scholarly journals MODERN HYDROACTIVE POLYURETHANE FOR RESTORATION OF WATERPROOFING CAPABILITY OF HYDROTECHNICAL STRUCTURES

2019 ◽  
pp. 108-116
Author(s):  
O. V. Kovalenko
Keyword(s):  
Water Management ◽  
Environmental Temperature ◽  
Water Filtration ◽  
Polymerization Reaction ◽  
Foam Formation ◽  
Hydraulic Concrete ◽  
Rate Of Polymerization ◽  
Wide Range ◽  
Concrete Body ◽  
Two Component

The main material of the hydrotechnical structures of the water management and reclamation complex is concrete. Its durability is the main indicator of reliability of building operation. The high density of hydraulic concrete, which determines the water resistance, is a guarantee of its durability. At the same time, in hydraulic concrete during the operation under the influence of aggressive environmental factors various defects (cracks, dissected zones)develop, which reduce its waterproofing capability. These defectsare the main centers of water filtration through building structures. At first, drip filtration develops in buildings, which in the course of time increases into active jet filtration. That can lead to the complete destruction of the building. In this connection, the issue of restoration of monolithicity and waterproofing of concrete hydro-technical constructions is relevant. The solution of the problem may be the use of injection waterproofing of the structures when using hydroactive polyurethane resins. Due to the presence in the chain of macromolecules the final isocyanate (-NCO) groups, polyurethanes are capable for interacting with water molecules with the release of carbon dioxide, which leads to foaming. As a result, water blockage occurs in the concrete body and its waterproofing is restored. The analysis of the modern construction market shows that there is currently a sufficiently wide range of single- and two-component hydroactive polyurethane resins capable of reacting with water with foam formation. As the study has shown, the rate of polymerization, the beginning and the end of polyurethane compositionsfoaming substantially depend on the rate of catalyst or polymerization accelerator in the composition, as well as on the environmental temperature. So,when increasing the rate of catalyst in the mixture from 2 to 9%, the rate of polymerization reaction increases by 3,3-3,9 times, and when increasing the environmental temperature from 10 to 25 °C, the polymerization rate increases in 1,3-1,4 times. The foaming time of polyurethane compositions varies within 0,8 ... 16 minutes. Depending on the polyurethane formulations, the resins can be slow- reactive, fast-reactive and ultrafast-reactive, which opens a prospect for their application in the conditions of the filtration of different intensity: from drip to jet. Two-component polyurethane resins are the most promising for application in the technology of injection waterproofing on hydraulic engineering structures of water management and reclamation area, which enable to eliminate water leakage through the structures of different intensity: from drip to active jet filtration. Two-component polyurethane resins such as CarboPur, Tunnelinjekt, PenePurFoam, when contacting with water, form a rigid elastic foam with high physical and mechanical properties: bending strength up to 80 MPa, adhesion to water-saturated concrete to 2, 8 MPa. Field study proved the high efficiency of injecting waterproofing with the use of hydroactive polyurethane resins in the conditions of water filtration through the structures of docking facilities of pumping stations. In the course of implementation of the projects on the restoration of waterproofing of reinforced concrete structures, the following types of work were performed: eliminating leaks through the isolation joints of concrete, as well as through shrinkage and structural cracks; eliminating leaks in the adjacent zones of "wall-floor", "wall-ceiling"; sealing leaks through the places of engineering communications laying(pipelines); arrangement of shut-off and veal waterproofing in the walls (injection of resins into dilapidated zones of the structure).

scholarly journals Modern cement-based waterproofings for hydraulic structures protection

2020 ◽  
pp. 175-185
Author(s):  
O. V. Kovalenko
Keyword(s):  
Water Management ◽  
Reinforced Concrete ◽  
Concrete Structures ◽  
Operational Reliability ◽  
Water Filtration ◽  
Hydraulic Structures ◽  
Reinforced Concrete Structures ◽  
Two Component ◽  
Polymer Latex ◽  
Selection Of

