Christian Nagel

Learn More
Motivated by some results for linear programs and complementarity problems, this paper gives some new characterizations of the central path conditions for semidefinite programs. Exploiting these characterizations, some smoothing-type methods for the solution of semidefinite programs are derived. The search directions generated by these methods are(More)
We present a successive linearization method with a trust region-type globalization for the solution of nonlinear semidefinite programs. At each iteration, the method solves a quadratic semidefinite program, which can be converted to a linear semidefinite program with a second order cone constraint. A subproblem of this kind can be solved quite efficiently(More)
We consider a Newton-type method for the solution of semidefinite programs. This Newton-type method is based on a semismooth reformulation of the semidefinite program as a nonsmooth system of equations. We establish local quadratic convergence of this method under a linear independence assumption and a slightly modified nondegeneracy condition. In contrast(More)
Hereditary nevoid basal cell carcinoma syndrome (NBCCS) is caused by PTCH1 gene mutations that result in diverse neoplasms including medulloblastoma (MB). Epidemiological studies report reduced pediatric brain tumor risks associated with maternal intake of prenatal vitamins containing folic acid (FA) and FA supplements specifically. We hypothesized that low(More)
Four enzymes were separated from an extracellular preparation of Bacillus polymyxa by carboxymethylcellulose column chromatography. The pH optima were 8.3 to 8.5, 8.7 to 8.9, 9.2 to 9.4, and 9.5 to 9.6. All of the enzymes required calcium ion for maximum activity, whereas strontium ion was only partially effective in stimulating activity. Cobalt was the(More)
Homeostatic plasticity is an important attribute of neurons and their networks, enabling functional recovery after perturbation. Furthermore, the directed nature of this plasticity may hold a key to the restoration of locomotion after spinal cord injury. Here we studied the recovery of crawling in the leech Hirudo verbana after descending cephalic fibers(More)