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Biomedical subjects

Philipp Werner

Publications and source records attributed to Philipp Werner.

10 recordsLinked to original sources
PubMed2007

A comparison of outcomes after robotic open extended thymectomy for myasthenia gravis.

OBJECTIVE: The aim of this study was to analyze the effect of the surgical approach on surgical and neurologic outcomes after extended thymectomy for myasthenia gravis. METHODS: A retrospective analysis of the institutional extended thymectomies for myasthenia gravis within the last decade was performed. Patients of group A (open access by total median sternotomy; n=10; 1996-2002) and of group B (video assisted thoracoscopic surgery approach with the da Vinci robotic system; n=9; 2003-2006) did not differ with regard to gender distribution, age, body mass index, American Association of Anaesthetists score and Osserman classification of myasthenia gravis. Primary endpoints were surgical complications and the symptomatic/neurologic outcome of the extended thymectomy. Secondary endpoints were operating times and hospital stay. RESULTS: Median follow-up was 74+/-23 months in group A and 13+/-10 months in group B. Surgical complications occurred in 4 patients in group A (requiring 2 re-interventions) and in 1 patient in group B (p<0.05). The median dose of Pyridostigminbromid was reduced 3 and 6 months postoperatively in group A to 80% and 60% of the preoperative level and in group B to 66% and 60% of the preoperative level, respectively. Within the first postoperative year all patients of group B had an improvement of their disease whereas 2 patients of group A did not benefit from thymectomy or had a worsening of symptoms. Operating times were significantly shorter in group A (110 (42-152) min vs 154 (94-312) min, p<0.05), hospital stay was significantly shorter in group B (5 (4-15) vs 10 (10-23) days, p<0.05). CONCLUSIONS: The results of this small series favour the robotic approach for extended thymectomy for myasthenia gravis in respect of both surgical and early neurologic outcome. However, prospective randomized trials are required to prove a general validity.

Female↗
PubMed2006

Continuous-time solver for quantum impurity models.

We present a new continuous-time solver for quantum impurity models such as those relevant to dynamical mean field theory. It is based on a stochastic sampling of a perturbation expansion in the impurity-bath hybridization parameter. Comparisons with Monte Carlo and exact diagonalization calculations confirm the accuracy of the new approach, which allows very efficient simulations even at low temperatures and for strong interactions. As examples of the power of the method we present results for the temperature dependence of the kinetic energy and the free energy, enabling an accurate location of the temperature-driven metal-insulator transition.

Journal Article↗
PubMed2006

The osteoprotegerin/RANK/RANKL system: a bone key to vascular disease.

Owing to the common coincidence of osteoporosis and vascular disease, pathophysiological links between both disorders have long been sought. The osteoprotegerin (OPG)/receptor activator of NF-kappaB (RANK)/receptor activator of NF-kappaB ligand (RANKL) cytokine network, a key regulatory system in bone homeostasis, has been implicated recently in vascular calcification, changes in matrix composition and diabetic macroangiopathy, aortic aneurysm development, heart failure and, most importantly, advanced atherosclerosis, plaque destabilization and manifestation of cardiovascular diseases. The concept of an active role of RANKL and OPG in vascular pathophysiology is intriguing and is gaining increasing support from both epidemiological and basic research. OPG serum level is considered to be a stable and reliable indicator of the overall activity of the OPG/RANK/RANKL axis and may find application as a biomarker of vascular risk and prognosis. RANKL in turn may be a suitable target for novel therapies. Pharmacological strategies for specific interference with the OPG/RANK/RANKL axis are currently being developed and evaluated in osteoporosis therapy.

Biomarkers↗
PubMed2005

Efficient simulation of resistively shunted Josephson junctions.

We present a cluster algorithm for resistively shunted Josephson junctions or similar physical systems, which dramatically improves sampling efficiency, and apply it to the superconductor-to-metal transition in a single junction. Measuring the temperature dependence of the zero bias resistance, we confirm that the critical point does not depend on the strength of the Josephson coupling. However, we find that the correlation exponents vary continuously along the phase boundary, indicating that the Schmid-Bulgadaev transition is a line of fixed points.

