Feasibility of fluidized bed reactor systems for pressurized chemical looping combustion of natural gas

Chemical looping combustion (CLC) of natural gas at atmospheric pressure has been successfully demonstrated at technical laboratory scale (120 kWth) since 2009 (1,2). Scale-up studies to 10 MWth have been presented (3,4), but no pilot or demonstration projects have been executed so far. Instead, researchers have recently concentrated their activities on CLC of solid fuels (5). One reason for this is the deployment challenge for natural gas CLC power plants. State-of-the-art gas-turbine combined cycle (GT-CC) plants reach high electric efficiencies up to 60% and are superior to steam cycle concepts even if post combustion CO2 capture is applied. On the other hand, all the early studies on CLC focused on efficiency increase for GT-CC plants through application of CLC (6,7). The present contribution therefore seeks to address this mismatch and to assess the practical potential of natural gas CLC for power production. A principal baseline is the application of atmospheric pressure CLC and steam cycle power generation reaching electric efficiencies up to 45% dependent on steam parameters and plant size. In order to reach higher electric efficiencies, pressurized CLC and gas turbine cycles would need to be implemented. Fluidized bed systems have been proposed for CLC (8) and preferred so far for they combine good heat management and continuous operation. If CLC is used in combination with gas turbines, at increased pressure, the operation of fluidized bed systems is challenging. Process configurations have been compared based on mass- and energy balances and basic design calculations have been carried out based on fluidization engineering methods. It turns out that high gas turbine efficiencies can only be reached if turbine inlet conditions are sufficiently high and relative pressure losses are within reasonable limits. Based on the results of the present work, the efficiencies of CLC based power generation cycles remainsignificantly lower than standard GT-CC efficiencies without CO2 capture. An optimal range of operating conditions can be identified for operation of a pressurized CLC plant with increased efficiency and design considerations for a dual circulating fluidized bed reactor system are reported. Such systems are characterized by solids transport ducts and loop seals of increased dimensions relative to atmospheric pressure systems. Accordingly, also the fluidization gas (steam) demand for loop seals is relatively increased for pressurized systems. The outcome of this work may serve as a general basis for techno-economic evaluation of pressurized CLC systems for power generation. Please click Additional Files below to see the full abstract

Impact of hydrogel stiffness on differentiation of human adipose-derived stem cell microspheroids

Hydrogels represent an attractive material platform for realization of three-dimensional (3D) tissue-engineered constructs, as they have tunable mechanical properties, are compatible with different types of cells, and resemble elements found in natural extracellular matrices. So far, numerous hydrogel-cartilage/bone tissue engineering (TE)-related studies were performed by utilizing a single cell encapsulation approach. Although multicellular spheroid cultures exhibit advantageous properties for cartilage or bone TE, the chondrogenic or osteogenic differentiation potential of stem cell microspheroids within hydrogels has not been investigated much. This study explores, for the first time, how stiffness of gelatin-based hydrogels (having a storage modulus of 538, 3584, or 7263 Pa) affects proliferation and differentiation of microspheroids formed from telomerase-immortalized human adipose-derived stem cells (hASC/hTERT). Confocal microscopy indicates that all tested hydrogels supported cell viability during their 3- to 5-week culture period in the control, chondrogenic, or osteogenic medium. Although in the softer hydrogels cells from neighboring microspheroids started outgrowing and interconnecting within a few days, their protrusion was slower or limited in stiffer hydrogels or those cultured in chondrogenic medium, respectively. High expressions of chondrogenic markers (SOX9, ACAN, COL2A1), detected in all tested hydrogels, proved that the chondrogenic differentiation of hASC/hTERT microspheroids was very successful, especially in the two softer hydrogels, where superior cartilage-specific properties were confirmed by Alcian blue staining. These chondrogenically induced samples also expressed COL10A1, a marker of chondrocyte hypertrophy. Interestingly, the hydrogel itself (with no differentiation medium) showed a slight chondrogenic induction. Regardless of the hydrogel stiffness, in the samples stimulated with osteogenic medium, the expression of selected markers RUNX2, BGLAP, ALPL, and COL1A1 was not conclusive. Nevertheless, the von Kossa staining confirmed the presence of calcium deposits in osteogenically stimulated samples in the two softer hydrogels, suggesting that these also favor osteogenesis. This observation was also confirmed by Alizarin red quantification assay, with which higher amounts of calcium were detected in the osteogenically induced hydrogels than in their controls. The presented data indicate that the encapsulation of adipose-derived stem cell microspheroids in gelatin-based hydrogels show promising potential for future applications in cartilage or bone TE. Impact Statement Osteochondral defects represent one of the leading causes of disability in the world. Although numerous tissue engineering (TE) approaches have shown success in cartilage and bone tissue regeneration, achieving native-like characteristics of these tissues remains challenging. This study demonstrates that in the presence of a corresponding differentiation medium, gelatin-based hydrogels support moderate osteogenic and excellent chondrogenic differentiation of photo-encapsulated human adipose-derived stem cell microspheroids, the extent of which depends on hydrogel stiffness. Because photosensitive hydrogels are a convenient material platform for creating stiffness gradients in three dimensions, the presented microspheroid-hydrogel encapsulation strategy holds promise for future strategies of cartilage or bone TE

