Thermal Wave Propagation in Helium II

Landau's equations for the two-fluid model of liquid helium II are us ed as the basis for an investigation of the properties of thermal wave propagation. A number of assumptions are made which reduce the four original equations to a system of two non-linear partial differential equations valid to first order in the relative velocity of the two components. These equations are analogous to Riemann's equations which describe pressure waves in a classical fluid. This system of equations, when reduced to just one space dimension is shown to be hyperbolic and a set of characteristics and invariants is found. A particularly simple, one-dimensional problem is then formulated and an explicit solution is given. This solution is then studied in detail to show the distortion of a temperature pulse as it propagates and also to show effects such as non-linear breaking. Subsequently, the restrictive assumptions are eliminated individually and the equations are then valid to second order in the relative velocity; the effects of including thermal expansion and using the relative velocity as a thermodynamic variable are given. Also, some effects due to the interaction of first and second sound are investigated. In all cases, the results are compared with other results based on equations differing from the Landau equations and with results found by using perturbation techniques. Finally, equations based on the same Landau equations are derived and discussed which describe steady state shock (discontinuous) solutions. Suggestions for further theoretical and experimental work are made.</p

Decellularized Matrix from Tumorigenic Human Mesenchymal Stem Cells Promotes Neovascularization with Galectin-1 Dependent Endothelial Interaction

BACKGROUND: Acquisition of a blood supply is fundamental for extensive tumor growth. We recently described vascular heterogeneity in tumours derived from cell clones of a human mesenchymal stem cell (hMSC) strain (hMSC-TERT20) immortalized by retroviral vector mediated human telomerase (hTERT) gene expression. Histological analysis showed that cells of the most vascularized tumorigenic clone, -BD11 had a pericyte-like alpha smooth muscle actin (ASMA+) and CD146+ positive phenotype. Upon serum withdrawal in culture, -BD11 cells formed cord-like structures mimicking capillary morphogenesis. In contrast, cells of the poorly tumorigenic clone, -BC8 did not stain for ASMA, tumours were less vascularized and serum withdrawal in culture led to cell death. By exploring the heterogeneity in hMSC-TERT20 clones we aimed to understand molecular mechanisms by which mesenchymal stem cells may promote neovascularization. METHODOLOGY/PRINCIPAL FINDINGS: Quantitative qRT-PCR analysis revealed similar mRNA levels for genes encoding the angiogenic cytokines VEGF and Angiopoietin-1 in both clones. However, clone-BD11 produced a denser extracellular matrix that supported stable ex vivo capillary morphogenesis of human endothelial cells and promoted in vivo neovascularization. Proteomic characterization of the -BD11 decellularized matrix identified 50 extracellular angiogenic proteins, including galectin-1. siRNA knock down of galectin-1 expression abrogated the ex vivo interaction between decellularized -BD11 matrix and endothelial cells. More stable shRNA knock down of galectin-1 expression did not prevent -BD11 tumorigenesis, but greatly reduced endothelial migration into -BD11 cell xenografts. CONCLUSIONS: Decellularized hMSC matrix had significant angiogenic potential with at least 50 angiogenic cell surface and extracellular proteins, implicated in attracting endothelial cells, their adhesion and activation to form tubular structures. hMSC -BD11 surface galectin-1 expression was required to bring about matrix-endothelial interactions and for xenografted hMSC -BD11 cells to optimally recruit host vasculature

Integrate: Architecture Under the Influence of Climate Change

The projects selected for this publication show a range of approaches to making energy, carbon emissions, and their underpinning principles explicit in studio design work undertaken at the Department of Architecture at the Swiss Federal Institute of Technology in Zurich. Over the past decades the discussion of environmental sustainability in the building sectors has been regularly polarized between low- and high-tech, used as a superficial catchphrase, or perceived as restrictive to development. The projects in this book demonstrate that we must abandon overly simplistic mindsets toward systemic and life-cycle thinking. Additionally, the mix of included projects underscores that highly sustainable buildings can be produced from many different design perspectives, ranging from a focus on efficient technologies to materials and geometry.Für dieses Buch wurden Arbeiten vom Department für Architektur der ETH Zürich ausgewählt, die unterschiedliche Ansätze in der Umsetzung der Themen Energie, CO2-Emissionen und den dahinter liegenden Prinzipien im Entwurfsprozess thematisieren. Die Diskussion der ökologischen Nachhaltigkeit im Bausektor wurde in den letzten Jahrzehnten regelmässig von einer Polarisierung zwischen Low- und High-Tech geprägt, manchmal als oberflächliche Schlagwörter verwendet, oft als Einschränkung empfunden. Die Projekte in diesem Buch zeigen, dass wir allzu vereinfachende Denkweisen zugunsten eines systemischen und lebenszyklusbezogenen Denkens aufgeben müssen. Die Vielfalt der vorliegenden Projekte in diesem Buch zeigt auf, dass mit höchst unterschiedlichen gestalterischen Ansätzen zukunftsfähige Gebäude entworfen werden können – von Fokus auf effizienter Technologie bis hin zur Auseinandersetzung mit Material und Geometrie

The Lhx9-Integrin pathway is essential for positioning of the proepicardial organ

The development of the vertebrate embryonic heart occurs by hyperplastic growth as well as the incorporation of cells from tissues outside of the initial heart field. Amongst these tissues is the epicardium, a cell structure that develops from the precursor proepicardial organ on the right side of the septum transversum caudal to the developing heart. During embryogenesis, cells of the proepicardial organ migrate, adhere and envelop the maturing heart, forming the epicardium. The cells of the epicardium then delaminate and incorporate into the heart giving rise to cardiac derivatives, including smooth muscle cells and cardiac fibroblasts. Here, we demonstrate that the LIM homeodomain protein Lhx9 is transiently expressed in Xenopus proepicardial cells and is essential for the position of the proepicardial organ on the septum transversum. Utilizing a small-molecule screen, we found that Lhx9 acts upstream of integrin-paxillin signaling and consistently demonstrate that either loss of Lhx9 or disruption of the integrin-paxillin pathway results in mis-positioning of the proepicardial organ and aberrant deposition of extracellular matrix proteins. This leads to a failure of proepicardial cell migration and adhesion to the heart, and eventual death of the embryo. Collectively, these studies establish a requirement for the Lhx9-integrin-paxillin pathway in proepicardial organ positioning and epicardial formation