Ammonia transformation in a biotrickling air filter

[Abstract] A simple, tubular biotrickling filter was designed for optimal removal of ammonia and odour in ventilation air from a pig house. The removal and transformation of ammonia was studied in detail by analysis and modelling of chemical gradients through the filter. Good correspondence between measurements and model was obtained by using conventional substrate and inhibition kinetics of ammonium and nitrite oxidizing bacteria. Highest rates of ammonia removal were observed in the central section of the filter. Near the air outlet and water inlet the process was ammonia limited, while high nitrous acid concentrations almost excluded any biological activity near the air inlet and water outlet. Nitrous acid inhibition also stabilized pH at 6.5-7 all through the filter. Being sensitive to both ammonia and nitrous acid the nitrite oxidation process occurred mainly in the filter sections near the air outlet / water inlet, and only 8% of the nitrite was turned into nitrate. Water supply only exceeded evaporation by 20% but modelling indicated that additional watering would have limited effect on filter efficiency. The filter was also robust to varying loading, as a 4-fold increase in ammonia inlet concentration only reduced filter efficiency from 86 to 76%

Dynamical Surface Gravity in Spherically Symmetric Black Hole Formation

We study dynamical surface gravity in a general spherically symmetric setting using Painlev\'{e}-Gullstrand (PG) coordinates. Our analysis includes several definitions that have been proposed in the past as well as two new definitions adapted to PG coordinates. Various properties are considered, including general covariance, value at extremality, locality and static limit. We illustrate with specific examples of "dirty" black holes that even for spacetimes possessing a global timelike Killing vector, local definitions of surface gravity can differ substantially from "non-local" ones that require an asymptotic normalization condition. Finally, we present numerical calculations of dynamical surface gravity for black hole formation via spherically symmetric scalar field collapse. Our results highlight the differences between the various definitions in a dynamical setting and provide further insight into the distinction between local and non-local definitions of surface gravity.Comment: Final version to appear in Phys. Rev. D. Slight name change, further improvements to numerics and presentation, 25 pages, 7 figure

Deciphering the role of PRC2 accessory proteins in promoting cold-induced epigenetic switching in Arabidopsis thaliana

All cells in multicellular organisms contain the same genetic material. Cell differentiation and adaptation to environmental signals require the accurate switching of gene expression states and the maintenance of those states through cell division, even in the absence of the initial signal. Polycomb complexes play an important role in these switching and epigenetic silencing mechanisms. The Arabidopsis thaliana developmental regulator FLOWERING LOCUS C (FLC) has emerged as an excellent system to dissect Polycomb Repressive Complex 2 (PRC2) regulation. FLC is expressed as plants germinate in autumn to prevent premature flowering. The prolonged cold of winter epigenetically silences FLC, aligning flowering with the following spring. The epigenetic silencing involves a cold-induced PRC2 switch and deposition of the repressive chromatin mark H3K27me3 in the FLC nucleation region. This switch requires the core PRC2 and two accessory proteins VIN3 and VRN5, but the molecular mechanism underlying the switch and the subsequent memory of cold exposure remain largely unknown. The work in this thesis aimed to understand the role of VIN3 and VRN5 in the repression of FLC. In the first Results chapter, the mechanism of VIN3 binding at FLC is studied; VIN3 was shown to contain a domain that can associate with nucleic acids. The second Results chapter dissects the function of the conserved C-terminal domain of VIN3 and VRN5; this domain mediates protein-protein interactions between VIN3 and VRN5 and adopts a novel polymerization fold. In the third Results chapter, the local chromatin conformation at FLC is studied; the expression state of FLC was found to correlate with distinct 3D conformation. The 3’ end of FLC containing a promoter for FLC antisense transcripts is involved in setting this 3D conformation. Overall, the work advances our understanding of the molecular function of PRC2 accessory proteins in epigenetic silencing

Gennem mine årer fosser fjeldenes store elve”: Forestillinger om grønlandskhed hos det grønlandske rockband Sume, 1973-1976

Sume var det første rockband til at synge på grønlandsk, og i deres tekster fra 1973-1976 udtrykker de sig ofte om grønlandskhed. Bandet giver udtryk for en essentialistisk forståelse af grønlandsk identitet som en naturlig, autentisk størrelse, der er truet af den danske kolonisering. Med forskellige perspektiver på essentialisme fra hhv. Doreen Massey og Gayatri Chakravorty Spivak viser jeg i artiklen, hvordan det fra forskellige teoretiske ståsteder er muligt at anskue Sumes essentialisme som enten hæmmende og ekskluderende eller som et nødvendigt våben i en politisk, antikolonial mobilisering

Scheffersomyces stipitis: a comparative systems biology study with the Crabtree positive yeast Saccharomyces cerevisiae

