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11.
The monohydroperoxides of methyl palmitate oxidized at 150C were concentrated, purified, and reduced to yield a mixture of
isomers of monohydroxy palmitate. No evidence of unsaturation in these molecules could be obtained, and no direct method for
the resolution or identification of the individual isomers was found. Nuclear magnetic resonance (NMR) spectroscopy of the
reduced esters suggested that the hydroxy groups were not located at either end of the chain of the fatty ester.
To establish the location of the initial oxidative attack on saturated esters, the reduced esters of oxidized methyl palmitate
were chemically cleaved at the location of the hydroxy group by means of chromium trioxide oxidation and by the Beckmann transformation.
The resulting mono- and dibasic fatty acids were methylated and analyzed by gas chromatography. This analysis indicated that
the oxidation of methyl palmitate did not occur selectively at one location along the ester. Although all carbon atoms can
apparently be oxidized, preferential oxidation was observed toward the center of the molecule. 相似文献
12.
C Irving MA Nieto R DasGupta P Charnay DG Wilkinson 《Canadian Metallurgical Quarterly》1996,173(1):26-38
After segmentation of the vertebrate hindbrain, expression of the zinc-finger gene Krox-20 and the receptor tyrosine kinase gene Sek-1 is precisely restricted to rhombomeres (r) 3 and 5. This precise segmental expression is likely to reflect a critical requirement for these rhombomeres to acquire a distinct and homogeneous identity and raises the question as to how this relates to the intermingling and restriction of cell movement during segmentation. We have analysed Krox-20 and Sek-1 expression in the mouse and chick hindbrain at single-cell resolution using whole-mount in situ hybridisation and immunocytochemistry. We find that, in the mouse, the presumptive r3 and r5 expression domains each arise as narrow stripes that then broaden, suggestive of a recruitment of cells to an r3/r5 identity and/or a segmental regulation of cell proliferation. In addition, we find that expression of these genes initially occurs in fuzzy domains, and that these are progressively restricted to segmental domains, although occasional "violating" cells are observed even after segmentation. We propose that the establishment and maintenance of these segmental domains may involve both a dynamic regulation of r3/r5 identity and the restriction of cell movement across rhombomere boundaries. 相似文献
13.
14.
Robert C. Mathews Irving M. Lane Lewis G. Roussel Mark S. Nagy Dawn E. Haptonstahl Drew B. Brock 《人工智能实验与理论杂志》2013,25(3-4):259-276
Three experiments investigated procedures derived from research on knowledge acquisition, group processes, and artificial intelligence for facilitating the development of expertise. In each experimental session, subjects learned to control a simulated sugar production factory. Then they formulated written policies for controlling sugar production either alone as individuals or in small groups. An adaptive AI system provided feedback on policy quality. The research also investigated the use of forced reflective practice in which learners attempted to predict what their policy would do while performing the task. The AI system provided feedback about what their policy would have done in each situation and the outcome based on their policy's response or their suggested alternative response. Results indicated that group interaction and feedback from the AI system improved policy quality. However, only when all three procedures were employed, group interaction, AI feedback, and forced reflective practice, was the development of individual expertise on the task enhanced. 相似文献
15.
Preston C. Bowes Jonathon N. Baker Douglas L. Irving 《Journal of the American Ceramic Society》2020,103(2):1156-1173
Unintentional impurities often found in strontium titanate (doped or undoped) have hindered efforts to study individual impurities experimentally. To fill this gap, a computational survey of acceptor-type point defects of common intentional or unintentional impurities (Al, Cu, Fe, K, Mg, Mn, N, Na, Ni, and Zn) is presented. Utilizing defect formation energies from density functional theory using hybrid exchange correlation functionals in a grand canonical model of the defect chemistry, the equilibrium Fermi level (μe) was calculated as a function of processing conditions for pure SrTiO3, SrTiO3 individually doped with each impurity, and SrTiO3 co-doped with Al and N. Above a certain concentration, each impurity reduced the maximum predicted hole concentration relative to the intrinsic case. Al, Mg, Zn, K, and Na exhibited similar trends and behaved more like ideal acceptors while N, Ni, Fe, Mn, and Cu were all unique and pinned μe near or above the mid-gap in most conditions. Al/N:SrTiO3 also exhibited similar trends at 800°C for all Al/N ratios, but more variation at 25°C. Additionally, the behavior of Al:SrTiO3 was not recovered until Al/N = 104. This suggests that to achieve SrTiO3 with free holes at room temperature, the concentration of most impurities must be controlled. 相似文献
16.
