An updated review of nanotechnologies for the space elevator tether

The space elevator tether requires an extraordinary specific ultimate strength (ratio between ultimate strength and density) and carbon nanotubes (CNTs) have been identified as the ideal candidate because of their astonishing strength. This paper reviews CNT manufacture and measured strengths

Optical fibre nanowire technology and applications

A review of optical fibre nanowires and their applications is presented

Nanostructuring of glass micro-nanowires

In the past decade, glass fiber tapers with micron or sub-micron diameter have attracted much attention and found a wide range of applications in optics [1] including mode filtering, supercontinuum generation, high-Q resonators and resonant sensing, optical trapping and optical propulsion. Nanofabrication can add new application opportunities, like Fabry-Perot resonators, Scanning near-field optical microscopy (SNOM) probe and surface plasmon resonators

Polarization effects in microcoil resonators

Optical microcoil resonators (OMRs), formed by coiling a micron-diameter fibre around a rod as shown in Figure 1a, provide a unique resonator geometry in which light can evanescently couple between adjacent turns to produce high Q resonances. Furthermore, OMRs fabricated from a pigtailed fibre taper offer much lower coupling losses than cavity resonators. Applications in fields such as fluidic and temperature sensing have already been investigated, and the small fibre diameter and effective modal area indicate that OMRs are a promising platform for studying nonlinear interactions. A detailed understanding of OMR optical characteristics is crucial for further development, but theoretical studies have thus far neglected any polarization dependency. In this work, the influence of the fibre’s birefringence on the polarization of propagating light was studied by numerically solving polarization dependant coupled mode equations. The resulting transmission and dispersion properties are discussed for different degrees of fibre twist (Figure 1b). In addition to the linear behaviour, the nonlinear regime was explored, by incorporating a Kerr term, and found to be strongly enhanced around resonances

Farm Productivity and Market Structure. Evidence From Cotton Reforms in Zambia

This paper investigates the impacts of cotton marketing reforms on farm productivity, a key element for poverty alleviation, in rural Zambia. The reforms comprised the elimination of the Zambian cotton marketing board that was in place since 1977. Following liberalization, the sector adopted an outgrower scheme, whereby firms provided extension services to farmers and sold inputs on loans that were repaid at the time of harvest. There are two distinctive phases of the reforms: a failure of the outgrower scheme, and a subsequent period of success of the scheme. Our findings indicate that the reforms led to interesting dynamics in cotton farming. During the phase of failure, farmers were pushed back into subsistence and productivity in cotton declined. With the improvement of the outgrower scheme of later years, farmers devoted larger shares of land to cash crops, and farm productivity significantly increased.cotton marketing reforms, farm productivity

Farm productivity and marketstructure : evidence from cotton reforms in Zambia

This paper investigates the impacts of cotton marketing reforms on farm productivity, a key element for poverty alleviation, in rural Zambia. The reforms comprised the elimination of the Zambian cotton marketing board that was in place since 1977. Following liberalization, the sector adopted an outgrower scheme, whereby firms provided extension services to farmers and sold inputs on loans that were repaid at the time of harvest. There are two distinctive phases of the reforms: a failure of the outgrower scheme, and a subsequent period of success of the scheme. The authors'findings indicate that the reforms led to interesting dynamics in cotton farming. During the phase of failure, farmers were pushed back into subsistence and productivity in cotton declined. With the improvement of the outgrower scheme of later years, farmers devoted larger shares of land to cash crops, and farm productivity significantly increased.Crops&Crop Management Systems,Economic Theory&Research,Livestock&Animal Husbandry,Rural Poverty Reduction,Rural Development Knowledge&Information Systems

Photochemical long-period grating fabrication in pure-fused-silica photonic crystal fiber

We report on first photochemical recording of a long-period fiber grating (LPFG) in a pure fused silica photonic crystal fiber (PCF), which is based on two-photon absorption (TPA) of high-intensity femtosecond 264 nm pulses. The main disadvantage of previously used nonphotochemical methods of LPFG inscription in PCF fiber (electric arc, mechanical pressure or CO2 laser irradiation) is that they easily damage the fragile holey structure, especially in PCFs with large hole diameters. Besides, photochemical LPFG fabrication in PCF not only allows recording by adding new periods to the grating, but also by repetitive exposure over the fixed number of periods. This important improvement results in production of stronger grating resonances with narrower bandwidths

Poincare' invariance and the heavy-quark potential

We derive and discuss the constraints induced by Poincare' invariance on the form of the heavy-quark potential up to order 1/m^2. We present two derivations: one uses general arguments directly based on the Poincare' algebra and the other follows from an explicit calculation on the expression of the potential in terms of Wilson loops. We confirm relations from the literature, but also clarify the origin of a long-standing false statement pointed out recently.Comment: 20 pages, 4 figure