Sediment microbial taxonomic and functional diversity in a natural salinity gradient challenge Remane’s “species minimum” concept

Several models have been developed for the description of diversity in estuaries and other brackish habitats, with the most recognized being Remane's Artenminimum (``species minimum'') concept. It was developed for the Baltic Sea, one of the world's largest semi-enclosed brackish water body with a unique permanent salinity gradient, and it argues that taxonomic diversity of macrobenthic organisms is lowest within the horohalinicum (5 to 8 psu). The aim of the present study was to investigate the relationship between salinity and sediment microbial diversity at a freshwater-marine transect in Amvrakikos Gulf (Ionian Sea, Western Greece) and assess whether species composition and community function follow a generalized concept such as Remane's. DNA was extracted from sediment samples from six stations along the aforementioned transect and sequenced for the 16S rRNA gene using high-throughput sequencing. The metabolic functions of the OTUs were predicted and the most abundant metabolic pathways were extracted. Key abiotic variables, i.e., salinity, temperature, chlorophyll-a and oxygen concentration etc., were measured and their relation with diversity and functional patterns was explored. Microbial communities were found to differ in the three habitats examined (river, lagoon and sea) with certain taxonomic groups being more abundant in the freshwater and less in the marine environment, and vice versa. Salinity was the environmental factor with the highest correlation to the microbial community pattern, while oxygen concentration was highly correlated to the metabolic functional pattern. The total number of OTUs showed a negative relationship with increasing salinity, thus the sediment microbial OTUs in this study area do not follow Remane's concept

Pressure screening in the interior of primary shells in double-wall carbon nanotubes

The pressure response of double-wall carbon nanotubes has been investigated by means of Raman spectroscopy up to 10 GPa. The intensity of the radial breathing modes of the outer tubes decreases rapidly but remain observable up to 9 GPa, exhibiting a behavior similar (but less pronounced) to that of single-wall carbon nanotubes, which undergo a shape distortion at higher pressures. In addition, the tangential band of the external tubes broadens and decreases in amplitude. The corresponding Raman features of the internal tubes appear to be considerably less sensitive to pressure. All findings lead to the conclusion that the outer tubes act as a protection shield for the inner tubes whereas the latter increase the structural stability of the outer tubes upon pressure application.Comment: PDF with 15 pages, 3 figures, 1 table; submitted to Physical Review

Metagenomics : tools and insights for analyzing next-generation sequencing data derived from biodiversity studies

Advances in next-generation sequencing (NGS) have allowed significant breakthroughs in microbial ecology studies. This has led to the rapid expansion of research in the field and the establishment of “metagenomics”, often defined as the analysis of DNA from microbial communities in environmental samples without prior need for culturing. Many metagenomics statistical/computational tools and databases have been developed in order to allow the exploitation of the huge influx of data. In this review article, we provide an overview of the sequencing technologies and how they are uniquely suited to various types of metagenomic studies. We focus on the currently available bioinformatics techniques, tools, and methodologies for performing each individual step of a typical metagenomic dataset analysis. We also provide future trends in the field with respect to tools and technologies currently under development. Moreover, we discuss data management, distribution, and integration tools that are capable of performing comparative metagenomic analyses of multiple datasets using well-established databases, as well as commonly used annotation standards

Raman spectra of MgB2 at high pressure and topological electronic transition

Raman spectra of the MgB2 ceramic samples were measured as a function of pressure up to 32 GPa at room temperature. The spectrum at normal conditions contains a very broad peak at ~590 cm-1 related to the E2g phonon mode. The frequency of this mode exhibits a strong linear dependence in the pressure region from 5 to 18 GPa, whereas beyond this region the slope of the pressure-induced frequency shift is reduced by about a factor of two. The pressure dependence of the phonon mode up to ~ 5GPa exhibits a change in the slope as well as a "hysteresis" effect in the frequency vs. pressure behavior. These singularities in the E2g mode behavior under pressure support the suggestion that MgB2 may undergo a pressure-induced topological electronic transition.Comment: 2 figure

Scaling up experimental ocean acidification and warming research: from individuals to the ecosystem

NERC UK Ocean Acidification Research Programme NE/HO1747X/1 The full text is under embargo until 17.08.1

Refugee Mobilities and Institutional Changes: Local Housing Policies and Segregation Processes in Greek Cities

