Integral Cohomology and Detection of -basic 2-groups

In this paper we compute the cohomology of all -basic 2-groups with integral coefficients twisted by the orientation character . We also calculate appropriate restiction maps and thus prove that the cohomology of any -basic group is detected by subgroups isomorphic to one of five types, and we provide a sample application of this main theorem.

     

Asymptotic optimality of statistical multiplexing in pipelined processing

The throughput of pipelined processing ofheterogeneous multitasked jobs is computed and optimized in this study. There areK job classes. Each job hasM tasks which have to be processed in a given order (same for all tasks) on a pipeline ofM processors. Tasks have random processing times. The jobs of each class form a stationary and ergodic sequence (with respect to their task processing times). Classes are differentiated by distinct statistics and may not be jointly stationary or ergodic. Thus, the jobs are overall statistically heterogeneous. We are interested in the average execution time per job , when the job populations of the various classes become very large (asymptotically). This is shown to depend on the order in which jobs enter the pipeline. Under the natural class-based ordering, where all jobs of the first class enter first, followed by those of the second, third, and so on, the quantity is computed, but is shownnot to attain its minimal value in general. On the contrary, appropriate statistical multiplexing of jobs of different classes on the pipeline is shown to minimize the average execution time per job on every sample path (with probability one). The procedure, calledbalanced statistical multiplexing, is constructed and the minimal is computed in terms of the average execution times of the job tasks.     

Influence of methanol as a buffer additive on the mobilities of organic cations in capillary electrophoresis

The mobilities of a series of aromatic ammonium ions, ranging in charge from +1 to + 3, were investigated by capillary electrophoresis using buffers consisting of 0-75% v/v methanol. This is an extension of our previous studies involving anion mobility in methanol-water media [1]. Absolute mobilities were determined by extrapolation of the effective mobilities to zero ionic strength according to the Pitts' equation. For all of the buffer compositions studied, the ionic strength effect increased with increasing cation charge, and varied as a function of solvent 1/eta epsilon (1/2) as predicted by the electrophoretic term within the Pitts' equation. In the presence of methanol, the ionic strength effects became more dramatic. The absolute mobilities of the cations were altered by the addition of methanol to the electrophoretic media. For example, at 75% MeOH, a migration order reversal was observed between the + 2 and + 3 ammonium ions. These solvent-induced selectivity changes are attributed to dielectric friction. As predicted by the Hubbard-Onsager dielectric friction model, dielectric friction increased with increasing methanol content and with increasing analyte charge. Further, the changes in cation mobility correlated to the changes in solvent relaxation time (tau), epsilon and eta. Although not predicted by the Hubbard-Onsager theory, the + 3 ammonium ion experienced more dielectric friction than the - 3 sulfonate and - 3 carboxylate investigated previously [1]. This apparent failure of the Hubbard-Onsager model results from its continuum nature, whereby ion-solvent interactions are not taken into account.     

Bromoporphyrins as versatile synthons for modular construction of chiral porphyrins: cobalt-catalyzed highly enantioselective and diastereoselective cyclopropanation

5,10-Bis(2',6'-dibromophenyl)porphyrins bearing various substituents at the 10 and 20 positions were demonstrated to be versatile synthons for modular construction of chiral porphyrins via palladium-catalyzed amidation reactions with chiral amides. The quadruple carbon-nitrogen bond formation reactions were accomplished in high yields with different chiral amide building blocks under mild conditions, forming a family of D2-symmetric chiral porphyrins. Cobalt(II) complexes of these chiral porphyrins were prepared in high yields and shown to be active catalysts for highly enantioselective and diastereoselective cyclopropanation under a practical one-pot protocol (alkenes as limiting reagents and no slow addition of diazo reagents).     

Quantitative determination of the polypeptide motilin in rat plasma by externally calibrated liquid chromatography/electrospray ionization mass spectrometry

We present a method for the quantitation of motilin from rat plasma by protein precipitation and liquid chromatography/mass spectrometry (LC/MS). Using external calibration, the method was linear over the concentration range 10-1000 ng/mL with an initial sample volume of 150 microL. The LC system included a C(18) column with a 300 A pore size. A linear gradient was used with a mobile phase consisting of water and acetonitrile, each with 0.2% acetic acid and 0.02% trifluoroacetic acid. Motilin was detected with the mass spectrometer in positive ion mode monitoring the 4+ charge state at m/z 675.5. The approximated limit of detection was less than 1 ng/mL and the lower limit of quantitation (LLOQ) was 10 ng/mL. The method showed a high degree of precision and accuracy both within and between runs at five validation points, including the LLOQ.     

Multi-conformational Luminescence and Phosphorescence of Few Phenazine 1,2,3-triazole Molecules

Journal of Fluorescence - Dropcast films produced from blends solutions of phenazine 1,2,3-triazole molecules in very low concentrations in a 1,3-Bis (N-carbazolyl) benzene (mCP) matrix...     

Viscoelastic behavior of poly(ether imide) incorporated with multiwalled carbon nanotubes

There is significant potential in improving the mechanical, electrical, and thermal properties of engineering plastics, including poly(ether imide) (PEI), with various nanoinclusions such as multiwalled carbon nanotubes (MWCNTs). However, this potential can only be fully realized through a thorough understanding of the rheological behavior and the thermomechanical histories that the nanocomposites are exposed to during their preparation and the resulting effective properties. In this study, nanocomposites of PEI and MWCNTs were prepared using a solution processing method under different dispersion conditions, and the viscoelastic material functions of the nanocomposites were characterized as functions of concentration of CNTs in the 1–5% by weight range (volume fraction, ? = 0.006–0.03) and temperature. The storage modulus and magnitude of complex viscosity values of the PEI nanosuspensions increased by as much as 3500% and 800%, respectively, at ? = 0.03, along with similar orders of magnitude increases observed or predicted in other viscoelastic material functions. Such increases reflect how nanotube incorporation and network formation can drastically alter the flow and deformation behavior of the PEI/CNT nanosuspensions at processing‐relevant temperatures and deformation rates. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Features of the turbulent wall pressure field on a long towed cylinder

Turbulent wall pressure fluctuation correlation functions were measured in water on a towed cylindrical model of length 129.8 m and diameter 3.8 cm for steady speeds ranging from 6.2 to 15.5 m/s. The drag on the model was measured with a strut-mounted load cell to provide estimates of the momentum thickness and friction velocity that are used for scaling the correlation functions. Very high momentum thickness Reynolds numbers Re_θ were achieved, and varied from 4.8 × 10⁵ to 1.1 × 10⁶. The ratio of boundary layer thickness to cylinder radius was approximately 24, which is an order of magnitude greater than previous laboratory investigations. The ratio of momentum thickness to viscous length scale is significantly greater than for flat plate cases at comparable Re_θ. A similarity scaling is shown to be more effective than outer or inner boundary layer scalings for collapsing the correlation functions. Comparisons with the early streamwise and transverse correlation measurements of Willmarth and Yang are favorable, and show consistent trends of a more rapid loss of correlated energy for cylindrical turbulent boundary layers than for flat plate cases. Convection velocities are also presented and shown to collapse well with separation scaled on outer variables. A simple model that relates the peak of the correlation function to the average coherence levels is shown to be valid for spatial separations less than the approximate momentum thickness.