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61.
Antonia Mielgo Dr. Irene Velilla Claudio Palomo Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(25):7496-7502
In the presence of p‐nitrobenzoic acid, the O‐nitroso aldol reaction of nitrosobenzene with enolisable aldehydes may be promoted by commercially available α,α‐diphenylprolinol trimethylsilyl ether. The reaction proceeds with good yields and essentially complete enantioselectivity, with catalyst loadings in the 5–10 mol % range. The resulting α‐oxyaldehyde adducts may be transformed in situ into α‐oxyimines, which provide 1,2‐amino alcohols upon treatment with Grignard reagents, in good overall yield (45–59 %) and with typical diastereomeric ratios ≥95:5. 相似文献
62.
Antonia Camacho Montserrat Montaña Isabel Vallés Ricard Devesa Raquel Céspedes-Sánchez Isabel Serrano 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(1):297-306
22 sludge samples were analyzed from three municipal wastewater treatment plants to assess both the occurrence and the temporal behavior of radioactivity during 8 sampling campaigns carried out over the period 2007–2009. As regards natural gamma emitters radionuclides from the natural 238U series (such as 234Th, 214Pb, 214Bi, 210Pb) and the 232Th series (such as 228Ac, 212Pb, 212Bi and 208Tl) and other natural gamma emitters such as 7Be, 210Pbu or 40K were measured. In the case of man-made radionuclides small amounts of 137Cs were found, while significant amounts of 131I were detected in some samples. Correlations were found between radionuclides with the same origin. No seasonal variation for the 238U and 232Th series was found in the studied period but 7Be and 210Pbu showed seasonal variation that was explained by the monthly rainfall. The internal and external hazard indices were calculated and the results indicate that the radiological characteristics of the sludge do not present a significant radiological risk and make them suitable for future applications. 相似文献
63.
Remedios Fernández-Fernández Juan Carlos López-Martínez Roberto Romero-González José Luis Martínez-Vidal María Isabel Alarcón Flores Antonia Garrido Frenich 《Chromatographia》2010,72(1-2):55-62
A rapid, reliable and sensitive method has been developed to determine malic and citric acid in fruits and vegetables. The methodology is based on simple extraction with an aqueous solution of ethanol (80% v/v) and subsequent chromatographic analysis by liquid chromatography coupled to mass spectrometry. Electrospray ionization in negative mode was used. The best response for citric and malic acid was provided by molecular ions [M?H]? at m/z 191 and 133 respectively. These ions were used for quantification, whereas other fragments were used as confirmation ions. Different variables involved in the separation and detection process, such as mobile phase, gradient profile and flow rate have been optimised. Linearity, repeatability, recovery and limits of quantification were evaluated. Good linearity was obtained up to 5,000 mg kg?1. Recovery ranged from 90.0 to 104.6%, repeatability (expressed as RSD) was <8% for tested matrices, and limits of quantification were equal or lower than 65 mg kg?1. Finally, the method was applied to the analysis of samples of orange, tomato and pepper. 相似文献
64.
65.
We compare two methods of calibrating the yaw response of hot-wire probes: (i) the assumption that an effective angle, independent
of the flow speed, can be deduced; (ii) the more general approach of determining the yaw response at a number of different
speeds. The first, simpler, approach is shown to give surprisingly reasonable results for the usual turbulence statistics,
even in high turbulence intensity flows. Some differences in the distribution of the inclination of the instantaneous velocity
vector are observed. There is no advantage in using thek
2 factor to allow for longitudinal cooling. 相似文献
66.
This paper considers the effect the Reynolds number has on a turbulent boundary layer that is subjected to concentrated suction, applied through a short porous wall strip. The response of the skin friction coefficient to suction is strongly modulated by the momentum thickness Reynolds number R 0. The magnitude and wavelength of the variation of the skin friction decrease as R 0 increases. Measurements clearly show that it is the combination of R 0 and the suction rate that controls the boundary layer response. Relaminarisation of the near-wall flow, which occurs just downstream of the suction strip when =5.5 and R 0=660, could not be achieved at higher Reynolds numbers. It is suggested that the ratio R 0/ should not exceed a (as yet undetermined) critical value if pseudo-relaminarisation is to occur. The mean velocity profiles differ from the undisturbed profile for all the values of R 0 and considered here. Although the redistribution of the turbulent kinetic energy among the normal Reynolds stresses is affected by , a variation in R 0 does not appear to alter the effect of on this redistribution. 相似文献
67.
