Light Scattering by Cholesteric Skyrmions

We study the light scattering by localized quasi planar excitations of a Cholesteric Liquid Crystal known as spherulites. Due to the anisotropic optical properties of the medium and the peculiar shape of the excitations, we quantitatively evaluate the cross section of the axis-rotation of polarized light. Because of the complexity of the system under consideration, first we give a simplified, but analytical, description of the spherulite and we compare the Born approximation results in this setting with those obtained by resorting to a numerical exact solution. The effects of changing values of the driving external static electric (or magnetic) field is considered. Possible applications of the phenomenon are envisaged.Comment: 18 pages, 14 figure

Optimal tuning of adaptive augmenting controller for launch vehicles in atmospheric flight

In this Note, two novel and effective tuning methodologies for an adaptive augmenting control (AAC) system, realized to consistently improve performance and robustness of a standard launch vehicle single-axis attitude controller in atmospheric flight, have been presented. To this end, a methodology for AAC parameter tuning is presented where a robust design optimization (RDO) problem is formulated, and the goal is to maximize a statistical metric that describes FCS performance measured over a set of representative simulations of LV flight. In more detail, adaptive law parameters are tuned with the aim of minimizing attitude error and traversal aerodynamic loads. As major advantages, the occurrence of Loss of vehicle (LOV) events and the issues and burden of the manual trial-and-error procedures currently adopted for the design of the adaption law may be reduced

Comparison of Ni-Cr and Co-based alloys for fuel injectors

Presentazione orale al convegno TMS 2011 - 140th Annual Meeting & Exhibition, svoltosi a San Diego, USA, dal 27/02/2011 al 03/03/201

Fatigue behavior of dual-phase and TWIP steels for lightweight automotive structures

Presentazione orale al convegno Euromat 2011, svoltosi a Montpellier, Francia, dal 12/09/2011 al 15/09/201

Microstructural, mechanical and fatigue properties of Cobalt alloys

Presentazione orale al convegno TMS 2010 - 139th Annual Meeting & Exhibition, svoltosi a Seattle (USA) dal 14/02/2010 al 18/02/201

Cell biology:Collagen secretion explained

Cells package proteins into vesicles for secretion to the extracellular milieu. A study shows that an enzyme modifies the packaging machinery to encapsulate unusually large proteins such as collagen

The impact of peri-natal stress on psychosis risk: Results from the Bo-FEP incidence study

Objective: According to the gene-environment interaction model the pathogenesis of psychosis relies on an adverse neuro-socio-developmental pathway. Perinatal stress represents an important risk factor for the development of psychosis because of the increasingly evident interference with socio-neuro-development in the earlier phases of life. We aim to investigate the correlation of perinatal risk factors with the onset of psychosis with a case-control-incidence study. Results: Patients (and their mothers) were eligible if they presented with first-episode psychosis at the Bologna West Community Mental Health Centre (Bo-West CMHC) between 2002 and 2012. The Bo-West CMHC serves a catchment area of about 200,000 people. The controls were recruited in the same catchment area and study period. 42 patients, 26 controls and their mothers were included. We collected the history of peri-natal stress and calculated crude and adjusted Odds Ratios for onset of first-episode psychosis. Adjusted logistic regression showed that psychosis onset was significantly associated with stressful situations during pregnancy, lower level of maternal physical health before or during pregnancy, use of anti-inflammatory drugs during pregnancy, and low level of maternal education. The results of our study suggest that stress during perinatal period increases the risk of developing psychosis

Experimental and Numerical Study of Perforated Steel Plate Shear Panels

Thin perforated Steel Plate Shear (SPS) Walls are among the most common types of energy dissipating systems. The applied holes reduce the shear strength of the plate and allow to decrease the profile size of the members at the boundary of the panel when these systems are used in the typical design of structures. On the other hand, the different fracture locations of these panels are visible when considering the different perforation patterns. This paper reports on the results obtained from the experimental study under cyclic loading of the effect of different hole patterns on the seismic response of the systems and the location of the fracture. According to this, two perforated specimens by different patterns were considered. In addition, a plate without holes for a better comparison of the fracture location was chosen. The results showed that changing the pattern of the holes causes a change in the fracture location. Moreover, in perforated specimens, the amount of shear strength did not reduce suddenly after the fracture phenomenon. In the specimen which was perforated around the web plate, the pinching force was more than any other in the low cycle of the drifts. For this reason, the energy dissipation and initial stiffness were more than up to 3% drift. The experimental specimens were then simulated with a Finite Element (FE) method using the ABAQUS. Finally, a parametric FE analysis on different series of perforated panels, by changing the diameter of the holes and the plate thickness, has been carried out

Room temperature plastic flow localization in a Mn-alloyed austenitic steel

A fully austenitic steel containing 0.5 wt.% C and 22 wt.% Mn was recently proposed for the fabrication of automotive body structures by room-temperature sheet forming, the goal being weight reduction and better crash performance owing to its much higher yield stress and elongation (as compared to presently employed ferritic and multiphase steels). Full-thickness tensile specimens, cut from as-produced sheets, were polished and tested at different strain rates, and the macroscopic surface relief eventually induced by the plastic deformation was recorded with a video camera. Between 0.3 and 0.4 true strain, successive macroscopic deformation bands (forming about 45° angle with the tensile axis and involving the full specimen width) travel along the specimen, a new one being nucleated as the previous reaches one of the specimen heads, whereas the gage displacement vs. stress curve shows a series of steps, each corresponding to the transit of a band through the gage length, and the cross-head displacement vs. stress curve shows isolated stress peaks, each immediately preceding the nucleation of a new band. Afterwards, and up to rupture, a series of stationary deformation bands appear, most being immediately adjacent to the preceding ones, with the stress vs. strain curve showing a series of serrations with large stress drops. As the strain rate is increased from 0.0004 to 0.4 s-1, the overall flow stress slightly decreases and the mentioned plastic localization phenomena become less evident