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21.
Reed M. Izatt Robert M. Haws John D. Lamb David V. Dearden Philip R. Brown Don W. McBride Jr. James J. Christensen 《Journal of membrane science》1984,20(3):273-284
Cation fluxes were determined for various three-component, equimolar mixtures of alkali metal, alkaline earth, and Pb2+ cations in a H2O---CHCl3---H2O liquid membrane system incorporating macrocyclic polyethers as carriers. Carrier ligands studied were 18-crown-6, dicyclohexano-18-crown-6, 1,10-diaza-18-crown-6, 21-crown-7, dibenzo-24-crown-8, and cryptand [2.2.2]. Correlations were found between transport and relative cation:polyether cavity radii, the type of substituents present on the polyether ring, and the type and number of donor atoms present. All the ligands studied transported Pb2+ at higher rates than the other Mn+ in the mixtures. Transport behavior in these multi-cation systems can be predicted from Mn+—polyether complex stability constant data in most cases. 相似文献
22.
Cheng-Xian Lin Mikhail Sekachev Zhiyu Hu Don Dareing 《Journal of nanoparticle research》2010,12(3):865-876
In this article, various energies and geometries of pure platinum nanoparticles and those of platinum nanoparticles with adsorbed
OH were investigated. Fourteen different platinum clusters of 3–40 atoms were studied using spin-unrestricted density functional
theory (DFT) with a double numerical plus polarization basis set. This range of sizes gave enough information for establishing
the general trends that were the primary goal of the study. Three different shapes of platinum clusters were presented, and
the effect of cluster size on binding energy, total energy, and HOMO–LUMO energy gap was investigated. Subsequently, same
calculations were performed for those selected Pt clusters with OH adsorbate on the surface. The results show that the stability
of both the pure clusters and the clusters with adsorbed OH molecule increases with an increase of cluster size. This fact
indicates that direct influence of the size of Pt cluster on the reaction rate is possible, and the understanding of how cluster
size would affect binding energy is important. As expected, the effect of cluster size on total energy of molecule was shown
to be a linear function independent of cluster type. We also found that optimized (stable) Pt clusters were bigger in size
than that of the initial clusters, or clusters with bulk geometry. 相似文献
23.
An asymmetric anti-aldol addition process of ketone-derived donors that is not limited by the structure of the ketone is described. This is achieved by merging the enantioselective α,α-bisalkylation of N-amino cyclic carbamate (ACC) hydrazones with the asymmetric anti-aldol addition of ACC hydrazones. The products of this process are obtained with essentially perfect stereoselectivity. Using this procedure it is possible to gain access to ketone-based anti-aldol addition products that are inaccessible in a controlled sense via direct aldol methods. 相似文献
24.
Yuetian Yan Guodong Chen Hui Wei Richard Y.-C. Huang Jingjie Mo Don L. Rempel Adrienne A. Tymiak Michael L. Gross 《Journal of the American Society for Mass Spectrometry》2014,25(12):2084-2092
Epitope mapping is an important tool for the development of monoclonal antibodies, mAbs, as therapeutic drugs. Recently, a class of therapeutic mAb alternatives, adnectins, has been developed as targeted biologics. They are derived from the 10th type III domain of human fibronectin (10Fn3). A common approach to map the epitope binding of these therapeutic proteins to their binding partners is X-ray crystallography. Although the crystal structure is known for Adnectin 1 binding to human epidermal growth factor receptor (EGFR), we seek to determine complementary binding in solution and to test the efficacy of footprinting for this purpose. As a relatively new tool in structural biology and complementary to X-ray crystallography, protein footprinting coupled with mass spectrometry is promising for protein–protein interaction studies. We report here the use of fast photochemical oxidation of proteins (FPOP) coupled with MS to map the epitope of EGFR-Adnectin 1 at both the peptide and amino-acid residue levels. The data correlate well with the previously determined epitopes from the crystal structure and are consistent with HDX MS data, which are presented in an accompanying paper. The FPOP-determined binding interface involves various amino-acid and peptide regions near the N terminus of EGFR. The outcome adds credibility to oxidative labeling by FPOP for epitope mapping and motivates more applications in the therapeutic protein area as a stand-alone method or in conjunction with X-ray crystallography, NMR, site-directed mutagenesis, and other orthogonal methods. Figure
? 相似文献
25.
Jerry A. Darsey Ashish G. Soman Don W. Noid 《Macromolecular theory and simulations》1993,2(5):711-719
In this work, a neural network was used to learn features in potential energy surfaces and relate those features to conformational properties of a series of polymers. Specifically, we modeled Monte Carlo simulations of 20 polymers in which we calculated the characteristic ratio and the temperature coefficient of the characteristic ratio for each polymer. We first created 20 rotational potential energy surfaces using MNDO procedures and then used these energy surfaces to produce 10000 chains, each chain 100 bonds long. From these results we calculated the mean-square end-to-end distance, the characteristic ratio and its corresponding temperature coefficient. A neural network was then used to model the results of these Monte Carlo calculations. We found that artificial neural network simulations were highly accurate in predicting the outcome of the Monte Carlo calculations for polymers for which it was not trained. The overall average error for prediction of the characteristic ratio was 4,82%, and the overall average error for prediction of the temperature coefficient was 0,89%. 相似文献
26.
