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61.
Maria Cazacu Mihai Marcu Gheorghe I. Rusu 《Journal of organometallic chemistry》2004,689(19):3005-3011
New high complex polymeric structures containing metal chelate sequences alternating, through esteric bridges, with silane units were obtained. The azomethine of 2,4-dihydroxybenzaldehyde with 1,3-bis(aminopropyl)tetramethyldisiloxane has been synthesized and in situ complexed with copper (II), nickel (II), cobalt (II) and cadmium (II). The obtained bis-phenolic chelates were covalently inserted in polymeric linear structures by their polycondensation with bis(p-carboxyphenyl)diphenylsilane as a diacid chloride. The structures of the obtained polymers were confirmed by IR, UV, 1H NMR and elemental analysis. The characterization was made by TGA, DSC, solubility tests and GPC. The electrical conductivity of both chelate monomers and their polymers was investigated, all compounds showing typical semiconducting behaviors. 相似文献
62.
E. Culea I. Milea Maria Rusu Monica Culea 《Fresenius' Journal of Analytical Chemistry》1996,355(3-4):359-360
An optical spectroscopic investigation has been performed on some borate glasses containing 1mol% UF4, UO2 and UO3. The optical data confirm the presence of uranium ions in valence stages of +6, +5 and +4. The influence of the composition of the glass matrix and of the -irradiation on the redox equilibrium of uranium ions was discussed. 相似文献
63.
64.
V. V. Zalamai V. V. Ursaki I. M. Tiginyanu A. Burlacu E. V. Rusu C. Klingshirn J. Fallert J. Sartor H. Kalt 《Applied physics. B, Lasers and optics》2010,99(1-2):215-222
High optical quality, well end leg faceted ZnO microtetrapods with leg length between 1 and 12 μm have been grown by carbothermal chemical vapor deposition. Lasing with mode quality factors of 2500–3000 is demonstrated. The origin of laser resonator cavity is discussed as a function of the tetrapod size. It is shown that in big tetrapods with legs of 12 μm in length the laser emission lines are well explained by longitudinal Fabry–Pérot modes generated in cavities formed by individual tetrapod legs. The dispersion of the ZnO refractive index is experimentally determined from the position of lasing modes in the temperature interval from 10 to 300 K. It is shown that the lasing mode structure is seriously affected by the decrease of the tetrapod size. For a small tetrapod with a leg length of 1 μm, the lasing modes cannot be explained anymore by the formation of longitudinal Fabry–Pérot modes in separate tetrapod legs, and the generation of guided modes by multiple total internal reflections in single tetrapod legs or in pairs of legs should be taken into account. The correlations between the lasing threshold and the tetrapod size are discussed. 相似文献
65.
We generalize and improve several inequalities of the ?eby?ev-Grüss-type using least concave majorants of the moduli of continuity of the functions involved. Our focus is on normalized positive linear functionals. We discuss a problem posed by the two Gavreas and also give the solution of a stronger one. In a section about the non-multiplicativity of positive linear operators it is demonstrated that the previous use of second moments is not quite the right choice. This is documented in the case of the classical Hermite-Fejér and de La Vallée Poussin convolution operators. 相似文献
66.
C. B. Collins A. C. Rusu N. C. Zoita M. C. Iosif D. T. Camase F. Davanloo C. A. Ur I. I. Popescu J. M. Pouvesle R. Dussart V. I. Kirischuk N. V. Strilchuk F. J. Agee 《Hyperfine Interactions》2001,135(1-4):51-70
Because of the high density of energy storage and the large cross section for its release, nuclear spin isomers have attracted
considerable recent interest. The triggering of induced gamma emission from them has encouraged efforts to develop intense
sources of short-wavelength radiation. One of the more interesting examples is the 16+ 4-qp isomer of 178Hf which stores 2.445 MeV for a half-life of 31 years meaning that as a material, such isomeric 178Hf would store 1.3 GJ/g. Recently, a sample containing 6.3×1014 nuclei of the isomer of 178Hf was irradiated with X-ray pulses derived from a device operated at 15 mA to produce bremsstrahlung radiation with end point
energies set to values between 60 and 90 keV. Emission of gamma radiation from the sample was increased by 1–2% above the
quiescent value of spontaneous emission. Such an accelerated decay of the 178Hf isomer is consistent with an integrated cross section of 2.2×10−22 cm2 keV if the resonant absorption of the X-rays takes place below 20 keV as indicated by the use of selective absorbing filters
in the irradiating beam. The work reported here describes the current experimental focus and results recently obtained with
the use of coincident detection of emitted gamma photons by several detectors.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
67.
