555 research outputs found
Automatic measurement of glacier ice ablation using thermistor strings
In this work we tested the suitability of thermistor strings as automatic tools for the continuous
measurement of glacier ice ablation. Experimental data collected in summer 2017 over an Italian
glacier provided ice ablation readings with accuracy similar to manual measurements with ablation
stakes and other automatic systems, like the draw-wire method and the B\uf8ggild ablatometer.
Thermistor strings have potential for future applications in remote glacier monitoring, thanks to their
flexibility, simple construction, and robustness
Novel Scintillating Materials Based on Phenyl-Polysiloxane for Neutron Detection and Monitoring
Neutron detectors are extensively used at many nuclear research facilities
across Europe. Their application range covers many topics in basic and applied
nuclear research: in nuclear structure and reaction dynamics (reaction
reconstruction and decay studies); in nuclear astrophysics (neutron emission
probabilities); in nuclear technology (nuclear data measurements and
in-core/off-core monitors); in nuclear medicine (radiation monitors,
dosimeters); in materials science (neutron imaging techniques); in homeland
security applications (fissile materials investigation and cargo inspection).
Liquid scintillators, widely used at present, have however some drawbacks given
by toxicity, flammability, volatility and sensitivity to oxygen that limit
their duration and quality. Even plastic scintillators are not satisfactory
because they have low radiation hardness and low thermal stability. Moreover
organic solvents may affect their optical properties due to crazing. In order
to overcome these problems, phenyl-polysiloxane based scintillators have been
recently developed at Legnaro National Laboratory. This new solution showed
very good chemical and thermal stability and high radiation hardness. The
results on the different samples performance will be presented, paying special
attention to a characterization comparison between synthesized phenyl
containing polysiloxane resins where a Pt catalyst has been used and a
scintillating material obtained by condensation reaction, where tin based
compounds are used as catalysts. Different structural arrangements as a result
of different substituents on the main chain have been investigated by High
Resolution X-Ray Diffraction, while the effect of improved optical
transmittance on the scintillation yield has been elucidated by a combination
of excitation/fluorescence measurements and scintillation yield under exposure
to alpha and {\gamma}-rays.Comment: InterM 2013 - International Multidisciplinary Microscopy Congres
Air temperature variability over three glaciers in the Ortles-Cevedale (Italian Alps): Effects of glacier fragmentation, comparison of calculation methods, and impacts on mass balance modeling
Glacier mass balance models rely on accurate spatial calculation of input data, in particular air temperature. Lower temperatures (the so-called glacier cooling effect), and lower temperature variability (the so-called glacier damping effect) generally occur over glaciers, compared to ambient conditions. These effects, which depend on the geometric characteristics of glaciers and display a high spatial and temporal variability, have been mostly investigated on medium- to large-size glaciers so far, while observations on smaller ice bodies are scarce. Using a dataset from 8 on-glacier and 4 off-glacier weather stations, collected in summer 2010 and 2011, we analyzed the air temperature distribution variability and wind regime over three different glaciers in the Ortles-Cevedale. The magnitude of the cooling effect and the occurrence of katabatic boundary layer (KBL) processes showed remarkable differences among the three ice bodies, highlighting suggesting the likely existence of important reinforcing mechanisms during glacier decay and disintegration. None of the methods proposed in the literature for calculating on-glacier temperature from off-glacier data fully reproduced our observations. Among them, the more physically-based procedure of Greuell and B\uf6hm [1998] provided the best overall results where the KBL prevail, but it was not effective elsewhere (i.e. on smaller ice bodies and close to the glacier margins). The accuracy of air temperature estimations strongly impacted the results from a mass balance model which was applied to the three investigated glaciers. Most importantly, even small temperature deviations caused distortions in parameter calibration, thus compromising the model generalizability
Probing the chemical environment of 3-hydroxyflavone doped ormosils by a spectroscopic study of excited state intramolecular proton transfer
Abstract The spectroscopic properties of 3-hydroxyflavone (3-HF) molecules entrapped in films and in monoliths of sol–gel derived organically modified silicates (Ormosils) xerogels are studied by excitation and fluorescence spectroscopy as a function of the sol–gel precursors used for the synthesis. Different molar ratios of tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and phenyltriethoxysilane (PTES) as precursors are used for the sol preparation. Emission and excitation spectra in the ultraviolet–visible range and photo-degradation curves as a function of time are collected with a spectrofluorimeter. The 3-hydroxyflavone optical properties change in the different networks, owing to the effects of the chemical environment on the excited state intramolecular proton transfer and to the solubility of the dye molecules in the different sol–gel systems. It turns out that the spectroscopic features can be used to probe the chemical state of the dye molecules microenvironment
High-Resolution monitoring of current rapid transformations on glacial and periglacial environments
Glacial and periglacial environments are highly sensitive to climatic changes. Processes of cryosphere degradation may strongly impact human activities and infrastructures, and need to be monitored for improved understanding and for mitigation/adaptation. Studying glacial and periglacial environments using traditional techniques may be difficult or not feasible, but new remote sensing techniques like terrestrial and aerial laser scanner opened new possibilities for cryospheric studies. This work presents an application of the terrestrial laser scanner (TLS) for monitoring the current rapid changes occurring on the Montasio Occidentale glacier (Eastern Italian alps), which is representative of low-altitude, avalanche-fed and debris-cover glaciers. These glaciers are quite common in the Alps but their reaction to climate changes is still poorly known. The mass balance, surface velocity fields, debris cover dynamics and effects of meteorological extremes were investigated by repeat high-resolution TLS scanning from September 2010 to October 2012. The results were encouraging and shed light on the peculiar response of this glacier to climatic changes, on its current dynamics and on the feedback played by the debris cover, which is critical for its preservation. The rapid transformations in act, combined with the unstable ice mass, large amount of loose debris and channeled runoff during intense rainfalls, constitute a potential area for the formation of large debris flows, as shown by field evidences and documented by the recent literature