Use is made of acoustic excitation to enhance the coherent vortical structures that form in both a plane jet and a passively modified plane jet. The Strouhal number for the preferred mode based on the nozzle height of the jet is found to be unaffected by the passive modification. The existence of the jet column mode of stable pairing in the excited plane jet is unambiguously confirmed. Measurements in the excited and modified plane jet show that the passive modification suppresses this mode. Finally, the work shows the existence of a new mode of stable pairing. Both time- and phase-averaged measurements are presented to examine this mode. 相似文献
68.
Measurements in grid turbulence with a three-component hot-wire vorticity probe are compared with results obtained from a direct numerical simulation of decaying homogeneous turbulence at a similar Reynolds number. There is adequate agreement for both spectra and probability density functions of all three vorticity fluctuations. This supports the treatment of the measured data, in particular the corrections that need to be applied for the finite spatial resolution of the probe. The comparison does, however, highlight some inaccuracies in the way the instantaneous dissipation rate fluctuations were obtained experimentally. 相似文献
69.
Dr. Hamed Shaykhalishahi Dr. Aziz Gauhar Michael M. Wördehoff Dr. Clara S. R. Grüning Antonia N. Klein Dr. Oliver Bannach Dr. Matthias Stoldt Prof. Dr. Dieter Willbold Prof. Dr. Torleif Härd Dr. Wolfgang Hoyer 《Angewandte Chemie (International ed. in English)》2015,54(30):8837-8840
Conversion of the intrinsically disordered protein α‐synuclein (α‐syn) into amyloid aggregates is a key process in Parkinson’s disease. The sequence region 35–59 contains β‐strand segments β1 and β2 of α‐syn amyloid fibril models and most disease‐related mutations. β1 and β2 frequently engage in transient interactions in monomeric α‐syn. The consequences of β1–β2 contacts are evaluated by disulfide engineering, biophysical techniques, and cell viability assays. The double‐cysteine mutant α‐synCC, with a disulfide linking β1 and β2, is aggregation‐incompetent and inhibits aggregation and toxicity of wild‐type α‐syn. We show that α‐syn delays the aggregation of amyloid‐β peptide and islet amyloid polypeptide involved in Alzheimer’s disease and type 2 diabetes, an effect enhanced in the α‐synCC mutant. Tertiary interactions in the β1–β2 region of α‐syn interfere with the nucleation of amyloid formation, suggesting promotion of such interactions as a potential therapeutic approach. 相似文献
70.
Christian Wenz Coral Barbas Ángeles López‐Gonzálvez Antonia Garcia Fernando Benavente Victoria Sanz‐Nebot Tim Blanc Gordon Freckleton Philip Britz‐McKibbin Meera Shanmuganathan Francois de l′Escaille Johann Far Rob Haselberg Sean Huang Carolin Huhn Martin Pattky David Michels Si Mou Feng Yang Christian Neusuess Nora Tromsdorf Edward E.K. Baidoo Jay D. Keasling SungAe Suhr Park 《Journal of separation science》2015,38(18):NA-NA
A collaborative study on the robustness and portability of a capillary electrophoresis‐mass spectrometry method for peptide mapping was performed by an international team, consisting of 13 independent laboratories from academia and industry. All participants used the same batch of samples, reagents and coated capillaries to run their assays, whereas they utilized the capillary electrophoresis‐mass spectrometry equipment available in their laboratories. The equipment used varied in model, type and instrument manufacturer. Furthermore, different types of sheath‐flow capillary electrophoresis–mass spectrometry interfaces were used. Migration time, peak height and peak area of ten representative target peptides of trypsin‐digested bovine serum albumin were determined by every laboratory on two consecutive days. The data were critically evaluated to identify outliers and final values for means, repeatability (precision within a laboratory) and reproducibility (precision between laboratories) were established. For relative migration time the repeatability was between 0.05 and 0.18% RSD and the reproducibility between 0.14 and 1.3% RSD. For relative peak area repeatability and reproducibility values obtained were 3–12 and 9–29% RSD, respectively. These results demonstrate that capillary electrophoresis‐mass spectrometry is robust enough to allow a method transfer across multiple laboratories and should promote a more widespread use of peptide mapping and other capillary electrophoresis‐mass spectrometry applications in biopharmaceutical analysis and related fields. 相似文献