Chemical Mass Research Articles

Identification of new hot subdwarf binary systems by means of Virtual Observatory tools

ABSTRACT The estimation of the binary fraction of hot subdwarfs is key to shed light on the different evolution scenarios proposed to explain the loss of the hydrogen envelope during the red giant branch phase. In this paper, we analyse the spectral energy distribution of the hot subdwarfs included in a recent and comprehensive catalogue with the aim of identifying companions. Our methodology shows a performance superior to the photometric criteria used in that study, identifying 202 objects wrongly classified as binaries according to their spectral energy distributions, and finding 269 new binaries. Out of an initial sample of 3186 objects, we classified 2469 as single and 615 as binary hot subdwarfs. The rest of the objects (102) were not classified because of their inadequate spectral energy distribution fitting due, in turn, to poor quality photometry. Effective temperatures, luminosities, and radii were computed for 192 singles and 42 binaries. They, in particular the binary sample, constitute an excellent data set to further perform a more careful spectroscopic analysis that could provide detailed values for the chemical composition, masses, ages, rotation properties, or reflection effects for the shortest period systems. The results obtained in this paper will be used as a reference for a forthcoming work where we aim to generalize binary and single hot subdwarf classification using Artificial Intelligence-based techniques.

Evaluation of irregularly manufactured garrafadas and syrups seized in the state of Amapá, Brazil

Introduction: The garrafadas, mixtures of plants with medicinal purposes conveyed in alcoholic beverages, do not have regulation and, for being presented with many therapeutic indications and no contraindication, they can be risky for the population. Methods: For this reason, the objective of this study was to evaluate the Brix degree°, evaluate the presence of pathogenic microorganisms, analyze the chemical characteristics pH and mass spectrometry (FT-ICR MS) and evaluate the label of syrup samples and garrafadas suspicious of adulteration seized by police. Results: The degree Brix° value of the samples was within the standards. The chemical analysis of the pH of the garrafadas and syrups samples obtained acid pH values, which can cause chemical instability on the components. Through the mass spectrometry, it was possible to detect some fragments of compounds related to the plants described on the labels, and no synthetic chemicals or drugs of abuse were found. The result of the microbiological evaluation detected Staphylococcus spp. in 4 samples, and, in 2 syrups, fungus growth occurred, beeing for fungi the growth were within limits established in the Farmacopeia Brasileira for this microorganism. In only four of the twelve samples evaluated, it was possible to detect mass fragments related to chemical substances of the plants described on the labels of the packages and most of them was made up of sugars only. Conclusions: Based on the results found, these products are not safe for consumers, as there is no way to guarantee their safety and efficacy.

SOME ASPECTS OF MATHEMATICAL MODELING OF ELECTRIC STEEL MELTING PROCESS

The article discusses some aspects of mathematical modeling of the process of melting electric steel on the basis of innovative metallurgical technologies. It was noted that the production of electric steel mainly consists of three stages - preparation of the charge, melting and casting of liquid steel. The most important of these stages is the mathematical modeling of the melting process, especially the physicochemical processes that take place during melting. All physicochemical processes controlled in order to obtain the required chemical composition of electric steel for modeling are combined into two main groups, such as metal refining and alloying. Possibilities of mathematical modeling of electric steel melting processes have been identified: to successfully solve different types of problems without conducting pro¬duc¬tion experiments; to ensure optimal modes of melting in specific production conditions. The problems to be solved by mathematical modeling have been identified: con¬struc¬tion of a model for specific conditions that allow to achieve the required value of any parameter of the solution; possibility to purchase electric steel in specific conditions; minimum cost of material, time, labor and energy and required chemical composition, temperature and mass melting of steel; automatic control of all parameters of the solution. To solve these problems, the characteristics of static, dynamic and mixed mathematical models have been identified. It has been shown that a deterministic mathematical model can be applied to a system of equations expressing the functional relationships between the parameters of the solution and the factors affecting them. The mixed mathematical model includes equations expressing functional correlations. This model is actually a deterministic static model. Depending on the problem, the expediency of using appropriate models in the melting of electric steel is justified. In general, the creation of a mathematical model of melting processes of electric steel includes: dividing the melting into elementary physicochemical processes within the limits of each period, ie decomposing the melting process; to give a quantitative description of each elementary process, ie to describe the process mathematically; write a mathematical model of each cycle of melting by combining the quantitative characteristics of the parameters and elementary processes controlled on the basis of the equations of material and heat balances; to obtain a mathematical model of the solution as a whole by combining mathematical models of different periods. As an example of the application of mathematical modeling in electroplating processes, the amount of pores formed during the steel melting process in the main braided electric arc furnace was calculated using scrap metal. Keywords: electroplating steel, mathematical modeling, static model, dynamic model, deterministic model, mixed model, functional relationships.

