330 research outputs found
Effects of Sidewall Compression and Relaminarization in a Scramjet Inlet
No full textThis paper presents the numerical simulations and the performance analysis of a scramjet inlet as part of a combined experimental and numerical study. A well-validated finite volume flow solver was used to simulate a scramjet inlet with a double ramp configuration for outer compression, including varying degrees of sidewall compression. The computed wall pressure and heat transfer in the symmetry plane are in close agreement with the measurements, and the numerical results indicate that the weak sidewall compression alters the inlet performance significantly. The effects of partial relaminarization over the expansion corner, before the interior part of the inlet, is isolated and investigated in both the experiment and simulation. It is shown that relaminarization of a boundary layer is predicted accurately using the current numerical methods. This work represents a contribution to the understanding of the effects of sidewall compression and relaminarization in designing a scramjet inlet
Production of methyl ethyl ketone from biomass using a hybrid biochemical/catalytic approach
No full textThe recent demand for sustainable routes to fuels and chemicals has led to an increased amount of research in conversion of natural resources. A potential approach for conversion of biomass to fuels and chemicals is to combine biochemical and chemical processes. This research used microbial fermentation to produce 2,3-butanediol, which was then converted to methyl ethyl ketone by dehydration over a solid acid catalyst. The fermentation process was performed using the bacteria Klebsiella oxytoca (K.O). 2,3-butanediol then dehydrated to form methyl ethyl ketone on a solid acid catalyst, the proton form of ZSM-5, and heat. The goal was to determine the reaction kinetics of 2,3-butanediol dehydration over ZSM-5, and to demonstrate the hybrid biochemical/thermochemical approach for synthesizing chemicals from biomass. It was found that ZSM-5 produced methyl ethyl ketone with high selectivity (greater than 90%), and could convert fermentative 2,3-butanediol to methyl ethyl ketone. The reaction order of 2,3-butanediol dehydration was found to be slightly large than one, and an activation energy of 32.3 kJ/mol was measured
Ethanol fermentation from food processing waste
No full textThis study focuses on the use of restaurant waste for production of ethanol. Food wastes (corn, potatoes, and pasta) were converted to ethanol in a two-step process: a two-part enzymatic digestion of starch using alpha-amylase and glucoamylase and then fermentation of the resulting sugars to ethanol using yeast. Because of the low initial composition of starch in the food waste, low ethanol concentrations were achieved: at best 8 mg/ml ethanol (0.8 % by mass). Ethanol concentration increased with increasing enzyme dosage levels. Calculations were conducted to evaluate whether waste heat from restaurant waste could be used to drive flash vaporization to purify ethanol. If the solution produced by fermenting food waste is flashed at a temperature of
99.7°C, 77% of the ethanol is recovered in a vapor stream with 1.14 mole% ethanol (2.87 mass %). Waste heat could provide over a third of the energy for this vaporization process. If 4 mole% ethanol could be produced in the fermentation step by increasing the initial starch content in the waste solution and improving the fermentation process, then a single flash at 98.9°C will recover nearly 99% of the ethanol, giving a mass concentration of ethanol of 10.3%, which is similar to that achieved in industrial grain fermentation
Geostatistics and Petroleum Geology
No full textThis is the sixth contribution to the Computer Methods in the Geosciences series and it continues the tradition of being practical, germaine, and easy to read. Michael Hohn in his presentation, Geostatistics and Petroleum Geology, nicely compliments the other books in the series and brings to the readers some new techniques by which to analyze their data. New approaches always result in new ideas or enhancement of old ones. The French School of Geostatistiques (Fontainebleau, France) was founded and developed by Georges Matheron in response to problems in mining explo ration and exploitation. This approach has been used successfully in that industry since the mid-1960s, but only recently applied to similar problems in petroleum. Likewise, these applications have been successful in this applied field as well and here Hohn gives examples. Standard subjects of the field of geostatistics are explored and discussed-the semivariogram, kriging, cokriging, nonlinear and parametric estimation, and conditional simulation. These may be unrecognizable terms to the readers now, but upon completion of reading the book, they will be fimiliar ones. Each subject is discussed in detail with appropriate and pertinent case studies, taken from the author's own research or from the literature. The author notes the book is for working geologists in the petroleum industr
Analysis of a Three-Dimensional, High Pressure Ratio Scramjet Inlet with Variable Internal Contraction
No full textWe conducted an extensive experimental examination of the operational behavior of a three-dimensional scramjet inlet featuring a movable cowl to adapt the internal contraction according to the respective operation conditions. The experiments were conducted in the H2K wind tunnel of the DLR Cologne at Mach 7. The parameters investigated include different flight path angles (both angle of attack and angle of yaw), internal contraction ratio and Reynolds number. The critical internal contraction for inlet starting was found to agree well with common relations for starting of 3D-inlets. With increasing internal contraction, the inlet performance was found to improve and the inlet operated more stable. It was successfully tested for angles of attack up to ± 6° and angles of yaw up to 6°. Reynolds-Number had rather small effects on the performance and starting behavior of the inlet. Infraredthermography also gave some insight into the flow structure in the external part of the inlet
Epigenetic regulation of endogenous plant pararetroviruses
No full textThis thesis focuses on epigenetic processes involved in the regulation of gene expression in endogenous pararetroviruses (EPRVs), exemplified by endogenous Petunia vein clearing virus (ePVCV-1) and its episomal form, PVCV. Since ePVCV-1/PVCV was found to have features characteristic of retrotransposon and endogenous retroviruses (Richert-Poggeler and Shepherd, 1997), detailed analysis of these retroelements in different systems gives a deep insight to understand the interconnection of these elements and their regulation by the host cellular machinery as described in chapter one.