Hydrotechnical structures of water management and land reclamation complex from the moment of commissioning are subject to aggressive environmental effects: hydrostatic water pressure, alternating freezing and thawing, moistening and drying, corrosive action of salts dissolved in water, dynamic action of ice. The trouble-free operation of structures with long-term aggressive environmental factors is possible only in the case of providing their protection (reinforcement) with effective insulating, anticorrosive, high-strength, wear-resistant and cavitation-resistant composite materials. Waterproofing coatings, which arrange on the surface of reinforced concrete structures, plays an important role in ensuring operational reliability and durability of hydraulic structures. Having rather low cost of waterproofing coatings as compared to the cost of structures the fate of their responsibility in terms of ensuring the durability and operational reliability of the structures is high enough. Waterproofing coatings serve as a barrier to an aggressive environment and thus protect structures from destruction. Notwithstanding the importance of waterproofing protection, this issue is not given due attention today. Therefore, filtration of water through the structures of water-reclamation facilities is a common phenomenon. Water filtration through damaged concrete of hydraulic structures causes dissolution and leaching of water with calcium hydroxide (leaching), which further causes the decomposition of other components of the cement stone and leads to the dilution of the concrete structure and to the strengthening of drip filtration. Drip filtration increases over time, then jet filtration develops, which can lead to complete destruction of the structure. Therefore, providing waterproofing protection of structures is an important engineering task in their construction and operation. One of the determining factors for the effectiveness of waterproofing is the right selection of material. Traditional waterproofing materials on a bituminous basis have insufficient physical-mechanical properties and durability. However, modern technologies of waterproofing protection of concrete and reinforced concrete structures are based on the use of effective composite materials with high physical, mechanical and protective properties. Depending on the type of binder, waterproofing materials can be based on bitumen, bituminous-mineral, bitumen-polymer, coal, polymer compositions, as well as on the basis of cements and polymer cements. The selection of a waterproofing material should be made taking into account the specifics of the operating environment and the conditions of use. The most common in the construction of gluing roll materials on a bituminous basis can only partially satisfy the need for hydraulic engineering, as for the waterproofing of hydraulic structures. There are high requirements with regard to the aggressiveness of the environment and their low repairsability. The most promising for use in the technology of arrangement of waterproofing coatings on concrete and reinforced concrete structures of hydraulic engineering facilities of water management and reclamation complex are polymer cement mixtures, binders in which are Portland cement modified with polymer latex dispersion powder (for two-component). Creation of effective polymer cement waterproofing compositions is based on optimization of the ratio of interpenetrating meshes of polymers and crystal matrix hydrates. Modification of cement systems by polymers allows to increase adhesion and deformation characteristics, fracture resistance and corrosion resistance of polymer cement composites. Depending on the components included in the mixture, waterproofing coatings may be rigid or elastic. Rigid formulations are a water-mixed, dry mixture that includes a vinyl acetate copolymer and designed for waterproofing concrete and reinforced concrete structures with low water filtration. Elastic waterproofing materials are usually two-component. These materials are used for waterproofing structures that are susceptible to deformation, as well as surfaces with a high degree of water filtration and where cracks up to 1 mm are formed. Elastic two-component formulations are dry mixtures with the addition of redispersible polymer powders. They consist of two components: a dry mixture of modified fine cement and aqueous latex polymer, usually acrylic. The content of polymer latex in the mixture has a significant effect on the rheological properties of polymer-cement mixtures and on the physical and mechanical properties of waterproofing coatings made of them. Thus, the introduction of a redispersible polymer powder Axilat L 8262 in a waterproofing mixture in the amount of up to 10% by weight of cement increases the mobility of the mixture from 3,2 to 8,0 cm, increases the adhesive strength of the coating to concrete from 0,45 to 1,95 MPa, increases its bending strength from 6,9 to 7,9 MPa, reduces its water absorption in 24 hours from 7,02% to 0,35% .  

The co-polymerization of styrene and butyl acrylate in benzene solution

1954 ◽  
Vol 222 (1151) ◽  
pp. 456-470 ◽  
Keyword(s):  
Butyl Acrylate ◽  
Benzene Solution ◽  
Polymerization Reaction ◽  
Monomer Reactivity Ratios ◽  
Increase With Increase ◽  
Rate Of Polymerization ◽  
Wide Range ◽  
Benzene Concentration ◽  
Monomer Feed ◽  
Radioactive Assay

An investigation has been made of the co-polymerization of styrene and butyl acrylate in benzene solution with the object of determining the effect of environment on the several steps of a typical co-polymerization reaction. The reaction at 60° was thermally initiated by 14 C-labelled αα'-azobis iso butyronitrile. The rate of polymerization was obtained from the weight of polymer isolated and the rate of initiation by radioactive assay of initiator and polymer. Microanalysis of the pure co-polymers for carbon allowed calculation of the monomer reactivity ratios which were found to be constant over a wide range of benzene concentration. For each monomer the quantity δ = k t 1/α / k D , calculated by the rate equation for mutual termination, was found to increase with increase of the benzene concentration. The appropriate values of δ were used, along with other relevant quantities, to calculate the ϕ factor, which measures the tendency for termination of chains by interaction of unlike rather than like radicals. This factor is independent of the benzene concentration but is markedly dependent on the monomer feed. In the light of these results the effect of environment and structure of radicals on the rate of their interaction is discussed.

