922017 research outputs found
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Did the Siebel Systems Case Limit the SEC's Ability to Enforce Regulation Fair Disclosure?
No full textWe examine whether a shock to the enforceability of Regulation Fair Disclosure (Reg FD) limited its ability to restrict the flow of private information between managers and investors. While prior work provides evidence that Reg FD reduced managers’ selective disclosure of material information immediately following its promulgation, we posit that private information flows returned as a result of the SEC’s public enforcement failure in SEC v. Siebel Systems, Inc. Using multiple settings, we find consistent evidence suggesting that Siebel changed the cost-benefit tradeoff for Reg FD compliance and effectively reversed the initial effects of the regulation. We also find that Siebel disrupted the equilibrium of selective disclosure activity, resulting in an unleveling effect among investors with respect to private information advantages. Finally, we find that Siebel also had real effects by altering managers’ capital structure decisions. Our findings run counter to the prevailing “mosaic theory” and gradual learning explanations for private information advantages in the extended post-Reg FD period and highlight the importance of enforcement in achieving intended regulatory outcomes
Summary of Model Checking C++ Programs
No full textThis is an extended abstract of the article “Model Checking C++ Programs” by Felipe R. Monteiro, Mikhail R. Gadelha, and Lucas C. Cordeiro. We describe and evaluate anovel verification approach based on bounded model checking (BMC) and satisfiability modulo theories (SMT) to verify C++ programs. Our verification approach analyzes bounded C++ programs by encoding into SMT various sophisticated features that the C++ programming language offers, such as templates, inheritance, polymorphism, exception handling, and the StandardTemplate Libraries. We implemented our verification approach on top of ESBMC. We compare ESBMC to LLBMC and DIVINE, which are state-of-the-art verifiers to check C++ programs directly from the LLVM bitcode. Experimental results show thatESBMC can handle a wide range of C++ programs, presenting a higher number of correct verification results. Additionally, ESBMC has been applied to a commercial C++ application in the telecommunication domain and successfully detected arithmeticoverflow errors, which could lead to security vulnerabilities.Index Terms—C++, memory safety, model checking, SMT, software verification<br/
A Molecular Simulation Study into the Stability of Hydrated Graphene Nanochannels used in Nanofluidics Devices
No full textGraphene-based nanochannels are a popular choice in emerging nanofluidics applications because of their tunable and nanometer-scale channels. In this work, molecular dynamics (MD) simulations were employed both to i) assess the stability of dry and hydrated graphene nanochannels and ii) elucidate the properties of water confined in these channels, using replica-scale models with 0.66 – 2.38 nm channel heights. The use of flexible nanochannel walls allows the nanochannel height to relax in response to the solvation forces arising from the confined fluid and the forces between the confining surfaces, without the need for application of arbitrarily high external pressures. Dry nanochannels were found to completely collapse if the initial nanochannel height was less than 2 nm, due to attractive van der Waals interactions between the confining graphene surfaces. However, the presence of water was found to prevent total nanochannel collapse, due to repulsive hydration forces opposing the attractive van der Waals force. For nanochannel heights less than ~1.7 nm, the confining surfaces must be relaxed to obtain accurate hydration pressures and water diffusion coefficients, by ensuring commensurability between the number of confined water layers and the channel height. For very small (~0.7 nm), hydrated channels a pressure of 231 MPa due to the van der Waals forces was obtained. In the same system, the confined water forms a mobile, liquid monolayer with a diffusion coefficient of 4.0 × 10–5 cm2 s–1, much higher than bulk liquid water. Although this finding conflicts with most classical MD simulations, which predict in-plane order and arrested dynamics, it is supported by experiments and recently published first-principles MD simulations. Classical simulations can therefore be used to predict the properties of water confined in sub-nanometre graphene channels, providing sufficiently realistic molecular models and accurate intermolecular potentials are employed
Non-thermal plasma catalytic ammonia synthesis over Ni catalyst supported on MgO/SBA-15
