Almost sure existence of global weak solutions for super-critical Navier-Stokes equations

In this paper we show that after suitable data randomization there exists a large set of super-critical periodic initial data, in $H^{-\alpha}({\mathbb T}^d)$ for some $\alpha(d) > 0$, for both 2d and 3d Navier-Stokes equations for which global energy bounds are proved. As a consequence, we obtain almost sure super-critical global weak solutions. We also show that in 2d these global weak solutions are unique.Comment: 22 pages, a revised argument in Section 5, the $d=3$ cas

A pilot project to limit the human impacts on the fragile antarctic biota: Mitigation of a runway through vegetation transplantation

Background: Antarctica is among the world\u2019s last great wildernesses, but the anthropogenic activities and associated infrastructures threaten its fragile biota. We quantify the impact of the construction of a 2200 m long gravel runway airstrip for airfreight operations of the Italian research station on vegetation ecosystems at Boulder Clay (continental Antarctica). We propose a pilot project to mitigate this impact through the transplantation of vegetation from the runway to safe sites. Methods: A vegetation field survey was performed through phytosociological relev\ue9s and vegetation mapping and data were analyzed through multivariate analysis. Results: We quantify the destructive impact of the runway construction on the flora and vegetation of Boulder Clay. Based on vegetation characteristics, 28 priority areas were transplanted from the runway to safe sites, with 89% of survival. Conclusions: To our knowledge, this is the first time that vegetation transplantation was performed in Antarctica to mitigate the consequences of human actions, as formerly it was used only for scientific experiments. This pilot project provides a tool to support management decisions, involving the quantitative evaluation of the infrastructure impacts and showing the suitability of practical mitigation actions. This pilot project proposes a practical tool exportable to all Antarctica and beyond and suggests to link the permissions\u2019 release for the new infrastructures in Antarctica to the realization of specific conservation and mitigation actions

Solar-Powered Rankine Cycle Assisted by an Innovative Calcium Looping Process as an Energy Storage System

Solar energy is an intermittent resource, and thus an energy storage system is required for practical applications of the collected solar irradiance. This work deals with the integration of a thermo-chemical energy storage (TCES) system based on the calcium looping (CaL) process with a concentrated solar tower power (CSP) plant. The objective of this work is the integration of a conventional 320 MWe Rankine cycle with a direct calcination for energy harvesting. Particularly, this work addresses the use of CO2 as the working fluid of a compressed-gas energy storage (CGES) system for hybrid energy storage with the CaL process. The hybrid TC/CG-ES (thermo-chemical/compressed-gas energy storage) system can increase the competitiveness of the CSP with respect to conventional fossil-based power plants leading to a reduction in CO2 emissions. The thermal integration with the calcium looping (CaL) system is optimized by means of the pinch analysis methodology. The obtained results show a reduction in the electrical efficiency of about four percentage points with respect to the conventional Rankine power cycle without the CSP unit: the net electrical efficiency reduces from 43.7% to 39.5% while the global (thermal and electrical) efficiency of the plant reaches the peak value of 51.5% when low enthalpy energy is recovered (e.g., district heating network, district cooling network). This paper highlights the importance of the thermochemical CaO based material. With a conversion of CaO to CaCO3 of 80% the storage efficiency is defined as the ratio of the energy released during the carbonation and the CO2 expansion to the energy collected by the solar field and required during the CO2 compression, which is 87.3%

A Review on CO2 Capture Technologies with Focus on CO2-Enhanced Methane Recovery from Hydrates

