Formation and Organization of Amino Terminated Self-assembled Layers on Si(001) Surface

We have investigated the effects of dipping time, solution concentration and solvent type on the formation of self-assembled monolayers with aminosiloxane molecules (i.e., N-(3 trimethoxysilylpropyl)diethylenetriamine (TPDA)) on the Si(001) surface. Studies performed with an ellipsometer showed that monolayers with a thickness of about 1.2 nm were formed when the dipping time is about 2 h, while multilayer were observed for longer time periods. The effect of the TPDA concentration on the thickness of the deposited layer was not very profound, however, the contact angle data exhibit importance of concentration on the surface coverage. The type of the solvent used in the formation of the monolayers was found an important parameter. Monolayers were formed with solvent having larger dielectric constants. Relatively thick multilayer was observed when benzene was used as the solvent, due to its quite low dielectric constant (hydrophobicity).     

Nitrogen-promoted active carbons as DeNOx catalysts: 1. The influence of modification parameters on the structure and catalytic properties

The influence of modification by post-treatment of active carbon with ammonia or urea on catalytic reduction of NO with ammonia was studied. The amount of nitrogen introduced into the structure depended on the pre-treatment of active carbon. The formed N-species were mainly pyridinic or pyrrole/pyridone in nature. No amine, amide or cyano species were found. Both modification procedures (ammonia or urea) led to the increase in activity in SCR and selectivity to N₂. The extent of the improvement depended on the pre-oxidation of active carbon before N-introduction and was higher for urea than ammonia treatment.     

Influence of the V2O5 Loading on the Structure and Activity of V2O5/TiO2 SCR Catalysts for Vehicle Application

In this paper the effect of the vanadium oxide loading on the surface vanadia structure and the activity as well as selectivity in the catalytic reduction of NO with NH₃ was studied for a V₂O₅/TiO₂ model system. A series of TiO₂ (WO _x stabilized anatase) supported vanadia catalysts with varying loadings were characterized by laser Raman spectroscopy, ⁵¹V MAS-NMR, V K XANES. To determine the acidic properties, DRIFTS measurements were done with pyridine adsorbed on the samples. The measurements indicate that with increasing active phase loading square pyramidal coordinated surface vanadia species are replaced by an amorphous highly dispersed vanadium oxide phase with a coordination like V₂O₅. In addition, the ratio of Brønsted to Lewis acid sites is shifted from a comparatively low to an equal level at high loadings. This structural change is accompanied by a clearly improved catalytic activity and selectivity.     

Predicting toxicity of tall larkspur (Delphinium barbeyi): measurement of the variation in alkaloid concentration among plants and among years

Tall larkspur (Delphinium barbeyi) is the principal mountain larkspur responsible for the majority of cattle deaths on mountain rangelands in western Colorado and central and southern Utah in the United States. Ten plants in each of two tall larkspur populations in the mountains near Ferron and Salina, Utah, were marked, and single stalks were harvested periodically through the growing season for 4 yr. Toxic alkaloid concentration [alkaloids containing the N-(methylsuccimimido)-anthranilik ester group] was determined by Fourier transform infrared (FTIR) spectroscopy. Individual larkspur plants varied in alkaloid concentrations, especially in early growth (14–38 mg/g). As the concentration declined over the growing season, variation among plants also declined. There were yearly differences in alkaloid concentration among individual plants (P < 0.01) and populations (P < 0.001), even after accounting for differences in phenological growth between years. Variables such as precipitation, temperature, days since snow melt, growing degree days (sum of mean temperature each day from snow melt), and plant height and weight were all considered in a Mallows Cp multiple regression selection procedure to predict alkaloid concentration. The mixed model procedure in SAS adjusted the regression equation for locations and years. Growing degree days was the best single predictor of alkaloid levels: ln y = (3.581 – 0.00423 GDD), R ² = 0.85. Internal validation of this equation within individual years and locations from which the equation was developed, produced correlations between observed versus predicted values ranging from r = 0.73 to 0.93. External validations on nine other larkspur populations produced correlations ranging from r = 0.76 to 0.99. This predictive equation can provide a tool for ranchers and land managers to make management decisions of when to graze cattle in larkspur areas.     

