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71.
We review our recent work in the implementation of optical single-sideband (OSSB) modulation and in the application of this modulation format to microwave photonics and optical testing systems. We have developed an enhanced OSSB modulator for wide-band operation, the so-called bidirectional OSSB modulator, and a simplification of this scheme for narrow-band applications. These OSSB modulators are based on the use of a standard single-electrode Mach-Zehnder electro-optic modulator (MZ-EOM) and passive fiber-optic components. In both designs, the OSSB operation is shown to be independent of the MZ-EOM bias. Therefore, the optical modulation depth at the output of the device can be enhanced using minimum transmission biasing to provide suppression of the optical carrier. Finally, we demonstrate the application of OSSB modulators to the improvement of microwave/millimeter-wave subcarrier multiplexing fiber-optic links and to narrow-band fiber radio systems. In addition, we analyzed the feasibility and the limitations of an optical vector network analysis technique based on OSSB modulation that can provide sub-picometer wavelength resolution. 相似文献
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73.
Pablo Jimnez Wolfgang K. Maser Pere Castell M. Teresa Martínez Ana M. Benito 《Macromolecular rapid communications》2009,30(6):418-422
Water dispersible nanofibrilar polyaniline (NF‐PANI) provides a novel and direct route towards carbon nanotube water dispersions of high concentration. Carrying out the chemical synthesis of NF‐PANI in the presence of carbon nanotubes (CNTs) results in an entirely nanostructured nanofibrilar polyaniline/carbon nanotube (NF‐PANI/CNT) composite material that contains well segregated CNTs partially coated by NF‐PANI. This new approach is simple, fast, and inexpensive, and enables the direct preparation of stable and homogeneous dispersions of the composites in water at concentrations up to 10 mg · mL−1, even for the highest CNT loadings of 50 wt.‐% without the participation of surfactants or stabilizers.
74.
Simplicio González-Montiel Benito Flores-Chávez José G. Alvarado-Rodríguez Noemí Andrade-López Juan Antonio Cogordan 《Polyhedron》2009
Treatment of Ph2PbCl2 with O(C6H4SH)2 (1a), S(C6H4SH)2 (2a) and S(C6H3SH)2O (3a) afforded the stable organolead compounds [{O(C6H4S)2}PbPh2] (1b), [{S(C6H4S)2}PbPh2] (2b) and [{S(C6H3S)2O}PbPh2] (3b). X-ray structure determinations of dithiolate-diphenyl lead compounds 1b–3b revealed that the trichalcogenated ligands are tridentate in 1b and 2b, and bidentate in 3b. The lead atom acts as an acceptor atom exhibiting weak intramolecular transannular interactions with the donor D atom, with tetrahedral distortions of 48% for 1b, 51% for 2b and 45% for 3b. The local geometry at the lead atom is described as monocapped tetrahedral. The crystal packing of title compounds is stabilized by several non-bonded interactions. 相似文献
75.
Benito Alcaide Prof. Dr. Pedro Almendros Dr. Teresa Martínez del Campo Elena Soriano Dr. José L. Marco‐Contelles Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(8):1909-1928
Calculating cyclization : Theoretical work directed towards the elucidation of the mechanisms of the gold‐, palladium‐, and lanthanum‐catalyzed oxycyclizations (5‐exo versus 6‐endo versus 7‐endo) of γ‐allenols has been pursued in close relationship with the experimental study (Part 1, accompanying paper) and has corroborated the bench results to provide a complete study of the reactivity of γ‐allenols under different metal‐catalyzed conditions.
76.
