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51.
52.
Juan Antonio Padilla-Sánchez Patricia Plaza-Bolaños Roberto Romero-González Antonia Garrido-Frenich José Luis Martínez Vidal 《Journal of chromatography. A》2010,1217(36):5724-5731
Due to the different physico-chemical properties of phenols, the development of a methodology for the simultaneous extraction and determination of phenolic compounds belonging to several families, such as chlorophenols (CPs), alkylphenols (APs), nitrophenols (NTPs) and cresols is difficult. This study shows the development and validation of a method for the analysis of 13 phenolic compounds (including CPs, APs, NTPs and cresols) in agricultural soils. For this purpose, a quick, easy, cheap, effective, rugged and safe (QuEChERS)-based procedure was developed, validated and applied to the analysis of real samples. A derivatization step prior to the final determination by gas chromatography (GC) coupled to a triple quadrupole analyzer operating in tandem mass spectrometry (QqQ-MS/MS) was performed by using acetic acid anhydride (AAA) and pyridine (Py). The optimized procedure was validated, obtaining average extraction recoveries in the range 69–103% (10 μg kg−1), 65–98% (50 μg kg−1), 76–112% (100 μg kg−1) and 76–112% (300 μg kg−1), with precision values (expressed as relative standard deviation, RSD) ≤ 22% (except for 4-chlorophenol) involving intra-day and inter-day studies. Furthermore, 15 real soil samples were analyzed by the proposed method in order to assess its applicability. Some phenolic compounds (e.g. 2,4,6-trichlorophenol or 4-tert-octylphenol) were found in the samples at trace levels (<10 μg kg−1). 相似文献
53.
Marcella Reale Antonia Patruno Maria A De Lutiis Mirko Pesce Mario Felaco Massimo Di Giannantonio Marta Di Nicola Alfredo Grilli 《BMC neuroscience》2011,12(1):13
Background
The exact cause of schizophrenia is not known, although several aetiological theories have been proposed for the disease, including developmental or neurodegenerative processes, neurotransmitter abnormalities, viral infection and immune dysfunction or autoimmune mechanisms. Growing evidence suggests that specific cytokines and chemokines play a role in signalling the brain to produce neurochemical, neuroendocrine, neuroimmune and behavioural changes. A relationship between inflammation and schizophrenia was supported by abnormal cytokines production, abnormal concentrations of cytokines and cytokine receptors in the blood and cerebrospinal fluid in schizophrenia. Since the neuropathology of schizophrenia has recently been reported to be closely associated with microglial activation we aimed to determined whether spontaneous or LPS-induced peripheral blood mononuclear cell chemokines and cytokines production is dysregulated in schizophrenic patients compared to healthy subjects. We enrolled 51 untreated first-episode schizophrenics (SC) and 40 healthy subjects (HC) and the levels of MCP-1, MIP-1α, IL-8, IL-18, IFN-γ and RANTES were determined by Elisa method in cell-free supernatants of PBMC cultures. 相似文献54.
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
55.
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
56.
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
57.
58.
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
59.
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
60.
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