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Liquid-filled pores of Fischer-Tropsch catalyst lead to slow diffusion of the reactants and can cause internal transport limitations leading to a significant decrease of selectivity and productivity. As an approach to overcome these limitations, transport pores can be added to provide an additional pathway for mass transport. In this work, a 3D isothermal model was developed, which takes the effect of concentration gradients within the transport pores into account. A comparison with a 1D model showed, that a description by a 3D model is necessary for transport pores with diameters larger than 10 µm.

High-throughput sequencing has emerged as the favoured method to study microRNA (miRNA) expression, but biases introduced during library preparation have been reported. To assist researchers choose the most appropriate library preparation kit, we recently compared the performance of six commercially-available kits on synthetic miRNAs and human RNA, where library preparation was performed by the vendors. We hereby supplement this study with data from two further commonly used kits (NEBNext, NEXTflex) whose manufacturers initially declined to participate. As before, performance was assessed with respect to sensitivity, reliability, titration response and differential expression. Despite NEXTflex employing partially-randomised adapter sequences to minimise bias, we reaffirm that biases in miRNA abundance are kit-specific, complicating the comparison of miRNA datasets generated using different kits.

The automated reaction mechanism generator (RMG) is used to investigate the methanation of CO2 on the Ni(111) and Ni(211) surface. Linear scaling relations are applied for the thermochemistry of the adsorbates, which are compared to state-of-the-art electronic structure calculations and show a reasonable predictability. RMG discovers nearly the same amount of species and reactions for both facets. However, a reaction path analysis in a reactor simulation shows that the reaction pathways on both surfaces differ significantly, which is caused by the difference in the binding energy of the adsorbates. Reactor simulations reveal a lower methane production rate compared to experiments obtained in a Berty reactor with a Ni/Al2O3 catalyst, which is a result of a high surface coverage with CO⁎ and demands, therefore, the inclusion of a coverage dependent heat of formation of the adsorbates.

Kod proizvodnje energije iz obnovljivih izvora, u posljednje se vrijeme poseban naglasak posvećuje proizvodnji biovodika iz različitih vrsta biomase procesom tamne fermentacije. Tamna fermentacija je proces s niskom ugljičnom bilancom, kojem niska učinkovitost pretvorbe supstrata u vodik i nezadovoljavajuća stabilnost procesa u kontinuiranom režimu rada zasad još uvijek ograničavaju učinkovit prijenos procesa na komercijalnu razinu. Iz tog su razloga trenutačna istraživanja usmjerena na proučavanje postupaka za povećanje učinkovitosti procesa anaerobne mikrobne razgradnje organskih tvari te istovremeno i optimiranje proizvodnje biovodika kao konačnog produkta. Istraživanja su usmjerena na testiranje različitih otpadnih organskih sirovina kao supstrata za proizvodnju biovodika, među kojima izraziti potencijal pokazuju otpadna hrana, poluproizvodi iz prehrambene industrije te organski otpad iz kućanstva. Na proizvodnju vodika utječu brojni okolišni i procesni čimbenici, kao i izvor te predpriprema djelujućih anaerobnih mikroorganizama. Danas se najviši prinosi vodika ostvaruju kada se mikrobna zajednica koja potječe iz metanogenog bioreaktora izlaže termičkoj obradi pri temperaturi 80 °C tijekom nekoliko sati. Tijekom termičke obrade, uništavaju se metanogene arheje, a vodiko-producirajuće bakterije (prije svega vrste iz roda Clostridium i Baciullus) pri tome sporuliraju i dalje prelaze u vegetativni oblik pri procesnoj temperaturi od 37 °C, koja je optimalna za proizvodnju vodika. Proizvodnju vodika također pospješuje i imobilizacija bakterija na različite nosače kao što su aktivni ugljen i ekspandirana glina. Trenutna su istraživanja usmjerena prije svega na dizajniranje proizvodnje biovodika pri niskim pH vrijednostima (4±2), odnosno u području gdje je proizvodnja tehnološki i ekonomski najpovoljnija. Visoke prinose i stabilnu proizvodnju vodika istraživači su postigli ne samo na modelnom supstratu – glukozi, već i primjenom kuhinjskog otpada kao supstrata (168 NL H2/kg organske tvari). Godišnje u EU kao otpad završi gotovo 88 milijuna tona hrane tako da poljoprivredno- prehrambena proizvodnja značajno utječe na emisije CO2. Stoga se kao jedna od mogućnosti smanjenja tih emisija nameće konverzija otpadne hrane u biovodik, jedan od najčišćih energenata.

