44 research outputs found
Entropy production of cyclic population dynamics
Entropy serves as a central observable in equilibrium thermodynamics.
However, many biological and ecological systems operate far from thermal
equilibrium. Here we show that entropy production can characterize the behavior
of such nonequilibrium systems. To this end we calculate the entropy production
for a population model that displays nonequilibrium behavior resulting from
cyclic competition. At a critical point the dynamics exhibits a transition from
large, limit-cycle like oscillations to small, erratic oscillations. We show
that the entropy production peaks very close to the critical point and tends to
zero upon deviating from it. We further provide analytical methods for
computing the entropy production which agree excellently with numerical
simulations.Comment: 4 pages, 3 figures and Supplementary Material. To appear in Phys.
Rev. Lett.
Probing the structural and electronic response of Magnus green salt compounds [Pt(NH2R)4][PtCl4] (R = H, CH3) to pressure
Resistance to antiangiogenic therapy is directed by vascular phenotype, vessel stabilization, and maturation in malignant melanoma
Angiogenesis is not only dependent on endothelial cell invasion and proliferation, it also requires pericyte coverage of vascular sprouts for stabilization of vascular walls. Clinical efficacy of angiogenesis inhibitors targeting the vascular endothelial growth factor (VEGF) signaling pathway is still limited to date. We hypothesized that the level of vessel maturation is critically involved in the response to antiangiogenic therapies. To test this hypothesis, we evaluated the vascular network in spontaneously developing melanomas of MT/ret transgenic mice after using PTK787/ZK222584 for anti-VEGF therapy but also analyzed human melanoma metastases taken at clinical relapse in patients undergoing adjuvant treatment using bevacizumab. Both experimental settings showed that tumor vessels, which are resistant to anti-VEGF therapy, are characterized by enhanced vessel diameter and normalization of the vascular bed by coverage of mature pericytes and immunoreactivity for desmin, NG-2, platelet-derived growth factor receptor ÎČ, and the late-stage maturity marker α smooth muscle actin. Our findings emphasize that the level of mural cell differentiation and stabilization of the vascular wall significantly contribute to the response toward antiangiogenic therapy in melanoma. This study may be useful in paving the way toward a more rational development of second generation antiangiogenic combination therapies and in providing, for the first time, a murine model to study this
Metaphysics or Modernity? Contributions to the Bamberg Summer School 2012
This collection of essays originated in the Summer School âMetaphysics or Modernity?â, which was held at the University of Bamberg in August 2012. Designed as a forum for graduate students in philosophy, the Summer School brought together a highly diverse group of young academics who â more often than not â came from utterly different schools and traditions of thought.
This pluralism is reflected in the pages of this book. While the volume is roughly divided into two halves â one with a more historical focus, the other with a more systematic focus â the reader will find an unusually wide array of topics and questions treated here. Since the aforementioned pluralism was one of the main strengths of our Summer School, this is something in which we take much prid
Thermally stratified compression ignition enabled by wet ethanol with a split injection strategy: A CFD simulation study
Effects of geometrical isomerism on emissive behaviour of heteroleptic cyclometalated Ir( iii
AL3810, a multi-tyrosine kinase inhibitor, exhibits potent anti-angiogenic and anti-tumour activity via
FRS2 via Fibroblast Growth Factor Receptor 1 Is Required for Platelet-derived Growth Factor Receptor ÎČ-mediated Regulation of Vascular Smooth Muscle Marker Gene Expression*
Vascular smooth muscle cells (VSMC) exhibit phenotypic plasticity and change from a quiescent contractile phenotype to a proliferative synthetic phenotype during physiological arteriogenesis and pathological conditions such as atherosclerosis and restenosis. Platelet-derived growth factor (PDGF)-BB is a potent inducer of the VSMC synthetic phenotype; however, much less is known about the role of fibroblast growth factor-2 (FGF2) in this process. Here, we show using signal transduction mutants of FGF receptor 1 (FGFR1) expressed in rat VSMC that the adaptor protein FRS2 is essential for FGFR1-mediated phenotypic modulation and down-regulation of VSMC smooth muscle α-actin (SMA) gene expression. In addition, we show that PDGF-BB and FGF2 act synergistically to induce cell proliferation and down-regulate SMA and SM22α in VSMC. Furthermore, we show that PDGF-BB induces tyrosine phosphorylation of FGFR1 and that this phosphorylation is mediated by PDGF receptor-ÎČ (PDGFRÎČ), but not c-Src. We demonstrate that FRS2 co-immunoprecipitates with PDGFRÎČ in a complex that requires FGFR1 and that both the extracellular and the intracellular domains of FGFR1 are required for association with PDGFRÎČ, whereas the cytoplasmic domain of FGFR1 is required for FRS2 association with the FGFR1-PDGFRÎČ complex. Knockdown of FRS2 in VSMC by RNA interference inhibited PDGF-BB-mediated down-regulation of SMA and SM22α without affecting PDGF-BB mediated cell proliferation or ERK activation. Together, these data support the notion that PDGFRÎČ down-regulates SMA and SM22α through formation of a complex that requires FGFR1 and FRS2 and prove novel insight into VSMC phenotypic plasticity
Copper(II) complexes of pyridine-oxazoline (Pyox) ligands: Coordination chemistry, ligand stability, and catalysis
The coordination chemistry of copper(II) complexes bearing pyridine-oxazoline (âPyoxâ) ligands has been studied, with an aim of investigating their catalytic ability. Interestingly, the stability of the coordinated ligands has been shown to be much less than previously assumed: hydrolysis of the ligands by fortuitous water gives rise to 2-pyridine carboxylate formation, which encapsulate the copper in a two-dimensional coordination polymer 3. The complexes [Cu(R-Pyox)(NCMe)2(ClO4)2] {R = benzyl (Bn) 2a, phenyl (Ph) 2b, isopropyl (iPr) 2c} have been prepared, of which the benzyl derivative has been analysed by CW EPR spectroscopy. The complex [Cu(Bn-Pyox)(NCMe)2(ClO4)2] and the afore-mentioned coordination polymer have been crystallographically characterised. The performance of complexes 2aâc in the asymmetric allylic oxidation of cyclohexene is describe