Pseudo--magnetorotational instability in a Taylor-Dean flow between electrically connected cylinders

We consider a Taylor-Dean-type flow of an electrically conducting liquid in an annulus between two infinitely long perfectly conducting cylinders subject to a generally helical magnetic field. The cylinders are electrically connected through a remote, perfectly conducting endcap, which allows a radial electric current to pass through the liquid. The radial current interacting with the axial component of magnetic field gives rise to the azimuthal electromagnetic force, which destabilizes the base flow by making its angular momentum decrease radially outwards. This instability, which we refer to as the pseudo--magnetorotational instability (MRI), looks like an MRI although its mechanism is basically centrifugal. In a helical magnetic field, the radial current interacting with the azimuthal component of the field gives rise to an axial electromagnetic force, which drives a longitudinal circulation. First, this circulation advects the Taylor vortices generated by the centrifugal instability, which results in a traveling wave as in the helical MRI (HMRI). However, the direction of travel of this wave is opposite to that of the true HMRI. Second, at sufficiently strong differential rotation, the longitudinal flow becomes hydrodynamically unstable itself. For electrically connected cylinders in a helical magnetic field, hydrodynamic instability is possible at any sufficiently strong differential rotation. In this case, there is no hydrodynamic stability limit defined in the terms of the critical ratio of rotation rates of inner and outer cylinders that would allow one to distinguish a hydrodynamic instability from the HMRI. These effects can critically interfere with experimental as well as numerical determination of MRI.Comment: 10 pages, 5 figures, minor revision, to appear in Phys. Rev.

The denatured state of N-PGK is compact and predominantly disordered

The Organisation of the structure present in the chemically denatured N-terminal domain of phosphoglycerate kinase (N-PGK) has been determined by paramagnetic relaxation enhancements (PREs) to define the conformational landscape accessible to the domain. Below 2.0 M guanidine hydrochloride (GuHCl), a species of N-PGK (denoted I-b) is detected, distinct from those previously characterised by kinetic experiments [folded (F), kinetic intermediate (I-k) and denatured (D)]. The transition to I-b is never completed at equilibrium, because F predominates below 1.0 M GuHCl. Therefore, the ability of PREs to report on transient or low population species has been exploited to characterise I-b. Five single cysteine variants of N-PGK were labelled with the nitroxide electron spin-label MTSL [(1-oxyl-2,2,5,5-tetramethyl-3-pyrroline-3-methyl)methanesulfonate] and the denaturant dependences of the relaxation properties of the amide NMR signals between 1.2 and 3.6 M GuHCl were determined. Significant PREs for I-b were obtained, but these were distributed almost uniformly throughout the sequence. Furthermore, the PREs indicate that no specific short tertiary contacts persist. The data indicate a collapsed state with no coherent three-dimensional structure, but with a restricted radius beyond which the protein chain rarely reaches. The NMR characteristics Of I-b indicate that it forms from the fully denatured state within 100 mu s, and therefore a rapid collapse is the initial stage of folding of N-PGK from its chemically denatured state. By extrapolation, I-b is the predominant form of the denatured state under native conditions, and the non-specifically collapsed structure implies that many non-native contacts and chain reversals form early in protein folding and must be broken prior to attaining the native state topology. (C) 2008 Elsevier Ltd. All rights reserved

The cognitive interview: a tiered approach in the real world

This chapter will examine how the cognitive interview (CI) has been applied into the real world of policing. We will consider the impact the CI has had on every-day policing, ranging from front-line communication, to being utilised within a visually recorded interview, which may replace live evidence in the court-room (depending on the legislative framework of the country it is being applied). As the CI is utilised in a multitude of different types of information and evidence gathering scenarios the way in which the CI needs to be applied, and thus trained should reflect the context within which it is to be used in the field. Accordingly, the UK has developed the ‘Tiered approach’ to interview training (Clarke & Milne, 2011), whereby interviewers learn interviewing skills (including the CI) incrementally, across a police investigator’s career span. This approach has been adopted in numerous countries and the chapter will explain the approach, outline a model of training to maximize transference of skills into the workplace, and the research base examining its effectiveness in the field

Analysis of QTL for high grain protein content in Canadian durum wheat

Non-Peer ReviewedDurum wheat (Triticum turgidum L. var. durum) varieties with high grain protein concentration (GPC) produce pasta products with greater cooking firmness and increased tolerance to overcooking. However, the large environmental effect on expression of GPC and the negative correlation between GPC and grain yield slow breeding progress of durum wheat varieties with elevated GPC. Identification of molecular markers associated with high GPC would aid durum wheat breeders to select for this important trait earlier. The objectives of this study were to identify molecular markers associated with quantitative trait loci (QTL) for elevated GPC in durum wheat. A preliminary genetic map was constructed by screening polymorphic microsatellite markers on a set of 95 double haploid lines derived from the cross Strongfield (high GPC) X DT695 (low GPC). QTL analysis using single marker regression was performed on GPC data collected at Swift Current and Regina in 2002 and Swift Current, Regina and Saskatoon in 2003. To date, we have identified two QTL for GPC flanked by Xgwm448 and Xgwm558 on chromosome 2AS, and on chromosome 2BL at wmc332. No QTL for high GPC could be detected on chromosome 6BS, the location of a high GPC gene isolated previously from durum, wheat suggesting that Strongfield contains novel QTL for high GPC not previously reported in the literature. The molecular markers flanking the QTL identified in this study can be used by durum wheat breeders to enhance selection of high GPC in durum wheat

