Nucleotide sequence of the aliphatic amidase regulator gene (amiR) of Pseudomonas aeruginosa

AbstractThe nucleotide sequence of a 1001 bp ClaI/XhoI DNA fragment encoding the amidase regulator gene (amiR) from Pseudomonas aeruginosa has been determined. The sequence derives from strain PAC433, a constitutive high expressing amidase mutant, and contains two overlapping open reading frames. Analysis of the sequence has identified one of the reading frames as amiR. The gene encodes a 196 amino acid polypeptide which shows a strong bias towards codons with G or C in the third position. The amiR gene shows no sequence homology with other bacterial regulator proteins

Evaluation of a self-guided transport vehicle for remote transportation of transuranic and other hazardous waste

Between 1952 and 1970, over two million cubic ft of transuranic mixed waste was buried in shallow pits and trenches in the Subsurface Disposal Area at the Idaho National Engineering Laboratory`s Radioactive Waste Management Complex. Commingled with this two million cubic ft of waste is up to 10 million cubic ft of fill soil. The pits and trenches were constructed similarly to municipal landfills with both stacked and random dump waste forms such as barrels and boxes. The main contaminants are micron-sized particles of plutonium and americium oxides, chlorides, and hydroxides. Retrieval, treatment, and disposal is one of the options being considered for the waste. This report describes the results of a field demonstration conducted to evaluate a technology for transporting exhumed transuranic wastes at the Idaho National Engineering and Environmental Laboratory (INEEL) and at other hazardous or radioactive waste sites through the U.S. Department of Energy complex. The full-scale demonstration, conducted at the INEEL Robotics Center in the summer of 1995, evaluated equipment performance and techniques for remote transport of exhumed buried waste. The technology consisted of a Self-Guided Transport Vehicle designed to remotely convey retrieved waste from the retrieval digface and transport it to a receiving/processing area with minimal human intervention. Data were gathered and analyzed to evaluate performance parameters such as precision and accuracy of navigation and transportation rates

Hysteresis in the Mott Transition between Plasma and Insulating Gas

We show that hysteresis can occur in the transition between a neutral plasma and the insulating gas consisting of neutral pairs bound by Coulomb attraction. Since the transition depends sensitively on the screening length in the plasma, regions of bistability occur in density--temperature phase space. We present numerical results which indicate where these regions occur for systems such as spin-polarized hydrogen, positronium gas, and excitons in a semiconductor.Comment: 9 pages (Latex/RevTex), 6 postscript figures which are in compressed and uuencoded file, prepared using the utility "uufiles" and separately submitted. They should be automatically included with the text when it is downloaded. Figures also available in hard copy from the authors ([email protected]; [email protected]); paper submitted to Phys. Rev.

Orbit spaces of free involutions on the product of two projective spaces

Let $X$ be a finitistic space having the mod 2 cohomology algebra of the product of two projective spaces. We study free involutions on $X$ and determine the possible mod 2 cohomology algebra of orbit space of any free involution, using the Leray spectral sequence associated to the Borel fibration $X \hookrightarrow X_{\mathbb{Z}_2} \longrightarrow B_{\mathbb{Z}_2}$. We also give an application of our result to show that if $X$ has the mod 2 cohomology algebra of the product of two real projective spaces (respectively complex projective spaces), then there does not exist any $\mathbb{Z}_2$-equivariant map from $\mathbb{S}^k \to X$ for $k \geq 2$ (respectively $k \geq 3$), where $\mathbb{S}^k$ is equipped with the antipodal involution.Comment: 14 pages, to appear in Results in Mathematic

