salt brine aerosols, for which no complete kinetic equilibrium data previously existed. We measured the Henry’s law solubility of H2O2 to close that gap. We also calculated the reaction rate as the particle transforms continuously from concentrated NaCl brine to eventually a mixed NaHSO4 plus H2SO4more » brine solution. The reaction rate of the SO2 oxidation by H2O2 was found to be influenced by the change in ionic strength as the particle undergoes compositional transformation, following closely the dependence of the third order rate constant on ionic strength as predicted rates using previously established rate equations. This is the first study that has measured the ionic strength dependence of sulfate formation (in non-aqueous media) from oxidation of mixed salt brine aerosols in the presence of H2O2. It also gives the first report of the Henry’s law constant of H2O2 dependence on ionic strength.« less

Random-anisotropy model: Monotonic dependence of the coercive field on D/J

NASA Astrophysics Data System (ADS)

Saslow, W. M.; Koon, N. C.

1994-02-01

We present the results of a numerical study of the zero-temperature remanence and coercivity for the random anisotropy model (RAM), showing that, contrary to early calculations for this model, the coercive field increases monotonically with increases in the strength D of the random anisotropy relative to the strength J at the exchange field. Local-field adjustments with and without spin flips are considered. Convergence is difficult to obtain for small values of the anisotropy, suggesting that this is the likely source of the nonmonotonic behavior found in earlier studies. For both large and small anisotropy, each spin undergoes about one flip per hysteresis cycle, and about half of the spin flips occur in the vicinity of the coercive field. When only non-spin-flip adjustments are considered, at large anisotropy the coercivity is proportional to the anisotropy. At small anisotropy, the rate of convergence is comparable to that when spin flips are included.

Size dependence of yield strength simulated by a dislocation-density function dynamics approach

NASA Astrophysics Data System (ADS)

Leung, P. S. S.; Leung, H. S.; Cheng, B.; Ngan, A. H. W.

2015-04-01

The size dependence of the strength of nano- and micron-sized crystals is studied using a new simulation approach in which the dynamics of the density functions of dislocations are modeled. Since any quantity of dislocations can be represented by a density, this approach can handle large systems containing large quantities of dislocations, which may handicap discrete dislocation dynamics schemes due to the excessive computation time involved. For this reason, pillar sizes spanning a large range, from the sub-micron to micron regimes, can be simulated. The simulation results reveal the power-law relationship between strength and specimen size up to a certain size, beyond which the strength varies much more slowly with size. For specimens smaller than ∼4000b, their strength is found to be controlled by the dislocation depletion condition, in which the total dislocation density remains almost constant throughout the loading process. In specimens larger than ∼4000b, the initial dislocation distribution is of critical importance since the presence of dislocation entanglements is found to obstruct deformation in the neighboring regions within a distance of ∼2000b. This length scale suggests that the effects of dense dislocation clusters are greater in intermediate-sized specimens (e.g. 4000b and 8000b) than in larger specimens (e.g. 16 000b), according to the weakest-link concept.

Solar magnetic field studies using the 12 micron emission lines. II - Stokes profiles and vector field samples in sunspots

NASA Technical Reports Server (NTRS)

Hewagama, Tilak; Deming, Drake; Jennings, Donald E.; Osherovich, Vladimir; Wiedemann, Gunter; Zipoy, David; Mickey, Donald L.; Garcia, Howard

1993-01-01

Polarimetric observations at 12 microns of two sunpots are reported. The horizontal distribution of parameters such as magnetic field strength, inclination, azimuth, and magnetic field filling factors are presented along with information about the height dependence of the magnetic field strength. Comparisons with contemporary magnetostatic sunspot models are made. The magnetic data are used to estimate the height of 12 micron line formation. From the data, it is concluded that within a stable sunspot there are no regions that are magnetically filamentary, in the sense of containing both strong-field and field-free regions.

Morphology dependent near-field response in atomistic plasmonic nanocavities.

PubMed

Chen, Xing; Jensen, Lasse

2018-06-21

In this work we examine how the atomistic morphologies of plasmonic dimers control the near-field response by using an atomistic electrodynamics model. At large separations, the field enhancement in the junction follows a simple inverse power law as a function of the gap separation, which agrees with classical antenna theory. However, when the separations are smaller than 0.8 nm, the so-called quantum size regime, the field enhancement is screened and thus deviates from the simple power law. Our results show that the threshold distance for the deviation depends on the specific morphology of the junction. The near field in the junction can be localized to an area of less than 1 nm2 in the presence of an atomically sharp tip, but the separation distances leading to a large confinement of near field depend strongly on the specific atomistic configuration. More importantly, the highly confined fields lead to large field gradients particularly in a tip-to-surface junction, which indicates that such a plasmonic structure favors observing strong field gradient effects in near-field spectroscopy. We find that for atomically sharp tips the field gradient becomes significant and depends strongly on the local morphology of a tip. We expect our findings to be crucial for understanding the origin of high-resolution near-field spectroscopy and for manipulating optical cavities through atomic structures in the strongly coupled plasmonic systems.

ARE THERE DIFFERENCES IN STRENGTH TESTS USING ISOKINETIC DYNAMOMETRY BETWEEN FIELD AND INDOOR PROFESSIONAL SOCCER PLAYERS?

PubMed Central

de Aguiar Leonardi, Adriano Barros; Martinelli, Mauro Olivio; Junior, Aires Duarte

2015-01-01

Objective: The objective of this study was to conduct a comparative analysis on isokinetic strength assessments between field and indoor male professional soccer players and correlate the findings with the higher levels of injury risk described in the literature. Methods: We analyzed 16 field soccer players and 15 indoor soccer players. All these professionals were male. Isokinetic muscle strength assessments were made on their knees. Results: The mean weight was 81.81 kg for field soccer and 80.33 kg for indoor soccer. The right and left peak extensor torque left and right for field soccer and indoor soccer were, respectively, 302.50 and 313.31 Nm and 265.20 and 279.80 Nm, and for flexors, 178 and 184.88 Nm and 158.27 and 154 Nm. The peak torque rates according to body weight for the left and right extensors for field soccer and indoor soccer were, respectively, 3.84 and 3.7 Nm/kg and 3.32 and 3.52 Nm/kg, and for flexors, 2.17 and 2.26 Nm/kg and 1.98 and 1.93 Nm/kg. The balance relationships between flexors and extensors on the right and left sides for field soccer and indoor soccer were, respectively, 59.81 and 59.44% and 60.47% and 54.80%. The relationships for extensors between the right and left sides for field soccer and indoor soccer were, respectively, 11.44 and 9.20%, and for the flexors, 7.31 and 8.80%. Conclusions: In accordance with international parameters, comparative analysis on isokinetic strength assessments between field and indoor male professional soccer players before the season showed that there was muscle balance and low probability of injury. There were no statistically significant differences in the parameters analyzed between the players of the two types of soccer. PMID:27042649

Reliability Stress-Strength Models for Dependent Observations with Applications in Clinical Trials

NASA Technical Reports Server (NTRS)

Kushary, Debashis; Kulkarni, Pandurang M.

1995-01-01

We consider the applications of stress-strength models in studies involving clinical trials. When studying the effects and side effects of certain procedures (treatments), it is often the case that observations are correlated due to subject effect, repeated measurements and observing many characteristics simultaneously. We develop maximum likelihood estimator (MLE) and uniform minimum variance unbiased estimator (UMVUE) of the reliability which in clinical trial studies could be considered as the chances of increased side effects due to a particular procedure compared to another. The results developed apply to both univariate and multivariate situations. Also, for the univariate situations we develop simple to use lower confidence bounds for the reliability. Further, we consider the cases when both stress and strength constitute time dependent processes. We define the future reliability and obtain methods of constructing lower confidence bounds for this reliability. Finally, we conduct simulation studies to evaluate all the procedures developed and also to compare the MLE and the UMVUE.

Parasitism and a shortage of refuges jointly mediate the strength of density dependence in a reef fish.

PubMed

Forrester, Graham E; Finley, Rachel J

2006-05-01

Various predator-prey, host-pathogen, and competitive interactions can combine to cause density dependence in population growth. Despite this possibility, most empirical tests for density-dependent interactions have focused on single mechanisms. Here we tested the hypothesis that two mechanisms of density dependence, parasitism and a shortage of refuges, jointly influence the strength of density-dependent mortality. We used mark-recapture analysis to estimate mortality of the host species, the bridled goby (Coryphopterus glaucofraenum). Sixty-three marked gobies were infected with a copepod gill parasite (Pharodes tortugensis), and 188 were uninfected. We used the spatial scale at which gobies were clustered naturally (approximately 4 m2) as an ecologically relevant neighborhood and measured goby density and the availability of refuges from predators within each goby's neighborhood. Goby survival generally declined with increasing density, and this decline was steeper for gobies with access to few refuges than for gobies in neighborhoods where refuges were common. The negative effects of high density and refuge shortage were also more severe for parasitized gobies than for gobies free of parasites. This parasite has characteristics typical of emerging diseases and appears to have altered the strength of a preexisting density-dependent interaction.

Self-healing slip pulses in dynamic rupture models due to velocity-dependent strength

USGS Publications Warehouse

Beeler, N.M.; Tullis, T.E.

1996-01-01

Seismological observations of short slip duration on faults (short rise time on seismograms) during earthquakes are not consistent with conventional crack models of dynamic rupture and fault slip. In these models, the leading edge of rupture stops only when a strong region is encountered, and slip at an interior point ceases only when waves from the stopped edge of slip propagate back to that point. In contrast, some seismological evidence suggests that the duration of slip is too short for waves to propagate from the nearest edge of the ruptured surface, perhaps even if the distance used is an asperity size instead of the entire rupture dimension. What controls slip duration, if not dimensions of the fault or of asperities? In this study, dynamic earthquake rupture and slip are represented by a propagating shear crack. For all propagating shear cracks, slip velocity is highest near the rupture front, and at a small distance behind the rupture front, the slip velocity decreases. As pointed out by Heaton (1990), if the crack obeys a negative slip-rate-dependent strength relation, the lower slip velocity behind the rupture front will lead to strengthening that further reduces the velocity, and under certain circumstances, healing of slip can occur. The boundary element method of Hamano (1974) is used in a program adapted from Andrews (1985) for numerical simulations of mode II rupture with two different velocity-dependent strength functions. For the first function, after a slip-weakening displacement, the crack follows an exponential velocity-weakening relation. The characteristic velocity V0 of the exponential determines the magnitude of the velocity-dependence at dynamic velocities. The velocity-dependence at high velocity is essentially zero when V0 is small and the resulting slip velocity distribution is similar to slip weakening. If V0 is larger, rupture propagation initially resembles slip-weakening, but spontaneous healing occurs behind the rupture front. The

Carrier-envelope phase-dependent field-free molecular orientation

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

Shu Chuancun; Yuan Kaijun; Hu Wenhui

2009-07-15

We present a strategy to achieve carrier-envelope phase-dependent field-free molecular orientation with the use of carrier-envelope phase (CEP) stabilization and asymmetric few-cycle terahertz (THz) laser pulses. The calculations are performed on the LiH molecule by an exact solution of the full time-dependent Schroedinger equation including both the vibrational and the rotational degrees of freedom. Our calculations show that an efficient field-free molecular orientation can be obtained even at considerable temperatures. Moreover, we find a simple dependence of the field-free orientation on the CEP, which implies that the CEP becomes an important parameter for control of molecular orientation. More importantly, themore » realization of this scenario is appealing based on the fact that the intense few-cycle THz pulse with duration as short as a few optical cycles is available as a research tool.« less

Is there scale-dependent bias in single-field inflation?

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

De Putter, Roland; Doré, Olivier; Green, Daniel, E-mail: rdputter@caltech.edu, E-mail: Olivier.P.Dore@jpl.nasa.gov, E-mail: drgreen@cita.utoronto.ca

2015-10-01

Scale-dependent halo bias due to local primordial non-Gaussianity provides a strong test of single-field inflation. While it is universally understood that single-field inflation predicts negligible scale-dependent bias compared to current observational uncertainties, there is still disagreement on the exact level of scale-dependent bias at a level that could strongly impact inferences made from future surveys. In this paper, we clarify this confusion and derive in various ways that there is exactly zero scale-dependent bias in single-field inflation. Much of the current confusion follows from the fact that single-field inflation does predict a mode coupling of matter perturbations at the levelmore » of f{sub NL}{sup local}; ≈ −5/3, which naively would lead to scale-dependent bias. However, we show explicitly that this mode coupling cancels out when perturbations are evaluated at a fixed physical scale rather than fixed coordinate scale. Furthermore, we show how the absence of scale-dependent bias can be derived easily in any gauge. This result can then be incorporated into a complete description of the observed galaxy clustering, including the previously studied general relativistic terms, which are important at the same level as scale-dependent bias of order f{sub NL}{sup local} ∼ 1. This description will allow us to draw unbiased conclusions about inflation from future galaxy clustering data.« less

The JCMT BISTRO Survey: The Magnetic Field Strength in the Orion A Filament

NASA Astrophysics Data System (ADS)

Pattle, Kate; Ward-Thompson, Derek; Berry, David; Hatchell, Jennifer; Chen, Huei-Ru; Pon, Andy; Koch, Patrick M.; Kwon, Woojin; Kim, Jongsoo; Bastien, Pierre; Cho, Jungyeon; Coudé, Simon; Di Francesco, James; Fuller, Gary; Furuya, Ray S.; Graves, Sarah F.; Johnstone, Doug; Kirk, Jason; Kwon, Jungmi; Lee, Chang Won; Matthews, Brenda C.; Mottram, Joseph C.; Parsons, Harriet; Sadavoy, Sarah; Shinnaga, Hiroko; Soam, Archana; Hasegawa, Tetsuo; Lai, Shih-Ping; Qiu, Keping; Friberg, Per

2017-09-01

We determine the magnetic field strength in the OMC 1 region of the Orion A filament via a new implementation of the Chandrasekhar-Fermi method using observations performed as part of the James Clerk Maxwell Telescope (JCMT) B-Fields In Star-forming Region Observations (BISTRO) survey with the POL-2 instrument. We combine BISTRO data with archival SCUBA-2 and HARP observations to find a plane-of-sky magnetic field strength in OMC 1 of {B}{pos}=6.6+/- 4.7 mG, where δ {B}{pos}=4.7 mG represents a predominantly systematic uncertainty. We develop a new method for measuring angular dispersion, analogous to unsharp masking. We find a magnetic energy density of ˜ 1.7× {10}-7 J m-3 in OMC 1, comparable both to the gravitational potential energy density of OMC 1 (˜10-7 J m-3) and to the energy density in the Orion BN/KL outflow (˜10-7 J m-3). We find that neither the Alfvén velocity in OMC 1 nor the velocity of the super-Alfvénic outflow ejecta is sufficiently large for the BN/KL outflow to have caused large-scale distortion of the local magnetic field in the ˜500 yr lifetime of the outflow. Hence, we propose that the hourglass field morphology in OMC 1 is caused by the distortion of a primordial cylindrically symmetric magnetic field by the gravitational fragmentation of the filament and/or the gravitational interaction of the BN/KL and S clumps. We find that OMC 1 is currently in or near magnetically supported equilibrium, and that the current large-scale morphology of the BN/KL outflow is regulated by the geometry of the magnetic field in OMC 1, and not vice versa.

Shear localization and size-dependent strength of YCd 6 quasicrystal approximant at the micrometer length scale

DOE PAGES

Song, Gyuho; Kong, Tai; Dusoe, Keith J.; ...

2018-01-24

Mechanical properties of materials are strongly dependent of their atomic arrangement as well as the sample dimension, particularly at the micrometer length scale. Here in this study, we investigated the small-scale mechanical properties of single-crystalline YCd 6, which is a rational approximant of the icosahedral Y-Cd quasicrystal. In situ microcompression tests revealed that shear localization always occurs on {101} planes, but the shear direction is not constrained to any particular crystallographic directions. Furthermore, the yield strengths show the size dependence with a power law exponent of 0.4. Shear localization on {101} planes and size-dependent yield strength are explained in termsmore » of a large interplanar spacing between {101} planes and the energetics of shear localization process, respectively. The mechanical behavior of the icosahedral Y-Cd quasicrystal is also compared to understand the influence of translational symmetry on the shear localization process in both YCd 6 and Y-Cd quasicrystal micropillars. Finally, the results of this study will provide an important insight in a fundamental understanding of shear localization process in novel complex intermetallic compounds.« less

Shear localization and size-dependent strength of YCd 6 quasicrystal approximant at the micrometer length scale

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

Song, Gyuho; Kong, Tai; Dusoe, Keith J.

Mechanical properties of materials are strongly dependent of their atomic arrangement as well as the sample dimension, particularly at the micrometer length scale. Here in this study, we investigated the small-scale mechanical properties of single-crystalline YCd 6, which is a rational approximant of the icosahedral Y-Cd quasicrystal. In situ microcompression tests revealed that shear localization always occurs on {101} planes, but the shear direction is not constrained to any particular crystallographic directions. Furthermore, the yield strengths show the size dependence with a power law exponent of 0.4. Shear localization on {101} planes and size-dependent yield strength are explained in termsmore » of a large interplanar spacing between {101} planes and the energetics of shear localization process, respectively. The mechanical behavior of the icosahedral Y-Cd quasicrystal is also compared to understand the influence of translational symmetry on the shear localization process in both YCd 6 and Y-Cd quasicrystal micropillars. Finally, the results of this study will provide an important insight in a fundamental understanding of shear localization process in novel complex intermetallic compounds.« less

Relationship of magnetic field strength and brightness of fine-structure elements in the solar temperature minimum region

NASA Technical Reports Server (NTRS)

Cook, J. W.; Ewing, J. A.

1990-01-01

A quantitative relationship was determined between magnetic field strength (or magnetic flux) from photospheric magnetograph observations and the brightness temperature of solar fine-structure elements observed at 1600 A, where the predominant flux source is continuum emission from the solar temperature minimum region. A Kitt Peak magnetogram and spectroheliograph observations at 1600 A taken during a sounding rocket flight of the High Resolution Telescope and Spectrograph from December 11, 1987 were used. The statistical distributions of brightness temperature in the quiet sun at 1600 A, and absolute value of magnetic field strength in the same area were determined from these observations. Using a technique which obtains the best-fit relationship of a given functional form between these two histogram distributions, a quantitative relationship was determined between absolute value of magnetic field strength B and brightness temperature which is essentially linear from 10 to 150 G. An interpretation is suggested, in which a basal heating occurs generally, while brighter elements are produced in magnetic regions with temperature enhancements proportional to B.

Field-dependent hopping conduction

NASA Astrophysics Data System (ADS)

Hayashi, T.; Tokura, Y.; Fujiwara, A.

2018-07-01

We have numerically calculated transport characteristics on a Miller-Abraham network in a non-linear regime by solving the Kirchhoff's current law at each site. Assuming the Mott model, we obtained the relation between current density and electric field, J ∝exp(γ√{ E}) , which has often been observed in low-mobility materials and whose mechanism has been a source of controversy for over half a century. Our numerical calculation makes it possible to analyze the energy configuration of relevant hopping sites and visualize percolation networks. Following the percolation theory proposed by Shklovskii [Shklovskii, Sov. Phys. Semicond. 10, 855 (1976)], we show that the main mechanism of the field dependence is the replacement of dominating resistances accompanied by the geometrical evolution of the percolation networks. Our calculation is so general that it can be applied to hopping transport in a variety of systems.

CONSTRAINING THE SOLAR CORONAL MAGNETIC FIELD STRENGTH USING SPLIT-BAND TYPE II RADIO BURST OBSERVATIONS

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

Kishore, P.; Ramesh, R.; Hariharan, K.

2016-11-20

We report on low-frequency radio (85–35 MHz) spectral observations of four different type II radio bursts, which exhibited fundamental-harmonic emission and split-band structure. Each of the bursts was found to be closely associated with a whitelight coronal mass ejection (CME) close to the Sun. We estimated the coronal magnetic field strength from the split-band characteristics of the bursts, by assuming a model for the coronal electron density distribution. The choice of the model was constrained, based on the following criteria: (1) when the radio burst is observed simultaneously in the upper and lower bands of the fundamental component, the locationmore » of the plasma level corresponding to the frequency of the burst in the lower band should be consistent with the deprojected location of the leading edge (LE) of the associated CME; (2) the drift speed of the type II bursts derived from such a model should agree closely with the deprojected speed of the LE of the corresponding CMEs. With the above conditions, we find that: (1) the estimated field strengths are unique to each type II burst, and (2) the radial variation of the field strength in the different events indicate a pattern. It is steepest for the case where the heliocentric distance range over which the associated burst is observed is closest to the Sun, and vice versa.« less

Magnetic field dependence of Griffith phase and magnetocaloric effect in Ca0.85Dy0.15MnO3

NASA Astrophysics Data System (ADS)

Nag, Ripan; Sarkar, Bidyut; Pal, Sudipta

2018-03-01

Temperature and Magnetic field dependent magnetization properties of electron doped polycrystalline sample Ca0.85Dy0.15MnO3 (CDMO) prepared by solid state reaction method have been studied. The sample undergoes ferromagnetic to paramagnetic phase transition at about 111k. From the study of magnetic properties in terms of Arrot plots it is observed that the phase transition is of 2nd order. The Griffith phase behavior of the sample is suppressed with the increase of the applied magnetic field strength H. We have estimated the magnetic entropy change from experimental magnetization and temperature data. For a magnetic field change of 8000 Oe, the maximum value of magnetic entropy change arrives at a value of 1.126 J-kg-1 k-1 in this magnetocaloric material.

A feasibility study of high-strength Bi-2223 conductor for high-field solenoids

NASA Astrophysics Data System (ADS)

Godeke, A.; Abraimov, D. V.; Arroyo, E.; Barret, N.; Bird, M. D.; Francis, A.; Jaroszynski, J.; Kurteva, D. V.; Markiewicz, W. D.; Marks, E. L.; Marshall, W. S.; McRae, D. M.; Noyes, P. D.; Pereira, R. C. P.; Viouchkov, Y. L.; Walsh, R. P.; White, J. M.

2017-03-01

We performed a feasibility study on a high-strength Bi{}2-xPb x Sr2Ca2Cu3O{}10-x(Bi-2223) tape conductor for high-field solenoid applications. The investigated conductor, DI-BSCCO Type HT-XX, is a pre-production version of Type HT-NX, which has recently become available from Sumitomo Electric Industries. It is based on their DI-BSCCO Type H tape, but laminated with a high-strength Ni-alloy. We used stress-strain characterizations, single- and double-bend tests, easy- and hard-way bent coil-turns at various radii, straight and helical samples in up to 31.2 T background field, and small 20-turn coils in up to 17 T background field to systematically determine the electro-mechanical limits in magnet-relevant conditions. In longitudinal tensile tests at 77 K, we found critical stress- and strain-levels of 516 MPa and 0.57%, respectively. In three decidedly different experiments we detected an amplification of the allowable strain with a combination of pure bending and Lorentz loading to ≥slant 0.92 % (calculated elastically at the outer tape edge). This significant strain level, and the fact that it is multi-filamentary conductor and available in the reacted and insulated state, makes DI-BSCCO HT-NX highly suitable for very high-field solenoids, for which high current densities and therefore high loads are required to retain manageable magnet dimensions.

A Feasibility Study of High-Strength Bi-2223 Conductor for High-Field Solenoids

PubMed Central

Godeke, A; Abraimov, D V; Arroyo, E; Barret, N; Bird, M D; Francis, A; Jaroszynski, J; Kurteva, D V; Markiewicz, W D; Marks, E L; Marshall, W S; McRae, D M; Noyes, P D; Pereira, R C P; Viouchkov, Y L; Walsh, R P; White, J M

2017-01-01

We performed a feasibility study on a high-strength Bi2−xPbxSr2Ca2Cu3O10−x (Bi-2223) tape conductor for high-field solenoid applications. The investigated conductor, DI-BSCCO Type HT-XX, is a pre-production version of Type HT-NX, which has recently become available from Sumitomo Electric Industries (SEI). It is based on their DI-BSCCO Type H tape, but laminated with a high-strength Ni-alloy. We used stress-strain characterizations, single- and double-bend tests, easy- and hard-way bent coil-turns at various radii, straight and helical samples in up to 31.2 T background field, and small 20-turn coils in up to 17 T background field to systematically determine the electro-mechanical limits in magnet-relevant conditions. In longitudinal tensile tests at 77 K, we found critical stress- and strain-levels of 516 MPa and 0.57%, respectively. In three decidedly different experiments we detected an amplification of the allowable strain with a combination of pure bending and Lorentz loading to ≥ 0.92% (calculated elastically at the outer tape edge). This significant strain level, and the fact that it is multi-filamentary conductor and available in the reacted and insulated state, makes DI-BSCCO HT-NX highly suitable for very high-field solenoids, for which high current densities and therefore high loads are required to retain manageable magnet dimensions. PMID:28360455

Character Strengths and Intellectual and Developmental Disability: A Strengths-Based Approach from Positive Psychology

ERIC Educational Resources Information Center

Niemiec, Ryan M.; Shogren, Karrie A.; Wehmeyer, Michael L.

2017-01-01

There has been limited focus in the disability field on assessing and intervening to promote strengths of character. However, character strengths have received significant attention in the broader field of positive psychology. This paper provides an overview of the growing science of character strengths and explores why and how character strengths…

Type II solar radio burst band-splitting: Measure of coronal magnetic field strength

NASA Astrophysics Data System (ADS)

Mahrous, Ayman; Alielden, Khaled; Vršnak, Bojan; Youssef, Mohamed

2018-07-01

Studies of the relationship between solar radio bursts and CMEs are essential for understanding of the nature of type II bursts. In this study, we examine the type II solar radio burst recorded on 16 March 2016 by the Learmonth radio spectrograph and compare its characteristics with the kinematics of the associated CMEs observed by STEREO and SOHO spacecraft. The burst showed a well-defined band-split, which was used to estimate the magnetic field strength in the solar corona. The magnetic field decreases from ≈ 4 G at R ≈ 2.6 R⊙ to 0.62 G at R ≈ 3.77 R⊙ depending on the coronal electron density model employed. We found that two CMEs occurred successively in a 4-h interval. During this interval, a type II radio burst occurred, lasting for about 10 min. Tracking of the shock that produced type II burst and comparison with the CMEs heights as observed by STEREO and SOHO spacecraft help us to deduce the driver of the shock. According to the analysis, the type II burst occurrence was associated with the interaction of the shock driven by the second CME with a streamer located south of the first CME, since that the type II band-split significantly increased during the shock-streamer interaction. Our results show that the analysis of the type II burst band-split supplemented by the coronagraphic observations of the corona is an important tool for the understanding of the coronal eruptive processes.

The fracture strength and frictional strength of Weber Sandstone

USGS Publications Warehouse

Byerlee, J.D.

1975-01-01

The fracture strength and frictional strength of Weber Sandstone have been measured as a function of confining pressure and pore pressure. Both the fracture strength and the frictional strength obey the law of effective stress, that is, the strength is determined not by the confining pressure alone but by the difference between the confining pressure and the pore pressure. The fracture strength of the rock varies by as much as 20 per cent depending on the cement between the grains, but the frictional strength is independent of lithology. Over the range 0 2 kb, ??=0??5 + 0??6??n. This relationship also holds for other rocks such as gabbro, dunite, serpentinite, granite and limestone. ?? 1975.

Internuclear separation dependent ionization of the valence orbitals of I2 by strong laser fields.

PubMed

Chen, H; Tagliamonti, V; Gibson, G N

2012-11-09

Using a pump-dump-probe technique and Fourier-transform spectroscopy, we study the internuclear separation R dependence and relative strength of the ionization rates of the π and σ electrons of I2, whose valence orbitals are σ(g)(2)π(u)(4)π(g)(4)σ(u)(0). We find that ionization of the highest occupied molecular orbital (HOMO)-2 (σ(g)) has a strong dependence on R while the HOMO and HOMO-1 do not. Surprisingly, the ionization rate of the HOMO-2 exceeds the combined ionization rate of the less bound orbitals and this branching ratio increases with R. Since our technique produces target molecules that are highly aligned with the laser polarization, the σ orbitals will be preferentially ionized and undergo enhanced ionization at larger R compared to the π orbitals. Nevertheless, it is highly unusual that an inner orbital provides the dominant strong field ionization pathway in a small molecule.

Internuclear Separation Dependent Ionization of the Valence Orbitals of I2 by Strong Laser Fields

NASA Astrophysics Data System (ADS)

Chen, H.; Tagliamonti, V.; Gibson, G. N.

2012-11-01

Using a pump-dump-probe technique and Fourier-transform spectroscopy, we study the internuclear separation R dependence and relative strength of the ionization rates of the π and σ electrons of I2, whose valence orbitals are σg2πu4πg4σu0. We find that ionization of the highest occupied molecular orbital (HOMO)-2 (σg) has a strong dependence on R while the HOMO and HOMO-1 do not. Surprisingly, the ionization rate of the HOMO-2 exceeds the combined ionization rate of the less bound orbitals and this branching ratio increases with R. Since our technique produces target molecules that are highly aligned with the laser polarization, the σ orbitals will be preferentially ionized and undergo enhanced ionization at larger R compared to the π orbitals. Nevertheless, it is highly unusual that an inner orbital provides the dominant strong field ionization pathway in a small molecule.

Earthquake nucleation on faults with rate-and state-dependent strength

USGS Publications Warehouse

Dieterich, J.H.

1992-01-01

Dieterich, J.H., 1992. Earthquake nucleation on faults with rate- and state-dependent strength. In: T. Mikumo, K. Aki, M. Ohnaka, L.J. Ruff and P.K.P. Spudich (Editors), Earthquake Source Physics and Earthquake Precursors. Tectonophysics, 211: 115-134. Faults with rate- and state-dependent constitutive properties reproduce a range of observed fault slip phenomena including spontaneous nucleation of slip instabilities at stresses above some critical stress level and recovery of strength following slip instability. Calculations with a plane-strain fault model with spatially varying properties demonstrate that accelerating slip precedes instability and becomes localized to a fault patch. The dimensions of the fault patch follow scaling relations for the minimum critical length for unstable fault slip. The critical length is a function of normal stress, loading conditions and constitutive parameters which include Dc, the characteristic slip distance. If slip starts on a patch that exceeds the critical size, the length of the rapidly accelerating zone tends to shrink to the characteristic size as the time of instability approaches. Solutions have been obtained for a uniform, fixed-patch model that are in good agreement with results from the plane-strain model. Over a wide range of conditions, above the steady-state stress, the logarithm of the time to instability linearly decreases as the initial stress increases. Because nucleation patch length and premonitory displacement are proportional to Dc, the moment of premonitory slip scales by D3c. The scaling of Dc is currently an open question. Unless Dc for earthquake faults is significantly greater than that observed on laboratory faults, premonitory strain arising from the nucleation process for earthquakes may by too small to detect using current observation methods. Excluding the possibility that Dc in the nucleation zone controls the magnitude of the subsequent earthquake, then the source dimensions of the smallest

Effect of dislocation pile-up on size-dependent yield strength in finite single-crystal micro-samples

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

Pan, Bo; Shibutani, Yoji, E-mail: sibutani@mech.eng.osaka-u.ac.jp; Zhang, Xu

2015-07-07

Recent research has explained that the steeply increasing yield strength in metals depends on decreasing sample size. In this work, we derive a statistical physical model of the yield strength of finite single-crystal micro-pillars that depends on single-ended dislocation pile-up inside the micro-pillars. We show that this size effect can be explained almost completely by considering the stochastic lengths of the dislocation source and the dislocation pile-up length in the single-crystal micro-pillars. The Hall–Petch-type relation holds even in a microscale single-crystal, which is characterized by its dislocation source lengths. Our quantitative conclusions suggest that the number of dislocation sources andmore » pile-ups are significant factors for the size effect. They also indicate that starvation of dislocation sources is another reason for the size effect. Moreover, we investigated the explicit relationship between the stacking fault energy and the dislocation “pile-up” effect inside the sample: materials with low stacking fault energy exhibit an obvious dislocation pile-up effect. Our proposed physical model predicts a sample strength that agrees well with experimental data, and our model can give a more precise prediction than the current single arm source model, especially for materials with low stacking fault energy.« less

The Relationship between Ultraviolet Line Emission and Magnetic Field Strength in Magnetic Cataclysmic Variables

NASA Astrophysics Data System (ADS)

Howell, Steve B.; Cash, Jennifer; Mason, Keith O.; Herzog, Adrienne E.

1999-02-01

We present the first UV spectral observations of six magnetic cataclysmic variables discovered by the ROSAT Wide Field Camera (WFC). Using the^ International Ultraviolet Explorer (IUE), 1200-3400 Å spectra were obtained of the AM Herculis stars RE 0531-46, RE 1149+28, RE 1844-74, QS Tel (RE 1938-46), and HU Aqr (RE 2107-05) and the DQ Herculis star PQ Gem (RE 0751+14). The high-state UV spectra are dominated by strong emission lines. Continuum flux distributions for these stars (from 100 to 5500 Å) reveal that over this entire range, none of the spectral energy distributions can be fitted by a single-valued blackbody. Our new UV observations and additional archival IUE spectra were used to discover a correlation between the strength of the high-state UV emission lines and the strength of the white dwarf magnetic field. Model spectral results are used to confirm the production of the UV emission lines by photoionization from X-ray and EUV photons.

