Jumping bristletail (Insecta: Apterygota: Microcoryphia) records in the southeastern United States

Few records of Microcoryphia exist for the southeastern United States, with named species being reported only from Arkansas, Tennessee, and the mid-Atlantic states, and with an unnamed species being reported from Georgia. Records are here provided from 291 specimens housed in the Mississippi Entomological Museum, including ten new species-level state records. This is also the first published report of the order Microcoryphia from Alabama and Mississippi. Species include the machilids Pedetontoides atlanticus Mendes in Alabama, Arkansas, Georgia, Mississippi, and North Carolina; Pedetontus cf. atlanticus in Kentucky; Pedetontus (Verhoeffilis) gershneri Allen in Arkansas; and Pedetontus (Pedetontus) saltator Wygodzinsky and Schmidt in Mississippi and North Carolina; and the meinertellid Machiloides banksi (Silvestri) in Alabama, Arkansas, Mississippi, and North Carolina

Gene Regulation by Riboswitches with and without Negative Feedback Loop

Riboswitches, structured elements in the untranslated regions of messenger RNAs, regulate gene expression by binding specific metabolites. We introduce a kinetic network model that describes the functions of riboswitches at the systems level. Using experimental data for flavin mono nucleotide riboswitch as a guide we show that efficient function, implying a large dynamic range without compromising the requirement to suppress transcription, is determined by a balance between the transcription speed, the folding and unfolding rates of the aptamer, and the binding rates of the metabolite. We also investigated the effect of negative feedback accounting for binding to metabolites, which are themselves the products of genes that are being regulated. For a range of transcription rates negative feedback suppresses gene expression by nearly 10 fold. Negative feedback speeds the gene expression response time, and suppresses the change of steady state protein concentration by half relative to that without feedback, when there is a modest spike in DNA concentration. A dynamic phase diagram expressed in terms of transcription speed, folding rates, and metabolite binding rates predicts different scenarios in riboswitch-mediated transcription regulation.Comment: 12 pages, 8 figure

Interferometry using spatial adiabatic passage in quantum dot networks

We show that techniques of spatial adiabatic passage can be used to realise an electron interferometer in a geometry analogous to a conventional Aharonov-Bohm ring, with transport of the particle through the device modulated using coherent transport adiabatic passage. This device shows an interesting interplay between the adiabatic and non-adiabatic behaviour of the system. The transition between non-adiabatic and adiabatic behaviour may be tuned via system parameters and the total time over which the protocol is enacted. Interference effects in the final state populations analogous to the electrostatic Aharonov-Bohm effect are observed.Comment: Version accepted in Phys. Rev. B, 8 pages, 6 figure

Fragility of iron-based glasses

The viscosity of various iron-based bulk-glass-forming liquids is measured around the glass transition, and the associated fragility is calculated. Fragility is found to vary broadly between compositions, from a low value of ~43, which indicates fairly “strong” liquid behavior, to ~65, well within the region of “fragile” behavior. Despite a strong covalent bonding identified in the structure of this class of metal/metalloid glasses, their liquid fragility can be remarkably high, exceeding even the very fragile palladium and platinum bulk-glass formers. An inverse correlation between glass-forming ability and fragility is identified, suggesting that iron-based glasses are effectively “kinetically” stabilized