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101.
We report on the investigation of thermal effects in high-repetition-rate pulsed optical parametric oscillators emitting in the mid-IR. We find that the thermal load induced by the nonresonant idler absorption plays a critical role in the emergence of thermally induced bistability. We then demonstrate a significant improvement of the conversion efficiency (more than 30%) when a proper axial temperature gradient is applied to the nonlinear crystal by use of a two-zone temperature-controlled oven. 相似文献
102.
Besson E Gue AM Sudor J Korri-Youssoufi H Jaffrezic N Tardy J 《Langmuir : the ACS journal of surfaces and colloids》2006,22(20):8346-8352
This work describes how selective patterning of hydrophobic and hydrophilic areas inside microchannels of microfluidic devices can be achieved by combining well-known chemical protocols and standard photolithography equipment (365 nm). Two techniques have been performed and compared. The first technique is based on the preparation of self-assembled monolayers of photocleavable organosilane and the second one on photoassisted grafting (365 nm) of self-assembled monolayers (SAMs) on a silicon or glass substrate. In the first case, we begin with monolayers carrying an o-nitrobenzyl function (hydrophobic area) that is photochemically cleaved, revealing a carboxylic acid group (hydrophilic area). The problem is that the energy necessary to cleave this monolayer is too high and the reaction time is more than 1 h with 50 mW/cm(2) irradiation flux. To overcome this practical disadvantage, we propose another approach that is based on the thiol-ene reaction with benzophenone as photoinitiator. In this approach, a monolayer of mercaptopropyltrimethoxysilane (MPTS) is prepared first. Subsequently, a hydrocarbon chain is photografted locally onto the thiol layer, forming a hydrophobic surface while the reminding unmodified thiol surface is oxidized into sulfonic acid (hydrophilic area). We demonstrated the feasibility of this approach and synthesized high-quality self-assembled monolayers by UV grafting with an irradiation time of 30 s at 365 nm (50 mW/cm(2)). The modified surfaces have been characterized by contact angle measurements, X-ray photoelectron spectroscopy (XPS), AFM, and multiple internal reflection infrared spectroscopy (MIR-FTIR). The difference in the contact angles on the hydrophilic and hydrophobic surfaces reached a remarkable 77 degrees. We have also demonstrated that this method is compatible with selective surface grafting inside microfluidic channels. 相似文献
103.
Rivasseau C Boisson AM Mongélard G Couram G Bastien O Bligny R 《Journal of chromatography. A》2006,1129(2):283-290
A fast, reliable capillary zone electrophoresis (CZE) method with indirect UV detection was optimized and validated to determine the main organic acids contained in plants. Citric, malic, succinic, oxalic, formic, fumaric, acetic acids, and phosphate were quantified. A rapid separation while keeping a good resolution was obtained by optimizing capillary length, separation voltage, electrolyte composition, and pH. Analyses were performed in a 30 cm uncoated fused-silica capillary (length to the detector window) in the co-electroosmotic mode with reversed electroosmotic flow and anodic detection using a -30 kV separation voltage. The pH 9.0 electrolyte contained 3 x 10(-4)mol/L tetradecyltrimethylammonium and 10(-2)mol/L trimellitate. Separation with baseline return was achieved in 100 s. Linearity, detection limits, repeatability, reproducibility, and recoveries were evaluated. Mean precision values of 0.2 and 3.4% for migration times and time-corrected peak areas, respectively, enabled accurate identification and quantification whether in standard solutions or in samples. Such performances were perfectly adapted to high-throughput routine determinations of organic acids in research or industry. Organic acids were assayed in different plant tissues and cells, including sycamore, arabidopsis, buttercup, and pea. Citrate and malate were the most abundant in all plants tested with concentrations reaching 18.9 and 22.3 micromol/g fresh matter, respectively. Cadmium effect on pea leaves metabolism was also assessed. 相似文献
104.
