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141.
Claudia Andreea Milea Elena Ienei Cristina Bogatu Anca Duţã 《Journal of Sol-Gel Science and Technology》2013,67(1):112-120
Porous alumina powders for solar thermal applications, prepared by sol–gel were comparatively investigated, starting from an organo-metallic precursor (aluminum isopropoxide) and an inorganic precursor (aluminum chloride hexahydrate). As morphology controlling agents, HCl and poly (ethylene glycol) were added in the precursor solutions. X-Ray Diffraction, Atomic Force Microscopy, Differential Scanning Calorimetry, Fourier Transform Infrared Spectra and UV–VIS-NIR spectroscopy were used to characterize the materials. The chemical composition, the phase structure and morphological properties are influenced by the additive type and by the heat treatment temperature. The results shows that optimized conditions lead to high quality matrix for solar-thermal absorbers, with absorptance in the visible region varying from 0.13 to 0.47 and low thermal emittance (εT = 0.02–0.09) in the infrared region of the solar spectrum. 相似文献
142.
Immobilized Laccase on a New Cryogel Carrier and Kinetics of Two Anthraquinone Derivatives Oxidation
Stanescu MD Sanislav A Ivanov RV Hirtopeanu A Lozinsky VI 《Applied biochemistry and biotechnology》2011,165(7-8):1789-1798
A coordinatively immobilized laccase was prepared using a new cryogel type carrier. The support has a wide-pore texture facilitating diffusion of different substrates to the enzyme reaction center. The biocatalyst proved to be efficient in decolorization of two anthraquinone derivatives, namely Acid Blue 62 and bromaminic acid. After 24 h over 80% of the two substrates have been oxidated. The kinetic data (K (m) and V (max)) for the oxidation of the two anthraquinone derivatives, with the free and immobilized enzyme, have been determined and compared. Other parameters, like k (cat) and the specificity constant have been calculated and analyzed. The influence of substrate properties (hydrophobicity, polarity, etc.) has been discussed. 相似文献
143.
Carmen Limban Alexandru V. Missir Ileana C. Chirita George M. Nitulescu Miron T. Caproiu Mariana C. Chifiriuc Anca M. Israil 《Chemical Papers》2011,65(1):60-69
New acylthiourea derivatives, 2-((4-ethylphenoxy)methyl)-N-(phenylcarbamothioyl)benzamides, were tested by qualitative and quantitative methods on various bacterial and fungal strains
and proved to be active at low concentrations against Gram-positive and Gram-negative bacteria as well as fungi. These compounds
were prepared by the reaction of 2-((4-ethylphenoxy)methyl)benzoyl isothiocyanate with various primary aromatic amines, and
were characterised by melting point and solubility. The structures were identified by elemental analysis, 1H and 13C NMR, and IR spectral data. The level of antimicrobial activity of the new 2-((4-ethylphenoxy)methyl)benzoylthiourea derivatives
was dependent on the type, number and position of the substituent on the phenyl group attached to thiourea nitrogen. The iodine
and nitro substituents favoured the antimicrobial activity against the Gram-negative bacterial strains, while the highest
inhibitory effect against Gram-positive and fungal strains was exhibited by compounds with electron-donating substituents
such as the methyl and ethyl groups. 相似文献
144.
Alpar Pöllnitz Vito Lippolis Massimiliano Arca Anca Silvestru 《Journal of organometallic chemistry》2011,696(15-16):2837-2844
Cleavage of the Se–Se bond in [2-(Et2NCH2)C6H4]2Se2 (1) with SO2Cl2 (1:1 molar ratio) yielded the organoselenium(II) chloride [2-(Et2NCH2)C6H4]SeCl (2). Treatment of 2 with excess of KX yielded the organoselenium(II) halides [2-(Et2NCH2)C6H4]SeX [X = Br (3), I (4)]. The new compounds 2–4 were characterized by solution NMR spectroscopy (1H, 13C, 77Se, 2D experiments). The solid-state molecular structures of 2, 2·HCl and 3 were established by single crystal X-ray diffraction. Distorted T-shaped coordination geometries of type (C,N)SeX (X = Cl, Br) and CSeCl2 were found for the neutral halides 2 and 3, and the zwitterionic species [2-{Et2N+(H)CH2}C6H4]SeCl2 ̄ (2·HCl), respectively. DFT calculations were performed on 2–4 and the related tellurium compounds [2-(Et2NCH2)C6H4]TeX [X = Cl (5), Br (6) and I (7)] in order to elucidate the bond nature and FT-Raman features of this class of organochalcogen(II) derivatives. 相似文献
145.
Ioana Moleavin Constanta Ibanescu Anca Hodorog-Rusu Ecaterina Peptu Florica Doroftei Nicolae Hurduc 《Central European Journal of Chemistry》2011,9(6):1117-1125
Amphiphilic macromolecular micelles are advantageous for drug delivery applications due to the decrease of side-effects, ease
of screening drugs against degradation, long-term stability, targeted delivery and control of the amount of the released drug.
