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排序方式: 共有109条查询结果,搜索用时 46 毫秒
61.
Eva Gallego Francisco Javier Roca José Francisco Perales Xavier Guardino Enrique Gadea 《International journal of environmental analytical chemistry》2015,95(4):291-311
An analytical method based on TD-GC/MS was developed and validated for the determination of volatile organic compounds (VOCs), including linear and cyclic volatile methylsiloxanes (VMSs), in biogas. Biogas was first sampled in Supel? Inert Film bags and subsequently dynamically sampled onto multisorbent bed tubes (Carbotrap, Carbopack X and Carboxen 569) using portable pump equipment. Two sample volumes, 100 and 250 ml, were evaluated. Desorption efficiency values for both volumes are in the range of 99–100% for almost all studied compounds while breakthrough values (%VOC on sample tube back section) are below 1% for most evaluated VOCs. However, acetaldehyde, carbon disulphide, ethanol and 1,3-butadiene have breakthrough values higher than 5%. Method detection limits were in the range of 0.01–0.8 ng per sample. The most abundant VOCs in biogas were terpenes with concentrations between 500 and 700 mg m?3. Other important families were ketones, aromatic hydrocarbons and alkanes, with concentrations in the range of 36–46 , 20–35 and 14–16 mg m?3, respectively. VMSs presented average concentrations of 4.9 ± 0.4 mg m?3. Additionally, the Supel? Inert Film bags were evaluated for stability for 4 days at room temperature. Although several VOC families’ concentrations in the bag increased or decreased significantly (t-test; p ≤ 0.01, n = 5) 2 days after collection, recoveries were around 70–130% for most studied VOCs. The results shown demonstrate that the presented methodology is reliable and satisfactory for the evaluation of VOCs in biogas and presents an alternative to the currently existing biogas analytical techniques. 相似文献
62.
León IR Neves-Ferreira AG Valente RH Mota EM Lenzi HL Perales J 《Journal of mass spectrometry : JMS》2007,42(6):781-792
Matrix-assisted laser desorption ionization (MALDI), Peptide Mass Fingerprinting (PMF) and MALDI-MS/MS ion search (using MASCOT) have become the preferred methods for high-throughput identification of proteins. Unfortunately, PMF can be ambiguous, mainly when the genome of the organism under investigation is unknown and the quality of spectra generated is poor and does not allow confident identification. The post-source decay (PSD) fragmentation of singly charged tryptic peptide ions generated by MALDI-TOF/TOF typically results in low fragmentation efficiency and/or complex spectra, including backbone fragmentation ions (series b and y), internal fragmentation etc. Interpreting these data either manually and/or using de novo sequencing software can frequently be a challenge. To overcome this limitation when studying the proteome of adult Angiostrongylus costaricensis, a nematode with unknown genome, we have used chemical N-terminal derivatization of the tryptic peptides with 4-sulfophenyl isothiocyanate (SPITC) prior to MALDI-TOF/TOF MS. This methodology has recently been reported to enhance the quality of MALDI-TOF/TOF-PSD data, allowing the obtainment of complete sequence of most of the peptides and thus facilitating de novo peptide sequencing. Our approach, consisting of SPITC derivatization along with manual spectra interpretation and Blast analysis, was able to positively identify 76% of analyzed samples, whereas MASCOT analysis of derivatized samples, MASCOT analysis of nonderivatized samples and PMF of nonderivatized samples yielded only 35, 41 and 12% positive identifications, respectively. Moreover, de novo sequencing of SPITC modified peptides resulted in protein sequences not available in NCBInr database paving the way to the discovery of new protein molecules. 相似文献
63.
Anna Avi?ó Sandra M. Ocampo Clara Caminal José Carlos Perales Ramon Eritja 《Molecular diversity》2009,13(3):287-293
Oligoribonucleotide conjugates carrying nuclear localization peptide sequences at the 3′-end were prepared stepwise on a single
support. The siRNA duplex carrying the nuclear localization peptide sequence at the 3′-end of the passenger strand has similar
inhibitory properties as those of unmodified or cholesterol-modified RNA duplexes. 相似文献
64.
65.
Homoallylic thioethers facilitate the platinum-catalyzed hydrosilylation of olefins with phenyldimethylsilane. As a control, thioether substrates are shown to hydrosilylate at room temperature under conditions where no hydrosilylation is observed for isosteric substrates that lacked thioether groups. Modest diastereoselection is observed, between 2 and 5 to 1. Hydrogenation is a competing reaction that becomes prominent for internal olefins. The internal diene 6a undergoes regioselective 1,2-hydrogenation of the double bond proximal to the homoallyl thioether moiety. 相似文献
66.
67.
Minimum volume stability limits for axisymmetric liquid bridges subject to steady axial acceleration
In this paper the influence of an axial microgravity on the minimum volume stability limit of axisymmetric liquid bridges between unequal disks is analyzed both theoretically and experimentally. The results here presented extend the knowledge of the static behaviour of liquid bridges to fluid configurations different from those studied up to now (almost equal disks). Experimental results, obtained by simulating microgravity conditions by the neutral buoyancy technique, are also presented and are shown to be in complete agreement with theoretical ones. 相似文献
68.
Arturo San Feliciano Alejandro F. Barrero Manuel Medarde Jose M.Miguel Del Corral Arrate Aramburu Aurea Perales Jose Fayos Francisco Sanchez-Ferrando 《Tetrahedron》1985,41(23):5711-5717
The application of X-ray diffraction methods has shown that the configurations of Asteriscunolides A and B at the Δ9 double bond are Z, rather than those previously proposed E, while the stereochemistries of Asteriscunolides C and D were correctly established. Some unexpected NMR data and the new assignment of the spectral signals, based on 2D-NMR correlations and NOE-difference experiments are reported. 相似文献
69.
J. Grucker J.-C. Karam F. Correia F. Perales G. Vassilev V. Bocvarski S. M. Chérif J. Baudon M. Ducloy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):467-474
Diffraction of thermal velocity metastable atoms by non-magnetic and
magnetic reflection gratings of micrometric period has been observed. This
observation is made possible by the use of an ultra narrow beam generated by
metastability exchange. Grazing incidence angles are exploited to minimise
the quenching of metastable atoms on the grating surface. Potential
applications are beam splitting, atom holography and probing of micro-sized
solid surfaces. 相似文献
70.
J. Grucker J. Baudon F. Perales G. Dutier V. Bocvarski J.-C. Karam G. Vassilev M. Ducloy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):427-431
Surface-induced exo-energetic inelastic transitions among atomic Zeeman
states in a magnetic field (“van der Waals – Zeeman” transitions) are
useable as tuneable beam splitters. A transversally coherent atom beam
impinging a pair of opposite surfaces (e.g. 2 edges of a slit or of an ensemble
of periodic slits) gives rise to two coherently diffracted wave packets.
Within the wave packet overlap, non-localised interference fringes of the
Young-slit type are predicted. From the diffraction pattern observed in the
Fraunhofer regime (Schlieren image), detailed information about the
transition amplitude on a scale of a few nanometers should be derived. 相似文献