A quadratic kernel for computing the hybridization number of multiple trees

It has recently been shown that the NP-hard problem of calculating the minimum number of hybridization events that is needed to explain a set of rooted binary phylogenetic trees by means of a hybridization network is fixed-parameter tractable if an instance of the problem consists of precisely two such trees. In this paper, we show that this problem remains fixed-parameter tractable for an arbitrarily large set of rooted binary phylogenetic trees. In particular, we present a quadratic kernel

Optimizing the internal electric field distribution of alternating current driven organic light-emitting devices for a reduced operating voltage

This work was funded with financial means of the European Social Fund and the Free State of Saxony through the OrthoPhoto project.The influence of the thickness of the insulating layer and the intrinsic organic layer on the driving voltage of p-i-n based alternating current driven organic light-emitting devices (AC-OLEDs) is investigated. A three-capacitor model is employed to predict the basic behavior of the devices, and good agreement with the experimental values is found. The proposed charge regeneration mechanism based on Zener tunneling is studied in terms of field strength across the intrinsic organic layers. A remarkable consistency between the measured field strength at the onset point of light emission (3-3.1 MV/cm) and the theoretically predicted breakdown field strength of around 3 MV/cm is obtained. The latter value represents the field required for Zener tunneling in wide band gap organic materials according to Fowler-Nordheim theory. AC-OLEDs with optimized thickness of the insulating and intrinsic layers show a reduction in the driving voltage required to reach a luminance of 1000 cd/m2 of up to 23% (8.9 V) and a corresponding 20% increase in luminous efficacy.Publisher PDFPeer reviewe

The Seal suite of distributed software for high-throughput sequencing

23-23Pubblicat

A heuristic approach based on Leiden rankings to identify outliers: evidence from Italian universities in the european landscape

We propose an innovative use of the Leiden Rankings (LR) in institutional management. Although LR only consider research output of major universities reported in Web of Science (WOS) and share the limitations of other existing rankings, we show that they can be used as a base of a heuristic approach to identify “outlying” institutions that perform significantly below or above expectations. Our approach is a non-rigorous intuitive method (“heuristic”) because is affected by all the biases due to the technical choices and incompleteness that affect the LR but offers the possibility to discover interesting findings to be systematically verified later. We propose to use LR as a departure base on which to apply statistical analysis and network mapping to identify “outlier” institutions to be analyzed in detail as case studies. Outliers can inform and guide science policies about alternative options. Analyzing the publications of the Politecnico di Bari in more detail, we observe that “small teams” led by young and promising scholars can push the performance of a university up to the top of the LR. As argued by Moed (Applied evaluative informetrics. Springer International Publishing, Berlin, 2017a), supporting “emerging teams”, can provide an alternative to research support policies, adopted to encourage virtuous behaviours and best practices in research. The results obtained by this heuristic approach need further verification and systematic analysis but may stimulate further studies and insights on the topics of university rankings policy, institutional management, dynamics of teams, good research practice and alternative funding methods

Enhanced light emission from top-emitting organic light-emitting diodes by optimizing surface plasmon polariton losses

We demonstrate enhanced light extraction for monochrome top-emitting organic light-emitting diodes (OLEDs). The enhancement by a factor of 1.2 compared to a reference sample is caused by the use of a hole transport layer (HTL) material possessing a low refractive index (1.52). The low refractive index reduces the in-plane wave vector of the surface plasmon polariton (SPP) excited at the interface between the bottom opaque metallic electrode (anode) and the HTL. The shift of the SPP dispersion relation decreases the power dissipated into lost evanescent excitations and thus increases the outcoupling efficiency, although the SPP remains constant in intensity. The proposed method is suitable for emitter materials owning isotropic orientation of the transition dipole moments as well as anisotropic, preferentially horizontal orientation, resulting in comparable enhancement factors. Furthermore, for sufficiently low refractive indices of the HTL material, the SPP can be modeled as a propagating plane wave within other organic materials in the optical microcavity. Thus, by applying further extraction methods, such as micro lenses or Bragg gratings, it would become feasible to obtain even higher enhancements of the light extraction.Comment: 11 pages, 6 figures, will be submitted to PR

Enabling data-intensive biomedical studies

The constantly increasing size and complexity of datasets involved in biomedical projects is deeply transforming approaches to their solution. Large scale studies require specifically designed computational frameworks that are capable of fulfilling many diverse requirements, the most important of which can be summarized in the fundamental properties of scalability, reproducibility and traceability. Although in recent years several new technologies have emerged that help deal with the issues raised by data-intensive research projects, applying them to the construction of a computational solution for the specific problem at hand is far from trivial, as no one-size-fits-all recipe exists for such a task. This work describes a methodology for approaching this new class of studies through several examples of solutions applied to concrete research problems

Strain engineering in Ge/GeSn core/shell nanowires

Strain engineering in Sn-rich group IV semiconductors is a key enabling factor to exploit the direct band gap at mid-infrared wavelengths. Here, we investigate the effect of strain on the growth of GeSn alloys in a Ge/GeSn core/shell nanowire geometry. Incorporation of Sn content in the 10-20 at.% range is achieved with Ge core diameters ranging from 50nm to 100nm. While the smaller cores lead to the formation of a regular and homogeneous GeSn shell, larger cores lead to the formation of multi-faceted sidewalls and broadened segregation domains, inducing the nucleation of defects. This behavior is rationalized in terms of the different residual strain, as obtained by realistic finite element method simulations. The extended analysis of the strain relaxation as a function of core and shell sizes, in comparison with the conventional planar geometry, provides a deeper understanding of the role of strain in the epitaxy of metastable GeSn semiconductors

RO-Crate community update 2024

Here we give an update of the community development and adoption of RO-Crate for FAIR Digital Object since FDO2022. It is notable that programmatic access and more detailed profiles have received high attention, as well as several FDO implementations that use RO-Crate

Black flies (Diptera, Simuliidae) as ecological indicators of stream ecosystem health in an urbanizing area (Rome, Italy)

Introduction. The effectiveness of Simuliidae (Diptera, Nematocera) as indicators of stream health was tested in the urbanizing area of Rome, Central Italy. Methods. 108 sampling sites were investigated in the spring to acquire data on environmental variables and black fly species.Results and discussion.The comparison of sampling and literature data highlighted the disappearance of some species (Simulium reptans, S. vernum, S. liriense), possibly due to water pollution and land use changes. Correspondence analysis confirms altitude as the main factor influencing black fly species’ distribution. However, water quality becomes predominant when considering exclusively plain sites: “ornatum” and “equinum” species groups show the greatest tolerance to chemical pollution. The high course of the Aniene river and its tributaries were sampled bimonthly, confirming the spatial-temporal black fly successions previously observed in central Apennines. The results also indicate that S. ornatum may supplant all other species in areas where the rural use is substituted by urban landscape.Conclusion. In conclusion, black flies can be considered good environmental indicators to assess ecological health of both watercourses and surrounding landscapes