Design of a New Reactor to Work at Low Volume Liquid/Surface Solid Ratio and High Pressure and Temperature: Dissolution Rate Studies of UO2 Under Both Anoxic and Reducing Conditions.

2014 ◽  
Vol 1665 ◽  
pp. 303-309
Author(s):  
A. Martínez-Torrents ◽  
J. Giménez ◽  
I. Casas ◽  
J. de Pablo
Keyword(s):  
Hydrogen Peroxide ◽  
High Pressure ◽  
High Pressures ◽  
Liquid Surface ◽  
High Surface ◽  
High Pressure And Temperature ◽  
Solid Ratio ◽  
Reducing Conditions ◽  
Flow Through ◽  
Low Volume

ABSTRACTA flow-through experimental reactor has been designed in order to perform studies at both high pressure and high temperature conditions. A chromatographic pump is used to impulse the leachant throughout the reactor in order to work at very low flows but high pressures. Therefore, high surface solid to volume leachant ratios, similar to the ones predicted in the final repository, can be obtained. The reactor allows working at different atmospheres at pressures up to 50 bars. The temperature inside the reactor can be set using a jacket.Using this new reactor the evolution of uranium concentrations released from an UO2 sample was studied at different conditions.The results show that at hydrogen pressures between 5 and 7 bars, hydrogen peroxide does not seem to significantly oxidize the uranium (IV) oxide. Uranium concentrations in those experiments remain between 10-8 mol·l-1 and 10-9 mol·l-1.

Evaluation of Chemical and Physical (High-Pressure and Temperature) Treatments To Improve the Safety of Minimally Processed Mung Bean Sprouts during Refrigerated Storage

2006 ◽  
Vol 69 (10) ◽  
pp. 2395-2402 ◽  
Author(s):  
MARINA MUÑOZ ◽  
BEGOÑA DE ANCOS ◽  
CONCEPCIÓN SÁNCHEZ-MORENO ◽  
M. PILAR CANO
Keyword(s):  
Hydrogen Peroxide ◽  
High Pressure ◽  
Response Surface Methodology ◽  
Mung Bean ◽  
Model System ◽  
Refrigerated Storage ◽  
Minimally Processed ◽  
High Pressure And Temperature ◽  
Mung Bean Sprouts ◽  
Bean Sprouts

The objective of this study was to compare the effects of combined high hydrostatic pressure and temperature treatments with different chemical sanitation treatments (water, sodium hypochlorite, and hydrogen peroxide) on the microbiological properties of mung bean sprouts. In a first study, the raw product was subjected to several combined high-pressure and temperature treatments for calculating a mathematical model by a response surface methodology. The number of pressure-temperature (150 to 400 MPa; 20 to 40°C) combinations was limited to 10. In addition, a model system consisting of mung bean sprout juice was inoculated with Listeria monocytogenes (CECT 4032). Microbial inactivation with this model system was also investigated by a response surface methodology. The highest aerobic mesophilic bacteria and L. monocytogenes inactivation was achieved at maximum pressure and temperature (5.5 and 1.8 log cycles, respectively). In a second study, the effect of five different processing lines on the microbial load reduction of minimally processed mung bean sprouts during refrigerated storage was studied. All treatments reduced the initial population of aerobic mesophilic bacteria and fecal coliforms, with the physical treatment of 400 MPa and 40°C being the most effective, showing initial reductions of 5.8 and 7.8 log CFU/g, respectively. Recovery of bacteria from sprouts treated under these conditions was not observed during storage. However, the sprouts that received washing treatments with water, sodium hypochlorite, and hydrogen peroxide exhibited increases in aerobic mesophilic and fecal coliform counts after 3 days of storage at 4°C.

