Toward understanding the ionization of biomarkers from micrometer particles by bio-aerosol mass spectrometry

The appearance of informative signals in the mass spectra of laser-ablated bio-aerosol particles depends on the effective ionization probabilities (EIP) of individual components during the laser ionization process. This study investigates how bio-aerosol chemical composition governs the EIP values of specific components and the overall features of the spectra from the bio-aerosol mass spectrometry (BAMS). EIP values were determined for a series of amino acid, dipicolinic acid, and peptide aerosol particles to determine what chemical features aid in ionization. The spectra of individual amino acids and dipicolinic acid, as well as mixtures, were examined for extent of fragmentation and the presence of molecular ion dimers, which are indicative of ionization conditions. Standard mixtures yielded information with respect to the significance of secondary ion plume reactions on observed spectra. A greater understanding of how these parameters affect EIP and spectra characteristics of bio-aerosols will aid in the intelligent selection of viable future biomarkers for the identification of bio-terrorism agents.     

Recherches sur la structure électronique de composés soufrés (méthode L.C.A.O. améliorée)

Improved L.C.A.O. method primitively built for conjugated molecules holding only atoms of second row in the periodic classification is extended to molecules holding atoms of the third row. The application is done for thiophen, thioketones, SO₂ and SO₃. d orbitals are not introduced in this study. Discussion about results shows that d orbitals must be introduced when the sulphur atom is strongly positively charged like in sulphur oxides.     

Palladium-tetraphosphine complex: an efficient catalyst for the coupling of aryl halides with alkynes

The cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)-cyclopentane-[PdCl(eta3-C3H5)]2 system catalyses the coupling of aryl halides with alkynes with very high ratios of substrates-catalyst in good yields; a turnover number of 2600000 can be obtained for the reaction of 4-trifluoromethylbromobenzene with phenylacetylene in the presence of this catalyst.     

Significance of oligomerization reactions in the transesterification of dimethyl terephthalate with ethylene glycol

Experimental investigations dealing with and mathematical models proposed for the kinetics of the transesterification of dimethyl terephthalate with ethylene glycol were critically reviewed. The models were found to be inadequate, while the investigations were found to be entirely lacking in information about the significance of oligomerization reactions. The significance of these reactions was deduced to be negligible by carrying out an analysis of the kinetics of possible ester interchange and transesterification reactions by use of data on methanol reported in the reviewed literature. This analysis was made possible by the application of numerical quadrature routines in testing the assumed models by the integral method.     

Die Bestimmung des Gresamtschwefels in Viscose

Zusammenfassung Die Bestimmung des Gesamtschwefels in Viscose wurde untersucht. Es wurde gezeigt, da\ die gravimetrische Bestimmung, wobei mit Wasserstoffperoxyd oxydiert wird, nicht als Bezugsmethode betrachtet werden darf. Eine neue Bezugsmethode wird vorgeschlagen, wobei die Viscose durch Erhitzen mit einem Gemisch von SalzsÄure, JodwasserstoffsÄure und unterphosphoriger SÄure zersetzt wird.Mittels der Behandlung mit diesem reduzierenden SÄuregemisch werden die in der Viscose vorhandenen Schwefelverbindungen quantitativ in Schwefelwasserstoff und Schwefelkohlenstoff übergeführt.Der Autor wünscht der Direktion der N.V. Onderzoekingsinstituut Research zu danken für die Genehmigung, diese Arbeit zu veröffentlichen.     

Hydrogen-bonding contributions to the lattice energy of salts for second harmonic generation

The lattice energies of a series of organic dihydrogenphosphate salts capable of second harmonic generation (SHG) have been calculated. These calculations, coupled with empirical data, indicate that a minimum of 20–25% of the lattice energy arises from hydrogen-bond interactions. Hydrogen bonding is shown to be a strong enough force to have a profound effect on the overall packing and crystal geometry of such ionic materials, and is thus an important factor to consider for crystal engineering.     

Energy levels of paramagnetic ions: Algebra. III. The case of dN ions in cubical symmetry

The formalism developed in the first two papers of this series is applied to the investigation of a new weak-field model. This crystal-field model lies on the use of a symmetry-adapted weak-field basis and an effective Hamiltonian involving in a symmetrical way both spin- and orbit-dependent contributions. Some general properties of this Hamiltonian are studied and complete calculation of its matrix elements is conducted in a symmetry-adapted weak-field basis in the case of an arbitrary configuration nl^N in any symmetry. The case of a configuration nd^N in octahedral symmetry is fully explored. In this case, the proposed weak-field model is restricted to a 12-parameter model which accounts for isotropic and anisotropic Coulomb interactions, isotropic and anisotropic spin-orbit interactions, and crystal-field interactions. A comparison between this 12-parameter weak-field model and the 14-parameter strong-field model is established. Equivalence between the latter two models requires two constraint relations to be satisfied for some strong-field parameters. These two relations are examined with various viewpoints.     

Heck arylations of pent-4-enoates or allylmalonate using a palladium/tetraphosphine catalyst

The Heck reaction of aryl halides with functionalised alk-1-enes should be a powerful method for the synthesis of functionalised (E)-1-arylalk-1-ene derivatives. The major problem of this reaction is the palladium-catalysed migration of the carbon-carbon double bond along the alkyl chain when there are no substituents on the C3 carbon of the alk-1-enes. We observed that for the arylation of ethyl pent-4-enoate, ethyl 2-methylpent-4-enoate or dimethyl allylmalonate this migration could be partially or completely controlled using appropriate reaction conditions. The ramification on the alkyl chain and the substituents on the aryl halide have also an important influence on this migration. Moreover, the cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane/1/2[PdCl(C₃H₅)]₂ system catalyses this reaction with a wide range of aryl bromides using very high ratio substrate/catalyst in good yields.