The effects of storage conditions on viability of Clostridium difficile vegetative cells and spores and toxin activity in human faeces

AIMS: Clostridium difficile is a common nosocomial pathogen and as such diagnostic and research methods may necessitate storage of faecal specimens for long periods, followed by subsequent re-examination. This study investigated the effects of storage conditions upon the viability of this organism and its toxin. METHODS: Three genotypically distinct strains of C difficile (two clinical isolates including the UK epidemic strain, and an environmental isolate) were grown anaerobically at 37°C for 72 hours in a pool of five faecal emulsions. Aliquots of each emulsion were stored at either -20°C (frozen) or 4°C (refrigerated). Emulsions were assayed for viable cells, spores, and cytotoxin titre before storage and at days 1, 3, 5, 7, 14, 28, and 56. An aliquot of each emulsion was also removed, assayed, and replaced in storage at each time point to investigate the effects of multiple freezing/refrigeration/thawing . RESULTS: Neither storage temperature nor multiple cycles of refrigeration/freezing and thawing adversely affected the viability of C difficilevegetative cells or spores. Single and multiple exposures of samples to 4°C had little effect upon the C difficile toxin titre. Toxin titres of multiply frozen and thawed faeces became significantly lower than for refrigerated faeces (p < 0.01) by day 5 of the experiment in two of the three strains, and in all strains by day 28. Toxin titres of singly frozen faeces became significantly lower than for refrigerated faeces (p < 0.01) by day 56 of the experiment in two of the three strains. CONCLUSION: Storage temperature and multiple cycles of freezing (refrigeration)/thawing had minimal effects upon the viability of C difficile or its spores. Storage at 4°C has no discernible effect on C difficile cytotoxin. However, storage at -20°C has a detrimental effect upon C difficile cytotoxin, and multiple cycles of freezing and thawing may further adversely effect toxin titres

New geochemical and isotopic constraints on the genesis of the Oliveira Azeméis granitoid melts (Porto-Tomar Shear Zone, Iberian Variscan Chain, Central-Western Portugal).

The Porto-Tomar Shear Zone (PTSZ) is a very important tectonic structure that separates, in central-western Portugal, two of the major tectonic units of the Iberian Variscan Chain: the Ossa-Morena Zone, to the west, and the Central Iberian Zone, to the east. The Oliveira de Azeméis area lies in the northern sector of the PTZC and it is characterized by the occurrence of strongly deformed granitoids. Country rocks are dominantly pelitic metasediments which, according to recent geological mapping (Pereira et al., 2007), belong to the Precambrian Lourosa Formation and the Ordovician São João de Ver Formation. Using Rb-Sr whole-rock isotopic data, Pinto (1979) proposed an age of 379 12 Ma for the Oliveira de Azeméis granitoids. In this work, new results were obtained on these granitoids in the area between the villages of Travanca and Curval, especially in the Sacramento quarry. In this critical outcrop, strongly deformed two-mica granite (displaying S-C structures, with dextral NNW-SSE shear planes) pass into diatexites and metatexites with garnet, cordierite and sillimanite-bearing melanosomes. Leucosomes seem to have mainly granitic s.s. compositions, but cm-thick bands of leucotonalite were also found. Major element geochemistry of granite samples shows the following ranges: 71.4% SiO2 74.2%; 0.74% Fe2O3t 2.48%; 0.35% MgO 0.60%; 0.49% CaO 1.32%; 2.90% Na2O 3.11%; 4.70% K2O 5.47%; 1.17 ASI 1.36. Trace element data reveal a strong fractionation between highly incompatible LILE and less incompatible HFSE (248 PM normalized Rb/Y 671) and between LREE and HREE (18.6 PM normalized La/Lu 54.7). These features, in particular the peraluminous composition, the high K contents and the distinct rare-earth fractionation suggest that the Oliveira de Azeméis granites are mostly the result of partial melting of metasediments with a large pelitic component and that garnet is a likely residual phase. Isotope geochemistry data show that the previously reported isochron should not correspond to a true age since the 87Sr/86Sr(380Ma) obtained in the granite samples analysed in the present work are very low, varying from 0.6978 to 0.7063, with an average value of 0.7023, which are unrealistic in S-type granitic melts. Probably, the 380 Ma date is the consequence of mixing of different melt source components in the samples used in its calculation. Using the granite whole-rock samples collected in this work, a 328 28 Ma errorchron (MSWD=4.0; initial 87Sr/86Sr=0,7106 0.0045) is now obtained. Assuming a typical syn-tectonic Variscan age of 320 Ma for the studied granites, 87Sr/86Sr and "Nd range from 0.7100 to 0.7133 and from -6.5 to -7.9, respectively. A micaschist sample collected in this area displays 87Sr/86Sr(320Ma) = 0.7146 and "Nd(320Ma) = -9.2. Therefore, the Sr and Nd isotope composition agrees with the clearly dominance of a melt component derived by anatexis of a metapelitic source. Two samples of a garnet-bearing (and comparatively zircon-rich) diatexite show 87Sr/86Sr(320Ma) values (0.7120 and 0.7102) similar to those found in granites, but have higher "Nd(320Ma): -2.0 and -1.6. This may be explained by either (a) the involvement of a different source in the genesis of this diatexite or (b) the occurrence of Nd isotope disequilibrium during the melting process, with the preservation of high 143Nd/144Nd ratios in refractory phases such as garnet and/or zircon. A Rb-Sr wr-feldspar-biotite-muscovite isochron of 301.2 5.6 Ma (MSWD=0.42; initial 87Sr/86Sr=0,71516 0.00074) in a granite sample is interpreted as recording the final stage of the operation of the shear zone, which was accompanied by mica recrystallization. Funding: projects Petrochron (PTDC/CTE-GIX/112561/2009) and Geobiotec (PEst-C/CTE/UI4035/2011). References Pereira E. et allia (2007) – Carta Geológica 1/50000 de Oliveira de Azeméis. INETI, Lisboa. Pinto M.S. (1979) – PhD Thesis. Univ. Leed

