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971.
To understand and engineer applications for mixed conducting oxides, it is desirable to have explicit, analytical expressions
for the functional dependence of defect concentration and transport properties on the partial pressure of the external gas
phase. To fulfill this need, general expressions are derived for the functional dependence of defect concentration on the
oxygen partial pressure () for the mixed ionic electronic conductors. The model presented in this paper differs from expressions obtained using the
popular Brouwer approach because they are continuous across multiple Brouwer regions.
相似文献
Eric D. WachsmanEmail: |
972.
973.
974.
In the presence of NaBH(OAc)(3), a 1,5-keto-aldehyde, contained within a side-chain of an eta(4)-dienetricarbonyliron complex, undergoes a double reductive amination sequence with a series of primary amines, to provide the corresponding piperidine products in good to excellent yield. The dienetricarbonyliron complex functions as a powerful chiral auxiliary in this cascade process, exerting complete control over the stereoselectivity of the reaction, with the formation of a single diastereoisomeric product. The sense of stereoinduction has been confirmed by X-ray crystallography. Removal of the tricarbonyliron moiety can be effected with CuCl(2) to afford the corresponding 2-dienyl-substituted piperidine in excellent yield. Attempted extension of this cyclisation strategy to the corresponding azepane ring system using a 1,6-keto-aldehyde as the cyclisation precursor was unsuccessful; in this case, the reaction stopped after a single reductive amination on the aldehyde to provide an acyclic keto-amine product. 相似文献
975.
There had been little progress in development of the theoretical basis of rectangular chromatography columns until Spangler made great progress by using a more exact model than Golay's. Unfortunately, there was a deficiency in his calculations, which led to a conclusion inconsistent with the previous theories. In this paper, a simpler formula with defined variables was first established to calculate the mean permeability coefficient for a rectangular GC column. A formula was also established to calculate the height equivalent to a theoretical plate (HETP) for a rectangular column based on this work and the correction of Spangler's theory. By comparing both our predictions and Spangler's predictions with Golay's, respectively, we could demonstrate that our theory is more exact. Further, one parameter (A) was found to be not monotonous. This finding leads to the conclusion that the square column has the highest performance among all the rectangular-shaped columns used for chromatography, and that a width/depth ratio of around three is desirable if the column is used for mixing reactants in lab-on-a-chip systems, instead of for chromatography. The conclusions are applicable not only for gas but also for liquid chromatography columns. 相似文献
976.
Scaffidi A Stubbs KA Dennis RJ Taylor EJ Davies GJ Vocadlo DJ Stick RV 《Organic & biomolecular chemistry》2007,5(18):3013-3019
The synthesis of an analogue of 6-epi-valienamine bearing an acetamido group and its characterisation as an inhibitor of beta-N-acetylglucosaminidases are described. The compound is a good inhibitor of both human O-GlcNAcase and human beta-hexosaminidase, as well as two bacterial beta-N-acetylglucosaminidases. A 3-D structure of the complex of Bacteroides thetaiotaomicron BtGH84 with the inhibitor shows the unsaturated ring is surprisingly distorted away from its favoured solution phase conformation and reveals potential for improved inhibitor potency. 相似文献
977.
Wear KA 《The Journal of the Acoustical Society of America》2007,121(4):2431-2437
Commercial bone sonometers measure broadband ultrasonic attenuation and/or speed of sound (SOS) in order to assess bone status. Phase velocity, which is usually measured in frequency domain, is a fundamental material property of bone that is related to SOS, which is usually measured in time domain. Four previous in vitro studies indicate that phase velocity in human cancellous bone decreases with frequency (i.e., negative dispersion). In order to investigate frequency-dependent phase velocity in vivo, through-transmission measurements were performed in 73 women using a GE Lunar Achilles Insight commercial bone sonometer. Average phase velocity at 500 kHz was 1489 +/- 55 m/s (mean +/- standard deviation). Average dispersion rate was -59 +/- 52 m/sMHz. Group velocity was usually lower than phase velocity, as is expected for negatively dispersive media. Using a stratified model to represent cancellous bone, the reductions in phase velocity and dispersion rate in vivo as opposed to in vitro can be explained by (1) the presence of marrow instead of water as a fluid filler, and (2) the decreased porosity of bones of living (compared with deceased) subjects. 相似文献
978.
Wear KA 《The Journal of the Acoustical Society of America》2007,122(1):636-644
Time-domain speed-of-sound (SOS) measurements in calcaneus are effective predictors of osteoporotic fracture risk. High attenuation and dispersion in bone, however, produce severe distortion of transmitted pulses that leads to ambiguity of time-domain SOS measurements. An equation to predict the effects of system parameters (center frequency and bandwidth), algorithm parameters (pulse arrival-time marker), and bone properties (attenuation coefficient and thickness) on time-domain SOS estimates is derived for media with attenuation that varies linearly with frequency. The equation is validated using data from a bone-mimicking phantom and from 30 human calcaneus samples in vitro. The data suggest that the effects of dispersion are small compared with the effects of frequency-dependent attenuation. The equation can be used to retroactively compensate data. System-related variations in SOS are shown to decrease as the pulse-arrival-time marker is moved toward the pulse center. Therefore, compared with other time-domain measures of SOS, group velocity exhibits the minimum system dependence. 相似文献
979.
Gwendolyn M. Cramer Edmund K. Moon Keith A. Cengel Theresa M. Busch 《Photochemistry and photobiology》2020,96(5):954-961
Immune checkpoints including PD-1 and CTLA-4 help to regulate the intensity and timeframe of the immune response. Since they become upregulated in cancer and prevent sufficient antitumor immunity, monoclonal antibodies against these checkpoints have shown clinical promise for a range of cancers. Multimodal treatment plans combining immune checkpoint inhibitors with other therapies, including photodynamic therapy (PDT), may help to expand treatment efficacy and minimize side effects. PDT's cytotoxic effects are spatially limited by the light activation process, constraining PDT direct effects to the treatment field. The production of damage-associated molecular patterns and tumor-associated antigens from PDT can encourage accumulation and maturation of antigen-presenting cells and reprogram the tumor microenvironment to be more susceptible to therapies targeting immune checkpoints. 相似文献
980.
Robinson I. Roacho Alejandro J. Metta‐Magaña Eduardo Peña‐Cabrera Keith H. Pannell 《Journal of Physical Organic Chemistry》2013,26(4):345-351
Fluorescent members of the 4, 4‐difluoro‐4‐bora‐3a, 4a‐diaza‐s‐indacene (BODIPY) family are widely used for a range of markers, dyes, and sensors. The capacity to substitute the basic framework is an attractive feature permitting a range of differently substituted materials to be formed. New isomeric BODIPYs, o‐, m‐, and p‐8‐[R‐C6H4]‐BODIPY (R = CH2OH, 2a (o), 2b (m), 2c (p); R = OMe, 3a (o), 3b (m), 3c (p)), have been synthesized and characterized by nuclear magnetic resonance, absorbance and emission spectroscopy, and single crystal X‐ray diffraction. The o‐isomers have a very high quantum yield emission in non‐polar solvents, while the m‐ and p‐ analogs showed weak fluorescence under the same conditions. Spectroscopic analysis, as well as X‐ray structural characterization, suggested that substitution in the ortho‐position of the phenyl ring is sufficient to increase the steric hindrance and hence impede the rotation of the phenyl moiety about the 8C‐C axis, thereby favoring radiative compared to non‐radiative relaxation. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献