46 research outputs found
Stima della traspirazione dell’olea sylvestris in un tipico ecosistema mediterraneo in condizioni idriche limitanti
No full textOn the estimate of the transpiration in Mediterranean heterogeneous ecosystems with the coupled use of eddy covariance and sap flow techniques
No full textFixed and variable components of evapotranspiration in a Mediterranean wild-olive - grass landscape mosaic
No full textDry regions are typically characterized by heterogeneous ecosystems where trees are competing with the surrounding grasses for limited amount of water. In these regions, evapotranspiration (ET) is the leading loss term in the soil water budget, and its estimate, and the dynamic contribution of each ET component (i.e. tree and grass transpiration, and dry bare soil and wet surface evaporation), are still poorly quantified. In a typical heterogeneous Mediterranean ecosystem in Sardinia, we combined eddy-covariance estimates of ET with sap flux and energy balance estimates of wild-olive tree transpiration, a common tree species of the region, and with modeled evapotranspiration from the seasonal grass. Trees located in the southern edge of clumps, thus receiving more radiation, transpired more and showed a greater sensitivity to increasing vapor pressure deficit and soil moisture than trees located in clump centers or northern edges. Transpiration of the tree clumps in the footprint (Et), summed up with the modeled evapotranspiration components of the surrounding grass (mostly transpiration during the wet season and evaporation during the dry season), matched latent heat flux measurements, lending confidence in the estimates. Proper accounting for heterogeneity of sources within the eddy covariance footprint seems to have overcome potential errors from not preserving an important assumption of the method, the land-surface homogeneity, highlighting the methods reliability in such inhomogeneous ecosystem. Compared to ET, Et of wild olives was nearly constant over the hydrologic year, insensitive to variation in soil moisture and atmospheric conditions. In contrast, under favorable spring environmental conditions (radiation, vapor pressure deficit, and soil moisture), the pasture leaf area transpires at high rates, contributing to, and dominating the high ET during that season. Conversely, in dry periods, when evapotranspiration from the grass cover is dominated by low evaporation from the, principally, bare soil, Et dominants ecosystem ET
L'erbario del Prof. Manlio Chiappini (1924-1998) in Herbarium CAG
No full textThe herbarium of Chiappini, held in Herbarium CAG of Cagliari University, is presented. Prof. Manlio Chiappini, who dead the 4th of january 1998, teached Botany at the Athenaeum of Cagliari from 1965 to 1987 and from 1965 to 1986 he was director of Botanical Institute and Botanical gardens of Cagliari University. From a research carried out in Herbarium CAG is shown that Chiappini’s herbarium is compound of 1262 exsiccata, referred to 630 specific and subspecific entities (about the 30% of Sardinian flora), of which 45 referred to endemic species (about the 20% of Sardinian flora) and that the Museum Herbarium CAG itself is depositary of a number of 4 species pointed out, by the Author himself, for the first time to Sardinia
Sulla stima della traspirazione in un ecosistema Mediterraneo tramite l’uso associato delle tecniche eddy covariance e sap flow
No full textAn in Silico Study on Nanocomposite Magnetic Implants for Microwave Cancer Theranostics
No full textMicrowave (MW) hyperthermia (HT) is a novel cancer therapy to treat deep-seated tumors, such as bone cancers. The heat administration can be troublesome if external antennas are used. So, magnetic nanocomposite biomaterials, termed magnetic scaffolds, have been proposed as local thermo-seeds for controlling local recurrence rate of bone tumors. However, the possibility of using magneto-dielectric biocompatible implant as MW-responsive theranostic agents has poorly been assessed. In this work, an in silico study based on a 1D MW propagation model in a multilayer structure has been proposed to study if magnetic scaffolds can be used to perform and, contemporary, monitor the HT. The numerical study identified that a matching medium of relative dielectric permittivity of 40 would enables sufficient signal transmission at the frequencies of 0.434, 1.25, 2.45 and 5.8 GHz, thus enabling the HT and the MW monitoring. Indeed, by performing a differential analysis of the variation of the transmission coefficient during the HT, it has been assessed the possibility of using magnetic scaffolds as MW theranostic agents
In silico re-foundation of strain-based healing assessment of fractures treated with an external fixator
