First-order melting of a weak spin-orbit Mott insulator into a correlated metal

The electronic phase diagram of the weak spin-orbit Mott insulator (Sr(1-x)Lax)3Ir2O7 is determined via an exhaustive experimental study. Upon doping electrons via La substitution, an immediate collapse in resistivity occurs along with a narrow regime of nanoscale phase separation comprised of antiferromagnetic, insulating regions and paramagnetic, metallic puddles persisting until x~0.04. Continued electron doping results in an abrupt, first-order phase boundary where the Neel state is suppressed and a homogenous, correlated, metallic state appears with an enhanced spin susceptibility and local moments. As the metallic state is stabilized, a weak structural distortion develops and suggests a competing instability with the parent spin-orbit Mott state.Comment: 5 pages, 4 figure

Quantum key distribution using a triggered quantum dot source emitting near 1.3 microns

We report the distribution of a cryptographic key, secure from photon number splitting attacks, over 35 km of optical fiber using single photons from an InAs quantum dot emitting ~1.3 microns in a pillar microcavity. Using below GaAs-bandgap optical excitation, we demonstrate suppression of multiphoton emission to 10% of the Poissonian level without detector dark count subtraction. The source is incorporated into a phase encoded interferometric scheme implementing the BB84 protocol for key distribution over standard telecommunication optical fiber. We show a transmission distance advantage over that possible with (length-optimized) uniform intensity weak coherent pulses at 1310 nm in the same system.Comment: 4 pages, 4 figure

The internationalisation of the Spanish SME sector

As part of a wider research program, we analysed the theoretical framework and the recent developments of the process of internationalisation (transnationalisation) of the small- and medium-sized enterprises in Spain. The paper highlights the main trends and barriers of this internationalisation process. Methodology included document analyses, interviews, and the analyses of statistical databases

Radiative Transfer in Prestellar Cores: A Monte Carlo Approach

We use our Monte Carlo radiative transfer code to study non-embedded prestellar cores and cores that are embedded at the centre of a molecular cloud. Our study indicates that the temperature inside embedded cores is lower than in isolated non-embedded cores, and generally less than 12 K, even when the cores are surrounded by an ambient cloud of small visual extinction (Av~5). Our study shows that the best wavelength region to observe embedded cores is between 400 and 500 microns, where the core is quite distinct from the background. We also predict that very sensitive observations (~1-3 MJy/sr) at 170-200 microns can be used to estimate how deeply a core is embedded in its parent molecular cloud. Finally, we present preliminary results of asymmetric models of non-embedded cores.Comment: 8 pages, 15 figures, to appear in the conference proceedings of "Open Issues in Local Star Formation and Early Stellar Evolution", held in Ouro Preto (Brazil), April 5-10, 200

Threshold Corrections in Precision LHC Physics: QED otimes QCD

With an eye toward LHC processes in which theoretical precisions of 1 percent are desired, we introduce the theory of the simultaneous YFS resummation of QED and QCD to compute the size of the expected resummed soft radiative threshold effects in precision studies of heavy particle production at the LHC. Our results show that both QED and QCD soft threshold effects must be controlled to be on the conservative side to achieve such precision goals.Comment: 4 pages, no figures; presented by B.F.L. Ward in DPF200

Development of a 'millimanipulation' device to study the removal of soft solid fouling layers from solid substrates and its application to cooked lard deposits

A mm-scale scraping device was developed to study the removal behaviour of soft solid fouling layers (thickness 0.5 to 10 mm) from solid substrates. A blade is dragged through the circular or rectangular samples at controlled speed and the resistance forces measured. Tests with a viscous liquid (honey) and viscoplastic material (a Vaseline-carbon black paste) indicated that cohesive deformation dominated the measured force. Two model food soils were: (i) unbaked lard, and (ii) lard baked for different times with and without added ovalbumin. The cohesive strength of the baked lard, and its removal behaviour, changed noticeably following autoxidative polymerisation. Ovalbumin delayed the onset of polymerisation.An EPSRC studentship for AA is gratefully acknowledged, as it project support and a summer studentship for JP from Proctor & Gamble.This is the final version. It was first published by Elsevier at http://www.sciencedirect.com/science/article/pii/S0960308514000972

On Theoretical Uncertainties of the W Angular Distribution in W-Pair Production at LEP2 Energies

We discuss theoretical uncertainties of the distribution in the cosine of the W polar angle projected into a measurement of the anomalous triple gauge-boson coupling \lambda=\lambda_{\gamma}=\lambda_Z at LEP2 energies for the tandem of the Monte Carlo event generators KoralW and YFSWW3 and for the Monte Carlo event generator RacoonWW. Exploiting numerical results of these programs and cross-checks with experimental fitting procedures, we estimate that the theoretical uncertainty of the value of \lambda due to electroweak corrections, as obtained at LEP2 with the help of these programs, is ~0.005, about half of the expected experimental error for the combined LEP2 experiments (~0.010). We use certain idealized event selections; however, we argue that these results are valid for realistic LEP2 measurements.Comment: 14 pages, 3 Postscript figure

The Effects of Chemical and Mechanical Control of Woody Plants on Resprouting and Seedling Production in Communal Rangelands

In many African countries, communal rangelands are threatened by woody plant encroachment. We sought to explore potential solutions for communal ranchers that would be cost-effective. We conducted two field experiments to determine (1) the effects of various tree removal treatments (10%, 20%, 50%, 75% and 100%), and herbicide application on resprouting ability and vigour of several woody plant species; and (2) the effectiveness of Tree Poppers® (a weed wrench) as a low-cost mechanical control tool to physically uproot seedlings and saplings of woody species. In the first experiment, we examined 12 plant species from 20 plots (30 m x 30 m) each subjected to tree removal, followed by herbicide application on half of the stumps for each plot. In the second experiment, eight dominant tree species were grouped into three height classes (0-49 cm, 50-99 cm, 100-150 cm) of ten seedlings and saplings per species per height class. All the tree species in this study resprouted six months after cutting. Herbicide application significantly reduced the resprouting ability of Dichrostachys cinerea (L.) Wight & Arn, Ehretia rigida (Thunb.) Druce, Vachellia robusta (Burch.) Kyalangalilwa & Boatwright and Ziziphus mucronata Willd. Tree removal positively influenced the resprouting ability and vigour of only Euclea crispa (Thunb.) Gürke. The diameter of stumps was an important factor in determining resprouting ability, with shoot production decreasing with increasing stump diameter. We found no significant differences in the number of seedlings and saplings uprooted by Tree Poppers® among the different size classes. There were significant differences in the number of juveniles uprooted using a weed wrench with only a few individuals of Vachellia species uprooted. Woody plants are more likely to resprout and survive as juveniles than as adults after cutting. Communal ranchers may mechanically control shallow-rooted tree seedlings with a weed wrench but not deep-rooted ones, such as Vachellia species

Report of the Working Group on `W Mass and QCD' (Phenomenology Workshop on LEP2 Physics, Oxford, April 1997)

The W Mass and QCD Working Group discussed a wide variety of topics relating to present and future measurements of M(W) at LEP2, including QCD backgrounds to W+W- production. Particular attention was focused on experimental issues concerning the direct reconstruction and threshold mass measurements, and on theoretical and experimental issues concerning the four jet final state. This report summarises the main conclusions.Comment: 43 pages LaTeX and 15 encapsulated postscript figures. Uses epsfig and ioplppt macros. Full Proceedings to be published in Journal of Physics