No abstract available

[en] Multicellular spheroids of V79-4 Chinese hamster cells and TU 197 Tr1 human tumor cells were investigated by scanning electron microscopy. Spheroids of human tumor cells and Chinese hamster cells did not show any essential differences. On an average the tumor cells were somewhat larger, their surface was more intensively structured. The surfaces of V79-4 cells in the outer spheroid cell layers were covered with numerous microvilli which could be seen in the fissure of a burst spheroid. In split spheroids prepared by blunt dissection of fixed and sputtered spheroids according to the technique described for cell aggregates by Gershman and Rosen the fracture in spheroids run across the cells of the outer proliferating shell and no cell surfaces could be seen as in cell aggregates. That means that the cell-cell contact in spheroids is stronger than in young cell aggregates. The X irradiation procedures revealed some alterations of the spheroid surface which, however, could not be related to radiation doses and the period after irradiation. (author)

[en] After special preparation and staining of bloodsmears the plasma-protein film of rat erythrocytes can be revealed as a marginal zone (breadth of 1.0 - 1.4 μm) of erythrocytes by phase-contrast microscopy and scanning electronmicroscopy, resp. If Wistar rats were exposed to a single whole-body irradiation of 0.10 Gy, alterations of the marginal zone and of the pallor area of erythrocytes were demonstrated 1 hour postirradiation. Possible reasons for the erythrocyte alterations are discussed. It seems to be a practicable method to register biological radiation effects after single low dose irradiation. (author)

No abstract available

[en] We measure the Λ_b⁰ lifetime in the fully reconstructed decay Λ_b⁰ → J/ψΛ⁰ using 10.4 fb^-1 of p(bar p) collisions collected with the D0 detector at √s = 1.96 TeV. The lifetime of the topologically similar decay channel B⁰ → J/ψK_S⁰ is also measured. We obtain τ(Λ_b⁰) = 1.303 ± 0.075(stat) ± 0.035(syst) ps and τ(B⁰) = 1.508 ± 0.025(stat) ± 0.043(syst) ps. Using these measurements, we determine the lifetime ratio of τ(Λ_b⁰)/τ(B⁰) = 0.864 ± 0.052(stat) ± 0.033(syst).

[en] We present searches for the anomalous γWW and ZWW trilinear gauge boson couplings from WW and WZ production using lepton plus dijet final states and a combination with results from Wγ, WW, and WZ production with leptonic final states. The analyzed data correspond to up to 8.6 fb^-1 of integrated luminosity collected by the D0 detector in pp^¯ collisions at √(s)=1.96 TeV. We set the most stringent limits at a hadron collider to date assuming two different relations between the anomalous coupling parameters Δκ_γ, λ, and Δg₁^Z for a cutoff energy scale Λ=2 TeV. The combined 68% C.L. limits are −0.057<Δκ_γ<0.154, -0.015<λ<0.028, and -0.008<Δg₁^Z<0.054 for the LEP parameterization, and -0.007<Δκ<0.081 and -0.017<λ<0.028 for the equal couplings parameterization. We also present the most stringent limits of the W boson magnetic dipole and electric quadrupole moments.

[en] We present measurements of the differential cross section dσ/dp_T^γ for the associated production of a c-quark jet and an isolated photon with rapidity |y^γ|<1.0 and transverse momentum 30< p_T^γ<300 GeV. The c-quark jets are required to have |y^jet|<1.5 and p_T^jet>15 GeV. The ratio of differential cross sections for γ+c to γ+b production as a function of p_T^γ is also presented. The results are based on data corresponding to an integrated luminosity of 8.7 fb⁻¹ recorded with the D0 detector at the Fermilab Tevatron pp^¯ Collider at √(s)=1.96 TeV. The obtained results are compared to next-to-leading order perturbative QCD calculations using various parton distribution functions, to predictions based on the k_T-factorization approach, and to predictions from the SHERPA and PYTHIA Monte Carlo event generators

[en] We present a search for the standard model Higgs boson in 9.5 fb^-1 of pp^¯ collisions at √(s)=1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The final state considered contains a pair of b jets and is characterized by an imbalance in transverse energy, as expected from pp^¯→ZH→νν^¯bb^¯ production. The search is also sensitive to the WH→ℓνbb^¯ channel when the charged lepton is not identified. The data are found to be in good agreement with the expected background. For a Higgs boson mass of 125 GeV, we set a limit at the 95% C.L. on the cross section σ(pp^¯→[Z/W]H), assuming standard model branching fractions, that is a factor of 4.3 times larger than the theoretical standard model value, while the expected factor is 3.9. The search is also used to measure a combined WZ and ZZ production cross section that is a factor of 0.94±0.31(stat)±0.34(syst) times the standard model prediction of 4.4 pb, with an observed significance of 2.0 standard deviations.

[en] We present measurements of the differential cross section dσ/dp_T^γ for the inclusive production of a photon in association with a b-quark jet for photons with rapidities |y^γ|<1.0 and 30< p_T^γ<300 GeV, as well as for photons with 1.5<|y^γ|<2.5 and 30< p_T^γ<200 GeV, where p_T^γ is the photon transverse momentum. The b-quark jets are required to have p_T>15 GeV and rapidity |y^jet|<1.5. The results are based on data corresponding to an integrated luminosity of 8.7 fb^-1, recorded with the D0 detector at the Fermilab Tevatron pp^¯ Collider at √(s)=1.96 TeV. The measured cross sections are compared with next-to-leading order perturbative QCD calculations using different sets of parton distribution functions as well as to predictions based on the k_T-factorization QCD approach, and those from the SHERPA and PYTHIA Monte Carlo event generators.

[en] We present a measurement of the cross section for W boson production in association with at least one b-quark jet in proton–antiproton collisions. The measurement is made using data corresponding to an integrated luminosity of 6.1 fb⁻¹ recorded with the D0 detector at the Fermilab Tevatron pp^¯ Collider at √(s)=1.96 TeV. We measure an inclusive cross section of σ(W(→μν)+b+X)=1.04±0.05(stat.)±0.12(syst.) pb and σ(W(→eν)+b+X)=1.00±0.04(stat.)±0.12(syst.) pb in the phase space defined by p_T^ν>25 GeV, p_T^b-jet>20 GeV, |η^b-jet|<1.1, and a muon (electron) with p_T^ℓ>20 GeV and |η^μ|<1.7 (|η^e|<1.1 or 1.5<|η^e|<2.5). The combined result per lepton family is σ(W(→ℓν)+b+X)=1.05±0.12(stat.+syst.) pb for |η^ℓ|<1.7. The results are in agreement with predictions from next-to-leading order QCD calculations using MCFM, σ(W+b)⋅B(W→ℓν)=1.34_−0.34^+0.41(syst.) pb, and also with predictions from the SHERPA and MADGRAPH Monte Carlo event generators.