Bridging the banking sector with the real economy: a financial stability perspective

This paper builds a macro-prudential tool designed to assess whether the banking sector is adequately prepared to orderly withstand losses resulting from normal or stressed macroeconomic and microeconomic scenarios. The link between the banking sector and the real sector is established via the corporate sector channel. The macro-prudential tool consists of a two-step approach. In the first step, we build a model for the probability of default (PD) in the corporate sector, so as to quantify oneyear ahead developments in the quality of banks' corporate loans. The framework is established using micro data, with a bottom-up approach. The second step consists of bridging the PD model with a macroeconomic module in order to capture the feedback effects from the macroeconomic stance into the banking sector, via the corporate sector channel. The macro-prudential tool is tested on the Romanian economy

A brief review of the literature on the malignant ureteral obstruction

Malignant ureteral obstruction (MUO) caused by a primarily urological tumor or secondary to a late-stage malignancy can be difficult for the urologist to manage. Due to a lack of clinical data on the management of MUO, every case is particular and should be aborted individually. Lack of specific treatment, either palliative or definitive, can severely damage renal function and lifetime expectancy in patients, causing even more damage that could otherwise be avoided. Prompt management directed at the recovery of renal function is the main goal in such cases. Even after urinary flow is restored, life threatening post-obstructive diuresis needs to be managed

Role of Physical Mechanisms in Biological Self-Organization

URL:http://link.aps.org/doi/10.1103/PhysRevLett.95.178104 DOI:10.1103/PhysRevLett.95.178104Organs form during morphogenesis, the process that gives rise to specialized biological structures of specific shape and function in early embryonic development. Morphogenesis is under strict genetic control, but shape evolution itself is a physical process. Here we report the results of experimental and modeling biophysical studies on in vitro biological structure formation. Experimentally, by controlling the interaction between cells and their embedding matrices, we were able to build living structures of definite geometry. The experimentally observed shape evolution was reproduced by Monte Carlo simulations, which also shed light on the biophysical basis of the process. Our work suggests a novel way to engineer biological structures of controlled shape.This work was supported by NSF (IBN-0083653; FIBR-0526854) and NASA (NAG2-1611)

Relating Biophysical Properties Across Scales

A distinguishing feature of a multicellular living system is that it operates at various scales, from the intracellular to organismal. Genes and molecules set up the conditions for the physical processes to act, in particular to shape the embryo. As development continues the changes brought about by the physical processes lead to changes in gene expression. It is this coordinated interplay between genetic and generic (i.e. physical and chemical) processes that constitutes the modern understanding of early morphogenesis. It is natural to assume that in this multi- scale process the smaller defines the larger. In case of biophysical properties, in particular, those at the subcellular level are expected to give rise to those at the tissue level and beyond. Indeed, the physical properties of tissues vary greatly from the liquid to solid. Very little is known at present on how tissue level properties are related to cell and subcellular properties. Modern measurement techniques provide quantitative results at both the intracellular and tissue level, but not on the connection between these. In the present work we outline a framework to address this connection. We specifically concentrate on the morphogenetic process of tissue fusion, by following the coalescence of two contiguous multicellular aggregates. The time evolution of this process can accurately be described by the theory of viscous liquids. We also study fusion by Monte Carlo simulations and a novel Cellular Particle Dynamics (CPD) model, which is similar to the earlier introduced Subcellular Element Model (SEM; (Newman, 2005)). Using the combination of experiments, theory and modeling we are able to relate the measured tissue level biophysical quantities to subcellular parameters. Our approach has validity beyond the particular morphogenetic process considered here and provides a general way to relate biophysical properties across scales.This work was supported by the National Science Foundation under Grant FIBR-0526854. We gratefully acknowledge the computational resources provided by the University of Missouri Bioinformatics Consortium

Experimental evaluation of apparent tissue surface tension based on the exact solution of the Laplace equation

The notion of apparent tissue surface tension offered a systematic way to interpret certain morphogenetic processes in early development. It also allowed deducing quantitative information on cellular and molecular parameters that is otherwise difficult to obtain. To accurately determine such tensions we combined novel experiments with the exact solution of the Laplace equation for the profile of a liquid drop under the employed experimental conditions and used the exact solution to evaluate data collected on tissues. Our results confirm that tissues composed of adhesive and motile cells indeed can be characterized in terms of well-defined apparent surface tension. Our experimental technique presents a way to measure liquid interfacial tensions under conditions when known methods fail.This work was supported by the National Science Foundation [FIBR-0526854]

Kinetic Monte Carlo and Cellular Particle Dynamics Simulations of Multicellular Systems

Computer modeling of multicellular systems has been a valuable tool for interpreting and guiding in vitro experiments relevant to embryonic morphogenesis, tumor growth, angiogenesis and, lately, structure formation following the printing of cell aggregates as bioink particles. Computer simulations based on Metropolis Monte Carlo (MMC) algorithms were successful in explaining and predicting the resulting stationary structures (corresponding to the lowest adhesion energy state). Here we present two alternatives to the MMC approach for modeling cellular motion and self-assembly: (1) a kinetic Monte Carlo (KMC), and (2) a cellular particle dynamics (CPD) method. Unlike MMC, both KMC and CPD methods are capable of simulating the dynamics of the cellular system in real time. In the KMC approach a transition rate is associated with possible rearrangements of the cellular system, and the corresponding time evolution is expressed in terms of these rates. In the CPD approach cells are modeled as interacting cellular particles (CPs) and the time evolution of the multicellular system is determined by integrating the equations of motion of all CPs. The KMC and CPD methods are tested and compared by simulating two experimentally well known phenomena: (1) cell-sorting within an aggregate formed by two types of cells with different adhesivities, and (2) fusion of two spherical aggregates of living cells.Comment: 11 pages, 7 figures; submitted to Phys Rev