Life cycle assessment in the automotive industry: comparison between aluminium and cast iron cylinder blocks
The continuous search for lighter materials in the automotive industry is justified by the environmental advantage deriving from the reduction of fuel consumption and, therefore, lower CO2 emissions throughout the vehicles? use phase. However, a correct evaluation of the environmental effects related to the choice of "light" materials should involve not only the use but the whole life of the vehicle. This paper presents the results of the comparison between the environmental load of cast iron and aluminium cylinder blocks. The methodological approach adopted for the analysis is Life Cycle Assessment (LCA) since it allows to consider the environmental effects of a product during the production, use and end-of-life treatment phases. The study demonstrates that, while during the production stage the environmental load related to the aluminium block is higher than the one related to the cast iron block, during use and end-of-life treatment the gain of aluminium over cast iron makes the aluminium cylinder block more environment friendly than the cast iron one
Removal of ammonium from wastewater with geopolymer sorbents fabricated via additive manufacturing
Geopolymers have been recently explored as sorbents for wastewater treatment, thanks to their mechanical and chemical stability and to their low-energy manufacturing process. One specific application could be the removal of ammonium (NH4+) through exchange with Na+ ions. Additive manufacturing (AM) represents an especially interesting option for fabrication, as it allows to tailor the size, distribution, shape, and interconnectivity of pores, and therefore the access to charge-bearing sites. The present study provides a proof of concept for NH4+ removal from wastewater using porous geopolymer components fabricated via direct ink writing (DIW) AM approach. A metakaolin-based ink was employed for the fabrication of a log-pile structure with 45\ub0 rotation between layers, producing continuous yet tortuous macropores which are responsible for the high permeability of the sorbents. The ink consolidates in an amorphous, mesoporous network, with the mesopores acting as preferential sites for ion exchange. The printed sorbents were characterized for their physicochemical and mechanical properties and the NH4+ removal capacity in continuous-flow column experiments by using a model effluent. The lattices present high permeability and high cation exchange capacity and maintained a high amount of active ions after four cycles, allowing to reuse them multiple times
ZnS (Mn) Nanoparticles as Luminescent Centers for Siloxane Based Scintillators
Synthesis of oleic acid stabilized ZnS nanocrystals activated with Mn is pursued. A hydrothermal method where high pressure and temperature are applied to control the nanocrystals growth is adopted. Capping the nanoparticle surface with oleic acid (OA) improved light output. Samples loaded with both the phosphor and the neutron sensitizer have been produced and tested in a preliminary test as alpha particle detectors and secondly as thermal neutron detectors. The results support further development for siloxane-based scintillator detectors employing ZnS (Mn) nanoparticles
The current deglaciation of the Ortles-Cevedale massif (Eastern Italian Alps): impacts, controls and degree of imbalance.
The Ortles-Cevedale is the largest glacierized mountain group of the Italian Alps hosting 112 ice bodies, with a
total area of 76.8 km2. Since the 1980\u2019s, this massif is undergoing a rapid deglaciation, as most of the mountain
ranges in the European Alps. The aims of this work were: i) to quantify area and volume change of the Ortles-
Cevedale glacier system from the 1980s to the 2000s; ii) to improve the knowledge of factors controlling the spatial
variability of the deglaciation; and iii) to assess the degree of imbalance of individual glaciers with respect to the
present climate conditions.
Two inventories were created, based on Landsat5 TM scenes of 20-09-1987 and 31-08-2009. Contrast-enhanced
composites (bands TM5, TM4 and TM3), aerial photos and field surveys (for the most recent period) were used
to correct the automatic delineation of glaciers derived from a hard classification based on a threshold applied to
a TM3/TM5 ratio image. Since Landsat scenes were acquired at the end of the ablation seasons and fresh snow
was absent, the accumulation areas could be roughly determined by mapping the snow covered area. This region
was identified from the difference in reflectance between snow and ice in the near infrared band of Landsat (TM4),
and mapped after correcting topographic effects to determine surface reflectance. The area-averaged geodetic mass
budget was then calculated for the individual glaciers by differencing two Digital Terrain Models (2000s minus
1980s, derived from LiDAR and aerial photogrammetry) and combining the result with the glacier outlines. Afterwards,
we examined the mass balance data using statistical analyses (Correlation matrices, Principal Component
Analysis, Cluster Analysis). This allowed us highlighting clusters of glaciers, which exhibit a similar behavior,
identify the outlayers and the relative influence of the factors controlling spatial variability of the mass losses.
Finally, we assessed the degree of imbalance of individual glaciers by comparing the current Accumulation Area
Ratios (AAR) with the balanced-budget AAR (AAR0), the latter also accounting for the debris cover of glaciers.
We found that the total area loss of the Ortles-Cevedale glaciers from 1987 to 2009 amounts to 23.5 km2, i.e.
23.4% of the initial area. On the other hand, the AAR of the entire glacier system was 0.3 in both investigated
years. The overall debris cover increased from 10.5% to 16.3%. The geodetic mass balance rate was -0.7 m w.e.
y1(as an average on 112 ice bodies), ranging from -0.1 to -1.7 m w.e. y1. We also found that the main controls
of the differing change of single glaciers are related to their hypsometry (elevation range and slope), AAR, feeding
source and debris cover. Interestingly, a significant correlation was found between AAR, AAR0 and debris cover.
This information was used to assess and visualize the needed additional reduction of individual glaciers to reach
equilibrium with the current size of their accumulation areas. This amounts on average to a further reduction of
40% of the current areal extent of glaciers
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