scholarly journals MisR/MisS Two-Component Regulon in Neisseria meningitidis

2007 ◽  
Vol 76 (2) ◽  
pp. 704-716 ◽  
Author(s):  
Yih-Ling Tzeng ◽  
Charlene M. Kahler ◽  
Xinjian Zhang ◽  
David S. Stephens
Keyword(s):  
Neisseria Meningitidis ◽  
Target Genes ◽  
Inner Core ◽  
Consensus Sequence ◽  
Meningococcal Infection ◽  
Type I ◽  
Mobility Shift ◽  
Iron Assimilation ◽  
Wide Range ◽  
Two Component

ABSTRACT Two-component regulatory systems are involved in processes important for bacterial pathogenesis. Inactivation of the misR/misS system in Neisseria meningitidis results in the loss of phosphorylation of the lipooligosaccharide inner core and causes attenuation in a mouse model of meningococcal infection. One hundred seventeen (78 up-regulated and 39 down-regulated) potential regulatory targets of the MisR/MisS (MisR/S) system were identified by transcriptional profiling of the NMBmisR mutant and the parental wild-type meningococcal strain NMB. The regulatory effect was further confirmed in a subset of target genes by quantitative real-time PCR and β-galactosidase transcriptional fusion reporter assays. The MisR regulon includes genes encoding proteins necessary for protein folding in the bacterial cytoplasm and periplasm, transcriptional regulation, metabolism, iron assimilation, and type I protein transport. Mutation in the MisR/S system caused increased sensitivity to oxidative stress and also resulted in decreased susceptibility to complement-mediated killing by normal human serum. To identify the direct targets of MisR regulation, electrophoretic mobility shift assays were carried out using purified MisR-His6 protein. Among 22 genes examined, misR directly interacted with 14 promoter regions. Six promoters were further investigated by DNase I protection assays, and a MisR-binding consensus sequence was proposed. Thus, the direct regulatory targets of MisR and the minimal regulon of the meningococcal MisR/S two-component signal transduction system were characterized. These data indicate that the MisR/S system influences a wide range of biological functions in N. meningitidis either directly or via intermediate regulators.

scholarly journals Water Filtration Membranes Based on Non-Woven Cellulose Fabrics: Effect of Nanopolysaccharide Coatings on Selective Particle Rejection, Antifouling, and Antibacterial Properties

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1752
Author(s):  
Blanca Jalvo ◽  
Andrea Aguilar-Sanchez ◽  
Maria-Ximena Ruiz-Caldas ◽  
Aji P. Mathew
Keyword(s):  
Cellulose Nanofibers ◽  
Antibacterial Properties ◽  
Surface Characteristics ◽  
Water Filtration ◽  
Separation Performance ◽  
Nonwoven Fabrics ◽  
Filtration Membranes ◽  
Wide Range ◽  
Dry Conditions ◽  
Cellulose Fabrics

This article presents a comparative study of the surface characteristics and water purification performance of commercially available cellulose nonwoven fabrics modified, via cast coating, with different nano-dimensioned bio-based carbohydrate polymers, viz. cellulose nanocrystals (CNC), TEMPO-oxidized cellulose nanofibers (T-CNF), and chitin nanocrystals (ChNC). The surface-modified nonwoven fabrics showed an improvement in wettability, surface charge modification, and a slight decrease of maximum pore size. The modification improved the water permeance in most of the cases, enhanced the particle separation performance in a wide range of sizes, upgraded the mechanical properties in dry conditions, and showed abiotic antifouling capability against proteins. In addition, T-CNF and ChNC coatings proved to be harmful to the bacteria colonizing on the membranes. This simple surface impregnation approach based on green nanotechnology resulted in highly efficient and fully bio-based high-flux water filtration membranes based on commercially available nonwoven fabrics, with distinct performance for particle rejection, antifouling and antibacterial properties.

scholarly journals GIS use in solving water supplying and water environmental problems of Urban Territories

2018 ◽  
Vol 170 ◽  
pp. 04008
Author(s):  
Nadezhda Kurepina ◽  
Irina Rybkina
Keyword(s):  
Water Management ◽  
Research Work ◽  
Environmental Problems ◽  
Geoinformation Systems ◽  
Step Procedure ◽  
Wide Range ◽  
Urban Territories ◽  
Cartographic Modeling ◽  
Academy Of Sciences ◽  
Regional Water

