The omega equation and potential vorticity

Two fundamental perspectives on the dynamics of midlatitude weather systems are provided by potential vorticity (PV) and the omega equation. The aim of this paper is to investigate the link between the two perspectives, which has so far received very little attention in the meteorological literature. It also aims to give a quantitative basis for discussion of quasi-geostrophic vertical motion in terms of components associated with system movement, maintaining a constant thermal structure, and with the development of that structure. The former links with the isentropic relative-flow analysis technique. Viewed in a moving frame of reference, the measured development of a system depends on the velocity of that frame of reference. The requirement that the development should be a minimum provides a quantitative method for determining the optimum system velocity. The component of vertical velocity associated with development is shown to satisfy an omega equation with forcing determined from the relative advection of interior PV and boundary temperature. The analysis carries through in the presence of diabatic heating provided the omega equation forcing is based on the interior PV and boundary thermal tendencies, including the heating effect. The analysis is shown to be possible also at the level of the semi-geostrophic approximation. The analysis technique is applied to a number of idealized problems that can be considered to be building blocks for midlatitude synoptic-scale dynamics. They focus on the influences of interior PV, boundary temperature, an interior boundary, baroclinic instability associated with two boundaries, and also diabatic heating. In each case, insights yielded by the new perspective are sought into the dynamical behaviour, especially that related to vertical motion. Copyright © 2003 Royal Meteorological Society

The United Nations and the African Union: Assessing a partnership for peace in Darfur

In Resolution 1556, the Security Council, with the conflict in Darfur clearly in mind, determined that the ‘situation in Sudan constitutes a threat to international peace and security and to stability in the region’. This article focuses on the response by the United Nations, in particular the Security Council, and the African Union to the Darfur conflict. It begins by exploring the role of peacekeeping operations and regional arrangements or agencies in the overarching architecture of international peace and security. Having laid this frame of reference, it then looks at the modalities of peacekeeping in Darfur. These operations began with the African Union acting in isolation but have transitioned to an increasingly important role being played by the United Nations and a hybrid peacekeeping presence. Finally, this article asks whether, assuming that a legally dispositive conclusion can be drawn that genocide has taken place in Darfur since the outbreak of hostilities there in 2003, there exists a legal justification, or even obligation, for non-compliance by states with the sanctions regime established by Security Council Resolutions 1556 and 1591. This regime of sanctions has played an important part in the Security Council's approach to Darfur but has been, unfortunately, left largely unexamined from the standpoint of international legality.

Neocolonialism and international law, with specific reference to customary counterterrorism obligations and the principle of self-defence

Has international law ever, and, if it has not, can it ever, truly freed itself from the strictures of neocolonialism and the drive by a privileged elite to dominate the world scene? This article begins by inquiring into the nature of neocolonialism and, in so doing, pays particular attention to the writings of former Ghanaian President Kwame Nkrumah. It then proceeds to determine how neocolonialist designs surface in international law today by briefly looking at two aspects of international law in particular, namely customary international law, with specific reference to the counterterrorism context, and the principle of self-defence. In the final analysis, this article argues for a necessary and eternal scepticism of international law and the agendas of its privileged gatekeepers. Like classic State power, it opens itself to, and often operates as, neocolonial overreach, and to quote Nkrumah, “[t]he cajolement, the wheedlings, the seductions and the Trojan horses of neo-colonialism must be stoutly resisted, for neo-colonialism is a latter-day harpy, a monster which entices its victims with sweet music.”

Cost-benefit analysis model of badger (Meles meles) culling to reduce cattle herd tuberculosis breakdowns in Britain, with particular reference to badger perturbation

Bovine tuberculosis (TB)is an important economic disease. Badgers (Meles meles) are the wildlife source implicated in many cattle outbreaks of TB in Britain, and extensive badger control is a controversial option to reduce the disease. A badger and cattle population model was developed, simulating TB epidemiology; badger ecology, including postcull social perturbation; and TB-related farm management. An economic cost-benefit module was integrated into the model to assess whether badger control offers economic benefits. Model results strongly indicate that although, if perturbation were restricted, extensive badger culling could reduce rates in cattle, overall an economic loss would be more likely than a benefit. Perturbation of the badger population was a key factor determining success or failure of control. The model highlighted some important knowledge gaps regarding both the spatial and temporal characteristics of perturbation that warrant further research.

Allelic size standards and reference genotypes to unify international cocoa (Theobroma cacao L.) microsatellite data

Standardisation of microsatellite allele profiles between laboratories is of fundamental importance to the transferability of genetic fingerprint data and the identification of clonal individuals held at multiple sites. Here we describe two methods of standardisation applied to the microsatellite fingerprinting of 429 Theobroma cacao L. trees representing 345 accessions held in the worlds largest Cocoa Intermediate Quarantine facility: the use of a partial allelic ladder through the production of 46 cloned and sequenced allelic standards (AJ748464 to AJ48509), and the use of standard genotypes selected to display a diverse allelic range. Until now a lack of accurate and transferable identification information has impeded efforts to genetically improve the cocoa crop. To address this need, a global initiative to fingerprint all international cocoa germplasm collections using a common set of 15 microsatellite markers is in progress. Data reported here have been deposited with the International Cocoa Germplasm Database and form the basis of a searchable resource for clonal identification. To our knowledge, this is the first quarantine facility to be completely genotyped using microsatellite markers for the purpose of quality control and clonal identification. Implications of the results for retrospective tracking of labelling errors are briefly explored.

