1,716 research outputs found
Repeated pulse feeding induces functional stability in anaerobic digestion
Anaerobic digestion is an environmental key technology in the future bio-based economy. To achieve functional stability, a minimal microbial community diversity is required. This microbial community should also have a certain “elasticity”, i.e. the ability to rapidly adapt to sub-optimal conditions or stress. In this study it was evaluated whether a higher degree of functional stability could be achieved by changing the feeding pattern, which can change the evenness, dynamics and richness of the bacterial community. The first reactor (CSTRstable) was fed on daily basis, whereas the second reactor (CSTRdynamic) was fed every two days. Average biogas production was 0.30L CH4 L-1 d-1 in both reactors, although daily variation was up to four times higher in the CSTRdynamic compared to the CSTRstable during the first 50 days. Bacterial analysis revealed that this CSTRdynamic had a two times higher degree of bacterial community dynamics. The CSTRdynamic also appeared to be more tolerant to an organic shock load of 8 g COD L-1 and ammonium levels up to 8000 mg TAN L-1. These results suggest that the regular application of a limited pulse of organic material and/or a variation in the substrate composition might promote higher functional stability in anaerobic digestion
Astro2020 Project White Paper: The Cosmic Accelerometer
We propose an experiment, the Cosmic Accelerometer, designed to yield
velocity precision of cm/s with measurement stability over years to
decades. The first-phase Cosmic Accelerometer, which is at the scale of the
Astro2020 Small programs, will be ideal for precision radial velocity
measurements of terrestrial exoplanets in the Habitable Zone of Sun-like stars.
At the same time, this experiment will serve as the technical pathfinder and
facility core for a second-phase larger facility at the Medium scale, which can
provide a significant detection of cosmological redshift drift on a 6-year
timescale. This larger facility will naturally provide further detection/study
of Earth twin planet systems as part of its external calibration process. This
experiment is fundamentally enabled by a novel low-cost telescope technology
called PolyOculus, which harnesses recent advances in commercial off the shelf
equipment (telescopes, CCD cameras, and control computers) combined with a
novel optical architecture to produce telescope collecting areas equivalent to
standard telescopes with large mirror diameters. Combining a PolyOculus array
with an actively-stabilized high-precision radial velocity spectrograph
provides a unique facility with novel calibration features to achieve the
performance requirements for the Cosmic Accelerometer
Redox changes during the cell cycle in the embryonic root meristem of Arabidopsis thaliana
Aims: The aim of this study was to characterize redox changes in the nuclei and cytosol occurring during the mitotic cell cycle in the embryonic roots of germinating Arabidopsis seedlings, and to determine how redox cycling was modified in mutants with a decreased capacity for ascorbate synthesis. Results: Using an in vivo reduction-oxidation (redox) reporter (roGFP2), we show that transient oxidation of the cytosol and the nuclei occurred at G1 in the synchronized dividing cells of the Arabidopsis root apical meristem, with reduction at G2 and mitosis. This redox cycle was absent from low ascorbate mutants in which nuclei were significantly more oxidized than controls. The cell cycle-dependent increase in nuclear size was impaired in the ascorbate-deficient mutants, which had fewer cells per unit area in the root proliferation zone. The transcript profile of the dry seeds and size of the imbibed seeds was strongly influenced by low ascorbate but germination, dormancy release and seed aging characteristics were unaffected. Innovation: These data demonstrate the presence of a redox cycle within the plant cell cycle and that the redox state of the nuclei is an important factor in cell cycle progression. Conclusions: Controlled oxidation is a key feature of the early stages of the plant cell cycle. However, sustained mild oxidation restricts nuclear functions and impairs progression through the cell cycle leading to fewer cells in the root apical meristem
Evidence for anomalous dust-correlated emission at 8 GHz
In 1969 Edward Conklin measured the anisotropy in celestial emission at 8 GHz
with a resolution of 16.2 degrees and used the data to report a detection of
the CMB dipole. Given the paucity of 8 GHz observations over large angular
scales and the clear evidence for non-power law Galactic emission near 8 GHz, a
new analysis of Conklin's data is informative. In this paper we compare
Conklin's data to that from Haslam et al. (0.4 GHz), Reich and Reich (1.4 GHz),
and WMAP (23-94 GHz). We show that the spectral index between Conklin's data
and the 23 GHz WMAP data is beta=-1.7+-0.1, where we model the emission
temperature as T \propto nu^beta. Free-free emission has beta \approx -2.15,
synchrotron emission has beta \approx -2.7 to -3. Thermal dust emission (beta
\approx1.7) is negligible at 8 GHz. We conclude that there must be another
distinct non-power law component of diffuse foreground emission that emits near
10 GHz, consistent with other observations in this frequency range. By
comparing to the full complement of data sets, we show that a model with an
anomalous emission component, assumed to be spinning dust, is preferred over a
model without spinning dust at 5 sigma (Delta chi2= 31). However, the source of