A series of amphiphilic azo-polymers having a flexible or rigid main-chain were synthesized and characterized. The presence
of chlorobenzyl side-groups allowed both the easy bonding of photo-sensitive or hydrophilic groups and good control of the
degree of substitution. The chemical structure was confirmed by 1H-NMR. The critical concentration of aggregation (CCA) was calculated using the fluorescence emission spectrum of pyrene.
The interest was focused on a preliminary study concerning the disaggregation capacity of micelles under UV irradiation. The
presence of micellar aggregates was confirmed by DLS and SEM and different organization of the amphiphilic polymers was evidenced
depending on polymers concentration and polymers structure. In low polymer concentrations in water predominantly globular
aggregates were formed. The increase in concentration increased the polydispersity index due to the fusion of micelles and
formation of associates of globular aggregates, inter-micellar associates (clusters) and vesicles.
相似文献
146.
Fabio Bottari Giulia Moro Nick Sleegers Anca Florea Todd Cowen Sergey Piletsky Alexander L. N. van Nuijs Karolien De Wael 《Electroanalysis》2020,32(1):135-141
By combining molecular modelling and electrochemistry we envision the creation of modified electrodes tailored for a more sensitive and selective detection of a single analyte. In this study we report on a graphite screen printed electrode modified with electropolymerized o‐phenylenediamine, selected by rational design, which promotes the detection of nafcillin (NAF), an antibiotic. Parameters such as monomer concentration, pH and number of electropolymerization cycles were optimized to obtain the highest current signal for the target upon amperometric detection. NAF identification was based on the redox process at +1.1 V (vs pseudo Ag), ascribed to the oxidation of the C‐7 side chain. With the optimized modification protocol, a two‐fold increase in nafcillin signal could be obtained: the calibration plot in 0.1 M Britton‐Robinson buffer pH 4 showed a limit of detection of 80 nM with improved sensitivity and reproducibility (RSD<5 %) compared to the detection at non‐modified electrodes. 相似文献
147.
Raouia Ben Sadok Neculai Plugaru Anca Birsan Victor Kuncser Dalila Hammoutène 《International journal of quantum chemistry》2020,120(10):e26172
First-principles calculations within density functional theory were performed on a series of halide perovskite compounds ABX3(A: Cs or Rb; B:Pb or Sn). Their electronic structure, lattice dynamics, and dielectric properties were studied in relationship with the change in atom species at each one of the three inequivalent crystallographic sites, to explain the origin of these properties. Thus, the variation of the bandgap with the overlap between the B cation lone pair and the electronic states of halide atoms, as well as with the distortion of the BX6 octahedra network is discussed. It is shown that the vibrational modes, phonon frequencies, atomic displacements, and the possible ferroelectric instability in these compounds are dependent on masses of atoms, volume of AX12 polyhedron, as well as on streoactivity of Pb lone pair. Also, the Born effective charges, dielectric constant, spontaneous polarization, and infrared spectra are calculated. The relation between these dielectric properties and the ions dynamics is discussed. 相似文献
148.
Ratbay?Myrzakulov Diego?Sáez-GómezEmail author Anca?Tureanu 《General Relativity and Gravitation》2011,43(6):1671-1684
In the context of the so-called Gauss–Bonnet gravity, where the gravitational action includes function of the Gauss–Bonnet
invariant, we study cosmological solutions, especially the well-known ΛCDM model. It is shown that the dark energy contribution and even the inflationary epoch can be explained in the frame of
this kind of theories with no need of any other kind of component. Other cosmological solutions are constructed and the rich
properties that this kind of theories provide are explored. 相似文献
149.
We obtain explicit upper bounds for the number of irreducible factors for a class of compositions of polynomials in several
variables over a given field. In particular, some irreducibility criteria are given for this class of compositions of polynomials. 相似文献
150.
Molokanova O Bogdan A Vysotsky MO Bolte M Ikai T Okamoto Y Böhmer V 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(21):6157-6170
The exclusive formation of hydrogen-bonded dimers between tetraaryl and tetratosylurea calix[4]arenes has been used to prepare a series of ten "bisloop" tetraurea calix[4]arenes 3, in which adjacent phenylurea groups are covalently linked through alpha,omega-dioxyalkane chains. This dimerization with tetratosylurea 2 as template preorganizes the alkenyl residues of tetra(m-alkenyloxyphenyl) ureas 1 and enables their selective connection in high yield (up to 95 %) by olefin metathesis followed by hydrogenation. The "bisloop" calixarenes 3 also exclusively form heterodimers with 1. Thus, in a separated metathesis/hydrogenation sequence, a series of 14 cyclic bis[2]catenanes 4, in which two calix[4]arenes are connected through their wide rims by two pairs of interlocked rings (total size 29 to 41 atoms), were prepared in yields of up to 97 %. Optical resolution of these chiral bis[2]catenanes was studied by HPLC on chiral stationary phases. The single-crystal X-ray structure of one example (4(P,10)) confirmed the interlocking rings and revealed that the hydrogen-bonded dimeric capsule of the calix[4]arene can be "completely" opened. 相似文献