Geoinformation systems (GIS) are actively used in modern scientific research, including the field of Urban Territories’ management. The lack of a universal methodology for their application requires an individual approach in the study of water management and water and environmental problems in the region. The purpose of this article is to demonstrate concrete examples of GIS successful use in solving some water supplying problems. One of the leading research methods is geoinformation-cartographic modeling, which has a wide range of possibilities and contributes to the effective solution of water-related and water-ecological regional problems. The developed algorithm for GIS using in solving regional water, a step-by-step procedure organizes for carrying out research work, the presented structure of the thematic database facilitates the systematizatin of thematic data large volume with the base a GIS project is created, where information is integrated, calculations, and a cartographic model is created that visualizes the regional water management and water-e logical situation. The research examples carried out in the Institute of Hydrometeorology of the Russian Academy of Sciences (Siberian Branch) on regional water management and water ecological problems by means of GIS and using the method of geoinformation-cartographic modeling considered in this paper prove the effectiveness and their use expediency.

Influence of water filtration on the determination of a wide range of dissolved contaminants at parts-per-trillion levels

2007 ◽  
Vol 583 (1) ◽  
pp. 202-209 ◽  
Author(s):  
Anna Gómez-Gutiérrez ◽  
Eric Jover ◽  
Josep M. Bayona ◽  
Joan Albaigés
Keyword(s):  
Water Filtration ◽  
Wide Range ◽  
Influence Of Water

Histidine kinases in signal transduction pathways of eukaryotes

1997 ◽  
Vol 110 (10) ◽  
pp. 1141-1145 ◽  
Author(s):  
W.F. Loomis ◽  
G. Shaulsky ◽  
N. Wang
Keyword(s):  
Signal Transduction ◽  
Response Regulator ◽  
Signal Transduction Pathways ◽  
Response Regulators ◽  
Histidine Kinases ◽  
Camp Phosphodiesterase ◽  
Wide Range ◽  
Two Component ◽  
Two Component Signal Transduction ◽  
Dependent Protein

Autophosphorylating histidine kinases are an ancient conserved family of enzymes that are found in eubacteria, archaebacteria and eukaryotes. They are activated by a wide range of extracellular signals and transfer phosphate moieties to aspartates found in response regulators. Recent studies have shown that such two-component signal transduction pathways mediate osmoregulation in Saccharomyces cerevisiae, Dictyostelium discoideum and Neurospora crassa. Moreover, they play pivotal roles in responses of Arabidopsis thaliana to ethylene and cytokinin. A transmembrane histidine kinase encoded by dhkA accumulates when Dictyostelium cells aggregate during development. Activation of DhkA results in the inhibition of its response regulator, RegA, which is a cAMP phosphodiesterase that regulates the cAMP dependent protein kinase PKA. When PKA is activated late in the differentiation of prespore cells, they encapsulate into spores. There is evidence that this two-component system participates in a feedback loop linked to PKA in prestalk cells such that the signal to initiate encapsulation is rapidly amplified. Such signal transduction pathways can be expected to be found in a variety of eukaryotic differentiations since they are rapidly reversible and can integrate disparate signals.

Intervention of Climate Smart Agriculture Practices in Farmers Field to Increase Production and Productivity of Winter Maize in Terai Region of Nepal

2018 ◽  
Vol 35 (1) ◽  
pp. 59-66
Author(s):  
J. J. Gairhe ◽  
M. Adhikari
Keyword(s):  
Climate Change ◽  
Water Management ◽  
Plant Density ◽  
Cropping System ◽  
Appropriate Technology ◽  
Residue Management ◽  
Zero Tillage ◽  
Yield Attributes ◽  
Wide Range ◽  
Smart Agriculture

Climate change has been the burning issue in agriculture sector. The research world is focused on developing appropriate technology, innovations and concept to cope up this change. The Climate Smart Agriculture [CSA] has been adapted globally for cultivation and crop management in changing context without compromising yield and productivity. The CSA involves wide range altered techniques and innovations like using resilient varieties, water management, zero tillage, legumes incorporation, cover cropping, site specific fertilizer management, variation in planting date etc. Grounding on the similar practices and principles of CSA, the research in maize was conducted in 2014 in farmers' field of Eastern Nepal. Three progressive farmers with 1 hector of land were selected and Maize was cultivated using Zero tillage seed cum fertilizer driller tractor. This field experiment considers farmers as replication with six different treatments. All treatments differ to each other based on nutrient management, water management, residue management, tillage practice, crop establishment, and inclusion of legumes in the cropping system. Six treatments are coded as follows: Current Irrigated (CI), Improved Irrigated Low (IIL), Improved Irrigated High (IIH), Climate Smart Agriculture-Low (CSA-L), Climate Smart Agriculture-Medium (CSA-M), and Climate Smart Agriculture-High (CSA-H). Significant impact of intervention was observed in yield and yield attributes in the trial with climate smart agriculture practices than in conventional practices of farmers. Plant density, ear number, filled grains per cob and grain yield was substantially higher in climate smart practices revealing CSA to be the appropriate technology to minimize potential loss of climate change.