Chapter two describes the different silencing states of ePVCV-1 in two distinct Petunia hybrida lines, “white 138” (W138) and “rose du ciel” (Rdc). Despite of ePVCV-1 integration into the pericentromeric regions of the Petunia hybrida chromatin, we found that this position still allows for a low level of transcription that increases with increasing plant age and is higher in W138 than Rdc. To correlate these findings with epigenetic marks, we compared these cultivars in respect to DNA- and histone-methylation and siRNA production. Using bisulfite treatment, ePVCV-1 sequences were found to be methylated at cytosines in all contexts. Astonishingly, however, in both hosts the methylation rate in the non-coding region containing the promoter is relatively low. This might indicate a special ability of the viral promoter to escape complete inactivation by methylation. In Rdc, nearly all histones covering the ePVCV-1 coding region were methylated at lysine 9 of histone 3 (H3K9), a flag for heterochromatin, while in W138 about half of them were of the H3K9- and half of the H3K4-type, the latter representing active chromatin. Interestingly and in accordance with the DNA methylation data, the H3K4/H3K9 ratio was relatively high for the promoter region of both cultivars. The higher H3K4/H3K9 ratio in W138 correlates with an increased rate of ePVCV-1 induction. Furthermore, we show the production of siRNAs of three different size classes (24, 22 and 21 nt) in both cultivars, all of
which are weaker in W138 than in Rdc. Together our observations indicate that W138 is less efficient in silencing of the endogenous viral sequences than Rdc.
In chapter three, I investigated the promoter region of PVCV and determined its ability to direct transcription in transgenic plants. Furthermore, I analyzed the regulatory elements of this particular promoter in comparison with those of other plant pararetrovirus promoters. In particular I studied the functionality of an as-1 like element and its contribution to PVCV promoter expression. Although originally of medium strength, the promoter could be improved to about 50% strength of that of the CaMV 35S promoter by “repairing“ a pair of degenerated as-1 enhancer elements. We show, that the promoter includes upstream and downstream enhancer elements, and that it can be improved considerably by restoring two degenerated as-1 elements.
The concept of creating virus-resistant plants by transformation with genes derived from the pathogen genome is a well-exploited and highly effective procedure to fight viruses as causal agents of diseases in plants (Fichen and Beachy, 1993). Recently it has been demonstrated that RNA interference (RNAi) can be successfully triggered against plant viruses by transient expression of an inverted repeat of target sequences (Pooggin et al., 2003; Tenllado et al., 2004). In chapter four, we use this technique to develop RNA-mediated banana streak virus resistance via TGS and/or PTGS and the method should prevent the outbreak of virus infection upon rare spontaneous induction of endogenous BSV in tissue culture.
Chapter five is a publication in EMBO journal to which I contributed in major ways. This paper describes the production of cloned PVCV originating directly from Petunia plants and from a Petunia gene library. Our findings allowed comparative and direct analysis of horizontally and vertically transmitted virus forms and demonstrated their infectivity using biolistic transformation of a provirus-free petunia species. Some integrants within the genome of P.hybrida were found to be arranged in tandem, allowing direct release of virus by transcription. In addition to known inducers of endogenous pararetroviruses, such as genome hybridization, tissue culture and abiotic stresses, we observed
activation of PVCV after wounding. Our data also support the hypothesis that the host plant uses DNA methylation to control the endogenous pararetrovirus.
In a preamble I point out, which part of this paper is based on my own experimentation and interpretation. on to control the endogenous pararetrovirus.
