A rare case of three rearrangements during the cycloaddition-elimination reaction of 4-methyl-5-phenylimino-Δ2-1,2,3,4-thiatriazoline with 2-pyridyl isothiocyanate

2-Pyridyl isothiocyanate ( 7 ), with its electrophilic and basic properties, gives a series of ring-transformation reactions with 4-methyl-5-phenylimino-1,2,3,4-thiatriazoline ( 1 ) at 60°. Two dithiazolidines, 8 and 10 , are formed as major products at an early stage of the reaction, whereas two thiadiazolidines, 9 and 11 , predominate at the end. The mechanism (Schemes II and III) has been elucidated by following the reaction course under a variety of conditions and by analyzing the products by ¹³C nmr spectroscopy.     

Synthesis of regiospecifically meta-substituted poly(phenylacetylene)s and some of their electrical properties

The syntheses, characterizations, and electrical properties of four regiospecifically substituted poly(phenylacetylene)s are described. Tungsten(VI) chloride/tetra-n-butyltin (WCl₆/n-Bu₄Sn) catalyst system (Higashimura–Masuda, H.–M. catalyst) was used to polymerize 3-bromo-, 3-chloro-, 3-trimethylsilyl-, and 3-trimethylstannylphenylacetylenes in order to obtain high-molecular-weight and soluble materials. Characterizations of these polymers were done by IR and UV spectroscopic methods, GPC, DSC, and elemental analysis. The electrical conductivities of the polymers were measured on the surface of pressed pellets by a four-point probe.     

Use of modifiers in on-line and off-line supercritical fluid extraction

For many applications using supercritical fluid extraction (SFE), modifiers may be required.This paper will present some findings regarding the use of various modifiers including methanol, hexane, acetone, chloroform, dichloromethane, toluene, and tributylphosphate, in on-line and off-line SFE with cryogenic adsorbent trapping. The specific applications involved the extractions of petroleum hydrocarbons and pesticides from naturally incurred soils.     

Laser-induced breakdown detection combined with asymmetrical flow field-flow fractionation: application to iron oxi/hydroxide colloid characterization

The combination of asymmetrical flow field-flow fractionation (AsFlFFF) with the laser-induced breakdown detection (LIBD) is presented as a powerful tool for the determination of colloid size distribution at trace particle concentrations. Detection limits (D1) of 1, 4, and 20 microg/L have been determined for a mixture of polystyrene reference particles with 20, 50, and 100 nm in size, respectively. This corresponds to injected masses of 1, 4, and 20 pg, which is lower than found in a previous study with the symmetrical FlFFF (SyFlFFF). The improvement is mainly due to the lower colloid background discharged from the AsFlFFF channel. The combined method of AsFlFFF-LIBD is then applied to the analysis of iron oxi/hydroxide colloids being considered as potential carriers for the radionuclide migration from a nuclear waste repository. Our LIBD arrangement is less sensitive for iron colloid detection as compared to reference polystyrene particles which results in a detection limit of approximately 240 microg/L FeOOH for the AsFlFFF-LIBD analysis. This is superior to the detection via UV-Vis absorbance and comparable to ICP-MS detection. Size information (mean size 11-18 nm) for different iron oxi/hydroxide colloids supplied by the present method is comparable to that obtained by sequential ultrafiltration and dynamic light scattering. A combined on-line ICP-MS detection is used to gain insight into the colloid-borne main and trace elements.     

DEVELOPMENT OF A PLAQUE REDUCTION ASSAY AND APPLICATION TO THE STUDY OF PSORALEN-DAMAGED DNA

Abstract— We have developed a procedure called a plaque reduction assay to assess the biological activity of duplex circular DNA modified by covalent adduct formation with psoralen derivatives. The replicating form (RF) of bacteriophage DNA modified by photochemical addition of a psoralen derivative was introduced into bacterial cells using the CaCI₂ transfection method. The transfected cells. plated upon a confluent lawn of cells permissive for the bacteriophage in the inoculum, provided a measure of the reduction in infectivity of the RF DNA which resulted from its covalent modification. Use of this assay is illustrated in studies which screened and compared the activities of several recently synthesized psoralen derivatives. We describe two new compounds. β-(8-psoralenoxy)-ethanol and β-(8-psoralenoxy)ethylamine that are significantly more active than either 8-methoxypsoralen or trioxsalen in the biological assay     

An automated, sheathless capillary electrophoresis-mass spectrometry platform for discovery of biomarkers in human serum

A capillary electrophoresis-mass spectrometry (CE-MS) method has been developed to perform routine, automated analysis of low-molecular-weight peptides in human serum. The method incorporates transient isotachophoresis for in-line preconcentration and a sheathless electrospray interface. To evaluate the performance of the method and demonstrate the utility of the approach, an experiment was designed in which peptides were added to sera from individuals at each of two different concentrations, artificially creating two groups of samples. The CE-MS data from the serum samples were divided into separate training and test sets. A pattern-recognition/feature-selection algorithm based on support vector machines was used to select the mass-to-charge (m/z) values from the training set data that distinguished the two groups of samples from each other. The added peptides were identified correctly as the distinguishing features, and pattern recognition based on these peptides was used to assign each sample in the independent test set to its respective group. A twofold difference in peptide concentration could be detected with statistical significance (p-value < 0.0001). The accuracy of the assignment was 95%, demonstrating the utility of this technique for the discovery of patterns of biomarkers in serum.     

Simulating Withdrawal Behaviors in Work Organizations: An Example of a Virtual Society

This article discusses computational modeling as a research discipline increasingly accessible to researchers in the social and behavioral sciences, a method necessary to allow us to address several important questions. Construction and use of virtual societies in which complex behavioral processes may be simulated in exquisite detail is possible because of the capacity and speed of desk top computers combined with requisite theoretical and methodological developments. Modeling has strengths orthogonal and complementary to those of the experimental tradition and correlational analyses of individual differences. These strengths can be exploited in many areas of psychology. Behavioral processes within a segment of a virtual society can be simulated with extreme levels of realism using overarching theoretical and empirical framework; segments can be combined to provide more macro statements. Variables that represent forces impinging on individuals from the macro-environment; variables that characterize relatively more micro-environments such as a work organization or the family or a classroom; and individual-level variables that summarize attitudinal, cognitive, and value states or traits can be included easily in simulations. Researchers can decompose and evaluate the interplay of multi-level causal forces as they interact within different theoretical models of how individuals enact different, interrelated behaviors. Temporal dynamics of behavioral processes, not well addressed by traditional research disciplines, can be exploited in modeling to permit the realistic study of dynamical, nonlinear systems. These points are illustrated by results from a program designed to simulate the process by which individuals withdraw from aversive work situations.     

A note on the interlacing of zeros and orthogonality

Let be a sequence of monic polynomials with deg(t_n)=n such that, for each n∈N, the zeros of t_n are real and simple and t_n and t_n+1 have no common zeros. We discuss the connection between the orthogonality of the sequence, the positivity of a certain ratio, and the interlacing of the zeros of t_n and t_n+1 for n≥1, n∈N.