An electrochemiluminescence-based competitive displacement immunoassay for the type-2 brevetoxins in oyster extracts

A new competitive electrochemiluminescence-based immunoassay for the type-2 brevetoxins in oyster extracts was developed. The assay was verified by spiking known amounts of PbTx-3 into 80% methanol extracts of Gulf Coast oysters. We also provide preliminary data demonstrating that 100% acetone extracts, aqueous homogenates, and the clinical matrixes urine and serum can also be analyzed without significant matrix interferences. The assay offers the advantages of speed ( 2 h analysis time); simplicity (only 2 additions, one incubation period, and no wash steps before analysis); low limit of quantitation (conservatively, 50 pg/mL = 1 ng/g tissue equivalents); and a stable, nonradioactive label. Due to the variety of brevetoxin metabolites present and the lack of certified reference standards for liquid chromatography-mass spectrometry confirmation, a true validation of brevetoxins in shellfish extracts is not possible at this time. However, our assay correlated well with another brevetoxin immunoassay currently in use in the United States. We believe this assay could be useful as a regulatory screening tool and could support pharmacokinetic studies in animals and clinical evaluation of neurotoxic shellfish poisoning victims.     

Synthesis,Structure, and Electrochemical Properties of Sterically Protected Molybdenum Trihydride Redox Pairs: A Paramagnetic “Stretched” Dihydrogen Complex?

Complexes [MoCp(#)(PMe(3))(2)H(3)] (Cp(#)=1,2,4-C(5)H(2)tBu(3), 2 a; C(5)HiPr(4), 2 b) have been synthesized from the corresponding compounds [MoCp(#)Cl(4)] (1 a, 1 b) and fully characterized, including by X-ray crystallography and by a neutron diffraction study for 2 a. Protonation of 2 a led to complex [Mo(1,2,4-C(5)H(2)tBu(3))(PMe(3))(2)H(4)](+) (3 a) in THF and to [Mo(1,2,4-C(5)H(2)tBu(3))(PMe(3))(2)(MeCN)H(2)](+) (4 a) in MeCN. Complex 4 b analogously derives from protonation of 2 b in MeCN, whereas the tetrahydride complex 3 b is unstable. One-electron oxidation of 2 a and 2 b by [FeCp(2)]PF(6) produces the EPR-active 17-electron complexes 2 a(+) and 2 b(+). The former is thermally more stable than the latter and could be crystallographically characterized as the PF(6) (-) salt by X-ray diffraction, providing evidence for the presence of a stretched dihydrogen ligand (H...H=1.36(6) angstroms). Controlled thermal decomposition of 2 a(+) yielded the product of H(2) elimination, the 15-electron monohydride complex [Mo(1,2,4-C(5)H(2)tBu(3))(PMe(3))(2)H]PF(6) (5 a), which was characterized by X-ray crystallography and by EPR spectroscopy at liquid He temperature. The compound establishes an equilibrium with the solvent adduct in THF. An electrochemical study by cyclic voltammetry provides further evidence for a rapid H(2) elimination process from the 17-electron complexes. In contrast to the previously investigated [MoCp*(dppe)H(3)](+) system (dppe=1,2-bis(diphenylphosphino)ethane; Cp*=pentamethylcyclopentadienyl), the decomposition of 2 a(+) by H(2) substitution with a solvent molecule appears to follow a dissociative pathway in MeCN.     

Genetic and phytochemical difference between some Indian and Italian plants of Withania somnifera (L.) Dunal

The geographical distribution of Withania somnifera (L.) Dunal is quite wide. However, in Italy, this species is very rare and grows spontaneously only in Sicily and in Sardinia. The PCR-RAPD technique has been utilized in this work to determine the genetic relationship among Sicilian, Sardinian and Indian samples and the HPLC analysis of whitaferin A was used as a marker to evaluate the phytochemical differences. The genetic difference between Indian and Sicilian plants of W. somnifera turned out to be smaller than that between Indian and Sardinian plants of this species. The phytochemical analysis as well showed that the Sardinian specimen strongly differed from the Indian and Sicilian ones in its contents of withaferin A. Our results seem to confirm the hypothesis that the Italian populations of this species may not be indigenous but naturalised. Due to the high withaferin A content of the Sardinian samples, these plants could be used as a source for pharmaceutical purposes.     

Experimental Evidence for the Superdeformation in 81Rb

High-spin states in ⁸¹Rb were populated in the ⁵⁵Mn(³⁰Si, 2p2n) reaction at 130 MeV. Prompt γγγ-charged particle coincidences were observed using the GASP spectrometer in conjunction with the ΔE-E silicon ball (ISIS). A superdeformed band consisting of seven γ-ray transitions has been identified. The dynamic moment of inertia for the band is constant with a value of approximately 26.7 h²/MeV throughout the whole observed rotational frequency. This band is interpreted to have a π5¹v5² intrinsic intruder configuration with a quadruple deformation β₂ of 0.51.     