Polymer architecture as key to unprecedented high-resolution 3D-printing performance : the case of biodegradable hexa-functional telechelic urethane-based poly-ε-caprolactone

Two-photon polymerization (2PP) is a high-resolution 3D-printing technology with a very rapidly expanding field of applications, including tissue engineering (TE). In this field, 2PP offers unprecedented possibilities for systematic studies of both cell–cell and cell–material interactions in 3D. For TE applications, the reliable production of biodegradable micro-scaffolds in porous, complex architectures is essential. However, the number of biodegradable materials that support the required level of spatial resolution is very limited, being a major bottleneck for the use of 2PP in the TE field. Herein, we introduce a hexa-functional urethane-based biodegradable precursor that overcomes the limitations associated with the high-resolution printing of current biodegradable precursors. The precursor is a telechelic urethane-based poly-ε-caprolactone (PCL) possessing three acrylate functionalities at each polymer end group which enables the reliable production of complex architectures owing to its superior physical properties as compared to the traditional di-acrylate terminated analogs. The newly developed hexa-functional telechelic urethane-based PCL reveals enhanced crosslinking kinetics and one order of magnitude higher Young’s modulus compared to the di-functional precursor (57.8 versus 6.3 MPa), providing an efficient and solvent-free 2PP processing at fast scanning speeds of up to 100 mm s−1 with unprecedented feature resolutions (143 ± 18 nm at 100 mm s−1 scanning speed). The crosslinked hexa-functional polymer combines strength and flexibility owing to the segregation between its hard polyacrylate and soft PCL segments, which makes it suitable for biological systems in contrast to the highly crosslinked and rigid structures typically manufactured by 2PP. Furthermore, it revealed lower degradation rate compared to its di-functional analog, which can be considered as an advantage in terms of biocompatibility due to the slower formation of acidic degradation products. Extracts of the developed polymers did not show a cytotoxic effect on the L929 fibroblasts as confirmed via ISO 10993-5 standard protocol. The presented precursor design constitutes a simple and effective approach that can be easily translated towards other biodegradable polymers for the manufacturing of biodegradable constructs with nano-scale precision, offering for the first time to use the true capabilities of 2PP for TE applications with the use of synthetic biodegradable polymers

Energy management (Renewable Energy)

