The microbial ecology and colonisation of surfaces in selected hot springs - a molecular-and culture-based approach

Traditionally, culture-based approaches have been used to investigate the microbial ecology of thermal habitats. The emergence of alternate molecular approaches based on DNA sequences has shown that terrestrial thermal environments have a rich diversity of uncultured prokaryotes. To the best of our knowledge these latter approaches have not previously been applied to New Zealand thermal environments and this became the central aim of this study. The major objective of the study was to target the metabolically active members of the hot pool community by applying a suite of molecular and microscopical techniques to those species colonising surfaces incubated in situ in the hot pools. Two neutral pH pools were investigated in some detail; pool KP1 at 75°C and pool AQ1 at 95°C. Surfaces in pool KP1 were colonised by a high diversity of bacteria (archaea were not detected), as evidenced by complex denaturing gradient gel electrophoresis (DGGE) profiles, and many different species were obtained in enrichment culture. Although colonisation rates were greater in pool AQ1, this was entirely due to only two observed morphotypes and was reflected in DGGE profiles that reflected only two dominant archaeal species. A 16S rDNA clone library of the AQ1 pool water and DGGE profiles of both pool water and colonised slides were dominated by rods of the species Pyrobaculum. Slides incubated deep within AQ1 were also colonised by cocci, the closest cultured relative being Aeropyrum pernix, a marine hyperthermophile. Two pure cultures were obtained from pool AQ1, Pyrobaculum sp. (AQ1.S2) and a novel crenarchaeaotal coccus, (AQ1.S1T). Isolations of the latter organism were also obtained from two other pools in New Zealand. These were obtained as obligate co-cultures with Pyrobaculum rods and could not be isolated into pure culture. A full description of this novel genus of organisms has been accepted for publication in the International Journal of Systematic and Evolutionary Microbiology, with the isolate from pool AQ1 named as the type strain lgnisphaera aggregans AQl .S1T. The techniques used to follow colonisation were then applied to a survey of high-temperature pools of New Zealand (>80°C, pH 5.5-9.7), White Island (72-94°C, pH 1.5-3.8) and Yellowstone National Park (75-92.5°C, pH 5.0-8.0). For New Zealand, bacteria were detected by DGGE on colonised slides in pools below 88°C, and archaea, only in pools above 83°C. Bacterial colonisers with dominant signatures included those of Thermodesulfobacteria and Aquificales species, though interestingly, isolations of these organisms were not obtained. The archaeal colonisers were pH dependent: pools with a pH of 6.0-7.0 had a dominant Thermofilum signature; pools above pH 7.0 had both a Pyrobaculum sp. and a relative of the Desulfurococcales; and the acidic pools (including White Island) were dominated by Sulfolobus sp. Pool water DGGE profiles of the New Zealand pools differed from slide colonisation profiles in some respects, e.g. Thermococcus sp. were only detected in pool water. In contrast to the New Zealand results, the Yellowstone National Park slides were dominated by bacteria, with bacterial signatures detected in high-temperature pools (87-92.5°C); representative DGGE bands were sequenced and found to be related to the Aquificales. Nanoarchaeal l 6S rDNA PCR amplicons were also obtained from pool water for most of the New Zealand pools (closest relative of AQ1 amplicon being a nanoarchaeal clone from the Uzon Caldera), including the Pyrobaculum sp. AQl .S2 culture. Attempts were also made to isolate marine nanoarchaea from nascent hydrothermal vents situated on the East Pacific Rise; however, these were unsuccessful

Rare earth oxycarbonates as a material class for chemoresistive CO2 gas sensors

AbstractIn this work we compare the CO2 gas sensing properties of two new materials synthesized from rare earth hydroxide (La(OH)3,Pr(OH)3) precursors, with the already reported ones for neodymium oxycarbonate, which was synthesized from the corresponding Nd(OH)3 precursor. In-situ XRD measurements show that by following similar thermal treatment, praseodymium hydroxide is transforming to the metal oxide while lanthanum hydroxide forms an oxycarbonate, like in the case of neodymium. The chemoresistive effects we found for the lanthanum oxycarbonate were even higher than the ones recorded for the neodymium oxycarbonate; for the praseodymium metal oxide we could not find any CO2 sensitivity. Accordingly, we think that the condition for CO2 sensing is the formation of the rare earth oxycarbonate

