New Calix[4]arene Dibenzocrown Ethers for Selective Sensing of Cesium Ion in an Aqueous Environment

1998 ◽  
Vol 58 (2) ◽  
pp. 225-235 ◽  
Author(s):  
Jong Seung Kim ◽  
Ill Yong Yu ◽  
Jin Hyun Pang ◽  
Jong Kuk Kim ◽  
Yong-Ill Lee ◽  
...  
Keyword(s):  
Aqueous Environment ◽  
Dibenzocrown Ethers ◽  
Cesium Ion

Cesium-ion selective electrodes based on calix[4]arene dibenzocrown ethers

Talanta ◽  
1999 ◽  
Vol 48 (3) ◽  
pp. 705-710 ◽  
Author(s):  
JongSeung Kim ◽  
Akira Ohki ◽  
Rina Ueki ◽  
Tomoko Ishizuka ◽  
Tomohiro Shimotashiro ◽  
...  
Keyword(s):  
Ion Selective Electrodes ◽  
Dibenzocrown Ethers ◽  
Cesium Ion

Prospects for scanned-probe microscopy

1994 ◽  
Vol 52 ◽  
pp. 6-7
Author(s):  
Jean-Paul Revel
Keyword(s):  
High Vacuum ◽  
Physiological Saline ◽  
Scanning Probe ◽  
Aqueous Environment ◽  
Whole Cells ◽  
Material Scientist ◽  
Biological Objects ◽  
Spatially Resolved ◽  
Atomic Force ◽  
Scanned Probe Microscopy

In the last 50+ years the electron microscope and allied instruments have led the way as means to acquire spatially resolved information about very small objects. For the material scientist and the biologist both, imaging using the information derived from the interaction of electrons with the objects of their concern, has had limitations. Material scientists have been handicapped by the fact that their samples are often too thick for penetration without using million volt instruments. Biologists have been handicapped both by the problem of contrast since most biological objects are composed of elements of low Z, and also by the requirement that sample be placed in high vacuum. Cells consist of 90% water, so elaborate precautions have to be taken to remove the water without losing the structure altogether. We are now poised to make another leap forwards because of the development of scanned probe microscopies, particularly the Atomic Force Microscope (AFM). The scanning probe instruments permit resolutions that electron microscopists still work very hard to achieve, if they have reached it yet. Probably the most interesting feature of the AFM technology, for the biologist in any case, is that it has opened the dream of high resolution in an aqueous environment. There are few restrictions on where the instrument can be used. AFMs can be made to work in high vacuum, allowing the material scientist to avoid contamination. The biologist can be made happy as well. The tips used for detection are made of silicon nitride,(Si3N4), and are essentially unaffected by exposure to physiological saline (about which more below). So here is an instrument which can look at living whole cells and at atoms as well.

On the Adsorption of Aspartate Derivatives to Calcite Surfaces in Aqueous Environment

2020 ◽  
Author(s):  
Robert Stepic ◽  
Lara Jurković ◽  
Ksenia Klementyeva ◽  
Marko Ukrainczyk ◽  
Matija Gredičak ◽  
...  
Keyword(s):  
Active Sites ◽  
Realistic Model ◽  
Binding Energies ◽  
Inhibition Mechanism ◽  
Aqueous Environment ◽  
Binding Modes ◽  
Carboxylate Groups ◽  
Dissolved Ions ◽  
Living Organisms ◽  
Dynamics Simulations

In many living organisms, biomolecules interact favorably with various surfaces of calcium carbonate. In this work, we have considered the interactions of aspartate (Asp) derivatives, as models of complex biomolecules, with calcite. Using kinetic growth experiments, we have investigated the inhibition of calcite growth by Asp, Asp2 and Asp3.This entailed the determination of a step-pinning growth regime as well as the evaluation of the adsorption constants and binding free energies for the three species to calcite crystals. These latter values are compared to free energy profiles obtained from fully atomistic molecular dynamics simulations. When using a flat (104) calcite surface in the models, the measured trend of binding energies is poorly reproduced. However, a more realistic model comprised of a surface with an island containing edges and corners, yields binding energies that compare very well with experiments. Surprisingly, we find that most binding modes involve the positively charged, ammonium group. Moreover, while attachment of the negatively charged carboxylate groups is also frequently observed, it is always balanced by the aqueous solvation of an equal or greater number of carboxylates. These effects are observed on all calcite features including edges and corners, the latter being associated with dominant affinities to Asp derivatives. As these features are also precisely the active sites for crystal growth, the experimental and theoretical results point strongly to a growth inhibition mechanism whereby these sites become blocked, preventing further attachment of dissolved ions and halting further growth.

