The regulation of genes of unknown function implicated in nitrosative stress tolerance in Escherichia coli K-12

This study was designed to determine the regulatory network that controls expression from two $Escherichia$ $coli$ K-12 promoters, $pyeaR$ and $pogt$, during anaerobic growth. These promoters were identified from transcriptomic studies as being positively regulated by NarL independently of FNR, the master regulator of anaerobic respiration. Biochemical and genetic analyses presented in this study confirmed that expression from both the $yeaR$ and $ogt$ promoters is dependent upon NarL, which binds to a single site in the $yeaR$ promoter and two sites in the $ogt$ promoter. The nucleoid-associated protein, Fis, repressed transcription from both promoters, especially in rich medium, by binding to sites that overlap the NarL site, excluding the essential activator. Both promoters were more active in the absence of functional FNR. However, mutational analysis revealed that FNR does not bind to the $yeaR$ promoter region, so this effect is indirect. How the absence of functional FNR might affect NarL-dependent nitrite signalling was investigated. The Ogt protein is known function as an O$^6$-alkyguanine methyltransferase. However, the functions of the gene products of $yeaR-yoaG$ and another operon implicated in nitrosative stress management, $hcp-hcr$, were unknown. Strains carrying a chromosomal $yeaR-yoaG$ deletion were not more sensitive to nitric oxide or hydroxylamine compared with the parental strain, suggesting that the products of this operon are not essential for dealing with these toxic nitrogen species. Conversely, a strain deleted in $hcp-hcr$ was shown to be slightly more sensitive to both nitric oxide and hydroxylamine, implicating Hcp and Hcr in nitrosative stress management.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

PERCEPTIONS OF UNDERGRADUATE DIPLOMA TEACHERS CONCERNING THE USEFULNESS OF THE COURSES OFFERED FOR TRAINING SECONDARY AGRICULTURAL EDUCATION TEACHERS AT THE BOTSWANA COLLEGE OF AGRICULTURE

Abstract The study was a descriptive survey, designed to determine the graduates &apos

Two-dimensional plasma expansion in a magnetic nozzle: Separation due to electron inertia

A previous axisymmetric model of the supersonic expansion of a collisionless, hot plasma in a divergent magnetic nozzle is extended here in order to include electron-inertia effects. Up to dominant order on all components of the electron velocity, electron momentum equations still reduce to three conservation laws. Electron inertia leads to outward electron separation from the magnetic streamtubes. The progressive plasma filling of the adjacent vacuum region is consistent with electron-inertia being part of finite electron Larmor radius effects, which increase downstream and eventually demagnetize the plasma. Current ambipolarity is not fulfilled and ion separation can be either outwards or inwards of magnetic streamtubes, depending on their magnetization. Electron separation penalizes slightly the plume efficiency and is larger for plasma beams injected with large pressure gradients. An alternative nonzero electron-inertia model [E. Hooper, J. Propul. Power 9, 757 (1993)] based on cold plasmas and current ambipolarity, which predicts inwards electron separation, is discussed critically. A possible competition of the gyroviscous force with electron-inertia effects is commented briefly

Economic evaluation of short treatment for multidrugresistant tuberculosis, Ethiopia and South Africa : the STREAM trial

OBJECTIVE STREAM was a phase-III non-inferiority randomised controlled trial (RCT) to evaluate a shortened regimen for multi-drug resistant tuberculosis (MDR-TB), and included the first-ever within-trial economic evaluation of such regimens, reported here. METHODS We compared the costs of ‘Long’ (20-22 months) and ‘Short’ (9-11 months) regimens in Ethiopia and South Africa. Cost data were collected from trial participants, and health system costs estimated using ‘bottom-up’ and ‘top-down’ costing approaches. A cost-effectiveness analysis was conducted with the trial primary outcome as the measure of effectiveness, including a probabilistic sensitivity analysis (PSA) to illustrate decision uncertainty. FINDINGS The Short-regimen reduced healthcare costs per case by 21% in South Africa (US$8,341 Long vs US$6,619 Short) and 25% in Ethiopia (US$6,097 Long vs US$4,552 Short). The largest component of this saving was medication in South Africa (67%) and social support in Ethiopia (35%). In Ethiopia, participants on the Short-regimen reported reductions in dietary supplementation expenditure (US$225 per case (95$13 (95%CI 11-14), South Africa US$64 (95$19,000 (Ethiopia) or <US$14,500 (South Africa). CONCLUSION The Short-regimen provided substantial health system cost savings and reduced financial burden on participants. Shorter regimens are likely to be cost-effective in most settings, and an effective strategy to support the WHO goal of eliminating catastrophic costs in T

