Modeling shallow marine carbonate depositional systems

Geological Process Models (GPMs) have been used in the past to simulate the distinctive stratigraphies formed in carbonate sediments, and to explore the interaction of controls that produce heterogeneity. Previous GPMs have only indirectly included the supersaturation of calcium carbonate in seawater, a key physicochemical control on carbonate production in reef and lagoon environments, by modifying production rates based on the distance from open marine sources. We here use the residence time of water in the lagoon and reef areas as a proxy for the supersaturation state of carbonate in a new process model, Carbonate GPM. Residence times in the model are calculated using a particle-tracking algorithm. Carbonate production is also controlled by water depth and wave power dissipation. Once deposited, sediment can be eroded, transported and re-deposited via both advective and diffusive processes. We show that using residence time as a control on production might explain the formation of non-ordered, three-dimensional carbonate stratigraphies by lateral shifts in the locus of carbonate deposition on timescales comparable to so-called 5th-order sea-level oscillations. We also show that representing supersaturation as a function of distance from open marine sources, as in previous models, cannot correctly predict the supersaturation distribution over a lagoon due to the intricacies of the flow regime.     

Synthesis of hybrid nanocomposites based on new triazeno copolymers and montmorillonite used for detecting metal ions

The modern synthesis of novel functional materials with improved properties includes that of hybrid nanocomposites composed of inorganic nanoparticles and organic derivatives, where controlling the molecular structure at atomic and macroscopic dimensions is a key factor, with a major effect on performance. An extension of this approach to the field of nanocomposites containing photopolymers with triazene groups attached on a methacrylic backbone could be of great interest in the future development of chemosensors and photoresists, among others. Photopolymer/clay nanocomposites were prepared by in situ free radical copolymerization of 1‐(phenyl)‐3‐(2‐methacryloyloxyethylcarbamoyloxyethyl)‐3‐methyltriazene‐1 or 1‐(p‐methoxyphenyl)‐3‐(2‐methacryloyloxyethylcarbamoyloxyethyl)‐3‐methyltriazene‐1 and vinyl acetate or styrene in solution and in the presence of 3 and 5 wt% of organically modified montmorillonite. The characterization of the nanocomposites and pure copolymers was achieved through ¹H NMR and Fourier transform infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis, X‐ray diffraction, atomic force microscopy and fluorescence analysis. The morphologies and properties of the nanocomposites are dependent on the nature of the triazene, on the co‐monomer structure and on the organoclay content. Also, the fluorescence response of these nanocomposites towards certain metal ions (Fe³⁺, Cu²⁺, Hg²⁺, Ni²⁺) in dimethylformamide solution was investigated. The effect of uranyl ions on the fluorescence intensity of the nanocomposites in solution or as films could be exploited in the development of ‘turn‐off’ or ‘turn‐on’ chemosensors for this type of analyte. Triazeno copolymer/organophilic montmorillonite nanocomposites with exfoliated (not completely exfoliated) or exfoliated and intercalated structures exhibit distinct characteristics concerning their fluorescence behaviour, a higher sensing ability towards certain target compounds (Fe³⁺, UO₂²⁺) being evidenced for those incorporating 3 wt% organoclay in solution and as films. Copyright © 2010 Society of Chemical Industry     

Polyethylene as an Additive for Mineral Oils — Part II: EHL Traction Behavior

In Part I of the paper ((1999), Trib. Trans., 42, pp. 851–859) we investigated the effect of the polyethylene concentration on the film forming properties in a rolling bearing. This second part presents the influence of the polymer additive concentration on the traction behavior experienced using a two-disk machine at different temperatures and contact pressures.

By using the traction data, a semi-empirical approach for determining the effective lubricant theological parameters in EHL contacts was performed. Using this approach, the effect of polymer concentration upon rheological parameters that appear in the Johnson and Tevaarwerk model with Eyring stress was quantified.     

Energy cultures: A framework for understanding energy behaviours

Achieving a ‘step-change’ in energy efficiency behaviours will require enhanced knowledge of behavioural drivers, and translation of this knowledge into successful intervention programmes. The ‘Energy Cultures’ conceptual framework aims to assist in understanding the factors that influence energy consumption behaviour, and to help identify opportunities for behaviour change. Building on a history of attempts to offer multi-disciplinary integrating models of energy behaviour, we take a culture-based approach to behaviour, while drawing also from lifestyles and systems thinking. The framework provides a structure for addressing the problem of multiple interpretations of ‘behaviour’ by suggesting that it is influenced by the interactions between cognitive norms, energy practices and material culture.     

