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1.
R. Grac M. Pugnet J.H. Collet B. Lambert C. De Matos H. L'Haridon A. Le Corre J.O. White 《Superlattices and Microstructures》1997,22(4):505-509
We report new results on the diffraction properties of photoinduced gratings in InGaAs/InGaAsP MQW structures. The original feature of this device is that the QWs are enclosed in an asymmetric Fabry–Perot microcavity in order to increase the diffraction efficiency. We observe oscillations in the diffraction efficiency due to resonant effects in the microcavity. The experimental spectra are compared with theory. Diffraction efficiency at 1.55 μm attains a maximum value of 2.7% at a write beam fluence of 260 μ J cm−2, and then decreases at higher fluences. We explain this phenomenon by an absorption saturation at high excitation. 相似文献
2.
T. S. Martins J. R. Matos G. Vicentini P. C. Isolani 《Journal of Thermal Analysis and Calorimetry》2005,82(1):77-82
Summary Rare earth picrate (RE) complexes with L-lysine (Lys) were synthesized and characterized. Elemental analysis (CHN), EDTA titrations and thermogravimetry data suggest
a general formula RE(pic)3·2Lys·2H2O, where RE=La-Lu (without Pm) and Y, pic=picrate). IR spectra suggest that Lys is coordinated to the central ion through the nitrogen of the α-amino group. Parameters
obtained from the absorption spectrum of the Nd compound indicated that the metal-ligand bonds are essentially electrostatic.
Emission spectrum and biexponential behavior of the luminescence decay of the Eu compound suggest the existence of polymeric
species. Thermogravimetric/derivative thermogravimetric (TG/DTG) and differential scanning calorimetry (DSC) curves of all
complexes are very similar, with five events. The final products are the corresponding rare earth oxides and their X-ray diffraction
patterns are identical to the calcinated oxides.</o:p> 相似文献
3.
P. Miranda Jr. J. Zukerman-Schpector J. R. Matos M. F. Máduar E. M. Aricó M. Linardi L. B. Zinner G. Vicentini 《Journal of Thermal Analysis and Calorimetry》2004,75(2):577-582
The complexes [Ln(pic)3(DTSO)3] (Ln=La, Lu and Y; pic=picrate; DTSO=1,3-dithiane-1-oxide) were synthesized and characterized. Indirect structural determination by far infrared
spectroscopy is presented. Results from thermal decomposition of these complexes by TG/DTG and DSC techniques are reported.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
Franoise Arnaud-Neu Marie-Christine Almasio Bernard Spiess Marie-Jos Schwing-Weill Sally A. Sullivan Jean-Marie Lehn 《Helvetica chimica acta》1985,68(4):831-839
Nature and Stability of Some Metallic Complexes of Dinucleating Cryptands in Solution II. Polythiamacrotricycles and Related Monocyclic Subunits The stability constants of the Cu2+ and Ag+ complexes of the cylindrical macrotricycle 1a (1,7,13,19-tetraaza 4,16-dioxa 10,22,27,32-tetrathiatricyclo[17.5.5.5]tetratriacontane) have been determined by pH-metry, as well as those of the Cu2+, Co2+, Zn2+, Cd2+, Pb2+, and Ag+ complexes of the monocyclic subunit 2a (1,7-dimethyl-1,7-diaza 4,10-dithiacyclododecane), in aqueous solutions (NaClO4) at 25°. In the Cu(II) systems, equilibria were reached slowly, and the results established by pH-metry were confirmed by UV/VIS spectrophotometric studies. The tricycle 1a forms dinuclear cryptates with copper and silver, with overall stability constants log β210 (Cu2- 1a )4+ = 18.5, log β21-2 (Cu2- 1a (OH)2)2+ = 4.8, log β210(Ag2- 1a )2+ = 23.0. Ag+ also forms a mononuclear (Ag- 1a )+ complex, with log β110 = 13.1, but no mononuclear species were detected in the Cu- 1a system. The absorption spectra of the bis-Cu(II) complexes of 1a and 2a in aqueous medium, MeOH and propylene carbonate (PC) are given, as well as those, in MeOH and PC, of the bis-copper complexes of the related monocycles 3 and 4 (1,7-diaza-4,10,13-trithiacyclopentadecane and 1.10-diaza 4,7,13,16-tetrathiacyclooctadecane, respectively), and tricycle 5 with two benzyl groups in the lateral chains. The complexing properties of the polyoxa- and polythia macrotricycles (Parts I and II of this series) are compared to those of other bis-chelating ligands, the bicyclic bis-tren and the monocyclic bis-dien. 相似文献
5.