ESRC/SFC Scoping Study into Quantitative Methods Capacity Building in Scotland

Final report for the following ITT: "The ESRC and the Funding Councils recognise that there is a growing body of evidence that highlights the need to develop quantitative skills amongst the social science population. In particular, this needs to take place during the earliest stages of career development, to ensure that there is a sufficient supply of quantitatively trained social science researchers entering the academic, public and voluntary sectors. To meet this need the ESRC is working with the Funding Councils to develop an integrated strategy which aims to improve the supply of quantitatively trained social scientists. To inform the development of this strategy the ESRC and SFC wish to commission a scoping study to identify the particular quantitative capacity building needs in Scotland. Tenders are currently being sought from individuals or teams interested in undertaking the study."There has been widespread concern about a UK-wide deficit in quantitative skills amongst social scientists since the 1960s, especially in relation to the rapid pace of change within the industry and the lack of adequately trained computing scientists. • Despite experiencing a relatively industrious period in the late 1960s and 1970s, Scotland’s provision of quantitative methods within social science is now extremely patchy and as bad, if not worse, than that in the rest of the UK. • Scotland has a similar demographic profile to the rest of the UK in terms of social sciences; but Scottish Higher Educational Institutions (HEI) are under-represented in other respects (e.g. representation at the Essex Summer School). • In Scotland, disciplines such as Economics, Accountancy, Business Studies and Psychology, which already have a quantitative reputation, have better resources for assessment, training and improvement of mathematical, statistical and general quantitative skills of their graduate students than other disciplines. • Undergraduate courses are mainly focused around generic rather than specialised quantitative methods teaching, although there is more specialist provision at postgraduate level, but this again is centred around the ‘usual’ disciplines. • Most teaching and research involves fairly general methods and statistical techniques, although there are a few people experienced in more ‘advanced’ methods. There is a widespread need for continuing professional development training in Scotland across all sectors, mainly at the more advanced level. There are a few, small-scale centres of expertise in Scotland, but most quantitative researchers are spread across a range of institutions and disciplines. There are no large-scale networks or centres, and this is viewed as key to building capacity. • There are three general barriers to developing quantitative methods capacity in Scotland. In order of importance, these are ‘antipathy’ (reluctance by students, staff and HEI colleagues to engage with quantitative methods); ‘accessibility’ (availability of/time for training); and ‘enabling’ (lack of funding, collaborative opportunities and data access). • Scotland is a relatively ‘data rich’ country, with a proliferation in recent years of Government funded surveys. However, self-reported usage of Scottish datasets is low and there is a general failure to make the most of available data in Scotland. • Computing and library support services are not well tuned to the needs of quantitative capacity building. Basic levels of support, such as finding resources on the web and offering assistance to access these, are provided; however, students get little extensive user support or instruction in use of datasets and staff do not get support for statistical consultancy or teaching data analysis skills in computer labs. Greater communication and collaboration between support and research staff is needed. • There is support in Scotland for a long-term, strategic approach to building capacity and there are good reasons for developing a specifically Scottish strategy. • A national strategy must include a variety of activities at a range of different levels, such as: boosting numeracy in secondary schools; better engagement with both undergraduate and graduate students; strengthening links between academia and potential employers; more training through continuing professional development; and mentoring for early career researchers. Boosting capacity will require cultural and structural changes within many institutions and disciplinary areas. Universities and funding bodies must provide strategic investment in order to build a strong infrastructure capable of supporting a critical mass of quantitative trained researchers in Scotland. The recommendations from this study include creating a Scottish Centre for Social Science Research Methods and establishing a Scottish Summer School

Role of multiple subband renormalization in the electronic transport of correlated oxide superlattices

Metallic behavior of band-insulator/ Mott-insulator interfaces was observed in artificial perovskite superlattices such as in nanoscale SrTiO3/LaTiO3 multilayers. Applying a semiclassical perspective to the parallel electronic transport we identify two major ingredients relevant for such systems: i) the quantum confinement of the conduction electrons (superlattice modulation) leads to a complex, quasi-two dimensional subband structure with both hole- and electron-like Fermi surfaces. ii) strong electron-electron interaction requires a substantial renormalization of the quasi-particle dispersion. We characterize this renormalization by two sets of parameters, namely, the quasi-particle weight and the induced particle-hole asymmetry of each partially filled subband. In our study, the quasi-particle dispersion is calculated self-consistently as function of microscopic parameters using the slave-boson mean-field approximation introduced by Kotliar and Ruckenstein. We discuss the consequences of strong local correlations on the normal-state free-carrier response in the optical conductivity and on the thermoelectric effects.Comment: 11 pages, 4 figure

Nonadiabatic approach to dimerization gap and optical absorption coefficient of the Su-Schrieffer-Heeger model

An analytical nonadiabatic approach has been developed to study the dimerization gap and the optical absorption coefficient of the Su-Schrieffer-Heeger model where the electrons interact with dispersive quantum phonons. By investigating quantitatively the effects of quantum phonon fluctuations on the gap order and the optical responses in this system, we show that the dimerization gap is much more reduced by the quantum lattice fluctuations than the optical absorption coefficient is. The calculated optical absorption coefficient and the density of states do not have the inverse-square-root singularity, but have a peak above the gap edge and there exist a significant tail below the peak. The peak of optical absorption spectrum is not directly corresponding to the dimerized gap. Our results of the optical absorption coefficient agree well with those of the experiments in both the shape and the peak position of the optical absorption spectrum.Comment: 14 pages, 7 figures. to be published in PR