Radu‐Dan Rusu Mariana‐Dana Damaceanu Luminita Marin Maria Bruma 《Journal of polymer science. Part A, Polymer chemistry》2010,48(19):4230-4242
New copolyimides containing perylenediimide, oxadiazole and hexafluoroisopropylidene moieties were prepared by one‐step polycondensation reaction in solution at high temperature of aromatic diamines containing preformed oxadiazole ring with a mixture of a dianhydride having a perylene ring and another dianhydride with hexafluoroisopropylidene unit. The thermal stability and glass transition temperatures of these copolyimides were measured and compared with those of related polyimides. The solid polymers were also studied by polarized light microscopy and X‐ray diffraction which revealed a semicrystalline state consisting of face‐to‐face arranged columns of perylenediimide units. The film‐forming ability and properties of the resulting thin films were investigated by using atom force microscopy and scanning electron microscopy which showed that the films were organized into self‐assembled rod‐like structures. The UV‐Vis and photoluminescence properties in solution and in solid state were also investigated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4230–4242, 2010 相似文献
68.
Mariana‐Dana Damaceanu Radu‐Dan Rusu Alina Nicolescu Maria Bruma 《Journal of polymer science. Part A, Polymer chemistry》2011,49(4):893-906
New polyamides containing 1,3,4‐oxadiazole and naphthalene rings were prepared by low‐temperature solution polycondensation reaction of a new diamine containing preformed oxadiazole ring with various aromatic diacid chlorides. Elemental analysis, mass, infrared, and nuclear magnetic resonance spectroscopy were used to confirm the structure of the monomers and corresponding polymers. The thermal stability and glass transition temperatures of these poly(oxadiazole‐amide)s were measured and compared with those of related polymers. Their good solubility allows them to be processed in very thin films with smooth surfaces, without pinholes or cracks, when studied by atomic force microscopy. Upon irradiation with UV light the polymers showed photoluminescence maxima in the blue spectral range, both in solution and in solid state. Cyclic voltammetry (CV) was performed in order to obtain information about the electrochemical stability and reversibility of the redox processes of these polyamides. The highest occupied molecular orbital and the lowest unoccupied molecular orbital energy levels, and electrochemical and optical band gap values were calculated by using the results of CV and UV/vis, respectively, showing very good electron and hole injection and transport characteristics. These properties make the present polymers suitable for application in electroluminescent devices. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
69.
Claudia Gordin Christelle Delaite Sophie Bistac Anne-Sophie Schuller Daniela Rusu Mihai Rusu 《Polymer Testing》2009,28(4):446-451
Films composed of poly(vinyl chloride)/poly(?-caprolactone)/poly(?-caprolactone)-b-poly(dimethylsiloxane) [PVC/PCL/(PCL-b-PDMS)] blends were prepared by solvent casting from tetrahydrofuran. The PVC content was kept constant (60 wt %) while varying the PCL and PCL-b-PDMS contents, part of the PCL (0–20 wt %) in the PVC/PCL (60/40) blend being replaced with PCL-b-PDMS with different molecular weights of the PCL blocks. The prepared blends were investigated by infrared spectroscopy and contact angle measurements. FTIR analysis and contact angle measurements indicate that the PDMS blocks tend to migrate towards the surface and this migration is preferential to the side in contact with air. 相似文献
70.
N. M. Belomoina E. G. Bulycheva A. L. Rusanov R. D. Rusu M. D. Damaceanu M. Bruma 《Polymer Science Series B》2010,52(9-10):558-563
Polynaphthylimides containing 1,3,4-oxadiazole cycles in main chains of macromolecules are prepared via the interaction of isomeric 2,5-bis[(aminophenoxy)phenyl]-1,3,4-oxadiazoles with dianhydrides of naphthalene-1,4,5,8-tetracarboxylic acid and 1,3-bis(1,8-dicarboxynaphthoyl-4)benzene. These polymers are synthesized through high-temperature polycyclocondensation in N-methylpyrrolidone and molten phenol. The relationships between the solubility and thermal characteristics of polynaphthylimides and their structure are studied, and the optical properties of the polymers are estimated. 相似文献