Relaxation imaging to characterize lightweight polymer-crosslinked aerogels

Silica aerogels are three-dimensional assemblies of silica nanoparticles with extremely low densities. In some instances, the internal void volume is more than 90% of the total volume. The highly porous structure of the aerogels leads to attractive properties for thermal and noise insulation, due to very low thermal conductivity and very high acoustic impedance. The strength of silica aerogels has been substantially improved by casting a thin conformal polymer coating over the entire internal porous surfaces of the nanostructure. The coating reinforces the interparticle connections without significantly compromising the internal void space. To analyze and compare the properties of several lightweight polymer-crosslinked silica aerogels, spatially resolved T₁ and T₂ relaxation studies were conducted. The polymer-crosslinked aerogels were precision-machined to snugly fit into the lower parts of standard NMR tubes. A mixture of equal amounts of acetone and deuterated acetone was used as the liquid to fill the void volume of the aerogels. Spin-echo and saturation-recovery relaxation sequences were used as part of a standard one-dimensional gradient-recalled echo imaging sequence. For comparison, native aerogels without the polymer coating were examined with the same pulse sequences. Because of the fragile nanoparticle network, native gels could not be machined but were generated directly inside the NMR tubes. The porosity of the gels was determined using the relaxation profiles. The relaxation times were found to have a significant dependence on the coating polymer and also on the formation process of the aerogels. In addition, the relationship between the pore size and relaxation time was also analyzed --Abstract, page iii

Modeling the emergence of a new language: Naming Game with hybridization

In recent times, the research field of language dynamics has focused on the investigation of language evolution, dividing the work in three evolutive steps, according to the level of complexity: lexicon, categories and grammar. The Naming Game is a simple model capable of accounting for the emergence of a lexicon, intended as the set of words through which objects are named. We introduce a stochastic modification of the Naming Game model with the aim of characterizing the emergence of a new language as the result of the interaction of agents. We fix the initial phase by splitting the population in two sets speaking either language A or B. Whenever the result of the interaction of two individuals results in an agent able to speak both A and B, we introduce a finite probability that this state turns into a new idiom C, so to mimic a sort of hybridization process. We study the system in the space of parameters defining the interaction, and show that the proposed model displays a rich variety of behaviours, despite the simple mean field topology of interactions.Comment: 12 pages, 10 figures, presented at IWSOS 2013 Palma de Mallorca, the final publication will be available at LNCS http://www.springer.com/lnc

Hidden Error Variance Theory. Part II: An Instrument That Reveals Hidden Error Variance Distributions from Ensemble Forecasts and Observations

Abstract In Part I of this study, a model of the distribution of true error variances given an ensemble variance is shown to be defined by six parameters that also determine the optimal weights for the static and flow-dependent parts of hybrid error variance models. Two of the six parameters (the climatological mean of forecast error variance and the climatological minimum of ensemble variance) are straightforward to estimate. The other four parameters are (i) the variance of the climatological distribution of the true conditional error variances, (ii) the climatological minimum of the true conditional error variance, (iii) the relative variance of the distribution of ensemble variances given a true conditional error variance, and (iv) the parameter that defines the mean response of the ensemble variances to changes in the true error variance. These parameters are hidden because they are defined in terms of condition-dependent forecast error variance, which is unobservable if the condition is not sufficiently repeatable. Here, a set of equations that enable these hidden parameters to be accurately estimated from a long time series of (observation minus forecast, ensemble variance) data pairs is presented. The accuracy of the equations is demonstrated in tests using data from long data assimilation cycles with differing model error variance parameters as well as synthetically generated data. This newfound ability to estimate these hidden parameters provides new tools for assessing the quality of ensemble forecasts, tuning hybrid error variance models, and postprocessing ensemble forecasts

So That the People May Live (Hecel Lena Oyate Ki Nipi Kte): Lakota and Dakota Elder Women as Reservoirs of Life and Keepers of Knowledge about Health Protection and Diabetes Prevention

