Doping dependence of semiconductor–metal transition in InP at high pressures

1986 ◽  
Vol 405 (1829) ◽  
pp. 345-353 ◽  
Keyword(s):  
High Pressure ◽  
Liquid Phase ◽  
Hydrostatic Pressure ◽  
Doping Concentration ◽  
High Pressures ◽  
Metallic Phase ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Transition Pressure ◽  
High Concentrations

The resistivity of selenium-doped n-InP single crystal layers grown by liquid-phase epitaxy with electron concentrations varying from 6.7×10 18 to 1.8×10 20 cm -3 has been measured as a function of hydrostatic pressure up to 10 GPa. Semiconductor-metal transitions were observed in each case with a change in resistivity by two to three orders of magnitude. The transition pressure p c decreased monotonically from 7.24 to 5.90 GPa with increasing doping concentration n according to the relation p c = p o [1 - k ( n / n m ) α ], where n m is the concentration (per cubic centimetre) of phosphorus donor sites in InP atoms, p o is the transition pressure at low doping concentrations, k is a constant and α is an exponent found experimentally to be 0.637. The decrease in p c is considered to be due to increasing internal stress developed at high concentrations of ionized donors. The high-pressure metallic phase had a resistivity (2.02–6.47)×10 -7 Ω cm, with a positive temperature coefficient dependent on doping.

scholarly journals High pressures increase α-chymotrypsin enzyme activity under perchlorate stress

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Stewart Gault ◽  
Michel W. Jaworek ◽  
Roland Winter ◽  
Charles S. Cockell
Keyword(s):  
High Pressure ◽  
Enzyme Activity ◽  
Phase Space ◽  
High Pressures ◽  
Extreme Environments ◽  
Combined Effects ◽  
Deep Subsurface ◽  
Subsurface Environments ◽  
Dissolved Ions ◽  
High Concentrations

Abstract Deep subsurface environments can harbour high concentrations of dissolved ions, yet we know little about how this shapes the conditions for life. We know even less about how the combined effects of high pressure influence the way in which ions constrain the possibilities for life. One such ion is perchlorate, which is found in extreme environments on Earth and pervasively on Mars. We investigated the interactions of high pressure and high perchlorate concentrations on enzymatic activity. We demonstrate that high pressures increase α-chymotrypsin enzyme activity even in the presence of high perchlorate concentrations. Perchlorate salts were shown to shift the folded α-chymotrypsin phase space to lower temperatures and pressures. The results presented here may suggest that high pressures increase the habitability of environments under perchlorate stress. Therefore, deep subsurface environments that combine these stressors, potentially including the subsurface of Mars, may be more habitable than previously thought.

scholarly journals Evaluating the Anti-Inflammatory and Antioxidant Effects of Broccoli Treated with High Hydrostatic Pressure in Cell Models

Foods ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 167
Author(s):  
Yi-Yuan Ke ◽  
Yuan-Tay Shyu ◽  
Sz-Jie Wu
Keyword(s):  
High Pressure ◽  
Hydrostatic Pressure ◽  
High Hydrostatic Pressure ◽  
High Pressures ◽  
High Pressure Processing ◽  
Total Phenolic ◽  
Anti Inflammatory ◽  
Functional Components ◽  
Antioxidant Effects ◽  
Myrosinase Activity

Isothiocyanates (ITCs) are important functional components of cruciferous vegetables. The principal isothiocyanate molecule in broccoli is sulforaphane (SFN), followed by erucin (ERN). They are sensitive to changes in temperature, especially high temperature environments where they are prone to degradation. The present study investigates the effects of high hydrostatic pressure on isothiocyanate content, myrosinase activity, and other functional components of broccoli, and evaluates its anti-inflammatory and antioxidant effects. Broccoli samples were treated with different pressures and for varying treatment times; 15 min at 400 MPa generated the highest amounts of isothiocyanates. The content of flavonoids and vitamin C were not affected by the high-pressure processing strategy, whereas total phenolic content (TPC) exhibited an increasing tendency with increasing pressure, indicating that high-pressure processing effectively prevents the loss of the heat-sensitive components and enhances the nutritional content. The activity of myrosinase (MYR) increased after high-pressure processing, indicating that the increase in isothiocyanate content is related to the stimulation of myrosinase activity by high-pressure processing. In other key enzymes, the ascorbate peroxidase (APX) activity was unaffected by high pressure, whereas peroxidase (POD) and polyphenol oxidase (PPO) activity exhibited a 1.54-fold increase after high-pressure processing, indicating that high pressures can effectively destroy oxidases and maintain food quality. With regards to efficacy evaluation, NO production was inhibited and the expression levels of inducible nitric oxide synthase (iNOS) and Cyclooxygenase-2 (COX-2) were decreased in broccoli treated with high pressures, whereas the cell viability remained unaffected. The efficacy was more significant when the concentration of SFN was 60 mg·mL−1. In addition, at 10 mg·mL−1 SFN, the reduced/oxidized glutathione (GSH/GSSG) ratio in inflammatory macrophages increased from 5.99 to 9.41. In conclusion, high-pressure processing can increase the isothiocyanate content in broccoli, and has anti-inflammatory and anti-oxidant effects in cell-based evaluation strategies, providing a potential treatment strategy for raw materials or additives used in healthy foods.

