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1.
The self-organizing map (a neural network) was applied to the spectral pattern recognition of voice quality in 34 subjects: 15 patients operated on because of insufficient glottal closure and 19 subjects not treated for voice disorders. The voice samples, segments of sustained /a/, were perceptually rated by six experts. A self-organized acoustic feature map was first computed from tokens of /a/ and then used for the analysis of the samples. The locations of the samples on the map were determined and the distances from a normal reference were compared with the perceptual ratings. The map locations corresponded to the degree of audible disorder: the samples judged as normal were overlapping or close to the normal reference, whereas the samples judged as dysphonie were located further away from it. The comparison of pre- and postoperative samples of the patients showed that the perceived improvement of voice quality was also detected by the map. 相似文献
2.
Antibacterial activity of methylated chitosan and chitooligomer derivatives: Synthesis and structure activity relationships 总被引:1,自引:0,他引:1
Ögmundur Vidar Rúnarsson Tapio Nevalainen Tomi Järvinen Jón M. Einarsson Margrét Valdimarsdóttir 《European Polymer Journal》2007,43(6):2660-2671
The purpose of this study was to synthesize series of methylated chitosaccharide derivatives, possessing various degree of methylation, and to determine their structure activity relationship (SAR) with regard to their antibacterial effect against Staphylococcus aureus. Chitosan polymer and chitooligomers were used as starting materials and were methylated by reaction with methyl iodide. Depending on the reaction conditions the degree of N-quaternization ranged from 0% to 74%, with varying degree of N,N-dimethylation, N-monomethylation and O-methylation. More selective N-quaternization could be obtained with protection group strategy. At pH 5.5 the chitosaccharide polymers and their methylated derivatives were active against S. aureus with minimal inhibitory concentration (MIC) ranging from 16 to 512 μg/mL. At pH 7.2 the non-quaternized derivatives were inactive but their highly N-quaternized derivatives showed MIC as low as 8 μg/mL. The chitooligomers, as well as their derivatives, were inactive at both pH’s. The SAR studies revealed that N-quaternization was mainly responsible for the antibacterial effects at pH 7.2, whereas it did not contribute to the antibacterial activity under acidic conditions. 相似文献
3.
Huikko K Kotiaho T Kostiainen R 《Rapid communications in mass spectrometry : RCM》2002,16(16):1562-1568
This study was focused on examining the influence of gas flow parameters on capillary electrophoresis/mass spectrometry (CE /MS) performance using sheath-liquid CE /MS interfaces. The effects of nebulizing and drying gas velocity and drying gas temperature on CE separation and MS detection sensitivity were systematically determined. Nebulizing gas velocity was observed to be a critical parameter in the optimization of CE /MS method, since it affected both MS detection sensitivity, and also CE separation efficiency for one interface design tested. Better detection sensitivity was obtained when the nebulizing gas velocity was increased. However, high velocity of the nebulizing gas flow can cause a hydrodynamic bulk flow inside the CE capillary, thus clearly increasing the apparent mobility and decreasing the resolution obtained for the compounds studied. Increasing the drying gas velocity or temperature did not affect the apparent mobility or the separation efficiency and the temperature could be increased to achieve the optimal detection sensitivity in the CE /MS analysis. For comparison, the effects of nebulizing gas flow were studied using a different design of the coaxial sheath-liquid CE /MS interface, and in this case better detection sensitivity but no effect on CE separation efficiency was observed with increased nebulizing gas velocity. These different effects of nebulizing gas flow on the CE bulk flow were concluded to result from pressure differences at the tip of the CE capillaries for the different CE /MS interface arrangements. It is therefore recommended that the cross-sectional dimensions of the fused-silica and steel capillaries, and the gas streamlines, should be optimized when CE /MS interfaces are built. Moreover, the effect of gas flow on CE separation should be studied when optimizing the CE /MS operation parameters. 相似文献
4.
2, 3, 4-Trimethoxybenzaldehyde, -acetophenone and -benzoic acid give the corresponding 2, 3-dihydroxy-4-methoxy compounds in good yield on treatment with BCl3. 相似文献
5.
Dileep Kumar Kian-Eang Neo Malik Abdul Rub Ze Lene Tan Woan Lin Beh Hann Ling Wong 《Journal of Dispersion Science and Technology》2013,34(11):1657-1664
The present work is aimed at studying the interaction between copper-glycyltyrosine [(Cu(II)-Gly-Tyr)]+ and ninhydrin in water and in micelles formed by cetyltrimethylammonium bromide (CTAB) using spectrophometric measurements at 80°C and pH 5.0. The order of reaction remains the same in the two systems, that is, first- and fractional-order kinetics with respect to [Cu(II)-Gly-Tyr]+ and [ninhydrin], respectively, in the excess of ninhydrin over [Cu(II)-Gly-Tyr]+. It was observed that the product formed is same in both the media. The reaction is catalyzed by CTAB, and the maximum rate enhancement is about three fold. Quantitative kinetic analysis of kψ–[CTAB] data was explained in terms of pseudo-phase of the micelles (assuming the association/incorporation of both the reactants at the micellar surface). 相似文献
6.
Catalytic conversion of carbohydrates into value-added products and platform chemicals became a trend in recent years. Microwave activation used in the processes of carbohydrate conversion coupled with the proper choice of catalysts makes it possible to enhance dramatically the efficiency and sometimes the selectivity of catalysts. This mini-review presents a brief literature survey related to state-of-the-art methods developed recently by the world research community to solve the problem of rational conversion of carbohydrates, mostly produced from natural resources and wastes (forestry and agriculture wastes) including production of hydrogen, synthesis gas, furanics, and alcohols. The focus is made on microwave technologies used for processing carbohydrates. Of particular interest is the use of heterogeneous catalysts and hybrid materials in processing carbohydrates. 相似文献
7.
8.
Bernas A Kumar N Mäki-Arvela P Laine E Holmbom B Salmi T Murzin DY 《Chemical communications (Cambridge, England)》2002,(10):1142-1143
Development of a new heterogeneous catalytic pathway for isomerization of linoleic acid to conjugated linoleic acids at mild reaction conditions over Ni/H-MCM-41 in a soluted system. 相似文献
9.
We describe a novel single atom detector that uses the high electric field surrounding a charged single-walled carbon nanotube to attract and subsequently field-ionize neutral atoms. A theoretical study of the field-ionization tunneling rates for atomic trajectories in the attractive potential near a nanowire shows that a broadly applicable, high spatial resolution, low-power, neutral-atom detector with nearly 100% efficiency is realizable with present-day technology. Calculations also show that the system can provide the first opportunity to study quantized conductance phenomena when detecting cold neutral atoms with mean velocities less than 15 m/s. 相似文献
10.
Tolić-Nørrelykke IM Munteanu EL Thon G Oddershede L Berg-Sørensen K 《Physical review letters》2004,93(7):078102
The viscoelastic properties of the cytoplasm of living yeast cells were investigated by studying the motion of lipid granules naturally occurring in the cytoplasm. A large frequency range of observation was obtained by a combination of video-based and laser-based tracking methods. At time scales from 10(-4) to 10(2) s, the granules typically perform subdiffusive motion with characteristics different from previous measurements in living cells. This subdiffusive behavior is thought to be due to the presence of polymer networks and membranous structures in the cytoplasm. Consistent with this hypothesis, we observe that the motion becomes less subdiffusive upon actin disruption. 相似文献