87,581 research outputs found
ON THE PRESUMED ULF MAGNETIC PRECURSORS OF EARTHQUAKES
No full textDuring the last twenty years many researchers investigated ULF (Ultra-Low-
Frequency) magnetic data in the hope of finding seismogenic signals. After the report of Fraser- Smith et al. (1990) several ULF stations were installed and many papers documented the observations of pre-earthquake magnetic anomalies. These claims motivate the belief that one day
short-term earthquake prediction based on magnetic data may become a routine technique. Shortterm earthquake prediction has been the topic of several scientific debates but at present the entire subject remains still controversial. In order to be useful, short-term prediction requires reproducible earthquake precursors which provide information regarding intensity, location and time of the predicted earthquake together with error estimates for each parameter. Thus, a serious problem
concerns the identification of reliable earthquake precursors. Recently, some researchers have given rise to a re-examination process of dubious earthquake precursors and published their findings. For
example Masci (2010, 2011a), by means of global geomagnetic Kp index time-series, demonstrated that many presumed magnetic seismogenic signatures are not related to the subsequent earthquakes but are normal variations driven by the geomagnetic activity level. More precisely, as pointed out by Masci (2011a, 2012a), since the Kp index is representative of the geomagnetic field average disturbances over planetary scale, we should not expect that a good correlation between an ULF parameter of the geomagnetic field and Kp will always and everywhere exist during a long-time range. On the contrary, if a close correspondence between these changes of an ULF geomagnetic
field parameter and Kp exists during a period of time, this indicates that the changes are part of normal global geomagnetic field variations driven by solar-terrestrial interactions and cannot be
described as earthquake-related signals.
Here, some examples of questioned earthquake precursors are reported hoping to shed light on the usefulness of the ULF magnetic measurements to study the occurrence of pre-earthquake seismogenic signals. In addition, the results of the analysis of magnetic data from the Geomagnetic Observatory of L’Aquila during the period of the 2009 L’Aquila seismic sequence are reported as well.PublishedPotenza, 20-22 novenber 20122.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attiveope
On the reliability of the Spatial Scintillation Index to detect earthquake precursors in the ionosphere
No full textThe scientific literature includes many reports of ionospheric phenomena that are retrospectively identified prior to seismic events. These disturbances of the Earth’s ionosphere are considered to be possible precursors of the impending earthquakes. However, a causal relationship between ionospheric phenomena and earthquakes has never been definitively demonstrated and attempts at identifying precursory effects in the ionosphere have been called into question by several studies [see, e.g., Masci and Thomas, 2014; Masci et al., 2014]. Among the candidate indicators of ionospheric precursors there is the Spatial Scintillation Index (SSI) proposed by Pulinets et al. [2007]. The usefulness of this index in the search for precursory effects of earthquakes has been criticized by Thomas et al. [2012] and Masci [2013]. In a recent report, Pulinets and Davidenko [2014] attempt to briefly respond to the remarks of these researchers. Here we cast doubt that Pulinets and Davidenko [2014] have shown that SSI is a reliable indicator of precursory effects of earthquakes in the ionosphere.Published745–7531A. Geomagnetismo e PaleomagnetismoJCR Journalrestricte
Secessionismi Autonomismi Federalismi. Frammenti di una rosa olografica
No full textPubblicazione degli atti del convegno dal titolo "Secessionismi Autonomismi Federalismi. Frammenti di una rosa olografica
Comment on "Ultra Low Frequency (ULF) European multi station magnetic field analysis before and during the 2009 earthquake at L'Aquila regarding regional geotechnical information" by Prattes et al. (2011)
No full textPrattes et al. (2011) report ULF magnetic anomalous signals claiming them to be possibly precursor of the 6 April 2009 <i>M</i><sub>W</sub> = 6.3 L'Aquila earthquake. This comment casts doubts on the possibility that the observed magnetic signatures could have a seismogenic origin by showing that these pre-earthquake signals are actually part of normal global geomagnetic activity
Playing construction with the monomer toy box for the synthesis of multi-stimuli responsive copolymers by reversible deactivation radical polymerization protocols
No full textIn this review article, we survey the 2016–June 2021 scientific literature on the synthesis of multi-stimuli responsive (MSR) polymers, the main focus being on reversible deactivation radical polymerization techniques (RDRPs, also known as controlled radical polymerizations). In fact, along more than 40 years of extensive research, RDRPs have boosted the synthesis of stimuli-responsive polymers. RDRPs are now robust, versatile, relatively user-friendly and even interconvertible, thus allowing control over composition, sequence, and topology of polymers. Such control can afford materials with well-defined responses to physical, chemical, and biological external stimuli. Furthermore, “click” reactions are used to combine macromolecular precursors or to introduce specific functional groups in the target structure. As a result, MSR polymers are obtained from diverse combinations of commercial or specially synthesized building blocks arranged at will into desired sequences and architectures. Thanks to this versatility, self-assembling polymeric structures are designed either to respond to triggers and perform specific applicative tasks, or to investigate the influence of structural variables on the responsivity of polymers. The “green” trend emerging in the field of responsive polymers and RDRPs is also briefly discussed