1 引言 光电传感器是指利用光电效应作为传感原理的传感器件,它主要由光源、光学通路、光电探测器等部分.光源发出的光照射到待检测的目标物体上,被目标物体调制后被光电探测器所接收. 相似文献
17.
18.
A. G. Peele T. H. K. Irving K. A. Nugent D. C. Mancini N. Moldovan T. R. Christenson 《Microsystem Technologies》2002,9(1-2):55-60
A square packed array of square-channels with long channel axis aligned radially is a useful structure for condensing grazing
incidence flux to a focus. These devices, known as Lobster-eye optics for their similarity to the eyes of the macruran crustaceans,
show great promise as the focusing optic in the next generation of X-ray all-sky monitors. At X-ray wavelengths the optimal
Lobster-eye structure requires an aspect ratio of channel length to width of greater than 30:1. Following recent success in
fabricating a low aspect ratio Lobster-eye structure, we discuss some of the parameters for, and production issues involved
in making, a useful Lobster-eye prototype using LIGA. We report on our initial attempts to produce high aspect ratio Lobster-eye
optics using the LIGA process with a graphite substrate.
Received: 10 August 2001/Accepted: 24 September 2001
AGP gratefully acknowledges receipt of an ARC post-doctoral fellowship. This work was supported by the Australian Synchrotron
Research Program, which is funded by the Commonwealth of Australia under the Major National Research Facilities Program. Use
of the Advanced Photon Source was supported by the U.S. Department of Energy, Basic Energy Sciences, Office of Energy Research,
under Contract No. W-31-109-Eng-38.
This paper was presented at the Fourth International Workshop on High Aspect Ratio Microstructure Technology HARMST 2001
in June 2001. 相似文献
19.
Dicopper(II) tetrakis(3,5-diisopropylsalicylate), [Cu(II)(2)(3,5-DIPS)(4)], is effective in increasing survival of lethally irradiated mice when it is administered after irradiation. The possibility that this radiorecovery activity might also facilitate recovery from radiation-induced impaired increase in body mass and locomotion was examined. Cu(II)(2)(3,5-DIPS)(4) was used to treat LD 50/30 gamma irradiated female C57BL/6 mice after irradiation. A dose of 0, 5, 10, or 20 mumol Cu(II)(2) (3, 5-DIPS)(4) /kilogram of body mass was administered subcutaneously 3 hrs after LD 50/30 irradiation and change in body mass and locomotor activity measured daily throughout the 30 day post-irradiation period. Treatment with 5, 10, or 20 mumol Cu(II)(2) (3,5-DIPS)(4) /kg of body mass increased survival, which was statistically significant for the 10 mumol /kg of body mass-treated group compared to the vehicle-treated group (P<0.05), significantly (P<0.05) increased recovery of locomotion from days 13 to 15 post-irradiation onward for all treated groups compared to vehicle-treated mice, and increased recovery of body mass gain from day 14 onward for the 20 mumol /kg of body mass-treated group (P<0.001) and day 21, although not statistically significant, for the 10 mumol /kg of body mass-treated group. There were no statistically significant differences between the increase in survival, recovered increase in body mass, and recovered increase in locomotion for mice treated with 10 mumol or 20 mumol Cu(II)(2)(3,5-DIPS)(4) /kg on day 30 post-irradiation. It is concluded that Cu(II)(2)(3,5-DIPS)(4) in addition to increasing survival of irradiated mice increases the rate of recovery of radiation-induced decrease in body mass and locomotion. 相似文献