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971.
Odlyha M. Cohen N. S. Foster G. M. Aliev A. Verdonck E. Grandy D. 《Journal of Thermal Analysis and Calorimetry》2003,71(3):939-951
DMA and solid state 13C NMR techniques were used to measure historical parchment samples within the framework of the project (MAP) Micro Analysis
of Parchment (EC contract No. SMT4-96-2101) in collaboration with the School of Conservation in Copenhagen. DMA was used in
both thermal scan and creep modes. Thermal scans provided information on the transitions associated with the collagen polymer.
Microthermal analysis was also used to obtain information on the topography and thermal conductivity of sample areas of 100
μm. Localised heating enabled measurements of softening transitions in the sample. This behaviour is influenced by the chemical
composition of parchment. 13C NMR provided information on the carbon atoms associated with the polypeptide chains of the collagen
in parchment. The behaviour of samples immersed in water and measured in DMA creep mode was used to measure the shrinkage
behaviour of the parchment samples. The different but complementary techniques provided a means for characterising the physicochemical
state of parchment samples.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
972.
Summary A combination of high resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer has been used to
study the thermal decomposition of liebigite. Water is lost in two steps at 44 and 302°C. Two mass loss steps are observed
for carbon dioxide evolution at 456 and 686°C. The product of the thermal decomposition was found to be a mixture of CaUO4 and Ca3UO6. The thermal decomposition of liebigite was followed by hot-stage Raman spectroscopy. Two Raman bands are observed in the
50°C spectrum at 3504 and 3318 cm-1 and shift to higher wavenumbers upon thermal treatment; no intensity remains in the bands above 300°C. Three bands assigned
to the υ1 symmetric stretching modes of the (CO3)2- units are observed at 1094, 1087 and 1075 cm-1 in agreement with three structurally distinct (CO3)2- units. At 100°C, two bands are found at 1089 and 1078 cm-1. Thermogravimetric analysis is undertaken as dynamic experiment with a constant heating rate whereas the hot-stage Raman
spectroscopic experiment occurs as a staged experiment. Hot stage Raman spectroscopy supports the changes in molecular structure
of liebigite during the proposed stages of thermal decomposition as observed in the TG-MS experiment. 相似文献
973.
Bismuth as BiCl4− and BH4− ware successively retained in a column (150 mm × 4 mm, length × i.d.) packed with Amberlite IRA-410 (strong anion-exchange resin). This was followed by passage of an injected slug of hydrochloric acid resulting in bismuthine generation (BiH3). BiH3 was stripped from the eluent solution by the addition of a nitrogen flow and the bulk phases were separated in a gas–liquid separator. Finally, bismutine was atomized in a quartz tube for the subsequent detection of bismuth by atomic absorption spectrometry. Different halide complexes of bismuth (namely, BiBr4−, BiI4− and BiCl4−) were tested for its pre-concentration, being the chloride complexes which produced the best results. Therefore, a concentration of 0.3 mol l−1 of HCl was added to the samples and calibration solutions. A linear response was obtained between the detection limit (3σ) of 0.225 and 80 μg l−1. The R.S.D.% (n = 10) for a solution containing 50 μg l−1 of Bi was 0.85%. The tolerance of the system to interferences was evaluated by investigating the effect of the following ions: Cu2+, Co2+, Ni2+, Fe3+, Cd2+, Pb2+, Hg2+, Zn2+, and Mg2+. The most severe depression was caused by Hg2+, which at 60 mg l−1 caused a 5% depression on the signal. For the other cations, concentrations between 1000 and 10,000 mg l−1 could be tolerated. The system was applied to the determination of Bi in urine of patients under therapy with bismuth subcitrate. The recovery of spikes of 5 and 50 μg l−1 of Bi added to the samples prior to digestion with HNO3 and H2O2 was in satisfactory ranges from 95.0 to 101.0%. The concentrations of bismuth found in six selected samples using this procedure were in good agreement with those obtained by an alternative technique (ETAAS). Finally, the concentration of Bi determined in urine before and after 3 days of treatment were 1.94 ± 1.26 and 9.02 ± 5.82 μg l−1, respectively. 相似文献
974.
Walrand J Lengelé M Blanquet G 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(14):3299-3303
Using diode-laser spectroscopy, the intensities of 58 lines of the v(1) + v(1/2) - v(1/2) band and 36 lines of the 2v(1) - v(1) band of OCS have been measured. The corresponding band strengths S(0)(v) and the vibrational transition dipoles micro(v) have been derived through least squares fitting of these individual intensities. The band strengths values have been determined with a precision better than 2.5%. 相似文献
975.
