A magnetic field probe for hostile environments

Peer Reviewe

Estudio no destructivo del interior de piezas de valor histórico mediante gammagrafías

La tecnología de Tomografía de Hormigón Armado desarrollada por THASA ha sido aplicada al estudio de piezas ornamentales y otras de valor histórico con el objeto de examinar el interior de las mismas e investigar, en algunos casos, la existencia, configuración y condición de refuerzos metálicos y en otro caso, la existencia de huecos producidos por termitas en vigas de madera. En este trabajo se discuten detalles metodológicos y resultados alcanzados en los casos de las estatuas ubicadas en el coronamiento del Palacio de Tribunales en la Ciudad Autónoma de Buenos Aires, en dragones colgantes de las torres de la Basílica de Luján y en las vigas del techo de la Capilla Doméstica, construida en 1660 y declarada patrimonio de la humanidad por la UNESCO, ubicada en la manzana jesuítica en la Ciudad de Córdoba. El carácter pionero de la investigación de oquedades en madera realizada en este último caso hizo necesario la construcción de modelos de simulación que resultan de utilidad para otras aplicaciones similares

Contribution of sortase A to the regulation of Listeria monocytogenes LPXTG surface proteins

Gram-positive bacteria of the genus Listeria contain many surface proteins covalently bound to the peptidoglycan. In the pathogenic species Listeria monocytogenes, some of these surface proteins mediate adhesion and entry into host cells. Specialized enzymes called sortases anchor these proteins to the cell wall by a mechanism involving processing and covalent linkage to the peptidoglycan. How bacteria coordinate the production of sortases and their respective protein substrates is currently unknown. The present work investigated whether the functional status of the sortase influences the level at which its cognate substrates are produced. The relative amounts of surface proteins containing an LPXTG sorting motif recognized by sortase A (StrA) were determined in isogenic wild-type and ΔsrtA strains of L. monocytogenes. The possibility of regulation at the transcriptional level was also examined. The results showed that the absence of SrtA did not affect the expression of any of the genes encoding LPXTG proteins. However, marked differences were found at the protein level for some substrates depending on the presence/absence of SrtA. In addition to the known mis-sorting of some LPXTG proteins caused by the absence of SrtA, the total amount of certain LPXTG protein species was lower in the ΔsrtA mutant. These data suggested that the rate of synthesis and/or the stability of a subset of LPXTG proteins could be regulated post-transcriptionally depending on the functionality of SrtA. For some LPXTG proteins, the absence of SrtA resulted in only a partial loss of the protein that remained bound to the peptidoglycan, thus providing support for additional modes of cell-wall association in some members of the LPXTG surface protein familyThis study was funded by grant BIO2010-18962 of the Spanish Ministry of Economy and Competitiveness to M.G.P

Application of a semi-microscopic core-particle coupling method to the backbending in odd deformed nuclei

In two previous papers, the Kerman-Klein-Donau-Frauendorf (KKDF) model was used to study rotational bands of odd deformed nuclei. Here we describe backbending for odd nuclei using the same model. The backbending in the neighboring even nuclei is described by a phenomenological two band model, and this core is then coupled to a large single-particle space, as in our previous work. The results obtained for energies and M1 transition rates are compared with experimental data for 165Lu and for energies alone to the experimental data for 179W. For the case of 165Lu comparison is also made with previous theoretical work.Comment: 16 pages including 8 figure(postscript), submitted to Phys.Rev.

DYNAMIC STRAY CURRENT MEASURING METHODS IN URBAN AREAS

In areas where urban tracks are used as public transportation, dynamic stray currents cause high maintenance costs for the tracks and metal structures near the tracks. Stray currents caused by rail vehicles depend on many factors (traffic density, vehicle speed, acceleration and deceleration, soil and track moisture), so it is very difficult to get a clear picture of the harmfulness of the stray current based on the results of a single field measurement. However, there are several measurement methods that can be used to determine the presence of stray currents and predict appropriate track maintenance actions. Some of these methods are described in this article, namely the use of stray current mapper, measurement of rail potential and rail current, measurement at the stray current collection system, and the use of nondestructive sensors. In track construction, measuring the electrical potential between rail and ground is one of the most common methods of detecting the damaging influence of stray current

Evaluation of mechanical characteristics of steel bars by nondestructive Vickers micro-hardness tests

Materials’ properties evaluation represents a crucial aspect for the static and seismic assessment of existing Reinforced Concrete (RC) structures and infrastructures. While concrete's mechanical characteristics are classically investigated by both destructive tests (DTs) and non-destructive tests (NDTs), for steel reinforcing bars the use of NDTs is not consolidated: a large number of samplings are planned as part of the survey campaign, requiring strong effort to be both extracted and restored and being, moreover, not always sufficient to reliably determine the characteristics of each type of steel grade/rebar used in the structure. Within NTDs, the determination of the hardness value could be a viable way to estimate rebars’ tensile strength. Many experimental studies were proposed in the past and current scientific literature, most of them performed through laboratory tests and therefore requiring a strong time and economic effort: the adoption of portable instruments for the determination of the in-situ hardness of rebars can be a good possibility to reduce the impact on the structure/infrastructure and to optimize timing and restoration operations. Of course, the methodology adopted shall be opportunely calibrated and attention shall be paid to the interpretation of the achieved data. The present research work aims at testing the effectiveness of NDT Vickers micro-hardness tests in the estimation of the mechanical properties of steel reinforcing bars. A methodology is proposed to achieve reliable correlations between hardness values and tensile strength of rebars, accounting for parameters affecting in-situ measures and different typologies of steel grades/rebars

Influence of Impedance Interaction & Comparability on Spectral Aggregation (2-150 kHz) in DC Grids

The reported higher levels of conducted emissions in DC grids in the 2-150 kHz range are caused by the spectral aggregations resulting from the converter's switching harmonics. The dominant influence for these spectral aggregates is the impedance correlation between the DC-link capacitor and the converters. This paper analyses the impedance interaction & comparability between the DC-link and the DC/DC converters at the point of common coupling in the DC grid. Simulations with four DC-link capacitors and forty parallel DC/DC converters are conducted, with full (non-linear) and equivalent-source (linear) models for comparison. The dB/JV values for the first spectral aggregate decrease as the augmenting DC-side impedance becomes comparable with the smaller DC-link impedance, lowering the electromagnetic interference in the DC grid. This understanding may provide insights into the DC-link capacitor design from an electromagnetic compatibility perspective, and towards developing a framework for DC power quality standards in the 2-150 kHz range

Pantograph-To-OHL Arc: Conducted Effects in DC Railway Supply System

The electrical arc occurring in the sliding contact between the supply contact line and the current collector (pantograph) of an electrical locomotive is a fast transient phenomenon able to degrade progressively the line-To-pantograph contact quality and, consequently, the continuity of operation. In order to increase the energy efficiency of the railway system, an inexpensive solution is constituted by the detection of the arc event by the analysis of voltage and current measurements already available on-board train. An essential activity to reach this objective is to set up a reliable electrical model of the railway system in which the arc events originate. To this end, this paper presents a combination of experimental and simulation analysis for the development of an electrical model of a direct current (dc) 3 kV railway system, which is aimed at better understanding the propagation of conducted effects generated by arc events. First, a laboratory experimental activity is carried out to investigate the electrical dynamic characteristics of the arc in a controlled environment. Then, a model of the dc railway system is derived and validated by using the experimental data collected in a measurement campaign on-board train. Finally, a sensitivity analysis of the main model parameters is carried out