Investigating the role of c-Jun N-terminal kinases in the proliferation of Werner syndrome fibroblasts using diaminopyridine inhibitors

To develop more potent small molecules with enhanced free radical scavenger properties, a series of N-substituted isatin derivatives was synthesized, and the cytoprotective effect on the apoptosis of PC12 cells induced by H₂O₂ was screened. All these compounds were found to be active, and N-ethyl isatin was found with the most potent activity of 69.7% protective effect on PC12 cells. Structure-activity relationship analyses showed the bioactivity of N-alkyl isatins decline as the increasing of the chain of the alkyl group, furthermore odd-even effect was found in the activity, which is interesting for further investigation.     

-Particle radioactivity from LR 115 by two methods of analysis

LR115 track detectors were exposed to samples of Moroccan phosphate and phosphogypsum to measure their -particle radioactivity. Then two formalisms were used for the dosimetry: simulation by a Monte Carlo method and determination of concentrations from a numerically integrated track registration equation. The results were compared with those deduced γ-ray spectrometry.     

Multi-jet event rates in deep inelastic scattering and determination of the strong coupling constant

Jet event rates in deep inelastic ep scattering at HERA are investigated applying the modified JADE jet algorithm. The data are corrected for detector and hadronization effects and then compared with perturbative QCD predictions using next-to-leading order calculations. The strong coupling constant is determined evaluating the jet event rates. Values of are extracted in four different bins of the negative squared momentum transfer in the range from 40 GeV to 4000 GeV. A combined fit of the renormalization group equation to these several values results in     

Measurement of neutral and charged current cross sections in electron-proton collisions at high Q^2

The inclusive single and double differential cross sections for neutral and charged current processes are measured with the H1 detector at HERA, in the range of four-momentum transfer squared between 150 and 30 000 GeV, and Bjorken x between 0.002 and 0.65. The data were taken in 1998 and 1999 with a centre-of-mass energy of 320 GeV and correspond to an integrated luminosity of 16.4 pb. The data are compared with recent measurements of the inclusive neutral and charged current cross sections. For clear evidence is observed for an asymmetry between and neutral current scattering and the generalised structure function is extracted for the first time at HERA. A fit to the charged current data is used to extract a value for the W boson propagator mass. The data are found to be in good agreement with Standard Model predictions. Received: 21 December 2000 / Published online: 15 March 2001     

Measurement and QCD analysis of jet cross sections in deep-inelastic positron-proton collisions at \sqrt{s} of 300 GeV

Jet production is studied in the Breit frame in deep-inelastic positron-proton scattering over a large range of four-momentum transfers and transverse jet energies GeV. The analysis is based on data corresponding to an integrated luminosity of taken in the years 1995–1997 with the H1 detector at HERA at a center-of-mass energy GeV. Dijet and inclusive jet cross sections are measured multi-differentially using and angular ordered jet algorithms. The results are compared to the predictions of perturbative QCD calculations in next-to-leading order in the strong coupling constant . QCD fits are performed in which and the gluon density in the proton are determined separately. The gluon density is found to be in good agreement with results obtained in other analyses using data from different processes. The strong coupling constant is determined to be . In addition an analysis of the data in which both and the gluon density are determined simultaneously is presented.     

Charged particle cross sections in photoproduction and extraction of the gluon density in the photon

Photoproduction data collected with the H1 detector at HERA in 1994 are used to study the cross-sections for inclusive charged particle production and the structure of the photon. The differential cross-sections , for in the HERA laboratory frame, and for GeV/c and GeV/c have been measured. Model calculations of these cross-sections, based on perturbative QCD, indicate that the results are sensitive to the parton densities of the photon as well as to higher order effects, which are phenomenologically treated by multiple interactions. This sensitivity is exploited to determine the leading order distribution of partons in the photon using a new method based on high charged particles. The gluon content of the photon is extracted and found to rise with decreasing . Received: 8 October 1998 / Published online: 8 September 1999     

Inclusive photoproduction of neutral pions in the photon hemisphere at HERA

The inclusive cross section for the photoproduction of neutral pions has been measured as a function of the transverse momentum, rapidity, and Feynman x of the mesons at an average photon–proton centre-of-mass energy of 208 GeV and for photon virtualities below GeV. The measurement extends the range covered by previous charged particle measurements at HERA by two units of rapidity in the photon direction down to a value of in the centre-of-mass frame. The transverse momentum distribution is well described over the whole measured range by a power law ansatz, while an exponential fit falls below the data at transverse momentum values above 1.5 GeV/c. Good agreement with the predictions of the Monte Carlo models PYTHIA and PHOJET is found. In the context of the PYTHIA model the data are inconsistent with large intrinsic transverse momentum values in the photon. Received: 14 June 2000 / Published online: 27 November 2000