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排序方式: 共有1069条查询结果,搜索用时 15 毫秒
61.
62.
Mark Van Strydonck Mathieu Boudin Víctor M. Guerrero Ayuso Manuel Calvo Josep M. Fullola M. Àngeles Petit 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(7-8):990-994
The Cova des Pas cave is a karstic cave in the cliffs of the Barranc (canyon) de Trebalúger. It is a small cave only 6.5 m deep, 4.5 m wide and 1.7 m high. Yet more than 70 burials, in foetal position, from the Early Iron Age were found in this small cave. The conservation of the archaeological remains was very unusual. Not only wood, ropes and other plant material was found, but also remains of body tissue, hair and leather. In spite of the remarkable preservation of the bodies and artefacts, the state of conservation of the bone material was very bad. The bones contained little and heavily deteriorated collagen and the organic plant material was very fragile. The special environmental conditions of the cave are the cause of these unusual preservation conditions. Although the cave is situated in a limestone cliff, the soil of the cave is very acid. Unexpectedly bad sample quality seemed to be the major drawback for AMS radiocarbon dating on hair, wood, ropes and bone collagen, as well as on bio-apatite. 相似文献
63.
Nicolas Vogel Mathieu Jung Noelia L. Bocchio Markus Retsch Maximilian Kreiter Ingo Köper 《Small (Weinheim an der Bergstrasse, Germany)》2010,6(1):104-109
Nanoparticle arrays created by nanosphere lithography are widely used in sensing applications since their localized surface plasmon resonances are extremely sensitive to changes in the local dielectric environment. A major drawback for any biologically oriented sensing application of conventionally produced particle arrays is the lack of stability of the nanoparticles in aqueous media and buffer solutions. Here, a robust and reusable nanoscale sensing platform based on localized surface plasmon resonances of gold nanoparticles embedded in a silicon dioxide matrix is presented. The architecture exhibits extremely high stability in aqueous environments and can be regenerated several times by simple mechanical cleaning of the surface. The platforms surface is ultraflat by design, thus making it an ideal substrate for any bio‐oriented sensing application. 相似文献
64.
Wayne D Cook Fei Chen Derek W Pattison Peyton Hopson Mathieu Beaujon 《Polymer International》2007,56(12):1572-1579
The thermal polymerization of a tetrafunctional thiol (PETMP) and divinyl ether (TEGDVE) was monitored by temperature‐ramping differential scanning calorimetry (DSC) and the effects of inhibitor type and concentration, oxygen inhibition and initiator type were studied. The incorporation of inhibitors was required to produce a stable system at room temperature. Butylated hydroxytoluene (BHT) inhibited polymerization at low temperatures, but was inefficient at high temperatures and polymerization rates, and hence BHT is an ideal stabilizer. In contrast, a nitroxide inhibitor (NO‐67) was a very effective inhibitor and no polymerization occurred until all of the nitroxide was depleted. The presence of oxygen retarded the onset of polymerization but did not change the final conversion significantly. Polymerization with initiators having higher half‐life temperatures shifted the DSC peak to higher temperature because the rate of initiator decomposition and thus initiation was slower. Rheological investigations of the cure at different temperatures revealed that the gel time decreased significantly with increasing cure temperature, and the calculated apparent activation energy for PETMP/TEGDVE was 54 kJ mol?1. Dynamical mechanical thermal analysis of the cured material was undertaken and frequency‐superposed results revealed that the glass transition region of PETMP/TEGDVE/azobisisobutyronitrile was much narrower than that of free‐radically cured dimethacrylate, but was similar to that of an epoxy resin cured with an aromatic diamine. This behaviour could be attributed to PETMP/TEGDVE network homogeneity, or to the less constrained crosslinks in the PETMP/TEGDVE network. Copyright © 2007 Society of Chemical Industry 相似文献
65.
Patrick Mullen Yiying Tong Pierre Alliez Mathieu Desbrun 《Computer Graphics Forum》2008,27(5):1487-1494
We present a spectral approach to automatically and efficiently obtain discrete free‐boundary conformal parameterizations of triangle mesh patches, without the common artifacts due to positional constraints on vertices and without undue bias introduced by sampling irregularity. High‐quality parameterizations are computed through a constrained minimization of a discrete weighted conformal energy by finding the largest eigenvalue/eigenvector of a generalized eigenvalue problem involving sparse, symmetric matrices. We demonstrate that this novel and robust approach improves on previous linear techniques both quantitatively and qualitatively. 相似文献
66.
David Levinson Jean Michel Mathieu David Gillen Adib Kanafani 《The Annals of Regional Science》1997,31(2):189-215
This paper examines the full costs, defined as the sum of private and social costs, of a high-speed rail system proposed
for a corridor connecting Los Angeles and San Francisco in California. The full costs include infrastructure, fleet capital
and operating expenses, the time users spend on the system, and the social costs of externalities, such as noise, pollution,
and accidents. Comparing these full costs to those of other competing modes contributes to the evaluation of the feasibility
of high-speed rail in the corridor. The paper concludes that high-speed rail is significantly more costly than expanding existing
air service, and marginally more expensive than auto travel. This suggests that high-speed rail is better positioned to serve
shorter distance markets where it competes with auto travel than longer distance markets where it substitutes for air.
Received: May 1996 / Accepted in revised form: December 1996 相似文献
67.
The paper was aimed at modelling hydrodynamics in lab-scale polymer electrolyte fuel cells, more particularly in the distribution plates. Residence time distributions (RTD) were measured in a wide range of flow rates, using UV absorption of ozone injected as a tracer in the cell. The volume of the inlet and outlet systems, being of the order of the volume of the gas circuit machined in the distribution plates, was taken into account in calculations. Hydrodynamic behaviour of two flow patterns of the commercialised fuel cell investigated was successfully described using ideal reactor models. 相似文献
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