Short turn-around intercontinental clock synchronization using very-long-baseline interferometry

During the past year work was accomplished to bring into regular operation a VLBI system for making intercontinental clock comparisons with a turn around of a few days from the time of data taking. Earlier VLBI systems required several weeks to produce results. The present system, which is not yet complete, incorporates a number of refinements not available in earlier systems, such as dual frequency inosopheric delay cancellation and wider synthesized bandwidths with instrumental phase calibration

Internet and e-Commerce Use by Agribusiness Firms: 2004

In 2001, the dot.com bubble burst and U.S. e-commerce growth slowed. Slower e-commerce growth may signal changes in the use and perceptions of the Internet and e-commerce in agribusiness companies. Agribusiness firm managers were surveyed in 2004 to identify agribusiness use of the Internet and e-commerce and to solicit their perceptions about the Internet and e-commerce. The survey was developed from a similar survey conducted in 1999. In 2004, agribusiness firms were using e-commerce more with their suppliers than with their customers. Perceptions regarding Internet and e-commerce varied by the intensity of e-commerce use. Given the variety of opinions regarding the Internet and e-commerce, e-commerce capabilities in the agribusiness industry will remain highly diverse in the near term.agribusiness, e-commerce, Internet, Agribusiness, Research and Development/Tech Change/Emerging Technologies,

ADOPTION OF E-COMMERCE STRATEGIES FOR AGRIBUSINESS FIRMS

This paper analyzes the factors guiding Internet and e-commerce implementation by agribusiness firms. The relationship between Internet/e-commerce strategies and manager perceptions on the barriers and factors to e-commerce adoption are analyzed in a supply-chain management framework. Using factor analysis and an ordered Probit model, results indicate that the implementation of Internet/e-commerce strategies is more likely to be adopted in larger firms with a global scope. Also, manager perceptions regarding supply-chain functions influencing transaction costs are more strongly associated with Internet/e-commerce adoption than other functions influencing production costs.e-commerce, supply-chain, transaction costs, factor analysis, order Probit, Agribusiness, Marketing,

An extended model of the quantum free-electron laser

Previous models of the quantum regime of operation of the Free Electron Laser (QFEL) have performed an averaging and the application of periodic boundary conditions to the coupled Maxwell - Schrodinger equations over short, resonant wavelength intervals of the interaction. Here, an extended, one-dimensional model of the QFEL interaction is presented in the absence of any such averaging or application of periodic boundary conditions, the absence of the latter allowing electron diffusion processes to be modeled throughout the pulse. The model is used to investigate how both the steady-state (CW) and pulsed regimes of QFEL operation are affected. In the steady-state regime it is found that the electrons are confined to evolve as a 2-level system, similar to the previous QFEL models. In the pulsed regime Coherent Spontaneous Emission (CSE) due to the shape of the electron pulse current distribution is shown to be present in the QFEL regime for the first time. However, unlike the classical case, CSE in the QFEL is damped by the effects of quantum diffusion of the electron wavefunction. Electron recoil from the QFEL interaction can also cause a diffusive drift between the recoiled and non-recoiled parts of the electron pulse wavefunction, effectively removing the recoiled part from the primary electron-radiation interaction.Comment: Submitted to Optics Expres

E-Business and Distribution Channel Strategies in Agribusiness Industries

The explosion of e-business activity presents many challenges to manufacturers, distributors, and dealers as they select a distribution channel for the delivery of products, services, and information. The expected growth in Internet sales by agribusiness firms is analyzed to provide insight into the selection of an e-business distribution channel. Agribusiness firm managers were surveyed regarding the application and perceived impacts of e-business activity on their firm's operations. Firm characteristics and manager perceptions regarding the impact of e-business activity were analyzed descriptively and in regression analysis to understand the drivers of expected Internet sales growth. Expected Internet sales growth was found to vary by the firm's position in the distribution channel. Yet, firms with greater levels of existing e-communication with either customers or suppliers and with managers perceiving greater ability of e-business activity to improve inventory management and logistics issues have higher levels of expected Internet sales.Agribusiness,

