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排序方式: 共有91条查询结果,搜索用时 15 毫秒
11.
Mohammed Larbi Labbi 《Mathematische Nachrichten》2015,288(4):402-411
The Weitzenböck curvature operators are the curvature terms of order zero that appear in the well‐known classical Weitzenböck formula. In this paper, we use the formalism of double forms to prove a simple formula for these operators and to study their geometric properties. 相似文献
12.
Naima Bouyahia Mohamed Larbi Hamlaoui Mouna Hnaien Florence Lagarde Nicole Jaffrezic-Renault 《Bioelectrochemistry (Amsterdam, Netherlands)》2011,80(2):155-161
In this work, a new biosensor was prepared through immobilization of bovine liver catalase in a photoreticulated poly (vinyl alcohol) membrane at the surface of a conductometric transducer. This biosensor was used to study the kinetics of catalase–H202 reaction and its inhibition by cyanide. Immobilized catalase exhibited a Michaelis–Menten behaviour at low H202 concentrations (< 100 mM) with apparent constant KMapp = 84 ± 3 mM and maximal initial velocity VMapp = 13.4 μS min? 1. Inhibition by cyanide was found to be non-competitive and inhibition binding constant Ki was 13.9 ± 0.3 μM. The decrease of the biosensor response by increasing cyanide concentration was linear up to 50 μM, with a cyanide detection limit of 6 μM. In parallel, electrochemical characteristics of the catalase/PVA biomembrane and its interaction with cyanide were studied by cyclic voltammetry and impedance spectroscopy. Addition of the biomembrane onto the gold electrodes induced a significant increase of the interfacial polarization resistance RP. On the contrary, cyanide binding resulted in a decrease of Rp proportional to KCN concentration in the 4 to 50 μM range. Inhibition coefficient I50 calculated by this powerful label-free and substrate-free technique (24.3 μM) was in good agreement with that determined from the substrate-dependent conductometric biosensor (24.9 μM). 相似文献
13.
Hossini I Harrad MA Ait Ali M El Firdoussi L Karim A Valerga P Puerta MC 《Molecules (Basel, Switzerland)》2011,16(7):5886-5895
Friedel-Craft acylation at 100 °C of 2,5,9,9-tetramethyl-6,7,8,9-tetrahydro-5H-benzocycloheptene [ar-himachalene], a sesquiterpenic hydrocarbon obtained by catalytic dehydrogenation of α-, β- and γ-himachalenes, produces a mixture of two compounds: (3,5,5,9-tetramethyl-6,7,8,9-tetrahydro-5H-benzocyclohepten-2-yl)-ethanone (2, in 69% yield), with a conserved reactant backbone, and 3, with a different skeleton, in 21% yield. The crystal structure of 3 reveals it to be 1-(8-ethyl-8-hydroperoxy-3,5,5-trimethyl-5,6,7,8-tetrahydronaphthalen-2-yl)-ethanone. In this compound O-H…O bonds form dimers. These hydrogen-bonds, in conjunction with weaker C-H…O interactions, form a more extended supramolecular arrangement in the crystal. 相似文献
14.
Harrad MA Valerga P Puerta MC Houssini I Ali MA El Firdoussi L Karim A 《Molecules (Basel, Switzerland)》2011,16(1):367-372
A recyclable catalyst, Ni(0)-CMC-Na, composed of nickel colloids dispersed in a water soluble bioorganic polymer, sodium carboxymethylcellulose (CMC-Na), was synthesized by a simple procedure from readily available reagents. The catalyst thus obtained is stable and highly active in alkene hydrogenations. 相似文献
15.
Let X be a standard Markov process. We prove that a space inversion property of X implies the existence of a Kelvin transform of X‐harmonic, excessive and operator‐harmonic functions and that the inversion property is inherited by Doob h‐transforms. We determine new classes of processes having space inversion properties amongst transient processes satisfying the time inversion property. For these processes, some explicit inversions, which are often not the spherical ones, and excessive functions are given explicitly. We treat in details the examples of free scaled power Bessel processes, non‐colliding Bessel particles, Wishart processes, Gaussian Ensemble and Dyson Brownian Motion. 相似文献
16.
Belmesnaoui Aqzzouz Redouane Nouira Larbi Zraoula 《Proceedings of the American Mathematical Society》2006,134(4):1161-1165
Nous donnons des conditions nécessaires et suffisantes pour que tout opérateur de Dunford-Pettis positif sur un treillis de Banach, soit faiblement compact et nous déduisons quelques conséquences.
