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991.
Transport in Porous Media - Magnetic pore fabrics (MPF) are an efficient way to characterize pore space anisotropy, i.e., the average pore shape and orientation. They are determined by impregnating... 相似文献
992.
XAS analysis of iron and palladium bonded to a polysaccharide produced anaerobically by a strain of Klebsiella oxytoca 下载免费PDF全文
Iztok Arčon Stefano Paganelli Oreste Piccolo Michele Gallo Katarina Vogel‐Mikuš Franco Baldi 《Journal of synchrotron radiation》2015,22(5):1215-1226
Klebsiella oxytoca BAS‐10 ferments citrate to acetic acid and CO2, and secretes a specific exopolysaccharide (EPS), which is able to bind different metallic species. These biomaterials may be used for different biotechnological purposes, including applications as innovative green biogenerated catalysts. In production of biogenerated Pd species, the Fe(III) as ferric citrate is added to anaerobic culture of K. oxytoca BAS‐10, in the presence of palladium species, to increase the EPS secretion and improve Pd‐EPS yield. In this process, bi‐metallic (FePd‐EPS) biomaterials were produced for the first time. The morphology of bi‐metallic EPS, and the chemical state of the two metals in the FePd‐EPS, are investigated by transmission electron microscopy, Fourier transform infra‐red spectroscopy, micro‐X‐ray fluorescence, and X‐ray absorption spectroscopy methods (XANES and EXAFS), and compared with mono‐metallic Pd‐EPS and Fe‐EPS complexes. Iron in FePd‐EPS is in the mineralized form of iron oxides/hydroxides, predominantly in the form of Fe3+, with a small amount of Fe2+ in the structure, most probably a mixture of different nano‐crystalline iron oxides and hydroxides, as in mono‐metallic Fe‐EPS. Palladium is found as Pd(0) in the form of metallic nanoparticles with face‐centred cubic structure in both bi‐metallic (FePd‐EPS) and mono‐metallic (Pd‐EPS) species. In bi‐metallic species, Pd and Fe nanoparticles agglomerate in larger clusters, but they remain spatially separated. The catalytic ability of bi‐metallic species (FePd‐EPS) in a hydrodechlorination reaction is improved in comparison with mono‐metallic Pd‐EPS. 相似文献
993.
994.
Michele Silvestri Lucia BertacchiniCaterina Durante Andrea MarchettiElisa Salvatore Marina Cocchi 《Analytica chimica acta》2013
A hierarchical data fusion approach has been developed proposing multivariate curve resolution (MCR) as a variable reduction tool. 相似文献
995.
Melvin R. Euerby William A. Gibbons Michele P. Learmonth 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4)
Abstract N-Phosphorylated guanidines (phosphagens,I), found in living tissue, act as high energy phosphate regulators of adenosine triphosphate. Vertebrates possess phosphocreatine (Ia) as their sole phosphagen whereas in invertebrates phosphoarginine (Ib) predominates. However, in certain non-parasitic helminths (Annelida), a novel class of phosphagens exists based on a phosphodiester structure (Ic) exemplified by phospholombricine (R′= CH2 CH(NH2)CO2H). 相似文献
996.
Annarita Baldan Hugo Ent Adriaan M. H. van der Veen Andrea Held Manuela Ulberth-Buchgraber Romeu J. Daroda Valnei S. da Cunha Stephen A. Wise Michele Schantz Paul J. Brewer Richard J. C. Brown Gavin O’Connor 《Accreditation and quality assurance》2013,18(1):19-28
There is an increasing demand to accurately measure the quality of biofuel products (e.g. biodiesel and bio-ethanol). This demand is driven in Europe by directives promoting the use of renewable sources of energy and worldwide by national and international legislation setting out quality requirements for these fuels. Until now, there has been no international consensus on the minimum technical specifications to ensure biofuel quality. Furthermore, it is unclear which reference materials and measurement techniques are needed to provide the quality assurance and quality control framework to underpin these legislative requirements. As part of the European Commission’s 7th Framework Programme, the BIOREMA project (REference MAterials for BIOfuel specifications) demonstrated the feasibility of preparing biodiesel and bio-ethanol reference materials with reference values traceable to the international system of units for a range of parameters at levels relevant to technical specifications. However, the project concluded also that further research is needed to improve the current measurement capabilities for some parameters. Within the BIOREMA project, two global interlaboratory comparisons were carried out, using the biodiesel and bio-ethanol test materials prepared during the feasibility stage of the project, as well as two biodiesel standard reference materials from the National Institute of Standards and Technology (NIST, USA). The exercises showed that the measurement capabilities of the field laboratories were in many cases satisfactory, whereas for other laboratories the availability and regular use of certified reference materials would likely enhance the measurement capabilities for many of the parameters studied. A general overview of the BIOREMA project is presented in this paper. The details of the production of the two types of BIOREMA reference materials, and the results of the interlaboratory comparison for the bio-ethanol and biodiesel study materials, are discussed in parts 2 and 3 of this series of papers. 相似文献
997.
