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71.
Joseph P. Crisler Nelson T. Lao Lucia C. Tang Bartolome A. Serrano Alston Shields 《Microchemical Journal》1973,18(1):77-84
The analytical micromethod discussed here has been found to be very rapid, accurate, and relatively inexpensive for the determination of blood and urine leads. It has the distinct advantage in that a determination can be repeated. The sensitivity of the method is 1.37 × 10?10 g per 1% absorption at 283.3 nm. Our laboratories have analyzed 7353 specimens in duplicate or more from March 17, 1971 to April 30, 1972.Considering the many possible sources of contamination (the mobile unit being more so than a clinic) it is the Division of Chemistry's conclusion that an agreement of 84% is good and that a finger-stick method is feasible, and therefore, a complete micro-screening for blood lead is possible. 相似文献
72.
E. Serrano C. Piñ eiro J. M. Delgado 《Proceedings of the American Mathematical Society》2006,134(3):689-695
Let and be Banach spaces. We say that a set denotes the space of all compact operators from into ) is equicompact if there exists a null sequence in such that for all and all . It is easy to show that collectively compactness and equicompactness are dual concepts in the following sense: is equicompact iff is collectively compact. We study some properties of equicompact sets and, among other results, we prove: 1) a set is equicompact iff each bounded sequence in has a subsequence such that is a converging sequence uniformly for ; 2) if does not have finite cotype and is a maximal equicompact set, then, given and a finite set in , there is an operator such that for and all .
73.
Weissker HC Serrano J Huotari S Bruneval F Sottile F Monaco G Krisch M Olevano V Reining L 《Physical review letters》2006,97(23):237602
We present an investigation of the dynamic structure factor and of the dielectric function epsilonM(Q,omega) of the prototypical semiconductor silicon for finite momentum transfer, combining inelastic x-ray scattering experiments and ab initio calculations. In contrast with optical spectra, for finite momentum transfer time-dependent density-functional theory in the adiabatic local-density approximation together with lifetime broadening describes the physics of valence excitations correctly. Major structures in the spectra, governed by short-range crystal and exchange-correlation local-field effects, are strongly influenced by a mixing of transitions of positive and negative energies, in striking difference to spectra for vanishing momentum transfer. This mixing gives rise to a pronounced Fano asymmetry. 相似文献
74.
We develop a theoretical approach to percolation in random clustered networks. We find that, although clustering in scale-free networks can strongly affect some percolation properties, such as the size and the resilience of the giant connected component, it cannot restore a finite percolation threshold. In turn, this implies the absence of an epidemic threshold in this class of networks, thus extending this result to a wide variety of real scale-free networks which shows a high level of transitivity. Our findings are in good agreement with numerical simulations. 相似文献
75.
Alvarez Ruiz J Kivimäki A Stankiewicz M Melero García E Coreno M Ali S Koperski J Rachlew E Vall-Llosera I Serrano G Feyer V Tuckett R 《Physical chemistry chemical physics : PCCP》2006,8(44):5199-5206
The interaction of SF(5)CF(3) with vacuum-UV radiation has been investigated by photon induced fluorescence spectroscopy. Total fluorescence yield and dispersed fluorescence spectra of SF(5)CF(3) were recorded in the 200-1000 nm fluorescence window. In all cases, the fluorescence spectra resemble those of CF(3)X (X = H, F, Cl, and Br) molecules. At photon energies below 20 eV, the emission is attributed to the excited CF(3) and CF(2) fragments. The threshold for the CF(3) emission is 10.2 +/- 0.2 eV, giving an upper limit estimate for the SF(5)-CF(3) bond dissociation energy of 3.9 +/- 0.3 eV. The excitation functions of the CF(3) and CF(2) emissions were measured in the photon energy range 13.6-27.0 eV. The resonant structures observed in SF(5)CF(3) are attributed to electronic transitions from valence to Rydberg orbitals, following similar assignments in CF(3)X molecules. The photoabsorption spectrum of SF(5)CF(3) shows features at the same energies, indicating a strong contribution from Rydberg excitations. 相似文献
76.
77.
Alberto Castellón Serrano José Antonio Cuenca Mira Cándido Martín González 《代数通讯》2013,41(10):4699-4706
This work, jointly with [9], completes the structure theory and classification of the Jordan H *- triple systems. The problem of describing the Jordan H *-triple systems is reduced in [5] to that of describing the topologically simple ones. Ruling out the finite-dimensional case, we have that any of these H *-triples has an underlying triple system structure of quadratic type (and these can be fully described), or it is the H *-triple system associated to the odd part of a topologically simple Z2-graded Jordan H *-algebra, whose classification is given in [13]. 相似文献
78.
