Michael Ratz

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The early pathophysiology of diabetic retinopathy and the involvement of neural and vascular malfunction are poorly understood. Glial cells provide structural and metabolic support for retinal neurons and blood vessels, and the cells become reactive in certain injury states. We therefore used the streptozotocin rat model of short-term diabetic retinopathy(More)
The relationship between neuronal glutamate turnover, the glutamate/glutamine cycle and de novo glutamate synthesis was examined using two different model systems, freshly dissected rat retinas ex vivo and in vivo perfused rat brains. In the ex vivo rat retina, dual kinetic control of de novo glutamate synthesis by pyruvate carboxylation and transamination(More)
Consistent uplifting of AdS vacua in string theory often requires extra light degrees of freedom in addition to those of a (Kähler) modulus. Here we consider the possibility that de Sitter and Minkowski vacua arise due to hidden sector matter interactions. We find that, in this scheme, the hierarchically small supersymmetry breaking scale can be explained(More)
Retinas of diabetic individuals develop early functional changes measurable by electrophysiological and psychometric testing. Using a rat model of diabetes, we previously identified diabetes-induced alterations in metabolism of the neurotransmitter glutamate which may ultimately lead to accumulation of glutamate in the retina (Diabetes, 47: 815, 1998). We(More)
We show that nanoscopy based on the principle called RESOLFT (reversible saturable optical fluorescence transitions) or nonlinear structured illumination can be effectively parallelized using two incoherently superimposed orthogonal standing light waves. The intensity minima of the resulting pattern act as 'doughnuts', providing isotropic resolution in the(More)
We systematically analyze quantum corrections in see-saw scenarios, including effects from above as well as below the see-saw scales. We derive approximate renormalization group equations for neutrino masses, lepton mixings and CP phases, yielding an analytic understanding and a simple estimate of the size of the effects. Even for hierarchical masses, they(More)
We present a [FORMULA: SEE TEXT] orbifold compactification of the E8xE8 heterotic string which leads to the (supersymmetric) standard model gauge group and matter content. The quarks and leptons appear as three 16-plets of SO(10), whereas the Higgs fields do not form complete SO(10) multiplets. The model has large vacuum degeneracy. For generic vacua, no(More)
In the context of flux compactifications, metastable vacua with a small positive cosmological constant are obtained by combining a sector where supersymmetry is broken dynamically with the sector responsible for moduli stabilization, which is known as the F–uplifting. We analyze this procedure in a model–independent way and study phenomenological properties(More)