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Traditional forms of Crowdsourcing such as open source software development harness crowd contributions to democratize the creation of software. However, potential contributors must first overcome joining barriers forcing casually committed contributors to spend days or weeks onboarding and thereby reducing participation. To more effectively harness potential contributions from the crowd, we propose a method for programming in which work occurs entirely through microtasks, offering contributors short, self-contained tasks such as implementing part of a function or updating a call site invoking a function to match a change made to the function. In microtask programming, microtasks involve changes to a single artifact, are automatically generated as necessary by the system, and nurture quality through iteration. A study examining the feasibility of microtask programming to create small programs found that developers were able to complete 1008 microtasks, onboard and submit their first microtask in less than 15 minutes, complete all types of microtasks in less than 5 minutes on average, and create 490 lines of code and 149 unit tests. The results demonstrate the potential feasibility as well as revealing a number of important challenges to address to successfully scale microtask programming to larger and more complex programs.

Phytoplankton species can produce resting stages that persist in the sediment over long periods and accomplish important ecological functions. With the aim of investigating the phytoplankton assemblage structure in relation to environmental drivers and human pressures, we analyzed resting stages of diatoms and dinoflagellates, including harmful algal bloom taxa, in the surface sediments of 3 Mediterranean regional areas. Abundance of resting stages was determined by molecular quantitative polymerase chain reaction assay. Multivariate data analysis confirmed that the abundance of resting-stage assemblages seemed related to depth. Regional differences in the composition of the resting-stage assemblages were evident and environmental drivers were correlated with those regional differences. Three main groups of samples were defined according to SST and depth thresholds. Samples from the northern and central Adriatic Sea (average SST < 18°C) formed the richest assemblages, both in terms of abundance and species richness, while deep samples from all other basins (depth > 368 m) were poorer and less diverse than those from shallower sites (depth ≤ 368 m). Resting-stage taxa contributed differently to the 3 groups. Diatom spores and dinoflagellate cysts were the most abundant taxa, but Alexandrium minutum cysts and Ditylum brightwellii spores also accounted for a large share of the overall inter-group compositional distance. The structure of resting-stage assemblages can be regarded as a time- and space-integrated response of a subset of phytoplankton species to environmental conditions, including the physical oceanographic dynamics that favor or prevent sedimentation of resting stages.

Many studies have indicated that the response to therapy and the prognostic impact of a pathologic complete response after neoadjuvant treatment differ among breast cancer subtypes. The aim of our study is to evaluate the effect of this treatment on the expression of estrogen and progesterone receptors, human epidermal growth hormone receptor 2 and Ki67 in breast cancer. We identified 125 patients. The estrogen receptor modified its expression from positive to negative in 8% patients and from negative to positive in 22%; progesterone in 21% and in 37% cases. Median Ki-67 value was 20.9% at biopsy and 18% after, HER-2 status did not show a remarkable change before or after neoadjuvant chemotherapy (NACT). We have identified a significant reduction in Ki-67 expression levels after chemotherapy in patients with a pathologic response. Detection of pretreatment Ki-67 could identify patients most likely to benefit from NACT. NACT can change the status of ER, PgR, and Ki-67 expression in patients with breast adenocarcinoma, but it did not exert a significant effect on HER-2 status; HER-2 amplification appears to be more stable. We have identified a prognostic role for a decreased expression of PgR and Ki-67 after preoperative chemotherapy in breast cancer patients.

