Educational content is consistently adapted to enhance the learning experience of students at all experience and skill levels. Student motivation and accessibility are key factors in teaching science to a broad audience. The presented experiments engage the students by relating the content to that which is immediately relevant to them: the threat of global water scarcity. Through a series of experiments, students discover a potential solution employing metal–organic frameworks (MOFs), porous materials capable of harvesting water from the atmosphere, even at low relative humidity. To make this laboratory experience accessible to everyone, the experiments and required equipment are simplified without compromising the performance of the MOF, as confirmed through characterization by powder X-ray diffraction and water sorption measurements. A post-lab assessment indicates that the cutting-edge nature of the materials and related research fuels student motivation and spurs a broader conversation about ongoing scientific research.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis of poly(p-hydroxy-α-methylstyrene) by cationic polymerization and chemical modificationHiroshi Ito, C. Grant Willson, Jean M. J. Frechet, M. Jean Farrall, and Eva EichlerCite this: Macromolecules 1983, 16, 4, 510–517Publication Date (Print):April 1, 1983Publication History Published online1 May 2002Published inissue 1 April 1983https://pubs.acs.org/doi/10.1021/ma00238a004https://doi.org/10.1021/ma00238a004research-articleACS PublicationsRequest reuse permissionsArticle Views698Altmetric-Citations74LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
: Fracture by the progressive growth of incipient flaws under cyclically varying loads, i.e., by fatigue, must now be considered as the principal cause of in-service failures of engineering structures and components, whether associated with mechanical sliding and friction (fretting fatigue), rolling contact, aggressive environments (corrosion fatigue), rolling contact, aggressive environments (corrosion fatigue), or elevated temperatures (creep-fatigue). Of particular importance are the early stages of fatigue damage, involving the initial extension of microcracks and their subsequent growth at very low velocities, as these processes tend to dominate overall lifetime. This has been reflected by trends in fatigue research over the past five years, which have focused largely on so-called 'small cracks,' of dimensions comparable with the scale of microstructure or local plasticity, and on crack growth in the near-threshold regime, i.e., at stress intensities approaching the fatigue threshold below which cracks are presumed dormant. In addition, associated mechanistic studies have highlighted the critical role of crack tip shielding in fatigue, which arises predominantly from crack closure and deflection, and this has proved to be important in modeling aspects of environmentally-assisted cracking and behavior under variable amplitude loads, and in rationalizing the classical stress/strain-life and defect-tolerant design approaches. The series of international conferences 'Fatigue '87' covered a wide range of diverse views of the fundamental and applied aspects of fatigue. This included questions of cyclic deformation, crack initiation and propagation, small cracks, crack closure, variable amplitude effects, and environmentally-influenced behavior.
Objectives The aim of this project has been to increase knowledge and to contribute to the research community in the area of copper corrosion in a repository environment. For SSM, the most important subject is to provide better conditions for a science based evaluation of a repository for spent nuclear fuel. In this respect, this project aimed at conducting a comprehensive theoretical study on corrosion of copper in repository environment based on an expected composition of dissolved species in the groundwater in the Forsmark area. In addition the thermodynamic immunity of copper in pure anoxic water has been especially addressed as this was one of the initial conditions made by SKB for selecting copper as canister material. Results The authors have shown, in so-called corrosion Domain Diagrams, that copper in a thermodynamic sense can be considered as immune in pure anoxic water (without dissolved oxygen) only under certain conditions. It is shown that copper will corrode in pure anoxic water with very low concentrations of [Cu+] and very low partial pressures of hydrogen gas. At higher concentrations of [Cu+] and partial pressures of hydrogen, copper is found to be thermodynamically immune and will not corrode. The rate of copper corrosion in the repository water environment will thus depend on the transport of corrosion products away from the copper surface or the transport of corroding species to the copper surface. The degree to which this affects the corrosion of copper canisters in the repository environment has not been further studied. Still, the result shows that copper cannot be considered as thermodynamically immune in the presence of pure anoxic water, this implicate that one of SKB:s initial conditions for selecting copper as a canister material can be questioned. To what degree this may influence the corrosion of copper canisters in the repository environment still needs to be investigated. Of other species present in the water at repository depth in Forsmark, different sulphur species was found to be most deleterious causing copper to corrode in an anoxic environment under hydrogen gas evolution. In order to find out what species that can be present in a repository environment a Gibbs Energy Minimisation algorithm was employed. By this method it was concluded that (S2-, HS- and H{sub 2}S) are predicted to be present in the entire anoxic period at sufficient concentrations to cause corrosion of copper. It is finally concluded that the corrosion rate of copper canisters will be determined by the very complex interaction between copper, buffer material and bedrock in order to reduce corrosion of copper to an acceptable level
We have investigated the electromagnetic properties of a 3D wire mesh in a geometry resembling covalently bonded diamond. The frequency and wave vector dispersion show forbidden bands at those frequencies ${\ensuremath{\nu}}_{0}$, corresponding to the lattice spacing, just as dielectric photonic crystals do. But they have a new forbidden band which commences at zero frequency and extends, in our geometry, to $\ensuremath{\sim}\frac{1}{2}{\ensuremath{\nu}}_{0}$, acting as a type of plasma cutoff frequency. Wire mesh photonic crystals appear to support a longitudinal plane wave, as well as two transverse plane waves. We identify an important new regime for microwave photonic crystals, an effective medium limit, in which electromagnetic waves penetrate deeply into the wire mesh through the aid of an impurity band.
