Publications

Sequencing in an Assembly Line with Blocking to Minimize Cycle Time

We consider an assembly line with m stations in series having finite capacity buffers. Blocking occurs when buffers are full. There are M different types of products to be assembled, each with its own processing requirements. There is a production target set for each type. The problem is to operate the line to maximize throughput. We propose heuristic approaches to this problem based on an equivalent maximum flow problem and on critical path techniques.

PHOTOMETRICALLY TRIGGERED KECK SPECTROSCOPY OF<i>FERMI</i>BL LACERTAE OBJECTS

We report on Keck spectra of ten Fermi blazars. J0622+3326, previously\nunobserved, is shown to be a flat-spectrum radio quasar at redshift z=1.062.\nThe others are known BL Lac-type objects that have resisted previous attempts\nto secure redshifts. Using a photometric monitoring campaign with the 0.76 m\nKatzman Automatic Imaging Telescope at Lick Observatory, we identified epochs\nwhen the relativistic jet emission was fainter than usual, thus triggering the\nKeck spectroscopy. This strategy gives improved sensitivity to stars and\nionized gas in the host galaxy, thereby providing improved redshift constraints\nfor seven of these sources.\n

Isolation and Characterization of a Starchless Mutant of <i>Arabidopsis thaliana</i> (L.) Heynh Lacking ADPglucose Pyrophosphorylase Activity

A mutant of Arabidopsis thaliana lacking ADPglucose pyrophosphorylase activity (EC 2.7.7.27) was isolated (from a mutagenized population of plants) by screening for the absence of leaf starch. The mutant grows as vigorously as the wild type in continuous light but more slowly than the wild type in a 12 hours light/12 hours dark photoperiod. Genetic analysis showed that the deficiency of both starch and ADPglucose pyrophosphorylase activity were attributable to a single, nuclear, recessive mutation at a locus designated adg1. The absence of starch in the mutant demonstrates that starch synthesis in the chloroplast is entirely dependent on a pathway involving ADPglucose pyrophosphorylase. Analysis of leaf extracts by two-dimensional polyacrylamide gel electrophoresis followed by Western blotting experiments using antibodies specific for spinach ADPglucose pyrophosphorylase showed that two proteins, present in the wild type, were absent from the mutant. The heterozygous F(1) progeny of a cross between the mutant and wild type had a specific activity of ADPglucose pyrophosphorylase indistinguishable from the wild type. These observations suggest that the mutation in the adg1 gene in TL25 might affect a regulatory locus.

The influence of steps on the oxidation of molybdenum single crystal surfaces

Eigenvalue estimation of differential operators with a quantum algorithm (11 pages)

Progress towards microwave readout of a silicon double quantum dot

CCDC 1886178: Experimental Crystal Structure Determination

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.

Delayed sleep–wake phase disorder in young adults: prevalence and correlates from a national survey of Norwegian university students

Photoinduced β-Hydrogen Elimination and Radical Formation with CpW(CO)₃(CH₂CH₃):  Ultrafast IR and DFT Studies

The initial steps of β-hydrogen elimination from the complex CpW(CO)3(CH2CH3) were studied using ultrafast infrared and step-scan FTIR spectroscopy combined with density functional theory calculations. The reaction was initiated by a pulse of UV light at 266 nm and followed with infrared light on the femto- to microsecond timescale, allowing for the identification and kinetic characterization of transients. In the process of β-H elimination, the primary photoproduct was found to be an α-H stabilized complex and the dynamics of the elusive species cis-CpW(CO)3(H)(CH2CH2) were resolved, allowing for a full kinetic and thermodynamic analysis of the reaction. In a side reaction, CpW(CO)3• is formed via ethyl ligand dissociation; the measured formation rate indicates that the complex forms from a vibrationally excited parent complex. Density functional theory calculations of all relevant transient intermediates and transition states involved in β-H elimination of CpW(CO)3(CH2CH3) are presented. These calculations show two principle mechanisms of β-H elimination, which are discussed in the context of the experimental data.

Flood Basalts--Bigger and Badder

During episodes of flood volcanism, vast amounts of mass and energy are transferred from Earth's interior to the surface within relatively short periods of time. Episodes of major flood volcanism coincided with severe mass extinctions, and perhaps also with large meteor impacts. In his Perspective, [Renne][1] discusses recent studies into the causes of these events and the extent of the flood basalt provinces created by them. He highlights the report by [ Reichow et al .][2], who show that the Siberian Traps are much larger than previously thought, making it the largest (by volume) of all known flood provinces. [1]: http://www.sciencemag.org/cgi/content/full/296/5574/1812 [2]: http://www.sciencemag.org/cgi/content/short/296/5574/1846

From Commodity to Fiat and Now to Crypto: What Does History Tell Us?