Many studies have explored the dynamics of immigrant and refugee settlement at the local level, highlighting that it is actually a two-way process: On the one hand, the local socio-political context specifies the conditions for refugee inclusion, and on the other, migrant mobility leads to the transformation of localities in various ways. In Greek cities, the social practices of local actors have played an important role in the implementation of the immigration policy, where refugees were perceived as a threat to personal and community security. Yet, new forms of social mobilisation and solidarity by individual citizens and community initiatives have worked to alter these attitudes, mitigating tensions and obstacles in refugee acceptance. The article draws on the Greek experience to explore the role and importance of the local socio-political texture in refugee inclusion, shedding light on how it gave rise to various local initiatives that inform refugee allocation as well as urban transformation and institutional change. In methodological terms, the article considers three neighbouring Greek cities as case studies to identify the different institutional and policy responses to refugee accommodation, giving rise to different paths and forms of social inclusion. The study reveals the complexity and context of the social-spatial diversity that refugees face but also the transformation dynamics of local states and civil society.The paper draws on the Greek experience to explore the role and importance of social infrastructure in refugee integration, shedding light on how these qualities, materialized in local initiatives for refugee integration to influence urban transformation and institutional change. In methodological terms, the paper employs three small and medium-size Greek cities as case studies to identify the different institutional and policy responses to refugee accommodation followed, giving rise to different paths and forms of social inclusion and urban transformation. The study reveals the complexity and the contextuality of the social spatial diversity that refugees face but also the transformation of local states and civil society

11^{11}B NMR study of pure and lightly carbon doped MgB2_2 superconductors

We report a $^{11}$B NMR line shape and spin-lattice relaxation rate ($1/(T_1T)$) study of pure and lightly carbon doped MgB$_{2-x}$C$_{x}$ for $x=0$, 0.02, and 0.04, in the vortex state and in magnetic field of 23.5 kOe. We show that while pure MgB$_2$ exhibits the magnetic field distribution from superposition of the normal and the Abrikosov state, slight replacement of boron with carbon unveils the magnetic field distribution of the pure Abrikosov state. This indicates a considerable increase of $H_{c2}^c$ with carbon doping with respect to pure MgB$_2$. The spin-lattice relaxation rate $1/(T_1T)$ demonstrates clearly the presence of a coherence peak right below $T_c$ in pure MgB$_2$, followed by a typical BCS decrease on cooling. However, at temperatures lower than $\approx 10$K strong deviation from the BCS behavior is observed, probably from residual contribution of the vortex dynamics. In the carbon doped systems both the coherence peak and the BCS temperature dependence of $1/(T_1T)$ weaken, an effect attributed to the gradual shrinking of the $\sigma$ hole cylinders of the Fermi surface with electron doping.Comment: 8 pages, 6 figures, submitted to Phys. Rev.

Urban open spaces as commons: The case of the self-governed Navarinou park

Η διαμόρφωση κοινών στους κενούς, ανοιχτούς, αστικούς χώρους αποτελεί μια καινοτόμο λύση για τη βιώσιμη διαχείρισή τους και την αντιμετώπιση των περιβαλλοντικών, οικονομικών και κοινωνικών προκλήσεων που αντιμετωπίζουν οι πόλεις. Η εργασία εστιάζει στο αυτοδιαχειριζόμενο πάρκο Ναυαρίνου για να συζητήσει το ζήτημα, να αποτιμήσει την εμπειρία του και να προτείνει ενδεχόμενες πολιτικές για επιτυχείς τέτοιες δράσεις. Ειδικότερα υιοθετεί το μεθοδολογικό πλαίσιο SES της Οστρομικής προσέγγισης για να σκιαγραφήσει το Πάρκο ως κοινό και να αναλύσει τα στοιχεία του. Συμπεραίνεται ότι το Πάρκο διαμορφώνει έναν λειτουργικό και αξιόπιστο θεσμό και, ως εκ τούτου, ενδεδειγμένη παρέμβαση αποτελεί η αναγνώριση των συλλογικών δικαιωμάτων και πρακτικών και η διαμόρφωση ενός θεσμικού πλαισίου που να επιτρέπει τέτοια εγχειρήματα να ευδοκιμήσουν.Creating commons in vacant, open, urban spaces constitutes an innovative solution for the sustainable management of these places and the mitigation of the environmental, economic and social burdens that urban dwellers face. The paper uses the self-governed Navarinou park as a case study, in order to discuss the issue, evaluate its experience and propose possible policies for successful such actions. In particular, it employs the SES methodological framework of the Ostromian approach to outline the Park as a commons institution and to explore its variables. It concludes that the Park constitutes a functional and credible institution, and as such an advisable intervention would be the recognition of collective rights and practices alongside the development of a framework that would allow such endeavors to thrive