Susceptibility of the aphids Myzus persicae and Brevicoryne brassicae to systemic pesticides

Imperial Users onl

Programmed schedule holds for improving launch vehicle holds

Baseline definition and system optimization are used for the analysis of programmed holds developed through prelaunch system analysis. Identification of design specifications for ground support equipment and maintenance concepts, and design specifications are used to describe the functional utilization of the overall flow process

Perturbed Spherically Symmetric Dust Solution of the Field Equations in Observational Coordinates with Cosmological Data Functions

Using the framework for solving the spherically symmetric field equations in observational coordinates given in Araujo and Stoeger (1999), their formulation and solution in the perturbed FLRW sperically symmetric case with observational data representing galaxy redshifts, number counts and observer area distances, both as functions of redshift on our past light cone, are presented. The importance of the central conditions, those which must hold on our world line C, is emphasized. In detailing the solution for these perturbations, we discuss the gauge problem and its resolution in this context, as well as how errors and gaps in the data are propagated together with the genuine perturbations. This will provide guidance for solving, and interpreting the solutions of the more complicated general perturbation problem with observational data on our past light cone.Comment: Latex 23 pages, no figures, submitted to Astrophysical Journa

Perturbation expansions for a class of singular potentials

Harrell's modified perturbation theory [Ann. Phys. 105, 379-406 (1977)] is applied and extended to obtain non-power perturbation expansions for a class of singular Hamiltonians H = -D^2 + x^2 + A/x^2 + lambda/x^alpha, (A\geq 0, alpha > 2), known as generalized spiked harmonic oscillators. The perturbation expansions developed here are valid for small values of the coupling lambda > 0, and they extend the results which Harrell obtained for the spiked harmonic oscillator A = 0. Formulas for the the excited-states are also developed.Comment: 23 page

Siren songs or path to salvation? Interpreting the visions of web technology at a UK regional newspaper in crisis, 2006-11

A 5-year case study of an established regional newspaper in Britain investigates journalists about their perceptions of convergence in digital technologies. This research is the first ethnographic longitudinal case study of a UK regional newspaper. Although conforming to some trends observed in the wider field of scholarship, the analysis adds to skepticism about any linear or directional views of innovation and adoption: the Northern Echo newspaper journalists were observed to have revised their opinions of optimum Web practices, and sometimes radically reversed policies. Technology is seen in the period as a fluid, amorphous entity. Central corporate authority appeared to diminish in the period as part of a wider reduction in formalism. Questioning functionalist notions of the market, the study suggests cause and effect models of change are often subverted by contradictory perceptions of particular actions. Meanwhile, during technological evolution, the ‘professional imagination’ can be understood as strongly reflecting the parent print culture and its routines, despite pioneering a new convergence partnership with an independent television company

Generation of many-particle entanglement in an ion trap by adiabatic ground-state transitions

We discuss the creation of many-particle entanglement in an ion trap where all ions are simultaneously coupled to bichromatic laser fields. It is shown that in a time-averaged, coarse-grained picture the system can be mapped onto a spin ensemble with controllable collective interactions. An adiabatic change of laser parameters allows a transfer from separable to entangled eigenstates of the many-particle Hamiltonian. Of particular interest is a transition in the ground state which in some cases corresponds to a quantum phase transition. The influence of decoherence mechanisms can be substantially reduced if at all times a sufficiently large energy gap between the ground state and the first excited state is maintained.Comment: 4 pages, 3 figure

Effects of Backflow Correlation in the Three-Dimensional Electron Gas: Quantum Monte Carlo Study

The correlation energy of the homogeneous three-dimensional interacting electron gas is calculated using the variational and fixed-node diffusion Monte Carlo methods, with trial functions that include backflow and three-body correlations. In the high density regime the effects of backflow dominate over those due to three-body correlations, but the relative importance of the latter increases as the density decreases. Since the backflow correlations vary the nodes of the trial function, this leads to improved energies in the fixed-node diffusion Monte Carlo calculations. The effects are comparable to those found for the two-dimensional electron gas, leading to much improved variational energies and fixed-node diffusion energies equal to the release-node energies of Ceperley and Alder within statistical and systematic errors.Comment: 14 pages, 5 figures, submitted to Physical Review

A low-density hot Jupiter in a near-aligned, 4.5-day orbit around a VV = 10.8, F5V star

We report the independent discovery and characterisation of a hot Jupiter in a 4.5-d, transiting orbit around the star TYC 7282-1298-1 ($V$ = 10.8, F5V). The planet has been pursued by the NGTS team as NGTS-2b and by ourselves as WASP-179b. We characterised the system using a combination of photometry from WASP-South and TRAPPIST-South, and spectra from CORALIE (around the orbit) and HARPS (through the transit). We find the planet's orbit to be nearly aligned with its star's spin. From a detection of the Rossiter-McLaughlin effect, we measure a projected stellar obliquity of $\lambda = -19 \pm 6^\circ$. From line-profile tomography of the same spectra, we measure $\lambda = -11 \pm 5^\circ$. We find the planet to have a low density ($M_{\rm P}$ = 0.67 $\pm$ 0.09 $M_{\rm Jup}$, $R_{\rm P}$ = 1.54 $\pm$ 0.06 $R_{\rm Jup}$), which, along with its moderately bright host star, makes it a good target for transmission spectroscopy. We find a lower stellar mass ($M_*$ = $1.30 \pm 0.07$ $M_\odot$) than reported by the NGTS team ($M_*$ = $1.64 \pm 0.21$ $M_\odot$), though the difference is only $1.5$ $\sigma$.Comment: Submitted to AJ. 9 pages, 6 figures, 5 table

Phase boundary exchange coupling in the mixed magnetic phase regime of a Pd-doped FeRh epilayer

Spin-wave resonance measurements were performe in the mixed magnetic phase regime of a Pd-doped FeRh epilayer that appears as the first-order ferromagnetic-antiferromagnetic phase transition takes place. It is seen that the measured value of the exchange stiffness is suppressed throughout the measurement range when compared to the expected value of the fully ferromagnetic regime, extracted via the independent means of a measurement of the Curie point, for only slight changes in the ferromagnetic volume fraction. This behavior is attributed to the influence of the antiferromagnetic phase: inspired by previous experiments that show ferromagnetism to be most persistent at the surfaces and interfaces of FeRh thin films, we modelled the antiferromagnetic phase as forming a thin layer in the middle of the epilayer through which the two ferromagnetic layers are coupled up to a certain critical thickness. The development of this exchange stiffness is then consistent with that expected from the development of an exchange coupling across the magnetic phase boundary, as a consequence of a thickness dependent phase transition taking place in the antiferromagnetic regions and is supported by complimentary computer simulations of atomistic spin-dynamics. The development of the Gilbert damping parameter extracted from the ferromagnetic resonance investigations is consistent with this picture