290 research outputs found
Concordance of Bing doubles and boundary genus
Cha and Kim proved that if a knot K is not algebraically slice, then no
iterated Bing double of K is concordant to the unlink. We prove that if K has
nontrivial signature , then the n-iterated Bing double of K is not
concordant to any boundary link with boundary surfaces of genus less than
. The same result holds with replaced by , twice
the Ozsvath-Szabo knot concordance invariant.Comment: 13 pages, 7 figure
On the nonorientable 4-genus of double twist knots
We investigate the nonorientable 4-genus of a special family of
2-bridge knots, the twist knots and double twist knots . Because the
nonorientable 4-genus is bounded by the nonorientable 3-genus, it is known that
. By using explicit constructions to obtain upper
bounds on and known obstructions derived from Donaldson's
diagonalization theorem to obtain lower bounds on , we produce
infinite subfamilies of where and , respectively.
However, there remain infinitely many double twist knots where our work only
shows that lies in one of the sets , or
. We tabulate our results for all with and up
to 50. We also provide an infinite number of examples which answer a conjecture
of Murakami and Yasuhara.Comment: Some exposition is revised, a figure is added, and typos are
corrected, following comments from the refere
Synthesis of a 3D network of Pt nanowires by atomic layer deposition on carbonaceous template
The formation of a 3D network composed of free standing and interconnected Pt
nanowires is achieved by a two-step method, consisting of conformal deposition
of Pt by atomic layer deposition (ALD) on a forest of carbon nanotubes and
subsequent removal of the carbonaceous template. Detailed characterization of
this novel 3D nanostructure was carried out by transmission electron microscopy
(TEM) and electrochemical impedance spectroscopy (EIS). These characterizations
showed that this pure 3D nanostructure of platinum is self-supported and offers
an enhancement of the electrochemically active surface area by a factor of 50
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