Antioxidative effect of Ajowan in a model system

Model conditions were utilized to test the antioxidative activity of a methanolic extract of ajowan (Carum coptimum) (MEA). MEA was less effective than butylated hydroxytoluene in protecting against oxidation of emulsified linoleic acid measured by coupled oxidation of linoleic acid-β-carotene, conjugated diene values, and the thiobarbituric acid values. Ajowan may have potential as a source of natural antioxidant.     

Squash leaf glandular trichome volatiles: Identification and influence on behavior of female pickleworm moth [Diaphania nitidalis (Stoll.)] (Lepidoptera: Pyralidae)

Fourteen volatile compounds occurring in leaf trichomes of yellow squash (Cucurbita pepo L. cv. Early Prolific Straightneck) were identified. These compounds accounted for 83.5% of the volatile matrix. Ubiquitous constituents of the epidermis (myristic, palmitic, and stearic acids,n-tricosane, andn-pentacosane) accounted for 73.7%; these compounds were not bioassayed. The volatileso-,m-, andp-xylene, toluene, 2-heptanone, (R)-(+)- and (S)-(–)-limonene, and germacrene D were tested for their influence on attraction and oviposition by the pickleworm moth (Diaphania nitidalis Stoll.). No single compound, except germacrene D, was attractive. (R)-(+)-Limonene and 2-heptanone were weakly repellent. Mixtures of the highly volatile fractions were as attractive as volatiles emanating from whole, intact leaves. Oviposition levels on treated artificial sites corresponded with levels of visitation. Oviposition was significantly stimulated by whole-leaf volatiles, and (S)-(–)-limonene caused a slight but significant reduction.Mention of a trade name or proprietary product does not constitute a warranty or guarantee by the U.S. Department of Agriculture, nor does it imply exclusion of other products that may also be suitable.     

Aphid deterrence by glucose esters in glandular trichome exudate of the wild tomato,Lycopersicon pennellii

Settling of the potato aphid,Macrosiphum euphorbiae, on feeding membranes was deterred by methanolic leaf rinses ofLycopersicon pennellii, or of its F₁ with tomato,L. esculentum. The active compounds in theL. pennellii rinsates were identified as 2,3,4-tri-O-acylglucoses bearing short to medium chain length fatty acids. These compounds are localized in the glandular exudate of the type IV trichomes and may accumulate to levels in excess of 400 g/cm². In choice assays, purified glucose esters fromL. pennellii reduced aphid settling at concentrations as low as 25 g/cm²; at concentrations of 150 g/cm² or more, all aphids avoided treated areas. Glucose esters were also active in deterring aphid settling in no-choice assays. At 100 g/ cm², these esters resulted in increased levels of mortality after 48 hr.     

Scandinavian Thins on Top of Cake: New and Improved Algorithms for Stacking and Packing

We show how to compute the smallest rectangle that can enclose any polygon, from a given set of polygons, in nearly linear time; we also present a PTAS for the problem, as well as a linear-time algorithm for the case when the polygons are rectangles themselves. We prove that finding a smallest convex polygon that encloses any of the given polygons is NP-hard, and give a PTAS for minimizing the perimeter of the convex enclosure. We also give efficient algorithms to find the smallest rectangle simultaneously enclosing a given pair of convex polygons.     

Hydrogels based on graft copolymers of collagen synthesis

Graft copolymerization of 2-hydroxyethyl methacrylate in combination with hydrophobic monomers onto soluble collagen was employed in the synthesis of hydrogels. The hydrogels were formed by simultaneous graft copolymerization and crosslinking. In order to study the effect of various crosslinking agents on the water retention character of the hydrogels, three different crosslinking agents, namely, N,N′-methylene bis acrylamide, 1,4-butanediol dimethacrylate, and hexamethylene urethanediacrylate were used. Hexamethylene urethanediacrylate crosslinked systems require a minimum amount of crosslinking agent to attain maximum water content in comparison to the other systems.     

Axial pressure profiles in non-newtonian flow: Part I: Theoretical and experimental considerations

The flow behavior of polymeric fluids in tubes can be determined from measurements of the radial stress profile in the flow direction. This subject, the focus of our research, will be examined in Part II of this communication. Part I describes a research designed to test the accuracy of stress measurement with pressure transducers in a variety of recess mount geometries. No mount geometry errors were detected for the fluids used in this work over a shear rate range of 1 to 2000 sec^?1. Part I also contains a survey of the literature and theoretical considerations pertinent to the entire work.     

Modification of industrial polypropylene film by grafting of poly(acrylic acid)

Grafting of poly(acrylic acid) onto commercial polypropylene films following irradiation by γ-rays was carried out in order to improve their surface properties. The amount of grafting with the irradiation dose was found not to follow the expected linear dependence as it is normally observed for polypropylene films prepared in laboratory amounts. We therefore analyzed the influence of the industrial manufacture process in terms of orientation of the film and addition of antioxidants by determining the peroxide surface density and the extent of grafting therefrom. The unoriented polypropylene film presented the highest peroxide concentration and was thus the most adapated material for successful grafting. Whereas phenol antioxidants limit the peroxide formation and thus must be removed from the film for grafting, the thickness of the chemical modification and can be controlled by means of phosphites. Atomicforce microscopy and wettability measurements showed that the grafted poly(acrylic acid) was heterogeneously distributed on the surface of the film, explaining the observed low reproducibility of the grafting reaction. However, we observed that the polarity of the surface was increased by the grafting. © 1995 John Wiley & Sons, Inc.     

Studies on the cure characteristics and vulcanizate properties of 50/50 NR/SBR blend

Blends of 50/50 natural rubber (NR) and styrene-butadiene rubber (SBR) are vulcanized using several conventional and semi-EV systems. The cure characteristics and vulcanizate properties are compared. The quantity and quality of crosslinks in each case are deciphered by chemical probes to correlated them with the vulcanizate properties.     

A cation exchange resin from poly(N-vinyl carbazole)

Poly(N-vinyl carbazole) was sulfonated with different sulfonating agents and ion exchange capacities of the resins produced were evaluated. A maximum capacity of 4.5 meq · g^?1 of dry resin was realized when sulfonation was done with 98.8% H₂SO⁴ at 30°C for 10 h. The pH titration curves reveal the nature of a strong monofunctional cation exchanger with a pK value of 2.2. The resin exhibits a moderate rate of exchange with NaCl and is thermally stable up to ca. 250°C.     

采用间苯二酚-甲醛树脂优化钢丝帘线粘合

新品种的间苯二酚-甲醛树脂中的游离间苯二酚含量极低，且不再具有吸湿性。考察了间苯二酚-甲醛树脂(Penacolite B-20-S)、硼酰化钴和不溶性硫黄的用量对钢丝粘合胶与镀铜钢丝粘合性能的影响。结果表明，树脂／钴盐粘合体系比单纯的钴盐粘合体系的粘合性能好得多。仅考虑粘合性能时，粘合体系最佳配方为：Penacolite B-20-S树脂4，硼酰化钴(活性钴)0．1，不溶性硫黄(活性)7．1，HMMM(活性)2．66。