Binet C Bourrier D Dilhan M Estève D Ferrère S Garrigue JC Granier H Lattes A Gué AM Mauzac M Mingotaud AF 《Talanta》2006,69(3):757-762
Liquid crystalline thin films elastomers that are able to bind pesticides have been developed. The synthesis involves grafting mesogen and crosslinkable groups on a polysiloxane chain in the presence of a template molecule. The molecular imprinted material is obtained after thin film deposition, UV crosslinking and washing. Experiments of readsorption of pesticide are presented. Development of a multisensor platform based on thermal and capacitive sensors is described and tests of deposition of the polymer film are presented. 相似文献
105.
Harrison AM South DR Willett P Artymiuk PJ 《Journal of computer-aided molecular design》2003,17(8):537-549
We describe a graph theoretic method designed to perform efficient searches for substructural patterns in nucleic acid structural coordinate databases using a simplified vectorial representation. Two vectors represent each nucleic acid base and the relative positions of bases with respect to one another are described in terms of distances between the defined start and end points of the vectors on each base. These points comprise the nodes and the distances the edges of a graph, and a pattern search can then be performed using a subgraph isomorphism algorithm. The minimal representation was designed to facilitate searches for complex patterns but was first tested on simple, well-characterised arrangements of bases such as base pairs and GNRA-tetraloop receptor interactions. The method performed very well for these interaction types. A survey of side-by-side base interactions, of which the adenosine platform is the best known example, also locates examples of similar base rearrangements that we consider to be important in structural regulation. A number of examples were found, with GU platforms being particularly prevalent. A GC platform in the RNA of the Thermus thermophilus small ribosomal subunit is in an analogous position to an adenosine platform in other species. An unusual GG platform is also observed close to one of the substrate binding sites in Haloarcula marismortui large ribosomal subunit RNA. 相似文献
106.
Résumé Etant donnée {M
p
}
p0 une suite de réels strictement positifs, on considère la classe de CarlemanC{p!M
p
} (resp. BeurlingB{p!M
p
}) des fonctionsf indéfiniment dérivables sur
n
. SoitE un sous ensemble compact de
n
; on peut associer à la classeC{p!M
p
} (resp.B{p!M
p
}) la classe des jets de Whitney surE,C
E
{p!M
p
}, (resp.B
E
{p!M
p
}) et on a une application de restriction naturelle deC{p!M
p
} dansC
E
{p!M
p
} (resp.B{p!M
p
} dansB
E
{p!M
p
}).Dans ce travail, on donne des conditions sur deux suites {M
p
}
p0 et {M
p
}
p0 pour que l'on ait les inclusions suivantes ou Ceci est, en quelque sorte, une généralisation du problème de prolongement de Whitney.
相似文献
相似文献
107.
Béatrice Serckx-Poncin Anne-Marie Hesbain-Frisque Léon Ghosez 《Tetrahedron letters》1982,23(32):3261-3264
The α,β unsaturated hydrazone reacts regioselectivity with a wide range of dienophiles to give the corresponding [4+2] adducts. Reductive cleavage of the NN bond in the adducts gives tetrahydropyridines. 相似文献
108.
Darcos V Duréault A Taton D Gnanou Y Marchand P Caminade AM Majoral JP Destarac M Leising F 《Chemical communications (Cambridge, England)》2004,(18):2110-2111
A first generation phosphorus-containing dendrimer with twelve terminal benzyl dithiobenzoate functions was designed and subsequently used as a multifunctional agent to derive hybrid star copolymers consisting of a dendritic core surrounded by twelve polystyrene branches by reversible addition-fragmentation chain transfer (RAFT). 相似文献
109.
110.
The title compound, isolated from leaves, is a new alkyl-3-phthalide characterized by an acylated side chain. It has been identified by spectral analysis as [3-(1-β-D-glucosyloxy)-2-hydroxy]benzoyl 3-(3-phthalidyl)-propyl ester. 相似文献