Teaching introductory undergraduate Physics using commercial video games

Commercial video games are increasingly using sophisticated physics simulations to create a more immersive experience for players. This also makes them a powerful tool for engaging students in learning physics. We provide some examples to show how commercial off-the-shelf games can be used to teach specific topics in introductory undergraduate physics. The examples are selected from a course taught predominantly through the medium of commercial video games.Comment: Accepted to Physics Education, Fig1 does not render properly in this versio

Naturally Rehearsing Passwords

We introduce quantitative usability and security models to guide the design of password management schemes --- systematic strategies to help users create and remember multiple passwords. In the same way that security proofs in cryptography are based on complexity-theoretic assumptions (e.g., hardness of factoring and discrete logarithm), we quantify usability by introducing usability assumptions. In particular, password management relies on assumptions about human memory, e.g., that a user who follows a particular rehearsal schedule will successfully maintain the corresponding memory. These assumptions are informed by research in cognitive science and validated through empirical studies. Given rehearsal requirements and a user's visitation schedule for each account, we use the total number of extra rehearsals that the user would have to do to remember all of his passwords as a measure of the usability of the password scheme. Our usability model leads us to a key observation: password reuse benefits users not only by reducing the number of passwords that the user has to memorize, but more importantly by increasing the natural rehearsal rate for each password. We also present a security model which accounts for the complexity of password management with multiple accounts and associated threats, including online, offline, and plaintext password leak attacks. Observing that current password management schemes are either insecure or unusable, we present Shared Cues--- a new scheme in which the underlying secret is strategically shared across accounts to ensure that most rehearsal requirements are satisfied naturally while simultaneously providing strong security. The construction uses the Chinese Remainder Theorem to achieve these competing goals

An adaptive technique for content-based image retrieval

We discuss an adaptive approach towards Content-Based Image Retrieval. It is based on the Ostensive Model of developing information needs—a special kind of relevance feedback model that learns from implicit user feedback and adds a temporal notion to relevance. The ostensive approach supports content-assisted browsing through visualising the interaction by adding user-selected images to a browsing path, which ends with a set of system recommendations. The suggestions are based on an adaptive query learning scheme, in which the query is learnt from previously selected images. Our approach is an adaptation of the original Ostensive Model based on textual features only, to include content-based features to characterise images. In the proposed scheme textual and colour features are combined using the Dempster-Shafer theory of evidence combination. Results from a user-centred, work-task oriented evaluation show that the ostensive interface is preferred over a traditional interface with manual query facilities. This is due to its ability to adapt to the user's need, its intuitiveness and the fluid way in which it operates. Studying and comparing the nature of the underlying information need, it emerges that our approach elicits changes in the user's need based on the interaction, and is successful in adapting the retrieval to match the changes. In addition, a preliminary study of the retrieval performance of the ostensive relevance feedback scheme shows that it can outperform a standard relevance feedback strategy in terms of image recall in category search

Turbulence and jet-driven zonal flows: Secondary circulation in rotating fluids due to asymmetric forcing

We report on experiments and modeling on a rotating confined liquid that is forced by circumferential jets coaxial with the rotation axis, wherein system-scale secondary flows are observed to emerge. The jets are evenly divided in number between inlets and outlets and have zero net mass transport. For low forcing strengths the sign of this flow depends on the sign of a sloped end cap, which simulates a planetary β plane. For increased forcing strengths the secondary flow direction is insensitive to the slope sign, and instead appears to be dominated by an asymmetry in the forcing mechanism, namely, the difference in radial divergence between the inlet and outlet jet profiles. This asymmetry yields a net radial velocity that is affected by the Coriolis force, inducing secondary zonal flow

The gaming involvement and informal learning framework

Aim. This article presents a model of how gaming involvement and informal learning come together in practice. Method. Based on a series of interviews, case studies, and a wider survey, the Gaming Involvement and Informal Learning (GIIL) framework indicates how involvement with a variety of gaming practices can lead to a range of different learning experiences. Results. The framework is able to account for both how and what people learn from gaming while also highlighting the influence of player identity. Further, the iterative relationship between identity, involvement, and learning is emphasized: The more strongly someone identifies themselves as a gamer, the greater their micro- and macro-level involvement and the more likely they are to learn from their gaming experiences. Conclusion. The implications of the findings are discussed with regard to informal and formal learning