Surface lipids of the social waspPolistes annularis (L.) and its nest and nest pedicel

Cuticular lipids were recovered fromPolistes annularis workers and characterized by combined gas-chromatography-mass spectrometry. These lipids were found to be straight-chain and methyl-branched hydrocarbons with the major components being 13,17-dimethylhentriacontane (18%), 3-methyl-nonacosane (13%), and 3-methylheptacosane (11%). Cuticular lipids with a very similar composition were found on the surface of the larvae, eggs, and adult males ofPolistes annularis as well as on the surface of the nest and nest pedicel of the wasp. Hexadecanoic acid and octadecenoic acid were also found on the surface of the nest pedicel and these acids and/or the hydrocarbons may play a defensive role for the wasps.     

Ultrastructural and chemical examination of paper and pedicel from laboratory and field nests of the social waspPolistes metricus say

The ultrastructure and chemical composition of paper and pedicel from nests ofPolistes metricus that were constructed in the laboratory from known building material were compared to paper and pedicel from nests constructed in the field. Scanning electron micrographs showed the addition of a gluelike secretion from the wasp to the construction material. Solid-state [¹³C]NMR, elemental analyses, and amino acid analyses indicate that this secretion is a silklike protein with serine, glycine, alanine, and proline comprising 65–73% of the identified residues.     

Surface lipids of social waspPolistes melricus say and its nest and nest pedicel and their relation to nestmate recognition

In eight replicate laboratory tests wherePolistes metricus adults were allowed to choose between their own nest, a second nest, and neither nest, they selected their own nest 66% of the observed time. When the surface hydrocarbons had been extracted from the nests, the wasps chose their own nest only 8% of the time, but after the hydrocarbons were reapplied to the surface of the respective nests, they selected their own nest 47% of the time. These changes are significant. The cuticular lipids were analyzed from individualP. metricus adult females collected from 13 colonies. Surface lipids were recovered from the paper and pedicels of their nests. Eighteen hydrocarbons were identified in these lipid fractions. The major components of the wasp cuticular lipids weren-heptacosane,n-nonacosane, methylhentriacontane, and methyltritriacontane. Factor analysis revealed that extracts of pedicels are all similar in composition, while cuticle and paper extracts vary, sometimes similarly according to colony identity.     

Discriminant analysis of cuticular hydrocarbons of social waspPolistes exclamans viereck and surface hydrocarbons of its nest paper and pedicel

The articular lipids were analyzed from individualPolistes exclamans workers collected from 10 nests. Surface lipids were also recovered from the paper and pedicels of these nests. Twenty-two hydrocarbons were identified in these lipid fractions. The major components of the wasp cuticular lipids weren-heptacosane,n-nonacosane, methylhentriacontane, and methyltritriacontane. Discriminant analysis of the hydrocarbon profiles of the adult wasps showed that the wasps group together according to their respective colonies. Several colonies from the same geographical location clustered more closely together than colonies from diverse locations. The nest papers and pedicels did not group with the wasps from their respective colonies, but the nest papers clustered together separately, as did the nest pedicels.     

Cuticular hydrocarbons of the paper wasp,Polistes fuscatus: A search for recognition pheromones

The cuticular chemicals of 124 individual wasps (foundresses and workers) from 23 colonies ofPolistes fuscatus were analyzed. The compounds identified, all of which were hydrocarbons, were similar to those of other vespid wasps in that the bulk of the hydrocarbons were 23–33 carbons in chain length. However, the hydrocarbon profile ofP. fuscatus differed from those of its congeners in its proportions of straight-chain alkanes, methylalkanes, and alkenes. Three of the 20 identified hydrocarbons, 13- and 15-MeC₃₁, 11,15- and 13,17-diMeC₃₁, and 13-, 15-, and 17-MeC₃₃, had properties postulated for recognition pheromones: colony specificity, efficacy in assigning wasps to the appropriate colony, heritability, lack of differences between foundresses and workers, and distinctive stereochemistry.     

Cuticular lipid profiles of queens,workers, and males of social waspPolistes metricus say are colony-specific

The cuticular lipids ofPolistes metricus queens, workers and males from seven laboratory-maintained colonies were extracted and analyzed by combined gas chromatography-mass spectrometry. Males had higher proportions of alkenes (20.5%) in their cuticular lipids than did queens (2.3%) or workers (7.7%). Discriminant analyses of the cuticular lipid profiles of the adult wasps showed that males group separately from females. Additional analyses showed that queens group with their respective workers by colony and that queens group even more closely with males by colony. The most distinct groupings occurred with workers only by colony and with males only by colony. Stepwise discriminant analyses showed that each type of grouping was dependent upon a different combination of cuticular lipids.     