Agrarische Roh- und Reststoffe können zur Bereitstellung von Biotreibstoffen für mobile An-wendungen (z.B.: Biodiesel, Biomethan, Bioethanol, …), von Strom und Wärme (z.B.: über Biogasproduktion mit anschließender Verstromung) sowie von Wärme (über Verbrennung) eingesetzt werden. Alternativ kann der Anbau von Feldfrüchten unter Photovoltaikpaneelen erfolgen, welcher eine Mehrfachnutzung des Bodens ermöglicht und zur Entschärfung der Flächenkonkurrenz beiträgt. Die Strategien einer stofflichen und energetischen Nutzung von Ackerfrüchten als Substitut fossiler Rohstoffe stehen teilweise in Konkurrenz zur Lebensmit-telproduktion. In eine nachhaltige Nutzungsstrategie müssen die Biomassepotentiale in Pro-duktionssystemen mit dem Ziel der Erfüllung der 4F (Food, Feed, Fiber and Fuels) genutzt werden.Agricultural raw and waste materials can be used to produce biofuels for transport (e.g. bio-diesel, biomethane, bioethanol, etc.), as well as electricity and heat (e.g. from biogas produc-tion with subsequent combustion in a gas engine, heat from incineration). Alternatively, culti-vating crops under photovoltaic panels allows shared usage of soil and eases land use com-petition. Substituting fossil resources with the material and energetic utilization of crops can-not be achieved without competing with food production. A sustainable utilization strategy must implement the biomass potentials with the goal of fulfilling the 4Fs (food, feed, fiber and fuels)

Effects of a single administration of prostaglandin F2alpha, or a combination of prostaglandin F2alpha and prostaglandin E2, or placebo on fertility variables in dairy cows 3–5 weeks post partum, a randomized, double-blind clinical trial

BACKGROUND: Delayed uterine involution has negative effects on the fertility of cows; use of prostaglandin F2alpha alone as a single treatment has not been shown to consistently improve fertility. Combined administration of PGF2alpha and PGE2 increased uterine pressure in healthy cows. We hypothesized, that the combination of both prostaglandins would accelerate uterine involution and have, therefore, a positive effect on fertility variables. In commercial dairy farming, the benefit of a single post partum combined prostaglandin treatment should be demonstrated. METHODS: 383 cows from commercial dairy farms were included in this study. Uterine size and secretion were evaluated at treatment 21–35 days post partum and 14 days later. Cows were randomly allocated to one of three treatment groups: PGF2alpha and PGE2, PGF2alpha or placebo. For every animal participating in the study, the following reproduction variables were recorded: Interval from calving to first insemination, days open, number of artificial inseminations (AI) to conception; subsequent treatment of uterus, subsequent treatment of ovaries. Plasma progesterone level at time of treatment was used as a covariable. For continuous measurements, analysis of variance was performed. Fisher's exact test for categorical non-ordered data and exact Kruskal-Wallis test for ordered data were used; pairwise group comparisons with Bonferroni adjustment of significance level were performed. RESULTS: There was no significant difference among treatment groups in uterine size. Furthermore, there was no significant difference among treatments concerning days open, number of AI, and subsequent treatment of uterus and ovaries. Days from calving to first insemination tended to be shorter for cows with low progesterone level given PGF2alpha and PGE2 in combination than for the placebo-group (P = 0.024). CONCLUSION: The results of this study indicate that the administration of PGF2alpha or a combination of PGF2alpha and PGE2 21 to 35 days post partum had no beneficial effect upon measured fertility variables. The exception was a tendency for a shorter interval from calving to first insemination after administration of the combination of PGF2alpha and PGE2, as compared to the placebo group. Further research should be done in herds with reduced fertility and/or an increased incidence of postpartum vaginal discharge

La formation des pharmaciens à Zurich. Bähler-Borner (Andrea), Die akademische Ausbildung der Apotheker im Kanton Zürich bis 1990. Die Entwicklung des Apothekerberufs von einer handwerklichen zu einer wissenschaftlichen Disziplin. Publications de la Société suisse d’histoire de la pharmacie, vol. 31, Berne, 2013

Zerobin Kleist Claudia. La formation des pharmaciens à Zurich. Bähler-Borner (Andrea), Die akademische Ausbildung der Apotheker im Kanton Zürich bis 1990. Die Entwicklung des Apothekerberufs von einer handwerklichen zu einer wissenschaftlichen Disziplin. Publications de la Société suisse d’histoire de la pharmacie, vol. 31, Berne, 2013. In: Revue d'histoire de la pharmacie, 101e année, N. 382, 2014. pp. 266-267