Iria González-Mariño José Benito QuintanaIsaac Rodríguez Rosario RodilJavier González-Peñas Rafael Cela 《Journal of chromatography. A》2009,1216(48):8435-8441
Recent studies have shown that amphetamines and other drugs of abuse residues occur in wastewater. Consequently, several methods have been developed for their determination by solid-phase extraction (SPE) and liquid chromatography–tandem mass spectrometry (LC–MS/MS). However, a major drawback of these methods is the lack of selectivity during SPE that results in reduced sensitivity, due to matrix effects, and in some cases in low precision and poor accuracy. In order to tackle this problem, three different SPE alternatives have been evaluated in this work for the determination of five amphetamines: common hydrophilic balance (Oasis HLB), mixed-mode (Oasis MCX) and molecularly imprinted polymers (MIPs) sorbents. Among them, Oasis HLB showed the worst performance, as three amphetamines (MDA, MDMA and MDEA) could not be determined because of interfering signals in the LC–MS/MS chromatogram, and amphetamine recoveries could not be corrected by the use of the deuterated analogue internal standard. Oasis MCX permitted the determination of all target analytes, but with still strong signal suppression: ca. 70% signal drop with wastewater samples, which could in this case be corrected by the internal standards providing acceptable trueness (overall recoveries: 101–137%), precision (RSD: 2.0–12%) and limits of detection (LOD: 1.5–4.4 ng/L). Alternatively, MIPs rendered cleaner extracts with less matrix effects (ca. 30% signal drop), and thus lower LODs (0.5–2.7 ng/L) and even better trueness (91–114% overall recovery) and precision (1.5–4.4%RSD). The final application of the method with MIP cartridges showed the presence of MDA and MDMA in the seven analysed wastewaters at the 4–20 ng/L level. 相似文献
77.
Villaverde-de-Sáa E Quintana JB Rodil R Ferrero-Refojos R Rubí E Cela R 《Analytical and bioanalytical chemistry》2012,402(1):509-518
Perfluorinated compounds (PFCs) have been used for over 40 years in different commercial and industrial applications mainly
as surfactants and surface protectors and have become an important class of marine emerging pollutants. This study presents
the development and validation of a new analytical method to determine the simultaneous presence of eight PFCs in different
kinds of mollusks using matrix solid-phase dispersion (MSPD) followed by liquid chromatography–tandem mass spectrometry (LC-MS/MS).
Simplicity of the analytical procedure, low volume of solvent and quantity of sample required, low global price, and integration
of extraction and clean-up into a single step, are the most important advantages of the developed methodology. Solvent, solid
support (dispersing agent), clean-up sorbent, and their amounts were optimized by means of an experimental design. In the
final method, 0.5 g of sample are dispersed with 0.2 g of diatomaceous earth and transferred into a polypropylene syringe
containing 4 g of silica as clean-up sorbent. Then, analytes are eluted with 20 mL of acetonitrile. The extract is finally
concentrated to a final volume of 0.5 mL in methanol, avoiding extract dryness in order to prevent evaporation losses and
injected in the LC-MS/MS. The combination of this MSPD protocol with LC-MS/MS afforded detection limits from 0.05 to 0.3 ng g−1. Also, a good linearity was established for the eight PFCs in the range from limit of quantification (LOQ) to 500 ng mL−1 with R
2 > 0.9917. The recovery of the method was studied with three types of spiked mollusk and was in the 64–126% range. Moreover,
a mussel sample was spiked and aged for more than 1 month and analyzed by the developed method and a reference method, ion-pair
extraction, for comparison, producing both methods statistically equal concentration values. The method was finally applied
to the determination of PFCs in different kinds of mollusks revealing concentrations up to 8.3 ng g−1 for perfluoroundecanoic acid. 相似文献
78.
I Ortea A Pascoal B Cañas JM Gallardo J Barros-Velázquez P Calo-Mata 《Electrophoresis》2012,33(15):2201-2211
Although seafood species identification has traditionally relied on morphological analysis, sometimes this is difficult to apply for the differentiation among penaeid shrimps owing to their phenotypic similarities and to the frequent removal of external carapace during processing. The objective of this review is to provide an updated and extensive overview on the molecular methods for shrimp and prawn species authentication, in which several omics approaches based on protein and DNA analysis are described. DNA-based methods include the amplification by PCR of different genes, commonly the mitochondrial 16S ribosomal RNA and cytochrome oxidase I genes. A recently described method based on RFLP coupled to PCR turned out to be particularly interesting for species differentiation and origin identification. Protein analysis methods for the characterization and detection of species-specific peptides are also summarized, emphasizing some novel proteomics-based approaches, such as phyloproteomics, peptide fragmentation, and species-specific peptide detection by HPLC coupled to multiple reaction monitoring (MRM) MS, the latter representing the fastest method described to date for species authentication in food. 相似文献
79.
Cover Picture: A Versatile Approach to CF3‐Containing 2‐Pyrrolidones by Tandem Michael Addition–Cyclization: Exemplification in the Synthesis of Amidine Class BACE1 Inhibitors (Chem. Eur. J. 33/2015) 下载免费PDF全文
80.