196,289 research outputs found
Estimates of Vs30 Based on Constrained H/V Ratio Measurements Alone
No full text"One more use of H/V of microtremors is described by S. Castellaro and F. Mulargia. They propose a method to infer the ever-needed Vs 30 by fitting the observed H/V spectrum to the theoretical one computed under assumption taht noise wavefield is composed of the fundamental mode Rayleigh waves. The authors find their technique superior and more informative than all popular array methods, allowing detection of deviations from 1-D subsoil geometry over lengths of a few meters!" (CASSIDY J., MUCCIARELLI M., HERAK M. 8eds.), Increasing Seismic Safety by Combining Engineering Technologies and Seismological Data, p.2
H/V: un contributo oltre Vs30
No full textLe norme tecniche sulle costruzioni di diverse nazioni prevedono
una classificazione semplificata del suolo di fondazione articolata intorno al parametro Vs30 (velocità delle onde di taglio di uno strato
omogeneo equivalente a 30 m), sulla base di una presunta correlazione tra questo valore e il fattore di amplificazione sismica stratigrafica. Tuttavia, prima di chiedersi qual sia il metodo migliore per misurare Vs30, è importante chiedersi perché si debba misurare Vs30
Reply to “Comment on ‘A Unified Seismic Catalog for the Iranian Plateau (1900–2011)’ by Mohammad P. Shahvar, Mehdi Zaré, and Silvia Castellaro” by Noorbakhsh Mirzaei, Elham Shabani, and Seyed Hasan Mousavi Bafrouei
No full textDeterminazione dello spessore di un corpo sabbioso di spiaggia emersa con metodi di sismica passiva
No full textHow five different isoforms of N,N,N-Tris(tert-butoxycarbonyl)-L-arginine whose reactivity in esterification reactions was subsequently investigated were obtained
No full textL-arginine, nowadays, is more and more used to functionalize scaffolds for producing delivery systems with high transfection activity and low toxicity. For these purposes it is better to be protected to basic nitrogen atoms. A well known protective residue is tert-butoxycarbonyl group (BOC) and three protocols of BOC-protection selected by us assured that the widely cited (E)-αN,ωN,ω’N-tris(tert-butyloxycarbonyl)-L-arginine would be the only product obtainable. Surprisingly we achieved also other four isoforms (Figure 1) [1]. With the first tested procedure [2] αN,ωN,ω’N-Tris(tert-butyloxycarbonyl)-L-arginine was never obtained. The second one [3] provided the goal compound but in mixture with the Z rotamer while the third protocol [4] led to a single very pure isoform in high yield but with an unreported symmetrical structure. Since BOC protection is transient this discovery would seem of poor interest but investigations about the behavior of each one of the isoforms obtained in esterification reactions, whose results have been described in details in another work by us presented in this context, shown that their reactivity depends on their structure. With this work we reported a thorough description of this unexpected results and the meticulous NMR investigation performed with particular care for double bonds geometry and position which confirmed the structures.
References: 1. S. Alfei, S. Castellaro, Res. Chem. Intermediat. 44, 1811 (2018) DOI: 10.1007/s11164-017-3199-6. 2. H. Konno, K. Kubo, H. Makabe, E. Toshiro, N. Hinoda, K. Nosakaa, K: Akaji, Tetrahedron 63, 9502 (2007) doi:10.1016/j.tet.2007.06.082.3. J. Izdebski, T. Gers, D. Kunce, P. Markovsky, J. Pept. Sci. 11, 60 (2005) doi: 10.1002/psc.585.4. M. A. Jones, A. D. Hislop, J. S. Snaith, Org. Biomol. Chem. 4, 3769 (2006) doi: 10.1039/b611170
Seismic soil classification from a different perspective
No full textThe simplified seismic soil classification in many countries still basically relies on the Vs30 parameter as a proxy to the amplification factor. The pros and cons of this approach have already been extensively debated in the literature.
We present an attempt to classify the subsoils in a seismic perspective which is based on expedite geophysical field procedures (passive/active single station and multichannel surveys, all based on the surface waves analysis) aimed at determining the resonance frequencies and the very shallow Vs profile.
We will show how the same effort used to measure Vs30 can be used to overcome many limits of a Vs30-based classification and to get more representative classifications.
In particular, this approach 1) implies accepting the concept that the site class is not a “universal” concept but is strictly linked to the type of structure which is planned to be built on that site, 2) implies a shift from the “depth-domain” concept (30 m or 20 m or 10 m suggested by different authors) to the “frequency-domain” concept and 3) does not take into account an “average” stiffness but the abrupt stiffness changes, which play a big role in seismic amplification.
