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951.
Magen C Algarabel PA Morellon L Araújo JP Ritter C Ibarra MR Pereira AM Sousa JB 《Physical review letters》2006,96(16):167201
The onset of a Griffiths-like phase has been observed in Tb5Si2Ge2 (TC=110 K) by means of magnetic susceptibility and small-angle neutron scattering experiments. We show the growth of a ferromagnetic cluster system characterized by an inverse susceptibility exponent lower than unity at TC相似文献
952.
953.
The optical limiting performance of a water-soluble porphyrin derivative is shown to be improved when small-sized (400-nm-diameter) nonabsorbing polystyrene spheres are added to the solution. The optical limiting enhancement is attributed to absorption of diffusive photons that experience longer light pathways than ballistic photons. The effect is demonstrated for nanosecond laser excitation at 532 nm. 相似文献
954.
We develop a simple, but highly effective technique for evaluating three-meson couplings in the context of the3 P 0 quark-pair-creation model. The method combines the use of realistic, numerical wave-functions with the ease of amplitude calculation associated with the harmonic-oscillator basis. As a first application we discuss the properties of 1?? ‘strangeonium’ states between 1 and 2 GeV. 相似文献
955.
Jamie M. Messman Robson F. Storey 《Journal of polymer science. Part A, Polymer chemistry》2004,42(24):6238-6247
Polymerization rates were proportional to initial Sn(Oct)2 concentration at low [Sn(Oct)2]0/[PrOH]0 values, but began to level off at higher values. When [Sn(Oct)2]0/[PrOH]0 was significantly greater than unity, the opposite behavior occurred. Tin(II) alkoxide concentration became limited by the initial PrOH concentration and independent of initial Sn(Oct)2 concentration. Addition of 2‐ethylhexanoic acid caused polymerization rate retardation, without affecting molecular weight. A control polymerization was conducted in the absence of PrOH. The molecular weight of the resulting polymer was consistent with the measured water content (3.7 wt % by Karl Fisher titration) of the as‐received Sn(Oct)2. The polymerization rate in the absence of PrOH was slow, and this suggested that water is less efficient than an alcohol in creating polymerization‐active stannyl ether bonds. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6238–6247, 2004 相似文献
956.
Mössbauer spectroscopy and X-ray diffraction analysis indicate that the only iron compound present in the Ibitira meteorite is the pyroxene (Mg, Fe, Ca)2Si2O6 known as pigeonite [1]. The Mössbauer spectrum shows Fe2+ in the two different crystallographic sites, M1 and M2, and the population ratio Fe2+ (M1)/Fe2+ (M2) indicates a reasonable degree of cation order. Comparison between our results and results obtained from pyroxene shocked under controlled conditions in the laboratory [2] suggests that, the meteorite was subjected to a impact of low intensity. 相似文献
957.
Manual integration of the amino acid peaks from physiological samples produced by conventional anion exchange liquid chromatography is a time-consuming process. This paper describes a combined unit, consisting of an analog to digital converter and a personal computer, which was connected in parallel with the chart recorder and the analyser's 570 nm channel of the colorimeter. The computer was programmed to log the digitized data, detect the start, maximum and end of each chromatographic peak, calculate the area under the peak and its retention time and provide a printout of the results at the end of the elution program. The computer program successfully exploited the Trigg Tracking Signal as both a peak detection and as a moving baseline monitoring device. This approach proved to have an equivalent performance to the manual method for 17 out of the 19 amino acids normally quantitated in physiological samples. The automated detection and quantitation of arginine was unsatisfactory due to its characteristically low profile peak shape, and proline was not measured because the device was not connected to the 440 nm channel of the colorimeter. The automated system provided economic and analytically acceptable solutions to the problem of providing an online integrator versatile enough to be used with the 255 min long amino acid analysis of physiological fluids. 相似文献
958.
De Araújo Álvaro Alberto Santana Maria Helena Andrade 《Applied biochemistry and biotechnology》1996,57(1):543-550
Applied Biochemistry and Biotechnology - Immobilized cells ofAcetobacter sp. were used as a model system of aerobic cells to study the influence of gel particle density in fermentation carried out... 相似文献
959.
Kubová J Stresko V Bujdos M Matús P Medved' J 《Analytical and bioanalytical chemistry》2004,379(1):108-114
In this work, a multicommutated flow system incorporating a sol–gel optical sensor is proposed for direct spectrophotometric determination of Cu(II) in urine. The optical sensor was developed by physical entrapment of 4-(2-pyridylazo)resorcinol (PAR) in sol–gel thin films by means of a base-catalysed process. The immobilised PAR formed a red 2:1 complex with Cu(II) with maximum absorbance at 500 nm. Optical transduction was based on a dual-colour light-emitting diode (LED) (green/red) light source and a photodiode detector. The sensor had optimum response and good selectivity towards Cu(II) at pH 7.0 and its regeneration was accomplished with picolinic acid. Linear response was obtained for Cu(II) concentrations between 5.0 and 80.0 g L–1, with a detection limit of 3.0 g L–1 and sampling frequency of 14 samples h–1. Interference from foreign ions was studied at a 10:1 (w/w) ion:Cu(II) ratio. Results obtained from analysis of urine samples were in very good agreement with those obtained by inductively coupled plasma mass spectrometry (ICP–MS); there was no significant differences at a confidence level of 95%. 相似文献
960.