Over time, there has been a tendency for political jurisdictions and residents to converge on a single currency. Monopoly over seigniorage is a source of political power and a valuable lifeline when sovereignty is threatened. Moreover a uniform currency, insofar as it is free of counterparty and liquidity risk, facilitates economic activity. But will digital currencies now reverse this trend toward uniformity, given the apparent ease with which they can be created? The information sensitivity of those units, evident in the fact that they trade at varying prices, suggests that they do not yet provide the core functions of money. So-called stable coins are intended to bridge this gap, but whether they can be successfully scaled up and maintain their stability is doubtful. The one unit that can clearly meet these challenges is central bank digital currency. But there would be both costs and benefits of moving in this direction.

The salmonid and the subsurface: Hillslope storage capacity determines the quality and distribution of fish habitat

Abstract Water in rivers is delivered via the critical zone (CZ)—the living skin of the Earth, extending from the top of the vegetation canopy through the soil and down to fresh bedrock and the bottom of significantly active groundwater. Consequently, the success of stream‐rearing salmonids depends on the structure and resulting water storage and release processes of this zone. Physical processes below the land surface (the subsurface component of the CZ) ultimately determine how landscapes “filter” climate to manifest ecologically significant streamflow and temperature regimes. Subsurface water storage capacity of the CZ has emerged as a key hydrologic variable that integrates many of these subsurface processes, helping to explain flow regimes and terrestrial plant community composition. Here, we investigate how subsurface storage controls flow, temperature, and energetic regimes that matter for salmonids. We illustrate the explanatory power of broadly applicable, storage‐based frameworks across a lithological gradient that spans the Eel River watershed of California. Study sites are climatically similar but differ in their geologies and consequent subsurface CZ structure that dictates water storage dynamics, leading to dramatically different hydrographs, temperature, and riparian regimes—with consequences for every aspect of salmonid life history. Lithological controls on the development of key subsurface CZ properties like storage capacity suggest a heretofore unexplored link between salmonids and geology, adding to a rich literature that highlights various fluvial and geomorphic influences on salmonid diversity and distribution. Rapidly advancing methods for estimating and observing subsurface water storage dynamics at large scales present new opportunities for more clearly identifying landscape features that constrain the distributions and abundances of organisms, including salmonids, at watershed scales.

Fracture and Fatigue

Abstract : In the last twenty years, much progress has been made with the continuum mechanics characterization of crack growth rates through the application of linear elastic and elastic-plastic fracture mechanics, and such analyses are now in widespread use for defect-tolerant design codes. Similarly, an understanding of the role of microstructure in improving the resistance to fracture and fatigue has emerged to the point where alloy design guidelines exist for the production of alloys with optimum resistance to fatigue failure. However, much work remains in the definition of mechanisms associated with environmentally-influenced crack growth, with the effect of variable amplitude loading, with the problem of the short flaw, and in the fracture of microscopic structures (e.g., packaging problems in the electronics industry).

Dynamic Boundary Layer Simulation of Pulsed CO₂ Electrolysis on a Copper Catalyst

Pulsed electrolysis has been demonstrated to improve the faradaic efficiency (FE) to C&lt;sub&gt;2+&lt;/sub&gt; products during the electrochemical reduction of CO&lt;sub&gt;2&lt;/sub&gt; over a Cu catalyst, but the nature of this enhancement is poorly understood. Herein, we developed a time-dependent continuum model of pulsed CO&lt;sub&gt;2&lt;/sub&gt; electrolysis on Cu in 0.1 M CsHCO&lt;sub&gt;3&lt;/sub&gt; that faithfully represents the experimentally observed effects of pulsed electrolysis. This work shows that pulsing results in dynamic changes in the pH and CO&lt;sub&gt;2&lt;/sub&gt; concentration near the Cu surface, which lead to an enhanced C&lt;sub&gt;2+&lt;/sub&gt; FE as a consequence of repeatedly accessing a transient state of heightened pH and CO&lt;sub&gt;2&lt;/sub&gt; concentration at high cathodic overpotential. Using these insights, a variety of pulse shapes were explored to establish operating conditions that maximize the rate of C&lt;sub&gt;2+&lt;/sub&gt; product formation and minimize the rates of H&lt;sub&gt;2&lt;/sub&gt; and C&lt;sub&gt;1&lt;/sub&gt; product formation.

CCDC 866258: Experimental Crystal Structure Determination

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.

Warm Spring Reduced Impact of Summer Drought on Carbon Cycling

Free-riding and whitewashing in peer-to-peer systems

We develop a model to study the phenomenon of free-riding in peer-to-peer (P2P) systems. At the heart of our model is a user of a certain type, an intrinsic and private parameter that reflects the user's willingness to contribute resources to the system. A user decides whether to contribute or free-ride based on how the current contribution cost in the system compares to her type. When the societal generosity (i.e., the average type) is low, intervention is required in order to sustain the system. We present the effect of mechanisms that exclude low type users or, more realistic, penalize free-riders with degraded service. We also consider dynamic scenarios with arrivals and departures of users, and with whitewashers: users who leave the system and rejoin with new identities to avoid reputational penalties. We find that when penalty is imposed on all newcomers in order to avoid whitewashing, system performance degrades significantly only when the turnover rate among users is high.

Hospital-physician joint ventures : results and lessons from a national demonstration in primary care