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Almost six years ago we started the Spark project at UC Berkeley. Spark is a cluster computing engine that is optimized for in-memory processing, and unifies support for a variety of workloads, including batch, interactive querying, streaming, and iterative computations. Spark is now the most active big data project in the open source community, and is already being used by over one thousand organizations. One of the reasons behind Spark's success has been our early bet on the continuous increase in the memory capacity and the feasibility to fit many realistic workloads in the aggregate memory of typical production clusters. Today, we are witnessing new trends, such as Moore's law slowing down, and the emergence of a variety of computation and storage technologies, such as GPUs, FPGAs, and 3D Xpoint. In this talk, I'll discuss some of the lessons we learned in developing Spark as a unified computation platform, and the implications of today's hardware and software trends on the development of the next generation of big data processing systems.
Abstract Synthesis of transportation fuel from lignocellulosic biomass is an attractive solution to the green alternative‐energy problem. The production of biodiesel, in particular, involves the process of upgrading biomass‐derived small molecules to diesel precursors containing a specific carbon range (C 11 –C 23 ). Herein, a carbon‐upgrading process utilizing an acid‐catalyzed condensation of furanic platform molecules from biomass is described. Various types of sulfonic acid catalysts have been evaluated for this process, including biphasic and solid supported catalysts. A silica‐bound alkyl sulfonic acid catalyst has been developed for promoting carbon–carbon bond formation of biomass‐derived carbonyl compounds with 2‐methylfuran. This hydrophobic solid acid catalyst exhibits activity and selectivity that are comparable to those of a soluble acid catalyst. The catalyst can be readily recovered and recycled, possesses appreciable hydrolytic stability in the presence of water, and retains its acidity over multiple reaction cycles. Application of this catalyst to biomass‐derived platform molecules led to the synthesis of a variety of furanic compounds, which are potential biodiesel precursors.
Objective To examine the relationship of physician versus hospital ownership of small‐ and medium‐sized practices with spending and utilization of care. Data Source/Study Setting/Data Collection Survey data for 1,045 primary care‐based practices of 1–19 physicians linked to Medicare claims data for 2008 for 282,372 beneficiaries attributed to the 3,010 physicians in these practices. Study Design We used generalized linear models to estimate the associations between practice characteristics and outcomes (emergency department visits, index admissions, readmissions, and spending). Principal Findings Beneficiaries linked to hospital‐owned practices had 7.3 percent more emergency department visits and 6.4 percent higher total spending compared to beneficiaries linked to physician‐owned practices. Conclusions Physician practices are increasingly being purchased by hospitals. This may result in higher total spending on care.
Germanium nanowires are synthesized in bulk quantities and high purity using a simple vapor transport process. X-ray diffraction, scanning electron microscopy and transmission electron microscopy studies show that these wires are single crystalline with [111] growth direction; they have diameters ranging from 5 to 300 nm, and lengths up to hundreds micrometer. With brief vacuum thermal treatment, the average diameters of the wires can be further reduced to 16 nm.
Monomeric, three-coordinate arylpalladium(II) halide complexes undergo reductive elimination of aryl halide to form free haloarene and Pd(0). Reductive elimination of aryl chlorides, bromides, and iodides were observed upon the addition of P(t-Bu)3 to Pd[P(t-Bu)3](Ar)(X) (X = Cl, Br, I). Conditions to observe the equilibrium between reductive elimination and oxidative addition were established with five haloarenes. Reductive elimination of aryl chloride was most favored thermodynamically, and elimination of aryl iodide was the least favored. However, reductive elimination from the aryl chloride complex was the slowest, and reductive elimination from the aryl bromide complex was the fastest. These data show that the electronic properties of the halide, not the thermodynamic driving force for the addition of elimination reaction, control the rates for addition and elimination of haloarenes. Mechanistic data suggest that reversible reductive elimination of aryl bromide to form Pd[P(t-Bu)3] and free aryl bromide is followed by rate-limiting coordination of P(t-Bu)3 to form Pd[P(t-Bu)3]2.
The concept of self-assembled dendrimers is explored for the creation of discrete nanoparticle assemblies. Hybridization of branched DNA trimers and nanoparticle-DNA conjugates results in the synthesis of nanoparticle trimer and tetramer complexes. Multiple tetramer architectures are investigated, utilizing Au-DNA conjugates with varying secondary structural motifs. Hybridization products are analyzed by gel electrophoresis, and discrete bands are observed corresponding to structures with increasing numbers of hybridization events. Samples extracted from each band are analyzed by transmission electron microscopy, and statistics compiled from micrographs are used to compare assembly characteristics for each architecture. Asymmetric structures are also produced in which both 5 and 10 nm Au particles are assembled on branched scaffolds.
Abstract not Available.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffects of solvent structure on the distribution of silicate anions in mixed aqueous/organic solutions of alkaline tetramethylammonium silicateW. M. Hendricks, Alexis T. Bell, and C. J. RadkeCite this: J. Phys. Chem. 1991, 95, 23, 9519–9524Publication Date (Print):November 1, 1991Publication History Published online1 May 2002Published inissue 1 November 1991https://pubs.acs.org/doi/10.1021/j100176a088https://doi.org/10.1021/j100176a088research-articleACS PublicationsRequest reuse permissionsArticle Views212Altmetric-Citations24LEARN 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 options Get e-Alerts
A robot planning algorithm that constructs a global skeleton of free-space by incremental local methods is described. The curves of the skeleton are the loci of maxima of an artificial potential field that is directly proportional to the distance of the robot from obstacles. The method has the advantage of fast convergence of local methods in uncluttered environments, but it also has a deterministic and efficient method of escaping local extremal points of the potential function. The authors present a general algorithm, for configuration spaces of any dimension, and describe instantiations of the algorithm for robots with two and three degrees of freedom.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
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.