Hydrogele auf Basis von Hyaluronsäure

Abweichender Titel nach Übersetzung der Verfasserin/des VerfassersHydrogele spielen eine große Rolle im Bereich der Biomaterialien, wobei diese bereits weitgehend für die Geweberekonstruktion (tissue engineering) genutzt werden. Beschädigtes oder entferntes Gewebe kann mithilfe dieser Hydrogele ersetzt werden, da diese Materialien ähnliche physikochemische Eigenschaften zu extrazellulärer Matrix zeigen. Wegen ihrer Durchlässigkeit für Nährstoffe und ihrem hohen Wassergehalt werden sie besonders oft zur Weichgeweberegeneration verwendet. Damit Zelladhäsion und proliferation innerhalb einer Matrix entsprechend stattfinden kann, sind nebst anderen Faktoren definierte strukturelle Eigenschaften dieser Hydrogele notwendig. Über generative Fertigungsverfahren, vor allem Zwei Photonen Polymerisation (2PP), können Gewebestrukturen mit diesen Anforderungen hergestellt werden. 2PP erlaubt im Speziellen die hochauflösende Fertigung von photopolymerisierbaren Makromolekülen (Präkursoren) basierend auf natürlichen Polymeren. Aufgrund der hohen Transparenz von biologischem Gewebe bezüglich des verwendeten gepulsten Nah Infrarot Lasers können hohe Eindringtiefen bei gleichzeitig geringem Schaden der umgebenden Matrix erreicht werden. Obwohl bereits eine Vielzahl an unterschiedlichen Präkursoren (z.B. Meth(acrylate)) entwickelt wurden, weisen diese gewisse Nachteile wie Zytotoxizität innerhalb der extrazellulären Matrix auf. Innerhalb dieser Arbeit wurden neu entwickelte Präkursoren basierend auf Hyaluronsäure (HA) über eine enzymatische Umesterung mit Divinyladipat synthetisiert. HA Präkursoren, die mit Vinylester modifiziert wurden (HAVE), weisen verglichen mit Meth(acrylaten) eine höhere Biokompatibilität auf. Eine effektive Vernetzung von HAVE kann durch die Zugabe von Thiolen zu der Präkursorformulierung erreicht werden (Thiol-En Chemie). Die langsame Homopolymerisation der HAVE wird somit über die Einführung von multifunktionellen Thiolen überwunden. Unterschiedliche Thiole und deren Effekt auf die Hydrogelmatrix konnten somit untersucht werden. Mittels photorheologische Studien wurde außerdem der Beitrag von HAVE Makromolekülen auf die viskoelastischen Eigenschaften der Hydrogele untersucht. Anhand des Verlaufes des Speichermoduls wurde der Einfluss von Makromergröße, Substitutionsgrad, Makromergehalt und Art des Thiols auf die Vernetzungsdichte und die Reaktivität der Formulierung untersucht. Über die Synthese von HAVE ist es möglich, die mechanischen Eigenschaften von Hydrogelen anhand ihrer Kettenlänge und Nummer der polymerisierbaren Gruppen anzupassen. Zusätzlich wurde ein neues Konzept vorgestellt, bei dem HAVE in Kombination mit Kollagen als interpenetrierendes Netzwerk verwendet wurde. Außerdem wurden mit 2PP Zellen in eine HAVE Hydrogelmatrix eingebettet und deren Überleben untersucht.Hydrogels are an important class of biomaterials, widely used in tissue engineering. With these hydrogels, scientists aim to replace injured or removed functional tissue, because these materials show physicochemical similarity to extracellular matrix (ECM). Their permeability for nutrients, as well as their high water content are accounting for their application in soft tissue regeneration. Cells require amongst other factors, defined structural properties of hydrogels, to properly attach and proliferate within a matrix. Consequently, 3D fabrication of scaffolds can be realized by Additive Manufacturing Techniques, such as Two-Photon Polymerization (2PP). Macromolecules with natural origin, having photopolymerizable groups (precursors) can be fabricated via 2PP with high spatial resolution. The applied near-infrared laser offers high transparency towards biological tissues, being able to realize high penetration depth and little photo-damage of native matrices. Despite research has introduced a variety of different state of the art precursors [meth(acrylates)], these are potentially irritant and cytotoxic, when used as scaffolds to mimic ECM. Within this thesis, recently developed photopolymerizable precursors, based on hyaluronic acid (HA) were synthesized via an enzymatic transesterification reaction using divinyl adipate. Compared to their cytotoxic counterparts [meth(acrylates)], vinyl ester modified HA precursors (HAVE) show promising biocompatibility. The introduction of thiols into the precursor formulation enables effective crosslinking under high conversion using the concept of thiol ene chemistry. The slow homopolymerization rate of HAVE can thereby be overcome and multifunctional thiols can be used to study their effect on hydrogel matrices. The contribution of HAVE macromers on viscoelastic properties of hydrogels was investigated via photorheology. Based on the characteristics of the storage modulus, the effect of macromer size, degree of substitution, macromer content and type of thiol component on the crosslinking density, as well as on the reactivity of the formulation was investigated. Synthesized HAVE macromers, with different chain length and number of polymerizable groups on the HA backbone allow the fabrication of hydrogels with tailored mechanical properties. Additionally, a new approach was studied, to use HAVE in combination with collagen as interpenetrating network. Finally, cells were encapsulated via 2PP in the presence of HAVE macromers and their survival was studied.14