Carolina Castao Mariana P. Serrano Carolina Lorente Claudio D. Borsarelli Andrs H. Thomas 《Photochemistry and photobiology》2019,95(1):220-226
Unconjugated oxidized pterins accumulate in the skin of patients suffering from vitiligo and, under UVA irradiation, photosensitize the oxidation of amino acids. In this work, we study the interaction of the singlet and triplet excited states of pterin (Ptr), the parent compound of oxidized pterins, with four oxidizable amino acids: tryptophan (Trp), tyrosine (Tyr), histidine (His) and methionine (Met). Steady‐state and time‐resolved fluorescence measurements and laser flash photolysis experiments were performed to investigate the quenching of the Ptr excited states by the amino acids in aqueous solution. The singlet excited states of Ptr are quenched by Met mainly via a dynamic process and by Trp via a combination of dynamic and static processes. His does not quench singlet excited states of Ptr, and quenching by Tyr could not be investigated due to the low solubility of this amino acid. The triplet excited states of Ptr are quenched by the four studied amino acids, and the corresponding bimolecular quenching rate constants are in the range of diffusion controlled limit. The assessment of the results in the context of the Ptr‐photosensitization of amino acids suggests that triplet excited state of Ptr is the species that initiates the photochemical processes. 相似文献
79.
Javier S. Acevedo Cortez Thelma Serrano Lucy T. González Oxana V. Kharissova 《Journal of Dispersion Science and Technology》2019,40(6):884-891
Natural sorbent materials have practical advantages for the oil spill cleanup, whose advantages are their low-cost, feasibility for real-life applications and environmental adaptability. In this work, absorption capacity was determined for lyophilized aloe, nopal and agar and their composites with silica, Fe3O4/polysterene and multi-wall carbon nanotubes (MWCNTs). Freeze-drying was performed in order to preserve the structure and increase the internal volume of sorbents. The structures of lyophilized sorbents and composites were analyzed by scanning electron microscopy (SEM). SEM images for lyophilized sorbents show a tridimensional arrangement formed by plant-derived materials, which allows the oil absorption. The composites keep their tridimensional structure after freeze-drying and composite formation and exhibit coupling between both materials. Absorption capacity of aloe, nopal and agar are 9?g/g, 3?g/g, and 26?g/g, respectively without any pretreatment. Composites with Fe3O4/polysterene own capacities of 5.8?g/g, 2.8?g/g, and 14?g/g, respectively. Finally, for MWCNT composites, capacities are 7.8?g/g, 2.9?g/g and 23?g/g. A significant difference of adsorption capacity between lyophilized sorbents and composites is attributed to lyophilized materials absorbing oil, water and other compounds. Meanwhile, for composites the absorption is a more selective process, since the hydrophobization does not allow the absorption of water. 相似文献
80.
Dihydrogen Catalysis of the Reversible Formation and Cleavage of CH and NH Bonds of Aminopyridinate Ligands Bound to (η5‐C5Me5)IrIII 下载免费PDF全文
Dr. Ana Zamorano Dr. Nuria Rendón Dr. Joaquín López‐Serrano Dr. José E. V. Valpuesta Dr. Eleuterio Álvarez Prof. Dr. Ernesto Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2576-2587
This study focuses on a series of cationic complexes of iridium that contain aminopyridinate (Ap) ligands bound to an (η5‐C5Me5)IrIII fragment. The new complexes have the chemical composition [Ir(Ap)(η5‐C5Me5)]+, exist in the form of two isomers ( 1+ and 2+ ) and were isolated as salts of the BArF? anion (BArF=B[3,5‐(CF3)2C6H3]4). Four Ap ligands that differ in the nature of their bulky aryl substituents at the amido nitrogen atom and pyridinic ring were employed. In the presence of H2, the electrophilicity of the IrIII centre of these complexes allows for a reversible prototropic rearrangement that changes the nature and coordination mode of the aminopyridinate ligand between the well‐known κ2‐N,N′‐bidentate binding in 1+ and the unprecedented κ‐N,η3‐pseudo‐allyl‐coordination mode in isomers 2+ through activation of a benzylic C?H bond and formal proton transfer to the amido nitrogen atom. Experimental and computational studies evidence that the overall rearrangement, which entails reversible formation and cleavage of H?H, C?H and N?H bonds, is catalysed by dihydrogen under homogeneous conditions. 相似文献