Development and testing of passive tracking markers for different field strengths and tracking speeds.

PubMed

Peeters, J M; Seppenwoolde, J-H; Bartels, L W; Bakker, C J G

2006-03-21

Susceptibility markers for passive tracking need to be small in order to maintain the shape and mechanical properties of the endovascular device. Nevertheless, they also must have a high magnetic moment to induce an adequate artefact at a variety of scan techniques, tracking speeds and, preferably, field strengths. Paramagnetic markers do not satisfy all of these requirements. Ferro- and ferrimagnetic materials were therefore investigated with a vibrating sample magnetometer and compared with the strongly paramagnetic dysprosium oxide. Results indicated that the magnetic behaviour of stainless steel type AISI 410 corresponds the best with ideal marker properties. Markers with different magnetic moments were constructed and tested in in vitro and in vivo experiments. The appearance of the corresponding artefacts was field strength independent above magnetic saturation of 1.5 T. Generally, the contrast-to-noise ratio decreased at increasing tracking speed and decreasing magnetic moment. Device depiction was most consistent at a frame rate of 20 frames per second.

Landau problem with time dependent mass in time dependent electric and harmonic background fields

NASA Astrophysics Data System (ADS)

Lawson, Latévi M.; Avossevou, Gabriel Y. H.

2018-04-01

The spectrum of a Hamiltonian describing the dynamics of a Landau particle with time-dependent mass and frequency undergoing the influence of a uniform time-dependent electric field is obtained. The configuration space wave function of the model is expressed in terms of the generalised Laguerre polynomials. To diagonalize the time-dependent Hamiltonian, we employ the Lewis-Riesenfeld method of invariants. To this end, we introduce a unitary transformation in the framework of the algebraic formalism to construct the invariant operator of the system and then to obtain the exact solution of the Hamiltonian. We recover the solutions of the ordinary Landau problem in the absence of the electric and harmonic fields for a constant particle mass.

Initial experience of using high field strength intraoperative MRI for neurosurgical procedures.

PubMed

Raheja, Amol; Tandon, Vivek; Suri, Ashish; Sarat Chandra, P; Kale, Shashank S; Garg, Ajay; Pandey, Ravindra M; Kalaivani, Mani; Mahapatra, Ashok K; Sharma, Bhawani S

2015-08-01

We report our initial experience to optimize neurosurgical procedures using high field strength intraoperative magnetic resonance imaging (IOMRI) in 300 consecutive patients as high field strength IOMRI rapidly becomes the standard of care for neurosurgical procedures. Three sequential groups (groups A, B, C; n=100 each) were compared with respect to time management, complications and technical difficulties to assess improvement in these parameters with experience. We observed a reduction in the number of technical difficulties (p<0.001), time to induction (p<0.001) and total anesthesia time (p=0.007) in sequential groups. IOMRI was performed for neuronavigation guidance (n=252) and intraoperative validation of extent of resection (EOR; n=67). Performing IOMRI increased the EOR over and beyond the primary surgical attempt in 20.5% (29/141) and 18% (11/61) of patients undergoing glioma and pituitary surgery, respectively. Overall, EOR improved in 59.7% of patients undergoing IOMRI (40/67). Intraoperative tractography and real time navigation using re-uploaded IOMRI images (accounting for brain shift) helps in intraoperative planning to reduce complications. IOMRI is an asset to neurosurgeons, helping to augment the EOR, especially in glioma and pituitary surgery, with no significant increase in morbidity to the patient. Copyright © 2015 Elsevier Ltd. All rights reserved.

Determination of the electric field strength of filamentary DBDs by CARS-based four-wave mixing

NASA Astrophysics Data System (ADS)

Böhm, P.; Kettlitz, M.; Brandenburg, R.; Höft, H.; Czarnetzki, U.

2016-10-01

It is demonstrated that a four-wave mixing technique based on coherent anti-Stokes Raman spectroscopy (CARS) can determine the electric field strength of a pulsed-driven filamentary dielectric barrier discharge (DBD) of 1 mm gap, using hydrogen as a tracer medium in nitrogen at atmospheric pressure. The measurements are presented for a hydrogen admixture of 10%, but even 5% H2 admixture delivers sufficient infrared signals. The lasers do not affect the discharge by photoionization or by other radiation-induced processes. The absolute values of the electric field strength can be determined by the calibration of the CARS setup with high voltage amplitudes below the ignition threshold of the arrangement. This procedure also enables the determination of the applied breakdown voltage. The alteration of the electric field is observed during the internal polarity reversal and the breakdown process. One advantage of the CARS technique over emission-based methods is that it can be used independently of emission, e.g. in the pre-phase and in between two consecutive discharges, where no emission occurs at all.

Strength and Anisotropy in Tournemire Shale: Temperature, Pressure and Time Dependences

NASA Astrophysics Data System (ADS)

Bonnelye, A.; Schubnel, A.; Zhi, G.; David, C.; Dick, P.

2017-12-01

Time and temperature dependent rock deformation has both scientific and socio-economic implications for natural hazards, the oil and gas industry and nuclear waste disposal. During the past decades, most studies on brittle creep have focused on igneous rocks and porous sedimentary rocks. To our knowledge, only few studies have been carried out on the brittle creep behavior of shale. We conducted a series of creep experiments on shale specimens coming from the French Institute for Nuclear Safety (IRSN) underground research laboratory located in Tournemire, France, under two different temperatures (26°C, 75°C) and confining pressures (10 MPa, 80 MPa), for three orientations (σ1along, perpendicular and 45° to bedding). In these long-term experiments (approximately 10 days), stress and strains were recorded continuously, while ultrasonic acoustic velocities were recorded every 1 15 minutes. The brittle creep failure stress of our Tournemire shale samples was systematically observed 50% higher than its short-term peak strength, with larger final axial strain accumulated. During creep, ultrasonic wave velocities first decreased, and then increased gradually. The magnitude of elastic wave velocity variations showed an important orientation and temperature dependence: velocities measured perpendicular to bedding showed increased variation, variation that was enhanced at higher temperature and higher pressure. The case of complete elastic anisotropy reversal was observed for sample deformed perpendicular to bedding, with amount of axial strain needed to reach anisotropy reversal reduced at higher temperature. SEM observations highlight the competition between crack growth, sealing/healing, and possibly mineral rotation, pressure solution or anisotropic compaction during creep defromation. Our study highlights that the short-term peak strength has little meaning in shale material, which can over-consolidate importantly by `plastic' flow. In addition, we show that elastic

Angle-dependent strong-field molecular ionization rates with tuned range-separated time-dependent density functional theory.

PubMed

Sissay, Adonay; Abanador, Paul; Mauger, François; Gaarde, Mette; Schafer, Kenneth J; Lopata, Kenneth

2016-09-07

Strong-field ionization and the resulting electronic dynamics are important for a range of processes such as high harmonic generation, photodamage, charge resonance enhanced ionization, and ionization-triggered charge migration. Modeling ionization dynamics in molecular systems from first-principles can be challenging due to the large spatial extent of the wavefunction which stresses the accuracy of basis sets, and the intense fields which require non-perturbative time-dependent electronic structure methods. In this paper, we develop a time-dependent density functional theory approach which uses a Gaussian-type orbital (GTO) basis set to capture strong-field ionization rates and dynamics in atoms and small molecules. This involves propagating the electronic density matrix in time with a time-dependent laser potential and a spatial non-Hermitian complex absorbing potential which is projected onto an atom-centered basis set to remove ionized charge from the simulation. For the density functional theory (DFT) functional we use a tuned range-separated functional LC-PBE*, which has the correct asymptotic 1/r form of the potential and a reduced delocalization error compared to traditional DFT functionals. Ionization rates are computed for hydrogen, molecular nitrogen, and iodoacetylene under various field frequencies, intensities, and polarizations (angle-dependent ionization), and the results are shown to quantitatively agree with time-dependent Schrödinger equation and strong-field approximation calculations. This tuned DFT with GTO method opens the door to predictive all-electron time-dependent density functional theory simulations of ionization and ionization-triggered dynamics in molecular systems using tuned range-separated hybrid functionals.

Angle-dependent strong-field molecular ionization rates with tuned range-separated time-dependent density functional theory

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

Sissay, Adonay; Abanador, Paul; Mauger, François

2016-09-07

Strong-field ionization and the resulting electronic dynamics are important for a range of processes such as high harmonic generation, photodamage, charge resonance enhanced ionization, and ionization-triggered charge migration. Modeling ionization dynamics in molecular systems from first-principles can be challenging due to the large spatial extent of the wavefunction which stresses the accuracy of basis sets, and the intense fields which require non-perturbative time-dependent electronic structure methods. In this paper, we develop a time-dependent density functional theory approach which uses a Gaussian-type orbital (GTO) basis set to capture strong-field ionization rates and dynamics in atoms and small molecules. This involves propagatingmore » the electronic density matrix in time with a time-dependent laser potential and a spatial non-Hermitian complex absorbing potential which is projected onto an atom-centered basis set to remove ionized charge from the simulation. For the density functional theory (DFT) functional we use a tuned range-separated functional LC-PBE*, which has the correct asymptotic 1/r form of the potential and a reduced delocalization error compared to traditional DFT functionals. Ionization rates are computed for hydrogen, molecular nitrogen, and iodoacetylene under various field frequencies, intensities, and polarizations (angle-dependent ionization), and the results are shown to quantitatively agree with time-dependent Schrödinger equation and strong-field approximation calculations. This tuned DFT with GTO method opens the door to predictive all-electron time-dependent density functional theory simulations of ionization and ionization-triggered dynamics in molecular systems using tuned range-separated hybrid functionals.« less

Microchip capillary gel electrophoresis using programmed field strength gradients for the ultra-fast analysis of genetically modified organisms in soybeans.

PubMed

Kim, Yun-Jeong; Chae, Joon-Seok; Chang, Jun Keun; Kang, Seong Ho

2005-08-12

We have developed a novel method for the ultra-fast analysis of genetically modified organisms (GMOs) in soybeans by microchip capillary gel electrophoresis (MCGE) using programmed field strength gradients (PFSG) in a conventional glass double-T microchip. Under the programmed electric field strength and 0.3% poly(ethylene oxide) sieving matrix, the GMO in soybeans was analyzed within only 11 s of the microchip. The MCGE-PFSG method was a program that changes the electric field strength during GMO analysis, and was also applied to the ultra-fast analysis of PCR products. Compared to MCGE using a conventional and constantly applied electric field, the MCGE-PFSG analysis generated faster results without the loss of resolving power and reproducibility for specific DNA fragments (100- and 250-bp DNA) of GM-soybeans. The MCGE-PFSG technique may prove to be a new tool in the GMO analysis due to its speed, simplicity, and high efficiency.

Bandstructure modulation for Si-h and Si-g nanotubes in a transverse electric field: Tight binding approach

NASA Astrophysics Data System (ADS)

Chegel, Raad; Behzad, Somayeh

2013-11-01

We have investigated the electronic properties of SiNTs, under the external electric field, using Tight Binding (TB) approximation. It was found that the energy levels, energy gaps, and density of states (DOS) strongly depend on the electric field strength. The large electric strength leads to coupling the neighbor subbands and induce destruction of subband degeneracy, increase of low-energy states, and strong modulation of energy gap which these effects reflect in the DOS spectrum. It has been shown that, the band gap reduction of Si g-NTs is linearly proportional to the electric field strength. The band gap variation for Si h-NTs increases first and later decreases (Metallic) or first remains constant and then decreases (semiconductor). Also we show that the larger diameter tubes are more sensitive to the field strength than smaller ones. The semiconducting metallic transition or vice versa can be achieved through an increasing of applied fields. Number and position of peaks in DOS spectrum are dependent on electric field strength.

Short-term Periodization Models: Effects on Strength and Speed-strength Performance.

PubMed

Hartmann, Hagen; Wirth, Klaus; Keiner, Michael; Mickel, Christoph; Sander, Andre; Szilvas, Elena

2015-10-01

avoided because it does not provide an adequate training stimulus for gains in muscle cross-sectional area and strength performance. High-volume circuit strength training performed over 2 years negatively affected the development of the power output and maximal strength of the upper extremities in professional rugby players. Indeed, meta-analyses and results with weightlifters, American Football players, and throwers confirm the necessity of the habitual use of ≥80% 1 RM: (1) to improve maximal strength during the off-season and in-season in American Football, (2) to reach peak performance in maximal strength and vertical jump power during tapering in track-and-field, and (3) to produce hypertrophy and strength improvements in advanced athletes. The integration and extent of hypertrophy strength training in in-season conditioning depend on the duration of the contest period, the frequency of the contests, and the proportion of the conditioning program. Based on the literature, 72 h between hypertrophy strength training and strength-power training should be provided to allow for adequate regeneration times and therefore maximal stimulus intensities in training. This conclusion is only valid if the muscle is not trained otherwise during this regeneration phase. Thus, rotating hypertrophy and strength-power sessions in a microcycle during the season is a viable option. Comparative studies in competitive athletes who integrated strength training during pre-season conditioning confirm a tendency for gains in explosive strength and statistically significant improvements in medicine ball throw through SPP but not through daily undulating periodization. These findings indicate that to maximize the speed-strength in the short term (peaking), elite athletes should perform strength-power training twice per week. It is possible to perform a single strength-power session with the method of maximum explosive strength actions moving high-weight loads (90% 1 repetition maximum [RM]) at

Electrophoresis in strong electric fields.

PubMed

Barany, Sandor

2009-01-01

Two kinds of non-linear electrophoresis (ef) that can be detected in strong electric fields (several hundred V/cm) are considered. The first ("classical" non-linear ef) is due to the interaction of the outer field with field-induced ionic charges in the electric double layer (EDL) under conditions, when field-induced variations of electrolyte concentration remain to be small comparatively to its equilibrium value. According to the Shilov theory, the non-linear component of the electrophoretic velocity for dielectric particles is proportional to the cubic power of the applied field strength (cubic electrophoresis) and to the second power of the particles radius; it is independent of the zeta-potential but is determined by the surface conductivity of particles. The second one, the so-called "superfast electrophoresis" is connected with the interaction of a strong outer field with a secondary diffuse layer of counterions (space charge) that is induced outside the primary (classical) diffuse EDL by the external field itself because of concentration polarization. The Dukhin-Mishchuk theory of "superfast electrophoresis" predicts quadratic dependence of the electrophoretic velocity of unipolar (ionically or electronically) conducting particles on the external field gradient and linear dependence on the particle's size in strong electric fields. These are in sharp contrast to the laws of classical electrophoresis (no dependence of V(ef) on the particle's size and linear dependence on the electric field gradient). A new method to measure the ef velocity of particles in strong electric fields is developed that is based on separation of the effects of sedimentation and electrophoresis using videoimaging and a new flowcell and use of short electric pulses. To test the "classical" non-linear electrophoresis, we have measured the ef velocity of non-conducting polystyrene, aluminium-oxide and (semiconductor) graphite particles as well as Saccharomice cerevisiae yeast cells as a

R1 dispersion contrast at high field with fast field-cycling MRI

NASA Astrophysics Data System (ADS)

Bödenler, Markus; Basini, Martina; Casula, Maria Francesca; Umut, Evrim; Gösweiner, Christian; Petrovic, Andreas; Kruk, Danuta; Scharfetter, Hermann

2018-05-01

Contrast agents with a strong R1 dispersion have been shown to be effective in generating target-specific contrast in MRI. The utilization of this R1 field dependence requires the adaptation of an MRI scanner for fast field-cycling (FFC). Here, we present the first implementation and validation of FFC-MRI at a clinical field strength of 3 T. A field-cycling range of ±100 mT around the nominal B0 field was realized by inserting an additional insert coil into an otherwise conventional MRI system. System validation was successfully performed with selected iron oxide magnetic nanoparticles and comparison to FFC-NMR relaxometry measurements. Furthermore, we show proof-of-principle R1 dispersion imaging and demonstrate the capability of generating R1 dispersion contrast at high field with suppressed background signal. With the presented ready-to-use hardware setup it is possible to investigate MRI contrast agents with a strong R1 dispersion at a field strength of 3 T.

Magnetic field dependent atomic tunneling in non-magnetic glasses

NASA Astrophysics Data System (ADS)

Ludwig, S.; Enss, C.; Hunklinger, S.

2003-05-01

The low-temperature properties of insulating glasses are governed by atomic tunneling systems (TSs). Recently, strong magnetic field effects in the dielectric susceptibility have been discovered in glasses at audio frequencies at very low temperatures. Moreover, it has been found that the amplitude of two-pulse polarization echoes generated in non-magnetic multi-component glasses at radio frequencies and at very low temperatures shows a surprising non-monotonic magnetic field dependence. The magnitude of the latter effect indicates that virtually all TSs are affected by the magnetic field, not only a small subset of systems. We have studied the variation of the magnetic field dependence of the echo amplitude as a function of the delay time between the two excitation pulses and at different frequencies. Our results indicate that the evolution of the phase of resonant TSs is changed by the magnetic field.

Repair strength dependence on solder protein concentration: a study in laser tissue-welding.

PubMed

Lauto, A

1998-01-01

A novel laser-activated solid solder has been coupled with a diode laser to investigate the dependence of the solder protein concentration on the tensile strength of the soldered tissues. The uncertainty of laser welding, due to the fluid glue, was overcome using the solid solder. Sixty-two severed rat tibial nerves and vas deferens were repaired using rectangular protein bands with two different albumin concentrations (58% and 68% by weight). The laser power (90 mW and 140 mW), dose (12.9 +/- 0.7 J/mg, mean +/- s.d.), and solder dimensions (thickness = 0.15 +/- 0.01 mm, surface area = 7.8 +/- 0.4 mm2) were kept constant during the operations. The laser welds with high protein solder concentration were significantly (P < 0.05) stronger (28 +/- 3.5 g) than the welds with low protein solder concentration (23 +/- 5 g). The average tensile strength of the laser soldered tissues increased as the protein solder concentration increased.

Magnetic field strengths in high-redshift galaxies - Can the galactic dynamo be tested?

NASA Technical Reports Server (NTRS)

Perry, Judith J.; Watson, Alan M.; Kronberg, Philipp P.

1993-01-01

The hypothesis that the population of strong H I absorption systems is responsible for a significant excess Faraday rotation measure in quasars is discussed, and it is concluded that the case is unproved, in contrast to a recent analysis by Wolf et al. (1991). The limitations and pitfalls inherent in attempts to derive firm magnetic field strengths from the existing integrated rotation measures of quasars are discussed, and it is shown that although it is premature to use integrated quasar rotation measures to either confirm or rule out particular mechanisms of magnetic field amplification in galaxy disks, the present observations may call for reexamination of current theories of large-scale magnetic field generation. The sources of rotation measure in the double quasar 0957+561 are also discussed.

Experimental investigation of the visual field dependency in the erect and supine positions

NASA Technical Reports Server (NTRS)

Lichtenstein, J. H.; Saucer, R. T.

1972-01-01

The increasing utilization of simulators in many fields, in addition to aeronautics and space, requires the efficient use of these devices. It seemed that personnel highly influenced by the visual scene would make desirable subjects, particularly for those simulators without sufficient motion cues. In order to evaluate this concept, some measure of the degree of influence of the visual field on the subject in necessary. As part of this undertaking, 37 male and female subjects, including eight test pilots, were tested for their visual field dependency or independency. A version of Witkin's rod and frame apparatus was used for the tests. The results showed that nearly all the test subjects exhibited some degree of field dependency, the degree varying from very high field dependency to nearly zero field dependency in a normal distribution. The results for the test pilots were scattered throughout a range similar to the results for the bulk of male subjects. The few female subjects exhibited a higher field dependency than the male subjects. The male subjects exhibited a greater field dependency in the supine position than in the erect position, whereas the field dependency of the female subjects changed only slightly.

Signal-to-noise ratio, T2 , and T2* for hyperpolarized helium-3 MRI of the human lung at three magnetic field strengths.

PubMed

Komlosi, Peter; Altes, Talissa A; Qing, Kun; Mooney, Karen E; Miller, G Wilson; Mata, Jaime F; de Lange, Eduard E; Tobias, William A; Cates, Gordon D; Mugler, John P

2017-10-01

To evaluate T 2 , T2*, and signal-to-noise ratio (SNR) for hyperpolarized helium-3 ( 3 He) MRI of the human lung at three magnetic field strengths ranging from 0.43T to 1.5T. Sixteen healthy volunteers were imaged using a commercial whole body scanner at 0.43T, 0.79T, and 1.5T. Whole-lung T 2 values were calculated from a Carr-Purcell-Meiboom-Gill spin-echo-train acquisition. T2* maps and SNR were determined from dual-echo and single-echo gradient-echo images, respectively. Mean whole-lung SNR values were normalized by ventilated lung volume and administered 3 He dose. As expected, T 2 and T2* values demonstrated a significant inverse relationship to field strength. Hyperpolarized 3 He images acquired at all three field strengths had comparable SNR values and thus appeared visually very similar. Nonetheless, the relatively small SNR differences among field strengths were statistically significant. Hyperpolarized 3 He images of the human lung with similar image quality were obtained at three field strengths ranging from 0.43T and 1.5T. The decrease in susceptibility effects at lower fields that are reflected in longer T 2 and T2* values may be advantageous for optimizing pulse sequences inherently sensitive to such effects. The three-fold increase in T2* at lower field strength would allow lower receiver bandwidths, providing a concomitant decrease in noise and relative increase in SNR. Magn Reson Med 78:1458-1463, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Learning by Employing Educational Multimedia in Field-Dependent and Field-Independent Cognitive Styles

ERIC Educational Resources Information Center

Karamaerouz, Mohamad Javad; Abdi, Ali; Laei, Soosan

2013-01-01

Cognitive learning styles are relatively fixed procedures using which individuals receive, process and organize information. This paper aims to examine academic achievement in English for both field dependence and field independence learning styles using educational multimedia. The sample of the study consisted of 40 second-grade female students…

Strength loss in southern pine poles damaged by woodpeckers

Treesearch

R.W. Rumsey; G.E. Woodson

1973-01-01

Woodpecker damage caused extensive reductions in strength of 50-foot, class-2 utility poles, the amount depending on the cross-sectional area of wood removed and its distance from the apex. Two methods for estimating when damaged poles should be replaced proved to be conservative when applied to results of field tests. Such conservative predictions of falling loads...

Strength loss in southern pine poles damaged by woodpeckers

Treesearch

R.L. Rumsey; George E. Woodson

1973-01-01

Woodpecker damage caused extensive reductions in strength of 50-foot, class-2 utility poles, the amount depending on the cross-sectional area of wood removed and its distance from the apex. Two methods for estimating when damaged poles should be replaced proved to be conservative when applied to results of field rests. Such conservative predictions of failing loads...

Field Dependency and Performance in Mathematics

ERIC Educational Resources Information Center

Onwumere, Onyebuchi; Reid, Norman

2014-01-01

Mathematics is an important school subject but one which often poses problems for learners. It has been found that learners do not possess the cognitive capacity to handle understanding procedures, representations, concepts, and applications at the same time. while the extent of field dependency may hold the key to one way by which the working…

Field-size dependence of doses of therapeutic carbon beams.

PubMed

Kusano, Yohsuke; Kanai, Tatsuaki; Yonai, Shunsuke; Komori, Masataka; Ikeda, Noritoshi; Tachikawa, Yuji; Ito, Atsushi; Uchida, Hirohisa

2007-10-01

To estimate the physical dose at the center of spread-out Bragg peaks (SOBP) for various conditions of the irradiation system, a semiempirical approach was applied. The dose at the center of the SOBP depends on the field size because of large-angle scattering particles in the water phantom. For a small field of 5 x 5 cm2, the dose was reduced to 99.2%, 97.5%, and 96.5% of the dose used for the open field in the case of 290, 350, and 400 MeV/n carbon beams, respectively. Based on the three-Gaussian form of the lateral dose distributions of the carbon pencil beam, which has previously been shown to be effective for describing scattered carbon beams, we reconstructed the dose distributions of the SOBP beam. The reconstructed lateral dose distribution reproduced the measured lateral dose distributions very well. The field-size dependencies calculated using the reconstructed lateral dose distribution of the therapeutic carbon beam agreed with the measured dose dependency very well. The reconstructed beam was also used for irregularly shaped fields. The resultant dose distribution agreed with the measured dose distribution. The reconstructed beams were found to be applicable to the treatment-planning system.

An open, multi-vendor, multi-field-strength brain MR dataset and analysis of publicly available skull stripping methods agreement.

PubMed

Souza, Roberto; Lucena, Oeslle; Garrafa, Julia; Gobbi, David; Saluzzi, Marina; Appenzeller, Simone; Rittner, Letícia; Frayne, Richard; Lotufo, Roberto

2018-04-15

This paper presents an open, multi-vendor, multi-field strength magnetic resonance (MR) T1-weighted volumetric brain imaging dataset, named Calgary-Campinas-359 (CC-359). The dataset is composed of images of older healthy adults (29-80 years) acquired on scanners from three vendors (Siemens, Philips and General Electric) at both 1.5 T and 3 T. CC-359 is comprised of 359 datasets, approximately 60 subjects per vendor and magnetic field strength. The dataset is approximately age and gender balanced, subject to the constraints of the available images. It provides consensus brain extraction masks for all volumes generated using supervised classification. Manual segmentation results for twelve randomly selected subjects performed by an expert are also provided. The CC-359 dataset allows investigation of 1) the influences of both vendor and magnetic field strength on quantitative analysis of brain MR; 2) parameter optimization for automatic segmentation methods; and potentially 3) machine learning classifiers with big data, specifically those based on deep learning methods, as these approaches require a large amount of data. To illustrate the utility of this dataset, we compared to the results of a supervised classifier, the results of eight publicly available skull stripping methods and one publicly available consensus algorithm. A linear mixed effects model analysis indicated that vendor (p-value<0.001) and magnetic field strength (p-value<0.001) have statistically significant impacts on skull stripping results. Copyright © 2017 Elsevier Inc. All rights reserved.

Effects of Menstrual Phase-Dependent Resistance Training Frequency on Muscular Hypertrophy and Strength.

PubMed

Sakamaki-Sunaga, Mikako; Min, Seokki; Kamemoto, Kayoko; Okamoto, Takanobu

2016-06-01

The present study investigated how different training frequencies during menstrual phases affect muscle hypertrophy and strength. Fourteen eumenorrheic women performed 3 sets of arm curls (8-15 repetitions) until failure for 12 weeks. Depending on the menstrual cycle phase, each subject trained each arm separately after either a 3- or a 1-d·wk training protocol during the follicular phase (FP-T) and a 3- or 1-d·wk training protocol during the luteal phase (LP-T). Cross-sectional area (CSA), 1 repetition maximum, and maximum voluntary contraction significantly increased 6.2 ± 4.4, 36.4 ± 11.9, and 16.7 ± 5.6%, respectively (p ≤ 0.05 vs. before training), in the FP-T group and 7.8 ± 4.2, 31.8 ± 14.1, and 14.9 ± 12.7%, respectively (p ≤ 0.05 vs. before training), in the LP-T group. Changes in CSA between the FP-T and the LP-T groups significantly and positively correlated (r = 0.54, p ≤ 0.05). There were no major differences among the different training protocols with regard to muscle hypertrophy and strength. Therefore, we suggest that variations in female hormones induced by the menstrual cycle phases do not significantly contribute to muscle hypertrophy and strength gains during 12 weeks of resistance training.

Activity-dependent regulation of synaptic strength by PSD-95 in CA1 neurons.

PubMed

Zhang, Peng; Lisman, John E

2012-02-01

CaMKII and PSD-95 are the two most abundant postsynaptic proteins in the postsynaptic density (PSD). Overexpression of either can dramatically increase synaptic strength and saturate long-term potentiation (LTP). To do so, CaMKII must be activated, but the same is not true for PSD-95; expressing wild-type PSD-95 is sufficient. This raises the question of whether PSD-95's effects are simply an equilibrium process [increasing the number of AMPA receptor (AMPAR) slots] or whether activity is somehow involved. To examine this question, we blocked activity in cultured hippocampal slices with TTX and found that the effects of PSD-95 overexpression were greatly reduced. We next studied the type of receptors involved. The effects of PSD-95 were prevented by antagonists of group I metabotropic glutamate receptors (mGluRs) but not by antagonists of ionotropic glutamate receptors. The inhibition of PSD-95-induced strengthening was not simply a result of inhibition of PSD-95 synthesis. To understand the mechanisms involved, we tested the role of CaMKII. Overexpression of a CaMKII inhibitor, CN19, greatly reduced the effect of PSD-95. We conclude that PSD-95 cannot itself increase synaptic strength simply by increasing the number of AMPAR slots; rather, PSD-95's effects on synaptic strength require an activity-dependent process involving mGluR and CaMKII.

Granular cells in the presence of magnetic field

NASA Astrophysics Data System (ADS)

Jurčák, J.; Lemmerer, B.; van Noort, M.

2017-10-01

We present a statistical study of the dependencies of the shapes and sizes of the photospheric convective cells on the magnetic field properties. This analysis is based on a 2.5 hour long SST observations of active region NOAA 11768. We have blue continuum images taken with a cadence of 5.6 sec that are used for segmentation of individual granules and 270 maps of spectropolarimetric CRISP data allowing us to determine the properties of the magnetic field along with the line-of-sight velocities. The sizes and shapes of the granular cells are dependent on the the magnetic field strength, where the granules tend to be smaller in regions with stronger magnetic field. In the presence of highly inclined magnetic fields, the eccentricity of granules is high and we do not observe symmetric granules in these regions. The mean up-flow velocities in granules as well as the granules intensities decrease with increasing magnetic field strength.

Strength deficit of knee flexors is dependent on hip position in adults with chronic hemiparesis.

PubMed

Michaelsen, Stella M; Ovando, Angélica C; Bortolotti, Adriano; Bandini, Bruno

2013-01-01

The extent to which muscle length affects force production in paretic lower limb muscles after stroke in comparison to controls has not been established. To investigate knee flexor strength deficits dependent on hip joint position in adults with hemiparesis and compare with healthy controls. a cross-sectional study with ten subjects with chronic (63±40 months) hemiparesis with mild to moderate lower limb paresis (Fugl-Meyer score 26±3) and 10 neurologically healthy controls. Isometric knee flexion strength with the hip positioned at 90° and 0° of flexion was assessed randomly on the paretic and non-paretic side of hemiparetic subjects and healthy controls. Subjects were asked to perform a maximal isometric contraction sustained for four seconds and measured by a dynamometer. The ratio of knee flexor strength between these two hip positions was calculated: Hip 0°/Hip 90°. Also, locomotor capacity was evaluated by the timed up and go test and by walking velocity over 10 meters. In subjects with hemiparesis, absolute knee flexion torque decreased (p<0.001) with the hip in extension (at 0°). The ratio of knee flexor torque Hip 0°/Hip 90° on the paretic side in hemiparetics was lower than in controls (p=0.02). Weakness dependent on joint position is more significant in the paretic lower limb of adults with hemiparesis when compared to controls. More attention should be given to lower limb muscle strengthening exercises in individuals with stroke, with emphasis on the strengthening exercises in positions in which the muscle is shortened.

Magnetically responsive nanoparticles for drug delivery applications using low magnetic field strengths.

PubMed

McGill, Shayna L; Cuylear, Carla L; Adolphi, Natalie L; Osiński, Marek; Smyth, Hugh D C

2009-03-01

The purpose of this study is to investigate the potential of magnetic nanoparticles for enhancing drug delivery using a low oscillating magnetic field (OMF) strength. We investigated the ability of magnetic nanoparticles to cause disruption of a viscous biopolymer barrier to drug delivery and the potential to induce triggered release of drug conjugated to the surfaces of these particles. Various magnetic nanoparticles were screened for thermal response under a 295-kHz OMF with an amplitude of 3.1 kA/m. Based on thermal activity of particles screened, we selected the nanoparticles that displayed desired characteristics for evaluation in a simplified model of an extracellular barrier to drug delivery, using lambda DNA/HindIII. Results indicate that nanoparticles could be used to induce DNA breakage to enhance local diffusion of drugs, despite low temperatures of heating. Additional studies showed increased diffusion of quantum dots in this model by single-particle tracking methods. Bimane was conjugated to the surface of magnetic nanoparticles. Fluorescence and transmission electron microscope images of the conjugated nanoparticles indicated little change in the overall appearance of the nanoparticles. A release study showed greater drug release using OMF, while maintaining low bulk heating of the samples (T = 30 degrees C). This study indicates that lower magnetic field strengths may be successfully utilized for drug delivery applications as a method for drug delivery transport enhancement and drug release switches.

Surface Magnetic Field Strengths: New Tests of Magnetoconvective Models of M Dwarfs

NASA Astrophysics Data System (ADS)

MacDonald, James; Mullan, D. J.

