An improvement to the volcano-scan algorithm for atmospheric correction of CRISM and OMEGA spectral data

The observations of Mars by the CRISM and OMEGA hyperspectral imaging spectrometers require correction for photometric, atmospheric and thermal effects prior to the interpretation of possible mineralogical features in the spectra. Here, we report on a simple, yet non-trivial, adaptation to the commonly-used volcano-scan correction technique for atmospheric CO₂, which allows for the improved detection of minerals with intrinsic absorption bands at wavelengths between 1.9 and 2.1 μm. This volcano-scan technique removes the absorption bands of CO₂ by ensuring that the Lambert albedo is the same at two wavelengths: 1.890 and 2.011 μm, with the first wavelength outside the CO₂ gas bands and the second wavelength deep inside the CO₂ gas bands. Our adaptation to the volcano-scan technique moves the first wavelength from 1.890 μm to be instead within the gas bands at 1.980 μm, and for CRISM data, our adaptation shifts the second wavelength slightly, to 2.007 μm. We also report on our efforts to account for a slight ∼0.001 μm shift in wavelengths due to thermal effects in the CRISM instrument.     

Synthesis,TEM characterization and thermal behaviour of LiNiSi<Subscript>2</Subscript>O<Subscript>6</Subscript> pyroxene

A pyroxene with composition LiNiSi₂O₆ was synthesized at T = 1,473 K and P = 2.0 GPa; the cell parameters at T = 298 K are a = 9.4169(6) Å, b = 8.4465(7) Å, c = 5.2464(3) Å, β = 110.534(6)°, V = 390.78(3) Å³. TEM examination of the LiNiSi₂O₆ pyroxene showed the presence of h + k odd reflections indicative of a primitive lattice, and of antiphase domains obtained by dark field imaging of the h + k odd reflections. A HT in situ investigation was performed by examining TEM selected area diffraction patterns collected at high temperature and synchrotron radiation powder diffraction. In HTTEM the LiNiSi₂O₆ was examined together with LiCrSi₂O₆ pyroxene. In LiCrSi₂O₆ the h + k odd critical reflections disappear at about 340 K; they are sharp up to the transition temperature and do not change their shape until they disappear. In LiNiSi₂O₆ the h + k odd reflections are present up to sample deterioration at 650 K. A high temperature synchrotron radiation powder diffraction investigation was performed on LiNiSi₂O₆ between 298 and 773 K. The analysis of critical reflections and of changes in cell parameters shows that the space group is P-centred up to the highest temperature. The comparative analysis of the thermal and spontaneous strain contributions in P2₁/c and C2/c pyroxenes indicates that the high temperature strain in P-LiNiSi₂O₆ is very similar to that due to thermal strain only in C2/c spodumene and that a spontaneous strain contribution related to pre-transition features is not apparent in LiNiSi₂O₆. A different high-temperature behaviour in LiNiSi₂O₆ with respect to other pyroxenes is suggested, possibly in relation with the presence of Jahn–Teller distortion of the M1 polyhedron centred by low-spin Ni³⁺.     

Sediment chemical contamination of a shallow water area close to the industrial zone of Porto Marghera (Venice Lagoon, Italy)

The industrial zone of Porto Marghera is one the most important "contaminated sites of national interest" (SIN) in Italy, being identified as an area of high environmental risk. The site includes a wide shallow water area of the Venice Lagoon extending toward the city of Venice, which was investigated in order to acquire information on the pollutant level and distribution. Grain-size, heavy metal, nutrient, and organic micropollutant concentrations were determined in the surface sediment layers (0-5 and 5-10 cm depths) of 51 sites. A generally low contamination was found, except for Hg concentration, which increases the toxicological risk in most of the sites of the area, according to the results of a comparison with Sediment Quality Guidelines. A heavy pollution fingerprint (Cd, Cu, Hg, Pb, and Zn up to 15.2, 257, 11.9, 248, and 3010 mg/kg d.w., respectively) was instead found near the Tresse Island, which is ascribed to the spill of pollutants from the contaminated sediment disposed therein. Grain-size and heavy metal profiles down to a depth of 40 cm in eight selected sites, finally show a probable decrease of the pollution affecting the area in recent years.     

Atmospheric Aerosol Characterization Over Naples During 2000–2003 EARLINET Project: Planetary Boundary-Layer Evolution and Layering

The evolution of the planetary boundary layer and the influence of local circulation phenomena over Naples (southern Italy, 40.838° N, 14.183° E, 118 m above sea level) have been studied by systematic lidar measurements of aerosol optical properties and vertical distributions carried out from May 2000 to August 2003, in the course of the EARLINET project. In particular, our data show the development of aerosol layers typically located in the range between 1,000 and 2,300 m, with variable thickness. The optical properties of the observed layers have been determined. In order to analyse the evolution of the planetary boundary layer, detailed observations of complete diurnal cycles have also been performed. The analysis of lidar measurements of vertical profiles of wind speed and wind direction and air mass back-trajectories allowed us to characterize the sea-breeze circulation influence on both the planetary boundary-layer evolution and the observed aerosol vertical distribution.     

