Survey of the Chemical Defence Potential of Diatoms: Screening of Fifty Species for α,β,γ,δ-unsaturated aldehydes

In recent years a negative influence of diatom-derived ,,,-unsaturated aldehydes (PUA) on the reproductive success of copepods and invertebrates has been suggested. Since adverse chemical properties of diatoms would question the traditional view of the marine food web, this defense mechanism has been investigated in detail, but the PUA-release by test organisms has only been determined in a few cases. The observed effects were nevertheless frequently discussed from a general point of view often leading to contradictory conclusions. We have examined the PUA-production of 50 diatom species (71 isolates) in order to provide a basis for the interpretation of laboratory and field results on the influence of diatom food on the reproductive success of their consumers. PUA-production is species and strain dependent. Thirty-six percent of the investigated species (38% of the cultivated isolates) release ,,,-unsaturated aldehydes upon cell disruption in concentrations from 0.01 to 9.8 fmol per cell. Thalassiosira rotula and Thalassiosira pacifica, major spring-bloom forming diatoms isolated from Roscoff (Bretagne, English Channel, France) and Puget Sound (Washington, USA) were among the PUA-producing strains.     

CJChE, Your Forum of Profession

Starting from the year of 2006, the Chinese Journal of Chemical Engineering will be available on-line via ScienceDirect from Elsevier, a world-leading publisher of scientific, technical and medical information products and services. The Chemical Industry and Engineering Society of China/Chemical Industry Press (CIESC/CIP) and Elsevier reached a cooperative publishing agreement for the Chinese Journal of Chemical Engineering late in 2005. This event also represents an important step …     

Kinetics,mechanism, and simulation of hydrogen transfer reaction of α, β-unsaturated aldehydes to allylic alcohols

Homogeneous hydrogen transfer reactions of methacrolein (MAL) and isopropanol to methallyl alcohol (MAA) were investigated in batch reactor (Conv. 89%, Select 93.1%) and tubular reactor (Conv. 88.1%, Select 95%) using aluminum isopropoxide (Al(OPrⁱ)₃) as catalyst. Kinetic experiments on hydrogen transfer reactions and reaction order were investigated in batch reactor and tubular reactor. Response surface methodology was applied to optimize the optimum reaction conditions of hydrogen transfer reaction. Purification process of MAA from product mixture after hydrogen transfer reaction was simulated with Aspen Plus software; theoretical stages, reflux ratio, and feed stage of distillation tower were optimized. Density functional theory was used to investigate viable reaction pathway and to probe the catalytic mechanism between reactants and catalyst, including dehydrogenation, coupling, and hydrogenation reaction. Microscopic mechanisms of hydrogen transfer reaction from MAA to MAL were acquired in detail and could be easily extended to other series of hydrogen transfer reaction.     

Comparison of the structural properties of compounds containing the XSSX moiety (X = H,Me, R,Cl, Br,F, OR)

A comparison of the structural parameters of a wide variety of compounds containing the S–S bond is summarized.     

gy, Beijing 100022, China; School of Info

k. They are IG-C1, IG-C2 and IG-C, which classifies unlabeled text according to features' weight generated in feature selection phase. All these approaches have two characteristics: lower time complexity and simpler implementation. The performance comparison between these algorithms and Naive Bayes, Vector Space Model using retuers 21578 and 20 newsgroup data sets     

Effect of α-, β-, γ-, and δ-Tocotrienol on the Oxidative Stability of Lard

Despite the structural similarity of tocopherols, the antioxidative activities of tocotrienol homologues have not been studied often. In this study, the antioxidant activities of α-, β-, γ-, and δ-tocotrienols at various concentrations from 100 to 1,000 ppm in lard were evaluated. Headspace oxygen content of the lard without tocotrienol decreased from 21.1 to 10.7 % and the peroxide value increased from 0.4 to 33.4 mequiv/kg after 7 days of storage at 55 °C in the dark. α-Tocotrienol at 100 ppm and β-tocotrienol at 100 and 200 ppm effectively improved the oxidative stability of lard; however, the antioxidative activities of α- and β-tocotrienol reduced as the concentration increased to 1,000 ppm. The γ- and δ-tocotrienols improved the oxidation stability of lard and the effectiveness was essentially same at all concentrations (p > 0.05). The antioxidative activities of tocotrienols in the autoxidation of lard increased in the order of α-, β-, γ-, and δ-tocotrienols. The activities of tocotrienols in lard were different depending on the type of homologues and concentrations.     

