Abstract Overhead electrical transmission line conductors are prone to aeolian vibrations, resulting from the alternate shedding of vortices in the wake of the cable. Aeolian vibrations are ...characterized by small-amplitude high-frequency flexural oscillations and, whenever not properly controlled, can induce wear damage and fatigue failures of the conductor. The standard technical approach to the assessment of aeolian vibrations and residual life of overhead conductors is based on the Energy Balance Method (EBM) and the Poffenberger-Swart formula for bending stresses. This approach relies on the main simplifying assumption of mono-modal oscillations. Typical aeolian vibration records, however, clearly show that several modes can be simultaneously excited due to wind variations in time and along the span. In this work a new approach is proposed for the prediction of aeolian vibrations of conductors within a probabilistic framework. The proposed approach allows to account both for non-linearities typical of internal damping of metallic cables and multi-modal contributions to aeolian vibrations in a straightforward and mechanically sound way. The proposed approach paves the way to a full probabilistic description of the Poffenberger-Swart bending stresses, making a further step towards a more refined methodology to define of the expected life of overhead conductors.
Summary
In Arabidopsis, lateral root (LR) development is mainly controlled by several known auxin‐regulated transcription factors (TFs). Here, we show that AtHB23 (a homeodomain‐leucine zipper I TF) ...participates in this intricate network. Our study of the expression pattern of AtHB23 revealed that it is transcriptionally activated in the early stages of secondary LR primordium (LRP). We found that AtHB23 directly limits the expression of LBD16, a key factor in LR initiation, and also directly induces the auxin transporter gene LAX3. We propose that this HD‐Zip I mediates the regulation of LAX3 by ARF7/19. Furthermore, AtHB23 plays distinct roles during the formation of secondary and tertiary roots, exhibiting differential expression patterns. ATHB23 is expressed throughout the tertiary root primordium, whereas it is restricted to early stages in secondary primordia, likely later repressing LBD16 in tertiary LR development and further inhibiting root emergence. Our results suggest that different genetic programs govern the formation of LRP from the main or secondary roots, thereby shaping the global dynamic architecture of the root system.
Significance Statement
The homeodomain‐leucine zipper transcription factor AtHB23 exhibits different expression patterns in primary and secondary roots. It directly represses LBD16, and induces LAX3 expression in primary and secondary roots, respectively, and it is directly regulated by ARF7/19 to become a molecular link between ARF7/19 and LAX3. The research results hint that different genetic programs govern the formation of lateral root primordia from the main or secondary roots.
The well-known Crab Nebula is at the center of the SN1054 supernova remnant. It consists of a rotationally powered pulsar interacting with a surrounding nebula through a relativistic particle wind. ...The emissions originating from the pulsar and nebula have been considered to be essentially stable. Here, we report the detection of strong gamma-ray (100 mega-electron volts to 10 giga-electron volts) flares observed by the AGILE satellite in September 2010 and October 2007. In both cases, the total gamma-ray flux increased by a factor of three compared with the non-flaring flux. The flare luminosity and short time scale favor an origin near the pulsar, and we discuss Chandra Observatory x-ray and Hubble Space Telescope optical follow-up observations of the nebula. Our observations challenge standard models of nebular emission and require power-law acceleration by shock-driven plasma wave turbulence within an approximately 1-day time scale.
•Effects of the spatial variability of earthquake input motion.•Single rigid foundation and multiple foundations.•Rocking effects in the isolation system of special structures.•Influence of the ...rotational components in structures having tall members.•Case studies: base isolated nuclear reactor building and cable-supported bridge structures.
This work deals with the evaluation of the effects of the spatial variability of earthquake input motion on the dynamic response of structures. The variability of the free-field motion both over the area of a single foundation as well as over the distance between independent foundations of large structures is considered.
Two significant applications of the proposed numerical procedure are presented. In the first one a base isolated nuclear reactor building is considered where the issue of the rocking excitation on the peak value of axial forces in the isolation devices and acceleration in the building structure is investigated. Extended structures having tall members are considered as second application. A cable-supported bridge model, formerly studied within a simpler representation of the seismic ground motion, serves as case study in which spatial variability acts at different scales.