Adoption of Internet Strategies by Agribusiness Firms

This paper explores the factors guiding Internet adoption by agribusiness firms. The relationship between Internet strategies and manager perceptions on the barriers to and catalysts for Internet adoption are analyzed in a supply-chain management framework. Using factor analysis and an ordered Probit model, results indicate that Internet strategies are more likely to be adopted in larger firms with a global scope. Also, manager perceptions regarding the impact of Internet adoption on transaction costs are just as likely to influence adoption as the perceived impacts on more traditional production costs.Internet, E-commerce, Supply-chain, Transaction costs, Ordered Probit, Agribusiness, Research and Development/Tech Change/Emerging Technologies,

Yang-Mills Theory on a Cylinder Coupled to Point Particles

We study a model of quantum Yang-Mills theory with a finite number of gauge invariant degrees of freedom. The gauge field has only a finite number of degrees of freedom since we assume that space-time is a two dimensional cylinder. We couple the gauge field to matter, modeled by either one or two nonrelativistic point particles. These problems can be solved {\it without any gauge fixing}, by generalizing the canonical quantization methods of Ref.\[rajeev] to the case including matter. For this, we make use of the geometry of the space of connections, which has the structure of a Principal Fiber Bundle with an infinite dimensional fiber. We are able to reduce both problems to finite dimensional, exactly solvable, quantum mechanics problems. In the case of one particle, we find that the ground state energy will diverge in the limit of infinite radius of space, consistent with confinement. In the case of two particles, this does not happen if they can form a color singlet bound state (`meson').Comment: 37 pages, UR-1327 ER-40685-77

Coordination chemistry of 3- and 4-mercaptobenzoate ligands: Versatile hydrogen-bonding isomers of the thiosalicylate (2-mercaptobenzoate) ligand

This review summarises the coordination chemistry of the isomeric 3- and 4-mercaptobenzoate ligands, derived from HSC6H4COOH, being isomers of the widely-studied 2-mercaptobenzoate (thiosalicylate) ligand. The 3- and 4-mercaptobenzoate ligands show a wide range of coordination modes, including monodentate (through either S or less commonly O), chelation through the carboxylate group alone, as well as a wide range of bridging modes. However, S,O-chelation, which is prevalent for thiosalicylate complexes, is not found in the 3MBA and 4MBA isomers. In the solid-state, complexes of 3MBA and 4MBA ligands containing protonated carboxylic acid groups typically undergo aggregation through formation of classical hydrogen-bonded carboxylic acid dimer motifs, which can be supplemented by additional interactions such as aurophilic (Au� � �Au) interactions in the case of gold(I) complexes. The hybrid hard-soft nature of 3MBA and 4MBA ligands facilitates the use of these ligands in the construction of early-late heterobimetallic complexes. These ligands also find numerous applications (such as the protection of metallic gold and silver nanoparticles), which are especially prevalent for 4MBA where the para carboxylate/carboxylic acid group is remote from the sulfur coordination site

Impact of non-Poisson activity patterns on spreading processes

Halting a computer or biological virus outbreak requires a detailed understanding of the timing of the interactions between susceptible and infected individuals. While current spreading models assume that users interact uniformly in time, following a Poisson process, a series of recent measurements indicate that the inter-contact time distribution is heavy tailed, corresponding to a temporally inhomogeneous bursty contact process. Here we show that the non-Poisson nature of the contact dynamics results in prevalence decay times significantly larger than predicted by the standard Poisson process based models. Our predictions are in agreement with the detailed time resolved prevalence data of computer viruses, which, according to virus bulletins, show a decay time close to a year, in contrast with the one day decay predicted by the standard Poisson process based models.Comment: 4 pages, 3 figure

Family Size and Educational Attainment in England and Wales

In this paper, we use linked census data from England and Wales to investigate whether having a large number of siblings leads to lower educational attainment. There is a large literature suggesting that with large sibship size, parental resources will be diluted and this, in turn, will lead to lower educational attainment. Using twin births and the sex composition of the sibling group as instrumental variables, we find that the evidence of a family size effect on educational attainment is rather uncertain. Similar results are obtained when we use occupational attainment as the dependent variable. We also demonstrate the confounding of birth order and family size effects, and show that an adjusted birth order index proposed by Booth and Kee provides an effective solution to this estimation problem