Generic singular spectrum for ergodic Schrödinger operators

We consider Schrödinger operators with ergodic potential V_ω(n) = f(T^n(ω)), n Є Z, ω Є Ω, where T : Ω → Ω is a nonperiodic homeomorphism. We show that for generic f Є C(Ω), the spectrum has no absolutely continuous component. The proof is based on approximation by discontinuous potentials which can be treated via Kotani theory

Sustainability criteria associated with urbanization regulations

The recent formalization in the country a National Urban Policy and Housing attempts urgent attention to the problems associated with a sector whose development in recent decades has been marked by continued dissociation between urban growth and population growth way, based on models disproportionate, irrational and unsustainable territorial expansion, with high costs in economic, social and environmental issues. Urban segregation, deteriorating environmental conditions of the physical built environment, vulnerability to natural disasters, depletion of land reserves in several metropolitan areas and social exclusion and inequality in terms of the supply of infrastructure, services or equipment are some of the most serious consequences of the effective realization of such models in Mexican cities, especially for areas with little population confined to living on the peripheries of urban sprawl income. Combining this with the guidance of environmental policies at the international level to the reduction of greenhouse gases in all sectors of society and with the explicit intention of the municipality of Zapopan to promote sustainability criteria associated with urbanization within of its territory, it is that the framework that motivates the development of this standard Sustainable Construction is set. The rule here is issued aims to establish linked, in this case, the regulation of planning urban renewal actions and / or promoting new municipality under the requirements of sustainability criteria and indicators for the implementation of urban planning instruments ; all embedded in a management framework and an evaluation process according the urban regulations

The molecular and electronic structures of some radical ions

This thesis reports an investigation into the molecular and electronic structures of some aromatic and heteroaromatic radical ions (predominantly cations). The radical ions were identified and characterised by electron spin resonance spectroscopy. Computer-simulated molecular structures of some were optimized by semi-empirical (AM1) and molecular mechanics calculations; these calculations support the experimental observations. The conformational inversion of the cyclohexene ring in two radical cations containing the benzocyclohexene moiety was observed at a range of temperatures, yielding contrasting barriers to inversion. These were found to be in accord with molecular mechanics calculations on the neutral molecules. The permethylbenzocyclohexenes 9,10-dimethyl-1,2,3,4,5,6,7,8-tetrahydroanthracene and 1,2,3,4-tetramethyl-5,6,7,8-tetrahydronaphthalene exhibited unusual molecular orbital perturbation. The radical cations and anions of methylated biphenylenes, tetraphenylene, and octa-β-methyltetraphenylene were investigated. The pairing principle of alternant π-systems was confirmed in all examples where both radical cations and anions could be studied. The tetra-α-methylbiphenylene exhibited mercurideprotonation when its radical cation was generated in trifluoroacetic acid containing mercury(II) trifluoroacetate. When tetra-β-methylbiphenylene in tetrahydrofuran was treated with lithium, reduction and ring opening apparently occurred. The electron distribution observed in the radical cation of octa-β-methyltetraphenylene confirmed the prediction of a perturbation of molecular orbitals approach. The radical cations of a variety of compounds containing the pyrrole moiety are discussed. A series of p-phenylene-bis(dialkylpyrroles) showed no hyperfine coupling to the arene unit, and electron release into the pyrrole ring by 2,5-diethyl groups was found to be greater than by 2,5-dimethyl substituents. X-Ray crystallography showed that the 2,2',5,5'-tetramethylbi-(N-pyrrolyl) has an orthogonal structure and its radical cation shows the unpaired electron to be delocalised over both rings. The radical cation of 8b,8c-diazapyracyclene, which is isoelectronic with the radical anion of pyracyclene, has been observed and undergoes mercurideprotonation. The spectrum of the radical cation of 1-phenyl-2,3,4,5-tetramethylarsole is in accord with the photoelectron spectra and calculations which suggest that the heteroatom is pyramidal and that arsoles may be considered as non-aromatic hetero[5]annulenes

Assessment of Mercury Content in Louisiana\u27s Freshwater Fish and its Association to Se Concentrations

