Behavior of Extra Electrons in the Liquids Methane, Ethane, and Propane

1971 ◽  
Vol 49 (6) ◽  
pp. 984-985 ◽  
Author(s):  
M. G. Robinson ◽  
P. G. Fuochi ◽  
G. R. Freeman
Keyword(s):  
Field Strength ◽  
Ion Pairs ◽  
Liquid Argon ◽  
Low Field ◽  
Electrical Conductances ◽  
Radiation Induced ◽  
Liquid Methane ◽  
Field Strengths

The radiation induced electrical conductances of liquids methane, ethane, and propane have been measured. At a field strength of 5 kV/cm the number of ion pairs collected at the electrodes per 100 eV absorbed by the liquid was 1.5 in methane (−160°), 0.20 in ethane (−90°), and 0.14 in propane (−90°). The short-lived conductance transient (k/u overshoot) observed at low field strengths in methane was 40% as large as that in argon. No transient was observable in ethane or propane. The freeness of motion of electrons in liquid methane is nearly as great as that in liquid argon and much greater than that in ethane or propane.

Excess Electrons and Positive Charge Carriers in Liquid Methane. I

1973 ◽  
Vol 28 (3-4) ◽  
pp. 511-518 ◽  
Author(s):  
George Bakale ◽  
Werner F. Schmidt
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Drift Velocity ◽  
Positive Charge ◽  
Charge Carriers ◽  
Excess Electrons ◽  
Radiation Induced ◽  
Liquid Methane ◽  
Increasing Temperature ◽  
Field Strengths

AbstractThe drift velocities of radiation-induced excess electrons and positive charge carriers in liquid methane were measured at different electric field strengths and several temperatures. For the excess electrons the drift velocity increases up to 1.5 kV cm-1 proportional to the electric field strength and a mobility of (400±50) cm2 V-1 s-1 at T = 111 °K was obtained. Above 1.5 kV cm-1 the drift velocity varies with E½. The temperature coefficient of the mobility is negative. For the positive charge carriers the measurements were carried out up to electric field strengths of 50 kV cm-1 and the drift velocity remained proportional to the field giving a mobility of (2.5 ± 0.5) · 10-3 cm2 V-1 s-1 at 7 = 111 °K. The mobility increased with increasing temperature. The reaction of excess electrons with oxygen was also studied and a rate constant of 8.4 · 1011 l mole-1 s-1 was obtained.

scholarly journals On the Validity of the Two-term Approximation of the Electron Distribution Function

1971 ◽  
Vol 24 (4) ◽  
pp. 835 ◽  
Author(s):  
RE Robson ◽  
Kailash Kumar
Keyword(s):  
Distribution Function ◽  
Field Strength ◽  
Drift Velocity ◽  
Electron Distribution ◽  
Electron Distribution Function ◽  
Polynomial Expansion ◽  
Neutral Gas ◽  
Low Field ◽  
Term Approximation ◽  
Field Strengths

The Boltzmann equation for electrons moving in a neutral gas under the influence of an externally applied field is solved by expanding the electron distribution function in terms of Legendre and Sonine polynomials. The solution is given in terms of infinite matrices which have elements ordered by the Sonine polynomial index, and which are dependent upon the field strength. From the structure of the formulae, it is possible to infer that truncation of the Legendre polynomial expansion after two terms is a good approximation at all field strengths. This is supported by calculations of the electron drift velocity at low field strengths, which show that the error introduced by making the two-term approximation is small, even when the deviation from equilibrium is significant. The convergence of the Sonine polynomial expansion is shown to be strongly depende:r;J.t upon field strength, and large matrices are required in the drift velocity formula at even small field strengths.

scholarly journals Effect of Mineral Composition on Transverse Relaxation Time Distributions and MR Imaging of Tight Rocks from Offshore Ireland

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 232
Author(s):  
Stian Almenningen ◽  
Srikumar Roy ◽  
Arif Hussain ◽  
John Georg Seland ◽  
Geir Ersland
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Mr Imaging ◽  
Field Strength ◽  
High Field ◽  
Transverse Relaxation Time ◽  
Transverse Relaxation ◽  
The Core ◽  
Low Field ◽  
Field Strengths

