An SCC-DFTB/MD Study of the Adsorption of Zwitterionic Glycine on a Geminal Hydroxylated Silica Surface in an Explicit Water Environment

2011 ◽  
Vol 115 (19) ◽  
pp. 9615-9621 ◽  
Author(s):  
Y. L. Zhao ◽  
S. Köppen ◽  
T. Frauenheim
Keyword(s):  
Silica Surface ◽  
Water Environment ◽  
Explicit Water

scholarly journals Theoretical Study of HOCl-Catalyzed Keto–Enol Tautomerization of β-Cyclopentanedione in an Explicit Water Environment

2013 ◽  
Vol 117 (35) ◽  
pp. 8437-8448 ◽  
Author(s):  
Cassian D’Cunha ◽  
Alexander N. Morozov ◽  
David C. Chatfield
Keyword(s):  
Theoretical Study ◽  
Water Environment ◽  
Explicit Water

scholarly journals Understanding the Exceptional Properties of Nitroacetamides in Water: A Computational Model Including the Solvent

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3308 ◽  
Author(s):  
Giovanni La Penna ◽  
Fabrizio Machetti
Keyword(s):  
Proton Transfer ◽  
Density Functional ◽  
Water Environment ◽  
Average Energy ◽  
Thermal Fluctuations ◽  
Energy Difference ◽  
Tautomeric Forms ◽  
Geminal Proton ◽  
Solvent Molecules ◽  
Explicit Water

Proton transfer in water involving C–H bonds is a challenge and nitro compounds have been studied for many years as good examples. The effect of substituents on acidity of protons geminal to the nitro group is exploited here with new p K a measurements and electronic structure models, the latter including explicit water environment. Substituents with the amide moiety display an exceptional combination of acidity and solubility in water. In order to find a rationale for the unexpected p K a changes in the (ZZ ′ )NCO- substituents, we measured and modeled the p K a with Z=Z ′ =H and Z=Z ′ =methyl. The dominant contribution to the observed p K a can be understood with advanced computational experiments, where the geminal proton is smoothly moved to the solvent bath. These models, mostly based on density-functional theory (DFT), include the explicit solvent (water) and statistical thermal fluctuations. As a first approximation, the change of p K a can be correlated with the average energy difference between the two tautomeric forms (aci and nitro, respectively). The contribution of the solvent molecules interacting with the solute to the proton transfer mechanism is made evident.

EFFECTS AND ROLE OF WATER ENVIRONMENT ON A GEMINAL HYDROXYLATED SILICA SURFACE — SELF-CONSISTENT CHARGE DENSITY FUNCTIONAL TIGHT BINDING THEORY BASED MOLECULAR DYNAMICS SIMULATION

2012 ◽  
Vol 11 (01) ◽  
pp. 155-162 ◽  
Author(s):  
Y. L. ZHAO
Keyword(s):  
Hydrogen Bonds ◽  
Charge Density ◽  
Density Functional ◽  
Silica Surface ◽  
Water Environment ◽  
Tight Binding ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Self Consistent ◽  
The Impact

The presence of aqueous solution is inevitable in complex systems involving biological and material components and could affect the interaction between them substantially. To properly simulate such an interaction system, it is necessary to quantitatively explore the effects and specific roles of the water environment on the material surface. In this work, a silica surface was adopted as an example to study the impact of water environment ( 144H2O ) on the structure and energetics using a self-consistent charge density functional tight binding/molecular dynamic method. First, we demonstrated that the silica surface in a vacuum involves a large deformation due to the formation of hydrogen bonds among the surface silanols; in contrast, the deformation is eased in water environment because water molecules could locate in between the silanols and form many hydrogen bonds with the silanols. Therefore, water molecules play an important role to maintain surface from not getting heavily deformed. Our work not only tested the feasible computational methodology of studying nanoscale large systems under water environment at a quantum-mechanical level of theory, but also provided clear evidence on the impact of water environment to the inorganic surface.