Machine learning for event selection in high energy physics

The field of high energy physics aims to discover the underlying structure of matter by searching for and studying exotic particles, such as the top quark and Higgs boson, produced in collisions at modern accelerators. Since such accelerators are extraordinarily expensive, extracting maximal information from the resulting data is essential. However, most accelerator events do not produce particles of interest, so making effective measurements requires event selection, in which events producing particles of interest (signal) are separated from events producing other particles (background). This article studies the use of machine learning to aid event selection. First, we apply supervised learning methods, which have succeeded previously in similar tasks. However, they are suboptimal in this case because they assume that the selector with the highest classification accuracy will yield the best final analysis; this is not true in practice, as such analyses are more sensitive to some backgrounds than others. Second, we present a new approach that uses stochastic optimization techniques to directly search for selectors that maximize either the precision of top quark mass measurements or the sensitivity to the presence of the Higgs boson. Empirical results confirm that stochastically optimized selectors result in substantially better analyses. We also describe a case study in which the best selector is applied to real data from the Fermilab Tevatron accelerator, resulting in the most precise top quark mass measurement of this type to date. Hence, this new approach to event selection has already contributed to our knowledge of the top quark's mass and our understanding of the larger questions upon which it sheds light.     

Recruitment efforts to reduce adverse impact: Targeted recruiting for personality, cognitive ability, and diversity.

Noting the presumed tradeoff between diversity and performance goals in contemporary selection practice, the authors elaborate on recruiting-based methods for avoiding adverse impact while maintaining aggregate individual productivity. To extend earlier work on the primacy of applicant pool characteristics for resolving adverse impact, they illustrate the advantages of simultaneous cognitive ability– and personality-based recruiting. Results of an algebraic recruiting model support general recruiting for cognitive ability, combined with recruiting for conscientiousness within the underrepresented group. For realistic recruiting effect sizes, this type of recruiting strategy greatly increases average performance of hires and percentage of hires from the underrepresented group. Further results from a policy-capturing study provide initial guidance on how features of organizational image can attract applicants with particular job-related personalities and abilities, in addition to attracting applicants on the basis of demographic background. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Soft solution fluorine-free synthesis of anatase nanoparticles with tailored morphology

TiO₂ nanoparticles with tailored morphology have been synthesized under exceptionally soft conditions. The strategy is based on the use of a non-aqueous alcoholic reaction medium in which water traces, coming either from the air (atmospheric water) or from an ethanol–water azeotropic mixture (ethanol 96%), are incorporated in order to accelerate hydrolysis of the Ti–precursor. Moreover, organic surfactants have been used as capping agents so as to tailor crystal growth in certain preferential directions. Combinations of oleic acid and oleylamine, which lead to the formation of another surfactant, dioleamide, are employed instead of fluorine-based compounds, thus increasing the sustainability of the process. As a result, TiO₂ nanostructured hierarchical microspheres and individual nanoparticles with exposed high-energy facets can be obtained at atmospheric pressure and temperatures as low as 78 °C.     

Neural basis for recognition confidence in younger and older adults.

Although several studies have examined the neural basis for age-related changes in objective memory performance, less is known about how the process of memory monitoring changes with aging. The authors used functional magnetic resonance imaging to examine retrospective confidence in memory performance in aging. During low confidence, both younger and older adults showed behavioral evidence that they were guessing during recognition and that they were aware they were guessing when making confidence judgments. Similarly, both younger and older adults showed increased neural activity during low- compared to high-confidence responses in the lateral prefrontal cortex, anterior cingulate cortex, and left intraparietal sulcus. In contrast, older adults showed more high-confidence errors than younger adults. Younger adults showed greater activity for high compared to low confidence in medial temporal lobe structures, but older adults did not show this pattern. Taken together, these findings may suggest that impairments in the confidence–accuracy relationship for memory in older adults, which are often driven by high-confidence errors, may be primarily related to altered neural signals associated with greater activity for high-confidence responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recipes for Spatial Statistics with Global Datasets: A Martian Case Study

The Mars Odyssey Gamma Ray Spectrometer has yielded planetary data of global extent. Such remote-sensing missions usually assign the value of a continuous-valued geospatial attribute to a uniform latitude-longitude grid of bins. Typical attributes include elemental-mass fraction, areal fraction of a mineral type, areal fraction of rocks, thermal inertia, etc. The fineness of the grid is chosen according to the spatial resolution of the orbiter and concomitant data processing. We describe methods to maximize the information extracted from both bin and regional data. Rigorous use of statistical parameters and related methods for inter- and intra- regional comparisons are also discussed. While we discuss results from the Mars Odyssey mission, the techniques we describe are applicable whenever continuous-valued attributes of a planet’s surface are characterized with bins and regions. Our goal is to distill the simplest statistical methods for regional comparisons that would be intuitively accessible to planetary scientists.