scholarly journals Calcite Precipitation at Cement–Bentonite Interface. Part 2: Accelera-tion of Transport by an Electrical Gradient

2021 ◽  
Vol 19 (5) ◽  
pp. 447-461
Author(s):  
Kenichiro Nakarai ◽  
Masaki Watanabe ◽  
Kiyoshi Koibuchi ◽  
Georg Kosakowski
Keyword(s):  
Calcite Precipitation ◽  
Electrical Gradient

scholarly journals Effects of Different Types of Fibers on the Physical and Mechanical Properties of MICP-Treated Calcareous Sand

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 268
Author(s):  
Jitong Zhao ◽  
Huawei Tong ◽  
Yi Shan ◽  
Jie Yuan ◽  
Qiuwang Peng ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Water Absorption ◽  
Glass Fiber ◽  
Physical And Mechanical Properties ◽  
Polyester Fiber ◽  
Engineering Properties ◽  
Fiber Types ◽  
Calcite Precipitation ◽  
Calcareous Sand ◽  
Hemp Fiber

Microbial-induced calcite precipitation (MICP) has been a promising method to improve geotechnical engineering properties through the precipitation of calcium carbonate (CaCO3) on the contact and surface of soil particles in recent years. In the present experiment, water absorption and unconfined compressive strength (UCS) tests were carried out to investigate the effects of three different fiber types (glass fiber, polyester fiber, and hemp fiber) on the physical and mechanical properties of MICP-treated calcareous sand. The fibers used were at 0%, 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, and 0.40% relative to the weight of the sand. The results showed that the failure strain and ductility of the samples could be improved by adding fibers. Compared to biocemented sand (BS), the water absorption of these three fiber-reinforced biocemented sands were, respectively, decreased by 11.60%, 21.18%, and 7.29%. UCS was, respectively, increased by 24.20%, 60.76%, and 6.40%. Polyester fiber produced the best effect, followed by glass fiber and hemp fiber. The optimum contents of glass fiber and polyester fiber were 0.20% and 0.25%, respectively. The optimum content of hemp fiber was within the range of 0.20–0.25%. Light-emitting diode (LED) microscope and scanning electron microscope (SEM) images lead to the conclusion that only a little calcite precipitation had occurred around the hemp fiber, leading to a poor bonding effect compared to the glass and polyester fibers. It was therefore suggested that polyester fiber should be used to improve the properties of biocemented sand.

scholarly journals Zerumbone Inhibits Helicobacter pylori Urease Activity

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2663
Author(s):  
Hyun Jun Woo ◽  
Ji Yeong Yang ◽  
Pyeongjae Lee ◽  
Jong-Bae Kim ◽  
Sa-Hyun Kim
Keyword(s):  
Helicobacter Pylori ◽  
Carbon Atom ◽  
Natural Compound ◽  
Urease Activity ◽  
Negative Charge ◽  
Positive Charge ◽  
Gastric Epithelium ◽  
Functional Inhibition ◽  
Electrical Gradient ◽  
H Pylori

Helicobacter pylori (H. pylori) produces urease in order to improve its settlement and growth in the human gastric epithelium. Urease inhibitors likely represent potentially powerful therapeutics for treating H. pylori; however, their instability and toxicity have proven problematic in human clinical trials. In this study, we investigate the ability of a natural compound extracted from Zingiber zerumbet Smith, zerumbone, to inhibit the urease activity of H. pylori by formation of urease dimers, trimers, or tetramers. As an oxygen atom possesses stronger electronegativity than the first carbon atom bonded to it, in the zerumbone structure, the neighboring second carbon atom shows a relatively negative charge (δ−) and the next carbon atom shows a positive charge (δ+), sequentially. Due to this electrical gradient, it is possible that H. pylori urease with its negative charges (such as thiol radicals) might bind to the β-position carbon of zerumbone. Our results show that zerumbone dimerized, trimerized, or tetramerized with both H. pylori urease A and urease B molecules, and that this formation of complex inhibited H. pylori urease activity. Although zerumbone did not affect either gene transcription or the protein expression of urease A and urease B, our study demonstrated that zerumbone could effectively dimerize with both urease molecules and caused significant functional inhibition of urease activity. In short, our findings suggest that zerumbone may be an effective H. pylori urease inhibitor that may be suitable for therapeutic use in humans.

scholarly journals Low-temperature calcite precipitation in sand using CIPS

2016 ◽  
Vol 169 (1) ◽  
pp. 36-41 ◽  
Author(s):  
Anders Palmén ◽  
Graham Price ◽  
Morgan Axelsson ◽  
Stefan Larsson
Keyword(s):  
Low Temperature ◽  
Calcite Precipitation

Enhancing the Strength of Sandy Soil Through Enzyme-Induced Calcite Precipitation

2021 ◽  
Vol 7 (2) ◽  
Author(s):  
Abubakar Sadiq Muhammed ◽  
Khairul Anuar Kassim ◽  
Muttaqa U. Zango ◽  
Kamarudin Ahmad ◽  
Jodin Makinda
Keyword(s):  
Sandy Soil ◽  
Calcite Precipitation

Chemical Evolution of the System Calcite–Gypsum–Water

1973 ◽  
Vol 10 (2) ◽  
pp. 306-315 ◽  
Author(s):  
T. M. L. Wigley
Keyword(s):  
Carbon Dioxide ◽  
Chemical Evolution ◽  
Degree Of Saturation ◽  
Carbon Dioxide Content ◽  
Calcite Precipitation ◽  
Arbitrary Temperature

The effect of the addition of gypsum to a solution of calcite in water (or the addition of calcite to a solution of gypsum in water) is determined theoretically for arbitrary temperature, carbon dioxide content, and degree of saturation with respect to calcite (or gypsum). The results can be used to study the chemical evolution of waters flowing through alternating gypsum and limestone strata, to predict conditions which will lead to the precipitation of calcite and/or gypsum, and to predict the chemical evolution of evaporating calcite–gypsum solutions. It is shown that under some circumstances, simultaneous gypsum (or calcite) precipitation and calcite (or gypsum) solution may occur. Coprecipitation of gypsum and calcite is found to be unavoidable if a solution is evaporated to dryness, although the initial precipitate will be a single mineral. The methods used and many of the conclusions drawn are applicable to other systems of two or more minerals.

Sedimentary Phosphate Fractions Related to Calcite Precipitation in an Eutrophic Hardwater Lake (Lake Alserio, Northern Italy)

2006 ◽  
Vol 35 (1) ◽  
pp. 55-64 ◽  
Author(s):  
I. de Vicente ◽  
K. Cattaneo ◽  
L. Cruz-Pizarro ◽  
A. Brauer ◽  
P. Guilizzoni
Keyword(s):  
Northern Italy ◽  
Calcite Precipitation

scholarly journals A revised model for microbially induced calcite precipitation: Improvements and new insights based on recent experiments

2015 ◽  
Vol 51 (5) ◽  
pp. 3695-3715 ◽  
Author(s):  
Johannes Hommel ◽  
Ellen Lauchnor ◽  
Adrienne Phillips ◽  
Robin Gerlach ◽  
Alfred B. Cunningham ◽  
...  
Keyword(s):  
Calcite Precipitation ◽  
Microbially Induced Calcite Precipitation
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