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排序方式: 共有155条查询结果,搜索用时 15 毫秒
1.
Open circuit voltage (OCV) measurements in H2O/air concentration cells at T<580 K using Yb-doped SrCeO3 electrolyte indicate that under these conditions, protons are transported through the electrolyte as -ve ions, possibly as
hydroxyl (OH−) ions. The H+ ionic transport, which is generally reported, becomes the dominant mode for H2O/air concentration cells at temperatures greater than 750 K or when H2O/air electrodes are replaced by H2/Ar, and the anomalous OCV sign disappears. The combination of low temperature and the presence of hydrogen and oxygen as
provided by the H2O/air system appears to be necessary for the postulated hydroxyl ion electrode reactions to take place.
In addition to OCV measurements, results from impedance spectroscopy are used to provide evidence in support of the suggested
hydroxyl ion mode of protonic transport under the specified conditions. These findings are directly relevant in the development
of novel humidity sensors in the temperature range 450–580K and is reported in a separate paper in this conference.
Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996 相似文献
2.
3.
Kochocki JA Allison WW Alner GJ Ambats I Ayres DS Balka LJ Barr GD Barrett WL Benjamin D Border P Brooks CB Cobb JH Cockerill DJ Coover K Courant H Dahlin B DasGupta U Dawson JW Edwards VW Fields TH Kirby-Gallagher LM Garcia-Garcia C Giles RH Goodman MC Heller K Heppelman S Hill N Hoftiezer JH Jankowski DJ Johns K Joyce T Kafka T Litchfield PJ Lopez FV Lowe M Mann WA Marshak ML May EN McMaster L Milburn RH Miller W Napier A Oliver WP Pearce GF Perkins DH Peterson EA Price LE Roback D Rosen DB 《Physical review D: Particles and fields》1990,42(9):2967-2973
4.
Andrew M. Steer Hannah L. Bolt William D.G. Brittain Steven L. Cobb 《Tetrahedron letters》2018,59(27):2644-2646
Herein the synthesis of an Fmoc/OtBu orthogonally protected iodotyrosine derivative is reported. This has been achieved via a simple two-step process in an overall 58% yield from commercially available Fmoc-Tyr(tBu)-OH. The Fmoc/OtBu orthogonally protected iodotyrosine was also shown to be amenable to Suzuki-Miyaura cross-coupling to deliver a novel bi-aryl tyrosine derivative. 相似文献
5.
Daniel Townsend Prof. Dr. Kenneth Shankland Dr. Alex Weymouth-Wilson Dr. Zofia Komsta Dr. Tim Evans Dr. Alexander J. A. Cobb 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(16):3504-3508
A highly enantioselective, organocatalytic, and scalable synthesis of a very unusual cis-decalin-cis-hydrindane tricyclic diterpenoid system has been achieved. Despite the prevalent pharmacological space that the related trans,trans and trans,cis-systems occupy, there have been no reports of an asymmetric synthesis of the cis,cis systems in the literature until now. We demonstrate the flexibility of our approach not only through access to a diverse range of products, all of which are attained in exceptionally high selectivities, but also by showing their easy conversion to the corresponding trans,cis-system and other derivatives. 相似文献
6.
Hiroshi Awata George P. Cobb Todd A. Anderson 《International journal of environmental analytical chemistry》2013,93(1):41-49
Abstract Aging is one of several processes that are known to affect exposure of chemicals to organisms by decreasing the available fraction of chemical contaminants in soil. This phenomenon has important implications in the assessment of the hazards of chemicals and regulations for soil cleanup. Passive sampling devices (PSDs) are potentially direct chemical indicators for assessing bioavailability of pesticides (and other chemicals). PSDs consist of lipophilic material within a semi-permeable membrane, similar to biological systems. In this study, a pesticide mixture was aged in soil for up to eight months. Earthworms and PSDs were placed in soil and chemical uptake into both was determined over time. Uptake rates into PSDs and maximum concentrations were observed to positively correlate with uptake rates and maximum concentrations in earthworms for both of the soil types studied (sandy loam, silt loam). These results indicate that PSDs may be used as a surrogate for earthworms and provide a chemical technique for assessing the availability of aged chemical residues in soil. 相似文献
7.