17.
Larbi Berrahmoune 《Journal of Mathematical Analysis and Applications》2010,372(2):645-655
We consider bilinear control systems of the form y′(t)=Ay(t)+u(t)By(t) where A generates a strongly continuous semigroup of contraction (etA)t?0 on an infinite-dimensional Hilbert space Y whose scalar product is denoted by 〈.,.〉. We suppose that this system is unbounded in the sense that the linear operator B is unbounded from the state Y into itself. Tacking into account eventual control saturation, we study the problem of stabilization by (possibly nonquadratic) feedback of the form u(t)=−f(〈By(t),y(t)〉). Applications to the heat equation is considered. 相似文献
18.
Asma Kaoukabi Larbi Belachemi Mohammed Lahcini Marie‐Claude Viaud Massuard Ccile Croix 《Journal of heterocyclic chemistry》2019,56(4):1260-1274
In an attempt to improve anticancer activity, a series of retinoids–chromene hybrids was described. The novel heterocyclic chromene–retinoids hybrid including oxygen as a heteroatom in a six‐membered cyclic ring (2H‐chromene or 2H‐1‐benzopyran) was designed and synthesized by introducing different groups such as an aromatic or styrylphenyl ring in 6‐position of 2H‐chromene. These novel compounds were synthesized by using the efficient cascades one‐pot process involving Wittig–Horner–Emmons reaction and Suzuki–Miyaura cross‐coupling pallado‐catalyzed reactions with 60% to 90% overall yields. These new compounds were tested against glioblastoma multiforme brain cancer, medulloblastoma, neuroblastoma cell lines, and breast cancer MCF‐7 cell lines. Two of them exhibited an appreciable anti‐tumor activity in the low micromolar range, which opens new perspectives for therapeutic application on humans. 相似文献
19.
Ayoub Abdelkader Mekkaoui Abderrazak Aberkouks Lahcen Fkhar Mustapha Ait Ali Larbi El Firdoussi Soufiane El Houssame 《应用有机金属化学》2020,34(11):e5917
Various ratios of palladium nanoparticles supported on mesoporous natural phosphate (Pd@NP) were prepared using the wetness impregnation method. The prepared catalysts were characterized by IR, XRD, CV, SEM, EDX, XRF, TEM and BET analysis. The reduction and preparation of the palladium nanoparticles afford a crystallite size of 10.88 nm. The performance of the synthesized catalyst was investigated in the solvent-free dehydroaromatization of α-, β- and γ-himachalene mixture from Cedrus atlantica oil as a model substrate. In order to achieve an efficient and selective catalysis, the catalytic dehydroaromatization of various terpenes such as limonene, limonaketone, carvone, carveol and perillyl alcohol was studied. The Pd@NP catalyst performed a high catalytic activity, selectivity and recyclability in the terpenes dehydroaromatization reaction. 相似文献
20.
Z. Lamari S. Landsberger J. Braisted H. Neggache R. Larbi 《Journal of Radioanalytical and Nuclear Chemistry》2008,276(1):95-99
Neutron activation analysis (INAA) has been applied to multielemental determination of eleven medicinal plants used to cure
the urinary tract diseases observed in Algeria. These plants include Androgena Citratus, Ceratonia Siliquata, Punica Granatum, Glyryrrhiza Glabra, Lausaunia Alba, Fragaria Vesca, Arbutus Unedol,
Hordeum Vulgaris, Papieteria Officinalis, Zea Mays L, and Davallia Seae. Concentrations of twenty elements Ba, Br, Ca, Cl, Co, Cu, Cr, Fe, I, Mn, Na, Mg, Rb, Sb, Se, Sc, Sr, Ti, V, and Zn have
been determined by short, and long irradiation times with a thermal and epithermal flux of 1.4·1012 n·cm−2·s−1 and 1.4·1011 n·cm−2·s−1, respectively. These analyses were performed in conjunction with Compton suppression. In almost herbs studied the Co, Cr,
Cu, Rb, Sb, Sc, Se and V are found to be present at trace levels, Br, Mn, and Zn at the minor level, and Ca, Cl, Fe, Mg and
Na are generally at the major level. The accuracy of the measurements has been evaluated by analyzing NIST-botanical references
materials. 相似文献