THE EFFECTS OF PRESSURE AND MAGNETIC FIELD ON THE CONDUCTIVITY OF FeCl4 DOPED POLYACETYLENE: THE INFLUENCE OF SCATTERING BY LOW-ENERGY EXCITATIONS

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3097-3100
Author(s):  
A. N. ALESHIN ◽  
T. J. KIM ◽  
D.-S. SUH ◽  
Y. W. PARK ◽  
H. KANG ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Pressure ◽  
Hydrostatic Pressure ◽  
Ambient Pressure ◽  
Weak Localization ◽  
Low Energy ◽  
Metallic State ◽  
Dephasing Time ◽  
Two Level Systems ◽  
Resistivity Minimum

The effects of hydrostatic pressure and magnetic field on the conductivity of oriented polyacetylene films doped with FeCl 4- up to metallic state have been studied at T = 0.35-300 K. It was found that application of pressure up to 10 kBar increases the conductivity at 300 K by a factor of 1.3 and suppresses the resistivity minimum in ρ (T) at 270 - 280 K. At T < 2 K the temperature dependence of resistivity ρ (T) ~ ln T (at ambient pressure and at 10 kBar) which remains unaltered by a magnetic field up to 14 Tesla. Transverse magnetoresistance (MR) was found to be negative, linear and temperature independent at T < 2 K (at ambient and high pressure). We attribute the observed ρ (T) and MR behavior to weak localization accompanied by effect of electron dephasing time saturation due to scattering by two-level systems of a special type. More strong behavior of ρ (T) and MR at T > 2 K related to further suppression of weak localization due to scattering by low-energy excitations of a "glassy" type.

Effect of high hydrostatic pressure on the enzymic hydrolysis of β-lactoglobulin B by trypsin, thermolysin and pepsin

1996 ◽  
Vol 63 (1) ◽  
pp. 111-118 ◽  
Author(s):  
Henrik Stapelfeldt ◽  
Per Hjort Petersen ◽  
Kristian Rotvig Kristiansen ◽  
Karsten Bruun Qvist ◽  
Leif H. Skibsted
Keyword(s):  
High Pressure ◽  
Hydrostatic Pressure ◽  
High Hydrostatic Pressure ◽  
Pressure Effect ◽  
Ambient Pressure ◽  
Apparent Volume ◽  
Enzymic Hydrolysis ◽  
Ambient Conditions ◽  
Β Lactoglobulin ◽  
Hydrolysis Of

SummaryHydrolysis of β-lactoglobulin B (β-lg B) by pepsin, a process slow at ambient conditions, is facilitated at a moderately high hydrostatic pressure such as 300 MPa, corresponding to an apparent volume of activation ΔV# = −63 ml mol−1 at pH 2·5, 30 °C and Γ/2=0·16. Digestion of β-lg by trypsin and thermolysin is likewise enhanced by pressure, and the pressure effect has been traced to pressure denaturation of β-lg B, which by high-pressure fluorescence spectroscopy has been shown to have a large negative volume of reaction, ΔV° = −98 ml mol−1, at pH 6·7, 30 °C and Γ/2 = 0·16. Pressure denaturation is only slowly reversed following release of pressure and the enhanced digestibility is maintained at ambient pressure for several hours.

scholarly journals Response of Nautilus to Variation in Ambient Pressure

1988 ◽  
Vol 137 (1) ◽  
pp. 175-189 ◽  
Author(s):  
Michael Jordan ◽  
John A. Chamberlain ◽  
Rebecca B. Chamberlain
Keyword(s):  
High Pressure ◽  
Hydrostatic Pressure ◽  
Ambient Pressure ◽  
Behaviour Pattern ◽  
Pressure Sensing ◽  
Sensing Mechanism ◽  
Pressure Decrease ◽  
Hydrostatic Load ◽  
Alarm Behaviour

Juvenile Nautilus, tested in a high-pressure animal maintenance apparatus, are sensitive to increases in ambient hydrostatic pressure as small as lx105Nm−2 (= 1 atm = 100kPa). They respond to such pressure increases in a characteristic ‘depth alarm’ behaviour pattern, which consists primarily of rapid upward swimming. These activity bursts may serve to restore them to their original depth. The animals apparently continue this behaviour until fatigued. Pressure decrease elicits no obvious response. The pressure-sensing mechanism may be located within the statocyst, or possibly in the posterior mantle or siphuncle. The operation of. the latter two mechanisms involves tensional strain induced by the hydrostatic load in the outermost septum and wall of the siphuncular tube.

Electronic, Magnetic and Structural Properties of the RFeO3 Antiferromagnetic-Perovskites at Very High Pressures

2002 ◽  
Vol 718 ◽  
Author(s):  
Moshe P. Pasternak ◽  
W. M. Xu ◽  
G. Kh. Rozenberg ◽  
R. D. Taylor
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Ambient Pressure ◽  
Magnetic Ordering ◽  
Exchange Interactions ◽  
Volume Reduction ◽  
Metallic State ◽  
First Order Phase Transition ◽  
Diamond Anvil ◽  
First Order Phase

