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11.
We have studied the potential degradation of poly(lactic acid)-based fabrics treated with commercial softeners and stored under two sets of conditions for one year. Initial wet-processing caused a fall in molecular weight of about 28%, irrespective of after-treatment. Storage at 40 °C and 80% RH produced further degradation which, with few exceptions, was aggravated by the presence of softeners. Ultimately, all samples degraded beyond the point of commercial usefulness. No clear distinction could be made between the effects of softeners having differing compositions. In contrast, fabrics stored under milder conditions of 23 °C and 50% RH showed no significant time-dependent polymer degradation, irrespective of the treatment applied. There were slight changes in tensile properties and some evidence of physical structural effects having occurred, which we attribute to physical aging. However, we do not believe these to be so serious as to call into question the long-term viability of PLA-based textile products. 相似文献
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Ozan Unsalan Yusuf Erdogdu M. Tahir Gulluoglu 《Journal of Raman spectroscopy : JRS》2009,40(5):562-570
In this study, the experimental and theoretical results on the molecular structures of some flavonoid derivatives (Baicalein and Naringenin) are presented. The FT‐IR and FT‐Raman spectra of the compounds have been recorded together for the first time between 4000–400 cm−1 and 3500–5 cm−1 regions, respectively. The molecular geometry and vibrational wavenumbers of the compounds have been also calculated in their ground states by using ab initio HF and DFT/B3LYP functional with 6‐31G(d,p) basis set used in calculations. The calculations were utilized to the C1 symmetries of the molecules. All calculations were performed with Gaussian 98 software. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. Scale factors have been used in order to compare how the calculated and experimental data are in agreement. Theoretical infrared intensities were also reported. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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A. Ertoprak B. Cederwall C. Qi M. Doncel U. Jakobsson B. M. Nyakó G. Jaworski P. Davies G. de France I. Kuti D. R. Napoli R. Wadsworth S. S. Ghugre R. Raut B. Akkus H. Al Azri A. Algora G. de Angelis A. Atac T. Bäck A. Boso E. Clément D. M. Debenham Zs. Dombrádi S. Ertürk A. Gadea F. Ghazi Moradi A. Gottardo T. Hüyük E. Ideguchi H. Li C. Michelagnoli V. Modamio J. Nyberg M. Palacz C. M. Petrache F. Recchia M. Sandzelius M. Siciliano J. Timár J. J. Valiente-Dobón Z. G. Xiao 《The European Physical Journal A - Hadrons and Nuclei》2018,54(9):145
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Nuclear magnetic resonance (NMR) spectroscopy is one of the most important and powerful instrumental analytical techniques
for structural elucidation of unknown small and large (complex) isolated and synthesized compounds in organic and inorganic
chemistry. X-ray crystallography, neutron scattering (neutron diffraction), and NMR spectroscopy are the only suitable methods
for three-dimensional structure determination at atomic resolution. Moreover, these methods are complementary. However, by
means of NMR spectroscopy, reaction dynamics and interaction processes can also be investigated. Unfortunately, this technique
is very insensitive in comparison with other spectrometric (e.g., mass spectrometry) and spectroscopic (e.g., infrared spectroscopy)
methods. Mainly through the development of stronger magnets and more sensitive solenoidal microcoil flow probes, this drawback
has been successfully counteracted. Capillary NMR spectroscopy increases the mass-based sensitivity of the NMR spectroscopic
analysis up to 100-fold compared with conventional 5-mm NMR probes, and thus can be coupled online and off-line with other
microseparation and detection techniques. It offers not only higher sensitivity, but in many cases provides better quality
spectra than traditional methods. Owing to the immense number of compounds (e.g., of natural product extracts and compound
libraries) to be examined, single microcoil flow probe NMR spectroscopy will soon be far from being sufficiently effective
as a screening method. For this reason, an inevitable trend towards coupled microseparation–multiple microcoil flow probe
NMR techniques, which allow simultaneous online and off-line detection of several compounds, will occur. In this review we
describe the current status and possible future developments of single and multiple microcoil capillary flow probe NMR spectroscopy
and its application as a high-throughput tool for the analysis of a large number of mass-limited samples. The advantages and
drawbacks of different coupled microseparation–capillary NMR spectroscopy techniques, such as capillary high-performance liquid
chromatography–NMR spectroscopy, capillary electrophoresis–NMR spectroscopy, and capillary gas chromatography–NMR spectroscopy,
are discussed and demonstrated by specific applications. Another subject of discussion is the progress in parallel NMR detection
techniques. Furthermore, the applicability and mixing capability of tiny reactor systems, termed “microreactors” or “micromixers,”
implemented in NMR probes is demonstrated by carbamate- and imine-forming reactions. 相似文献
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The complex Ag(CN)[P(C7H7)3] is the first (and so far only) mononuclear 1:1 derivative of AgCN with a tertiary phosphane ligand. 相似文献
16.
Yusuf Erdogdu Ozan Unsalan M. Tahir Gulluoglu 《Journal of Raman spectroscopy : JRS》2010,41(7):820-828
In this study, experimental and theoretical vibrational spectral results of the molecular structures of 6,8‐dichloroflavone (6,8‐dcf) and 6,8‐dibromoflavone (6,8‐dbf) are presented. The FT‐IR and FT‐Raman spectra of the compounds have been recorded together between 4000 and 400 cm−1 and 3500–5 cm−1 regions, respectively. The molecular geometry and vibrational wavenumbers of 6,8‐dcf and 6,8‐dbf in their ground state have been calculated by using DFT/B3LYP functional, with 6‐31 + + G(d,p) basis set used in calculations. All calculations were performed with Gaussian03 software. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. Scale factors have been used in order to compare how the calculated and experimental data are in agreement. Theoretical infrared intensities are also reported. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
17.
We present a new local tomographic algorithm applicable to electron microscopy tomography. Our algorithm applies to the standard data acquisition method, single-axis tilting, as well as for more arbitrary acquisition methods. Using microlocal analysis we put the reconstructions in a mathematical context, explaining which singularities are stably visible from the limited data given by the data collection protocol in the electron microscope. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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We introduce a method for calculating the amount of deflection angle of light passing close to a massive object. It is based on Fermat’s principle. The varying refractive index of medium around the massive object is obtained from the Buckingham pi-theorem. 相似文献
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