An in-Depth Analysis of the Swelling,Mechanical, Electrical,and Drug Release Properties of Agar–Gelatin Co-Hydrogels

Agar–gelatin-based co-hydrogels were prepared with different compositions of the agar and the gelatin fractions. The intermolecular hydrogen bonding was higher in the co-hydrogels as compared to the gelatin hydrogel. Swelling studies indicated diffusion-mediated swelling. The electrical stability of the co-hydrogels was higher as compared to the gelatin hydrogel. Though the firmness of the co-hydrogels was higher, Weichert model of viscoelasticity indicated that the inherent mechanical stability of the gelatin hydrogel was superior. The release of ciprofloxacin hydrochloride was predominately Fickian diffusion-mediated. In gist, the co-hydrogels can be tried as polymeric constructs for controlled drug delivery applications.     

Experimental Measurement and Correlation of the Solubility of Methyl-acetyl-naphthalene in n-Heptane,n-Octane,and n-Dodecane

1 INTRODUCTION 2-Methyl-6-acetylnaphthalene (2,6-MAN) is a type of white or pale yellow, powdery crystal, with a melting point of 332.15K. It is an important interme- diate[1] used for producing 2,6-naphthalene dicarbox- ylic acid (2,6-NDA), which has very extensive appli- cations in not only the light, electronic, and defense industries, but in many other areas. In particular, 2,6-NDA is an important monomer of liquid crystal polyester material (LCP) and polyethylene naphtha- lene-2…     

Evaluation of the presence of bacteria in food and environment of an Oncological Service of a National Hospital, San José, Costa Rica

The microbiological quality of 92 samples from the Oncological Service of a National Hospital, San José, Costa Rica was evaluated during the months of February to July, 2002. Of these samples, 48 were from salads, refreshments, and fruits and 44 from surfaces, air and hands of the medical personnel. The presence of total and fecal coliforms was determined by the total plate count technique, using Violet Red Bile Agar for the isolation of total and fecal coliforms, Baird-Parker Agar for Staphylococcus aureus, Cetrimide Agar for Pseudomonas and Listeria was enriched in University of Vermont Broth, Fraizer Broth and isolated in Oxford Agar. From the food samples analyzed, 77% were positive for at least one of the parameters studied; the fruits presented the greater contamination (94%) and the cooked salads the minor, even though Listeria was isolated in 13% of them. All tested salads (100%) were positive for fecal coliforms. Pseudomonas and S. aureus were isolated from fruits, raw salads, and refreshments. All the analyzed surfaces, with an exception, were negative for the parameters evaluated. 75% of the hands of the medical personnel were positive for at least one of the parameters evaluated; 25% had total coliforms (2.8x10(3) UFC/hand), 13% fecal coliforms (2.4x10(3) UFC/ hand), 69% S. aureus (1.3x10(3) UFC/hand) and 19% Pseudomonas sp. 115 isolates were randomly selected, and identified using miniaturized tests (API). When comparing these identifications with the 166 isolations done at the Clinical Laboratory of the Hospital from the infected patients of oncology, by means of variance analysis, it was determined that both bacterial populations were statistically similar.     

Effect of α-, β-, γ-, and δ-Tocotrienol on the Singlet Oxygen Oxidation of Lard

The impacts of four different types of tocotrienol homologues on the singlet oxygen oxidation of lard were evaluated by measuring the headspace oxygen content and the peroxide value. Singlet oxygen oxidation of lard was induced by chlorophyll photosensitization. Samples of 0.100, 0.250, and 0.400 M lard in methylene chloride containing chlorophyll and α‐, β‐, γ‐, or δ‐tocotrienol were prepared and stored under light at 3,000 lux for 4 h. All tocotrienol homologues at 1.20 mM significantly prevented the singlet oxygen oxidation of lard. Chlorophyll under light produced singlet oxygen at 1.09 μmol oxygen/mL headspace/h. A steady state kinetic study showed that tocotrienols reduced the singlet oxygen oxidation of lard by quenching the singlet oxygen. Singlet oxygen reacted with lard at 6.50 × 10⁴M^?1 s^?1. α‐, β‐, γ‐, and δ‐tocotrienol quenched singlet oxygen with the rate of 2.16, 1.99, 2.05, and 0.800 × 10⁷M^?1 s^?1, respectively. Among them, α‐tocotrienol significantly prevented singlet oxygen oxidation of lard.     