scholarly journals The Evanescent GacS Signal

2020 ◽  
Vol 8 (11) ◽  
pp. 1746
Author(s):  
Xavier Latour
Keyword(s):  
Biofilm Formation ◽  
Plant Protection ◽  
Signal Transduction Pathway ◽  
Low Molecular Weight ◽  
Transduction Pathway ◽  
Significant Progress ◽  
Two Component System ◽  
Wide Range ◽  
Two Component ◽  
Bacterial Fitness

The GacS histidine kinase is the membrane sensor of the major upstream two-component system of the regulatory Gac/Rsm signal transduction pathway. This pathway governs the expression of a wide range of genes in pseudomonads and controls bacterial fitness and motility, tolerance to stress, biofilm formation, and virulence or plant protection. Despite the importance of these roles, the ligands binding to the sensor domain of GacS remain unknown, and their identification is an exciting challenge in this domain. At high population densities, the GacS signal triggers a switch from primary to secondary metabolism and a change in bacterial lifestyle. It has been suggested, based on these observations, that the GacS signal is a marker of the emergence of nutritional stress and competition. Biochemical investigations have yet to characterize the GacS signal fully. However, they portray this cue as a low-molecular weight, relatively simple and moderately apolar metabolite possibly resembling, but nevertheless different, from the aliphatic organic acids acting as quorum-sensing signaling molecules in other Proteobacteria. Significant progress in the development of metabolomic tools and new databases dedicated to Pseudomonas metabolism should help to unlock some of the last remaining secrets of GacS induction, making it possible to control the Gac/Rsm pathway.

Kinetics of Isoprenepolymerization Initiated with TiCl4—Trialkyl Aluminum

1960 ◽  
Vol 33 (3) ◽  
pp. 696-698
Author(s):  
S. E. Bresler ◽  
M. I. Mosevitskiĭ
Keyword(s):  
Active Sites ◽  
Reaction Medium ◽  
Heat Evolution ◽  
Polymerization Reaction ◽  
Reaction Conditions ◽  
Low Viscosity ◽  
Rate Of Polymerization ◽  
Rate Of Reaction ◽  
Entire Experiment ◽  
Kinetics Of

Abstract For the study of the mechanism of polymerization by means of complexes of aluminum organic compounds with titanium chlorides, data on the kinetics of polymerization is of great interest. Up to the present time, the rate of polymerization of propylene has been studied but the interpretation of the kinetic data is difficult because the polymer, which is practically insoluble in the reaction medium, entraps the catalyst resulting in a rate of reaction which is dependent on the diffusion of monomer through the polymer to the active sites. In this work the polymerization of isoprene, which yields polymers soluble in the monomer, in saturated hydrocarbons and in benzene, was studied. The rate of the polymerization reaction was measured by the thermal effect in a calorimeter consisting of a 3.5 1. Dewar flask, with a lid, immersed in a thermostated air bath maintained at approximately the temperature of the reaction. Low viscosity spindle oil, heated to the temperature of the reaction (about 32°), served as the calorimeter fluid. The ampoule holder extended outside of the calorimeter and was connected to a shaking apparatus. The ampoule was divided by a thin partition into two sections each holding 45–50 cc. Into one section previously purified monomers and solvent were distilled. The other section was filled with catalyst components from a Shlenk container. The change in temperature of the calorimeter was determined with a Beckman thermometer with an accuracy of 0.01 °. When the temperature of the calorimeter containing the ampoule remained constant to within 0.01–0.02° for 30–40 minutes, the shaking apparatus was connected and the partition was broken with a striker. Intensive shaking was continued during the entire experiment resulting in mixing of the reaction mixture and of the calorimeter fluid. The rate of reaction was determined by the rate of heat evolution ; in other words, by the temperature rise in the calorimeter. For a rise of 0.1–0.5° the reaction conditions remained practically isothermal. This rise permits the kinetics of the reaction to be observed with sufficient accuracy. Adiabaticity of the calorimeter and the effect of mechanical heat were controlled in separate experiments.

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