Photoinitiatoren und Monomere für die 2 Photonen Polymerisation

Abweichender Titel nach Übersetzung der Verfasserin/des VerfassersDer 3D Druck und besonders der Einsatz von Photopolymeren für die Geweberekonstruktion sind heutzutage von außerordentlicher Bedeutung für die Biomedizin. Bei der klassischen UV-Polymerisation wird hochenergetisches, kurzwelliges Licht angewandt, wobei es durch Absorption von biologischem Gewebe zur Schädigung von Zellen sowie Verbrennungen der Matrix kommen kann. Zwei-Photonen Polymerisation basiert auf der Technologie von gepulsten, fokussierten Infrarotlasern und ermöglicht aufgrund der Transparenz von biologischem Gewebe gegenüber dem eingesetzten Infrarotlicht, die Herstellung hoch aufgelöster, komplexer drei dimensionaler Strukturen mit einer minimalinvasiven Technik. Hierfür sind wasserlösliche Matrixkomponenten unabdingbar (Monomere sowie Photoinitiatoren), um natürliches Gewebe bestmöglich nachzubilden. Nicht nur die Wasserlöslichkeit, sondern auch ein hohes Maß an Biokompatibilität aller Matrixkomponenten sind für eine effiziente Zwei-Photonen Polymerisation in Gegenwart von Zellen unerlässlich. Außerdem kann es aufgrund von angeregten Zuständen der Photoinitiatoren und der Bildung von reaktiven Sauerstoffspezies zu erheblichem Schaden des umgebenden Gewebes kommen.Um diese Limitierungen zu reduzieren, befasst sich diese Arbeit mit der gezielten Entwicklung spaltbarer Photoinitiatoren. Getrieben durch die Freisetzung von Kohlenstoffdioxid bzw. Stickstoff können spaltbare funktionelle Gruppen die Bildung von reaktiven Sauerstoffspezies reduzieren und somit zu einer vielversprechenden Biokompatibilität beitragen. Nebst Photoinitiatoren werden in dieser Arbeit auch Makromere weiterentwickelt, die auf einem natürlich vorkommenden Polysaccharid basieren (Hyaluronsäure), um natürliches Gewebe in Form von Hydrogelen optimal nachzubilden. Im Gegensatz zu den bisherig entwickelten Photoinitiatoren, konnten zwei Klassen an spaltbaren Photoinitiatoren synthetisiert werden. Die erste Klasse an Photoinitiatoren wurde über die gezielte Einbindung spaltbarer Oximester Gruppen in bereits etablierte Zykloketon-Kernstrukturen erhalten und die zweite Klasse über die Einführung spaltbarer Azosulfonat Gruppen in einen kommerziell erhältlichen Azofarbstoff. Die Spaltbarkeit der Photoinitiatoren wurde mithilfe von Photoreaktor-studien überprüft, wobei vor allem auf die Fotoprodukte der Stilben-basierten Azosulfonate eingegangen wurde, die als Konkurrenz-reaktion eine außerordentliche Tendenz zur Photoisomerisierung aufweisen. Die Wirksamkeit beider Photoinitiator-klassen wurde mittels Zwei-Photonen Lithographie in Gelatine-basierten Makromeren bestätigt. Hierbei wurde vor allem der Schwellenwert der Polymerisation von Azosulfonaten bei verschiedenen Wellenlängen ermittelt. Zusätzlich konnte durch Stammzellenstudien eine hohe Biokompatibilität der Azosulfonate bewiesen werden. Die Makromere basierend auf Hyaluronsäure konnten sogar dafür verwendet werden, um in Gegenwart von Zellen komplexe 3D Hydrogele zu drucken. Demnach wurde die Entwicklung und Anwendung neuer Zwei-Photonen Initiatoren über die Inkorporation spaltbarer Funktionalitäten (Oximester, Azosulfonate) erfolgreich durchgeführt. Außerdem wurde Hyaluronsäure als hervorragende Basiskomponente für die Entwicklung