2014-05-01

Precision modeling of M dwarfs has become worthwhile in recent years due to the increasingly precise values of masses and radii which can be obtained from eclipsing binary studies. In a recent paper, Torres has identified four prime M dwarf pairs with the most precise empirical determinations of masses and radii. The measured radii are consistently larger than standard stellar models predict by several percent. These four systems potentially provide the most challenging tests of precision evolutionary models of cool dwarfs at the present time. We have previously modeled M dwarfs in the context of a criterion due to Gough & Tayler in which magnetic fields inhibit the onset of convection according to a physics-based prescription. In the present paper, we apply our magnetoconvective approach to the four prime systems in the Torres list. Going a step beyond what we have already modeled in CM Dra (one of the four Torres systems), we note that new constraints on magnetoconvective models of M dwarfs are now available from empirical estimates of magnetic field strengths on the surfaces of these stars. In the present paper, we consider how well our magnetoconvective models succeed when confronted with this new test of surface magnetic field strengths. Among the systems listed by Torres, we find that plausible magnetic models work well for CM Dra, YY Gem, and CU Cnc. (The fourth system in Torres's list does not yet have enough information to warrant magnetic modeling.) Our magnetoconvection models of CM Dra, YY Gem, and CU Cnc yield predictions of the magnetic fluxes on the stellar surface which are consistent with the observed correlation between magnetic flux and X-ray luminosity.

Is inertial flywheel resistance training superior to gravity-dependent resistance training in improving muscle strength? A systematic review with meta-analyses.

PubMed

Vicens-Bordas, J; Esteve, E; Fort-Vanmeerhaeghe, A; Bandholm, T; Thorborg, K

2018-01-01

The primary aim of this systematic review was to determine if inertial flywheel resistance training is superior to gravity-dependent resistance training in improving muscle strength. The secondary aim was to determine whether inertial flywheel resistance training is superior to gravity-dependent resistance training in improving other muscular adaptations. A systematic review with meta-analyses of randomised and non-randomised controlled trials. We searched MEDLINE, Scopus, SPORTDiscus, Web of Science and Cochrane Central Register of Controlled Trials with no publication date restrictions until November 2016. We performed meta-analyses on randomised and non-randomised controlled trials to determine the standardized mean difference between the effects of inertial flywheel and gravity-dependent resistance training on muscle strength. A total of 76 and 71 participants were included in the primary and secondary analyses, respectively. After systematic review, we included three randomised and four non-randomised controlled trials. In the primary analysis for the primary outcome muscle strength, the pooled results from randomised controlled trials showed no difference (SMD=-0.05; 95%CI -0.51 to 0.40; p=0.82; I 2 =0%). In the secondary analyses of the primary outcome, the pooled results from non-randomised controlled trials showed no difference (SMD=0.02; 95%CI -0.45 to 0.49; p=0.93; I 2 =0%; and SMD=0.03; 95%CI -0.43 to 0.50; p=0.88; I 2 =0%). Meta-analysis on secondary outcomes could not be performed. Based on the available data, inertial flywheel resistance training was not superior to gravity-dependent resistance training in enhancing muscle strength. Data for other strength variables and other muscular adaptations was insufficient to draw firm conclusions from. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Spin polarization transfer mechanisms of SABRE: A magnetic field dependent study.

PubMed

Pravdivtsev, Andrey N; Ivanov, Konstantin L; Yurkovskaya, Alexandra V; Petrov, Pavel A; Limbach, Hans-Heinrich; Kaptein, Robert; Vieth, Hans-Martin

2015-12-01

We have investigated the magnetic field dependence of Signal Amplification By Reversible Exchange (SABRE) arising from binding of para-hydrogen (p-H2) and a substrate to a suitable transition metal complex. The magnetic field dependence of the amplification of the (1)H Nuclear Magnetic Resonance (NMR) signals of the released substrates and dihydrogen, and the transient transition metal dihydride species shows characteristic patterns, which is explained using the theory presented here. The generation of SABRE is most efficient at low magnetic fields due to coherent spin mixing at nuclear spin Level Anti-Crossings (LACs) in the SABRE complexes. We studied two Ir-complexes and have shown that the presence of a (31)P atom in the SABRE complex doubles the number of LACs and, consequently, the number of peaks in the SABRE field dependence. Interestingly, the polarization of SABRE substrates is always accompanied by the para-to-ortho conversion in dihydride species that results in enhancement of the NMR signal of free (H2) and catalyst-bound H2 (Ir-HH). The field dependences of hyperpolarized H2 and Ir-HH by means of SABRE are studied here, for the first time, in detail. The field dependences depend on the chemical shifts and coupling constants of Ir-HH, in which the polarization transfer takes place. A negative coupling constant of -7Hz between the two chemically equivalent but magnetically inequivalent hydride nuclei is determined, which indicates that Ir-HH is a dihydride with an HH distance larger than 2Å. Finally, the field dependence of SABRE at high fields as found earlier has been investigated and attributed to polarization transfer to the substrate by cross-relaxation. The present study provides further evidence for the key role of LACs in the formation of SABRE-derived polarization. Understanding the spin dynamics behind the SABRE method opens the way to optimizing its performance and overcoming the main limitation of NMR, its notoriously low sensitivity

Spin polarization transfer mechanisms of SABRE: A magnetic field dependent study

NASA Astrophysics Data System (ADS)

Pravdivtsev, Andrey N.; Ivanov, Konstantin L.; Yurkovskaya, Alexandra V.; Petrov, Pavel A.; Limbach, Hans-Heinrich; Kaptein, Robert; Vieth, Hans-Martin

2015-12-01

We have investigated the magnetic field dependence of Signal Amplification By Reversible Exchange (SABRE) arising from binding of para-hydrogen (p-H2) and a substrate to a suitable transition metal complex. The magnetic field dependence of the amplification of the 1H Nuclear Magnetic Resonance (NMR) signals of the released substrates and dihydrogen, and the transient transition metal dihydride species shows characteristic patterns, which is explained using the theory presented here. The generation of SABRE is most efficient at low magnetic fields due to coherent spin mixing at nuclear spin Level Anti-Crossings (LACs) in the SABRE complexes. We studied two Ir-complexes and have shown that the presence of a 31P atom in the SABRE complex doubles the number of LACs and, consequently, the number of peaks in the SABRE field dependence. Interestingly, the polarization of SABRE substrates is always accompanied by the para-to-ortho conversion in dihydride species that results in enhancement of the NMR signal of free (H2) and catalyst-bound H2 (Ir-HH). The field dependences of hyperpolarized H2 and Ir-HH by means of SABRE are studied here, for the first time, in detail. The field dependences depend on the chemical shifts and coupling constants of Ir-HH, in which the polarization transfer takes place. A negative coupling constant of -7 Hz between the two chemically equivalent but magnetically inequivalent hydride nuclei is determined, which indicates that Ir-HH is a dihydride with an HH distance larger than 2 Å. Finally, the field dependence of SABRE at high fields as found earlier has been investigated and attributed to polarization transfer to the substrate by cross-relaxation. The present study provides further evidence for the key role of LACs in the formation of SABRE-derived polarization. Understanding the spin dynamics behind the SABRE method opens the way to optimizing its performance and overcoming the main limitation of NMR, its notoriously low sensitivity.

Laboratory measurements of ice tensile strength dependence on density and concentration of silicate and polymer impurities at low temperatures

NASA Astrophysics Data System (ADS)

Litwin, K. L.; Beyeler, J. D.; Polito, P. J.; Zygielbaum, B. R.; Sklar, L. S.; Collins, G. C.

2009-12-01

The tensile strength of ice bedrock on Titan should strongly influence the effectiveness of the erosional processes responsible for carving the extensive fluvial drainage networks and other surface features visible in images returned by the Cassini and Huygens probes. Recent measurements of the effect of temperature on the tensile strength of low-porosity, polycrystalline ice, without impurities, suggest that ice bedrock at the Titan surface temperature of 93 K may be as much as five times stronger than ice at terrestrial surface temperatures. However, ice bedrock on Titan and other outer solar system bodies may have significant porosity, and impurities such silicates or polymers are possible in such ices. In this laboratory investigation we are exploring the dependence of tensile strength on the density and concentration of impurities, for polycrystalline ice across a wide range of temperatures. We use the Brazilian tensile splitting test to measure strength, and control temperature with dry ice and liquid nitrogen. The 50 mm diameter ice cores are made from a log-normally distributed seed crystal mixture with a median size of 1.4 mm. To control ice density and porosity we vary the packing density of the seed grains in core molds and vary the degree of saturation of the matrix with added near-freezing distilled water. We also vary ice density by blending in a similarly-sized mixture of angular fragments of two types of impurities, a fine-grained volcanic rock and a polyethylene polymer. Because both types of impurities have greater tensile strength than ice at Earth surface temperatures, we expect higher concentrations of impurities to correlate with increased strength for ice-rock and ice-polymer mixtures. However, at the ultra-cold temperatures of the outer planets, we expect significant divergence in the temperature dependence of ice tensile strength for the various mixtures and resulting densities. These measurements will help constrain the range of possible

Simulation of field-induced molecular dissociation in atom-probe tomography: Identification of a neutral emission channel

NASA Astrophysics Data System (ADS)

Zanuttini, David; Blum, Ivan; Rigutti, Lorenzo; Vurpillot, François; Douady, Julie; Jacquet, Emmanuelle; Anglade, Pierre-Matthieu; Gervais, Benoit

2017-06-01

We investigate the dynamics of dicationic metal-oxide molecules under large electric-field conditions, on the basis of ab initio calculations coupled to molecular dynamics. Applied to the case of ZnO2 + in the field of atom probe tomography (APT), our simulation reveals the dissociation into three distinct exit channels. The proportions of these channels depend critically on the field strength and on the initial molecular orientation with respect to the field. For typical field strength used in APT experiments, an efficient dissociation channel leads to emission of neutral oxygen atoms, which escape detection. The calculated composition biases and their dependence on the field strength show remarkable consistency with recent APT experiments on ZnO crystals. Our work shows that bond breaking in strong static fields may lead to significant neutral atom production, and therefore to severe elemental composition biases in measurements.

47 CFR 27.55 - Power strength limits.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 2 2011-10-01 2011-10-01 false Power strength limits. 27.55 Section 27.55... COMMUNICATIONS SERVICES Technical Standards § 27.55 Power strength limits. (a) Field strength limits. For the following bands, the predicted or measured median field strength at any location on the geographical border...

Frequency-dependent local field factors in dielectric liquids by a polarizable force field and molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Davari, Nazanin; Haghdani, Shokouh; Åstrand, Per-Olof

2015-12-01

A force field model for calculating local field factors, i.e. the linear response of the local electric field for example at a nucleus in a molecule with respect to an applied electric field, is discussed. It is based on a combined charge-transfer and point-dipole interaction model for the polarizability, and thereby it includes two physically distinct terms for describing electronic polarization: changes in atomic charges arising from transfer of charge between the atoms and atomic induced dipole moments. A time dependence is included both for the atomic charges and the atomic dipole moments and if they are assumed to oscillate with the same frequency as the applied electric field, a model for frequency-dependent properties are obtained. Furthermore, if a life-time of excited states are included, a model for the complex frequency-dependent polariability is obtained including also information about excited states and the absorption spectrum. We thus present a model for the frequency-dependent local field factors through the first molecular excitation energy. It is combined with molecular dynamics simulations of liquids where a large set of configurations are sampled and for which local field factors are calculated. We are normally not interested in the average of the local field factor but rather in configurations where it is as high as possible. In electrical insulation, we would like to avoid high local field factors to reduce the risk for electrical breakdown, whereas for example in surface-enhanced Raman spectroscopy, high local field factors are desired to give dramatically increased intensities.

Perturbation theory for arbitrary coupling strength?

NASA Astrophysics Data System (ADS)

Mahapatra, Bimal P.; Pradhan, Noubihary

2018-03-01

We present a new formulation of perturbation theory for quantum systems, designated here as: “mean field perturbation theory” (MFPT), which is free from power-series-expansion in any physical parameter, including the coupling strength. Its application is thereby extended to deal with interactions of arbitrary strength and to compute system-properties having non-analytic dependence on the coupling, thus overcoming the primary limitations of the “standard formulation of perturbation theory” (SFPT). MFPT is defined by developing perturbation about a chosen input Hamiltonian, which is exactly solvable but which acquires the nonlinearity and the analytic structure (in the coupling strength) of the original interaction through a self-consistent, feedback mechanism. We demonstrate Borel-summability of MFPT for the case of the quartic- and sextic-anharmonic oscillators and the quartic double-well oscillator (QDWO) by obtaining uniformly accurate results for the ground state of the above systems for arbitrary physical values of the coupling strength. The results obtained for the QDWO may be of particular significance since “renormalon”-free, unambiguous results are achieved for its spectrum in contrast to the well-known failure of SFPT in this case.

Size-dependent reactivity of magnetite nanoparticles: a field-laboratory comparison

USGS Publications Warehouse

Swindle, Andrew L.; Elwood Madden, Andrew S.; Cozzarelli, Isabelle M.; Benamara, Mourad

2014-01-01

Logistic challenges make direct comparisons between laboratory- and field-based investigations into the size-dependent reactivity of nanomaterials difficult. This investigation sought to compare the size-dependent reactivity of nanoparticles in a field setting to a laboratory analog using the specific example of magnetite dissolution. Synthetic magnetite nanoparticles of three size intervals, ∼6 nm, ∼44 nm, and ∼90 nm were emplaced in the subsurface of the USGS research site at the Norman Landfill for up to 30 days using custom-made subsurface nanoparticle holders. Laboratory analog dissolution experiments were conducted using synthetic groundwater. Reaction products were analyzed via TEM and SEM and compared to initial particle characterizations. Field results indicated that an organic coating developed on the particle surfaces largely inhibiting reactivity. Limited dissolution occurred, with the amount of dissolution decreasing as particle size decreased. Conversely, the laboratory analogs without organics revealed greater dissolution of the smaller particles. These results showed that the presence of dissolved organics led to a nearly complete reversal in the size-dependent reactivity trends displayed between the field and laboratory experiments indicating that size-dependent trends observed in laboratory investigations may not be relevant in organic-rich natural systems.

Strain-rate dependence of ramp-wave evolution and strength in tantalum

DOE PAGES

Lane, J. Matthew D.; Foiles, Stephen M.; Lim, Hojun; ...

2016-08-25

We have conducted molecular dynamics (MD) simulations of quasi-isentropic ramp-wave compression to very high pressures over a range of strain rates from 10 11 down to 10 8 1/s. Using scaling methods, we collapse wave profiles from various strain rates to a master profile curve, which shows deviations when material response is strain-rate dependent. Thus, we can show with precision where, and how, strain-rate dependence affects the ramp wave. We find that strain rate affects the stress-strain material response most dramatically at strains below 20%, and that above 30% strain the material response is largely independent of strain rate. Wemore » show good overall agreement with experimental stress-strain curves up to approximately 30% strain, above which simulated response is somewhat too stiff. We postulate that this could be due to our interatomic potential or to differences in grain structure and/or size between simulation and experiment. Strength is directly measured from per-atom stress tensor and shows significantly enhanced elastic response at the highest strain rates. As a result, this enhanced elastic response is less pronounced at higher pressures and at lower strain rates.« less

Field of first magnetic flux entry and pinning strength of superconductors for rf application measured with muon spin rotation

NASA Astrophysics Data System (ADS)

Junginger, T.; Abidi, S. H.; Maffett, R. D.; Buck, T.; Dehn, M. H.; Gheidi, S.; Kiefl, R.; Kolb, P.; Storey, D.; Thoeng, E.; Wasserman, W.; Laxdal, R. E.

2018-03-01

The performance of superconducting radiofrequency (SRF) cavities used for particle accelerators depends on two characteristic material parameters: field of first flux entry Hentry and pinning strength. The former sets the limit for the maximum achievable accelerating gradient, while the latter determines how efficiently flux can be expelled related to the maximum achievable quality factor. In this paper, a method based on muon spin rotation (μ SR ) is developed to probe these parameters on samples. It combines measurements from two different spectrometers, one being specifically built for these studies and samples of different geometries. It is found that annealing at 1400 °C virtually eliminates all pinning. Such an annealed substrate is ideally suited to measure Hentry of layered superconductors, which might enable accelerating gradients beyond bulk niobium technology.

Time/Temperature Dependent Tensile Strength of SiC and Al2O3-Based Fibers

NASA Technical Reports Server (NTRS)

Yun, Hee Mann; DiCarlo, James A.

1997-01-01

In order to understand and model the thermomechanical behavior of fiber-reinforced composites, stress-rupture, fast-fracture, and warm-up rupture studies were conducted on various advanced SiC and Al2O3-based fibers in the,temperature range from 20 to 1400 C in air as well as in inert environments. The measured stress-rupture, fast fracture, and warm-up rupture strengths were correlated into a single master time/temperature-dependent strength plot for each fiber type using thermal activation and slow crack growth theories. It is shown that these plots are useful for comparing and selecting fibers for CMC and MMC reinforcement and that, in comparison to stress rupture tests, the fast-fracture and warm-up tests can be used for rapid generation of these plots.

Monolayer phosphorene under time-dependent magnetic field

NASA Astrophysics Data System (ADS)

Nascimento, J. P. G.; Aguiar, V.; Guedes, I.

2018-02-01

We obtain the exact wave function of a monolayer phosphorene under a low-intensity time-dependent magnetic field using the dynamical invariant method. We calculate the quantum-mechanical energy expectation value and the transition probability for a constant and an oscillatory magnetic field. For the former we observe that the Landau level energy varies linearly with the quantum numbers n and m and the magnetic field intensity B0. No transition takes place. For the latter, we observe that the energy oscillates in time, increasing linearly with the Landau level n and m and nonlinearly with the magnetic field. The (k , l) →(n , m) transitions take place only for l = m. We investigate the (0,0) →(n , 0) and (1 , l) and (2 , l) probability transitions.

ROLE OF MAGNETIC FIELD STRENGTH AND NUMERICAL RESOLUTION IN SIMULATIONS OF THE HEAT-FLUX-DRIVEN BUOYANCY INSTABILITY

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

Avara, Mark J.; Reynolds, Christopher S.; Bogdanovic, Tamara, E-mail: mavara@astro.umd.edu, E-mail: chris@astro.umd.edu, E-mail: tamarab@gatech.edu

2013-08-20

The role played by magnetic fields in the intracluster medium (ICM) of galaxy clusters is complex. The weakly collisional nature of the ICM leads to thermal conduction that is channeled along field lines. This anisotropic heat conduction profoundly changes the instabilities of the ICM atmosphere, with convective stabilities being driven by temperature gradients of either sign. Here, we employ the Athena magnetohydrodynamic code to investigate the local non-linear behavior of the heat-flux-driven buoyancy instability (HBI) relevant in the cores of cooling-core clusters where the temperature increases with radius. We study a grid of two-dimensional simulations that span a large rangemore » of initial magnetic field strengths and numerical resolutions. For very weak initial fields, we recover the previously known result that the HBI wraps the field in the horizontal direction, thereby shutting off the heat flux. However, we find that simulations that begin with intermediate initial field strengths have a qualitatively different behavior, forming HBI-stable filaments that resist field-line wrapping and enable sustained vertical conductive heat flux at a level of 10%-25% of the Spitzer value. While astrophysical conclusions regarding the role of conduction in cooling cores require detailed global models, our local study proves that systems dominated by the HBI do not necessarily quench the conductive heat flux.« less

Geometric properties-dependent neural synchrony modulated by extracellular subthreshold electric field

NASA Astrophysics Data System (ADS)

Wei, Xile; Si, Kaili; Yi, Guosheng; Wang, Jiang; Lu, Meili

2016-07-01

In this paper, we use a reduced two-compartment neuron model to investigate the interaction between extracellular subthreshold electric field and synchrony in small world networks. It is observed that network synchronization is closely related to the strength of electric field and geometric properties of the two-compartment model. Specifically, increasing the electric field induces a gradual improvement in network synchrony, while increasing the geometric factor results in an abrupt decrease in synchronization of network. In addition, increasing electric field can make the network become synchronous from asynchronous when the geometric parameter is set to a given value. Furthermore, it is demonstrated that network synchrony can also be affected by the firing frequency and dynamical bifurcation feature of single neuron. These results highlight the effect of weak field on network synchrony from the view of biophysical model, which may contribute to further understanding the effect of electric field on network activity.

Momentum dependence in pair production by an external field

NASA Astrophysics Data System (ADS)

Asakawa, M.

1992-08-01

The transverse and the longitudinal momentum dependences of the pair production under an adiabatically exerted uniform abelian external field are calculated with their importance in models for the production of quark-gluon plasma in ultrarelativistic heavy ion collisions in mind. The importance of the initial condition is revealed. We show that superposition of acceleration by the external field and barrier penetration is reflected in the longitudinal momentum dependence. The peculiar nature of the boost invariant system which is expected to be approximately realized in ultrarelativistic nuclear collisions is pointed out.

Time-dependent low field microwave absorption in the high temperature superconductors

NASA Astrophysics Data System (ADS)

Owens, F. J.; Iqbal, Z.

1990-11-01

It is observed that the hysteresis in the applied magnetic field position and the intensity at the peak of the low field non-resonant microwave absorption (recorded in an EPR experiment with a modulation amplitude of ∼ 10 G) in the superconducting state of the cuprate superconductors, is time-dependent after the removal of a DC magnetic field sizably greater than the lower critical field. This intrinsic time-dependence, which we attribute to flux creep, is reported here for two copper oxide-based high temperature superconductors.

Field Dependence-Independence and Physical Activity Engagement among Middle School Students

ERIC Educational Resources Information Center

Liu, Wenhao; Chepyator-Thomson, Jepkorir Rose

2009-01-01

Background: Field dependence-independence (FDI) is a tendency to rely on external frames (given situations and authoritative people) or internal frames (oneself, including one's own body) for one's information processing and behavior. Literature has constantly reported that field-dependent (FD) individuals, who are less autonomous in…

R1 dispersion contrast at high field with fast field-cycling MRI.

PubMed

Bödenler, Markus; Basini, Martina; Casula, Maria Francesca; Umut, Evrim; Gösweiner, Christian; Petrovic, Andreas; Kruk, Danuta; Scharfetter, Hermann

2018-05-01

Contrast agents with a strong R 1 dispersion have been shown to be effective in generating target-specific contrast in MRI. The utilization of this R 1 field dependence requires the adaptation of an MRI scanner for fast field-cycling (FFC). Here, we present the first implementation and validation of FFC-MRI at a clinical field strength of 3 T. A field-cycling range of ±100 mT around the nominal B 0 field was realized by inserting an additional insert coil into an otherwise conventional MRI system. System validation was successfully performed with selected iron oxide magnetic nanoparticles and comparison to FFC-NMR relaxometry measurements. Furthermore, we show proof-of-principle R 1 dispersion imaging and demonstrate the capability of generating R 1 dispersion contrast at high field with suppressed background signal. With the presented ready-to-use hardware setup it is possible to investigate MRI contrast agents with a strong R 1 dispersion at a field strength of 3 T. Copyright © 2018 Elsevier Inc. All rights reserved.

Child Mortality, Women's Status, Economic Dependency, and State Strength: A Cross-National Study of Less Developed Countries.

ERIC Educational Resources Information Center

Shen, Ce; Williamson, John B.

1997-01-01

Data from 86 developing countries suggest that foreign investment and debt dependency have adverse indirect effects on child mortality--effects mediated by variables linked to industrialism theory and gender stratification theory: women's education, health, and reproductive autonomy and rate of economic growth. State strength was related to lower…

A low-cost, high-field-strength magnetic resonance imaging-compatible actuator.

PubMed

Secoli, Riccardo; Robinson, Matthew; Brugnoli, Michele; Rodriguez y Baena, Ferdinando

2015-03-01

To perform minimally invasive surgical interventions with the aid of robotic systems within a magnetic resonance imaging scanner offers significant advantages compared to conventional surgery. However, despite the numerous exciting potential applications of this technology, the introduction of magnetic resonance imaging-compatible robotics has been hampered by safety, reliability and cost concerns: the robots should not be attracted by the strong magnetic field of the scanner and should operate reliably in the field without causing distortion to the scan data. Development of non-conventional sensors and/or actuators is thus required to meet these strict operational and safety requirements. These demands commonly result in expensive actuators, which mean that cost effectiveness remains a major challenge for such robotic systems. This work presents a low-cost, high-field-strength magnetic resonance imaging-compatible actuator: a pneumatic stepper motor which is controllable in open loop or closed loop, along with a rotary encoder, both fully manufactured in plastic, which are shown to perform reliably via a set of in vitro trials while generating negligible artifacts when imaged within a standard clinical scanner. © IMechE 2015.

Surface magnetic field strengths: New tests of magnetoconvective models of M dwarfs

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

MacDonald, James; Mullan, D. J., E-mail: jimmacd@udel.edu, E-mail: mullan@udel.edu

2014-05-20

Precision modeling of M dwarfs has become worthwhile in recent years due to the increasingly precise values of masses and radii which can be obtained from eclipsing binary studies. In a recent paper, Torres has identified four prime M dwarf pairs with the most precise empirical determinations of masses and radii. The measured radii are consistently larger than standard stellar models predict by several percent. These four systems potentially provide the most challenging tests of precision evolutionary models of cool dwarfs at the present time. We have previously modeled M dwarfs in the context of a criterion due to Goughmore » and Tayler in which magnetic fields inhibit the onset of convection according to a physics-based prescription. In the present paper, we apply our magnetoconvective approach to the four prime systems in the Torres list. Going a step beyond what we have already modeled in CM Dra (one of the four Torres systems), we note that new constraints on magnetoconvective models of M dwarfs are now available from empirical estimates of magnetic field strengths on the surfaces of these stars. In the present paper, we consider how well our magnetoconvective models succeed when confronted with this new test of surface magnetic field strengths. Among the systems listed by Torres, we find that plausible magnetic models work well for CM Dra, YY Gem, and CU Cnc. (The fourth system in Torres's list does not yet have enough information to warrant magnetic modeling.) Our magnetoconvection models of CM Dra, YY Gem, and CU Cnc yield predictions of the magnetic fluxes on the stellar surface which are consistent with the observed correlation between magnetic flux and X-ray luminosity.« less

Species invasion shifts the importance of predator dependence.

PubMed

Griffen, Blaine D; Delaney, David G

2007-12-01

The strength of interference between foraging individuals can influence per capita consumption rates, with important consequences for predator and prey populations and system stability. Here we demonstrate how the replacement of a previously established invader, the predatory crab Carcinus maenas, by the recently invading predatory crab Hemigrapsus sanguineus shifts predation from a species that experiences strong predator interference (strong predator dependence) to one that experiences weak predator interference (weak predator dependence). We demonstrate using field experiments that differences in the strength of predator dependence persist for these species both when they forage on a single focal prey species only (the mussel Mytilus edulis) and when they forage more broadly across the entire prey community. This shift in predator dependence with species replacement may be altering the biomass across trophic levels, consistent with theoretical predictions, as we show that H. sanguineus populations are much larger than C. maenas populations throughout their invaded ranges. Our study highlights that predator dependence may differ among predator species and demonstrates that different predatory impacts of two conspicuous invasive predators may be explained at least in part by different strengths of predator dependence.

In vivo field-cycling relaxometry using an insert coil for magnetic field offset.

PubMed

Pine, Kerrin J; Goldie, Fred; Lurie, David J

2014-11-01

The T(1) of tissue has a strong dependence on the measurement magnetic field strength. T(1) -dispersion could be a useful contrast parameter, but is unavailable to clinical MR systems which operate at fixed magnetic field strength. The purpose of this work was to implement a removable insert magnet coil for field-cycling T(1) -dispersion measurements on a vertical-field MRI scanner, by offsetting the static field over a volume of interest. An insert magnet coil was constructed for use with a whole-body sized 59 milli-Tesla (mT) vertical-field, permanent-magnet based imager. The coil has diameter 38 cm and thickness 6.1 cm and a homogeneous region (± 5%) of 5 cm DSV, offset by 5 cm from the coil surface. Surface radiofrequency (RF) coils were also constructed. The insert coil was used in conjunction with a surface RF coil and a volume-localized inversion-recovery pulse sequence to plot T(1) -dispersion in a human volunteer's forearm over a range of field strengths from 1 mT to 70 mT. T(1) -dispersion measurements were demonstrated on a fixed-field MRI scanner, using an insert coil. This demonstrates the feasibility of relaxation dispersion measurements on an otherwise conventional MR imager, facilitating the exploitation of T(1) -dispersion contrast for enhanced diagnosis. Copyright © 2013 Wiley Periodicals, Inc.

WE-G-18C-05: Characterization of Cross-Vendor, Cross-Field Strength MR Image Intensity Variations

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

Paulson, E; Prah, D

2014-06-15

Purpose: Variations in MR image intensity and image intensity nonuniformity (IINU) can challenge the accuracy of intensity-based image segmentation and registration algorithms commonly applied in radiotherapy. The goal of this work was to characterize MR image intensity variations across scanner vendors and field strengths commonly used in radiotherapy. Methods: ACR-MRI phantom images were acquired at 1.5T and 3.0T on GE (450w and 750, 23.1), Siemens (Espree and Verio, VB17B), and Philips (Ingenia, 4.1.3) scanners using commercial spin-echo sequences with matched parameters (TE/TR: 20/500 ms, rBW: 62.5 kHz, TH/skip: 5/5mm). Two radiofrequency (RF) coil combinations were used for each scanner: bodymore » coil alone, and combined body and phased-array head coils. Vendorspecific B1- corrections (PURE/Pre-Scan Normalize/CLEAR) were applied in all head coil cases. Images were transferred offline, corrected for IINU using the MNI N3 algorithm, and normalized. Coefficients of variation (CV=σ/μ) and peak image uniformity (PIU = 1−(Smax−Smin)/(Smax+Smin)) estimates were calculated for one homogeneous phantom slice. Kruskal-Wallis and Wilcoxon matched-pairs tests compared mean MR signal intensities and differences between original and N3 image CV and PIU. Results: Wide variations in both MR image intensity and IINU were observed across scanner vendors, field strengths, and RF coil configurations. Applying the MNI N3 correction for IINU resulted in significant improvements in both CV and PIU (p=0.0115, p=0.0235). However, wide variations in overall image intensity persisted, requiring image normalization to improve consistency across vendors, field strengths, and RF coils. These results indicate that B1- correction routines alone may be insufficient in compensating for IINU and image scaling, warranting additional corrections prior to use of MR images in radiotherapy. Conclusions: MR image intensities and IINU vary as a function of scanner vendor, field strength, and

Evaluation of the Interplanetary Magnetic Field Strength Using the Cosmic-Ray Shadow of the Sun

NASA Astrophysics Data System (ADS)

Amenomori, M.; Bi, X. J.; Chen, D.; Chen, T. L.; Chen, W. Y.; Cui, S. W.; Danzengluobu, Ding, L. K.; Feng, C. F.; Feng, Zhaoyang; Feng, Z. Y.; Gou, Q. B.; Guo, Y. Q.; He, H. H.; He, Z. T.; Hibino, K.; Hotta, N.; Hu, Haibing; Hu, H. B.; Huang, J.; Jia, H. Y.; Jiang, L.; Kajino, F.; Kasahara, K.; Katayose, Y.; Kato, C.; Kawata, K.; Kozai, M.; Labaciren, Le, G. M.; Li, A. F.; Li, H. J.; Li, W. J.; Liu, C.; Liu, J. S.; Liu, M. Y.; Lu, H.; Meng, X. R.; Miyazaki, T.; Mizutani, K.; Munakata, K.; Nakajima, T.; Nakamura, Y.; Nanjo, H.; Nishizawa, M.; Niwa, T.; Ohnishi, M.; Ohta, I.; Ozawa, S.; Qian, X. L.; Qu, X. B.; Saito, T.; Saito, T. Y.; Sakata, M.; Sako, T. K.; Shao, J.; Shibata, M.; Shiomi, A.; Shirai, T.; Sugimoto, H.; Takita, M.; Tan, Y. H.; Tateyama, N.; Torii, S.; Tsuchiya, H.; Udo, S.; Wang, H.; Wu, H. R.; Xue, L.; Yamamoto, Y.; Yamauchi, K.; Yang, Z.; Yuan, A. F.; Yuda, T.; Zhai, L. M.; Zhang, H. M.; Zhang, J. L.; Zhang, X. Y.; Zhang, Y.; Zhang, Yi; Zhang, Ying; Zhaxisangzhu, Zhou, X. X.; Tibet AS γ Collaboration

2018-01-01

We analyze the Sun's shadow observed with the Tibet-III air shower array and find that the shadow's center deviates northward (southward) from the optical solar disk center in the "away" ("toward") interplanetary magnetic field (IMF) sector. By comparing with numerical simulations based on the solar magnetic field model, we find that the average IMF strength in the away (toward) sector is 1.54 ±0.21stat±0.20syst (1.62 ±0.15stat±0.22syst ) times larger than the model prediction. These demonstrate that the observed Sun's shadow is a useful tool for the quantitative evaluation of the average solar magnetic field.

Evaluation of the Interplanetary Magnetic Field Strength Using the Cosmic-Ray Shadow of the Sun.

