Bifurcations in dissipative fermionic dynamics

The Boltzmann-Langevin One-Body model (BLOB), is a novel one-body transport approach, based on the solution of the Boltzmann-Langevin equation in three dimensions; it is used to handle large-amplitude phase-space fluctuations and has a broad applicability for dissipative fermionic dynamics. We study the occurrence of bifurcations in the dynamical trajectories describing heavy-ion collisions at Fermi energies. The model, applied to dilute systems formed in such collisions, reveals to be closer to the observation than previous attempts to include a Langevin term in Boltzmann theories. The onset of bifurcations and bimodal behaviour in dynamical trajectories, determines the fragment-formation mechanism. In particular, in the proximity of a threshold, fluctuations between two energetically favourable mechanisms stand out, so that when evolving from the same entrance channel, a variety of exit channels is accessible. This description gives quantitative indications about two threshold situations which characterise heavy-ion collisions at Fermi energies. First, the fusion-to-multifragmentation threshold in central collisions, where the system either reverts to a compact shape, or splits into several pieces of similar sizes. Second, the transition from binary mechanisms to neck fragmentation (in general, ternary channels), in peripheral collisions.Comment: Conf. proc. ECHIC November 6-8, 2013 Messina (Italy

Determining short-term changes in the hydraulic properties of a sandy-loam soil by a three-run infiltration experiment

Soil structure-dependent parameters can vary rapidly as a consequence of perturbing events such as intense rainfall. Investigating their short-term changes is therefore essential to understand the general behaviour of a porous medium. The aim of this study is to gain insight into the effects of wetting, perturbation and recovery processes through different sequences of Beerkan infiltration experiments performed on a sandy-loam soil. Two different three-run infiltration experiments (LHL and LLL) were carried out by pouring water at low (L, non-perturbing) and high (H, perturbing) heights above the soil surface and at short time intervals (hours, days). The results demonstrate that the proposed method allows one to capture short-term variations in soil structure-dependent parameters. The developed methodology is expected to simplify the parameterization of hydrological models with temporally variable soil hydraulic properties

Rapid and accurate measurement methods for determining soil hydraulic properties: A review

The determination of soil hydraulic properties is important in several environmental sciences but may be expensive and time consuming. Therefore, during the last decades, a great effort has been made in soil sciences to develop relatively easy, robust, and inexpensive methods for soil hydraulic characterization. In this manuscript, we reviewed and discussed different infiltrometer techniques in light of the available experimental applications. More specifically, we considered the simplified falling head (SFH) infiltrometer technique and the single-ring infiltration experiment of the Beerkan type. Concerning this latter method, we considered different algorithms for data analysis: Two simplified methods based on the analysis of transient (TSBI) and steady (SSBI) Beerkan infiltration data, and the Beerkan Estimation of Soil pedoTransfer parameters algorithm (BEST), that allows to estimate the soil characteristics curves, i.e., the soil water retention curve and hydraulic conductivity functions. For a given method, after dealing briefly theory and practice, available literature references were reported to account for specific applications in order to provide findings on method validation and application. With the aim to provide practical information on available tools for a simpler application of the reviewed methods, several video tutorials were reported to show i) how to conduct correctly field experiments and ii) how to calculate saturated hydraulic conductivity or soil hydraulic functions using user-friendly tools for data analysis. Finally, details on a new automated single-ring infiltrometer for Beerkan infiltration experiments (i.e., construction, assembly and field use) were presented

Advances in Ecohydrology for Water Resources Optimization in Arid and Semi-Arid Areas

Conserving water resources is a current challenge that will become increasingly urgent in future due to climate change. The arid and semi-arid areas of the globe are expected to be particularly affected by changes in water availability. Consequently, advances in ecohydrology sciences, i.e., the interplay between ecological and hydrological processes, are necessary to enhance the understanding of the critical zone, optimize water resources’ usage in arid and semi-arid areas, and mitigate climate change. This Special Issue (SI) collected 10 original contributions on sustainable land management and the optimization of water resources in fragile environments that are at elevated risk due to climate change. In this context, the topics mainly concern transpiration, evapotranspiration, groundwater recharge, deep percolation, and related issues. The collection of manuscripts presented in this SI represents knowledge of ecohydrology. It is expected that ecohydrology will have increasing applications in the future. Therefore, it is realistic to assume that efforts to increase environmental sustainability and socio-economic development, with water as a central theme, will have a greater chance of success