Natural gas is considered a helpful transition fuel in order to reduce the greenhouse gas emissions of other conventional power plants burning coal or liquid fossil fuels. Natural Gas Hydrates (NGHs) constitute the largest reservoir of natural gas in the world. Methane contained within the crystalline structure can be replaced by carbon dioxide to enhance gas recovery from hydrates. This technical review presents a techno-economic analysis of the full pathway, which begins with the capture of CO2 from power and process industries and ends with its transportation to a geological sequestration site consisting of clathrate hydrates. Since extracted methane is still rich in CO2, on-site separation is required. Focus is thus placed on membrane-based gas separation technologies widely used for gas purification and CO2 removal from raw natural gas and exhaust gas. Nevertheless, the other carbon capture processes (i.e., oxy-fuel combustion, pre-combustion and post-combustion) are briefly discussed and their carbon capture costs are compared with membrane separation technology. Since a large-scale Carbon Capture and Storage (CCS) facility requires CO2 transportation and storage infrastructure, a technical, cost and safety assessment of CO2 transportation over long distances is carried out. Finally, this paper provides an overview of the storage solutions developed around the world, principally studying the geological NGH formation for CO2 sinks

Salix shrub encroachment along a 1000 m elevation gradient triggers a major ecosystem change in the European Alps

Shrub encroachment, a globally recognized response to climate warming, usually involves late successional species in mountain environments, without alteration to climax communities. We show that a major ecosystem change is occurring in the European Alps across a 1000 m elevation gradient, with pioneer hygrophilous Salix shrubs, previously typical of riparian forests, wetlands and avalanche ravines, encroaching into the climax communities of subalpine and alpine belts shrublands and grasslands, as well as snowbeds, pioneer vegetation and barren grounds in the nival belt. We analyzed Salix recruitment through dendrochronological methods, and assessed its relationships with climate and atmospheric CO2 concentration. The dendrochronological data indicated that Salix encroachment commenced in the 1950s (based on the age of the oldest Salix individuals, recruited in 1957), and that it was correlated with increasing atmospheric CO2 concentration, spring warming and snow cover decrease. Hygrophilous Salix shrubs are expanding their distribution both through range filling and upwards migration, likely achieving competitive replacement of species of subalpine and alpine climax communities. They benefit from climate warming and CO2 fertilization and are not sensitive to spring frost damage and soil limitations, being observed across a gradient of soil conditions from loose glacial sediments in recently deglaciated areas (where soils had not had sufficient time to develop) to mature soils such as podzols (when colonizing late successional subalpine shrublands). Salix encroachment may trigger ecosystem and landscape transformations, promoting the development of forests that replace pre-existing subalpine shrublands, and of open woodlands invading alpine grasslands and snowbeds, making the alpine environment similar to sub-Arctic and Arctic areas. This results in a new threat to the conservation of the plant species, communities and landscapes typical of the alpine biota, as mountain ranges such as the Alps provide limited opportunities for upward migration and range-shift

Effects of 5-year experimental warming in the Alpine belt on soil Archaea: Multi-omics approaches and prospects

We currently lack a predictive understanding of how soil archaeal communities may respond to climate change, particularly in Alpine areas where warming is far exceeding the global average. Here, we characterized the abundance, structure, and function of total (by metagenomics) and active soil archaea (by metatranscriptomics) after 5-year experimental field warming (+1°C) in Italian Alpine grasslands and snowbeds. Our multi-omics approach unveiled an increasing abundance of Archaea during warming in snowbeds, which was negatively correlated with the abundance of fungi (by qPCR) and micronutrients (Ca and Mg), but positively correlated with soil water content. In the snowbeds transcripts, warming resulted in the enrichment of abundances of transcription and nucleotide biosynthesis. Our study provides novel insights into possible changes in soil Archaea composition and function in the climate change scenario

Fine properties of self-similar solutions of the Navier-Stokes equations

We study the solutions of the nonstationary incompressible Navier--Stokes equations in $\R^d$, $d\ge2$, of self-similar form $u(x,t)=\frac{1}{\sqrt t}U\bigl(\frac{x}{\sqrt t}\bigr)$, obtained from small and homogeneous initial data $a(x)$. We construct an explicit asymptotic formula relating the self-similar profile $U(x)$ of the velocity field to its corresponding initial datum $a(x)$

Comparison of endometrial polyp recurrence in fertile women after office hysteroscopic endometrial polypectomy using two widely spread techniques