In this paper, we investigate the effect of magnetic field strength on the transverse relaxation time constant (T2) in six distinct core plugs from four different rock types (three sandstones, one basalt, one volcanic tuff and one siltstone), retrieved from offshore Ireland. The CPMG pulse-sequence was used at two different magnetic field strengths: high-field at 4.70 T and low-field at 0.28 T. Axial images of the core plugs were also acquired with the RAREst sequence at high magnetic field strength. Thin-sections of the core plugs were prepared for optical imaging and SEM analysis, and provided qualitative information on the porosity and quantification of the elemental composition of the rock material. The content of iron varied from 4 wt. % to close to zero in the rock samples. Nevertheless, the effective T2 distributions obtained at low-field were used to successfully predict the porosity of the core plugs. Severe signal attenuations from internal magnetic gradients resulted in an underestimation of the porosity at high-field. No definitive trend was identified on the evolution of discrete relaxation time components between magnetic field strengths. The low-field measurements demonstrate that NMR is a powerful quantitative tool for petrophysical rock analysis as compared to thin-section analysis. The results of this study are of interest to the research community who characterizes natural gas hydrates in tight heterogeneous core plugs, and who typically relies on MR imaging to distinguish between solid hydrates and fluid phases. It further exemplifies the importance of selecting appropriate magnetic field strengths when employing NMR/MRI for porosity calculation in tight rock.

The Lake Mungo geomagnetic excursion

1976 ◽  
Vol 281 (1305) ◽  
pp. 515-542 ◽  
Keyword(s):  
Field Strength ◽  
Geomagnetic Excursion ◽  
Southeastern Australia ◽  
Low Field ◽  
The World ◽  
Very High ◽  
Geomagnetic Field Strength ◽  
Different Parts ◽  
Field Strengths

Archaeomagnetic studies have been made of prehistoric aboriginal fireplaces occurring along the ancient shore of Lake Mungo, a dried out lake in southeastern Australia. Directions of magnetization preserved in ovenstones and baked hearths show that wide departures of up to 120° from the axial dipole field direction occurred about 30000 years ago. The determination of the variation in geomagnetic field strength from the baked material is complicated by non-ideal behaviour during Thellier’s double heating method. The problem appears to arise from the subsequent (postfiring) formation of iron oxyhydroxides during a period in which the water level in the lake rose. During laboratory heatings these oxyhydroxides dehydrate causing the non-ideal behaviour observed. The ancient field strengths deduced are therefore probably minimum values. The geomagnetic excursion recorded between at least 30780 ±520 and 28140 ±370 years b.p. on the conventional radiocarbon time scale is associated with very high field strengths between 1 and 2 Oe (1 Oe » 79.6 A m_ 1 ). The field strength subsequently decreased to between 0.2 and 0.3 Oe after the excursion. This main excursion is referred to as the Lake Mungo geomagnetic excursion. There is evidence that a second excursion associated with low field strengths of 0.1-0.2 Oe occurred around 26000 years b.p. A review of geomagnetic excursions less than 40 000 years in age shows that it may be premature to assume that these are world-wide synchronous features. The range of ages and their groupings in different parts of the world may indicate they are temporary non-dipole features of continental extent. However, the duration of most excursions (order of 103 years) is very similar to that of polarity transitions and this could indicate they are aborted reversals.

Effect of Electric Field Strength on the Free Ion Yields in the X-Radiolysis of Liquids: Influence of Molecular Structure and Temperature

1972 ◽  
Vol 50 (11) ◽  
pp. 1617-1626 ◽  
Author(s):  
J.-P. Dodelet ◽  
P. G. Fuochi ◽  
G. R. Freeman
Keyword(s):  
Field Strength ◽  
Liquid Argon ◽  
Separation Distance ◽  
Relative Increase ◽  
Distribution Functions ◽  
Electron Pairs ◽  
Gaussian Distribution Function ◽  
Free Ion ◽  
Liquid Methane ◽  
Ion Yields

The relative increase in the free ion yield with increasing field strength E, expressed as [Formula: see text] is smaller when the following quantities are larger: (1) dielectric constant, (2) temperature, and (3) separation distance between the geminate ion–electron pairs. The field dependence [Formula: see text] equals 9.7/εT2 cm/V at low E, but at higher fields it is affected by the above three factors and by E itself. Results obtained from the liquids propane (123–233 °K), 2-methylpropane (isobutane, 148–294 °K), 2,2-dimethylpropane (neopentane, 295 °K), argon (87 °K), oxygen (87 °K) and argon–oxygen solutions (87 °K) are presented and analyzed according to a theoretical model. Several types of ion–electron separation (y) distribution functions are tested. Within the framework of the model a power function F(> y) = yminy−x with x < 4 provides a good interpretation of the results when [Formula: see text] a Gaussian distribution function provides the best interpretation of the field effects when [Formula: see text] Either the y distribution has a Gaussian core with a more gently sloping tail, or distributions are more Gaussian-like in liquids in which the electron ranges are greater. The electron range in pure argon (b = 1300 Å) is much smaller than had been expected and is only 2.6 times greater than that in liquid methane (b = 500 Å at 120 °K). Phonon emission by 10–0.01 eV electrons in liquid argon may be relatively efficient and might involve transient states of the type [Formula: see text]