Extension of plasticity theory to debonding,grain dissolution,and chemical damage of calcarenites

The mechanical properties of calcarenites are known to be significantly affected by water saturation: both stiffness and strength decrease for wetting in the short term and for chemical dissolution in the long term. Both processes mainly affect bonds among grains: immediately after inundation depositional bonds fall in suspension, whereas diagenetic bonds dissolve more slowly. In this paper, the authors started from the micro‐structural analysis of the weathering processes to conceive a strain hardening hydro‐chemo‐mechanical coupled elastoplastic constitutive model. The concept of extended hardening rules is here enriched: weathering functions have been determined by employing a micro to macro simplified upscaling procedure. Chemical damage is incorporated into the formulation by means of a scalar damage function. Its evolution is also described by using a multiscale approach. A new term is added to the strain rate tensor in order to incorporate the dissolution induced chemical deformations developing once the soft rock is turned into a granular material. A calibration procedure for the constitutive parameters is suggested, and the model is validated by using both coupled and uncoupled chemo‐mechanical experimental test results. Copyright © 2015 John Wiley & Sons, Ltd.     

Street-Frontage-Net: urban image classification using deep convolutional neural networks

ABSTRACT

Quantifying aspects of urban design on a massive scale is crucial to help develop a deeper understanding of urban designs elements that contribute to the success of a public space. In this study, we further develop the Street-Frontage-Net (SFN), a convolutional neural network (CNN) that can successfully evaluate the quality of street frontage as either being active (frontage containing windows and doors) or blank (frontage containing walls, fences and garages). Small-scale studies have indicated that the more active the frontage, the livelier and safer a street feels. However, collecting the city-level data necessary to evaluate street frontage quality is costly. The SFN model uses a deep CNN to classify the frontage of a street. This study expands on the previous research via five experiments. We find robust results in classifying frontage quality for an out-of-sample test set that achieves an accuracy of up to 92.0%. We also find active frontages in a neighbourhood has a significant link with increased house prices. Lastly, we find that active frontage is associated with more scenicness compared to blank frontage. While further research is needed, the results indicate the great potential for using deep learning methods in geographic information extraction and urban design.     

From solid to granular gases: the steady state for granular materials

This paper aims at extending the well‐known critical state concept, associated with quasi‐static conditions, by accounting for the role played by the strain rate when focusing on the steady, simple shear flow of a dry assembly of identical, inelastic, soft spheres. An additional state variable for the system, the granular temperature, is accounted for. The granular temperature is related to the particle velocity fluctuations and measures the agitation of the system. This state variable, as is in the context of kinetic theories of granular gases, is assumed to govern the response of the material at large strain rates and low concentrations. The stresses of the system are associated with enduring, frictional contacts among particles involved in force chains and nearly instantaneous collisions. When the first mechanism prevails, the material behaves like a solid, and constitutive models of soil mechanics hold, whereas when inelastic collisions dominate, the material flows like a granular gas, and kinetic theories apply. Considering a pressure‐imposed flow, at large values of the normal stress and small values of the shear rate, the theory predicts a nonmonotonic shear rate dependence of the stress ratio at the steady state, which is likely to govern the evolution of landslides. Copyright © 2013 John Wiley & Sons, Ltd.     

A visco‐elasto‐plastic model for granular materials under simple shear conditions

The numerical simulation of rapid landslides is quite complex mainly because constitutive models capable of simulating the mechanical behaviour of granular materials in the pre‐collapse and post‐collapse regimes are still missing. The goal of this paper is to introduce a constitutive model capable of capturing the response of dry granular flows from quasi‐static to dynamic conditions, in particular when the material experiences a sort of solid‐to‐fluid phase transition. An ideal assembly of identical spheres under simple shear conditions is considered. In the constitutive model, void ratio and granular temperature have been chosen as state variables, and both shear and normal stresses are computed as the sum of two contributions: the quasi‐static one and the collisional one. The former is determined by using a perfect elasto‐plastic model including the critical state concept, while the latter is derived from the kinetic theory of granular gases. The evolution of the granular temperature, fundamentally governing the material phase transition, is obtained by imposing the kinetic fluctuating energy balance. The constitutive relationship has been integrated, under both constant pressure and constant volume conditions, and the influence of shear strain rate, initial void ratio and normal pressure on the mechanical response has been investigated. Copyright © 2015 John Wiley & Sons, Ltd.     

Evidence of a shallow magma intrusion beneath the NE Rift system of Mt. Etna during 2013

Continuous GPS (CGPS) data, collected at Mt. Etna between April 2012 and October 2013, clearly define inflation/deflation processes typically observed before/after an eruption onset. During the inflationary process from May to October 2013, a particular deformation pattern localised in the upper North Eastern sector of the volcano suggests that a magma intrusion had occurred a few km away from the axis of the summit craters, beneath the NE Rift system. This is the first time that this pattern has been recorded by CGPS data at Mt. Etna. We believe that this inflation process might have taken place periodically at Mt. Etna and might be associated with the intrusion of batches of magma that are separate from the main feeding system. We provide a model to explain this unusual behaviour and the eruptive regime of this rift zone, which is characterised by long periods of quiescence followed by often dangerous eruptions in which vents can open at low elevation and thus threaten the villages in this sector of the volcano.