A Bayesian Networks Approach to Operational Risk

A system for Operational Risk management based on the computational paradigm of Bayesian Networks is presented. The algorithm allows the construction of a Bayesian Network targeted for each bank using only internal loss data, and takes into account in a simple and realistic way the correlations among different processes of the bank. The internal losses are averaged over a variable time horizon, so that the correlations at different times are removed, while the correlations at the same time are kept: the averaged losses are thus suitable to perform the learning of the network topology and parameters. The algorithm has been validated on synthetic time series. It should be stressed that the practical implementation of the proposed algorithm has a small impact on the organizational structure of a bank and requires an investment in human resources limited to the computational area

A coupled thermal-analytical and mechanical approach to investigate the behavior of bonded anchors cured at sub-zero temperatures

In post-installed connection in reinforced concrete structures, bonded anchors are commonly adopted when elevated mechanical performances are required. Such performances may be significantly impaired by adverse service conditions, above all temperature variations with respect to room ambient one. It is also generally acknowledged that the curing temperature may impact on the anchor performances, to the extent that all the main existing qualification procedures assess the anchor behavior when cured at different temperatures, in particular below zero Celsius degree. However, among the few investigations focusing on the impact of a low curing temperature on the long term behavior of an anchor, a low effort exists in addressing the relationship between the anchor mechanical behavior and the thermal properties of the bonding agent. The paper proposes a coupled thermal-analytical and mechanical approach to detect potential critical issues in the long term mechanical behavior of the anchor as a function of the adhesive behavior, as investigated by thermal or thermo-mechanical analyses. To the scope, a wide investigation on two adhesives is carried out comprising MDSC, DMA, pull-out and sustained load tests. On the basis of the obtained results, it is concluded that some thresholds in the variations of degree of conversion and phase transition temperatures may indicate a negligible impact of a low curing temperature on the anchor mechanical behavior, but also that existing qualification procedures are not able to capture the anchor behavior, when cured at low temperatures and subjected, during its service life, to temperatures higher than room ambient one

The External TEA Binding Site and C-Type Inactivation in Voltage-Gated Potassium Channels

AbstractThe location of the tetraethylammonium (TEA) binding site in the outer vestibule of K+ channels, and the mechanism by which external TEA slows C-type inactivation, have been considered well-understood. The prevailing model has been that TEA is coordinated by four amino acid side chains at the position equivalent to Shaker T449, and that TEA prevents a constriction that underlies inactivation via a foot-in-the-door mechanism at this same position. However, a growing body of evidence has suggested that this picture may not be entirely correct. In this study, we reexamined these two issues, using both the Kv2.1 and Shaker potassium channels. In contrast to results previously obtained with Shaker, substitution of the tyrosine at Kv2.1 position 380 (equivalent to Shaker 449) with a threonine or cysteine had a relatively minor effect on TEA potency. In both Kv2.1 and Shaker, modification of cysteines at position 380/449 by 2-(trimethylammonium)ethyl methanethiosulfonate (MTSET) proceeded at identical rates in the absence and presence of TEA. Additional experiments in Shaker demonstrated that TEA bound well to C-type inactivated channels, but did not interfere with MTSET modification of C449 in inactivated channels. Together, these findings rule out the possibility that TEA binding involves an intimate interaction with the four side chains at the position equivalent to Shaker 449. Moreover, these results argue against the model whereby TEA slows inactivation via a foot-in-the-door mechanism at position 449, and also argue against the hypothesis that the position 449 side chains move toward the center of the conduction pathway during inactivation. Occupancy by TEA completely prevented MTSET modification of a cysteine in the outer-vestibule turret (Kv2.1 position 356/Shaker position 425), which has been shown to interfere with both TEA binding and the interaction of K+ with an external binding site. Together, these data suggest that TEA is stabilized in a more external position in the outer vestibule, and does not bind via direct coordination with any specific outer-vestibule residues

On the Number of Cosmic Strings

The number of cosmic strings in the observable universe is relevant in determining the probability of detecting such cosmic defects through their gravitational signatures. In particular, we refer to the observation of gravitational lensing events and anisotropy in the CMB radiation induced by cosmic strings. In this paper, a simple method is adopted to obtain an approximate estimate of the number of segments of cosmic strings, crossing the particle horizon, which fall inside the observed part of the universe. We show that there is an appreciable difference in the expected number of segments which differentiates cosmic strings arising in Abelian Higgs and Nambu-Goto models, and that a different choice of setting for the cosmological model can lead to significant differences in the expected number of cosmic string segments. Of this number, the fraction realistically detectable may be considerably smaller.Comment: LaTex2e, 15 pages, 1 figure, 5 tables. Subject extended to other cosmological scenarios from Sect. 3 on hence, it follows a modification in the title; three tables and references added. Version to appear in MNRA

Synthesis, spectroscopic characterization and in vitro antitumor activity of new trans 1-heteroaryl-2-(1-methylpyridinium-2-yl) ethylenes

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The Missing Matter Problem: From the Dark Matter Search to Alternative Hypotheses

Dark matter is among the most important open problems in both astrophysics and particle physics. We review the status of art of dark matter search at theoretical and experimental level discussing also alternative hypotheses

Control of Single Channel Conductance in the Outer Vestibule of the Kv2.1 Potassium Channel

Current magnitude in Kv2.1 potassium channels is modulated by external [K+]. In contrast to behavior expected from the change in electrochemical driving force, outward current through Kv2.1 channels becomes larger when extracellular [K+] is increased within the physiological range. The mechanism that underlies this unusual property involves the opening of Kv2.1 channels into one of two different outer vestibule conformations, which are defined by their sensitivity to TEA. Channels that open into a TEA-sensitive conformation generate larger macroscopic currents, whereas channels that open into a TEA-insensitive conformation generate smaller macroscopic currents. At higher [K+], more channels open into the TEA-sensitive conformation. In this manuscript, we examined the mechanism by which the conformational change produced a change in current magnitude. We started by testing the simplest hypothesis: that each pharmacologically defined channel conformation produces a different single channel conductance, one smaller and one larger, and that the [K+]-dependent change in current magnitude reflects the [K+]-dependent change in the percentage of channels that open into each of the two conformations. Using single channel and macroscopic recordings, as well as hidden Markov modeling, we were able to quantitatively account for [K+]-dependent regulation of macroscopic current with this model. Combined with previously published work, these results support a model whereby an outer vestibule lysine interferes with K+ flux through the channel, and that the [K+]-dependent change in orientation of this lysine alters single channel conductance by changing the level of this interference. Moreover, these results provide an experimental example of single channel conductance being modulated at the outer end of the conduction pathway by a mechanism that involves channel activation into open states with different outer vestibule conformations