Polytechnic University of Milan

About: Polytechnic University of Milan is a education organization based out in Milan, Italy. It is known for research contribution in the topics: Finite element method & Population. The organization has 18231 authors who have published 58416 publications receiving 1229711 citations. The organization is also known as: PoliMi & L-NESS.

Compartmental analysis of breathing in the supine and prone positions by optoelectronic plethysmography.

Abstract: Optoelectronic plethysmography (OEP) has been shown to be a reliable method for the analysis of chest wall kinematics partitioned into pulmonary rib cage, abdominal rib cage, abdomen, and right and left side in the seated and erect positions. In this paper, we extended the applicability of this method to the supine and prone positions, typically adopted in critically ill patients. For this purpose we have first developed proper geometrical and mathematical models of the chest wall which are able to provide consistent and reliable estimations of total and compartmental volume variations in these positions suitable for clinical settings. Then we compared chest wall (CW) volume changes computed from OEP(deltaVCW) with lung volume changes measured with a water seal spirometer (SP) (deltaVSP) in 10 normal subjects during quiet (QB) and deep (DB) breathing on rigid and soft supports. We found that on a rigid support the average differences between deltaVSP and deltaVCW were -4.2% +/- 6.2%, -3.0% +/- 6.1%, -1.7% +/- 7.0%, and -4.5% +/- 9.8%, respectively, during supine/QB, supine/DB, prone/QB, and prone/DB. On the soft surface we obtained -0.1% +/- 6.0%, -1.8% +/- 7.8%, 18.0% +/- 11.7%, and 10.2% +/- 9.6%, respectively. On rigid support and QB, the abdominal compartment contributed most of the deltaVCW in the supine (63.1% +/- 11.4%) and prone (53.5% +/- 13.1%) positions. deltaVCW was equally distributed between right and left sides. In the prone position we found a different chest wall volume distribution between pulmonary and abdominal rib cage (22.1% +/- 8.6% and 24.4% +/- 6.8%, respectively) compared with the supine position (23.3% +/- 9.3% and 13.6% +/- 13.0%).

The emergence of the knowledge spillover theory of entrepreneurship

Abstract: In the past decade, a new and promising literature has been established linking endogenous growth theory to knowledge spillovers and entrepreneurship theory: the knowledge spillover theory of entrepreneurship (KSTE). This study conducts a bibliometric analysis of scholarly research on this fruitful and promising strand of the literature. It highlights the increasing importance and acceptance of KSTE in the scientific community worldwide, its emergence across different fields in economics, management and policy and also the issues and questions raised. Based on all articles on KSTE published in refereed journals in the past 15 years (1999–2013), we identify the key academic journals, the main issues and subjects addressed and the backward and forward citations. We also identify the authors and their connections in terms of coauthorships to reconstruct the scientific community debating on KSTE. We are confident that our work will benefit scholars intending to leverage KSTE in their research in that it summarizes the main academic conversations within this theoretical perspective and set the boundaries of the network of scholars developing it.

Modeling evaluation of the fluid-dynamic microenvironment in tissue-engineered constructs: a micro-CT based model.

Abstract: Natural cartilage remodels both in vivo and in vitro in response to mechanical stresses, hence mechanical stimulation is believed to be a potential tool to modulate extra-cellular matrix synthesis in tissue-engineered cartilage. Fluid-induced shear is known to enhance chondrogenesis in engineered cartilage constructs. The quantification of the hydrodynamic environment is a condition required to study the biochemical response to shear of 3D engineered cell systems. We developed a computational model of culture medium flow through the microstructure of a porous scaffold, during direct- perfused culture. The 3D solid model of the scaffold micro-geometry was reconstructed from 250 micro-computed tomography (micro-CT) images. The results of the fluid dynamic simulations were analyzed at the central portions of the fluid domain, to avoid boundary effects. The average, median and mode shear stress values calculated at the scaffold walls were 3.48, 2.90, and 2.45 mPa respectively, at a flow rate of 0.5 cm(3)/min, perfused through a 15 mm diameter scaffold, at an inlet fluid velocity of 53 microm/s. These results were compared to results estimated using a simplified micro-scale model and to results estimated using an analytical macro-scale porous model. The predictions given by the CT-based model are being used in conjunction with an experimental bioreactor model, in order to quantify the effects of fluid-dynamic shear on the growth modulation of tissue-engineered cartilage constructs, to potentially enhance tissue growth in vitro.

Photoluminescence Mechanisms in Anatase and Rutile TiO2

Abstract: Photoluminescence (PL) represents a sensitive tool for probing molecular adsorption and surface reactions in photocatalytic materials. Titanium dioxide (TiO2) is one of the most widely used photocatalysis, and clarifying its basic PL mechanism can give important information. However, differently from other electronic and surface processes, the actual PL mechanisms of TiO2 are not extensively studied. In this work, we address the topic by focusing our investigation on which are the different states that trigger the PL activity and on identifying the specific recombination pathways acting in the two stable TiO2 polymorphs (rutile and anatase). On the basis of our experimental results on PL emission, PL excitation, and oxygen-induced and photoinduced PL modifications, we sketch an interpretative scheme for both the polymorphs. Excitation-resolved PL and recombination quenching caused by molecular oxygen evidence distinct contributions to anatase PL, originating from different kinds of hole-trapping and elect...