The complete analysis of the polyorganosiloxanes formed by the trimethylsilylation of the minerals olivine and suzorite

Methods are reported for the separation and complete quantitative estimation of the polyorganosiloxanes prepared by the trimethylsilylation of mineral silicates. Quantitative methods for the determination of low molecular weight oligomers up to Q₆M₁₂ (Q≡SiO_4/2; M≡(CH₃)₃SiO_1/2) are well known but there are no previously reported methods for the determination of high molecular weight species. This paper describes the application of gel permeation chromatography and quantitative high performance liquid chromatography to the study of these higher molecular weight species. Polyorganosiloxanes prepared from suzorite (a phlogopite) and from olivine (an orthosilicate) are used as examples. A further example is a study of the formation of higher molecular weight species on heating these polymers.     

Effect of the viscosity of the resin on the properties of resin — Dolomite — Magnesite refractories

Conclusions Calcined dolomite with a porosity up to 5% is not impregnated by resins of different viscosities (from 86 to 1200 sec at 40°C).Unfired products made from pastes in soft resins are characterized by a high degree of hydration and relatively low strength. Products in hard resins have better properties. The properties of the products after coking calcination are practically identical.Aging of the pastes does not substantially change the properties of unfired products. An increase in the aging time from 3 to 10 days leads to a noticeable worsening of the properties of the products after coking calcination.Since the properties of the products in resins of different viscosity after coking calcination are practically identical, in the production of resindolomite — magnesite products for converters, successful use can be made of resins of different viscosity, but with a coking number no less than 28–32%. The choice of the resin is determined by the technological flowsheet of the process for production of converter refractories: resins with low viscosity (C ₄₀ ¹⁰ up to 100 sec) by the cold process, resins with high viscosity (C ₄₀ ¹⁰ more than 1000 sec) by the hot process for preparation of the products.Translated from Ogneupory, No.4, pp. 39–45, April, 1968.     

An update on the mechanism of the graphene–NO reaction

Cognizant of the key experimental facts from studies of carbonaceous solids ranging from soot to graphite, we performed a quantum chemistry study of the interaction of NO monomer or dimer with one or more zigzag sites. Thermodynamic and kinetic results were used to examine two alternative mechanisms proposed in the literature, and to compare them with the graphene–O₂ reaction mechanism. The chemisorption stoichiometry similarities are striking; but the differences, especially regarding the intermediate role of N₂O, have important practical implications. Monomer chemisorption on an isolated site is a dead-end and temporarily inhibiting process, similar to that of formation of a stable C–O surface complex in the graphene–O₂ reaction. When two sites are available, successive monomer adsorption eventually leads to N₂O formation subsequent to parallel reorientation of the first NO molecule. If three contiguous sites are available, N₂ and CO are the principal products. Chemisorption of the dimer provides a straightforward path to N₂ and CO₂ when one site is available and to N₂ and CO when two sites are available. The formation of N₂O is also feasible in this case, both during adsorption and desorption; in the adsorption phase it is very sensitive to the details of the electron pairing processes.     

On the origin of the sigmoid shape in the UO2 oxidation weight gain curves

Cracking and spalling are known to occur during the oxidation of UO₂. However, these phenomena are not considered by the existing kinetic models of the oxidation of UO₂ into U₃O₈. In this study the oxidation of UO₂ samples of various sizes from the single crystal to nanopowders, has been followed by isothermal and isobaric thermogravimetry, environmental scanning electron microscopy and in situ X-ray diffraction at temperatures ranging from 250 to 370 °C in air. It has been shown that cracking occurs once a critical layer thickness of intermediate oxide has been reached, which corresponds to the beginning of the sigmoid kinetic curve. Cracking contribution to the sigmoid kinetic curve is then discussed as a function of temperature, and on the basis of nucleation and growth processes.     

Modelling coal combustion: the current position

At the present time, computer models for coal combustion are not sufficiently accurate to enable the design of combustion plant or the selection of a coal based on combustion behaviour. Most comprehensive combustion models can predict with reasonable accuracy flow fields and heat transfer, but usually with a much lesser degree of accuracy than the combustion of the coal particles through to char burnout. Many research programmes are aimed at developing a much more accurate predictive tool for assessing coals specially fired in burners or furnaces employing a range of NO_x abatement technologies. Some of the current developments in CFD coal combustion modelling are outlined here. Particular attention is paid to the first step, where the devolatilisation pre-processor code is used to compute the pyrolysis rate, the yields and the composition of volatiles and char. These parameters are used as inputs to the devolatilisation and volatile combustion sub-models, where various options can be used, and also the char burnout sub-models. The accuracy of the sub-models is examined using data from four well-studied coals, three from the UK and one from the US. The main network devolatilisation codes are compared with experimental data. Two char combustion models have also been investigated in order to compare char burnout predictions and the development of char morphology and surface area during burnout are considered. The applications of these sub-models to two combustion situations were considered. These involve reactions in a drop tube furnace and a low NO_x industrial burner and in both cases, the model predictions were compared with experimental measurements.     