scholarly journals Hydrodynamics of the leucon sponge pump

2019 ◽  
Vol 16 (150) ◽  
pp. 20180630 ◽  
Author(s):  
Seyed Saeed Asadzadeh ◽  
Poul S. Larsen ◽  
Hans Ulrik Riisgård ◽  
Jens H. Walther
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Pressure Rise ◽  
Pump Efficiency ◽  
Pressure Losses ◽  
Positive Displacement ◽  
System Pressure ◽  
Flow Through ◽  
Mechanical Pump ◽  
Pumping Units

Leuconoid sponges are filter-feeders with a complex system of branching inhalant and exhalant canals leading to and from the close-packed choanocyte chambers. Each of these choanocyte chambers holds many choanocytes that act as pumping units delivering the relatively high pressure rise needed to overcome the system pressure losses in canals and constrictions. Here, we test the hypothesis that, in order to deliver the high pressures observed, each choanocyte operates as a leaky, positive displacement-type pump owing to the interaction between its beating flagellar vane and the collar, open at the base for inflow but sealed above. The leaking backflow is caused by small gaps between the vaned flagellum and the collar. The choanocyte pumps act in parallel, each delivering the same high pressure, because low-pressure and high-pressure zones in the choanocyte chamber are separated by a seal (secondary reticulum). A simple analytical model is derived for the pump characteristic, and by imposing an estimated system characteristic we obtain the back-pressure characteristic that shows good agreement with available experimental data. Computational fluid dynamics is used to verify a simple model for the dependence of leak flow through gaps in a conceptual collar–vane–flagellum system and then applied to models of a choanocyte tailored to the parameters of the freshwater demosponge Spongilla lacustris to study its flows in detail. It is found that both the impermeable glycocalyx mesh covering the upper part of the collar and the secondary reticulum are indispensable features for the choanocyte pump to deliver the observed high pressures. Finally, the mechanical pump power expended by the beating flagellum is compared with the useful (reversible) pumping power received by the water flow to arrive at a typical mechanical pump efficiency of about 70%.

Comparative Study of Pressure-Induced Germination of Bacillus subtilis Spores at Low and High Pressures

1998 ◽  
Vol 64 (9) ◽  
pp. 3220-3224 ◽  
Author(s):  
Elke Y. Wuytack ◽  
Steven Boven ◽  
Chris W. Michiels
Keyword(s):  
Hydrogen Peroxide ◽  
High Pressure ◽  
Bacillus Subtilis ◽  
High Pressures ◽  
Uv Light ◽  
Early Stage ◽  
Dipicolinic Acid ◽  
Heat Sensitivity ◽  
Spore Resistance ◽  
Atp Generation

ABSTRACT We have studied pressure-induced germination of Bacillus subtilis spores at moderate (100 MPa) and high (500 to 600 MPa) pressures. Although we found comparable germination efficiencies under both conditions by using heat sensitivity as a criterion for germination, the sensitivity of pressure-germinated spores to some other agents was found to depend on the pressure used. Spores germinated at 100 MPa were more sensitive to pressure (>200 MPa), UV light, and hydrogen peroxide than were those germinated at 600 MPa. Since small, acid-soluble proteins (SASPs) and dipicolinic acid (DPA) are known to be involved in spore resistance to UV light and hydrogen peroxide, we studied the fate of these compounds during pressure germination. DPA was released upon both low- and high-pressure germination, but SASP degradation, which normally accompanies nutrient-induced germination, occurred upon low-pressure germination but not upon high-pressure germination. These results adequately explain the UV and hydrogen peroxide resistance of spores germinated at 600 MPa. The resistance to pressure inactivation of 600-MPa-germinated spores could also, at least partly, be attributed to α/β-type SASPs, since mutants deficient in α/β-type SASPs were more sensitive to inactivation at 600 MPa. Further, germination at 100 MPa resulted in rapid ATP generation, as is the case in nutrient-induced germination, but no ATP was formed during germination at 600 MPa. These results suggest that spore germination can be initiated by low- and high-pressure treatments but is arrested at an early stage in the latter case. The implications for the use of high pressure as a preservation treatment are discussed.