Semiconducting BaTiO3 ceramic prepared by low temperature liquid phase sintering

1998 ◽  
Vol 13 (3) ◽  
pp. 660-664 ◽  
Author(s):  
I. Zajc ◽  
M. Drofenik
Keyword(s):  
Liquid Phase ◽  
Grain Boundary ◽  
Sintering Temperature ◽  
Positive Temperature Coefficient ◽  
Liquid Phase Sintering ◽  
Positive Temperature ◽  
Sintering Aid ◽  
Ptcr Effect ◽  
Temperature Coefficient Of Resistivity ◽  
Temperature Liquid

Donor-doped BaTiO3 ceramics were prepared by adding PbO B2O3 SiO2 as a sintering aid. Semiconducting BaTiO3 was obtained at a sintering temperature of 1100 °C. The sintered samples exhibit the Positive Temperature Coefficient of Resistivity (PTCR) effect, which depends on the amount of liquid phase, the concentration of the donor-dopant, and the sintering temperature. The cold resistivity of the samples decreases when the sintering temperature increases. The increase of the grain boundary resistivity and hence of the cold resistivity at lower sintering temperatures was explained by applying the diffusion grain boundary layer model.

scholarly journals Effects of hydrostatic pressure on membrane processes. Sodium channels, calcium channels, and exocytosis.

1987 ◽  
Vol 90 (6) ◽  
pp. 765-778 ◽  
Author(s):  
S H Heinemann ◽  
F Conti ◽  
W Stühmer ◽  
E Neher
Keyword(s):  
High Pressure ◽  
Hydrostatic Pressure ◽  
High Pressures ◽  
Mean Amplitude ◽  
National Academy Of Sciences ◽  
Na Currents ◽  
Experimental Resolution ◽  
Adrenal Chromaffin ◽  
Academy Of Sciences ◽  
Ca Currents

A patch-clamp study under high hydrostatic pressure was performed by transferring cells or membrane patches into a pressure vessel (Heinemann, S. H., W. Stühmer, and F. Conti, 1987, Proceedings of the National Academy of Sciences, 84:3229-3233). Whole-cell Na currents as well as Ca currents were measured at pressures up to 40 MPa (approximately 400 atm; 1 MPa = 9.87 atm) in bovine adrenal chromaffin cells. Ca currents were found to be independent of pressure within experimental resolution. The mean amplitude and the gating kinetics of Na currents were affected by less than 20% at 10 MPa. This lack of a pronounced effect is surprising since the high-pressure nervous syndrome (HPNS), a disorder at high pressures known to result from impaired nervous transmission, manifests itself at pressures as low as 5 MPa. The results show that ion channels involved in transmission cannot be implicated in HPNS. However, when exocytosis was studied at high pressure by monitoring the cell capacitance (Neher, E., and A. Marty, 1982, Proceedings of the National Academy of Sciences, 79:6712-6716), more drastic effects were seen. The degranulation evoked by dialyzing the cell with 1 microM free Ca2+ could be slowed by a factor of 2 by application of 10 MPa. The same effect was observed for the degranulation of rat peritoneal mast cells stimulated with 40 microM of the GTP analogue GTP-gamma-S. According to these results, the process of exocytosis is the most likely site at which hydrostatic pressure can act to produce nervous disorders. Furthermore, we demonstrate that pressure can be a useful tool in the investigation of other cellular responses, since we were able to separate different steps occurring during exocytosis owing to their different activation volumes.

scholarly journals Molecular Responses to High Hydrostatic Pressure in Eukaryotes: Genetic Insights from Studies on Saccharomyces cerevisiae

Biology ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 1305
Author(s):  
Fumiyoshi Abe
Keyword(s):  
Saccharomyces Cerevisiae ◽  
High Pressure ◽  
Hydrostatic Pressure ◽  
High Hydrostatic Pressure ◽  
High Pressures ◽  
Strong Association ◽  
Pressure Effects ◽  
Basic Knowledge ◽  
Challenger Deep ◽  
Human Joints