Santosh K. Shrestha Heiko Timmers Aidan P. Byrne Wayne D. Hutchison Don H. Chaplin Rakesh Dogra 《Hyperfine Interactions》2004,158(1-4):407-411
A radioisotope ion implanter has been developed using a cesium-sputtering, negative ion source, which offers versatility and
sustained operation. Employing the molecular 111In16O− ion, μCi activities of the radioisotope probe 111In/Cd have been implanted into different material hosts. The implanted tracer activity has been shown to be sufficient for
LTNO, NMRON and PAC. A new NMRON resonance for 111InAg was observed at 75.08 MHz. In2O3 powder performed well as the radioisotope carrier in the ion source, with the ratio of radioisotope and parasitic ion current
being typically 4 × 10−4. 相似文献
27.
M Don C W Ponton J J Eggermont B Kwong 《The Journal of the Acoustical Society of America》1998,104(4):2280-2289
Derived-band auditory brainstem responses (ABRs) were obtained in 43 normal-hearing and 80 cochlear hearing-impaired individuals using clicks and high-pass noise masking. The response times across the cochlea [the latency difference between wave V's of the 5.7- and 1.4-kHz center frequency (CF) derived bands] were calculated for five levels of click stimulation ranging from 53 to 93 dB p.-p.e. SPL (23 to 63 dB nHL) in 10-dB steps. Cochlear response times appeared to shorten significantly with hearing loss, especially when the average pure tone (1 to 8 kHz) hearing loss exceeded 30 dB. Examination of derived-band latencies indicates that this shortening is due to a dramatic decrease of wave V latency in the lower CF derived band. Estimates of cochlear filter times in terms of the number of periods to maximum response (Nmax) were calculated from derived-band latencies corrected for gender-dependent cochlear transport and neural conduction times. Nmax decreased as a function of hearing loss, especially for the low CF derived bands. The functions were similar for both males and females. These results are consistent with broader cochlear tuning due to peripheral hearing loss. Estimating filter response times from ABR latencies enhances objective noninvasive diagnosis and allows delineation of the differential effects of pathology on the underlying cochlear mechanisms involved in cochlear transport and filter build-up times. 相似文献
28.
Leanne Jill Rylands Don Shearman 《International Journal of Mathematical Education in Science & Technology》2018,49(8):1133-1147
This paper considers the effects of both free optional mathematics learning support and engagement on the mathematics performance in a foundation mathematics subject of a cohort of engineering students entering university with poor mathematical skills. New engineering students were directed to either a foundation or standard mathematics subject based on the results of a placement test. For students in the foundation subject, it was found that high levels of learning support were associated with greater improvement over the semester. Some form of learning support was used by 57.9% of the students, a reasonably high proportion of the cohort. Some factors for this high level of use of learning support are considered. One possible factor, the placement test, appears to have had a positive effect. Engagement in the subject activities as measured by tutorial attendance and learning management system use was found to have a positive association with final mark. Students who utilized a high level of learning support were more likely to be more engaged with the subject, making it impossible to draw conclusions about improvements being solely due to the use of learning support. 相似文献
29.
Mehdi Asghari‐Khiavi Bayden R. Wood Pejman Hojati‐Talemi Andrew Downes Don McNaughton Adam Mechler 《Journal of Raman spectroscopy : JRS》2012,43(2):173-180
Tip‐enhanced Raman scattering (TERS) spectroscopy is a promising technique for nanoscale chemical analysis. However, there are several challenges preventing widespread application of this technology, including reproducible fabrication of efficient TERS probes. These problems reflect a lack of clear understanding of the origins of, and the parameters influencing TERS. It is believed that the coating characteristics at the apex of the tip have a major effect on the near‐field optical enhancement and thus the TERS activity of a metalized probe. Here we show that the aspect ratio of the tip can play a significant role in the efficiency of TERS probes. We argue that the electrostatic field arising from the lightning‐rod effect has a substantial role in the observed TERS effect. This argument is supported by ‘edge‐enhanced Raman scattering’ which is shown for a noble metal film. Furthermore, it is reported that an associated tip‐surface‐enhanced Raman scattering effect can be achieved by using a TERS‐inactive metalized probe on a surface‐enhanced Raman spectroscopy‐inactive roughened surface. This observation can be explained by an interparticle enhancement of the electromagnetic field. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
30.
Don S. Lemons Dan Winske William Daughton Brian Albright 《Journal of computational physics》2009,228(5):1391-1403
We construct and investigate a set of stochastic differential equations that incorporate the physics of velocity-dependent small-angle Coulomb collisions among the plasma particles in a particle-in-cell simulation. Each particle is scattered stochastically from all the other particles in a simulation cell modeled as one or more Maxwellians. Total energy and momentum are conserved by linear transformation of the velocity increments. In two test simulations the proposed “particle-moment” collision algorithm performs well with time steps as large as 10% of the relaxation time – far larger than a particle-pairing collision algorithm, in which pairs of particles are scattered from one another, requires to achieve the same accuracy. 相似文献