Space weather effects on drilling accuracy in the North Sea

The oil industry uses geomagnetic field information to aid directional drilling operations when drilling for oil and gas offshore. These operations involve continuous monitoring of the azimuth and inclination of the well path to ensure the target is reached and, for safety reasons, to avoid collisions with existing wells. Although the most accurate method of achieving this is through a gyroscopic survey, this can be time consuming and expensive. An alternative method is a magnetic survey, where measurements while drilling (MWD) are made along the well by magnetometers housed in a tool within the drill string. These MWD magnetic surveys require estimates of the Earth’s magnetic field at the drilling location to correct the downhole magnetometer readings. The most accurate corrections are obtained if all sources of the Earth’s magnetic field are considered. Estimates of the main field generated in the core and the local crustal field can be obtained using mathematical models derived from suitable data sets. In order to quantify the external field, an analysis of UK observatory data from 1983 to 2004 has been carried out. By accounting for the external field, the directional error associated with estimated field values at a mid-latitude oil well (55 N) in the North Sea is shown to be reduced by the order of 20%. This improvement varies with latitude, local time, season and phase of the geomagnetic activity cycle. By accounting for all sources of the field, using a technique called Interpolation In-Field Referencing (IIFR), directional drillers have access to data from a “virtual” magnetic observatory at the drill site. This leads to an error reduction in positional accuracy that is close to matching that of the gyroscopic survey method and provides a valuable independent technique for quality control purposes

Pathological changes in the spleens of gamma interferon receptor-deficient mice infected with murine gammaherpesvirus:a role for CD8 T cells

Murine gammaherpesvirus is a natural rodent pathogen which causes a primary infection in the lungs and establishes a persistent infection in B lymphocytes. During the primary infection, large amounts of gamma interferon (IFN-gamma) are produced by spleen, mediastinal, and cervical lymph node cells. To investigate the role of IFN-gamma in control of the virus infection, mice lacking the cellular receptor for IFN-gamma (IFN-gamma R-/- mice) were infected with murine gammaherpesvirus 68 (MHV68). IFN-gamma R-/- mice showed no difference from wild-type mice in the titers of infectious virus in the lungs or in the rate of clearance of the lung infection. In the spleen, however, clear differences were observed. By 14 days postinfection, spleens from IFN-gamma R-/- mice were pale, shrunken, and fibrous. Histological examination showed that there was an early (day 10) infiltration of granulocytes followed by widespread destruction of splenic architecture (days 14 to 17). A marked decrease in the number of splenic B cells and CD4+ and CD8+ T cells occurred. These changes were accompanied by a 10- to 100-fold greater load of latently infected cells in IFN-gamma R-/- mice than in wild-type mice at 14 to 17 days postinfection, but this was reduced to the levels found in wild-type mice by 21 days postinfection. Treatment of the mice with the antiviral drug 2'-deoxyl-5-ethyl-beta-4'-thiouridine from 6 days postinfection did not prevent the occurrence of these changes. The changes were, however, completely reversed by depletion of CD8+ T cells prior to and during the primary infection. Depletion of CD4+ T cells also reversed the major pathological and virological changes, although in this case there was evidence of some histological changes. Thus, the lack of IFN-gamma receptor had profound consequences in spleens of MHV68-infected mice. The possible mechanisms involved in these changes are discussed

Modifying fertiliser practices

If modified fertiliser practices are adopted phosphorus losses from the Peel-Harvey catchment can be reduced. Farmers can save money on fertiliser applications and the need for more expensive catchment management measures to reduce algal pollution of the estuary will be avoided. Research data available so far indicate that, with farmer co-operation and the use of the new slow release fertiliser New Coastal Superphosphate, long-term phosphorus application rates can be reduced by 30-40 per cent - and possibly even halved - without lowering agricultural production. This will also reduce phosphorus loss to drainage water. Although much of the research since 1982 has concentrated on the Peel-Harvey catchment, many of the results apply to all of the high rainfall coastal belt between Perth and Albany. Already farmers throughout this area have benefited from the researc

Wrinkling of a bilayer membrane

The buckling of elastic bodies is a common phenomenon in the mechanics of solids. Wrinkling of membranes can often be interpreted as buckling under constraints that prohibit large amplitude deformation. We present a combination of analytic calculations, experiments, and simulations to understand wrinkling patterns generated in a bilayer membrane. The model membrane is composed of a flexible spherical shell that is under tension and that is circumscribed by a stiff, essentially incompressible strip with bending modulus B. When the tension is reduced sufficiently to a value \sigma, the strip forms wrinkles with a uniform wavelength found theoretically and experimentally to be \lambda = 2\pi(B/\sigma)^{1/3}. Defects in this pattern appear for rapid changes in tension. Comparison between experiment and simulation further shows that, with larger reduction of tension, a second generation of wrinkles with longer wavelength appears only when B is sufficiently small.Comment: 9 pages, 5 color figure

The clearing of discs around late type T Tauri stars: constraints from the infrared two colour plane

