137 research outputs found
Drazepinone, a trisubstituted tetrahydronaphthofuroazepinone with herbicidal activity produced by Drechslera siccans
When grown in a minimal-defined medium, a strain of Drechslera siccans, a pathogenic fungus isolated from seeds of Lolium perenne, produced phytotoxic metabolites. This strain is one of the best toxin producers among several grass pathogenic fungal strains collected and tested to find phytotoxins to be used as natural herbicides of monocot weeds. From the culture filtrates of D. siccans, we isolated a new phytotoxic trisubstituted naphthofuroazepinone, named drazepinone, and characterised it as a 3,5,12a-trimethyl-2,5,5a,12a-tetrahydro- 1H-naphtho[2′,3′:4,5]furo[2,3-b]azepin-2-one. Assayed at 2 μg μl-1 solution the novel metabolite proved to have broad-spectrum herbicidal properties, without antibacterial and antifungal activities, and low zootoxic activity. Its original chemical structure and the interesting biological properties make drazepinone a potential natural herbicide. © 2005 Elsevier Ltd. All rights reserved
The momentum and photon energy dependence of the circular dichroic photoemission in the bulk Rashba semiconductors BiTeX (X = I, Br, Cl)
Bulk Rashba systems BiTeX (X = I, Br, Cl) are emerging as important
candidates for developing spintronics devices, because of the coexistence of
spin-split bulk and surface states, along with the ambipolar character of the
surface charge carriers. The need of studying the spin texture of strongly
spin-orbit coupled materials has recently promoted circular dichroic Angular
Resolved Photoelectron Spectroscopy (cd-ARPES) as an indirect tool to measure
the spin and the angular degrees of freedom. Here we report a detailed photon
energy dependent study of the cd-ARPES spectra in BiTeX (X = I, Br and Cl). Our
work reveals a large variation of the magnitude and sign of the dichroism.
Interestingly, we find that the dichroic signal modulates differently for the
three compounds and for the different spin-split states. These findings show a
momentum and photon energy dependence for the cd-ARPES signals in the bulk
Rashba semiconductor BiTeX (X = I, Br, Cl). Finally, the outcome of our
experiment indicates the important relation between the modulation of the
dichroism and the phase differences between the wave-functions involved in the
photoemission process. This phase difference can be due to initial or final
state effects. In the former case the phase difference results in possible
interference effects among the photo-electrons emitted from different atomic
layers and characterized by entangled spin-orbital polarized bands. In the
latter case the phase difference results from the relative phases of the
expansion of the final state in different outgoing partial waves.Comment: 6 pages, 4 figure
THE 9TH JULY 1998 FAIAL EARTHQUAKE: COMPARISON OF STOCHASTIC FINITE FAULT DAMAGE SIMULATION WITH SURVEYED DATA
The Azores earthquake, July 9, 1998 (Mw 6.2) caused a large damage to the stock of old masonry buildings, with maximum felt intensity Is=VIII (MMI). A stochastic strong ground motion (SM) was simulated on the islands struck by the earthquake using published fault solution, to derive maps of average Peak Ground Acceleration (PGA) at bedrock. Detailed analysis was done at the Horta station comparing stochastic-computed and observed PGA, PGV, Response Acceleration Spectra and Response Spectrum Intensity (SI) values. Although recordings on Faial (Horta) and Terceira Islands are not enough to fully constrain the simulation parameters, they can define the range of possible variation. Relationships between PGA and MMI were used to retrieve intensity. Retrieved and observed intensities allowed to derive an average damage index according to the EMS-98 classification
Assessing seismic damage through stochastic simulation of ground shaking: the case of the 1998 Faial Earthquake (Azores Islands)
In July 1998, an Mw = 6.2 earthquake struck the islands of Faial, Pico and San Jorge (in the Azores Archipelago), registering VIII on the Modified Mercalli Intensity scale and causing major destruction in the northeastern part of Faial. The main shock was located offshore, 8 km North East of the island, and it triggered a seismic sequence that lasted for several weeks. The existing data for this earthquake include both the general tectonic environment of the region and the teleseismic information. This is accompanied by one strong-motion record obtained 15 km from the epicentre, the epicentre location of aftershocks, and a large collection of the damage inflicted to the building stock (as poor rubble masonry, of 2-3 storeys). The present study was carried out in two steps: first, with a finite-fault stochastic simulation method of ground motion at sites throughout the affected islands, for two possible locations of the rupturing fault and for a large number of combinations of rupture mechanisms (as a parametric analysis); secondly, the damage to buildings was modelled using a well-known macroseismic method that considers the building typologies and their associated vulnerabilities. The main intent was to integrate different data (geological, seismological and building features) to produce a scenario model to reproduce and justify the level of damage generated during the Faial earthquake. Finally, through validation of the results provided by these different approaches, we obtained a complete procedure for the parameters of a first model for the production of seismic damage scenarios for the Azores Islands region
Emergence of pseudogap from short-range spin-correlations in electron doped cuprates
Electron interactions are pivotal for defining the electronic structure of
quantum materials. In particular, the strong electron Coulomb repulsion is
considered the keystone for describing the emergence of exotic and/or ordered
phases of quantum matter as disparate as high-temperature superconductivity and
charge- or magnetic-order. However, a comprehensive understanding of
fundamental electronic properties of quantum materials is often complicated by
the appearance of an enigmatic partial suppression of low-energy electronic
states, known as the pseudogap. Here we take advantage of ultrafast
angle-resolved photoemission spectroscopy to unveil the temperature evolution
of the low-energy density of states in the electron-doped cuprate
NdCeCuO, an emblematic system where
the pseudogap intertwines with magnetic degrees of freedom. By photoexciting
the electronic system across the pseudogap onset temperature T*, we report the
direct relation between the momentum-resolved pseudogap spectral features and
the spin-correlation length with an unprecedented sensitivity. This transient
approach, corroborated by mean field model calculations, allows us to establish
the pseudogap in electron-doped cuprates as a precursor to the incipient
antiferromagnetic order even when long-range antiferromagnetic correlations are
not established, as in the case of optimal doping.Comment: 17 pages, 3 figure
“Urban Disaster Prevention Strategies Using MAcroseismic Fields and FAult Sources”
In the framework of EU research project “Urban Disaster Prevention Strategies Using MAcroseismic Fields and FAult Sources” (Grant Agreement n. 230301/2011/613486/SUB/A5) innovative approaches are proposed to improve critical points in the procedures for assessing probabilistic hazard and seismic risk; they are tested in particular locations – Mt. Etna, Vesuvius and Campi Flegrei areas (Italy), Azores Islands and areas hit by offshore activity (Portugal), Alicante-Murcia area (Spain) and South Iceland including Reykjavik surrounding urban area (Iceland).
