3,102 research outputs found
A Bose-Einstein Approach to the Random Partitioning of an Integer
Consider N equally-spaced points on a circle of circumference N. Choose at
random n points out of on this circle and append clockwise an arc of
integral length k to each such point. The resulting random set is made of a
random number of connected components. Questions such as the evaluation of the
probability of random covering and parking configurations, number and length of
the gaps are addressed. They are the discrete versions of similar problems
raised in the continuum. For each value of k, asymptotic results are presented
when n,N both go to infinity according to two different regimes. This model may
equivalently be viewed as a random partitioning problem of N items into n
recipients. A grand-canonical balls in boxes approach is also supplied, giving
some insight into the multiplicities of the box filling amounts or spacings.
The latter model is a k-nearest neighbor random graph with N vertices and kn
edges. We shall also briefly consider the covering problem in the context of a
random graph model with N vertices and n (out-degree 1) edges whose endpoints
are no more bound to be neighbors
Electronic transport coefficients from ab initio simulations and application to dense liquid hydrogen
Using Kubo's linear response theory, we derive expressions for the
frequency-dependent electrical conductivity (Kubo-Greenwood formula),
thermopower, and thermal conductivity in a strongly correlated electron system.
These are evaluated within ab initio molecular dynamics simulations in order to
study the thermoelectric transport coefficients in dense liquid hydrogen,
especially near the nonmetal-to-metal transition region. We also observe
significant deviations from the widely used Wiedemann-Franz law which is
strictly valid only for degenerate systems and give an estimate for its valid
scope of application towards lower densities
Norwegian National Program for Lifetime Commissioning and Energy Efficient Operation of Buildings
The project “Life-Time Commissioning for Energy Efficient Operation of Buildings” is actually a network of industrial companies, private and public entities, and R&D organizations. The overall objective of the project is to contribute to the implementation of life-long commissioning of building HVAC systems, so that this becomes a standardized way of building, operating and maintaining the HVAC systems in Norway. The project is organized as an industry research program with minimum duration of five years. Project members pay an annual membership fee. The main goal for the project is to develop, verify, document and implement suitable tools for functional control of energy and indoor environment in buildings under continuous operation during the entire operational life of the building. This will improve energy efficiency and ensure a rational use of energy and a sound indoor environment. All achievements concerning energy improvement will also contribute to the decrease of CO2 emissions
Topological states of multiband superconductors with interband pairing
We study the effects of interband pairing in two-band s-wave and d-wave
superconductors with D4h symmetry in both time-reversal invariant as well as
time-reversal symmetry breaking states. The presence of interband pairing
qualitatively changes the nodal structure of the superconductor: nodes can
(dis)appear, merge, and leave high-symmetry locations when interband pairing is
tuned. Furthermore, in the d-wave case, we find that also the boundary modes
change qualitatively when interband pairing increases: flat zero-energy Andreev
bound states gap out and transition to helical edge states.Comment: 19 pages, 11 figure
Curvature condensation and bifurcation in an elastic shell
We study the formation and evolution of localized geometrical defects in an
indented cylindrical elastic shell using a combination of experiment and
numerical simulation. We find that as a symmetric localized indentation on a
semi-cylindrical shell increases, there is a transition from a global mode of
deformation to a localized one which leads to the condensation of curvature
along a symmetric parabolic crease. This process introduces a soft mode in the
system, converting a load-bearing structure into a hinged, kinematic mechanism.
Further indentation leads to twinning wherein the parabolic crease bifurcates
into two creases that move apart on either side of the line of symmetry. A
qualitative theory captures the main features of the phenomena and leads to
sharper questions about the nucleation of these defects.Comment: 4 pages, 5 figures, submitted to Physical Review Letter
What Is an L-Cell and How Do We Study the Secretory Mechanisms of the L-Cell?
Synthetic glucagon-like peptide-1 (GLP-1) analogues are effective anti-obesity and anti-diabetes drugs. The beneficial actions of GLP-1 go far beyond insulin secretion and appetite, and include cardiovascular benefits and possibly also beneficial effects in neurodegenerative diseases. Considerable reserves of GLP-1 are stored in intestinal endocrine cells that potentially might be mobilized by pharmacological means to improve the body’s metabolic state. In recognition of this, the interest in understanding basic L-cell physiology and the mechanisms controlling GLP-1 secretion, has increased considerably. With a view to home in on what an L-cell is, we here present an overview of available data on L-cell development, L-cell peptide expression profiles, peptide production and secretory patterns of L-cells from different parts of the gut. We conclude that L-cells differ markedly depending on their anatomical location, and that the traditional definition of L-cells as a homogeneous population of cells that only produce GLP-1, GLP-2, glicentin and oxyntomodulin is no longer tenable. We suggest to sub-classify L-cells based on their differential peptide contents as well as their differential expression of nutrient sensors, which ultimately determine the secretory responses to different stimuli. A second purpose of this review is to describe and discuss the most frequently used experimental models for functional L-cell studies, highlighting their benefits and limitations. We conclude that no experimental model is perfect and that a comprehensive understanding must be built on results from a combination of models
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