The preparation of polymer microcapsules of well defined size in the range of 10–50 μm with different shell thickness to
core diameter ratios is described. An aerosol of monodisperse droplets of a homogeneous ternary liquid system which contained
a hydrophobic component and a hydrophilic component dissolved in a high-volatile mutual solvent, was produced by dispersing
with a vibrating-orifice aerosol generator. After the evaporation of the solvent in a nitrogen atmosphere the particles demix
and form a two-phase droplet of core-shell type. These droplets were illuminated with UV light and polymerized to highly monodisperse
microcapsules with a solid polymer shell and a liquid core. The properties of the resulting particles (size, size distribution,
shell thickness, shape and surface characteristics) were investigated by scanning electron microscopy, Raman spectroscopy
on single optically levitated particles, and confocal Raman micro spectroscopy. The microcapsules were highly monodisperse
and have spherical shape.
Received: 24 July 1996 Accepted: 29 August 1996 相似文献
976.
In this review, thin films of SiO2 on Mo(1 1 2) and MgO(1 0 0) on Mo(1 0 0) have been characterized using metastable impact electron and ultraviolet photoelectron spectroscopies (metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy). The electronic and chemical properties of the thin films are identical to those of the corresponding bulk oxides. For different prepared defective SiO2 surfaces, additional features are observed in the band-gap region. These features arise from vacancies or excess oxygen and are consistent with theoretical predictions of additional occupied states in the band-gap due to point defects. Extended defect sites on SiO2 and MgO are identified using MIES by a narrowing of the O(2p) features with a reduction in the density of extended defect sites. MIES of adsorbed Xe (MAX) is also used to estimate the density of extended defect sites. Furthermore, it is shown that CO is an appropriate probe molecule for estimating the defect density of MgO surfaces. Upon Ag exposure, the change in the work function of a low defect MgO(1 0 0) versus a high defect surface is markedly different. For a sputter-damaged MgO(1 0 0) surface, an initial decrease of the work function was found, implying that small Ag clusters on this surface are electron deficient. In contrast, for SiO2 no significant change of the work function upon Ag exposure with increasing defect density was observed. On MgO(1 0 0), the presence of defect sites markedly alter the electronic and chemical properties of supported Ag clusters. Such a strong influence of defect sites was not found for Ag clusters on SiO2. 相似文献
977.
The mechanism of photooxidation of phenothiazine in liquid and frozen (77 K) aqueous micellar solutions of the surfactant (sodium dodecyl sulfate) was studied by ESR. The main reaction of electrons formed by the photochemical oxidation of phenothiazine in a liquid micellar solution of the anionic surfactant is the reduction of molecular oxygen dissolved in the aqueous bulk phase. 10-Methylphenothiazine was used as a stable radical cation probe in a liquid solution. The influence of electrolytes on the photoionization yield in both frozen and liquid solutions of the surfactant was studied. 相似文献
978.
Investigation of the Interactions of β‐Peptides with DNA Duplexes by Circular Dichroism Spectroscopy
Kenji Namoto James Gardiner Thierry Kimmerlin Dieter Seebach 《Helvetica chimica acta》2006,89(12):3087-3103
The interaction of β‐peptides with the DNA duplexes of dA20dT20 and a GCN4‐binding CRE sequence was examined. To gauge the factors that govern these interactions, two β‐pentadecapeptides, 1 and 2 , a β‐dodecapeptide, 3 , three β‐decapeptides, 4 – 6 , three β‐heptapeptides, 7 – 9 , and β‐octaarginine 10 were designed and synthesized. The β‐peptides were conceived to adopt a β‐peptide 314 helix, in which the side chains at position i and i + 3 are aligned vertically along one side of the helix. The side chains of Lys, Asn, and Arg were positioned such that potential H‐bonding sites were created for a helical conformation to interact with the base pairs of DNA. CD Analysis showed that β‐peptides 1, 2 , and 10 interacted with dA20dT20. In addition, β‐peptides 1 and 2 showed significant interaction with a DNA‐duplex 20mer containing the ATF/CREB recognition sequence for the regulatory protein GCN4. It is impossible, at this stage of the investigation, to make a safe proposal about the actual nature of the interaction of the structures(s) of the complexes, the formation of which is suggested by the CD spectra reported herein. 相似文献
979.
980.
D. L. Lipilin A. M. Churakov Yu. A. Strelenko V. A. Tartakovsky 《Russian Chemical Bulletin》2007,56(8):1566-1568
Treatment of 2-(tert-butyl-NNO-azoxy)anilines with phosgene at 20 °C was proposed as a novel route to 1,2,4-benzotriazin-3(4H )-one 1-oxides. This method involves a new reaction, viz., an intramolecular interaction of the tert-butyl-NNO-azoxy group with a C-electrophile (leading to the formation of the N(2)—C(3) bond of the triazine ring) followed by elimination
of the tert-butyl group. Complete assignment of the signals in the 1H and 13C NMR spectra of the compounds obtained was performed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1507–1509, August, 2007. 相似文献