11,698 research outputs found
Leading order infrared quantum chromodynamics in Coulomb gauge
A truncation scheme for the Dyson-Schwinger equations of quantum
chromodynamics in Coulomb gauge within the first order formalism is presented.
The truncation is based on an Ansatz for the Coulomb kernel occurring in the
action. Results at leading loop order and in the infrared are discussed for
both the Yang-Mills and quark sectors. It is found that the resulting equations
for the static gluon and quark propagators agree with those derived in a
quasi-particle approximation to the canonical Hamiltonian approach. Moreover, a
connection to the heavy quark limit is established. The equations are analyzed
numerically and it is seen that in both the gluonic and quark sectors, a
nontrivial dynamical infrared mass scale emerges.Comment: 27 pages, 11 figure
Hidden heat transfer in equilibrium states implies directed motion in nonequilibrium states
We study a class of heat engines including Feynman's ratchet, which exhibits
a directed motion of a particle in nonequilibrium steady states maintained by
two heat baths. We measure heat transfer from each heat bath separately, and
average them using a careful procedure that reveals the nature of the heat
transfer associated with directed steps of the particle. Remarkably we find
that steps are associated with nonvanishing heat transfer even in equilibrium,
and there is a quantitative relation between this ``hidden heat transfer'' and
the directed motion of the particle. This relation is clearly understood in
terms of the ``principle of heat transfer enhancement'', which is expected to
apply to a large class of highly nonequilibrium systems.Comment: 4 pages, 4 figures; revise
A heat pump at a molecular scale controlled by a mechanical force
We show that a mesoscopic system such as Feynman's ratchet may operate as a
heat pump, and clarify a underlying physical picture. We consider a system of a
particle moving along an asymmetric periodic structure . When put into a
contact with two distinct heat baths of equal temperature, the system transfers
heat between two baths as the particle is dragged. We examine Onsager relation
for the heat flow and the particle flow, and show that the reciprocity
coefficient is a product of the characteristic heat and the diffusion constant
of the particle. The characteristic heat is the heat transfer between the baths
associated with a barrier-overcoming process. Because of the correlation
between the heat flow and the particle flow, the system can work as a heat pump
when the particle is dragged. This pump is particularly effective at molecular
scales where the energy barrier is of the order of the thermal energy.Comment: 7 pages, 5 figures; revise
Filling dependence of a new type of charge ordered liquid on a triangular lattice system
We study the recently reported characteristic gapless charge ordered state in
a spinless fermion system on a triangular lattice under strong inter-site
Coulomb interactions. In this state the charges are spontaneously divided into
solid and liquid component, and the former solid part aligns in a Wigner
crystal manner while the latter moves among them like a pinball. We show that
such charge ordered liquid is stable over a wide range of filling, ,
and examine its filling dependent nature.Comment: 3 pages 3 figure
Assessment of the Potential Impact and Cost-effectiveness of Self-Testing for HIV in Low-Income Countries.
Studies have demonstrated that self-testing for human immunodeficiency virus (HIV) is highly acceptable among individuals and could allow cost savings, compared with provider-delivered HIV testing and counseling (PHTC), although the longer-term population-level effects are uncertain. We evaluated the cost-effectiveness of introducing self-testing in 2015 over a 20-year time frame in a country such as Zimbabwe
Mutations in shaking-B prevent electrical synapse formation in the Drosophila giant fiber system
The giant fiber system (GFS) is a simple network of neurons that mediates visually elicited escape behavior in Drosophila. The giant fiber (GF), the major component of the system, is a large, descending interneuron that relays visual stimuli to the motoneurons that innervate the tergotrochanteral jump muscle (TTM) and dorsal longitudinal flight muscles (DLMs). Mutations in the neural transcript from the shaking-B locus abolish the behavioral response by disrupting transmission at some electrical synapses in the GFS. This study focuses on the role of the gene in the development of the synaptic connections. Using an enhancer-trap line that expresses lacZ in the GFs, we show that the neurons develop during the first 30 hr of metamorphosis. Within the next 15 hr, they begin to form electrical synapses, as indicated by the transfer of intracellularly injected Lucifer yellow. The GFs dye-couple to the TTM motoneuron between 30 and 45 hr of metamorphosis, to the peripherally synapsing interneuron that drives the DLM motoneurons at approximately 48 hr, and to giant commissural interneurons in the brain at approximately 55 hr. Immunocytochemistry with shaking-B peptide antisera demonstrates that the expression of shaking-B protein in the region of GFS synapses coincides temporally with the onset of synaptogenesis; expression persists thereafter. The mutation shak-B2, which eliminates protein expression, prevents the establishment of dye coupling shaking-B, therefore, is essential for the assembly and/or maintenance of functional gap junctions at electrical synapses in the GFS
Mapping of Large Scale 158 micron [CII] Line Emission: Orion A
We present the first results of an observational programme undertaken to map
the fine structure line emission of singly ionized carbon ([CII] 157.7409
micron) over extended regions using a Fabry Perot spectrometer newly installed
at the focal plane of a 100cm balloon-borne far-infrared telescope. This new
combination of instruments has a velocity resolution of ~200 km/s and an
angular resolution of 1.5'. During the first flight, an area of 30'x15' in
Orion A was mapped. The observed [CII] intensity distribution has been compared
with the velocity-integrated intensity distributions of 13CO(1-0), CI(1-0) and
CO(3-2) from the literature. The observed line intensities and ratios have been
analyzed using the PDR models by Kaufman et al. 1999 to derive the incident UV
flux and volume density at a few selected positions.Comment: To appear in Astronomy & Astrophysic
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