Exact solution for a two-phase Stefan problem with variable latent heat and a convective boundary condition at the fixed face

Recently it was obtained in [Tarzia, Thermal Sci. 21A (2017) 1-11] for the classical two-phase Lam\'e-Clapeyron-Stefan problem an equivalence between the temperature and convective boundary conditions at the fixed face under a certain restriction. Motivated by this article we study the two-phase Stefan problem for a semi-infinite material with a latent heat defined as a power function of the position and a convective boundary condition at the fixed face. An exact solution is constructed using Kummer functions in case that an inequality for the convective transfer coefficient is satisfied generalizing recent works for the corresponding one-phase free boundary problem. We also consider the limit to our problem when that coefficient goes to infinity obtaining a new free boundary problem, which has been recently studied in [Zhou-Shi-Zhou, J. Engng. Math. (2017) DOI 10.1007/s10665-017-9921-y].Comment: 16 pages, 0 figures. arXiv admin note: text overlap with arXiv:1610.0933

Tree rings as ecological indicator of geomorphic activity in geoheritage studies

Mountain areas are characterized by geomorphic processes, especially mass wasting and snow avalanches, which may impact the landscape affecting also the biological component, trees included. If sites colonized by trees are characterized by geomorphic features with a high Global and Scientific Value, including Representativeness of geomorphological processes, Educational Exemplarity, and Integrity, they can be considered geomorphosites. In the framework of assessment of the Scientific Value of geomorphosites, Ecological Support Role is of great importance. Hence, tree rings derived information can be used as indicators to refine the Scientific Value of the sites and also to propose multidisciplinary approaches to understand landscape dynamics. In fact, trees colonizing sites of geomorphological interest are used for detecting past and present events and tree rings may be considered ecological indicators under different points of view. Arboreal vegetation can register growth disturbances in terms of morphological features, at macro- (particular morphologies of trunks) and micro-scale (annual growth rings, stress indicators like compression wood, traumatic resin ducts), becoming a powerful indicator of the geomorphic activity affecting the landscape. In some cases, combined with other techniques like climate data analysis, they may allow refining the often lacunose historical records of geomorphic events impacting different territories. The integrated analysis carried out in the Loana Valley (Sesia Val Grande UNESCO Geopark, Western Italian Alps), considering a selection of geomorphosites affected by mass wasting processes and snow avalanches and located along a touristic trail, allowed to detect which meteorological thresholds favour hydrogeological instability (i.e. overcome of Mean Annual Rainfall of 6\u201310%). Tree rings data coming from the investigated sites provided information on the recurrence of geomorphic activity, allowing filling gaps within the historical archives, by individuating years during which hydrogeological or snow-related events probably occurred and that were missed (i.e. 1986, 1989, 2001, 2007), and adding details on sites for which temporal constraints had not been found before (i.e. Pizzo Stagno Complex System). Finally, investigated sites demonstrated to differently record the history of instability affecting the area and this difference is mirrored in the sites values that are adopted in the framework of geoheritage analysis (Scientific Value, Ecological Support Role and Educational Exemplarity). The proposed multidisciplinary approach, including geomorphology, dendrogeomorphology and climatology, represents, hence, a useful tool in geoheritage valorisation and management strategies

Planning coastal Mediterranean stone pine (Pinus pinea L.) reforestations as a green infrastructure: combining GIS techniques and statistical analysis to identify management options

Mediterranean stone pine reforestations are common characteristics of the Italian Tyrrhenian coast, which mostly maintain uniform and monolayered stand structures. However, improving structural diversity is an effective climate change adaptation strategy in forest management. The aim of this study was to implement a methodology which allows distinct reforested areas such as a single green infrastructure to be managed according to the surrounding land use and the characteristics of the forest stands. 240 hectares of Mediterranean stone pine forests located along a 16 km strip of the Lazio coast (Central Italy) were mapped. Twelve attributes describing the pine stands and showing possible constraints for future management decisions were associated to each forest patch. A hierarchical cluster analysis was performed to group the pinewood patches according to their similarity level and five different groups were identified. For each group, different silvicultural methods were proposed to guide the compositional and structural evolution of the stands, in order to make them suitable for providing services required locally and increasing overall diversity at landscape scale. The results of the study highlight how coastal land uses can offer effective inputs to differentiate the management of forest systems and therefore achieve greater variety and resilience in the landscape over time. This approach is particularly useful in the case of very homogeneous stands such as the stone pine reforestations under study