In a preamble I point out, which part of this paper is based on my own experimentation and interpretation
High Enthalpy Flow Characterization Using Tunable Diode Laser Absorption Spectroscopy
No full textThis research aims at analysing thermo-chemical properties of the hypersonic high-enthalpy flow in the L2K wind tunnel, situated in Köln at the German Aerospace Center (DLR). In the L2K wind tunnel, Martian atmosphere can be created, and the facility can simulate heat load conditions encountered during atmospheric entry of Martian missions. The focus of this project is the analysis of the non-intrusive experimental technique "Tunable Diode Laser Absorption Spectroscopy" (TDLAS), based on line of sight absorption spectroscopy, and applied to hypersonic flow. A simplified Martian atmosphere (97% CO2 and 3% N2) was used. A new interpretation for CO-TDLAS experimental technique applied to hypersonic wind tunnel flow analysis was developed. Numerical simulations with the DLR-TAU non-equilibrium flow solver were used as support of this analysis, and match between simulations and experiments was observed. Flow speed and absorption line’s width were measured, and the knowledge of L2K’s flow structure was extended
Acid monolayer functionalized iron oxide nanoparticles as catalysts for carbohydrate hydrolysis
No full textSuperparamagnetic iron oxide nanoparticles were functionalized with a quasi-monolayer of 11-sulfoundecanoic acid and 10-phosphono-1-decanesulfonic acid ligands to create separable solid acid catalysts. The ligands are bound through carboxylate or phosphonate bonds to the magnetite core. The ligand-core bonding surface is separated by a hydrocarbon linker from an outer surface with exposed sulfonic
acid groups. The more tightly packed monolayer of the phosphonate ligand corresponded to a higher sulfonic acid loading by weight, a reduced agglomeration of particles, a greater tendency to remain suspended in solution in the presence of an external magnetic field, and a higher catalytic activity per sulfonic acid group. The particles were characterized by thermogravimetric analysis (TGA), transmission
electron microscopy (TEM), potentiometric titration, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), inductively coupled plasma optical emission spectrometry (ICP-OES), and dynamic light scattering (DLS). In sucrose catalysis reactions, the phosphonic–sulfonic nanoparticles (PSNPs) were seen to be incompletely recovered by an external magnetic field, while the carboxylic–sulfonic nanoparticles (CSNPs) showed a trend of increasing activity over the first four recycle runs. The activity of the acid-functionalized nanoparticles was compared to the traditional solid acid catalyst Amberlyst-15 for the hydrolysis of starch in aqueous solution. Catalytic activity for starch hydrolysis was in the order PSNPs > CSNPs > Amberlyst-15. Monolayer acid functionalization of iron oxides presents a novel strategy for the development of recyclable solid acid catalysts
Martian flow characterization using tunable diode laser absorption spectroscopy, in high enthalpy facilities
No full textThis research aims at analyzing thermo-chemical properties of the hypersonic high-enthalpy flow in the L2K wind tunnel, situated in Koln at the German Aerospace Center (DLR). In the L2K wind tunnel, Martian atmosphere can be created, and the facility can simulate heat load conditions encountered during atmospheric entry of Martian missions. The focus of this project is the analysis of the non-intrusive experimental technique "Tunable Diode Laser Absorption Spectroscopy"(TDLAS), based on line of sight absorption spectroscopy, and applied to hypersonic flow. A simplified Martian atmosphere (97% CO2 and 3% N2) was used. A new interpretation for CO-TDLAS experimental technique applied to hypersonic wind tunnel flow analysis was developed. Numerical simulations with the DLR-TAU non-equilibrium flow solver were used as support of this analysis, and match between simulations and experiments was observed. Flow speed and absorption line's width were measured, and the knowledge of L2K's flow structure was extended
Untersuchungen zur reversen Transkription und dem Kerneintritt von HERV-K(HML-2)
No full textDas menschliche Genom besteht zu 8% aus retroviralen Sequenzen. Die Unterfamilie HML-2 von HERV-K ist dabei die einzige Linie, die seit der Divergenz zwischen Menschen und Schim-panse im menschlichen Genom repliziert hat. Viele der Loci sind in der menschlichen Popu-lation nicht fixiert, haben intakte Open Reading Frames (ORF) und wenig oder keinen Se-quenzunterschied zwischen den flankierenden LTRs, welche bei der Integration absolut iden-tisch sind (Belshaw und Tristem 2009). Trotzdem konnten bisher keine replikationskompeten-ten endogenen HERVs im menschlichen Genom identifiziert werden, was vermuten lässt, dass es einen Postentry/ Preintegration Block gibt. Zur genaueren Untersuchung möglicher Rest-riktionsprozesse von HERV-K(HML-2) wurden Methoden und Infektionsversuche etabliert, um Prozesse der Reversen Transkription und des Kerneintritts genauer zu analysieren.