Lipids, Chloroform, and Their Intertwined Histories

Lipids and their fatty acid constituents, in particular, have been the subject of academic and industrial research initiatives since their isolation by Michel-Eugène Chevreul in 1813. Fatty acids can be saturated or unsaturated, their physical properties depending on the aliphatic chain length and degree of saturation. They constitute the building blocks of many lipid groups, such as triglycerides and phospholipids; are key additives in commercial foods, pharmaceuticals, and cosmetics; and can cross cell membranes. Chloroform was synthesized in 1831 by Samuel Guthrie and has had a tortuous history of interactions with mankind: from an anesthetic in obstetrics, dentistry, and surgery, to being labeled as a potential carcinogen in the 1970s. It has also had important nonmedical applications, such as in chemical engineering mass transfer systems designed to estimate binary gas diffusion coefficients. Although chemically dissimilar, lipids and chloroform intertwined their scientific paths through the work of Jordi Folch and associates in the 1940s-1950s, in which many lipid-based brain molecules were isolated and characterized. This article outlines the separate histories of lipids and chloroform, and those research initiatives in which they have acted synergistically. The narrative covers the interplay of chemical compounds with different historical backgrounds, but with physical properties which continue to foster their modern-day interaction.

Validation of Computationally Efficient Simulations of Douglas Fir Pyrolysis and Combustion Using Time-Resolved Frequency Comb Laser Measurements

Computational simulations have the potential to provide low-cost, low-risk insights into wildland fire structure and dynamics. Simulation accuracy is limited, however, by the difficulty of modeling physical processes that span a wide range of spatial scales. These processes include heat transfer via radiation and turbulent advection, as well as both solid- and gas-phase chemistry. In the present study, we perform large eddy simulation (LES) with adaptive mesh refinement to model the multi-phase pyrolysis and combustion of dry Douglas fir, where temperature-based lookup tables corresponding to a multi-step pyrolysis mechanism are used to represent the composition of gas-phase pyrolysis products. Gas-phase and surface temperatures, mass loss, and water vapor mole fraction from the LES are shown to compare favorably with experimental measurements of a radiatively heated Douglas fir fuel sample undergoing pyrolysis and combustion beneath a cone calorimeter. Using frequency comb laser diagnostics, optical and infrared cameras, and a load cell, the experiments provide simultaneous in situ, time-resolved measurements of chemical composition, temperature, and mass loss. The present study thus combines cutting edge computational and experimental techniques with multi-step chemical pyrolysis modeling to provide a validated computational tool for the prediction of solid fuel pyrolysis and combustion relevant to wildland fires.

