6,251 research outputs found
The Laplacian Eigenvalues and Invariants of Graphs
In this paper, we investigate some relations between the invariants
(including vertex and edge connectivity and forwarding indices) of a graph and
its Laplacian eigenvalues. In addition, we present a sufficient condition for
the existence of Hamiltonicity in a graph involving its Laplacian eigenvalues.Comment: 10 pages,Filomat, 201
Increase in neuroexcitability of unmyelinated C-type vagal ganglion neurons during initial postnatal development of visceral afferent reflex functions
BACKGROUND:
Baroreflex gain increase up closely to adult level during initial postnatal weeks, and any interruption within this period will increase the risk of cardiovascular problems in later of life span. We hypothesize that this short period after birth might be critical for postnatal development of vagal ganglion neurons (VGNs).
METHODS:
To evaluate neuroexcitability evidenced by discharge profiles and coordinate changes, ion currents were collected from identified A- and C-type VGNs at different developmental stages using whole-cell patch clamping.
RESULTS:
C-type VGNs underwent significant age-dependent transition from single action potential (AP) to repetitive discharge. The coordinate changes between TTX-S and TTX-R Na(+) currents were also confirmed and well simulated by computer modeling. Although 4-AP or iberiotoxin age dependently increased firing frequency, AP duration was prolonged in an opposite fashion, which paralleled well with postnatal changes in 4-AP- and iberiotoxin-sensitive K(+) current activity, whereas less developmental changes were verified in A-types.
CONCLUSION:
These data demonstrate for the first time that the neuroexcitability of C-type VGNs increases significantly compared with A-types within initial postnatal weeks evidenced by AP discharge profiles and coordinate ion channel changes, which explain, at least in part, that initial postnatal weeks may be crucial for ontogenesis in visceral afferent reflex function
Fermion sign bounds theory in quantum Monte Carlo simulation
Sign problem in fermion quantum Monte Carlo (QMC) simulation appears to be an
extremely hard problem. Traditional lore passing around for years tells people
that when there is a sign problem, the average sign in QMC simulation
approaches zero exponentially fast with the space-time volume of the
configurational space. We, however, analytically show this is not always the
case and manage to find physical bounds for the average sign. Our understanding
is based on a direct connection between the sign bounds and a well-defined
partition function of reference system and could distinguish when the bounds
have the usual exponential scaling, and when they are bestowed on an algebraic
scaling at low temperature limit. We analytically explain such algebraic sign
problems found in flat band moir\'e lattice models at low temperature limit. At
finite temperature, a domain size argument based on sign bounds also explains
the connection between sign behavior and finite temperature phase transition.
Sign bounds, as a well-defined observable, may have ability to ease or even
make use of the sign problem.Comment: 11 pages, 3 figure
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