The ground state of binary systems with a periodic modulation of the linear coupling

We consider a quasi-one-dimensional two-component systm, described by a pair of Nonlinear Schr\"{o}dinger/Gross-Pitaevskii Equations (NLSEs/GPEs), which are coupled by the linear mixing, with local strength $\Omega$, and by the nonlinear incoherent interaction. We assume the self-repulsive nonlinearity in both components, and include effects of a harmonic trapping potential. The model may be realized in terms of periodically modulated slab waveguides in nonlinear optics, and in Bose-Einstein condensates too. Depending on the strengths of the linear and nonlinear couplings between the components, the ground states (GSs) in such binary systems may be symmetric or asymmetric. In this work, we introduce a periodic spatial modulation of the linear coupling, making $\Omega$ an odd, or even function of the coordinate. The sign flips of $\Omega (x)$ strongly modify the structure of the GS in the binary system, as the relative sign of its components tends to lock to the local sign of $\Omega$. Using a systematic numerical analysis, and an analytical approximation, we demonstrate that the GS of the trapped system contains one or several kinks (dark solitons) in one component, while the other component does not change its sign. Final results are presented in the form of maps showing the number of kinks in the GS as a function of the system's parameters, with the odd/even modulation function giving rise to the odd/even number of the kinks. The modulation of $\Omega (x)$ also produces a strong effect on the transition between states with nearly equal and strongly unequal amplitudes of the two components.Comment: 8 pages, 3 figure

Elastic behaviour of the carotid artery in intact spontaneously hypertensive rats

Intact spontaneously hypertensive rats (SHR) were studied to assess the effect of prolonged antihypertensive treatment on the elastic behaviour of the external carotid artery. Thirty-week-old SHR received the ACE inhibitor captopril, the ateriolar dilator hydralazine or their vehicle for 6 weeks. These rats were compared to normotensive, vehicle treated WKY rats. The internal diameter of the carotid artery was measured continuously in halothane-anaesthetized rats using an echo-tracking device, and intra-arterial pressure was also monitored continuously, on the controlateral side. Captopril- and hydralazinetreated SHR as well as normotensive controls had similar blood pressure values. No significant shift in the distensibility-pressure curves was observed among vehicle-treated SHR and WKY rats or the SHR which had received captopril or hydralazine. Histological examination of the carotid artery fixed ex vivo with paraformaldehyde showed a significant increase in cross-sectional area in vehicle-treated SHR as compared to their normotensive counterparts. These results therefore suggest that the elastic behaviour of elastic arteries is not necessarily altered by the structural changes developing in response to hypertensio

Cholesterol-lowering properties of Ganoderma lucidum in vitro, ex vivo, and in hamsters and minipigs

INTRODUCTION: There has been renewed interest in mushroom medicinal properties. We studied cholesterol lowering properties of Ganoderma lucidum (Gl), a renowned medicinal species. RESULTS: Organic fractions containing oxygenated lanosterol derivatives inhibited cholesterol synthesis in T9A4 hepatocytes. In hamsters, 5% Gl did not effect LDL; but decreased total cholesterol (TC) 9.8%, and HDL 11.2%. Gl (2.5 and 5%) had effects on several fecal neutral sterols and bile acids. Both Gl doses reduced hepatic microsomal ex-vivo HMG-CoA reductase activity. In minipigs, 2.5 Gl decreased TC, LDL- and HDL cholesterol 20, 27, and 18%, respectively (P < 0.05); increased fecal cholestanol and coprostanol; and decreased cholate. CONCLUSIONS: Overall, Gl has potential to reduce LDL cholesterol in vivo through various mechanisms. Next steps are to: fully characterize bioactive components in lipid soluble/insoluble fractions; evaluate bioactivity of isolated fractions; and examine human cholesterol lowering properties. Innovative new cholesterol-lowering foods and medicines containing Gl are envisioned