Formation and Chemical Transformations of Steel Corrosion Products in the Primary Systems of Nuclear Power Plants

Improvement of the corrosion situation during nuclear power plant (NPP) operation is associated with the enhancement of construction steel resistance against general (uniform) corrosion, with the routes of chemical transformations and corrosion product mass transfer in the coolant under different water chemistry conditions. Based on a look-back analysis of the obtained research results and a comparison of these results with those in available publications, the following conclusions were made: 1. The morphology of corrosion products formed on the inside surfaces of NPP systems has a four-layer structure. a. A layer of solid corrosion deposits tightly bonded with the surface is formed above the oxide film. b. Tightly bonded deposits are under loosely bonded (“loose” or dissipative) corrosive deposit layers that are dynamically balanced with the corrosion product particles dispersed in the water coolant. 2. By an aggregate state, the coarse/medium fractions (particle size more than 0.45 µm) and the fine fractions (particle size less than 0.45 µm) are conventionally referred to as nonsoluble and conditionally soluble corrosion products, respectively. 3. The chemical composition of all corrosion products depends on the presence of iron compounds, including the alloy element impurities (Cr, Ni, Mn, and Ti). 4. The radionuclide composition of all corrosion products is qualitatively the same and is presented by the activation products of reactor materials, such as 51Cr, 59Fe, 54Mn, 58Co, and 60Co. 5. The phase composition of solid corrosion products depends on the presence of ferrous (II) and ferric (III) iron oxide-hydroxide compounds whose ratio depends on water chemistry conditions: a. Under reducing water chemistry conditions, the phase composition of all corrosion products is determined by a spinel structure of magnetite (Fe3O4). b. Under oxidizing water chemistry conditions, the partial oxidation of ferrous (II) iron ions results in the formation of a defect structure of nonstoichiometric magnetite FeА 3+ [Fe2+ 1-хFe3+]BO4-х, where А and B are two nonequivalent positions in the magnetite structure. At х = 1, a nonstoichiometric magnetite structure changes into hematite, a α-Fe2O3 or maghemite γ-Fe2O3 structure. It is noted that the mathematical models nowadays used for describing the mass exchange and mass transfer of corrosion products in NPP primary systems do not consider physicochemical processes leading to the formation of such complex (phase, disperse, chemical, radionuclide) compositions of corrosion products. A widely known electrochemical mechanism that considers corrosion as a coupled anodic-cathodic process fails to explain actually observed steel dissolution and the contribution of soluble iron forms to oxide film formation on the corroding steel surface at potentials of cathodic polarization and anodic dissolution. This paper presents a diffusion model for corrosion product mass exchange and mass transfer in the steel-water coolant system as an alternative to the electrochemical model for general corrosion. This model is based on Frank-Kamenetkiy’s [Diffusion and Heat Transfer in Chemical Kinetics, Nauka (1987)] concept of the macroscopic kinetics of heterogeneous processes with simultaneous chemical transformations of the corrosion product ionic forms and the formation of solid-phase products in the water coolant and on the surface of corrosive steel. The diffusion model provided better insight into understanding how the phase, disperse, chemical, and radionuclide compositions of steel corrosion products are formed in the coolant of the NPP primary system.

Bayesian model calibration for vacuum-ultraviolet photoionisation mass spectrometry

We investigate the calibration of an instrument model for a high-pressure chemical reactor and vacuum ultraviolet photoionisation mass spectrometry apparatus, using a collection of ‘static’ mass spectrometry data (i.e. from unreactive samples). A Bayesian calibration method is applied to characterise the uncertainty of the model parameters, the associated model error, and the predicted mass spectrum. A partitioning algorithm is introduced to decompose the mass spectrum into several independent calibration problems, making the analysis of complex mass spectrometry data sets tractable. The a priori mass spectrometer model poorly predicts some portions of the ion time-of-flight spectrum due to both, parametric (i.e. uncertain parameter values) and mechanistic (i.e. missing physics) inadequacies; however, by incorporating an additive model error the prediction model is vastly improved and closely replicates the measured spectrum. We found that the model calibration and additive model error reveals a set of experimental problems, including chemical contamination of the sample, the presence of high harmonics of the ionising radiation, and a systematic fluctuation in ion flight times due to instability of the ion optics power supplies. This approach results in a calibrated instrument model with well-defined parameter uncertainties, which is critical to the analysis of ‘dynamic’ data (i.e. from reacting gas samples).

