High Temperature Oxidation of the Austenitic (35Fe27Cr31Ni) Alloy Sanicro 28 in O2 + H2O Environment

The present study investigates the high temperature oxidation of alloy Sanicro 28 (35Fe27Cr31Ni) in 5% O₂ and in 5% O₂ + 40% H₂O. Polished steel coupons were isothermally exposed in a tube furnace at 600, 700 and 800 °C for up to 168 h. The samples were investigated by gravimetry, grazing angle X-ray diffraction (XRD), Auger electron spectroscopy (AES), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning transmission electron microscopy/energy dispersive X-rays (STEM/EDX). The results show that the material forms a protective scale in both environments. The scale is duplex. The inner part of the scale consists of corundum type chromium-rich (Cr _x Fe_1?x )₂O₃, and the outer layer consists of spinel type oxide. Chromia is lost from the protective oxide by vaporization of CrO₂(OH)₂ in O₂ + H₂O environment. The capacity of Sanicro 28 to suffer chromia vaporization without forming a rapidly growing iron-rich oxide is attributed to its high Cr/Fe ratio. The spinel formed at the oxide/gas interface could in addition be beneficial for oxidation behavior in wet oxygen because it may slow down chromia evaporation.     

Microstructural Investigation of the HCl-Induced Corrosion of the Austenitic Alloy 310S (52Fe26Cr19Ni) at 500 °C

This paper investigates the influence of 500 ppm HCl in a 5 %O₂–95 %N₂ atmosphere on the oxidation of the austenitic stainless steel AISI 310S at 500 °C. Laboratory exposures were made for one, 24, 72 and 168 h and the samples were analysed with XRD, SEM/EDX, FIB and TEM/EDX. When exposed in oxygen a thin and protective chromium-rich oxide scale forms. Addition of HCl causes significantly accelerated corrosion. Within the first hour of exposure, accumulations of FeCl₂, CrCl₂ and NiCl₂ forms below the chromium-rich oxide, especially at steel grain boundaries. The chlorine-induced corrosion is suggested to occur through an electrochemical reaction, in which the dissociation of HCl to form chloride ions at the scale surface is coupled to the oxidation of the metal surface beneath the scale by an outwards electronic current and inwards diffusion of chloride ions along oxide grain boundaries.     

Partial purification and characterization of acylester hydrolase from Lupinus mutabilis

An alkaline acylester hydrolase was partially purified from germinated seeds of Lupinus mutabilis. Hydrolytic activity was absent in the crude extract of ungerminated lupine seed, but it increased and peaked at the fourth day in the germinating seedling. The purification scheme involved homogenization, centrifugation, acetone precipitation, anion exchange chromatography, pH precipitation, and hydrophobic interaction chromatography. The acylester hydrolase was purified 126-fold, and the overall activity yield was 10%. The molecular weight estimated by sodium dodecylsulfate-polyacrylamide gel electrophoresis was 60 kDa. The enzyme had an isoelectric point of 6.2 and showed maximal activity at pH 8.0. The enzyme showed good stability between pH 5.0 and 9.0. In the pH range 7.0–7.5, enzyme precipitation was observed. The enzyme was stable from 0 to 25°C for 5 h and at 45°C lost 50% of its activity in the same period of time. At higher temperatures, the enzyme showed low thermal stability. However, the highest initial activity was found to be at 45°C. Nonionic surfactants and cholic acid enhanced the activity of the enzyme. The activity was reduced by the addition of toluene and isooctane and increased by the addition of diethyl ether, acetonitrile, methanol, and pyridine. The activity was reduced by 37% in the presence of 1 mM Cu²⁺ ions. The enzyme-hydrolyzed triolein showing no positional specificity.     

Modelling and simulation of local mechanical properties of high silicon solution-strengthened ferritic compacted graphite iron

This study focuses on the modelling and simulation of local mechanical properties of compacted graphite iron cast at different section thicknesses and three different levels of silicon, ranging from about 3.6% up to 4.6%. The relationship between tensile properties and microstructure is investigated using microstructural analysis and statistical evaluation. Models are generated using response surface methodology, which reveal that silicon level and nodularity mainly affect tensile strength and 0.2% offset yield strength, while Young′s modulus is primarily affected by nodularity. Increase in Si content improves both the yield and tensile strength, while reduces elongation to failure. Furthermore, mechanical properties enhance substantially in thinner section due to the high nodularity. The obtained models have been implemented into a casting process simulation, which enables prediction of local mechanical properties of castings with complex geometries. Very good agreement is observed between the measured and predicted microstructures and mechanical properties, particularly for thinner sections.     