We have undertaken SED modeling of discs around low mass T Tauri stars in order to delineate regions of the infrared two colour plane (K - [8] versus K - [24]) that correspond to discs in different evolutionary stages. This provides a ready tool for classifying the nature of star-disc systems based on infrared photometry. In particular we demonstrate the distinct loci followed by discs that undergo `uniform draining' (reduction in surface density by a spatially uniform factor) from those that clear from the inside out. We draw attention to the absence of objects on this `draining locus' in those star forming regions where the 24um sensitivity would permit their detection, as compared with the ~20 objects in these regions with colours suggestive of inner holes. We thus conclude that discs predominantly clear from the inside out. We also apply our classification of the infrared two colour plane to stars of spectral type M3-M5 in the IC 348 cluster and show that some of its members (dubbed `weak excess' sources by Muzerolle et al 2010) that had previously been assumed to be in a state of clearing are instead likely to be optically thick discs in which the dust is well settled towards the mid-plane. Nevertheless, there are many discs in a state of partial clearing in IC 348, with their abundance (relative to the total population of disc bearing stars) being around four times higher than for comparable stars in Taurus. However, the number of partially cleared discs relative to the total number of late type stars is similarly low in both regions (10 and 20 % respectively). We therefore conclude that IC 348 represents a more evolved version of the Taurus population (with more of its discs being highly settled or partially cleared) but that the timescale for clearing is similarly short (a few times 10^5 years) in both cases.Comment: 9 pages, 6 figures, accepted, MNRA

Flight Test of the F/A-18 Active Aeroelastic Wing Airplane

Successful flight-testing of the Active Aeroelastic Wing airplane was completed in March 2005. This program, which started in 1996, was a joint activity sponsored by NASA, Air Force Research Laboratory, and industry contractors. The test program contained two flight test phases conducted in early 2003 and early 2005. During the first phase of flight test, aerodynamic models and load models of the wing control surfaces and wing structure were developed. Design teams built new research control laws for the Active Aeroelastic Wing airplane using these flight-validated models; and throughout the final phase of flight test, these new control laws were demonstrated. The control laws were designed to optimize strategies for moving the wing control surfaces to maximize roll rates in the transonic and supersonic flight regimes. Control surface hinge moments and wing loads were constrained to remain within hydraulic and load limits. This paper describes briefly the flight control system architecture as well as the design approach used by Active Aeroelastic Wing project engineers to develop flight control system gains. Additionally, this paper presents flight test techniques and comparison between flight test results and predictions

Development and Testing of Control Laws for the Active Aeroelastic Wing Program

The Active Aeroelastic Wing research program was a joint program between the U.S. Air Force Research Laboratory and NASA established to investigate the characteristics of an aeroelastic wing and the technique of using wing twist for roll control. The flight test program employed the use of an F/A-18 aircraft modified by reducing the wing torsional stiffness and adding a custom research flight control system. The research flight control system was optimized to maximize roll rate using only wing surfaces to twist the wing while simultaneously maintaining design load limits, stability margins, and handling qualities. NASA Dryden Flight Research Center developed control laws using the software design tool called CONDUIT, which employs a multi-objective function optimization to tune selected control system design parameters. Modifications were made to the Active Aeroelastic Wing implementation in this new software design tool to incorporate the NASA Dryden Flight Research Center nonlinear F/A-18 simulation for time history analysis. This paper describes the design process, including how the control law requirements were incorporated into constraints for the optimization of this specific software design tool. Predicted performance is also compared to results from flight

Potassium, Calcium, and Magnesium Bridging of AOT to Mica at Constant Ionic Strength.

The bridging effect of a series of common cations between the anionic mica surface and the AOT anion has been studied in a condition of constant ionic strength and surfactant concentration. It was found that sodium ions did not show any bridging effect in this system; however, calcium, magnesium, and potassium all caused adsorption of the organic to the mica surface. The concentrations at which bridging occurred was probed, revealing that only a very low bridging cation concentration was required for binding. The bridged layer stability was also investigated, and the interaction was shown to be a weak one, with the bound layer in equilibrium with the species in the bulk and easily removed. Even maintaining ionic strength and bridging ion concentration was not sufficient to retain the layer when the free organic in solution was removed.We thank EPSRC and BP plc for the funding (RG8620) that made this work possible

Coccolithophores: Functional Biodiversity, Enzymes and Bioprospecting

Emiliania huxleyi is a single celled, marine phytoplankton with global distribution. As a key species for global biogeochemical cycling, a variety of strains have been amassed in various culture collections. Using a library consisting of 52 strains of E. huxleyi and an ‘in house’ enzyme screening program, we have assessed the functional biodiversity within this species of fundamental importance to global biogeochemical cycling, whilst at the same time determining their potential for exploitation in biocatalytic applications. Here, we describe the screening of E. huxleyi strains, as well as a coccolithovirus infected strain, for commercially relevant biocatalytic enzymes such as acid/alkali phosphodiesterase, acid/alkali phosphomonoesterase, EC1.1.1-type dehydrogenase, EC1.3.1-type dehydrogenase and carboxylesterase