A New Calculation Method for Distinguishing Endo- from Exo-Polygalacturonases

A method which uses a comparison ratio (CR) of fluidity (1/n)sp)/μmoles reducing groups is proposed for comparing and distinguishing endo- and exo-polygalacturonases (PGases). This method is faster, easier and as accurate a method as the percent hydrolysis method. The CR method can also be used as a measure of the purity of endo- PGase with respect to exo-PGase.     

Microstructure and Growth Model for Rice-Hull-Derived SiC Whiskers

The microstructure of silicon carbide whiskers grown from rice hulls has been studied using methods of high-resolution analytical electron microscopy. Small, partially crystalline inclusions (∼10 nm) containing calcium, manganese, and oxygen are concentrated in whisker core regions, while peripheral regions are generally inclusion free. The distinct microphase distribution is evidence of a two-stage growth process in which the core region grows first, followed by normal growth toward whisker sides. Partial dislocations extend radially from the core region to the surface and tend to be paired in V-shaped configurations. Whisker surfaces exhibit microroughness due to a tendency to develop small facets on close-packed planes. The microstructural data obtained from TEM observations are used as a basis for discussion of the mechanisms involved in whisker growth, and a model of the growth process is proposed. The model includes a two-dimensional growth mechanism involving vapor, liquid, and solid phases, although it is significantly different from the classical vapor-liquid-solid (VLS) process of whisker growth.     

BIOFUMIGANT COMPOUNDS RELEASED BY FIELD PENNYCRESS (<Emphasis Type="Italic">Thlaspi arvense</Emphasis>) SEEDMEAL

Defatted field pennycress (Thlaspi arvense L.) seedmeal was found to completely inhibit seedling germination/emergence when added to a sandy loam soil containing wheat (Triticum aestivum L.) and arugula [Eruca vesicaria (L.) Cav. subsp. sativa (Mill.) Thell.] seeds at levels of 1.0% w/w or higher. Covering the pots with Petri dishes containing the soil-seedmeal mixture decreased germination of both species at the lowest application rate (0.5% w/w), suggesting that the some of the phytotoxins were volatile. CH₂Cl₂, MeOH, and water extracts of the wetted seedmeal were bioassayed against wheat and sicklepod (Senna obtusifolia (L.) H. S. Irwin & Barneby) radicle elongation. Only the CH₂Cl₂ extract was strongly inhibitory to both species. Fractionation of the CH₂Cl₂ extract yielded two major phytotoxins, identified by gas chromatography–mass spectrometry and NMR as 2-propen-1-yl (allyl) isothiocyanate (AITC) and allyl thiocyanate (ATC), which constituted 80.9 and 18.8%, respectively, of the active fraction. When seeds of wheat, arugula and sicklepod were exposed to volatilized AITC and ATC, germination of all three species was completely inhibited by both compounds at concentrations of 5 ppm or less. In field studies, where seedmeal was applied at 0.50, 1.25, and 2.50 kg/m² and tarped with black plastic mulch, all of the treatments significantly reduced dry weight of bioassay plants compared to the tarped control, with the highest seedmeal rate decreasing dry matter to less than 10% of the control 30 d after seedmeal application. Field pennycress seedmeal appears to offer excellent potential as a biofumigant for high-value horticultural crops for both conventional and organic growers.Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

GENOMIC HARDWIRING AND PHENOTYPIC PLASTICITY OF TERPENOID-BASED DEFENSES IN CONIFERS

Over evolutionary history, conifers have faced a myriad of threats from phloem- and xylem-feeding insects, defoliating insects, and fungal pathogens. Among the trees defenses, terpenoids appear to play a major role by harming, disabling, deterring, repelling, or otherwise reducing the fitness of potential invaders. Each of the three classes of terpenoids in conifers, monoterpenes, sesquiterpenes, and diterpenes, are composed of a large number of representative compounds. In most cases, the presence of a particular terpenoid compound in the oleoresin or volatile emissions from a specific conifer can be accounted for by the expression of one of many committed terpene synthase (TPS) genes. However, while each TPS may produce one or a few major products, many produce a variety of minor products with relatively constant component ratios in the product blends. TPS genes exist in conifers in large and functionally diverse, yet monophyletic, gene families. Within these gene families, new biochemical functions of TPS appear to have evolved by gene duplication and changes in the amino acid sequence of the enzymes active site. In addition, TPS genes may be differentially expressed prior to, during, and following attack by insects or pathogens. Thus, while the production of any particular terpenoid is hardwired into a conifers genome, these trees have the capacity to change the mixture of terpenoids in oleoresin secretions and volatile emissions. Anatomical changes may also accompany induced terpenoid production, supplementing the plasticity of the molecular and biochemical events.     

A phase-plate mode transducer for TE1n gyrotron modes

A means is described to increase the on-axis component of the far-field energy pattern of radiation emitted from the open end of a circular waveguide containing a high order TE_1n gyrotron mode. While the sidelobe power is higher than that of some other approaches, this technique is relatively broadband and compact, and should be easy to fabricate. The method uses a phase-plate at the output of the waveguide to rectify the negative portion(s) of the electric field of the circular TE mode in the waveguide.     

Partial Separation and Characterization of Papaya Endo- and Exo-Polygalacturonase

Exo- and endo-polygalacturonases (EC 3.2.1.40 and EC 3.2.1.15) in papayas were extracted, purified 20- and 90-fold, respectively, and characterized. Both enzymes functioned optimally at pH 4.6 and 45°C. Heat inactivation of the papaya PGases was biphasic and both phases followed first order kinetics. Decreasing the pH from 4.6 to 3.6 decreased the time required for their heat inactivation. The activation energies for the thermal inactivation at pH 3.6 and 4.6 were 85 and 92 kcal/mol, respectively, for endo-PGase (PG I) and 140 and 102 kcal/mol, respectively, for exo-PGase (PG II). The apparent molecular weight was determined by gel filtration to be 164,000 daltons for PG I and 34,000 daltons for PG II.     

Network Competition and the Provision of Universal Service

As providers of basic infrastructure services, telecommunicationsproviders have traditionally been required to provide servicesand to serve customers that would not provide a reasonable returnon investment in an unregulated marketplace. Today there arestill important telecommunications policy goals that are unlikelyto be achieved through competition alone. A successful transitionfrom monopoly to competition requires the development of newmechanisms for achieving these goals that do not impede competitionin services and in geographic areas where it would otherwisebe feasible. This paper examines the problem of providing basictelephone service to low income households in urban areas largeenough to support two or more competing providers of telephoneservice. It shows that there are plausible circumstances underwhich, even without public support, low income households unwillingto pay the cost of connection to the public network will stillbe provided service by telephone companies who want to makethem available to other subscribers willing to pay more. Thiscan happen if there is a mechanism that allows service providersto accurately distinguish between low income and high incomesubscribers.