Paper published as part of the special topic on Electronic Structure Software, ABINIT is probably the first electronic-structure package to have been released under an open-source license about 20 years ago. It implements density functional theory, density-functional perturbation theory (DFPT), many-body perturbation theory (GW approximation and Bethe–Salpeter equation), and more specific or advanced formalisms, such as dynamical mean-field theory (DMFT) and the “temperaturedependent effective potential” approach for anharmonic effects. Relying on planewaves for the representation of wavefunctions, density, and other space-dependent quantities, with pseudopotentials or projector-augmented waves (PAWs), it is well suited for the study of periodic materials, although nanostructures and molecules can be treated with the supercell technique. The present article starts with a brief description of the project, a summary of the theories upon which ABINIT relies, and a list of the associated capabilities. It then focuses on selected capabilities that might not be present in the majority of electronic structure packages either among planewave codes or, in general, treatment of strongly correlated materials using DMFT; materials under finite electric fields; properties at nuclei (electric field gradient, Mössbauer shifts, and orbital magnetization); positron annihilation; Raman intensities and electro-optic effect; and DFPT calculations of response to strain perturbation (elastic constants and piezoelectricity), spatial dispersion (flexoelectricity), electronic mobility, temperature dependence of the gap, and spin-magnetic-field perturbation. The ABINIT DFPT implementation is very general, including systems with van der Waals interaction or with noncollinear magnetism. Community projects are also described: generation of pseudopotential and PAW datasets, high-throughput calculations (databases of phonon band structure, second-harmonic generation, and GW computations of bandgaps), and the library LIBPAW. ABINIT has strong links with many other software projects that are briefly mentioned., This work (A.H.R.) was supported by the DMREF-NSF Grant No. 1434897, National Science Foundation OAC-1740111, and U.S. Department of Energy DE-SC0016176 and DE-SC0019491 projects. N.A.P. and M.J.V. gratefully acknowledge funding from the Belgian Fonds National de la Recherche Scientifique (FNRS) under Grant No. PDR T.1077.15-1/7. M.J.V. also acknowledges a sabbatical “OUT” grant at ICN2 Barcelona as well as ULiège and the Communauté Française de Belgique (Grant No. ARC AIMED G.A. 15/19-09). X.G. and M.J.V. acknowledge funding from the FNRS under Grant No. T.0103.19-ALPS. X.G. and G.-M. R. acknowledge support from the Communauté française de Belgique through the SURFASCOPE Project (No. ARC 19/24-057). X.G. acknowledges the hospitality of the CEA DAM-DIF during the year 2017. G.H. acknowledges support from the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under Contract No. DE-AC02-05-CH11231 (Materials Project Program No. KC23MP). The Belgian authors acknowledge computational resources from supercomputing facilities of the University of Liège, the Consortium des Equipements de Calcul Intensif (Grant No. FRS-FNRS G.A. 2.5020.11), and Zenobe/CENAERO funded by the Walloon Region under Grant No. G.A. 1117545. M.C. and O.G. acknowledge support from the Fonds de Recherche du Québec Nature et Technologie (FRQ-NT), Canada, and the Natural Sciences and Engineering Research Council of Canada (NSERC) under Grant No. RGPIN-2016-06666. The implementation of the libpaw library (M.T., T.R., and D.C.) was supported by the ANR NEWCASTLE project (Grant No. ANR-2010-COSI-005-01) of the French National Research Agency. M.R. and M.S. acknowledge funding from Ministerio de Economia, Industria y Competitividad (MINECO-Spain) (Grants Nos. MAT2016-77100-C2-2-P and SEV-2015-0496) and Generalitat de Catalunya (Grant No. 2017 SGR1506). This work has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation program (Grant Agreement No. 724529). P.G. acknowledges support from FNRS Belgium through PDR (Grant No. HiT4FiT), ULiège and the Communauté française de Belgique through the ARC project AIMED, the EU and FNRS through M.ERA.NET project SIOX, and the European Funds for Regional Developments (FEDER) and the Walloon Region in the framework of the operational program “Wallonie-2020.EU” through the project Multifunctional thin films/LoCoTED. The Flatiron Institute is a division of the Simons Foundation. A large part of the data presented in this paper is available directly from the Abinit Web page www.abinit.org. Any other data not appearing in this web page can be provided by the corresponding author upon reasonable request.

Long-term data series (1971&ndash, 2015) of physical and biogeochemical parameters were analyzed in order to assess trends and variability of oceanographic conditions in the northern Adriatic Sea (NAS), a mid-latitude shallow continental shelf strongly impacted by river discharges, human activities and climate changes. Interpolation maps and statistical models were applied to investigate seasonal and spatial variability, as well as decadal trends of temperature, salinity, chlorophyll-a and nutrients. This analysis shows that sea surface temperature increased by +0.36% year&minus, 1 over four decades. Annual mean flow of the Po River markedly changed due to the occurrence of periods of persistent drought, whereas the frequency of flow rates higher than 3000 m3 s&minus, 1 decreased between 2006 and 2015. Moreover, we observed a long-term decrease in surface phosphate concentrations in Po River water (&minus, 1.34% year&minus, 1) and in seawater (in summer &minus, 2.56% year&minus, 1) coupled, however, to a significant increase in nitrate concentration in seawater (+3.80% year&minus, 1) in almost all seasons. These changes indicate that the nutrient concentrations in the NAS have been largely modulated, in the last forty years, by the evolution of environmental management practices and of the runoff. This implies that further alteration of the marine environment must be expected as a consequence of the climate changes.

