An efficient phosphaannulation via palladium(II)‐catalyzed C H activation/oxidative cyclization by the 6‐endo mode is reported for the synthesis of 3‐substituted phosphaisocoumarins from the reaction of arylphosphonic acids with unactivated alkenes under aerobic conditions. Also, α,α‐disubstituted benzylphosphonic acids were phosphaannulated with unactivated alkenes, producing phosphaisochromanones having (Z)‐alkylidenyl groups via anti‐phosphoryloxypalladation by the 6‐exo mode.
A protocol using HCl-acidified 4-dimethylaminocinnamaldehyde (DMACA) was developed for screening proanthocyanidins (PA) in plants. Individual PA-containing cells could be observed following staining of decolourised leaves with DMACA. The quantitative assay using DMACA-HCl to detect soluble PA and butanol–HCl to detect insoluble PA could detect PA content lower than 0·4 mg g−1 dry matter (DM). The DMACA–HCl protocol is recommended for PA detection in low-PA plants because of its higher sensitivity than vanillin–acid protocols. Twenty-two forage legume species, most of which had been reported free of leaf PA but bloat-safe, were re-examined using the DMACA–HCl protocol. PA-positive cells were observed in leaves of 15 species. Measurable amounts of PA were detected in leaves of seven species, with the PA content ranging from 0·6 to 11 mg g−1 DM. White clover ( Trifolium repens L), red clover ( T pratense L) and lucerne ( Medicago sativa L) were also found to have PA-positive leaf trichomes. By analysis of these data and the literature, the threshold PA content for bloat safety in forage legumes was estimated to be 1–5 mg PA g−1 DM. 相似文献
The combined use of global positioning system (GPS) technology and motion sensors within the discipline of movement ecology has increased over recent years. This is particularly the case for instrumented wildlife, with many studies now opting to record parameters at high (infra-second) sampling frequencies. However, the detail with which GPS loggers can elucidate fine-scale movement depends on the precision and accuracy of fixes, with accuracy being affected by signal reception. We hypothesized that animal behaviour was the main factor affecting fix inaccuracy, with inherent GPS positional noise (jitter) being most apparent during GPS fixes for non-moving locations, thereby producing disproportionate error during rest periods. A movement-verified filtering (MVF) protocol was constructed to compare GPS-derived speed data with dynamic body acceleration, to provide a computationally quick method for identifying genuine travelling movement. This method was tested on 11 free-ranging lions (Panthera leo) fitted with collar-mounted GPS units and tri-axial motion sensors recording at 1 and 40 Hz, respectively. The findings support the hypothesis and show that distance moved estimates were, on average, overestimated by greater than 80% prior to GPS screening. We present the conceptual and mathematical protocols for screening fix inaccuracy within high-resolution GPS datasets and demonstrate the importance that MVF has for avoiding inaccurate and biased estimates of movement. 相似文献
The effects of genotype and growing environment on the tocopherols and fatty acids (FA) of experimental Brassica juncea and B. napus breeding lines were investigated. For both species, with the exception of a few genotypes, the concentration ratio of γ-tocopherols
to α-tocopherol was practically constant. The genotype influenced the tocopherol concentration in B. napus, and to a lesser degree, B. juncea. The environment also had a similar effect, and a positive correlation existed between the daily maximum temperature and
the α-tocopherol concentration in B. napus. Genotype effects on the FA composition were significant for the conventional but not for Clearfield or triazine tolerant
traits of B. napus. The genotype had no effect on the FA of the B. juncea genotypes. In contrast, the growing environment had a significant influence on the FA composition of both species with apparent
influence from temperature and rainfall. For both species, the concentration of γ-tocopherol as well as total tocopherols
was inversely related to the 18:3 concentration, which could have resulted from opposite and independent effects of temperature
on the two variables. No relationship existed between the concentrations of tocopherol and the remaining unsaturated FA 18:1
and 18:2. The positional distribution of unsaturated FA within the oil triacylglycerol was a function of their total concentration. 相似文献
The concept of affordance is relatively easy to define, but has proved to be remarkably difficult to engineer. This paradox has sparked numerous debates as to its true nature. The discussion presented here begins with a review of the use of the term from which emerges evidence for a two-fold classification—simple affordance and complex affordance. Simple affordance corresponds to Gibson's original formulation, while complex affordances embody such things as history and practice. In trying to account for complex affordance, two contrasting, but complementary philosophical treatments are considered. The first of these is Ilyenkov's account of significances which he claims are ‘ideal’ phenomena. Ideal phenomena occupy are objective characteristics of things and are the product of human purposive activity. This makes them objective, but not independent (of any particular mind or perception) hence their similarity to affordances.
The second perspective is Heidegger's phenomenological treatment of ‘familiarity’ and ‘equipment’. As will be seen, Heidegger has argued that familiarity underpins our ability to cope in the world. A world, in turn, which itself comprises the totality of equipment. We cope by making use of equipment. Despite the different philosophical traditions both Ilyenkov and Heidegger have independently concluded that a thing is identified by its use and that use, in turn, is revealed by way of its affordances/significances. Finally, both authors—Heidegger directly and Ilyenkov indirectly—equate context and use, leading to the conclusion that affordance and context are one and the same. 相似文献
Abstract— The De Montfort University (DMU) autostereoscopic 3‐D display, intended for television applications, is described. It provides freedom of viewer movement over a typical “living room” sized area, with no restrictions on viewer's head positions. The display is capable of supplying 3‐D images to multiple viewers who do not need to wear special glasses. It operates by producing regions (exit pupils) in the viewing field where either a left or a right image is perceived. The positions of the exit pupils are steered to the viewers' eyes by the use of head tracking. Design issues that became apparent during the construction of a first prototype, and the findings from tests on it, are described. In addition, the current status of a more advanced prototype is reported. 相似文献
Listeria monocytogenes Scott A grown in the minimal chemically defined medium M6LT was challenged to a concentration of either 35 or 65 g l(-1) of NaCl for 1 h in the presence of a [35S]cysteine-[35S]methionine labelling mix. The protein patterns were analysed by 2D-electrophoresis in the two conditions and isoosmotic condition (5 g l(-1) of NaCl in M6LT). A great number of proteins which were synthesized under isoosmotic conditions were either completely repressed or expressed at a reduced level, at 65 g l(-1) and to a lesser extent at 35 g l(-1) of NaCl. At 35 g l(-1) of NaCl, six proteins were up-regulated, five proteins showed no change in expression level and five were repressed. Among the proteins up-regulated at 35 g l(-1) of NaCl, a single one (18.7 kDa, pI 5.05) was up-regulated at 65 g l(-1) too. We observed 21 proteins which were repressed at 65 g l(-1) of NaCl, among which 11 completely disappeared. Some of the up-regulated proteins have characteristics of molecular weight and isoelectric point close to those of stress proteins reported elsewhere: the protein induced both at 35 and 65 g l(-1) might correspond to a previously proposed universal stress protein of Listeria. Some proteins which were repressed at 65 g l(-1) have molecular weights close to those of virulence proteins. 相似文献
Patterns of reading disability were examined in 2 longitudinal studies. The major findings were (a) that on the basis of the observed data, remission of reading disability was relatively common with up to 37% of reading-disabled children showing remission of this disability within a 2-year period, and (b) when the data were analyzed with a latent Markov model that took account of measurement errors in test scores, the estimated true rate of remission of reading disability was between 15% and 19% over a 2-year period. The presence of measurement error in reading disability classifications may lead to an inflated and misleading impression of the rate of remission of these problems. General implications of these findings for interpreting patterns of stability and change in longitudinal developmental data were discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献