The PL calibration for Milky Way Cepheids and its implications for the distance scale

The rationale behind recent calibrations of the Cepheid PL relation using the Wesenheit formulation is reviewed and reanalyzed, and it is shown that recent conclusions regarding a possible change in slope of the PL relation for short-period and long-period Cepheids are tied to a pathological distribution of HST calibrators within the instability strip. A recalibration of the period-luminosity relation is obtained using Galactic Cepheids in open clusters and groups, the resulting relationship, described by log L/L_sun = 2.415(+-0.035) + 1.148(+-0.044)log P, exhibiting only the moderate scatter expected from color spread within the instability strip. The relationship is confirmed by Cepheids with HST parallaxes, although without the need for Lutz-Kelker corrections, and in general by Cepheids with revised Hipparcos parallaxes, albeit with concerns about the cited precisions of the latter. A Wesenheit formulation of Wv = -2.259(+-0.083) - 4.185(+-0.103)log P for Galactic Cepheids is tested successfully using Cepheids in the inner regions of the galaxy NGC 4258, confirming the independent geometrical distance established for the galaxy from OH masers. Differences between the extinction properties of interstellar and extragalactic dust may yet play an important role in the further calibration of the Cepheid PL relation and its application to the extragalactic distance scale.Comment: Accepted for Publication (Astrophysics & Space Science

RRS James Cook Cruise 36, 19 Jul-28 Jul 2009. The Geobiology of Whittard Submarine Canyon

The biological and geological research programme for James Cook cruise 36 was built around a series of ROV video transects to determine variations in species and community structure and composition in different geological and topographic settings down the canyon. ROV transects were planned to undertake detailed studies of recognised biological hotspots on both hard and soft substrates, to collect specimens for taxonomic studies, including molecular genetics, and to carry out biological experiments, including the use of in situ incubation chambers and tracer feeding experiments to study the physiology of deep-water fauna. Additional coring, CTD and water column particulate sampling programmes were planned to investigate the recent geological history of the canyon, and, in particular, to investigate whether significant sediment is currently accumulating in any part of the canyon, to sample macro- and meiofauna in areas of soft substrate, and to investigate the fate of organic carbon in the canyon. JC36 was highly successful. The cruise built on the successful mapping of the canyon, using swath bathymetry and 30 kHz sidescan sonar, undertaken during JC35. The main achievements of JC36 included the completion of 26 ROV dives, totalling 340 hr. Seafloor video and photographs along 12 transects from the eastern and western canyon branches between 500 and 3600 m waterdepth were collected. A collection of over 240 biological specimens was collected to verify species identification from the video transects. Pushcores for sedimentology, organic geochemistry, biology and microbiology were also collected. Ultra high-resolution swath bathymetry of the canyon floor using the multibeam system mounted on the ROV was collected on 8 dives. A total of 10 dives were dedicated to placing, initiating and recovering a variety of biological experiments on the seafloor, mainly to examine respiration rates of individual animals or animal communities. The coring programme completed 19 successful piston core stations and 29 successful megacore stations. Most of the latter were processed for macrofauna and meiofauna but some were subsampled for sedimentology and geochemistry. A preliminary assessment suggests that most of the sediment recovered is late glacial in age, and that little Holocene sediment has been deposited in the canyon. 6 CTD profiles and 5 SAPS (stand-alone pump) stations were completed to characterise the suspended particulate matter above the canyon floor. A total of 30 pushcores and megacores also sampled for organic geochemistry

RRS Charles Darwin Cruise 126, 11 Mar-20 Mar 2001. Piston coring of debris flows and turbidites west and south of the Canary Islands

The major cruise objective was to obtain sediment cores at various locations to the west and southwest of the Canary Islands with the aims of :· Sampling debris flow sediments in the Canary and Saharan debris flows· Obtaining dateable sediments immediately above and below the debris flow sediments· Sampling turbidite sediments associated with the debris flows· Sampling sediments on either flank of a sediment wave west of La PalmaIn addition, it was planned to:· obtain seabed video footage, using the SHRIMP towed camera station, at several localities where downslope sediment transport was believed to be active at the present day, and undertake some test deployments of the SOC Scatterometer syste

RV Pelagia Cruise 64PE219, 05 Nov – 24 Nov 2003. TOBI surveys of Setubal and Nazarre Canyons and of the MV Prestige wreck site, west of Iberia