Abinit is a material- and nanostructure-oriented package that implements density-functional theory (DFT) and many-body perturbation theory (MBPT) to find, from first principles, numerous properties including total energy, electronic structure, vibrational and thermodynamic properties, different dielectric and non-linear optical properties, and related spectra. In the special issue to celebrate the 40th anniversary of CPC, published in 2009, a detailed account of Abinit was included [Gonze et al. (2009)], and has been amply cited. The present article comes as a follow-up to this 2009 publication. It includes an analysis of the impact that Abinit has had, through for example the bibliometric indicators of the 2009 publication. Links with several other computational materials science projects are described. This article also covers the new capabilities of Abinit that have been implemented during the last three years, complementing a recent update of the 2009 article published in 2016. Physical and technical developments inside the abinit application are covered, as well as developments provided with the Abinit package, such as the multibinit and a-tdep projects, and related Abinit organization developments such as AbiPy . The new developments are described with relevant references, input variables, tests, and tutorials. Program summary Program Title: Abinit Program Files doi: http://dx.doi.org/10.17632/csvdrr4d68.1 Licensing provisions: GPLv3 Programming language: Fortran2003, Python Journal reference of previous version: X .Gonze et al, Comput. Phys. Commun. 205 (2016) 106–131 Does the new version supersede the previous version?: Yes. The present 8.10.3 version is now the up-to-date stable version of abinit , and supercedes the 7.10.5 version. Reasons for the new version: New developments Summary of revisions: • Many new capabilities of the main abinit application, related to density-functional theory, density-functional perturbation theory, GW, the Bethe-Salpeter equation, dynamical mean-field theory, etc. • New applications in the package: multibinit (second-principles calculations)and tdep (temperature-dependent properties) Nature of problem: Computing accurately material and nanostructure properties: electronic structure, bond lengths, bond angles, primitive cell, cohesive energy, dielectric properties, vibrational properties, elastic properties, optical properties, magnetic properties, non-linear couplings, electronic and vibrational lifetimes, etc. For large-scale systems, second-principles calculations, building upon the first-principles results, are also possible. Solution method: Software application based on density-functional theory and many-body perturbation theory, pseudopotentials, with plane waves or wavelets as basis functions. Different real-time algorithms are implemented for second-principles calculations.

In the Adriatic Sea, massive rainfall events are causing flooding of rivers and streams, with severe consequences on the environment. The consequent bacterial contamination of bathing water poses public health risks besides damaging tourism and the economy. This study was conducted in the framework of WATERCARE, an EU Interreg Italy-Croatia Project, which aims at reducing the impact of microbial contamination on Adriatic bathing water due to heavy rainfall events drained in the local sewage network and; enhancing the quality of local waters; and providing support for the decision-making processes regarding the management of bathing water in line with EU regulations. The study involved the development of an innovative water quality integrated system that helps meet these objectives. It consists of four components: a real time hydro-meteorological monitoring system; an autosampler to collect freshwater samples during and after significant rainfall events; a forecast system to simulate the dispersion of pollutants in seawater; and a real-time alert system that can predict the potential ecological risk from the microbial contamination of seawater. The system was developed and tested at a pilot site (Fano, Italy). These preliminary results will be used to develop guidelines for urban wastewater and coastal system quality assessments to contribute to develop policy actions and final governance decisions.