Sulfonation of macroporous poly(styrene-co-divinylbenzene) beads: Effect of the proportion of isomers on their cation exchange capacity

The influence of the proportions of the meta- and para-isomers of divinylbenzene and ethylstyrene in the degree of sulfonation of macroporous poly(styrene-co-divinylbenzene) (poly(ST-co-DVB)) beads has been investigated. The first step in this work was the synthesis of poly(ST-co-DVB) beads, with different porous structures, by variation of the proportions of cross-linking agent (%DVB) and of the volume fraction of monomers in the organic phase (Fm) of the polymerization mixture. The next step involved transformation of the polymeric beads obtained into cation exchange resins by means of hot sulphuric acid treatment. The quantitative extent of the sulfonation reaction was evaluated by measuring the ion exchange capacity (q) of each type of resin. The Design of Experiments (DOE) methodology was used to study the effects of %DVB and Fm on q and it was found that only the %DVB factor exerted a significant effect on this parameter, its influence being non-linear and negative. To obtain more reliable results, a new set of experiment was performed in which the range of %DVB values was expanded, covering from 25% to 80% DVB. The results indicated again that the influence of the %DVB factor on q was non-linear and negative; that is, an increase of %DVB in the synthesis process led to a decrease in q. Since this effect can be thought to be due to the hindered penetration of the sulfonation mixture into the very cross-linked gel-type nanoparticles comprising the beads, an attempt was made to find an interrelationship between the specific surface area (S_BET) of each type of bead and their q, trying to determine whether the sulfonation was merely a surface process. However, it was found that not only did sulfonation of the surface of the nanoparticles occur but also that the sulfonation agent penetrated into their interior. Taking these observations into account, it was suspected that one or more of the isomers present in the commercial DVB polymerize in such a way that their sulfonation is not complete. To check this possibility, the proportion of the DVB isomers and q were correlated The quantitative relationship found indicated that the absence of a completely homogeneous sulfonation of poly(ST-co-DVB) beads seems to be due to an insufficient sulfonation of the benzene rings of the para-isomers present in commercial DVB.     

Chemistry and Defensive Efficacy of Secretion of Burrowing Bug (Sehirus cinctus cinctus)

Adult Sehirus cinctus cinctus emit a volatile secretion from their metathoracic scent glands when tactually stimulated. We identified the volatile components by gas chromatography, high-performance liquid chromatography, and mass spectrometry. The secretion of both sexes contained (1R)-(+)--pinene, (1S)-(–)--pinene, -myrcene, (R)-(+)-limonene, and -terpinolene. Two additional compounds were found in only female secretions: (E)-2-hexenyl acetate and (E)-2-octenal. We also tested the defensive capability of this insect by offering it to various predators. Anoles, starlings, and a killdeer rejected S. c. cinctus after an initial sampling. These findings suggest that the secretion plays a defensive role.     

Synthesis and surface properties of chemodegradable anionic surfactants: Sodium carboxylates of cis-1,3-dioxane derivatives

The 2-n-alkyl-5-carboxy-5-methyl-1,3-dioxanes were obtained in good yield from the reaction of aliphatic aldehydes with 2,2-bis(hydroxymethyl)propionic acid in dichloromethane solution, catalyzed by p-toluenesulfonic acid monohydrate. Nuclear magnetic resonance analysis indicated that they were pure cis-isomers with the axial configuration of the carboxylic group at the C-5 carbon atom of the 1,3-dioxane ring. The acids were converted, with retention of the configuration, to their sodium salts by reaction with sodium methoxide or sodium hydroxide in methanol. The physicochemical properties of the acids and sodium salts, as well as their surface properties at the aqueous solution-air interface, were determined. Critical micelle concentration, surface excess concentration, surface area demand per molecule of sodium salts at the monomolecular surface layer, and standard free energy of micellization were determined based on surface tension measurements. Part XXXIV in the series: Chemical Structure and Surface Activity. Part XXXIII: A. Piasecki, A. Sokolowski, B. Burczyk, R. Gancarz, and U. Kotlewska, Synthesis, Surface Properties and Hydrolysis of Chemodegradable Anionic Surfactants: Diastereomerically Pure cis- and trans-2,5-Disubstituted-1,3-dioxanes. J. Colloid Interface Sci. 192:74–82 (1997).     

Sex pheromone of the European grapevine moth,Lobesia botrana Schiff. (Lepidoptera: Tortricidae): Synthesis and effect of isomeric purity on biological activity

A short synthesis of (E, Z)-7,9-dodecadien-1-yl acetate from propargyl alcohol and 6-bromohexanol via acetylenic-allenic isomerization of the resulting bis-THP-1,9-non-2-yn-diol is described. The field test of several preparations showed that theE,E isomer does not interfere with the biological activity of the pheromone. It was found that the crude preparation has higher activity than purified pheromone or virgin females.     

