Stabilized Spin-Polarized Jellium Model and Odd-Even Alternations in Jellium Metal Clusters

In this paper, we have considered the mechanical stability of a jellium system in the presence of spin degrees of freedom and have generalized the stabilized jellium model, introduced by J. P. Perdew, H. Q. Tran, and E. D. Smith [Phys. Rev. B42, 11627 (1990)], to a spin-polarized case. By applying this generalization to metal clusters (Al, Ga, Li, Na, K, Cs), we gain additional insights about the odd-even alternations, seen in their ionization potentials. In this generalization, in addition to the electronic degrees of freedom, we allow the positive jellium background to expand as the clusters' polarization increases. In fact, our self-consistent calculations of the energetics of alkali metal clusters with spherical geometries, in the context of density functional theory and local spin density approximation, show that the energy of a cluster is minimized for a configuration with maximum spin compensation (MSC). That is, for clusters with even number of electrons, the energy minimization gives rise to complete compensation ($N_\uparrow=N_\downarrow$), and for clusters with odd number of electrons, only one electron remains uncompensated ($N_\uparrow-N_\downarrow=1$). It is this MSC-rule which gives rise to alternations in the ionization potentials. Aside from very few exceptions, the MSC-rule is also at work for other metal culsters (Al, Ga) of various sizes.Comment: 18 pages, Rev_Tex, 14 figures in PostScript, Extended and improved version of our recent article with the same titl

Growth performance of rainbow trout (Oncorhynchus mykiss) with respect to nutritional factors in north Iran (Haraz River)

Monthly samples of six fish farms from January 2010 to December 2010 in the northern Iran, Haraz River, were used to determine relationship between chemical parameters of main water, inlet and outlet and their effects on fish growth and production. Results revealed that concentration of nutrients in outlet was more than that of inlet of farms, and statistical analysis showed that there were significant differences between stations (p0.05) in different months. Correlation between daily growth, SGR, FCR, production and chemical parameters of water were analyzed by Pearson correlation. The results revealed negative correlation (α= 0.01) between nitrite and daily growth (P=0.004, Pearson correlation=-0.24), ammonium and SGR (P=0.0001, Pearson correlation=-0.272), although there were no correlation for FCR, and nutritional parameters (p>0.05)

Effect of fentanyl on the success of inferior alveolar nerve block for teeth with symptomatic irreversible pulpitis: a randomized clinical trial

Aim: The purpose of this prospective, randomized, double-blind study was to evaluate the effect of adding fentanyl to lidocaine 2% with epinephrine 1:80,000 on the success of the inferior alveolar nerve block in mandibular molar teeth with symptomatic irreversible pulpitis. Methodology: 100 healthy adult patients with diagnosis of symptomatic irreversible pulpitis in one of the mandibular molar tooth were selected and randomly divided in two groups of 50 patients each. In the first group (fentanyl group), 0.25 ml of a cartridge of 1.8 ml of 2% lidocaine with 1:80,000 epinephrine solution was drained and the same amount from 50μg/ ml fentanyl solution was added to the cartridge. In the second group (non-fentanyl group) 0.25 ml of a cartridge of 1.8 ml of 2% lidocaine with 1:80,000 epinephrine solution was drained and the same amount from saline solution was added to the cartridge. Each group received two cartridges of prepared soloution with inferior alveolar nerve block injection technique. Access cavity preparation started 15 minautes after injection and after confirming the lip numbness. Success defined as no pain or mild pain on the basis of Heft-Parker visual analog scale during access cavity preparation or initial instrumentation. Data were analyzed by T-test and Chi-square Results: The success rate of inferior alveolar nerve block injection was 58% for Fentanyl group and 46% for Non-Fentanyl group. There was no significant difference between the two groups (P=0.23). Conclusions: The addition of fentanyl to lidocaine 2% with epinephrine 1:80,000 did not increase the success rate of the inferior alveolar nerve block in mandibular molar teeth with symptomatic irreversible pulpitis

Flood loss modelling with FLF-IT: a new flood loss function for Italian residential structures