Highly isotactic poly(vinyl alcohol) derived from tert-butyl vinyl ether. Part IV. Some physical properties, structure and hydrogen bonding of highly isotactic poly(vinyl alcohol) films

Some basic physical properties, structure and hydrogen bonding have been characterized for different stereoregular PVA films including highly isotactic PVAs (HI-PVAs), which were recently succeeded in synthesis, as functions of the mm fraction by using different analytical methods. The melting temperature, degree of crystallinity, and ¹³C spin-lattice relaxation time of the crystalline component are found to have their own clear minima at the mm fraction of about 0.4-0.5. This fact suggests that structural disordering associated with the decrease in crystallinity may be most strongly induced at this mm fraction. The formation of the new crystal form of PVA has been reconfirmed for HI-PVAs with the mm fractions higher than about 0.55 by FTIR spectroscopy and the structure and hydrogen bonding have been investigated in detail by solid-state ¹³C NMR spectroscopy. It is found that all OH groups are allowed to form successive intramolecular hydrogen bonding along the respective chains in the crystalline region for HI-PVAs with the mm fractions higher than about 0.7. Since these chains should contain some amount of r units even in the crystalline region, a slightly helical structure with a considerably long period may be adopted by them as an energetically stable state. On the basis of the line shape analysis of the CP/MAS ¹³C NMR spectra of the crystalline components, structural causes of the appearance of the minima of the physical values described above are also discussed in relation to the introduction of disordered units mainly associated with hydrogen bonding to the syndiotactic or isotactic sequences forming successive intermolecular or intramolecular hydrogen bonding, respectively.     

Mechanical properties, morphology and molecular characteristics of poly(ethylene terephthalate) toughened by natural rubber

The melt blending of poly(ethylene terephthalate) (PET) and natural rubber (NR) in a twin-screw extruder is studied. Parameters affecting the blend properties such as the amounts of the NR in the blends and screw speeds are investigated. Increased toughness of the PET/NR blend was found as the amount of NR was increased. The impact strength of the PET/NR (80/20 wt%) blend using a screw speed of 100 rpm, increased up to seven-fold when compared to that of pure PET. The morphology of the blend was investigated by SEM. The molecular characteristic was evaluated by spectroscopic technique. The toughening effect of NR on the PET might come from the possible interaction between the two phases, which was clearly evidenced by solid-state CP/MAS ¹³C NMR data. The data revealed an increase in the cross polarization time (T_D) of the carbonyl carbon and a decrease of the relaxation of the carbonyl groups in the PET/NR blend. This should come from the interaction between the carbonyl group of PET with some abnormal groups such as hydroxyl function in the NR, resulting in an improvement of the compatibility of the studied blends.     

Synthesis of cis-12, 13-epoxy-cis-9-octadecenol and 12(13)-hydroxy-cis-9-octadecenol from vernonia oil using lithium aluminum hydride

Reduction of vernonia oil methyl esters (VOME) into epoxy fatty alcohol and diols was achieved with lithium aluminum hydride (LAH), under reflux and room temperature conditions, by using hexane and tetrahydrofuran (THF) as solvents. The reactions of VOME with LAH in hexane produced cis-12,13-epoxy-cis-9-octadecenol as a major product with an isolated yield of 73.6%, whereas the reaction with LAH in THF gave isomers of 12(13)-hydroxy-cis-9-octadecenol as the major products with an isolated yield of 95.1%. LAH was similarly reacted with vernonia oil (VO) to give the same products in lower yields. ¹H nuclear magnetic resonance (NMR), ¹³C NMR, gas chromatography-mass spectrometry, and infrared were used to characterize these products. This study demonstrates the ability to control the reactivity of the epoxy functionality in VO or VOME with the choice of polar or nonpolar solvents, and extends the range of oleochemicals that can be derived from vernonia oil.     

Modifications of carbon for polymer composites and nanocomposites

The various forms of carbon used in composite preparation include mainly carbon-black, carbon nanotubes and nanofibers, graphite and fullerenes. This review presents a detailed literature survey on the various modifications of the carbon nanostructures for nanocomposite preparation focusing upon the works published in the last decade. The modifications of each form of carbon are considered, with a compilation of structure-property relationships of carbon-based polymer nanocomposites. Modifications in both bulk and surface modifications have been reviewed, with comparison of their mechanical, thermal, electrical and barrier properties. A synopsis of the applications of these advanced materials is presented, pointing out gaps to motivate potential research in this field.