We extend the density functional perturbation theory formalism to the case of non-collinear magnetism. The main problem comes with the exchange-correlation (XC) potential derivatives, which are the only ones that are affected by the non-collinearity of the system. Most of the present XC functionals are constructed at the collinear level, such that the off-diagonal (containing magnetization densities along $x$ and $y$ directions) derivatives cannot be calculated simply in the non-collinear framework. To solve this problem, we consider here possibilities to transform the non-collinear XC derivatives to a local collinear basis, where the $z$ axis is aligned with the local magnetization at each point. The two methods we explore are i) expanding the spin rotation matrix as a Taylor series, ii) evaluating explicitly the XC for the local density approximation through an analytical expression of the expansion terms. We compare the two methods and describe their practical implementation. We show their application for atomic displacement and electric field perturbations at the second order, within the norm-conserving pseudopotential methods.

The aim of this study was to monitor for the first time the oligosaccharide pattern in the northwestern Adriatic Sea. Oligosaccharides are components of the low-molecular-weight fraction of dissolved organic matter (DOM). They perform an important ecological function in the microbial loop prompting substrates for bacterial degradation. In particular, our investigation focused on maltooligosaccharides (glucose α 1–4 linked). The analyses were carried out using a dialysis-charcoal column sorption pre-concentration method, followed by liquid chromatography-tandem mass spectrometry analyses with a triple quadrupole mass spectrometer operating in multiple reaction monitoring mode. During the study period, the concentration of maltooligosaccharides with a low degree of polymerisation (ranging from maltose to maltotetraose) was higher than other maltooligosaccharides (maltopentaose and maltoeptaose) and all together they reached their highest concentration in June. This concentration was temporally shift...

According to theoretical predictions [Phys. Rev. Lett. 114, 136601 (2015)], Sb substitution in $\mathrm{F}{\mathrm{e}}_{2}\mathrm{TiSn}$ full-Heusler compounds is thought to enhance the $n$-type thermoelectric power factors. We prepare $\mathrm{F}{\mathrm{e}}_{2}\mathrm{TiSn}$ samples with 0%, 10%, and 20% Sb substitution on the Sn site and study the effects of the heat treatment protocol and of Sb substitution by structural characterization, electrical, thermoelectrical, and thermal transport measurements from room temperature down to 10 K, and by comparison with ab initio calculations. For the undoped $\mathrm{F}{\mathrm{e}}_{2}\mathrm{TiSn}$ phase, we find a bad metallic gapless transport behavior in the as-cast sample and a small gap semiconducting behavior for the annealed samples. These observations, together with the $p$-type character emerging from the Hall effect and Seebeck effect, are explained by ab initio calculations, provided that antisite disorder and vacancy defects are included. In these undoped $\mathrm{F}{\mathrm{e}}_{2}\mathrm{TiSn}$ samples, we find that increasing thermal annealing temperature up to 800 \ifmmode^\circ\else\textdegree\fi{}C slightly decreases the carrier concentration, enhances the Seebeck coefficient in the low-temperature regime (below 100--200 K), induces magnetic ordering at low temperature $(l150\phantom{\rule{0.16em}{0ex}}\mathrm{K})$, and improves the thermoelectric figure of merit and power factor in the low-temperature regime (below \ensuremath{\sim}200 K). As for Sb substitution, we find that 10% substitution increases hole carrier concentration and induces a weakly metallic behavior as compared to the semiconducting behavior of the corresponding undoped annealed samples. On the other hand, 20% substitution lowers the carrier density and increases the resistivity by a factor \ensuremath{\sim}50, with semiconducting behavior measured in the whole temperature range. We interpret the observed effect of Sb doping as a complement to disorder. Indeed, using first-principles techniques we unearth the experimental signature related to density of states features induced by native impurities in the realized samples. The Seebeck coefficient exhibits a maximum at around 200--250 K for the undoped and 20%-doped samples, as typical of semiconducting compounds, while it increases monotonically with temperature for the metallic 10%-doped sample. The latter behavior, joined with the good electrical properties of the 10% sample, determines the room-temperature power factor of $\ensuremath{\sim}1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\phantom{\rule{0.16em}{0ex}}\mathrm{W}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}2}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}1}$ in the 10% Sb-doped sample, more than twice as much as to the value of the undoped sample.