Antonio Dell'Isola Dr. Matthew M. W. McLachlan Dr. Benjamin W. Neuman Hawaa M. N. Al‐Mullah Alexander W. D. Binks Warren Elvidge Dr. Kenneth Shankland Dr. Alexander J. A. Cobb 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(37):11685-11689
An efficient synthesis of spirocyclic triazolooxazine nucleosides is described. This was achieved by the conversion of β‐D ‐psicofuranose to the corresponding azido‐derivative, followed by alkylation of the primary alcohol with a range of propargyl bromides, obtained by Sonogashira chemistry. The products of these reactions underwent 1,3‐dipolar addition smoothly to generate the protected spirocyclic adducts. These were easily deprotected to give the corresponding ribose nucleosides. The library of compounds obtained was investigated for its antiviral activity using MHV (mouse hepatitis virus) as a model wherein derivative 3 f showed the most promising activity and tolerability. 相似文献
8.
Structural characterization of intact proteins is enhanced by prevalent fragmentation pathways rarely observed for peptides 总被引:2,自引:0,他引:2
Jennifer S. Cobb Michael L. Easterling Jeffrey N. Agar 《Journal of the American Society for Mass Spectrometry》2010,21(6):949-959
While collisionally activated dissociation (CAD) pathways for peptides are well characterized, those of intact proteins are
not. We systematically assigned CAD product ions of ubiquitin, myoglobin, and bovine serum albumin generated using high-yield,
in-source fragmentation. Assignment of >98% of hundreds of product ions implies that the fragmentation pathways described
are representative of the major pathways. Protein dissociation mechanisms were found to be modulated by both source declustering
potential and precursor ion charge state. Like peptides, higher charge states of proteins fragmented at lower energies next
to Pro, via mobile protons, while lower charge states fragmented at higher energies after Asp and Glu, via localized protons.
Unlike peptides, however, predominant fragmentation channels of proteins occurred at intermediate charge states via non-canonical
mechanisms and produced extensive internal fragmentation. The non-canonical mechanisms include prominent cleavages C-terminal
to Pro and Asn, and N-terminal to Ile, Leu, and Ser; these cleavages, along with internal fragments, led to a 45% increase
in sequence coverage, improving the specificity of top-down protein identification. Three applications take advantage of the
different mechanisms of protein fragmentation. First, modulation of declustering potential selectively fragments different
charge states, allowing the source region to be used as the first stage of a low-resolution tandem mass spectrometer, facilitating
pseudo-MS3 of product ions with known parent charge states. Second, development and integration of automated modulation of
ion funnel declustering potential allows users access to a particular fragmentation mechanism, yielding facile cleavage on
a liquid chromatography timescale. Third, augmentation of a top-down search engine improved protein characterization. 相似文献
9.
We report an approach to achieving continuous focus tracking and a depth-independent transverse resolution for real-time optical coherence tomography (OCT) imaging. Continuous real-time focus tracking is permitted by use of a lateral-priority image acquisition sequence in which the depth-scanning rate is equivalent to the imaging frame rate. Real-time OCT imaging with continuous focus tracking is performed at 1 frame/s by reciprocal translation of a rapid lateral-scanning miniature imaging probe (e.g., an endoscope). The optical path length in the reference arm is scanned synchronously to ensure that the coherence gate coincides with the imaging beam focus. The image quality improvement is experimentally demonstrated by imaging a tissue phantom embedded with polystyrene microspheres and rabbit esophageal tissues. 相似文献
10.
Cobb SL Deng H Hamilton JT McGlinchey RP O'Hagan D 《Chemical communications (Cambridge, England)》2004,(5):592-593
5'-Fluoro-5'-deoxy-D-ribose-1-phosphate (FDRP) is identified as a biosynthetic intermediate during fluorometabolite biosynthesis in Streptomyces cattleya. 相似文献