Phytoplankton pigment analysis by high-performance liquid chromatography (HPLC) is widely used to characterize community composition, support satellite algorithm validation, and advance aquatic biogeochemical research. However, conventional HPLC methods often rely on toxic solvents, require relatively long analysis times, and may have difficulty resolving structurally similar pigments such as mono- and divinyl chlorophylls and xanthophyll isomers. In this study, we developed and validated a novel ultra-high-performance liquid chromatography (UHPLC) method optimized for the separation of ecologically significant phytoplankton pigments. The method used a core-shell C8 column (100 & times; 4.6 mm, 2.6 mu m) maintained at 60 degrees C with a linear gradient of ethanol and solvent B (56 mM tetrabutylammonium hydroxide in water adjusted to pH 7) over 22.5 min, followed by a 3-min hold at 100% ethanol, reducing solvent toxicity while maintaining chromatographic performance. Method development was guided by a Design of Experiments (DoE) approach to optimize the resolution of challenging pigment pairs, such as divinyl/monovinyl chlorophyll a and lutein/zeaxanthin. The final method achieved identification of 33 pigments and showed excellent reproducibility, with retention time variation below 0.6% and a peak area variation below 12%. Validation was performed using pigment standards, laboratory cultures, and natural samples from the northern Adriatic Sea, and by comparison an established validated method, demonstrating robust performance across a wide range of concentrations and matrix complexities. Overall, the study provided a rapid, reproducible, and environmentally safer alternative UHPLC method for phytoplankton pigment analysis in marine research and operational monitoring programs.

This study investigated the succession of prokaryotic and eukaryotic communities on polystyrene panels deployed for 25 weeks in a harbour environment influenced by anthropogenic activities. These activities resulted in an excess of nutrients from sewage and agricultural discharges, as well as the release of hydrocarbons and other pollutants. An eDNA metabarcoding approach targeting the 16S and 18S rRNA genes was used. This innovative methodology allowed a detailed analysis of the community development and succession, providing an in-depth view of biodiversity and ecological dynamics associated with plastic substrates. The microbial biofilm community remained stable throughout the experiment enriched in Rhodobacteraceae (16.97 %) and Flavobacteriaceae (17.99 %). Only minor differences observed between the early and late stages, consistent with their identification as key components of the biofilm. For the eukaryotic community, the early colonization stages were dominated by Alveolata (63.39 %) and Stramenopiles (23.53 %). Later stages showed changes in the community with Chlorophyta (20.14 %) and Opisthokonta (94.32 %) being the most abundant phyla. Richness, as alpha diversity index based on retrieved ASVs, varied from 1875 to 2481 and from 159 to 405 for prokaryotes and eukaryotes, respectively. This indicated an adaptive succession of plastic-associated communities in aquatic ecosystems. Potential plastic-degrading groups found in the prokaryotic community showed a dynamic distribution across colonization stages. Trophic dynamics on plastic debris showed that heterotrophs dominated the eukaryotic community. Our results confirmed the role of plastics as vectors in marine ecosystems, for complex communities composed of bacteria, algae, and invertebrates. This highlighted potential risks to the health of marine ecosystems.

Coastal systems are under increasing threat from human activity and climate-driven disturbances, yet the specific impact of different weather conditions on microbial contamination remains insufficiently resolved. It was hypothesized that precipitation regimes, intensified by climate change, act as primary drivers of fecal microbial pollution and nutrient mobilization in riverine and coastal systems. To test this hypothesis, the Arzilla river (located in the western Adriatic Sea, Italy) and its adjacent coastal waters were investigated using an event-based spatial sampling design. Nutrients and total suspended matter were analysed, and the occurrence of Escherichia coli and intestinal enterococci were examined under contrasting weather conditions (ranging from drought to heavy rainfall). Despite its small size, the Arzilla watershed represents a model of a Mediterranean system where geomorphological, hydrological, and anthropogenic factors converge, making it representative for ecological and management considerations at a larger scale. Rainfall intensity has been demonstrated to exert a significant influence on the expression of microbial responses. An extreme precipitation event with levels in excess of 100 mm, resulted in elevated microbial loads exceeding regulatory thresholds at both river and marine stations. The range of microbial loads at the river stations was from 20 to >30,000 CFU/100 mL, while at the marine stations it was from <10 to >140,000 CFU/100 mL. These findings underscore, the vulnerability of coastal waters to climate change-related disturbances. An increase of nutrients and TSM concentrations during periods of wet conditions was observed, indicating an enhancement in runoff-driven transport. Enterococci exhibited greater persistence and delayed peaks compared to E. coli. The findings of this study provide mechanistic insight into the short-term dynamics linking precipitation regimes, microbial pollution, and nutrient mobilization at the land-sea interface. The findings emphasize the vulnerability of small Mediterranean catchments to climate-driven disturbances and underscore the need to integrate adaptive, event-based monitoring methodologies into European management frameworks.

