609 research outputs found
The subzero microbiome: Microbial activity in frozen and thawing soils
No full textMost of the Earth's biosphere is characterized by low temperatures (<5 °C) and cold-adapted microorganisms are widespread. These psychrophiles have evolved a complex range of adaptations of all cellular constituents to counteract the potentially deleterious effects of low kinetic energy environments and the freezing of water. Microbial life continues into the subzero temperature range, and this activity contributes to carbon and nitrogen flux in and out of ecosystems, ultimately affecting global processes. Microbial responses to climate warming and in particular, thawing of frozen soils are not yet well understood although the threat of microbial contribution to positive feedback of carbon flux is substantial. To date, several studies have examined microbial community dynamics in frozen soils and permafrost due to changing environmental conditions, and some have undertaken the complicated task of characterizing microbial functional groups and how their activity changes with changing conditions, either in situ or by isolating and characterizing macromolecules. With increasing temperature and wetter conditions microbial activity of key microbes and subsequent efflux of greenhouse gases also increase. In this review, we aim to provide an overview of microbial activity in seasonally frozen soils and permafrost. With a more detailed understanding of the microbiological activities in these vulnerable soil ecosystems, we can begin to predict and model future expectations for carbon release and climate change.Peer reviewe
VISUALISASI 3 DIMENSI WISATA SEJARAH KERKHOF PEUCUT KOTA BANDA ACEH
No full textABSTRAKPenelitian ini bertujuan memvisualisasikan 3 Dimensi Wisata Sejarah Kerkhof Peucut Kota Banda Aceh. Visualisasi 3 Dimensi ini dilakukan dengan metode pengumpulan data, perancangan objek dan visualisasi 3 dimensi. Tahap perancangan objek meliputi tahap analisir, perancangan objek, implementasi objek dan pengkajian objek. disebabkan belum tersedianya Visualisasi 3 Dimensi Wisata Sejarah Kerkhof Peucut Kota Banda Aceh, Penulis mengambil topik proyek akhir dengan judul tersebut. Visualisasi 3 Dimensi akan dibuat menggunakan Software Blender v2.79. Visualisasi 3 Dimensi Wisata Sejarah Kerkhof Peucut yang dihasilkan berdurasi 1 menit.Kata Kunci: 3 Dimensi, Kerkhof Peucut, Visualisasi.ABSTRACTThe purpose of this research is to visualize the 3 Dimensions of the Historical Tourism of the Kerkhof Peucut City of Banda Aceh. 3 Dimensional Visualization is done by the method of data collection, object design, and 3-dimensional visualization. The object design phase includes the analysis phase, object design, object implementation, and object review. due to the unavailability of 3-Dimensional Visualization of Tourism History of the Kerkhof Peucut City of Banda Aceh, the author takes the topic of the final project with that title. 3 Dimensional Visualization will be created using Blender v2.79 Software. 3 Dimensional Visualization of Kerkhof Peucut Historical Tourism produced 1-minute duration.Key Word: 3 Dimentional, Kerkhof Peucut, Visualization
Rotterdam Binnenrotte kerkhof Laurenskerk. Archeologisch onderzoek van het kerkhof en bebouwing aan de oostzijde van de Laurenskerk.
No full textDe bodemingrepen voor de herinrichting van de Binnenrotte, en dan voornamelijk de aanleg van de zogenaamde Laurenstuin aan de oostzijde van de Laurenskerk, bood de mogelijkheid om over een oppervlakte van circa 1300 m2 onderzoek te doen naar het voormalige kerkhof. aan de oostzijde van de kerk. Tussen 4 en 15 april 2016 vond het archeologisch onderzoek plaats op het voormalige kerkhof. Het onderzoek richtte zich niet alleen op de graven; ook zijn de funderingen van gebouwen gedocumenteerd die vanaf de 17e eeuw tegen de kerk zijn gebouwd. Door middel van grondboringen is tevens aandacht besteed aan de opbouw van de bodem rondom de oostzijde van de kerk. Hierbij is een zo ontdekte ophogingslaag van een terp uit de prestedelijke nederzetting Rotta op botanische macroresten onderzocht
Identification of a Ruminococcaceae Species as the Methyl tert-Butyl Ether (MTBE) Degrading Bacterium in a Methanogenic Consortium
No full textThe widespread use of methyl tert-butyl ether (MTBE) has caused major contamination of groundwater sources and is a concern due to its taste and odor problems, as well as toxicity. MTBE can be degraded anaerobically which makes bioremediation of contaminated aquifers a potential solution. Nevertheless, the organisms and mechanisms that are responsible for anaerobic MTBE degradation are still unknown. The aim of our research was to identify the organisms actively degrading MTBE. For this purpose we characterized an anaerobic methanogenic culture enriched with MTBE as the sole carbon source from the New Jersey Arthur Kill intertidal strait sediment. The cultures were analyzed using stable isotope probing (SIP) combined with terminal restriction fragment length polymorphism (T-RFLP), high-throughput sequencing and clone library analysis of bacterial 16S rRNA genes. The sequence data indicated that phylotypes belonging to the Ruminococcaceae in the Firmicutes were predominant in the methanogenic cultures. SIP experiments also showed sequential incorporation of the 13C labeled MTBE by the bacterial community with a bacterium most closely related to Saccharofermentans acetigenes identified as the bacterium active in O-demethylation of MTBE. Identification of the microorganisms responsible for the activity will help us better understand anaerobic MTBE degradation processes in the field and determine biomarkers for monitoring natural attenuation.Peer reviewe
Novel Reductive Dehalogenases from the Marine Sponge Associated Bacterium Desulfoluna spongiiphila