Heterogeneous Catalytic Esterification of ω-Sulfhydryl Fatty Acids: Avoidance of Thioethers,Thioesters, and Disulfides

Two mesoporous silicas functionalized with propylsulfonic (SBA-15-PSA) and arenesulfonic (SBA-15-ASA) acid groups, and a highly acidic, functionalized styrene divinylbenzene copolymer ion exchange resin (Amberlyst-15) were examined for their ability to catalyze the ethanolic esterification of the ω-sulfhydryl fatty acid, 11-mercaptoundecanoic acid (MUA), without catalyzing unwanted side reactions at the sulfhydryl group. All three solid acid catalysts catalyzed the MUA esterification in excess ethanol. The activation energy for the catalytic esterifications were determined from 50 to 75 °C, resulting in apparent E _a of 54, 71, and 59 kJ/mol for SBA-15-PSA, SBA-15-ASA, and Amberlyst-15, respectively. GC–MS analysis determined that all three catalysts produced near quantitative conversion of MUA to its ethyl ester with very little reactivity towards the sulfhydryl group. This was a marked improvement over the esterifications catalyzed by sulfuric and p-toluenesulfonic acids which produced thioethers and disulfide side products. The MUA ethyl ester synthesis was demonstrated on a gram scale at 70 °C catalyzed by Amberlyst-15, and the desired product was isolated in 80% yield at >95% purity with a minimum of purification.     

Overview of Heat-Pump–Assisted Drying Systems,Part I: Integration,Control Complexity,and Applicability of New Innovative Concepts

Over the last two decades, many academic R&D studies on drying used heat pumps to improve the overall energy efficiency of the process as well as the quality of dried materials. Part I of this overview focuses on a number of proposed new and innovative heat-pump-assisted drying concepts. It investigates the accuracy of integration configurations and associated control methods, and tries to evaluate their industrial application potential. This article aims to help identify as well as promote the most promising technological advancements and the application of industrial heat-pump-assisted drying systems.     

Comparison of the Activity of Pd–M (M: Ag,Co, Cu,Fe, Ni,Zn) Bimetallic Electrocatalysts for Oxygen Reduction Reaction

Topics in Catalysis - Carbon-supported 7.5 wt% Pd–2.5 wt% M (M: Ag, Co, Cu, Fe, Ni, Zn) bimetallic catalysts were synthesized via wet impregnation and assessed as...     

Growth,doping and characterization of epitaxial thin films and patterned structures of AlN,GaN, and AlxGa1−xN

Advancements in the doping of GaN and Al_xGa_1−xN thin films, and the growth of GaN and Al_xGa_1−xN structures on patterned heterostructure substrates via metalorganic vapor phase epitaxy are reported. The acceptor-type behavior of Mg-doped GaN films grown in N₂ diluents is presented. Net ionized impurity concentrations up to 8×10¹⁸ cm⁻³ and Hall mobilities up to ≈14 cm² V⁻¹ s⁻¹ were measured for Mg-doped films grown in N₂ in the as-grown condition. Donor and acceptor doping of Al_xGa_1−xN alloys was performed. Acceptor doping of Al_xGa_1−xN for x≤0.13 and donor doping for x≤0.58 were achieved for films deposited at 1100 °C. Lateral epitaxial overgrowth of GaN and Al_xGa_1−xN layers was investigated. The growth and coalescence of GaN and Al_xGa_1−xN stripes patterned in SiO₂ and/or SiN_x masks deposited on GaN, including aligned second lateral epitaxial overgrowth on initial laterally overgrown GaN layers, are discussed.     

Influence of source,rate, and method of applicating controlled release fertilizer on nutrient release and growth of ‘Savannah’ holly

An experiment was conducted to determine the effect of rate of fertilizer application and method of application on the rate of nutrient release and growth of Savannah holly (Ilex ×attenuata Ashe) using three controlled release fertilizers. The controlled release fertilizers used were Osmocote 17N—3P—9.9K, Sierrablen 17N—3P—8.3K, and High-N 24N—1.7P—5.8K, all 12 to 14 month formulations. The three fertilizers had different release rates as determined by leachate nitrate—N and electrical conductivity (EC) measurements. Topdressing of fertilizer had the greatest release rate at seven days after treatment compared to fertilizer incorporation which had the lowest EC readings at 120 days after treatment. Fertilizer source had no effect on the shoot growth of Savannah holly. Growth index and shoot dry weight of Savannah holly increased linearly as N rate increased from 0.9 to 2.1 kg N m^–3. A significant linear relationship (R² = 0.97, Nitrate—N = 409 (EC)) between nitrate—N and EC indicates that nitrate—N concentration can be estimated from EC readings when the pour-through method is used with multicoated controlled release fertilizers. The controlled release fertilizers used in this study provided adequate nutrient release rates for up to four months under outdoor nursery conditions during the months of June through October.