Christian V. Stevens

Bio: Christian V. Stevens is an academic researcher from Ghent University. The author has contributed to research in topics: Ionic liquid & Bicyclic molecule. The author has an hindex of 45, co-authored 467 publications receiving 11742 citations. Previous affiliations of Christian V. Stevens include Katholieke Universiteit Leuven & University of Minnesota.

Effect of type of bleaching earth on the final color of refined palm oil

Abstract: Although studies indicate chemical changes during bleaching such as carotene and unsaturated fatty acids oxidation, which are probably responsible for the color fixation of palm oil, this process is not very clear. The objective of this study was to investigate the effect of type and amount of bleaching earth (BE) on the final quality of refined palm oils, especially on the oxidative state and color. Two types of bleaching earth were tested, one natural (NBE) and one acid-activated (ABE) (0.5–3.0% w/w). Crude palm oils were bleached at 105 °C, during 30 min at 50 mmHg pressure. Afterwards, a deodorization step was performed at 260 °C, 3 mbar, 1.5% steam during 60 min. These refining procedures were evaluated after each step by measuring β-carotene, color, peroxide (PV) and p-anisidine (pAV) values. It was observed that both BE can decompose peroxides. However, a maximum pAV followed by a decrease was observed for ABE while the pAV remains approximately constant at a maximum for NBE, suggesting only ABE catalytically decomposes secondary oxidation products. The color after deodorization was inversely proportional to pAV when bleaching was performed with ABE, even though the oil has a lighter color after deodorization.

Enhancement of fungicidal and insecticidal activity by reductive alkylation of chitosan

Abstract: A series of N-alkyl chitosan (NAC) derivatives were synthesized using a reductive alkylation reaction to examine their fungicidal and insecticidal activity The chemical structures were characterized by IR and 1H NMR spectroscopy, and the degree of substitution (DS) ranged from 002 to 037 Their fungicidal activity was evaluated against the grey mould Botrytis cinerea Pers ex Fr (Leotiales: Sclerotiniaceae) and the rice leaf blast pathogen Pyricularia grisea Sacc [Teleomorph: Magnaporthe grisea (Hebert) Barr] by a radial growth bioassay It was of interest that most of the NAC derivatives were more active against both fungi than chitosan itself The most active derivative was N-(2,2-diphenylethyl)chitosan with EC50 values of 0031 and 023 g L−1 against B cinerea and P grisea respectively In addition, some derivatives, at higher concentrations up to 10 g L−1, inhibited the mycelial growth and spore formation of P grisea Bioassays against larvae of the cotton leafworm, Spodoptera littoralis (Boisd) (Lepidoptera: Noctuidae) with the NAC derivatives at a rate of 50 g kg−1 in artificial diet demonstrated that N-(3-phenylbutyl)chitosan was the most active compound In addition, N-propylchitosan, N-undecanylchitosan and N-(3-phenylpropyl)chitosan derivatives strongly inhibited larval weight gain in S littoralis, with respective reductions of 76, 66 and 65% after 4 days of feeding on treated diet Copyright © 2006 Society of Chemical Industry

Synthesis of 2-acetyl-1-pyrroline, the principal rice flavor component

Abstract: A new straightforward synthesis of 2-acetyl-1-pyrroline, the principal rice flavor component with a cracker-like flavor, is reported. The reaction sequence involves the conversion of pyrrolidine into tripyrroline, subsequent hydrocyanation of the latter into 2-cyanopyrrolidine, oxidation into 2-cyano-1-pyrroline, and Grignard addition of methylmagnesium iodide, affording an overall yield of 16-19% from pyrrolidine. In similar way, 2-propionyl-1-pyrroline, a recently discovered flavor component of popcorn, was prepared in addition to several higher analogues, i.e., 2-acyl-1-pyrrolines. Also, the synthesis of 2-(acetyl-d 3 )-1-pyrroline, a deuterated derivative of the rice flavor compound which is useful for the stable isotope dilution assay, is described

Enyne Metathesis–Oxidation Sequence for the Synthesis of 2‐Phosphono Pyrroles: Proof of the “Yne‐then‐Ene” Pathway

Abstract: A new tandem reaction sequence has been developed for the synthesis of 2-phosphono pyrroles. The sequence consists of ring-closing enyne metathesis of a substituted aminophosphonate, containing a terminal alkyne and an internal alkene, in combination with in situ oxidation of the produced 3-pyrrolines using tetrachloroquinone. By analyzing the formation of the end and certain byproducts, taking into account the difference in reactivity of different substrates and carefully studying spectroscopic data, it was found that the reaction proceeds by means of the "yne-then-ene" pathway. During the initiation phase, a new ruthenium carbene is formed which continues the propagation cycle.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Production of first and second generation biofuels: A comprehensive review

Abstract: Sustainable economic and industrial growth requires safe, sustainable resources of energy. For the future re-arrangement of a sustainable economy to biological raw materials, completely new approaches in research and development, production, and economy are necessary. The ‘first-generation’ biofuels appear unsustainable because of the potential stress that their production places on food commodities. For organic chemicals and materials these needs to follow a biorefinery model under environmentally sustainable conditions. Where these operate at present, their product range is largely limited to simple materials (i.e. cellulose, ethanol, and biofuels). Second generation biorefineries need to build on the need for sustainable chemical products through modern and proven green chemical technologies such as bioprocessing including pyrolysis, Fisher Tropsch, and other catalytic processes in order to make more complex molecules and materials on which a future sustainable society will be based. This review focus on cost effective technologies and the processes to convert biomass into useful liquid biofuels and bioproducts, with particular focus on some biorefinery concepts based on different feedstocks aiming at the integral utilization of these feedstocks for the production of value added chemicals.

Chitosan chemistry and pharmaceutical perspectives.

Abstract: Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S. A. S. Nagar,Mohali, Punjab-160 062, India, Institute of Biochemistry, Faculty of Medicine, Polytechnic University, Via Ranieri 67, IT-60100 Ancona, Italy,Green Biotechnology Research Group, The Special Division for Human Life Technology, National Institute of Advanced Industrial Science andTechnology, 1-8-31 Midorigaoka, Ikeda, Osaka-563-8577, Japan, and Department of Medicinal Chemistry & Natural Products,The Hebrew University of Jerusalem, School of Pharmacy-Faculty of Medicine, Jerusalem 91120, IsraelReceived March 2, 2004