No full textIn the last decades, the literature has demonstrated a renewed interest in finding quantitative and non-invasive techniques for the assessment of bone fractures, by replacing X-ray images. Many different approaches have been proposed from ultrasounds to vibrations. This study aims to numerically assess the foundation of a method firstly proposed in 70’ years, based on strain gauges measurements on external fixators for fracture healing monitoring. The theoretical basis consists in the load transfer from the fixator to the bone caused by the callus stiffening during healing. The feasibility is questioned since the level of fixator strain and its variation in in vivo conditions should be high enough to be detectable by the sensors. A finite element model of a fractured tibia phantom treated with a monolateral external fixator was developed and validated experimentally. Then, this reference model was used to simulate bone healing and to investigate the sensitivity of virtual strain measurements to callus geometry and loading conditions. The analysis of load distribution among fixator components and their strain maps allowed to identify optimum strain gauges locations which resulted on the pins more distant from the callus, regardless of the simulated conditions. Even in the worst case of a very thin (3 mm) transverse callus in constrained compression conditions, the strain level (≈100 με/100 N) and its variation per week (-50 με/100 N/wk) resulted measurable in the first healing phase, before plateau conditions occurring after about 6 weeks from fixation. A thicker callus causes higher strain levels and can significantly improve measurements, whilst the callus orientation and the loading conditions have a minor effect. However, in case of a free compression loading, also the rods could provide useful indications if sensorized. The results support the method applicability in in vivo conditions for the considered test case. Further investigations will be addressed to evaluate the effect of the fixator structure and configuration as well as of patient specific healing timing on the method sensitivity
Feasibility Analysis of Theranostic Magnetic Scaffolds for Microwave Monitoring of Hyperthermia Treatment of Bone Tumors
No full textMagnetic biomaterials are multifunctional tools currently under investigation as theranostic platforms for biomedical applications. They can be implanted in bone tissue after bone cancer resection to perform local interstitial hyperthermia treatment. Given the requirements of high quality treatment, the hyperthermia therapy should be performed monitoring the system temperature, to avoid hot spots and control the treatment outcome. It is known that the magnetic properties of such implants vary with temperature. It is hypotesized that the treatment dynamic could be monitored using a microwave monitoring system. The variation of the electromagnetic properties of the biological tissues and the magnetic implant during the therapy would result in a different propagation of the microwave signal. This work investigates the feasibility of using microwaves to non-invasively monitor hyperthermia treatments with a simplified monodimensional propagation model. The forward problem is solved to identify the working frequencies, the matching medium properties and study several candidate materials. By using the numerical solutions from nonlinear and multiphysics simulations of the bone tumor hyperthermia treatment using magnetic scaffolds, the microwave signal propagation dynamic is studied. From our feasibility analysis, we found that it is possible to correlate the average tumor temperature with significant (~20 dB) variations in the transmission coefficient during a typical interstitial hyperthermia session using magnetic scaffolds. Our work brings together, for the first time, the electromagnetic material properties, the physio-pathology and physics of the hyperthermia treatment and the microwave propagation problem, thus paving the route for the development of an innovative theranostic system.</p
Optimized Design and Multiphysics Analysis of a Ka-band Stacked Antenna for CubeSat Applications
No full textNowadays, the use of CubeSats for telecommunications and interplanetary missions is ever-increasing, thanks to their appealing low-cost character, as well as the space environment, which poses challenging multiphysics constraints on the antenna design. In this framework, the use of Ka-band for communication is explored. We present the design of a stacked patch antenna working across the down- and uplink Ka-bands. Materials and geometry of the radiator have been selected by accounting for the trade-off between electromagnetic, thermal and mechanical requirements. The design of the antenna is performed with a particle swarm optimization algorithm developed to control the bandwidth and matching. A bandwidth of [email protected] GHz has been obtained, with a gain around 8 dB. Furthermore, a multiphysics thermal analysis is performed to verify the operational stability of the optimized array, mounted on a 1 U satellite, in a case-study mission. The temperature patterns in the array are evaluated during the orbital period, and the influence of the operative temperature on the antenna responses and gain was considered. We found that the thermal loads can affect the antenna matching. However, thanks to the optimized design, the proposed stacked antenna can operate from −100 ∘ C to 100 ∘ C, with an almost constant gain. Finally, following a damage-tolerant approach, the level of mechanical deformation, which could be induced on the communication system, was studied. The stress analysis reveals that the stacked geometry can be used in a space mission. From the investigation of the strain and displacement field, we found a negligible impact on the antenna performance