Type II migration strikes back – an old paradigm for planet migration in discs

In this paper, we analyse giant gap-opening planet migration in proto-planetary discs, focusing on the type II migration regime. According to standard type II theory, planets migrate at the same rate as the gas in the disc, as they are coupled to the disc viscous evolution; however, recent studies questioned this paradigm, suggesting that planets migrate faster than the disc material. We study the problem through 2D long-time simulations of systems consistent with type II regime, using the hydrodynamical grid code FARGO3D. Even though our simulations confirm the presence of an initial phase characterized by fast migration, they also reveal that the migration velocity slows down and eventually reaches the theoretical prediction if we allow the system to evolve for enough time. We find the same tendency to evolve towards the theoretical predictions at later times when we analyse the mass flow through the gap and the torques acting on the planet. This transient is related to the initial conditions of our (and previous) simulations, and is due to the fact that the shape of the gap has to adjust to a new profile, once the planet is set into motion. Secondly, we test whether the type II theory expectation that giant planet migration is driven by viscosity is consistent with our simulation by comparing simulations with the same viscosity and different disc masses (or vice versa). We find a good agreement with the theory, since when the discs are characterized by the same viscosity, the migration properties are the same

The Stellar-Disk Electric (Short) Circuit: Observational Predictions for a YSO Jet Flow

We discuss the star-disk electric circuit for a young stellar object (YSO) and calculate the expected torques on the star and the disk. We obtain the same disk magnetic field and star-disk torques as given by standard magnetohydrodynamic (MHD) analysis. We show how a short circuit in the star-disk electric circuit may produce a magnetically-driven jet flow from the inner edge of a disk surrounding a young star. An unsteady bipolar jet flow is produced that flows perpendicular to the disk plane. Jet speeds of order hundreds of kilometres per second are possible, while the outflow mass loss rate is proportional to the mass accretion rate and is a function of the disk inner radius relative to the disk co-rotation radius.Comment: 6 pages, 8 figures, Accepted for publication in Astrophysics & Space Scienc

Temperature and ac Effects on Charge Transport in Metallic Arrays of Dots

We investigate the effects of finite temperature, dc pulse, and ac drives on the charge transport in metallic arrays using numerical simulations. For finite temperatures there is a finite conduction threshold which decreases linearly with temperature. Additionally we find a quadratic scaling of the current-voltage curves which is independent of temperature for finite thresholds. These results are in excellent agreement with recent experiments on 2D metallic dot arrays. We have also investigated the effects of an ac drive as well as a suddenly applied dc drive. With an ac drive the conduction threshold decreases for fixed frequency and increasing amplitude and saturates for fixed amplitude and increasing frequency. For sudden applied dc drives below threshold we observe a long time power law conduction decay.Comment: 6 pages, 7 postscript figure

The deep water fisheries of the Rockall trough: some insights gleaned from Irish survey data

This article was originally published by ICES on their website http://www.ices.dk/The Fisheries Research Centre (FRC) has conducted trawl and longline surveys in the Rockall Trough since 1993, fishing a total of 223 stations over the depth range 201 to 4,945m. Trawls produced greater species diversity and higher discard rates than longlines, which selected larger squalifurm sharks. In 1997, limited selectivity work, based on ten comparative tows, showed that the size range of roundnose grenadier (Coryphaenoides rupestris) caught using a commercial trawl (llOmm), with and without a small mesh end liner (30mm), were similar. This indicates that mesh size, because of poor selectivity and perceived low survival rates of escapees, may not be a useful management tool in the regulation of the trawl fishery

Lesbian and bisexual women's experiences of sexuality-based discrimination and their appearance concerns

Lesbian and bisexual women frequently experience sexuality-based discrimination, which is often based on others' judgements about their appearance. This short article aims to explore whether there is a relationship between lesbian and bisexual women's experiences of sexuality-based discrimination and their satisfaction with the way that they look. Findings from an online survey suggest that discrimination is negatively related to appearance satisfaction for lesbian women, but not for bisexual women. It is argued that this difference exists because lesbian appearance norms are more recognisable and distinctive than bisexual women's appearance norms

Comparison of the effects of exploitation on theoretical long-lived fish species with different life-history strategies and the implications for management

This article was originally published by ICES on their website http://www.ices.dk/.A stage-based simulation model is used to investigate the effect of exploitation on theoretical populations representing long-lived elasmobranch and teleost species with different life-history strategies. A comparison is made between the effect of exploitation on the elasmobranch ‘k-strategists’ and other teleost species that are ‘r-strategists’. We demonstrate the effects of stage-based exploitation on a typical long-lived elasmobranch population and discuss the implications of this when designing a management plan to ensure survival of the stock