The damage triggered by different flood events costs the Italian economy millions of euros each year. This cost is likely to increase in the future due to climate variability and economic development. In order to avoid or reduce such significant financial losses, risk management requires tools which can provide a reliable estimate of potential flood impacts across the country. Flood loss functions are an internationally accepted method for estimating physical flood damage in urban areas. In this study, we derived a new flood loss function for Italian residential structures (FLF-IT), on the basis of empirical damage data collected from a recent flood event in the region of Emilia-Romagna. The function was developed based on a new Australian approach (FLFA), which represents the confidence limits that exist around the parameterized functional depth–damage relationship. After model calibration, the performance of the model was validated for the prediction of loss ratios and absolute damage values. It was also contrasted with an uncalibrated relative model with frequent usage in Europe. In this regard, a three-fold cross-validation procedure was carried out over the empirical sample to measure the range of uncertainty from the actual damage data. The predictive capability has also been studied for some sub-classes of water depth. The validation procedure shows that the newly derived function performs well (no bias and only 10 % mean absolute error), especially when the water depth is high. Results of these validation tests illustrate the importance of model calibration. The advantages of the FLF-IT model over other Italian models include calibration with empirical data, consideration of the epistemic uncertainty of data, and the ability to change parameters based on building practices across Italy

Kondo lattice model at half-filling

The single- and two-channel Kondo lattice model consisting of localized spins interacting antiferromagnetically with the itinerent electrons, are studied using dynamical mean field theory. As an impurity solver for the effective single impurity Anderson model we used the exact diagonalization (ED) method. Using ED allowed us to perform calculations for low temperatures and couplings of arbitrary large strength. Our results for the single-channel case confirm and extend the recent investigations. In the two-channel case we find a symmetry breaking phase transition with increasing coupling strength.Comment: 11 pages, 5 figure

Quantum Hall effect in single wide quantum wells

We study the quantum Hall states in the lowest Landau level for a single wide quantum well. Due to a separation of charges to opposite sides of the well, a single wide well can be modelled as an effective two level system. We provide numerical evidence of the existence of a phase transition from an incompressible to a compressible state as the electron density is increased for specific well width. Our numerical results show a critical electron density which depends on well width, beyond which a transition incompressible double layer quantum Hall state to a mono-layer compressible state occurs. We also calculate the related phase boundary corresponding to destruction of the collective mode energy gap. We show that the effective tunneling term and the interlayer separation are both renormalised by the strong magnetic field. We also exploite the local density functional techniques in the presence of strong magnetic field at $\nu=1$ to calculate renormalized $\Delta_{SAS}$. The numerical results shows good agreement between many-body calculations and local density functional techniques in the presence of a strong magnetic field at $\nu=1$. we also discuss implications of this work on the $\nu=1/2$ incompressible state observed in SWQW.Comment: 30 pages, 7 figures (figures are not included

Ladder approximation to spin velocities in quantum wires

The spin sector of charge-spin separated single mode quantum wires is studied, accounting for realistic microscopic electron-electron interactions. We utilize the ladder approximation (LA) to the interaction vertex and exploit thermodynamic relations to obtain spin velocities. Down to not too small carrier densities our results compare well with existing quantum Monte-Carlo (QMC) data. Analyzing second order diagrams we identify logarithmically divergent contributions as crucial which the LA includes but which are missed, for example, by the self-consistent Hartree-Fock approximation. Contrary to other approximations the LA yields a non-trivial spin conductance. Its considerably smaller computational effort compared to numerically exact methods, such as the QMC method, enables us to study overall dependences on interaction parameters. We identify the short distance part of the interaction to govern spin sector properties.Comment: 6 pages, 6 figures, to appear in Physical Review

Surface Modifications by Field Induced Diffusion

By applying a voltage pulse to a scanning tunneling microscope tip the surface under the tip will be modified. We have in this paper taken a closer look at the model of electric field induced surface diffusion of adatoms including the van der Waals force as a contribution in formations of a mound on a surface. The dipole moment of an adatom is the sum of the surface induced dipole moment (which is constant) and the dipole moment due to electric field polarisation which depends on the strength and polarity of the electric field. The electric field is analytically modelled by a point charge over an infinite conducting flat surface. From this we calculate the force that cause adatoms to migrate. The calculated force is small for voltage used, typical 1 pN, but due to thermal vibration adatoms are hopping on the surface and even a small net force can be significant in the drift of adatoms. In this way we obtain a novel formula for a polarity dependent threshold voltage for mound formation on the surface for positive tip. Knowing the voltage of the pulse we then can calculate the radius of the formed mound. A threshold electric field for mound formation of about 2 V/nm is calculated. In addition, we found that van der Waals force is of importance for shorter distances and its contribution to the radial force on the adatoms has to be considered for distances smaller than 1.5 nm for commonly used voltages