1,739 research outputs found
Fast DNA translocation through a solid-state nanopore
We report translocation experiments on double-strand DNA through a silicon
oxide nanopore. Samples containing DNA fragments with seven different lengths
between 2000 to 96000 basepairs have been electrophoretically driven through a
10 nm pore. We find a power-law scaling of the translocation time versus
length, with an exponent of 1.26 0.07. This behavior is qualitatively
different from the linear behavior observed in similar experiments performed
with protein pores. We address the observed nonlinear scaling in a theoretical
model that describes experiments where hydrodynamic drag on the section of the
polymer outside the pore is the dominant force counteracting the driving. We
show that this is the case in our experiments and derive a power-law scaling
with an exponent of 1.18, in excellent agreement with our data.Comment: 5 pages, 2 figures. Submitted to PR
Large upper critical field in non-centrosymmetric superconductor Y2C3
We determine the upper critical field of
non-centrosymmetric superconductor using two distinct methods: the
bulk magnetization M(T) and the tunnel-diode oscillator (TDO) based impedance
measurements. It is found that the upper critical field reaches a value of 30T
at zero temperature which is above the weak-coupling Pauli paramagnetic limit.
We argue that the observation of such a large in
could be attributed to the admixture of spin-singlet and spin-triplet pairing
states as a result of broken inversion symmetry.Comment: 4 pages, 3 figures, accepted by J. Phys. Chem. Solid
Layer-specific hole concentrations in Bi2Sr2(Y1-xCax)Cu208+[delta] as probed by XANES spectroscopy and coulometric redox analysis
Induction of holes not only in the superconductive CuO2 plane but also in the Bi2O2+δ charge reservoir of the Bi2Sr2(Y1-xCax)Cu2O8+δ superconductor upon CaII-for-YIII substitution is evidenced by means of two independent techniques, i.e., high-resolution x-ray-absorption near-edge structure (XANES) spectroscopy measurements and coulometric redox titrations. The absolute values derived for the CuO2-plane hole concentration from the Cu L2,3-edge XANES spectra are in good agreement with those obtained from the coulometric redox analysis. The CuO2-plane hole concentration is found to increase from 0.03 to 0.14 concomitantly with the increase in the BiO1+δ/2-layer hole concentration from 0.00 to 0.13 as the Ca-substitution level, x, increases from 0 to 1. The threshold CuO2-plane hole concentration for the appearance of superconductivity is determined at 0.06, while the highest Tc is obtained at the hole concentration of 0.12. In the O K-edge XANES spectrum, the increases in the CuO2-plane and BiO1+δ/2-layer hole concentrations with increasing x are seen as enhancement in the relative intensities of the pre-edge peaks at ∼528.3 and ∼530.5 eV, respectively.Peer reviewe
Layered-specific hole concentrations in Bi2Sr2(Y1-xCax)Cu2O8+d as probed by XANES spectroscopy and coulometric redox analysis
Induction of holes not only in the superconductive CuO2 plane but also in the
Bi2O2+d charge reservoir of the Bi2Sr2(Y1-xCax)Cu2O8+d superconductor upon
CaII-for-YIII substitution is evidenced by means of two independent techniques,
i.e., high-resolution x-ray-absorption near-edge structure (XANES) spectroscopy
measurements and coulometric redox titrations. The absolute values derived for
the CuO2-plane hole concentration from the Cu L2,3-edge XANES spectra are in
good agreement with those obtained from the coulometric redox analysis. The
CuO2-plane hole concentration is found to increase from 0.03 to 0.14
concomitantly with the increase in the BiO1+d/2-layer hole concentration from
0.00 to 0.13 as the Ca-substitution level, x, increases from 0 to 1. The
threshold CuO2-plane hole concentration for the appearance of superconductivity
is determined at 0.06, while the highest Tc is obtained at the hole
concentration of 0.12. In the O K-edge XANES spectrum, the increases in the
CuO2-plane and BiO1+d/2-layer hole concentrations with increasing x are seen as
enhancement in the relative intensities of the pre-edge peaks at ~528.3 and
\~530.5 eV, respectively.Comment: 12 pages, 6 figures, to appear in Phys. Rev.
Pore-blockade Times for Field-Driven Polymer Translocation
We study pore blockade times for a translocating polymer of length ,
driven by a field across the pore in three dimensions. The polymer performs
Rouse dynamics, i.e., we consider polymer dynamics in the absence of
hydrodynamical interactions. We find that the typical time the pore remains
blocked during a translocation event scales as ,
where is the Flory exponent for the polymer. In line with our
previous work, we show that this scaling behaviour stems from the polymer
dynamics at the immediate vicinity of the pore -- in particular, the memory
effects in the polymer chain tension imbalance across the pore. This result,
along with the numerical results by several other groups, violates the lower
bound suggested earlier in the literature. We discuss why
this lower bound is incorrect and show, based on conservation of energy, that
the correct lower bound for the pore-blockade time for field-driven
translocation is given by , where is the viscosity of
the medium surrounding the polymer.Comment: 14 pages, 6 figures, slightly shorter than the previous version; to
appear in J. Phys.: Cond. Ma
Doping-dependence of nodal quasiparticle properties in high- cuprates studied by laser-excited angle-resolved photoemission spectroscopy
We investigate the doping dependent low energy, low temperature ( = 5 K)
properties of nodal quasiparticles in the d-wave superconductor
BiSrCaCuO (Bi2212). By utilizing ultrahigh
resolution laser-excited angle-resolved photoemission spectroscopy, we obtain
precise band dispersions near , mean free paths and scattering rates
() of quasiparticles. For optimally and overdoped, we obtain very sharp
quasiparticle peaks of 8 meV and 6 meV full-width at half-maximum,
respectively, in accord with terahertz conductivity. For all doping levels, we
find the energy-dependence of , while () shows a monotonic increase from overdoping to underdoping. The doping
dependence suggests the role of electronic inhomogeneity on the nodal
quasiparticle scattering at low temperature (5 K \lsim 0.07T_{\rm c}),
pronounced in the underdoped region
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