Mussel farming is a strategic economic activity for several coastal regions, where seawater and mussels are regularly monitored for the presence of the toxic dinoflagellate Dinophysis and associated toxins. This study analysed the ecological dynamics of Dinophysis species assemblages in relation to the toxicity events recorded in mussel farms and environmental variables over the multi-year (1998-2023) continuous observations along the Emilia-Romagna and Marche coasts (northwestern Adriatic Sea). DSP (diarrhetic shellfish poisoning) toxicity events were mainly recorded in autumn and winter and were associated with the abundance of D. caudata, D. fortii and D. tripos species (rs = 0.84, rs = 0.83, and rs = 0.66, respectively, p < 0.05). The Dinophysis species showed a clear seasonality with a succession of D. acuminata, D. sacculus in spring-summer, followed by D. caudata and finally D. fortii and D. tripos in autumn. In addition, each Dinophysis species showed its own optimum temperature for maximum growth. Furthermore, interannual trends showed an increase in Dinophysis spp. absence and a decrease in toxicity in bivalve mussels (5.35 and -3.31 % year-1, respectively), accompanied by a decreasing trend in DIN, phosphate and total phosphorus, and chlorophyll a (-1.97 %, -2.64 %, -3.3 % and -1.73 % year-1, respectively). In 2015 and 2022, prolonged toxicity events occurred when the surface waters were colder and slightly saltier than the long-term average. The data analysis highlighted the importance of the long-term observations for understanding the variability of DSP events and Dinophysis dynamics in relation to the environmental conditions to improve the management of aquaculture activities.

The dynamics of hydrographic and biogeochemical properties in a Northwestern coastal area of the Adriatic Sea were investigated. The time series data from continuous observation (2007-2022) allowed the investigation of annual trends and seasonal cycles along a coastal transect influenced by local river discharge. Various statistical models were used to investigate water temperature, salinity, chlorophyll a, dissolved organic, inorganic and particulate nutrients, precipitation and river discharge. It was found that the local river discharge regime played an essential role in interannual, and seasonal biogeochemical dynamics associated with global climate change in the Mediterranean region. A significant trend towards oligotrophic conditions was detected, as evidenced by the downward trend in the river mouth and on the sea of chlorophyll a (-0.2 μg L-1 in the sea), dissolved organic and inorganic nitrogen and phosphorus (i.e., -0.43 μM yr-1 of DON in the sea and -6.67 of DIN μM yr-1 in the river mouth or -0.07 μM yr-1 of DOP and -0.02 μM yr-1 of DIP in the river mouth) and silicate (-2.47 μM yr-1 in the river mouth) concentrations. Salinity showed a long-term increase in the sea (0.08 yr-1), corresponding to a significant decrease in water discharge from the local river (-0.27 m3 s-1 yr-1) and precipitation (-0.06 mm yr-1). The dissolved organic and inorganic nutrients highlighted a different seasonal accumulation under the river runoff regime. The nutrient enrichment was predominantly driven by river contribution. Data analysis showed that the coastal biogeochemical properties dynamics were mostly influenced by river discharge and precipitation regimes, which in turn are driven by climate change variability in the North- western Adriatic Sea.