L'Osservatorio Geofisico di Lipari ed i 40 anni della Rete Sismica Permanente del Tirreno Meridionale

In 1966, the Istituto Internazionale di Vulcanologia (I.I.V.), gave the go ahead to the ambitious project of setting up a seismic network in the southern Tyrrhenian Sea, an area of extraordinary geophysical interest, which until then was not covered by seismic monitoring. At the time, there were single seismic stations on the rest of the italian peninsula. These were inside universities, public and private bodies and at the numerous observatories of the Istituto Nazionale di Geofisica (founded in 1936 by Antonino Lo Surdo and becoming independent of the Consiglio Nazionale delle Ricerche (C.N.R,. in 1945) and still used mechanical seismographs, with masses weighing from 80 up to 1300 Kg. On the Aeolian Islands instead, electromagnetic seismometers were employed from the start. The experimental network, planned in the Willmore laboratories at Edinburgh and tested in the Aeolian Islands over a two-year period, represented the starting point for the Permanent Seismic Network (PSN) of the Southern Tyrrhenian. After the experience of the Laboratorio Internazionale per le Ricerche Vulcanologiche (L.I.R.V. - C.N.R.), of the Istituto di Vulcanologia of the University of Catania, the independent I.I.V. - C.N.R., together with the observatory, was launched in 1969. In the course of the seventies, every island of the Aeolian archipelago, was equipped with at least a seismic station and the 3 sensor systems (triaxial systems) began to become widely used. In the eighties, the “Sismologia Eolie” project was started, aimed at a further develop and update the seismic net. With the wide use of magnetic tape recording, the instrumental data stored could be more readily transported on suitable drums to the main centre in Catania for analysis. Here, Research Units were established in order to prepare the way for enhanced interaction between technical staff and research groups. The instrumental geophysical investigations, progressively extended and in a permanente form to Eastern Sicily and particular around Etna. From the nineties, operations room in Catania was fully active, working 24/24, and ensuring the seismic and volcanic surveillance of Etna, Stromboli and Vulcano. The Geophysical Observatory of Lipari and the main centre of the Institute in Catania, were merged in 2001 into the new Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the network of the Aeolian Islands became an integral part of the Permanent Seismic Network (PSN) of Eastern Sicily and Southern Calabria. Special prominence will be given in the course of this historical reconstruction to the evolution of instrumental seismology, thanks to forty years of continuous input, indispensable for the understanding of the seismogenetic processes in the area, this still represents the chief undertaking of the geophysical observatory on Lipari, whose important scientific but also social role must be acknowledged in the growing interaction between research and civil protection

Large-scale lateral saturated soil hydraulic conductivity as a metric for the connectivity of subsurface flow paths at hillslope scale

Lateral saturated soil hydraulic conductivity, Ks,l, is the soil property governing subsurface water transfer in hillslopes, and the key parameter in many numerical models simulating hydrological processes at the hillslope and catchment scales. Likewise, the hydrological connectivity of the lateral flow paths plays a significant role in determining the rate of the subsurface flow at various spatial scales. This study investigates the relationship between Ks,l and hydrological connectivity at the hillslope spatial scale. Ks,l was determined by the subsurface flow rates intercepted by drains and water table depths observed in a well network. The hydrological connectivity was evaluated by the synchronicity among water table peaks, and between these and the peaks of the drained flow. Rainfall and soil moisture were used to investigate the influence of the transient hydrological soil condition on connectivity and Ks,l. As the synchronicity of the water table response between wells increased, the lag times between the peaks of water levels and those of the drained subsurface flow decreased. Moreover, the most synchronic water table rises determined the highest drainage rates. The relationships between Ks,l and water table depths were highly non-linear, with a sharp increase in the values for water table levels close to the soil surface. Estimated Ks,l values for the full saturated soil were in the order of thousands of mm h−1, suggesting the activation of macropores in the root zone. The Ks,l values determined at the peak of the drainage events were correlated with the indicators of synchronicity. The sum of cumulative rainfall and antecedent soil moisture was correlated with the connectivity indicators and Ks,l. We suggest that, for simulating realistic processes at the hillslope scale, the hydrological connectivity could be implicitly considered in hydrological modelling through an evaluation of Ks,l at the same spatial scale

