The relative efficiency of option hedging strategies using the third-order stochastic dominance

Computational Management Science - The selection of an appropriate portfolio hedging strategy is a concern for both investment theory and practice. Options are believed to be flexible and useful...     

The Gender Productivity Gap in Croatian Science: Women Are Catching up with Males and Becoming Even Better

How much different genders contribute to citations and whether we see different gender patterns between STEM and non-STEM researchers are questions that have long been studied in academia. Here we analyze the research output in terms of citations collected from the Web of Science of males and females from the largest Croatian university, University of Zagreb. Applying the Mann–Whitney statistical test, for most faculties, we demonstrate no gender difference in research output except for seven faculties, where males are significantly better than females on six faculties. We find that female STEM full professors are significantly more cited than male colleagues, while male non-STEM assistant professors are significantly more cited than their female colleagues. There are ten faculties where females have the larger average citations than their male colleagues and eleven faculties where the most cited researcher is woman. For the most cited researchers, our Zipf plot analyses demonstrate that both genders follow power laws, where the exponent calculated for male researchers is moderately larger than the exponent for females. The exponent for STEM citations is slightly larger than the exponent obtained for non-STEM citations, implying that compared to non-STEM, STEM research output leads to fatter tails and so larger citations inequality than non-STEM.     

Quantitative Voronovskaya-Type Results for Polynomially Bounded Functions

We prove quantitative Voronovskaya-type results and Grüss–Voronovskaya inequalities for polynomially bounded functions. The results are given in terms of suitable K-functionals and applied to linking Szász–Mirakyan and Baskakov operators.     

Microbial growth on pall rings

Biogas is upgraded using an absorption with water-wash technique by 11 of a total of 14 upgrading plants in Sweden. However, problems with microbial growth on the pall rings in the absorption column, and in one case in the desorption column, have a negative impact on the upgrading of raw gas to vehicle gas. Five of the nine biogas plants studied here have experienced problems with microbial growth. The objectives of this study were to identify such microbial growth and to determine possible factors for its control, in order to provide recommendations for process management. A questionnaire was sent out and visits were made to the upgrading plants to collect information about the upgrading process. Phospholipid fatty acid (PLFA) analysis was performed to determine microbial biomass and community structure in samples from four upgrading plants. In samples from two of the plants, methane-oxidizing bacteria (type I methanotrophs) were indicated, while samples from one of the other plants showed biomarkers indicating actinomycetes. Factors affecting development of microbial growth were found to be water quality and the pH and temperature of the process water. Plants that used wastewater in the upgrading process experienced far more problems than those using clean water of drinking quality.     

Ultra‐high performance supercritical fluid chromatography of lignin‐derived phenols from alkaline cupric oxide oxidation

Traditional chromatographic methods for the analysis of lignin‐derived phenolic compounds in environmental samples are generally time consuming. In this work, an ultra‐high performance supercritical fluid chromatography method with a diode array detector for the analysis of major lignin‐derived phenolic compounds produced by alkaline cupric oxide oxidation was developed. In an analysis of a collection of 11 representative monomeric lignin phenolic compounds, all compounds were clearly separated within 6 min with excellent peak shapes, with a limit of detection of 0.5–2.5 μM, a limit of quantification of 2.5–5.0 μM, and a dynamic range of 5.0–2.0 mM (R² > 0.997). The new ultra‐high performance supercritical fluid chromatography method was also applied for the qualitative and quantitative analysis of lignin‐derived phenolic compounds obtained upon alkaline cupric oxide oxidation of a commercial humic acid. Ten out of the previous eleven model compounds could be quantified in the oxidized humic acid sample. The high separation power and short analysis time obtained demonstrate for the first time that supercritical fluid chromatography is a fast and reliable technique for the analysis of lignin‐derived phenols in complex environmental samples.     

Mass spectrometry of heterocyclic compounds. I—the behaviour of some quaternary heterocyclic iodides under electron impact

The mass spectra of five quaternary heterocyclic iodides have been investigated. The main thermal process is the anhydro base formation by HI elimination. The influence of the second heteroatom, X, on the fragmentation mode of the thermally produced anhydro bases is analysed.     

Metal-bridging mechanism for O-O bond cleavage in cytochrome C oxidase

Density functional theory (B3LYP) has been applied to large models of the Fe(II)-Cu(I) binuclear center in cytochrome oxidase, investigating the mechanism of O-O bond cleavage in the mixed valence form of the enzyme. To comply with experimental information, the O(2) molecule is assumed to be bridging between iron and copper during the O-O bond cleavage, leading to the formation of a ferryl-oxo group and a cupric hydroxide. In accord with previous suggestions, the calculations show that it is energetically feasible to take the fourth electron needed in this reaction from the tyrosine residue that is cross-linked to one of the copper ligands, resulting in the formation of a neutral tyrosyl radical. However, the calculations indicate that simultaneous transfer of an electron and a proton from the tyrosine to dioxygen during bond cleavage leads to a barrier more than 10 kcal/mol higher than that experimentally determined. This may be overcome in two ways. If an extra proton in the binuclear center assists in the mechanism, the calculated reaction barrier agrees with experiment. Alternatively, the fourth electron might initially be supplied by a residue in the vicinity other than the tyrosine.     

Metal Complexes with Macrocyclic Ligands. Part XLIII. Tetraazamacrocyclic nickel(II) and copper(II) complexes with aliphatic methylthio- and methoxy-substituted pendant chains

The 14-membered tetraazamacrocyclic Ni²⁺ and Cu²⁺ complexes of 4 (1, 4, 8-trimethyl-11-[(2-methylthio)ethyl]-1, 4, 8, 11-tetraazacyclotetradecane), 5 . (1, 4-dimethyl-8, 11-bis[2-(methylthio)ethyl]-l, 4, 8, 11-tetraazacyclotetradecane), and 7 (1, 4, 8, ll-tetrakis[2-(methylthio)ethyl]-1, 4, 8, 11-tetraazacyclotetradecane), with pne, two, and four methylthio-substituted pendant chains, respectively, and the Ni²⁺ complex of 6 (1, 4-dimethyl-8, 11-bis (2-methoxyethyl)-1, 4, 8, 11-tetraazacyclotetradecane), with two methoxy-substituted pendant chains, were synthesized and their chemistry studied with regard to modelling F430. Solution spectra in H₂O, MeCN, and DMF indicate participation of the side chain in metal coordination when the donor group is a thioether, whereas no coordination with the metal ion is observed with the ether group. Similarly the X-ray structures of the thioether-containing compounds [Ni( 5 )](ClO₄)₂, [Cu( 5 )](ClO₄)₂, and [Cu( 7 )](ClO₄)₂ show a coordination number of 5, whereas that of [Ni( 6 )](ClO₄)₂ with ether pendant chains, shows a coordination number of 4. Cyclic voltammetry of these complexes in MeCN reveals that Ni²⁺ is reversibly reduced to Ni⁺ between ?0.64 and ?0.77 V vs. SCE, the potential being influenced by the nature and number of the pendant chains. At more negative potentials, the thioether is cleaved, whereby a thiol is formed; the thiol is then oxidized at ca. + 0.8 V vs. SCE, when a glassy carbon electrode is used, or at ca. 0 V vs. SCE at a dropping Hg electrode. No cleavage of the ether bond in [Ni( 6 )](ClO₄)₂ is observed under similar conditions.