the new component cannot be determined uniquely.Comment: 6 pages, 5 figures. Submitted to Ap
A Century of Cosmology
In the century since Einstein's anno mirabilis of 1905, our concept of the
Universe has expanded from Kapteyn's flattened disk of stars only 10 kpc across
to an observed horizon about 30 Gpc across that is only a tiny fraction of an
immensely large inflated bubble. The expansion of our knowledge about the
Universe, both in the types of data and the sheer quantity of data, has been
just as dramatic. This talk will summarize this century of progress and our
current understanding of the cosmos.Comment: Talk presented at the "Relativistic Astrophysics and Cosmology -
Einstein's Legacy" meeting in Munich, Nov 2005. Proceedings will be published
in the Springer-Verlag "ESO Astrophysics Symposia" series. 10 pages Latex
with 2 figure
Socially-augmented argumentation tools: rationale, design and evaluation of a debate dashboard
Collaborative Computer-Supported Argument Visualization (CCSAV) is a technical methodology that offers support for online collective deliberation over complex dilemmas. As compared with more traditional conversational technologies, like wikis and forums, CCSAV is designed to promote more critical thinking and evidence-based reasoning, by using representations that highlight conceptual relationships between contributions, and through computational analytics that assess the structural integrity of the network. However, to date, CCSAV tools have achieved adoption primarily in small-scale educational contexts, and only to a limited degree in real world applications. We hypothesise that by reifying conversations as logical maps to address the shortcomings of chronological streams, CCSAV tools underestimate the importance of participation and interaction in enhancing collaborative knowledge-building. We argue, therefore, that CCSAV platforms should be socially augmented in order to improve their mediation capability. Drawing on Clark and Brennan’s influential Common Ground theory, we designed a Debate Dashboard, which augmented a CCSAV tool with a set of widgets that deliver meta-information about participants and the interaction process. An empirical study simulating a moderately sized collective deliberation scenario provides evidence that this experimental version outperformed the control version on a range of indicators, including usability, mutual understanding, quality of perceived collaboration, and accuracy of individual decisions. No evidence was found that the addition of the Debate Dashboard impeded the quality of the argumentation or the richness of content
Extinction of cue-evoked drug-seeking relies on degrading hierarchical instrumental expectancies
There has long been need for a behavioural intervention that attenuates cue-evoked drug-seeking, but the optimal method remains obscure. To address this, we report three approaches to extinguish cue-evoked drug-seeking measured in a Pavlovian to instrumental transfer design, in non-treatment seeking adult smokers and alcohol drinkers. The results showed that the ability of a drug stimulus to transfer control over a separately trained drug-seeking response was not affected by the stimulus undergoing Pavlovian extinction training in experiment 1, but was abolished by the stimulus undergoing discriminative extinction training in experiment 2, and was abolished by explicit verbal instructions stating that the stimulus did not signal a more effective response-drug contingency in experiment 3. These data suggest that cue-evoked drug-seeking is mediated by a propositional hierarchical instrumental expectancy that the drug-seeking response is more likely to be rewarded in that stimulus. Methods which degraded this hierarchical expectancy were effective in the laboratory, and so may have therapeutic potential
A mutation in GDP-mannose pyrophosphorylase causes conditional hypersensitivity to ammonium, resulting in Arabidopsis root growth inhibition, altered ammonium metabolism, and hormone homeostasis
Ascorbic acid (AA) is an antioxidant fulfilling a multitude of cellular functions. Given its pivotal role in maintaining the rate of cell growth and division in the quiescent centre of the root, it was hypothesized that the AA-deficient Arabidopsis thaliana mutants vtc1-1, vtc2-1, vtc3-1, and vtc4-1 have altered root growth. To test this hypothesis, root development was studied in the wild type and vtc mutants grown on Murashige and Skoog medium. It was discovered, however, that only the vtc1-1 mutant has strongly retarded root growth, while the other vtc mutants exhibit a wild-type root phenotype. It is demonstrated that the short-root phenotype in vtc1-1 is independent of AA deficiency and oxidative stress. Instead, vtc1-1 is conditionally hypersensitive to ammonium (NH4+). To provide new insights into the mechanism of NH4+ sensitivity in vtc1-1, root development, NH4+ content, glutamine synthetase (GS) activity, glutamate dehydrogenase activity, and glutamine content were assessed in wild-type and vtc1-1 mutant plants grown in the presence and absence of high NH4+ and the GS inhibitor MSO. Since VTC1 encodes a GDP-mannose pyrophosphorylase, an enzyme generating GDP-mannose for AA biosynthesis and protein N-glycosylation, it was also tested whether protein N-glycosylation is affected in vtc1-1. Furthermore, since root development requires the action of a variety of hormones, it was investigated whether hormone homeostasis is linked to NH4+ sensitivity in vtc1-1. Our data suggest that NH4+ hypersensitivity in vtc1-1 is caused by disturbed N-glycosylation and that it is associated with auxin and ethylene homeostasis and/or nitric oxide signalling
- …