Non-adiabatic Current Excitation in Quantum Rings

We investigate the difference in the response of a one-dimensional semiconductor quantum ring and a finite-width ring to a strong and short-lived time-dependent perturbation in the THz regime. In both cases the persistent current is modified through a nonadiabatic change of the many-electron states of the system, but by different mechanisms in each case.Comment: LaTeX, 5 pages with 6 embedded postscript figures, submitted to 20th Nordic Semiconductor Meeting, Tampere (2003

Carrier scattering, mobilities and electrostatic potential in mono-, bi- and tri-layer graphenes

The carrier density and temperature dependence of the Hall mobility in mono-, bi- and tri-layer graphene has been systematically studied. We found that as the carrier density increases, the mobility decreases for mono-layer graphene, while it increases for bi-layer/tri-layer graphene. This can be explained by the different density of states in mono-layer and bi-layer/tri-layer graphenes. In mono-layer, the mobility also decreases with increasing temperature primarily due to surface polar substrate phonon scattering. In bi-layer/tri-layer graphene, on the other hand, the mobility increases with temperature because the field of the substrate surface phonons is effectively screened by the additional graphene layer(s) and the mobility is dominated by Coulomb scattering. We also find that the temperature dependence of the Hall coefficient in mono-, bi- and tri-layer graphene can be explained by the formation of electron and hole puddles in graphene. This model also explains the temperature dependence of the minimum conductance of mono-, bi- and tri-layer graphene. The electrostatic potential variations across the different graphene samples are extracted.Comment: 18 pages, 7 figure

Coherent transport through graphene nanoribbons in the presence of edge disorder

We simulate electron transport through graphene nanoribbons of experimentally realizable size (length L up to 2 micrometer, width W approximately 40 nm) in the presence of scattering at rough edges. Our numerical approach is based on a modular recursive Green's function technique that features sub-linear scaling with L of the computational effort. We identify the influence of the broken A-B sublattice (or chiral) symmetry and of K-K' scattering by Fourier spectroscopy of individual scattering states. For long ribbons we find Anderson-localized scattering states with a well-defined exponential decay over 10 orders of magnitude in amplitude.Comment: 8 pages, 6 Figure

Pengaruh Panjang Entres Terhadap Keberhasilan Sambung Pucuk Dan Pertumbuhan Benih Jambu Mete

The research was to obtain proper length of upper stem to the success rate of grafting and grwoth of the seedling cashew nut plants have been conducted in the Garden Experiments Cikampek, Karawang regency, West Java. Soil types was rocky laterite andesite, type C climate and altitude of 50 meters above sea level. The research was conducted in August 2009 until April 2010. While the materials used cashew seed type B 02 for both rootstock and to the upper stem. Grafting was done after 3 months old seedlings with seedlings about 60 cm high and 0.6 cm diameter stems of seedlings. Experiments prepared following the randomized block design was repeated three times that consisting of 10 plants. The treatments were tested namely long scion 10, 15 and 20 cm. Plants grew in polybags with size 15 x 25 cm. The indicators were observed covering the base of the cuttings scion diameter, cutting the base color of entres, the percentage of shoots continued success, increased plant height, leaf number and stem diameter of the seed.The results showed that the length of entres effect on continued success grafting of seedling cashew. Scion length was 20 cm which gave the highest grafting success is as much as 78%

From convoy to parting ways? Post-crisis divergence between European and US macroeconomic policies

The response in 2008-09 to the global financial crisis was in many ways a high water mark for transatlantic policy coordination. The major economies of the EU and the US rapidly agreed on a series of measures to limit the crisis. However, the common approach has since unraveled. This paper explores why the 'London consensus' has not survived for much more than a year. We identify four non-competing explanations: (a) divergence in economic developments, especially the productivity response to the recession; (b) domestic political economy factors, notably the pressure to act against unemployment in the US; (c) differences in beliefs as regards the nature of the recovery from the common shock, about which there is much more supplyside optimism in the US ; (d) institutional factors such as the lack of a central fiscal authority in the EU. In response to this situation we suggest a critical quantum of coordination. Key measures include a commitment to avoiding deliberate currency depreciation and unilateral intervention; agreement to give the IMF an enhanced monitoring role; the adoption by parliaments of medium-term fiscal plans ; and cooperation on the issue of Chinese undervaluation