2,752 research outputs found
Miocene Central Volcanoes, NW New South Wales: Genesis over a Lithospheric Cavity (?)
Basalt fields and central volcanoes form a curved south-migrating trace through NW New South Wales. A segment of East Australian intraplate volcanism, it traces Australia’s northern plate motion north over a mantle plume system. This created the western New England basalt field (24 – 21 Ma), Nandewar central volcano (19 – 18 Ma), Warrumbungle central volcano (18 – 15 mya), Mount Canobolas central volcano (13 – 11 Ma) and minor alkaline eruptions near Oberon (10 – 9 Ma). This ‘boomerang-shaped’ segment initially swelled south-westerly with increasing mantle melting and basaltic evolution. After initial fluid basaltic outpourings in New England, it formed two large central volcanoes along its outward curve before bending southerly to form a smaller central volcano and a scattered tail of small late-eruptions. This volcanic trace did not match Australia’s linear plate motion trend between 24 – 9 Ma. Neither did it correspond with adjacent plume trend seen in the leucititic lavas to the west, the coastal NSW plume volcanoes and Tasman Sea submarine plume chains to the east. Recent seismic tomography has revealed ‘cavities’ within the underlying lithosphere-asthenosphere boundary (LAB). The anomalous NW New South Wales plume upwelling underwent diversion by its interaction along the western edge of a LAB ‘cavity’
Thermalization of acoustic excitations in a strongly interacting one-dimensional quantum liquid
We study inelastic decay of bosonic excitations in a Luttinger liquid. In a
model with linear excitation spectrum the decay rate diverges. We show that
this difficulty is resolved when the interaction between constituent particles
is strong, and the excitation spectrum is nonlinear. Although at low energies
the nonlinearity is weak, it regularizes the divergence in the decay rate. We
develop a theoretical description of the approach of the system to thermal
equilibrium. The typical relaxation rate scales as the fifth power of
temperature
UV-light-driven prebiotic synthesis of iron–sulfur clusters
Iron–sulfur clusters are ancient cofactors that play a fundamental role in metabolism and may have impacted the prebiotic chemistry that led to life. However, it is unclear whether iron–sulfur clusters could have been synthesized on prebiotic Earth. Dissolved iron on early Earth was predominantly in the reduced ferrous state, but ferrous ions alone cannot form polynuclear iron–sulfur clusters. Similarly, free sulfide may not have been readily available. Here we show that UV light drives the synthesis of [2Fe–2S] and [4Fe–4S] clusters through the photooxidation of ferrous ions and the photolysis of organic thiols. Iron–sulfur clusters coordinate to and are stabilized by a wide range of cysteine-containing peptides and the assembly of iron–sulfur cluster-peptide complexes can take place within model protocells in a process that parallels extant pathways. Our experiments suggest that iron–sulfur clusters may have formed easily on early Earth, facilitating the emergence of an iron–sulfur-cluster-dependent metabolism
Long Range Interaction Models and Yangian Symmetry
The generalized Sutherland-Romer models and Yan models with internal spin
degrees are formulated in terms of the Polychronakos' approach and RTT relation
associated to the Yang-Baxter equation in consistent way. The Yangian symmetry
is shown to generate both models. We finally introduce the reflection algebra
K(u) to the long range models.Comment: 13 pages, preprint of Nankai Institute of Mathematics ( Theoretical
Physics Division ), published in Physical Review E of 1995. For hard copy,
write to Prof. Mo-lin GE directly. Do not send emails to this accoun
Thermalisation of self-interacting solar flare fast electrons
Most theoretical descriptions of the production of solar flare bremsstrahlung
radiation assume the collision of dilute accelerated particles with a cold,
dense target plasma, neglecting interactions of the fast particles with each
other. This is inadequate for situations where collisions with this background
plasma are not completely dominant, as may be the case in, for example,
low-density coronal sources. We aim to formulate a model of a self-interacting,
entirely fast electron population in the absence of a dense background plasma,
to investigate its implications for observed bremsstrahlung spectra and the
flare energy budget. We derive approximate expressions for the time-dependent
distribution function of the fast electrons using a Fokker-Planck approach. We