Development of a Fully Automated Analytical Platform Based on Static Headspace-Gas Chromatography-Positive Chemical Ionization-Tandem Mass Spectrometry for the Analysis of Five N-Nitrosamines in Dried Aquatic Products of Animal Origin

Development of a Fully Automated Analytical Platform Based on Static Headspace-Gas Chromatography-Positive Chemical Ionization-Tandem Mass Spectrometry for the Analysis of Five N-Nitrosamines in Dried Aquatic Products of Animal Origin

Verification of the mechanisms of thermal transformations of 1,1-diamino-2,2-dinitroethylene (DADNE) based on quantum chemical calculations, thermal analysis and mass spectroscopy of gaseous products

ABSTRACT Thermolysis of 1,1-diamino-2,2-dinitroethylene (1) has been investigated in the temperatures 303–623 K by means of differential scanning calorimetry and thermogravimetry, with mass-spectroscopic registration of gaseous products. Under these conditions, thermal decomposition of 1 proceeds in two stages – mass loss curves and ionic currents have maxima at 508.2 and 558.8 K. Quantum-chemical modeling of thermal transformation of 1 showed that products with the masses of 42 can be formed via the channel involving hydrogen transfer to carbon, and products with the masses of 17 and 43 can be formed via the decomposition of various aci forms of 1.

New insights on the age and stratigraphy of the Cisuralian succession in the Cooper Basin, Australia, based on U–Pb CA-TIMS dating of volcanic air-fall tuffs

Absolute age constraints for Cisuralian units in the Cooper Basin have been hampered by poorly calibrated palynostratigraphic schemes, with implications for pan-Australian and global correlations. New U–Pb CA-TIMS (uranium–lead chemical abrasion-thermal ionisation mass spectrometry) dates acquired from volcanic air-fall tuff beds from the Patchawarra Formation combined with legacy palynological data offer new insights on the age, stratigraphy and tectonic history of the basin. Six tuffs from different regions of the Cooper Basin give dates from 284.87 to 277.36 Ma, which suggest that the Patchawarra Formation was deposited between the Artinskian and Kungurian rather than from the Sakmarian to Kungurian, as previously thought. The new dates indicate a possible unconformity at the base of the Patchawarra Formation and the underlying Tirrawarra Sandstone. They also suggest that the overlying REM succession (Roseneath Shale, Epsilon Formation and Murteree Shale) is entirely Guadalupian age rather than ranging from the Cisuralian to the Guadalupian. Consequently, existing Cisuralian and Guadalupian high-resolution spore-pollen zonations should be used with care when applied in conjunction with U–Pb CA-TIMS dates. The tuff dates in the thin Patchawarra Formation over the prominent Gidgealpa–Merrimelia–Innamincka Ridge within the Cooper Basin support the interpretation that the ridge was an area of relatively slow subsidence rather than being a positive feature during deposition. Compacted sediment accumulation rates of between 25 and ∼40 m/My for this unit are faster than for most cratonic basins, which raise questions on the tectonic setting of the Cooper Basin. The use and further acquisition of tuff dates will enhance correlations and facilitate improved paleogeographic reconstructions and our understanding of the late Paleozoic ice age. KEY POINTS Six volcanic air-fall tuff beds dated from the Cisuralian Patchawarra Formation, Cooper Basin. U–Pb CA-TIMS dates range from 284.87 to 277.36 Ma. Dates suggest deposition occurred between the Artinskian and Kungurian. New insights on basin tectonics, sedimentation rates and basin stratigraphy.