Brief communication "On the recent reaffirmation of ULF magnetic earthquakes precursors"
No full textHayakawa et al. (2009) and Hayakawa (2011) have recently reviewed some "anomalous" ULF signatures in the geomagnetic field which previous publications have claimed to be earthquake precursors. The motivation of this review is "<i>to offer a further support to the definite presence of those anomalies</i>". Here, these ULF precursors are reviewed once again. This brief communication shows that the reviewed anomalies do not "<i>increase the credibility on the presence of electromagnetic phenomena associated with an earthquake</i>" since these anomalous signals are actually caused by normal geomagnetic activity. Furthermore, some of these ULF precursors have just been rebutted by previous publications
Valorizzazione dei prodotti tipici e turismo rurale: considerazioni sulle filiere corte
No full textIl ruolo delle filiere corte dei prodotti tipici nello sviluppo dei comprensori rurali è indagato con riferimento ad un contesto territoriale circoscritto. Le indicazioni formulate conseguono dalla caratterizzazione degli acquirenti disponibili a recarsi in azienda per acquistare un particolare prodotto tipico (pomodorino di Corbara). Gli strumenti statistici utilizzati sono l'analisi delle corrispondenze multiple e i modelli a scelta discreta
Prodotti tipici e sviluppo rurale: indicazioni metodologiche a partire da un caso studio
No full textIl ruolo dei prodotti tipici nella promozione dello sviluppo socio-economico delle aree rurali si esprime attraverso gli effetti diretti e indiretti sull’evoluzione strutturale dell’economia locale. Il lavoro si articola in una proposta di tipologia delle aziende agricole di produzione del prodotto tipico (ACM analysis and clustering) e nell'analisi della disponibilità ad aumentare la produzione da parte delle aziende e per i consumatori in quella ad acquistare in azienda (discrete choice models). Nelle conclusioni sono raccolte le principali indicazioni metodologiche e operative per formulare iniziative rivolte alle aziende e ai consumatori al fine di delineare strategie di valorizzazione del prodotto
Inferential Tools for Assessing Dependence Across Response Categories in Multinomial Models with Discrete Random Effects
No full textWe propose a discrete random effects multinomial regression model to deal with estimation and inference issues in the case of categorical and hierarchical data. Random effects are assumed to follow a discrete distribution with an a priori unknown number of support points. For a K-categories response, the modelling identifies a latent structure at the highest level of grouping, where groups are clustered into subpopulations. This model does not assume the independence across random effects relative to different response categories, and this provides an improvement from the multinomial semi-parametric multilevel model previously proposed in the literature. Since the category-specific random effects arise from the same subjects, the independence assumption is seldom verified in real data. To evaluate the improvements provided by the proposed model, we reproduce simulation and case studies of the literature, highlighting the strength of the method in properly modelling the real data structure and the advantages that taking into account the data dependence structure offers
Switching on the activity of 1,5-diaryl-pyrrole derivatives against drug-resistant ESKAPE bacteria
No full textAntibiotic resistance represents a significant threat worldwide. There is an urgent need to discover structurally innovative antibacterial agents for which no pre-existing resistance is known.
With the aim to speed up the drug discovery process and to reduce the limitations of target-based high-through put screenings (HTS) we described the synthesis and biological evaluation of a novel series of 1,5-diphenylpyrroles active against a wide panel of ESKAPE bacteria. In particular, a subsequent structure-activity relationship (SAR) study revealed that the modification of the functional groups can switch the selectivity and the antimicrobial activity from mycobacteria to Gram positive and Gram negative bacteria [1,2].
The new compounds show high activity against both wild type and drug-resistant Gram positive and Gram negative bacteria at concentrations similar than levofloxacin.
Microbiology studies revealed that the plausible target of this class of compounds is the bacterial DNA gyrase, with the pyrrole derivatives displaying similar inhibitory activity to levofloxacin against the wild type enzyme and retaining activity against the fluoroquinolone-resistant enzyme.
References:
[1] Bhakta, S.; Manetti, F.; Castagnolo, D. et al (2016) Design and Synthesis of 1-((1,5-Bis(4-chlorophenyl)-2-methyl-1H-pyrrol-3-yl)methyl)-4-methylpiperazine (BM212) and N-Adamantan-2-yl-N′-((E)-3,7-dimethylocta-2,6-dienyl)ethane-1,2-diamine (SQ109) Pyrrole Hybrid Derivatives: Discovery of Potent Antitubercular Agents Effective against Multidrug-Resistant Mycobacteria. J. Med. Chem.59:2780-2793.
[2] Masci, D.; Hind, C.; K. Islam, M.; Toscani, A.; Clifford, M.; Coluccia, A.; Conforti, I.; Touitou, M.; Wei, X.; Memdouh, S.; La Regina, G.; Silvestri, R; Sutton, M.; Castagnolo, D. (2019) Switching on the activity of 1,5-diaryl-pyrrole derivatives against drug-resistant ESKAPE bacteria: structure-activity relationships and mode of action studies. Eur. J. Med. Chem. 178:500-514
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