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991.
T. E. Sale J. S. Roberts J. Woodhead J. P. R. David P. N. Robson 《Journal of Crystal Growth》1997,170(1-4):399-403
We compare the materials parameters for visible emitting, vertical cavity surface emitting lasers (VCSELs) and conclude that AlGaAs-based materials are a good choice. All-AlGaAs devices were produced by metalorganic vapour phase epitaxy (MOVPE) growth using ultra-high purity source reagents. Lasing was obtained at wavelengths in the range of 683 to 713 nm using four 45 Å wide Al0.18Ga0.82 As quantum wells in the active region. A threshold current density of 3.8 kA cm−2 was measured for a cavity wavelength of 692 nm at room temperature. Growth of the epitaxial mirrors at 5.2 μm/h results in a total device growth time of only two and a half hours. 相似文献
992.
Felicia Phei Lin Lim Lee Ming Hu Edward R.T. Tiekink Anton V. Dolzhenko 《Tetrahedron letters》2018,59(42):3792-3796
A highly selective and efficient method for the synthesis of 3,3′(5,5′)-polymethylene-bis(1H-1,2,4-triazol-5(3)-amines) was developed using the reaction of dicarboxylic acids and aminoguanidine in an aqueous medium. This one-pot, microwave-promoted method was proved to be scalable affording the desired products in good yields and purity. The scope of the method was successfully explored by the preparation of a small library of polymethylene-bis(1H-1,2,4-triazol-5(3)-amines) with different alkyl chain linkers. The annular prototropic tautomerism in the prepared compounds was studied using NMR spectroscopy and X-ray crystallography. 相似文献
993.
M. J. Jackson C. Gilligan A. V. Davies R. Britton J. I. Friese L. R. Greenwood B. D. Pierson Z. S. Finch B. N. Gartman D. Dry I. May N. C. Smythe A. J. Gaunt E. R. Thomas K. E. Roberts N. K. Harward K. J. Thomas P. T. Woody P. Zhao 《Journal of Radioanalytical and Nuclear Chemistry》2018,318(1):107-115
Samarium-153 (\({}^{153}\hbox {Sm}\)) is a short-lived radionuclide that decays to stable europium-153 via beta emission, with subsequent de-excitation via gamma emission and internal conversion. Historical measurements of \({}^{153}\hbox {Sm}\) by gamma spectrometry and beta liquid scintillation counting have shown a low bias compared to beta proportional counting. In order to investigate this, four national laboratories jointly conducted an experimental inter-comparison exercise on a certified \({}^{153}\hbox {Sm}\) sample, created from neutron activation of samarium-152. Radiometric measurements were conducted using gamma spectrometry, liquid scintillation counting, gas proportional counting, and passivated implanted planar silicon detectors and compared across the four institutions against the certified value. The results from this experiment are presented together with a number of conclusions which suggest that the current published cumulative fission yield for \({}^{153}\hbox {Sm}\), as used by many laboratories, is approximately 15% high and is the likely cause of the previously observed bias. 相似文献
994.
John J. Goodell Christine M. Egnatuk Stephen W. Padgett Corey C. Keith Todd A. Bredeweg Norris K. Harward Bryan B. Bandong Kevin E. Roberts Alice C. Mignerey 《Journal of Radioanalytical and Nuclear Chemistry》2018,316(2):475-483
Theoretical activation calculations for Fe, Ni, and stainless steel foils were compared against irradiated foil measurements from a critical assembly. Calculated/experiment values spanning 0.62–1.31 showed that the restricted approach used here is insufficient for experiment planning, with the collapsed cross-section being the primary source of error. The effect of decay time on gamma-ray spectroscopy measurement reliability was investigated using a Monte Carlo HPGe detector model. Simulations showed no correlation with decay time, absent interferences. Specific interferences for Fe-59 (Ni) and Co-60 (stainless steel) activation product ratios suggested optimal measurement windows having respective decay times of 9–11 days and 4–7 days. 相似文献
995.
