In the Volga River water, sulfate ions rank second among the main anions in terms of their contribution to water mineralization. To study the seasonal variability of sulfate concentration, an ...analysis of long-term data of hydrological and hydrochemical observations obtained on the River Volga (in the outlet section of the Kuibyshev reservoir) has been carried out. For the period of 2001-2018 the average annual water consumption in the dam section varied in the range of 6.2-9.0 thousand m3/s, the average annual concentration of sulfates was 55 mg/dm3, the highest - 64 mg/dm3, and the lowest - 45 mg/dm3. The content of sulfates in the reservoir is formed mainly under the influence of the Volga River water coming from the Cheboksary reservoir and the Kama River water coming from the Nizhnekamsk reservoir. The sulfate content is characterized by significant seasonal variability. During the winter low-water period, the highest concentrations of sulfates were observed with a maximum in April, before the beginning of the spring flood (67 mg/dm3). During the flood, the content of sulfates decreased, reaching the lowest values during the summer low-water period in August (44 mg/dm3), and then, from September, the concentration of sulfates gradually increased, reaching 57 mg/dm3 at the beginning of the winter low-water period. Over a long-term observation period, the amplitude of sulfate fluctuations was 34-87 mg/dm3, and its value depended on the water content of a particular year. In dry years, the concentration of sulfates in the water increased, and in dry years, it decreased. In the seasonal context, the main differences in sulfate concentrations in dry and high-water years occurred during the spring flood and winter low-water period, and during the summer - autumn low-water period, the differences became minimal.
The essential role of water in extra- and intracellular coiled coil structures of proteins is critically evaluated, and the different protein types incorporating coiled coil units are overviewed. The ...following subjects are discussed: i) influence of water on the formation and degradation of the coiled coil domain together with the stability of this conformer type; ii) the water’s paradox iii) design of coiled coil motifs and iv) expert opinion and outlook is presented. The clear and dark sides refer to the positive and negative aspects of the water molecule, as it may enhance or inhibit a given folding event. This duplicity can be symbolized by the Roman ‘
-face’ which means that water may facilitate and stimulate coiled coil structure formation, however, it may contribute to the fatal processes of oligomerization and amyloidosis of the very same polypeptide chain.
The possibility of adsorption of polluting gases (nitrogen dioxide, methane, ammonia, sulfur dioxide, hydrogen sulfide, ozone, carbon monoxide, carbon monoxide, chlorine) on the surface of ...iron-containing PAN was evaluated. A model of an iron-containing PAN cluster has been built. The method of molecular modeling was used to determine the thermodynamic parameters of systems: Fe-PAN cluster–gas molecule, Fe-PAN cluster–oxygen molecule, Fe-PAN cluster–water molecule, Fe-PAN cluster–oxygen molecule–gas molecule, Fe-PAN cluster – water molecule is a gas molecule and their comparison is made. The effect of oxygen on polluting gases adsorption on the iron-containing PAN cluster surface is revealed, while the influence of water molecules in the immediate vicinity of the cluster is not observed. The capability of iron-containing PAN to adsorb chlorine and carbon monoxide has been revealed in our calculations.
Based on the chemical model of coal, slit micropores with different pore sizes are established and structures are optimized in the software of materials studio. As the temperature rises, absolute ...adsorption capacities of H
2
O are slightly affected, while absolute adsorption capacities of CO
2
and CH
4
gradually decrease. As the fugacity rises, excess adsorption curves of CO
2
experience increase-decrease-gentle three stages, while the curves of CH
4
gradually decrease. With the increase of pore size, adsorption capacities of H
2
O increase, while adsorption capacities of CO
2
and CH
4
gradually decrease. H
2
O firstly adsorbs on the oxygen-containing functional group, so the walls of pore are the preferential area for H
2
O, while CO
2
and CH
4
choose to adsorb on–C–C–, therefore the walls are the primary area for CO
2
and CH
4
. Strong potential in micropores and hydrogen bond among water molecules will promote the water adsorption, while the adsorptions of CO
2
and CH
4
are only induced by the Van der Waals interaction, but the difference between adsorption density and bulk density of CO
2
and CH
4
decides the change of excess adsorption capacity.
The catalytic activity of Au-TiO2 -In2 O3 catalyst in the oxidation of CO in the presence and absence of added water vapour and using different pretreatment conditions was tested and compared with ...that of a Au-TiO2 sample prepared using a commercial support used as a reference catalyst. The Au-TiO2 -In2 O3 samples showed less activity than the standard Au-TiO2 sample but could be reused after reaction up to 500 °C without loss of activity. The activity of Au-TiO2 -In2 O3 catalysts for CO oxidation was relatively insensitive to the pretreatment procedures but showed quite distinct light-off curves compared with those of Au-TiO2 . Differences between the catalytic behaviour of the two Au-supported catalysts indicate differences in the relative ease by which the oxides become dehydroxylated by thermal treatments. Results for Au-TiO2 -In2 O3 are consistent with a scheme in which at low temperatures (= or <, slanted264 °C), CO2 formation involves gold sites with participation of hydroxyl groups of the support. Above this temperature, dehydroxylation of the support leaves the gold component with low activity, and the rate of CO2 formation becomes equivalent to the rate obtained over the support alone. Cooling the samples back to room temperature recovers the initial activity of the gold, confirming that deactivation is completely reversible. Experiments conducted involving deliberate addition of water show that the deactivation caused by an excess of H 2 O for both Au-TiO2 and Au-TiO2 -In2 O3 is also reversible, and that the extent to which water is retained is quite different for the two catalysts. Reaction mechanisms, taking into account the involvement of H2 O, are discussed.
The reduction of NO by CO over gold catalysts supported on ceria doped by rare earth metals (Y, La, Sm and Gd) was studied. The mixed oxide supports, containing 10
wt% of the dopant, were prepared by ...co-precipitation and then 2
wt% gold was loaded by deposition–precipitation method. Gold catalysts, supported on lanthanides doped ceria showed a high activity and stability. The conversions both of NO and CO at 250
°C were close to 100% using Sm, La or Gd as dopants. Below 250
°C the Au catalyst on Sm doped ceria exhibited a little higher activity. The lowest catalytic activity was observed using Y as a modifier. The lattice parameter
a of ceria and the average size of ceria crystallites were evaluated by XRD. The defective structure of ceria, including oxygen vacancies, caused by the introduction of Me
3+ dopant, was estimated by Raman spectroscopy data. The redox behaviour of fresh gold samples as well as after their reoxidation at 220
°C was established by TPR technique. The low temperature reducibility of the reoxidized gold catalysts supported on doped CeO
2 showed a good correlation with the catalytic properties. It was established that the addition of water to the gas feed improved the catalysts’ selectivity to N
2.
An analysis of the causes of erosion-induced wear of the metal in pipe bends of evaporator heating pipe surfaces is performed based on experience gained from the operation of the heat-recovery ...boilers of combined-cycle (steam-gas) power plants. Damage to the evaporator tubes of a low-pressure boiling circuit is caused by the destruction of the protective oxide film due to intensive turbulization of the near-wall layer of water (which is at saturation temperature) travelling through the bend, inducing cavitation due to the formation of steam bubbles and their condensation. The protective oxide film formed in the hydrate water chemistry regime possesses the greatest stability.
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