Normal Auger spectra of Br in alkali bromide molecules

Molecular Auger electron spectra following the bromine 3d ionization in gas-phase alkali bromides and in HBr were studied both experimentally and theoretically. The AES for HBr and CsBr were measured using photoexcitation, and for LiBr, NaBr, and KBr by using electron impact. These results are compared with the theoretical spectra from nonrelativistic ab initio calculations and one-center approximation and with the spectra of Br(-), computed with the multiconfiguration Dirac-Fock method.     

Planar chip device for PCR and hybridization with surface acoustic wave pump

We have developed a microfluidic device operating at a planar surface instead of a closed channel network. The fluid is transported in single droplets using surface acoustic waves (SAW) on a piezoelectric LiNbO(3) substrate. The surface of the piezo is chemically structured to induce high contact angles of the droplets or enclose areas where the liquid can wet the substrate. Combining the SAW technique with thin film resistance heaters, a biological analysis chip with integrated DNA amplification by PCR and hybridization was designed. To prevent evaporation of the PCR reagents at high temperatures the sample is enclosed in droplets of mineral oil. On this chip the SAW resolves dried primers, shifts the oil capped liquid between the two heaters and mixes during hybridization. The chip is able to perform a highly sensitive, fast and specific PCR with a volume as low as 200 nl. During the temperature cycles an online monitoring of the DNA concentration is feasible with an optical unit, providing a sensitivity of 0.1 ng. After PCR the product is moved to the second heater for the hybridization on a spotted DNA array. With our chip we were able to detect a single nucleotide polymorphism (SNP) responsible for the Leiden Factor V syndrome from human blood.     

Top down characterization of secreted proteins from Mycobacterium tuberculosis by electron capture dissociation mass spectrometry

Secreted proteins of Mycobacterium tuberculosis are implicated in its disease pathogenesis and so are considered as potential diagnostic and vaccine candidates. The search for these has been slow, even though the entire genome sequence of M. tuberculosis is now available; of the 620 protein spots resolved by 2-D gel electrophoresis, 114 secreted proteins have been identified, but for only 13 has the primary structure been partly characterized. For comparison, in this top down mass spectrometry (MS) approach the secreted proteins were precipitated from cell culture filtrate, resuspended, and examined directly by electrospray ionization (ESI) Fourier transform MS. The ESI spectra of three precipitates showed 93, 535, and 369 molecular weight (M(r)) values, for a total of 689 different values. However, only approximately 10% of these values matched (+/-1 Da) the DNA predicted M(r) values, but these identifications were unreliable. Of nine molecular ions characterized by MS/MS, only one protein match was confirmed, and its isotopic molecular ions were overlapped by those of another protein. MS/MS identified a total of ten proteins by sequence tag search, of which three were unidentified previously. The low success of M(r) matching was due to unusually extensive posttranslational modifications, including loss of a signal sequence, loss of the N-terminal residue, proteolytic degradation, oxidation, and glycosylation. Although in eubacteria the latter is relatively rare, a 9 kDa protein showed 7 hexose attachments and two 20 kDa proteins each had 20 attachments. For MS/MS, electron capture dissociation was especially effective.     

NMR diffusion studies of translational properties of oil inside core-shell latex particles

The diffusion behavior of core-shell latex particles with a liquid core of hexadecane and a solid polystyrene shell in water solution has been studied using the pulsed field gradient spin-echo (PFG-SE) NMR technique. The apparent diffusion coefficient and the root mean square displacement of oil were strongly dependent on the diffusion time Delta. With increasing diffusion time, the obstructing effect from the particle wall caused a decrease in the apparent oil diffusion coefficient. The root mean square displacement of oil inside the particle core was constant for all diffusion times and was used for the calculation of the particle radius. The volume fraction dependence of the apparent diffusion coefficient was found to be roughly consistent with the hard-sphere model. The diffraction pattern in the echo decay predicted from the q-space formalism for molecules diffusing inside a spherical cavity was almost completely smeared out due to polydispersity and wall relaxation effects. It was observed that 10-20% (w/w) of the particle shell consisted of hexadecane. This fact imparted a slow component to the echo decay, since the exchange time between oil in the shell and oil in the cavity was slow, which further contributed to the smearing out of the diffraction pattern. It was concluded that by using the core-shell concept very good signal-to-noise is obtained in the PFG-SE experiment, thus making possible studies of translational properties of colloidal particles in different environments to an extent that previously has been very difficult to perform.     

The mechanism of η(η5:η5-fulvalene)-di-μ-chloro-bis (η5-cyclopentadienyltitanium) formation in the system Cp2TiCl2 : LiAlH4 : Olefinic solvent

Summary The reduction of Cp₂TiCl₂ with LiAlH₄ in olefinic solvents at temperatures above 100° leads to the formation of µ-( ⁵ : ⁵-fulvalene)-di-µ-chloro-bis( ⁵-cyclopentadienyl-titanium) (1) and finally to µ-( ⁵ : ¹⁵-fulvalene)-di-µ-hydrido-bis ( ⁵-cyclopentadienyltitanium). The first step of the reduction includes mainly the formation of the dimer of bis( ⁵-cyclopentadienyl)titanium(III) chloride, (Cp₂TiCl)₂. The mechanism of its conversion into (1) involves the formation of an intermediate bis( ⁵-cyclopentadienyl)titanium(III) hydride species which reacts immediately with the olefinic solvent to give bis( ⁵-cyclopentadienyl)alkyltitanium(III) compounds. The formation of the fulvalene ligand in (1) is explained by the interaction of the alkyltitanium compound with the cyclopentadienyl ligands of (Cp₂TiCl)₂ resulting in hydrogen transfer to the olefinic solvent.     

The constant flow rate problem for fluids with increasing yield stress in a pipe

Experiments show that the degradation effect observed during both stirring and pipelining tests of some coal-water slurries is mainly to be ascribed to the increase of the yield stress. Regardless of the particular mathematical model adopted to investigate the dynamics of these fluids, engineering applications force us to consider the problem of how long a constant flow rate can be maintained during the pipelining process. We choose a Bingham model where the yield stress is assumed to increase with the dissipated energy as in [5]. It is first shown that the constant flow rate problem is equivalent to solving a nonlinear functional equation in the unknown pressure gradient that generalizes the classical algebraic Buckingham equation for the same problem with constant rheological parameters. By means of a fixed-point argument we also prove that the functional equation has one and only one solution which is local in time. We finally find an estimate from below of the interval of the interval of existence. Numerical results are rather good and agree with those expected from the engineering point of view.     

A note on the first Betti number of submanifolds with nonnegative Ricci curvature in codimension two

We show that a complete submanifold in codimension two with nonnegative Ricci curvature which contains no lines and is covered by has nonnegative sectional curvatures. This implies some results about the first Betti number of such a submanifold.