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151.
Cory A. Hawkins Ilya A. Shkrob Carol J. Mertz Mark L. Dietz Michael D. Kaminski 《Analytica chimica acta》2012
A method has been developed for the isolation of strontium from human urine for subsequent determination in sample volumes as low as 5–20 mL. This method involves the acidification of the sample using methanesulfonic acid and its decolorization using charcoal, treatment of the filtrate with Diphonix® resin, and subsequent concentration of strontium on Sr resin. Data from retention model simulations provided the initial conditions which were then optimized by actual column separations. Diphonix® resin was shown to be effective at removing alkali metal ions from the urine matrix under conditions that retain higher valence ions. The suggested processing method provides 99% recovery of Sr2+, a concentration factor of 50, and an expected per sample processing time of less than 1 h. 相似文献
152.
Putta M. Reddy Carol Viragh Ildiko M. Kovach 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1597-1600
Seven new aryl methyl g -ketophosphonate esters were synthesized. The hydrolytic rates of the compounds under physiological conditions were studied. Most of the compounds are effective inhibitors of acetylcholinesterase. The enzyme recovers on the 10-50 h time scale from its adducts with two of the inhibitors. 相似文献
153.
Darcy Fallaise Hannah Balkwill Tweedie Julie Konzuk Carol Cheyne E. Erin Mack James G. Longstaffe 《Magnetic resonance in chemistry : MRC》2019,57(2-3):93-100
Nonaqueous phase liquids (NAPLs) located at the surface of the water table and/or below the water table are often a significant source for groundwater contamination near current or former commercial/industrial facilities. Due to the complex and long history of many industrial sites, these NAPLs often contain a complex mixture of contaminants and as such can be difficult to fully characterize using conventional analytical methods. Remediation and risk assessment activities at sites containing NAPLs may, subsequently, be hindered as the contamination profile may not be fully understood. This paper demonstrates the application of bench-scale 1H nuclear magnetic resonance (NMR) spectroscopy as a practical tool to assist with the characterization of complex NAPLs. Here, a NAPL collected from a contaminated site situated near a former chemical manufacturing facility was analyzed using a combination of one-dimensional (1D) 1H NMR spectroscopy and two-dimensional (2D) 1H J-resolved spectroscopy (JRES). It is shown that 1D NMR experiments are useful in the rapid identification of the classes of compounds present, whereas 2D JRES NMR experiments are useful in identifying specific compounds. The use of benchtop NMR spectroscopy as a simple and cost effective tool to assist in the analysis of contaminated sites may help improve the practical characterization of many heavily contaminated sites and facilitate improved risk assessments and remedial strategies. 相似文献
154.
Dr. Leonhard H. Urner Katharina Goltsche Marleen Selent Dr. Idlir Liko Marc-Philip Schweder Prof. Carol V. Robinson Prof. Dr. Kevin Pagel Prof. Dr. Rainer Haag 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(7):2537-2542
Dendrons are an important class of macromolecules that can be used for a broad range of applications. Recent studies have indicated that mixtures of oligoglycerol detergent (OGD) regioisomers are superior to individual regioisomers for protein extraction. The origin of this phenomenon remains puzzling. Here we discuss the synthesis and characterization of dendritic oligoglycerol regioisomer mixtures and their implementation into detergents. We provide experimental benchmarks to support quality control after synthesis and investigate the unusual utility of OGD regioisomer mixtures for extracting large protein quantities from biological membranes. We anticipate that our findings will enable the development of mixed detergent platforms in the future. 相似文献
155.
Carol T. Zamfirescu 《Graphs and Combinatorics》2010,26(1):141-146
We answer an open question on planar non-hamiltonian bihomogeneously traceable digraphs without opposite arcs by constructing
an infinite family of such graphs. 相似文献
156.
157.
Carol O. Doucet 《International Journal of Mathematical Education in Science & Technology》2013,44(1):141-145
In this note, a simple and quick method is shown for reducing some trigonometric expressions by using a diagram called a ‘carousel’. These expressions can be reduced using other methods, such as: (i) reduction formulae for sum/difference of angles; and (ii) graph shifting techniques. 相似文献
158.
