The white pine cone beetle, Conophthorus coniperda, exhibited dose and enantiospecific responses to -pinene in stands of mature eastern white pine, Pinus strobus, in a seed orchard near Murphy, North Carolina, USA. (–)--Pinene significantly increased catches of cone beetles to traps baited with (± )-trans-pityol. (+)--Pinene did not increase catches of beetles to pityol-baited traps and interrupted the response of beetles to traps baited with (±)-trans-pityol and (–)--pinene. Maximal attraction of cone beetles to pityol-baited traps was obtained with lures releasing (–)--pinene at a rate of 103 mg/day at 23°C. Lures releasing (–)--pinene at rates lower or higher than 103 mg/day resulted in reduced catches to traps baited with (±)-trans-pityol. The sex ratio in all catches was heavily male biased. Attraction of the clerid predator, Thanasimus dubius, to traps baited with (±)-trans-pityol increased significantly with the presence of -pinene, irrespective of enantiomeric composition. Maximal attraction of T. dubius to pityol-baited traps occurred with devices releasing (–)--pinene at the highest rate tested, 579 mg/d at 23°C, a sub optimal rate for cone beetles. 相似文献
Separation of sterol esters from wax esters in the lipids of vernix caseosa and adult human skin surface was accomplished
by column chromatography on MgO. The fatty acids of the sterol esters and wax esters of both samples were separated into saturates
and monoenes, and examined in detail by gas liquid chromatography (GLC). The saturated fatty acids of the wax esters of vernix
caseosa and of adult human skin surface were remarkably similar. They ranged in chain length from at least C11 to C30, six skeletal types being present: straight even, straight odd, iso, anteiso, other monomethyl branched and dimethyl branched.
A large number of patterns of monoenes were observed, each pattern consisting of desaturation of a specific chain at Δ6 or
Δ9 plus its extension or degradation products. The mole per cent of the total Δ6 and Δ9 patterns of wax ester fatty acid monoenes
of vernix caseosa were 87% and 12%, respectively, and 98% and 1%, respectively, for adult human skin surface lipid. The sterol
ester fatty acids of vernix caseosa were much different from those of adult human skin surface: vernix caseosa saturates were
largely branched and of lengths greater than C18, whereas the saturates of adult human surface lipid resembled the wax ester fatty acids. Of the vernix caseosa monoene patterns,
the mole per cent was 30% Δ6 and 70% Δ9, whereas of the adult human skin surface sterol ester fatty acids 89% were Δ6 and
11% Δ9. Chain extension was particularly pronounced in the sterol ester fatty acid monoenes of vernix caseosa amounting to
7–8 C2 units in some cases. The fatty acids of the sterol esters of both vernix caseosa and adult human skin surface appear to be
derived from the sebaceous gland and from the keratinizing epidermis, but those of the wax esters are from the sebaceous glands
only. 相似文献
The loss in activity of Pt-promoted and unpromoted 25 wt% Co–Al2O3 catalysts has been compared under identical conditions except for adjustment of the space velocity to give the same initial CO-conversion. Both catalysts underwent a 200 h period of rapid, initial decline in CO conversion and then a slower, linear decline during the next 1000 h. Pt-promotion did not alter the cobalt dispersion (or average particle size) from that of the unpromoted catalyst but did increase the amount of cobalt that was reduced. When compared not by time-on-stream, but by the moles of Co converted per unit weight of catalyst, both the Pt-promoted and unpromoted catalysts decline in activity at the same rate. 相似文献
The incorporation of inorganic phosphate (as NaH2PO4) into the phospholipids of sheep red blood cells was studied in vitro in blood samples from five highpotassium (HK) and five
low-potassium (LK) sheep. The erythrocytes from HK sheep incorporated more activity in 4 hr than those from the LK sheep.
