ParaHox gene expression in larval and postlarval development of the polychaete Nereis virens (Annelida, Lophotrochozoa).

RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.BACKGROUND: Transcription factors that encode ANTP-class homeobox genes play crucial roles in determining the body plan organization and specification of different organs and tissues in bilaterian animals. The three-gene ParaHox family descends from an ancestral gene cluster that existed before the evolution of the Bilateria. All three ParaHox genes are reported from deuterostomes and lophotrochozoans, but not to date from any ecdysozoan taxa, and there is evidence that the ParaHox genes, like the related Hox genes, were ancestrally a single chromosomal cluster. However, unlike the Hox genes, there is as yet no strong evidence that the ParaHox genes are expressed in spatial and temporal order during embryogenesis. RESULTS: We isolated fragments of the three Nereis virens ParaHox genes, then used these as probes for whole-mount in situ hybridization in larval and postlarval worms. In Nereis virens the ParaHox genes participate in antero-posterior patterning of ectodermal and endodermal regions of the digestive tract and are expressed in some cells in the segment ganglia. The expression of these genes occurs in larval development in accordance with the position of these cells along the main body axis and in postlarval development in accordance with the position of cells in ganglia along the antero-posterior axis of each segment. In none of these tissues does expression of the three ParaHox genes follow the rule of temporal collinearity. CONCLUSION: In Nereis virens the ParaHox genes are expressed during antero-posterior patterning of the digestive system (ectodermal foregut and hindgut, and endodermal midgut) of Nereis virens. These genes are also expressed during axial specification of ventral neuroectodermal cell domains, where the expression domains of each gene are re-iterated in each neuromere except for the first parapodial segment. These expression domains are probably predetermined and may be directed on the antero-posterior axis by the Hox genes, whose expression starts much earlier during embryogenesis. Our results support the hypothesis that the ParaHox genes are involved in antero-posterior patterning of the developing embryo, but they do not support the notion that these genes function only in the patterning of endodermal tissues

THE DEEP STRUCTURE OF THE L'AQUILA BASIN INVESTIGATED USING ARRAY MEASUREMENTS

We present velocity profiles obtained through surface-wave methods in the historical city of L’Aquila (Italy). The city suffered severe damage (VIII-IX EMS intensity) during the April 6th 2009 Mw 6.3 earthquake. The area is characterized by the deep (up to 300-400 meters) basin of the Aterno river valley filled by lacustrine sediments over limestone bedrock. In downtown L'Aquila an outcropping unit basically composed of stiff conglomerates (Breccia) is over-imposed to ancient lacustrine sediments with a possible velocity inversion at a depth ranging from few tens up to one hundred meters. We deployed five 2-D arrays of seismic stations and 1-D array of vertical geophones in the city center. The 2-D arrays recorded ambient noise, whereas the 1-D array recorded signals produced by active sources. Surface-wave dispersion and spatial autocorrelation curves, calculated using array methods, were inverted through a neighborhood algorithm jointly with the microtremor HVNSR ellipticity. We obtain shear-wave velocity profiles (Vs) representative of the southern and northern sector of downtown L'Aquila. The resulting Vs profiles are used to compare the 1-D transfer functions to aftershock data results. We apply a convolution approach evaluating synthetic time-histories in sites where surface stratigraphy is known and comparing them to recorded strong-motion data

Characterization of the breccia deposits in downtown L’Aquila (Central Italy) through multichannel analysis of surface waves