Effect of a carboxylic acid on the rheological behavior of an aluminous cement paste and consequences on the properties of the hardened material

Aluminous cement pastes (Secar 71 from Lafarge) containing increasing quantities of acetic acid, HOAc, are prepared ((w_HOAc/w_cement) × 100 ranges from 0 to 10%). Pastes containing HOAc present a Newtonian behavior. The best dispersion is obtained when the mass content of acid with respect to the cement is equal to 0.5%. Microstructural characterizations of samples aged for 4 days at 20 °C and 95% relative humidity reveal a significant increase in density, a reduction in porosity as well as a displacement of pore diameter towards low sizes. The open porous volume decreases with time from 25 to 9 vol.% when samples are 4 days and 6 months old, respectively. The addition of HOAc also has a beneficial effect on the flexural strength of set samples.     

A study of the scaling height of the tropospheric aerosol and its extinction coefficient profile

A method is proposed to determine a so-called scaling height of the tropospheric aerosol and the exponent-type aerosol extinction coefficient profile from the pyrheliometer or sunphotometer measurements and surface visibility data. Using the method, characteristics of seasonally/yearly mean scaling heights and aerosol extinction profiles over 11 sites in China during 1994–2001 are analyzed. The yearly-mean scaling heights over the 11 sites change between 1.30 and 2.67 km, and they are very variable for different seasons, being usually larger in spring. As far as the yearly-mean scaling heights of all 11 sites are concerned, they change between 1.88 and 2.11 km during 1994–2001, having an increasing trend. The scaling heights from pyrheliometer data are compared with those from AERONET sunphotometer data, and a good agreement between them is obtained.     

Experimental and Modeling Studies of the Stream-Wise Filter Vibration Effect on the Filtration Efficiency

The stream-wise vibration effect of a fibrous filter is studied experimentally and numerically for the purpose of evaluating filtration efficiency. The particle sizes range from 0.02 to 10 μ m and the face velocity ranges from 3 to 10 cm/s. The vibrational peak velocity also varied from 0 to 50 cm/s. The filtration efficiency for this wide size range is obtained by combining the individual test results for fine particles (0.02 to 0.5 μ m) and large particles (0.5 to 10.0 μ m). For the fine particle experiment, Arizona Road Dust (ARD) test particles are generated by an atomizer after an ultrasonic process and measured by a Scanning Mobility Particle Sizer (SMPS). For the large particle experiment, the test particles are generated by a fluidized bed and measured by an Aerodynamic Particle Sizer (APS). When the particles are generated by the atomizer after ultrasonicating, the majority of the particles are in nano scale without the agglomerates on the large particle surface, while particles generated by the fluidized bed are mostly in micro-scale because many nanoparticles are agglomerated on large particle surface. The filtration efficiency increases with the vibrational peak velocity in the impaction-dominant region (D _p > 0.1 μ m) and diffusion-dominant region (D _p < 0.1 μ m), due to the increased relative velocity between the particle and the filter fiber and the increased diffusion intensity from turbulence around the fiber, respectively. A model for the filter vibration effect is established with a modified Stokes number for the impaction-dominant region and an empirical analysis for the diffusion-dominant region.     

Quantum chemical calculations of the thermochemistry of tantalum oxyhydroxide species

Tantalum pentoxide and water vapor are predicted to react at elevated temperatures to form TaO(OH)₃(g), TaO₂(OH)(g), and Ta(OH)₅(g). The thermochemistry of these species is calculated with quantum chemistry methods. Geometries and vibrational frequencies are determined from B3LYP DFT methods. Energetics are calculated from high levels of theory—CCSD(T) and larger basis sets for Ta, O, and H. We report the enthalpies of formation at 0 K and 298.15 K, entropy at 298.15 K, and heat capacity. These quantities are used to calculate vapor pressures at 1400-1800 K and 50% water vapor. TaO(OH)₃(g) is found to be the dominant species. The calculated vapor pressure of TaO(OH)₃(g) is converted to a vapor flux and compared to previous experimental flux measurements from a flat plate in a slowly flowing H₂O/Ar gas and also vapor flux from a steam jet experiment. These “open system” experiments result in lower fluxes that are within 1.12-17X of the calculated equilibrium fluxes. This suggests that the experimental measurements are near equilibrium or have a small kinetic barrier.     