use these expressions to generate synthetic bremsstrahlung X-ray spectra as
would be seen from a corresponding coronal source. We find that our model
qualitatively reproduces the observed behaviour of some flares. As the flare
progresses, the model's initial power-law spectrum is joined by a lower energy,
thermal component. The power-law component diminishes, and the growing thermal
component proceeds to dominate the total emission over timescales consistent
with flare observations. The power-law exhibits progressive spectral hardening,
as is seen in some flare coronal sources. We also find that our model requires
a factor of 7 - 10 fewer accelerated electrons than the cold, thick target
model to generate an equivalent hard X-ray flux. This model forms the basis of
a treatment of self-interactions among flare fast electrons, a process which
affords a more efficient means to produce bremsstrahlung photons and so may
reduce the efficiency requirements placed on the particle acceleration
mechanism. It also provides a useful description of the thermalisation of fast
electrons in coronal sources.Comment: 9 pages, 7 figures, accepted for Astronomy & Astrophysics; this
version clarifies arguments around Eqs. (11) and (20
Some formal results for the valence bond basis
In a system with an even number of SU(2) spins, there is an overcomplete set
of states--consisting of all possible pairings of the spins into valence
bonds--that spans the S=0 Hilbert subspace. Operator expectation values in this
basis are related to the properties of the closed loops that are formed by the
overlap of valence bond states. We construct a generating function for spin
correlation functions of arbitrary order and show that all nonvanishing
contributions arise from configurations that are topologically irreducible. We
derive explicit formulas for the correlation functions at second, fourth, and
sixth order. We then extend the valence bond basis to include triplet bonds and
discuss how to compute properties that are related to operators acting outside
the singlet sector. These results are relevant to analytical calculations and
to numerical valence bond simulations using quantum Monte Carlo, variational
wavefunctions, or exact diagonalization.Comment: 22 pages, 14 figure
Quantum integrable system with two color components in two dimensions
The Davey-Stewartson 1(DS1) system[9] is an integrable model in two
dimensions. A quantum DS1 system with 2 colour-components in two dimensions has
been formulated. This two-dimensional problem has been reduced to two
one-dimensional many-body problems with 2 colour-components. The solutions of
the two-dimensional problem under consideration has been constructed from the
resulting problems in one dimensions. For latters with the -function
interactions and being solved by the Bethe ansatz, we introduce symmetrical and
antisymmetrical Young operators of the permutation group and obtain the exact
solutions for the quantum DS1 system. The application of the solusions is
discussed.Comment: 14 pages, LaTeX fil
Dynamics of Giant-Gravitons in the LLM geometry and the Fractional Quantum Hall Effect
The LLM's 1/2 BPS solutions of IIB supergravity are known to be closely
related to the integer quantum Hall droplets with filling factor , and
the giant gravitons in the LLM geometry behave like the quasi-holes in those
droplets. In this paper we consider how the fractional quantum Hall effect may
arise in this context, by studying the dynamics of giant graviton probes in a
special LLM geometry, the AdS_5 X S^5 background, that corresponds to a
circular droplet. The giant gravitons we study are D3-branes wrapping on a
3-sphere in S^5. Their low energy world-volume theory, truncated to the 1/2 BPS
sector, is shown to be described by a Chern-Simons finite-matrix model. We
demonstrate that these giant gravitons may condense at right density further
into fractional quantum Hall fluid due to the repulsive interaction in the
model, giving rise to the new states in IIB string theory. Some features of the
novel physics of these new states are discussed.Comment: 32 pages, 1 figure; v.2: references added, the relation between the
level shift and filling fraction elaborate
A quinazoline-based HDAC inhibitor affects gene expression pathways involved in cholesterol biosynthesis and mevalonate in prostate cancer cells
Chronic inflammation can lead to the development of cancers and resolution of inflammation is an ongoing challenge.</p
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