Communication strategies for complex problems in the field of chemical and process engineering is becoming more and more important. Especially computational fluid dynamics (CFD) results require well-established spatial reasoning skills. In this contribution, we show how we implemented virtual reality (VR) into the Master course “CFD for process engineering” at Clausthal University of Technology. We discuss advantages and disadvantages of applying VR during the course. In addition, we show how VR can enable students to get a thorough understanding of the interplay between reactor design and performance.

In this contribution, we present a detailed three-dimensional computational fluid dynamics (CFD) model of a fixed-bed reactor processing the catalytic CO2 methanation reaction. Due to the small tube-to-particle-diameter ratio, particle-resolved CFD simulations are carried out, since they can locally account for transport phenomena, i.e. momentum, heat, and mass transfer. In addition to the interstitial flow simulation, three-dimensional diffusion plus reaction is modelled inside the catalytic pellets. The comparison in terms of axial temperature with a one-dimensional model shows the discrepancy between the models. Additional CFD simulations with different pellet shapes show that the shape has little influence on the heat transfer in these slender fixed-bed arrangements. Experimental results of axial concentration profiles will further validate the CFD model.

Chromatin immunoprecipitation (ChIP) enables mapping of specific histone modifications or chromatin-associated factors in the genome and represents a powerful tool in the study of chromatin and genome regulation. Importantly, recent technological advances that couple ChIP with whole-genome high-throughput sequencing (ChIP-seq) now allow the mapping of chromatin factors throughout the genome. However, the requirement for large amounts of ChIP-seq input material has long made it challenging to assess chromatin profiles of cell types only available in limited numbers. For many cell types, it is not feasible to reach high numbers when collecting them as homogeneous cell populations in vivo. Nonetheless, it is an advantage to work with pure cell populations to reach robust biological conclusions. Here, we review (a) how ChIP protocols have been scaled down for use with as little as a few hundred cells; (b) which considerations to be aware of when preparing small-scale ChIP-seq and analyzing data; and (c) the potential of small-scale ChIP-seq datasets for elucidating chromatin dynamics in various biological systems, including some examples such as oocyte maturation and preimplantation embryo development. This article is categorized under: Laboratory Methods and Technologies > Genetic/Genomic Methods Developmental Biology > Developmental Processes in Health and Disease Biological Mechanisms > Cell Fates.

Die ortsaufgeloste Modellierung von katalytischen Festbetten mit kleinem Rohr‐zu‐Pelletdurchmesser‐Verhaltnis wird hinsichtlich Morphologie, resultierender Geschwindigkeiten, Warmetransport und heterogener Katalyse untersucht und experimentalen Daten gegenubergestellt.

One of the major issues for particle-resolved CFD simulations of fixed beds are particle–particle and particle–wall contacts. A fixed bed of cylinders is studied with different local contact modifications (i.e., caps and bridges method for line and area contacts, and caps and united method for overlaps resulting from composite DEM particles). Effects are analyzed regarding pressure drop, local velocity, and local heat transfer for 191 < Rep < 763. Modeling particle–wall contacts is becoming more important with increasing Rep. Contact modifications inside the bed are becoming less important because convective heat transfer is dominant. The stable caps method shows promising results in comparison with heat-transfer predictions. However, it overestimates convective heat transfer in the contact regions for high flow rates. The bridges method shows good results for pressure drop and heat-transfer predictions. A difficulty remains the choice of the thermal conductivity of these bridges.

