Processes of flats induced by higher dimensional processes III

Stationary processes of k-flats in ^d can be thought of as point processes on the Grassmannian _k ^d of k-dimensional subspaces of ^d . If such a process is sampled by a (d–k+ j)-dimensional space F, it induces a process of j-flats in F. In this work we will investigate the possibility of determining the original k-process from knowledge of the intensity measures of the induced j-processes. We will see that this is impossible precisely when 1<k<d–1 and j=0,...,2[r/2]–1, where r is the rank of the manifold _k ^d . We will show how the problem is equivalent to the study of the kernel of various integral transforms, these will then be investigated using harmonic analysis on Grassmannian manifolds.The research of the first and third authors was supported in part by NSF grants DMS-9207019 and DMS-9304284. The research of the second author was supported in part by NFR contract number R-RA 4873-306 and the Swedish Academy of Sciences.     

Magnetic exchange interactions in tetrabromocuprate compounds

Magnetic and structural data for 28 compounds containing the tetrabromocuprate ion are presented. The parameters which affect the strength and sign of the magnetic superexchange interaction via non-bonding contacts between bromide ions are described and a system for describing the topology of the interaction between tetrahedra is proposed. Analysis of the data suggests that the primary factors affecting the magnetic exchange are the Br?Br distance, the Cu-Br?Br angle and the Cu-Br?Br-Cu dihedral angle.     

Chiral environments for asymmetric hydrogenation of model didehydro-amino acid residues

Dedicated to Professor John C. Sheehan on the occasion of his sixty-fifth birthday Nmr and glc analysis of diastereoisomeric mixtures of dipeptides has been used to study the asymmetric hydrogenation of model benzoyldidehydro- and trifluoroacetyldidehydro-dipeptide methyl esters. Chiral enhancement of one isomeric form appears to be independent of the N-terminal acyl group, but is significantly influenced by the choice of amino-acid in the C-terminal position. C-Terminal aromatic amino-acids and their derivatives give the best chiral enhancement during hydrogenation of a neighbouring dehydroamino-acid residue.     

Dynamic behavior of potentiometric ammonia-sensing probes in samples of high osmolarity

Results are presented for potentiometric ammonia gas-sensors which show that the response times increase significantly with age of the sensor when ammonium picrate is used as internal electrolyte and the samples have greater osmolarities than the internal electrolyte solution. A build-up of ammonium picrate crystals on the inner side of the gas-permeable membrane is responsible for this increasein response time. The use of ammonium chloride as internal electrolyte provides constant response times indepent of sample osmotic strength, and is recommended as a means of ensuring that optimal dynamic response characteristics are maintained.     

Effects of Solar UVB Radiation on Growth, Flowering and Yield of Central and Southern European Maize Cultivars (Zea mays L.)

Abstract— Different cultivars of maize ( Zea mays L.) originating from Central and South Europe were grown from June to September 1994 for 16 weeks in two greenhouses covered with different UVB-absorbing (280–320 nm) plastic foils. Using the ambient UVB radiation level of a southern location (Portugal, 38.7°N) in one of the greenhouses as an enhanced radiation compared to the reduced radiation in the second greenhouse, an increase of about 12% of UVB was simulated. Six of the eight cultivars examined showed significant reductions in height of up to 18.9% at all developmental stages under increased UVB. In contrast to this, the fresh and dry weight as well as the leaf area was reduced under UVB only at early developmental stages, but with ongoing development the UVB stressed plants caught up. The total content of absorbing compounds of the maize cultivars was completely unaffected by UVB. A flowering delay up to a maximum of 5 days was observed under higher UVB in several cultivars. Probably due to this delay in the cob development the yield decreased to 27.7% under higher UVB at the first harvest after 12 and 14 weeks, whereas at the second harvest after 14 and 16 weeks yield reduction levelled off.     

Synthesis and reactions of some dihydro and tetrahydro-4H-imidazo[5,4,1-ij]quinoline derivatives

Reaction of phenyl N-(8-quinolinyl)carbamate with sodium borohydride afforded 1,2-dihydro-4H-imidazo-[5,4,1-ij]quinolin-2-one, 2a . The 5,6-double bond of 2a was functionalized by reaction with nitrosyl chloride to give the nitroolefin 4 and by reaction with hypobromous acid to give the trans-bromohydrin 5 . Reaction of 5 with sodium azide led to the rearranged trans-6-azido-5-ol 7 , the structure of which was determined by ¹H nmr studies.     

Fast peroxyoxalate chemiluminescence for minimized analytical separation systems

The maximum intensity, Imax, and time required to reach the maximum emission, taumax, for 1-aminopyrene monitored in 1,1'-oxalyldi-4-methylimidazole (OD4MI) chemiluminescence (CL) reactions are approximately 61 times higher and 16 times faster than their respective values for bis(2,4,6-trichlorophenyl)oxalate (TCPO) CL reactions in the presence of imidazole (ImH).     

Splicing I: Using mixed basis sets in ab initio calculations

The effect of mixing (or “splicing”) extended and minimal basis sets on molecular properties such as geometries, Mulliken charges, dipoles, and internal rotation barriers was studied for several test molecules. The effect is gauged by comparison with full extended basis set calculations. It is found that splicing improves most properties relative to full minimal basis set calculations, and little accuracy is lost if the splicing is done in a judicious manner.     

Chemical modification of a viral cage for multivalent presentation

Here we present generalized methods for chemically modifying the surface of a viral protein cage; this exploits the chemistry of native and engineered surface exposed functional groups for multivalent presentation of ligands.