We report the detection by the Astrorivelatore Gamma a Immagini Leggero (AGILE) satellite of terrestrial gamma ray flashes (TGFs) obtained with the minicalorimeter (MCAL) detector operating in the ...energy range 0.3–100 MeV. We select events typically lasting a few milliseconds with spectral and directional selections consistent with the TGF characteristics previously reported by other space missions. During the period 1 June 2008 to 31 March 2009 we detect 34 high‐confidence events showing millisecond durations and a geographical distribution peaked over continental Africa and Southeast Asia. For the first time, AGILE‐MCAL detects photons associated with TGF events up to 40 MeV. We determine the cumulative spectral properties of the spectrum in the range 0.5–40 MeV, which can be effectively described by a Bremsstrahlung spectrum. We find that both the TGF cumulative spectral properties and their geographical distribution are in good agreement with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) results.
In the paper a numerical procedure is described for the dynamic analysis of seabed anchored floating structures, with particular reference to the so-called Archimedes bridge solution for deep water ...crossings; attention is devoted to the design solution encompassing slender bars as anchor elements. A geometrically nonlinear finite element, developed in previous work, is here refined extending its capabilities to full 3-D analysis and to nonlinear modelling of hydrodynamic loads due to steady current and wind waves. The element is implemented in a numerical procedure for the dynamic time domain step-by-step analysis of nonlinear discretized systems; consistently, hydrodynamic and seismic loading are introduced by generating artificial time-histories of spatially variable seismic motion and wind waves.
An example of on application is shown regarding the behavior of the dynamic model of a submerged tunnel proposed for the Messina Strait crossing. The model is subjected to an extreme multiple-support seismic loading having a PGA equal to
0.64
g
and to an extreme wave loading with significant wave height of 16 m. The dynamic behaviour in the two loading situations is illustrated and compared, showing interesting facets, especially in terms of interaction between the tunnel and anchoring bars oscillations.
The supernova remnant (SNR) IC 443 is an intermediate-age remnant well known for its radio, optical, X-ray, and gamma-ray energy emissions. In this Letter, we study the gamma-ray emission above 100 ...MeV from IC 443 as obtained by the AGILE satellite. A distinct pattern of diffuse emission in the energy range 100 MeV-3 GeV is detected across the SNR with its prominent maximum (source "A") localized in the northeastern shell with a flux F = (47 +/- 10) x 10(-8) photons cm(-2) s(-1) above 100 MeV. This location is the site of the strongest shock interaction between the SNR blast wave and the dense circumstellar medium. Source "A" is not coincident with the TeV source located 0.4. away and associated with a dense molecular cloud complex in the SNR central region. From our observations, and from the lack of detectable diffuse TeV emission from its northeastern rim, we demonstrate that electrons cannot be the main emitters of gamma rays in the range 0.1-10 GeV at the site of the strongest SNR shock. The intensity, spectral characteristics, and location of the most prominent gamma-ray emission together with the absence of cospatial detectable TeV emission are consistent only with a hadronic model of cosmic-ray acceleration in the SNR. A high-density molecular cloud (cloud "E") provides a remarkable "target" for nucleonic interactions of accelerated hadrons; our results show enhanced gamma-ray production near the molecular cloud/shocked shell interaction site. IC 443 provides the first unambiguous evidence of cosmic-ray acceleration by SNRs.
Carboxymethylcellulose (CMC), a polymer derived from biomass, was intercalated into layered double hydroxides (LDH) composed by M2+/Al3+ (M2Al-CMC, M = Mg or Zn) and evaluated as precursors for the ...preparation of biocarbon-based nanocomposites by pyrolysis. M2Al-CMC hybrids were obtained by coprecipitation and characterized by X ray diffraction (XRD), vibrational spectroscopies, chemical analysis, and thermal analysis coupled to mass spectrometry. Following, pyrolyzed materials obtained between 500–1000 °C were characterized by XRD, Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Above 600 °C, Raman spectra of all samples showed the presence of graphitic carbon, which plays a role in the degree of crystallinity of produced inorganic phases (for comparison purposes, M2Al-CO3 materials were investigated after calcination in the same experimental conditions). XRD patterns of Mg2Al-CMC pyrolyzed between 600–1000 °C showed poorly crystallized MgO and absence of spinel reflections, whereas for Zn2Al-CMC, it was observed well crystallized nanometric ZnO at 800 °C, and ZnAl2O4 and γ-Al2O3 phases at 1000 °C. Above 800 °C, the carbothermic reaction was noticed, transforming ZnO to zinc vapour. This study opens perspectives for nanocomposites preparation based on carbon and inorganic (mixed) oxides through precursors having organic-inorganic interactions at the nanoscale domain.
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