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201.
Amel Ben Abda Fahmi Ben Hassen Juliette Leblond Moncef Mahjoub 《Mathematical and Computer Modelling》2009,49(11-12):2213-2223
We are concerned with an inverse problem related to sources detection from boundary data in a 2D medium with piecewise constant conductivity. It stands as a 2D version of the inverse problem of electroencephalography, where pointwise sources model epilepsy foci, with the so-called multi-layer spherical model of the head (scalp, skull, brain). When overdetermined electrical measurements (potential and current flux) are available on the scalp, one wants to recover the current sources (conductivity defaults) located in the brain (inner boundary). This recovery issue reduces to a number of inverse problems, where the sources identification process makes use of best rational approximation in the disk, whereas the preliminary cortical mapping step (Cauchy type issue) relies on best constrained harmonic or analytic approximation in an annulus (bounded extremal problems). 相似文献
202.
Reaction of 2,4-diketoesters 3a-c with aqueous formaldehyde using potassium carbonate solution as base affords the corresponding α-methylene-β-hydroxyalkanones 4a-c which provide a route to α,β-unsaturated alkyl ketones 6a-e via coupling of α-acetoxymethyl alkyl vinyl ketone 5a with Grignard reagents in the presence of a catalytic amount of LiCuBr2 at low temperature. 相似文献
203.
Bis(trimethylsilyl)-tert-butylaldimines 3 react with aldehydes in the presence of zinc bromide at room temperature to give, after hydrolysis, the desired α-alkyl α,β-ethylenic aldehydes in good yield and with very high E stereoselectivity. The reaction was believed to proceed via the α-silyl β-siloxyimines 4. 相似文献
204.
Naceur Hamdi Mustapha Saoud Antonio Romerosa Rached Ben Hassen 《Journal of heterocyclic chemistry》2008,45(6):1835-1842
The reactions between oligoethylene glycol diglycidyl ethers 2a‐c with both 7‐hydroxy‐4‐methyl‐2H‐chromen‐2‐one and 4‐hydroxy‐2H‐chromen‐2‐one lead to new hydroxy ethers 3 and 4 containing coumarin moieties in good yield. The synthesis of 3‐(3‐(dimethylamino)acryloyl)‐4‐hydroxy‐2H‐chromen‐2‐one 5 and new heterocyclic compounds 4‐hydroxy‐3‐(1H‐pyrazol‐3‐yl)‐2H‐chromen‐2‐one 6a , 4‐hydroxy‐3‐(1‐phenylpyrazol‐3‐yl)‐2H‐chromen‐2‐one 6b and 4‐hydroxy‐3‐(isoxazol‐3‐yl)‐2H‐chromen‐2‐one 6c is also described. All compounds were characterized by 1H NMR, 13C{1H} NMR, 2D‐1H‐13C HMBC, 2D‐1H NOESY NMR, IR, and MS spectroscopy. Additionally, the antibacterial activity of the new products containing coumarin moiety was evaluated. This activity is clearly dependent on the chemical structure of compounds. 相似文献
205.
206.
Jaafar H Vileno B Thibon A Mandon D 《Dalton transactions (Cambridge, England : 2003)》2011,40(1):92-106
We report that the oxygen sensitivity of some Fe(II) complexes with tripodal ligands can be used, with benefit, in the oxidation of cyclohexane under mild conditions. Depending on the solvent, two very different reaction pathways are involved, which share the coordination of O(2) to the metal as the common initial step. We have synthesized a series of α-chlorinated tripods in the tris(2-pyridylmethyl)amine series Cl(n)TPA (n = 1-3) and fully characterized the corresponding FeX(2) complexes (X = Cl, CF(3)SO(3)). The single-crystal X-ray structure analyses of the FeCl(2) complexes are reported. In CH(3)CN, the FeCl(2) complexes react smoothly with O(2), whereas the Fe(CF(3)SO(3))(2) complexes are non-sensitive. In CH(3)CN, the reaction of the oxygen-sensitive Cl(n)TPAFeCl(2) (n = 0-3) with O(2), acetic acid and zinc amalgam, in the presence of cyclohexane, affords a mixture of cyclohexanol/one in an ≈ ol/one ratio of 3.1 and a selectivity of the C3°/C2° in the adamantane conversion that is consistent with a metal-oxo based oxidation. Limited efficiency (≈ 2 TON) was observed for the parent TPAFeCl(2) complex and Cl(1)TPAFeCl(2), whereas both other complexes turned out to be poorly active. The TPAFeCl(2) complex was used to address mechanistic questions: when the reaction was carried out in pyridine, the ol/one ratio shifted to 0.15 while efficiency was improved by 7-fold. In pyridine and in the presence of a spin trap (DMPO), the radical-based character of the reaction was definitely established, by contrast with acetonitrile, where no oxygenated radicals were detected. Thus, the reactivity differences arise from involvement of two distinct active species. The dichotomous radical/biomimetic pathway is discussed to interpret these results. 相似文献
207.
Ismail Mukhlis M. Salman Odi N. Ali Thamir Hassen 《Journal of Solid State Electrochemistry》2021,25(8-9):2429-2441
Journal of Solid State Electrochemistry - Hydrothermally produced perovskite-type barium strontium titanate Ba0.8Sr0.2TiO3 (BST) nanorods deposited on TiO2 substrate for 2 h at... 相似文献
208.
Maqsood MARYAM Sang Loon TAN Karen Ann CROUSE Mohamed Ibrahim MOHAMED TAHIR Hui-Yee CHEE 《Turkish Journal of Chemistry》2020,44(5):1395
A series of Schiff bases have been successfully synthesized through the acid-catalyzed condensation of S-substituted dithiocarbazates and three enantiomerically pure monoterpenes, (1 R )-(+)-camphor, (1 S )-(-)-camphor, (1 R )-(-)-camphorquinone, (1 S )-(+)-camphorquinone, ( R )-(-)-carvone and ( S )-(+)-carvone. Spectroscopic results revealed that the Schiff bases containing camphor or carvone likely adopted an E -configuration along the characteristic imine bond while those containing camphorquinone assumed a Z -configuration. The antidengue potential of these compounds was evaluated based on DENV 2 caused cytopathic effect (CPE) reduction-based in vitro evaluation. The compounds were validated through secondary foci forming unit reduction assay (FFURA). Compounds were also tested for their cytotoxicity against Vero cells. The compounds showed variable degrees of antiviral activity with the camphor compounds displaying the highest antidengue potential. The enantiomers of the compounds behaved almost similarly during the antiviral evaluation. 相似文献
209.
210.
S. Hamdi S. Ouni H. Chaker J. Rohlicek R. Ben Hassen 《Journal of solid state chemistry》2011,184(11):2897-2901
A new compound DySr5Ni2.4Cu0.6O12−δ has been prepared by sol gel method and annealed at 1473 K in 1 atm of Ar gas flow. The X-ray diffraction (XRD) is used for phase identification. The sample shows to adopt the K2NiF4-type structure based on tolerance factor calculation. XRD analysis using the Rietveld method was carried out and it was found that DySr5Ni2.4Cu0.6O12−δ (Dy0.33Sr1.67Ni0.8Cu0.2O4−δ′) compound crystallizes in tetragonal symmetry with space group I4/mmm (Z=2). The lattice parameters are found to be at room temperature a=3.7696(5) Å and c=12.3747(2) Å. The final reliability indices were: RB=5.219% and χ2=3.47. Four probe electrical resistivity measurements were performed versus temperature in the range 294–579 K. A semiconducting behaviour over the whole range of temperature, with a conductivity maximum of 0.4 S cm−1 is observed at 510 K. 相似文献