Rondahl Stina Holmgren Pointurier Fabien Ahlinder Linnea Ramebäck Henrik Marie Olivier Ravat Brice Delaunay François Young Emma Blagojevic Ned Hester James R. Thorogood Gordon Nelwamondo Aubrey N. Ntsoane Tshepo P. Roberts Sarah K. Holliday Kiel S. 《Journal of Radioanalytical and Nuclear Chemistry》2018,315(2):395-408
Journal of Radioanalytical and Nuclear Chemistry - This work presents the results for identification of chemical phases obtained by several laboratories as a part of an international nuclear... 相似文献
996.
997.
Combinatorial Probes for High‐Throughput Electrochemical Analysis of Circulating Nucleic Acids in Clinical Samples 下载免费PDF全文
Dr. Jagotamoy Das Dr. Ivaylo Ivanov Dr. Tina S. Safaei Prof. Edward H. Sargent Prof. Shana O. Kelley 《Angewandte Chemie (International ed. in English)》2018,57(14):3711-3716
The analysis of circulating tumour nucleic acids (ctNAs) provides a minimally invasive way to assess the mutational spectrum of a tumour. However, effective and practical methods for analyzing this emerging class of markers are lacking. Analysis of ctNAs using a sensor‐based approach has notable challenges, as it is vital to differentiate nucleic acids from normal cells from mutation‐bearing sequences emerging from tumours. Moreover, many genes related to cancer have dozens of different mutations. Herein, we report an electrochemical approach that directly detects genes with mutations in patient serum by using combinatorial probes (CPs). The CPs enable detection of all of the mutant alleles derived from the same part of the gene. As a proof of concept, we analyze mutations of the EGFR gene, which has more than 40 clinically relevant alterations that include deletions, insertions, and point mutations. Our CP‐based approach accurately detects mutant sequences directly in patient serum. 相似文献
998.
Fast Exfoliation and Functionalisation of Two‐Dimensional Crystalline Carbon Nitride by Framework Charging 下载免费PDF全文
Dr. Jingjing Jia Dr. Edward R. White Dr. Adam J. Clancy Dr. Noelia Rubio Theo Suter Dr. Thomas S. Miller Kit McColl Prof. Paul F. McMillan Dr. Veronika Brázdová Prof. Furio Corà Dr. Christopher A. Howard Robert V. Law Dr. Cecilia Mattevi Prof. Milo S. P. Shaffer 《Angewandte Chemie (International ed. in English)》2018,57(39):12656-12660
Two‐dimensional (2D) layered graphitic carbon nitride (gCN) nanosheets offer intriguing electronic and chemical properties. However, the exfoliation and functionalisation of gCN for specific applications remain challenging. We report a scalable one‐pot reductive method to produce solutions of single‐ and few‐layer 2D gCN nanosheets with excellent stability in a high mass yield (35 %) from polytriazine imide. High‐resolution imaging confirmed the intact crystalline structure and identified an AB stacking for gCN layers. The charge allows deliberate organic functionalisation of dissolved gCN, providing a general route to adjust their properties. 相似文献
999.
Let k be a positive integer and let P = (X,≤) be a poset. We call P a k-sphere order provided there is a mapping f which assigns to each element x $ \in$ X a ball f(x) in Rk so that x ≤ y in P if and only if f(x) $ \subseteq$ f(y). We ask: Given that P is a k-sphere order, does there necessarily exist a representation f with the property that every minimal element of P is assigned a ball of radius zero? The answer is “yes” for k = 1, but “no” for all k ≥ 2. 相似文献
1000.
For a given convex subset Ω of Euclidean n-space, we consider the problem of minimizing the perimeter of subsets of Ω subject
to a volume constraint. The problem is to determine whether in general a minimizer is also convex. Although this problem is
unresolved, we show that if Ω satisfies a “great circle” condition, then any minimizer is convex. We say that Ω satisfies
a great circle condition if the largest closed ball B contained in Ω has a great circle that is contained in the boundary
of Ω. A great circle of B is defined as the intersection of the boundary of B with a hyperplane passing through the center
of B. 相似文献