PubMed

Amenomori, M; Bi, X J; Chen, D; Chen, T L; Chen, W Y; Cui, S W; Danzengluobu; Ding, L K; Feng, C F; Feng, Zhaoyang; Feng, Z Y; Gou, Q B; Guo, Y Q; He, H H; He, Z T; Hibino, K; Hotta, N; Hu, Haibing; Hu, H B; Huang, J; Jia, H Y; Jiang, L; Kajino, F; Kasahara, K; Katayose, Y; Kato, C; Kawata, K; Kozai, M; Labaciren; Le, G M; Li, A F; Li, H J; Li, W J; Liu, C; Liu, J S; Liu, M Y; Lu, H; Meng, X R; Miyazaki, T; Mizutani, K; Munakata, K; Nakajima, T; Nakamura, Y; Nanjo, H; Nishizawa, M; Niwa, T; Ohnishi, M; Ohta, I; Ozawa, S; Qian, X L; Qu, X B; Saito, T; Saito, T Y; Sakata, M; Sako, T K; Shao, J; Shibata, M; Shiomi, A; Shirai, T; Sugimoto, H; Takita, M; Tan, Y H; Tateyama, N; Torii, S; Tsuchiya, H; Udo, S; Wang, H; Wu, H R; Xue, L; Yamamoto, Y; Yamauchi, K; Yang, Z; Yuan, A F; Yuda, T; Zhai, L M; Zhang, H M; Zhang, J L; Zhang, X Y; Zhang, Y; Zhang, Yi; Zhang, Ying; Zhaxisangzhu; Zhou, X X

2018-01-19

We analyze the Sun's shadow observed with the Tibet-III air shower array and find that the shadow's center deviates northward (southward) from the optical solar disk center in the "away" ("toward") interplanetary magnetic field (IMF) sector. By comparing with numerical simulations based on the solar magnetic field model, we find that the average IMF strength in the away (toward) sector is 1.54±0.21_{stat}±0.20_{syst} (1.62±0.15_{stat}±0.22_{syst}) times larger than the model prediction. These demonstrate that the observed Sun's shadow is a useful tool for the quantitative evaluation of the average solar magnetic field.

Field Dependence/Independence Cognitive Style and Problem Posing: An Investigation with Sixth Grade Students

ERIC Educational Resources Information Center

Nicolaou, Aristoklis Andreas; Xistouri, Xenia

2011-01-01

Field dependence/independence cognitive style was found to relate to general academic achievement and specific areas of mathematics; in the majority of studies, field-independent students were found to be superior to field-dependent students. The present study investigated the relationship between field dependence/independence cognitive style and…

Synaptic Strength Is Bidirectionally Controlled by Opposing Activity-Dependent Regulation of Nedd4-1 and USP8

PubMed Central

Scudder, Samantha L.; Goo, Marisa S.; Cartier, Anna E.; Molteni, Alice; Schwarz, Lindsay A.; Wright, Rebecca

2014-01-01

The trafficking of AMPA receptors (AMPARs) to and from synapses is crucial for synaptic plasticity. Previous work has demonstrated that AMPARs undergo activity-dependent ubiquitination by the E3 ubiquitin ligase Nedd4-1, which promotes their internalization and degradation in lysosomes. Here, we define the molecular mechanisms involved in ubiquitination and deubiquitination of AMPARs. We report that Nedd4-1 is rapidly redistributed to dendritic spines in response to AMPAR activation and not in response to NMDA receptor (NMDAR) activation in cultured rat neurons. In contrast, NMDAR activation directly antagonizes Nedd4-1 function by promoting the deubiquitination of AMPARs. We show that NMDAR activation causes the rapid dephosphorylation and activation of the deubiquitinating enzyme (DUB) USP8. Surface AMPAR levels and synaptic strength are inversely regulated by Nedd4-1 and USP8. Strikingly, we show that homeostatic downscaling of synaptic strength is accompanied by an increase and decrease in Nedd4-1 and USP8 protein levels, respectively. Furthermore, we show that Nedd4-1 is required for homeostatic loss of surface AMPARs and downscaling of synaptic strength. This study provides the first mechanistic evidence for rapid and opposing activity-dependent control of a ubiquitin ligase and DUB at mammalian CNS synapses. We propose that the dynamic regulation of these opposing forces is critical in maintaining synapses and scaling them during homeostatic plasticity. PMID:25505317

Measuring Plasma Formation Field Strength and Current Loss in Pulsed Power Diodes

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

Johnston, Mark D.; Patel, Sonal G.; Falcon, Ross Edward

This LDRD investigated plasma formation, field strength, and current loss in pulsed power diodes. In particular the Self-Magnetic Pinch (SMP) e-beam diode was studied on the RITS-6 accelerator. Magnetic fields of a few Tesla and electric fields of several MV/cm were measured using visible spectroscopy techniques. The magnetic field measurements were then used to determine the current distribution in the diode. This distribution showed that significant beam current extends radially beyond the few millimeter x-ray focal spot diameter. Additionally, shielding of the magnetic field due to dense electrode surface plasmas was observed, quantified, and found to be consistent with themore » calculated Spitzer resistivity. In addition to the work on RITS, measurements were also made on the Z-machine looking to quantify plasmas within the power flow regions. Measurements were taken in the post-hole convolute and final feed gap regions on Z. Dopants were applied to power flow surfaces and measured spectroscopically. These measurements gave species and density/temperature estimates. Preliminary B-field measurements in the load region were attempted as well. Finally, simulation work using the EMPHASIS, electromagnetic particle in cell code, was conducted using the Z MITL conditions. The purpose of these simulations was to investigate several surface plasma generations models under Z conditions for comparison with experimental data.« less

Asymptotic expansion of pair production probability in a time-dependent electric field

NASA Astrophysics Data System (ADS)

Arai, Takashi

2015-12-01

We study particle creation in a single pulse of an electric field in scalar quantum electrodynamics. We investigate the parameter condition for the case where the dynamical pair creation and Schwinger mechanism respectively dominate. Then, an asymptotic expansion for the particle distribution in terms of the time interval of the applied electric field is derived. We compare our result with particle creation in a constant electric field with a finite-time interval. These results coincide in an extremely strong field, however they differ in general field strength. We interpret the reason of this difference as a nonperturbative effect of high-frequency photons in external electric fields. Moreover, we find that the next-to-leading-order term in our asymptotic expansion coincides with the derivative expansion of the effective action.

Wave function for time-dependent harmonically confined electrons in a time-dependent electric field.

PubMed

Li, Yu-Qi; Pan, Xiao-Yin; Sahni, Viraht

2013-09-21

The many-body wave function of a system of interacting particles confined by a time-dependent harmonic potential and perturbed by a time-dependent spatially homogeneous electric field is derived via the Feynman path-integral method. The wave function is comprised of a phase factor times the solution to the unperturbed time-dependent Schrödinger equation with the latter being translated by a time-dependent value that satisfies the classical driven equation of motion. The wave function reduces to that of the Harmonic Potential Theorem wave function for the case of the time-independent harmonic confining potential.

Oscillator strength and quantum-confined Stark effect of excitons in a thin PbS quantum disk

NASA Astrophysics Data System (ADS)

Oukerroum, A.; El-Yadri, M.; El Aouami, A.; Feddi, E.; Dujardin, F.; Duque, C. A.; Sadoqi, M.; Long, G.

2018-01-01

In this paper, we report a study of the effect of a lateral electric field on a quantum-confined exciton in a thin PbS quantum disk. Our approach was performed in the framework of the effective mass theory and adiabatic approximation. The ground state energy and the stark shift were determined by using a variational method with an adequate trial wavefunction, by investigating a 2D oscillator strength under simultaneous consideration of the geometrical confinement and the electric field strength. Our results showed a strong dependence of the exciton binding and the Stark shift on the disk dimensions in both axial and longitudinal directions. On the other hand, our results also showed that the Stark shift’s dependence on the electric field is not purely quadratic but the linear contribution is also important and cannot be neglected, especially when the confinement gets weaker.

FIELD DEPENDENCE OF THE SPIN REORIENTATION TEMPERATURE IN MICRO AND NANOCRYSTALLINE FORMS OF Nd{sub 2}Fe{sub 14}B.

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

LEWIS,L.H.; HARLAND,C.L.

2002-08-18

Insight into the anisotropy behavior of Nd{sub 2}Fe{sub 14}B may be obtained by measurements of the spin reorientation temperature T{sub S} where the overall magnetocrystalline anisotropy changes to allow the magnetic moment to relax from an easy axis to an easy cone configuration. DC magnetization measurements made at various applied fields on sintered and nanocrystalline forms of Nd{sub 2}Fe{sub 14}B indicate a T{sub S} that remains constant for the sintered sample but is strongly field-dependent for the nanocrystalline forms of the material. Specifically, T{sub S} decreases with decreasing applied fields of strengths 5 T, 1 T and 0.01 T. Amore » simple model that minimizes the total energy of the system leads to the conclusion that the spin reorientation temperature is insensitive to applied field. Therefore it is concluded that the apparent decrease in the system's spin reorientation temperatures with decrease in measuring field can be attributed to the nanoscale structure of the system and a difference in the anisotropy constants compared to their bulk values.« less

Discrepancies Between Theory and Experiment for Field-Dependence and f-wave Interactions in Superfluid ^3He-B

NASA Astrophysics Data System (ADS)

Collett, C. A.; Pollanen, J.; Li, Jia; Gannon, W. J.; Halperin, W. P.

2012-02-01

We have performed transverse acoustics experiments in superfluid ^3He-B, exploring the magnetic field splitting of the imaginary squashing mode (ISQ), a collective mode of the order parameter labelled by its total angular momentum J=2. We have compared theoretical calculationsootnotetextJ.A. Sauls and J.W. Serene, Phys. Rev. Lett. 49, 1183 (1982). of the Zeeman splitting, g2^-, and its dependence on the strength of f-wave pairing interactions, x3-1, with our recent experimental data, showing unexpected discrepancies. We suggest that the origin of these discrepancies can be traced to limits on the applicability of the theoretical calculations at high magnetic field and at frequencies some distance from the order parameter collective mode. We discuss the analysis done by Davis et al. in light of those limitations.ootnotetextJ.P. Davis et al., Phys. Rev. Lett. 100, 015301 (2008). This work was supported by the National Science Foundation DMR-1103625.

The Role of Sink Strength and Nitrogen Availability in the Down-Regulation of Photosynthetic Capacity in Field-Grown Nicotiana tabacum L. at Elevated CO2 Concentration.

PubMed

Ruiz-Vera, Ursula M; De Souza, Amanda P; Long, Stephen P; Ort, Donald R

2017-01-01

Down-regulation of photosynthesis is among the most common responses observed in C 3 plants grown under elevated atmospheric CO 2 concentration ([CO 2 ]). Down-regulation is often attributed to an insufficient capacity of sink organs to use or store the increased carbohydrate production that results from the stimulation of photosynthesis by elevated [CO 2 ]. Down-regulation can be accentuated by inadequate nitrogen (N) supply, which may limit sink development. While there is strong evidence for down-regulation of photosynthesis at elevated [CO 2 ] in enclosure studies most often involving potted plants, there is little evidence for this when [CO 2 ] is elevated fully under open-air field treatment conditions. To assess the importance of sink strength on the down-regulation of photosynthesis and on the potential of N to mitigate this down-regulation under agriculturally relevant field conditions, two tobacco cultivars ( Nicotiana tabacum L. cv. Petit Havana; cv. Mammoth) of strongly contrasting ability to produce the major sink of this crop, leaves, were grown under ambient and elevated [CO 2 ] and with two different N additions in a free air [CO 2 ] (FACE) facility. Photosynthetic down-regulation at elevated [CO 2 ] reached only 9% in cv. Mammoth late in the season likely reflecting sustained sink strength of the rapidly growing plant whereas down-regulation in cv. Petit Havana reached 25%. Increased N supply partially mitigated down-regulation of photosynthesis in cv. Petit Havana and this mitigation was dependent on plant developmental stage. Overall, these field results were consistent with the hypothesis that sustained sink strength, that is the ability to utilize photosynthate, and adequate N supply will allow C 3 crops in the field to maintain enhanced photosynthesis and therefore productivity as [CO 2 ] continues to rise.

The Electron Drift Technique for Measuring Electric and Magnetic Fields

NASA Technical Reports Server (NTRS)

Paschmann, G.; McIlwain, C. E.; Quinn, J. M.; Torbert, R. B.; Whipple, E. C.; Christensen, John (Technical Monitor)

1998-01-01

The electron drift technique is based on sensing the drift of a weak beam of test electrons that is caused by electric fields and/or gradients in the magnetic field. These quantities can, by use of different electron energies, in principle be determined separately. Depending on the ratio of drift speed to magnetic field strength, the drift velocity can be determined either from the two emission directions that cause the electrons to gyrate back to detectors placed some distance from the emitting guns, or from measurements of the time of flight of the electrons. As a by-product of the time-of-flight measurements, the magnetic field strength is also determined. The paper describes strengths and weaknesses of the method as well as technical constraints.

Effect of prior performance on subsequent performance evaluation by field independent-dependent raters.

PubMed

Sisco, Howard; Leventhal, Gloria

2007-12-01

The importance of accurate performance appraisals is central to many aspects of personnel activities in organizations. This study examined threats due to past performance to accuracy of evaluation of subsequent performance by raters differing in scores on field dependence. 162 college students were classified as Field-dependent (n = 81) or Field-independent (n = 81), using a median split on the Group Embedded Figures Test. Past performance (a lecture) was good or poor, presented directly via a videotape or indirectly via a written evaluation to the Field-independent or Field-dependent groups. Analysis indicated the hypothesized contrast effect (ratings in the opposite direction from that of prior ratings) in the Direct condition and an unexpected, albeit smaller, contrast effect in the Indirect condition. There were also differential effects of performance, presentation, and field dependency on rating of lecturer's style and ability.

Field of first magnetic flux entry and pinning strength of superconductors for rf application measured with muon spin rotation

DOE PAGES

Junginger, Tobias; Abidi, S. H.; Maffett, R. D.; ...

2018-03-16

Here, the performance of superconducting radiofrequency (SRF) cavities used for particle accelerators depends on two characteristic material parameters: field of first flux entry H entry and pinning strength. The former sets the limit for the maximum achievable accelerating gradient, while the latter determines how efficiently flux can be expelled related to the maximum achievable quality factor. In this paper, a method based on muon spin rotation (μSR) is developed to probe these parameters on samples. It combines measurements from two different spectrometers, one being specifically built for these studies and samples of different geometries. It is found that annealing atmore » 1400°C virtually eliminates all pinning. Such an annealed substrate is ideally suited to measure H entry of layered superconductors, which might enable accelerating gradients beyond bulk niobium technology.« less

Earth-strength magnetic field affects the rheotactic threshold of zebrafish swimming in shoals.

PubMed

Cresci, Alessandro; De Rosa, Rosario; Putman, Nathan F; Agnisola, Claudio

2017-02-01

Rheotaxis, the unconditioned orienting response to water currents, is a main component of fish behavior. Rheotaxis is achieved using multiple sensory systems, including visual and tactile cues. Rheotactic orientation in open or low-visibility waters might also benefit from the stable frame of reference provided by the geomagnetic field, but this possibility has not been explored before. Zebrafish (Danio rerio) form shoals living in freshwater systems with low visibility, show a robust positive rheotaxis, and respond to geomagnetic fields. Here, we investigated whether a static magnetic field in the Earth-strength range influenced the rheotactic threshold of zebrafish in a swimming tunnel. The direction of the horizontal component of the magnetic field relative to water flow influenced the rheotactic threshold of fish as part of a shoal, but not of fish tested alone. Results obtained after disabling the lateral line of shoaling individuals with Co 2+ suggest that this organ system is involved in the observed magneto-rheotactic response. These findings constitute preliminary evidence that magnetic fields influence rheotaxis and suggest new avenues for further research. Copyright © 2016 Elsevier Inc. All rights reserved.

Environment-dependent interfacial strength using first principles thermodynamics: The example of the Pt-HfO2 interface

NASA Astrophysics Data System (ADS)

Cardona Quintero, Y.; Ramanath, Ganpati; Ramprasad, R.

2013-10-01

A parameter-free, quantitative, first-principles methodology to determine the environment-dependent interfacial strength of metal-metal oxide interfaces is presented. This approach uses the notion of the weakest link to identify the most likely cleavage plane, and first principles thermodynamics to calculate the average work of separation as a function of the environment (in this case, temperature and oxygen pressure). The method is applied to the case of the Pt-HfO2 interface, and it is shown that the computed environment-dependent work of separation is in quantitative agreement with available experimental data.

Electromagnetic field strength prediction in an urban environment: A useful tool for the planning of LMSS

NASA Technical Reports Server (NTRS)

Vandooren, G. A. J.; Herben, M. H. A. J.; Brussaard, G.; Sforza, M.; Poiaresbaptista, J. P. V.

1993-01-01

A model for the prediction of the electromagnetic field strength in an urban environment is presented. The ray model, that is based on the Uniform Theory of Diffraction (UTD), includes effects of the non-perfect conductivity of the obstacles and their surface roughness. The urban environment is transformed into a list of standardized obstacles that have various shapes and material properties. The model is capable of accurately predicting the field strength in the urban environment by calculating different types of wave contributions such as reflected, edge and corner diffracted waves, and combinations thereof. Also, antenna weight functions are introduced to simulate the spatial filtering by the mobile antenna. Communication channel parameters such as signal fading, time delay profiles, Doppler shifts and delay-Doppler spectra can be derived from the ray-tracing procedure using post-processing routines. The model has been tested against results from scaled measurements at 50 GHz and proves to be accurate.

Zeeman splitting of 6.7 GHz methanol masers. On the uncertainty of magnetic field strength determinations

NASA Astrophysics Data System (ADS)

Vlemmings, W. H. T.; Torres, R. M.; Dodson, R.

2011-05-01

Context. To properly determine the role of magnetic fields during massive star formation, a statistically significant sample of field measurements probing different densities and regions around massive protostars needs to be established. However, relating Zeeman splitting measurements to magnetic field strengths needs a carefully determined splitting coefficient. Aims: Polarization observations of, in particular, the very abundant 6.7 GHz methanol maser, indicate that these masers appear to be good probes of the large scale magnetic field around massive protostars at number densities up to nH2 ≈ 109 cm-3. We thus investigate the Zeeman splitting of the 6.7 GHz methanol maser transition. Methods: We have observed of a sample of 46 bright northern hemisphere maser sources with the Effelsberg 100-m telescope and an additional 34 bright southern masers with the Parkes 64-m telescope in an attempt to measure their Zeeman splitting. We also revisit the previous calculation of the methanol Zeeman splitting coefficients and show that these were severely overestimated making the determination of magnetic field strengths highly uncertain. Results: In total 44 of the northern masers were detected and significant splitting between the right- and left-circular polarization spectra is determined in >75% of the sources with a flux density >20 Jy beam-1. Assuming the splitting is due to a magnetic field according to the regular Zeeman effect, the average detected Zeeman splitting corrected for field geometry is ~0.6 m s-1. Using an estimate of the 6.7 GHz A-type methanol maser Zeeman splitting coefficient based on old laboratory measurements of 25 GHz E-type methanol transitions this corresponds to a magnetic field of ~120 mG in the methanol maser region. This is significantly higher than expected using the typically assumed relation between magnetic field and density (B∝ n_H_20.47) and potentially indicates the extrapolation of the available laboratory measurements is invalid

The Response to and Recovery From Maximum-Strength and -Power Training in Elite Track and Field Athletes.

PubMed

Howatson, Glyn; Brandon, Raphael; Hunter, Angus M

2016-04-01

There is a great deal of research on the responses to resistance training; however, information on the responses to strength and power training conducted by elite strength and power athletes is sparse. To establish the acute and 24-h neuromuscular and kinematic responses to Olympic-style barbell strength and power exercise in elite athletes. Ten elite track and field athletes completed a series of 3 back-squat exercises each consisting of 4 × 5 repetitions. These were done as either strength or power sessions on separate days. Surface electromyography (sEMG), bar velocity, and knee angle were monitored throughout these exercises and maximal voluntary contraction (MVC), jump height, central activation ratio (CAR), and lactate were measured pre, post, and 24 h thereafter. Repetition duration, impulse, and total work were greater (P < .01) during strength sessions, with mean power being greater (P < .01) after the power sessions. Lactate increased (P < .01) after strength but not power sessions. sEMG increased (P < .01) across sets for both sessions, with the strength session increasing at a faster rate (P < .01) and with greater activation (P < .01) by the end of the final set. MVC declined (P < .01) after the strength and not the power session, which remained suppressed (P < .05) 24 h later, whereas CAR and jump height remained unchanged. A greater neuromuscular and metabolic demand after the strength and not power session is evident in elite athletes, which impaired maximal-force production for up to 24 h. This is an important consideration for planning concurrent athlete training.

Long-term Trends in Interplanetary Magnetic Field Strength and Solar Wind Structure during the 20th Century

NASA Technical Reports Server (NTRS)

Richardson, I. G.; Cliver, E. W.; Cane, H. V.; White, Nicholas E. (Technical Monitor)

2002-01-01

Lockwood et al have recently reported an approximately 40% increase in the radial component of the interplanetary magnetic field (IMF) at Earth between 1964 and 1996. We argue that this increase does not constitute a secular trend but is largely the consequence of lower than average fields during solar cycle 20 (1964-1976) in comparison with surrounding cycles. For times after 1976 the average IMF strength has actually decreased slightly. Examination of the cosmic ray intensity, an indirect measure of the IMF strength, over the last five solar cycles (19-23) also indicates that cycle averages of the IMF strength have been relatively constant since approximately 1954. We also consider the origin of the well-documented increase in the geomagnetic alphaalpha index that occurred primarily during the first half of the twentieth century. We surmise that the coronal mass ejection (CME) rate for recent solar cycles was approximately twice as high as that for solar cycles 100 years ago. However, this change in the CME rate and the accompanying increase in 27-day recurrent storm activity reported by others are unable to account completely for the increase in alphaalpha. Rather, the CMEs and recurrent high-speed streams at the beginning of the twentieth century must have been embedded in a background of slow solar wind that was less geoeffective (having, for example, lower IMF strength and/or flow speed) than its modern counterpart.

The electric field distribution in the brain during TTFields therapy and its dependence on tissue dielectric properties and anatomy: a computational study

NASA Astrophysics Data System (ADS)

Wenger, Cornelia; Salvador, Ricardo; Basser, Peter J.; Miranda, Pedro C.

2015-09-01

Tumor treating fields (TTFields) are a non-invasive, anti-mitotic and approved treatment for recurrent glioblastoma multiforme (GBM) patients. In vitro studies have shown that inhibition of cell division in glioma is achieved when the applied alternating electric field has a frequency in the range of 200 kHz and an amplitude of 1-3 V cm-1. Our aim is to calculate the electric field distribution in the brain during TTFields therapy and to investigate the dependence of these predictions on the heterogeneous, anisotropic dielectric properties used in the computational model. A realistic head model was developed by segmenting MR images and by incorporating anisotropic conductivity values for the brain tissues. The finite element method (FEM) was used to solve for the electric potential within a volume mesh that consisted of the head tissues, a virtual lesion with an active tumour shell surrounding a necrotic core, and the transducer arrays. The induced electric field distribution is highly non-uniform. Average field strength values are slightly higher in the tumour when incorporating anisotropy, by about 10% or less. A sensitivity analysis with respect to the conductivity and permittivity of head tissues shows a variation in field strength of less than 42% in brain parenchyma and in the tumour, for values within the ranges reported in the literature. Comparing results to a previously developed head model suggests significant inter-subject variability. This modelling study predicts that during treatment with TTFields the electric field in the tumour exceeds 1 V cm-1, independent of modelling assumptions. In the future, computational models may be useful to optimize delivery of TTFields.

The electric field distribution in the brain during TTFields therapy and its dependence on tissue dielectric properties and anatomy: a computational study.

PubMed

Wenger, Cornelia; Salvador, Ricardo; Basser, Peter J; Miranda, Pedro C

2015-09-21

Tumor treating fields (TTFields) are a non-invasive, anti-mitotic and approved treatment for recurrent glioblastoma multiforme (GBM) patients. In vitro studies have shown that inhibition of cell division in glioma is achieved when the applied alternating electric field has a frequency in the range of 200 kHz and an amplitude of 1-3 V cm(-1). Our aim is to calculate the electric field distribution in the brain during TTFields therapy and to investigate the dependence of these predictions on the heterogeneous, anisotropic dielectric properties used in the computational model. A realistic head model was developed by segmenting MR images and by incorporating anisotropic conductivity values for the brain tissues. The finite element method (FEM) was used to solve for the electric potential within a volume mesh that consisted of the head tissues, a virtual lesion with an active tumour shell surrounding a necrotic core, and the transducer arrays. The induced electric field distribution is highly non-uniform. Average field strength values are slightly higher in the tumour when incorporating anisotropy, by about 10% or less. A sensitivity analysis with respect to the conductivity and permittivity of head tissues shows a variation in field strength of less than 42% in brain parenchyma and in the tumour, for values within the ranges reported in the literature. Comparing results to a previously developed head model suggests significant inter-subject variability. This modelling study predicts that during treatment with TTFields the electric field in the tumour exceeds 1 V cm(-1), independent of modelling assumptions. In the future, computational models may be useful to optimize delivery of TTFields.

The electric field distribution in the brain during TTFields therapy and its dependence on tissue dielectric properties and anatomy: a computational study

PubMed Central

Wenger, Cornelia; Salvador, Ricardo; Basser, Peter J; Miranda, Pedro C

2015-01-01

Tumor Treating Fields (TTFields) are a non-invasive, anti-mitotic and approved treatment for recurrent glioblastoma multiforme (GBM) patients. In vitro studies have shown that inhibition of cell division in glioma is achieved when the applied alternating electric field has a frequency in the range of 200 kHz and an amplitude of 1 - 3 V/cm. Our aim is to calculate the electric field distribution in the brain during TTFields therapy and to investigate the dependence of these predictions on the heterogeneous, anisotropic dielectric properties used in the computational model. A realistic head model was developed by segmenting MR images and by incorporating anisotropic conductivity values for the brain tissues. The finite element method (FEM) was used to solve for the electric potential within a volume mesh that consisted of the head tissues, a virtual lesion with an active tumour shell surrounding a necrotic core, and the transducer arrays. The induced electric field distribution is highly non-uniform. Average field strength values are slightly higher in the tumour when incorporating anisotropy, by about 10% or less. A sensitivity analysis with respect to the conductivity and permittivity of head tissues shows a variation in field strength of less than 42% in brain parenchyma and in the tumour, for values within the ranges reported in the literature. Comparing results to a previously developed head model suggests significant inter-subject variability. This modelling study predicts that during treatment with TTFields the electric field in the tumour exceeds 1 V/cm, independent of modelling assumptions. In the future, computational models may be useful to optimize delivery of TTFields. PMID:26350296

Field quantization and squeezed states generation in resonators with time-dependent parameters

NASA Technical Reports Server (NTRS)

Dodonov, V. V.; Klimov, A. B.; Nikonov, D. E.

1992-01-01

The problem of electromagnetic field quantization is usually considered in textbooks under the assumption that the field occupies some empty box. The case when a nonuniform time-dependent dielectric medium is confined in some space region with time-dependent boundaries is studied. The basis of the subsequent consideration is the system of Maxwell's equations in linear passive time-dependent dielectric and magnetic medium without sources.

Dependence of optical phase modulation on anchoring strength of dielectric shield wall surfaces in small liquid crystal pixels

NASA Astrophysics Data System (ADS)

Isomae, Yoshitomo; Shibata, Yosei; Ishinabe, Takahiro; Fujikake, Hideo

2018-03-01

We demonstrated that the uniform phase modulation in a pixel can be realized by optimizing the anchoring strength on the walls and the wall width in the dielectric shield wall structure, which is the needed pixel structure for realizing a 1-µm-pitch optical phase modulator. The anchoring force degrades the uniformity of the phase modulation in ON-state pixels, but it also keeps liquid crystals from rotating against the leakage of an electric field. We clarified that the optimal wall width and anchoring strength are 250 nm and less than 10-4 J/m2, respectively.

Measuring magnetic field vector by stimulated Raman transitions

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

Wang, Wenli; Wei, Rong, E-mail: weirong@siom.ac.cn; Lin, Jinda

2016-03-21

We present a method for measuring the magnetic field vector in an atomic fountain by probing the line strength of stimulated Raman transitions. The relative line strength for a Λ-type level system with an existing magnetic field is theoretically analyzed. The magnetic field vector measured by our proposed method is consistent well with that by the traditional bias magnetic field method with an axial resolution of 6.1 mrad and a radial resolution of 0.16 rad. Dependences of the Raman transitions on laser polarization schemes are also analyzed. Our method offers the potential advantages for magnetic field measurement without requiring additional bias fields,more » beyond the limitation of magnetic field intensity, and extending the spatial measurement range. The proposed method can be widely used for measuring magnetic field vector in other precision measurement fields.« less

MR imaging detection of cerebral microbleeds: effect of susceptibility-weighted imaging, section thickness, and field strength.

PubMed

Nandigam, R N K; Viswanathan, A; Delgado, P; Skehan, M E; Smith, E E; Rosand, J; Greenberg, S M; Dickerson, B C

2009-02-01

The emergence of cerebral microbleeds (CMB) as common MR imaging findings raises the question of how MR imaging parameters influence CMB detection. To evaluate the effects of modified gradient recalled-echo (GRE) MR imaging methods, we performed an analysis of sequence, section thickness, and field strength on CMB imaging properties and detection in subjects with cerebral amyloid angiopathy (CAA), a condition associated with microhemorrhage. Multiple MR images were obtained from subjects with probable CAA, with varying sequences (GRE versus susceptibility-weighted imaging [SWI]), section thicknesses (1.2-1.5 versus 5 mm), and magnetic field strengths (1.5T versus 3T). Individual CMB were manually identified and analyzed for contrast index (lesion intensity normalized to normal-appearing white matter signal intensity) and diameter. CMB counts were compared between 1.5T thick-section GRE and thin-section SWI for 3 subjects who underwent both protocols in the same scanning session. With other parameters constant, use of SWI, thinner sections, and a higher field strength yielded medium-to-large gains in CMB contrast index (CI; Cohen d 0.71-1.87). SWI was also associated with small increases in CMB diameter (Cohen d <0.3). Conventional thick-section GRE identified only 33% of CMB (103 of 310) seen on thin-section SWI. Lesions prospectively identified on GRE had significantly greater CI and diameter measured on the GRE image than those not prospectively identified. The examined alternatives to conventional GRE MR imaging yield substantially improved CMB contrast and sensitivity for detection. Future studies based on these techniques will most likely yield even higher prevalence estimates for CMB.

MR Imaging Detection of Cerebral Microbleeds: Effect of Susceptibility-Weighted Imaging, Section Thickness, and Field Strength

PubMed Central

Nandigam, R.N.K.; Viswanathan, A.; Delgado, P.; Skehan, M.E.; Smith, E.E.; Rosand, J.; Greenberg, S.M.; Dickerson, B.C.

2009-01-01

BACKGROUND AND PURPOSE: The emergence of cerebral microbleeds (CMB) as common MR imaging findings raises the question of how MR imaging parameters influence CMB detection. To evaluate the effects of modified gradient recalled-echo (GRE) MR imaging methods, we performed an analysis of sequence, section thickness, and field strength on CMB imaging properties and detection in subjects with cerebral amyloid angiopathy (CAA), a condition associated with microhemorrhage. MATERIALS AND METHODS: Multiple MR images were obtained from subjects with probable CAA, with varying sequences (GRE versus susceptibility-weighted imaging [SWI]), section thicknesses (1.2–1.5 versus 5 mm), and magnetic field strengths (1.5T versus 3T). Individual CMB were manually identified and analyzed for contrast index (lesion intensity normalized to normal-appearing white matter signal intensity) and diameter. CMB counts were compared between 1.5T thick-section GRE and thin-section SWI for 3 subjects who underwent both protocols in the same scanning session. RESULTS: With other parameters constant, use of SWI, thinner sections, and a higher field strength yielded medium-to-large gains in CMB contrast index (CI; Cohen d 0.71–1.87). SWI was also associated with small increases in CMB diameter (Cohen d <0.3). Conventional thick-section GRE identified only 33% of CMB (103 of 310) seen on thin-section SWI. Lesions prospectively identified on GRE had significantly greater CI and diameter measured on the GRE image than those not prospectively identified. CONCLUSIONS: The examined alternatives to conventional GRE MR imaging yield substantially improved CMB contrast and sensitivity for detection. Future studies based on these techniques will most likely yield even higher prevalence estimates for CMB. PMID:19001544

Cryptochrome Mediates Light-Dependent Magnetosensitivity of Drosophila's Circadian Clock

PubMed Central

Yoshii, Taishi; Ahmad, Margaret; Helfrich-Förster, Charlotte

2009-01-01

Since 1960, magnetic fields have been discussed as Zeitgebers for circadian clocks, but the mechanism by which clocks perceive and process magnetic information has remained unknown. Recently, the radical-pair model involving light-activated photoreceptors as magnetic field sensors has gained considerable support, and the blue-light photoreceptor cryptochrome (CRY) has been proposed as a suitable molecule to mediate such magnetosensitivity. Since CRY is expressed in the circadian clock neurons and acts as a critical photoreceptor of Drosophila's clock, we aimed to test the role of CRY in magnetosensitivity of the circadian clock. In response to light, CRY causes slowing of the clock, ultimately leading to arrhythmic behavior. We expected that in the presence of applied magnetic fields, the impact of CRY on clock rhythmicity should be altered. Furthermore, according to the radical-pair hypothesis this response should be dependent on wavelength and on the field strength applied. We tested the effect of applied static magnetic fields on the circadian clock and found that flies exposed to these fields indeed showed enhanced slowing of clock rhythms. This effect was maximal at 300 μT, and reduced at both higher and lower field strengths. Clock response to magnetic fields was present in blue light, but absent under red-light illumination, which does not activate CRY. Furthermore, cryb and cryOUT mutants did not show any response, and flies overexpressing CRY in the clock neurons exhibited an enhanced response to the field. We conclude that Drosophila's circadian clock is sensitive to magnetic fields and that this sensitivity depends on light activation of CRY and on the applied field strength, consistent with the radical pair mechanism. CRY is widespread throughout biological systems and has been suggested as receptor for magnetic compass orientation in migratory birds. The present data establish the circadian clock of Drosophila as a model system for CRY-dependent

Magnetic field induced dynamical chaos.