Incorporation of Multi Wall Carbon Nanotubes into Glass-Surfaces via Laser-Treatment

2003 ◽  
Vol 772 ◽  
Author(s):  
T. Seeger ◽  
G. de la Fuente ◽  
W.K. Maser ◽  
A.M. Benito ◽  
A. Righi ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Continuous Wave ◽  
Silica Surface ◽  
Multi Wall Carbon Nanotubes ◽  
Composite Formation ◽  
Multi Walled Carbon Nanotubes ◽  
Glass Surfaces ◽  
Walled Carbon Nanotubes ◽  
First Time ◽  
Scanning Electron

AbstractCarbon nanotubes (CNT) are interesting candidates for the reinforcement in robust composites and for conducting fillers in polymers due to their fascinating electronic and mechanical properties. For the first time, we report the incorporation of multi walled carbon nanotubes (MWNTs) into silica-glass surfaces by means of partial surface-melting caused by a continuous wave Nd:YAG laser. MWNTs were detected being well incorporated in the silica-surface. The composites are characterized using scanning electron microscopy (SEM) and Raman-spectroscopy. A model for the composite-formation is proposed based on heatabsorption by MWNTs and a partial melting of the silica-surface.

Establishing an empirical equation for the relationship between total suspended solids and total phosphorus concentrations in the downstream Red river water

2020 ◽  
Vol 20 (3) ◽  
pp. 325-332
Author(s):  
Le Nhu Da ◽  
Le Thi Phuong Quynh ◽  
Phung Thi Xuan Binh ◽  
Duong Thi Thuy ◽  
Trinh Hoai Thu ◽  
...  
Keyword(s):  
Total Phosphorus ◽  
Suspended Solids ◽  
Empirical Relationship ◽  
Water Environment ◽  
Total Suspended Solids ◽  
River System ◽  
Red River ◽  
Reservoir Impoundment ◽  
Downstream Section ◽  
Reasonable Prediction

Recently, the Asian rivers have faced the strong reduction of riverine total suspended solids (TSS) flux due to numerous dam/reservoir impoundment. The Red river system is a typical example of the Southeast Asian rivers that has been strongly impacted by reservoir impoundment in both China and Vietnam, especially in the recent period. It is known that the reduction in total suspended solids may lead to the decrease of some associated elements, including nutrients (N, P, Si) which may affect coastal ecosystems. In this paper, we establish the empirical relationship between total suspended solids and total phosphorus concentrations in water environment of the Red river in its downstream section from Hanoi city to the Ba Lat estuary based on the sampling campaigns conducted in the dry and wet seasons in 2017, 2018 and 2019. The results show a clear relationship with significant coefficient between total suspended solids and total phosphorus in the downstream Red river. It is expressed by a simple equation y = 0.0226x0.3867 where x and y stand for total suspended solids and total phosphorus concentrations (mg/l) respectively with the r2 value of 0.757. This equation enables a reasonable prediction of total phosphorus concentrations of the downstream Red river when the observed data of total suspended solids concentrations are available. Thus, this work opens up the way for further studies on the calculation of the total phosphorus over longer timescales using daily available total suspended solids values.

DEVELOPMENT OF INTEGRATED MONITORING NETWORK FOR MEASURING SALINITY OF SEA WATER

2018 ◽  
pp. 18-26
Author(s):  
Sima Ajdar qizi Askerova
Keyword(s):  
Surface Waters ◽  
Sea Water ◽  
Water Environment ◽  
Monitoring Network ◽  
Monitoring Networks ◽  
The Caspian Sea ◽  
Integrated Monitoring ◽  
Ecological Control ◽  
Different Depths ◽  
Optimal Construction

Monitoring of sea water condition is one of major requirements for carrying out the reliable ecological control of water environment. Monitoring networks contain such elements as sea buoys, beacons, etc. and are designated for measuringvarious hydrophysical parameters, including salinity of sea water. Development of specialized network and a separate buoy system for measuring thesea water salinity at different depths makes it possible to determine major regularities of processes of pollution and self-recovery of the sea waters. The article describes the scientific and methodological basics for development of this specialized network and questions of its optimal construction. It is well-known that at a depth of 30-45 m of the Caspian Sea salinity decreases and then at a depth of 45-60 m salinity is fully recovered. The mentioned changes of salinity at the relatively upper layer of sea waters is of special interest for studying the effect of ocean-going processes on the climate forming in the Caspian area. In terms of informativeness of measurements of surface waters salinity, the most informative is a layer ata 30-60 m depth, where inversion and recovery of salinity take place. It is shown that in most informative subrange of measurements, i. e. at a depth of 30-60 m optimization of regime of measurements complex should be carried out in order to increase the effectiveness of held researches. It is shown that at a depth of 35-50 m choice of the optimum regime of measurements makes it possible to obtain the maximum amount of information.

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