Selective Pharmacophore Models of Dopamine D1 and D2 Full Agonists Based on Extended Pharmacophore Features

This study is focused on the identification of structural features that determine the selectivity of dopamine receptor agonists toward D₁ and D₂ receptors. Selective pharmacophore models were developed for both receptors. The models were built by using projected pharmacophoric features that represent the main agonist interaction sites in the receptor (the Ser residues in TM5 and the Asp in TM3), a directional aromatic feature in the ligand, a feature with large positional tolerance representing the positively charged nitrogen in the ligand, and sets of excluded volumes reflecting the shapes of the receptors. The sets of D₁ and D₂ ligands used for modeling were carefully selected from published sources and consist of structurally diverse, conformationally rigid full agonists as active ligands together with structurally related inactives. The robustness of the models in discriminating actives from inactives was tested against four ensembles of conformations generated by using different established methods and different force fields. The reasons for the selectivity can be attributed to both geometrical differences in the arrangement of the features, e.g., different tilt angels of the π system, as well as shape differences covered by the different sets of excluded volumes. This work provides useful information for the design of new D₁ and D₂ agonists and also for comparative homology modeling of D₁ and D₂ receptors. The approach is general and could therefore be applied to other ligand–protein interactions for which no experimental protein structure is available.     

Inhibition of Human DHODH by 4‐Hydroxycoumarins,Fenamic Acids,and N‐(Alkylcarbonyl)anthranilic Acids Identified by Structure‐Guided Fragment Selection

A strategy that combines virtual screening and structure‐guided selection of fragments was used to identify three unexplored classes of human DHODH inhibitor compounds: 4‐hydroxycoumarins, fenamic acids, and N‐(alkylcarbonyl)anthranilic acids. Structure‐guided selection of fragments targeting the inner subsite of the DHODH ubiquinone binding site made these findings possible with screening of fewer than 300 fragments in a DHODH assay. Fragments from the three inhibitor classes identified were subsequently chemically expanded to target an additional subsite of hydrophobic character. All three classes were found to exhibit distinct structure–activity relationships upon expansion. The novel N‐(alkylcarbonyl)anthranilic acid class shows the most promising potency against human DHODH, with IC₅₀ values in the low nanomolar range. The structure of human DHODH in complex with an inhibitor of this class is presented.     

Tetranorsesquiterpenoids as Attractants of Yucca Moths to Yucca Flowers

Journal of Chemical Ecology - The obligate pollination mutualism between Yucca and yucca moths is a classical example of coevolution. Oviposition and active pollination by female yucca moths occur...     

Improvement of a grass-clover silage-fed biogas process by the addition of cobalt

Batch assays were performed with samples from a silage-fed mesophilic biogas process accumulating acetate to examine if the addition of single trace elements (iron, nickel, cobalt and molybdenum) or a mixture of trace elements could improve the process. The results from the batch assays led to the addition of cobalt to reach a concentration of 0.2 mg L⁻¹. This made it possible to increase the organic loading rate (OLR) above that in a parallel process not receiving any extra cobalt. Problems with low gas production and decreasing pH were overcome by the daily supply of this single element in small amounts. Acetate conversion to methane was improved, which was confirmed by increased specific methanogenic activity (SMA) with acetate as a substrate. As a consequence, an OLR of 7.0 g VS L⁻¹ day⁻¹ was achieved at a hydraulic retention time (HRT) of 20 days with an equivalent increase in methane production. Without cobalt addition, an OLR of 5.0 g VS L⁻¹ day⁻¹ with an HRT of 20 days was reached after 70 weeks operation.     

Measurements of methane emissions from landfills using a time correlation tracer method based on FTIR absorption spectroscopy

Methane is an important climate gas contributing significantly to global warming. A large part of the anthropogenic emissions of methane comes from landfills. Due to the biogenic origin of these emissions and the inhomogeneous characteristics of landfills and their soil cover, these emissions show large spatial variation. Thus, development of reliable and cost-effective methods for measurements of these emissions is an important task and a challenge to the scientific community. Traditionally, field chamber methods have been used but also different area integrating methods based on downwind plume measurements. These measurements have been supported by meteorological data either directly from local measurements or by controlled release of tracer gas from the landfill providing the dispersion characteristics of the plume. In this paperwe describe a method,the Time Correlation Tracer method, combining controlled tracer gas release from the landfill with time-resolved concentration measurements downwind the landfill using FTIR absorption spectroscopy. The method has been tested and used on measurements at a landfill in southern Sweden over the past 1.5 years. The method has proven to be a usable method for measurements of total methane emission from landfills, and under favorable meteorological conditions we estimate an achievable accuracy of 15-30%. The real time analysis capability of the FTIR makes it possible to judge the success of the measurement already on site and to decide whether more measurements are necessary. The measurement strategy is relatively simple and straightforward, and one person can make a measurement from a medium sized landfill (1-4 ha) within a few days to a week depending on the meteorological situation.     

Evaluation of the oxidation and Cr evaporation properties of selected FeCr alloys used as SOFC interconnects

In recent years, a number of ferritic interconnect materials for use in solid oxide fuel cells (SOFC) have been developed and are now commercially available. Although similar, there are substantial variations in minor alloying elements. This study compares the oxidation performance of five such interconnect materials: Crofer 22 H, Crofer 22 APU (ThyssenKrupp VDM), Sanergy HT (Sandvik Materials Technology), ZMG232 G10 (Hitachi Metals) and E-Brite (ATI Allegheny Ludlum).