rangeland ecosystems shift across dynamic thresholds between differentecological states in response to natural or human-induced factors. these differentecological states are the result of interactions among climate, soils, grazing history,and management practices. the notion of a single ‘‘pristine’’ final state is onlyconceptual in nature, and because of this, dynamic thresholds and the effects...

we apply the two-sector production function developed by ram (1986) to estimate the threshold regression model for iran, concerning the effect of government size on economic growth. three government size indicators are used to find out the different threshold points. the results show a non-linear relationship of the armey curve in iran, in which the threshold effects corresponding to total gove...

The effect of surface roughness on the Seebeck coefficient in the sub-50-nm scale silicon ultra thin films is investigated theoretically using nonequilibrium Green's function formalism. For systematic studies, the surface roughness is modelled by varying thickness periodically with square wave profile characterized by two parameters: amplitude (A 0) and wavelength (λ). Since high Seebeck coeffi...

introduction: gully erosion is an important type of soil erosion in iran and ardebil province (moghimi and salami, 2011; khatibi, 2006). increasing the cross section of gullies is an indicator for gully developing (deng et al, 2015). topography and soil properties are two important factors in gully developing in various regions of worldwide (poesena et al, 2003). despite the importance of soil ...

Digital subtraction angiography (DSA) images were obtained of a phantom containing 1 mm diameter vessels. The iodine concentrations ranged from 5 to 50 mg/cc, which permitted the determination of the detection threshold concentration of iodine. The source to image receptor distance was 105 cm, and image magnification was varied between 1.15 and 2.0. One experiment was performed at an input expo...

We investigate laser ablation of crystalline silicon induced by a femtosecond optical vortex beam, addressing how beam properties can be obtained by analyzing the ablation crater. The morphology of the surface structures formed in the annular crater surface allows direct visualization of the beam polarization, while analysis of the crater size provides beam spot parameters. We also determine th...

We have developed an evaporative cooling technique that accelerates the rotation of an ultracold 87Rb gas, confined in a static harmonic potential. As a normal gas is evaporatively spun up and cooled below quantum degeneracy, it is found to nucleate vorticity in a Bose-Einstein condensate. Measurements of the condensate's aspect ratio and surface-wave excitations are consistent with effective r...

We present transport measurements of a nondegenerate two-dimensional electron system on the surface of liquid helium at a point constriction. The constriction is formed in a microchannel by a split gate beneath the helium surface. The electrostatic energy of the electron system, which depends in part on the electron density, determines the split-gate voltage threshold of current flow through th...

Threshold photoemission yields for As and In terminated reconstructions of InAs ~001! are measured in situ and the variation of the photoyield is correlated with the surface stoichiometry. A significant excess in the measured photoelectron yield is found for the In terminated surfaces. These results are compared to a semiempirical model based on density-functional theory calculations of the sur...

Cl2, Br2, HBr, Br2/Cl2, and HBr/Cl2 feed gases diluted in Ar (50%–50% by volume) were used to study etching of p-type Si(100) in a rf inductively coupled, Faraday-shielded plasma, with a focus on the photo-assisted etching component. Etching rates were measured as a function of ion energy. Etching at ion energies below the threshold for ion-assisted etching was observed in all cases, with Br2/A...