139 research outputs found
Langfristiges Wachstum durch Forschung und Innovation
Dietmar Harhoff, LMU und Expertenkommission Forschung und Innovation, sieht Handlungsbedarf bei der Innovationsfinanzierung und im Wissens- und Technologietransfer. Da Deutschland zu sehr auf inkrementelle und zu wenig auf radikale Innovationen setze, sollte das Steuersystem „eigenkapital- und innovationsfreundlicher“ und die Rahmenbedingungen für Wagniskapitalgeber verbessert werden. Im Bereich Technologietransfer sollte die Unterstützung von Public Private Partnerships ausgebaut, die Handhabung des Neuheitsschutzes im Patentrecht verbessert und die Beteiligung von Hochschulen an Ausgründungen erleichtert werden. Auch in der Innovationspolitik werde deutlich, dass der Staat durch bessere Rahmenbedingungen für Gründungen und radikale Neuerungen viel dazu beitragen könne, die langfristigen Wachstumsaussichten zu verbessern.Wirtschaftswachstum, Technischer Fortschritt, Forschungs- und Technologiepolitik, Wirtschaftspolitische Wirkungsanalyse, Deutschland
Impact of Criticality and Phase Separation on the Spin Dynamics of the One-Dimensional t–J Model
The recursion method is used to determine the T=0 spin dynamic structure factor S zz (q,ω) in the Luttinger liquid state and in the phase‐separated state of the one‐dimensional t–J model. As the exchange coupling increases from zero, the dispersions and line shapes of the dominant spin excitations are observed to undergo a major metamorphosis between the free‐fermion limit and the onset of phase separation. The familiar two‐spinon spectrum of the Heisenberg antiferromagnetic chain emerges gradually in the strongly phase‐separated state
Impact of porcine cytomegalovirus on long-term orthotopic cardiac xenotransplant survival
Xenotransplantation using pig organs has achieved survival times up to 195 days in pig orthotopic heart transplantation into baboons. Here we demonstrate that in addition to an improved immunosuppressive regimen, non-ischaemic preservation with continuous perfusion and control of post-transplantation growth of the transplant, prevention of transmission of the porcine cytomegalovirus (PCMV) plays an important role in achieving long survival times. For the first time we demonstrate that PCMV transmission in orthotopic pig heart xenotransplantation was associated with a reduced survival time of the transplant and increased levels of IL-6 and TNF alpha were found in the transplanted baboon. Furthermore, high levels of tPA-PAI-1 complexes were found, suggesting a complete loss of the pro-fibrinolytic properties of the endothelial cells. These data show that PCMV has an important impact on transplant survival and call for elimination of PCMV from donor pigs
Bosonization of interacting fermions in arbitrary dimension beyond the Gaussian approximation
We use our recently developed functional bosonization approach to bosonize
interacting fermions in arbitrary dimension beyond the Gaussian
approximation. Even in the finite curvature of the energy dispersion at
the Fermi surface gives rise to interactions between the bosons. In higher
dimensions scattering processes describing momentum transfer between different
patches on the Fermi surface (around-the-corner processes) are an additional
source for corrections to the Gaussian approximation. We derive an explicit
expression for the leading correction to the bosonized Hamiltonian and the
irreducible self-energy of the bosonic propagator that takes the finite
curvature as well as around-the-corner processes into account. In the special
case that around-the-corner scattering is negligible, we show that the
self-energy correction to the Gaussian propagator is negligible if the
dimensionless quantities are
small compared with unity for all patches . Here is the cutoff
of the interaction in wave-vector space, is the Fermi wave-vector,
is the chemical potential, is the usual dimensionless Landau
interaction-parameter, and is the {\it{local}} density of
states associated with patch . We also show that the well known
cancellation between vertex- and self-energy corrections in one-dimensional
systems, which is responsible for the fact that the random-phase approximation
for the density-density correlation function is exact in , exists also in
, provided (1) the interaction cutoff is small compared with
, and (2) the energy dispersion is locally linearized at the Fermi the
Fermi surface. Finally, we suggest a new systematic method to calculate
corrections to the RPA, which is based on the perturbative calculation of the
irreducible bosonic self-energy arising from the non-Gaussian terms of the
bosonized Hamiltonian.Comment: The abstract has been rewritten. No major changes in the text
Charge and spin dynamics in the one-dimensional and models
The impact of the spin-flip terms on the (static and dynamic) charge and spin
correlations in the Luttinger-liquid ground state of the 1D model is
assessed by comparison with the same quantities in the 1D model, where
spin-flip terms are absent. We employ the recursion method combined with a
weak-coupling or a strong-coupling continued-fraction analysis. At
we use the Pfaffian representation of dynamic spin correlations. The changing
nature of the dynamically relevant charge and spin excitations on approach of
the transition to phase separation is investigated in detail. The
charge excitations (but not the spin excitations) at the transition have a
single-mode nature, whereas charge and spin excitations have a complicated
structure in the model. In the model, phase separation is
accompanied by N\'eel long-range order, caused by the condensation of electron
clusters with an already existing alternating up-down spin configuration
(topological long-range order). In the model, by contrast, the spin-flip
processes in the exchange coupling are responsible for continued strong spin
fluctuations (dominated by 2-spinon excitations) in the phase-separated state.Comment: 11 pages (RevTex). 14 Figures available from author
Ordering and fluctuations in the ground state of the one-dimensional and two-dimensional S
Modeling of Photovoltage and Photocurrent in Dye-Sensitized Titanium Dioxide Solar Cells
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