排序方式: 共有21条查询结果,搜索用时 187 毫秒
11.
Fremlin L Farrugia M Piggott AM Khalil Z Lacey E Capon RJ 《Organic & biomolecular chemistry》2011,9(4):1201-1211
Chemical analysis of fermentation products from two Australian Streptomyces isolates yielded all four known and twelve new examples of the rare reveromycin class of polyketide spiroketals, including hemi-succinates, hemi-fumarates and hemi-furanoates. Reveromycins were identified with the aid of HPLC-DAD-MS and HPLC-DAD-SPE-NMR methodology, and structures were assigned by detailed spectroscopic analysis. The structural and mechanistic requirements for an unprecedented hemi-succinate?:?ketal-succinyl equilibrium were defined and provided a basis for proposing that reveromycin 4'-methyl esters and 5,6-spiroketals were artifacts. A plausible reveromycin polyketide biosynthesis is proposed, requiring a 2-methylsuccinyl-CoA starter unit, with flexible incorporation of a C(6-8) polyketide chain extension and diacid esterification units. Structure activity relationship investigations by co-metabolites were used to assess the anticancer, antibacterial and antifungal properties of reveromycins. 相似文献
12.
Disjoint sequence methods from the theory of Riesz spaces are used to study compact operators on Banach lattices. A principal
new result of the paper is that each positive map from a Banach latticeE to a Banach latticeF with compact majorant is itself compact provided the norms onE′ andF are order continuous. 相似文献
13.
B. J. Thomas D. Vartsky D. J. Hawkes J. H. Fremlin 《Journal of Radioanalytical and Nuclear Chemistry》1977,37(1):369-373
Nuclear resonance scattering has been applied to the measurement of copper. It has been shown that this method is sufficiently
sensitive to measure, in-vivo, liver copper accumulations associated with certain diseases. The method and some preliminary
results are described. 相似文献
14.
H. C. Biggin N. S. Chen K. V. Ettinger J. H. Fremlin W. D. Morgan R. Nowotny M. J. Chamberlain T. C. Harvey 《Journal of Radioanalytical and Nuclear Chemistry》1974,19(2):207-214
Conclusions The neutron activation method is capable of indicating the presence of cadmium in man in vivo and quantitative determinations
may be possible in the future. The sensitivity of the method is such that the detection threshold lies within the accepted
‘normal’ concentrations and is significantly below the encountered toxic levels. The method can be used for screening cadmium
poisoning suspects as the radiation dose necessary for this purpose can be made as low as 0.5 rem. Another possible application
of the technique is in the study of the role of cadmium in renal disorders, bone disease and hypertension. The measurement
takes less than 0.5 hour with the minimum of discomfort to the patient.
Résumé On peut déterminer la présence de cadmium chez l'homme à l'aide de technique de l'analyse par activation neutronique in vivo. La capture des neutrons thermiques par113Cd conduit à une émission γ prompt qui peut être détectée au moyen d'un semi-conducteur convenable. On a réalisé une installation à l'Université de Birmingham pour produire au moyen d'un cyclotron un faisceau de neutrons pulsés. Une série d'expérience a été faites sur des cadavres; ces expériences ont prouvé qu'il est possible de détecter le cadmium à une concentration de 2,0 ppm dans le volume d'un foie humain pour une dose de 1 rem. On discute des résultats et des applications possibles de cette étude.相似文献
15.
J. T. Dabek D. Vartsky P. W. Dykes J. Hardwicke B. J. Thomas J. H. Fremlin H. M. James 《Journal of Radioanalytical and Nuclear Chemistry》1977,37(1):325-331
Whole body nitrogen has been measured absolutely in male volunteers and patients by in-vivo neutron activation analysis using
whole body hydrogen as an internal standard. The 10.8 MeV and 2.2 MeV prompt gamma rays from nitrogen and hydrogen respectively
give a result reproducible to 4% for a dose of 100 mRem. Whole body potassium measured by whole body counting natural40K and whole body nitrogen have been correlated in normal adult males and patients. In the normals the correlation coefficient
was 0.96 with coefficient of variation 4%. In the patients these parameters were 0.92 and 8% in 140 measurements. The ratio
of N/K increased significantly as the degree of clinical wasting progressed. 相似文献
16.
D. H. Fremlin 《manuscripta mathematica》1981,33(3-4):387-405
I show that if (X, ) is a Radon measure space and Y is a metric space, then a function from X to Y is -measurable iff it is almost continuous (=Lusin measurable). I discuss other cases in which measurable functions are almost continuous.Part of the work of this paper was done during a visit to Japan supported by the United Kingdom Science Research Council and Hokkaido University 相似文献
17.
18.
It is well-known that highly-energetic heavily charged particles arising both from the fissioning of heavy elements and from cosmic and solar radiations leave tracks which have been found in glasses and crystal-line minerals recovered from lunar and meteoritic material. It has been shown that an appropriate analysis of these tracks can provide informationabout periods since solidification and the thermal and dynamic history of the specimen, as well as insight into the nature and temporal variation of the cosmic ray flux.1-2 An understanding of the track registration characteristics of crystals is clearly an important pre-requisite to an appropriate interpretation of the natural tracks. 3-6 This letter describes briefly some observations we have recently made on one particular aspect of this-the anisotropy in track distributions which seems to result from the inherently anisotropic structure of crystals. This effect seems so far to have received little attention. 相似文献
19.
D. H. Fremlin 《manuscripta mathematica》1975,15(4):323-327
I give an example of a positive compact operator on L2[0,1] which is not representable by any Lebesgue measurable function on [0,1]2. This example can be adapted to answer a question of H.H.Schaefer (§4 below). 相似文献
20.
Skeletons and Central Sets 总被引:1,自引:0,他引:1
Let be an open proper subset of Rn. Its skeleton is the setof points with more than one nearest neighbour in the complementof its central set is the set of centres in maximal open ballsincluded in . Intuitively, if we think of as a land mass inwhich height is proportional to distance from the sea, its skeletonand central set can be thought of as corresponding to ridgesin the mountains of . In this note I discuss the metric andtopological properties of such sets. I show that any skeletonin Rn is F, and has dimension at most n 1, by any ofthe usual measures of dimension; that if is bounded and connected,its skeleton and central set are connected; and that separatesRn iff its skeleton does iff its central set does. Any centralset in Rn is a G set of topological dimension at most n 1. In the plane, I show that both skeletons and central setsare locally path-connected, and indeed include many paths offinite length. For any , its central set includes its skeleton;I give examples to show that the central set can be significantlylarger than the skeleton. 1991 Mathematics Subject Classification:54F99. 相似文献