Ample evidence has demonstrated the neurotoxic properties of organic Hg to humans. However, recent studies have proposed the protective effects of Se against organic Hg detected in marine fish. Louisiana’s freshwater bodies are exploited by recreational anglers that enjoy fishing as recreational activity and food source. Thus, testing of Hg in Louisiana was resumed in 2017 to update the state advisories. However, before drawing conclusions based solely on organic Hg, it might be useful to see how much Se is present in freshwater fish. The main objective of this study was to determine the Se:Hg molar ratio in Louisiana’s freshwater fish; the ratios should be greater than 1.0 to expect Se’s protective effects. Five waterbodies were surveyed (University lake, Calcasieu lake, Toledo Bend, Atchafalaya River, and Henderson lake). The last three are listed in the state advisory. The fish’s fillet from species such as: Black drum, Catfish, Largemouth bass, Bluegill, Gizzard shad; were tested for total Hg via Direct Mercury Analyzer. Testing for Se used the same fish samples for determination via ICP-MS. The results revealed Hg concentrations on Louisiana’s fish were all under the 1 ppm EPA limit and LDEQ limit of 0.88 ppm (from 0.0063 to 0.67 ppm). However, Se concentrations were variable for different species and locations (from 0.024 to 0.886 ppm). Therefore, the calculated Se:Hg molar ratios were variable. Some ratios may suggest a relationship by species; like in Black drum and Catfish. Notwithstanding, large species (Bass) accumulate large amounts of Hg that exceed Se concentrations. That explained the low ratios for Se in Henderson lake’s bass but, is not true for Atchafalaya’s bass. Thus, fish from locations highly polluted with Hg apparently have Se:Hg molar ratios less than 1. There is no clear dominant variable (species or location) on the ratio determination. In conclusion, the predicted variability of Se in freshwater fish by other scholars were observed in this study. Apparently, location and species are variables with unpredictable dominant roles. For proper evaluation of state advisory, both might be considered independently for any particular freshwater body

Explaining Aviation Safety Incidents Using Deep Temporal Multiple Instance Learning

Although aviation accidents are rare, safety incidents occur more frequently and require a careful analysis to detect and mitigate risks in a timely manner. Analyzing safety incidents using operational data and producing event-based explanations is invaluable to airline companies as well as to governing organizations such as the Federal Aviation Administration (FAA) in the United States. However, this task is challenging because of the complexity involved in mining multi-dimensional heterogeneous time series data, the lack of time-step-wise annotation of events in a flight, and the lack of scalable tools to perform analysis over a large number of events. In this work, we propose a precursor mining algorithm that identifies events in the multidimensional time series that are correlated with the safety incident. Precursors are valuable to systems health and safety monitoring and in explaining and forecasting safety incidents. Current methods suffer from poor scalability to high dimensional time series data and are inefficient in capturing temporal behavior. We propose an approach by combining multiple-instance learning (MIL) and deep recurrent neural networks (DRNN) to take advantage of MIL's ability to learn using weakly supervised data and DRNN's ability to model temporal behavior. We describe the algorithm, the data, the intuition behind taking a MIL approach, and a comparative analysis of the proposed algorithm with baseline models. We also discuss the application to a real-world aviation safety problem using data from a commercial airline company and discuss the model's abilities and shortcomings, with some final remarks about possible deployment directions

The Spectrum of Schr\"odinger Operators with Randomly Perturbed Ergodic Potentials

We consider Schr\"odinger operators in $\ell^2(\mathbb{Z})$ whose potentials are given by the sum of an ergodic term and a random term of Anderson type. Under the assumption that the ergodic term is generated by a homeomorphism of a connected compact metric space and a continuous sampling function, we show that the almost sure spectrum arises in an explicitly described way from the unperturbed spectrum and the topological support of the single-site distribution. In particular, assuming that the latter is compact and contains at least two points, this explicit description of the almost sure spectrum shows that it will always be given by a finite union of non-degenerate compact intervals. The result can be viewed as a far reaching generalization of the well known formula for the spectrum of the classical Anderson model.Comment: 11 page