90,470 research outputs found
Noise of Kondo dot with ac gate: Floquet-Green's function and Noncrossing Approximation Approach
The transport properties of an ac-driving quantum dot in the Kondo regime are
studied by the Floquet-Green's function method with slave-boson infinite-
noncrossing approximation. Our results show that the Kondo peak of the local
density of states is robust against weak ac gate modulation. Significant
suppression of the Kondo peak can be observed when the ac gate field becomes
strong. The photon-assisted noise of Kondo resonance as a function of dc
voltage does not show singularities which are expected for noninteracting
resonant quantum dot. These findings suggest that one may make use of the
photon-assisted noise measurement to tell apart whether the resonant transport
is via noninteracting resonance or strongly-correlated Kondo resonance
Insulating state and the importance of the spin-orbit coupling in CaCoRhO
We have carried out a comparative theoretical study of the electronic
structure of the novel one-dimensional CaCoRhO and CaFeRhO
systems. The insulating antiferromagnetic state for the CaFeRhO can be
well explained by band structure calculations with the closed shell high-spin
(Fe) and low-spin (Rh) configurations. We
found for the CaCoRhO that the Co has a strong tendency to be
(Co) rather than (Co), and that there is an orbital
degeneracy in the local Co electronic structure. We argue that it is the
spin-orbit coupling which will lift this degeneracy thereby enabling local spin
density approximation + Hubbard U (LSDA+U) band structure calculations to
generate the band gap. We predict that the orbital contribution to the magnetic
moment in CaCoRhO is substantial, i.e. significantly larger than 1
per formula unit. Moreover, we propose a model for the contrasting
intra-chain magnetism in both materials.Comment: 7 pages, 4 figures, and 1 tabl
CP Violation in Mixing
The existence of mixing at a detectable level requires
new physics, which effectively yields a superweak interaction.
In general this interaction may involve significant CP violation. For small
values of the mixing it may be much easier to detect the CP-violating part of
the mixing than the CP-conserving part.Comment: 3 pages, latex, no figure
Roles of the Bloom's syndrome helicase in the maintenance of genome stability
The RecQ family of DNA helicases is highly conserved in evolution from bacteria to humans. Of the five known human RecQ family members, three (BLM, WRN and RECQ4, which cause Bloom's syndrome, Werner's syndrome and Rothmund-Thomson syndrome respectively) are mutated in distinct clinical disorders associated with cancer predisposition and/or premature aging. BLM forms part of a multienzyme complex including topoisomerase IIIalpha, replication protein A and a newly identified factor called BLAP75. Together, these proteins play a role in the resolution of DNA structures that arise during the process of homologous recombination repair. In the absence of BLM, cells show genomic instability and a high incidence of sister-chromatid exchanges. In addition to a DNA structure-specific helicase activity, BLM also catalyses Holliday-junction branch migration and the annealing of complementary single-stranded DNA molecules
Molecular line and continuum study of the W40 cloud
The dense cloud associated with W40, one of the nearby H II regions, has been
studied in millimeter-wave molecular lines and in 1.2 mm continuum. Besides,
1280 MHz and 610 MHz interferometric observations have been done. The cloud has
complex morphological and kinematical structure, including a clumpy dust ring
and an extended dense core. The ring is probably formed by the "collect and
collapse" process due to the expansion of neighboring H II region. Nine dust
clumps in the ring have been deconvolved. Their sizes, masses and peak hydrogen
column densities are: pc, and cm, respectively. Molecular lines are observed
at two different velocities and have different spatial distributions implying
strong chemical differentiation over the region. The CS abundance is enhanced
towards the eastern dust clump 2, while the NH, NH, and
HCO abundances are enhanced towards the western clumps. HCN and
HCO do not correlate with the dust probably tracing the surrounding gas.
Number densities derived towards selected positions are: cm. Two western clumps have kinetic temperatures 21 K and 16 K and
are close to virial equilibrium. The eastern clumps 2 and 3 are more massive,
have higher extent of turbulence and are probably more evolved than the western
ones. They show asymmetric CS(2--1) line profiles due to infalling motions
which is confirmed by model calculations. An interaction between ionized and
neutral material is taking place in the vicinity of the eastern branch of the
ring and probably trigger star formation.Comment: 16 pages, 6 figure
Projected climate effects on soil workability and trafficability determine the feasibility of converting permanent grassland to arable land
CONTEXT
Adapting to changes in climate and in consumer demand for commodities will force us to diversify land uses from the current status. Livestock grazing systems are dominant agricultural practices in the western regions of the British Isles. It has been suggested that grasslands in the region could be converted to other land uses, e.g. growing of cereal crops. We hypothesized that soil workability and trafficability would be important factors determining the feasibility and environmental impact of such conversion.