John Bowers Gillian Mould Carol Marshall 《The Journal of the Operational Research Society》2015,66(7):1212-1221
Many healthcare systems are being redesigned to deliver local care with more services within the community. Relocation may enhance access but other aspects of healthcare quality should also be considered, notably waiting times and equity of care. This study examined a musculoskeletal physiotherapy service using a discrete-event simulation with simple heuristics to model patient behaviour. This combination provided an effective mechanism for incorporating the individuality of the patients in the flows along the patient pathways, subject to the varying availabilities of key resources. In particular, it captured the feedback that is critical in system performance, especially where waiting times are important. The model recognised the heterogeneity of patient attitudes and demonstrated how the behaviour of a relatively small proportion can affect the experience of all patients. The study suggested that, with careful operational management, more care could be delivered locally while exploiting many of the benefits of a centralised service. 相似文献
159.
Reactions of hydride complexes of ruthenium(II) with hydride acceptors have been examined for Ru(terpy)(bpy)H(+), Ru(terpy)(dmb)H(+), and Ru(η(6)-C(6)Me(6))(bpy)(H)(+) in aqueous media at 25 °C (terpy = 2,2';6',2'-terpyridine, bpy = 2,2'-bipyridine, dmb = 4,4'-dimethyl-2,2'-bipyridine). The acceptors include CO(2), CO, CH(2)O, and H(3)O(+). CO reacts with Ru(terpy)(dmb)H(+) with a rate constant of 1.2 (0.2) × 10(1) M(-1) s(-1), but for Ru(η(6)-C(6)Me(6))(bpy)(H)(+), the reaction was very slow, k ≤ 0.1 M(-1) s(-1). Ru(terpy)(bpy)H(+) and Ru(η(6)-C(6)Me(6))(bpy)(H)(+) react with CH(2)O with rate constants of (6 ± 4) × 10(6) and 1.1 × 10(3) M(-1) s(-1), respectively. The reaction of Ru(η(6)-C(6)Me(6))(bpy)(H)(+) with acid exhibits straightforward, second-order kinetics, with the rate proportional to [Ru(η(6)-C(6)Me(6))(bpy)(H)(+)] and [H(3)O(+)] and k = 2.2 × 10(1) M(-1) s(-1) (μ = 0.1 M, Na(2)SO(4) medium). However, for the case of Ru(terpy)(bpy)H(+), the protonation step is very rapid, and only the formation of the product Ru(terpy)(bpy)(H(2)O)(2+) (presumably via a dihydrogen or dihydride complex) is observed with a k(obs) of ca. 4 s(-1). The hydricities of HCO(2)(-), HCO(-), and H(3)CO(-) in water are estimated as +1.48, -0.76, and +1.57 eV/molecule (+34, -17.5, +36 kcal/mol), respectively. Theoretical studies of the reactions with CO(2) reveal a "product-like" transition state with short C-H and long M-H distances. (Reactant) Ru-H stretched 0.68 ?; (product) C-H stretched only 0.04 ?. The role of water solvent was explored by including one, two, or three water molecules in the calculation. 相似文献
160.
Jardim IC Maldaner L Lourenço J Fioravanti LM Collins CH 《Journal of separation science》2010,33(19):2917-2929
At the present time, more complex analyses of apolar compounds with similar chemical structures or of polar compounds, especially basic ones, having diverse properties require more selective stationary phases having better stabilities. This paper describes several new stationary phases with directed selectivities that were prepared by immobilizing two different phenyl group-containing siloxanes and a trifluoropropyl-containing siloxane onto chromatographic silica and, in the case of the fluorinated siloxane, onto zirconized silica, using thermal treatment or microware radiation. The chromatographic properties and stabilities of these new phases were determined and several applications were evaluated. The phenyl-containing phases showed excellent characteristics related to the separation of several different types of aromatic compounds while the fluorinated phases, which present a more polar character, revealed selectivity for the separation of positional isomers as well as for a mixture of basic pharmaceuticals. Stability tests indicate that immobilization of the polysiloxanes increases column lifetimes by making the stationary phases less susceptible to dissolution, while the phases immobilized with microwave radiation were somewhat more stable than those immobilized by thermal treatments. 相似文献