Different phytoplankton biomass estimations can provide information about abundance variation, but they are not able to describe the metabolic activity of species or groups within assemblages. Conversely, molecular traits are key for the metabolic dynamics in pelagic ecosystems. To investigate if the RNA/DNA and taxon-specific 18S ribosomal RNA (rRNA)/ribosomal DNA (rDNA) ratios could be used to assess and be indicators of metabolic activity in marine phytoplankton species, two Adriatic diatom species, Chaetoceros socialis and Skeletonema marinoi, were studied. Significant correlations between abundance, chlorophyll a, carbon content and proteins were found in individual and co-cultured growth experiments (from r(s) = 0.570 to r(s) = 0.986, P < 0.001). The biomass trend followed a logistic curve without providing additional information regarding diatom metabolic activity. In both experiments, the RNA/DNA and taxon-specific 18S rRNA/rDNA ratios of C. socialis and S. marinoi showed maximum values at the beginning of the growth phase, i.e as 23.2 +/- 1.5 and 15.3 +/- 0.8, and 16.2 +/- 1.6 and 30.1 +/- 5.4 after 2 and 6 days, respectively, in individual cultures, with a subsequent significant decrease in these values for both species in individual and co-culture experiments. Our results showed that these molecular rRNA/rDNA ratios expressed an activation of metabolism before the abundance increases, even in the presence of interspecific interaction between C. socialis and S. marinoi.

This study is based on assessing fecal indicator bacteria contamination along meteorological, hydrological and physical-chemical variables after high rainy events during the summer period. The study focused on four different coastal sites in the western and eastern Adriatic coast characterized by various geomorphological and hydrological features, levels of urbanization and anthropogenic pressures, with the aim of finding appropriate and effective solutions to ensure the safety and sustainability of tourism and public health. Detailed in-situ survey revealed a wide range of fecal indicator bacterial (FIB) across the different river mouths with concentrations of E. coli ranging from 165 to 6700 CFU 100 mL-1. It was found that nitrogen compounds track microbial load and acted as tracers for fecal contaminants. Further, a modelling tool was also used to analyze the spatial and temporal distribution of fecal pollution at these coastal sites. The integrated monitoring through high frequent survey in river waters and modeling framework allowed for the estimation of fecal indicator bacterial load at the river mouth and examination of fecal pollutant dispersion in recreational waters, considering different scenarios of fecal dispersion along the coast. This study formed the basis of a robust decision support system aimed at improving the management of recreational areas and ensuring the protection of water bodies through efficient management of bathing areas.

The potential of Fe2TiSn full-Heusler compounds for thermoelectric applications has been suggested theoretically, but not yet proven experimentally, due to the difficulty in obtaining reproducible, homogeneous, phase-pure and defect-free samples. In this work, we studied Fe2TiSn1-xSbx polycrystals (x from 0 to 0.6), fabricated by high-frequency melting and long-time high-temperature annealing. We obtained fairly good phase purity, a homogeneous microstructure, and good matrix stoichiometry. Although the intrinsic p-type transport behavior is dominant, n-type charge compensation by Sb-doping is demonstrated. Calculations of the formation energy of defects and electronic properties carried out using the density functional theory formalism reveal that charged iron vacancies VFe2- are the dominant defects responsible for the intrinsic p-type doping of Fe2TiSn under all types of (except Fe-rich) growing conditions. In addition, Sb substitutions at the Sn site give rise either to SbSn, SbSn1+, which are responsible for n-type doping and magnetism (SbSn) or to magnetic SbSn1-, which act as additional p-type dopants. Our experimental data highlight good thermoelectric properties close to room temperature, with Seebeck coefficients up to 56 μV/K in the x = 0.2 sample and power factors up to 4.8 × 10-4 W m-1 K-2 in the x = 0.1 sample. Our calculations indicate the appearance of a pseudogap under Ti-rich conditions and a large Sb-doping level, possibly improving further the thermoelectric properties.