Alpine gullies system evolution : erosion drivers and control factors. Two examples from the western Italian Alps

Denudation processes affecting mountain slopes may vary according to different factors (e.g., lithology and structural setting of bedrock, climate, relief features), which may be very diverse at the local scale. Gully complex systems, characterised by morphological features similar to those developing in other climate contexts (i.e., pseudo-badlands) are also becoming common at higher altitudes and latitudes. The selected study cases of Gran Gorgia (Susa Valley) and Saint Nicolas (Aosta Valley), in the Western Italian Alps, are sites of geomorphological interest as they are specifically relevant for their scientific features. The aims of this work are (i) reconstructing the morphometric evolution of gully systems and vegetation colonisation time by means of multitemporal spatial analysis on surface morphological changes under water erosion; (ii) reconstructing in detail, through dendrogeomorphological analysis, the progressive spatial surface denudation and changes in erosion rates, by analysing trees and exposed roots and using different indicators (i.e., compression wood, traumatic resin ducts); (iii) obtaining data on successive aggradation/degradation episodes along slopes surrounding such hotspots through geopedological investigations; and (iv) identifying which control factors exert a predominant role on denudation patterns in such contexts. Multidisciplinary analyses regarding the study sites allowed for detailing of erosional history of the studied slopes detecting the prevailing drivers of their evolution. According to the results and considering the common climate and bedrock conditions, the structural background seems to have more influence on slope evolution at the Saint Nicolas site, while superficial geomorphic processes seem to be more relevant at the Gran Gorgia site. Because the sites have already been recognised as part of geoheritage by local authorities, the data obtained in the present research on their genesis, evolution, and local drivers affecting the rates of denudation (i.e., scientific relevance of the site) suggests that description of the sites for dissemination purposes should include links to the entire slope history

Phycobiliproteins from Arthrospira Platensis (Spirulina): A New Source of Peptides with Dipeptidyl Peptidase-IV Inhibitory Activity

Arthrospira platensis (spirulina) is a cyanobacterium, which contains mainly two phycobiliproteins (PBP), i.e., C-phycocyanin (C-PC) and allophycocyanin (APC). In this study, PBP were hydrolyzed using trypsin, and the composition of the hydrolysate was characterized by HPLC-ESI-MS/MS. Furthermore, the potential anti-diabetic activity was assessed by using either biochemical or cellular techniques. Findings suggest that PBP peptides inhibit DPP-IV activity in vitro with a dose-response trend and an IC50 value falling in the range between 0.5 and 1.0 mg/mL. A lower inhibition of the DPP-IV activity expressed by Caco-2 cells was observed, which was explained by a secondary metabolic degradation exerted by the same cells

An Assessment of Coordinate Rotation Methods in Sonic Anemometer Measurements of Turbulent Fluxes over Complex Mountainous Terrain

The measurement of turbulent fluxes in the atmospheric boundary layer is usually performed using fast anemometers and the Eddy Covariance technique. This method has been applied here and investigated in a complex mountainous terrain. A field campaign has recently been conducted at Alpe Veglia (the Central-Western Italian Alps, 1746 m a.s.l.) where both standard and micrometeorological data were collected. The measured values obtained from an ultrasonic anemometer were analysed using a filtering procedure and three different coordinate rotation procedures: Double (DR), Triple Rotation (TR) and Planar Fit (PF) on moving temporal windows of 30 and 60 min. A quality assessment was performed on the sensible heat and momentum fluxes and the results show that the measured turbulent fluxes at Alpe Veglia were of a medium-high quality level and rarely passed the stationary flow test. A comparison of the three coordinate procedures, using quality assessment and sensible heat flux standard deviations, revealed that DR and TR were comparable, with significant differences, mainly under low-wind conditions. The PF method failed to satisfy the physical requirement for the multiple planarity of the flow, due to the complexity of the mountainous terrain