PubMed

Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra

2013-12-01

In this article, we have studied the dynamics of a particle having charge in the presence of a magnetic field. The motion of the particle is confined in the x-y plane under a two dimensional nonlinear potential. We have shown that constant magnetic field induced dynamical chaos is possible even for a force which is derived from a simple potential. For a given strength of the magnetic field, initial position, and velocity of the particle, the dynamics may be regular, but it may become chaotic when the field is time dependent. Chaotic dynamics is very often if the field is time dependent. Origin of chaos has been explored using the Hamiltonian function of the dynamics in terms of action and angle variables. Applicability of the present study has been discussed with a few examples.

Physiological Effects of Strength Training and Various Strength Training Devices.

ERIC Educational Resources Information Center

Wilmore, Jack H.

Current knowledge in the area of muscle physiology is a basis for a discussion on strength training programs. It is now recognized that the expression of strength is related to, but not dependent upon, the size of the muscle and is probably more related to the ability to recruit more muscle fibers in the contraction, or to better synchronize their…

The Strength and Radial Profile of the Coronal Magnetic Field from the Standoff Distance of a Coronal Mass Ejection-Driven Shock

NASA Technical Reports Server (NTRS)

Gopalswamy, Nat; Yashiro, Seiji

2011-01-01

We determine the coronal magnetic field strength in the heliocentric distance range 6-23 solar radii (Rs) by measuring the shock standoff distance and the radius of curvature of the flux rope during the 2008 March 25 coronal mass ejection imaged by white-light coronagraphs. Assuming the adiabatic index, we determine the Alfven Mach number, and hence the Alfven speed in the ambient medium using the measured shock speed. By measuring the upstream plasma density using polarization brightness images, we finally get the magnetic field strength upstream of the shock. The estimated magnetic field decreases from approximately 48 mG around 6 Rs to 8 mG at 23 Rs. The radial profile of the magnetic field can be described by a power law in agreement with other estimates at similar heliocentric distances.

An Evaluation of a Numerical Prediction Method for Electric Field Strength of Low Frequency Radio Waves based on Wave-Hop Ionospheric Propagation

NASA Astrophysics Data System (ADS)

Kitauchi, H.; Nozaki, K.; Ito, H.; Kondo, T.; Tsuchiya, S.; Imamura, K.; Nagatsuma, T.; Ishii, M.

2014-12-01

We present our recent efforts on an evaluation of the numerical prediction method of electric field strength for ionospheric propagation of low frequency (LF) radio waves based on a wave-hop propagation theory described in Section 2.4 of Recommendation ITU-R P.684-6 (2012), "Prediction of field strength at frequencies below about 150 kHz," made by International Telecommunication Union Radiocommunication Sector (ITU-R). As part of the Japanese Antarctic Research Expedition (JARE), we conduct on-board measurements of the electric field strengths and phases of LF 40 kHz and 60 kHz of radio signals (call sign JJY) continuously along both the ways between Tokyo, Japan and Syowa Station, the Japanese Antarctic station, at 69° 00' S, 39° 35' E on East Ongul Island, Lützow-Holm Bay, East Antarctica. The measurements are made by a newly developed, highly sensitive receiving system installed on board the Japanese Antarctic research vessel (RV) Shirase. We obtained new data sets of the electric field strength up to approximately 13,000-14,000 km propagation of LF JJY 40 kHz and 60 kHz radio waves by utilizing a newly developed, highly sensitive receiving system, comprised of an orthogonally crossed double-loop antenna and digital-signal-processing lock-in amplifiers, on board RV Shirase during the 55th JARE from November 2013 to April 2014. We have made comparisons between those on-board measurements and the numerical predictions of field strength for long-range propagation of low frequency radio waves based on a wave-hop propagation theory described in Section 2.4 of Recommendation ITU-R P.684-6 (2012) to show that our results qualitatively support the recommended wave-hop theory for the great-circle paths approximately 7,000-8,000 km and 13,000-14,000 km propagations.

Oscillator strengths of the optical transitions in a semiconductor superlattice under an electric field

NASA Astrophysics Data System (ADS)

Tronc, P.

1992-04-01

The oscillator strengths of the optical transitions in a semiconductor superlattice under an electric field parallel to the growth axis can be calculated using a perturbative model with Bloch envelope functions. The applied electric field and the electron-hole interaction inducing formation of indirect excitons both induce strength asymmetry between the oblique +p and -p transitions of the Wannier-Stark ladder. Features of the photocurrent spectra recorded at low temperature can be accounted for by the present model in a very simple manner. Les forces d'oscillateur des transitions optiques dans un superréseau semiconducteur soumis à un champ électrique parallèle à la direction de croissance, peuvent être calculées à l'aide d'un modèle de perturbation avec des fonctions enveloppes de Bloch. Le champ électrique appliqué ainsi que l'interaction électron-trou, qui induit la formation d'excitons indirects, entraînent une asymétrie entre les forces d'oscillateur des transitions +p et -p dans l'échelle de Wannier-Stark. Certaines caractéristiques des spectres de photocourant enregistrés à basse température peuvent être prévues d'une manière très simple.

Using Educational Data Mining Methods to Assess Field-Dependent and Field-Independent Learners' Complex Problem Solving

ERIC Educational Resources Information Center

Angeli, Charoula; Valanides, Nicos

2013-01-01

The present study investigated the problem-solving performance of 101 university students and their interactions with a computer modeling tool in order to solve a complex problem. Based on their performance on the hidden figures test, students were assigned to three groups of field-dependent (FD), field-mixed (FM), and field-independent (FI)…

Comparison of electric field strength and spatial distribution of electroconvulsive therapy and magnetic seizure therapy in a realistic human head model

PubMed Central

Lee, Won Hee; Lisanby, Sarah H.; Laine, Andrew F.; Peterchev, Angel V.

2017-01-01

Background This study examines the strength and spatial distribution of the electric field induced in the brain by electroconvulsive therapy (ECT) and magnetic seizure therapy (MST). Methods The electric field induced by standard (bilateral, right unilateral, and bifrontal) and experimental (focal electrically administered seizure therapy and frontomedial) ECT electrode configurations as well as a circular MST coil configuration was simulated in an anatomically realistic finite element model of the human head. Maps of the electric field strength relative to an estimated neural activation threshold were used to evaluate the stimulation strength and focality in specific brain regions of interest for these ECT and MST paradigms and various stimulus current amplitudes. Results The standard ECT configurations and current amplitude of 800–900 mA produced the strongest overall stimulation with median of 1.8–2.9 times neural activation threshold and more than 94% of the brain volume stimulated at suprathreshold level. All standard ECT electrode placements exposed the hippocampi to suprathreshold electric field, although there were differences across modalities with bilateral and right unilateral producing respectively the strongest and weakest hippocampal stimulation. MST stimulation is up to 9 times weaker compared to conventional ECT, resulting in direct activation of only 21% of the brain. Reducing the stimulus current amplitude can make ECT as focal as MST. Conclusions The relative differences in electric field strength may be a contributing factor for the cognitive sparing observed with right unilateral compared to bilateral ECT, and MST compared to right unilateral ECT. These simulations could help understand the mechanisms of seizure therapies and develop interventions with superior risk/benefit ratio. PMID:27318858

Last three millennia Earth's Magnetic field strength in Mesoamerica and southern United States: Implications in geomagnetism and archaeology

NASA Astrophysics Data System (ADS)

Goguitchaichvili, Avto; Ruiz, Rafael García; Pavón-Carrasco, F. Javier; Contreras, Juan Julio Morales; Arechalde, Ana María Soler; Urrutia-Fucugauchi, Jaime

2018-06-01

Earth's Magnetic Field variation strength may provide crucial information to understand the geodynamo mechanism and elucidate the conditions on the physics of the Earth's deep interiors. Aimed to reveal the fine characteristics of the geomagnetic field during the last three millennia in Mesoamerica, we analyzed the available absolute geomagnetic intensities associated to absolute radiometric dating as well some ages provided by historical documents. This analysis is achieved using thermoremanent magnetization carried by volcanic lava flows and burned archaeological artefacts. A total of 106 selected intensities from Mesoamerica and other 100 from the southern part of the United States represent the main core of the dataset to construct the variation curve using both combined bootstrap method and temporal penalized B-spline methods. The obtained intensity paleosecular variation curve for Mesoamerica generally disagrees with the values predicted by the global geomagnetic field models. There is rather firm evidence of eastward drift when compared to similar reference curves in Western Europe, Asia and Pacific Ocean. The recent hypothesis about the relationship between the geomagnetic field strength and paleoclimate is also critically analyzed in the light of this new data compilation.

ATPase activity and light scattering of acto-heavy meromyosin: dependence on ATP concentration and on ionic strength.

PubMed

Dancker, P

1975-01-01

1. The dependence on ATP concentration of ATPase activity and light scattering decrease of acto-HMM could be described at very low ionic strength by one hyperbolic adsorption isotherm with a dissociation constant of 3 X 10(-6)M. Hence the increase of ATP ase activity was paralleled by a decrease in light scattering. At higher values of ionic strength ATPase activity stopped rising before HMM was completely saturated with ATP. Higher ionic strength prevented ATPase activity from further increasing when the rigor links (links between actin and nucleotide-free myosin), which have formerly protected the ATPase against the suppressing action of higher ionic strength have fallen below a certain amount. This protecting influence of rigor links did not require tropomyosin-troponin. 2. For complete activation of ATPase activity by actin less actin was needed when HMM was incompletely saturated with ATP than when it was completely saturated with ATP. 3. The apparent affinity of ATP to regulated acto-HMM (which contained tropomyosin-troponin) was lower than to unregulated acto-HMM (which was devoid of tropomyosin-troponin). In the presence of rigor complexes (indicated by an incomplete decrease of light scattering) the ATPase activity of regulated acto-HMM was higher than that of unregulated acto-HMM. At increasing ATP concentrations the ATPase activity of regulated acto-HMM stopped rising at a similar degree of saturation with ATP as the ATPase activity of unregulated acto-HMM at the same ionic strength.

Temperature dependence of lower critical field of YBCO superconductor

NASA Astrophysics Data System (ADS)

Rani, Poonam; Hafiz, A. K.; Awana, V. P. S.

2018-05-01

We report the detailed study of the temperature dependence of the lower critical field (Hc1) of the YBa2Cu3O7 superconductor by magnetization measurements. The curve shows the multiband gap behavior of the sample. It is found that the sample is not a single BCS type superconductor. Hc1 is measured as the point at which the curve deviates from a Meissner-like linear M(H) curve to a nonlinear path. The Hc1 for YBCO at different temperatures from 10K to 85K has been determined by magnetization measurements M(H) with applied field parallel to the c-axis. The sample phase purity has been confirmed by Rietveld fitted X-ray diffraction data. The amplitude (1-17Oe) dependent AC susceptibility confirms the granular nature of superconducting compound. Using Bean model we calculated the temperature dependency of inter-grain critical current density and Jc(0) is found as 699.14kAcm-2.

Concrete probe-strength study : final report.

DOT National Transportation Integrated Search

1969-12-01

The Windsor probe - test system was evaluated for determining compressive strength of concrete by comparing probe strengths against cylinder and core strengths from both laboratory and field-poured concrete. Advantages and disadvantages of this syste...

Scaling submillimeter single-cycle transients toward megavolts per centimeter field strength via optical rectification in the organic crystal OH1.

PubMed

Ruchert, Clemens; Vicario, Carlo; Hauri, Christoph P

2012-03-01

We present the generation of high-power single-cycle terahertz (THz) pulses in the organic salt crystal 2-[3-(4-hydroxystyryl)-5.5-dimethylcyclohex-2-enylidene]malononitrile or OH1. Broadband THz radiation with a central frequency of 1.5 THz (λ(c)=200 μm) and high electric field strength of 440 kV/cm is produced by optical rectification driven by the signal of a powerful femtosecond optical parametric amplifier. A 1.5% pump to THz energy conversion efficiency is reported, and pulse energy stability better than 1% RMS is achieved. An approach toward the realization of higher field strength is discussed. © 2012 Optical Society of America

A generic signature of a fluctuating magnetic field: An additional turnover prior to the Kramers' one

NASA Astrophysics Data System (ADS)

Mondal, Shrabani; Baura, Alendu; Das, Sudip; Bag, Bidhan Chandra

2018-07-01

In this paper we have presented the dynamics of a Brownian particle which is coupled to a thermal bath in the presence of a fluctuating magnetic field (FMF). By virtue of the FMF the Brownian particle experiences a time dependent damping strength for the x -direction motion even in the presence of a stationary Markovian thermal bath. There is a transition state along this direction. The time dependent damping strength leads to appear a bi-turnover phenomenon in the variation of the barrier crossing rate as a function of the thermal bath induced damping strength. It is a generic signature of the fluctuating magnetic field.

Investigation of the temperature dependent field emission from individual ZnO nanowires for evidence of field-induced hot electrons emission.

PubMed

Chen, Yicong; Zhang, Zhipeng; Li, Zhi-Bing; She, Juncong; Deng, Shaozhi; Xu, Ning-Sheng; Chen, Jun

2018-06-27

ZnO nanowires as field emitters have important applications in flat panel display and X-ray source. Understanding the intrinsic field emission mechanism is crucial for further improving the performance of ZnO nanowire field emitters. In this article, the temperature dependent field emission from individual ZnO nanowires was investigated by an in-situ measurement in ultra-high vacuum. The divergent temperature-dependent Fowler-Nordheim plots is found in the low field region. A field-induced hot electrons emission model that takes into account penetration length is proposed to explain the results. The carrier density and temperature dependence of the field-induced hot electrons emission current are derived theoretically. The obtained results are consistent with the experimental results, which could be attributed to the variation of effective electron temperature. All of these are important for a better understanding on the field emission process of semiconductor nanostructures. © 2018 IOP Publishing Ltd.

National surveys of radiofrequency field strengths from radio base stations in Africa

PubMed Central

Joyner, Ken H.; Van Wyk, Marthinus J.; Rowley, Jack T.

2014-01-01

The authors analysed almost 260 000 measurement points from surveys of radiofrequency (RF) field strengths near radio base stations in seven African countries over two time frames from 2001 to 2003 and 2006 to 2012. The results of the national surveys were compared, chronological trends investigated and potential exposures compared by technology and with frequency modulation (FM) radio. The key findings from thes data are that irrespective of country, the year and mobile technology, RF fields at a ground level were only a small fraction of the international human RF exposure recommendations. Importantly, there has been no significant increase in typical measured levels since the introduction of 3G services. The mean levels in these African countries are similar to the reported levels for countries of Asia, Europe and North America using similar mobile technologies. The median level for the FM services in South Africa was comparable to the individual but generally lower than the combined mobile services. PMID:24044904

Two-dimensional Fermi gas in spin-dependent magnetic fields

NASA Astrophysics Data System (ADS)

Anzai, Takaaki; Nishida, Yusuke

Experimental techniques in ultracold atoms allow us to tune parameters of the system at will. In particular, synthetic magnetic fields have been created by using the atom-light coupling and, therefore, it is interesting to study what kinds of quantum phenomena appear in correlated ultracold atoms subjected to synthetic magnetic fields. In this work, we consider a two-dimensional Fermi gas with two spin states in spin-dependent magnetic fields which are assumed to be antiparallel for different spin states. By studying the ground-state phase diagram within the mean-field approximation, we find quantum spin Hall and superfluid phases separated by a second-order phase transition. We also show that there are regions where the superfluid gap parameter is proportional to the attractive coupling, which is in marked contrast to the usual exponential dependence. Moreover, we elucidate that the universality class of the phase transition belongs to that of the XY model at special points of the phase boundary, while it belongs to that of a dilute Bose gas anywhere else. International Research Center for Nanoscience and Quantum Physics, Tokyo Institute of Technology.

Baseline-dependent sampling and windowing for radio interferometry: data compression, field-of-interest shaping, and outer field suppression

NASA Astrophysics Data System (ADS)

Atemkeng, M.; Smirnov, O.; Tasse, C.; Foster, G.; Keimpema, A.; Paragi, Z.; Jonas, J.

2018-07-01

Traditional radio interferometric correlators produce regular-gridded samples of the true uv-distribution by averaging the signal over constant, discrete time-frequency intervals. This regular sampling and averaging then translate to be irregular-gridded samples in the uv-space, and results in a baseline-length-dependent loss of amplitude and phase coherence, which is dependent on the distance from the image phase centre. The effect is often referred to as `decorrelation' in the uv-space, which is equivalent in the source domain to `smearing'. This work discusses and implements a regular-gridded sampling scheme in the uv-space (baseline-dependent sampling) and windowing that allow for data compression, field-of-interest shaping, and source suppression. The baseline-dependent sampling requires irregular-gridded sampling in the time-frequency space, i.e. the time-frequency interval becomes baseline dependent. Analytic models and simulations are used to show that decorrelation remains constant across all the baselines when applying baseline-dependent sampling and windowing. Simulations using MeerKAT telescope and the European Very Long Baseline Interferometry Network show that both data compression, field-of-interest shaping, and outer field-of-interest suppression are achieved.

Renormalization of optical transition strengths in semiconductor nanoparticles due to band mixing

DOE PAGES

Velizhanin, Kirill A.

2016-05-25

We report that unique optical properties of semiconductor nanoparticles (SN) make them very promising in the multitude of applications including lasing, light emission and photovoltaics. In many of these applications it is imperative to understand the physics of interaction of electrons in a SN with external electromagnetic fields on the quantitative level. In particular, the strength of electron–photon coupling determines such important SN parameters as the radiative lifetime and absorption cross section. This strength is often assumed to be fully encoded by the so called Kane momentum matrix element. This parameter, however, pertains to a bulk semiconductor material and, asmore » such, is not sensitive to the quantum confinement effects in SNs. In this work we demonstrate that the quantum confinement, via the so called band mixing, can result in a significant suppression of the strength of electron interaction with electromagnetic field. Within the envelope function formalism we show how this suppression can be described by introducing an effective energy-dependent Kane momentum. Then, the effect of band mixing on the efficiencies of various photoinduced processes can be fully captured by the conventional formulae (e.g., spontaneous emission rate), once the conventional Kane momentum is substituted with the renormalized energy-dependent Kane momentum introduced in here. Lastly, as an example, we evaluate the energy-dependent Kane momentum for spherical PbSe and PbS SNs (i.e., quantum dots) and show that neglecting band mixing in these systems can result in the overestimation of absorption cross sections and emission rates by a factor of ~2.« less

Exchange field and Hc dependence on the ferromagnetic material in exchange couples with CoO (abstract)

NASA Astrophysics Data System (ADS)

Takano, Kentaro; Berkowitz, A. E.

1997-04-01

As recording density increases, magnetoresistive (MR) sensors are becoming increasingly important in read heads. NixCo(1-x)O is receiving technological attention for biasing magnetoresistive sensors as a robust alternative to FeMn. The interfacial exchange coupling between a ferromagnetic (FM) layer and an antiferromagnetic (AFM) is observed as an exchange field and an enhanced coercive field of the FM layer. The AFM/FM coupling is sensitive to the interfacial structure and the AFM and FM magnetic parameters. In this work, we deposited various FM layers on similar 300 Å CoO base layers to study the dependence of the FM exchange integral parameter J on the exchange HE and coercive HC fields. CoO was selected as the AFM material because (i) its simple spin and crystal structures facilitate the structural characterization and modeling of its magnetic properties, and (ii) it's modest Néel temperature of 300 K facilitates the use of a superconducting quantum interference device for the magnetic measurements at temperatures ranging from 5 to 400 K. The 300 Å CoO films were reactively sputtered on silicon substrates and capped with various 300 Å FM films, Ni, Co, Fe, and permalloy (Ni81Fe19). The 300 Å CoO base layer films were polycrystalline with columnar grains. The CoO deposition conditions were reproduced to ensure similar structural and magnetic interfacial AF environments. The observed HE temperature dependence cannot be explained by current theoretical models. The temperature dependence of the exchange fields have the common features (i) a blocking temperature Tb=300 K, which corresponds to the bulk Néel temperature of CoO, (ii) a rise in the exchange field with decreasing temperature, (iii) an intermediate temperature region of constant HE (plateau value), and (iv) a second region of linearly increasing HE with decreasing temperatures down to 0 K. The plateau value of the HE decreased inversely with increasing FM magnetization as predicted by theory. The

Light field reconstruction robust to signal dependent noise

NASA Astrophysics Data System (ADS)

Ren, Kun; Bian, Liheng; Suo, Jinli; Dai, Qionghai

2014-11-01

Capturing four dimensional light field data sequentially using a coded aperture camera is an effective approach but suffers from low signal noise ratio. Although multiplexing can help raise the acquisition quality, noise is still a big issue especially for fast acquisition. To address this problem, this paper proposes a noise robust light field reconstruction method. Firstly, scene dependent noise model is studied and incorporated into the light field reconstruction framework. Then, we derive an optimization algorithm for the final reconstruction. We build a prototype by hacking an off-the-shelf camera for data capturing and prove the concept. The effectiveness of this method is validated with experiments on the real captured data.

Experimental study of the electric dipole strength in the even Mo nuclei and its deformation dependence

NASA Astrophysics Data System (ADS)

Erhard, M.; Junghans, A. R.; Nair, C.; Schwengner, R.; Beyer, R.; Klug, J.; Kosev, K.; Wagner, A.; Grosse, E.

2010-03-01

Two methods based on bremsstrahlung were applied to the stable even Mo isotopes for the experimental determination of the photon strength function covering the high excitation energy range above 4 MeV with its increasing level density. Photon scattering was used up to the neutron separation energies Sn and data up to the maximum of the isovector giant resonance (GDR) were obtained by photoactivation. After a proper correction for multistep processes the observed quasicontinuous spectra of scattered photons show a remarkably good match to the photon strengths derived from nuclear photoeffect data obtained previously by neutron detection and corrected in absolute scale by using the new activation results. The combined data form an excellent basis to derive a shape dependence of the E1 strength in the even Mo isotopes with increasing deviation from the N=50 neutron shell (i.e., with the impact of quadrupole deformation and triaxiality). The wide energy coverage of the data allows for a stringent assessment of the dipole sum rule and a test of a novel parametrization developed previously which is based on it. This parametrization for the electric dipole strength function in nuclei with A>80 deviates significantly from prescriptions generally used previously. In astrophysical network calculations it may help to quantify the role the p-process plays in cosmic nucleosynthesis. It also has impact on the accurate analysis of neutron capture data of importance for future nuclear energy systems and waste transmutation.

Local spectrum analysis of field propagation in an anisotropic medium. Part II. Time-dependent fields.

PubMed

Tinkelman, Igor; Melamed, Timor

2005-06-01

In Part I of this two-part investigation [J. Opt. Soc. Am. A 22, 1200 (2005)], we presented a theory for phase-space propagation of time-harmonic electromagnetic fields in an anisotropic medium characterized by a generic wave-number profile. In this Part II, these investigations are extended to transient fields, setting a general analytical framework for local analysis and modeling of radiation from time-dependent extended-source distributions. In this formulation the field is expressed as a superposition of pulsed-beam propagators that emanate from all space-time points in the source domain and in all directions. Using time-dependent quadratic-Lorentzian windows, we represent the field by a phase-space spectral distribution in which the propagating elements are pulsed beams, which are formulated by a transient plane-wave spectrum over the extended-source plane. By applying saddle-point asymptotics, we extract the beam phenomenology in the anisotropic environment resulting from short-pulsed processing. Finally, the general results are applied to the special case of uniaxial crystal and compared with a reference solution.

Spatial electron density and electric field strength measurements in microwave cavity experiments

NASA Technical Reports Server (NTRS)

Peters, M.; Rogers, J.; Whitehair, S.; Asmussen, J.; Kerber, R.

1984-01-01

Measurements of electron density and electric field strength have been made in an argon plasma contained in a resonant microwave cavity at 2.45 GHz. Spatial measurements of electron density, n sub e, are correlated with fluorescence observations of the discharge. Measurements of n sub e were made with Stark broadening and compared with n sub 3 calculated from measured plasma conductivity. Additional measurements of n sub 3 as a function of pressure and in mixtures of argon and oxygen are presented for pressures from 10 Torr to 1 atm. Measurements in flowing gases and in static systems are presented. In addition, limitations of these measurements are identified.

Non-neutral plasma diode in the presence of a transverse magnetic field

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

Pramanik, Sourav; Chakrabarti, Nikhil; Kuznetsov, V. I.

An analytical study of the plasma states in non-neutral plasma diodes in the presence of an external transverse magnetic field is presented for an arbitrary neutralization parameter γ. Considerations are restricted to the regime where no electrons are turned around by the magnetic field. The emitter electric field strength E{sub 0} is used as a characteristic function to investigate the existence of solutions depending on the diode length, the applied voltage, the neutralization parameter, and the magnetic field strength. The potential distribution has a wave form for small magnitudes of the external magnetic field, as well as for the casemore » when magnetic field is absent. A new family of solutions appears along with the Bursian ones. On the other hand, as the Larmor radius becomes comparable with the beam Debye length, oscillations in the potential disappear, and only the Bursian branches remain. Unlike the vacuum diode, there are steady state solutions for the negative values of the emitter field strength. As the neutralization parameter (γ) increases, the emitter field strength relating to the SCL (space charge limit) bifurcation point diminishes, and at γ > 1, the value of the emitter's electric field strength at the space charge limit (E{sub 0,SCL}) turns out to be negative.« less

A highly optimized code for calculating atomic data at neutron star magnetic field strengths using a doubly self-consistent Hartree-Fock-Roothaan method

NASA Astrophysics Data System (ADS)

Schimeczek, C.; Engel, D.; Wunner, G.

2012-07-01

Our previously published code for calculating energies and bound-bound transitions of medium-Z elements at neutron star magnetic field strengths [D. Engel, M. Klews, G. Wunner, Comput. Phys. Comm. 180 (2009) 302-311] was based on the adiabatic approximation. It assumes a complete decoupling of the (fast) gyration of the electrons under the action of the magnetic field and the (slow) bound motion along the field under the action of the Coulomb forces. For the single-particle orbitals this implied that each is a product of a Landau state and an (unknown) longitudinal wave function whose B-spline coefficients were determined self-consistently by solving the Hartree-Fock equations for the many-electron problem on a finite-element grid. In the present code we go beyond the adiabatic approximation, by allowing the transverse part of each orbital to be a superposition of Landau states, while assuming that the longitudinal part can be approximated by the same wave function in each Landau level. Inserting this ansatz into the energy variational principle leads to a system of coupled equations in which the B-spline coefficients depend on the weights of the individual Landau states, and vice versa, and which therefore has to be solved in a doubly self-consistent manner. The extended ansatz takes into account the back-reaction of the Coulomb motion of the electrons along the field direction on their motion in the plane perpendicular to the field, an effect which cannot be captured by the adiabatic approximation. The new code allows for the inclusion of up to 8 Landau levels. This reduces the relative error of energy values as compared to the adiabatic approximation results by typically a factor of three (1/3 of the original error), and yields accurate results also in regions of lower neutron star magnetic field strengths where the adiabatic approximation fails. Further improvements in the code are a more sophisticated choice of the initial wave functions, which takes into

Magnetic-Field Density-Functional Theory (BDFT): Lessons from the Adiabatic Connection.

PubMed

Reimann, Sarah; Borgoo, Alex; Tellgren, Erik I; Teale, Andrew M; Helgaker, Trygve

2017-09-12

We study the effects of magnetic fields in the context of magnetic field density-functional theory (BDFT), where the energy is a functional of the electron density ρ and the magnetic field B. We show that this approach is a worthwhile alternative to current-density functional theory (CDFT) and may provide a viable route to the study of many magnetic phenomena using density-functional theory (DFT). The relationship between BDFT and CDFT is developed and clarified within the framework of the four-way correspondence of saddle functions and their convex and concave parents in convex analysis. By decomposing the energy into its Kohn-Sham components, we demonstrate that the magnetizability is mainly determined by those energy components that are related to the density. For existing density functional approximations, this implies that, for the magnetizability, improvements of the density will be more beneficial than introducing a magnetic-field dependence in the correlation functional. However, once a good charge density is achieved, we show that high accuracy is likely only obtainable by including magnetic-field dependence. We demonstrate that adiabatic-connection (AC) curves at different field strengths resemble one another closely provided each curve is calculated at the equilibrium geometry of that field strength. In contrast, if all AC curves are calculated at the equilibrium geometry of the field-free system, then the curves change strongly with increasing field strength due to the increasing importance of static correlation. This holds also for density functional approximations, for which we demonstrate that the main error encountered in the presence of a field is already present at zero field strength, indicating that density-functional approximations may be applied to systems in strong fields, without the need to treat additional static correlation.

Pressure and temperature dependence of shear modulus and yield strength for aluminum, copper, and tungsten under shock compression

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

Peng Jianxiang; Jing Fuqian; Li Dahong

2005-07-01

Experimental data for the shear modulus and yield strength of shocked aluminum, copper, and tungsten were systematically analyzed. Comparisons between these data and calculations using the Steinberg-Cochran-Guinan (SCG) constitutive model [D. J. Steinberg, S. G. Cochran, and M. W. Guinan, J. Appl. Phys. 51, 1498 (1980)] indicate that the yield strength has the same dependence on pressure and temperature as the shear modulus for aluminum for shock pressures up to 50 GPa, for copper to 100 GPa, and for tungsten to 200 GPa. Therefore, the assumption of Y{sub p}{sup '}/Y{sub 0}=G{sub p}{sup '}/G{sub 0},Y{sub T}{sup '}/Y{sub 0}=G{sub T}{sup '}/G{sub 0}more » is basically acceptable for these materials, and the SCG model can be used to describe the shear modulus and yield strength of the shocked material at high pressure and temperature.« less

A new test statistic for climate models that includes field and spatial dependencies using Gaussian Markov random fields

DOE PAGES

Nosedal-Sanchez, Alvaro; Jackson, Charles S.; Huerta, Gabriel

2016-07-20

A new test statistic for climate model evaluation has been developed that potentially mitigates some of the limitations that exist for observing and representing field and space dependencies of climate phenomena. Traditionally such dependencies have been ignored when climate models have been evaluated against observational data, which makes it difficult to assess whether any given model is simulating observed climate for the right reasons. The new statistic uses Gaussian Markov random fields for estimating field and space dependencies within a first-order grid point neighborhood structure. We illustrate the ability of Gaussian Markov random fields to represent empirical estimates of fieldmore » and space covariances using "witch hat" graphs. We further use the new statistic to evaluate the tropical response of a climate model (CAM3.1) to changes in two parameters important to its representation of cloud and precipitation physics. Overall, the inclusion of dependency information did not alter significantly the recognition of those regions of parameter space that best approximated observations. However, there were some qualitative differences in the shape of the response surface that suggest how such a measure could affect estimates of model uncertainty.« less

A new test statistic for climate models that includes field and spatial dependencies using Gaussian Markov random fields

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

Nosedal-Sanchez, Alvaro; Jackson, Charles S.; Huerta, Gabriel

A new test statistic for climate model evaluation has been developed that potentially mitigates some of the limitations that exist for observing and representing field and space dependencies of climate phenomena. Traditionally such dependencies have been ignored when climate models have been evaluated against observational data, which makes it difficult to assess whether any given model is simulating observed climate for the right reasons. The new statistic uses Gaussian Markov random fields for estimating field and space dependencies within a first-order grid point neighborhood structure. We illustrate the ability of Gaussian Markov random fields to represent empirical estimates of fieldmore » and space covariances using "witch hat" graphs. We further use the new statistic to evaluate the tropical response of a climate model (CAM3.1) to changes in two parameters important to its representation of cloud and precipitation physics. Overall, the inclusion of dependency information did not alter significantly the recognition of those regions of parameter space that best approximated observations. However, there were some qualitative differences in the shape of the response surface that suggest how such a measure could affect estimates of model uncertainty.« less

Vocational Psychology: Using One of Counseling Psychology's Strengths to Foster Human Strength

ERIC Educational Resources Information Center

Robitschek, Christine; Woodson, Shelley Janiczek

2006-01-01

At several points in the history of their field, counseling psychologists have emphasized that fostering human strengths is part of their mission. Vocational psychology is an area of counseling psychology that has focused consistently on human strengths. In keeping with the Major Contribution's theme, this article examines the following: (a)…

Effect of electrical field strength applied by PEF processing and storage temperature on the outgrowth of yeasts and moulds naturally present in a fresh fruit smoothie.