Um die Sensitivität für Infektionsexperimente zu verstärken, wurde hierfür zunächst das auf dem HERV-Kcon- Molekularklon codierte EGFP-Reportergen gegen die Luciferase ausge-tauscht. Anhand eines Infektionsexperimentes konnte für beide Reportersysteme gezeigt wer-den, dass bei den humanen Zelllinien HEK293T und HeLa eine stabile Reporteraktivität nach-gewiesen werden kann. Dies lässt nicht nur eine stabile Integration des Reportergens vermu-ten, sondern spricht auch dafür, dass Prozesse auf Ebene des Kerneintritts erfolgreich durch-laufen werden.
Des Weiteren wurden die Reporterviren zur Identifikation zellulärer Restriktionsfaktoren ein-gesetzt. In Anlehnung an ein Infektionsexperiment von Kramer et al. sollte die Hypothese über-prüft werden, ob es zelluläre Restriktionen gegen HERV-K(HML-2) gibt, welche durch Koinfektion mit einem anderen Virus aufgehoben werden können. Der Effekt der Inhibitorsättigung, welcher in der Vergangenheit mit CMVoriLuc-basierten Reporterviren beobachtet wurde, konnte im Rahmen des Experiments mit HERV-Kcon nicht nachgewiesen werden (Kramer et al. 2016).
Zudem wurden Prozesse auf Ebene der Reversen Transkription näher untersucht. Hierzu galt es virale cDNA als Produkt der reversen Transkription nachzuweisen. Um zu verhindern, dass anstatt viraler cDNA kontaminierende Plasmid-DNA detektiert wird, wurde eine kurze Markersequenz in die U3-Region der 3´LTR eingefügt. Da diese während der Reversen Transkription durch intramolekulare Umlagerungen verdoppelt wird, ist diese in der viralen genomischen cDNA sowohl in der 3´LTR, als auch 5´LTR vorhanden und unterscheidet sich damit von der Sequenz der Plasmid-DNA. Mit dieser Methode konnte gezeigt werden, dass spezifisch virale cDNA in HEK293T nachgewiesen werden kann und die Mutation in der U3-Region als ein geeignetes Tool für den Nachweis viraler cDNA dient. Die Vermutung über Restriktionen auf Ebene der Reversen Transkription können damit für die humane Zelllinie HEK293T widerlegt werden.The human genome consists of 8% retroviral sequences. The HML-2 subfamily of HERV-K is the only lineage that has replicated in the human genome since the divergence between humans and chimpanzees. Many of the loci are not fixed in the human population, have intact open reading frames (ORF) and little or no sequence difference between the flanking LTRs, which are absolutely identical upon integration (Belshaw und Tristem 2009). Despite numerous studies, no replication-competent endogenous HERVs have yet been identified in the human genome, suggesting that there is a post-entry/pre-integration block. To precisely study possible restriction processes of HERV-K(HML-2), methods and infection experiments were established to analyze the process of reverse transcription and nuclear entry.
To improve the sensitivity for infection experiments, the EGFP-reporter gene encoded on the HERV-Kcon molecular clone was exchanged for the luciferase gene. Based on a long-term infection experiment, it was successfully demonstrated for each reporter system that stable reporter activity can be detected in the human cell lines HEK293T and HeLa. This not only indicates a stable integration of the reporter gene, but also suggests that processes at the level of nuclear entry are being successfully completed.
Furthermore, the reporter viruses were used to identify cellular restriction factors. In accordance with an infection experiment by Kramer et al., the hypothesis was verified whether there are cellular restrictions against HERV-K(HML-2), which can be abrogated by coinfection with another virus. The effect of inhibitor saturation, which was observed in the past with CMVoriLuc-based reporter viruses, could not be demonstrated in the infection experiment with HERV-Kcon (Kramer et al. 2016).
In addition, processes at the level of reverse transcription were investigated. The aim was to detect viral cDNA as a product of reverse transcription. To prevent contaminating plasmid DNA from being detected instead of viral cDNA, a short marker sequence was inserted into the U3-region of the 3'LTR. Since the mutated sequence is duplicated during reverse transcription by intramolecular rearrangements, it is present in both, the 3'LTR and 5'LTR, and can thus be distinguished from the contaminating plasmid DNA. This method successfully demonstrated that the mutation in the U3-region is an effective tool to specifically detect viral cDNA by a PCR system. The hypothesis about restrictions at the level of reverse transcription can thus be disproved for the cell line HEK293T
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