Around the world, Type 2 diabetes is on the rise, affecting adults and youth from societies in the throes of industrialization. Over time, uncontrolled diabetes can leave in its wake people facing renal failure, blindness, and heart disease, and communities daunted by new, chaotic phenomena. Westernized lifestyles are a recognized explanation for the escalating prevalence. The web of causation, however, may be broader and thicker, woven by complex interactions with environmental, sociological, and historical roots. The purpose of this participatory ethnographic study was to document, understand, and support Lakota and Dakota elder women’s beliefs and knowledge about health protection and diabetes prevention. In-depth interviews were conducted with nine elder women to learn: (1) about the factors attributable to diabetes, (2) about related narratives addressing health protection and diabetes prevention, and (3) how knowledge about health protection is shared. The elders saw diabetes as an outside, unnatural disorder, the contributing influences of which are external as well as internal. They offered narratives about chaos, restitution, testimony, and quests for cures and meaning. The elders connected health to traditional values and ways, the land, and memory. Reservoirs of wisdom reside in the knowledge systems of tribal elders who remember when diabetes was unknown. Health leaders at local and national levels would be wise to respect and draw upon this knowledge for guidance in program planning and policy development

Social preferences for adaptation measures to conserve Australian birds threatened by climate change

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Debate about climate change adaptation for biodiversity, and the ethics and consequences of assisted colonization in particular, has polarized professional opinion but the views of the wider community are unknown. We tested four hypotheses about the acceptability of adaptation strategies among a sample of the Australian general public using a combination of direct questions and a choice experiment. We found that (1) among the 80% who wanted extinction avoided, increased in situ management of wild populations was preferred to captive breeding or assisted colonization, (2) preferences for adaptation strategies were not explained by gender, income, education or knowledge about birds, (3) genetically distinctive taxa were not actively preferred, (4) > 60% of respondents were content for conservation managers to make decisions about strategies rather than local communities or the general public. The results provide Australian policy makers with a mandate to bolster efforts to retain existing populations but suggest that assisted colonization and captive breeding could be accepted if essential

Nurses\u27 Alumnae Association Bulletin, May 1960

Accreditation of Programs in Nursing Alumnae Meetings, 1959 Committee Reports Greetings from the President Highlights from first issue of Alumnae Bulletin Living in the new nurses residence Lost Members Marriages Necrology New Arrivals Notices Personal Items of Interest Report of the School of Nursing and Nursing Services Staff Nurses Association Student Activities Year of tremendous growth and expansio

Inelastic neutron scattering studies of methyl chloride synthesis over alumina

Not only is alumina the most widely used catalyst support material in the world, it is also an important catalyst in its own right. One major chemical process that uses alumina in this respect is the industrial production of methyl chloride. This is a large scale process (650 000 metric tons in 2010 in the United States), and a key feedstock in the production of silicones that are widely used as household sealants. In this Account, we show how, in partnership with conventional spectroscopic and reaction testing methods, inelastic neutron scattering (INS) spectroscopy can provide additional insight into the active sites present on the catalyst, as well as the intermediates present on the catalyst surface.<p></p> INS spectroscopy is a form of vibrational spectroscopy, where the spectral features are dominated by modes involving hydrogen. Because of this, most materials including alumina are largely transparent to neutrons. Advantageously, in this technique, the entire “mid-infrared”, 0–4000 cm<sup>–1</sup>, range is accessible; there is no cut-off at 1400 cm<sup>–1</sup> as in infrared spectroscopy. It is also straightforward to distinguish fundamental modes from overtones and combinations. <p></p> A key parameter in the catalyst’s activity is the surface acidity. In infrared spectroscopy of adsorbed pyridine, the shifts in the ring stretching modes are dependent on the strength of the acid site. However, there is a very limited spectral range available. We discuss how we can observe the low energy ring deformation modes of adsorbed pyridine by INS spectroscopy. These modes can undergo shifts that are as large as those seen with infrared inspectroscopy, potentially enabling finer discrimination between acid sites. <p></p> Surface hydroxyls play a key role in alumina catalysis, but in infrared spectroscopy, the presence of electrical anharmonicity complicates the interpretation of the O–H stretch region. In addition, the deformations lie below the infrared cut-off. Both of these limitations are irrelevant to INS spectroscopy, and all the modes are readily observable. When we add HCl to the catalyst surface, the acid causes changes in the spectra. We can then deduce both that the surface chlorination leads to enhanced Lewis acidity and that the hydroxyl group must be threefold coordinated. <p></p> When we react η-alumina with methanol, the catalyst forms a chemisorbed methoxy species. Infrared spectroscopy clearly shows its presence but also indicates the possible coexistence of a second species. Because of INS spectroscopy’s ability to discriminate between fundamental modes and combinations, we were able to unambiguously show that there is a single intermediate present on the surface of the active catalyst. This work represents a clear example where an understanding of the chemistry at the molecular level can help rationalize improvements in a large scale industrial process with both financial and environmental benefits. <p></p&gt