Closing the global N2O budget: nitrous oxide emissions through the agricultural nitrogen cycle

In 1995 a working group was assembled at the request of OECD/IPCC/IEA to revise the methodology for N₂O from agriculture for the National Greenhouse Gas Inventories Methodology. The basics of the methodology developed to calculate annual country level nitrous oxide (N₂O) emissions from agricultural soils is presented herein. Three sources of N₂O are distinguished in the new methodology: (i) direct emissions from agricultural soils, (ii) emissions from animal production, and (iii) N₂O emissions indirectly induced by agricultural activities. The methodology is a simple approach which requires only input data that are available from FAO databases. The methodology attempts to relate N₂O emissions to the agricultural nitrogen (N) cycle and to systems into which N is transported once it leaves agricultural systems. These estimates are made with the realization that increased utilization of crop nutrients, including N, will be required to meet rapidly growing needs for food and fiber production in our immediate future. Anthropogenic N input into agricultural systems include N from synthetic fertilizer, animal wastes, increased biological N-fixation, cultivation of mineral and organic soils through enhanced organic matter mineralization, and mineralization of crop residue returned to the field. Nitrous oxide may be emitted directly to the atmosphere in agricultural fields, animal confinements or pastoral systems or be transported from agricultural systems into ground and surface waters through surface runoff. Nitrate leaching and runoff and food consumption by humans and introduction into sewage systems transport the N ultimately into surface water (rivers and oceans) where additional N₂O is produced. Ammonia and oxides of N (NO_x) are also emitted from agricultural systems and may be transported off-site and serve to fertilize other systems which leads to enhanced production of N₂O. Eventually, all N that moves through the soil system will be either terminally sequestered in buried sediments or denitrified in aquatic systems. We estimated global N₂O–N emissions for the year 1989, using midpoint emission factors from our methodology and the FAO data for 1989. Direct emissions from agricultural soils totaled 2.1 Tg N, direct emissions from animal production totaled 2.1 Tg N and indirect emissions resulting from agricultural N input into the atmosphere and aquatic systems totaled 2.1 Tg N₂O–N for an annual total of 6.3 Tg N₂O–N. The N₂O input to the atmosphere from agricultural production as a whole has apparently been previously underestimated. These new estimates suggest that the missing N₂O sources discussed in earlier IPCC reports is likely a biogenic (agricultural) one.     

The Fifth WS/DGAT Enzyme of the Bacterium Marinobacter aquaeolei VT8

Wax esters (WE) belong to the class of neutral lipids. They are formed by an esterification of a fatty alcohol and an activated fatty acid. Dependent on the chain length and desaturation degree of the fatty acid and the fatty alcohol moiety, WE can have diverse physicochemical properties. WE derived from monounsaturated long-chain acyl moieties are of industrial interest due to their very good lubrication properties. Whereas WE were obtained in the past from spermaceti organs of the sperm whale, industrial WE are nowadays mostly produced chemically from fossil fuels. In order to produce WE more sustainably, attempts to produce industrial WE in transgenic plants are steadily increasing. To achieve this, different combinations of WE producing enzymes are expressed in developing Arabidopsis thaliana or Camelina sativa seeds. Here we report the identification and characterization of a fifth wax synthase from the organism Marinobacter aquaeolei VT8, MaWSD5. It belongs to the class of bifunctional wax synthase/acyl-CoA:diacylglycerol O-acyltransferases (WSD). The protein was purified to homogeneity. In vivo and in vitro substrate analyses revealed that MaWSD5 is able to synthesize WE but no triacylglycerols. The protein produces WE from saturated and monounsaturated mid- and long-chain substrates. Arabidopsis thaliana seeds expressing a fatty acid reductase from Marinobacter aquaeolei VT8 and MaWSD5 produce WE. Main WE synthesized are 20:1/18:1 and 20:1/20:1. This makes MaWSD5 a suitable candidate for industrial WE production in planta.     