AbstractAt ambient pressure the orthorhombic perovskites R-orthoferrites (R Ξ Lu, Eu, Y, Pr, and La) exhibit very large optical gaps. These large- gap Mott insulators in which the 3d5 high-spin ferric ions carry large local moments and magnetically order at TN > 600 K, undergo a sluggish structural first-order phase transition in the 30-50 GPa range, with the exception of the LuFeO3 which undergoes an isostructural volume reduction resulting from a high to low-spin crossover. High-pressure methods to 170 GPa using Mossbauer spectroscopy, resistance, and synchrotronbased XRD in diamond anvil cells were applied. Following the quasi-isostructural volume reduction (3-5%) the new phase the magnetic-ordering temperature is drastically reduced, to ∼ 100 K, the direct and super-exchange interactions are drastically weakened, and the charge-transfer gap is substantially reduced. The high-pressure (HP) phases of the La and Pr oxides, at their inception, are composed of high- and low-spin Fe3+ magnetic sublattices, the abundance of the latter increasing with pressure but HP phases of the Eu, Y, and Lu oxides consist solely of low-spin Fe3+. Resistance and Mössbauer studies in La and Pr orthoferrites reveal the onset of a metallic state with moments starting at P > 120 GPa. Based on the magnetic and electrical data of the latter species, a Mott phase diagram was established.

scholarly journals HIGH PRESSURE APPARATUS FOR TRANSPORT PROPERTIES STUDY IN HIGH MAGNETIC FIELD

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3330-3333 ◽  
Author(s):  
F. HONDA ◽  
V. SECHOVSKÝ ◽  
O. MIKULINA ◽  
J. KAMARÁD ◽  
A. M. ALSMADI ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Pressure ◽  
Hydrostatic Pressure ◽  
Transport Properties ◽  
High Magnetic Field ◽  
Electrical Transport ◽  
Low Temperatures ◽  
Electrical Transport Properties ◽  
High Pressure Cell ◽  
High Pressure Apparatus

We have designed a high pressure apparatus for measuring electrical-transport properties at low temperatures, high magnetic field and hydrostatic pressure up to 10 kbar. Details of the high-pressure cell and an exemplary study on UNiAl are described and discussed briefly.

Transfer optics for high spatial resolution electron spectroscopy

1988 ◽  
Vol 46 ◽  
pp. 666-667
Author(s):  
G. G. Hembree ◽  
Luo Chuan Hong ◽  
P.A. Bennett ◽  
J.A. Venables
Keyword(s):  
Magnetic Field ◽  
Scanning Transmission Electron Microscope ◽  
Low Energy ◽  
Objective Lens ◽  
State University ◽  
Arizona State University ◽  
Initial Field ◽  
Resolution Electron ◽  
Scanning Transmission ◽  
Low Energy Electrons

A new field emission scanning transmission electron microscope has been constructed for the NSF HREM facility at Arizona State University. The microscope is to be used for studies of surfaces, and incorporates several surface-related features, including provision for analysis of secondary and Auger electrons; these electrons are collected through the objective lens from either side of the sample, using the parallelizing action of the magnetic field. This collimates all the low energy electrons, which spiral in the high magnetic field. Given an initial field Bi∼1T, and a final (parallelizing) field Bf∼0.01T, all electrons emerge into a cone of semi-angle θf≤6°. The main practical problem in the way of using this well collimated beam of low energy (0-2keV) electrons is that it is travelling along the path of the (100keV) probing electron beam. To collect and analyze them, they must be deflected off the beam path with minimal effect on the probe position.

STABLE hc/e VORTICES IN SUPERCONDUCTORS WITH SPIN-CHARGE SEPARATION

1992 ◽  
Vol 06 (05n06) ◽  
pp. 509-526
Author(s):  
Subir Sachdev
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Normal State ◽  
Phenomenological Model ◽  
Charge Separation ◽  
Cuprate Superconductors ◽  
Superconducting Phase ◽  
Low Energy ◽  
Large N ◽  
Normal State Properties

A phenomenological model, F, of the superconducting phase of systems with spin-charge separation and antiferromagnetically induced pairing is studied. Above Hc1, magnetic flux can always pierce the superconductor in vortices with flux hc/2e, but regimes are found in which vortices with flux hc/e are preferred. Little-Park and other experiments, which examine periodicities with a varying magnetic field, always observe a period of hc/2e. The low energy properties of a symplectic large-N expansion of a model of the cuprate superconductors are argued to be well described by F. This analysis and some normal state properties of the cuprates suggest that hc/e vortices should be stable at the lowest dopings away from the insulating state at which superconductivity first occurs.

scholarly journals Study on the Phase Selection and Debye Temperature of Hyper-Peritectic Al-Ni Alloy under High Pressure

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 84
Author(s):  
Xiaohong Wang ◽  
Zhipeng Chen ◽  
Duo Dong ◽  
Dongdong Zhu ◽  
Hongwei Wang ◽  
...  
Keyword(s):  
High Pressure ◽  
Ambient Pressure ◽  
Competitive Growth ◽  
Phase Selection ◽  
Debye Temperatures ◽  
Ni Alloy ◽  
Temperature Heat ◽  
Low Temperature Heat Capacity ◽  
New Phase ◽  
Selection Of

The phase selection of hyper-peritectic Al-47wt.%Ni alloy solidified under different pressures was investigated. The results show that Al3Ni2 and Al3Ni phases coexist at ambient pressure, while another new phase α-Al exists simultaneously when solidified at high pressure. Based on the competitive growth theory of dendrite, a kinetic stabilization of metastable peritectic phases with respect to stable ones is predicted for different solidification pressures. It demonstrates that Al3Ni2 phase nucleates and grows directly from the undercooled liquid. Meanwhile, the Debye temperatures of Al-47wt.%Ni alloy that fabricated at different pressures were also calculated using the low temperature heat capacity curve.

Magnetic-Field-Induced Metallic State in β-US2

2011 ◽  
Vol 80 (Suppl.A) ◽  
pp. SA104 ◽  
Author(s):  
Kiyohiro Sugiyama ◽  
Yusuke Hirose ◽  
Kentaro Enoki ◽  
Shugo Ikeda ◽  
Etsuji Yamamoto ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Metallic State
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