Gas gain on single wire chambers filled with pure isobutane at low pressure

The gas gain of single-wire chambers filled with isobutane, with cell cross-section 12x12 mm and wire diameters of 15, 25, 50 and 100 $\mu$m, has been measured at pressures ranging 12-92 Torr. Contrary to the experience at atmospheric pressure, at very low pressures the gas gain on thick wires is higher than that on thin wires at the same applied high voltage as was recently shown. Bigger wire diameters should be used in wire chambers operating at very low pressure if multiple scattering on wires is not an issue.Comment: 9 pages, 6 figure

Enhancing structural robustness by complexity maximisation

Structural robustness is considered a fundamental prerequisite in the design of structures. In particular, attention has to be paid to events that are unforecastable and with no known magnitude. Referring to an idea by Donald Rumsfeld, these are unknown unknowns. Among all the possible strategies for ensuring robustness, alternating the load paths on the structures may represent a feasible design solution. Structural complexity is a novel metrics for measuring the amount of interaction between hypothetical load paths on a structure. Maximum complexity corresponds to maximum interaction. In the paper, the links between structural complexity and robustness are investigated

Archetypal Use of Artificial Intelligence for Bridge Structural Monitoring

Structural monitoring is a research topic that is receiving more and more attention, especially in light of the fact that a large part our infrastructural heritage was built in the Sixties and is aging and approaching the end of its design working life. The detection of damage is usually performed through artificial intelligence techniques. In contrast, tools for the localization and the estimation of the extent of the damage are limited, mainly due to the complete datasets of damages needed for training the system. The proposed approach consists in numerically generating datasets of damaged structures on the basis of random variables representing the actions and the possible damages. Neural networks were trained to perform the main structural monitoring tasks: damage detection, localization, and estimation. The artificial intelligence tool interpreted the measurements on a real structure. To simulate real measurements more accurately, noise was added to the synthetic dataset. The results indicate that the accuracy of the measurement devices plays a relevant role in the quality of the monitoring

An Efficient Reliability-based Design Approach to Reduce Rockfall Risk Below a Target Threshold

Rockfalls are expected to increase due to global warming and extreme events induced by climate change. An accurate quantification of the risk is fundamental for Administrations to predispose effective risk mitigation plans. Risk value should account for all the possible events that can occur in a specific time, i.e. for a magnitude (block volume) frequency relationship. Among structural protective measures, rockfall barriers are widely selected. Despite their design method has been almost defined, even not standardized, the widely adopted safety factors approach with fixed factors does not allow obtaining a specific probability of failure. Moreover, the event magnitude-frequency relationship is not accounted. A novel time- independent reliability-based approach has been recently conceived by the Authors, allowing obtaining the design values for a specific failure probability. The method accounts for all the possible events, integrating them in time with their probability. In this way, an increase of rockfall events can been accurately considered. The obtained barrier failure probability can be used to compute the risk reduction in a given time or, conversely, to define the maximum failure probability of a barrier that could be accepted

A fixed combination of probiotics and herbal extracts attenuates intestinal barrier dysfunction from inflammatory stress in an in vitro model using Caco-2 cells.

Background: Inflammatory Bowel Diseases (IBD), are considered a growing global disease, with about ten million people being affected worldwide. Maintenance of intestinal barrier integrity is crucial for preventing IBD onset and exacerbations. Some recent patents regarding oily formulations containing probiotics (WO2010122107A1 and WO2010103374A9) and the use of probiotics for gastrointestinal complaints (US20110110905A1 and US9057112B2) exist, or are pending application. Objective: In this work, we studied the effect of a fixed combination of registered Lactobacillus reuteri and Lactobacillus acidophilus strains and herbal extracts in an in vitro inflammation experimental model. Methods: Caco-2 cell monolayer was exposed to INF-\u3b3+TNF-\u3b1 or to LPS; Trans Epithelial Electrical Resistance (TEER) and paracellular permeability were investigated. ZO-1 and occludin Tight Junctions (TJs) were also investigated by mean of immunofluorescence. Results: Pre-treatment with the fixed combination of probiotics and herbal extracts prevented the inflammation-induced TEER decrease, paracellular permeability increase and TJs translocation. Conclusions: In summary, the fixed combination of probiotics and herbal extracts investigated in this research was found to be an interesting candidate for targeting the re-establishment of intestinal barrier function in IBD conditions