Expression of target and reference genes in Daphnia magna exposed to ibuprofen

Background: Transcriptomic techniques are now being applied in ecotoxicology and toxicology to measure the impact of stressors and develop understanding of mechanisms of toxicity. Microarray technology in particular offers the potential to measure thousands of gene responses simultaneously. However, it is important that microarrays responses should be validated, at least initially, using real-time quantitative polymerase chain reaction (QPCR). The accurate measurement of target gene expression requires normalisation to an invariant internal control e. g., total RNA or reference genes. Reference genes are preferable, as they control for variation inherent in the cDNA synthesis and PCR. However, reference gene expression can vary between tissues and experimental conditions, which makes it crucial to validate them prior to application. Results: We evaluated 10 candidate reference genes for QPCR in Daphnia magna following a 24 h exposure to the non-steroidal anti-inflammatory drug (NSAID) ibuprofen (IB) at 0, 20, 40 and 80 mg IB l(-1). Six of the 10 candidates appeared suitable for use as reference genes. As a robust approach, we used a combination normalisation factor (NF), calculated using the geNorm application, based on the geometric mean of three selected reference genes: glyceraldehyde-3-phosphate dehydrogenase, ubiquitin conjugating enzyme and actin. The effects of normalisation are illustrated using as target gene leukotriene B4 12-hydroxydehydrogenase (Ltb4dh), which was upregulated following 24 h exposure to 63-81 mg IB l(-1). Conclusions: As anticipated, use of the NF clarified the response of Ltb4dh in daphnids exposed to sublethal levels of ibuprofen. Our findings emphasise the importance in toxicogenomics of finding and applying invariant internal QPCR control(s) relevant to the study conditions.

The "freedom to frame questions... worth asking" or three stories and three (other) fragments of research

In our state of centralised control of the curriculum and high-stakes testing an examination subject's assessment objectives have become high profile. Some of the anomalous effects of this profile are shown in the teaching, question-setting, and marking of English literature. Glimpses of earlier times are revealed, all three secondary school key stages are considered, examination performances are discussed, and the views of beginning teachers about teaching to the test are sought.

Molecular characterisation of the gut microflora of healthy and inflammatory bowel disease cats using fluorescence in situ hybridisation with special reference to Desulfovibrio spp

Inflammatory bowel disease (IBD) is a common cause of chronic large bowel diarrhoea in cats. Although the aetiology of IBD is unknown, an immune-mediated response to a luminal antigen is thought to be involved. As knowledge concerning the colonic microflora of cats is limited and requires further investigation, the purpose of this study was to determine the presence of specific bacterial groups in normal and IBD cats, and the potential role they play in the health of the host. Total bacterial populations, Bacteroides spp., Bifidobacterium spp., Clostridium histolyticum subgp., Lactobacillus-Enterococcus subgp. and Desulfovibrio spp. were enumerated in 34 healthy cats and 11 IBD cats using fluorescence in situ hybridisation. The study is one of the first to show the presence of Desulfovibrio in cats. Total bacteria, Bifidobacterium spp. and Bacteroides spp. counts were all significantly higher in healthy cats when compared with IBD cats, whereas Desulfovibrio spp. (producers of toxic sulphides) numbers were found to be significantly higher in colitic cats. The information obtained from this study suggests that modulation of bacterial flora by increasing bifidobacteria and decreasing Desulfovibrio spp. may be beneficial to cats with IBD. Dietary intervention may be an important aspect of their treatment.

Disparity with respect to a local reference plane as a dominant cue for stereoscopic depth relief

Earlier studies showed that the disparity with respect to other visible points could not explain stereoacuity performance, nor could various spatial derivatives of disparity [Glennerster, A., McKee, S. P., & Birch, M. D. (2002). Evidence of surface-based processing of binocular disparity. Current Biology, 12:825-828; Petrov, Y., & Glennerster, A. (2004). The role of the local reference in stereoscopic detection of depth relief. Vision Research, 44:367-376.] Two possible cues remain: (i) local changes in disparity gradient or (ii) disparity with respect to an interpolated line drawn through the reference points. Here, we aimed to distinguish between these two cues. Subjects judged.. in a two AFC paradigm, whether a target dot was in front of a plane defined by three reference dots or, in other experiments, in front of a line defined by two reference dots. We tested different slants of the reference line or plane and different locations of the target relative to the reference points. For slanted reference lines or plane, stereoacuity changed little as the target position was varied. For judgments relative to a frontoparallel reference line, stereoacuity did vary with target position, but less than would be predicted by disparity gradient change. This provides evidence that disparity with respect to the reference plane is an important cue. We discuss the potential advantages of this measure in generating a representation of surface relief that is invariant to viewpoint transformations. (c) 2006 Elsevier Ltd. All rights reserved.

Freeze-frame: a new infant inhibition task and its relation to frontal cortex tasks during infancy and early childhood

The current study investigated a new, easily administered, visual inhibition task for infants termed the Freeze-Frame task. In the new task, 9-month-olds were encouraged to inhibit looks to peripheral distractors. This was done by briefly freezing a central animated stimulus when infants looked to the distractors. Half of the trials presented an engaging central stimulus, and the other half presented a repetitive central stimulus. Three measures of inhibitory function were derived from the task and compared with performance on a set of frontal cortex tasks administered at 9 and 24 months of age. As expected, infants' ability to learn to selectively inhibit looks to the distractors at 9 months predicted performance at 24 months. However, performance differences in the two Freeze-Frame trial types early in the experiment also turned out to be an important predictor. The results are discussed in terms of the validity of the Freeze-Frame task as an early measure of different components of inhibitory function. (C) 2007 Elsevier Inc. All rights reserved.