University of Hamburg

About: University of Hamburg is a education organization based out in Hamburg, Germany. It is known for research contribution in the topics: Population & Laser. The organization has 45564 authors who have published 89286 publications receiving 2850161 citations. The organization is also known as: Hamburg University.

Biosynthesis of very-long-chain polyunsaturated fatty acids in transgenic oilseeds: constraints on their accumulation.

Abstract: ω6- and ω3-polyunsaturated C20 fatty acids represent important components of the human diet. A more regular consumption and an accordingly sustainable source of these compounds are highly desirable. In contrast with the very high levels to which industrial fatty acids have to be enriched in plant oils for competitive use as chemical feedstocks, much lower percentages of very-long-chain polyunsaturated fatty acids (VLCPUFA) in edible plant oils would satisfy nutritional requirements. Seed-specific expression in transgenic tobacco (Nicotiana tabacum) and linseed (Linum usitatissimum) of cDNAs encoding fatty acyl-desaturases and elongases, absent from all agronomically important plants, resulted in the very high accumulation of Δ6-desaturated C18 fatty acids and up to 5% of C20 polyunsaturated fatty acids, including arachidonic and eicosapentaenoic acid. Detailed lipid analyses of developing seeds from transgenic plants were interpretated as indicating that, after desaturation on phosphatidylcholine, Δ6-desaturated products are immediately channeled to the triacylglycerols and effectively bypass the acyl-CoA pool. Thus, the lack of available Δ6-desaturated acyl-CoA substrates in the acyl-CoA pool limits the synthesis of elongated C20 fatty acids and disrupts the alternating sequence of lipid-linked desaturations and acyl-CoA dependent elongations. As well as the successful production of VLCPUFA in transgenic oilseeds and the identification of constraints on their accumulation, our results indicate alternative strategies to circumvent this bottleneck.

Fast variability of tera-electron volt gamma rays from the radio galaxy M87.

Abstract: The detection of fast variations of the TeV (10^12 eV) gamma-ray flux, on time-scales of days, from the nearby radio galaxy M 87 is reported. These variations are ~10 times faster than that observed in any other waveband and imply a very compact emission region with a dimension similar to the Schwarzschild radius of the central black hole. We thus can exclude several other sites and processes of the gamma-ray production. The observations confirm that TeV gamma-rays are emitted by extragalactic sources other than blazars, where jets are not relativistically beamed towards the observer.

Parton Distribution Functions, $\alpha_s$ and Heavy-Quark Masses for LHC Run II

Abstract: We determine a new set of parton distribution functions (ABMP16), the strong coupling constant αs and the quark masses mc, mb and mt in a global fit to next-to-next-to-leading order (NNLO) in QCD. The analysis uses the MS¯ scheme for αs and all quark masses and is performed in the fixed-flavor number scheme for nf=3, 4, 5. Essential new elements of the fit are the combined data from HERA for inclusive deep-inelastic scattering (DIS), data from the fixed-target experiments NOMAD and CHORUS for neutrino-induced DIS, data from Tevatron and the LHC for the Drell-Yan process and the hadro-production of single-top and top-quark pairs. The theory predictions include new improved approximations at NNLO for the production of heavy quarks in DIS and for the hadro-production of single-top quarks. The description of higher twist effects relevant beyond the leading twist collinear factorization approximation is refined. At NNLO, we obtain the value αs(nf=5)(MZ)=0.1147±0.0008.

Soft tissue reactions to non-submerged unloaded titanium implants in beagle dogs.

Abstract: The soft tissue reactions to non-submerged unloaded titanium implants were examined. A total of 24 implants were placed in 6 beagle dogs. The implants differed in their crestal area by having either a rough sandblasted, a fine sandblasted, or a polished surface. After 3 months, all implants were firmly anchored in the bone and had no clinical signs of peri-implant inflammation. Undecalcified histologic sections demonstrated that all implants achieved osseointegration with direct bone contact. The epithelial structures showed a peri-implant sulcus with a non-keratinized sulcular epithelium and a junctional epithelium. None of the sections exhibited epithelial downgrowth to the alveolar crest. In the supracrestal area, a direct connective tissue contact to the implant post was observed. An approximately 50 to 100 microns wide zone of dense circular fibers was found close to the implant surface. It was free of blood vessels and resembled closely an inflammation-free scar tissue formation. This zone was surrounded by a looser connective tissue with a 3-dimensional network of collagen fibers running in different directions. No significant differences concerning soft tissue reactions were found between the 3 implant surfaces. In particular, the length of direct connective tissue contact was similar. Concerning bone reactions, a significantly shorter distance from the top of the implant to the most coronal bone-implant contact was observed for rough surfaces. It is concluded that non-submerged unloaded titanium implants achieved a complication-free tissue integration with a dense connective tissue in direct contact to the implant surface in the supracrestal area, and epithelial structures similar to those around natural teeth. The different surface textures did not influence the healing pattern of the soft tissues, but had an influence on the location of the most coronal bone-implant contact.