On the role of pre-existing defects and magnetic flux avalanches in the degradation of YBa2Cu3O7–x coated conductors by quenching

YBa₂Cu₃O_7–x (YBCO) coated conductors are emerging as an important option for magnets for energy systems and experimental science. One of the remaining challenges for YBCO superconducting magnets is quench protection, i.e. ensuring that the YBCO is not damaged due to a fault condition. One key issue is understanding the underlying causes of degradation during a quench. Here, the microstructure of a quenched, degraded sampled is compared to that of an unquenched control sample. To facilitate microstructural analysis of the YBCO surface, the Cu stabilizer and Ag cap layer were removed by etching. Reactions between the Cu etchant and YBCO proved to be a signature of Ag/YBCO delamination. Two types of pre-existing defects were identified as initiation points of degradation. Defects on the conductor edge resulting in delaminated Ag lead to dendritic flux avalanches and high local heating, which cause further Ag delamination. This self-propagating effect results in dendritic Ag delamination, which is seen through etchant–YBCO reactions. Defects within the YBCO layer result in breaches in the protective Ag layer such that Cu etchant penetrates and reacts with the YBCO. Energy-dispersive X-ray spectroscopy analysis showed similar reactions as in the edge degradation but also showed pure Ag particles, which indicates that the local temperature was sufficient to cause localized Ag melting.     

Field-Assisted Sintering of Nanocrystalline Titanium Nitride

Nanosized TiN powder was densified via field-assisted sintering at temperatures of 1150°–1350°C and a pressure of 66 MPa under vacuum. A maximum relative density of ∼97% and a maximum mean grain size of 150–200 nm were obtained. Densification and microstructural evolution have been discussed, in terms of superplasticity and electric-field effects.     

Thermally stable nanocrystallised mesoporous zirconia thin films

A supercritical fluid process method has been developed for fabricating mesoporous zirconia thin films with enhanced thermal stability up to a temperature of 850 °C. Both the supercritical CO₂ and the precursor tetramethoxysilane play an important role in enhancing the thermal stability of these films. Powder X-ray diffraction, Atomic force microscope, spectroscopic ellipsometry and transmission electron microscope analyses show that the thin films fabricated by the supercritical fluid process method have a highly ordered mesoporous structure, a nanocrystalline inorganic framework and a high optical transparency. These zirconia thin films have potential applications as electrodes in solid oxide fuel cells where high thermal stability is essential.     

Interaction of the σ2 Receptor Ligand PB28 with the Human Nucleosome: Computational and Experimental Probes of Interaction with the H2A/H2B Dimer

Sigma‐2 (σ₂) binding sites are an emerging target for anti‐neoplastic agents due to the strong apoptotic effect exhibited by σ₂ agonists in vitro and the overexpression of these sites in tumor cells. Nonetheless, no σ₂ receptor protein has been identified. Affinity chromatography using the high‐affinity σ₂ ligand PB28 and human SK‐N‐SH neuroblastoma cells was previously utilized to identify σ₂ ligand binding proteins, specifically histones H1, H2A, H2B, and H3.3a. To rationalize this finding, homology modeling and automated docking studies were employed to probe intermolecular interactions between PB28 and human nucleosomal proteins. These studies predicted interaction of PB28 with the H2A/H2B dimer at a series of sites previously found to be implicated in chromatin compaction and nucleosomal assembly. To experimentally verify this prediction, a competitive binding assay was performed on the reconstituted H2A/H2B dimer using [³H]PB28 as radioligand, and an IC₅₀ value of 0.50 nM was determined for PB28 binding. In addition, [³H]PB28 was found to accumulate with up to a fivefold excess in nuclear fractions over cytosolic fractions of SK‐N‐SH and MCF7 cells, indicating that PB28 is capable of entering the nucleus to interact with histone proteins. In conjunction with computational results, these data suggest that PB28 may exert its cytotoxic effect through direct interaction with nuclear material.     

Synthesis and electrical properties of the (PVA)0.7(KI)0.3·xH2SO4 (0 ≤ x ≤ 5) polymer electrolytes and their performance in a primary Zn/MnO2 battery

Solid acid polymer electrolytes (SAPE) were synthesised using polyvinyl alcohol, potassium iodide and sulphuric acid in different molar ratios by solution cast technique. The temperature dependent nature of electrical conductivity and the impedance of the polymer electrolytes were determined along with the associated activation energy. The electrical conductivity at room temperature was found to be strongly depended on the amorphous nature of the polymers and H₂SO₄ concentration. The ac (100 Hz to 10 MHz) and dc conductivities of the polymer electrolytes with different H₂SO₄ concentrations were analyzed. A maximum dc conductivity of 1.05 × 10⁻³ S cm⁻¹ has been achieved at ambient temperature for electrolytes containing 5 M H₂SO₄. The frequency and temperature dependent dielectric and electrical modulus properties of the SAPE were studied. The charge transport in the present polymer electrolyte was obtained using Wagner's polarization technique, which demonstrated the charge transport to be mainly due to ions. Using these solid acid polymer electrolytes novel Zn/SAPE/MnO₂ solid state batteries were fabricated and their discharge capacity was calculated. An open circuit voltage of 1.758 V was obtained for 5 M H₂SO₄ based Zn/SAPE/MnO₂ battery.     

