The dynamics of coastal lagoons and estuarine areas is characterized by a delicate balance between biological and physical processes and the comprehension and monitoring of such processes require ...observations over a wide range of temporal and spatial scales. Remote sensing techniques in this context are very advantageous and potentially allow overcoming the spatial limitations of traditional in situ point observations, providing new opportunities for a better understanding of the relevant bio-geomorphological processes and for the calibration and validation of spatially-distributed hydrodynamic and transport models. Remote sensing of suspended particulate matter (SPM) concentration in shallow waters must, however, overcome the difficulties associated with i) the influence of bottom reflection, which may interfere with an accurate retrieval; ii) the necessity of accurately knowing the optical properties of the suspended matter, and iii) the importance of providing an assessment of the uncertainty associated with the estimates produced. This work presents a method to estimate SPM concentration in lagoon/estuarine waters by use of a simplified radiative transfer model. We use a calibration/validation method based on cross-validation and bootstrap techniques to provide a statistically sound determination of model parameters and an evaluation of the uncertainty induced by their inaccurate determination as well as by the uncertain knowledge of the bottom sediment reflectance. The method is applied to the Venice lagoon, using observations from a network of turbidity sensors and from several multispectral satellite sensors (LANDSAT, ASTER and ALOS AVNIR). The bootstrap and cross-validation procedures employed show that consistent estimates of SPM concentration can indeed be retrieved from satellite remote sensing, provided that sufficient in situ ancillary information for appropriate calibration is available. The quantification of the estimation uncertainty shows that retrievals obtained from remote sensing are accurate, robust and repeatable. The SPM concentration maps produced show a general coherence with known features in the Venice lagoon and, together with suitable biological information, point to the role played by benthic vegetation in the stabilization of the bottom sediment.
Livestock play a significant role in rural livelihoods and the economies of developing countries. They are providers of income and employment for producers and others working in, sometimes complex, ...value chains. They are a crucial asset and safety net for the poor, especially for women and pastoralist groups, and they provide an important source of nourishment for billions of rural and urban households. These socio-economic roles and others are increasing in importance as the sector grows because of increasing human populations, incomes and urbanisation rates. To provide these benefits, the sector uses a significant amount of land, water, biomass and other resources and emits a considerable quantity of greenhouse gases. There is concern on how to manage the sector's growth, so that these benefits can be attained at a lower environmental cost. Livestock and environment interactions in developing countries can be both positive and negative. On the one hand, manures from ruminant systems can be a valuable source of nutrients for smallholder crops, whereas in more industrial systems, or where there are large concentrations of animals, they can pollute water sources. On the other hand, ruminant systems in developing countries can be considered relatively resource-use inefficient. Because of the high yield gaps in most of these production systems, increasing the efficiency of the livestock sector through sustainable intensification practices presents a real opportunity where research and development can contribute to provide more sustainable solutions. In order to achieve this, it is necessary that production systems become market-orientated, better regulated in cases, and socially acceptable so that the right mix of incentives exists for the systems to intensify. Managing the required intensification and the shifts to new value chains is also essential to avoid a potential increase in zoonotic, food-borne and other diseases. New diversification options and improved safety nets will also be essential when intensification is not the primary avenue for developing the livestock sector. These processes will need to be supported by agile and effective public and private institutions.
CT-based thermometry: An overview Fani, F.; Schena, E.; Saccomandi, P. ...
