The potential for technology and knowledge transfers between foreign and local firms: a study of the construction industry in Ghana

Multinational corporations (MNCs) and other foreign firms can be conduits for technology and knowledge (T&K) transfer to host countries in the developing world. Most of the existing research focuses on T&K transfers through FDI and are drawn from Asia not Sub-Saharan Africa (SSA), although SSA is increasingly receiving foreign investment. There is a paucity of research that gives insights into project-level T&K transfer issues in SSA countries. Using the Ghanaian construction industry as an empirical focus, this article explores T&K transfer potential. The findings reveal significant weaknesses in T&K transfer across industry subsectors and between foreign and local firms. This arises from the potentially complementary but dissimilar resource and knowledge bases. The weaknesses are compounded by the absence of coherent government T&K development policie

Singlet-Triplet Physics and Shell Filling in Carbon Nanotube Double Quantum Dots

An artifcial two-atomic molecule, also called a double quantum dot (DQD), is an ideal system for exploring few electron physics. Spin-entanglement between just two electrons can be explored in such systems where singlet and triplet states are accessible. These two spin-states can be regarded as the two states in a quantum two-state system, a so-called singlet-triplet qubit. A very attractive material for realizing spin based qubits is the carbon nanotube (CNT), because it is expected to have a very long spin coherence time. Here we show the existence of a gate-tunable singlet-triplet qubit in a CNT DQD. We show that the CNT DQD has clear shell structures of both four and eight electrons, with the singlet-triplet qubit present in the four-electron shells. We furthermore observe inelastic cotunneling via the singlet and triplet states, which we use to probe the splitting between singlet and triplet, in good agreement with theory.Comment: Supplement available at: http://www.fys.ku.dk/~hij/public/singlet-triple_supp.pd

Spin and Orbital Splitting in Ferromagnetic Contacted Single Wall Carbon Nanotube Devices

We observed the coulomb blockade phenomena in ferromagnetic contacting single wall semiconducting carbon nanotube devices. No obvious Coulomb peaks shift was observed with existing only the Zeeman splitting at 4K. Combining with other effects, the ferromagnetic leads prevent the orbital spin states splitting with magnetic field up to 2 Tesla at 4K. With increasing magnetic field further, both positive or negative coulomb peaks shift slopes are observed associating with clockwise and anticlockwise orbital state splitting. The strongly suppressed/enhanced of the conductance has been observed associating with the magnetic field induced orbital states splitting/converging

A spectroscopic study of the cycling transition 4s[3/2]_2-4p[5/2]_3 at 811.8 nm in Ar-39: Hyperfine structure and isotope shift

Doppler-free saturated absorption spectroscopy is performed on an enriched radioactive Ar-39 sample. The spectrum of the 3s^2 3p^5 4s [3/2]_2 - 3s^2 3p^5 4p [5/2]_3 cycling transition at 811.8 nm is recorded, and its isotope shift between Ar-39 and Ar-40 is derived. The hyperfine coupling constants A and B for both the 4s [3/2]_2 and 4p [5/2]_3 energy levels in Ar-39 are also determined. The results partially disagree with a recently published measurement of the same transition. Based on earlier measurements as well as the current work, the isotope shift and hyperfine structure of the corresponding transition in Ar-37 are also calculated. These spectroscopic data are essential for the realization of laser trapping and cooling of Ar-37 and Ar-39

KP solitons, total positivity, and cluster algebras

Soliton solutions of the KP equation have been studied since 1970, when Kadomtsev and Petviashvili proposed a two-dimensional nonlinear dispersive wave equation now known as the KP equation. It is well-known that the Wronskian approach to the KP equation provides a method to construct soliton solutions. The regular soliton solutions that one obtains in this way come from points of the totally non-negative part of the Grassmannian. In this paper we explain how the theory of total positivity and cluster algebras provides a framework for understanding these soliton solutions to the KP equation. We then use this framework to give an explicit construction of certain soliton contour graphs, and solve the inverse problem for soliton solutions coming from the totally positive part of the Grassmannian.Comment: published in Proc. Natl. Acad. Sci. online ahead of print May 11, 2011, doi:10.1073/pnas.110262710

Directly modulated lasers on InP membrane platform:design and simulation

Directly modulated laser (DML) design for InP membrane platform is proposed. In this platform, a stack containing contact layers and quantum wells is epitaxially grown on InP wafer, which is then adhesively bonded to Si substrate using BCB (benzo-cyclobutene). DML proposed makes use of weak tunable distributed Bragg grating to extend the modulation bandwidth by detuned loading and photon-photon resonance. Photonic crystal reflector is used to maximize Q-factor of the cavity. Up to 80 GHz 3dB bandwidth is obtained in simulation

Abundances of s-process elements in planetary nebulae: Br, Kr & Xe

We identify emission lines of post-iron peak elements in very high signal-to-noise spectra of a sample of planetary nebulae. Analysis of lines from ions of Kr and Xe reveals enhancements in most of the PNe, in agreement with the theories of s-process in AGB star. Surprisingly, we did not detect lines from Br even though s-process calculations indicate that it should be produced with Kr at detectable levels.Comment: 2 pages, 1 figure, to be published in the Proceedings of the IAU Symposium 234: Planetary Nebulae in Our Galaxy and Beyond, eds. M.J. Barlow, R.H. Mende