Synthesis and study of the surface properties of long-chain alkylnaphthalene sulfonates

Long-chain alkylnaphthalene sulfonates were synthesized by means of a Wurtz-Fittig reaction, and the basic properties were studied in water at 30°C. Through surface tension measurements, the following values were determined: the critical micelle concentration (CMC) and the surface tension at the CMC (γ_CMC). The following values were calculated: area per molecule at the CMC (A_CMC), standard free energy change of micellization (ΔG _mic ^o ), standard free energy of adsorption (ΔG _ad ^o ), and the “efficiency” of a surfactant in reducing surface tension (pC₂₀). The micelle aggregation numbers were measured through steady-state fluorescence-quenching methods. As the chain length of the hydrocarbon of n-alkylnaphthalene sulfonate increased, the Krafft temperature increased, the surface tension decreased, the value of CMC decreased, pC₂₀ increased, ΔG _ad ^o and ΔG _mic ^o became more negative, and the micelle aggregation number increased. The results showed that sodium α-(n-decyl)naphthalene sulfonate (DNS) had a high pC₂₀, low Krafft temperature, and lower CMC than other surfactants in this study. Thus, DNS and the other n-alkylnaphthalene surfactants studied exhibit desirable properties that may be of value in some fields such as detergency, oil recovery, and dyes.     

Dietary influences on terpenoids sequestered by the biological control agent Oxyops vitiosa: effect of plant volatiles from different Melaleuca quinquenervia chemotypes and laboratory host species

The weevil Oxyops vitiosa is an Australian species imported to Florida, USA, for the biological control of the invasive species Melaleuca quinquenervia. The larvae of this species feed on the leaves of their host and produce a shiny orange secretion that covers their integument. Previous results indicated that a major component of this secretion, viridiflorol, is sequestered from the host plant and repels a generalist predator, the red imported fire ant, Solenopsis invicta. When the larvae fed on a different chemotype of M. quinquenervia, which lacked viridiflorol but was rich in a different sesquiterpene, (E)-nerolidol, similar protection occurred. Solvent washes of these larvae indicated that (E)-nerolidol was sequestered from M. quinquenervia leaves and repelled S. invicta workers when applied to dog food baits at physiological concentrations (17.5, 35.0, and 52.5 g/mg). Additionally, -caryophyllene also repelled S. invicta workers when applied to dog food baits at concentrations that approximated those in the O. vitiosa larval secretions (3.5 and 35 g/mg). When the O. vitiosa larvae were fed leaves from laboratory hosts (nonfield hosts), similar repellent activity was found. This activity was traced to several of the same compounds (e.g., 1,8-cineole, viridiflorol) found to be active in their field host M. quinquenervia. These weevil larvae are opportunistic, sequestering the primary terpenoids in their host leaves that confer antipredator activity.     

Study of the Oxygen Diffusion on Three-Way Catalysts: A Kinetic Model

A computer model was developed to take into account all the phenomena that can occur in ¹⁸O/¹⁶O isotopic exchange over Pt/CeZrO _x materials: adsorption/desorption on the metal, surface and bulk O diffusion. Discriminating each step of the exchange process is no longer necessary: kinetic parameters and O diffusivity can be calculated in a single experiment.     

Investigation of Ammonia Oxidation over Copper with In Situ NEXAFS in the Soft X-Ray Range: Influence of Pressure on the Catalyst Performance

The oxidation of ammonia over polycrystalline copper was investigated by means of in situ NEXAFS (near-edge X-ray absorption fine structure) spectroscopy in the soft X-ray range. The reaction, carried out in a 1:12 excess of oxygen, was observed by mass spectrometry. The simultaneous detection of the surface electronic structure and its catalytic performance allows correlation of different reaction products to the current surface structure of the catalyst. It is shown that a change in total pressure from 0.4 to 1.2 mbar severely affects the reaction path. Copper(I) nitride was identified as poison and a copper oxide was found to be the active phase for the selective oxidation of ammonia to nitrogen.     