Elastic Modulus, Thermal Expansion, and Pyrolysis Shrinkage of Norway Spruce Under High Temperature

The orthotropic and temperature-dependent nature of the mechanical properties of wood is well recognized. However, past studies of mechanical properties at elevated temperatures are either limited to temperatures below 200 °C or focus only on the direction parallel to grain. The effect of time-dependent pyrolysis during measurement is often neglected. This paper presents a novel method for determining elastic modulus at high temperatures and thermal expansion coefficient in different orthotropic directions via Dynamic Mechanical-Thermal Analyser (DMTA). The method allows for drying, drying verification, and measurement in one chamber, eliminating the possibility of moisture reabsorption from ambient air. The repeatable measurements can be carried out in temperatures up to 325°C, adequate for observing time-dependent pyrolysis during measurement. Results of the measurements of Norway Spruce provide data of its mechanical response at temperature range previously not explored widely, as well as in the orthotropic direction. Time-dependent behaviour was observed in the thermal expansion and shrinkage experiment, where above 250°C the amount of shrinkage depends on heating rate. At such temperature, elastic moduli measurement also shows time dependence, where longer heating at certain temperature slightly increases the measured elastic modulus. Additionally, bilinear regression of the relationship between elastic moduli and temperature shows quantitatively good fit. Numerical simulation of the DMTA temperature history and wood chemical components mass losses show the onset of shrinkage and onset of hemicellulose mass loss occurring at around the same time, while decomposition of cellulose correlate with the sudden loss of elastic moduli.

Influence of biomass burning vapor wall loss correction on modeling organic aerosols in Europe by CAMx v6.50

Abstract. Increasing evidence from experimental studies suggests that the losses of semi-volatile vapors to chamber walls could be responsible for the underestimation of organic aerosol (OA) in air quality models that use parameters obtained from chamber experiments. In this study, a box model with a volatility basis set (VBS) scheme was developed, and the secondary organic aerosol (SOA) yields with vapor wall loss correction were optimized by a genetic algorithm based on advanced chamber experimental data for biomass burning. The vapor wall loss correction increases the SOA yields by a factor of 1.9–4.9 and leads to better agreement with measured OA for 14 chamber experiments under different temperatures and emission loads. To investigate the influence of vapor wall loss correction on regional OA simulations, the optimized parameterizations (SOA yields, emissions of intermediate-volatility organic compounds from biomass burning, and enthalpy of vaporization) were implemented in the regional air quality model CAMx (Comprehensive Air Quality Model with extensions). The model results from the VBS schemes with standard (VBS_BASE) and vapor-wall-loss-corrected parameters (VBS_WLS), as well as the traditional two-product approach, were compared and evaluated by OA measurements from five Aerodyne aerosol chemical speciation monitor (ACSM) or aerosol mass spectrometer (AMS) stations in the winter of 2011. An additional reference scenario, VBS_noWLS, was also developed using the same parameterization as VBS_WLS except for the SOA yields, which were optimized by assuming there is no vapor wall loss. The VBS_WLS generally shows the best performance for predicting OA among all OA schemes and reduces the mean fractional bias from −72.9 % (VBS_BASE) to −1.6 % for the winter OA. In Europe, the VBS_WLS produces the highest domain average OA in winter (2.3 µg m−3), which is 106.6 % and 26.2 % higher than VBS_BASE and VBS_noWLS, respectively. Compared to VBS_noWLS, VBS_WLS leads to an increase in SOA by up to ∼80 % (in the Balkans). VBS_WLS also leads to better agreement between the modeled SOA fraction in OA (fSOA) and the estimated values in the literature. The substantial influence of vapor wall loss correction on modeled OA in Europe highlights the importance of further improvements in parameterizations based on laboratory studies for a wider range of chamber conditions and field observations with higher spatial and temporal coverage.

Application of Galvanic Zinc-Iron Coating in the Repair of Transport and Technological Machines

The article presents the results of experimental studies to determine the relationship between the electrolysis modes and the properties of electroplating coatings for mathematical modeling of the dynamics of the electrolytic process (MDEP), described by a system of ordinary differential equations due to the complex relationship of the kinetics of chemical reactions, hydrodynamics and mass transfer in the electrolyte flow, the kinematics of electrode plates, and the influence of the electric field of the "anode-cathode" pair on all these processes. At the same time, the experimental base was a series of full-scale experiments to restore the seats of the root supports of cylinder blocks with electroplated coatings. The final result of the research is the procedure for constructing an optimal resource-saving mode of electroplating, which is a zinc-iron alloy.

