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Nanotechnology
for fast DNA
sequencing
 One
of the great scientific and technological problems
of today is understanding the structure and function
of DNA and closely related development of
inexpensive methods for DNA sequencing. The latter
promises to revolutionize both our understanding of
DNA as well as significantly advance personalized
medicine...
Other areas: Photovoltaics;
Quantum-mechanical disordered and chaotic systems;
Quasicrystals;
High-performance scientific programming.
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Dna translocations
 Determination
of genetic code embedded in DNA molecules is
fundamental to molecular biology and medicine.
Alternative,
fast
and low-cost methods for DNA sequencing are in high
demand. We report on DNA translocations experiments
through the solid state nanopores, a technique that
has potential to meet those demands. We measured
translocation of λ-DNA through 5 and 10 nm silicon
nitride nanopores...
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Time-dependent
non-equilibrium transport
through molecule in nonorthogonal basis set
Microscopic
theory of non-equilibrium electronic transport under
time-dependent bias through the molecule (or quantum
dot) embedded between two semi-infinite metallic
electrodes is developed in the non-orthogonal
single-particle basis set using ab-initio formalism
of Greens functions. The equilibrium zeroth order
electron Green’s function and self-energy are
corrected by the corresponding time- inhomogeneous
dynamical contributions, derived in Hartree
approximation in steady-state linear-response
regime. It was shown that nonorthogonality
contributes to these dynamical contributions by
introducing terms related to the central
region-electrode interface, appearing only in
time-dependent case. The expression for current is
also derived, where nonorthogonal-induced dynamical
correction give an additional current, not present
in the orthogonal description. It is shown that the
obtained expression for current is gauge-invariant
and demonstrated that the omission of the additional
current violates charge conservation. It is also
shown that the additional current term vanishes in
orthogonal case.
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Interaction of UV light with amorphous
small-molecule organic thin films
We study interaction of thin
films of small-molecule organic blue-emitter
materials, such as
N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)benzidine
(TPD) and 4,4′-bis(2,2-diphenylvinyl)-1,1′-biphenyl
(DPVBi), with UV light. Films are stable in vacuum,
but readily degrade in the presence of oxygen. Thus,
the necessary condition for interaction
(degradation) is the simultaneous presence of UV
light and oxygen. These impurities are responsible
for increased morphological stability of irradiated
films and quenching of photoluminescence (PL).
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Electrical transport and
magnetotransport properties of cuprates
 The
work in this field of research is being done as a
part of long-lasting collaboration with solid state
physics laboratory in Orsay, LPS (Laboratoire de
Physique des Solides, Universite Paris-Sud, Orsay,
France) and especially with dr Helene Raffy.
Experiments were conducted in LPS (dr H. Raffy, dr
Z.Z. Li, dr L. Fruchter and dr F. Bouquet) and also
in NHMFL in Grenoble, with the help of dr P. Monceau
and dr G. Reményi.
Other areas:
Organic quasi-2D superconductors
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Micro-rods of oxidized pentacene
Pentacene is material widely. Pentacene is hole-type
semiconductor used in organic electronic devices,
well-known for its high charge carrier mobility as
high as 35 cm2V-1s-1 at room temperature.
Performance of devices made from organic thin films
strongly depends on their morphology and it is often
limited by the presence of molecular disorder and
grain boundaries, which reduce mobility of charge
carriers of a material.
To improve charge transport properties thermal
annealing could be used. Prolonged annealing of
pentacene films leads to surprising result: nano-
and micro-scale rod-shaped structures are forming on
film surface. Based on scanning electron microscopy
measurements, it is supposed that these structures
are crystalline. Their UV-vis absorbance indicates
that they are composed of more than one species of
oxidized pentacene molecules, including
6,13-pentacenequinone.
Images of crystal-like structures (micro-rods and
micro-crystals) formed on the surface of pentacene
films obtained by a), d) optical and b), c) scanning
electron microscopes.
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