Significant enhancement of the oxidation of CO by H2 and/or H2O on a FeO x /Pt/TiO2 catalyst

Oxidation of CO on the FeO _x /Pt/TiO₂ catalyst is markedly enhanced by H₂ and/or H₂O at 60 °C, but no such enhancement is observed on the Pt/TiO₂ catalyst, but shift reaction (CO + H₂O → H₂ + CO₂) does not occur on the FeO _x /Pt/TiO₂ catalyst at 60 °C. DRIFT-IR spectroscopy reveals that the fraction of bridge bonded CO increases while that of linearly bonded CO decreases on the FeO _x loaded Pt/TiO₂ catalyst. The in-situ DRIFT IR spectra proved that the bridged CO is more reactive than the linearly bonded CO with respect to O₂, and the reaction of the bridge-bonded CO with O₂ as well as of the linearly bonded CO is markedly enhanced by adding H₂ to a flow of CO + O₂. From these results, we deduced that the promoting effect of H₂ and/or H₂O is responsible for the preferential oxidation (PROX) reaction of CO on the FeO _x /Pt/TiO₂ catalyst, and a following new mechanism via the hydroxyl carbonyl or bicarbonate intermediate is proposed for the oxidation of CO in the presence of H₂O.      

Synthesis, X-ray structure and Hg, Se CP MAS NMR studies on the first tris(imidazolidine-2-selone) mercury complex: {Chloro-tris[N-methyl-2(3H)-imidazolidine-2- selone]mercury(II)}chloride

A novel cationic Hg(II) complex has been synthesized with N-methyl-imidazolidine-2-selone ligand. The tris(N-Methyl-imidazolidine-2-selone) mercury(II) complex, [(MeImSe)₃HgCl]⁺Cl⁻ (1), has been characterized by single crystal X-ray analysis and CP MAS ¹⁹⁹Hg and ⁷⁷Se NMR.     

Effect of qualitative and quantitative variation in allelochemicals on a generalist insect: Iridoid glycosides and the southern armyworm

The behavioral and physiological effects of plant allelochemicals have been difficult to demonstrate; it is not often clear whether the compounds are deterrent, toxic, or both. In this study, we compared the qualitative and quantitative effects of several iridoid glycosides on a generalist lepidopteran herbivore,Spodoptera eridania (Noctuidae). Larval growth and survivorship and larval preference or avoidance were measured on artificial diets containing different iridoid glycosides at different concentrations. We also tested the toxicity/deterrence of these compounds. We found that iridoid glycosides retarded larval growth significantly at relatively low concentrations and that they were usually avoided in preference tests. The toxicity/ deterrence test did not always reflect the results of these other tests. The merits of using a variety of methods for determining deterrence and/or toxicity of plant allelochemicals are discussed.     

Sex attractant pheromone of the red-shouldered stink bug Thyanta pallidovirens: a pheromone blend with multiple redundant components

The male-produced sex pheromone of the red-shouldered stink bug, Thyanta pallidovirens (Stål) (Hemiptera: Pentatomidae) consists of a blend of methyl (E2,Z4,Z6)-decatrienoate (E2,Z4,Z6–10:COOMe), and the sesquiterpenes (+)-curcumene, (–)-zingiberene, and (–) --sesquiphellandrene. In laboratory bioassays, sexually mature males attracted sexually mature females but not males, and females did not attract either sex. Extracts of volatiles collected from sexually mature males contained compounds not present in extracts from females or sexually immature males, and male-produced extract was attractive to females. Biological activity was lost when the extract was fractionated, indicating that the pheromone consisted of at least two components having different chemical properties. Individually, pheromone components were not attractive to females, but E2,Z4,Z6–10:COOMe in combination with at least one of the three male-produced sesquiterpenes was attractive. The presence of more than one sesquiterpene in the blend did not increase attraction, indicating redundancy in the pheromone signal. Male extract was as attractive as a blend reconstructed from synthesized compounds, indicating all biologically active components had been identified. In bioassays conducted at dusk in a 1- × 1- × 1-m screen field cage, females were attracted to synthetic pheromone lures. In field trials, adult female T. pallidovirens were attracted to pheromone-baited traps in relatively low numbers. The profile of volatiles released by sexually mature males of a congeneric species, Thyanta accerra custator McAtee, was remarkably similar to that of male T. pallidovirens, with the exception that the former species produced (E)-2-decenal, a compound that was not found in T. pallidovirens extracts.     

