Evaluation of major factors influencing the TBC topcoat formation in axial suspension plasma spraying (SPS)

Suspension plasma spraying (SPS) is ideally suited to produce porous or dense columnar, strain-tolerant thermal barrier coatings (TBCs) and also offers the possibility of producing other microstructures such as feathery and dense vertically cracked coatings. The specific properties of the TBC are significantly influenced by the formed microstructure, that is, affected by feedstock material and process parameters. In this work, the effects of various process parameters in the SPS process are investigated. It was found that the suspension feed rate has a significant effect on the microstructure, especially on the column density of the coating, whereas the suspension solids content mainly affects the coating porosity. Additionally, the surface roughness and topography of the bond coat are crucial for the formation of columnar coatings and were therefore investigated. Despite comparable roughness values for as-sprayed bond coats for high velocity oxy fuel and vacuum plasma spray produced coatings, the surface structures differ significantly from each other and affect the microstructure of the deposited topcoat. Characterization of mechanical properties by means of micro-indenter can be suitable for columnar coatings to determine Young's modulus within a column. However, due to the heterogeneity of the coating, the method is not suitable to describe the mechanical properties of the topcoat.     

Sintering behavior,microstructure and thermoelectric properties of calcium cobaltite thick films for transversal thermoelectric multilayer generators

The sintering behavior and the thermoelectric performance of Ca₃Co₄O₉ multilayer laminates were studied, and a multilayer thermoelectric generator was fabricated. Compacts and multilayer samples with anisotropic microstructure and residual porosity were obtained after conventional sintering at 920 °C, whereas dense and isotropic multilayer samples were prepared by firing at 1200 °C and reoxidation at 900 °C. A hot-pressed sample has a dense and anisotropic microstructure. Samples sintered at 920 °C exhibit low electrical conductivity due to the low density, whereas the Seebeck coefficient is not sensitive to preparation conditions. However, thermal conductivity of multilayers is very low, and, hence acceptable ZT values are obtained. A transversal multilayer thermoelectric generator (TMLTEG) was fabricated by stacking layers of Ca₃Co₄O₉ green tapes, AgPd conductor printing, and co-firing at 920 °C. The TMLTEG has a power output of 3 mW at ΔT = 200 K in the temperature interval of 25 °C to 300 °C.     

Combined TPS, XPS, EXAFS, and NO-TPD study of the sulfiding of Mo/Al2O3

The sulfiding of Mo/Al₂O₃ in H₂S/Ar versus in H₂S/H₂ has been studied by temperature-programmed sulfiding (TPS), X-ray photon electron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and temperature-programmed desorption of NO (NO-TPD). All the applied techniques agree on the sulfur content in the sulfided catalysts and the findings are in accord with a model for the H₂S production reaction. The nucleation and growth of well-ordered MoS₂ clusters are probed by XPS during sulfiding with and without the presence of hydrogen. The resulting dispersion of the MoS₂ phase is evaluated on the basis of XPS, EXAFS, and NO-TPD, and is found to be highest when the sulfiding occurs in the presence of hydrogen.     

Extraction Behavior of Americium and Curium on Selected Extraction Chromatography Resins from Pure Acidic Matrices

Due to the similar chemical properties between the neighboring trivalent actinide elements americium and curium, their extraction behavior is often perceived as indistinguishable. In this work, the characterization of seven extraction chromatography resins (TEVA, TRU, DGA(N), Actinide, Ln, Ln2, and Ln3) for these trivalent actinides from acidic matrices (HNO₃, HCl, and HBr) has provided some evidence to the contrary. In most cases, Am(III) and Cm(III) exhibit identical extraction properties. However, separation is possible with TRU and DGA(N) resins as demonstrated in this study. The extraction shows a strong dependency on the specific anion in solution that follows the order NO₃^?>Br^?>Cl^?.     

Studies on the Effect of Physico‐Chemical Soot Properties and Feed Gas Composition on the Kinetics of Soot Oxidation on Fe2O3 Catalyst

Three commercial carbon black samples as well as self‐made C₃H₆ soot were investigated for their reactivity in the oxidation on an α‐Fe₂O₃ catalyst. These studies were performed by temperature programmed oxidation (TPO) using a packed bed. For reference purposes, TPO studies in the absence of the catalyst were made as well. The carbon black samples were characterized towards the content of C, H, N and O as well as higher heating value, specific surface area, moisture and volatile matter and were deemed to be suitable model substances for diesel soot of different maturity. The correlation of these physico‐chemical properties with the kinetics in catalytic TPO indicated that the soot oxidation on Fe₂O₃ is significantly affected by the initial number of surface oxygen compounds of the soot. The decomposition of these surface species causes the formation of active carbon sites, which are supposed to accelerate the soot oxidation.     

