1,217 research outputs found
BoltzTraP. A code for calculating band-structure dependent quantities
A program for calculating the semi-classic transport coefficients is
described. It is based on a smoothed Fourier interpolation of the bands. From
this analytical representation we calculate the derivatives necessary for the
transport distributions. The method is compared to earlier calculations, which
in principle should be exact within Boltzmann theory, and a very convincing
agreement is found
Impact of land use changes and management practices on groundwater resources in Kolar district, Southern India
Study region: This study analyzes the impact of land use changes on the hydrology of Kolar district in the state of Karnataka, India. Kolar receives on average 565 mm (Ï = 130) rainfall during June to October and has a wide gap between its water supply and demand.
Study focus: This research identifies the reasons and causes of the gap. A water balance model was successfully calibrated and validated against measurements of groundwater level, recharge and surface runoff.
New hydrological insights for the region: The study revealed that between 1972 and 2011, there was a major shift from grass and rainfed crop lands to eucalyptus plantation and irrigated cultivation. About 17.7 % and 18 % of the district area converted into eucalyptus plantation and irrigated lands during this period, respectively. Eucalyptus plantations tended to cause large losses by ET leading to increase in soil moisture deficit and reduction in the recharge to groundwater and in surface runoff (approx. 30 %). The irrigation demand of the district increased from 57 mm (1972) to 140 mm (2011) which resulted in increased groundwater abstraction by 145 %. The expansion of the irrigated area is the major contributing factor for widening the demand-supply gap (62 %) of the freshwater availability. Results could help various stakeholders, including district and national authorities to develop the most suitable water management strategies in order to close the gap between water supply and demand
Silicon Pad Detectors for the PHOBOS Experiment at RHIC
The PHOBOS experiment is well positioned to obtain crucial information about
relativistic heavy ion collisions at RHIC, combining a multiplicity counter
with a multi-particle spectrometer. The multiplicity arrays will measure the
charged particle multiplicity over the full solid angle. The spectrometer will
be able to identify particles at mid-rapidity. The experiment is constructed
almost exclusively of silicon pad detectors. Detectors of nine different types
are configured in the multiplicity and vertex detector (22,000 channels) and
two multi-particle spectrometers (120,000 channels). The overall layout of the
experiment, testing of the silicon sensors and the performance of the detectors
during the engineering run at RHIC in 1999 are discussed.Comment: 7 pages, 7 figures, 1 table, Late
Impurity-induced transition and impurity-enhanced thermopower in the thermoelectric oxide NaCo_{2-x}Cu_x$O_4
Various physical quantities are measured and analysed for the Cu-substituted
thermoelectric oxide NaCo_{2-x}Cu_xO_4. As was previously known, the
substituted Cu enhances the thermoelectric power, while it does not increase
the resistivity significantly. The susceptibility and the electron
specific-heat are substantially decreased with increasing x, which implies that
the substituted Cu decreases the effective-mass enhancement. Through a
quantitative comparison with the heavy fermion compounds and the valence
fluctuation systems, we have found that the Cu substitution effectively
increases the coupling between the conduction electron and the magnetic
fluctuation. The Cu substitution induces a phase transition at 22 K that is
very similar to a spin-density-wave transition.Comment: 8 pages, 7 figures, submitted to Phys. Rev.
