A conic bundle description of Moishezon twistor spaces without effective divisors of degree one

In [K2] Moishezon twistor spaces over the connected sum (), which do not contain effective divisors of degree one, were constructed as deformations of the twistor spaces introduced in [LeB]. We study their structure for by constructing a modification which is a conic bundle over . We show that they are rational. In case n = 4 we give explicit equations for such conic bundles and use them to construct explicit birational maps between these conic bundles and . Received October 8, 1996; in final form May 16, 1997     

Observation of inclusive η production in ee annihilation at CM energies of 34 GeV

The inclusive production of η mesons at CM energies around 34 GeV has been studied for e⁺e⁻ annihilation into hadrons. The average number of η-mesons per event is found to be 0.72 ± 0.10 (stat.) ± 0.18 (syst.). The abundance of η's is studied as a function of event shape parameters and it is compared to the corresponding π⁰ rates.     

Predation, death, and survival in a biofilm: Bdellovibrio investigated by atomic force microscopy

Biofilms are complex microbial communities that are resistant to attack by bacteriophages and to removal by drugs and chemicals. Here we use atomic force microscopy (AFM) to image the attack on Escherichia coli biofilms by Bdellovibrio bacteriovorus 109J. Bdellovibrio is a small, predatory bacterium that invades and devours other Gram-negative bacteria. We demonstrate that under dilute nutrient conditions, bdellovibrios can prevent the formation of simple bacterial biofilms and destroy established biofilms; under richer conditions the prey bacteria persist and are not eradicated, but may be shifted toward solution populations. Using AFM we explore these bacterial interactions with more detail and accuracy than available by more traditional staining assays or optical microscopy. AFM also allows us to investigate the nanoscale morphological changes of the predator, especially those related to motility. This demonstration of Bdellovibrio's successful predation in a biofilm inspires us to consider ways that it might be used productively for industrial, medical, agricultural, and biodefensive purposes.     

Photocyclization reactions of cyclohexa- and cyclopenta-fused pyridinium salts. Factors governing regioselectivity

The results of studies described in this report show that irradiation of 1,2-cyclopenta-fused pyridinium perchlorate in aqueous base promotes a remarkably regioselective photocyclization reaction that results in exclusive formation of a single tricyclic allylic alcohol. Moreover, transformation of this photoproduct to a spirocyclic amido diester followed by enzymatic desymmetrization produces an enantiomerically pure monoalcohol. This chemistry comprises a highly concise sequence for the preparation of what should become a useful synthon in synthetic organic chemistry.     

Spotlight Tiling

This article introduces spotlight tiling, a type of covering which is similar to tiling. The distinguishing aspects of spotlight tiling are that the “tiles” have elastic size, and that the order of placement is significant. Spotlight tilings are decompositions, or coverings, and can be considered dynamic as compared to typical static tiling methods. A thorough examination of spotlight tilings of rectangles is presented, including the distribution of such tilings according to size, and how the directions of the spotlights themselves are distributed. The spotlight tilings of several other regions are studied, and suggest that further analysis of spotlight tilings will continue to yield elegant results and enumerations.     

A unique heterobimetallic benzyl calciate--an organometallic mixed-metal species involving a heavy alkaline-earth metal

A co-complexation reaction utilizing homometallic benzylcalcium and benzyllithium affords a rare example of a heterobimetallic benzyl calciate.     

β‐Alkyloxazolochlorins: Revisiting the Ozonation of Octaalkylporphyrins,and Beyond

The reaction of β‐octaalkylporphyrins (octaethylporphyrin and etioporphyrin I) with ozone generated the corresponding heptaalkyloxazolochlorinhemiacetals in which a pyrrolic subunit of the porphyrins was replaced by an oxazoline moiety. Thus, a pyrrolic β‐carbon with its alkyl substituent was excised and replaced by an oxygen atom, and the neighboring β‐carbon was hydroxylated. This work clarifies the nature of the products first described by Fischer and De?eli?, in 1933, and verifies the work by Shulg′a and coworkers, from 1977. Furthermore, the chemistry of the oxazolochlorin hemiacetals was studied: They could be dehydroxylated or converted to alkyl acetals and gem‐dialkyl derivatives, all possessing chlorin‐type optical spectra. Their oxidative conversions generated a unique tetrahydrofuran‐linked oxazolochlorin dimer and a hexaethylporpholactone. The work expands on the knowledge of converting porphyrins to porphyrinoids of potential utility containing nonpyrrolic building heterocycles.     

Fast and comprehensive analysis of secondary metabolites in cocoa products using ultra high‐performance liquid chromatography directly after pressurized liquid extraction

Fast methods for the extraction and analysis of various secondary metabolites from cocoa products were developed and optimized regarding speed and separation efficiency. Extraction by pressurized liquid extraction is automated and the extracts are analyzed by rapid reversed‐phase ultra high‐performance liquid chromatography and normal‐phase high‐performance liquid chromatography methods. After extraction, no further sample treatment is required before chromatographic analysis. The analytes comprise monomeric and oligomeric flavanols, flavonols, methylxanthins, N‐phenylpropenoyl amino acids, and phenolic acids. Polyphenols and N‐phenylpropenoyl amino acids are separated in a single run of 33 min, procyanidins are analyzed by normal‐phase high‐performance liquid chromatography within 16 min, and methylxanthins require only 6 min total run time. A fourth method is suitable for phenolic acids, but only protocatechuic acid was found in relevant quantities. The optimized methods were validated and applied to 27 dark chocolates, one milk chocolate, two cocoa powders and two food supplements based on cocoa extract.     

Oxidation reactivity channels for 2-(pyridin-2-yl)-N,N-diphenylacetamides

Synthetic routes to 2-(pyridin-2-yl)-N,N-diphenylacetamide and 2-(6-methylpyridin-2-yl)-N,N-diphenyl-acetamide are described along with results from the chemical oxidation of these compounds with peracetic acid, m-chloroperbenzoic acid, and OXONE. In each case, oxidations generate four products in varying amounts depending on the oxidant and reaction conditions. Each product has been characterized by spectroscopic methods and the molecular structures of several of the new compounds have been confirmed by X-ray crystallography.