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21.
A. Cork D. J. Chamberlain P. S. Beevor D. R. Hall Brenda F. Nesbitt D. G. Campion M. R. Attique 《Journal of chemical ecology》1988,14(3):929-945
Ovipositor washings from virgin femaleEarias vittella (F.) (Lepidoptera: Noctuidae) moths were examined by gas chromatography (GC) linked to electroantennography (EAG). Six components were detected by the male moth. These were identified by comparison of their retention times with those of a range of synthetic standards on fused silica capillary GC columns as hexadecanal, (Z)-11-hexadecenal, (E,E)-10,12-hexadecadienal, octadecanal, (Z)-11-octadecenal, and (E,E)-10,12-hexadecadien-1-ol in 1210241 ratio. Field testing in Pakistan showed that a 2102 mixture of (Z)-11-hexadecenal, (E,E)-10,12-hexadecadienal, and (Z)-11-octadecenal was as attractive to maleE. vittella moths as the six-component mixture and equal in attractiveness to a virgin female moth. Omitting (Z)-11-hexadecenal or (Z)-11-octadecenal greatly reduced this attractiveness. It was found that synthetic lures must be protected from sunlight to prevent loss of attractiveness caused by isomerization of the conjugated diene aldehyde, and addition of (E,Z)-10,12-hexadecadienal, one of the products of isomerization, was shown to reduce attractiveness significantly. During this work, a 101 mixture of (E,E)-10, 12-hexadecadienal and (Z)-11-hexadecenal was shown to be as attractive toE. insulana (Boisd.) male moths as a virgin female moth, and the attractiveness of this mixture was further increased by addition of (E,Z)-10,12-hexadecadienal. 相似文献
22.
The construction of an entire optical access networks for connected customers requires the mastery of optical fibre cable installation. We are interested in the pushing process in urban areas and the understanding of the global behaviour during this process and the estimation of the pushing force before laying are important. The work of Griffioen [5] and Buler [4] were used to develop software (taking into account friction and cable rigidity), including some improvements coming from a collaboration between France Télécom R&D Lannion and the LM2S. To go further in this process, in the first part of our work, we will work without buckling phenomena, that will be included in our modelisation in the second part of this paper. In order to validate our modelisation, comparison will be made between finite element simulations and experimental results obtained on a life-sized bench at France Télécom R&D Lannion. 相似文献
23.
We have recently proposed a new model for the differentiation pathway of alphabeta TCR thymocytes, with the CD4 and CD8 coreceptors undergoing an unexpectedly complex series of expression changes. Taking into account this new insight, we reinvestigated the timing of thymic negative selection. We found that, although endogenous superantigen-driven thymic negative selection could occur at different steps during double-positive/single-positive cell transition, this event was never observed among CD4lowCD8low TCRint CD69+ thymocytes, i.e., within the first subset to be generated upon TCR-mediated activation of immature double-positive cells. We confirm a role for CD40/CD40L interaction, and the absence of involvement of CD28 costimulation, in thymic deletion in vivo. Surprisingly, we found that thymic negative selection was impaired in the absence of Fas, but not FasL, molecule expression. Finally, we show involvement in opposing directions for p59fyn and SHP-1 molecules in signaling for thymic negative selection. 相似文献
24.
Structure-function analysis of a conserved aromatic cluster in the N- terminal domain of human epidermal growth factor 总被引:1,自引:0,他引:1
Murray MB; Tadaki DK; Campion SR; Lamerdin JA; Serpersu EH; Bradrick TD; Niyogi SK 《Protein engineering, design & selection : PEDS》1998,11(11):1041-1050
The importance of a cluster of conserved aromatic residues of humanepidermal growth factor (hEGF) to the receptor binding epitope is suggestedby the interaction of His10 and Tyr13 of the A-loop with Tyr22 and Tyr29 ofthe N-terminal beta-sheet to form a hydrophobic surface on the hEGFprotein. Indeed, Tyr13 has previously been shown to contribute ahydrophobic determinant to receptor binding. The roles of His10, Tyr22 andTyr29 were investigated by structure-function analysis of hEGF mutantanalogues containing individual replacements of each residue. Substitutionswith aromatic residues or a leucine at position 10 retained receptoraffinities and agonist activities similar to wild- type indicating that anaromatic residue is not essential. Variants with polar, charged oraliphatic substitutions altered in size and/or hydrophobicity exhibitedreduced binding and agonist activities. 1- Dimensional 1H NMR spectra ofhigh, moderate and low-affinity analogues at position 10 suggested onlyminor alterations in hEGF native structure. In contrast, a variety ofreplacements were tolerated at position 22 or 29 indicating that neitheraromaticity nor hydrophobicity of Tyr22 and Tyr29 is required for receptorbinding. CD spectra of mutant analogues at position 22 or 29 indicated acorrelation between loss of receptor affinity and alterations in hEGFstructure. The results indicate that similar to Tyr13, His10 of hEGFcontributes hydrophobicity to the receptor binding epitope, whereas Tyr22and Tyr29 do not appear to be directly involved in receptor interactions.The latter conclusion, together with previous studies, suggests thathydrophobic residues on only one face of the N-terminal beta-sheet of hEGFare important in receptor recognition. 相似文献
25.
