347 research outputs found
Concrete Semantics with Coq and CoqHammer
The "Concrete Semantics" book gives an introduction to imperative programming
languages accompanied by an Isabelle/HOL formalization. In this paper we
discuss a re-formalization of the book using the Coq proof assistant. In order
to achieve a similar brevity of the formal text we extensively use CoqHammer,
as well as Coq Ltac-level automation. We compare the formalization efficiency,
compactness, and the readability of the proof scripts originating from a Coq
re-formalization of two chapters from the book
Physicochemical and Antibacterial Characterisation of a Novel Fluorapatite Coating
Peri-implantitis remains the major impediment to the long-term use of dental
implants. With increasing concern over growing antibiotic resistance there is
considerable interest in the preparation of antimicrobial dental implant coatings that
also induce osseointegration. One such potential coating material is fluorapatite
(FA). The aim of this study was to relate the antibacterial effectiveness of FA
coatings against pathogens implicated in peri-implantitis to the physicochemical
properties of the coating. Ordered and disordered FA coatings were produced on the
under and upper surface of stainless steel (SS) discs respectively, using a
hydrothermal method. Surface charge, surface roughness, wettability and fluoride
release were measured for each coating. Surface chemistry was assessed by X-ray
photoelectron spectroscopy and FA crystallinity by X-ray diffraction. Antibacterial
activity against periodontopathogens was assessed in vitro using viable counts,
confocal and scanning electron (SEM) microscopies. SEM showed that the
hydrothermal method produced FA coatings predominately aligned perpendicular to
the SS substrate or disordered FA coatings consisting of randomly aligned rod-like
crystals. Both FA coatings significantly reduced the growth of all the examined
bacterial strains in comparison to the control. The FA coatings, and especially the
disordered ones, presented significantly lower charge, higher roughness and area
when compared to the control, enhancing bacteriaâmaterial interactions and
therefore bacterial deactivation by fluoride ions. The ordered FA layer reduced not
only bacterial viability but adhesion too. Ordered FA crystals produced as a potential
novel implant coating showed significant antibacterial activity against bacteria
implicated in peri-implantitis which could be explained by a detailed understanding of
their physicochemical properties
Nuclear Quantum Effects in Water and Aqueous Systems: Experiment, Theory, and Current Challenges
Nuclear quantum effects influence the structure and dynamics of hydrogen-bonded systems, such as water, which impacts their observed properties with widely varying magnitudes. This review highlights the recent significant developments in the experiment, theory, and simulation of nuclear quantum effects in water. Novel experimental techniques, such as deep inelastic neutron scattering, now provide a detailed view of the role of nuclear quantum effects in water's properties. These have been combined with theoretical developments such as the introduction of the principle of competing quantum effects that allows the subtle interplay of water's quantum effects and their manifestation in experimental observables to be explained. We discuss how this principle has recently been used to explain the apparent dichotomy in water's isotope effects, which can range from very large to almost nonexistent depending on the property and conditions. We then review the latest major developments in simulation algorithms and theory that have enabled the efficient inclusion of nuclear quantum effects in molecular simulations, permitting their combination with on-the-fly evaluation of the potential energy surface using electronic structure theory. Finally, we identify current challenges and future opportunities in this area of research
Extending SMT Solvers to Higher-Order Logic
International audienceSMT solvers have throughout the years been able to cope with increasingly expressive formulas, from ground logics to full first-order logic (FOL). In contrast, the extension of SMT solvers to higher-order logic (HOL) is mostly un-explored. We propose a pragmatic extension for SMT solvers to support HOL reasoning natively without compromising performance on FOL reasoning, thus leveraging the extensive research and implementation efforts dedicated to efficient SMT solving. We show how to generalize data structures and the ground decision procedure to support partial applications and extensionality, as well as how to reconcile quantifier instantiation techniques with higher-order variables. We also discuss a separate approach for redesigning an HOL SMT solver from the ground up via new data structures and algorithms. We apply our pragmatic extension to the CVC4 SMT solver and discuss a redesign of the veriT SMT solver. Our evaluation shows they are competitive with state-of-the-art HOL provers and often outperform the traditional encoding into FOL
Unemployment Insurance and Low-Educated Single Working Mothers Before and After Welfare Reform
Using the Survey of Income and Program Participation (SIPP), a nationally representative, longitudinal survey, this study examines changing levels of Unemployment Insurance (UI) eligibility and benefit receipt among working low-educated single mothers, 1990â2005. It also examines changing participation in cash welfare and the Food Stamp Program (FSP). Relative to single childless women, there has been no increase in UI benefit receipt among single mothers entering a spell of unemployment in the postreform period, even though single mothers have increased their relative rates of UI eligibility. Because of declining cash assistance receipt, UI became a more common income support than cash assistance for this population during the period 2001â2005. Furthermore, the probability of accessing FSP for low-educated single mothers entering a spell of unemployment increased in the years 2001â2005. As a result, the proportion of this population accessing benefits from one or more of these programs remained virtually unchanged across the study period
Large-scale mutational analysis in the EXT1 and EXT2 genes for Japanese patients with multiple osteochondromas
The fate and behavior of selected endocrine disrupting chemicals in full scale wastewater and sludge treatment unit processes
Endocrine disrupting chemicals are discharged into the environment
mainly through wastewater treatment processes. There is a need for
better understanding of the fate of these compounds in the unit
processes of treatment plant to optimize their removal. The fate of
oestrone, 17ÎČ-estradiol, 17α-ethinyestradiol and nonylphenol
in the unit processes of full scale wastewater treatment plants in the
UK, including activated sludge plant, oxidation ditch, biofilter and
rotating biological contractor were investigated. The overall removal
efficiencies of all the compounds ranged from 41 % to 100 %. The
removals were predominantly during the secondary biological treatment
with the rates of removal related to the nitrification rates and the
sludge age. The removal efficiency of the treatment processes were in
the order activated sludge > oxidation ditch > biofilter >
rotating biological contractors. Activated sludge plant configured for
biological nutrient removal showed better removal of the endocrine
disrupting chemicals compared to conventional activated sludge plant
effluents. Tertiary treatment was also significant in the removal
process through solids removal. Overall mechanisms of removal were
biodegradation and sorption unto sludge biomass. Phytoremediation was
also significant in the removal processes. The endocrine disrupting
chemicals persisted in the anaerobic sludge digestion process with
percentage removals ranging fro 10-48 %. Sorption of the endocrine
disrupting chemicals onto the sludge increased with increasing values
for the partitioning coefficients and the organic carbon contents of
the sludge
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