Dynamics of the physical and biogeochemical properties in a temperate coastal area in the north-western Adriatic Sea were analyzed. Multi-year (1997-2019) continuous observations allowed assessing their trends at two sites directly influenced by the discharges of two minor rivers as well as by human activities and climate change. Statistical models were applied to investigate the temporal variability and trends of seawater temperature, salinity, chlorophyll a, nutrients, river discharges and precipitations. The analysis highlighted a role for the minor river inputs and for ecological processes on interannual and seasonal biogeochemical dynamics. We found a significant trend toward more oligotrophic conditions; in particular, chlorophyll a exhibited a long-term decline (-1.38% year(-1) and -1.5% year(-1) at the two Foglia and Metauro river transects, respectively) that was largely determined by low phosphate and nitrate seawater concentrations as a result of a significant reduction in the phosphate and nitrate loadings of the two minor rivers (respectively mean values of-4.65% year(-1) and-2.65% year(-1)). In contrast, salinity showed a long-term decrease of-0.24% year(-1) and-0.19% year(-1) at Foglia and Metauro, respectively, corresponding to a significant increase of the freshwater discharges of the two minor rivers (+1.86% and +1.57% year(-1) at Foglia and Metauro, respectively) possibly due to precipitations. Data analysis highlighted the conditions of temperate coastal areas affected by freshwater discharges. Nutrient load management and climate conditions such as precipitation regimes appear to be the main factors driving physical and biogeochemical dynamics in the north-western Adriatic Sea.

More than 80% of wastewaters are discharged into rivers or seas, with a negative impact on water quality along the coast due to the presence of potential pathogens of faecal origin. Escherichia coli and enterococci are important indicators to assess, monitor, and predict microbial water quality in natural ecosystems. During rainfall events, the amount of wastewater delivered to rivers and coastal systems is increased dramatically. This study implements measures capable of monitoring the pathways of wastewater discharge to rivers and the transport of faecal bacteria to the coastal area during and following extreme rainfall events. Spatio-temporal variability of faecal microorganisms and their relationship with environmental variables and sewage outflow in an area located in the western Adriatic coast (Fano, Italy) was monitored. The daily monitoring during the rainy events was carried out for two summer seasons, for a total of five sampling periods. These results highlight that faecal microbial contaminations were related to rainy events with a high flow of wastewater, with recovery times for the microbiological indicators varying between 24 and 72 h and influenced by a dynamic dispersion. The positive correlation between ammonium and faecal bacteria at the Arzilla River and the consequences in seawater can provide a theoretical basis for controlling ammonium levels in rivers as a proxy to monitor the potential risk of bathing waters pathogen pollution.

Phytoplankton assemblage structure was analyzed based on time series data (2008-2019) together with envi-ronmental variables in two coastal sites in the Northwestern Adriatic Sea. The main component of phytoplankton assemblage was the diatom group. Distinct seasonal and inter annual variations in the presence of taxa were observed within the phytoplankton assemblage over the study period. Mainly four taxa showed a non-random pattern in the binary time series, such as three diatoms Skeletonema marinoi, Thalassionema nitzschioides and Dactyliosolen fragilissimus, and undetermined Dinophyceae. S. marinoi was more frequent in winter and early spring, whereas T. nitzschioides showed an opposite pattern, being more frequent in late spring and summer. In both cases, deviation from randomness was caused by a clear and almost stationary annual cycle. On the con-trary, deviation from randomness depended on the long-term trend of D. fragilissimus time series, as this diatom showed an increasing frequency of occurrence since 2016. A clear phytoplankton assemblage structure affected by seasonal and environmental factors was observed. This was very evident for representative specie (i.e., S. marinoi associated with colder and rich nutrient waters or Heterocapsa niei and T. nitzschioides associated with high temperature and low nutrient conditions) and other species associated with various environmental pa-rameters. Furthermore, the analysis of the association among phytoplankton taxa showed a partial and varied pattern. Our results highlight that phytoplankton time series showed changes in assemblage structure exhibiting a regular 12-month period affected by environmental factors. The long time series observations are important to understand the phytoplankton assemblage structure in relation to environmental changes and human pressures, crucial to achieving the Good Environmental Status in compliance to environmental directives.

