10,000 publications from this institution
Cluster computing applications like MapReduce and Dryad transfer massive amounts of data between their computation stages. These transfers can have a significant impact on job performance, accounting for more than 50% of job completion times. Despite this impact, there has been relatively little work on optimizing the performance of these data transfers, with networking researchers traditionally focusing on per-flow traffic management. We address this limitation by proposing a global management architecture and a set of algorithms that (1) improve the transfer times of common communication patterns, such as broadcast and shuffle, and (2) allow scheduling policies at the transfer level, such as prioritizing a transfer over other transfers. Using a prototype implementation, we show that our solution improves broadcast completion times by up to 4.5X compared to the status quo in Hadoop. We also show that transfer-level scheduling can reduce the completion time of high-priority transfers by 1.7X.
Isoprenoids are a large and highly diverse group of natural products with many functions in plant primary and secondary metabolism. Isoprenoids are synthesized from common prenyl diphosphate precursors through the action of terpene synthases and terpene-modifying enzymes such as cytochrome P450 monooxygenases. Many isoprenoids have important applications in areas such as human health and nutrition, and much effort has been directed toward their production in microbial hosts. However, many hurdles must be overcome in the elucidation and functional microbial expression of the genes responsible for biosynthesis of an isoprenoid of interest. Here, we review investigations into isoprenoid function and gene discovery in plants as well as the latest advances in isoprenoid pathway engineering in both plant and microbial hosts.
The photogeneration of free amines or diamines from soluble organic precursors such as photoactive 2-nitrobenzyl carbamates is useful for the imidization of polymers containing amic acid or amic ester groups as part of their main-chain or their side-chain. The base-catalyzed reaction occurs at lower temperatures than the noncatalyzed thermal process and is applicable to the patterning of thin film coatings.
At its peak, SN 1993J was one of the brightest supernovae in this century, and it is being studied more thoroughly than any supernova except SN 1987A. It is proving to be similar to the transition object SN 1987K, which metamorphosed from being a hydrogen-rich Type II near peak to having a hydrogen-deficient nebular phase. SN 1993J has been observed throughout the electromagnetic spectrum and with optical spectropolarimetry. It is interacting with a dense circumstellar nebula and is generating radio and X-ray flux, but it has probably not been detected in gamma rays. The photometric and spectral evolution are consistent with a star of original mass ∼ 15 M⊙ that lost appreciable mass to a binary companion leaving an extended, helium-rich hydrogen envelope of ≲ 0.5 M⊙ and a helium core of ∼ 4 M⊙. The spectral evolution will put strong constraints on the mixing of 56Ni and other species.
The extent to which coal liquefaction catalysts promote the cleavage of aliphatic bridges was investigated. Bibenzyl was chosen as a model to represent an ethyl bridge between two aromatic centers. An initial screening of catalysts showed that Co molybdate on SiO/sub 2/-promoted Al/sub 2/O/sub 3/, WS/sub 2/, LiCl-SnCl/sub 2/, SnCl/sub 2/ promoted with NH/sub 4/Cl, ZnCl/sub 2/, and SbCl/sub 3/ were all inactive as catalysts. FeCl/sub 3/ caused the bibenzyl to undergo a disproportionation reaction yielding benzene plus a tarry substance. AlCl/sub 3/ brought about a complete conversion of bibenzyl to benzene, toluene, and ethylbenzene as the primary products and lesser amounts of cyclohexane- and diphenyl-type derivatives, as well as a tarry substance. p-Toluenesulfonic acid was found to decompose but did not cause the formation of products from bibenzyl. More extensive experiments were then performed with AlCl/sub 3/. Product yields and distributions as a function of temperature, H/sub 2/ pressure, and catalyst concentration were determined. Participation of benzene, the solvent, in these reactions was also investigated. Bibenzyl conversion and the yields of toluene and ethylbenzene were a strong function of temperature and catalyst concentration but not of H/sub 2/ pressure. The yield of cyclohexane derivatives increased with pressure. This suggested that the H/sub 2/ needed to form toluene and ethylbenzene is derived from the reactant or solvent but not from dissolved H/sub 2/. Conversely, the formation of cyclohexane derivatives does involve the consumption of dissolved H/sub 2/. Plausible mechanisms are discussed.
Programmers often search for usage examples for API methods. A tool that could generate realistic, idiomatic, and contextual usage examples for one or more APIs would be immensely beneficial to developers. Such a tool would relieve the need for a deep understanding of the API landscape, augment existing documentation, and help discover interactions among APIs. We present CodeScholar, a tool that generates idiomatic code examples demonstrating the common usage of API methods. It includes a novel neural-guided search technique over graphs that grows the query APIs into idiomatic code examples. Our user study demonstrates that in 70% of cases, developers prefer CodeScholar generated examples over state-of-the-art large language models (LLM) like GPT3.5. We quantitatively evaluate 60 single and 25 multi-API queries from 6 popular Python libraries and show that across-the-board CodeScholar generates more realistic, diverse, and concise examples. In addition, we show that CodeScholar not only helps developers but also LLM-powered programming assistants generate correct code in a program synthesis setting.
The ability to predict a semiconductor's band edge positions in solution is important for the design of water-splitting photocatalyst materials. In this paper, we introduce a first-principles method to compute the conduction-band minima of semiconductors relative to the water H2O/H2 [H subscript 2 O / H subscript 2] level using density functional theory with semilocal functionals and classical molecular dynamics. We test the method on six well known photocatalyst materials: TiO2 [Ti O subscript 2], WO3 [W O subscript 3], CdS, ZnSe, GaAs, and GaP. The predicted band edge positions are within 0.34 eV of the experimental data, with a mean absolute error of 0.19 eV.