TGFβ-1 Induced Cross-Linking of the Extracellular Matrix of Primary Human Dermal Fibroblasts

Excessive cross-linking is a major factor in the resistance to the remodelling of the extracellular matrix (ECM) during fibrotic progression. The role of TGFβ signalling in impairing ECM remodelling has been demonstrated in various fibrotic models. We hypothesised that increased ECM cross-linking by TGFβ contributes to skin fibrosis in Systemic Sclerosis (SSc). Proteomics was used to identify cross-linking enzymes in the ECM of primary human dermal fibroblasts, and to compare their levels following treatment with TGFβ-1. A significant upregulation and enrichment of lysyl-oxidase-like 1, 2 and 4 and transglutaminase 2 were found. Western blotting confirmed the upregulation of lysyl hydroxylase 2 in the ECM. Increased transglutaminase activity in TGFβ-1 treated ECM was revealed from a cell-based assay. We employed a mass spectrometry-based method to identify alterations in the ECM cross-linking pattern caused by TGFβ-1. Cross-linking sites were identified in collagens I and V, fibrinogen and fibronectin. One cross-linking site in fibrinogen alpha was found only in TGFβ-treated samples. In conclusion, we have mapped novel cross-links between ECM proteins and demonstrated that activation of TGFβ signalling in cultured dermal fibroblasts upregulates multiple cross-linking enzymes in the ECM.     

Human DDX17 Unwinds Rift Valley Fever Virus Non-Coding RNAs

Rift Valley fever virus (RVFV) is a mosquito-transmitted virus from the Bunyaviridae family that causes high rates of mortality and morbidity in humans and ruminant animals. Previous studies indicated that DEAD-box helicase 17 (DDX17) restricts RVFV replication by recognizing two primary non-coding RNAs in the S-segment of the genome: the intergenic region (IGR) and 5′ non-coding region (NCR). However, we lack molecular insights into the direct binding of DDX17 with RVFV non-coding RNAs and information on the unwinding of both non-coding RNAs by DDX17. Therefore, we performed an extensive biophysical analysis of the DDX17 helicase domain (DDX17_135–555) and RVFV non-coding RNAs, IGR and 5’ NCR. The homogeneity studies using analytical ultracentrifugation indicated that DDX17_135–555, IGR, and 5’ NCR are pure. Next, we performed small-angle X-ray scattering (SAXS) experiments, which suggested that DDX17 and both RNAs are homogenous as well. SAXS analysis also demonstrated that DDX17 is globular to an extent, whereas the RNAs adopt an extended conformation in solution. Subsequently, microscale thermophoresis (MST) experiments were performed to investigate the direct binding of DDX17 to the non-coding RNAs. The MST experiments demonstrated that DDX17 binds with the IGR and 5’ NCR with a dissociation constant of 5.77 ± 0.15 µM and 9.85 ± 0.11 µM, respectively. As DDX17_135–555 is an RNA helicase, we next determined if it could unwind IGR and NCR. We developed a helicase assay using MST and fluorescently-labeled oligos, which suggested DDX17_135–555 can unwind both RNAs. Overall, our study provides direct evidence of DDX17_135–555 interacting with and unwinding RVFV non-coding regions.     

Characterization of PA-12 specimens fabricated by projection sintering at various sintering parameters

Large area projection sintering (LAPS) promises to be a new method in the field of additive manufacturing. Developed in the Mechanical Engineering Department, University of South Florida, LAPS uses long exposure times over a broad area of powder to fuse into dense, reproducible materials. In contrast, LS, a common powder-based additive manufacturing, uses a focused beam of light scanned quickly over the material. Local regions of concentrated high-energy bursts of light lead to higher peak temperatures and differing cooling dynamics and overall crystallinity. The mechanical properties of laser sintered specimens suffer because of uneven particle fusion. LAPS offers the capacity to fine-tune fusion properties through enhanced thermodynamic control of the heating and cooling profiles for sintering. Further research is required to identify the relationship between LAPS build settings and part properties to enable the fabrication of custom parts with desired properties. This study examines the influence of LAPS sintering parameters on chemical structures, crystallinity, mechanical, and thermal properties of polyamide-12 specimens using powder X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, small-angle X-ray scattering, scanning electron microscopy, and microhardness testing. It was observed that higher crystallinity was imparted to specimens that were sintered for a shorter time and vice versa.     

Transcriptional Profiling of Cardiac Cells Links Age-Dependent Changes in Acetyl-CoA Signaling to Chromatin Modifications

Metabolism has emerged as a regulator of core stem cell properties such as proliferation, survival, self-renewal, and multilineage potential. Metabolites serve as secondary messengers, fine-tuning signaling pathways in response to microenvironment alterations. Studies show a role for central metabolite acetyl-CoA in the regulation of chromatin state through changes in histone acetylation. Nevertheless, metabolic regulators of chromatin remodeling in cardiac cells in response to increasing biological age remains unknown. Previously, we identified novel cardiac-derived stem-like cells (CTSCs) that exhibit increased functional properties in the neonatal heart (nCTSC). These cells are linked to a unique metabolism which is altered with CTSC aging (aCTSC). Here, we present an in-depth, RNA-sequencing-based (RNA-Seq) bioinformatic with cluster analysis that details a distinct epigenome present in nCTSCs but not in aCTSCs. Gene Ontology (GO) and pathway enrichment reveal biological processes, including metabolism, gene regulation enriched in nCTSCs, and STRING analysis that identifies a network of genes related to acetyl-CoA that can potentially influence chromatin remodeling. Additional validation by Western blot and qRT-PCR shows increased acetyl-CoA signaling and histone acetylation in nCTSCs compared to aCTSCs. In conclusion, our data reveal that the link between metabolism and histone acetylation in cardiac cells is altered with the aging of the cardiac tissue.