Epigenetic modifications are expected to occur at a much faster rate than genetic mutations, potentially causing isolated populations to stochastically drift apart, or if they are subjected to different selective regimes, to directionally diverge. A high level of genome‐wide epigenetic divergence between individuals occupying distinct habitats is therefore predicted. Here, we introduce bisulfite‐converted restriction site associated DNA sequencing (bsRADseq), an approach to quantify the level of DNA methylation differentiation across multiple individuals. This reduced representation method is flexible in the extent of DNA sequence interrogated. We showcase its applicability in three natural systems, each comprising individuals adapted to divergent environments: a diploid plant (Heliosperma, Caryophyllaceae), a tetraploid plant (Dactylorhiza, Orchidaceae) and an animal (Gasterosteusaculeatus, Gasterosteidae). We present a robust bioinformatic pipeline, combining tools for RAD locus assembly, SNP calling, bisulfite‐converted read mapping and DNA methylation calling to analyse bsRADseq data with or without a reference genome. Importantly, our approach accurately distinguishes between SNPs and methylation polymorphism (SMPs). Although DNA methylation frequency between different positions of a genome varies widely, we find a surprisingly high consistency in the methylation profile between individuals thriving in divergent ecological conditions, particularly in Heliosperma. This constitutive stability points to significant molecular or developmental constraints acting on DNA methylation variation. Altogether, by combining the flexibility of RADseq with the accuracy of bisulfite sequencing in quantifying DNA methylation, the bsRADseq methodology and our bioinformatic pipeline open up the opportunity for genome‐wide epigenetic investigations of evolutionary and ecological relevance in non‐model species, independent of their genomic features.

Chemie 4.0 und Diesel‐Fahrverbot - die technische Chemie setzt zunehmend auf modulare Anlagen auf Basis von Mikroverfahrenstechnik und Flow Chemistry, um die Produktion von Chemikalien flexibler zu gestalten. Zudem forciert sie die Anstrengungen in der Emissionskontrolle, insbesondere in der Abgasnachbehandlung von Verbrennungsmotoren.

With antimicrobial drug resistance becoming an increasing burden on human health, much attention has been focused on the potential use of bacteriophages and their enzymes as therapeutics. However, the investigations into the physiology of the complex interactions of bacteriophages with their hosts have attracted far less attention, in comparison. This work describes the molecular characterization of the infectious cycle of a bacteriophage in the important human pathogen Streptococcus pneumoniae and explores the intricate relationship between phase-variable host defense mechanisms and the virus. This is the first report showing how a phase-variable type I restriction-modification system is involved in bacteriophage restriction while it also provides an additional level of infection control through abortive infection., Virus-host interactions are regulated by complex coevolutionary dynamics. In Streptococcus pneumoniae, phase-variable type I restriction-modification (R-M) systems are part of the core genome. We hypothesized that the ability of the R-M systems to switch between six target DNA specificities also has a key role in preventing the spread of bacteriophages. Using the streptococcal temperate bacteriophage SpSL1, we show that the variants of both the SpnIII and SpnIV R-M systems are able to restrict invading bacteriophage with an efficiency approximately proportional to the number of target sites in the bacteriophage genome. In addition to restriction of lytic replication, SpnIII also led to abortive infection in the majority of host cells. During lytic infection, transcriptional analysis found evidence of phage-host interaction through the strong upregulation of the nrdR nucleotide biosynthesis regulon. During lysogeny, the phage had less of an effect on host gene regulation. This research demonstrates a novel combined bacteriophage restriction and abortive infection mechanism, highlighting the importance that the phase-variable type I R-M systems have in the multifunctional defense against bacteriophage infection in the respiratory pathogen S. pneumoniae. IMPORTANCE With antimicrobial drug resistance becoming an increasing burden on human health, much attention has been focused on the potential use of bacteriophages and their enzymes as therapeutics. However, the investigations into the physiology of the complex interactions of bacteriophages with their hosts have attracted far less attention, in comparison. This work describes the molecular characterization of the infectious cycle of a bacteriophage in the important human pathogen Streptococcus pneumoniae and explores the intricate relationship between phase-variable host defense mechanisms and the virus. This is the first report showing how a phase-variable type I restriction-modification system is involved in bacteriophage restriction while it also provides an additional level of infection control through abortive infection.