Generalized markushevich bases

Conditions for the embedding of a Banach space as a dense subspace of a continuous function space are studied. Necessary and sufficient conditions for a Banach space to be isomorphic to aP ₁ space are found.     

Determination of thorium and uranium at the nanogram per gram level in semiconductor potting plastics by neutron activation analysis

A method was developed to determine thorium and uranium in semiconductor potting plastics. The method is based on neutron activation and subsequent radiochemical separation to isolate and permit measurement of the daughter products²³³Pa and²³⁹Np of the induced²³³Th and²³⁹U. These plastics typically contain macro amounts of silicon, bromine and antimony and nanogram per gram amounts of thorium and uranium. The radiochemical method provides the necessary sensitivity and makes it possible to easily attain adequate decontamination of the tiny amounts of²³³Pa and²³⁹Np from the high levels of radioactive bromine and antimony.Deceased     

On minimal lengths of expressions of Coxeter group elements as products of reflections

It is shown that the absolute length of a Coxeter group element (i.e. the minimal length of an expression of as a product of reflections) is equal to the minimal number of simple reflections that must be deleted from a fixed reduced expression of so that the resulting product is equal to , the identity element. Also, is the minimal length of a path in the (directed) Bruhat graph from the identity element to , and is determined by the polynomial of Kazhdan and Lusztig.

     

Controlled diastereoselectivity at the alkene-geometry through selective encapsulation: E-Z photoisomerization of oxazolidinone-functionalized enecarbamates within hydrophobic nano-cavities

Photoisomerization of encapsulated Z-enecarbamates within the hydrophobic chiral cavities of gamma-CD showed higher diastereoselectivities in the photoproducts than those obtained in solution. The selective encapsulation of the enecarbamates and the following isomerization process are both diastereoselectively controlled by gamma-CD.     

A repetitively pulsed sealed-TE CO2 laser using an oxygen tolerant discharge scheme

A repetitively pulsed (40 Hz) TE CO₂ laser using an oxygen tolerant discharge scheme is described. Long lived (>10⁵ shots) stable discharges at high pump energy density (200 J.l^–1 atm^–1) have been achieved both with and without the use of additive gases.     

Determination of photo-oxidation products within photoyellowed bleached wool proteins

Photo-oxidative processes occurring in wool can lead to significant photoyellowing of the fiber. In particular, wool that has been chemically bleached photoyellows more rapidly and to a greater degree than untreated wool. Direct identification of the chromophores responsible for such yellow discoloration in irradiated wool has proven to be elusive for many years. This article describes the characterization and location of yellow photo-oxidation products within the proteins of photoyellowed bleached wool fabric, using advanced protein chemistry techniques. The discolored fabric was enzymatically digested and chromatographed by high-pressure liquid chromatography, with monitoring at 400 nm, to select out fractions containing yellow chromophoric species. Thorough tandem mass spectrometric analysis was then used to sequence peptides and, in turn, to characterize modifications to key amino acid residues that had resulted in yellow chromophore formation. In total, 11 separate yellow chromophoric species were identified, ten derived from tryptophan residues and one from tyrosine. The tryptophan-derived modifications characterized included hydroxytryptophan, N-formylkynurenine, hydroxyformylkynurenine, kynurenine, hydroxykynurenine, carbolines, tryptophandiones and nitrotryptophan. The tyrosine-derived modification of tyrosine to dopa was also identified. The range of photomodifications we observed provides insight into the photo-oxidation pathways occurring within irradiated fibrous proteins leading to the formation of yellow chromophores.     

Acoustically derived ice-fracture velocity in central Arctic pack ice

Sounds radiated by fractures in Arctic ice (called acoustic events) are used to estimate fracture velocity. Both speed and orientation are obtained by measuring Doppler shifts induced by source motion. Data from the SIMI experiment of 1994 in the central Arctic are used in the frequency window 10 to 350 Hz. The estimation procedure assumes that each fracture propagates unilaterally, i.e., unidirectionally. Results for a population of 186 events show fracture propagation speed to be mostly subsonic, in the range 100 to 1100 m/s, significantly lower than the Rayleigh wave speed (1700 m/s for sea ice) assumed in previous studies. The wide range of speeds observed indicates either the presence of distinct multiple fractures in each event, or of a single mechanism at different stages in its propagation.     

The RNase a superfamily: Generation of diversity and innate host defense

Summary The Ribonuclease A superfamily includes an extensive network of distinct and divergent gene lineages. Although all ribonucleases of this superfamily share invariant structural and catalytic elements and some degree of enzymatic activity, the primary sequences have diverged significantly, ostensibly to promote novel function. We will review the literature on the evolution and biology of the RNase A ribonuclease lineages that have been characterized specifically as involved in host defense including: (1) RNases 2 and RNases 3, also known as the eosinophil ribonucleases, which are rapidly-evolving cationic proteins released from eosinophilic leukocytes, (2) RNase 7, an anti-pathogen ribonuclease identified in human skin, and (3) RNase 5, also known as angiogenin, another rapidly-evolving ribonuclease known to promote blood vessel growth with recently-discovered antibacterial activity. Interestingly, some of the characterized anti-pathogen activities do not depend on ribonuclease activity per se. We discuss the ways in which the anti-pathogen activities characterized in vitro might translate into experimental confirmation in vivo. We will also consider the possibility that other ribonucleases, such as the dimeric bovine seminal ribonuclease and the frog oocyte ribonucleases, may have host defense functions and therapeutic value that remain to be explored. (190 words)     

Anionic surfactants and surfactant ionic liquids with quaternary ammonium counterions

Small-angle neutron scattering and surface tension have been used to characterize a class of surfactants (SURFs), including surfactant ionic liquids (SAILs). These SURFs and SAILs are based on organic surfactant anions (single-tail dodecyl sulfate, DS, double-chain aerosol-OT, AOT, and the trichain, TC) with substituted quaternary ammonium cations. This class of surfactants can be obtained by straightforward chemistry, being cheaper and more environmentally benign than standard cationic SAILs. A surprising aspect of the results is that, broadly speaking, the physicochemical properties of these SURFs and SAILs are dominated by the nature of the surfactant anion and that the chemical structure of the added cation plays only a secondary role.