Glass‐Like Thermal Conductivity of (010)‐Textured Lanthanum‐Doped Strontium Niobate Synthesized with Wet Chemical Deposition
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Michael J. Campion Douglas L. Medlin Patrick E. Hopkins 《Journal of the American Ceramic Society》2015,98(2):624-628
We have measured the cross‐plane thermal conductivity (κ) of (010)‐textured, undoped, and lanthanum‐doped strontium niobate (Sr2?xLaxNb2O7?δ) thin films via time‐domain thermoreflectance. The thin films were deposited on (001)‐oriented SrTiO3 substrates via the highly‐scalable technique of chemical solution deposition. We find that both film thickness and lanthanum doping have little effect on κ, suggesting that there is a more dominant phonon scattering mechanism present in the system; namely the weak interlayer‐bonding along the b‐axis in the Sr2Nb2O7 parent structure. Furthermore, we compare our experimental results with two variations of the minimum‐limit model for κ and discuss the nature of transport in material systems with weakly‐bonded layers. The low cross‐plane κ of these scalably‐fabricated films is comparable to that of similarly layered niobate structures grown epitaxially. 相似文献
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28.
J. E. Barralet G. J. P. Fleming C. Campion J. J. Harris A. J. Wright 《Journal of Materials Science》2003,38(19):3979-3993
Hydroxyapatite is used in a variety of clinical applications as a result of the apparent adherence to and mild reaction of bone and soft tissue to it owing to its structural similarity with bone mineral. Transparent hydroxyapatite has previously been fabricated by either or both of two methods; namely the application of pressure during sintering and/or the use of fine particle sized apatite prepared by either a sol-gel process or aqueous precipitation. Recently it has been shown that translucent carbonate hydroxyapatite may be formed by sintering nanocrystalline gels of carbonate hydroxyapatite in a wet carbon dioxide atmosphere. In this study we report for the first time that this atmosphere can be used to sinter microcrystalline powder compacts of hydroxyapatite to form translucent ceramics at ambient pressure. The effect of water partial pressure and sintering time at 1300°C on the optical transmission and microstructure of the ceramic was investigated. It was found that translucent ceramics were formed in all carbon dioxide atmospheres and that optical transmission varied with sintering time. Maximum transmission (13%) of 2 mm thick ceramic was obtained in materials sintered for four hours at 1300°C in a mixture of carbon dioxide containing water at a partial pressure of 4.6 kPa. 相似文献
29.
Advanced, synthetic haptic virtual environments require textured virtual surfaces. We found that texturing smooth surfaces often reduces the system passivity margin of a haptic simulation. As a result, a smooth virtual surface that can be rendered in a passive manner may loose this property once textured. We propose that any texture algorithm is associated with a characteristic number that expresses the relative change in loop gain. We further found that a passive virtual interaction can have severe unwanted artifacts if the synthesized force field is not conservative. The energy characteristics of seven algorithms are analyzed. Finally, a new texture synthesis algorithm, which operates by modulating a friction force during scanning, is shown to have several advantages over previous ones. 相似文献
30.
Van Iddekinge Chad H.; Morgeson Frederick P.; Schleicher Deidra J.; Campion Michael A. 《Canadian Metallurgical Quarterly》2011,96(5):941
Despite recent interest in the practice of allowing job applicants to retest, surprisingly little is known about how retesting affects 2 of the most critical factors on which staffing procedures are evaluated: subgroup differences and criterion-related validity. We examined these important issues in a sample of internal candidates who completed a job-knowledge test for a within-job promotion. This was a useful context for these questions because we had job-performance data on all candidates (N = 403), regardless of whether they passed or failed the promotion test (i.e., there was no direct range restriction). We found that retest effects varied by subgroup, such that females and younger candidates improved more upon retesting than did males and older candidates. There also was some evidence that Black candidates did not improve as much as did candidates from other racial groups. In addition, among candidates who retested, their retest scores were somewhat better predictors of subsequent job performance than were their initial test scores (rs = .38 vs. .27). The overall results suggest that retesting does not negatively affect criterion-related validity and may even enhance it. Furthermore, retesting may reduce the likelihood of adverse impact against some subgroups (e.g., female candidates) but increase the likelihood of adverse impact against other subgroups (e.g., older candidates). (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献