Muonium adduct radicals from vinyl-aromatic compounds

During irradiation of liquid samples of 1-vinylimidazole, 2-vinylnaphthalene, 2-vinylpyridine, 4-vinylpyridine and 1,1-diphenylethene with positive muons, radicals of the type MuCH₂ĊHAr (Ar=the appropriate aromatic group), and the MuCH₂ĊPh₂ radical were observed by transverse field μSR; the muon hyperfine couplings are considered in the context of the effectiveness of the aryl groups in delocalising the unpaired electron.     

Three-pencil lattices on triangulations

In this paper, three-pencil lattices on triangulations are studied. The explicit representation of a lattice, based upon barycentric coordinates, enables us to construct lattice points in a simple and numerically stable way. Further, this representation carries over to triangulations in a natural way. The construction is based upon group action of S ₃ on triangle vertices, and it is shown that the number of degrees of freedom is equal to the number of vertices of the triangulation.      

Multiscale Finite Element Modeling of Arc Dynamics in a DC Plasma Torch

The dynamics of the electric arc inside a direct current non-transferred arc plasma torch are simulated using a three-dimensional, transient, equilibrium model. The fluid and electromagnetic equations are solved numerically in a fully coupled approach by a multiscale finite element method. Simulations of a torch operating with argon and argon–hydrogen under different operating conditions are presented. The model is able to predict the operation of the torch in steady and takeover modes without any further assumption on the reattachment process except for the use of an artificially high electrical conductivity near the electrodes, needed because of the equilibrium assumption. The results obtained indicate that the reattachment process in these operating modes may be driven by the movement of the arc rather than by a breakdown-like process. It is also found that, for a torch operating in these modes and using straight gas injection, the arc will tend to re-attach to the opposite side of its original attachment. This phenomenon seems to be produced by a net angular momentum on the arc due to the imbalance between magnetic and fluid drag forces.     

Equivalence of regularity for the Bergman projection and the\bar \partial-neumann operator

A necessary and sufficient condition for regularity of the -Neumann operator on (0,q)-forms in a smooth bounded pseudoconvex domain in Cⁿ is that the orthogonal projections onto -closed forms of degrees (0,q−1), (0,q), and (0,q+1) all be regular. The first author partially supported by NSF Grant DMS-8701038     

A Three-Dimensional Two-Phase Model for Thermal Plasma Chemical Vapor Deposition with Liquid Feedstock Injection

In this paper, a comprehensive model for thermal plasma chemical vapor deposition (TPCVD) with liquid feedstock injection is documented. The gas flow is assumed to be steady, of a single temperature. Radiation and charged species contributions are excluded, but extensive homogeneous and heterogeneous chemistry is included. The liquid phase is traced by considering individual droplets. Discussion on the model's application to diamond production from acetone in a hydrogen–argon plasma is included. The major conclusions are: (1) Liquid injection possesses a capability to deliver the hydrocarbon precursor directly onto the deposition target. (2) For the case of complete evaporation of the droplet before reaching the substrate, the deposition rate is similar to that obtained with gaseous precursors. (3) The computational results compare well with experimental data. The modeling results can be used to optimize the injection parameters with regard to the deposition rate.     

Differential pulse adsorptive stripping voltammetry of osmium-modified peptides

Complexes of osmium tetroxide with nitrogen ligands were developed and used in our laboratory as probes of the DNA structure. Here, we show that the complex of osmium tetroxide with 2,2'-bipyridine (Os,bipy) can be used for modification and electrochemical detection of proteins at neutral pH. Salmon luteinizing hormone (SLH) containing two tryptophan (Trp) residues and human luteinizing hormone (HLH) containing one Trp were modified by Os,bipy and measured by differential pulse adsorptive stripping voltammetry (DPAdSV) at a hanging mercury drop electrode (HMDE). The intensity of the DPAdSV catalytic signals corresponded to the number of Trp residues in the peptide molecule. Decreasing pH of the background electrolyte from 6.6 to 3.8 led to the increase of DPAdSV signals, suggesting that at pH 3.8, the DPAdSV detection limit might be well below 1 ng/ml. Our results suggest that Os,bipy is potentially useful for chemical modification of proteins.     

Past, present and future of nucleic acids electrochemistry

Electrochemistry of nucleic acids was discovered about 40 years ago. During the first 15 years electrochemistry brought early evidence of DNA premelting and polymorphy of the DNA double helix. At present electrochemical methods working with stationary electrodes are able to detect DNA at attomol and in some cases, even at lower levels. A great progress in the development of electrochemical sensors for DNA hybridization and DNA damage achieved in recent years suggests that these sensors may soon become important tools in medicine and other areas of practical life of the 21st century.     

Die Veresterungsgeschwindigkeiten der Nitrobenzoesäuren in Äthylenglykol und der Naphtoesäuren in Glyzerin

Zusammenfassung Es werden die monomolekuren Geschwindigkeitskonstanten der durch Chlorwasserstoff katalysierten Veresterung der Nitrobenzoesäuren in Glykol und der Naphthoesäuren in Glyzerin bei 25° gemessen und als Funktionen der Wasser- (w) und Salzsäurekonzentration (c) des Mediums durch Intrapolationsformeln dargestellt.Diese Konstanten nehmen in wasserwarmem Glyzerin und Glykol und in wasserreicherem Glyzerin proportional der Chlorwasserstoffkonzentration zu, in wasserreicherem Glykol aber rascher, was mit früheren Beobachtungen übereinstimmt. Fürc=1/6 undw=0.065 ist das Verhältnis der monomolekularen Konstanten der Benzoesäure zu jenen dero-,m- undp-Nitrobenzoesäure und der- und-Naphthoesäure in Äthylalkohol 10.0540.570.700.391.00, in Glykol 10·0380·690·79, in Glyzerin 10·0680·630·800·610·93. Die sterische Hinderung durch die Orthosubstitution ist somit hier in Glyzerin kleiner, in Glykol größer als in Äthylalkohol. Daher wird auch die Orthonitrobenzoesäure in Glyzerin rascher als in Glykol verestert, während sonst meist das umgekehrte Verhältnis besteht.Bei geringem Wassergehalt sind die Veresterungsgeschwindigkeiten in beiden Medien kleiner als in Äthylalkohol, bei größerem aber größer wegen der weitaus stärkeren verzögernden Wirkung des Wassers in letzterem.Unter den Versuchsbedingungen findet praktisch vollständige Veresterung statt, so daß die Wiederverseifung nicht zu berücksichtigen ist.Bei 183° verläuft die Selbstveresterung der Naphthoesäuren in Glyzerin ebenso wie die der bisher gemessenen Säuren nach der Gleichung für sesquimolekulare Reaktionen, deren Konstanten in Glyzerin, das etwa zwei Mole Wasser im Liter enthält, um rund 20% kleiner sind als in ursprünglich absolutem. In letzterem sind sie bei der-Naphthoesäure neunmal, bei der-Naphthoesäure elfmal kleiner als bei der Benzoesäure, woraus geschlossen wird, daß diese in Glyzerin von 183° nicht nur stärker als die-, sondern auch als die-Naphthoesäure dissoziiert sein muß, falls es sich bei der Selbstveresterung hauptsächlich um eine Wasserstoffionenkatalyse handelt.In Glyzerin und Glykol bei 25° über die Geschwindigkeit der Chlorhydrinbildung ausgeführte Versuche bestätigen den Befund von Kailan und Goitein.