Plasma Carboxyl-Metabolome Is Associated with Average Daily Gain Divergence in Beef Steers.

Simple SummaryIn this study, we analyzed the plasma carboxyl-metabolome in beef steers with divergent average daily gain (ADG). Several short chain fatty acids were greater in beef steers with greater ADG. Conversely, several long chain fatty acids were greater in beef steers with lower ADG. Pathway analysis of the differential metabolites revealed alterations in abundance/activities of enzymes involved in fatty acid metabolism in the liver. The results of this study demonstrated that beef steers with divergent ADG had altered plasma carboxyl-metabolome, which is possibly caused by altered abundances and/or activities of enzymes involved in fatty acid oxidation and biosynthesis.We applied an untargeted metabolomics technique to analyze the plasma carboxyl-metabolome of beef steers with divergent average daily gain (ADG). Forty-eight newly weaned Angus crossbred beef steers were fed the same total mixed ration ad libitum for 42 days. On day 42, the steers were divided into two groups of lowest (LF: n = 8) and highest ADG (HF: n = 8), and blood samples were obtained from the two groups for plasma preparation. Relative quantification of carboxylic-acid-containing metabolites in the plasma samples was determined using a metabolomics technique based on chemical isotope labeling liquid chromatography mass spectrometry. Metabolites that differed (fold change (FC) ≥ 1.2 or ≤ 0.83 and FDR ≤ 0.05) between LF and HF were identified using a volcano plot. Metabolite set enrichment analysis (MSEA) of the differential metabolites was done to determine the metabolic pathways or enzymes that were potentially altered. In total, 328 metabolites were identified. Volcano plot analysis revealed 43 differentially abundant metabolites; several short chain fatty acids and ketone bodies had greater abundance in HF steers. Conversely, several long chain fatty acids were greater in LF steers. Five enzymatic pathways, such as fatty acyl CoA elongation and fatty-acid CoA ligase were altered based on MSEA. This study demonstrated that beef steers with divergent ADG had altered plasma carboxyl-metabolome, which is possibly caused by altered abundances and/or activities of enzymes involved in fatty acid oxidation and biosynthesis in the liver.

Control-oriented modeling of diesel oxidation catalyst

Diesel oxidation catalyst outlet temperature control is crucial for heat management to realize diesel particulate filter active regenerative control. In order to control the temperature of the active regeneration process in the filter, the temperature response process of the semi-physical oxidation catalyst model structure is proposed as a multi-stage inertia plus delay, and the equivalent inlet temperature step of the fuel oxidation reaction of the exhaust pipe. Combined with the test test, the control oriented oxidation catalyst model is established.A control-oriented oxidation catalyst model was constructed. By analysed the oxidation catalyst working process, the main chemical reactions, heat and mass transfer processes occurring inside the carrier were analyzed. Three-dimensional CFD model and one-dimensional chemical reaction kinetics model were established respectively. The radial and axial temperature distribution of the carrier was analyzed by model simulation. Based on the analysis of the system characteristics, the multi-step inertia plus delay semi-physical model structure was proposed. Combined with the test, the control oriented oxidation catalyst model is established. Select the appropriate working conditions to identify and verify the model parameters. The results show that the third order model can well indicate the temperature response characteristics of the oxidation catalyst outlet temperature. Considering the complexity of the system, the first-order and third-order model are selected as the basis of the control system design.

