SMT-Based Refutation of Spurious Bug Reports in the Clang Static Analyzer

We describe and evaluate a bug refutation extension for the Clang Static Analyzer (CSA) that addresses the limitations of the existing built-in constraint solver. In particular, we complement CSA's existing heuristics that remove spurious bug reports. We encode the path constraints produced by CSA as Satisfiability Modulo Theories (SMT) problems, use SMT solvers to precisely check them for satisfiability, and remove bug reports whose associated path constraints are unsatisfiable. Our refutation extension refutes spurious bug reports in 8 out of 12 widely used open-source applications; on average, it refutes ca. 7% of all bug reports, and never refutes any true bug report. It incurs only negligible performance overheads, and on average adds 1.2% to the runtime of the full Clang/LLVM toolchain. A demonstration is available at {\tt https://www.youtube.com/watch?v=ylW5iRYNsGA}.Comment: 4 page

Solution of a Puzzle: High-Level Quantum-Chemical Treatment of Pseudocontact Chemical Shifts Confirms Classic Semiempirical Theory

A recently popularized approach for the calculation of pseudocontact shifts (PCSs) based on first-principles quantum chemistry (QC) leads to different results than the classic “semiempirical” equation involving the susceptibility tensor. Studies that attempted a comparison of theory and experiment led to conflicting conclusions with respect to the preferred theoretical approach. In this Letter, we show that after inclusion of previously neglected terms in the full Hamiltonian, one can deduce the semiempirical equations from a rigorous QC-based treatment. It also turns out that in the long-distance limit, one can approximate the complete A tensor in terms of the g tensor. By means of Kohn–Sham density functional theory calculations, we numerically confirm the long-distance expression for the A tensor and the theoretically predicted scaling behavior of the different terms. Our derivation suggests a computational strategy in which one calculates the susceptibility tensor and inserts it into the classic equation for the PCS

Where does the forest come back from? Soil and litter seed banks and juvenile bank as sources of vegetation resilience in the face of land-use change in a semiarid Neotropical forest

The existence of reservoirs from which dominant species could recruit after disturbance is considered a key factor in ecosystem resilience. The literature on the role of soil seed banks in community regeneration is vast for sub-humid Holarctic systems, but much scarcer for semiarid Neotropical ones. Additionally, litter seed banks and juvenile plant banks have been scarcely studied worldwide. In this study, we aimed to analyze the different reservoirs from where dominant woody species regenerate from in the semiarid Neotropical Chaco forest of Córdoba, Argentina, and, whether the soil and litter seed banks, and the juvenile bank are effective sources of resilience of these forests in the face of different land use regimes. We selected four ecosystem types subjected to increasing long-term land-use intensity: primary forest (with no land use in the last 50 yr), secondary forest (with low land use intensity), closed species-rich shrubland (with moderate land use intensity), and open shrubland (with high land use intensity). We monitored four sites per ecosystem type. At each site we recorded the % cover of adults and the number of juveniles (saplings and seedlings) of all woody species. Additionally, we collected litter and soil samples that were then processed in the lab for taxonomic identification and germinability of seeds. We compared the species composition of the soil, litter and juvenile banks ("reservoirs") with that of the established vegetation within each ecosystem type. We also compared the reservoirs from different ecosystem types with the established vegetation of the primary forest, considered as the reference ecosystem. Woody species were absent from the soil seed bank, but were very well represented in the litter seed bank and juvenile bank from different ecosystem types. These two reservoirs showed high similarity with the established vegetation within each ecosystem type. However, increasing land use intensity decreased similarity between the reservoirs from each of the three ecosystem types subjected to land use and the established vegetation of the primary forest. Litter seed and juvenile banks, but not the soil seed bank are the main reservoirs of dominant woody species in the Chaco forest. However, the ability of these reservoirs to act as sources of resilience decreases as land use intensifies.Fil: Lipoma, Maria Lucrecia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Fortunato, Valentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; ArgentinaFil: Enrico, Lucas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina62nd Annual Symposium of the International Association for Vegetation ScienceBremenAlemaniaInternational Association for Vegetation Scienc