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7.
G. G. G. Oliveira H. G. Ferraz J. S. R. Matos 《Journal of Thermal Analysis and Calorimetry》2005,79(2):267-270
Summary Taking into account the problems of desertification and agricultural practices able to provide income to the population at the semi-arid region of North-East Brazil, this work presents the results of the chemical and thermal characterization by TG and DSC of the seed derivatives of Cnidoscolus quercifolius , hereinafter called faveleira, aiming at the application of these materials as an alternative of food source for animals and for the human population at this region. The faveleira seed derivatives present thermodynamic properties similar to the ones of other foods utilized for human use, as well as an acceptable calorific value. According to TG and DSC results, was verified that the faveleira derivatives presents good thermal and oxidative stabilities. 相似文献
8.
Supramolecular H-bonded assemblies of redox-active metallodendrimers and positive and unusual dendritic effects on the recognition of H2PO4- 总被引:1,自引:0,他引:1
The DSM polyamine dendrimers dend-DAB-(NH2)x of generations 1 (x = 4) to 4 (x = 32) form H-bonded dendritic assemblies with the phenol AB3 units p-HOC6H4C(CH2CHCH2)3 and p-HOC6H4C{(CH2)3SiCH2NHCOFc}3 (Fc = ferrocenyl), as shown by the shifts of the NH2 and OH signals giving a concentration-dependent common signal between 2.4 and 4.1 ppm in CDCl3. The supramolecular dendrimers efficiently recognize H2PO4- anions with positive and unusual dendritic effects upon electrochemical titration involving half-stoichiometry for G1, a sudden cyclovoltammetry wave change at the equivalent point, and a dramatic intensity decrease of the new wave. 相似文献
9.
This paper describes the use of a thin-layered dual-band electrochemical cell operating at flow conditions to determine dipyrone (sodium salt of 1-phenil-2,3-dimethyl-4-methylaminomethanesulfonate-5-pyrazolone) by reaction with electrogenerated iodine. The electrolytic cell consisted of two closely spaced gold electrodes, the upper stream electrode serving as the generator electrode and the downstream electrode working as the collector electrode. A linear dynamic range from 2 to 15 μmol l−1 dipyrone was obtained by using a sample volume of 100 μl, with a detection limit of 1.1 μmol l−1. Standard deviation (S.D.) of 3.4% for 20 repetitive injections of a 40 μmol l−1 dipyrone solution and sampling frequency of 90 h−1 were achieved. The results obtained with the thin-layered dual-band electrochemical cell for dipyrone determination in three different pharmaceutical samples compared well with those found by iodimetry with coulometrically generated iodine. 相似文献
10.
Quéméner B Cabrera Pino JC Ralet MC Bonnin E Thibault JF 《Journal of mass spectrometry : JMS》2003,38(6):641-648
Partially acetylated and methylated oligogalacturonides produced by enzymatic hydrolysis of sugar beet pectin were analysed by negative electrospray ionization ion trap mass spectrometry (ESI-ITMS). The (18)O labelling of the oligomer reducing end allowed the precise assignment of the fragments resulting from glycosidic bond and cross-ring cleavages. The collisional-induced dissociation of the C(i) and Z(j) fragment ions through sequential MS(n) experiments always displayed (0, 2)A-type cross-ring cleavage ions which were related to C(2)H(4)O(2) losses. These (0, 2)A ions appeared to be highly diagnostic ions allowing the precise location of the acetyl groups to the O-2 and/or O-3 of the acetylated galacturonic acid residues. 相似文献