However no activity was incorporated into the major phospholipids of the cells (phosphatidyl ethanolamine, phosphatidyl serine,
and sphingomyelin) of either group. The phosphatidic acid fraction was labeled in both groups and to a significantly greater
extent in the HK samples. However the highest activity in the phospholipid of sheep red-cells was located in three unknown
compounds not previously detected. Their specific activities were the same in the HK and the LK samples although they were
present in slightly larger amounts in the HK samples. In general, incorporation was at a rather low level, and from stoichiometric
considerations it was concluded that the metabolism in the red-cell phospholipids could not be directly involved in the active
transport of ions across the cell membrane. This work also confirmed a previous report that no quantitative differences exist
among the major phospholipid classes in the two types of cells. 相似文献
An infrared absorption spectroscopy study of the curing kinetics of a low (1.12) epoxide/hydroxyl-group ratio bisphenol A epoxy resin—phthalic anhydride system is reported. A full infrared peak assignment to molecular vibrational modes is given for the range 400 to 4000 cm?1, and the optical density behavior of all peaks during reaction is discussed in detail. Proposed rival reaction mechanisms are considered and their respective kinetic behavior discussed. The reaction was found to follow consecutive-step addition esterification and simultaneous addition etherification, and epoxide—hydroxyl group and carboxylic acid dimer hydrogen bonding was found to occur. The reaction behavior supports a proposed hydroxyl group-limited inhomogeneous bulk reaction mechanism of a colloid type. 相似文献
We present the design and analysis of a nearly-linear work parallel algorithm for solving symmetric diagonally dominant (SDD) linear systems. On input an SDD n-by-n matrix A with m nonzero entries and a vector b, our algorithm computes a vector \(\tilde{x}\) such that \(\|\tilde{x} - A^{+}b\|_{A} \leq\varepsilon\cdot\|{A^{+}b}\|_{A}\) in \(O(m\log^{O(1)}{n}\log {\frac{1}{\varepsilon}})\) work and \(O(m^{1/3+\theta}\log\frac{1}{\varepsilon})\) depth for any θ>0, where A+ denotes the Moore-Penrose pseudoinverse of A. The algorithm relies on a parallel algorithm for generating low-stretch spanning trees or spanning subgraphs. To this end, we first develop a parallel decomposition algorithm that in O(mlogO(1)n) work and polylogarithmic depth, partitions a graph with n nodes and m edges into components with polylogarithmic diameter such that only a small fraction of the original edges are between the components. This can be used to generate low-stretch spanning trees with average stretch O(nα) in O(mlogO(1)n) work and O(nα) depth for any α>0. Alternatively, it can be used to generate spanning subgraphs with polylogarithmic average stretch in O(mlogO(1)n) work and polylogarithmic depth. We apply this subgraph construction to derive a parallel linear solver. By using this solver in known applications, our results imply improved parallel randomized algorithms for several problems, including single-source shortest paths, maximum flow, minimum-cost flow, and approximate maximum flow. 相似文献
The effects of platinum (Pt) and silver (Ag) metallisation in the photocatalytic oxidation of resorcinol at pH 3 ± 0.5 have been investigated. The photocatalytic degradation of resorcinol was significantly improved by Pt/TiO2, while the presence of Ag/TiO2 enhanced the initial photocatalytic degradation rate of resorcinol slightly. Likewise, the photocatalytic mineralisation of resorcinol continued to be enhanced by Pt/TiO2, but it was retarded when Ag/TiO2 was used.
The function of Pt and Ag deposits on the surface of TiO2 has been found to be markedly influenced by the interaction of resorcinol and its degradation products with the metal deposits. The presence of Pt or Ag on the surface of TiO2 altered the distribution of degradation products of resorcinol as well as the production of photoactive species for the photocatalytic oxidation of resorcinol. The X-ray photoelectron spectroscopy (XPS), zeta potential and transmission electron microscopy (TEM) analyses have indicated that the contrasting effect of Pt and Ag deposits were governed by the oxidation states and the catalytic property of metal deposits. In addition to that, it has been found that the roles of metal deposits are specific and should not be generalised. 相似文献
An infrared absorption spectroscopy study of the curing (gelation and postcure) kinetics of a high (4.7) epoxide/hydroxyl group-ratio diglycidyl ether of bisphenol A (DGEBA)–mixed anhydride epoxy resin system is reported. Peak assignments to molecular vibrational modes are given for the range 400–4000 cm?1, and the optical density behavior of all peaks during reaction is discussed in detail. Chemical reaction was found to follow consecutive-step addition esterification and simultaneous addition etherification. Epoxide hydroxyl-group and carboxylic acid dimer hydrogen bonding was found to occur. The gelation phase of reaction is complex, exhibiting rapid initial hydroxyl–anhydride reactions followed by S-shaped kinetics approaching an incompletely reacted limit. Postcure exhibits functional group kinetic behavior similar to that occurring in low epoxide/hydroxyl group-ratio bisphenol A epoxy resin–phthalic anhydride systems and produces similar final chemical structures. The reaction behavior of low and high epoxide/hydroxyl group-ratio bisphenol A epoxy resin–anhydride systems arises from an hydroxyl group-limited inhomogeneous reaction mechanism involving bisphenol A epoxy resin molecular aggregates. The importance of free hydroxyl group content is discussed. 相似文献
The antioxidant vitamin E, -tocopherol, was tested as a candidate elicitor of alterable antiherbivory in soybean plants against cabbage looper larvae. Although a nonspecific antioxidant, vitamin E proved elicitory to the involved sulfhydryl-dependent receptor-energy transducer protein in soybean plasma membrane. Effects of -tocopherol were dependent on dosage, time, and space in the plant. The observed elicited effects were all decreases in herbivory. The best negative phytochemical correlate of looper feeding was the percentage of increased total HPLC peak area of extractables from elicited as compared to nonelicited leaves. Some specific compounds, e.g., glyceollins, were quantitatively major components of the total profile of secondary metabolites. 相似文献