The cytotoxicity of fatty acid/α‐lactalbumin complexes depends on the amount and type of fatty acid

Complexes of the milk protein, α‐lactalbumin, and the fatty acid, oleic acid, have previously been shown to be cytotoxic. Complexes of α‐lactalbumin and five different fatty acids (vaccenic, linoleic, palmitoleic, stearic, and elaidic acid) were prepared and compared to those formed with oleic acid. All complexes were cytotoxic to human promyelocytic leukemia‐derived (HL‐60) cells but to different degrees depending on the fatty acid. The amount of fatty acid per α‐lactalbumin molecule was found to correlate with the cytotoxicity; the higher the number of fatty acids per protein, the more cytotoxic the complex. Importantly, all the tested fatty acids were also found to be cytotoxic on their own in a concentration dependent manner. The cytotoxic effect of complexes between α‐lactalbumin and linoleic acid, vaccenic acid, or oleic acid was further investigated using flow cytometry and found to induce cell death resembling apoptosis on Jurkat cells. Practical applications: Cytotoxic complexes of α‐lactalbumin and several different fatty acids could be produced. The cytotoxicity of all the variants is similar to that previously determined for α‐lactalbumin/oleic acid complexes.     

Aqueous heterophase polymerization of styrene—a study by means of multi-angle laser light scattering

An online multi-angle laser light scattering study of ab initio surfactant-free styrene emulsion polymerization reveals unexpected results regarding the development of the dispersity during the whole reaction starting from mixing styrene and water at reaction temperature. The experimentally observed change in the dispersity, which is an indirect measure of the average characteristic size of the colloidal objects, allows the identification of three characteristic intervals. During interval A the equilibration of styrene in water is characterized by the formation of styrene domains, which increase in number and size until an equilibrium state is reached. This means that there is virtually no homogeneous/molecular styrene in water solution but rather nanodroplets of about 200 nm in diameter (assuming spherical shape) are formed. During interval B, after initiation of the polymerization and particle formation, the dispersity increases again as the average size decreases and the number of scattering objects increases. The polymer particles suck up the monomer from the monomer nanodroplets, which leads to the disappearance of the nanodroplets and to a decrease in the average size. During interval C the average size increases again due to the predominantly growth of the polystyrene particles.     

Impact of Spatially Heterogeneous Trop-2 Expression on Prognosis in Oral Squamous Cell Carcinoma

Oral cancer often presents with aggressive behavior and a high risk of recurrence and metastasis. For oral squamous cell carcinoma (OSCC), which is the most frequent histological subtype, therapy strategies include surgery, radiation therapy, chemotherapy, immune checkpoint inhibitors, and EGFR inhibitors. Recently, a Trop-2 antibody-drug conjugate (ADC) has been approved in the United States of America for the treatment of advanced triple-negative breast cancer. However, this ADC has also been tested in other solid tumors including head & neck squamous cell carcinoma. The prognostic impact of Trop-2 has already been reported for several cancers. We studied the prognostic influence of Trop-2 protein expression on OSCC patients’ survival. The cohort comprised n = 229 OSCC patients with available archived tumor tissue and corresponding non-neoplastic oral mucosa tissue. Using immunohistochemistry, we investigated Trop-2 expression in both the central and peripheral regions of each tumor and in corresponding non-neoplastic oral mucosa. In patients suffering from OSCC with combined high central and low peripheral Trop-2 expression, five-year overall survival (OS) was 41.2%, whereas 55.6% of OSCC patients who presented lower central and/or higher peripheral tumoral Trop-2 expression were alive after five years (p = 0.075). In multivariate Cox regression, the expression pattern of high central tumoral and lower peripheral Trop-2 expression was significantly correlated with impaired OS (HR = 1.802, 95%-CI: 1.134–2.864; p = 0.013) and recurrence-free survival (RFS) (HR = 1.633, 95%-CI: 1.042–2.560; p = 0.033), respectively, when adjusting for co-variables. Hence, Trop-2 may serve as an independent prognostic biomarker in OSCC. In subsequent studies, the pathophysiological meaning of downregulated Trop-2 expression in the OSCC periphery has to be analyzed.     

New inhibitors of the Tat-TAR RNA interaction found with a "fuzzy" pharmacophore model

TAR RNA is a potential target for AIDS therapy. Ligand-based virtual screening was performed to retrieve novel scaffolds for RNA-binding molecules capable of inhibiting the Tat-TAR interaction, which is essential for HIV replication. We used a "fuzzy" pharmacophore approach (SQUID) and an alignment-free pharmacophore method (CATS3D) to carry out virtual screening of a vendor database of small molecules and to perform "scaffold-hopping". A small subset of 19 candidate molecules were experimentally tested for TAR RNA binding in a fluorescence resonance energy transfer (FRET) assay. Both methods retrieved molecules that exhibited activities comparable to those of the reference molecules acetylpromazine and chlorpromazine, with the best molecule showing ten times better binding behavior (IC50 = 46 microM). The hits had molecular scaffolds different from those of the reference molecules.