PubMed

Timmermans, R A H; Nederhoff, A L; Nierop Groot, M N; van Boekel, M A J S; Mastwijk, H C

2016-08-02

Pulsed electrical field (PEF) technology offers an alternative to thermal pasteurisation of high-acid fruit juices, by extending the shelf life of food products, while retaining its fresh taste and nutritional value. Substantial research has been performed on the effect of electrical field strength on the inactivation kinetics of spoilage and pathogenic micro-organisms and on the outgrowth of spoilage micro-organisms during shelf life. However, studies on the effect of electrical field strength on the inactivation and outgrowth of surviving populations during shelf life are missing. In this study, we assessed the influence of electrical field strength applied by PEF processing and storage temperature on the outgrowth of surviving yeast and mould populations naturally present in fresh fruit smoothie in time. Therefore, an apple-strawberry-banana smoothie was treated in a continuous-flow PEF system (130L/h), using similar inlet and outlet conditions (preheating temperature 41°C, maximum temperature 58°C) to assure that the amount of energy across the different conditions was kept constant. Smoothies treated with variable electrical field strengths (13.5, 17.0, 20.0 and 24.0kV/cm) were compared to smoothies without treatment for outgrowth of yeasts and moulds. Outgrowth of yeasts and moulds stored at 4°C and 7°C was analysed by plating and visual observation and yeast growth was modelled using the modified logistic growth model (Zwietering model). Results showed that the intensity of the electrical field strength had an influence on the degree of inactivation of yeast cells, resulting in a faster outgrowth over time at lower electrical field strength. Outgrowth of moulds over time was not affected by the intensity of the electrical field strength used. Application of PEF introduces a trade-off between type of spoilage: in untreated smoothie yeasts lead to spoilage after 8days when stored at 4 or 7°C, whereas in PEF treated smoothie yeasts were (partly

Recasts, Field Dependence/Independence Cognitive Style, and L2 Development

ERIC Educational Resources Information Center

Rassaei, Ehsan

2015-01-01

While previous research has indicated that learners with field-dependence (FD) and field-independence (FI) cognitive styles benefit differentially from different instructional modes, previous corrective feedback studies have ignored the issue of matching error correction strategies to learners' cognitive style. To shed some light on this issue,…

The strength of metal matrix composites

NASA Astrophysics Data System (ADS)

Baxter, William J.

1992-11-01

There is intensive interest in metal matrix composites (MMCs) for automotive components, and the first production applications in Japan use discontinuous fibers as the reinforcements. These fibers are randomly oriented, resulting in an MMC with isotropic properties. However, there are conflicting reports on the tensile strengths attainable. In some cases, the strength increases with increasing volume fraction (V f) of fibers, while in other cases, there is little or no benefit. A simple method is proposed to calculate the strength of this type of MMC. It is shown that the fibers oriented perpendicular to the stress direction play a key role, and the strength depends upon the strength of the interfacial bond. Upper and lower limits of the composite strength are calculated. If the bond strength is larger than the matrix strength, the composite strength has a maximum value which increases with V f. If the bond strength is weaker than the matrix, the composite strength has a minimum value which is either weakly dependent or even independent of V f. These calculations are in good agreement with examples taken from the literature of aluminum composites reinforced with either A12O3, graphite, or SiC. The strength of the matrix alloy is shown to be a very important parameter: weak alloys are easily strengthened, while in certain cases, strong alloys may be weakened.

Influence of field dependent critical current density on flux profiles in high Tc superconductors

NASA Technical Reports Server (NTRS)

Takacs, S.

1990-01-01

The field distribution for superconducting cylinders and slabs with field dependent critical current densities in combined DC and AC magnetic fields and the corresponding magnetic fluxes are calculated. It is shown that all features of experimental magnetic-field profile measurements can be explained in the framework of field dependent critical current density. Even the quantitative agreement between the experimental and theoretical results using Kim's model is very good.

Local time dependence of turbulent magnetic fields in Saturn's magnetodisc

NASA Astrophysics Data System (ADS)

Kaminker, V.; Delamere, P. A.; Ng, C. S.; Dennis, T.; Otto, A.; Ma, X.

2017-04-01

Net plasma transport in magnetodiscs around giant planets is outward. Observations of plasma temperature have shown that the expanding plasma is heating nonadiabatically during this process. Turbulence has been suggested as a source of heating. However, the mechanism and distribution of magnetic fluctuations in giant magnetospheres are poorly understood. In this study we attempt to quantify the radial and local time dependence of fluctuating magnetic field signatures that are suggestive of turbulence, quantifying the fluctuations in terms of a plasma heating rate density. In addition, the inferred heating rate density is correlated with magnetic field configurations that include azimuthal bend forward/back and magnitude of the equatorial normal component of magnetic field relative to the dipole. We find a significant local time dependence in magnetic fluctuations that is consistent with flux transport triggered in the subsolar and dusk sectors due to magnetodisc reconnection.

Field Dependence-Independence Cognitive Style and Academic Achievement: A Review of Research and Theory.

ERIC Educational Resources Information Center

Tinajero, Carolina; Paramo, M. Fernanda

1998-01-01

Reviews research into the possible effects of field dependence/independence on achievement at school. Finds that field-independent subjects perform better than field-dependent subjects, whether in a specific discipline or across all subjects. Discusses possible explanations for this difference in performance. Includes a chart summarizing the…

Energy dependence of the ratio of isovector effective interaction strengths |JστJτ| from 0° (p,n) cross sections

NASA Astrophysics Data System (ADS)

Taddeucci, T. N.; Rapaport, J.; Bainum, D. E.; Goodman, C. D.; Foster, C. C.; Gaarde, C.; Larsen, J.; Goulding, C. A.; Horen, D. J.; Masterson, T.; Sugarbaker, E.

1982-02-01

Information concerning the ratio of the isovector effective interaction strengths |JστJτ| may be obtained from the ratio of (p,n) Gamow-Teller and isobaric analog state 0° differential cross sections. We have examined 0° (p,n) data for the energy range 5-200 MeV and find that for energies larger than 50 MeV and for targets with A=7-42 the product of the interaction-strength and distortion-factor ratios |JστJτ|(NστNτ)12 appears to be mass independent and linear as a function of bombarding energy. NUCLEAR REACTIONS 7Li, 13, 14C, 26Mg, 37Cl, 41Ca(p,n), measured σ(θ=0°), GT, IAS transitions, Ep=60-200 MeV. Deduced energy dependence, interaction strength ratio |JστJτ|.

Field-angle and DC-bias dependence of spin-torque diode in giant magnetoresistive microstripe

NASA Astrophysics Data System (ADS)

Li, X.; Zhou, Y.; Zheng, C.; Chan, P. H.; Chan, M.; Pong, Philip W. T.

2016-11-01

The spin torque diode effect in all metal spintronic devices has been proposed as a microwave detector with a high power limit and resistivity to breakdown. The previous works have revealed the field-angle dependence of the rectified DC voltage (VDC) in the ferromagnetic stripe. The giant magnetoresistive (GMR) microstripe exhibits higher sensitivity compared with the ferromagnetic stripe. However, the influence of the magnetic field direction and bias current in the spin rectification of GMR microstripe is not yet reported. In this work, the angular dependence and bias dependence of resonant frequency (fR) and VDC are investigated. A macrospin model concerning the contribution of magnetic field, shape anisotropy, and unidirectional anisotropy is engaged to interpret the experimental data. fR exhibits a |sin δH| dependence on the in-plane field angle (δH). VDC presents either |sin δH| or |sin2 δH cos δH | relation, depending on the magnitude of Hext. Optimized VDC of 24 μV is achieved under 4 mT magnetic field applied at δH = 170°. Under out-of-plane magnetic field, fR shows a cos 2θH reliance on the polar angle (θH), whereas VDC is sin θH dependent. The Oersted field of the DC bias current (IDC) modifies the effective field, resulting in shifted fR. Enhanced VDC with increasing IDC is attributed to the elevated contribution of spin-transfer torque. Maximum VDC of 35.2 μV is achieved, corresponding to 47% increase compared with the optimized value under zero bias. Higher IDC also results in enlarged damping parameter in the free layer, resulting in increased linewidth in the spin torque diode spectra. This work experimentally and analytically reveals the angular dependence of fR and VDC in the GMR microstripe. The results further demonstrate a highly tunable fR and optimized VDC by bias current without the external magnetic field. GMR microstripe holds promise for application as a high-power, frequency-tunable microwave detector that works under small

Driving chiral domain walls in antiferromagnets using rotating magnetic fields

NASA Astrophysics Data System (ADS)

Pan, Keming; Xing, Lingdi; Yuan, H. Y.; Wang, Weiwei

2018-05-01

We show theoretically and numerically that an antiferromagnetic domain wall can be moved by a rotating magnetic field in the presence of Dzyaloshinskii-Moriya interaction (DMI). Two motion modes are found: rigid domain wall motion at low frequency (corresponding to the perfect frequency synchronization) and the oscillating motion at high frequency. In the full synchronized region, the steady velocity of the domain wall is universal, in the sense that it depends only on the frequency of the rotating field and the ratio between DMI strength and exchange constant. The domain wall velocity is independent of the Gilbert damping and the rotating field strength. Moreover, a rotating field in megahertz is sufficient to move the antiferromagnetic domain wall.

Spatial and temporal dependence of the convective electric field in Saturn’s inner magnetosphere

NASA Astrophysics Data System (ADS)

Andriopoulou, M.; Roussos, E.; Krupp, N.; Paranicas, C.; Thomsen, M.; Krimigis, S.; Dougherty, M. K.; Glassmeier, K.-H.

2014-02-01

The recently established presence of a convective electric field in Saturn’s inner and middle magnetosphere, with an average pointing approximately towards midnight and an intensity less than 1 mV/m, is one of the most puzzling findings by the Cassini spacecraft. In order to better characterize the properties of this electric field, we augmented the original analysis method used to identify it (Andriopoulou et al., 2012) and applied it to an extended energetic electron microsignature dataset, constructed from observations at the vicinity of four saturnian moons. We study the average characteristics of the convective pattern and additionally its temporal and spatial variations. In our updated dataset we include data from the recent Cassini orbits and also microsignatures from the two moons, Rhea and Enceladus, allowing us to further extend this analysis to cover a greater time period as well as larger radial distances within the saturnian magnetosphere. When data from the larger radial range and more recent orbits are included, we find that the originally inferred electric field pattern persists, and in fact penetrates at least as far in as the orbit of Enceladus, a region of particular interest due to the plasma loading that takes place there. We perform our electric field calculations by setting the orientation of the electric field as a free, time-dependent parameter, removing the pointing constraints from previous works. Analytical but also numerical techniques have been employed, that help us overcome possible errors that could have been introduced from simplified assumptions used previously. We find that the average electric field pointing is not directed exactly at midnight, as we initially assumed, but is found to be stably displaced by approximately 12-32° from midnight, towards dawn. The fact, however, that the field’s pointing is much more variable in short time scales, in addition to our observations that it penetrates inside the orbit of Enceladus

Alternating Field Electronanofluidization

NASA Astrophysics Data System (ADS)

Espin, M. J.; Valverde, J. M.; Quintanilla, M. A. S.; Castellanos, A.

2009-06-01

The use of fluidized beds to remove submicron particles from gases has been investigated since 1949. High efficiency removal was achieved in the 1970's by imposing an electric field on a fluidized bed of semi-insulating granules that were able to collect the charged pollutant entrained in the fluidizing gas. In spite of their extended use nowadays, the collection efficiency of electrofluidized beds (EFB) is still hindered by gas bypassing associated to gas bubbling and the consequent requirement of too high gas flow and pressure drop. In this paper we report on the electromechanical behavior of an EFB of insulating nanoparticles. When fluidized by gas, these nanoparticles form extremely porous light agglomerates of size of the order of hundreds of microns that allow for a highly expanded nonbubbling fluidized state at reduced gas flow. It is found that fluidization uniformity and bed expansion are additionally enhanced by an imposed AC electric field for field oscillation frequencies of several tens of hertzs and field strengths of the order of 1 kV/cm. For oscillation frequencies of the order of hertzs, or smaller, bed expansion is hindered due to electrophoretic deposition of the agglomerates onto the vessel walls, whereas for oscillation frequencies of the order of kilohertzs, or larger, electrophoresis is nullified and bed expansion is not affected. According to a proposed model, the size of nanoparticle agglomerates stems from the balance between shear, which depends on field strength, and van der Waals forces. The optimum field strength for enhancing bed expansion produces an electric force on the agglomerates similar to their weight force, while the oscillation velocity of the agglomerates is similar to the gas velocity.

Effect of magnetic field inhomogeneity on ion cyclotron motion coherence at high magnetic field.

PubMed

Vladimirov, Gleb; Kostyukevich, Yury; Hendrickson, Christopher L; Blakney, Greg T; Nikolaev, Eugene

2015-01-01

A three-dimensional code based on the particle-in-cell algorithm modified to account for the inhomogeneity of the magnetic field was applied to determine the effect of Z(1), Z(2), Z(3), Z(4), X, Y, ZX, ZY, XZ(2) YZ(2), XY and X(2)-Y(2) components of an orthogonal magnetic field expansion on ion motion during detection in an FT-ICR cell. Simulations were performed for magnetic field strengths of 4.7, 7, 14.5 and 21 Tesla, including experimentally determined magnetic field spatial distributions for existing 4.7 T and 14.5 T magnets. The effect of magnetic field inhomogeneity on ion cloud stabilization ("ion condensation") at high numbers of ions was investigated by direct simulations of individual ion trajectories. Z(1), Z(2), Z(3) and Z(4) components have the largest effect (especially Z(1)) on ion cloud stability. Higher magnetic field strength and lower m/z demand higher relative magnetic field homogeneity to maintain cloud coherence for a fixed time period. The dependence of mass resolving power upper limit on Z(1) inhomogeneity is evaluated for different magnetic fields and m/z. The results serve to set the homogeneity requirements for various orthogonal magnetic field components (shims) for future FT-ICR magnet design.

Estimation of a coronal mass ejection magnetic field strength using radio observations of gyrosynchrotron radiation

NASA Astrophysics Data System (ADS)

Carley, Eoin P.; Vilmer, Nicole; Simões, Paulo J. A.; Ó Fearraigh, Brían

2017-12-01

Coronal mass ejections (CMEs) are large eruptions of plasma and magnetic field from the low solar corona into interplanetary space. These eruptions are often associated with the acceleration of energetic electrons which produce various sources of high intensity plasma emission. In relatively rare cases, the energetic electrons may also produce gyrosynchrotron emission from within the CME itself, allowing for a diagnostic of the CME magnetic field strength. Such a magnetic field diagnostic is important for evaluating the total magnetic energy content of the CME, which is ultimately what drives the eruption. Here, we report on an unusually large source of gyrosynchrotron radiation in the form of a type IV radio burst associated with a CME occurring on 2014-September-01, observed using instrumentation from the Nançay Radio Astronomy Facility. A combination of spectral flux density measurements from the Nançay instruments and the Radio Solar Telescope Network (RSTN) from 300 MHz to 5 GHz reveals a gyrosynchrotron spectrum with a peak flux density at 1 GHz. Using this radio analysis, a model for gyrosynchrotron radiation, a non-thermal electron density diagnostic using the Fermi Gamma Ray Burst Monitor (GBM) and images of the eruption from the GOES Soft X-ray Imager (SXI), we were able to calculate both the magnetic field strength and the properties of the X-ray and radio emitting energetic electrons within the CME. We find the radio emission is produced by non-thermal electrons of energies >1 MeV with a spectral index of δ 3 in a CME magnetic field of 4.4 G at a height of 1.3 R⊙, while the X-ray emission is produced from a similar distribution of electrons but with much lower energies on the order of 10 keV. We conclude by comparing the electron distribution characteristics derived from both X-ray and radio and show how such an analysis can be used to define the plasma and bulk properties of a CME.

Further constraints for the Plio-Pleistocene geomagnetic field strength: New results from the Los Tuxtlas volcanic field (Mexico)

NASA Astrophysics Data System (ADS)

Alva-Valdivia, L. M.; Goguitchaichvili, A.; Urrutia-Fucugauchi, J.

2001-09-01

A rock-magnetic, paleomagnetic and paleointensity study was carried out on 13 Plio-Pleistocene volcanic flows from the Los Tuxtlas volcanic field (Trans Mexican Volcanic Belt) in order to obtain some decisive constraints for the geomagnetic field strength during the Plio-Pleistocene time. The age of the volcanic units, which yielded reliable paleointensity estimates, lies between 2.2 and 0.8 Ma according to the available K/Ar radiometric data. Thermomagnetic investigations reveal that remanence is carried in most cases by Ti-poor titanomagnetite, resulting from oxy-exsolution that probably occurred during the initial flow cooling. Unblocking temperature spectra and relatively high coercivity point to 'small' pseudo-single domain magnetic grains for these (titano)magnetites. Single-component, linear demagnetization plots were observed in most cases. Six flows yield reverse polarity magnetization, five flows are normally magnetized, and one flow shows intermediate polarity magnetization. Evidence of a strong lightning-produced magnetization overprint was detected for one site. The mean pole position obtained in this study is Plat = 83.7°, Plong = 178.1°, K = 36, A95 = 8.1°, N =10 and the corresponding mean paleodirection is I = 31.3°, D = 352°, k = 37, a95 = 8.2°, which is not significantly different from the expected direction estimated from the North American apparent polar wander path. Thirty-nine samples were pre-selected for Thellier palaeointensity experiments because of their stable remanent magnetization and relatively weak-within-site dispersion. Only 21 samples, coming from four individual basaltic lava flows, yielded reliable paleointensity estimates with the flow-mean virtual dipole moments (VDM) ranging from 6.4 to 9.1 × 1022 Am2. Combining the coeval Mexican data with the available comparable quality Pliocene paleointensity results yield a mean VDM of 6.4 × 1022 Am2, which is almost 80% of the present geomagnetic axial dipole. Reliable

The development of the time dependence of the nuclear EMP electric field

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

Eng, C

The nuclear electromagnetic pulse (EMP) electric field calculated with the legacy code CHAP is compared with the field given by an integral solution of Maxwell's equations, also known as the Jefimenko equation, to aid our current understanding on the factors that affect the time dependence of the EMP. For a fair comparison the CHAP current density is used as a source in the Jefimenko equation. At first, the comparison is simplified by neglecting the conduction current and replacing the standard atmosphere with a constant density air slab. The simplicity of the resultant current density aids in determining the factors thatmore » affect the rise, peak and tail of the EMP electric field versus time. The three dimensional nature of the radiating source, i.e. sources off the line-of-sight, and the time dependence of the derivative of the current density with respect to time are found to play significant roles in shaping the EMP electric field time dependence. These results are found to hold even when the conduction current and the standard atmosphere are properly accounted for. Comparison of the CHAP electric field with the Jefimenko electric field offers a direct validation of the high-frequency/outgoing wave approximation.« less

New Limits on Extragalactic Magnetic Fields from Rotation Measures

NASA Astrophysics Data System (ADS)

Pshirkov, M. S.; Tinyakov, P. G.; Urban, F. R.

2016-05-01

We take advantage of the wealth of rotation measures data contained in the NRAO VLA Sky Survey catalog to derive new, statistically robust, upper limits on the strength of extragalactic magnetic fields. We simulate the extragalactic magnetic field contribution to the rotation measures for a given field strength and correlation length, by assuming that the electron density follows the distribution of Lyman-α clouds. Based on the observation that rotation measures from distant radio sources do not exhibit any trend with redshift, while the extragalactic contribution instead grows with distance, we constrain fields with Jeans' length coherence length to be below 1.7 nG at the 2 σ level, and fields coherent across the entire observable Universe below 0.65 nG. These limits do not depend on the particular origin of these cosmological fields.

Polarization-dependent optics using gauge-field metamaterials

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

Liu, Fu; Xiao, Shiyi; Li, Jensen, E-mail: j.li@bham.ac.uk

2015-12-14

We show that effective gauge field for photons with polarization-split dispersion surfaces, being realized using uniaxial metamaterials, can be used for polarization control with unique opportunities. The metamaterials with the proposed gauge field correspond to a special choice of eigenpolarizations on the Poincaré sphere as pseudo-spins, in contrary to those from either conventional birefringent crystals or optical active media. It gives rise to all-angle polarization control and a generic route to manipulate photon trajectories or polarizations in the pseudo-spin domain. As demonstrations, we show beam splitting (birefringent polarizer), all-angle polarization control, unidirectional polarization filter, and interferometer as various polarization controlmore » devices in the pseudo-spin domain. We expect that more polarization-dependent devices can be designed under the same framework.« less

Analysis of seafloor backscatter strength dependence on the survey azimuth using multibeam echosounder data

NASA Astrophysics Data System (ADS)

Lurton, Xavier; Eleftherakis, Dimitrios; Augustin, Jean-Marie

2018-06-01

The sediment backscatter strength measured by multibeam echosounders is a key feature for seafloor mapping either qualitative (image mosaics) or quantitative (extraction of classifying features). An important phenomenon, often underestimated, is the dependence of the backscatter level on the azimuth angle imposed by the survey line directions: strong level differences at varying azimuth can be observed in case of organized roughness of the seabed, usually caused by tide currents over sandy sediments. This paper presents a number of experimental results obtained from shallow-water cruises using a 300-kHz multibeam echosounder and specially dedicated to the study of this azimuthal effect, with a specific configuration of the survey strategy involving a systematic coverage of reference areas following "compass rose" patterns. The results show for some areas a very strong dependence of the backscatter level, up to about 10-dB differences at intermediate oblique angles, although the presence of these ripples cannot be observed directly—neither from the bathymetry data nor from the sonar image, due to the insufficient resolution capability of the sonar. An elementary modeling of backscattering from rippled interfaces explains and comforts these observations. The consequences of this backscatter dependence upon survey azimuth on the current strategies of backscatter data acquisition and exploitation are discussed.

Density matrix solutions for the susceptibilities of a three-level system with arbitrary relaxation rates and field strengths

NASA Technical Reports Server (NTRS)

Ryan, J. C.; Lawandy, N. M.

1986-01-01

The susceptibilities for a three-level system with arbitrary pump and signal field strengths are derived for arbitrary longitudinal and transverse relaxation rates. The results are of interest in connection with the calculation of the Raman gain in systems where resonance enhancement plays a dominant role.

Electric Field-Dependent Photoluminescence in Multilayer Transition Metal Dichalcogenides

NASA Astrophysics Data System (ADS)

Stanev, T. K.; Henning, A.; Sangwan, V. K.; Speiser, N.; Stern, N. P.; Lauhon, L. J.; Hersam, M. C.; Wang, K.; Valencia, D.; Charles, J.; Kubis, T. C.

Owing to interlayer coupling, transition metal dichalcogenides (TMDCs) such as MoS2 exhibit strong layer dependence of optical and electronic phenomena such as the band gap and trion and neutral exciton population dynamics. Here, we systematically measure the effect of layer number on the optical response of multilayer MoS2 in an external electric field, observing field and layer number dependent emission energy and photoluminescence intensity. These effects are studied in few (2-6) and bulk (11 +) layered structures at low temperatures. In MoS2\\ the observed layer dependence arises from several mechanisms, including interlayer charge transfer, band structure, Stark Effect, Fermi level changes, screening, and surface effects, so it can be challenging to isolate how these mechanisms impact the observables. Because it behaves like a stack of weakly interacting monolayers rather than multilayer or bulk, ReS2 provides a comparison to traditional TMDCs to help isolate the underlying physical mechanisms dictating the response of multilayers. This work is supported by the National Science Foundation MRSEC program (DMR-1121262), and the 2-DARE Grant (EFRI-1433510). N.P.S. is an Alfred P. Sloan Research Fellow.

Pulsed-field-gradient measurements of time-dependent gas diffusion

NASA Technical Reports Server (NTRS)

Mair, R. W.; Cory, D. G.; Peled, S.; Tseng, C. H.; Patz, S.; Walsworth, R. L.

1998-01-01

Pulsed-field-gradient NMR techniques are demonstrated for measurements of time-dependent gas diffusion. The standard PGSE technique and variants, applied to a free gas mixture of thermally polarized xenon and O2, are found to provide a reproducible measure of the xenon diffusion coefficient (5.71 x 10(-6) m2 s-1 for 1 atm of pure xenon), in excellent agreement with previous, non-NMR measurements. The utility of pulsed-field-gradient NMR techniques is demonstrated by the first measurement of time-dependent (i.e., restricted) gas diffusion inside a porous medium (a random pack of glass beads), with results that agree well with theory. Two modified NMR pulse sequences derived from the PGSE technique (named the Pulsed Gradient Echo, or PGE, and the Pulsed Gradient Multiple Spin Echo, or PGMSE) are also applied to measurements of time dependent diffusion of laser polarized xenon gas, with results in good agreement with previous measurements on thermally polarized gas. The PGMSE technique is found to be superior to the PGE method, and to standard PGSE techniques and variants, for efficiently measuring laser polarized noble gas diffusion over a wide range of diffusion times. Copyright 1998 Academic Press.

Effect of Aperture Field Variability, Flow Rate, and Ionic Strength on Colloid Transport in Single Fractures: Laboratory-Scale Experiments and Numerical Simulation

NASA Astrophysics Data System (ADS)

Zheng, Q.; Dickson, S.; Guo, Y.

2007-12-01

A good understanding of the physico-chemical processes (i.e., advection, dispersion, attachment/detachment, straining, sedimentation etc.) governing colloid transport in fractured media is imperative in order to develop appropriate bioremediation and/or bioaugmentation strategies for contaminated fractured aquifers, form management plans for groundwater resources to prevent pathogen contamination, and identify suitable radioactive waste disposal sites. However, research in this field is still in its infancy due to the complex heterogeneous nature of fractured media and the resulting difficulty in characterizing this media. The goal of this research is to investigate the effects of aperture field variability, flow rate and ionic strength on colloid transport processes in well characterized single fractures. A combination of laboratory-scale experiments, numerical simulations, and imaging techniques were employed to achieve this goal. Transparent replicas were cast from natural rock fractures, and a light transmission technique was employed to measure their aperture fields directly. The surface properties of the synthetic fractures were characterized by measuring the zeta-potential under different ionic strengths. A 33 (3 increased to the power of 3) factorial experiment was implemented to investigate the influence of aperture field variability, flow rate, and ionic strength on different colloid transport processes in the laboratory-scale fractures, specifically dispersion and attachment/detachment. A fluorescent stain technique was employed to photograph the colloid transport processes, and an analytical solution to the one-dimensional transport equation was fit to the colloid breakthrough curves to calculate the average transport velocity, dispersion coefficient, and attachment/detachment coefficient. The Reynolds equation was solved to obtain the flow field in the measured aperture fields, and the random walk particle tracking technique was employed to model the

Impact of field strength and iron oxide nanoparticle concentration on the linearity and diagnostic accuracy of off-resonance imaging.

PubMed

Farrar, Christian T; Dai, Guangping; Novikov, Mikhail; Rosenzweig, Anthony; Weissleder, Ralph; Rosen, Bruce R; Sosnovik, David E

2008-06-01

Off-resonance imaging (ORI) techniques are being increasingly used to image iron oxide imaging agents such as monocrystalline iron oxide nanoparticles (MION). However, the diagnostic accuracy, linearity, and field dependence of ORI have not been fully characterized. In this study, the sensitivity, specificity, and linearity of ORI were thus examined as a function of both MION concentration and magnetic field strength (4.7 and 14 T). MION phantoms with and without an air interface as well as MION uptake in a mouse model of healing myocardial infarction were imaged. MION-induced resonance shifts were shown to increase linearly with MION concentration. In contrast, the ORI signal/sensitivity was highly non-linear, initially increasing with MION concentration until T2 became comparable to the TE and decreasing thereafter. The specificity of ORI to distinguish MION-induced resonance shifts from on-resonance water was found to decrease with increasing field because of the increased on-resonance water linewidths (15 Hz at 4.7 T versus 45 Hz at 14 T). Large resonance shifts ( approximately 300 Hz) were observed at air interfaces at 4.7 T, both in vitro and in vivo, and led to poor ORI specificity for MION concentrations less than 150 microg Fe/mL. The in vivo ORI sensitivity was sufficient to detect the accumulation of MION in macrophages infiltrating healing myocardial infarcts, but the specificity was limited by non-specific areas of positive contrast at the air/tissue interfaces of the thoracic wall and the descending aorta. Improved specificity and linearity can, however, be expected at lower fields where decreased on-resonance water linewidths, reduced air-induced resonance shifts, and longer T2 relaxation times are observed. The optimal performance of ORI will thus likely be seen at low fields, with moderate MION concentrations and with sequences containing very short TEs. Copyright (c) 2007 John Wiley & Sons, Ltd.

Field-Dependence/Independence and Active Learning of Verbal and Geometric Material.

ERIC Educational Resources Information Center

Reardon, Richard; And Others

1982-01-01

Field-dependent and independent subjects sorted geometric and verbal material according to category exemplars, forcing active learning, and then recalled the category locations. Field-independent individuals generally performed better on learning and memory tasks with a more active approach. Active versus passive learning styles are discussed.…

Magnetic-field gradiometer based on ultracold collisions

NASA Astrophysics Data System (ADS)

Wasak, Tomasz; Jachymski, Krzysztof; Calarco, Tommaso; Negretti, Antonio

2018-05-01

We present a detailed analysis of the usefulness of ultracold atomic collisions for sensing the strength of an external magnetic field as well as its spatial gradient. The core idea of the sensor, which we recently proposed in Jachymski et al. [Phys. Rev. Lett. 120, 013401 (2018), 10.1103/PhysRevLett.120.013401], is to probe the transmission of the atoms through a set of quasi-one-dimensional waveguides that contain an impurity. Magnetic-field-dependent interactions between the incoming atoms and the impurity naturally lead to narrow resonances that can act as sensitive field probes since they strongly affect the transmission. We illustrate our findings with concrete examples of experimental relevance, demonstrating that for large atom fluences N a sensitivity of the order of 1 nT/√{N } for the field strength and 100 nT/(mm √{N }) for the gradient can be reached with our scheme.

Design of a New Superconducting Magnet System for High Strength Minimum-B Fields for ECRIS

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

Xie, D. Z.; Benitez, J. Y.; Hodgkinson, A.

A novel Mixed Axial and Radial field System (MARS) seeks to enhance the B fields inside the plasma chamber within the limits of a given conductor, thereby making it possible to raise the operating fields for Electron Cyclotron Resonance Ion Sources (ECRISs). The MARS concept consists of a hexagonally shaped closed-loop coil and a set of auxiliary solenoids. The application of MARS will be combined with a hexagonal plasma chamber to maximize the use of the radial fields at the chamber inner surfaces. Calculations using Opera's TOSCA-3D solver have shown that MARS can potentially generate up to 50% higher fieldsmore » and use of only about one half of the same superconducting wire, as compared with existing magnet designs in ECRISs. A MARS magnet system built with Nb 3 Sn coils could generate a high strength minimum-B field of maxima of ≥ 10 T on axis and ~6 T radially in an ECRIS plasma chamber. Following successful development, the MARS magnet system will be the best magnet scheme for the next generation of ECRISs. This paper will present the MARS concept, magnet design, prototyping a copper closed-loop coil, and discussions.« less

Design of a New Superconducting Magnet System for High Strength Minimum-B Fields for ECRIS

DOE PAGES

Xie, D. Z.; Benitez, J. Y.; Hodgkinson, A.; ...

