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991.
Panuwet P Nguyen JV Kuklenyik P Udunka SO Needham LL Barr DB 《Analytical and bioanalytical chemistry》2008,391(5):1931-1939
We have developed a method using on-line solid-phase extraction–high-performance liquid chromatography–tandem mass spectrometry
(SPE-HPLC-MS/MS) and isotope dilution quantification to measure atrazine and seven atrazine metabolites in urine. The metabolites
measured were hydroxyatrazine, diaminochloroatrazine, desisopropylatrazine, desethylatrazine, desethylatrazine mercapturate,
atrazine mercaturate and atrazine itself. Our method has good precision (relative standard deviations ranging from 4 to 20%
at 5, 10 and 50 ng/mL), extraction efficiencies of 67 to 102% at 5 and 25 ng/mL, relative recoveries of 87 to 112% at 5, 25,
50 and 100 ng/mL limits of detection (LOD) ranging from 0.03 to 2.80 ng/mL. The linear range of our method spans from the
analyte LOD to 100 ng/mL (40 ng/mL for atrazine and atrazine mercapturate) with R
2 values of greater than 0.999 and errors about the slope of less than 3%. Our method is rapid, cost-effective and suitable
for large-scale sample analyses and is easily adaptable to other biological matrices. More importantly, this method will allow
us to better assess human exposure to atrazine-related chemicals.
Figure A schematic representation showing the elution of the analytes from the solid-phase extraction cartridge onto the analytical
column for chromatographic separation prior to MS/MS analysis 相似文献
992.
We present herein the composition of bacterial communities occurring in ground chicken and the changes which arise in these
populations based upon nonselective partitioning by commercially-available Dynal anti-Salmonella and anti-E. coli O157 immunomagnetic beads (IMB). Our enumeration and colony selection protocol was based upon a 6 × 6 drop plate method (n = 18 for each 25-g sub-sampling) using a dilution which resulted in ca. 4–8 colonies per drop. An average of 82 ± 13 colonies
were selected from three 25-g ground chicken subsamplings per batch, each of which was repeated seasonally for one year. DNA
was extracted from each colony and the composition of Eubacteria in each of these harvests was determined by sequence-based
identification of 16S rDNA amplicons. The Gram-positive bacteria Brochothrix thermosphacta and Carnobacterium maltaromticum were the most commonly found organisms in both the total chicken wash (PBS) and in the IMB-bound (PBS-washed) fractions.
The remaining background organisms which also adhered to varying degrees to commercial IMBs were: Pseudomonas oleovorans, Acinetobacter lwoffi, Serratia spp., and one Rahnella spp. A large number of the organisms were also cladistically evaluated based on rDNA basepair disparities: all Brochothrices
were monophyletic; twelve different Pseudomonads were found along with eight Carnobacteria, seven Acinetobacteres, four Serratiae,
and two Rahnellae. Carnobacterium alone showed an IMB-based concentration enhancement (ca. two to sixfold).
Any reference to a brand or firm name does not constitute endorsement of the US Department of Agriculture over others of a
similar nature not mentioned 相似文献
993.
This paper gives lower estimates for the frequency modules of almost periodic solutions to equations of the form
, where A generates a strongly continuous semigroup in a Banach space
, F(t,x) is 2π-periodic in t and continuous in (t,x), and f is almost periodic. We show that the frequency module ℳ(u) of any almost periodic mild solution u of (*) and the frequency module ℳ(f) of f satisfy the estimate e
2π
iℳ(f)⊂e
2π
iℳ(u). If F is independent of t, then the estimate can be improved: ℳ(f)⊂ℳ(u). Applications to the nonexistence of quasi-periodic solutions are also given. 相似文献
994.
This paper deals with parallel predictor–corrector (PC) iteration methods based on collocation Runge–Kutta (RK) corrector methods with continuous output formulas for solving nonstiff initial-value problems (IVPs) for systems of first-order differential equations. At nth step, the continuous output formulas are used not only for predicting the stage values in the PC iteration methods but also for calculating the step values at (n+2)th step. In this case, the integration processes can be proceeded twostep-by-twostep. The resulting twostep-by-twostep (TBT) parallel-iterated RK-type (PIRK-type) methods with continuous output formulas (twostep-by-twostep PIRKC methods or TBTPIRKC methods) give us a faster integration process. Fixed stepsize applications of these TBTPIRKC methods to a few widely-used test problems reveal that the new PC methods are much more efficient when compared with the well-known parallel-iterated RK methods (PIRK methods), parallel-iterated RK-type PC methods with continuous output formulas (PIRKC methods) and sequential explicit RK codes DOPRI5 and DOP853 available from the literature. 相似文献
995.
Stoffelbach F Griffete N Bui C Charleux B 《Chemical communications (Cambridge, England)》2008,(39):4807-4809
This communication describes the first example of the efficient use of a simple amphiphilic molecule as both a surfactant and an initiator in the miniemulsion polymerization of methyl methacrylate under AGET and ARGET ATRP conditions. 相似文献
996.
Hollow, hexa-porphyrin prisms of two sizes were template-assembled and covalently locked, via cross-olefin metathesis, into permanent, torsionally rigid structures whose active sites (metal sites) can be both accessed and altered in a facile manner. 相似文献
997.
998.
999.
Karotsis G Jones LF Papaefstathiou GS Collins A Parsons S Nguyen TD Evangelisti M Brechin EK 《Dalton transactions (Cambridge, England : 2003)》2008,(36):4917-4925
We report the synthesis of a series of mixed valence Mn(II/IV) tetranuclear clusters [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(EtOH)(6)Br(2)]Br(2) (), [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(H(2)O)(2)Cl(4)].2EtOH.H(2)O (.2EtOH.H(2)O), [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(heedH(2))(2)](ClO(4))(4) (), [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(MeCN)(2)(H(2)O)(2)(bpy)(2)](ClO(4))(4) () and [Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(bpy)(2)Br(4)].2MeOH (.2MeOH). Clusters are constructed from the tripodal ligand N,N-bis(2-hydroxyethyl)ethylene diamine (heedH(2)) and represent rare examples of tetranuclear Mn clusters possessing the linear trans zig-zag topology, being the first Mn(II/IV) mixed-valent clusters of this type. The molecular clusters can then be used as building blocks in tandem with the (linear) linker dicyanamide ([N(CN)(2)](-), dca(-)) for the formation of a novel extended network {[Mn(II)(2)Mn(IV)(2)O(2)(heed)(2)(H(2)O)(2)(MeOH)(2)(dca)(2)]Br(2)}(n) (), which exhibits a rare form of the 2D herring bone topology. 相似文献
1000.
Ink detachment tests were carried out using a Couette device. During the test, the energy supplied to the operation of the device partially dissipated as heat. The fraction of energy dissipated increased with pulp consistency. The fraction of energy for peeling and pulling the ink from the printed samples were calculated. At 4% consistency, the energy for pulling was much higher than for peeling, while at higher consistencies, the peeling effect became more significant. The ink detachment was highly dependant on how the pulp interacted with the printed surface. This interaction was influenced by pulp consistency and the energy applied to the rotor of the Couette device. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献