No full textDesulfoluna spongiiphila strain AA1 is an organohalide respiring bacterium, isolated from the marine sponge Aplysina aerophoba, that can use brominated and iodinated phenols, in addition to sulfate and thiosulfate as terminal electron acceptors. The genome of Desulfoluna spongiiphila strain AA1 is approximately 6.5 Mb. Three putative reductive dehalogenase (rdhA) genes involved in respiratory metabolism of organohalides were identified within the sequence. Conserved motifs found in respiratory reductive dehalogenases (a twin arginine translocation signal sequence and two iron-sulfur clusters) were present in all three putative AA1 rdhA genes. Transcription of one of the three rdhA genes was significantly upregulated during respiration of 2,6-dibromophenol and sponge extracts. Strain AA1 appears to have the ability to synthesize cobalamin, the key cofactor of most characterized reductive dehalogenase enzymes. The genome contains genes involved in cobalamin synthesis and uptake and can grow without cobalamin supplementation. Identification of this target gene associated with debromination lays the foundation for understanding how dehalogenating bacteria control the fate of organohalide compounds in sponges and their role in a symbiotic organobromine cycle. In the sponge environment, D. spongiiphila strain AA1 may thus take advantage of both brominated compounds and sulfate as electron acceptors for respiration.Peer reviewe
Archeologisch onderzoek op het historische kerkhof van de O.-L.-V. van Goede Hoop-kerk te Vilvoorde (prov. Vlaams-Brabant)
No full textDit eindverslag beschrijft de resultaten van de archeologische opgraving van twee toevalvondsten ter
hoogte van het Heldenplein, rondom de O.-L.-V. van Goede Hoop te Vilvoorde. De site is grotendeels
binnen het historische kerkhof gelegen, dat met behulp van een combinatie aan dateringsmethoden
tussen de 11de tot 19de eeuw gedateerd kan worden. Zo goed als alle sporen zijn met het funeraire
karakter van de site te linken
Model Risk Analysis for Risk Management and Option Pricing.
No full textDue to the growing complexity of products in financial markets, market participants rely more and more on quantitative models for trading and risk management decisions. This introduces a fairly new type of risk, namely, model risk. In the first part of this thesis we investigate the quantitative influence of model risk on risk management with a main focus on regulation issues. We present frameworks for measuring model risk and backtesting procedures for evaluating model quality. Furthermore, we apply these frameworks to derivatives portfolios. The second part of the thesis concerns interest rate derivatives pricing models. We compare Libor market and discrete string models and find them observationally equivalent. Furthermore, we investigate the factor dependence and estimation risk for a range of exotic derivatives priced with these models.
Mineralisation of amethyst-bearing geodes in Ametista do Sul (Brazil) from low-temperature sedimentary brines: evidence from monophase liquid inclusions and stable isotopes
No full textFluid inclusion studies in combination with hydrogen, oxygen and sulphur isotope data provide novel insights into the genesis of giant amethyst-bearing geodes in Early Cretaceous Parana continental flood basalts at Amestita do Sul, Brazil. Monophase liquid inclusions in colourless quartz, amethyst, calcite, barite and gypsum were analysed by microthermometry after stimulating bubble nucleation using single femtosecond laser pulses. The salinity of the fluid inclusions was determined from ice-melting temperatures and a combination of prograde and retrograde homogenisation temperatures via the density maximum of the aqueous solutions. Four mineralisation stages are distinguished. In stage I, celadonite, chalcedony and pyrite formed under reducing conditions in a thermally stable environment. Low delta S-34(V-CDT) values of pyrite (-25 to -32 aEuro degrees) suggest biogenic sulphate reduction by organotrophic bacteria. During the subsequent stages II (amethyst, goethite and anhydrite), III (early subhedral calcite) and IV (barite, late subhedral calcite and gypsum), the oxidation state of the fluid changed towards more oxidising conditions and microbial sulphate reduction ceased. Three distinct modes of fluid salinities around 5.3, 3.4 and 0.3 wt% NaCl-equivalent characterise the mineralisation stages II, III and IV, respectively. The salinity of the stage I fluid is unknown due to lack of fluid inclusions. Variation in homogenisation temperatures and in delta O-18 values of amethyst show evidence of repeated pulses of ascending hydrothermal fluids of up to 80-90 A degrees C infiltrating a basaltic host rock of less than 45 A degrees C. Colourless quartz and amethyst formed at temperatures between 40 and 80 A degrees C, while the different calcite generations and late gypsum precipitated at temperatures below 45 A degrees C. Calculated oxygen isotope composition of the amethyst-precipitating fluid in combination with delta D values of amethyst-hosted fluid inclusions (-59 to -51 aEuro degrees) show a significant O-18-shift from the meteoric water line. This O-18-shift, high salinities of the fluid inclusions with chloride-sulphate composition, and high delta S-34 values of anhydrite and barite (7.5 to 9.9 aEuro degrees) suggest that sedimentary brines from deeper parts of the Guarani aquifer system must have been responsible for the amethyst mineralisation.Swiss National Science Foundation (SNSF) [200021-119966
Coexistence of Gaucher-Disease Type 1 and Joubert-Syndrome
No full textLetterRoyen-Kerkhof, van, A. ; Kleijer, W.J. ; Diggelen, van, O.P. ; Aerts, J.M.F.G. ; Hopwoud, J.J. ; Beemer, F.A
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