Last, the role of velocity inversions (i.e. negative Vs gradients) will also be considered from the “frequency-domain” point of view
Performance of Different ANNs in Microtremor H/V Peak Classification
No full textThe microtremor horizontal-to-vertical (H/V) technique is extensively used to both assess the seismic amplification potential of soils and, in combination with other surface wave-based techniques, to reconstruct the near-surface seismic stratigraphy. The H/V peak frequencies are traditionally interpreted in terms of soil resonances, and, in this case, they are assigned a “stratigraphic origin.” However, not all H/V peaks mark subsoil resonances, and some of them have “anthropic” or “artefactual” origin. Recognizing the nature of H/V peaks should be mandatory before any stratigraphic interpretation. Nonetheless, this problem is not given the attention it deserves. Because this classification is not easy to achieve using standard statistical techniques, we decided to train two supervised neural networks: a traditional artificial neural network using a set of input values extracted from the individual (horizontal and vertical) microtremor spectra and a convolutional neural network working on images of the microtremor spectra. The nets were trained on an Italian dataset and tested on a U.S. dataset, collected by different operators and with different instruments. Both the nets achieved a classification accuracy of ∼90%; however, the convolutional one showed a greater generalization capability compared to the traditional one. Such machine learning algorithms can be useful tools to discriminate the origin of H/V peaks, complementing the traditional SESAME guidelines, which do not go into much detail on this topic
Field measurements, laboratory tests and empirical relations for investigating the solid-to-fluid transition of a rapid earthflow
No full textEarthflows are widespread phenomena in the Mediterranean area. These landslides involve fine-grained soils and clay-bearing rocks, and despite their low speed are responsible for significant economic losses in vast areas. The dynamics of these landslides is still relatively obscure thus reducing our ability to forecast and mitigate their effects. In this study, we present a methodological approach for the characterization of active earthflows based on the combination of geophysical surveys, laboratory tests, and empirical formulas. Geophysical surveys consist of periodic measurements of Rayleigh wave velocities repeated over time to evaluate the change of stiffness with time of the landslide material. Laboratory tests combine Atterberg limits, fall cone and oedometric tests and allow to constrain the empirical correlations between geophysical and geotechnical properties. The method is designed to obtain relevant data when direct methods like boreholes or geotechnical soundings are not possible for safety reasons, with the aim of investigating the solid-to-fluid transition that can occur in rapid earthflows. We applied this approach to study the Montevecchio landslide (Northern Apennines of Italy), an active earthflow in young marine clays which was affected by multiple reactivations in the recent years. Results show that after a surge the earthflow material is very soft (shear wave velocity in the order of 50–60 m/s) and characterized by a high water content. However, the exact value of the Liquidity Index remains unknown due to the lack of direct measurements and to the uncertainty dictated by the empirical relationships
Seismic soil classification from a different perspective
No full textThe simplified seismic soil classification in many countries relies on the Vs30 parameter as a proxy to the amplification factor. The pros and cons of this approach have already been extensively debated in the literature. We present an alternative subsoil seismic classification which is based on expedite geophysical field procedures (passive/active single station and multichannel surveys, all relying on surface waves analysis) aimed at determining the resonance frequencies and the very shallow Vs profile. We show how the major drawbacks of the Vs30-based classification cab ne effectively overcome. In particular, the new approach 1) brings in the concept that the site class is not a universal concept but is strictly linked to the type of structure which is planned to be built on that site, 2) introduces a shift from the ‘depth-domain’ concept (30 m or 20 m or 10 m suggested by different authors) to the ‘frequency-domain’ concept and 3) does not take into account an ‘average’ stiffness but the abrupt stiffness changes, which play a major role in seismic amplificatio
An investigation about the reactivity of five isoforms of N, N, N-Tris(tert-butoxycarbonyl)-L-arginine in esterification reactions of a 1, 3-propandiol derivative
No full textL-arginine is often used to decorate lipid matrices and polymer or dendrimer scaffolds, to obtain synthetic vectors for gene therapy or drug delivery with increased transfection activity and reduced toxicity. For this purpose, its basic nitrogen atoms need protection for example with tert-butoxycarbonyl group. In a previous study, following three reported protocols which assured the achievement of the widely described (E)-αN,ωN,ω’N-Tris(tert-butoxycarbonyl)-L-arginine as pure isoform [1,2,3], further four isoforms were obtained: the rotamer Z, αN,δN,ωN- and αN,δN,ω’N-Tris(tert-butoxycarbonyl)-L-arginine and the unknown symmetric compound not affected by geometric isomerism, αN,ωN,ω’N-Tris(tert-butoxycarbonyl)-L-arginine [4]. Aiming at demonstrating the importance of the position of the protective groups, even if transients, we performed studies about the reactivity of any isoform in esterification reactions of a 1,3-propandiol derivative taken as model molecule. Then in this communication the obtained results were reported and discussed. We have shown that the structure of the isoform and BOC location influence its reactivity and have highlighted how much to prepare an isoform rather than another may have more or less advantageous repercussions on future reactions (Figure 1). Furthermore we described the preparation, isolation and characterization of two unreported first generation arginine dendrons achieved during the investigations and considered by us appealing fragments for decorating the periphery of polyesters or polyamidoamine dendrimer scaffolds for the obtainment of new synthetic polycationic vectors for gene transfection or drug delivery (Figure 2). Finally the isolation and spectral characterization of three unreported compounds (9a, 11 E/Z and 16) were also provided.
1. H. Konno, K. Kubo, H. Makabe, E. Toshiro, N. Hinoda, K. Nosakaa, K. Akaji, Tetrahedron 63, 9502 (2007) doi:10.1016/j.tet.2007.06.082. 2. J. Izdebski, T. Gers, D. Kunce, P. Markovsky, J. Pept. Sci. 11, 60 (2005) doi: 10.1002/psc.585. 3. M. A. Jones, A. D. Hislop, J. S. Snaith, Org. Biomol. Chem. 4, 3769 (2006) doi: 10.1039/b611170j. 4. S. Alfei, S. Castellaro, Res. Chem. Intermediat. 44, 1811 (2018) DOI: 10.1007/s11164-017-3199-6
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