On April 6th 2009 an Mw 6.3 earthquake hit the historical city of L’Aquila (Central Italy) causing about 300 causalities, more than 39000 homeless and strong damage in the city and in the surrounding villages. L’Aquila downtown suffered Mercalli-Cancani-Sieberg (MCS; Sieberg 1930) intensity > VIII. Heavy damage and collapses were concentrated in the unreinforced masonry buildings including historical churches. Starting from June 2009, the Italian Civil Defense Department promoted a microzoning study of the epicentral area, aimed at identifying, at a detailed scale, areas were local seismic amplification could occur due to the characteristics of surface geology. L’Aquila is founded on a terrace that slopes down moving in the southwest direction, and raises about 50 meters above the Aterno river bed. The terrace is formed by alluvial Quaternary breccias consisting of limestone clasts in a marly matrix. In the northern part of the city the terrace is in contact with outcropping limestone, while moving toward south, breccias are over imposed to lacustrine sediments formed mainly of silty and sandy layers and minor gravel beds. As found by boreholes, the thickness of the breccias formation ranges from tenths of meters at north to just few meters at south. The uppermost weathered part of breccias outcrops at south and is indicated as “limi rossi”. The presence of breccias and “limi rossi” in the northern and southern part of the city respectively, is well identified by collected geotechnical data. Shear wave velocity (Vs) are quite high in the northern sector and can reach values of about 1000 m/s, whereas in the southernmost part the Vs of “limi rossi” drops down to 300-400 m/s. The microzoning studies at L’Aquila evidenced the presence of low-frequency (about 0.6 Hz) amplification diffused in the historical center with high amplification factors in the southern area of the city were “limi rossi” outcrops. We here present the results of multichannel surface waves analysis (MASW) based on active and passive sources. Active methods consist of 1D linear arrays of 4.5 Hz-vertical geophones using a minigun as source. Passive methods consist of 2D arrays of seismic three-component sensors. In order to investigate the low-frequency amplification, the geometry of 2D arrays was accordingly designed, using 16 seismic stations with maximum aperture of 1 km that recorded many hours of ambient seismic noise. We deployed three 2D arrays, one in the northern part and two in the southern part of the city. The 1D linear array was dedicated to characterize the shallower part of “limi rossi”. With the aim to derive the shear wave velocity profiles, the apparent phase velocity estimated through arrays technique has been inverted through a neighborhood algorithm

Assessment of ground-motion amplification in the Fucino Basin (Central Italy) through seismic data

The Fucino basin (Central Italy) is one of the largest intermountain alluvial plain in the Appennines range. It has a tectonic origin related to the presence of important systems of faults located in its northern and eastern edges. Some of these faults are still active and capable of generating strong seismic events as the January 13th 1915 Ms 7.0 Avezzano earthquake (about 30000 casualties). Site effects related to the soft soils filling the basin can be very important also taking into account the presence of historical villages located at the edges of the basin and new settlements developed in the area. In this paper we show the preliminary results of a seismic network installed in the Fucino area in order to collect information about site amplification effects and geometry of the basin. A lake occupied the Fucino basin for many thousands of years and it was completely drained at the end of the 19th century. We analyze ambient seismic vibrations and recordings of about 150 local earthquakes mainly related to the seismic sequence of the April 6th 2009 Mw 6.3 L’Aquila event. Moreover the strongest events of L’Aquila sequence were analyzed at the three strong-motion permanent stations operating in the area. Using standard spectral techniques we investigate the variation of resonance frequencies within the basin. The ground motion recorded in the Fucino plain is mainly characterized by strong energy at low-frequencies (f < 1 Hz) affecting both horizontal and vertical components. This is particularly evident for stations deployed in correspondence of very thick deposits of sedimentary filling, where a significant increase of ground-motion amplitude and duration is caused by locally generated surface waves. The amplification at low-frequencies (< 1 Hz) on the horizontal components can reach up a factor of 10 in comparison to nearby stiff sites. However, we found evidences of seismic amplification phenomena also for stiff sites surrounding the basin, including stations of the Italian strong motion network. The independent geological information, the shallow shear-velocity profiles available for the basin can be combined with resonance frequencies of the sites for deriving representative geological sections to be used as base for future numerical 2D-3D modeling of the seismic wave propagation in the basin. Seismic modeling can be important to reduce the seismic hazard in the area

Characterization of the breccia deposits in downtown L’Aquila (Central Italy) through multichannel analysis of surface waves

