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排序方式: 共有80条查询结果,搜索用时 13 毫秒
41.
F. J. Cumming J. J. Frady D. R. Woodward 《Journal of Radioanalytical and Nuclear Chemistry》1992,161(1):21-25
A series of 20 mother-infant pairs were studied in Brisbane, Australia at 6–12 weeks post-partum. Mean breast milk selenium concentration (±SD) was 11.9±3.5 ng/g; infants' mean 24 hour selenium intakes (±SD) were 10.7±4.1 g. Mean selenium concentration in material blood was 101 (±SD 19) ng/g and in material serum 81 (±15) ng/g. 相似文献
42.
A study of the fracture mechanisms in pristine silica fibres utilising high speed imaging techniques
K.V. Tokmakov A. Cumming J. Hough R. Jones R. Kumar S. Reid S. Rowan N.A. Lockerbie A. Wanner G. Hammond 《Journal of Non》2012,358(14):1699-1709
The 40 kg test masses of the Advanced LIGO interferometric gravitational wave detector will each be suspended on four fibres fabricated from Heraeus Suprasil synthetic silica glass. The ultimate tensile breaking stress and fracturing process of loaded silica fibres was investigated in order to develop the technology required to suspend the test mass in a robust and safe manner. The majority of the fibres in this study were pulled by hand in a H2 ? O2 flame; for comparison, fibres were also pulled on a CO2 laser machine. Carefully prepared fibres were shown to be pristine, i.e. free of surface cracks. Such fibres exhibited breaking strengths as high as 5 ? 6 GPa. To analyse the mechanisms of fracture a high speed photographic setup was developed in addition to the use of a high speed video camera. The pristine fibres break in the zone of maximal stress as expected in the model of flawless fibres. Some fibres break at a lower stress and these fractures occur at the fibre ends. This type of fracture is related to the thermal stress induced by local heating which was used to align the fibre in the test structure. The most likely fracture mechanism is based on a thermo-kinetic approach. 相似文献
43.
James Grant Ivonne Escorcia‐Carranza Chong Li Iain J. H. McCrindle John Gough David R. S. Cumming 《Laser \u0026amp; Photonics Reviews》2013,7(6):1043-1048
In this article a monolithic resonant terahertz sensor element with a noise equivalent power superior to that of typical commercial room temperature single pixel terahertz detectors and capable of close to real time read‐out rates is presented. The detector is constructed via the integration of a metamaterial absorber and a micro‐bolometer sensor. An absorption magnitude of 57% at 2.5 THz, a minimum NEP of and a thermal time constant of 68 ms for the sensor are measured. As a demonstration of detector capability, it is employed in a practical Nipkow terahertz imaging system. The monolithic resonant terahertz detector is readily scaled to focal plane array formats by adding standard read‐out and addressing circuitry enabling compact, low‐cost terahertz imaging. 相似文献
44.
T. Westphal G. Bergmann A. Bertolini M. Born Y. Chen A. V. Cumming L. Cunningham K. Dahl C. Gr?f G. Hammond G. Heinzel S. Hild S. Huttner R. Jones F. Kawazoe S. K?hlenbeck G. Kühn H. Lück K. Mossavi J. H. P?ld K. Somiya A. M. van Veggel A. Wanner B. Willke K. A. Strain S. Go?ler K. Danzmann 《Applied physics. B, Lasers and optics》2012,106(3):551-557
The AEI 10 m prototype interferometer facility is currently being constructed at the Albert Einstein Institute in Hannover, Germany. It aims to perform experiments for future gravitational wave detectors using advanced techniques. Seismically isolated benches are planned to be interferometrically interconnected and stabilized, forming a low-noise testbed inside a 100 m3 ultra-high vacuum system. A well-stabilized high-power laser will perform differential position readout of 100 g test masses in a 10 m suspended arm-cavity enhanced Michelson interferometer at the crossover of measurement (shot) noise and back-action (quantum radiation pressure) noise, the so-called Standard Quantum Limit (SQL). Such a sensitivity enables experiments in the highly topical field of macroscopic quantum mechanics. In this article we introduce the experimental facility and describe the methods employed; technical details of subsystems will be covered in future papers. 相似文献
45.