Prosthesis-based techniques are the predominant form of breast reconstruction worldwide. The most performed surgical technique involves the placement of the expander in a partial submuscular plane. The coverage of the implant remains a difficult management problem that can lead to complications and poor outcomes. The use of the serratus fascia flap may be the best choice to create a subpectoral pocket for the placement of a tissue expander, with excellent results in terms of morbidity and cost-effectiveness. A total of 20 breast reconstructions with the inferolateral coverage with the serratus fascia were performed. Patients demonstrated a low overall complication rate (9.5%), such as seroma and infection, with complete resolution during the follow-up and no major complications. The US examination of the soft tissues over the implant reported thickness measurements that demonstrated a good coverage over the inferolateral area. Our study shows that using the serratus fascia flap to create a pocket with the pectoralis major for the placement of the tissue expander is an effective technique during two-stage breast reconstruction. The resulting low rate of morbidity and the US findings collected reveal the safety of this procedure. Its success relies on appropriate patient selection and specific intraoperative technique principles.

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.

The RNA/DNA ratio is used as indicator of growth in various marine organisms and to assess physiological status at species or community level. To evaluate the utility of the RNA/DNA ratio as a proxy of phytoplankton primary production, the relationships between phytoplankton RNA/DNA, taxon-specific diatom and dinoflagellate 18S rRNA/rDNA ratios and autotrophic phytoplankton biomass were investigated as a first step. Significant correlations between all phytoplankton ratios and total phytoplankton, diatom and dinoflagellate biomass as chlorophyll a (chl a) and carbon content were found. Diatoms showed higher correlation than dinoflagellates (18S rRNA/rDNA vs. chl a, r(s) = 0.74 and 0.64, P < 0.001; 18S rRNA/rDNA vs. carbon, r(s) = 0.66 and 0.53, P < 0.001, respectively), because they represented the most abundant and frequent group within sampled assemblages. Further, phytoplankton biomass production is known to be linked to protein biosynthesis and significant relationships between RNA/DNA ratios and protein content of phytoplankton assemblage were found (r(s) = 0.62 and 0.52, P < 0.001 for diatom and dinoflagellates, respectively). As taxon-specific RNA/DNA ratios were correlated with biomass and protein content, our results can be regarded as the first step toward further studies on the applicability of RNA/DNA ratios as indicators of growth rate and primary production in phytoplankton assemblages.

The aim of this study is to develop a relocatable modelling system able to describe the microbial contamination that affects the quality of coastal bathing waters. Pollution events are mainly triggered by urban sewer outflows during massive rainy events, with relevant negative consequences on the marine environment and tourism and related activities of coastal towns. A finite element hydrodynamic model was applied to five study areas in the Adriatic Sea, which differ for urban, oceanographic and morphological conditions. With the help of transport-diffusion and microbial decay modules, the distribution of Escherichia coli was investigated during significant events. The numerical investigation was supported by detailed in situ observational datasets. The model results were evaluated against water level, sea temperature, salinity and E. coli concentrations acquired in situ, demonstrating the capacity of the modelling suite in simulating the circulation in the coastal areas of the Adriatic Sea, as well as several main transport and diffusion dynamics, such as riverine and polluted waters dispersion. Moreover, the results of the simulations were used to perform a comparative analysis among the different study sites, demonstrating that dilution and mixing, mostly induced by the tidal action, had a stronger effect on bacteria reduction with respect to microbial decay. Stratification and estuarine dynamics also play an important role in governing microbial concentration. The modelling suite can be used as a beach management tool for improving protection of public health, as required by the EU Bathing Water Directive.

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.

Long-term data series (1971–2015) 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−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−1 decreased between 2006 and 2015. Moreover, we observed a long-term decrease in surface phosphate concentrations in Po River water (−1.34% year−1) and in seawater (in summer −2.56% year−1) coupled, however, to a significant increase in nitrate concentration in seawater (+3.80% year−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 Mimi - 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 ABImirorganization 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. (C) 2019 Elsevier B.V. All rights reserved.

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 "temperature-dependent 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.

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.