Complete Characterization of the O-Antigen from the LPS of Aeromonas bivalvium

Aeromonas species are found in the aquatic environment, drinking water, bottled mineral water, and different types of foods, such as meat, fish, seafood, or vegetables. Some of these species are primary or opportunistic pathogens for invertebrates and vertebrates, including humans. Among the pathogenic factors associated with these species, there are the lipopolysaccharides (LPSs). LPSs are the major components of the external leaflet of Gram-negative bacterial outer membrane. LPS is a glycoconjugate, generally composed of three portions: lipid A, core oligosaccharide, and O-specific polysaccharide or O-antigen. The latter, which may be present (smooth LPS) or not (rough LPS), is the most exposed part of the LPS and is involved in the pathogenicity by protecting infecting bacteria from serum complement killing and phagocytosis. The O-antigen is a polymer of repeating oligosaccharide units with high structural variability, particularly the terminal sugar, that confers the immunological specificity to the O-antigen. In this study, we established the structure of the O-chain repeating unit of the LPS from Aeromonas bivalvium strain 868 E^T (=CECT 7113^T = LMG 23376^T), a mesophilic bacterium isolated from cockles (Cardium sp.) and obtained from a retail market in Barcelona (Spain), whose biosynthesis core LPS cluster does not contain the waaE gene as most of Aeromonas species. After mild acid hydrolysis, the lipid A was removed by centrifugation and the obtained polysaccharide was fully characterized by chemical analysis and NMR spectroscopy. The polymer consists of a heptasaccharide repeating unit containing D-GalNAc, L-Rha, D-GlcNAc, and D-FucNAc residues.     

Statistical and electrical properties of the conduction electrons of a metal nanosphere in the region of metal-insulator transition

Statistical and electrical properties of the conduction electrons of a silver or gold sphere with a radius from 1 to 2 nm are shown to differ drastically from the properties of electrons in a bulk metal sample. If the radius of a noble metal sphere decreases from 10 to 1 nm, its conductivity oscillates around the bulk metal value with increasing amplitude and drops at the ''magic’ numbers of electrons. These numbers are equal to 186, 198, 254, 338, 440, 556, 676, 832, 912, 1,284, 1,502, and 1,760, in agreement with various experimental data. We show that the conductivity and capacitance of a metal nanosphere can be changed by several orders of magnitude by adding or removing just a few electrons.     

Kinetics of the enzymatic hydrolysis of lignocellulosic materials at different concentrations of the substrate

The kinetics of the enzymatic hydrolysis of two substrates—lignocellulosic materials from Miscanthus and oat hulls—in an acetate buffer is studied at different concentrations of the substrates. The substrates are obtained via single-step treatment with a dilute solution of nitric acid. The content of a nonhydrolyzable component—acid-insoluble lignin—for Miscanthus and oat hulls was 11 and 14%, respectively. A multi-enzyme composition of commercially available enzyme preparations CelloLux-A and BrewZyme BGX was used as a catalyst. It is shown that treatment with the nitric acid solution produces reactive substrates for the enzymatic hydrolysis. The innovative science of the results is confirmed by Russian patent 2533921. Kinetics of the enzymatic hydrolysis of these substrates in an acetate buffer can be described by a mathematical model based on a modified Michaelis–Menten equation. The main kinetic constants for both substrates are determined from the experimental data. The equilibrium concentrations of reducing substances (RSes) for the substrates are calculated from the initial substrate concentrations. It is found that within the studied range of substrate concentrations (33.3–120.0 g/L), the initial rate of enzymatic hydrolysis for the lignocellulosic material from oat hulls is higher than that for the lignocellulosic material from Miscanthus by 1 g/(L h). It is shown that the yield of RS depends of the initial concentration of the substrates: as the concentration rises from 33.3 to 120 g/L, the yield of RS falls 1.5–2.0 times, due to substrate inhibition. At low initial concentrations, the yields of RS are similar for the substrates from Miscanthus and oat hulls. When the initial concentration of the substrate reaches 120 g/L, the yield of reducing substances for the lignocellulosic material from Miscanthus is approximately 20% higher than that for the lignocellulosic material from oat hulls. The established dependences and the proposed mathematical model allow us to optimize the initial concentration of the substrate for efficient enzymatic hydrolysis.     

Modifications of the Chemical Profile of Hosts after Parasitism Allow Parasitoid Females to Assess the Time Elapsed Since the First Attack

In solitary parasitoids, only one adult can emerge from a given host. In some of these species, when several eggs are laid on the same host, supernumerary individuals are eliminated by lethal larval fights. In the solitary parasitoid Anisopteromalus calandrae, the probability of a second larva winning the fight depends on the time elapsed since the first oviposition. The older the first egg is at the moment a second egg is laid, the less chance the second egg has of winning the competition. As a consequence, females of this species lay their eggs preferentially on recently parasitized hosts rather than on hosts parasitized by an egg about to hatch. Anisopteromalus calandrae females parasitize bruchid larvae located in cowpea seeds. In a series of choice test experiments using an artificial seed system, we demonstrated that the cue that allows parasitoid females to differentiate between hosts parasitized for different lengths of time comes from the host and not from the artificial seed or the previously laid egg. This cue is perceived at short range, indicating that the chemicals involved are probably partly volatile. Interestingly, although parasitism stops host development, cuticular profiles continue to evolve, but in a different way from those of unparasitized hosts. This difference in the host’s cuticular profile after parasitism, therefore, probably underlies the parasitoid female’s discrimination.     