ИЗУЧЕНИЕ СТРУКТУРЫ ДНК В ПЛЕНКАХ МЕТОДОМ ИК-ФУРЬЕ-СПЕКТРОСКОПИИ

2020 ◽  
Vol 65 (6) ◽  
pp. 1058-1064
Author(s):  
С.В. Пастон ◽  
◽  
А.М. Поляничко ◽  
О.В. Шуленина ◽  
Д.Н. Осинникова ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Hydration Shell ◽  
Aqueous Environment ◽  
Ir Absorption ◽  
Sodium Ions ◽  
High Molecular Weight Dna ◽  
Dna Hydration ◽  
Na Ions ◽  
Phosphate Groups ◽  
Dna Film

The aqueous environment and ionic surrounding are the most important factors determining the conformation of DNA and its functioning in the cell. The specificity of the interaction between DNA and cations is especially pronounced with a decrease in water activity. In this work, we studied the B-A transition in high molecular weight DNA with a decrease of humidity in the film with different contents of Na+ ions using FTIR spectroscopy. The IR spectrum of DNA is not only very sensitive to the state of its secondary structure, but also allows us to estimate the amount of water bound to DNA. Upon dehydration of the DNA film, changes characteristic of the B-A transition were observed in the IR absorption spectrum. Using thermogravimetric analysis, it was shown that the degree of DNA hydration reaches the saturation level at a relative humidity of 60% and decreases slightly upon further drying. It has been established that with increasing Na+ concentration, the amount of water strongly bound to DNA decreases. Along with it, sodium ions destroy the hydration shell of DNA and are able to interact directly with phosphate groups.

Hydrogels: A Versatile Drug Delivery Carrier Systems

1970 ◽  
Vol 5 (3) ◽  
pp. 1745-1756
Author(s):  
L H Baldaniya ◽  
Sarkhejiya N A
Keyword(s):  
Drug Delivery ◽  
Protein Delivery ◽  
Structural Integrity ◽  
Healing Process ◽  
Polymer Chains ◽  
Wound Healing Process ◽  
Aqueous Environment ◽  
Preparation Methods ◽  
Control Drug

Hydrogels are the material of choice for many applications in regenerative medicine due to their unique properties including biocompatibility, flexible methods of synthesis, range of constituents, and desirable physical characteristics. Hydrogel (also called Aquagel) is a network of polymer chains that are hydrophilic, sometimes found as a colloidal gel in which water is the dispersion medium. Hydrogels are highly absorbent (contain ~99.9% water), natural or synthetic polymers. Hydrogel also possess a degree of flexibility very similar to natural tissue, due to its significant water content. It can serve as scaffolds that provide structural integrity to tissue constructs, control drug and protein delivery to tissues and cultures. Also serve as adhesives or barriers between tissue and material surfaces. The positive effect of hydrogels on wounds and enhanced wound healing process has been proven. Hydrogels provide a warm, moist environment for wound that makes it heal faster in addition to its useful mucoadhesive properties. Moreover, hydrogels can be used as carriers for liposomes containing variety of drugs, such as antimicrobial drugs. Hydrogels are water swollen polymer matrices, with a tendency to imbibe water when placed in aqueous environment. This ability to swell, under biological conditions, makes it an ideal material for use in drug delivery and immobilization of proteins, peptides, and other biological compounds. Hydrogels have been extensively investigated for use as constructs to engineer tissues in vitro. This review describes the properties, classification, preparation methods, applications, various monomer used in formulation and development of hydrogel products.

Corrosion Process of Incoloy-800 in High Pressure and Temperature Aqueous Environment

2008 ◽  
Vol 59 (9) ◽  
Author(s):  
Dumitra Lucan ◽  
Manuela Fulger ◽  
Gheorghita Jinescu
Keyword(s):  
Corrosion Behaviour ◽  
Gravimetric Method ◽  
Corrosion Process ◽  
Aqueous Environment ◽  
Accelerated Tests ◽  
Steam Generators ◽  
High Pressure And Temperature ◽  
Eds Analysis ◽  
Incoloy 800 ◽  
Steam Generator Tubes

The Steam Generators (SG), equipment that ensures the connection between the primary and secondary circuits, creates several safety problems during operation, mainly due to corrosion and mechanical damages. To provide information about the corrosion behaviour of the structural materials from CANDU SG under normal and abnormal conditions of operation and to identify the failure types produced by the corrosion were performed corrosion experiments consisting in chemical accelerated tests, static autoclaving and electrochemical methods. The gravimetric method, optical metallographic microscopy, XRD and EDS analysis, as well as electrochemical measurements have been used to evaluate the corrosion behavior of the steam generator tubes material (Incoloy-800).

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