10,000 publications from this institution
In response to worldwide environmental crises driven by declines in the availability or quality of freshwater, ecologists and water resource economists are searching for ways to collaborate in order to guide the difficult choices facing the public, land managers, and politicians. Scientists are challenged to detect and quantify both the drivers of ecosystem change and ecosystem responses, including positive and negative feedbacks that will determine the future states of inland waters. Predicting ecosystem shifts over large temporal and spatial scales has proven difficult or impossible, even in well-studied systems, where the drivers of change are known. New remote-sensing, monitoring, and tracer technologies, however, offer glimpses of watershed processes at unprecedented spatial and temporal scales. Several interdisciplinary groups, including scientists, information specialists, and engineers, are exploring the best ways to design sampling schemes using these new technologies, to interpret the extensive, spatially explicit dynamic data they will yield, and to use these data to formulate models useful for forecasting. Economists, in turn, can use this information to design management and policy tools for sustaining critical ecosystem components and processes.
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.
Numerical simulations are presented showing that over certain parameter ranges, the asymptotic behavior of a real-world digital filter having a wordlength of only 16 b is virtually indistinguishable from that of an infinite wordlength digital filter. It is suggested that for all practical purposes, a finite-state machine can behave in a chaotic way if its wordlength is sufficiently large. It is concluded that the chaotic nature of a real digital filter may be hidden because of short wordlengths, but the chaotic behavior must be considered in a real digital filter when the wordlength exceeds 16 b.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
It is shown that two-step, two-wave mixing makes a substantial contribution to the total three-wave mixing process in a noncentrosymmetric crystal. The efficiency of generating $2{\ensuremath{\omega}}_{1}\ensuremath{-}{\ensuremath{\omega}}_{2}$ was observed as a function of the difference frequency ${\ensuremath{\omega}}_{1}\ensuremath{-}{\ensuremath{\omega}}_{2}$, the electric polarization vector, and the propagation direction. This method allowed the determination of the true third-order susceptibility ${\ensuremath{\chi}}^{(3)}$, in both sign and magnitude, in terms of ${[{\ensuremath{\chi}}^{(2)}]}^{2}$.
The conversion of plant biomass provides a sustainable pathway towards the production of renewable fuels. Hemicellulose, a readily available form of biomass, can be catalytically converted to provide a range of fuel molecules, from furans and sugar alcohols to alkanes and aromatics. Using ionic liquids as solvent and Brønsted acid catalysts for biomass deconstruction, we investigated the kinetics of hemicellulose (xylan) hydrolysis and the subsequent dehydration/degradation reactions. These findings were compared to those found for similar reactions involving cellulose. In 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]) at 80 °C, we report that hemicellulose can be hydrolyzed to xylose in 90% yield, with 5 wt % dehydration products and 4 wt % humins, when water is added stepwise. This chemical process presents a viable pathway for producing sugars capable of being chemically (via dehydration/hydrogenation) or biologically (via fermentation) upgraded to potential fuel molecules.
More than 200 papers, two special issues (Journal of Circuits, Systems, and Computers, March, June, 1993, and IEEE Trans. on Circuits and Systems, vol. 40, no. 10, October, 1993), an International Workshop on Chua’s Circuit: chaotic phenomena and applica tions at NOLTA’93, and a book (edited by R.N. Madan, World Scientific, 1993) on Chua’s circuit have been published since its inception a decade ago. This review paper attempts to present an overview of these timely publications, almost all within the last six months, and to identify four milestones of this very active research area. An important milestone is the recent fabrication of a monolithic Chua’s circuit. The robustness of this IC chip demonstrates that an array of Chua’s circuits can also be fabricated into a monolithic chip, thereby opening the floodgate to many unconventional applications in information technology, synergetics, and even music. The second milestone is the recent global unfolding of Chua’s circuit, obtained by adding a linear resistor in series with the inductor to obtain a canonical Chua’s circuit— now generally referred to as Chua’s oscillator. This circuit is most significant because it is structurally the simplest (it contains only 6 circuit elements) but dynamically the most complex among all nonlinear circuits and systems described by a 21-parameter family of continuous odd-symmetric piecewise-linear vector fields. The third milestone is the recent discovery of several important new phenomena in Chua’s circuits, e.g., stochastic resonance, chaos-chaos type intermittency, 1/f noise spectrum, etc. These new phenomena could have far-reaching theoretical and practical significance. The fourth milestone is the theoretical and experimental demonstration that Chua’s circuit can be easily controlled from a chaotic regime to a prescribed periodic or constant orbit, or it can be synchronized with 2 or more identical Chua’s circuits, operating in an oscillatory, or a chaotic regime. These recent breakthroughs have ushered in a new era where chaos is deliberately created and exploited for unconventional applications, e.g. secure communication.
ADVERTISEMENT RETURN TO ISSUEPREVCommentNEXTThe Changing Landscape of Physical Chemistry at the Beginning of the 21st CenturyG. A. Somorjai and R. D. LevineView Author Information Department of Chemistry and Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720-1460, and Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095. Cite this: J. Phys. Chem. B 2005, 109, 19, 9853–9854Publication Date (Web):April 27, 2005Publication History Received10 December 2004Published online27 April 2005Published inissue 1 May 2005https://pubs.acs.org/doi/10.1021/jp040754qhttps://doi.org/10.1021/jp040754qarticle-commentaryACS PublicationsCopyright © 2005 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views560Altmetric-Citations2LEARN 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 PDF (13 KB) Get e-AlertscloseSUBJECTS:Catalysts,Molecular structure,Molecules,Physical chemistry,Selectivity Get e-Alerts
