Publications

40 Ar/ 39 Ar dating of drill core samples of a glassy melt rock recovered from beneath a massive impact breccia contained within the 180-kilometer subsurface Chicxulub crater in Yucatán, Mexico, has yielded well-behaved incremental heating spectra with a mean plateau age of 64.98 ± 0.05 million years ago (Ma). The glassy melt rock of andesitic composition was obtained from core 9 (1390 to 1393 meters) in the Chicxulub 1 well. The age of the melt rock is virtually indistinguishable from 40 Ar/ 39 Ar ages obtained on tektite glass from Beloc, Haiti, and Arroyo el Mimbral, northeastern Mexico, of 65.01 ± 0.08 Ma (mean plateau age for Beloc) and 65.07 ± 0.10 Ma (mean total fusion age for both sites). The 40 Ar/ 39 Ar ages, in conjunction with geochemical and petrological similarities, strengthen the recent suggestion that the Chicxulub structure is the source for the Haitian and Mexican tektites and is a viable candidate for the Cretaceous-Tertiary boundary impact site.

Abstract Cubic Na 3 PSe 4 as a solid‐state electrolyte for room temperature Na‐ion batteries is prepared by solid state reaction of stoichiometric amounts of Na 2 Se, red P, and Se under Ar (BN tube, 300 °C, 12 h).

We propose MiniCrypt, the first key-value store that reconciles encryption and compression without compromising performance. At the core of MiniCrypt is an observation on data compressibility trends in key-value stores, which enables grouping key-value pairs into small key packs, together with a set of distributed systems techniques for retrieving, updating, merging and splitting encrypted packs. Our evaluation shows that MiniCrypt compresses data by as much as 4 times with respect to the vanilla key-value store, and can increase the server's throughput by up to two orders of magnitude by fitting more data in main memory.

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.

ABSTRACT To aid in debugging efforts to increase yield, titer, and productivity of engineered metabolic pathways, computational models are increasingly needed to predict how changes in experimentally manipulable variables such as enzyme expression map to changes in pathway flux. Here, an ordinary differential equation model is developed for a heterologous mevalonate pathway in E. coli using kinetic parameters culled from literature and enzyme concentrations derived from Selective Reaction Monitoring Mass Spectrometry (SRM‐MS). To identify parameters most important to further experimental investigation, a global sensitivity analysis was performed, which pointed to amorphadiene synthase activity as the main limiting factor for amorphadiene production. Furthermore, the model predicted that in this local enzyme expression regime, the overall pathway flux is insensitive to farnesyl pyrophosphate (FPP)‐mediated inhibition of mevalonate kinase, not supporting a hypothesis that had previously been posited to be limiting amorphadiene production. To test these predictions experimentally, two strains were constructed: (1) a strain containing a homologous mevalonate kinase with weaker feedback inhibition, and (2) a strain with greater amorphadiene synthase expression. The experimental results validate the qualitative model hypotheses and accurately match the predicted productivities for the two strains, particularly when an in vivo‐derived k cat for amorphadiene synthase was substituted for the literature value. These results demonstrate the utility of using kinetic representations of engineered metabolic pathways parameterized with experimentally derived protein concentrations and enzyme kinetic constants to predict productivities and test hypotheses about engineering strategies. Biotechnol. Bioeng. 2015;112: 111–119. © 2014 Wiley Periodicals, Inc.

Conventional industrial agriculture in the United States (US) displays a number of recognizable characteristics. Market competition in agriculture, as compared with other sectors, tends to be particularly severe due to the large number of farms, their geographical dispersion, limited options for product differentiation, and the perishability of many crops, which inhibits farmers' ability to choose when to sell. Until 1996, cannabis production in California occurred outside of legal systems. In 1996, California voters approved the Compassionate Use Act (CUA), decriminalizing use and cultivation of cannabis for medical purposes. Fear of detection placed informal limits on farm size, especially on private property where plants could be tied to owners and property seizure and arrest was a real threat. The allowance of medical cannabis cultivation after 1996 affected production dynamics. Legal-medical protections, particularly physician recommendations, made it less risky to cultivate, thus fueling an expansion of the number of cultivators.