A unique probabilistic procedure has been used for seismic hazard evaluation processing both macroseismic fields and characteristics of fault sources. The direct application of probabilistic methodologies to observed and/or synthetic macroseismic fields allows us to carry out a more complete treatment of the uncertainties in the case of both point-wise and linear properties of a fault. An improvement of the urban scale vulnerability information on building and network systems (typologies, schools, strategic buildings, lifelines, and so on) has been introduced to use the new concept of global Disruption Index, with the objective to provide a systematic way to measure the earthquake impact in urbanized areas considered as a complex network. These measures have been then used to identify which nodes are likely to introduce major disruption in the whole urban system, and also which one of them suggests greater risk reduction if intervention takes place.
Besides the disaster prevention strategies based on the level of risk, another effective component of disaster-risk reduction is given by long-term activities using educational information systems. To reduce the absence of risk perception in the community some actions have been performed, such as the development of educational materials and the design of a mobile earthquake interactive experience with interactive panels for children and adults, and a central platform for the simulation of an earthquake
Collapse of superconductivity in cuprates via ultrafast quenching of phase coherence
The possibility of driving phase transitions in low-density condensates
through the loss of phase coherence alone has far-reaching implications for the
study of quantum phases of matter. This has inspired the development of tools
to control and explore the collective properties of condensate phases via phase
fluctuations. Electrically-gated oxide interfaces, ultracold Fermi atoms, and
cuprate superconductors, which are characterized by an intrinsically small
phase-stiffness, are paradigmatic examples where these tools are having a
dramatic impact. Here we use light pulses shorter than the internal
thermalization time to drive and probe the phase fragility of the
BiSrCaCuO cuprate superconductor, completely melting
the superconducting condensate without affecting the pairing strength. The
resulting ultrafast dynamics of phase fluctuations and charge excitations are
captured and disentangled by time-resolved photoemission spectroscopy. This
work demonstrates the dominant role of phase coherence in the
superconductor-to-normal state phase transition and offers a benchmark for
non-equilibrium spectroscopic investigations of the cuprate phase diagram.Comment: 24 pages, 9 figures, Main Text and Supplementary Informatio
An interactive travelling educational path on earthquakes and volcanoes
A mobile earthquake interactive path is an action of disaster-risk reduction given by long-term activities based
on an educational information system. The idea is to provide a realistic space and to design in it an interactive
path, aimed at both children and adults, explaining. issues related to seismic hazard especially in urban sectors
close to volcanic areas, such as Mt. Etna, Vesuvius and Campi Flegrei (Italy) and Azores Islands (Portugal). The
educational path would ideally include a wall with basic information on natural hazards related to seismic and
volcanic events, with hands on and interactive exhibits, a special "edutainment" corner focused on children, and
a central platform for people who will experience the simulation of an earthquake, while being instructed on how
to respond to the event. This educational information system represents a way of putting the results of the project
UPStrat-MAFA (Urban disaster Prevention Strategies using MAcroseismic Fields and FAult Sources ) to the
service of the entire community in order to strengthen people's awareness and preparedness related to seismic
and volcanic hazards. The fundamental aspect of the risk level for people living near a volcano is also included
in the educational experience
Quantitative seismic risk evaluation and mapping: cases of schools and residential facilities in Lisbon and Algarve
This contribution deals with activities within the framework of an EC-project, entitled "UPStrat-MAFA (Urban
prevention strategies using macroseismic and fault sources)", emphasising the inventory, vulnerability and
seismic risk of buildings. The cases considered deal with elementary and non-elementary public schools as well
as the residential building stock in Lisbon and Algarve in mainland Portugal. A new concept of global disruption
measures is introduced and discussed, with the objective of providing a systematic way to quantify earthquake
impact in urban areas. This approach provides civil protection, the authorities and local decision makers with a
new tool judged to be valuable in prioritizing mitigation measures and responses.Co-financed by the EU - Civil Protection Financial Instrument, in the framework the European project ”Urban disaster Prevention Strategies using MAcroseismic Fields and FAult Sources (Acronym: UPStrat-MAFA, Grant Agreement N. 23031/2011/613486/SUB/A5). http://ec.europa.eu/echo/funding/cp_projects2011_en.htmPublishedLisbon - Portugal4.1. Metodologie sismologiche per l'ingegneria sismicaope
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