2016-06-01

A novel Mixed Axial and Radial field System (MARS) seeks to enhance the B fields inside the plasma chamber within the limits of a given conductor, thereby making it possible to raise the operating fields for Electron Cyclotron Resonance Ion Sources (ECRISs). The MARS concept consists of a hexagonally shaped closed-loop coil and a set of auxiliary solenoids. The application of MARS will be combined with a hexagonal plasma chamber to maximize the use of the radial fields at the chamber inner surfaces. Calculations using Opera's TOSCA-3D solver have shown that MARS can potentially generate up to 50% higher fieldsmore » and use of only about one half of the same superconducting wire, as compared with existing magnet designs in ECRISs. A MARS magnet system built with Nb 3 Sn coils could generate a high strength minimum-B field of maxima of ≥ 10 T on axis and ~6 T radially in an ECRIS plasma chamber. Following successful development, the MARS magnet system will be the best magnet scheme for the next generation of ECRISs. This paper will present the MARS concept, magnet design, prototyping a copper closed-loop coil, and discussions.« less

Anomalous B-field Dependence of Spin-flip Time in High Purity InP

NASA Astrophysics Data System (ADS)

Linpeng, Xiayu; Karin, Todd; Barbour, Russell; Glazov, Mikhail; Fu, Kai-Mei

2015-03-01

We observe an anomalous B-field dependence of the spin-flip time (T1) of electrons bound to shallow donors which cannot be explained by current spin-relaxation theories. We conduct resonant pump-probe measurements in high-purity InP from the low to high magnetic field regimes, with a maximum T1 (400 μs) observed near the turning point gμB B ~=kB T . At low B, the T1 dependence on B is consistent with an electron correlation time (τc) in the tens of nanoseconds. The physical mechanism for the short τc in this high-purity sample (n ~= 2 ×1014 cm-3) is unclear, but a strong temperature (T) dependence indicates T1 can be further increased by lowering T below the 1.5 K experimental temperature. At high B, a B-3 dependence is observed, in contrast to the expected B-5 predicted by single-phonon spin-orbit mediated interactions. An understanding of the anomalous B-field dependence is expected to elucidate the effect of electron transport (low-field) and phonons (high-field) on T1 for shallow donors, which is of interest for both ensemble and single-spin quantum information applications. This material is based upon work supported by the National Science Foundation under Grant No. 1150647, DGE-0718124 and DGE-1256082. InP samples were graciously provided by Simon Watkins at Simon Fraser University.

Quantitative water content mapping at clinically relevant field strengths: a comparative study at 1.5 T and 3 T.

PubMed

Abbas, Zaheer; Gras, Vincent; Möllenhoff, Klaus; Oros-Peusquens, Ana-Maria; Shah, Nadim Joni

2015-02-01

Quantitative water content mapping in vivo using MRI is a very valuable technique to detect, monitor and understand diseases of the brain. At 1.5 T, this technology has already been successfully used, but it has only recently been applied at 3T because of significantly increased RF field inhomogeneity at the higher field strength. To validate the technology at 3T, we estimate and compare in vivo quantitative water content maps at 1.5 T and 3T obtained with a protocol proposed recently for 3T MRI. The proposed MRI protocol was applied on twenty healthy subjects at 1.5 T and 3T; the same post-processing algorithms were used to estimate the water content maps. The 1.5 T and 3T maps were subsequently aligned and compared on a voxel-by-voxel basis. Statistical analysis was performed to detect possible differences between the estimated 1.5 T and 3T water maps. Our analysis indicates that the water content values obtained at 1.5 T and 3T did not show significant systematic differences. On average the difference did not exceed the standard deviation of the water content at 1.5 T. Furthermore, the contrast-to-noise ratio (CNR) of the estimated water content map was increased at 3T by a factor of at least 1.5. Vulnerability to RF inhomogeneity increases dramatically with the increasing static magnetic field strength. However, using advanced corrections for the sensitivity profile of the MR coils, it is possible to preserve quantitative accuracy while benefiting from the increased CNR at the higher field strength. Indeed, there was no significant difference in the water content values obtained in the brain at 1.5 T and 3T. Copyright © 2014 Elsevier Inc. All rights reserved.

Helicon double layer thruster operation in a low magnetic field mode

NASA Astrophysics Data System (ADS)

Harle, T.; Pottinger, S. J.; Lappas, V. J.

2013-02-01

Direct thrust measurements are made of a helicon double layer thruster operating in a low magnetic field mode. The relationship between the imposed axial magnetic field and generated thrust is investigated for a radio frequency input power range 200-500 W for propellant flow rates of 16.5 and 20 sccm (0.46 and 0.55 mg s-1) of argon. The measured thrust shows a strong dependence on the magnetic field strength, increasing by up to a factor of 5 compared with the minimum thrust level recorded. A peak thrust of 0.4-1.1 mN depending on thruster operating conditions is obtained. This increase is observed to take place over a small range of peak magnetic field strengths in the region of 70-110 G. The magnitude of the thrust and the corresponding magnitude of the magnetic field at which the peak thrust occurs is shown to increase with increasing input power for a given propellant flow rate. The ion current determined using a retarding field energy analyser and the electron number density found using a microwave resonator probe both correlate with the observed trend in thrust as a function of applied magnetic field.

A cohesive-frictional force field (CFFF) for colloidal calcium-silicate-hydrates

NASA Astrophysics Data System (ADS)

Palkovic, Steven D.; Yip, Sidney; Büyüköztürk, Oral

2017-12-01

Calcium-silicate-hydrate (C-S-H) gel is a cohesive-frictional material that exhibits strength asymmetry in compression and tension and normal-stress dependency of the maximum shear strength. Experiments suggest the basic structural component of C-S-H is a colloidal particle with an internal layered structure. These colloids form heterogeneous assemblies with a complex pore network at the mesoscale. We propose a cohesive-frictional force field (CFFF) to describe the interactions in colloidal C-S-H materials that incorporates the strength anisotropy fundamental to the C-S-H molecular structure that has been omitted from recent mesoscale models. We parameterize the CFFF from reactive force field simulations of an internal interface that controls mechanical performance, describing the behavior of thousands of atoms through a single effective pair interaction. We apply the CFFF to study the mesoscale elastic and Mohr-Coulomb strength properties of C-S-H with varying polydispersity and packing density. Our results show that the consideration of cohesive-frictional interactions lead to an increase in stiffness, shear strength, and normal-stress dependency, while also changing the nature of local deformation processes. The CFFF and our coarse-graining approach provide an essential connection between nanoscale molecular interactions and macroscale continuum behavior for hydrated cementitious materials.

Is the relationship between increased knee muscle strength and improved physical function following exercise dependent on baseline physical function status?

PubMed

Hall, Michelle; Hinman, Rana S; van der Esch, Martin; van der Leeden, Marike; Kasza, Jessica; Wrigley, Tim V; Metcalf, Ben R; Dobson, Fiona; Bennell, Kim L

2017-12-08

Clinical guidelines recommend knee muscle strengthening exercises to improve physical function. However, the amount of knee muscle strength increase needed for clinically relevant improvements in physical function is unclear. Understanding how much increase in knee muscle strength is associated with improved physical function could assist clinicians in providing appropriate strength gain targets for their patients in order to optimise outcomes from exercise. The aim of this study was to investigate whether an increase in knee muscle strength is associated with improved self-reported physical function following exercise; and whether the relationship differs according to physical function status at baseline. Data from 100 participants with medial knee osteoarthritis enrolled in a 12-week randomised controlled trial comparing neuromuscular exercise to quadriceps strengthening exercise were pooled. Participants were categorised as having mild, moderate or severe physical dysfunction at baseline using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Associations between 12-week changes in physical function (dependent variable) and peak isometric knee extensor and flexor strength (independent variables) were evaluated with and without accounting for baseline physical function status and covariates using linear regression models. In covariate-adjusted models without accounting for baseline physical function, every 1-unit (Nm/kg) increase in knee extensor strength was associated with physical function improvement of 17 WOMAC units (95% confidence interval (CI) -29 to -5). When accounting for baseline severity of physical function, every 1-unit increase in knee extensor strength was associated with physical function improvement of 24 WOMAC units (95% CI -42 to -7) in participants with severe physical dysfunction. There were no associations between change in strength and change in physical function in participants with mild or moderate physical

Erythrocyte agglutination by wheat germ agglutinin: ionic strength dependence of the contact seam topology.

PubMed

Rolfe, M; Parmar, A; Hoy, T G; Coakley, W T

2001-01-01

The topology of the cell-cell contact seam formed when normal or pronase pre-treated (PPT) erythrocytes are exposed to wheat germ agglutinin (WGA) in isotonic media of different ionic strengths was examined here. Lectin uptake and cell agglutination were also quantified. Agglutination of normal cells was gradually and significantly inhibited as ionic strength (IS) was reduced from 0.15 (buffered 145 mm NaCl) to 0.105. Agglutination was less inhibited in PPT cells, even when IS was reduced to 0.09. Cell contact seams formed during agglutination showed patterns of localized contacts. The scale of the patterns, i.e. the average lateral separation distance of contact regions, was 0.62 microm for normal cells and was significantly shorter, at 0.44 microm, for PPT cells at an IS of 0.15. The scale increased significantly for both cell types when the IS was reduced to 0.09. Flow cytometry measurements showed that WGA uptake by normal cells increased slightly, whilst that for PPT cells was unchanged, as IS was decreased from 0.15 to 0.09. The results imply that, whilst ionic strength change does not exert a strong influence on intermolecular WGA-ligand binding, physico-chemical modification of the interaction between cells modulates not only the extent and progression of the biospecific lectin-induced cell-cell agglutination but also the topology of the contact seam. The IS dependence of contact separation in WGA-agglutinated cells is contrasted here with that reported for cells adhering in dextran solutions. The influence of IS change and pronase pre-treatment on contact pattern are consistent with predictions, from interfacial instability theory, of punctuate thinning of the aqueous layer separating bilayer membranes in close apposition.

47 CFR 27.55 - Power strength limits.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 2 2010-10-01 2010-10-01 false Power strength limits. 27.55 Section 27.55 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES MISCELLANEOUS WIRELESS COMMUNICATIONS SERVICES Technical Standards § 27.55 Power strength limits. (a) Field strength limits. For the...

Analytical solutions of the Schroedinger equation for a two-dimensional exciton in magnetic field of arbitrary strength

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

Hoang-Do, Ngoc-Tram; Hoang, Van-Hung; Le, Van-Hoang

2013-05-15

The Feranchuk-Komarov operator method is developed by combining with the Levi-Civita transformation in order to construct analytical solutions of the Schroedinger equation for a two-dimensional exciton in a uniform magnetic field of arbitrary strength. As a result, analytical expressions for the energy of the ground and excited states are obtained with a very high precision of up to four decimal places. Especially, the precision is uniformly stable for the whole range of the magnetic field. This advantage appears due to the consideration of the asymptotic behaviour of the wave-functions in strong magnetic field. The results could be used for variousmore » physical analyses and the method used here could also be applied to other atomic systems.« less

Terapascal static pressure generation with ultrahigh yield strength nanodiamond.

PubMed

Dubrovinskaia, Natalia; Dubrovinsky, Leonid; Solopova, Natalia A; Abakumov, Artem; Turner, Stuart; Hanfland, Michael; Bykova, Elena; Bykov, Maxim; Prescher, Clemens; Prakapenka, Vitali B; Petitgirard, Sylvain; Chuvashova, Irina; Gasharova, Biliana; Mathis, Yves-Laurent; Ershov, Petr; Snigireva, Irina; Snigirev, Anatoly

2016-07-01

Studies of materials' properties at high and ultrahigh pressures lead to discoveries of unique physical and chemical phenomena and a deeper understanding of matter. In high-pressure research, an achievable static pressure limit is imposed by the strength of available strong materials and design of high-pressure devices. Using a high-pressure and high-temperature technique, we synthesized optically transparent microballs of bulk nanocrystalline diamond, which were found to have an exceptional yield strength (~460 GPa at a confining pressure of ~70 GPa) due to the unique microstructure of bulk nanocrystalline diamond. We used the nanodiamond balls in a double-stage diamond anvil cell high-pressure device that allowed us to generate static pressures beyond 1 TPa, as demonstrated by synchrotron x-ray diffraction. Outstanding mechanical properties (strain-dependent elasticity, very high hardness, and unprecedented yield strength) make the nanodiamond balls a unique device for ultrahigh static pressure generation. Structurally isotropic, homogeneous, and made of a low-Z material, they are promising in the field of x-ray optical applications.

Terapascal static pressure generation with ultrahigh yield strength nanodiamond

PubMed Central

Dubrovinskaia, Natalia; Dubrovinsky, Leonid; Solopova, Natalia A.; Abakumov, Artem; Turner, Stuart; Hanfland, Michael; Bykova, Elena; Bykov, Maxim; Prescher, Clemens; Prakapenka, Vitali B.; Petitgirard, Sylvain; Chuvashova, Irina; Gasharova, Biliana; Mathis, Yves-Laurent; Ershov, Petr; Snigireva, Irina; Snigirev, Anatoly

2016-01-01

Studies of materials’ properties at high and ultrahigh pressures lead to discoveries of unique physical and chemical phenomena and a deeper understanding of matter. In high-pressure research, an achievable static pressure limit is imposed by the strength of available strong materials and design of high-pressure devices. Using a high-pressure and high-temperature technique, we synthesized optically transparent microballs of bulk nanocrystalline diamond, which were found to have an exceptional yield strength (~460 GPa at a confining pressure of ~70 GPa) due to the unique microstructure of bulk nanocrystalline diamond. We used the nanodiamond balls in a double-stage diamond anvil cell high-pressure device that allowed us to generate static pressures beyond 1 TPa, as demonstrated by synchrotron x-ray diffraction. Outstanding mechanical properties (strain-dependent elasticity, very high hardness, and unprecedented yield strength) make the nanodiamond balls a unique device for ultrahigh static pressure generation. Structurally isotropic, homogeneous, and made of a low-Z material, they are promising in the field of x-ray optical applications. PMID:27453944

Slow changing postural cues cancel visual field dependence on self-tilt detection.

PubMed

Scotto Di Cesare, C; Macaluso, T; Mestre, D R; Bringoux, L

2015-01-01

Interindividual differences influence the multisensory integration process involved in spatial perception. Here, we assessed the effect of visual field dependence on self-tilt detection relative to upright, as a function of static vs. slow changing visual or postural cues. To that aim, we manipulated slow rotations (i.e., 0.05° s(-1)) of the body and/or the visual scene in pitch. Participants had to indicate whether they felt being tilted forward at successive angles. Results show that thresholds for self-tilt detection substantially differed between visual field dependent/independent subjects, when only the visual scene was rotated. This difference was no longer present when the body was actually rotated, whatever the visual scene condition (i.e., absent, static or rotated relative to the observer). These results suggest that the cancellation of visual field dependence by dynamic postural cues may rely on a multisensory reweighting process, where slow changing vestibular/somatosensory inputs may prevail over visual inputs. Copyright © 2014 Elsevier B.V. All rights reserved.

Electric Field Strength Of Coherent Radio Emission In Rock Salt Concerning Ultra High-Energy Neutrino Detection

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

Watanabe, Y.; Chiba, M.; Yasuda, O.

2006-07-12

Detection possibility of ultra high-energy (UHE) neutrino (E >1015 eV) in natural huge rock salt formation has been studied. Collision between the UHE neutrino and the rock salt produces electromagnetic (EM) shower. Charge difference (excess electrons) between electrons and positrons in EM shower radiates radio wave coherently (Askar'yan effect). Angular distribution and frequency spectrum of electric field strength of radio wave radiated from 3-dimensional EM shower in rock salt are presented.

WE-G-17A-08: Electron Gun Operation for in Line MRI-Linac Configurations: An Assessment of Beam Fidelity and Recovery Techniques for Different SIDs and Magnetic Field Strengths

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

Whelan, B; Keall, P; Ingham Institute, Liverpool, Aus

Purpose: To test the functionality of medical electron guns within the fringe field of a purpose built superconducting MRI magnet, and to test different recovery techniques for a variety of imaging field strengths and SIDs. Methods: Three different electron guns were simulated using Finite Element Modelling; a standard diode gun, a standard triode gun, and a novel diode gun designed to operate within parallel magnetic fields. The approximate working regime of each gun was established by assessing exit current in constant magnetic fields of varying strength and defining ‘working’ as less than 10% change in injection current. Next, the 1.0Tmore » MRI magnet was simulated within Comsol Multiphysics. The coil currents in this model were also scaled to produce field strengths of .5, 1, 1.5 and 3T. Various magnetic shield configurations were simulated, varying the SID from 800 to 1300mm. The average magnetic field within the gun region was assessed together with the distortion in the imaging volume - greater than 150uT distortion was considered unacceptable. Results: The conventional guns functioned in fields of less than 7.5mT. Conversely, the redesigned diode required fields greater than .1T to function correctly. Magnetic shielding was feasible for SIDS of greater than 1000mm for field strengths of .5T and 1T, and 1100mm for 1.5 and 3.0T. Beyond these limits shielding resulted in unacceptable MRI distortion. In contrast, the redesigned diode could perform acceptably for SIDs of less than 812, 896, 931, and 974mm for imaging strengths of 0.5, 1.0, 1.5, 3.0T. Conclusions: For in-line MRIlinac configurations where the electron gun is operating in low field regions, shielding is a straight forward option. However, as magnetic field strength increases and the SID is reduced, shielding results in too great a distortion in the MRI and redesigning the electron optics is the preferable solution. The authors would like to acknowledge funding from the National Health and

The 'Arm Force Field' method to predict manual arm strength based on only hand location and force direction.

PubMed

La Delfa, Nicholas J; Potvin, Jim R

2017-03-01

This paper describes the development of a novel method (termed the 'Arm Force Field' or 'AFF') to predict manual arm strength (MAS) for a wide range of body orientations, hand locations and any force direction. This method used an artificial neural network (ANN) to predict the effects of hand location and force direction on MAS, and included a method to estimate the contribution of the arm's weight to the predicted strength. The AFF method predicted the MAS values very well (r 2  = 0.97, RMSD = 5.2 N, n = 456) and maintained good generalizability with external test data (r 2  = 0.842, RMSD = 13.1 N, n = 80). The AFF can be readily integrated within any DHM ergonomics software, and appears to be a more robust, reliable and valid method of estimating the strength capabilities of the arm, when compared to current approaches. Copyright © 2016 Elsevier Ltd. All rights reserved.

Force field dependent solution properties of glycine oligomers

PubMed Central

Drake, Justin A.

2015-01-01

Molecular simulations can be used to study disordered polypeptide systems and to generate hypotheses on the underlying structural and thermodynamic mechanisms that govern their function. As the number of disordered protein systems investigated with simulations increase, it is important to understand how particular force fields affect the structural properties of disordered polypeptides in solution. To this end, we performed a comparative structural analysis of Gly3 and Gly10 in aqueous solution from all-atom, microsecond MD simulations using the CHARMM 27 (C27), CHARMM 36 (C36), and Amber ff12SB force fields. For each force field, Gly3 and Gly10 were simulated for at least 300 ns and 1 μs, respectively. Simulating oligoglycines of two different lengths allows us to evaluate how force field effects depend on polypeptide length. Using a variety of structural metrics (e.g. end-to-end distance, radius of gyration, dihedral angle distributions), we characterize the distribution of oligoglycine conformers for each force field and show that each sample conformation space differently, yielding considerably different structural tendencies of the same oligoglycine model in solution. Notably, we find that C36 samples more extended oligoglycine structures than both C27 and ff12SB. PMID:25952623

Location of γ -ray emission and magnetic field strengths in OJ 287

DOE PAGES

Hodgson, J. A.; Krichbaum, T. P.; Marscher, A. P.; ...

2017-01-06

We report the γ-ray BL Lac object OJ 287 is known to exhibit inner-parsec “jet-wobbling”, high degrees of variability at all wavelengths and quasi-stationary features, including an apparent (≈100°) position-angle change in projection on the sky plane. Sub-50 micro-arcsecond resolution 86 GHz observations with the global mm-VLBI array (GMVA) supplement ongoing multi-frequency VLBI blazar monitoring at lower frequencies. Using these maps, together with cm/mm total intensity and γ-ray observations from Fermi-LAT from 2008-2014, we aim to Observations with the GMVA offer approximately double the angular resolution compared with 43 GHz VLBA observations and enable us to observe above the synchrotronmore » self-absorption peak frequency. Fermi-LAT γ-ray data were reduced and analysed. The jet was spectrally decomposed at multiple locations along the jet. From this, we could derive estimates of the magnetic field using equipartition and synchrotron self-absorption arguments. How the field decreases down the jet provided an estimate of the distance to the jet apex and an estimate of the magnetic field strength at the jet apex and in the broad line region. Combined with accurate kinematics, we attempt to locate the site of γ-ray activity, radio flares, and spectral changes. Strong γ-ray flares appeared to originate from either the so-called core region, a downstream stationary feature, or both, with γ-ray activity significantly correlated with radio flaring in the downstream quasi-stationary feature. Magnetic field estimates were determined at multiple locations along the jet, with the magnetic field found to be ≥1.6 G in the core and ≤0.4 G in the downstream quasi-stationary feature. Finally, we therefore found upper limits on the location of the VLBI core as ≲6.0 pc from the jet apex and determined an upper limit on the magnetic field near the jet base of the order of thousands of Gauss.« less

Location of γ -ray emission and magnetic field strengths in OJ 287

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

Hodgson, J. A.; Krichbaum, T. P.; Marscher, A. P.

We report the γ-ray BL Lac object OJ 287 is known to exhibit inner-parsec “jet-wobbling”, high degrees of variability at all wavelengths and quasi-stationary features, including an apparent (≈100°) position-angle change in projection on the sky plane. Sub-50 micro-arcsecond resolution 86 GHz observations with the global mm-VLBI array (GMVA) supplement ongoing multi-frequency VLBI blazar monitoring at lower frequencies. Using these maps, together with cm/mm total intensity and γ-ray observations from Fermi-LAT from 2008-2014, we aim to Observations with the GMVA offer approximately double the angular resolution compared with 43 GHz VLBA observations and enable us to observe above the synchrotronmore » self-absorption peak frequency. Fermi-LAT γ-ray data were reduced and analysed. The jet was spectrally decomposed at multiple locations along the jet. From this, we could derive estimates of the magnetic field using equipartition and synchrotron self-absorption arguments. How the field decreases down the jet provided an estimate of the distance to the jet apex and an estimate of the magnetic field strength at the jet apex and in the broad line region. Combined with accurate kinematics, we attempt to locate the site of γ-ray activity, radio flares, and spectral changes. Strong γ-ray flares appeared to originate from either the so-called core region, a downstream stationary feature, or both, with γ-ray activity significantly correlated with radio flaring in the downstream quasi-stationary feature. Magnetic field estimates were determined at multiple locations along the jet, with the magnetic field found to be ≥1.6 G in the core and ≤0.4 G in the downstream quasi-stationary feature. Finally, we therefore found upper limits on the location of the VLBI core as ≲6.0 pc from the jet apex and determined an upper limit on the magnetic field near the jet base of the order of thousands of Gauss.« less

Students' performance in accounting: differential effect of field dependence-independence as a learning style.

PubMed

Bernardi, Richard A

2003-08-01

This study examined the differential moderating effects associated with field dependence-independence and perceptions of stress on students' performance after controlling for SAT Mathematics and Verbal scores as well as students' actual effort on homework. The average performance of 178 third-year accounting majors over three examinations was used to evaluate their understanding of financial accounting. The students also took the Group Embedded Figures Test. While the data indicate that the most significant variables were students' effort, SAT Verbal scores, and their perceptions of stress, these variables were differentially associated with students' performance depending upon whether the student was classified as a field-independent or field-dependent learner.

Magnetic field induced optical gain in a dilute nitride quaternary semiconductor quantum dot

NASA Astrophysics Data System (ADS)

Mageshwari, P. Uma; Peter, A. John; Lee, Chang Woo

2016-10-01

Effects of magnetic field strength on the electronic and optical properties are brought out in a Ga0.661In0.339N0.0554As0.9446/GaAs quantum dot for the applications of desired wavelength in opto-electronic devices. The band alignment is obtained using band anticrossing model and the model solid theory. The magnetic field dependent electron-heavy hole transition energies with the dot radius in a GaInNAs/GaAs quantum dot are investigated. The magnetic field induced oscillator strength as a function of dot radius is studied. The resonant peak values of optical absorption coefficients and the changes of refractive index with the application of magnetic field strength in a GaInNAs/GaAs quantum dot are obtained. The magnetic field induced threshold current density and the maximum optical gain are found in a GaInNAs/GaAs quantum dot. The results show that the optimum wavelength for fibre optical communication networks can be obtained with the variation of applied magnetic field strength and the outcomes may be useful for the design of efficient lasers based on the group III-N-V semiconductors.

The consequences of improperly describing oscillator strengths beyond the electric dipole approximation.

PubMed

Lestrange, Patrick J; Egidi, Franco; Li, Xiaosong

2015-12-21

The interaction between a quantum mechanical system and plane wave light is usually modeled within the electric dipole approximation. This assumes that the intensity of the incident field is constant over the length of the system and transition probabilities are described in terms of the electric dipole transition moment. For short wavelength spectroscopies, such as X-ray absorption, the electric dipole approximation often breaks down. Higher order multipoles are then included to describe transition probabilities. The square of the magnetic dipole and electric quadrupole are often included, but this results in an origin-dependent expression for the oscillator strength. The oscillator strength can be made origin-independent if all terms through the same order in the wave vector are retained. We will show the consequences and potential pitfalls of using either of these two expressions. It is shown that the origin-dependent expression may violate the Thomas-Reiche-Kuhn sum rule and the origin-independent expression can result in negative transition probabilities.

The consequences of improperly describing oscillator strengths beyond the electric dipole approximation

NASA Astrophysics Data System (ADS)

Lestrange, Patrick J.; Egidi, Franco; Li, Xiaosong

2015-12-01

The interaction between a quantum mechanical system and plane wave light is usually modeled within the electric dipole approximation. This assumes that the intensity of the incident field is constant over the length of the system and transition probabilities are described in terms of the electric dipole transition moment. For short wavelength spectroscopies, such as X-ray absorption, the electric dipole approximation often breaks down. Higher order multipoles are then included to describe transition probabilities. The square of the magnetic dipole and electric quadrupole are often included, but this results in an origin-dependent expression for the oscillator strength. The oscillator strength can be made origin-independent if all terms through the same order in the wave vector are retained. We will show the consequences and potential pitfalls of using either of these two expressions. It is shown that the origin-dependent expression may violate the Thomas-Reiche-Kuhn sum rule and the origin-independent expression can result in negative transition probabilities.

Non-bridging Oxygen and Five-coordinated Aluminum in Aluminosilicate Glasses: A Cation Field Strength Study

NASA Astrophysics Data System (ADS)

Thompson, L. M.; Stebbins, J. F.

2011-12-01

Linda M. Thompson Jonathan F. Stebbins Dept. of Geological and Environmental Sciences, Stanford University, Stanford CA 94305 Although it is understood in aluminosilicate melts and glasses that non-bridging oxygens (NBO) have significant influence on thermodynamic and transport properties, questions remain about its role and the extent of its influence, particularly in metaluminous and peraluminous compositions. One major question persists regarding whether the formation of NBO is in any way coupled with the formation of VAl (AlO5), which is significantly impacted by cation field strength (defined as the cation charge divided by the square of the distance between the cation and oxygen atoms) (Kelsey et al., 2009). Previous work on calcium and potassium aluminosilicate glasses has shown the presence of NBO on the metaluminous join and persisting into the peraluminous region, with significantly more NBO present in Ca glasses compared to K glasses of similar composition (Thompson and Stebbins, 2011). However, it is unclear if there is any systematic impact on NBO content by cation field strength similar to the impact on VAl. Expanding on the previous study, barium aluminosilicate glasses were synthesized covering a range of compositions crossing the metaluminous (e.g. BaAl2O4-SiO2) join to observe changes in the NBO for comparison against the calcium aluminosilicate glasses, thus looking at the impact of cation size on NBO versus cation charge. In the barium glasses on the 30 mol% SiO2 isopleth, the highest NBO content was 6.9% for the barium rich glass (R = 0.51, where R is Ba2+ / (Ba2+ + 2Al3+)) while the most peraluminous glass (R = 0.45) had an NBO content of 1.9%. Comparison of these results to earlier data shows these numbers are similar to what is observed in the Ca glasses, indicating cation size alone does not have a significant impact on NBO content. However the VAl content does show a decrease (compared to calcium aluminosilicate glasses at similar R values

Potential and flux field landscape theory. I. Global stability and dynamics of spatially dependent non-equilibrium systems.

PubMed

Wu, Wei; Wang, Jin

2013-09-28

We established a potential and flux field landscape theory to quantify the global stability and dynamics of general spatially dependent non-equilibrium deterministic and stochastic systems. We extended our potential and flux landscape theory for spatially independent non-equilibrium stochastic systems described by Fokker-Planck equations to spatially dependent stochastic systems governed by general functional Fokker-Planck equations as well as functional Kramers-Moyal equations derived from master equations. Our general theory is applied to reaction-diffusion systems. For equilibrium spatially dependent systems with detailed balance, the potential field landscape alone, defined in terms of the steady state probability distribution functional, determines the global stability and dynamics of the system. The global stability of the system is closely related to the topography of the potential field landscape in terms of the basins of attraction and barrier heights in the field configuration state space. The effective driving force of the system is generated by the functional gradient of the potential field alone. For non-equilibrium spatially dependent systems, the curl probability flux field is indispensable in breaking detailed balance and creating non-equilibrium condition for the system. A complete characterization of the non-equilibrium dynamics of the spatially dependent system requires both the potential field and the curl probability flux field. While the non-equilibrium potential field landscape attracts the system down along the functional gradient similar to an electron moving in an electric field, the non-equilibrium flux field drives the system in a curly way similar to an electron moving in a magnetic field. In the small fluctuation limit, the intrinsic potential field as the small fluctuation limit of the potential field for spatially dependent non-equilibrium systems, which is closely related to the steady state probability distribution functional, is

Quantitative susceptibility mapping across two clinical field strengths: Contrast-to-noise ratio enhancement at 1.5T.

PubMed

Ippoliti, Matteo; Adams, Lisa C; Winfried, Brenner; Hamm, Bernd; Spincemaille, Pascal; Wang, Yi; Makowski, Marcus R

2018-04-16

Quantitative susceptibility mapping (QSM) is an MRI postprocessing technique that allows quantification of the spatial distribution of tissue magnetic susceptibility in vivo. Contributing sources include iron, blood products, calcium, myelin, and lipid content. To evaluate the reproducibility and consistency of QSM across clinical field strengths of 1.5T and 3T and to optimize the contrast-to-noise ratio (CNR) at 1.5T through bandwidth tuning. Prospective. Sixteen healthy volunteers (10 men, 6 women; age range 24-37; mean age 27.8 ± 3.2 years). 1.5T and 3T systems from the same vendor. Four spoiled gradient echo (SPGR) sequences were designed with different acquisition bandwidths. QSM reconstruction was achieved through a nonlinear morphology-enabled dipole inversion (MEDI) algorithm employing L1 regularization. CNR was calculated in seven regions of interest (ROIs), while reproducibility and consistency of QSM measurements were evaluated through voxel-based and region-specific linear correlation analyses and Bland-Altman plots. Interclass correlation, Wilcoxon rank sum test, linear regression analysis, Bland-Altman analysis, Welch's t-test. CNR analysis showed a statistically significant (P < 0.05) increase in four out of seven ROIs for the lowest bandwidth employed with respect to the highest (25.18% increase in CNR of caudate nucleus). All sequences reported an excellent correlation across field strength and bandwidth variation (R ≥ 0.96, widest limits of agreement from -18.7 to 25.8 ppb) in the ROI-based analysis, while the correlation was found to be good for the voxel-based analysis of averaged maps (R ≥ 0.90, widest limits of agreement from -9.3 to 9.1 ppb). CNR of QSM images reconstructed from 1.5T acquisitions can be enhanced through bandwidth tuning. MEDI-based QSM reconstruction demonstrated to be reproducible and consistent both across field strengths (1.5T and 3T) and bandwidth variation. 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018

Study Centres: Key to Success of Field Dependent Learners in Africa.

ERIC Educational Resources Information Center

Wilson, Charles D.

The literature indicates that Field Independent (FI) learners are more likely than Field Dependent (FD) learners to succeed at distance education. The question can be raised: How can distance education serve people in the developing world--most of whom are probably FD? It is the author's opinion that in order for FD learners to succeed at distance…

The Field Dependence-Independence Construct: Some, One, or None.

ERIC Educational Resources Information Center

Linn, Marcia C.; Kyllonen, Patrick

The field dependency/independency construct (FDI) was measured using tests of perception of the upright such as the Rod and Frame Test (RFT) and tests of cognitive restructuring such as the Hidden Figures Test (HFT); relationships between cognitive restructing and perception of the upright were investigated. High school seniors received 34 tests…

Chairside CAD/CAM materials. Part 2: Flexural strength testing.

PubMed

Wendler, Michael; Belli, Renan; Petschelt, Anselm; Mevec, Daniel; Harrer, Walter; Lube, Tanja; Danzer, Robert; Lohbauer, Ulrich

2017-01-01

Strength is one of the preferred parameters used in dentistry for determining clinical indication of dental restoratives. However, small dimensions of CAD/CAM blocks limit reliable measurements with standardized uniaxial bending tests. The objective of this study was to introduce the ball-on-three-ball (B3B) biaxial strength test for dental for small CAD/CAM block in the context of the size effect on strength predicted by the Weibull theory. Eight representative chairside CAD/CAM materials ranging from polycrystalline zirconia (e.max ZirCAD, Ivoclar-Vivadent), reinforced glasses (Vitablocs Mark II, VITA; Empress CAD, Ivoclar-Vivadent) and glass-ceramics (e.max CAD, Ivoclar-Vivadent; Suprinity, VITA; Celtra Duo, Dentsply) to hybrid materials (Enamic, VITA; Lava Ultimate, 3M ESPE) have been selected. Specimens were prepared with highly polished surfaces in rectangular plate (12×12×1.2mm 3 ) or round disc (Ø=12mm, thickness=1.2mm) geometries. Specimens were tested using the B3B assembly and the biaxial strength was determined using calculations derived from finite element analyses of the respective stress fields. Size effects on strength were determined based on results from 4-point-bending specimens. A good agreement was found between the biaxial strength results for the different geometries (plates vs. discs) using the B3B test. Strength values ranged from 110.9MPa (Vitablocs Mark II) to 1303.21MPa (e.max ZirCAD). The strength dependency on specimen size was demonstrated through the calculated effective volume/surface. The B3B test has shown to be a reliable and simple method for determining the biaxial strength restorative materials supplied as small CAD/CAM blocks. A flexible solution was made available for the B3B test in the rectangular plate geometry. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Flow Transitions in a Rotating Magnetic Field

NASA Technical Reports Server (NTRS)

Volz, M. P.; Mazuruk, K.

