Seismic source identification of the 9 November 2022 Mw 5.5 offshore Adriatic sea (Italy) earthquake from GNSS data and aftershock relocation.

The fast individuation and modeling of faults responsible for large earthquakes are fundamental for understanding the evolution of potentially destructive seismic sequences. This is even more challenging in case of buried thrusts located in offshore areas, like those hosting the 9 November 2022 Ml 5.7 (Mw 5.5) and ML 5.2 earthquakes that nucleated along the Apennines compressional front, offshore the northern Adriatic Sea. Available on- and offshore (from hydrocarbon platforms) geodetic observations and seismological data provide robust constraints on the rupture of a 15 km long, ca. 24° SSW-dipping fault patch, consistent with seismic reflection data. Stress increase along unruptured portion of the activated thrust front suggests the potential activation of longer portions of the thrust with higher magnitude earthquake and larger surface faulting. This unpleasant scenario needs to be further investigated, also considering their tsunamigenic potential and possible impact on onshore and offshore human communities and infrastructures.

How mantle heterogeneities drive continental subduction and magmatism in the Apennines.

Petrologic and geophysical observations floored the paradigm shift on the subduction of the continental lithosphere. In long-lived collisional boundaries like the Alpine Himalaya belt, portions of continental lithosphere are pushed down to great depths and then exhumed, as testified by outcrops of UHP materials. The Mediterranean region is a clear expression of this enigmatic process. On a short space and time scale, the Apennines exhibits a complex pattern of across-belt extension, associated with under-thrusting of continental lithosphere and a variegated suite of magmatic products. Here we show that the delamination of the crust is essential to favor the subduction of the continental lithosphere, a process that is controlled by pre-existing heterogeneity of the uppermost mantle. Teleseismic tomography revealed significant compositional anomalies in the uppermost mantle that controlled the way in which the lithosphere is delaminated. The continental subduction is associated with magmatism, where the variety of products reflects differences in mantle metasomatism that are only in part related to the subduction process.

QFib: Fast and Efficient Brain Tractogram Compression.

Diffusion MRI fiber tracking datasets can contain millions of 3D streamlines, and their representation can weight tens of gigabytes of memory. These sets of streamlines are called tractograms and are often used for clinical operations or research. Their size makes them difficult to store, visualize, process or exchange over the network. We propose a new compression algorithm well-suited for tractograms, by taking advantage of the way streamlines are obtained with usual tracking algorithms. Our approach is based on unit vector quantization methods combined with a spatial transformation which results in low compression and decompression times, as well as a high compression ratio. For instance, a 11.5GB tractogram can be compressed to a 1.02GB file and decompressed in 11.3 seconds. Moreover, our method allows for the compression and decompression of individual streamlines, reducing the need for a costly out-of-core algorithm with heavy datasets. Last, we open a way toward on-the-fly compression and decompression for handling larger datasets without needing a load of RAM (i.e. in-core handling), faster network exchanges and faster loading times for visualization or processing.

Dyke intrusion and stress-induced collapse of volcano flanks: The example of the 2018 event at Mt. Etna (Sicily, Italy).

Magmatic intrusions, eruptions and flank collapses are frequent processes of volcano dynamics, inter-connected at different space and time scales. The December 2018 recrudescent episode at Mt. Etna is an exemplary case where a sudden intrusive event culminated with a short eruption, intense seismicity and a shallow large strike-slip earthquake at the edge of the eastern sliding flank. Here, we show that high resolution velocity models and transient changes of VP and VP/VS resolve the magma intrusion through a dyke and local stress increase at the base of the unstable flank, inducing the collapse. Episodic brittle faulting occurs at the edge of the sliding sector, locally contributed by high fluid pressure. The feedback between magma ascent, stress changes and flank collapse is driving the volcano dynamics, with processes ranging from long term to transient episodes.

Systematic STM and LEED investigation of the Si/Ag(110) surface.

Interest in the Si/Ag(110) system, which forms highly ordered linear nanostructures coined 'silicon nanoribbons', was recently boosted by the claim that such nanoribbons may be formed by silicon atoms arranged in a 2D honeycomb structure as in graphene, i.e. silicene. Despite such a revived interest, many discrepancies still exist in the recently reported results. This paper reports on a systematic investigation by scanning tunneling microscopy and low-energy electron diffraction of the Si/Ag(110) system as a function of the amount of deposited silicon and the deposition temperature. This reveals a complex interplay between these two factors, resulting in a rich array of possible self-assembled nanostructures and surface reconstructions. Several novel findings and clarification of the contradictory results reported in the literature are discussed in this work. In particular, the deposition temperature is demonstrated to be a key parameter to control the width of the Si nanoribbons produced. Recently, massive linear nanostructures were reported to be 'multilayer silicene', forming once the deposited silicon amount exceeds full coverage. However, we show that such nanostructures are also observed at low silicon coverage, demonstrating that their formation is exclusively determined by a deposition temperature higher than 460 K. On the other hand, for Si amounts higher than one monolayer the surface presents a novel c(8 × 4) reconstruction, which is responsible for the ×4 periodicity detected by LEED measurements, previously attributed to the 1.6 nm-wide nanoribbons overlayer or to 'multilayer silicene'. Finally, the large collection of acquired data also allowed us to single out image artifacts that may explain the contradictory results appearing in previous papers.

