4,117 research outputs found
Decomposition theorem on matchable distributive lattices
A distributive lattice structure has been established on the
set of perfect matchings of a plane bipartite graph . We call a lattice {\em
matchable distributive lattice} (simply MDL) if it is isomorphic to such a
distributive lattice. It is natural to ask which lattices are MDLs. We show
that if a plane bipartite graph is elementary, then is
irreducible. Based on this result, a decomposition theorem on MDLs is obtained:
a finite distributive lattice is an MDL if and only if each factor
in any cartesian product decomposition of is an MDL. Two types of
MDLs are presented: and , where
denotes the cartesian product between -element
chain and -element chain, and is a poset implied by any
orientation of a tree.Comment: 19 pages, 7 figure
Carbon--The First Frontier of Information Processing
Information is often encoded as an aperiodic chain of building blocks. Modern
digital computers use bits as the building blocks, but in general the choice of
building blocks depends on the nature of the information to be encoded. What
are the optimal building blocks to encode structural information? This can be
analysed by substituting the operations of addition and multiplication of
conventional arithmetic with translation and rotation. It is argued that at the
molecular level, the best component for encoding discretised structural
information is carbon. Living organisms discovered this billions of years ago,
and used carbon as the back-bone for constructing proteins that function
according to their structure. Structural analysis of polypeptide chains shows
that an efficient and versatile structural language of 20 building blocks is
needed to implement all the tasks carried out by proteins. Properties of amino
acids indicate that the present triplet genetic code was preceded by a more
primitive one, coding for 10 amino acids using two nucleotide bases.Comment: (v1) 9 pages, revtex. (v2) 10 pages. Several arguments expanded to
make the article self-contained and to increase clarity. Applications pointed
out. (v3) 11 pages. Published version. Well-known properties of proteins
shifted to an appendix. Reformatted according to journal styl
Competing itinerant and localized states in strongly correlated BaVS
The electronic structure of the quasi-lowdimensional vanadium sulfide \bavs3
is investigated for the different phases above the magnetic ordering
temperature. By means of density functional theory and its combination with
dynamical-mean field theory, we follow the evolution of the relevant low-energy
electronic states on cooling. Hence we go in the metallic regime from the room
temperature hexagonal phase to the orthorhombic phase after the first
structural transition, and close with the monoclinic insulating phase below the
metal-insulator transition. Due to the low symmetry and expected intersite
correlations, the latter phase is treated within cellular dynamical mean-field
theory. It is generally discussed how the intriguing interplay between
band-structure and strong-correlation effects leads to the stabilization of the
various electronic phases with decreasing temperature.Comment: 12 pages, submitted to PR
Influence of Ibuprofen on Phospholipid Membranes
Basic understanding of biological membranes is of paramount importance as
these membranes comprise the very building blocks of life itself. Cells depend
in their function on a range of properties of the membrane, which are important
for the stability and function of the cell, information and nutrient transport,
waste disposal and finally the admission of drugs into the cell and also the
deflection of bacteria and viruses.
We have investigated the influence of ibuprofen on the structure and dynamics
of L-alpha-phosphatidylcholine (SoyPC) membranes by means of grazing incidence
small-angle neutron scattering (GISANS), neutron reflectometry and grazing
incidence neutron spin echo spectroscopy (GINSES). From the results of these
experiments we were able to determine that ibuprofen induces a two-step
structuring behavior in the SoyPC films, where the structure evolves from the
purely lamellar phase for pure SoyPC over a superposition of two hexagonal
phases to a purely hexago- nal phase at high concentrations. Additionally,
introduction of ibuprofen stiffens the membranes. This behavior may be
instrumental in explaining the toxic behavior of ibuprofen in long-term
application.Comment: -Improved indexing in Fig. 4e) -changed concentrations to mol%
-improved arguments, however conclusions stay unchange
- …