The Maine Economy—Through a Different Lens

William Knowles, a banker “from away” who has retired to Maine, gives his thoughts about the state’s economy, based on his reading, research, and conversations with a variety of Mainers. He structures his examination using four different “lenses,” which he terms: comparisons (how does Maine compare with other states and regions), cultivation (economic development), capital (especially human capital), and culture. Knowles challenges readers to think about whether Maine’s culture or belief system may be an important factor in restraining economic development

Retail Redlining: Are gasoline prices higher in poor and minority neighborhoods?

Higher retail prices are frequently cited as a cost of living in poor, minority neighborhoods. However, the empirical evidence, which primarilycomes from the grocery gap literature on food prices, has been mixed. This study uses new data on retail gasoline prices in three major U.S.cities to provide evidence on the relationship between neighborhood characteristics and consumer prices. We find that gasoline prices do not varygreatly with neighborhood racial composition, but that prices are higher in poor neighborhoods. For a 10 percentage point increase in the percentof families with incomes below the poverty line relative to families with incomes between 1 and 2 times the poverty line, retail gasoline prices are estimated to increase by an average of 0.70 percent. This differential is reduced to 0.22 percent once we add controls for costs, competition, and demand. Finally, we provide evidence that the remaining, small, price differential for poor neighborhoods is likely the result of traditional price discrimination in response to less competition and/or more inelastic demand in these locations.

Efficiency arcjet thruster with controlled arc startup and steady state attachment

An improved efficiency arcjet thruster has a constrictor and electrically-conductive nozzle anode defining an arc chamber, and an electrically-conductive rod having a tip spaced upstream from the constrictor and defining a cathode spaced from the anode by a gap generally coextensive with the arc chamber. An electrical potential is applied to the anode and cathode to generate an electrical arc in the arc chamber from the cathode to anode. Catalytically decomposed hydrazine is supplied to the arc chamber with generation of the arc so as to produce thermal heating and expansion thereof through the nozzle. The constrictor can have a electrically insulative portion disposed between the cathode tip and the nozzle anode, and an electrically-conductive anode extension disposed along the insulative portion so as to define an auxiliary gap with the cathode tip substantially smaller than the gap defined between the cathode and nozzle anode for facilitating startup of arc generation. The constrictor can also include an electrically-conductive electrode with a variable electrical potential to vary the shape of the arc generated in the arc chamber. Also, the cathode is mounted for axial movement such that the gap between its tip and the nozzle anode can be varied to facilitate a generally nonerosive generation of the electrical arc at startup and reliable steady state operation. Further, the arc chamber can have a nonparallel subsonic-to-supersonic transition configuration, or alternatively solely a nonparallel supersonic configuration, for improved arc attachment

“Transfer Talk” in Talk about Writing in Progress: Two Propositions about Transfer of Learning

This article tracks the emergence of the concept of “transfer talk”—a concept distinct from transfer of learning—and teases out the implications of transfer talk for theories of transfer of learning. The concept of transfer talk was developed through a systematic examination of 30 writing center transcripts and is defined as “the talk through which individuals make visible their prior learning (in this case, about writing) or try to access the prior learning of someone else.” In addition to including a taxonomy of transfer talk and analysis of which types occur most often in this set of conferences, this article advances two propositions about the nature of transfer of learning: (1) transfer of learning may have an important social, even collaborative, component and (2) although meta-awareness about writing has long been recognized as valuable for transfer of learning, more automatized knowledge may play an important role as well

Purification of a novel pyruvate kinase from a green alga

AbstractA chloroplast pyruvate kinase has been purified to homogeneity from the green alga Selenastrum minutum. The subunit composition of the enzyme differs markedly from pyruvate kinases from other sources. Subunit and native Mrs were 210 kDa and 235 kDa, respectively, indicating a monomeric structure. Immunological and peptide mapping analyses suggested structural homology to a bacterial, but not higher plant or mammalian pyruvate kinase

DNA-coated Functional Oil Droplets

Many industrial soft materials often include oil-in-water (O/W) emulsions at the core of their formulations. By using tuneable interface stabilizing agents, such emulsions can self-assemble into complex structures. DNA has been used for decades as a thermoresponsive highly specific binding agent between hard and, recently, soft colloids. Up until now, emulsion droplets functionalized with DNA had relatively low coating densities and were expensive to scale up. Here a general O/W DNA-coating method using functional non-ionic amphiphilic block copolymers, both diblock and triblock, is presented. The hydrophilic polyethylene glycol ends of the surfactants are functionalized with azides, allowing for efficient, dense and controlled coupling of dibenzocyclooctane functionalized DNA to the polymers through a strain-promoted alkyne-azide click reaction. The protocol is readily scalable due to the triblock's commercial availability. Different production methods (ultrasonication, microfluidics and membrane emulsification) are used with different oils (hexadecane and silicone oil) to produce functional droplets in various size ranges (sub-micron, $\sim 20\,\mathrm{\mu m}$ and $> 50\,\mathrm{\mu m}$), showcasing the generality of the protocol. Thermoreversible sub-micron emulsion gels, hierarchical "raspberry" droplets and controlled droplet release from a flat DNA-coated surface are demonstrated. The emulsion stability and polydispersity is evaluated using dynamic light scattering and optical microscopy. The generality and simplicity of the method opens up new applications in soft matter and biotechnological research and industrial advances.Comment: 7 pages, 2 figures, 1 tabl