Infrared and Raman spectroscopy of graphite-ferric chloride

We present the first detailed study of the stage dependence of the IR- and Raman-active optic graphitic modes in a graphite acceptor intercalation compound. The general frequency upshift observed with increasing FeCl₃ concentration for all optic modes is interpreted to indicate an in-plane compression within the graphitic layers. An identification of the IR-active modes with bounding and interior graphite layers is made. A lineshape analysis of the IR spectra implies IR dipole moments corresponding to ～70% of the effective charge in the graphite bounding layers, independent of stage, and ～30% distributed among the graphite interior layers for stage n?3 compounds.     

Spectral properties of alkenylboranes evidence for conjugative interactions of boron with carbon—carbon π-systems

Ultraviolet, proton magnetic resonance and infrared spectral studies of a number of alkenylboranes are reported. Appreciable conjugation of carbon—carbon π-systems with boron is indicated. Comparisons of the UV and PMR spectra of alkenylboranes with those of their corresponding methyllithium ate complexes are especially informative. A marked solvent effect upon the PMR spectra of lithium ate complexes of alkenylboranes has been observed.     

Categorical axiomatics of dynamic programming

In systems theory, we need some general framework to take into account various concepts from different fields (automata theory, dynamical systems, optimization theory, etc.). This work is a proposal for such a framework. A decision process model is given with the help of category theory. Sufficient conditions for the validity of the equation of optimality of Bellman are established in this model. This model also generalizes the concept of finite automaton. Thus we unify the concepts of automaton and decision system. Especially, we propose the new concept of “opt-automaton” (automaton which optimizes).     

The existence and nonexistence of perfect addition sets

A (v, k, λ, μ)-perfect addition set is a subset A of $\text{Z}\text{υZ}$ with k elements such that the expression a_i + a_j, for a_i ≠ a_j in A, represents 0 exactly μ times and each nonzero element exactly λ times. Several infinite classes of such sets using quadratic residues of primes, a few isolated examples using cubic residues, and a construction in certain cases when υ is twice an odd integer, are give. There is an efficient method, based on the Chinese remainder theorem, which decides the existence or nonexistence of a perfect addition set. Some further results on nonexistence are given. In particular, two previously unsolved cases of Isbell (Discrete Math. 24 (1978), 13–18) are settled. The article ends with a list of nontrivial perfect addition sets with k ? 20.     

Photophysical and electrochemical properties of 1,7-diaryl-substituted perylene diimides

Substituent effects on the photophysical and electrochemical properties of 1,7-diaryl-substituted perylene diimides (1,7-Ar(2)PDIs) have been carefully explored. Progressive red-shifts of the absorption and emission maxima were observed when the electron-donating ability of these substituents was increased. Linear Hammett correlations of 1/lambda(max) versus sigma(+) were observed in both spectral analyses. The positive slopes of the Hammett plots suggested that the electronic transitions carry certain amounts of photoinduced intramolecular charge-transfer (PICT) character from the aryl substituents to the perylene diimide core which leads to the reduction of the electron density on the substituents. The substituent electronic effects originated mainly from the perturbation of the core PDI HOMO energy level by the substituents. This conclusion was supported by PM3 analyses and confirmed by cyclic voltammetry experiments. More interestingly, the Ph(2)NC(6)H(4)-substituted PDI, 4i, showed an unusual dual-band absorption that spans from 450 to 750 nm. We tentatively assigned these two bands as the charge-transfer band and the PDI core absorption, respectively.     

Visual immunoprecipitate assay eight hour method for detection of enterohemorrhagic Escherichia coli O157:H7 in raw and cooked beef (modification of AOAC Official Method 996.09): collaborative study

AOAC Official Method 996.09, Visual Immunoprecipitate Assay (VIP) for Escherichia coli O157:H7, was modified to incorporate a new enrichment protocol using BioControl EHEC8 medium for testing raw and cooked beef. Foods were tested by VIP assay and the U.S. Department of Agriculture/Food Safety and Inspection Service (USDA/FSIS) enrichment procedure and the FDA Bacteriological Analytical Manual (BAM) isolation and confirmation techniques. A total of 15 collaborators participated. Raw and cooked ground beef were inoculated with E. coli O157:H7 at 2 different levels: a high level, where predominantly positive results were expected, and a low level where fractional recovery was anticipated. Collaborators tested 396 test portions and controls by both methods, for a total of 792 test portions. Of the 396 paired test portions, 75 were positive and 230 were negative by both the VIP and culture methods. Eleven test portions were presumptively positive by VIP and could not be confirmed culturally; 32 were negative by VIP, but confirmed positive by culture; and 65 were negative by the culture method, but confirmed positive by the VIP method. There was no statistical difference between results obtained with the VIP for EHEC 8 h method and the culture method except for cooked beef, where the VIP had significantly higher recovery for one inoculation level.     

Rapid and simultaneous analysis of some bioactive components in Eucommia ulmoides by capillary electrophoresis

A micellar electrokinetic chromatography method was established for the qualitative and quantitative determination of three groups of bioactive components, iridoids, flavonoids and phenolic compounds, in Eucommia ulmoides. Of the eleven bioactive components being studied, ten were successfully separated in 50 mM boric acid buffer at pH 9.5, with 50 mM sodium dodecylsulfate and 4% 1-butanol, at a voltage of 20 kV, temperature of 20 degrees C and injection under high pressure at 138 kPa for 5 s in a fused-silica capillary with peak detection at 214 nm. A high reproducibility and good linearity was obtained. The relative standard deviations of the migration times in eight injections of the standards ranged from 0.64 to 1.88% and those of the corrected peak area ranged from 2.79 to 6.62%. A good linearity, with correlation coefficients in the range of 0.995-1.000, was obtained in the calibration curves of each standard from 1 to 50 ppm. The amount of these bioactive components in the bark and leaves of Eucommia ulmoides were determined.