Numerical analysis of the carbon containing pellets direct reduction process

In view of the carbon-containing composite pellets direct reduction process in rotary hearth furnace, a mathematical model coupling heterogeneous chemical reaction kinetics, heat and mass transfer of this process was established. The effects of furnace temperature (from 1273.15 K to 1673.15 K) and pellet radius (from 6 mm to 16 mm) on the direct reduction of carbon-containing composite pellets were studied by adopting computational fluid dynamics software. The pellet temperature and composition changes under different operating conditions were analyzed. CO and CO2 fluxes, heat fluxes on the pellet surface were especially studied. Total heat absorption by the pellet, CO and CO2 overflow from the pellet surface together with pellet degree of metallization (DOM) and zinc removal rate (ZRR) were calculated. Results show that with the increasing of furnace temperature or the decreasing of the pellet radius, the temperature difference between pellet surface and its center and the final DOM, ZRR increased. The larger the pellet radius, the smaller the heat absorption, also the smaller CO and CO2 overflow. But heat absorption and CO overflow per unit volume are higher. There is an optimal pellet radius with high CO utilization efficiency. Pellet porosity decreases at first and then increases with reducing time. It is also found that effective thermal conductivity is a major factor limiting the pellets temperature increasing. The reduction sequence of the pellets is Fe2O3→Fe3O4→FeO→Fe.

Numerical Simulation of the Distribution of In Situ Cigarette Combustion-Generated Particulate Matter

This paper has established a two-dimensional (2D) mathematical model for the generation, growth, and deposition of cigarette total particulate matter (TPM) in the smoldering state. The model has covered the chemical reactions and mass transfer as well as the mechanism of generation, flow, and condensation of particulate matter inside a burning cigarette. Cigarette smoke was generated by puffing under a constant pressure, and the pressure of the filter outlet was −274 Pa. The peak of the concentration of particulate matter was spatially overlapped with the peaks of pyrolysis and oxidation. Pertaining to the cross section of the cigarette at the same axial position, the peak of the diameter of particulate matter along the radial distribution first appeared in the zone near the edge of the cigarette cross section, and then gradually moved to the center of the cigarette with the cigarette smoke moving away from the combustion cone. The maximum number density of particulate matter calculated by the 2D mathematical model at the same axial position of the cigarette and the corresponding particle diameter, as well as the filtration efficiency of the filter rod, are in good accordance with the experimental data reported in previous studies.

A Comparison of the Limits of Detection for a Number of Surrogates of Organophosphorus Toxic Agents and Methylphosphonic Acid Silyl Derivatives and its O-Alkyl Esters by Gas Chromatography/Mass Spectrometry with Various Ionization Methods and a Flameless Thermionic Ionization Detector

Electron ionization (EI) and chemical ionization (CI) mass spectra of methylphosphonic acid phosphates and phosphonates (surrogates of respective chemical war agents) and silyl derivatives and its O-alkyl esters (markers of hydrolysis products of chemical war agents) were investigated and respective limits of detection were determined by GC/MS (EI) and GC/MS (CI) in a single ion monitoring mode. Atmospheric pressure photo- and photochemical ionization (APPI/APPCI) mass spectra of the same compounds were investigated by GC/MS (APPI/APPCI) and conditions providing the registration of mass spectra consisting of only one peak, corresponding to the M+ or [M + H]+ ion, were chosen and the limits of detection in the single ion monitoring mode were determined. In addition, the limits of detection for all of the studied compounds by GC with a flameless thermionic detector (FTID) were determined. The limits of detection for phosphates and phosphonates by GC/MS (EI) (MS/MS), GC/MS (CI), GC/MS (APPI), and GC/MS (APPCI) and in the single ion monitoring mode were 0.2–1.0 pg, 1.0–6.0 pg, 10–30 pg, and 0.1–0.3 pg, respectively. For methylphosphonic acid silyl derivatives and its O-alkyl esters, the respective limits of detection were 0.2–4.0 pg, 1.0–5.0 pg, 10–25 pg, and 1.0–3.0 pg. The limits of detection for all the studied compounds by GC with FTID were 0.3–0.4 pg. This means that the rapid screening of the samples to be investigated should be based on the last named method and GC/MS must be used only for the selected samples.