High hydrostatic pressure is common mechanical stress in nature and is also experienced by the human body. Organisms in the Challenger Deep of the Mariana Trench are habitually exposed to pressures up to 110 MPa. Human joints are intermittently exposed to hydrostatic pressures of 3–10 MPa. Pressures less than 50 MPa do not deform or kill the cells. However, high pressure can have various effects on the cell’s biological processes. Although Saccharomyces cerevisiae is not a deep-sea piezophile, it can be used to elucidate the molecular mechanism underlying the cell’s responses to high pressures by applying basic knowledge of the effects of pressure on industrial processes involving microorganisms. We have explored the genes associated with the growth of S. cerevisiae under high pressure by employing functional genomic strategies and transcriptomics analysis and indicated a strong association between high-pressure signaling and the cell’s response to nutrient availability. This review summarizes the occurrence and significance of high-pressure effects on complex metabolic and genetic networks in eukaryotic cells and how the cell responds to increasing pressure by particularly focusing on the physiology of S. cerevisiae at the molecular level. Mechanosensation in humans has also been discussed.

Simulation of Fuel Temperature of Diesel Engine Heating by PTC Materials

2011 ◽  
Vol 480-481 ◽  
pp. 120-125 ◽  
Author(s):  
Xiao Lu Li ◽  
Le Feng Gu ◽  
Cang Su Xu ◽  
Ying Li
Keyword(s):  
High Pressure ◽  
Diesel Engine ◽  
Diesel Fuel ◽  
Heating Temperature ◽  
Rapid Heating ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Fuel Temperature ◽  
Lumped Parameter ◽  
Calculation Results

The PTC materials, as a kind of positive temperature coefficient materials, are used to heat diesel fuel in the high-pressure fuel pipe near the injector in Diesel engine, which have a lot of advantages, such as simple structure, safe and rapid heating, and fixed heating temperature around its Curie point. In order to study its heating effect on diesel fuel of the high pressure fuel pipe, the dynamical models for both the controlled object and PTC heater are presented by the way of lumped parameter, and the heating effects are also simulated and analyzed. The calculation results show that the diesel temperature is heated by the PTC materials effectively. Meanwhile, the heating law by PTC materials heating diesel fuel in the high pressure fuel pipe of engine is also summarized.

Characteristics of Low- and High-Fat Beef Patties: Effect of High Hydrostatic Pressure

1997 ◽  
Vol 60 (1) ◽  
pp. 48-53 ◽  
Author(s):  
J. CARBALLO ◽  
P. FERNANDEZ ◽  
A. V. CARRASCOSA ◽  
M. T. SOLAS ◽  
F. JIMENEZ COLMENERO
Keyword(s):  
High Pressure ◽  
Hydrostatic Pressure ◽  
High Hydrostatic Pressure ◽  
Shear Force ◽  
High Pressures ◽  
Lethal Effect ◽  
High Fat ◽  
Low Fat ◽  
Binding Properties ◽  
Beef Patties

The purpose of this study was to analyze the consequences of applying high pressures (100 and 300 MPa for 5 or 20 min) on characteristics such as water- and fat-binding properties, texture, color, microstructure, and microbiology of low-fat (9.2%) and high-fat (20.3%) beef patties. In nonpressurized patties, the low-fat product exhibited significantly poorer (P < 0.05) binding properties and higher (P < 0.05) Kramer shear force and Kramer energy than did high-fat patties. Although high pressure did not clearly influence the binding properties of low- and high-fat beef patties, it did produce a rise in the Kramer shear force and energy which were more pronounced at 300 MPa. High pressures altered patty color, the extent of alteration depending on fat content, pressure, and pressurizing time. Pressurizing high- and low-fat beef patties at 300 MPa not only produced a lethal effect (P < 0.05) on microorganisms, but caused sublethal damage as well.

Very High Pressure Generation at the Deep Sea

1983 ◽  
Vol 22 ◽  
Author(s):  
Kaichi Suito ◽  
Katsumi Yasukawa
Keyword(s):  
High Pressure ◽  
Hydrostatic Pressure ◽  
Natural Resources ◽  
Deep Sea ◽  
High Pressures ◽  
Large Area ◽  
High Pressure Apparatus ◽  
Very High

ABSTRACTIn the deep sea, truely hydrostatic pressure is produced in a very large area. This pressure may be used as natural resources. By utilizing these resources, very high pressures can be generated using a 6–8 type split-sphere high pressure apparatus. A preliminary experiment to generate very high pressure was undertaken in the deep sea at a depth of about 1000 m. Pressures of about 8.5 GPa were generated in the central part of the high pressure apparatus.

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