This article examines the transformation process undergone by the electrical system in the Paraíba Valley in the state of São Paulo and discusses the possibilities for developing the cities located along the transmission lines between the metropolises of Rio de Janeiro and São Paulo. From the 1930s to the 1950s, the Paraíba Valley went from a region whose electrical sector was fragmented and run by municipal enterprises, to one with an electrical system connected to the system of the Light company, and, finally, from the 1960s, the region began to receive its electricity from state companies. This study traces the trajectory of the electricity sector in this region and examines the relationship between this sector and economic development., El presente artículo pretende comprender el proceso de transformación delsistema eléctrico del Valle del Paraíba paulista, discutiendo las posibilidades dedesarrollo de las ciudades que se encontraban en la conexión entre las urbes deRío de Janeiro y São Paulo. En los años transcurridos entre las décadas de 1930y 1950, el Valle del Paraíba pasó de ser una región cuyo sector eléctrico estabafragmentado y organizado por medio de empresas municipales a integrarse alsistema interconectado de Light, para, finalmente, pasar a recibir energía decompañías estatales en la década de 1960. Este artículo pretende recuperar latrayectoria del sector eléctrico en la región, estableciendo una relación entreel sector eléctrico y el desarrollo económico.

In the northern Adriatic Sea, Mediterranean Sea, the mucilage phenomenon is usually related to the aggregation of extracellular organic matter of phytoplanktonic origin under special seasonal and trophic conditions. Environmental factors, such as temperature, salinity, nitrogen, phosphorus and N/P ratio as well as polysaccharide and monosaccharide levels in the presence and absence of mucilage were investigated in the northern Adriatic Sea. Variations in temperature and salinity during spring in years characterised by mucilage events have been recognised having an important role in preparing a favourable physical environment where mucilage formation could take place. Since the DIN/TP ratio increased markedly during the spring months (March–April) in 2002, 2003 and 2004, preceding the early summer mucilage outbreaks, it appeared that the DIN/TP ratio may be a more robust predictor than the DIN/DIP ratio, which, although more commonly used, exhibited a discontinuous trend. The contents of total carbohydrate...

A agricultura familiar brasileira, nos últimos anos, passou a ter um maior destaque com a criação de várias políticas públicas voltadas especificamente a esse setor. Neste artigo, destacamos o Programa de Aquisição de Alimentos - PAA. Por meio desse programa, o Governo Federal passou a adquirir produtos diretamente dos agricultores familiares. O presente estudo teve como objetivo identificar os recursos financeiros aplicados e as modalidades do programa mais utilizadas nos estados de Rondônia e Acre, no período de 2003 a 2008, comparando com os recursos financeiros aplicados e as modalidades utilizadas pelo PAA. A metodologia utilizada foi a bibliográfica documental, realizada por meio de um levantamento documental dos registros feitos pelos órgãos que operacionalizam o programa, com análise qualiquantitativa dos dados. Os resultados demonstram que, apesar do aumento quantitativo de recursos e no número de agricultores familiares beneficiados, os recursos direcionados para os estados de Rondônia e Acre, comparados com os demais estados e regiões do país, foram proporcionalmente baixos ou aquém da necessidade, considerando as características da agricultura familiar dos dois Estados.

The influence of inhomogeneity on magnetic materials is considered; in particular, we examine how it affects the magneto-optical (MO) response of films and multilayers. From ab initio calculations of the band structure, the optical conductivity tensor is derived, providing the basis for computing the MO spectra. The presence of magnetic nanoprecipitates is taken into account by modeling the system as an effective medium or as an infinitely thin layered structure. A possible depth concentration distribution of the magnetic species is also accounted for, by considering the structure as a sequence of layers. This formalism is applied to some real systems constituted by magnetic particles dispersed in a hosting nonmagnetic matrix. The agreement between theoretical and measured MO Kerr effect spectra supports the validity of the model and establishes its predictive power, suggesting that the analysis of experimental MO spectra can provide information not only on the magnetic, but also on the structural properties of heterogeneous magnetic systems.

