193,118 research outputs found
One-Dimensional Transition Metal-Benzene Sandwich Polymers: Possible Ideal Conductors for Spin Transport
We investigate the electronic and magnetic properties of the proposed
one-dimensional transition metal (TM=Sc, Ti, V, Cr, and Mn)-benzene (Bz)
sandwich polymers by means of density functional calculations.
[V(Bz)] is found to be a quasi-half-metallic ferromagnet and
half-metallic ferromagnetism is predicted for [Mn(Bz)]. Moreover, we
show that stretching the [TM(Bz)] polymers could have dramatic
effects on their electronic and magnetic properties. The elongated
[V(Bz)] displays half-metallic behavior, and [Mn(Bz)]
stretched to a certain degree becomes an antiferromagnetic insulator. The
possibilities to stabilize the ferromagnetic order in [V(Bz)] and
[Mn(Bz)] polymers at finite temperature are discussed. We suggest
that the hexagonal bundles composed by these polymers might display intrachain
ferromagnetic order at finite temperature by introducing interchain exchange
coupling
On the center of the ring of differential operators on a smooth variety over \bZ/p^n\bZ
We compute the center of the ring of PD differential operators on a smooth
variety over \bZ/p^n\bZ confirming a conjecture of Kaledin. More generally,
given an associative algebra over \bF_p and its flat deformation
over \bZ/p^{n+1}\bZ we prove that under a certain non-degeneracy condition
the center of is isomorphic to the ring of length Witt vectors over
the center of .Comment: 16 page
Visualizing mitochondrial FoF1-ATP synthase as the target of the immunomodulatory drug Bz-423
Targeting the mitochondrial enzyme FoF1-ATP synthase and modulating its
catalytic activities with small molecules is a promising new approach for
treatment of autoimmune diseases. The immuno-modulatory compound Bz-423 is such
a drug that binds to subunit OSCP of the mitochondrial FoF1-ATP synthase and
induces apoptosis via increased reactive oxygen production in coupled, actively
respiring mitochondria. Here we review the experimental progress to reveal the
binding of Bz-423 to the mitochondrial target and discuss how subunit rotation
of FoF1-ATP synthase is affected by Bz-423. Briefly, we report how F\"orster
resonance energy transfer (FRET) can be employed to colocalize the enzyme and
the fluorescently tagged Bz-423 within the mitochondria of living cells with
nanometer resolution.Comment: 10 pages, 2 figure
What is the Brillouin Zone of an Anisotropic Photonic Crystal?
The concept of the Brillouin zone (BZ) in relation to a photonic crystal
fabricated in an optically anisotropic material is explored both experimentally
and theoretically. In experiment, we used femtosecond laser pulses to excite
THz polaritons and image their propagation in lithium niobate and lithium
tantalate photonic crystal (PhC) slabs. We directly measured the dispersion
relation inside PhCs and observed that the lowest bandgap expected to form at
the BZ boundary forms inside the BZ in the anisotropic lithium niobate PhC. Our
analysis shows that in an anisotropic material the BZ - defined as the
Wigner-Seitz cell in the reciprocal lattice - is no longer bounded by Bragg
planes and thus does not conform to the original definition of the BZ by
Brillouin. We construct an alternative Brillouin zone defined by Bragg planes
and show its utility in identifying features of the dispersion bands. We show
that for an anisotropic 2D PhC without dispersion, the Bragg plane BZ can be
constructed by applying the Wigner-Seitz method to a stretched or compressed
reciprocal lattice. We also show that in the presence of the dispersion in the
underlying material or in a slab waveguide, the Bragg planes are generally
represented by curved surfaces rather than planes. The concept of constructing
a BZ with Bragg planes should prove useful in understanding the formation of
dispersion bands in anisotropic PhCs and in selectively tailoring their optical
properties.Comment: 9 pages, 6 figure
A simple model of the Belousov-Zhabotinsky reaction from first principles
The Belousov-Zhabotinsky (BZ) reaction is an example of a temporally oscillating chemical
reaction. An unusual and interesting feature of the reaction is that as it progresses on a twodimensional
plate, self-organized spirals are formed. Many computer models have been constructed
of the BZ reaction to simulate the evolution of these spirals. The models typically use
cellular automata to allow progression of a wavefront through a notional substrate. Usually a
single substrate is used with somewhat arbitrary transference rules. Here it is shown that cellular
automata models of BZ spirals can be created by using a very simple set of equations based
on a three substrate model with close connection to reaction-diffusion models, more closely resembling
the actual BZ reaction. Source code for the model is given in the Processing language
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