Benjamin P. Cumming Sukanta Debbarma Barry Luther-Davies Min Gu 《Applied physics. B, Lasers and optics》2012,109(2):227-232
We demonstrate compensation for the spherical aberration due to the refractive index mismatch that occurs when a laser beam is focused into a thick arsenic trisulfide (As $_2$ S $_3$ ) film with a high numerical aperture objective. The effects of the aberration at different focal depths on the point spread function have been calculated numerically and the axial response method shown to be a useful measure for compensating the spherical aberration. We show that with the addition of adaptive optics based on a spatial light modulator, the aberration can be significantly reduced, resulting in an increase in peak intensity by a factor of 2.4 and a decrease in axial elongation by a factor of 2.2. 相似文献
46.
We present a mass-conservative vertex-centred finite volume method for efficiently solving the mixed form of Richards’ equation
in heterogeneous porous media. The spatial discretisation is particularly well-suited to heterogeneous media because it produces
consistent flux approximations at quadrature points where material properties are continuous. Combined with the method of
lines, the spatial discretisation gives a set of differential algebraic equations amenable to solution using higher-order
implicit solvers. We investigate the solution of the mixed form using a Jacobian-free inexact Newton solver, which requires
the solution of an extra variable for each node in the mesh compared to the pressure-head form. By exploiting the structure
of the Jacobian for the mixed form, the size of the preconditioner is reduced to that for the pressure-head form, and there
is minimal computational overhead for solving the mixed form. 相似文献
47.
48.
Paul Cumming Milan Scheidegger Dario Dornbierer Mikael Palner Boris B. Quednow Chantal Martin-Soelch 《Molecules (Basel, Switzerland)》2021,26(9)
Hallucinogens are a loosely defined group of compounds including LSD, N,N-dimethyltryptamines, mescaline, psilocybin/psilocin, and 2,5-dimethoxy-4-methamphetamine (DOM), which can evoke intense visual and emotional experiences. We are witnessing a renaissance of research interest in hallucinogens, driven by increasing awareness of their psychotherapeutic potential. As such, we now present a narrative review of the literature on hallucinogen binding in vitro and ex vivo, and the various molecular imaging studies with positron emission tomography (PET) or single photon emission computer tomography (SPECT). In general, molecular imaging can depict the uptake and binding distribution of labelled hallucinogenic compounds or their congeners in the brain, as was shown in an early PET study with N1-([11C]-methyl)-2-bromo-LSD ([11C]-MBL); displacement with the non-radioactive competitor ketanserin confirmed that the majority of [11C]-MBL specific binding was to serotonin 5-HT2A receptors. However, interactions at serotonin 5HT1A and other classes of receptors and pleotropic effects on second messenger pathways may contribute to the particular experiential phenomenologies of LSD and other hallucinogenic compounds. Other salient aspects of hallucinogen action include permeability to the blood–brain barrier, the rates of metabolism and elimination, and the formation of active metabolites. Despite the maturation of radiochemistry and molecular imaging in recent years, there has been only a handful of PET or SPECT studies of radiolabeled hallucinogens, most recently using the 5-HT2A/2C agonist N-(2[11CH3O]-methoxybenzyl)-2,5-dimethoxy- 4-bromophenethylamine ([11C]Cimbi-36). In addition to PET studies of target engagement at neuroreceptors and transporters, there is a small number of studies on the effects of hallucinogenic compounds on cerebral perfusion ([15O]-water) or metabolism ([18F]-fluorodeoxyglucose/FDG). There remains considerable scope for basic imaging research on the sites of interaction of hallucinogens and their cerebrometabolic effects; we expect that hybrid imaging with PET in conjunction with functional magnetic resonance imaging (fMRI) should provide especially useful for the next phase of this research. 相似文献
49.
50.
Several new liquid crystalline compounds comprising Schiff's-base cinnamate cores and fluorocarbon alkoxy tails of varying lengths have been synthesized and characterized. The thermal properties of these materials are compared to those of their hydrocarbon analogues. The results show that fluorination stabilizes the crystalline phase, quite unexpectedly destabilizes the Sc phase, and for two of the compounds produces extraordinarily stable SA phases. 相似文献