INVESTIGATION OF THE TIME OF GAS FLOW THROUGH A HOLE IN LONG PIPELINES UNDER HIGH PRESSURE

2020 ◽  
Vol 58 (1) ◽  
pp. 30-43
Author(s):  
N.D. Yakimov ◽  
◽  
A.I. Khafizova ◽  
N.D. Chichirova ◽  
O.S. Dmitrieva ◽  
...  
Keyword(s):  
High Pressure ◽  
Gas Flow ◽  
Flow Through

Peculiarities of high-pressure hydrogen adsorption on Pt catalyzed Cu-BTC metal–organic framework

2021 ◽  
Vol 23 (7) ◽  
pp. 4277-4286
Author(s):  
S. V. Chuvikov ◽  
E. A. Berdonosova ◽  
A. Krautsou ◽  
J. V. Kostina ◽  
V. V. Minin ◽  
...  
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Hydrogen Adsorption ◽  
Metal Organic Framework ◽  
Pt Catalyst ◽  
Metal Organic ◽  
Pt Catalyzed ◽  
Pressure Hydrogen ◽  
Organic Framework

Pt-Catalyst plays a key role in hydrogen adsorption by Cu-BTC at high pressures.

scholarly journals Chemical Stability of FeOOH at High Pressure and Temperature, and Oxygen Recycling in Early Earth History

2021 ◽  
Author(s):  
Egor Koemets ◽  
Timofey Fedotenko ◽  
Saiana Khandarkhaeva ◽  
Maxim Bykov ◽  
Elena Bykova ◽  
...  
Keyword(s):  
High Pressure ◽  
Chemical Stability ◽  
Early Earth ◽  
High Pressure And Temperature ◽  
Earth History

scholarly journals Crystal and electronic structure engineering of tin monoxide by external pressure

2021 ◽  
Author(s):  
Kun Li ◽  
Junjie Wang ◽  
Vladislav A. Blatov ◽  
Yutong Gong ◽  
Naoto Umezawa ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Band Gap ◽  
High Pressures ◽  
Low Pressure ◽  
Widespread Application ◽  
Space Group ◽  
Tin Monoxide ◽  
High Possibility ◽  
Pressure Phase

AbstractAlthough tin monoxide (SnO) is an interesting compound due to its p-type conductivity, a widespread application of SnO has been limited by its narrow band gap of 0.7 eV. In this work, we theoretically investigate the structural and electronic properties of several SnO phases under high pressures through employing van der Waals (vdW) functionals. Our calculations reveal that a metastable SnO (β-SnO), which possesses space group P21/c and a wide band gap of 1.9 eV, is more stable than α-SnO at pressures higher than 80 GPa. Moreover, a stable (space group P2/c) and a metastable (space group Pnma) phases of SnO appear at pressures higher than 120 GPa. Energy and topological analyses show that P2/c-SnO has a high possibility to directly transform to β-SnO at around 120 GPa. Our work also reveals that β-SnO is a necessary intermediate state between high-pressure phase Pnma-SnO and low-pressure phase α-SnO for the phase transition path Pnma-SnO →β-SnO → α-SnO. Two phase transition analyses indicate that there is a high possibility to synthesize β-SnO under high-pressure conditions and have it remain stable under normal pressure. Finally, our study reveals that the conductive property of β-SnO can be engineered in a low-pressure range (0–9 GPa) through a semiconductor-to-metal transition, while maintaining transparency in the visible light range.

Chemical stability of FeOOH at high pressure and temperature, and oxygen recycling in early Earth history

2021 ◽  
Author(s):  
Egor Koemets ◽  
Timofey Fedotenko ◽  
Saiana Khandarkhaeva ◽  
Maxim Bykov ◽  
Elena Bykova ◽  
...  
Keyword(s):  
High Pressure ◽  
Chemical Stability ◽  
Early Earth ◽  
High Pressure And Temperature ◽  
Earth History
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