Improved optical filters for automated visual inspection

Sides of spatial filter slits are shaped so that their contribution to signal is reduced, thus minimizing the number of scanning errors

Microwave spectroscopy of some maser materials

Vapour phase rubies were examined by several techniques. X-rays showed that the c-axis varied from place to place in each boule by up to 3º. Superimposed on this was a distribution of mosaic structure with the c-axis varying from grain to grain by up to 3º. Annealing did not improve these imperfections. Boules grown in the 90º orientation showed less mosaic than those grown in other orientations. Polygonisation, observed by Scheuplein and Gibbs (1960), provided an explanation. X-ray examination of corundum gave similar results. The random dislocation density revealed by etching was about l0(^5) dislocations/cm(^2) in corundum and ruby, therefore, adding chromium did not produce dislocations. The imperfections did not correlate with the boules, crystallography. The paramagnetic resonance linewidth increases with the imperfection in the sample and this increase is angular dependent. The basic linewidth depends on the chromium concentration. Sample 337c showed little angular broadening in the + (^1)(-2) to + (^3_)(_2) and the – (^3)(_2) to – (^1)(^2) transitions. In G2a the latter transition showed a maximum broadening of about 2(^1)(_2) times near the polar angle 45º. X-rays showed that each sample had similar c-axis misorientations but G2a contained much more mosaic than 337c. The misorientation predicted by the broadening G2a is 0º 25. The – (^1)(_2) to + (^3)(_2) transition in 337c was about 22 oersteds wide and did not vary much with angle. In G2a this transition broadened to 33 oersteds at polar angles 45º and 30º. The chromium concentration predicted from the basic linewidth at 55º in both sample is 0.43 weight % of chromium. The concentrations given by chemical analysis are 0.052 weight % for 337c and between 0.02 and 0.032 weight % for G2a

Moon-tracking orbits using motorized tethers for continuous earth–moon payload exchanges

For human colonization of the moon to become reality, an efficient and regular means of exchanging resources between the Earth and the moon must be established. One possibility is to pass and receive payloads at regular intervals between a symmetrically laden motorized momentum-exchange tether orbiting about Earth and a second orbiting about the moon. There are significant challenges associated with this method, among the greatest of which is the development of a system that incorporates the complex motion of the moon into its operational architecture in addition to conducting these exchanges on a per-lunar-orbit basis. One way of achieving this is to use a motorized tether orbiting Earth and tracking the nodes of the moon’s orbit to allow payload exchanges to be undertaken periodically with the arrival of the moon at either of these nodes. Tracking these nodes is achieved by arranging the tether to orbit Earth with a critical inclination, thus rendering its argument of perigee stationary in addition to using the precession effects resulting from an oblate Earth. Using this in conjunction with pre-emptive adjustments to its angle of right ascension, the tether will periodically realign itself with these nodes simultaneously with the arrival of the moon

Seasonal Patterns of Nitrogen Fixation in Termites

Summary 1. Termite nitrogenase activity was highest in autumn and spring (≈ 3 µg N2 fixed termite fresh mass (g)–1 day–1) and lowest in winter and summer (≈ 0·8 µg N2 fixed termite fresh mass (g)–1 day–1). 2. The nitrogenase activity of worker termites was significantly higher than all other castes (1·58 ± 0·27 µg N2 fixed termite fresh mass (g)–1 day–1). 3. Worker termites constituted the largest proportion of all the castes throughout the study period (≈ 90%). 4. The localized input of fixed nitrogen by termites may reach 15·3 mg N log–1 day–1 and 5·6 g N log–1 year–1

High-fidelity readout of trapped-ion qubits

We demonstrate single-shot qubit readout with fidelity sufficient for fault-tolerant quantum computation, for two types of qubit stored in single trapped calcium ions. For an optical qubit stored in the (4S_1/2, 3D_5/2) levels of 40Ca+ we achieve 99.991(1)% average readout fidelity in one million trials, using time-resolved photon counting. An adaptive measurement technique allows 99.99% fidelity to be reached in 145us average detection time. For a hyperfine qubit stored in the long-lived 4S_1/2 (F=3, F=4) sub-levels of 43Ca+ we propose and implement a simple and robust optical pumping scheme to transfer the hyperfine qubit to the optical qubit, capable of a theoretical fidelity 99.95% in 10us. Experimentally we achieve 99.77(3)% net readout fidelity, inferring at least 99.87(4)% fidelity for the transfer operation.Comment: 4 pages, 3 figures; improved readout fidelity (numerical results changed

Production of Z' and W' via Drell-Yan processes in the 4D Composite Higgs Model at the LHC

We present an analysis of both the Neutral Current (NC) and Charged Current (CC) Drell-Yan processes at the LHC within a 4 Dimensional realization of a Composite Higgs model studying the cross sections and taking into account the possible impact of the extra fermions present in the spectrum.Comment: Conference proceeding, XII IFAE Edition, 3-5 April 2013, Cagliari. 2 pages, 2 figures; v2 typo correcte

Experimental recovery of a qubit from partial collapse

We describe and implement a method to restore the state of a single qubit, in principle perfectly, after it has partially collapsed. The method resembles the classical Hahn spin-echo, but works on a wider class of relaxation processes, in which the quantum state partially leaves the computational Hilbert space. It is not guaranteed to work every time, but successful outcomes are heralded. We demonstrate using a single trapped ion better performance from this recovery method than can be obtained employing projection and post-selection alone. The demonstration features a novel qubit implementation that permits both partial collapse and coherent manipulations with high fidelity.Comment: 5 pages, 3 figure