Transport regimes of cold gases in a two-dimensional anisotropic disorder

We numerically study the dynamics of cold atoms in a two-dimensional disordered potential. We consider an anisotropic speckle potential and focus on the classical regime, which is relevant to some recent experiments. First, we study the behavior of particles with a fixed energy and identify different transport regimes. For low energy, the particles are classically localized due to the absence of a percolating cluster. For high energy, the particles undergo normal diffusion and we show that the diffusion constants scale algebraically with the particle energy, with an anisotropy factor which significantly differs from that of the disordered potential. For intermediate energy, we find a transient sub-diffusive regime, which is relevant to the time scale of typical experiments. Second, we study the behavior of a cold-atomic gas with an arbitrary energy distribution, using the above results as a groundwork. We show that the density profile of the atomic cloud in the diffusion regime is strongly peaked and, in particular, that it is not Gaussian. Its behavior at large distances allows us to extract the energy-dependent diffusion constants from experimental density distributions. For a thermal cloud released into the disordered potential, we show that our numerical predictions are in agreement with experimental findings. Not only does this work give insights to recent experimental results, but it may also serve interpretation of future experiments searching for deviation from classical diffusion and traces of Anderson localization.Comment: 19 pages, 16 figure

Poly(phenylene methylene)-based coatings for corrosion protection : replacement of additives by use of copolymers

Poly(phenylene methylene) (PPM) is a thermally stable, hydrophobic, fluorescent hydrocarbon polymer. Recently, blended PPM has been proposed as a valuable anti-corrosion coating material, and, in particular, rheological additives such as external plasticizers resulted crucial to prevent crack formation. Accordingly, to avoid common problems related to the use of external plasticizers, the development of PPM-related copolymer-based coatings containing n-octyloxy side chains and their anti-corrosion behavior were explored in this study. The aluminum alloy AA2024, widely employed for corrosion studies, was selected as a substrate, covered with a thin layer of a polybenzylsiloxane in order to improve adhesion between the underlying hydrophilic substrate and the top hydrophobic coating. Gratifyingly, coatings with those copolymers were free of bubbles and cracks. The n-octyloxy side-chains may be regarded to adopt the role of a bound plasticizer, as the glass transition temperature of the copolymers decreases with increasing content of alkoxy side-chains. Electrochemical corrosion tests on PPM-substituted coatings exhibited good corrosion protection of the metal surface towards a naturally aerated near-neutrally 3.5% wt.% NaCl neutral solution, providing comparable results to blended PPM formulations, previously reported. Hence, the application of rheological additives can be avoided by use of proper design copolymers

Elastic behaviour of the carotid artery in intact spontaneously hypertensive rats

Intact spontaneously hypertensive rats (SHR) were studied to assess the effect of prolonged antihypertensive treatment on the elastic behaviour of the external carotid artery. Thirty-week-old SHR received the ACE inhibitor captopril, the arteriolar dilator hydralazine or their vehicle for 6 weeks. These rats were compared to normotensive, vehicle treated WKY rats. The internal diameter of the carotid artery was measured continuously in halothane-anaesthetized rats using an echo-tracking device, and intra-arterial pressure was also monitored continuously, on the contralateral side. Captopril- and hydralazine-treated SHR as well as normotensive controls had similar blood pressure values. No significant shift in the distensibility-pressure curves was observed among vehicle-treated SHR and WKY rats or the SHR which had received captopril or hydralazine. Histological examination of the carotid artery fixed ex vivo with paraformaldehyde showed a significant increase in cross-sectional area in vehicle-treated SHR as compared to their normotensive counterparts. These results therefore suggest that the elastic behaviour of elastic arteries is not necessarily altered by the structural changes developing in response to hypertension