Chirality transfer from a single chiral molecule to 2D superstructures in alaninol on the Cu(100) surface.

The formation of 2D chiral monolayers obtained by self-assembly of chiral molecules on surfaces has been widely reported in the literature. Control of chirality transfer from a single molecule to surface superstructures is a challenging and important aspect for tailoring the properties of 2D nanostructures. However, despite the wealth of investigations performed in recent years, how chiral transfer takes place on a large scale still remains an open question. In this paper we report a coupling of scanning tunneling microscopy and low energy electron diffraction measurements with an original theoretical approach, combining molecular dynamics and essential dynamics with density functional theory, to investigate self-assembled chiral structures formed when alaninol adsorbs on Cu(100). The peculiarity of this system is related to the formation of tetrameric molecular structures which constitute the building blocks of the self-assembled chiral monolayer. Such characteristics make alaninol/Cu(100) a good candidate to reveal chiral expression changes. We find that the deposition of alaninol enantiomers results in the formation of isolated tetramers that are aligned along the directions of the substrate at low coverage or when geometrical confinement prevents long-range order. Conversely, a rotation of 14° with respect to the Cu(100) unit vectors is observed when small clusters of tetramers are formed. An insight to the process leading to a 2D globally chiral surface has been obtained by monitoring molecular assemblies as they grow from the early stages of adsorption, suggesting that the distinctive orientation of the self-assembled monolayer originates from a balance of cooperating forces which start acting only when tetramers pack together to form small clusters.

Time-resolved seismic tomography detects magma intrusions at Mount Etna.

The continuous volcanic and seismic activity at Mount Etna makes this volcano an important laboratory for seismological and geophysical studies. We used repeated three-dimensional tomography to detect variations in elastic parameters during different volcanic cycles, before and during the October 2002-January 2003 flank eruption. Well-defined anomalous low P- to S-wave velocity ratio volumes were revealed. Absent during the pre-eruptive period, the anomalies trace the intrusion of volatile-rich (>/=4 weight percent) basaltic magma, most of which rose up only a few months before the onset of eruption. The observed time changes of velocity anomalies suggest that four-dimensional tomography provides a basis for more efficient volcano monitoring and short- and midterm eruption forecasting of explosive activity.

Ultrastructure of mature spermatozoids in the fern Asplenium onopteris L.

Asplenium onopteris L. spermatozoids are 8-8.5 microm long in the form of spirals with 4.5 turns. They have about 50 flagella. The nucleus occupies the last three posterior turns. Chromatin is partly honeycomb-shaped and partly highly condensed. An electron transparent space crossed by dense fibers delimits the condensed chromatin. Here, the nuclear membranes are closely apposed without any space between them and the plasmalemma often invaginates among elements of the microtubular ribbon, connecting with the outer nuclear membrane. An electron opaque body apparently links and anchors all anterior spermatozoid components. The cytoplasm contains plastids with starch grains, (lipid) bodies and different membrane systems, which are presumably plasmalemma derivatives involved in a process of cytoplasmic reduction.

Propagation-independent fields.

Nondiffracting beams are solutions of the wave equation which keep their shape during free propagation. Because of this property, they are widely studied, both as mechanical and electromagnetic waves. Another scheme, however, can be devised in order to find beams that, even if do not maintain their shape upon propagation, are independent on the propagation distance, apart from a phase factor. In this sense it can be said that these beams are also nondiffracting. In this work, the scheme leading to this different kind of nondiffracting fields, which we term propagation-independent beams, is presented. Closed-form expressions for a few of these fields, for 1-D sources, are found. A method, which in principle is able to produce beams of this type, is given. This also clarifies some of their properties. Finally, the item of finite realizations of these beams, which in principle require infinite-dimension sources, is analyzed through numerical simulations. It is also shown that the practical feasibility of these fields poses some limitations on the bandwidth they can present.

Optimization of wide-band linear arrays.

An optimization method is proposed for linear arrays to be used in ultrasound systems under wide-band operation. A fast algorithm, the threshold accepting, has been utilized to determine the element positions and weight coefficients of a linear array that generates a desired beam pattern. To reduce the computational burden in the optimization procedure, an efficient numerical routine for the beam pattern evaluation has been implemented. We address the optimization problem of both dense and sparse wide-band arrays. In the first case, the goal is to minimize the side-lobe energy by varying the element weights; we compare the optimized beam pattern with that obtained with classical shading functions, showing that better results can be achieved with a wide-band optimization. We also consider the optimization of the layout (positions and weights) of a sparse linear array to achieve a desired beam pattern with a fixed or minimum number of array elements. The comparison of the proposed method with a narrow-band optimization algorithm is presented, showing that better performances (about -7 dB further reduction of the side-lobe level) can be achieved with a wide-band sparse array optimization. Further numerical simulations are given, showing that the proposed method yields better results than wide-band sparse random arrays and periodic arrays with the same aperture width.