Old carbon contributes to aquatic emissions of carbon dioxide in the Amazon

Knowing the rate at which carbon is cycled is crucial to understanding the dynamics of carbon transfer pathways. Recent technical developments now support measurement of the &lt;sup&gt;14&lt;/sup&gt;C age of evaded CO&lt;sub&gt;2&lt;/sub&gt; from fluvial systems, which provides an important "fingerprint" of the source of C. Here we report the first direct measurements of the &lt;sup&gt;14&lt;/sup&gt;C age of effluxed CO&lt;sub&gt;2&lt;/sub&gt; from two small streams and two rivers within the western Amazonian Basin. The rate of degassing and hydrochemical controls on degassing are also considered. We observe that CO&lt;sub&gt;2&lt;/sub&gt; efflux from all systems except for the seasonal small stream was &lt;sup&gt;14&lt;/sup&gt;C -depleted relative to the contemporary atmosphere, indicating a contribution from "old" carbon fixed before ~ 1955 AD. Further, "old" CO&lt;sub&gt;2&lt;/sub&gt; was effluxed from the perennial stream in the rainforest; this was unexpected as here connectivity with the contemporary C cycle is likely greatest. The effluxed gas represents all sources of CO&lt;sub&gt;2&lt;/sub&gt; in the aquatic system and thus we used end-member analysis to identify the relative inputs of fossil, modern and intermediately aged C. The most likely solutions indicated a contribution from fossil carbon sources of between 3 and 9% which we interpret as being derived from carbonate weathering. This is significant as the currently observed intensification of weather has the potential to increase the future release of old carbon, which can be subsequently degassed to the atmosphere, and so renders older, slower C cycles faster. Thus &lt;sup&gt;14&lt;/sup&gt;C fingerprinting of evaded CO&lt;sub&gt;2&lt;/sub&gt; provides understanding which is essential to more accurately model the carbon cycle in the Amazon Basin

Experimental validation of the mechanical coupling response for hygro-thermally curvature-stable laminated composite materials

Stacking sequence configurations for hygro-thermally curvature-stable (HTCS) laminates have recently been identified in 9 classes of coupled laminate with standard ply angle orientations +45, "1245, 0 and 9

Living roots magnify the response of soil organic carbon decomposition to temperature in temperate grassland.