Effects of diterpene esters of tigliane,daphnane, ingenane,and lathyrane types on pink bollworm,Pectinophora gossypiella saunders (Lepidoptera: Gelechiidae)

Twenty esters, representing the biogenetically related tigliane, daphnane, ingenane, and lathyrane series of diterpenes, were screened for growth-inhibitory and insecticidal effects on newly hatched larvae of the North American cotton pest,Pectinophora gossypiella (pink bollworm). Among the tigliane derivatives tested, only 12-O-tetradecanoylphorbol-13-acetate and 12-O-(2-methyl)butyrylphorbol-13-decanoate, of seven phorbol diesters isolated from croton oil by a new procedure involving droplet countercurrent chromatography, were active againstP.gossypiella as both growth inhibitors and insecticides. The effects of the former compound were not significantly diminished by acetylation of its C-20 primary hydroxy group. Three other croton oil phorbol diester constituents, as well as daphnetoxin and daphnetoxin-5,20-diacetate, exhibited activity as growth inhibitors, but not as insecticidal agents, at the doses used. None of the ingenane or lathyrane derivatives investigated was active in either respect. 12-0-Tetradecanoylphorbol-13-acetate was found to cause 100% mortality on second-stadium larvae ofCulex pipiens at 0.6 ppm, but exhibited less significant effects onOncopeltus fasciatus (second-stadium nymphs) andTribolium confusion (adults) when applied at higher doses.     

Continuous production of poly(3-hydroxybutyrate-<Emphasis Type="Italic">co</Emphasis>-3-hydroxyvalerate): Effects of C/N ratio and dilution rate on HB/HV ratio

Ralstonia eutropha was cultivated in a continuous stirred fermenter with various C/N ratios (20, 30, and 40), dilution rates, and organic salt substrates (sodium propionate or sodium valerate) to explore the microbial growth and the poly(3HB-co-3HV) accumulation. When sodium propionate was used as the secondary carbon source, the HB/HV molar ratio at various C/N ratios and dilution rates did not change appreciably (approximately 90: 10). The highest poly(3HB-co-3HV) content in biomass (41.8%) and poly(3HB-co-3HV) productivity (0.100 g/(L·h)) occurred under the condition with a C/N ratio of 20 and dilution rate of 0.06 h⁻¹. When sodium valerate was used as the secondary carbon source, the productivity of poly(3HB-co-3HV) increased with increasing dilution rate for the C/N ratio of 30 and 40. The average HB/HV molar ratio ranged from 48: 52 to 78: 32. The feeding of sodium valerate promoted the accumulation of HV better than feeding sodium propionate did. This study shows that a potential strategy of manipulating by both C/N ratio and dilution rate could be used to control the HV unit fraction in poly(3HB-co-3HV) in a continuous cultivation.     

Components of the sex pheromone of the female spotted stalk borer,Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae): Identification and preliminary field trials

FemaleChilo partellus (Swinhoe) abdominal tip extracts were examined by gas-liquid chromatography (GLC) combined with simultaneous electroantennographic (EAG) recording from the male moth. Two olfactory stimulants were detected and identified as (Z)-11-hexadecenal (I) and (Z)-11-hexadecen-1-ol (II) by their GLC behavior, microchemical reactions, and comparison with synthetic materials. Both compounds were detected in volatiles emitted by the calling female moth. Synthetic (Z)-9-tetradecenyl formate, a structural analog of aldehyde (I), also elicited a significant EAG response from the male moth. Field trials carried out in India using synthetic (I) and (II) as bait in water traps showed that compound (I) was highly attractive to maleC. partellus; compound (II) was not attractive, and its addition to (I) significantly reduced trap catches.     

Study on Oleuropein Extraction from Olive Tree (Olea europaea) Leaves by means of SFE: Comparison of Water and Ethanol as Co-Solvent

The present study focuses on developing methods for olive leaf extraction and deals with obtaining extract, rich in oleuropein, which is the most abundant phenolic compound in olive leaves. Supercritical fluid extraction (SFE) was applied to the dried and ground olive leaves by using CO₂ as supercritical (SC) fluid in the presence of water and ethanol as co-solvent. The influences of operating parameters by means of co-solvent content (0-1 mL/min), temperature (50 and 100°C) and pressure (100-300 bar) on both extract and oleuropein yields were investigated. Quantitative analysis was performed by using a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) technique. The experimental results obtained by using SC-CO₂ alone were not satisfactory, and it was seen that addition of a polar modifier is necessary in order to improve yield and selectivity of the process. It was observed that CO₂ modified by water and ethanol showed nearly the same extract performance, where CO₂ modified by water is better for high oleuropein yield.