The influence of nonelectronegative molecules on the mobility of excess electrons in liquefied rare gases and tetramethylsilane

1977 ◽  
Vol 55 (11) ◽  
pp. 1885-1889 ◽  
Author(s):  
Ulrich Sowada ◽  
Werner F. Schmidt ◽  
George Bakale
Keyword(s):  
Cross Section ◽  
Drift Velocity ◽  
Collision Cross Section ◽  
Liquid Argon ◽  
Solute Concentration ◽  
Low Field ◽  
Field Mobility ◽  
Excess Electrons ◽  
Low Field Mobility ◽  
Field Strengths

Addition of nonelectronegative molecules (n-alkanes, alkenes, CO, CO2) to liquid argon, krypton, and xenon influences the drift velocity of excess electrons in an electric field. At high field strengths (104–105 V cm−1), where the electrons have mean energies exceeding kT, inelastic collisions with solute molecules lead to an increase of the drift velocity above the value of the pure solvent. Analysis of this effect yields the energy dependent product of collision cross section and mean fractional energy loss per collision.At low field strengths a decrease of the low field mobility with increasing solute concentration is observed from which the cross section for momentum transfer could be deduced. The influence of solutes on the low field mobility was also found in tetramethylsilane.

Improved Contrast in Ultra-Low-Field MRI with Time-Dependent Bipolar Prepolarizing Fields: Theory and NMR Demonstrations

2013 ◽  
Vol 20 (3) ◽  
pp. 327-336 ◽  
Author(s):  
Jaakko O. Nieminen ◽  
Jens Voigt ◽  
Stefan Hartwig ◽  
Hans Jürgen Scheer ◽  
Martin Burghoff ◽  
...  
Keyword(s):  
Field Strength ◽  
Time Course ◽  
Signal Strength ◽  
Relaxation Rates ◽  
Resonance Imaging ◽  
New Approach ◽  
Spin Lattice ◽  
Low Field ◽  
Low Field Mri ◽  
Magnetic Resonance Imaging Mri

Abstract The spin-lattice (T1) relaxation rates of materials depend on the strength of the external magnetic field in which the relaxation occurs. This T1 dispersion has been suggested to offer a means to discriminate between healthy and cancerous tissue by performing magnetic resonance imaging (MRI) at low magnetic fields. In prepolarized ultra-low-field (ULF) MRI, spin precession is detected in fields of the order of 10-100 μT. To increase the signal strength, the sample is first magnetized with a relatively strong polarizing field. Typically, the polarizing field is kept constant during the polarization period. However, in ULF MRI, the polarizing-field strength can be easily varied to produce a desired time course. This paper describes how a novel variation of the polarizing-field strength and duration can optimize the contrast between two types of tissue having different T1 relaxation dispersions. In addition, NMR experiments showing that the principle works in practice are presented. The described procedure may become a key component for a promising new approach of MRI at ultra-low fields

Characteristics of Magnetic Resonance Sequences Used for Imaging Silicone Gel, Saline, and Gel-Saline Implants at Low Field Strengths

1994 ◽  
Vol 29 (8) ◽  
pp. 781-786 ◽  
Author(s):  
STEVEN FRANKEL ◽  
KATHRYN OCCHIPINTI ◽  
LEON KAUFMAN ◽  
DAVID KRAMER ◽  
JOSEPH CARLSON ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Silicone Gel ◽  
Low Field ◽  
Field Strengths

Comparison of High-Field-Strength Versus Low-Field-Strength MRI of the Shoulder

2003 ◽  
Vol 181 (5) ◽  
pp. 1211-1215 ◽  
Author(s):  
Thomas Magee ◽  
Marc Shapiro ◽  
David Williams
Keyword(s):  
Field Strength ◽  
High Field ◽  
High Field Strength ◽  
Low Field

Chondrolysis of the Glenohumeral Joint After Arthroscopy: Findings on Radiography and Low-Field-Strength MRI

2007 ◽  
Vol 188 (4) ◽  
pp. 1094-1098 ◽  
Author(s):  
Timothy G. Sanders ◽  
Michael B. Zlatkin ◽  
Narayan Babu Paruchuri ◽  
Robert W. Higgins
Keyword(s):  
Field Strength ◽  
Glenohumeral Joint ◽  
Low Field
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