Explosions in the lower and middle atmosphere: The spherically symmetrical stage

The laws of evolution of spherically symmetrical explosions with a high initial energy concentration in the atmosphere at heights from 0 to 90 km are investigated. The processes of initial energy release are ignored, and the explosion is assumed to be massless, i.e., the initial data are specified in the form of a uniformly heated sphere with a constant air density. The results are obtained by radiative gasdynamic numerical calculations in the range of explosive energies from 4.2·10¹² J to 4.2·10¹⁶. J. Institute of Geosphere Dynamics. Russian Academy of Sciences, Moscow 117979. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 5, pp. 129–142, September–October, 1994.     

Determining the character of the damage to copper-coated specimens loaded by the explosion of a lamellar charge

Results are presented from a study of the fracture of specimens of low-carbon steel and copper with galvanic copper coating when the specimens are loaded by the explosion of a lamellar charge. Data on the dynamic adhesive strength of the copper coating and the cleavage strength of the steel is presented in the form of the dependence of the critical negative pressure at the fracture origin on the pressure gradient in the tensile pulse. Information on the character of the damage to the specimens is obtained by metallographic and automated quantitative analysis.VNIIÉF, Arzamas-16 607200. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 4, pp. 156–162, July–August, 1994.     

A method for the determination of the water-insoluble combined lactic acid content of shortenings containing lactylated emulsifiers

Shortenings containing glycerol lactopalmitates and glycerol lactostearates are analyzed for water-insoluble combined lactic acid content using a procedure adapted from that of Barker and Summerson (1). Water-soluble constituents are extracted from a chloroform solution of the shortening. The water-washed shortening is saponified and then acidified to release the lactic acid, which is degraded to acetaldehyde by heating with concentrated sulfuric acid. The acetaldehyde is reacted withp-phenyl phenol is concentrated acid solution to produce a purple colored reaction product. The intensity of the color is proportional to the concentration of the acetaldehyde. Absorption is read at 570 mμ using a lithium lactate solution as a standard. The method has been applied to the analysis of shortenings containing from 0.70 to 1.10% water-insoluble combined lactic acid.     

Magnesium-containing catalysts for the decarboxylation of bio-oil

At present, one of the most promising methods of processing renewable raw materials is pyrolysis, which allows liquid organic products (bio-oil) to be derived from biomass. For obtaining fuel products from bio-oil, the latter needs to be preliminarily upgraded. It is appropriate to carry out this process in two stages. The first stage—decarboxylation—is intended to reduce the corrosiveness (acidity) of the feedstock and hydrogen consumption at the second stage. Decarboxylation is usually conducted over noble metal-based catalysts. There are examples of employing cheaper catalysts based on alkaline-earth metals; however, these catalysts suffer from insufficient stability. Here, we report the activity of MgO-based catalysts in the decarboxylation of pentanoic acid, a model compound imitating bio-oil, and the effect of dopants on the stability of the magnesium-containing catalysts. The process has been carried out in an inert atmosphere at a temperature of 350°C and a pressure of 0.50 MPa. Raising the MgO calcination temperature to 1200°C and introducing stabilizing admixtures (Al₂O₃, SiO₂, and ZrO₂) affords catalysts that are mainly deactivated via carbonate formation rather than the formation of soluble magnesium salts and are, therefore, more promising from the standpoint of regenerability.     

On the Determination of the Surface Temperature of an Evaporating Liquid

Some methods for calculating the wet-bulb temperature are compared. These methods are based on different forms of equations relating the heat and mass transfer in evaporation of a liquid into a gas flow. It is hypothesized that the deviation from the similarity between heat and mass transfer is described by the first power of the Lewis number, for which the parameters of the gas mixture are calculated on the phase-transition surface. In this case, the heat-transfer coefficients calculated from the enthalpy and temperature gradients of the gas–vapor mixture are equal to each other. The wet-bulb temperature calculated using this approach is in satisfactory agreement with experimental data.