Increasing atmospheric carbon dioxide (CO2) concentration is both a strong driver of primary productivity and widely believed to be the principal cause of recent increases in global temperature. Soils are the largest store of the world's terrestrial C. Consequently, many investigations have attempted to mechanistically understand how microbial mineralisation of soil organic carbon (SOC) to CO2 will be affected by projected increases in temperature. Most have attempted this in the absence of plants as the flux of CO2 from root and rhizomicrobial respiration in intact plant-soil systems confounds interpretation of measurements. We compared the effect of a small increase in temperature on respiration from soils without recent plant C with the effect on intact grass swards. We found that for 48 weeks, before acclimation occurred, an experimental 3 °C increase in sward temperature gave rise to a 50% increase in below ground respiration (ca.0.4 kg C m−2; Q10=3.5), whereas mineralisation of older SOC without plants increased with a Q10 of only 1.7 when subject to increases in ambient soil temperature. Subsequent 14C dating of respired CO2 indicated that the presence of plants in swards more than doubled the effect of warming on the rate of mineralisation of SOC with an estimated mean C age of ca.8 y or older relative to incubated soils without recent plant inputs. These results not only illustrate the formidable complexity of mechanisms controlling C fluxes in soils, but also suggest that the dual biological and physical effects of CO2 on primary productivity and global temperature have the potential to synergistically increase the mineralisation of existing soil C

EUNIS E-Learning Snapshots 2008

The paper presents an analysis of the information obtained through the third EUNIS E-Learning Snapshots scheme. Around 50 member universities of EUNIS have contributed information on the way e-learning is organised and deployed at their universities along with their views on e-learning. The results of this survey present a picture of the deployment of e-learning in the universities represented in our sample. The Snapshots scheme is one of the activities of the EUNIS E-Learning Task Force, which met in Malta in February 2008

Enhancement of Xe-129 polarization by off-resonant spin exchange optical pumping

A high power narrow line width (38 W, 0.09 nm full width at half maximum) external cavity diode laser is investigated for rubidium spin exchange optical pumping of Xe-129. This tunable photon source has a constant line width, independent of operating power or wavelength within a 1 nm tuning range. When using this laser, an increase in the Xe-129 nuclear polarization is observed when optically pumping at a lower wavelength than the measured Rb electron D-1 absorption. The exact detuning from D1 for the highest polarization is dependent upon the gas density. Furthermore, at high power and/or high Rb density, a reduction in the polarization occurs at the optimum wavelength as previously reported in spin exchange optical pumping studies of He-3 which is consistent with high absorption close to the cell front face. These results are encouraging for moderate high throughput polarization of Xe-129 in the midpressure range of (0.5-2.0 amagat). (C) 2010 American Institute of Physics. [doi: 10.1063/1.3478707

Enhancement of Xe-129 polarization by off-resonant spin exchange optical pumping

A high power narrow line width (38 W, 0.09 nm full width at half maximum) external cavity diode laser is investigated for rubidium spin exchange optical pumping of Xe-129. This tunable photon source has a constant line width, independent of operating power or wavelength within a 1 nm tuning range. When using this laser, an increase in the Xe-129 nuclear polarization is observed when optically pumping at a lower wavelength than the measured Rb electron D-1 absorption. The exact detuning from D1 for the highest polarization is dependent upon the gas density. Furthermore, at high power and/or high Rb density, a reduction in the polarization occurs at the optimum wavelength as previously reported in spin exchange optical pumping studies of He-3 which is consistent with high absorption close to the cell front face. These results are encouraging for moderate high throughput polarization of Xe-129 in the midpressure range of (0.5-2.0 amagat). (C) 2010 American Institute of Physics. [doi: 10.1063/1.3478707

Minimization via duality

We show how to use duality theory to construct minimized versions of a wide class of automata. We work out three cases in detail: (a variant of) ordinary automata, weighted automata and probabilistic automata. The basic idea is that instead of constructing a maximal quotient we go to the dual and look for a minimal subalgebra and then return to the original category. Duality ensures that the minimal subobject becomes the maximally quotiented object

Crystallization and preliminary crystallographic data of the PAS domain of the NifL protein from Azotobacter vinelandii.

The Azotobacter vinelandii NifL protein is a redox-sensing flavoprotein which inhibits the activity of the nitrogen-specific transcriptional activator NifA. The N-terminal PAS domain has been overexpressed in Escherichia coli and crystallized by the hanging-drop vapour-diffusion method. The crystal belongs to the rhombohedral space group R32, with unit-cell parameters a = b = 65.0, c = 157.3 Å, and has one molecule in the asymmetric unit. Native data were collected to 3.0 Å on the BW7B synchrotron beamline at the EMBL Hamburg Outstation