Michele M. Schantz Gauthier Eppe Jean-François Focant Coreen Hamilton N. Alan Heckert Rebecca M. Heltsley Dale Hoover Jennifer M. Keller Stefan D. Leigh Donald G. Patterson Jr Adam L. Pintar Katherine E. Sharpless Andreas Sjödin Wayman E. Turner Stacy S. Vander Pol Stephen A. Wise 《Analytical and bioanalytical chemistry》2013,405(4):1203-1211
Four new Standard Reference Materials (SRMs) have been developed to assist in the quality assurance of chemical contaminant measurements required for human biomonitoring studies, SRM 1953 Organic Contaminants in Non-Fortified Human Milk, SRM 1954 Organic Contaminants in Fortified Human Milk, SRM 1957 Organic Contaminants in Non-Fortified Human Serum, and SRM 1958 Organic Contaminants in Fortified Human Serum. These materials were developed as part of a collaboration between the National Institute of Standards and Technology (NIST) and the Centers for Disease Control and Prevention (CDC) with both agencies contributing data used in the certification of mass fraction values for a wide range of organic contaminants including polychlorinated biphenyl (PCB) congeners, chlorinated pesticides, polybrominated diphenyl ether (PBDE) congeners, and polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) congeners. The certified mass fractions of the organic contaminants in unfortified samples, SRM 1953 and SRM 1957, ranged from 12 ng/kg to 2200 ng/kg with the exception of 4,4′-DDE in SRM 1953 at 7400 ng/kg with expanded uncertainties generally <14 %. This agreement suggests that there were no significant biases existing among the multiple methods used for analysis. Figure
Comparison of Concentrations of Selected Compounds in Human Serum and Human Milk Standard Reference Materials (SRMs) 相似文献
998.
Nicolò Mauro Amedea Manfredi Elisabetta Ranucci Patrizia Procacci Michele Laus Diego Antonioli Cristina Mantovani Valerio Magnaghi Paolo Ferruti 《Macromolecular bioscience》2013,13(3):332-347
This paper reports on the synthesis and physico‐chemical, mechanical, and biological characterization of two sets of poly(amidoamine) (PAA) hydrogels with potential as scaffolds for in vivo peripheral nerve regeneration. They are obtained by polyaddition of piperazine with N,N′‐methylenebis(acrylamide) or 1,4‐bis(acryloyl)piperazine with 1,2‐diaminoethane as cross‐linking agent and exhibit a combination of relevant properties, such as mechanical strength, biocompatibility, biodegradability, ability to induce adhesion and proliferation of Schwann cells (SCs) preserving their viability. Moreover, the most promising hydrogels, that is those deriving from 1,4‐bis(acryloyl)piperazine, allow the in vitro growth of the sensitive neurons of the dorsal root ganglia, thus getting around a critical point in the design of conduits for nerve regeneration.
999.
Riccardo Narizzano Fulvia Risso Alfredo Magherini Emanuele Magi Michele Giampieri Carla Devia Gloria Venturelli Eugenio Carlini 《Analytical and bioanalytical chemistry》2013,405(2-3):1115-1121
In the context of the entire analytical process, pre-treatment of soil samples is often inadequately considered although the reliability of the results is definitely compromised if the sample is not properly prepared. In this paper, the effect of drying conditions in soil sample pre-treatment on the determination of polycyclic aromatic hydrocarbons (PAHs) has been studied. A systematic approach has been adopted by varying soil type, drying temperatures and solvent polarity to highlight the effect on the analyte recovery; the relationship between PAH molecular structure and their evaporation process from soils is discussed. Experimental data demonstrate that, concerning temperature-assisted drying procedures, PAHs are divided in two distinct groups: PAHs lighter than pyrene, which are seriously affected by drying temperature; and heavier PAHs that can be considered as non-volatile compounds. For studies involving the analysis of lighter PAHs in environmental samples, working on as-received samples is necessary. 相似文献
1000.
Guangcai Xu Dr. Michele Crotti Dr. Thangavelu Saravanan Kim M. Kataja Prof. Dr. Gerrit J. Poelarends 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(26):10460-10464
Peroxygenases are heme-dependent enzymes that use peroxide-borne oxygen to catalyze a wide range of oxyfunctionalization reactions. Herein, we report the engineering of an unusual cofactor-independent peroxygenase based on a promiscuous tautomerase that accepts different hydroperoxides (t-BuOOH and H2O2) to accomplish enantiocomplementary epoxidations of various α,β-unsaturated aldehydes (citral and substituted cinnamaldehydes), providing access to both enantiomers of the corresponding α,β-epoxy-aldehydes. High conversions (up to 98 %), high enantioselectivity (up to 98 % ee), and good product yields (50–80 %) were achieved. The reactions likely proceed via a reactive enzyme-bound iminium ion intermediate, allowing tweaking of the enzyme's activity and selectivity by protein engineering. Our results underscore the potential of catalytic promiscuity for the engineering of new cofactor-independent oxidative enzymes. 相似文献