79Kr高自旋超形变的观测

通过５５Ｍｎ（３０Ｓｉ,αｐｎ）反应布居了７９Ｋｒ的高自旋态．用ＧＡＳＰ阵列配以由４０个ΔＥ×ＥＳｉ（Ａｕ）望远镜所组成的带电粒子球实现γγγ－带电粒子符合测量．观测到由相对强度为（２．７±０．３）％的８条级联γ跃迁所组成的７９Ｋｒ高自旋超形变转动带．除了在转动频率ω＞０．９５ＭｅＶ处急剧下降外,该带的动力学转动惯量近乎常数（22ñ2／ＭｅＶ）并被解释为具有四极形变参数β２＝０．５１以及本征侵入组态为π５０ν５１． High-spinstates in 79Kr were populated via the fusion evaporation reaction 55Mn (30Si,αpn)at 130 MeV.Promptγ γγ charged particle coincidences were measured by using the GASP array in conjunction with the ΔE×E Si(Au) charged particle ball.Asu perdeformed band consisting of 8 γ ray transitions with an intensity of (2.7±0.3)% has been indentified in 79Kr.The dynamic moment of inertia for the band is nearly constant at approxately 22ñ2/MeV below arotational frequency of 0.95 MeV...     

Evolving timetabling heuristics using a grammar-based genetic programming hyper-heuristic framework

This paper introduces a Grammar-based Genetic Programming Hyper-Heuristic framework (GPHH) for evolving constructive heuristics for timetabling. In this application GP is used as an online learning method which evolves heuristics while solving the problem. In other words, the system keeps on evolving heuristics for a problem instance until a good solution is found. The framework is tested on some of the most widely used benchmarks in the field of exam timetabling and compared with the best state-of-the-art approaches. Results show that the framework is very competitive with other constructive techniques, and did outperform other hyper-heuristic frameworks on many occasions.     

Dihydrogen to dihydride isomerization mechanism in [(C5Me5)FeH2(Ph2PCH2CH2PPh2)]+ through the experimental and theoretical analysis of kinetic isotope effects

The isomerization of complex [Cp*Fe(dppe)(eta2-H2)]+, generated in situ by low-temperature protonation of Cp*Fe(dppe)H with either HBF4 or CF3COOH, to the dihydride tautomer trans-[Cp*Fe(dppe)(H)2]+ is irreversible and follows first-order kinetics in the -10 to +15 degrees C range with Delta H double dagger = 21.6 +/- 0.8 kcal mol(-1) and DeltaS double dagger = 5 +/- 3 eu. The isomerization rate constant is essentially independent of the nature and quantity of a strong acid. Density functional theory (DFT) calculations on various models, including the complete system at both the quantum mechanics/molecular mechanics (QM/MM) and full QM levels, probe the relative importance of steric and electronic effects for the relative stability of the nonclassical and classical isomers and identify two likely isomerization mechanisms: a "direct" pathway involving simultaneous H-H bond breaking and cis-trans isomerization and a "via Cp" pathway involving agostic C5Me5H intermediates. Both pathways are characterized by activation energies in close correspondence with the experimental value (21.3 and 22.2 kcal mol(-1), respectively). Further kinetic studies were carried out for the Cp*Fe(dppe)H + CF3COOD and Cp*Fe(dppe)D + CF3COOD systems at 273 K. The [Cp*Fe(dppe)(eta2-HD)]+ complex establishes a very rapid isotope redistribution equilibrium with the eta2-H2 and eta2-D2 analogues. The equilibrium constant value (K = 3.3 +/- 0.3) indicates a significant equilibrium isotope effect. Simulation of the rate data provides access to the individual isomerization rate constants kHH, kHD, and kDD for the three isotopomers, yielding kinetic isotope effects: kHH/kHD = 1.24 +/- 0.01 and kHD/kDD = 1.58 +/- 0.01 (and, consequently, kHH/kDD = 1.96 +/- 0.02). The analysis of the DFT-calculated frequencies, using the [Cp*Fe(dhpe)H2]+ model system, for the [Cp*Fe(dhpe)(eta2-XY)]+ isotopomers as well as transition states for the "direct" (TSdir) and "via Cp" (TSrot) pathways (X = H, D) allowed the computation of the expected isotope effects. A comparison with the experiment strongly suggests that the mechanism occurs via the "direct" pathway for the present system, although the small difference in the calculated energy barriers suggests that the "via Cp" pathway may be preferred in other cases.     

Polarization splitter based on a square-lattice photonic-crystal fiber

A three-core polarization splitter based on a square-lattice photonic-crystal fiber is presented. The component separates the input field into two orthogonally polarized beams that are coupled to the horizontal and vertical output ports. The splitter has been designed through modal and beam propagation analysis by employing high-performance codes based on the finite-element method. Results obtained for a device length of 20 mm show extinction ratios as low as -23 dB with bandwidths as great as 90 nm.     

Nearest level spacing statistics in open chaotic systems: generalization of the Wigner surmise

We investigate the nearest level spacing statistics of open chaotic wave systems. To this end we derive the spacing distributions for the three Wigner ensembles in the one-channel case. The theoretical results give a clear physical meaning of the modifications on the spacing distributions produced by the coupling to the environment. Based on the analytical expressions obtained, we then propose general expressions of the spacing distributions for any number of channels, valid from weak to strong coupling. The latter expressions contain one free parameter. The surmise is successfully compared with numerical simulations of non-Hermitian random matrices and with experimental data obtained with a lossy electromagnetic chaotic cavity.