High Rate Performance of Drift Tubes

This article describes calculations and measurements of space charge effects due to high rate irradiation in high resolution drift tubes. Two main items are studied: the reduction of the gas gain and changes of the drift time. Whereas the gain reduction is similar for all gases and unavoidable, the drift time changes depend on the kind of gas that is used. The loss in resolution due to high particle rate can be minimized with a suitable gas. This behaviour is calculable, allowing predictions for new gas mixtures.Comment: 20 pages, submitted to Nuclear Instruments and Methods

Adaptive modulation control for visible light communication systems

Visible light communication (VLC) builds on the dual use of lightening infrastructure for communication. Even though the advantages of VLC are well known, as emerging communication paradigm, some open issues still need to be addressed in order to rely on it as a robust communication system. First of all, external interference as an extremely varying signal impacting on the reliability of the VLC system needs to be analyzed. In this paper, we propose a system where the link conditions (in terms of signal-to-noise-ratio (SNR)) drive the modulation scheme and this procedure is managed through the use of an uplink/channel, to assure a feedback path. The receiver is in charge of choosing the modulation scheme matching the requirement in terms of error rate on the basis of the measured SNR after noise mitigation. The feasibility of the system and its effectiveness are evaluated by designing and implementing a complete bi-directional system. In particular, an uplink channel sending the information regarding the specific selected modulation technique has been implemented and the whole system is based on a fine synchronization approach in order to “track” in real time the most suitable modulation scheme. Experimental results show the effectiveness of a bi-directional system in order to implement an adaptive VLC system able to follow the environmental changes (in terms of interference and noise)

foF2 seismo-ionospheric effect analysis: actual data and numerical simulations

Abstract. On the background of seasonal and helio-geomagnetic disturbances, disturbances of the ionization density near noon connected to earthquakes are investigated. The study is performed for some tens of earthquakes with magnitudes M>5 and depths h<70 km, which occur at distances from the vertical sounding stations "Tokyo", "Akita", and "Yamagawa" not larger than R=exp(M)+150 km. The analysis is performed using data registered by the three sounding stations every hour during 30 years. Especially methods of the statistical analysis are applied to search for regularities in the lithospheric-ionospheric links before and after earthquakes. The growth of the mean ionization density N at the F-layer electron density maximum Fof2 five-three days before earthquakes, and the decrease of N approaching the eruption and during a few days after the earthquake is investigated in dependence on both the magnitude of the earthquake M and the ionization density N near the F-layer maximum. It is found that some days before earthquakes the decrease of the ionization density ΔN is proportional to the values of M and N. After the earthquakes, ΔN depends much weaker on the magnitude M, and it is not influenced by the ionization density N. The variations of the ionization density three days before earthquakes do not depend on N and M (within the same order of approximation)

Daytime variations of foE connected to earthquakes

Abstract. In the present work it is shown that, in accordance with the observations of the vertical sounding station "Tashkent", the critical foE-frequency of the daytime E-layer increases about one day before winter-earthquakes with magnitudes M > 5 and depths of the epicentre of h < 60 km, which appeared at distances of R < 2000 km from the station. The reliability of the result is larger than 99 %. The phenomenon is not observed for summer-earthquakes. It seems to be determined by the atmospheric wind system. Further, the variations of the foE-frequency are compared with possible simultaneous variations of the critical frequency foF2 of the F2-layer. First results show that only very large changes of the ionisation density in the E-layer influence the ionisation density in the F-region. Therefore, no synchronous growth of the foE- and foF2-frequencies 1–2 days before seismic shocks could be observed

A simplified method for assessing the response of RC frame structures to sudden column removal

Column loss is a type of damage that can occur in frame structures subjected to explosions or impacts. The response of such structures largely depends on the capacity of the assembly of elements and on the inertia effects due to the sudden nature of the phenomenon. Frame structures are able to develop various resisting mechanisms that prevent the collapse to progress. The assessment of the robustness often requires complex and detailed numerical modelling. For the preliminary design of a robust frame, simplified methods to assess the effectiveness of the redistribution of the loads after the removal of a member are welcome. In the present paper, an approach based on the idealisation of the damaged structure into a single degree-of-freedom system with an elastic-plastic compliance law is proposed. The output of the method is the dynamic response of a target point, which can serve for assessing the residual safety of the structure. Comparing the obtained results with the outputs of a more sophisticated FE (Finite Elements) analysis, a satisfying accuracy is found