Aim: To compare the recurrence of benign endometrial polyps after office hysteroscopic polypectomy performed with a bipolar electrode (BE) or a small diameter hysteroscopic tissue removal system (HTRs). Methods: From July 2018 to December 2019 we evaluated the charts of 114 asymptomatic fertile women who underwent office hysteroscopic polypectomy, 1 year before, for a single large benign endometrial polyp (size between 10 and 20 mm) using a 4 mm continuous flow hysteroscope with a BE or a 5 mm HTRs. Patients, divided into two groups according to surgical procedure, each performed exclusively by one expert gynecologist, were scheduled for a 12-month postoperative transvaginal sonography to evaluate the recurrence of endometrial polyps. Results: Forty-eight women of the BE group and 42 of the HTRs group were considered for the 1-year transvaginal sonography follow-up. Five polyps were identified in the BE group and three in the HTRs group (5/48 vs 3/42, P = n.s.). All polyps were removed hysteroscopically (in three out of five and in two out of three cases, respectively, in the same places of the previous polypectomy) and evaluated as ‘benign’ by the pathologist. Conclusion: Office hysteroscopic endometrial polypectomy with small HTRs compared to BE revealed at a 1-year follow-up no difference in terms of complete removal and recurrence of polyps. HTRs polypectomy resulted in less pain and significantly quicker time of procedure compared to BE. This data should be kept in mind for patient comfort any time hysteroscopic polypectomy is planned in an office setting

Ethnic fragmentation and degree of urbanization strongly affect the discrimination power of Y-STR haplotypes in central Sahel

Y chromosome short tandem repeats (Y-STRs) are commonly used to identify male lineages for investigative and judicial purposes and could represent the only source of male-specific genetic information from unbalanced female-male mixtures. The Yfiler Plus multiplex, which includes twenty conventional and seven rapidly-mutating Y-STRs, represents the most discriminating patrilineal system commercially available to date. Over the past five years, this multiplex has been used to analyze several Eurasian populations, with a reported discrimination capacity (DC) approaching or corresponding to the highest possible value. However, despite the inclusion of rapidly mutating Y-STRs, extensive haplotype sharing was still reported for some African populations due to a number of different factors affecting the effective population size. In the present study, we analyzed 27 Y-STRs included in the Yfiler Plus multiplex and 82 Y-SNPs in central Sahel (northern Cameroon and western Chad), an African region characterized by a strong ethnic fragmentation and linguistic diversity. We evaluated the effects of population sub-structuring on genetic diversity by stratifying a sample composed of 431 males according to their ethnicity (44 different ethnic groups) and urbanization degree (four villages and four towns). Overall, we observed a low discrimination capacity (DC = 0.90), with 71 subjects (16.5 %) sharing 27 Y-STR haplotypes. Haplotype sharing was essentially limited to subjects with the same binary haplogroup, coming from the same location and belonging to the same ethnic group. Haplotype sharing was much higher in rural areas (average DC = 0.83) than urban settlements (average DC = 0.96) with a significant correlation between DC and census size (r = 0.89; p = 0.003). Notably, we found that genetic differentiation between villages from the same country (ΦST = 0.14) largely exceeded that found among countries (ΦST = 0.02). These findings have important implications for the choice of the appropriate reference population database to evaluate the statistical relevance of forensic Y-haplotype matches

Viscous-Inviscid Interactions in a Boundary-Layer Flow Induced by a Vortex Array

In this paper we investigate the asymptotic validity of boundary layer theory. For a flow induced by a periodic row of point-vortices, we compare Prandtl's solution to Navier-Stokes solutions at different $Re$ numbers. We show how Prandtl's solution develops a finite time separation singularity. On the other hand Navier-Stokes solution is characterized by the presence of two kinds of viscous-inviscid interactions between the boundary layer and the outer flow. These interactions can be detected by the analysis of the enstrophy and of the pressure gradient on the wall. Moreover we apply the complex singularity tracking method to Prandtl and Navier-Stokes solutions and analyze the previous interactions from a different perspective