1,403 research outputs found
The Distribution and Importance of Arthropods Associated with Agriculture and Forestry in Chile
Farm Management,
Spin instabilities and quantum phase transitions in integral and fractional quantum Hall states
The inter-Landau-level spin excitations of quantum Hall states at filling
factors nu=2 and 4/3 are investigated by exact numerical diagonalization for
the situation in which the cyclotron (hbar*omega_c) and Zeeman (E_Z) splittings
are comparable. The relevant quasiparticles and their interactions are studied,
including stable spin wave and skyrmion bound states. For nu=2, a spin
instability at a finite value of epsilon=hbar*omega_c-E_Z leads to an abrupt
paramagnetic to ferromagnetic transition, in agreement with the mean-field
approximation. However, for nu=4/3 a new and unexpected quantum phase
transition is found which involves a gradual change from paramagnetic to
ferromagnetic occupancy of the partially filled Landau level as epsilon is
decreased.Comment: 4 pages, 5 figures, submitted to Phys.Rev.Let
Electrostatic potential in a superconductor
The electrostatic potential in a superconductor is studied. To this end
Bardeen's extension of the Ginzburg-Landau theory to low temperatures is used
to derive three Ginzburg-Landau equations - the Maxwell equation for the vector
potential, the Schroedinger equation for the wave function and the Poisson
equation for the electrostatic potential. The electrostatic and the
thermodynamic potential compensate each other to a great extent resulting into
an effective potential acting on the superconducting condensate. For the
Abrikosov vortex lattice in Niobium, numerical solutions are presented and the
different contributions to the electrostatic potential and the related charge
distribution are discussed.Comment: 19 pages, 11 figure
An evaluation of metal removal during wastewater treatment: The potential to achieve more stringent final effluent standards
This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2011 Taylor & Francis.Metals are of particular importance in relation to water quality, and concern regarding the impact of these contaminants on biodiversity is being encapsulated within the latest water-related legislation such as the Water Framework Directive in Europe and criteria revisions to the Clean Water Act in the United States. This review undertakes an evaluation of the potential of 2-stage wastewater treatment consisting of primary sedimentation and biological treatment in the form of activated sludge processes, to meet more stringent discharge consents that are likely to be introduced as a consequence. The legislation, sources of metals, and mechanisms responsible for their removal are discussed, to elucidate possible pathways by which the performance of conventional processes may be optimized or enhanced. Improvements in effluent quality, achievable by reducing concentrations of suspended solids or biochemical oxygen demand, may also reduce metal concentrations although meeting possible requirements for the removal of copper my be challenging
Black Holes at Future Colliders and Beyond: a Topical Review
One of the most dramatic consequences of low-scale (~1 TeV) quantum gravity
in models with large or warped extra dimension(s) is copious production of mini
black holes at future colliders and in ultra-high-energy cosmic ray collisions.