On April 6th 2009 an Mw 6.3 earthquake hit the historical city of L’Aquila (Central Italy) causing about 300 causalities, more than 39000 homeless and strong damage in the city and in the surrounding villages. L’Aquila downtown suffered Mercalli-Cancani-Sieberg (MCS; Sieberg 1930) intensity > VIII. Heavy damage and collapses were concentrated in the unreinforced masonry buildings including historical churches. Starting from June 2009, the Italian Civil Defense Department promoted a microzoning study of the epicentral area, aimed at identifying, at a detailed scale, areas were local seismic amplification could occur due to the characteristics of surface geology. L’Aquila is founded on a terrace that slopes down moving in the southwest direction, and raises about 50 meters above the Aterno river bed. The terrace is formed by alluvial Quaternary breccias consisting of limestone clasts in a marly matrix. In the northern part of the city the terrace is in contact with outcropping limestone, while moving toward south, breccias are over imposed to lacustrine sediments formed mainly of silty and sandy layers and minor gravel beds. As found by boreholes, the thickness of the breccias formation ranges from tenths of meters at north to just few meters at south. The uppermost weathered part of breccias outcrops at south and is indicated as “limi rossi”. The presence of breccias and “limi rossi” in the northern and southern part of the city respectively, is well identified by collected geotechnical data. Shear wave velocity (Vs) are quite high in the northern sector and can reach values of about 1000 m/s, whereas in the southernmost part the Vs of “limi rossi” drops down to 300-400 m/s. The microzoning studies at L’Aquila evidenced the presence of low-frequency (about 0.6 Hz) amplification diffused in the historical center with high amplification factors in the southern area of the city were “limi rossi” outcrops. We here present the results of multichannel surface waves analysis (MASW) based on active and passive sources. Active methods consist of 1D linear arrays of 4.5 Hz-vertical geophones using a minigun as source. Passive methods consist of 2D arrays of seismic three-component sensors. In order to investigate the low-frequency amplification, the geometry of 2D arrays was accordingly designed, using 16 seismic stations with maximum aperture of 1 km that recorded many hours of ambient seismic noise. We deployed three 2D arrays, one in the northern part and two in the southern part of the city. The 1D linear array was dedicated to characterize the shallower part of “limi rossi”. With the aim to derive the shear wave velocity profiles, the apparent phase velocity estimated through arrays technique has been inverted through a neighborhood algorithm

Seismic noise in a geologically complex site (L’Aquila, central Italy) to fine-tune the subsoil model for seismic microzonation mapping

We present the fine scale investigations of seismic noise carried out in a geologically complex site in the Aterno R. Valley (L’Aquila, central Italy). The goals of the study are to point out the efficiency of seismic noise technique in geologically complex site by comparing those data with other geophysical investigations (active seismic techniques, gravimetric survey) and geological data (more than 60 well logs and a detailed fine scale geological mapping), to fine-tune the subsoil model and to locate the geometry of seismic and geological bedrock. The study area is located in the western part of L’Aquila intramontane plain which was struck by the recent April 6 earthquake (Mw: 6.3). L’Aquila intramontane plain is a typical Quaternary basin of central Apennines and it is a halfgraben extending in a WNW-ESE direction, along the Aterno River Valley. The carbonate bedrock is variably displaced by normal faults, with both Apennine (NW-SE) and anti-Apennine (NE-SW) directions, and by a N-dipping back-thrust. The alluvial deposits consist of more or less coarse gravels, sands and silty clays of fluvial and alluvial-fan environments organised in lenticular bodies. The model of subsoil was reconstructed by correlating borehole stratigraphies with data from geophysical tests (down-hole, cross-hole and microtremor measurements). In the study area the presence of a double amplification peak is the main characteristics of HVNSR data. This feature can be related to the presence of two strong impedance contrasts in the deposits filling the Aterno R. Valley. A first shallow contrast, due to the presence of the gravel layer found in the cross hole data, is responsible for the high frequency ( > 10Hz) HVNSR peak, while the deeper contrast between recent sedimentary layers and the limestone, acting as seismic bedrock,k at depth of few tents of meters produces the second peak centered at 3Hz. The inversion of microtremor data, constrained by stratigraphic logs and seismic in-hole tests (down-hole, cross-hole), made it possible to demarcate zones with constant Vs and to reconstruct the depth of the carbonate (or seismic) bedrock; this depth ranged from 0 to 52 m from ground level. The Vs velocities of the alluvial and slope covers range from 300 m/s to 600 m/s. The Vs velocities in the central sector of the valley exceed 400 m/s; this is due to the occurrence of gravely lenses, which reach their maximum thickness in this sector. This study is a good example of how the seismic noise could furnish a useful contribution to fine-tune the subsoil model also in geologically complex sites