The main objective of the cruise was to collect TOBI sidescan sonar imagery over three areas of the continental margin west of Iberia, where sediment transport studies are being undertaken as part of the EC funded ‘EUROSTRATFORM’ project. The three study areas were:1. The Setubal Canyon, between 38° to 38° 20’N on the continental margin. Here it wasplanned to image the canyon with a single 6 km-wide swath from the shelf edge near200m to the abyssal plain at depths exceeding 4800m2. The Nazarre Canyon, between 39° 30’ and 40°N on the continental margin. The survey plan was similar to that for Setubal Canyon, but with two parallel swaths over the lower reaches of the canyon, where it broadens into a 10 km wide channel crossing the continental rise.3. The Prestige tanker wreck site, at 42°N, 12°W, on the west flank of Galicia Bank, offnorthwest Spain. Here the aim was to investigate the stability of the slope where thetanker was lying. This part of the project was carried out jointly with UTM-CMIMA(CSIC), Barcelona, Spain.Although some time was lost to bad weather and equipment problems, excellent TOBI images were obtained over all three of the areas studied during Pelagia cruise 219. The cruise objectives were fully completed in areas 1 and 3, and about 60% of the expected area was surveyed in area 2, where almost three days were lost to bad weather

Zooplankton patchiness

This review considers three general aspects of research on zooplankton patchiness: the detection of patchiness, the description of patchiness and the causes of patchiness

Evaluating polarization data

A method is presented, which ensures that different polarization observables describing one reaction channel are consistent with each other. Using the connection of the observables to the same underlying reaction amplitudes, a constrained estimate of the observables is carried out using a Markov Chain Monte Carlo method. Initial results indicate that the new estimates are guaranteed to be physical, and will remove the need for artificial fudge factors when these processed data are used in subsequent fits

Linear Time LexDFS on Cocomparability Graphs

Lexicographic depth first search (LexDFS) is a graph search protocol which has already proved to be a powerful tool on cocomparability graphs. Cocomparability graphs have been well studied by investigating their complements (comparability graphs) and their corresponding posets. Recently however LexDFS has led to a number of elegant polynomial and near linear time algorithms on cocomparability graphs when used as a preprocessing step [2, 3, 11]. The nonlinear runtime of some of these results is a consequence of complexity of this preprocessing step. We present the first linear time algorithm to compute a LexDFS cocomparability ordering, therefore answering a problem raised in [2] and helping achieve the first linear time algorithms for the minimum path cover problem, and thus the Hamilton path problem, the maximum independent set problem and the minimum clique cover for this graph family

The role of price expectations in the UK housing market

Copyright University of HertfordshireThe objective of this paper is to explain and derive the non-linear, S-shaped diffusion path of price expectations and provide a forecasting model, three months ahead with the implications assessed. Bounded rationality means that various agents in the U.K. housing market, such as buyers,sellers, estate agents and chartered surveyors, play differing rôles in the overall formulation of expectations of prices. This is analogous to the logistic effect with a diffusion path of dis-equilibrium to the end-point of equilibrium. The empirical analysis makes use of the forwarding-looking price expectations data published by Royal Institution of Chartered Surveyors (RICS) with the actual observations produced by Mortgage lenders, the Halifax and the Nationwide

Advances in understanding autogyro flight dynamics

A comprehensive flight dynamics study of the autogyro is presented in this paper. A state of the art generic simulation of the vehicle type was developed and validated against flight data. This validation is presented in the paper and it is shown that the model can be applied to the autogyro with some confidence within well defined limitations bounds. It is also shown that the general stability characteristics of the autogyro can be considered as a mix of helicopter and fixed wing aircraft modes of flight. Most significantly the autogyro has a lightly damped, high frequency phugoid mode. Further, it is demonstrated that the only significant configurational effect is related to the relative vertical position of the centre of gravity with respect to the propeller thrustline, a centre of gravity which lies above the thrustline being more desirable. Results from preliminary handling qualities trials applying the techniques of ADS33 to an autogyro are also presented. Results from flight trials to investigate the teetering motion of the rotor are described, and the influence of the research on air accident investigation is also discussed

Improving rotorcraft survivability to RPG attack using inverse methods

This paper presents the results of a preliminary investigation of optimal threat evasion strategies for improving the survivability of rotorcraft under attack by rocket propelled grenades (RPGs). The basis of this approach is the application of inverse simulation techniques pioneered for simulation of aggressive helicopter manoeuvres to the RPG engagement problem. In this research, improvements in survivability are achieved by computing effective evasive manoeuvres. The first step in this process uses the missile approach warning system camera (MAWS) on the aircraft to provide angular information of the threat. Estimates of the RPG trajectory and impact point are then estimated. For the current flight state an appropriate evasion response is selected then realised via inverse simulation of the platform dynamics. Results are presented for several representative engagements showing the efficacy of the approach