Hawking radiation of these black holes is expected to be constrained mainly to
our three-dimensional world and results in rich phenomenology. In this topical
review we discuss the current status of astrophysical observations of black
holes and selected aspects of mini black hole phenomenology, such as production
at colliders and in cosmic rays, black hole decay properties, Hawking radiation
as a sensitive probe of the dimensionality of extra space, as well as an
exciting possibility of finding new physics in the decays of black holes.Comment: 31 pages, 10 figures To appear in the Journal of Physics
The calcium-Activated potassium channel KCa3.1 is an important modulator of hepatic injury
The calcium-Activated potassium channel KCa3.1 controls different cellular processes such as proliferation and volume homeostasis. We investigated the role of KCa3.1 in experimental and human liver fibrosis. KCa3.1 gene expression was investigated in healthy and injured human and rodent liver. Effect of genetic depletion and pharmacological inhibition of KCa3.1 was evaluated in mice during carbon tetrachloride induced hepatic fibrogenesis. Transcription, protein expression and localisation of KCa3.1 was analysed by reverse transcription polymerase chain reaction, Western blot and immunohistochemistry. Hemodynamic effects of KCa3.1 inhibition were investigated in bile duct-ligated and carbon tetrachloride intoxicated rats. In vitro experiments were performed in rat hepatic stellate cells and hepatocytes. KCa3.1 expression was increased in rodent and human liver fibrosis and was predominantly observed in the hepatocytes. Inhibition of KCa3.1 aggravated liver fibrosis during carbon tetrachloride challenge but did not change hemodynamic parameters in portal hypertensive rats. In vitro, KCa3.1 inhibition leads to increased hepatocyte apoptosis and DNA damage, whereas proliferation of hepatic stellate cells was stimulated by KCa3.1 inhibition. Our data identifies KCa3.1 channels as important modulators in hepatocellular homeostasis. In contrast to previous studies in vitro and other tissues this channel appears to be anti-fibrotic and protective during liver injury
Measuring space-time variation of the fundamental constants with redshifted submillimetre transitions of neutral carbon
We compare the redshifts of neutral carbon and carbon monoxide in the
redshifted sources in which the fine structure transition of neutral carbon,
[CI], has been detected, in order to measure space-time variation of the
fundamental constants. Comparison with the CO rotational lines measures gives
the same combination of constants obtained from the comparison fine structure
line of singly ionised carbon, [CII]. However, neutral carbon has the distinct
advantage that it may be spatially coincident with the carbon monoxide, whereas
[CII] could be located in the diffuse medium between molecular clouds, and so
any comparison with CO could be dominated by intrinsic velocity differences.
Using [CI], we obtain a mean variation of dF/F = (-3.6 +/- 8.5) x 10^-5, over z
= 2.3 - 4.1, for the eight [CI] systems, which degrades to (-1.5+/- 11) x
10^-5, over z = 2.3 - 6.4 when the two [CII] systems are included. That is,
zero variation over look-back times of 10.8-12.8 Gyr. However, the latest
optical results indicate a spatial variation in alpha, which describes a dipole
and we see the same direction in dF/F. This trend is, however, due to a single
source for which the [CI] spectrum is of poor quality. This also applies to one
of the two [CII] spectra previously used to find a zero variation in
alpha^2/mu. Quantifying this, we find an anti-correlation between |dF/F| and
the quality of the carbon detection, as measured by the spectral resolution,
indicating that the typical values of >50 km/s, used to obtain a detection, are
too coarse to reliably measure changes in the constants. From the fluxes of the
known z > 1 CO systems, we predict that current instruments are incapable of
the sensitivities required to measure changes in the constants through the
comparison of CO and carbon lines. We therefore discuss in detail the use of
ALMA for such an undertaking ... ABRIDGEDComment: Accepted for publication in Section 3 - Cosmology (including clusters
of galaxies) of Astronomy and Astrophysic
Meson-exchange Model for scattering and reaction
An effective Hamiltonian consisting of bare ,
vertex interactions and energy-independent meson-exchange transition operators is derived by applying a
unitary transformation to a model Lagrangian with , ,
, and fields. With appropraite phenomenological form factors
and coupling constants for and , the model can give a good
description of scattering phase shifts up to the excitation
energy region. It is shown that the best reproduction of the recent LEGS data
of the photon-asymmetry ratios in reactions
provides rather restricted constraints on the coupling strengths of the
electric and of the magnetic transitions of the bare vertex and the less well-determined coupling constant
of meson. Within the ranges that ,
, and , the predicted
differential cross sections and photon-asymmetry ratios are in an overall good
agreement with the data of , , and reactions from 180
MeV to the excitation region. The predicted and
multipole amplitudes are also in good agreement with the empirical values
determined by the amplitude analyses. The constructed effective Hamiltonian is
free of the nucleon renormlization problem and hence is suitable for nuclear
many-body calculations. We have also shown that the assumptions made in the
-matrix method, commonly used in extracting empirically the transition amplitudes from the data, are consistent withComment: 49 pages + 23 Figures, Revte
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