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51.
Nguyen Thanh Long Pham Ngoc Dinh Alain 《Mathematical Methods in the Applied Sciences》1993,16(4):281-295
We study the following initial and boundary value problem: In section 1, with u0 in L2(Ω), f continuous such that f(u) + ? non-decreasing for ? positive, we prove the existence of a unique solution on (0,T), for each T > 0. In section 2 it is proved that the unique soluition u belongs to L2(0, T; H ∩ H2) ∩ L∞(0, T; H) if we assume u0 in H and f in C1(?,?). Numerical results are given for these two cases. 相似文献
52.
Max Robba Jean-Charles Lancelot Daniel Maume Alain Rabaron 《Journal of heterocyclic chemistry》1978,15(7):1159-1163
1,2,4-Triazino[4,5-b]indazol-1(2H)one and its derivatives were prepared by transposition of 3-[2-(-1,3,4-oxadiazolyl)]indazole or by ring closure of indazole ethoxymethylidenehydrazides. The synthesis of 1,2,3,4-tetrahydro-l,2,4-triazino[4,5-b]indazole-1,4-dione was achieved by cyclising the N-carbethoxyhydrazide of indazole-3-carboxylic acid and the synthesis of 1,2,4-triazino-[4,5-b]indazol-4(3H)one was made by cyclising the N-carbethoxy-hydrazone of indazole-3-carboxaldehyde. The Oxydation of 1,2,4-triazino[4,5-b]indazole-l(2H)thione gave 1,2,4-triazino-[4,5-b]indazoles. Nmr spectral data are reported. 相似文献
53.
The composition of the essential oil of Bifora radians, an aldehyde-producing weed, has been investigated by capillary gas chromatography, coupled gas chromatography – mass spectrometry, on-line catalytic hydrogenation and coupled gas chromatography – infrared spectrometry. The nineteen compounds identified included eighteen aldehydes: seven alkanals (C6, C9, C10, C11, C12, C13, and C14), ten alkenals, including five (E)-2-alkenals (C12, C13, C14, C15, and C16), and one (E,E)-2,4-alkadienal (C13). Typical Bifora odors were attributed to three major (E)-2-alkenals, C12, C13, and C14. 相似文献
54.
A successful application of microwave irradiation, in which phthalocyanines were synthesized under solventless conditions from 1,2-phthalonitrile or phthalic anhydride and urea in the presence of metal templates is described. It was found that in comparison with conventional heating, the microwave process is a very useful alternative for cyclotetramerization processes because of reduction of the reaction time, better yield, and easy-to-perform procedure. 相似文献
55.
Alain H. Roux Daniel Hétu Gérald Perron Jacques E. Desnoyers 《Journal of solution chemistry》1984,13(1):1-25
Mixed micelles can be formed in water between various pairs of hydrophobic solutes such as surfactants, alcohols and hydrocarbons. These systems can often be studied through the thermodynamic functions of transfer of one of the solutes, usually kept near infinite dilution, from water to an aqueous solution of the other solute. When mixed micelles are formed, these functions change significantly, and often go through extrema, in the region where the binary system micellizes or undergoes some microphase transition.Three main effects are responsible for the observed trends: pair-wise interactions between both solutes in the monomeric form, a distribution of the reference solute between the aqueous and micellar phases and a shift in the monomer-micelle equilibrium in the vicinity of the reference solute. Simple equations can be derived for these three effects which can account for the sign and magnitude of the observed trends using parameters which are derived for the most part from the two binary systems. 相似文献
56.
Weeber JC Finot E Legay G Cathelat A Lacroute Y Dereux A 《Langmuir : the ACS journal of surfaces and colloids》2004,20(23):10179-10185
We report on the near-field imaging of microstructured polymer layers deposited on an homogeneous metal thin film on which a surface plasmon mode is excited. The microstructures in the polymer layers are designed by electron beam lithography, and the near-field imaging is performed with a photon scanning tunneling microscope (PSTM). We show that, despite their very small height, the microstructures can be conveniently imaged with a PSTM thanks to the field enhancement at the surface of the metal thin film supporting the surface plasmon. The influence of the illumination conditions on the contrast of the PSTM images is discussed. In particular, we show that both the field enhancement and the near-field intensity distribution around the microstructures depend dramatically upon the illumination conditions, leading to the conclusion that the PSTM is well suited for spatially resolved near-field surface plasmon sensing purposes. 相似文献
57.
Klein E Nghiêm HO Valleix A Mioskowski C Lebeau L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(20):4649-4655
Thiamine (vitamin B1) is an essential nutritional factor metabolized inside the body in its mono-, di-, and triphosphate forms. Although the action of thiamine and thiamine diphosphate have been intensely investigated, many questions remain unanswered and the role of thiamine triphosphate is still especially unknown. To probe recent hypotheses on the implication of thiamine triphosphate in a new phosphorylation pathway involving synaptic proteins, we synthesized a series of thiamine di- and triphosphate analogues that are resistant to both enzymatic and chemical hydrolyses. The key step in the preparation of the title compounds is the coupling of thiamine propyl disulfide with adequately protected methylenebis-phosphonic acid, the corresponding triphosphate analogue, and difluoromethylenebisphosphonic acid. 相似文献
58.
Synthesis of Novel Types of C-Glycosyl-derivatives from Acetylenic Sugars or Partial Synthetic Equivalents thereof The concept of synthetic equivalent is not unequivocal and, for example, α-fluoroenamines may behave in some cases as synthetic equivalents of ynamines and, in other situations, quite differently. Some uses of these α-fluoroenamines, ‘partial synthetic equivalents’ of ynamines, for the synthesis of C-glycosyl derivatives of coumarins, chromones, quinolines, quinolones, thietenes and isoxazoles are described. We also report the preparation of a series of mono- and diglycosylthiophenes by reacting HS? with mono- and diglycosylbutadiynes. Acetylenic sugar derivatives have also been used for the synthesis of a diglycosylazaphosphorine and a spirooxolenone. 相似文献
59.
Vincent BailliezRenata M. de Figueiredo Alain OleskerJeannine Cleophax 《Tetrahedron letters》2003,44(51):9151-9153
The macrocyclic core of cycloviracin and glucolipsin has been synthesised in ten steps from levoglucosan and (S)-(−)-dimethyl malate. The limited number of steps to obtain this macrolide makes it a valuable procedure for the synthesis of analogues of cycloviracin and glucolipsin. 相似文献
60.
Oxygen can be determined in a perfluorotributylamine emulsion used as a blood substitute by coulometry and polarography. The oxygen uptake of the emulsion (4.3 × 10?3 mol l?1 or 11 ml-% at 25°C and PO2 = 760 mm Hg) is about three times greater than that of water. The adsorption of surfactant on a dropping mercury electrode changes the electrochemical parameters E, α and k3. The marked difference between the diffusion coefficients of oxygen and hydrogen peroxide (ratio 2.6) seems to be proceed from the ejection of oxygen molecules from the perfluorotributylamine droplets and from the insolubility of hydrogen peroxide molecules in the droplets. The constant rate of oxygen release by these droplets was estimated to be 104 s?1 by a stopped-flow spectrophotometric method. This constant rate seems to be linked with the particle diameter (0.2 μm) and the diffusion coefficient in the perfluorotributylamine droplets (1.6 × 10?6 cm2 s?1). 相似文献