The dinoflagellate Alexandrium minutum is known for the production of potent neurotoxins affecting the health of human seafood consumers via paralytic shellfish poisoning (PSP). The aim of this study was to investigate the relationship between the toxin content and the expression level of the genes involved in paralytic shellfish toxin (PST) production. The algal cultures were grown both in standard f/2 medium and in phosphorus/nitrogen limitation. In our study, LC-HRMS analyses of PST profile and content in different Mediterranean A. minutum strains confirmed that this species was able to synthesize mainly the saxitoxin analogues Gonyautoxin-1 (GTX1) and Gonyautoxin-4 (GTX4). The average cellular toxin content varied among different strains, and between growth phases, highlighting a decreasing trend from exponential to stationary phase in all culture conditions tested. The absolute quantities of intracellular sxtA1 and sxtG mRNA were not correlated with the amount of intracellular toxins in the analysed A. minutum suggesting that the production of toxins may be regulated by post-transcriptional mechanisms and/or by the concerted actions of alternative genes belonging to the PST biosynthesis gene cluster. Therefore, it is likely that the sxtA1 and sxtG gene expression could not reflect the PST accumulation in the Mediterranean A. minutum populations under the examined standard and nutrient limiting conditions.

The project LODZ (Linked Open Data Zurich) adopts an experimental approach to merge data and develop a semantic web infrastructure to enable its discovery. For this purpose, three institutions in the field of art and design provided their metadata. The project cycle followed six steps: team building, gathering and cleaning of the original data, modelling, transforming, interlinking and exploration of the Linked Data set. The resulting pilot application offers innovative and attractive features based on the capability of the Linked Data, with the aim to provide a better user experience.The major challenge of this project was the creation of links between the internal datasets, and with external sources. An important lesson learnt is therefore to focus more on the interoperability of data at the time of cataloguing in the original databases, for example by integrating external identifiers rather than just terms in the form of strings.

The amazing possibility of magnetoelectric crystals to cross couple electric and magnetic properties without the need of time-dependent Maxwell's equations has attracted a lot of interest in material science. This enthusiasm has re-emerged during the last decade where magnetoelectric and multiferroic crystals have captivated a tremendous number of studies, mostly driven by the quest of low-power-consumption spintronic devices. While several new candidates have been discovered, the desirable magnetoelectric coupling at room temperature is still sparse and calls for new promising candidates. Here, we show from first-principles studies that the troilite phase of the iron sulfide based compounds, one of the most common mineral of Earth, Moon, Mars or meteors, is magnetoelectric up to temperatures as high as 415 K.

The mucilage phenomenon, a sporadic but massive accumulation of gelatinous material, can cause serious damage to the tourism and fishing industries along the Adriatic coast. Mucilage is presently thought to be the result of the aggregation of dissolved organic matter (DOM) into particulate organic matter (POM). Three principal classes of compounds have been identified in organic matter by spectrometric determination: carbohydrates, proteins and lipids. Carbohydrates are suspected to play a role in the first steps of DOM aggregation. Despite its importance in understanding the processes leading to mucilage formation, our present knowledge of the composition of the mucilage carbohydrate fraction is incomplete. Due to its high sensitivity and specificity, liquid chromatography coupled with electrospray-ionization tandem mass spectrometry (LC–ESIMS/MS) is gaining an increasing importance as a powerful technique for carbohydrate purification and characterization in complex samples. In this work, LC–ESIMS/MS is proposed as a useful method for the investigation of the oligosaccharide content in mucilage samples. The approach was applied using 3–7 unit maltooligosaccharides as reference compounds. The composition of the investigated mucilage sample was further investigated combining LC–ESIMS/MS with classic approaches, such as spectroscopic techniques and liquid chromatography coupled with the refractory index LC–RI.

Programming work is inherently interdependent, requiring developers to share and coordinate decisions that crosscut the structure of code. This is particularly challenging for programming in a microtasking context, in which developers are assumed to be transient and thus cannot rely on traditional learning and coordination mechanisms such as an extended onboarding process and code ownership. In this paper, we explore scaffolding coordination and knowledge sharing through a question and answer system, structuring project knowledge and coordination into questions and answers. To investigate its potential for enabling coordination in a microtask setting, we implemented a Q&A system for microtask programming work and conducted a user study where a crowd used it to coordinate their work on a software project over a 30-hour period. The results reveal both the potential for the use of Q&A systems for within project coordination and challenges that this approach brings.

