Ballistic electronic transport in Quantum Cables

We studied theoretically ballistic electronic transport in a proposed mesoscopic structure - Quantum Cable. Our results demonstrated that Qauntum Cable is a unique structure for the study of mesoscopic transport. As a function of Fermi energy, Ballistic conductance exhibits interesting stepwise features. Besides the steps of one or two quantum conductance units ($2e^2/h$), conductance plateaus of more than two quantum conductance units can also be expected due to the accidental degeneracies (crossings) of subbands. As structure parameters is varied, conductance width displays oscillatory properties arising from the inhomogeneous variation of energy difference betweeen adjoining transverse subbands. In the weak coupling limits, conductance steps of height $2e^2/h$ becomes the first and second plateaus for the Quantum Cable of two cylinder wires with the same width.Comment: 11 pages, 5 figure

Distilling entanglement from cascades with partial "Which Path" ambiguity

We develop a framework to calculate the density matrix of a pair of photons emitted in a decay cascade with partial "which path" ambiguity. We describe an appropriate entanglement distillation scheme which works also for certain random cascades. The qualitative features of the distilled entanglement are presented in a two dimensional "phase diagram". The theory is applied to the quantum tomography of the decay cascade of a biexciton in a semiconductor quantum dot. Agreement with experiment is obtained

Ultrashort pulses and short-pulse equations in (2+1)−(2+1)-dimensions

In this paper, we derive and study two versions of the short pulse equation (SPE) in $(2+1)-$dimensions. Using Maxwell's equations as a starting point, and suitable Kramers-Kronig formulas for the permittivity and permeability of the medium, which are relevant, e.g., to left-handed metamaterials and dielectric slab waveguides, we employ a multiple scales technique to obtain the relevant models. General properties of the resulting $(2+1)$-dimensional SPEs, including fundamental conservation laws, as well as the Lagrangian and Hamiltonian structure and numerical simulations for one- and two-dimensional initial data, are presented. Ultrashort 1D breathers appear to be fairly robust, while rather general two-dimensional localized initial conditions are transformed into quasi-one-dimensional dispersing waveforms

Metastable Reconstructions on Si(111)

We report unambiguous atomic scale evidence demonstrating that the atom density in the high temperature 1x1 phase of Si(111) is ~6% higher than the 7x7. Such evidence is provided by scanning tunneling microscopy (STM) observation of excess adatom density, and related island formation, on surfaces with very large terraces. The unusually large terraces were produced by heating the sample with DC current in the step-down direction at 1200°C. By trapping adatoms on the terraces through a quench, we have also created areas of metastable reconstructions, i.e., 9x9, 2x2, c2x4 and √3x√3, much larger than previously reported. For the first time, we have demonstrated the existence of metastable 11x11, 13x13 and c2x8 on Si(111). We have found that the c2x8 reconstruction can be stabilized as well as other members of the 2x2/c2x4/c2x8 family of reconstructions. An energetic model, based on the idea of atomic conservation, is proposed for the formation of the observed high atom density metastable reconstructions

Jet evolution from weak to strong coupling

Recent studies, using the AdS/CFT correspondence, of the radiation produced by a decaying system or by an accelerated charge in the N=4 supersymmetric Yang-Mills theory, led to a striking result: the 'supergravity backreaction', which is supposed to describe the energy density at infinitely strong coupling, yields exactly the same result as at zero coupling, that is, it shows no trace of quantum broadening. We argue that this is not a real property of the radiation at strong coupling, but an artifact of the backreaction calculation, which is unable to faithfully capture the space-time distribution of the radiation. This becomes obvious in the case of a decaying system ('virtual photon'), for which the backreaction is tantamount to computing a three-point function in the conformal gauge theory, which is independent of the coupling since protected by symmetries. Whereas this non-renormalization property is specific to the conformal N=4 SYM theory, we argue that the failure of the three-point function to provide a local measurement is in fact generic: it holds in any field theory with non-trivial interactions. To properly study a localized distribution, one should rather compute a four-point function, as standard in deep inelastic scattering. We substantiate these considerations with studies of the radiation produced by the decay of a time-like photon at both weak and strong coupling. We show that by computing four-point functions, in perturbation theory at weak coupling and, respectively, from Witten diagrams at strong coupling, one can follow the quantum evolution and thus demonstrate the broadening of the energy distribution. This broadening is slow when the coupling is weak but it proceeds as fast as possible in the limit of a strong coupling.Comment: 49 pages, 6 figure

Weakly Enforced Boundary Conditions for the NURBS-Based Finite Cell Method

In this paper, we present a variationally consistent formulation for the weak enforcement of essential boundary conditions as an extension to the finite cell method, a fictitious domain method of higher order. The absence of boundary fitted elements in fictitious domain or immersed boundary methods significantly restricts a strong enforcement of essential boundary conditions to models where the boundary of the solution domain coincides with the embedding analysis domain. Penalty methods and Lagrange multiplier methods are adequate means to overcome this limitation but often suffer from various drawbacks with severe consequences for a stable and accurate solution of the governing system of equations. In this contribution, we follow the idea of NITSCHE [29] who developed a stable scheme for the solution of the Laplace problem taking weak boundary conditions into account. An extension to problems from linear elasticity shows an appropriate behavior with regard to numerical stability, accuracy and an adequate convergence behavior. NURBS are chosen as a high-order approximation basis to benefit from their smoothness and flexibility in the process of uniform model refinement

Perbedaan Daya Hidup Nyamuk Aedes Aegypti Setelah Dipapar Lc50 Ekstrak Bangle (Zingiber Purpureum) Dan Anti Nyamuk Cair Berbahan Aktif D-allethrin Dan Transflutrin

Dengue hemorrhagic fever is a disease caused by the dengue virus and transmitted by Aedes aegypti. Mostly, mosquito control uses synthetic insecticides that can cause resistance in mosquitoes and pollution in the environment so we can choose alternative natural insecticides from plants such as bangle (Zingiber purpureum) which contain essential oils, saponins, flavonoids, tannins and resins. This study aimed to analyze the difference vitality of Aedes aegypti L. after exposed LC50 bangle extract (zingiber purpureum Roxb.) and liquid mosquito insecticides d-allethrin and transflutrin. This study was a true experiment with post test only group design used Aedes aegypti population with aged 2-5 days are reared in B2P2VRP Laboratory in Salatiga, Central Java and use 900 mosquitoes for samples. Results of probit analysis LC50 of bangle extract was 660.000 ppm, d-allethrin was 36 ppm and transfluthrin was 27 ppm. The study showed difference of longevity Aedes aegypti among control and exposed group bangle, bangle and d-allethrin, bangle and transfluthrin (p = 0.0001)(Post Hoc, Tukey). There was no difference of Aedes aegypti longevity among the control, d-allethrin (p = 0.074) and transfluthrin (p = 0.999), moreover there was also no difference of Aedes aegypti longevity between exposed group d-allethrin and transfluthrin (p = 0.094). The result showed no difference the number of surviving Aedes aegypti among control, exposed group of bangle, d-allethrin and transfluthrin (p = 0,607) (Kruskal Wallis)