<p>Abstract</p> <p>Background</p> <p><it>Scheffersomyces stipitis</it> is a Crabtree negative yeast, commonly known for its capacity to ferment pentose sugars. Differently from Crabtree positive yeasts such as <it>Saccharomyces cerevisiae</it>, the onset of fermentation in <it>S. stipitis</it> is not dependent on the sugar concentration, but is regulated by a decrease in oxygen levels. Even though <it>S. stipitis</it> has been extensively studied due to its potential application in pentoses fermentation, a limited amount of information is available about its metabolism during aerobic growth on glucose. Here, we provide a systems biology based comparison between the two yeasts, uncovering the metabolism of <it>S. stipitis</it> during aerobic growth on glucose under batch and chemostat cultivations.</p> <p>Results</p> <p>Starting from the analysis of physiological data, we confirmed through ¹³C-based flux analysis the fully respiratory metabolism of <it>S. stipitis</it> when growing both under glucose limited or glucose excess conditions. The patterns observed showed similarity to the fully respiratory metabolism observed for <it>S. cerevisiae</it> under chemostat cultivations however, intracellular metabolome analysis uncovered the presence of several differences in metabolite patterns. To describe gene expression levels under the two conditions, we performed RNA sequencing and the results were used to quantify transcript abundances of genes from the central carbon metabolism and compared with those obtained with <it>S. cerevisiae</it>. Interestingly, genes involved in central pathways showed different patterns of expression, suggesting different regulatory networks between the two yeasts. Efforts were focused on identifying shared and unique families of transcription factors between the two yeasts through <it>in silico</it> transcription factors analysis, suggesting a different regulation of glycolytic and glucoenogenic pathways.</p> <p>Conclusions</p> <p>The work presented addresses the impact of high-throughput methods in describing and comparing the physiology of Crabtree positive and Crabtree negative yeasts. Based on physiological data and flux analysis we identified the presence of one metabolic condition for <it>S. stipitis</it> under aerobic batch and chemostat cultivations, which shows similarities to the oxidative metabolism observed for <it>S. cerevisiae</it> under chemostat cultivations. Through metabolome analysis and genome-wide transcriptomic analysis several differences were identified. Interestingly, <it>in silico</it> analysis of transciption factors was useful to address a different regulation of mRNAs of genes involved in the central carbon metabolism. To our knowledge, this is the first time that the metabolism of <it>S. stiptis</it> is investigated in details and is compared to <it>S. cerevisiae</it>. Our study provides useful results and allows for the possibility to incorporate these data into recently developed genome-scaled metabolic, thus contributing to improve future industrial applications of <it>S. stipitis</it> as cell factory.</p

Human protein secretory pathway genes are expressed in a tissue-specific pattern to match processing demands of the secretome

Protein secretory pathway in eukaryal cells is responsible for delivering functional secretory proteins. The dysfunction of this pathway causes a range of important human diseases from congenital disorders to cancer. Despite the piled-up knowledge on the molecular biology and biochemistry level, the tissue-specific expression of the secretory pathway genes has not been analyzed on the transcriptome level. Based on the recent RNA-sequencing studies, the largest fraction of tissue-specific transcriptome encodes for the secretome (secretory proteins). Here, the question arises that if the expression levels of the secretory pathway genes have a tissue-specific tuning. In this study, we tackled this question by performing a meta-analysis of the recently published transcriptome data on human tissues. As a result, we detected 68 as called “extreme genes” which show an unusual expression pattern in specific gene families of the secretory pathway. We also inspected the potential functional link between detected extreme genes and the corresponding tissues enriched secretome. As a result, the detected extreme genes showed correlation with the enrichment of the nature and number of specific post-translational modifications in each tissue’s secretome. Our findings conciliate both the housekeeping and tissue-specific nature of the protein secretory pathway, which we attribute to a fine-tuned regulation of defined gene families to support the diversity of secreted proteins and their modifications

Kontanthjælpsmodtagerens kritiske register: Den civile, den industrielle og den domestiske protest

This article investigates different acts of political protests currently floating from unemployed citizens who are being affected by recent retrenchment policy reforms. Whereas most of the existing literature tends to portray political protest as either collective and public or individual and private, this article attempts instead to shed light on the plurality of normative resources activated by the unemployed in a highly critical situation. Thereby the analysis moves between the collective and the individual as well as between the public and the private. Using the theoretical framework developed by Laurent Thévenot and Luc Boltanski in their joint work on justification, the article analyses a specific case, namely unemployed Danish recipients of social assistance who are affected by a new policy initiative meaning that their income has been lowered. Drawing on newspaper articles and qualitative in-depth interviews with affected citizens, the analysis unfolds and theorizes upon three very different forms of protesting: a civic, an industrial and a domestic form of resistance