Journal Article↗
PubMed2005

Phase diagram and critical exponents of a dissipative Ising spin chain in a transverse magnetic field.

We consider a one-dimensional Ising model in a transverse magnetic field coupled to a dissipative heat bath. The phase diagram and the critical exponents are determined from extensive Monte Carlo simulations. It is shown that the character of the quantum phase transition is radically altered from the corresponding nondissipative model and the double well coupled to a dissipative heat bath with linear friction. Spatial couplings and the dissipative dynamics combine to form a new quantum criticality which is independent of dissipation strength.

Journal Article↗
PubMed2004

Universal conductance of nanowires near the superconductor-metal quantum transition.

We consider wires near a zero temperature transition between superconducting and metallic states. The critical theory obeys hyperscaling, which leads to a universal frequency, temperature, and length dependence of the conductance; quantum and thermal phase slips are contained within this critical theory. Normal, superconducting, and mixed (SN) leads on the wire determine distinct universality classes. For the SN case, wires near the critical point have a universal dc conductance which is independent of the length of the wire at low temperatures.

Journal Article↗
PubMed2003

Efficient evaluation of the effective dielectric function of a macromolecule in aqueous solution.

We propose an analytical approach to calculate the effective dielectric function of proteins in aqueous solution. The screening effect if quantified by a measure of enclosure which is based on the distribution of solute atomic volumes around a pair of charges in a macromolecule. For protein conformations that vary significantly in size and shape, a comparison with finite difference Poisson calculations shows that pair interaction energies, their sums and solvation energies are well reproduced. The approach rivals the speed of simple distance dependent dielectric functions and the accuracy of the generalized Born model.

Electric Conductivity↗
PubMed2003

A sphere-based model for the electrostatics of globular proteins.

We propose a model for the electrostatics of globular proteins in which the low dielectric region is replaced by concentric spheres of the appropriate size. The method uses analytical formulas for the dielectric sphere and allows an efficient and accurate treatment of bulk charges. For surface charges, we propose a numerical determination of the sphere radius based on the solvent exposure of the individual atoms. The present implementation of the sphere model yields a good approximation of finite-difference Poisson solvation and interaction energies for a test set of 12 proteins.

Models, Chemical↗
PubMed2002

Active and passive smoking, chronic infections, and the risk of carotid atherosclerosis: prospective results from the Bruneck Study.

BACKGROUND AND PURPOSE: Susceptibility of the vasculature to the injurious effects of smoking varies substantially, with some smokers developing severe premature atherosclerosis and others remaining free of advanced atheroma until high ages. The present study sought to estimate the contribution of chronic infections to the variability of atherosclerosis severity among smokers. METHODS: In the community-based Bruneck Study, 5-year changes in carotid atherosclerosis were assessed by high-resolution ultrasound. Early atherogenesis was defined by the development of nonstenotic plaques and advanced atherogenesis by the development/progression of vessel stenosis >40%. RESULTS: The risk of early atherogenesis strongly relied on lifetime smoking exposure and remained elevated long-term after cessation of smoking. Remarkably, current and ex-smokers faced an increased atherosclerosis risk only in the presence of chronic infections (odds ratios [95% CIs], 3.3 [1.8 to 6.2] and 3.4 [1.8 to 6.3]; P<0.001 each), whereas current, past, and nonsmokers without infections did not differ substantially in their estimated risk burden (odds ratios [95% CIs], 1.4 [0.8 to 2.4], 0.9 [0.6 to 1.6], and 1.0 [reference group]). In analogy to first-hand smoking, subjects exposed to environmental tobacco smoke were found to be vulnerable to the manifestation of chronic infection, and only those infected experienced a high atherosclerosis risk. The risk of advanced atherogenesis showed a dose-response relation with the number of daily cigarettes, returned to normal shortly after cessation of smoking, and emerged as independent of infectious illness. CONCLUSIONS: Our study provides the first epidemiological evidence that the proatherogenic effects of cigarette smoking are mediated in part by the chronic infections found in smokers. A better understanding of the vascular pathogenetic mechanisms of smoking may offer novel clues for disease prevention supplementary to the primary goal of achieving long-term abstinence.

Adult↗