Abstract Long‐term and direct measurements of CO 2 and water vapour exchange are needed over forested ecosystems to determine their net annual fluxes of carbon dioxide and water. Such measurements are also needed to parameterize and test biogeochemical, ecological and hydrological assessment models. Responding to this need, eddy covariance measurements of CO 2 and water vapour were made ever a deciduous forest growing near Oak Ridge, TN, between April 1993 and April 1994. Periodic measurements were made of leaf area index, stomatal resistance, soil moisture and pre‐dawn leaf water potential to characterize the gas exchange capacity of the canopy. Four factors had a disproportionate influence on the seasonal variation of CO 2 flux densities. These factors were photon flux densities (during the growing season), temperature (during the dormant season), leaf area index and the occurrence of drought The drought period occurred during the peak of the growing season and caused a significant decline in daily and hourly CO 2 flux densities, relative to observations over the stand when soil moisture was plentiful. The annual net uptake of carbon was calculated by integrating flux measurements and filling missing and spurious data with the relations obtained between measured CO 2 fluxes and environmental forcing variables. The net flux of carbon for the period between April 1993 and April 1994 was ‐525 g C m −2 y −1 . This value represents a net flux of carbon from the atmosphere and into the forest. The net annual carbon exchange of this southern temperate broadleaved forest exceeded values measured over a northern temperate forest (which experiences a shorter growing season and has less leaf area) by 200 g C m −2 y −1 (cf. Wofsy et al 1993). The seasonal variation of canopy evaporation (latent heat flux) was controlled mostly by changes in leaf area and net radiation. A strong depression in evaporation rates was not observed during the drought Over a broadleaved forest large vapour pressure deficits promote evaporation and trees in a mixed stand are able to tap a variety of deep and shallow water sources.
In many concentrated alloys of current interest, the observation of diffuse superlattice intensities by transmission electron microscopy has been attributed to chemical short-range order. We briefly review these findings and comment on the plausibility of widespread interpretations, noting the absence of expected peaks, conflicts with theoretical predictions, and the possibility of alternative explanations.
Crop loss due to soil salinization is an increasing threat to agriculture worldwide. This review provides an overview of cellular and physiological mechanisms in plant responses to salt. We place cellular responses in a time- and tissue-dependent context ...Read More
[Image: see text] A tantalum-catalyzed addition of N-alkylarylamine α-C–H bonds across olefins is reported. These reactions occur with mono- and 2,2-disubstituted olefins to form the branched insertion products in high yield and regioselectivity. The reactions encompass additions of the α-C–H bonds of cyclic and acyclic amines, as well as intramolecular additions. NMR studies indicate that the starting homoleptic, Ta(NMe(2))(5)precatalyst converts to bis- and tris(N-methylanilide) complexes (amongst others) in solution. Deuterium-labeling studies suggest that reversible ortho-metalation of the arene substituent occurs under the reaction conditions. However, several experiments imply that this ortho-metalation does not lie on the reaction pathway. Instead, these complexes are proposed to eliminate amine to form N-aryl imine complexes, which insert olefins into the Ta–C bond and undergo protonolysis to regenerate the active catalyst and eliminate the addition product.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
This volume of Seismic Engineering: Research and Practice contains papers from twenty-two sessions of the 1989 ASCE Structures Congress. These papers represent a wide-ranging interest in this field of seismic engineering. Papers were contributed not only by both ASCE's Structures and Engineering Mechanics Divisions; but, by the Structural Engineers Association of California; the International Structural Consultants Association; the Japan Structural Consultants Association; and by professionals in Taiwan. This variety of sources enable the coverage of a broad range of seismic engineering topics including: lessons learned from past earthquakes, evaluation and upgrade of existing structures, dynamic testing and monitoring of structures, design and analysis of special structures including bridges, dams, and liquid storage tanks and new approaches to earthquake-resistant design including base isolation.
Genes encoding synthetic hydroxyproline-rich peptides with repetitive (Ser-Pro) units linked to an extensin signal sequence and a tetracysteine (TC) sequence were expressed transiently in tobacco, and transiently and stably in Arabidopsis under control of a strong constitutive promoter Expression of these peptides could be visualized in live cells by confocal microscopy following labeling with FlAsH- or ReAsH-EDT2 reagents.
