2,257 research outputs found
Relativistic coupled-cluster-based linear response theory for ionization potentials of alkali-metal and alkaline-earth-metal atoms
We have developed and applied the relativistic coupled-cluster-based linear response theory (RCCLRT) for computing the principal as well as the shake-up ionization potentials (IP's) of Li, Be, Na, and Mg where the single-particle orbitals are generated by solving the relativistic Hartree-Fock-Roothaan equations using the Gaussian basis functions on a grid. The computed principal and shake-up ionization energies by the RCCLRT approach are in favorable agreement with the experimental results. Since for the (one-valence) IP problem, there is a formal equivalence between the principal IP values as obtained from the CCLRT and those obtained as eigenvalues of the multireference coupled-cluster theory, the computed quantities are fully size extensive. The approach via the RCCLRT has the additional advantage of providing the shake-up IP's as well. These are, however, not fully size extensive, but the error scales as the number of valence excitations (2h-1p), so the inextensivity error is rather small
Progress on the hybrid gun project at UCLA
UCLA/INFN-LNF/Univ. Rome has been developing the hybrid gun which has an RF gun and a short linac for velocity bunching in one structure. After the cavity was manufactured at INFN-LNF in 2012, tests of the gun was carried out at UCLA. The field in the standing wave part was 20 % smaller than the simulation but the phase advance was fine. The cavity was commissioned successfully up to 13 MW. The beam test was performed at 11.5 MW and demonstrated the bunch compression
Inelastic effects in electron transport studied with wave packet propagation
A time-dependent approach is used to explore inelastic effects during
electron transport through few-level systems. We study a tight-binding chain
with one and two sites connected to vibrations. This simple but transparent
model gives insight about inelastic effects, their meaning and the
approximations currently used to treat them. Our time-dependent approach allows
us to trace back the time sequence of vibrational excitation and electronic
interference, the ibrationally introduced time delay and the electronic phase
shift. We explore a full range of parameters going from weak to strong
electron-vibration coupling, from tunneling to contact, from one-vibration
description to the need of including all vibrations for a correct description
of inelastic effects in transport. We explore the validity of single-site
resonant models as well as its extension to more sites via molecular orbitals
and the conditions under which multi-orbital, multi-vibrational descriptions
cannot be simplified. We explain the physical meaning of the spectral features
in the second derivative of the electron current with respect to the bias
voltage. This permits us to nuance the meaning of the energy value of dips and
peaks. Finally, we show that finite-band effects lead to electron
back-scattering off the molecular vibrations in the regime of high-conductance,
although the drop in conductance at the vibrational threshold is rather due to
the rapid variation of the vibronic density of states.Comment: 38 pages, 14 figure
Long-term impacts of integrated nutrient management with equivalent nutrient doses to mineral fertilization on soil organic carbon sequestration in a sub-tropical Alfisol of India
Limited evidence is available on carbon sequestration potential of long-term integrated nutrient management (INM) versus mineral fertilization, when equivalent amounts of nutrients were added. Hence, this study was carried out to understand the impact of 60 years of INM with adjusted nutrient doses and mineral fertilization in an Alfisol in a maize (Zea maysL.)-wheat (Triticum aestivumL.) system on soil organic carbon (SOC) sequestration in surface (0-30 cm) and deep (30-60 cm) soil layers. Conventional tillage was done twice before sowing of both maize and wheat using a spade. In farmyard manure (FYM) and lime treated plots (FYMP'K'L: plots with nitrogen (N) applied in terms of FYM; additional dose of phosphorus (P) and potassium (K) and lime) total SOC concentration was nearly 83% higher than unfertilized control plots. The FYMP'K'L plots had similar to 11% more total SOC concentration than plots treated with mineral fertilizer and lime (NPKL: recommended dose of N, P, K and lime) in the 0-30 cm soil layer. Labile C, including KMnO4-C, was more in plots with FYM than NPKL plots, whereas the recalcitrant C stock was more in NPKL than FYM treated plots. In the 0-60 cm soil layer, the labile C stock was highest in FYMP'K'L plots, but the recalcitrant C stock was highest in NPKL. Total SOC accumulation rate (over unfertilized control plots) was highest for FYMP'K'L plots (0.38 Mg ha(-1 )year(-1)) in the surface soil layer, whereas SOC sequestration rate was highest in NPKL plots (0.18 Mg ha(-1 )year(-1)) in the deep layer and in the 0-60 cm layer. Overall, although NPKL management practice had the highest C sequestration in the 0-60 cm layer, FYMP'K'L had the best CMI and labile C pools. Thus, resource poor farmers need not to use full doses of NPK and FYM for soil C management in the region
Effect of different mercerization techniques on tactile comfort of cotton fabric
The effect of different mercerization techniques on tactile comfort properties of woven cotton fabric has been studied.Desized, scoured and bleached cotton fabrics are subjected to four different mercerization treatments at two levels oftemperature (20C and 65C) under two different conditions (tension and slack). Non-mercerized fabric is served as control.Results show that mercerization treatments improve the tensile strength of cotton fabrics owing to reduced fibre crystallinityafter mercerization. Highest increase in tensile strength is observed in case of hot mercerization in slack condition. Increasein low-stress mechanical properties, such as tensile energy, bending rigidity and shear rigidity values, indicates higherstiffness/toughness of mercerized fabrics. This is further reflected in their high Koshi (stiffness/firmness), low Sofutosa(softness) and medium Fukurami (fullness) values. However, mercerization causes significant decrease in frictionalcoefficient and surface roughness, and results in improved total hand value (THV). Total hand values range from 3 to 3.61;with highest being presented by fabric mercerized under hot and slack conditions. High hand value indicates fair suitabilityof this fabric in wear comfort
Study of low energy Si and Cs implantation induced amorphization effects in Si(100)
The damage growth and surface modifications in Si(100), induced by 25 keV
Si cluster ions, as a function of fluence, , has been studied using
atomic force microscopy (AFM) and channeling Rutherford backscattering
spectrometry (CRBS). CRBS results indicate a nonlinear growth in damage from
which it has been possible to get a threshold fluence, , for
amorphization as ions-cm. For below ,
a growth in damage as well as surface roughness has been observed. At a
of ions-cm, damage saturation coupled with a much
reduced surface roughness has been found. In this case a power spectrum
analysis of AFM data showed a significant drop, in spectral density, as
compared to the same obtained for a fluence, . This drop,
together with damage saturation, can be correlated with a transition to a
stress relaxed amorphous phase. Irradiation with similar mass Cs ions, at
the same energy and fluence, has been found to result in a reduced accumulation
of defects in the near surface region leading to reduced surface features.Comment: 7 pages, 4 figure
Near-horizon symmetries of extremal black holes
Recent work has demonstrated an attractor mechanism for extremal rotating
black holes subject to the assumption of a near-horizon SO(2,1) symmetry. We
prove the existence of this symmetry for any extremal black hole with the same
number of rotational symmetries as known four and five dimensional solutions
(including black rings). The result is valid for a general two-derivative
theory of gravity coupled to abelian vectors and uncharged scalars, allowing
for a non-trivial scalar potential. We prove that it remains valid in the
presence of higher-derivative corrections. We show that SO(2,1)-symmetric
near-horizon solutions can be analytically continued to give SU(2)-symmetric
black hole solutions. For example, the near-horizon limit of an extremal 5D
Myers-Perry black hole is related by analytic continuation to a non-extremal
cohomogeneity-1 Myers-Perry solution.Comment: 21 pages, latex. v2: minor improvements v3: Corrected error in
argument excluding de Sitter and Poincare-symmetric cases. Results unaffecte
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