Geographical co-location, social networks and inter-firm marketing co-operation : the case of the salmon industry

This study looks at the factors that influence the development of marketing co-operation among cluster-based firms. It examines data from SMEs operating within the salmon farming industry in two different regions: Scotland and Chile. Analyses indicate that informal social networks help explain the observed relationship between geographical proximity and inter-firm marketing co-operation, especially for firms located in peripheral rural communities. A theoretical model is proposed for further research in the field that, until recently, has been traditionally analysed only by economists. Practical implications are suggested for practitioners and policymaker

Small-angle scattering in a marginal Fermi-liquid

We study the magnetotransport properties of a model of small-angle scattering in a marginal Fermi liquid. Such a model has been proposed by Varma and Abrahams [Phys. Rev. Lett. 86, 4652 (2001)] to account for the anomalous temperature dependence of in-plane magnetotransport properties of the high-Tc cuprates. We study the resistivity, Hall angle and magnetoresistance using both analytical and numerical techniques. We find that small-angle scattering only generates a new temperature dependence for the Hall angle near particle-hole symmetric Fermi surfaces where the conventional Hall term vanishes. The magnetoresistance always shows Kohler's rule behavior.Comment: 4 pages, 3 figures, Revtex

Phase diagram and quasiparticle properties of the Hubbard model within cluster two-site DMFT

We present a cluster dynamical mean-field treatment of the Hubbard model on a square lattice to study the evolution of magnetism and quasiparticle properties as the electron filling and interaction strength are varied. Our approach for solving the dynamical mean-field equations is an extension of Potthoff's "two-site" method [Phys. Rev. B. 64, 165114 (2001)] where the self-consistent bath is represented by a highly restricted set of states. As well as the expected antiferromagnetism close to half filling, we observe distortions of the Fermi surface. The proximity of a van Hove point and the incipient antiferromagnetism lead to the evolution from an electron-like Fermi surface away from the Mott transition, to a hole-like one near half-filling. Our results also show a gap opening anisotropically around the Fermi surface close to the Mott transition (reminiscent of the pseudogap phenomenon seen in the cuprate high-Tc superconductors). This leaves Fermi arcs which are closed into pockets by lines with very small quasiparticle residue.Comment: 10 pages, 8 figures, latex (revtex4

Heat-transfer tests on the Rockwell International space shuttle orbiter with and without simulated protuberances

Aerothermodynamic tests on the forward half of the Rockwell International Space Shuttle Orbiter Configuration 140C were conducted at Mach number 8. The phase-change paint and thin-skin thermocouple techniques were used to determine the aerodynamic heating rates on the Orbiter models during simulated atmospheric reentry. Smooth 0.04-scale models and models with scaled protuberances and indentations which simulated the windshields, cargo bay door hinges, vents, and thruster nozzles were tested over an angle-of-attack range from 20 to 45 deg at yaw angles from -5 to 5 deg and at Reynolds numbers, based on the total Orbiter scaled length, from 2.15 to 15.9 million. Comparisons of the model heat-transfer rates obtained with a smooth surface and with scaled protuberances are presented

Natural environment support guidelines for space shuttle tests and operations

All space shuttle events from launch through solid rocket booster recovery and orbiter landing are considered in terms of constraints placed on those operations by the natural environment. Thunderstorm activity is discussed as an example of a possible hazard. The activities most likely to require advanced detection and monitoring techniques are identified as those from deorbit decision to Orbiter landing. The inflexible flight plan will require the transmission of real time wind profile information below 24 km and warnings of thunderstorms or turbulence in the Orbiter flight path. Extensive aerial reconnaissance and communication facilities and procedures to permit immediate transmission of aircraft reports to the mission control authority and to the Orbiter will also be required

Symplectic structure for elastic and chiral conducting cosmic string models

This article is based on the covariant canonical formalism and corresponding symplectic structure on phase space developed by Witten, Zuckerman and others in the context of field theory. After recalling the basic principles of this procedure, we construct the conserved bilinear symplectic current for generic elastic string models. These models describe current carrying cosmic strings evolving in an arbitrary curved background spacetime. Particular attention is paid to the special case of the chiral string for which the worldsheet current is null. Different formulations of the chiral string action are discussed in detail, and as a result the integrability property of the chiral string is clarified.Comment: 18 page

Evaluation of insulation materials and composites for use in a nuclear radiation environment, phase 2

The nuclear heating of the propellant in all of the four baseline RNS configurations studied was much lower than that of the nuclear flight module configuration with the 5000-MW NERVA analyzed previously. Although the nuclear heating has been reduced, the effect of nuclear heating on the propellant as well as the effect of nuclear heating on internal structures such as antivortex baffles, screens, and sump components cannot be neglected. In addition, it was found that the present analytical precedures were not able to predict boundary layer initiation and breakoff points with the accuracy necessary to predict propellant thermodynamic nonequilibrium (stratification) and/or mixing

B-R Colors of Globular Clusters in NGC 6166 (A2199)

We have analysed new R-band photometry of globular clusters in NGC 6166, the cD galaxy in the cooling flow cluster A2199. In combination with the earlier B photometry of Pritchet \& Harris (1990), we obtain B$-$R colours for $\sim$ 40 globular clusters in NGC 6166. The mean B$-$R is 1.26 $\pm$ 0.11, corresponding to a mean [Fe/H] = $-$1 $\pm$ 0.4. Given that NGC 6166 is one of the most luminous cD galaxies studied to date, our result implies significant scatter in the relationship between mean cluster [Fe/H] and parent galaxy luminosity. We obtain a globular cluster specific frequency of S$_N$ $\sim$ 9, with a possible range between 5 and 18. This value is inconsistent with the value of S$_N$ $\leq$ 4 determined earlier by Pritchet \& Harris (1990) from B-band photometry, and we discuss possible reasons for the discrepancy. Finally, we reassess whether or not cooling flows are an important mechanism for forming globular clusters in gE/cD galaxies.Comment: 8 pages, uuencoded, gzipped tar file with latex file, 6 figures (Fig 1 omitted because of size), and mn.sty file. Figures will be embedded into the postscript file. Accepted (March 1996) for publication in MNRA

The Grain Judging Club

June, 1924.Cover title

Chiral Vortons and Cosmological Constraints on Particle Physics

We investigate the cosmological consequences of particle physics theories that admit stable loops of current-carrying string - vortons. In particular, we consider chiral theories where a single fermion zero mode is excited in the string core, such as those arising in supersymmetric theories with a D-term. The resulting vortons formed in such theories are expected to be more stable than their non-chiral cousins. General symmetry breaking schemes are considered in which strings formed at one symmetry breaking scale become current-carrying at a subsequent phase transition. The vorton abundance is estimated and constraints placed on the underlying particle physics theories from cosmological observations. Our constraints on the chiral theory are considerably more stringent than the previous estimates for more general theories.Comment: minor corrections made. This version will appear in PR