von Hydrogelstrukturen bestätigt, sofern das Molekulargewicht der Wiederholungseinheit niedrig gehalten wird, um die Löslichkeit der Makromere zu bewahren.Three-dimensional printing and photopolymerization are powerful technologies for the reconstruction of tissue-like functional materials with great relevance for biomedicine. However, conventional high-energy lithographic techniques (UV-polymerization) exhibit considerable limitations, since the provided energy may induce collateral tissue damage along the irradiation pathway. The development of two-photon polymerization enabled the fabrication of hydrogel scaffolds with exceptional resolution, providing enough energy within the focal volume of a focused infrared laser to efficiently induce two-photon polymerization. The water-solubility of the matrix materials (monomers and photoinitiators) are of major importance for the reconstruction of tissue-like hydrogel scaffolds. Furthermore, the solubility in aqueous media and the biocompatibility of the compounds is essential for efficient two-photon polymerization in the presence of cells. Not only the compounds itself, but also the generation of reactive oxygen species, as a consequence of photoexcitation, are limiting factors regarding biocompatibility.The reduction of those limitations is targeted via a straightforward design of novel two-photon initiators and the association of cleavable moieties into pi-conjugated chromophores. The photolabile moieties could possibly reduce the formation of reactive oxygen species, due to their efficient dissociation mechanisms, while preserving biocompatibility. Furthermore, hyaluronic acid is investigated as endogenous substance for the development of hydrogel materials for tissue engineering. Two basic approaches were followed to synthesize cleavable two-photon initiators. On the one hand, photolabile oxime ester moieties were introduced into a well-established cycloketone core structure. On the other hand, photolabile azosulfonate moieties were incorporated into a commercially available azo dye. The photochemical behavior of the synthesized compounds was examined during comprehensive photoreactor studies, while focus was placed on the stilbene-based reference materials, which exhibited severe tendency towards photoisomerization. The efficiency of the novel two-photon initiators was confirmed via two-photon structuring tests in gelatin-based hydrogel formulations and the performance was compared to state-of the art initiators. Especially, the polymerization threshold of the azosulfonate-based two-photon initiators was studied in detail, since exceptionally stable hydrogel materials were obtained at various technically relevant femtosecond-laser wavelengths. Biocompatibility assays on various cell-lines proved their promising cytocompatibility. Finally, hyaluronic acid-based hydrogel formulations were successfully applied as material platform for three-dimensional cell encapsulation using two-photon polymerization. Summarizing, the association of photolabile groups (oxime esters, azosulfonates) to pi-conjugated chromophores was successful. Furthermore, hyaluronic acid was confirmed as promising candidate for the fabrication of tissue-like hydrogel materials as long as the molecular weight is kept moderate to ensure solubility in aqueous media.20