OBJECTIVE
Objectives were 1) to investigate the impacts of weather conditions under the current (baseline) climate on agronomic management and crop yield of winter wheat using the SPACSYS model; and 2) to assess potential impacts of the land use conversion (grassland converted into arable land) on the environment under soil conditions representative of the region under baseline and future climatic conditions.
METHODS
Using simulation modelling we investigated the impacts of baseline and future climates under the Representative Concentration Pathways (RCP2.6, 4.5 and RCP8.5) on soil workability and trafficability at sowing and harvest respectively of winter wheat and its consequences for crop productivity and key indices of environmental sustainability for three major soil types of the region.
RESULTS AND CONCLUSIONS
Under baseline and future projections, the probability of successfully sowing winter wheat on these soils was between 38 and 76%. Simulations showed that grassland conversion to arable in the region would not be sustainable in terms of carbon sequestration with a decline in soil carbon stock of 165 – 280 kg C ha–1 yr–1 on average over the simulation period. Rates of decline were greater when soil workability was taken into consideration. Although CO2eq emissions from silage–based grassland soil were higher than those from the converted arable land, these were offset by the greater net productivity of grassland making it a larger net sink for carbon. When soil workability at sowing was considered, the NUEcrop (crop N content/N fertilizer applied) for winter wheat was lower than that for perennial ryegrass on all soil types under the baseline climate and RCP2.6, but comparable or greater under RCP4.5 and RCP8.5. In terms of C sequestration, grassland conversion for production of winter wheat is unsustainable under these soil–climatic conditions.
SIGNIFICANCE
Our results demonstrated that soil workability is a major factor influencing the potential impact of land-use conversion in clay soils and a wetter climate
The explicit expression of the fugacity for weakly interacting Bose and Fermi gases
In this paper, we calculate the explicit expression for the fugacity for two-
and three-dimensional weakly interacting Bose and Fermi gases from their
equations of state in isochoric and isobaric processes, respectively, based on
the mathematical result of the boundary problem of analytic functions --- the
homogeneous Riemann-Hilbert problem. We also discuss the Bose-Einstein
condensation phase transition of three-dimensional hard-sphere Bose gases.Comment: 24 pages, 9 figure
Tunneling Anomaly in Superconductor above Paramagnetic Limit
We study the tunneling density of states (DoS) in the superconducting systems
driven by Zeeman splitting E_Z into the paramagnetic phase. We show that, even
though the BCS gap disappears, superconducting fluctuations cause a strong DoS
singularity in the vicinity of energies -E^* for electrons polarized along the
magnetic field and E^* for the opposite polarization. The position of the
singularity E^*=(1/2) (E_Z + \sqrt{E_Z^2- \Delta^2}) (where \Delta is BCS gap
at E_Z=0) is universal. We found analytically the shape of the DoS for
different dimensionality of the system. For ultrasmall grains the singularity
has the form of the hard gap, while in higher dimensions it appears as a
significant though finite dip. Our results are consistent with recent
experiments in superconducting films.Comment: 4 pages, 2 .eps figures include
X-ray photoelectron spectroscopy studies of non-stoichiometric superconducting NbB2+x
Polycrystalline samples of NbB2+x with nominal composition (B/Nb) = 2.0, 2.1,
2.2, 2.3, 2.4 and 2.5 were studied by X-ray photoelectron spectroscopy (XPS).
The spectra revealed Nb and B oxides on the surface of the samples, mainly B2O3
and Nb2O5. After Ar ion etching the intensity of Nb and B oxides decreased. The
Nb 3d5/2 and B 1s core levels associated with the chemical states (B/Nb) were
identified and they do not change with etching time. The Binding Energy of the
Nb 3d5/2 and B 1s core levels increase as boron content increases, suggesting a
positive chemical shift in the core levels. On the other hand, analysis of
Valence Band spectra showed that the contribution of the Nb 4d states slightly
decreased while the contribution of the B 2p(pi) states increased as the boron
content increased. As a consequence, the electronic and superconducting
properties were substantially modified, in good agreement with band-structure
calculations.Comment: 10 pages, 7 figures, 1 tabl
Nature of magnetism in CaCoO
We find using LSDA+U band structure calculations that the novel
one-dimensional cobaltate CaCoO is not a ferromagnetic half-metal
but a Mott insulator. Both the octahedral and the trigonal Co ions are formally
trivalent, with the octahedral being in the low-spin and the trigonal in the
high-spin state. The inclusion of the spin-orbit coupling leads to the
occupation of the minority-spin orbital for the unusually coordinated
trigonal Co, producing a giant orbital moment (1.57 ). It also results
in an anomalously large magnetocrystalline anisotropy (of order 70 meV),
elucidating why the magnetism is highly Ising-like. The role of the oxygen
holes, carrying an induced magnetic moment of 0.13 per oxygen, for
the exchange interactions is discussed.Comment: 5 pages, 4 figures, and 1 tabl
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