International journal of hyperthermia,
06/2014, Letnik:
30, Številka:
4
Journal Article
Recenzirano
Abstract
The dependence of computed tomography (CT) values on temperature has been pointed out by several authors since the late 1970s. They emphasised the importance of this phenomenon on the ...calibration process with water equivalent phantoms of the CT scanners. Few years later the potential of CT thermometry for non-invasive temperature mapping during thermal procedures was investigated. The interest on the employment of this technique during thermal treatments has been recently renewed with the improvement of modern CT scanner performances and with the increased popularity of minimally invasive thermal techniques for cancer treatment. A good thermometry allows avoiding unintended damage of the healthy tissues during the procedure by providing a detailed tissue temperature distribution; therefore, it is recommended in order to achieve good effectiveness of the thermal treatment. Researchers have been working on this issue for more than four decades and different non-invasive solutions have been proposed, i.e., microwave thermal imaging, infrared (IR)-, ultrasound-, magnetic-resonance (MR)-, and CT-based thermometry. This review aims to summarise the essential physics and the currently available data on CT-based thermometry and to elucidate the potential use of this technique during thermal procedures. Background information on measuring principle, an investigation of the performances achieved by this technique and the thermal sensitivity of the CT-number of different organs are provided and discussed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The emission of coherent XUV radiation from atomic or molecular gases exposed to intense infrared laser pulses, known as high harmonic generation, is of paramount interest in atomic and molecular ...physics as well as in attosecond science. The emitted radiation contains a wealth of information about the structure of its generating medium, which inspired vigorous efforts to tomographically image the valence orbital of atoms and molecules. The orbital retrieval is nevertheless seriously hindered by the complexity of the harmonic emission process, as recently demonstrated by several theoretical and experimental works. Here we present a novel approach for molecular orbital tomography that contributes to overcome those difficulties, opening intriguing perspectives on coherent XUV imaging of complex species by high-order harmonic generation. PUBLICATION ABSTRACT
Isolated Single-Cycle Attosecond Pulses Sansone, G; Benedetti, E; Calegari, F ...
Science (American Association for the Advancement of Science),
10/2006, Letnik:
314, Številka:
5798
Journal Article
Recenzirano
We generated single-cycle isolated attosecond pulses around ~36 electron volts using phase-stabilized 5-femtosecond driving pulses with a modulated polarization state. Using a complete temporal ...characterization technique, we demonstrated the compression of the generated pulses for as low as 130 attoseconds, corresponding to less than 1.2 optical cycles. Numerical simulations of the generation process show that the carrier-envelope phase of the attosecond pulses is stable. The availability of single-cycle isolated attosecond pulses opens the way to a new regime in ultrafast physics, in which the strong-field electron dynamics in atoms and molecules is driven by the electric field of the attosecond pulses rather than by their intensity profile.
Peat soils are typical deposits characterizing wetlands and reclaimed farmlands. They are important carbon reservoirs and when degraded (e.g., erosive processes, fires, draining and plowing) massive ...carbon dioxide volumes are released. This leads to increase greenhouse effect and induce serious land subsidence. Thus, mapping the volume of peat deposits is crucial in order to estimate the carbon mass and the potential release of carbon dioxide and consequent loss in soil elevation. Despite the importance of such estimations, forecasting and quantifying the peat thickness is still a challenge. Direct sediment coring provides local information that is difficult to extend to large territories. Indirect geophysical methods are unable to resolve lithological contrasts in the presence of saltwater contamination in coastal areas. In this work, we show the results obtained using two contact-less electromagnetic methods for the characterization of peat deposits in a peatland site of the Venice coastland, Italy. Specifically, a multi-frequency portable instrument (FDEM) and an airborne time-domain electromagnetic one (AEM), known for their very high and relatively low vertical resolution respectively, were used to collect data over a former wetland then reclaimed for agricultural purposes. Additional electrical resistivity tomography (ERT) data are used together with sediment core data to assess the effectiveness and accuracy of the contact-less methods. Results show that both FDEM and AEM are very effective in detecting the presence of the peat layer, despite its low thickness (<2 m) and the high electro-conductive subsoil because of saltwater contamination. However, the AEM method overestimated the peat thickness while the FDEM could accurately resolve the peat thickness even where the layer was thinner than 1 m. When compared to the electrical features extracted from the ERT, discrepancies are on average lower than 30%; when compared to the borehole data, discrepancies are on average slightly higher than 6%.
Display omitted
•Contact-less geophysical methods are effective in accurately detecting peat layers.•These methods are effective even when peat layers are thin.•Effective even when the carbon content is decreased by agricultural practices•These methods provide a cost-effective and fast approach to peat quantification.