Remote detection of past habitability at Mars-analogue hydrothermal alteration terrains using an ExoMars Panoramic Camera emulator

JKH is funded by a Birkbeck University of London Graduate Teaching Assistantship. CRC is funded by a Royal Society of Edinburgh Personal Research Fellowship co-funded by Marie Curie Actions. The Aberystwyth research leading to these results has been funded by the UK Space Agency, ExoMars Panoramic Camera (PanCam) Grant Nos. ST/G003114/1, ST/I002758/1, STL001454/1, and the UK Space Agency CREST2 PanCam-2020 research Grant No. ST/L00500X/1. Additional Aberystwyth funding has come from The European Community’s Seventh Framework Programme (FP7/2007-2013), Grant Agreement Nos. 21881 PRoVisG, 241523 PRoViScout, and Grant Agreement No. 312377 PRoViDE. PMG is funded by a UK Space Agency Aurora Fellowship (grants ST/J005215/1 and ST/L00254X/1).A major scientific goal of the European Space Agency’s ExoMars 2018 rover is to identify evidence of life within the martian rock record. Key to this objective is the remote detection of geological substrates that are indicative of past habitable environments, which will rely on visual (stereo wide-angle, and high resolution images) and multispectral (440–1000 nm) data produced by the Panoramic Camera (PanCam) instrument. We deployed a PanCam emulator at four hydrothermal sites in the Námafjall volcanic region of Iceland, a Mars-analogue hydrothermal alteration terrain. At these sites, sustained acidic–neutral aqueous interaction with basaltic substrates (crystalline and sedimentary) has produced phyllosilicate, ferric oxide, and sulfate-rich alteration soils, and secondary mineral deposits including gypsum veins and zeolite amygdales. PanCam emulator datasets from these sites were complemented with (i) NERC Airborne Research and Survey Facility aerial hyperspectral images of the study area; (ii) in situ reflectance spectroscopy (400–1000 nm) of PanCam spectral targets; (iii) laboratory X-ray Diffraction, and (iv) laboratory VNIR (350–2500 nm) spectroscopy of target samples to identify their bulk mineralogy and spectral properties. The mineral assemblages and palaeoenvironments characterised here are analogous to neutral–acidic alteration terrains on Mars, such as at Mawrth Vallis and Gusev Crater. Combined multispectral and High Resolution Camera datasets were found to be effective at capturing features of astrobiological importance, such as secondary gypsum and zeolite mineral veins, and phyllosilicate-rich substrates. Our field observations with the PanCam emulator also uncovered stray light problems which are most significant in the NIR wavelengths and investigations are being undertaken to ensure that the flight model PanCam cameras are not similarly affected.Publisher PDFPeer reviewe

Theory of inelastic lifetimes of low-energy electrons in metals

Electron dynamics in the bulk and at the surface of solid materials are well known to play a key role in a variety of physical and chemical phenomena. In this article we describe the main aspects of the interaction of low-energy electrons with solids, and report extensive calculations of inelastic lifetimes of both low-energy electrons in bulk materials and image-potential states at metal surfaces. New calculations of inelastic lifetimes in a homogeneous electron gas are presented, by using various well-known representations of the electronic response of the medium. Band-structure calculations, which have been recently carried out by the authors and collaborators, are reviewed, and future work is addressed.Comment: 28 pages, 18 figures, to appear in Chem. Phy

Stepped fans and facies-equivalent phyllosilicates in Coprates Catena, Mars

Stepped fan deposits and phyllosilicate mineralogies are relatively common features on Mars but have not previously been found in association with each other. Both of these features are widely accepted to be the result of aqueous processes, but the assumed role and nature of any water varies. In this study we have investigated two stepped fan deposits in Coprates Catena, Mars, which have a genetic link to light-toned material that is rich in Fe–Mg phyllosilicate phases. Although of different sizes and in separate, but adjacent, trough-like depressions, we identify similar features at these stepped fans and phyllosilicates that are indicative of similar formation conditions and processes. Our observations of the overall geomorphology, mineralogy and chronology of these features are consistent with a two stage formation process, whereby deposition in the troughs first occurs into shallow standing water or playas, forming fluvial or alluvial fans that terminate in delta deposits and interfinger with interpreted lacustrine facies, with a later period of deposition under sub-aerial conditions, forming alluvial fan deposits. We suggest that the distinctive stepped appearance of these fans is the result of aeolian erosion, and is not a primary depositional feature. This combined formation framework for stepped fans and phyllosilicates can also explain other similar features on Mars, and adds to the growing evidence of fluvial activity in the equatorial region of Mars during the Hesperian and Amazonian