Theoretical analysis of the long-distance limit of NMR chemical shieldings

After some years of controversy, it was recently demonstrated how to obtain the correct long-distance limit [point-dipole approximation (PDA)] of pseudo-contact nuclear magnetic resonance chemical shifts from rigorous first-principles quantum mechanics [Lang et al., J. Phys. Chem. Lett. 11, 8735 (2020)]. This result confirmed the classical Kurland–McGarvey theory. In the present contribution, we elaborate on these results. In particular, we provide a detailed derivation of the PDA both from the Van den Heuvel–Soncini equation for the chemical shielding tensor and from a spin Hamiltonian approximation. Furthermore, we discuss in detail the PDA within the approximate density functional theory and Hartree–Fock theories. In our previous work, we assumed a relatively crude effective nuclear charge approximation for the spin–orbit coupling operator. Here, we overcome this assumption by demonstrating that the derivation is also possible within the fully relativistic Dirac equation and even without the assumption of a specific form for the Hamiltonian. Crucial ingredients for the general derivation are a Hamiltonian that respects gauge invariance, the multipolar gauge, and functional derivatives of the Hamiltonian, where it is possible to identify the first functional derivative with the electron number current density operator. The present work forms an important foundation for future extensions of the Kurland–McGarvey theory beyond the PDA, including induced magnetic quadrupole and higher moments to describe the magnetic hyperfine field

STRONG POROUS GLASS-CERAMICS FROM ALKALI ACTIVATION AND SINTER-CRYSTALLIZATION OF VITRIFIED MSWI BOTTOM ASH

Vitrification of municipal solid waste incineration (MSWI) bottom ash is an effective method to produce a chemically stable glass, with metal recovery. In order to justify the high costs of this process, the vitrified residue can then be upcycled into potential marketable products. In this study, vitrified bottom ash was successfully converted into strong and chemically stable porous glass-ceramics by the combination of alkali activation and sintering. After the activation of the glass in a NaOH solution of low molarity, foams were easily produced by intensive mechanical stirring, with the aid of a surfactant, and stabilized by gelation. The obtained open-celled material was further consolidated by a sintering treatment, at 800-900\ub0C. The addition of recycled soda-lime glass allowed activation at low molarity and sintering at lower temperature, but it reduced the mechanical properties and the stabilization of heavy metals. On the other hand, the increase in molarity of the alkaline solution increased the porosity and also the strength of foams from vitrified bottom ash

Continuum versus discrete approach in modeling of wear processes

Wear of materials is a very complex phenomenon due to its tight correlation with all the other phenomena that take place at the interface of two bodies interacting with one another, like friction, contact and lubrication. When two opposing surfaces slide on one another, their asperities come into contact first, adhering and deforming (both elastically and plastically), finally separating again by brittle fracture, ductile fracture, or just by local transfer of atoms from one surface to the other. It is evident, as the process is highly non linear and multi-scale in nature, that quantifying all these aspects is a challenge, whether the approach is experimental, numerical or analytical. Consequently, hundreds of equations have been developed based on experimental fits [1], but none reaches the simplicity of Archard's wear law to quantify the wear volume [2]. When it comes to numerical simulations in solid mechanics, a body undergoing wear can be represented either as a continuum or as an ensemble of discrete particles. The aim of this pair presentation is to explain the advantages and disadvantages of the two approaches, and how they can be combined for scale-bridging. From a discrete perspective, atomistic simulations have been used to analyze what happens on the surface of bodies, with a focus at the micro-scale where wear mechanisms have been investigated since a few decades [3]. One of the advantages of this method, that is modeling the material behaviour at the detail of its micro-structure, is also its curse: systems at the engineering scale cannot be modeled yet because of the huge computational cost. Nonetheless, a recent important breakthrough in the field of wear was possible thanks to a particular atomistic approach [4] and showed that this approach can bring significant and fundamental insights in the understanding of the physics of wear. The continuum scale allows the simulation of several orders of magnitude in surface roughness, bringing simulation tools closer to the engineering scale, especially with boundary element methods [5], which offer unparalleled computational efficiency. However, its bane lies with non-linearities: on top of the complex problem of fractal-surface contact, plasticity, damage and fracture mechanics make it neigh-impossible to simulate a true wear process. Nonetheless, continuum methods can be used to upscale simple laws observed at the micro-scale [6]. In this presentation the two authors will each take the side of one of the two approaches, facing a duel where the merits and limits of each approach will clearly emerge, with the final intent of delivering awareness in the audience about the combined role of continuum and discrete modeling in the quest of a deeper understanding of wear related phenomena. ... what side will you take