Исследование стойкости к высокотемпературной газовой и солевой коррозии жаропрочного интерметаллидного титанового сплава ВТИ-4

We investigated high-temperature gaseous and salt corrosion resistance of heat-resistant intermetallic titanium VTI-4 (ВТИ-4) alloy samples by conducting accelerated cyclic laboratory testing in air, in a NaCl environment, and in a mixture of Na2SO4 and NaCl. While testing the VTI-4 (ВТИ-4) alloy in air, we observed corrosion of a chemical nature and pseudo-parabolic specific mass variation kinetics. After cyclic testing in a NaCl environment at 700 °C the surface of the VTI-4 (ВТИ-4) alloy was covered by a film consisting of two layers: a mixture of Al2O3 and (Ti, Nb)O2 oxides, and a (Ti, Nb)O2 layer. In a NaCl + Na2SO4 environment at temperatures of 650 and 700 °C a liquid ion conductor film may manifest on the alloy surface alongside the oxides, while corrosion becomes predominantly electrochemical, of the pitting type. Globular orthorhombic phase particles initiate the pitting process. We detected that the pit depth in the alloy after testing in a Na2SO4 + NaCl environment at 650 and 700 °C is twice that obtained in NaCl at 700 °C. At the temperatures of 650 °C in Na2SO4 + NaCl and 700 °C in NaCl and Na2SO4 + NaCl environments the specific mass variation becomes negative, which is due to the oxide film peeling and shedding as temperatures change. The corrosion rate for the VTI-4 (ВТИ-4) alloy in the Na2SO4 + NaCl environment at 650 °C is lower than those for the nickel alloys VV751P (ВВ751П) and VZh175-ID (ВЖ175-ИД)

PSII-6 Comparative effects of two multi-species direct-fed microbial products on rumen fermentation, bacterial community and metabolome of beef steers

Abstract We examined the effects of two direct-fed microbials (DFM) containing multiple microbial species and their fermentation products on ruminal fermentation, bacterial community and metabolome of beef steers. Nine rumen-cannulated Holstein steers were assigned to 3 treatments arranged in a 3 × 3 Latin square design with three 21-d periods. Dietary treatments were (1) CON (basal diet without additive), (2) PROB (basal diet plus 19 g/d of Commence), and (3) SYNB (basal diet plus 28 g/d of RX3). Commence is a blend of active S. cerevisiae, Enterococcus lactis, Bacillus subtilis, Enterococcus faecium, and L. casei, and their fermentation products. RX3 is a blend of active S. cerevisiae and the fermentation products of S. cerevisiae, Enterococcus lactis, Bacillus licheniformis, and Bacillus subtilis. Daily dry matter intake was calculated. On d 21 of each period, ruminal contents were sampled at 3, 6, 12, and 18 h after feeding for analysis of VFA, bacterial community via 16S rRNA sequencing, and metabolome via chemical isotope labeling liquid chromatography mass spectrometry. There was no effect on DMI. Compared to CON, supplementation of either PROB or SYNB increased or tended to increase (P ≤ 0.10) total VFA, propionate, and valerate concentrations. Compared to CON, PROB reduced (P ≤ 0.05) the relative abundance of Prevotella 1 and Prevotellaceae UCG-001, but increased those of Rikenellaceae RC9, Succinivibrionaceae UCG-001, Succiniclasticum, Ruminococcaceae UCG-014, and Ruminococcaceae UCG-002, whereas SYNB decreased (P ≤ 0.05) the relative abundance of Prevotella 1 and Prevotellaceae UCG-001, and increased those of Prevotella 7, Succinivibrio, Succiniclasticum, and Ruminococcaceae UCG-014. Metabolome analysis revealed that 8 ruminal metabolites, including some amino acids, were increased (P ≤ 0.05) by PROB, whereas no differences were found for SYNB. This study demonstrated that supplemental PROB or SYNB altered the ruminal bacterial community and metabolome differently to achieve a similar ruminal fermentation pattern.