9,018 research outputs found
Preferential binding and structural distortion by Fe2+ at RGGG-containing DNA sequences correlates with enhanced oxidative cleavage at such sequences.
Certain DNA sequences are known to be unusually sensitive to nicking via the Fe2+-mediated Fenton reaction. Most notable are a purine nucleotide followed by three or more G residues, RGGG, and purine nucleotides flanking a TG combination, RTGR. Our laboratory previously demonstrated that nicking in the RGGG sequences occurs preferentially 5' to a G residue with the nicking probability decreasing from the 5' to 3'end of these sequences. Using 1H NMR to characterize Fe2+ binding within the duplex CGAGTTAGGGTAGC/GCTACCCTAACTCG and 7-deazaguanine-containing (Z) variants of it, we show that Fe2+ binds preferentially at the GGG sequence, most strongly towards its 5' end. Substitutions of individual guanines with Z indicate that the high affinity Fe2+ binding at AGGG involves two adjacent guanine N7 moieties. Binding is accompanied by large changes in specific imino, aromatic and methyl proton chemical shifts, indicating that a locally distorted structure forms at the binding site that affects the conformation of the two base pairs 3' to the GGG sequence. The binding of Fe2+ to RGGG contrasts with that previously observed for the RTGR sequence, which binds Fe2+ with negligible structural rearrangements
A Complementary Resistive Switch-based Crossbar Array Adder
Redox-based resistive switching devices (ReRAM) are an emerging class of
non-volatile storage elements suited for nanoscale memory applications. In
terms of logic operations, ReRAM devices were suggested to be used as
programmable interconnects, large-scale look-up tables or for sequential logic
operations. However, without additional selector devices these approaches are
not suited for use in large scale nanocrossbar memory arrays, which is the
preferred architecture for ReRAM devices due to the minimum area consumption.
To overcome this issue for the sequential logic approach, we recently
introduced a novel concept, which is suited for passive crossbar arrays using
complementary resistive switches (CRSs). CRS cells offer two high resistive
storage states, and thus, parasitic sneak currents are efficiently avoided.
However, until now the CRS-based logic-in-memory approach was only shown to be
able to perform basic Boolean logic operations using a single CRS cell. In this
paper, we introduce two multi-bit adder schemes using the CRS-based
logic-in-memory approach. We proof the concepts by means of SPICE simulations
using a dynamical memristive device model of a ReRAM cell. Finally, we show the
advantages of our novel adder concept in terms of step count and number of
devices in comparison to a recently published adder approach, which applies the
conventional ReRAM-based sequential logic concept introduced by Borghetti et
al.Comment: 12 pages, accepted for IEEE Journal on Emerging and Selected Topics
in Circuits and Systems (JETCAS), issue on Computing in Emerging Technologie
Electric field and strain induced Rashba effect in hybrid halide perovskites
Using first principles density functional theory calculations, we show how
Rashba-type energy band splitting in the hybrid organic-inorganic halide
perovskites APbX (A=CHNH, CH(NH), Cs and X=I, Br)
can be tuned and enhanced with electric fields and anisotropic strain. In
particular, we demonstrate that the magnitude of the Rashba splitting of
tetragonal (CHNH)PbI grows with increasing macroscopic alignment of
the organic cations and electric polarization, indicating appreciable
tunability with experimentally-feasible applied fields, even at room
temperature. Further, we quantify the degree to which this effect can be tuned
via chemical substitution at the A and X sites, which alters amplitudes of
different polar distortion patterns of the inorganic PbX cage that directly
impact Rashba splitting. In addition, we predict that polar phases of CsPbI
and (CHNH)PbI with symmetry possessing considerable Rashba
splitting might be accessible at room temperature via anisotropic strain
induced by epitaxy, even in the absence of electric fields
Circularizing Planet Nine through dynamical friction with an extended, cold planetesimal belt
Unexpected clustering in the orbital elements of minor bodies beyond the
Kuiper belt has led to speculations that our solar system actually hosts nine
planets, the eight established plus a hypothetical "Planet Nine". Several
recent studies have shown that a planet with a mass of about 10 Earth masses on
a distant eccentric orbit with perihelion far beyond the Kuiper belt could
create and maintain this clustering. The evolutionary path resulting in an
orbit such as the one suggested for Planet Nine is nevertheless not easily
explained. Here we investigate whether a planet scattered away from the
giant-planet region could be lifted to an orbit similar to the one suggested
for Planet Nine through dynamical friction with a cold, distant planetesimal
belt. Recent simulations of planetesimal formation via the streaming
instability suggest that planetesimals can readily form beyond 100au. We
explore this circularisation by dynamical friction with a set of numerical
simulations. We find that a planet that is scattered from the region close to
Neptune onto an eccentric orbit has a 20-30% chance of obtaining an orbit
similar to that of Planet Nine after 4.6Gyr. Our simulations also result in
strong or partial clustering of the planetesimals; however, whether or not this
clustering is observable depends on the location of the inner edge of the
planetesimal belt. If the inner edge is located at 200au the degree of
clustering amongst observable objects is significant.Comment: Accepted to MNRA
Spoken words
Chiefly tablesIncludes bibliographical referencesSupported in part by the National Institute of Education under contract no. US-NIE-C-400-76-011
Behavioral Function of the Components and the Blend of the Sex Pheromone of the Cabbage Looper, Trichoplusia ni
Individual male cabbage looper moths, Trichoplusia ni, were tested in a sustained-flight tunnel to the sex pheromone, a 93:7 blend of (Z)-7-dodecenyl acetate and dodecyl acetate. Two experimental procedures were used to investigate the interaction of the two components in the upwind flight response of males. In the first test, chemical components were selectively removed from the moths' flight path at two distances from the source, corresponding to areas of the tunnel in which the blend was or was not active in increasing the number of upwind flights. In the second test, males were offered a choice between plumes, in their normal flight path, which contained different components. Results of both tests showed that males were unresponsive to dodecyl acetate alone at all phases of the flight response, responses to the blend were dependent on the two components being mixed in the same plume, and response to the blend altered the males subsequent flight response to Z7-12:Ac alon
- …