Metabolic profile of women with PCOS in Brazil : a systematic review and meta-analysis

Background: Polycystic ovary syndrome (PCOS) is a common endocrine disease affecting women of reproductive age and associated with reproductive and metabolic dysfunction. Few studies are available regarding metabolic traits in Brazilian women with PCOS. The aim of this systematic review and meta-analysis was to summarize the available evidence regarding metabolic traits and comorbidities in Brazilian women with polycystic ovary syndrome (PCOS). Methods: We systematically searched PubMed, Cochrane Central Register of Controlled Trials, and Embase for cross-sectional, case–control, or cohort studies focusing on populations of different regions from Brazil, published until July 31, 2019. Studies were selected if they reported PCOS diagnostic criteria. Studies without a control group were included if they presented relevant metabolic data. Results: Of 4856 studies initially identified, 27 were included in the systematic review and 12 were included in the meta-analysis, for a total of 995 women with PCOS defined by Rotterdam criteria and 2275 controls from different regions of Brazil. Obesity, metabolic syndrome and IGT were prevalent, and standard mean differences for BMI (SMD 0.67, 95% CI, 0.29, 1.05), waist circumference (SMD 0.22, 95% CI 0.02, 0.41), systolic (SMD 0.66, 95% CI 0.30, 1.01) and diastolic blood pressure (SMD 0.55, 95% CI 0.24, 0.87), glucose (SMD 0.21, 95% CI 0.04, 0.38) and HOMA (SMD 0.78, 95% CI 0.52, 1.04) were significantly higher in Brazilian women with PCOS compared to controls. Lipid profile was more adverse in PCOS vs. non-PCOS women. Between-study heterogeneities were low/moderate for glucose and HOMA and moderate/high for the other variables. Conclusions: The data of this systematic review and meta-analysis indicate that Brazilian women with PCOS have a worse metabolic profile than women without PCOS with no important regional differences. The prevalence of metabolic changes is intermediate in Brazil vs. other countries

Oil Seep Detection Using Microwave Remote Sensing at Espírito Santo Basin, Eastern Brazil

Hydrocarbon seepage phenomena can be found in most petroleum provinces located in both coastal and ocean regions. The present work aims to identify, map and quantify oil seep candidates in the maritime portion of the Espírito Santo Sedimentary Basin using Synthetic Aperture Radar imagery from Radarsat-2 and Sentinel-1. The selection of the SAR images was made based on their basin coverage area. Meteorological and oceanographic data, when available, were used to assist interpretation. Later, the presence of structures that may enable fluids to escape (faults, fractures, salt domes, etc.) was verified in 101 seismic lines. After detailed analysis, the obtained data were gathered, aiming to classify the oil seep candidates found according to their probability of happening. There were 3 parameters, subdivided into criteria, used in the ranking score: SAR (distance of vessels, number nearby possible seeps and feature size), Geological (morphotectonic domains) and Seismic (distance from seismic lines, presence of structures and distance from structure). Each criterion received grades ranging from 0.1 to 1.0. The final score is given by the arithmetic mean of the parameters. This allowed the seep candidates to be organized in a ranking. The methodology was successful in identifying 54 promising features in the Espírito Santo basin and northern Campos basin. Half of the seep candidates found, 27 features, obtained a grade higher than 0.7, which strengthens the idea of being oil seeps. As an outcome a map was made in 1:3,500,000 scale with the location of all oil seep candidates mapped in this petroleum province