As valuable and vulnerable blue carbon ecosystems, salt marshes require adaptable and robust monitoring methods that span a range of spatiotemporal scales. The application of unmanned aerial vehicle ...(UAV) based remote sensing is a key tool in achieving this goal. Due to the particular characteristics of tidal wetlands, however, there are challenges in obtaining research and management relevant data with the requisite level of accuracy. In this study, the spatial patterns in uncertainty stemming from scan angle, binning method, vegetation structure and platform surface morphology are examined in the context of UAV light detection and ranging (LiDAR) derived digital elevation models (DEM). The results demonstrate that overlapping the UAV flight paths sufficiently to avoid sole reliance on LIDAR data with scan angles exceeding 15 degrees is advisable. Furthermore, the spatial arrangement of halophyte species and marsh morphology has a clear influence on DEM accuracy. The largest errors were associated with sudden structural transitions at the marsh channel boundaries. The DEMmean was found to be the most accurate for bare ground, while the DEMmin was the most accurate for channels and the middle to high marsh vegetation (MAEs = −0.01m). For the low to middle vegetation, all the trialled DEMs returned a similar magnitude of mean error (MAE = ± 0.03m). The accuracy difference between the two vegetation associations examined appears to be connected to variations in coverage, height and biomass. Overall, these findings reinforce the link between salt marsh biogeomorphic complexity and the spatial distribution and magnitude of LiDAR DEM error.
We investigated the giant resonance in xenon by high-order harmonic generation spectroscopy driven by a two-color field. The addition of a nonperturbative second harmonic component parallel to the ...driving field breaks the symmetry between neighboring subcycles resulting in the appearance of spectral caustics at two distinct cutoff energies. By controlling the phase delay between the two color components it is possible to tailor the harmonic emission in order to amplify and isolate the spectral feature of interest. In this Letter we demonstrate how this control scheme can be used to investigate the role of electron correlations that give birth to the giant resonance in xenon. The collective excitations of the giant dipole resonance in xenon combined with the spectral manipulation associated with the two-color driving field allow us to see features that are normally not accessible and to obtain a good agreement between the experimental results and the theoretical predictions.
The identification of uncontrolled landfills is a central environmental problem in all developed and developing countries, where several illegal waste deposits exist as a result of rapid industrial ...growth over the past century. Remote sensing can potentially provide crucial information for the identification of contaminated sites, but surprisingly there is a marked lack of rigorously validated approaches. In this paper we introduce and validate a method that uses remotely sensed information and a geographic information system (GIS) to identify unknown landfills over large areas. The method is applied to a study area located in NE Italy (part of the Venice lagoon watershed) using IKONOS satellite data. Soil contamination effects on the radiometric properties of vegetation, calibrated using spectral signatures of stressed vegetation from known illegal landfill sites, were used to define numerous candidate sites that are most likely to host waste materials. Distributed geographical information, such as the position of the road network, the population density, and historical aerial photographs, have then been used to select the most likely contaminated sites among the candidates identified through remote sensing. The importance of the integration of GIS and remote sensing is highlighted and represents a key instrument for environmental management and for the spatially distributed characterization of possible uncontrolled landfill sites.
An ideal direct imaging system entails a method to illuminate on command a single diffraction-limited region in a generally thick and turbid volume. The best approximation to this is the use of ...large-aperture lenses that focus light into a spot. This strategy fails for regions that are embedded deep into the sample, where diffraction and scattering prevail. Airy beams and Bessel beams are solutions of the Helmholtz Equation that are both non-diffracting and self-healing, features that make them naturally able to outdo the effects of distance into the volume but intrinsically do not allow resolution along the propagation axis. Here, we demonstrate diffraction-free self-healing three-dimensional monochromatic light spots able to penetrate deep into the volume of a sample, resist against deflection in turbid environments, and offer axial resolution comparable to that of Gaussian beams. The fields, formed from coherent mixtures of Bessel beams, manifest a more than ten-fold increase in their undistorted penetration, even in turbid milk solutions, compared to diffraction-limited beams. In a fluorescence imaging scheme, we find a ten-fold increase in image contrast compared to diffraction-limited illuminations, and a constant axial resolution even after four Rayleigh lengths. Results pave the way to new opportunities in three-dimensional microscopy.
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