OPTYRE—Real time estimation of rolling resistance for intelligent tyres

The study of the rolling tyre is a problem framed in the general context of nonlinear elasticity. The dynamics of the related phenomena is still an open topic, even though few examples and models of tyres can be found in the technical literature. The interest in the dissipation effects associated with the rolling motion is justified by their importance in fuel-saving and in the context of an eco-friendly design. However, a general lack of knowledge characterizes the phenomenon, since not even direct experience on the rolling tyre can reveal the insights of the correlated different dissipation effects, as the friction between the rubber and the road, the contact kinematics and dynamics, the tyre hysteretic behaviour and the grip. A new technology, based on fibre Bragg grating strain sensors and conceived within the OPTYRE project, is illustrated for the specific investigation of the tyre dissipation related phenomena. The remarkable power of this wireless optical system stands in the chance of directly accessing the behaviour of the inner tyre in terms of stresses when a real-condition-rolling is experimentally observed. The ad hoc developed tyre model has allowed the identification of the instant grip conditions, of the area of the contact patch and allows the estimation of the instant dissipated power, which is the focus of this paper

Evanescent-wave coupled right angled buried waveguide: Applications in carbon nanotube mode-locking

In this paper we present a simple but powerful subgraph sampling primitive that is applicable in a variety of computational models including dynamic graph streams (where the input graph is defined by a sequence of edge/hyperedge insertions and deletions) and distributed systems such as MapReduce. In the case of dynamic graph streams, we use this primitive to prove the following results: -- Matching: First, there exists an $\tilde{O}(k^2)$ space algorithm that returns an exact maximum matching on the assumption the cardinality is at most $k$. The best previous algorithm used $\tilde{O}(kn)$ space where $n$ is the number of vertices in the graph and we prove our result is optimal up to logarithmic factors. Our algorithm has $\tilde{O}(1)$ update time. Second, there exists an $\tilde{O}(n^2/\alpha^3)$ space algorithm that returns an $\alpha$-approximation for matchings of arbitrary size. (Assadi et al. (2015) showed that this was optimal and independently and concurrently established the same upper bound.) We generalize both results for weighted matching. Third, there exists an $\tilde{O}(n^{4/5})$ space algorithm that returns a constant approximation in graphs with bounded arboricity. -- Vertex Cover and Hitting Set: There exists an $\tilde{O}(k^d)$ space algorithm that solves the minimum hitting set problem where $d$ is the cardinality of the input sets and $k$ is an upper bound on the size of the minimum hitting set. We prove this is optimal up to logarithmic factors. Our algorithm has $\tilde{O}(1)$ update time. The case $d=2$ corresponds to minimum vertex cover. Finally, we consider a larger family of parameterized problems (including $b$-matching, disjoint paths, vertex coloring among others) for which our subgraph sampling primitive yields fast, small-space dynamic graph stream algorithms. We then show lower bounds for natural problems outside this family

Assessment of ground-motion amplification in the Fucino Basin (Central Italy) through seismic data

The Fucino basin (Central Italy) is one of the largest intermountain alluvial plain in the Appennines range. It has a tectonic origin related to the presence of important systems of faults located in its northern and eastern edges. Some of these faults are still active and capable of generating strong seismic events as the January 13th 1915 Ms 7.0 Avezzano earthquake (about 30000 casualties). Site effects related to the soft soils filling the basin can be very important also taking into account the presence of historical villages located at the edges of the basin and new settlements developed in the area. In this paper we show the preliminary results of a seismic network installed in the Fucino area in order to collect information about site amplification effects and geometry of the basin. A lake occupied the Fucino basin for many thousands of years and it was completely drained at the end of the 19th century. We analyze ambient seismic vibrations and recordings of about 150 local earthquakes mainly related to the seismic sequence of the April 6th 2009 Mw 6.3 L’Aquila event. Moreover the strongest events of L’Aquila sequence were analyzed at the three strong-motion permanent stations operating in the area. Using standard spectral techniques we investigate the variation of resonance frequencies within the basin. The ground motion recorded in the Fucino plain is mainly characterized by strong energy at low-frequencies (f < 1 Hz) affecting both horizontal and vertical components. This is particularly evident for stations deployed in correspondence of very thick deposits of sedimentary filling, where a significant increase of ground-motion amplitude and duration is caused by locally generated surface waves. The amplification at low-frequencies (< 1 Hz) on the horizontal components can reach up a factor of 10 in comparison to nearby stiff sites. However, we found evidences of seismic amplification phenomena also for stiff sites surrounding the basin, including stations of the Italian strong motion network. The independent geological information, the shallow shear-velocity profiles available for the basin can be combined with resonance frequencies of the sites for deriving representative geological sections to be used as base for future numerical 2D-3D modeling of the seismic wave propagation in the basin. Seismic modeling can be important to reduce the seismic hazard in the area