Dijet photoproduction of massless charm jets at next-to-leading order of QCD

We compute the charm dijet photoproduction cross section at next-to-leading order of QCD in the zero-mass variable flavour number scheme, i.e. with active charm quarks in the proton and photon. The results are compared to recent measurements from the ZEUS experiment at HERA. The predictions for various distributions agree with the data, in particular for large momentum fractions of the partons in the photon, where direct photon processes dominate. At low momentum fractions, the predictions are quite sensitive to the charm content in the photon. The experimental data are shown to favour parameterizations with a substantial charm-quark density such as the one proposed by Cornet et al.     

Single-bubble sonoluminescence in air-saturated water

Single bubble sonoluminescence (SBSL) is realized in air-saturated water at ambient pressure and room temperature. The behavior is similar to SBSL in degassed water, but with a higher spatial variability of the bubble position. A detailed view on the dynamics of the bubbles shows agreement between calculated shape stability borders but differs slightly in the equilibrium radii predicted by a mass diffusion model. A comparison with results in degassed water is done as well as a time resolved characterization of bubble oscillation, translation, and light emission for synchronous and recycling SBSL. The formation of streamer structures is observed in the same parameter range, when bubble nuclei are present. This may lead to a unified interpretation of SBSL and multibubble sonoluminescence.     

Über die photometrische Bestimmung des Cergehaltes legierter Stähle

After review of literature and experimental work photometry with o-tolidine is preferred as a sensitive, exact and simple procedure to determine < 0.1% cerium in steel. The precipitation with oxalate, thoroughly worked out, is recommended as a simple method to separate cerium from the other elements occurring in steels. With high-alloy steels a double precipitation is necessary. This involves a loss of 4% of cerium which, however, is reproducible and thus can be considered in calibrating. Ce contents from 0.002% to 1,0% can be determined.     

Evidence for the color-octet mechanism from CERN LEP2 gamma gamma --> J/psi + X Data

We present theoretical predictions for the transverse-momentum distribution of J/psi mesons promptly produced in gammagamma collisions within the factorization formalism of nonrelativistic quantum chromodynamics, including the contributions from both direct and resolved photons, and we perform a conservative error analysis. The fraction of J/psi mesons from decays of bottom-flavored hadrons is estimated to be negligibly small. New data taken by the DELPHI Collaboration at LEP2 nicely confirm these predictions, while they disfavor those obtained within the traditional color-singlet model.     

Strong coupling constant from the photon structure function

We extract the value of the strong coupling constant alpha(s) from a single-parameter pointlike fit to the photon structure function F(gamma)(2) at large x and Q(2) and from a first five-parameter full (pointlike and hadronic) fit to the complete F(gamma)(2)data set taken at PETRA, TRISTAN, and LEP. In next-to-leading order and the MS renormalization and factorization schemes, we obtain alpha(s)(m(Z))=0.1183+/-0.0050(expt)(+0.0029)(-0.0028)(theor) (pointlike) and alpha(s)(m(Z))=0.1198+/-0.0028(expt)(+0.0034)(-0.0046)(theor) (pointlike and hadronic). We demonstrate that the data taken at LEP have reduced the experimental error by about a factor of 2, so that a competitive determination of alpha(s) from F(gamma)(2) is now possible.     

Increased torque transducer sensitivity via oversampling

The sensitivity of a commercial torque transducer under oscillatory shear conditions is extended by about a factor 3–5 into the small torque region. This increased sensitivity is a result of a straightforward data treatment in the time domain termed “on the fly oversampling”. This method is enabled by the emergence of modern ADC-cards. The underlying ideas of oversampling together with a first experimental verification of this method are described in detail. Received: 22 August 2000 Accepted: 14 November 2000     

Simultaneous Determination of 12 Sulfonylurea Herbicides in Drinking Water after SPE by LC-DAD

A liquid chromatographic method (LC) with diode array detection (DAD) for the routine screening and quantification of highly applicated polar herbicides in drinking water samples was developed. The investigated herbicides consisted of 12 sulfonylurea herbicides (amidosulfuron, flazasulfuron, foramsulfuron, iodosulfuron-methyl Na, mesosulfuron-methyl, metsulfuron-methyl, nicosulfuron, prosulfuron, thifensulfuron-methyl, triasulfuron and tritosulfuron) together with 6 polar pesticides of relevance (atrazine, desethylatrazine, desisopropylatrazine, chlortoluron, diuron, fluoxypyr). The herbicides were extracted and concentrated by off-line solid-phase extraction and subsequently eluates were analyzed by LC-DAD. Recoveries obtained from fortified water samples at 100 ng L^?1 were in the range of 84–107% with RSD’s <20%. The limit of detection varied from 2 to 16 ng L^?1.