1996-01-01

Critical Rayleigh numbers have been measured in a liquid metal cylinder of finite height in the presence of a rotating magnetic field. Several different stability regimes were observed, which were determined by the values of the Rayleigh and Hartmann numbers. For weak rotating magnetic fields and small Rayleigh numbers, the experimental observations can be explained by the existence of a single non-axisymmetric meridional roll rotating around the cylinder, driven by the azimuthal component of the magnetic field. The measured dependence of rotational velocity on magnetic field strength is consistent with the existence of laminar flow in this regime.

Applicability of post-ionization theory to laser-assisted field evaporation of magnetite

DOE PAGES

Schreiber, Daniel K.; Chiaramonti, Ann N.; Gordon, Lyle M.; ...

2014-12-15

Analysis of the mean Fe ion charge state from laser-assisted field evaporation of magnetite (Fe3O4) reveals unexpected trends as a function of laser pulse energy that break from conventional post-ionization theory for metals. For Fe ions evaporated from magnetite, the effects of post-ionization are partially offset by the increased prevalence of direct evaporation into higher charge states with increasing laser pulse energy. Therefore the final charge state is related to both the field strength and the laser pulse energy, despite those variables themselves being intertwined when analyzing at a constant detection rate. Comparison of data collected at different base temperaturesmore » also show that the increased prevalence of Fe2+ at higher laser energies is possibly not a direct thermal effect. Conversely, the ratio of 16O+:16O2+ is well-correlated with field strength and unaffected by laser pulse energy on its own, making it a better overall indicator of the field evaporation conditions than the mean Fe charge state. Plotting the normalized field strength versus laser pulse energy also elucidates a non-linear dependence, in agreement with previous observations on semiconductors, that suggests a field-dependent laser absorption efficiency. Together these observations demonstrate that the field evaporation process for laser-pulsed oxides exhibits fundamental differences from metallic specimens that cannot be completely explained by post-ionization theory. Further theoretical studies, combined with detailed analytical observations, are required to understand fully the field evaporation process of non-metallic samples.« less

Experimental investigation of the temperature dependence of polycrystalline ice strength and resistance to low-velocity impacts with application to Titan

NASA Astrophysics Data System (ADS)

Polito, P. J.; Litwin, K.; Zygielbaum, B. R.; Sklar, L. S.; Collins, G. C.

2009-12-01

Images from Cassini and Huygens reveal widespread fluvial dissection of Titan’s surface, where incision by low-velocity impacts of bedload sediments may be a dominant mechanism, much like fluvial systems on Earth. Models of fluvial erosion dynamics on Titan are currently limited by a lack of data on ice resistance to abrasive wear at ultra-low temperatures. Using the theoretical framework of a terrestrial bedrock incision model, we seek to quantify the temperature dependence of the abrasion resistance of ice. We use the saltation-abrasion model to calculate a non-dimensional abrasion resistance coefficient, kv=2ɛvE/σt2, where ɛv is the impact kinetic energy to detach a unit volume of material, E is the elastic modulus, and σt is the tensile strength. Here we present results of a laboratory investigation of the tensile strength and erodibility of polycrystalline water-ice at temperatures ranging from 270 K down to 135 K. We make ice samples by grinding small amounts clear ice in a snow-cone machine, pack the seed grains into a modified 55-gallon drum, and add near-freezing distilled water to make a large cylindrical block. We placed ice samples in an insulated box in a walk-in freezer. We chilled the samples with a combination of dry ice and liquid nitrogen to achieve a wide range of experimental conditions and eroded the samples by dropping limestone and ice clasts from 10 cm above, 500 drops per trial. We measured the volume of ice eroded using a topographic laser-scanning system. By taking a series of obliquely oriented photographs of a laser line shining on the ice surface, we created a topographic map. Subtracting subsequent scans, we were able to quantify volumetric changes between scans. We eroded two ice samples (A and B) at varying temperatures and calculated the temperature dependence of the kinetic energy required to detach a unit volume of ice (ɛv). We measured tensile strength (σt) using the Brazil tensile splitting method at temperatures

Nonequilibrium itinerant-electron magnetism: A time-dependent mean-field theory

NASA Astrophysics Data System (ADS)

Secchi, A.; Lichtenstein, A. I.; Katsnelson, M. I.

2016-08-01

We study the dynamical magnetic susceptibility of a strongly correlated electronic system in the presence of a time-dependent hopping field, deriving a generalized Bethe-Salpeter equation that is valid also out of equilibrium. Focusing on the single-orbital Hubbard model within the time-dependent Hartree-Fock approximation, we solve the equation in the nonequilibrium adiabatic regime, obtaining a closed expression for the transverse magnetic susceptibility. From this, we provide a rigorous definition of nonequilibrium (time-dependent) magnon frequencies and exchange parameters, expressed in terms of nonequilibrium single-electron Green's functions and self-energies. In the particular case of equilibrium, we recover previously known results.

MECHANICAL STRENGTH RESPONSES OF POLED LEAD ZIRCONATE TITANATE UNDER EXTREME ELECTRIC FIELD AND VARIOUS TEMPERATURE CONDITIONS

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

Wang, Hong; Matsunaga, Tadashi; Zhang, Kewei

PZT (lead zirconate titanate), particularly PZT-5A, is used in a variety of critical actuation and sensing systems because of its high Curie temperature and large piezoelectric coefficients. However, PZT is susceptible to mechanical failure. The evaluation of the mechanical strength of the material under the target working conditions is very important. This study presents part of the recent experimental developments in mechanical testing and evaluation of PZT materials at Oak Ridge National Laboratory. Ball-on-ring and four-point bending testing setups were used, with modifications made to account for testing requirements from high-level electric field and elevated temperature. The poled PZT-5A ormore » equivalent material was tested under various specimen and testing conditions. The parameters of the distribution of strengths (characteristic strength and Weibull modulus) are discussed in relation to the testing conditions. Fractographic results based on scanning electron microscopy are also presented and discussed. The related data can serve as input for the design of piezoceramic devices, not only those used in energy systems like fuel injectors in heavy-duty diesel engines, but also those used in structural health monitoring, energy harvesting, and other critical systems in aerospace and civil engineering.« less

Temperature and field dependent magnetization studies on nano-crystalline ZnFe2O4 thin films

NASA Astrophysics Data System (ADS)

Sahu, B. N.; Suresh, K. G.; Venkataramani, N.; Prasad, Shiva; Krishnan, R.

2018-05-01

Single phase nano-crystalline zinc ferrite (ZnFe2O4) thin films were deposited on fused quartz substrate using the pulsed laser deposition technique. The films were deposited at different substrate temperatures. The field dependence of magnetization at 10 K shows hysteresis loops for all the samples. Temperature dependence of the field cooled (FC) and zero field cooled (ZFC) magnetization indicated irreversible behavior between the FC and ZFC data, and the irreversibility depends on the measuring magnetic field. The thermo-magnetic irreversibility in the magnetization data is correlated with the magnitude of the applied field and the coercivity (HC) obtained from the M-H loops.

An Analysis of Strengthening Mechanisms and Rate-Dependence in a High Strength Aluminum Alloy

NASA Astrophysics Data System (ADS)

Cao, B.; Shaeffer, M.; Cadel, D.; Ramesh, K. T.; Prasad, S.

2017-11-01

We examine the strengthening mechanisms within a high-strength aluminum alloy with the objective of providing guidelines for increased strength. First, we measure the mechanical behavior of the age-hardenable Al-Cu-Mg-Ag alloy known as Al 2139 in the T8 condition, and observe strengths of 500 MPa at quasistatic strain rates and average strengths of up to 600 MPa at high strain rates. Next, we explore the reasons for the high strength of this alloy by considering the contributions of various strengthening mechanisms to the total strength of the material. Finally, we develop an analytical approach to estimating the strengthening developed through the mechanism of dislocation cutting of closely spaced plate-like semi-coherent precipitates. Our results suggest that dislocation cutting of the Ω phase is the primary strengthening mechanism in this alloy.

Axisymmetric Flow Properties for Magnetic Elements of Differing Strength

NASA Technical Reports Server (NTRS)

Rightmire-Upton, Lisa; Hathaway, David H.

2012-01-01

Aspects of the structure and dynamics of the flows in the Sun's surface shear layer remain uncertain and yet are critically important for understanding the observed magnetic behavior. In our previous studies of the axisymmetric transport of magnetic elements we found systematic changes in both the differential rotation and the meridional flow over the course of Solar Cycle 23. Here we examine how those flows depend upon the strength (and presumably anchoring depth) of the magnetic elements. Line of sight magnetograms obtained by the HMI instrument aboard SDO over the course of Carrington Rotation 2097 were mapped to heliographic coordinates and averaged over 12 minutes to remove the 5-min oscillations. Data masks were constructed based on the field strength of each mapped pixel to isolate magnetic elements of differing field strength. We used Local Correlation Tracking of the unmasked data (separated in time by 1- to 8-hours) to determine the longitudinal and latitudinal motions of the magnetic elements. We then calculated average flow velocities as functions of latitude and longitude from the central meridian for approx 600 image pairs over the 27-day rotation. Variations with longitude indicate and characterize systematic errors in the flow measurements associated with changes in the signal from disk center to limb. Removing these systematic errors reveals changes in the axisymmetric flow properties that reflect changes in flow properties with depth in the surface shear layer.

The assessment of electromagnetic field radiation exposure for mobile phone users.

PubMed

Buckus, Raimondas; Strukcinskiene, Birute; Raistenskis, Juozas

2014-12-01

During recent years, the widespread use of mobile phones has resulted in increased human ex- posure to electromagnetic field radiation and to health risks. Increased usage of mobile phones at the close proximity raises questions and doubts in safety of mobile phone users. The aim of the study was to assess an electromagnetic field radiation exposure for mobile phone users by measuring electromagnetic field strength in different settings at the distance of 1 to 30 cm from the mobile user. In this paper, the measurements of electric field strength exposure were conducted on different brand of mobile phones by the call-related factors: urban/rural area, indoor/outdoor setting and moving/stationary mode during calls. The different types of mobile phone were placed facing the field probe at 1 cm, 10 cm, 20 cm and 30 cm distance. The highest electric field strength was recorded for calls made in rural area (indoors) while the lowest electric field strength was recorded for calls made in urban area (outdoors). Calls made from a phone in a moving car gave a similar result like for indoor calls; however, calls made from a phone in a moving car exposed electric field strength two times more than that of calls in a standing (motionless) position. Electromagnetic field radiation depends on mobile phone power class and factors, like urban or rural area, outdoor or indoor, moving or motionless position, and the distance of the mobile phone from the phone user. It is recommended to keep a mobile phone in the safe distance of 10, 20 or 30 cm from the body (especially head) during the calls.

Linear-response time-dependent density-functional theory with pairing fields.

PubMed

Peng, Degao; van Aggelen, Helen; Yang, Yang; Yang, Weitao

2014-05-14

Recent development in particle-particle random phase approximation (pp-RPA) broadens the perspective on ground state correlation energies [H. van Aggelen, Y. Yang, and W. Yang, Phys. Rev. A 88, 030501 (2013), Y. Yang, H. van Aggelen, S. N. Steinmann, D. Peng, and W. Yang, J. Chem. Phys. 139, 174110 (2013); D. Peng, S. N. Steinmann, H. van Aggelen, and W. Yang, J. Chem. Phys. 139, 104112 (2013)] and N ± 2 excitation energies [Y. Yang, H. van Aggelen, and W. Yang, J. Chem. Phys. 139, 224105 (2013)]. So far Hartree-Fock and approximated density-functional orbitals have been utilized to evaluate the pp-RPA equation. In this paper, to further explore the fundamentals and the potential use of pairing matrix dependent functionals, we present the linear-response time-dependent density-functional theory with pairing fields with both adiabatic and frequency-dependent kernels. This theory is related to the density-functional theory and time-dependent density-functional theory for superconductors, but is applied to normal non-superconducting systems for our purpose. Due to the lack of the proof of the one-to-one mapping between the pairing matrix and the pairing field for time-dependent systems, the linear-response theory is established based on the representability assumption of the pairing matrix. The linear response theory justifies the use of approximated density-functionals in the pp-RPA equation. This work sets the fundamentals for future density-functional development to enhance the description of ground state correlation energies and N ± 2 excitation energies.

Experimental Examination of Intraspecific Density-Dependent Competition during the Breeding Period in Monarch Butterflies (Danaus plexippus)

PubMed Central

Flockhart, D. T. Tyler; Martin, Tara G.; Norris, D. Ryan

2012-01-01

A central goal of population ecology is to identify the factors that regulate population growth. Monarch butterflies (Danaus plexippus) in eastern North America re-colonize the breeding range over several generations that result in population densities that vary across space and time during the breeding season. We used laboratory experiments to measure the strength of density-dependent intraspecific competition on egg laying rate and larval survival and then applied our results to density estimates of wild monarch populations to model the strength of density dependence during the breeding season. Egg laying rates did not change with density but larvae at high densities were smaller, had lower survival, and weighed less as adults compared to lower densities. Using mean larval densities from field surveys resulted in conservative estimates of density-dependent population reduction that varied between breeding regions and different phases of the breeding season. Our results suggest the highest levels of population reduction due to density-dependent intraspecific competition occur early in the breeding season in the southern portion of the breeding range. However, we also found that the strength of density dependence could be almost five times higher depending on how many life-stages were used as part of field estimates. Our study is the first to link experimental results of a density-dependent reduction in vital rates to observed monarch densities in the wild and show that the effects of density dependent competition in monarchs varies across space and time, providing valuable information for developing robust, year-round population models in this migratory organism. PMID:22984614

Spin-dependent Seebeck effects in a graphene superlattice p-n junction with different shapes

NASA Astrophysics Data System (ADS)

Zhou, Benhu; Zhou, Benliang; Yao, Yagang; Zhou, Guanghui; Hu, Ming

2017-10-01

We theoretically calculate the spin-dependent transmission probability and spin Seebeck coefficient for a zigzag-edge graphene nanoribbon p-n junction with periodically attached stubs under a perpendicular magnetic field and a ferromagnetic insulator. By using the nonequilibrium Green’s function method combining with the tight-binding Hamiltonian, it is demonstrated that the spin-dependent transmission probability and spin Seebeck coefficient for two types of superlattices can be modulated by the potential drop, the magnetization strength, the number of periods of the superlattice, the strength of the perpendicular magnetic field, and the Anderson disorder strength. Interestingly, a metal to semiconductor transition occurs as the number of the superlattice for a crossed superlattice p-n junction increases, and its spin Seebeck coefficient is much larger than that for the T-shaped one around the zero Fermi energy. Furthermore, the spin Seebeck coefficient for crossed systems can be much pronounced and their maximum absolute value can reach 528 μV K-1 by choosing optimized parameters. Besides, the spin Seebeck coefficient for crossed p-n junction is strongly enhanced around the zero Fermi energy for a weak magnetic field. Our results provide theoretical references for modulating the thermoelectric properties of a graphene superlattice p-n junction by tuning its geometric structure and physical parameters.

SU-E-T-590: Optimizing Magnetic Field Strengths with Matlab for An Ion-Optic System in Particle Therapy Consisting of Two Quadrupole Magnets for Subsequent Simulations with the Monte-Carlo Code FLUKA

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

Baumann, K; Weber, U; Simeonov, Y

Purpose: Aim of this study was to optimize the magnetic field strengths of two quadrupole magnets in a particle therapy facility in order to obtain a beam quality suitable for spot beam scanning. Methods: The particle transport through an ion-optic system of a particle therapy facility consisting of the beam tube, two quadrupole magnets and a beam monitor system was calculated with the help of Matlab by using matrices that solve the equation of motion of a charged particle in a magnetic field and field-free region, respectively. The magnetic field strengths were optimized in order to obtain a circular andmore » thin beam spot at the iso-center of the therapy facility. These optimized field strengths were subsequently transferred to the Monte-Carlo code FLUKA and the transport of 80 MeV/u C12-ions through this ion-optic system was calculated by using a user-routine to implement magnetic fields. The fluence along the beam-axis and at the iso-center was evaluated. Results: The magnetic field strengths could be optimized by using Matlab and transferred to the Monte-Carlo code FLUKA. The implementation via a user-routine was successful. Analyzing the fluence-pattern along the beam-axis the characteristic focusing and de-focusing effects of the quadrupole magnets could be reproduced. Furthermore the beam spot at the iso-center was circular and significantly thinner compared to an unfocused beam. Conclusion: In this study a Matlab tool was developed to optimize magnetic field strengths for an ion-optic system consisting of two quadrupole magnets as part of a particle therapy facility. These magnetic field strengths could subsequently be transferred to and implemented in the Monte-Carlo code FLUKA to simulate the particle transport through this optimized ion-optic system.« less

Ecological change points: The strength of density dependence and the loss of history.

PubMed

Ponciano, José M; Taper, Mark L; Dennis, Brian

2018-05-01

Change points in the dynamics of animal abundances have extensively been recorded in historical time series records. Little attention has been paid to the theoretical dynamic consequences of such change-points. Here we propose a change-point model of stochastic population dynamics. This investigation embodies a shift of attention from the problem of detecting when a change will occur, to another non-trivial puzzle: using ecological theory to understand and predict the post-breakpoint behavior of the population dynamics. The proposed model and the explicit expressions derived here predict and quantify how density dependence modulates the influence of the pre-breakpoint parameters into the post-breakpoint dynamics. Time series transitioning from one stationary distribution to another contain information about where the process was before the change-point, where is it heading and how long it will take to transition, and here this information is explicitly stated. Importantly, our results provide a direct connection of the strength of density dependence with theoretical properties of dynamic systems, such as the concept of resilience. Finally, we illustrate how to harness such information through maximum likelihood estimation for state-space models, and test the model robustness to widely different forms of compensatory dynamics. The model can be used to estimate important quantities in the theory and practice of population recovery. Copyright © 2018 Elsevier Inc. All rights reserved.

The coil orientation dependency of the electric field induced by TMS for M1 and other brain areas.

PubMed

Janssen, Arno M; Oostendorp, Thom F; Stegeman, Dick F

2015-05-17

The effectiveness of transcranial magnetic stimulation (TMS) depends highly on the coil orientation relative to the subject's head. This implies that the direction of the induced electric field has a large effect on the efficiency of TMS. To improve future protocols, knowledge about the relationship between the coil orientation and the direction of the induced electric field on the one hand, and the head and brain anatomy on the other hand, seems crucial. Therefore, the induced electric field in the cortex as a function of the coil orientation has been examined in this study. The effect of changing the coil orientation on the induced electric field was evaluated for fourteen cortical targets. We used a finite element model to calculate the induced electric fields for thirty-six coil orientations (10 degrees resolution) per target location. The effects on the electric field due to coil rotation, in combination with target site anatomy, have been quantified. The results confirm that the electric field perpendicular to the anterior sulcal wall of the central sulcus is highly susceptible to coil orientation changes and has to be maximized for an optimal stimulation effect of the motor cortex. In order to obtain maximum stimulation effect in areas other than the motor cortex, the electric field perpendicular to the cortical surface in those areas has to be maximized as well. Small orientation changes (10 degrees) do not alter the induced electric field drastically. The results suggest that for all cortical targets, maximizing the strength of the electric field perpendicular to the targeted cortical surface area (and inward directed) optimizes the effect of TMS. Orienting the TMS coil based on anatomical information (anatomical magnetic resonance imaging data) about the targeted brain area can improve future results. The standard coil orientations, used in cognitive and clinical neuroscience, induce (near) optimal electric fields in the subject-specific head model in

Residual strength of GFR/POM as a function of damage

NASA Astrophysics Data System (ADS)

Zachariev, G.; Rudolph, H.-V.; Ivers, H.

2010-07-01

A relation between the residual strength and the dispersed damage accumulated in a short fiber reinforced polyoximethylene (GFR/POM) samples under tension is found. For that purpose dependencies of damage and residual strength on loading percentage are used. Damage as a function of loading percentage is known for the material under study. To find the dependency of residual strength on loading percentage a subsidiary function is introduced and a method is proposed for determination of the parameters in the dependency on the basis of the experimental data. Both damage and residual strength are measured after unloading samples that have been loaded applying different loading percentages. Damage is the accumulation of new internal surfaces that arise under mechanical loading in the whole volume of the material. They are registered by a new original method of X-ray refraction. The analytical relation between the residual strength and damage accumulated is compared to the experimental results found for the residual strength under different damage degrees.

Sources of strength-training information and strength-training behavior among Japanese older adults.

PubMed

Harada, Kazuhiro; Shibata, Ai; Lee, Euna; Oka, Koichiro; Nakamura, Yoshio

2016-03-01

The promotion of strength training is now recognized as an important component of public health initiatives for older adults. To develop successful communication strategies to increase strength-training behavior among older adults, the identification of effective communication channels to reach older adults is necessary. This study aimed to identify the information sources about strength training that were associated with strength-training behaviors among Japanese older adults. The participants were 1144 adults (60-74 years old) randomly sampled from the registry of residential addresses. A cross-sectional questionnaire survey was conducted. The independent variables were sources of strength-training information (healthcare providers, friends, families, radio, television, newspapers, newsletters, posters, books, magazines, booklets, the Internet, lectures, other sources), and the dependent variable was regular strength-training behavior. Logistic regression analysis was used to identify potential relationships. After adjusting for demographic factors and all other information sources, strength-training information from healthcare providers, friends, books and the Internet were positively related to regular strength-training behavior. The findings of the present study contribute to a better understanding of strength-training behavior and the means of successful communication directed at increasing strength training among older adults. The results suggest that healthcare providers, friends, books and the Internet are effective methods of communication for increasing strength-training behaviors among older adults. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Finite-size scaling with respect to interaction and disorder strength at the many-body localization transition

NASA Astrophysics Data System (ADS)

Kudo, Kazue; Deguchi, Tetsuo

2018-06-01

We present a finite-size scaling for both interaction and disorder strengths in the critical regime of the many-body localization (MBL) transition for a spin-1/2 X X Z spin chain with a random field by studying level statistics. We show how the dynamical transition from the thermal to MBL phase depends on interaction together with disorder by evaluating the ratio of adjacent level spacings, and thus, extend previous studies in which interaction coupling is fixed. We introduce an extra critical exponent in order to describe the nontrivial interaction dependence of the MBL transition. It is characterized by the ratio of the disorder strength to the power of the interaction coupling with respect to the extra critical exponent and not by the simple ratio between them.

Image Charge and Electric Field Effects on Hydrogen-like Impurity-bound Polaron Energies and Oscillator Strengths in a Quantum Dot

NASA Astrophysics Data System (ADS)

Vardanyan, L. A.; Vartanian, A. L.; Asatryan, A. L.; Kirakosyan, A. A.

2016-11-01

By using Landau-Pekar variational method, the ground and the first excited state energies and the transition frequencies between the ground and the first excited states of a hydrogen-like impurity-bound polaron in a spherical quantum dot (QD) have been studied by taking into account the image charge effect (ICE). We employ the dielectric continuum model to describe the phonon confinement effects. The oscillator strengths (OSs) of transitions from the 1 s-like state to excited states of 2 s, 2 p x , and 2 p z symmetries are calculated as functions of the applied electric field and strength of the confinement potential. We have shown that with and without image charge effect, the increase of the strength of the parabolic confinement potential leads to the increase of the oscillator strengths of 1 s - 2 p x and 1 s - 2 p z transitions. This indicates that the energy differences between 1 s- and 2 p x - as well as 1 s- and 2 p z -like states have a dominant role determining the oscillator strength. Although there is almost no difference in the oscillator strengths for transitions 1 s - 2 p x and 1 s -2 p z when the image charge effect is not taken into account, it becomes significant with the image charge effect.

Dependence of the microwave surface resistance of superconducting niobium on the magnitude of the rf field

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

Romanenko, A.; Grassellino, A.

Utilizing difference in temperature dependencies we decoupled Bardeen-Cooper-Schrieffer (BCS) and residual components of the microwave surface resistance of superconducting niobium at all rf fields up to B{sub rf}{approx}115 mT. We reveal that the residual resistance decreases with field at B{sub rf} Less-Than-Or-Equivalent-To 40 mT and strongly increases in chemically treated niobium at B{sub rf}>80 mT. We find that BCS surface resistance is weakly dependent on field in the clean limit, whereas a strong and peculiar field dependence emerges after 120 Degree-Sign C vacuum baking.

Field dependence of interface-trap buildup in polysilicon and metal gate MOS devices

NASA Astrophysics Data System (ADS)

Shaneyfelt, M. R.; Schwank, J. R.; Fleetwood, D. M.; Winokur, P. S.; Hughes, K. L.

1990-12-01

The electric field dependence of radiation-induced oxide- and interface-trap charge (Delta Vot and Delta Vit) generation for polysilicon- and metal-gate MOS transistors is investigated at electric fields (Eox) from -4.2 MV/cm to +4.7 MV/cm. If electron-hole recombination effects are taken into account, the absolute value of Delta Vot and the saturated value of Delta Vit for both polysilicon- and metal-gate transistors are shown to follow an approximate E exp -1/2 field dependence for Eox = 0.4 MV/cm or greater. An E exp -1/2 dependence for the saturated value of Delta Vit was also observed for negative-bias irradiation followed by a constant positive-bias anneal. The E exp -1/2 field dependence observed suggests that the total number of interface traps created in these devices may be determined by hole trapping near the Si/SiO2 interface for positive-bias irradiation or near the gate/SiO2 interface for negative bias irradiation, though H+ drift remains the likely rate-limiting step in the process. Based on these results, a hole-trapping/hydrogen transport model-involving hole trapping and subsequent near-interfacial H+ release, transport, and reaction at the interface-is proposed as a possible explanation of Delta Vit buildup in these polysilicon- and metal-gate transistors.

Dielectric strength, swelling and weight loss of the ITER Toroidal Field Model Coil insulation after low temperature reactor irradiation

NASA Astrophysics Data System (ADS)

Humer, K.; Weber, H. W.; Hastik, R.; Hauser, H.; Gerstenberg, H.

2000-04-01

The insulation system for the Toroidal Field Model Coil of ITER is a fiber reinforced plastic (FRP) laminate, which consists of a combined Kapton/R-glass-fiber reinforcement tape, vacuum-impregnated with an epoxy DGEBA system. Pure disk shaped laminates, FRP/stainless-steel sandwiches, and conductor insulation prototypes were irradiated at 5 K in a fission reactor up to a fast neutron fluence of 10 22 m -2 ( E>0.1 MeV) to investigate the radiation induced degradation of the dielectric strength of the insulation system. After warm-up to room temperature, swelling, weight loss, and the breakdown strength were measured at 77 K. The sandwich swells by 4% at a fluence of 5×10 21 m-2 and by 9% at 1×10 22 m-2. The weight loss of the FRP is 2% at 1×10 22 m-2. The dielectric strength remained unchanged over the whole dose range.

Kerr electro-optic field mapping study of the effect of charge injection on the impulse breakdown strength of transformer oil

NASA Astrophysics Data System (ADS)

Zhang, X.; Zahn, M.

2013-10-01

The smart use of charge injection to improve breakdown strength in transformer oil is demonstrated in this paper. Hypothetically, bipolar homo-charge injection with reduced electric field at both electrodes may allow higher voltage operation without insulation failure, since electrical breakdown usually initiates at the electrode-dielectric interfaces. To find experimental evidence, the applicability and limitation of the hypothesis is first analyzed. Impulse breakdown tests and Kerr electro-optic field mapping measurements are then conducted with different combinations of parallel-plate aluminum and brass electrodes stressed by millisecond duration impulse. It is found that the breakdown voltage of brass anode and aluminum cathode is ˜50% higher than that of aluminum anode and brass cathode. This can be explained by charge injection patterns from Kerr measurements under a lower voltage, where aluminum and brass electrodes inject negative and positive charges, respectively. This work provides a feasible approach to investigating the effect of electrode material on breakdown strength.

Proton and multinuclear magnetic resonance spectroscopy in the human brain at ultra-high field strength: A review.

PubMed

Henning, Anke

2018-03-01

Magnetic Resonance Spectroscopy (MRS) allows for a non-invasive and non-ionizing determination of in vivo tissue concentrations and metabolic turn-over rates of more than 20 metabolites and compounds in the central nervous system of humans. The aim of this review is to give a comprehensive overview about the advantages, challenges and advances of ultra-high field MRS with regard to methodological development, discoveries and applications from its beginnings around 15 years ago up to the current state. The review is limited to human brain and spinal cord application at field strength of 7T and 9.4T and includes all relevant nuclei ( 1 H, 31 P, 13 C). Copyright © 2017 Elsevier Inc. All rights reserved.

Reactive Strength Index: A Poor Indicator of Reactive Strength?

PubMed

Healy, Robin; Kenny, Ian; Harrison, Drew

2017-11-28

The primary aim was to assess the relationships between reactive strength measures and associated kinematic and kinetic performance variables achieved during drop jumps. A secondary aim was to highlight issues with the use of reactive strength measures as performance indicators. Twenty eight national and international level sprinters, consisting of fourteen men and women, participated in this cross-sectional analysis. Athletes performed drop jumps from a 0.3 m box onto a force platform with dependent variables contact time (CT), landing time (TLand), push-off time (TPush), flight time (FT), jump height (JH), reactive strength index (RSI, calculated as JH / CT), reactive strength ratio (RSR, calculated as FT / CT) and vertical leg spring stiffness (Kvert) recorded. Pearson's correlation test found very high to near perfect relationships between RSI and RSR (r = 0.91 to 0.97), with mixed relationships found between RSI, RSR and the key performance variables, (Men: r = -0.86 to -0.71 between RSI/RSR and CT, r = 0.80 to 0.92 between RSI/RSR and JH; Women: r = -0.85 to -0.56 between RSR and CT, r = 0.71 between RSI and JH). This study demonstrates that the method of assessing reactive strength (RSI versus RSR) may be influenced by the performance strategies adopted i.e. whether an athlete achieves their best reactive strength scores via low CTs, high JHs or a combination. Coaches are advised to limit the variability in performance strategies by implementing upper and / or lower CT thresholds to accurately compare performances between individuals.

Intrinsic electric fields and proton diffusion in immobilized protein membranes. Effects of electrolytes and buffers.

PubMed Central

Zabusky, N J; Deem, G S

1979-01-01

We present a theory for proton diffusion through an immobilized protein membrane perfused with an electrolyte and a buffer. Using a Nernst-Planck equation for each species and assuming local charge neutrality, we obtain two coupled nonlinear diffusion equations with new diffusion coefficients dependent on the concentration of all species, the diffusion constants or mobilities of the buffers and salts, the pH-derivative of the titration curves of the mobile buffer and the immobilized protein, and the derivative with respect to ionic strength of the protein titration curve. Transient time scales are locally pH-dependent because of protonation-deprotonation reactions with the fixed protein and are ionic strength-dependent because salts provide charge carriers to shield internal electric fields. Intrinsic electric fields arise proportional to the gradient of an "effective" charge concentration. The field may reverse locally if buffer concentrations are large (greater to or equal to 0.1 M) and if the diffusivity of the electrolyte species is sufficiently small. The "ideal" electrolyte case (where each species has the same diffusivity) reduces to a simple form. We apply these theoretical considerations to membranes composed of papain and bovine serum albumin (BSA) and show that intrinsic electric fields greatly enhance the mobility of protons when the ionic strength of the salts is smaller than 0.1 M. These results are consistent with experiments where pH changes are observed to depend strongly on buffer, salt, and proton concentrations in baths adjacent to the membranes. PMID:233570

Transport in a magnetic field modulated graphene superlattice.

PubMed

Li, Yu-Xian

2010-01-13

Using the transfer matrix method, we study the transport properties through a magnetic field modulated graphene superlattice. It is found that the electrostatic barrier, the magnetic vector potential, and the number of wells in a superlattice modify the transmission remarkably. The angular dependent transmission is blocked by the magnetic vector potential because of the appearance of the evanescent states at certain incident angles, and the region of Klein tunneling shifts to the left. The angularly averaged conductivities exhibit oscillatory behavior. The magnitude and period of oscillation depend sensitively on the height of the electrostatic barrier, the number of wells, and the strength of the modulated magnetic field.

Dependence of neoclassical toroidal viscosity on the poloidal spectrum of applied nonaxisymmetric fields