The effects of hydrostatic pressure and partial Na substitution on the normal-state properties and the superconducting transition temperature $({T}_{c})$ of ${\mathrm{K}}_{1\text{\ensuremath{-}}x}{\mathrm{Na}}_{x}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ single crystals were investigated. It was found that a partial Na substitution leads to a deviation from the standard ${T}^{2}$ Fermi-liquid behavior in the temperature dependence of the normal-state resistivity. It was demonstrated that non-Fermi-liquid like behavior of the resistivity for ${\mathrm{K}}_{1\text{\ensuremath{-}}x}{\mathrm{Na}}_{x}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ and some ${\mathrm{KFe}}_{2}{\mathrm{As}}_{2}$ samples can be explained by a disorder effect in the multiband system with rather different quasiparticle effective masses. Concerning the superconducting state our data support the presence of a shallow minimum around 2 GPa in the pressure dependence of ${T}_{c}$ for stoichiometric ${\mathrm{KFe}}_{2}{\mathrm{As}}_{2}$. The analysis of ${T}_{c}$ in ${\mathrm{K}}_{1\text{\ensuremath{-}}x}{\mathrm{Na}}_{x}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ at pressures below 1.5 GPa showed that the reduction of ${T}_{c}$ with Na substitution follows the Abrikosov-Gor'kov law with the critical temperature ${T}_{c0}$ of the clean system (without pair breaking), which linearly depends on the pressure. Our observations also suggest that ${T}_{c}$ of ${\mathrm{K}}_{1\text{\ensuremath{-}}x}{\mathrm{Na}}_{x}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ is nearly independent of the lattice compression produced by the Na substitution. Further, we theoretically analyzed the behavior of the band structure under pressure within the generalized gradient approximation (GGA). A qualitative agreement between the calculated and the recently measured---in de Haas--van Alphen experiments [T. Terashima et al., Phys. Rev. B 89, 134520 (2014)]---pressure dependencies of the Fermi-surface cross sections has been found. These calculations also indicate that the observed minimum around 2 GPa in the pressure dependence of ${T}_{c}$ may occur without a change of the pairing symmetry.

The successful fabrication of one monolayer FeSe on SrTiO$_{3}$ represented a real breakthrough in searching for high-T$_{c}$ Fe-based superconductors (Ref. 1). Motivated by this important discovery, we studied the effects of tensile strain on one monolayer and bulk iron-chalcogenide superconductors (FeSe and FeTe), showing that it produces important magnetic and electronic changes in the systems. We found that the magnetic ground state of bulk and monolayer FeSe is the block-checkerboard phase, which turns into the collinear stripe phase under in plane tensile strain. FeTe, in both bulk and monolayer phases, shows two magnetic transitions upon increasing the tensile strain: from bicollinear in the ground state to block-checkerboard ending up to the collinear antiferromagnetic phase which could bring it in the superconducting state. Finally, the study of the mechanical properties of both FeSe and FeTe monolayers reveals their enormous tensile strain limits and opens the possibility to grow them on different substrates., Comment: http://iopscience.iop.org/2053-1583/2/1/015001

Neutron diffraction data on liquid H2S, D2S and an equimolar mixture of the two are presented for two thermodynamic states along the liquid—vapour coexistence curve. Comparison of the site-site radial distribution functions obtained with those of a model fluid where orientational correlations are absent and with those of water demonstrates that, although hydrogen sulphide does not form hydrogen bonds, nevertheless weak orientational correlations between first neighbouring molecules are detectable in both thermodynamic states. An analysis of the molecular configurations compatible with the experimental data, as calculated by applying the empirical potential structural refinement, is presented also.

Latent Semantic Indexing (LSI) is an advanced method widely and successfully employed in Information Retrieval (IR). It is an extension of Vector Space Model (VSM) and it is able to overcome VSM in canonical IR scenarios where it is used on very large document repositories. LSI has also been used to semi-automatically generate traceability links between software artefacts. However, in such a scenario LSI is not able to overcome VSM. This contradicting result is probably due to the different characteristics of software artefact repositories as compared to document repositories. In this paper we present a preliminary empirical study to analyze how the size and the vocabulary of the repository-in terms of number of documents and terms (i.e., the vocabulary)-affects the retrieval accuracy. Even if replications are needed to generalize our findings, the study presented in this paper provides some insights that might be used as guidelines for selecting the more adequate methods to be used for traceability recovery depending on the particular application context.