Rapidity distribution as a probe for elliptical flow at intermediate energies
Interplay between the spectator and participant matter in heavy-ion
collisions is investigated within isospin dependent quantum molecular dynamics
(IQMD) model in term of rapidity distribution of light charged particles. The
effect of different types and size rapidity distributions is studied in
elliptical flow. The elliptical flow patterns show important role of the nearby
spectator matter on the participant zone. This role is further explained on the
basis of passing time of the spectator and expansion time of the participant
zone. The transition from the in-plane to out-of-plane is observed only when
the mid-rapidity region is included in the rapidity bin, otherwise no
transition occurs. The transition energy is found to be highly sensitive
towards the size of the rapidity bin, while weakly on the type of the rapidity
distribution. The theoretical results are also compared with the experimental
findings and are found in good agreement.Comment: 8 figure
Isotope Effect for the Penetration Depth in Superconductors
We show that various factors can lead to an isotopic dependence of the
penetration depth . Non-adiabaticity (Jahn-Teller crossing) leads to
the isotope effect of the charge carrier concentration and, consequently,
of in doped superconductors such as the cuprates. A general equation
relating the isotope coefficients of and of is presented for
London superconductors. We further show that the presence of magnetic
impurities or a proximity contact also lead to an isotopic dependence of
; the isotope coefficient turns out to be temperature dependent,
, in these cases. The existence of the isotope effect for the
penetration depth is predicted for conventional as well as for high-temperature
superconductors. Various experiments are proposed and/or discussed.Comment: 11 pages, 8 figures, accepted for publication in Phys. Rev.
Radio detection of cosmic ray air showers with LOPES
In the last few years, radio detection of cosmic ray air showers has
experienced a true renaissance, becoming manifest in a number of new
experiments and simulation efforts. In particular, the LOPES project has
successfully implemented modern interferometric methods to measure the radio
emission from extensive air showers. LOPES has confirmed that the emission is
coherent and of geomagnetic origin, as expected by the geosynchrotron
mechanism, and has demonstrated that a large scale application of the radio
technique has great potential to complement current measurements of ultra-high
energy cosmic rays. We describe the current status, most recent results and
open questions regarding radio detection of cosmic rays and give an overview of
ongoing research and development for an application of the radio technique in
the framework of the Pierre Auger Observatory.Comment: 8 pages; Proceedings of the CRIS2006 conference, Catania, Italy; to
be published in Nuclear Physics B, Proceedings Supplement
Hidden Order in the Cuprates
We propose that the enigmatic pseudogap phase of cuprate superconductors is
characterized by a hidden broken symmetry of d(x^2-y^2)-type. The transition to
this state is rounded by disorder, but in the limit that the disorder is made
sufficiently small, the pseudogap crossover should reveal itself to be such a
transition. The ordered state breaks time-reversal, translational, and
rotational symmetries, but it is invariant under the combination of any two. We
discuss these ideas in the context of ten specific experimental properties of
the cuprates, and make several predictions, including the existence of an
as-yet undetected metal-metal transition under the superconducting dome.Comment: 12 pages of RevTeX, 9 eps figure
Carbon dioxide rich microbubble acceleration of biogas production in anaerobic digestion
This paper addresses the use of anaerobic bacteria to convert carbon dioxide to biomethane as part of the biodegradation process of organic waste. The current study utilises gaslift bioreactors with microbubbles generated by fluidic oscillation to strip the methane produced in the gaslift bioreactor. Removal of methane makes its formation thermodynamically more favourable. In addition, intermittent sparging of microbubbles can prevent thermal stratification, maintain uniformity of the pH and increase the intimate contact between the feed and microbial culture with lower energy requirements than traditional mixing. A gaslift bioreactor with microbubble sparging has been implemented experimentally, using a range of carrier gas, culminating in pure carbon dioxide, in the anaerobic digestion process. The results obtained from the experiments show that the methane production rate is approximately doubled with pure carbon dioxide as the carrier gas for intermittent microbubble sparging
Knowledge-based energy functions for computational studies of proteins
This chapter discusses theoretical framework and methods for developing
knowledge-based potential functions essential for protein structure prediction,
protein-protein interaction, and protein sequence design. We discuss in some
details about the Miyazawa-Jernigan contact statistical potential,
distance-dependent statistical potentials, as well as geometric statistical
potentials. We also describe a geometric model for developing both linear and
non-linear potential functions by optimization. Applications of knowledge-based
potential functions in protein-decoy discrimination, in protein-protein
interactions, and in protein design are then described. Several issues of
knowledge-based potential functions are finally discussed.Comment: 57 pages, 6 figures. To be published in a book by Springe
- âŠ