A novel approach to the aperture windowing in medical imaging.

A new technique is proposed to improve the lateral resolution in the conventional B-mode imaging systems, which enables a simple array aperture windowing in the transmitting mode. Amplitude shaping is performed without modifying the transmitting voltage of the array elements, but only varying the excitation pulse length from one element to another. This method presents some attractive practical advantages, and the reduction of the sidelobe energy is comparable to that attainable with a conventional aperture windowing. Parametric plots are given, which transform an amplitude apodization into a 'time apodization' for any type of transducer array.

A new beamforming technique for ultrasonic imaging systems

We propose a simple, versatile and inexpensive beamforming method that performs the aperture windowing of an ultrasonic transducer array in the transmit mode, without modifying the driver voltage, but simply controlling the length of the electric pulse driving the array elements. A conversion formula has been determined that permits us to compute, for a desired emitted pulse amplitude, the corresponding driving pulse length to be applied. Any shading function can be implemented over any type of transducer array, using very low-cost hardware. Computer simulations and experimental measurements, with a 3.8 MHz convex array, confirm the effectiveness of this approach in enhancing the contrast resolution, since the off-axis intensity in the radiated beam pattern is largely reduced.

Dense and sparse 2-D array radiation patterns in lossy media.

Two-dimensional (2-D) transducer arrays are potentially able to generate real-time volumetric images of internal organs of the human body, and much work has been done on the subject in recent years. A 2-D array with high resolution and low grating lobe level requires a prohibitively large number of elements for existing technology. A successful solution to reduce the number of elements, without sacrificing the above mentioned characteristics, is to select a limited number of elements in a random way or combining transmitting and receiving apertures with element spacing greater than one-half of a wavelength. In this work, the effect of the human body attenuation on the performances of these so-called sparse arrays is investigated. We analytically demonstrate that, for continuous wave excitation and under paraxial approximation, the medium losses can be modeled as a Gaussian weighting function, acting off-axis in the observation plane. The variance of this weighting function decreases with the covered distance. Radiation patterns computed with both this simple model and with a more exact expression, are presented for sparse and dense 2-D arrays under continuous and pulsed wave operation. Comparisons between the results obtained with and without attenuation also are shown.

Efficient transmit beamforming in pulse-echo ultrasonic imaging.

A high performance ultrasound imaging system requires accurate control of the amplitude of the array elements, as well as of the time delays between them, both in the transmit and receive modes. In transmission, conventional array aperture windowing implies a different driving voltage for each element of the array, an expensive solution for systems with a large number of channels. In this paper, we present a simple, versatile, and inexpensive beamforming method that operates the aperture windowing in the transmit mode, simply controlling the lengths of the electric pulses driving the array elements. Computer simulations and experimental measurements are presented for different types of arrays. They confirm that the proposed beamforming technique improves the contrast resolution of the imaging system, reducing the off-axis intensity of the radiated field pattern. Moreover, the axial resolution is slightly enhanced, because the overall length of the transmitted ultrasonic pulse is reduced.

Effects of simulated acid rain on pollen physiology and ultrastructure in the apple.

Viability, germination and tube length were investigated in pollen grains of field-grown 'Summerred' apple trees (Malus domestica Borkh) exposed to deionized water, rainfall or simulated acid rain at pH 5.6, 4.0 and 3.0. Pollen viability and germination significantly decreased with lower values of pH and with increasing number of treatments. The effects of pH 5.6 and natural rainfall were not significant. Electron microscope investigation of vegetative pollen cells of plants exposed to acid rain at pH 4.0 and 3.0 showed modified features in mitochondria, plastids and endoplasmic reticulum.

Cell reabsorption in the Euphorbia dulcis endosperm.

Euphorbia dulcis endosperm is the site of controlled long lasting endocellular lysis involving segregation and autophagy of portions of the cytoplasm within the endoplasmic reticulum membrane. The lysis products may constitute a food source for the benefit of the early developing embryo.

The public sector response to the 1990 Iben Browning earthquake prediction

During 1990 citizens, goverments , and private industry in the Central Unites States were concerned about the effects of an unofficial earthquakes prediction made by Ibem Browning. The lack of a timely and public rebuttal of the earthquake prediction by the scientific community led to unnecessary efforts by local, state, and federal governments to respond to the public's demand for information on the validity on the prediction and howto prepared for the predicted earthquake. The prediction increased the level of earthquake awareness and short - term preparedness in the central U.S.; however, these advances may have been made at the expense of scientific credibility and geverment efficacy (AU)

[Magnesium and potassium aspartate during the third pregnancy trimester]. / Utilizzazione dell'aspartato di magnesio e di potassio durante il terzo trimestre di gravidanza.

Following a critical review of published reports on the use of magnesium during the third quarter of pregnancy, the paper examines the value of blood magnesium tests during pregnancy as well as the validity of administrating kalium aspartate and magnesium aspartate to treat the risk of premature birth.