No full textNon-thermal plasma (NTP) enabled ammonia synthesis is recently considered a sustainable technique as compared to the Haber–Bosch (HB) process. Herein we demonstrate the NTP catalytic ammonia synthesis in an dielectric barrier discharge (DBD) plasma reactor using mesoporous silica (SBA-15) supported Ni catalysts under ambient condition. Specifically, two types of MgO modified SBA-15 were developed (as the catalyst support) by the in situ doping and incipient wetness impregnation (IWI) methods, respectively. Experimental results demonstrated that the addition of Mg in SBA-15 via the IWI method favored the ammonia synthesis rate under NTP conditions. The developed Ni-Mg0.02/SBA-15-IWI catalyst exhibited the highest ammonia synthesis rate and energy efficiency value of 4.4 mmol h−1 gcat−1 and 1.05 gNH3 kWh−1, outperformed the Ni/SBA-15 and Ni-Mg0.02/SBA-15-In situ catalyst (i.e. the doping of Mg via in situ method). HRTEM and EDS mapping analysis showed that the addition of Mg (on SBA-15) via the IWI method favored the dispersion of Ni on the catalyst surface and the Ni-support interaction, i.e., uniform distribution of Ni nanoparticles of 5.1 ± 1.1 nm in the Ni-Mg0.02/SBA-15-IWI catalyst, which enhanced the ammonia synthesis performance. Finally, the developed Ni-Mg0.02/SBA-15-IWI catalyst displayed a slight decrease of ammonia synthesis rate from ~4.42 to ~3.89 mmol h−1 gcat−1 over a 40 h on stream, which could be attriburated to the aggregation of Ni particles based on the post-reaction HRTEM analysis.<br/
Controlling desolvation through polymer-assisted grinding
No full textWe demonstrate the ability to controllably desolvate a crystal-solvate system in step-wise fashion through polymer-assisted grinding by varying the type and proportion of polymer agent used. A plausible mechanistic explanation is proposed based on a combination of experimental evidence and computational analysis. Specifically, Raman spectroscopy, total scattering pair distribution function analysis and computed reaction energies suggest that the desolvation process is associated with preferred interactions between the solvent molecules and specific polymers. This approach could potentially be extended to any type of material, including heat-sensitive materials, where classical desolvation by thermal processes is not possible, and provides a new potential technique for formulation processing
SPLITTING HAIRS WITH TRANSCENDENTAL ENTIRE FUNCTIONS
No full textIn recent years, there has been significant progress in the understanding of the dynamics of transcendental entire functions with bounded postsingular set. In particular, for certain classes of such functions, a complete description of their topological dynamics in terms of a simpler model has been given inspired by methods from polynomial dynamics. In this paper, and for the first time, we give analogous results in cases when the postsingular set is unbounded. More specifically, we show that if f is of finite order, has bounded criticality on its Julia set J(f), and its singular set consists of finitely many critical values that escape to infinity and satisfy a certain separation condition, then J(f) is a collection of dynamic rays or hairs, that split at critical points, together with their corresponding landing points. In fact, our result holds for a much larger class of functions with bounded singular set. Moreover, this result is a consequence of a significantly more general one: we provide a topological model for the action of f on its Julia set
Grassland degradation-induced declines in soil fungal complexity reduce fungal community stability and ecosystem multifunctionality
No full textSoil microorganisms are major regulators of ecosystem functioning and are under threat from human-induced disturbances. Among these threats is grassland degradation, which is estimated to affect 49% of the grassland area worldwide, threatening biodiversity and ecosystem functioning. Yet, we currently lack an understanding of how grassland degradation influences belowground microbial communities, their stability, and functioning, and how effective restoration efforts are for the recovery of these important belowground properties. Here, we assessed soil fungal network complexity and a suite of ecosystem functions along a well-characterised gradient of grassland degradation and restoration on the Qinghai-Tibetan Plateau, and conducted an accompanying microcosm experiment designed to test the effects of complexity on stability in soil fungal communities. We found that with increasing levels of grassland degradation, soil fungal communities became less complex and were less compositionally stable when confronted with drought under laboratory conditions. Moreover, this degradation-induced reduction in fungal community complexity was associated with lower ecosystem multifunctionality. However, fungal communities and ecosystem multifunctionality failed to recover even after ten years of grassland restoration. Our results indicate that degradation-induced simplification of fungal communities can potentially impair fungal community stability and ecosystem multifunctionality, thereby highlighting the need to protect and restore healthy grasslands with complex belowground microbial communities
Implications of the changes to patient online records access in English primary care
No full textNHS England have announced that patients in England registered for online services such as the NHS App will soon be able to see all new entries in their primary care record by default. This includes free text, hospital letters, test results, and new data added to the detailed coded record. Despite documented benefits of online records access for patients, primary care staff have raised concerns which can be grouped into issues around: 1) workload, 2) safeguarding, 3) patient confusion or distress, and 4) health inequities. This editorial examines each of these in turn, and considers what the future might hold for patient online records access.<br/