Modeling host-parasite interaction in chagas disease with murine intestinal organoids

Chagas disease (CD) is a potentially life-threatening illness caused by the parasite Trypanosoma cruzi (T. cruzi). With around seven million people infected worldwide and over 10,000 deaths per year, CD is a major public health issue in Latin America. The main route of transmission to humans is through a triatomine bug (vector-borne) and, to a minor extent, by blood transfusion, organ transplantation, laboratory accidents, congenitally and orally (food-borne). The acute phase of CD presents mild symptoms. If left untreated, it develops into a long-lasting chronic illness, characterized by severely impaired cardiac, digestive, and neurological functions. The intestinal tissue appears to have a key role during oral transmission and chronic infection of CD. In these immune-privileged reservoirs, dormant/quiescent parasites have been suggested to contribute to disease persistence, infection relapse, and treatment failure. However, the interaction between the intestinal epithelium and T. cruzi has not been examined in depth, in part, due to the lack of in vitro models resembling the biological and structural complexity of this organ. Therefore, to understand the pathophysiological role played by the intestinal tissue during transmission and chronic infection, we evaluated the progression of T. cruzi infection of murine colon organoids. In order to model CD, 3D and 2D systems of murine intestinal organoids were infected with T. cruzi Dm28c, a strain that has been associated with high virulence and oral outbreaks. At different time points, the presence and load of parasites in the organoids, as well as the host cell morphology were evaluated by confocal microscopy, and compared to those obtained with a classical infection model (Vero cells). We show that the parasite invades and replicates in intestinal epithelial primary cells grown as intact organoids (3D) and monolayers (2D). The permissiveness to pathogen infection differed markedly between the primary and the tumoral (Vero) cells. So far, this represents the first evidence of the potential of these nearly physiological cellular systems to study host-pathogen interaction for CD and/or for the future evaluation of anti-chagasic drugs.Agencia Nacional de Investigación e Innovación (ANII)FOCEM (MERCOSUR Structural Convergence Fund

Murine colon organoids as a novel model to study Trypanosoma cruzi infection and interactions with the intestinal epithelium

Chagas disease (CD) is a life-threatening illness caused by the parasite Trypanosoma cruzi (T. cruzi). With around seven million people infected worldwide and over 50,000 deaths per year, CD is a major public health issue in Latin America. The main route of transmission to humans is through a triatomine bug (vector-borne), but congenital and oral transmission have also been reported. The acute phase of CD presents mild symptoms but may develop into a long-lasting chronic illness, characterized by severely impaired cardiac, digestive, and neurological functions. The intestinal tissue appears to have a key role during oral transmission and chronic infection of CD. In this immune-privileged reservoir, dormant/quiescent parasites have been suggested to contribute to disease persistence, infection relapse, and treatment failure. However, the interaction between the intestinal epithelium and T. cruzi has not been examined in depth, in part, due to the lack of in vitro models that approximate to the biological and structural complexity of this tissue. Therefore, to understand the role played by the intestinal tissue during transmission and chronic infection, physiological models resembling the organ complexity are needed. Here we addressed this issue by establishing and characterizing adult stem cell-derived colonoid infection models that are clinically relevant for CD. 3D and 2D systems of murine intestinal organoids infected with T. cruzi Dm28c (a highly virulent strain associated with oral outbreaks) were analyzed at different time points by confocal microscopy. T. cruzi was able to invade and replicate in intestinal epithelial primary cells grown as intact organoids (3D) and monolayers (2D). The permissiveness to pathogen infection differed markedly between organoids and cell lines (primate and intestinal human cell lines). So far, this represents the first evidence of the potential that these cellular systems offer for the study of host-pathogen interactions and the discovery of effective anti-chagasic drugs.Agencia Nacional de Investigación e InnovaciónPasteur NetworkFOCEM (MERCOSUR Structural Convergence Fund