Computational approaches to shed light on molecular mechanisms in biological processes

Computational approaches based on Molecular Dynamics simulations, Quantum Mechanical methods and 3D Quantitative Structure-Activity Relationships were employed by computational chemistry groups at the University of Milano-Bicocca to study biological processes at the molecular level. The paper reports the methodologies adopted and the results obtained on Aryl hydrocarbon Receptor and homologous PAS proteins mechanisms, the properties of prion protein peptides, the reaction pathway of hydrogenase and peroxidase enzymes and the defibrillogenic activity of tetracyclines. © Springer-Verlag 2007

3D numerical characterization of a dissipative connection system for retrofit of prefabricated existing RC sheds

Prefabricated industrial sheds featured a high seismic vulnerability during the 2012 Emilia earthquake (Italy). The buildings typically exhibited a rigid collapse mechanism that was a consequence of the loss of support between columns, beams and roof elements. The study presents a numerical characterization of a novel dissipative connection system (DCS) designed to improve the seismic performance of industrial sheds. The device, which is placed on the top of the columns, exploits the movement of a rigid body on a sloped surface to provide horizontal stiffness and control the lateral displacement of the beam. A 3D finite element model of the prototype is formulated in Abaqus and used to switch the backbone curve from the scaled model to the full-scale device. A parametric study is conducted to evaluate the influence of the slope of the contact surface and the coefficient of friction on the output force of the system. In the second part of the study, non-linear dynamic analyses are performed on a finite element model of a portal frame implementing, at beam-column joints, either the DCS or a pure friction connection. The results highlight the effectiveness of the DCS in controlling beam-to-column displacements, reducing shear forces on the top of columns, and limiting residual displacements that can accrue during ground motion sequence

ultrasonic vibration turning to increase the deposition efficiency of a silica based sol gel coating

Abstract Magnesium alloys are attracting more and more attention for producing temporary prosthetic devices thanks to their bioresorbable characteristics in human environment. However, they present a reduced corrosion resistance to body fluids, which still limits their applications to a great extent. One possible way to increase the corrosion performances is to coat the device with a suitable coating that provides a barrier to the body fluids corrosion. In this work, Ultrasonic Vibration Turning (UVT) is used to create a surface texture to the AZ31 magnesium alloy with the aim of improving the surface wettability and therefore helping the subsequent coating deposition. The obtained results showed that the surface texture induced by UVT contributed to increase the surface wettability of approximately 17% compared to the conventional turning case, regardless of the adopted cutting parameters. The UVT texture proved to improve the efficiency of the coating deposition since the thickness of the deposited sol-gel coating was increased when applied to UVT surfaces, especially at the lowest depth of cut and highest cutting speed that contributed to generate deeper dimples

on the surface integrity of electron beam melted ti6al4v after machining

Abstract The Additive Manufacturing process known as Electron Beam Melting (EBM) is increasingly used to produce Ti6Al4V biomedical parts, whose functional surfaces, however, need to be machined afterwards. The paper addresses the fundamental issue of surface integrity of EBM parts when subjected to machining operation under dry, flood and cryogenic cooling conditions. The machined surface integrity is evaluated in terms of microstructural and mechanical features, residual stresses, surface topography and defects. Results are then compared to the outcomes of the same machining tests carried out on the conventional wrought alloy. This study points out the different machinability of the two investigated alloys, highlighting that new insights into optimization of parameters for machining AM alloys are needed

Detecting (Absent) App-to-app authentication on cross-device short-distance channels

Short-distance or near-field communication is increasingly used by mobile apps for interacting or exchanging data in a cross-device fashion. In this paper, we identify a security issue, namely cross-device app-to-app communication hijacking (or CATCH), that affect Android apps using short-distance channels (e.g., Bluetooth and Wi-Fi-Direct). This issue causes unauthenticated or malicious app-to-app interactions even when the underlying communication channels are authenticated and secured. In addition to discovering the security issue, we design an algorithm based on data-flow analysis for detecting the presence of CATCH in Android apps. Our algorithm checks if a given app contains an app-to-app authentication scheme, necessary for preventing CATCH. We perform experiments on a set of Android apps and show the CATCH problem is always present on the whole analyzed applications set. We also discuss the impact of the problem in real scenarios by presenting two real case studies. At the end of the paper we reported limitations of our model along with future improvements

A multiple criteria approach to map ecological-inclusive business models for sustainable development

The paper presents the first attempt to apply a multiple criteria approach to map ecological-inclusive business models and to structure their main features, in terms of sustainable development. Ecological-inclusive business models are presented in this study, and 15 cases pertaining to agro-food organisations located in Sub-Saharan Africa are considered. These companies simultaneously deliver positive social and environmental value, and confirm a well-established market presence. As far as social value is concerned, the companies included in the sample use a Bottom-of-Pyramid approach, involving low-income customers and/or low-income business partners. As for environmental value, all the analysed companies implement frugal innovation or sustainable exploitation of natural resources in the afro-food sector. One of the results that has been achieved is that of disentangling the complexity behind a triple bottom-line business model through a multidimensional analysis framework that identifies the aspects that play a fundamental role in ecological-inclusive business models. An evaluation model and the application of a multiple criteria outranking method are proposed as examples of how some criteria, such as the extent of socio-environmental concerns, strategy orientation and value of partnerships can be used to compare, rank and/or select business models to facilitate decision makers. This work presents the results of an interdisciplinary study on the social entrepreneurship field of knowledge

large strain extrusion machining of magnesium alloys for biomedical applications

Abstract Recently, magnesium alloys are attracting more and more attention as degradable materials for manufacturing temporary biomedical devices, although their rapid degradation in physiological environment limits their clinical applications to a great extent. Different Severe Plastic Deformation (SPD) processes have been recently applied to magnesium alloys in order to improve the surface integrity, which is directly correlated to their corrosion resistance. The current study investigates the possibility of exploiting Large Strain Extrusion Machining (LSEM) as a processing route to increase corrosion resistance of magnesium alloys for biomedical applications. Different cooling conditions and cutting speeds were adopted during LSEM and their effects on the surface integrity and corrosion resistance on both the machined workpiece and obtained chips were studied. For the first time, liquid nitrogen was used as cooling medium in LSEM and its effect was properly investigated. Results showed that LSEM, regardless of the adopted cutting parameters, is an effective method to obtain a workpiece with improved functional performances. Similar results pertain to the chips, but a careful choice of process parameters is even more mandatory than in the case of the workpiece