2,846 research outputs found
Homfly Polynomials of Generalized Hopf Links
Following the recent work by T.-H. Chan in [HOMFLY polynomial of some
generalized Hopf links, J. Knot Theory Ramif. 9 (2000) 865--883] on reverse
string parallels of the Hopf link we give an alternative approach to finding
the Homfly polynomials of these links, based on the Homfly skein of the
annulus. We establish that two natural skein maps have distinct eigenvalues,
answering a question raised by Chan, and use this result to calculate the
Homfly polynomial of some more general reverse string satellites of the Hopf
link.Comment: Published by Algebraic and Geometric Topology at
http://www.maths.warwick.ac.uk/agt/AGTVol2/agt-2-2.abs.htm
Conjugacy for positive permutation braids
Positive permutation braids on n strings, which are defined to be positive n-braids where each pair of strings crosses at most once, form the elementary but non-trivial building blocks in many studies of conjugacy in the braid groups. We consider conjugacy among these elementary braids which close to knots, and show that those which close to the trivial knot or to the trefoil are all conjugate. All such n-braids with the maximum possible crossing number are also shown to be conjugate. We note that conjugacy of these braids for n<6 depends only on the crossing number. In contrast, we exhibit two such braids on 6 strings with 9 crossings which are not conjugate but whose closures are each isotopic to the (2,5) torus knot
Will spin-relaxation times in molecular magnets permit quantum information processing?
Using X-band pulsed electron spin resonance, we report the intrinsic
spin-lattice () and phase coherence () relaxation times in molecular
nanomagnets for the first time. In Cr heterometallic wheels, with = Ni
and Mn, phase coherence relaxation is dominated by the coupling of the electron
spin to protons within the molecule. In deuterated samples reaches 3
s at low temperatures, which is several orders of magnitude longer than
the duration of spin manipulations, satisfying a prerequisite for the
deployment of molecular nanomagnets in quantum information applications.Comment: 4 pages, 3 figures, in press at Physical Review Letter
Can the solar p-modes contribute to the high-frequency transverse oscillations of spicules?
Lateral motions of spicules serve as vital indicators of transverse waves in
the solar atmosphere, and their study is crucial for understanding the wave
heating process of the corona. Recent observations have focused on
"high-frequency" transverse waves (periods < 100 s), which have the potential
to transport sufficient energy for coronal heating. These high-frequency
spicule oscillations are distinct from granular motions, which have much longer
time scales of 5-10 min. Instead, it is proposed that they are generated
through the mode conversion from high-frequency longitudinal waves that arise
from a shock steepening process. Therefore, these oscillations may not solely
be produced by the horizontal buffeting motions of granulation but also by the
leakage of p-mode oscillations. To investigate the contribution of p-modes, our
study employs a two-dimensional magneto-convection simulation spanning from the
upper convection zone to the corona. During the course of the simulation, we
introduce a p-mode-like driver at the bottom boundary. We reveal a notable
increase in the mean velocity amplitude of the transverse oscillations in
spicules, ranging from 10% to 30%, and attribute this to the energy transfer
from longitudinal to transverse waves. This effect results in an enhancement of
the estimated energy flux by 30-80%.Comment: Accepted for publication in ApJ, 14 pages, 6 figures, 2 tables,
Comments are welcom
Lipid Transfer Inhibitor Protein (Apolipoprotein F) Concentration in Normolipidemic and Hyperlipidemic Subjects
Lipid transfer inhibitor protein (LTIP) is an important regulator of cholesteryl ester transfer protein function. We report the development of an immunoassay for LTIP and its use to quantify LTIP in plasma of varying lipid contents. A rabbit antibody against bacterially produced recombinant LTIP detected two LTIP isoforms in plasma differing in carbohydrate content. This antibody was used in a competitive, enzyme-linked immunoassay that uses partially purified LTIP bound to microtiter plates. To optimize LTIP immunoreactivity, plasma samples required preincubation in 1% Tween-20 and 0.5% Nonidet P-40. In normolipidemic plasma, LTIP averaged 83.5 mg/ml. LTIP was 31% higher in males than in females. LTIP was positively associated with HDL cholesterol in normolipidemic males but not in females. In hypertriglyceridemic males, LTIP was only 56% of control values, whereas in hypertriglyceridemic females, LTIP tended to increase. Additionally, in males with normal cholesterol and triglyceride (TG) ≤ 200 mg/dl, LTIP varied inversely with plasma TG. Overall, we have confirmed the negative association between plasma TG levels and LTIP previously suggested by a small data set, but now we demonstrate that this effect is seen only in males. The mechanisms underlying this gender-specific response to TG, and why LTIP and HDL levels correlate in males but not in females, remain to be determined
Electron spin coherence in metallofullerenes: Y, Sc and La@C82
Endohedral fullerenes encapsulating a spin-active atom or ion within a carbon
cage offer a route to self-assembled arrays such as spin chains. In the case of
metallofullerenes the charge transfer between the atom and the fullerene cage
has been thought to limit the electron spin phase coherence time (T2) to the
order of a few microseconds. We study electron spin relaxation in several
species of metallofullerene as a function of temperature and solvent
environment, yielding a maximum T2 in deuterated o-terphenyl greater than 200
microseconds for Y, Sc and La@C82. The mechanisms governing relaxation (T1, T2)
arise from metal-cage vibrational modes, spin-orbit coupling and the nuclear
spin environment. The T2 times are over 2 orders of magnitude longer than
previously reported and consequently make metallofullerenes of interest in
areas such as spin-labelling, spintronics and quantum computing.Comment: 5 pages, 4 figure
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