A Simple Correction Term to Model Infiltration in Water-Repellent Soils

Soil water repellency can substantially alter hydrologic processes, particularly the ability of soils to infiltrate water. Water repellency often changes through time, making it difficult to simulate infiltration behaviors of water-repellent soils using standard models. Here, we propose a simple rate-based correction term that starts with a value of zero at the beginning of the infiltration process (t = 0) and asymptotically approaches 1 as time increases, thus simulating decreasing soil water repellency through time. The correction term can be used with any infiltration model. For this study, we selected a simple two-term infiltration equation and then, using two data sets of infiltration measurements conducted in soils with varying water repellency, compared model error with versus without the added term. The correction substantially reduced model error, particularly in more repellent soils. At the same time, the rate constant parameter introduced in the new model may be useful to better understand dynamics of soil water repellency and to provide more consistent interpretations of hydraulic properties in water-repellent soils

Shade-grown coffee in colombia benefits soil hydraulic conductivity

Secondary tropical forests and coffee agroforestry systems contain fewer trees than native forests but can positively impact soil hydrological functions, such as water infiltration compared to the pasture land that they replace. However, for both land uses it remains in how far the soil hydraulic characteristics are comparable to that of native forest. Therefore, we investigated the saturated hydraulic conductivity (Ks ) and some hydrophysical soil attributes in four land-use types: (i) a shade-grown coffee; (ii) a natural regenerated forest 15 years ago; (iii) a pasture; and (iv) a reference forest, in the municipality of La Jagua de Ibirico, César department, Colombia. We determined historical land use and conducted soil sampling, using the Beerkan method to determine the Ks values. We also measured canopy cover, vegetation height, diameter at breast height and total number of trees in the forest covers. Our results indicate that Ks values were similar for the coffee and the reference forest, reflecting the positive effect of trees on soil hydrological functioning in agroforestry systems. Our results suggest that 15 years of forest regeneration after land abandonment in Sub-Andean Forest, can improve the soil hydraulic attributes. Additionally, soil water repellency was observed for the reference forest soil

A remote sensing and modeling integrated approach for constructing continuous time series of daily actual evapotranspiration

Satellite remote sensing-based surface energy balance (SEB) techniques have emerged as useful tools for quantifying spatialized actual evapotranspiration at various temporal and spatial scales. However, discontinuous data acquisitions and/or gaps in image acquisition due to cloud cover can limit the applicability of satellite remote sensing (RS) in agriculture water management where continuous time series of daily crop actual evapotranspiration (ETc act) are more valued. The aim of the research is to construct continuous time series of daily ETc act starting from temporal estimates of actual evapotranspiration obtained by SEB modelling (ETa eb) on Landsat-TM images. SEBAL model was integrated with the FAO 56 evaporation model, RS-retrieved vegetative biomass dynamics (by NDVI) and on-field measurements of soil moisture and potential evapotranspiration. The procedure was validated by an eddy covariance tower on a vineyard with partial soil coverage in the south of Sardinia Island, Italy. The integrated modeling approach showed a good reproduction of the time series dynamics of observed ETc act (R2 =0.71, MAE=0.54 mm d-1, RMSE=0.73 mm d-1). A daily and a cumulative monthly temporal analysis showed the importance of integrating parameters that capture changes in the soil-plant-atmosphere (SPA) continuum between Landsat acquisitions. The comparison with daily ETc act obtained by the referenced ET fraction (ETrF) method that considers only weather variability (by ETo) confirmed the lead of the proposed procedure in the spring/early summer periods when vegetation biomass changes and soil water evaporation have a significant weight in the ET process. The applied modelling approach was also robust in constructing the missing ETc act data under scenarios of limited cloud-free Landsat acquisitions. The presented integrated approach has a great potential for the near real time monitoring and scheduling of irrigation practices. Further testing of this approach with diverse dataset and the integration with the soil water modeling is to be analyzed in future work