198 research outputs found
Remembering ICC 16
No full textCitation: Hohn, K. (2016). Remembering ICC 16. Catalysts, 6(10), 1. doi:10.3390/catal6100153Every four years, a group of outstanding individuals, the best in their field, come together from all over the world. These individuals have spent years learning their craft, and now they assemble to show what they can do. Such a gathering happened in 2016
Catalysts-Looking Back and Peering Ahead
No full textCitation: Hohn, K. L. (2017). Catalysts-Looking Back and Peering Ahead. Catalysts, 7(2), 1. doi:10.3390/catal7020041I am pleased to report on the latest happenings at Catalysts. It is gratifying to me to look back at where we’ve been and what we’ve accomplished, but also inspiring to peer ahead to how we will grow and improve
Feature papers to celebrate the landmarks of catalysts
No full textCitation: Hohn, K. L. (2015). Feature papers to celebrate the landmarks of catalysts. Catalysts, 5(4), 2018-2023. doi:10.3390/catal5042018Catalysis is a critical scientific field that underpins much of the world’s chemical industry. For example, it is often quoted that catalysis plays a role in 90% of all industrial chemical products. This importance has led to numerous academic journals and specialized conferences on the subject, as practitioners seek outlets to publish their cutting-edge research on catalysis
A New Year of Catalysts
No full textCitation: Hohn, K. L. (2016). A New Year of Catalysts. Catalysts, 6(1), 2. doi:10.3390/catal6010016Excerpt: Welcome to a new year of Catalysts, an international, peer-reviewed open access journal. From time to time, I like to write about the status of the journal: what milestones have been reached, what special issues will be coming out, what conferences we will partner with, etc. As we turn to the New Year, this seems like an opportune time to provide an update on Catalysts
What's in a Number?
No full textCitation: Hohn, K. L. (2015). What's in a Number? Catalysts, 5(3), 1304-1305. doi:10.3390/catal5031304People like to distill complicated phenomenon into easily digestible numbers. Whether it’s a top ten list of the best movies of all time, the shooting percentage of our basketball team’s star, or a student’s score on an exam, we like to quantify phenomenon that is unquantifiable. We like the comfort of a number which we can use as the basis for our decisions. This is an imperfect process, as underlying human behavior can, ultimately, not be boiled down to a single number. But we try anyway
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
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
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
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
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