Nanoscopic Study of the Ion Dynamics in a LiAlSiO4_4 Glass Ceramic by means of Electrostatic Force Spectroscopy

We use time-domain electrostatic force spectroscopy (TD-EFS) for characterising the dynamics of mobile ions in a partially crystallised LiAlSiO$_4$ glass ceramic, and we compare the results of the TD-EFS measurements to macroscopic electrical conductivity measurements. While the macroscopic conductivity spectra are determined by a single dynamic process with an activation energy of 0.72 eV, the TD-EFS measurements provide information about two distinct relaxation processes with different activation energies. Our results indicate that the faster process is due to ionic movements in the glassy phase and at the glass-crystal interfaces, while the slower process is caused by ionic movements in the crystallites. The spatially varying electrical relaxation strengths of the fast and of the slow process provide information about the nano- and mesoscale structure of the glass ceramic.Comment: 5 pages, 4 figure

New Developments in the Field of Glass Ceramics

[no abstract available

Nucleation in a precursor glass for a Li2O-Al2O3-SiO2 glass ceramic Part 1. Nucleation kinetics

The nucleation of the parent glass of a Li2O-Al2O3-SiO2 glass ceramic is determined. The two-step development method is applied utilizing a specially developed device which allows quantitative determination of nucleation rates despite of the strong tendency for nucleation. The influence of nucleation on the transmission of the glass ceramic is investigated to obtain criteria for optimal nucleation conditions for ceramization of the glass. Nucleation is markedly characterized by non-stationary behaviour. The existence of delay times which depend as well on development temperature as on thermal history of the glass is of great importance for the processing of the glass. The impact of nucleation kinetics on the production of the glass ceramic is explained by means of TTT diagrams

A novel copper oxalate, Na2Cu(C2O4)2

The authors thank the Royal Society for the award of a Newton Fellowship (NF140881) to W.Y.A novel copper oxalate Na2Cu(C2O4)2 was synthesized through a hydrothermal method and characterized by single-crystal X-ray diffraction. It crystallizes in monoclinic system, P21/n space group with a = 72578(3) Å, b = 5.7711(4) Å, c = 8.6604(8) Å, β = 106.948(9)°. The structure displays a novel stacking pattern of [Cu(C2O4)2]2– units connected through electrostatic attraction by Na+ cations. Structural comparisons are made to related compounds.PostprintPeer reviewe

Nucleation at cordierite glass surfaces: Kinetic aspects

The surface nucleation of high-quartz sohd Solution crystals at fractured surfaces of glasses of the stoichiometric cordierite composition (2MgO · 2AI₂O₃ · 5SiO₂) was studied by optical microscopy. Particular attention was focused on the nucleation kinetics. Α constant nucleation density, Ν ≈ 10⁻⁴ μm⁻², was found not to be significantly influenced by the time and the temperature of nucleation treatment. Even a very fast heating of samples employing heating rates u p to 1200 K/min does not lower Ν substantially. However, for small average crystal diameters ( < 2 0 μm) a distribution of crystal size in the same order of magnitude is detectable indicating a simultaneous appearance of b o t h measurable nucleation rates and growth velocities. It can be concluded that the surface nucleation of µ-cordierite occurs during the thermal treatment from a limited number of preferred nucleation sites; these sites are "used Up" rapidly enough to cause a strong Saturation effect of nucleation, but slow enough to cause a crystal size distribution at the same time. The surface nucleation rate, Is , was calculated from the observed distribution of crystal sizes. Is progressively increases with rising temperature similar to the crystal growth velocity indicating a broad temperature ränge of essential nucleation activity. The latter must be regarded as t he main obstacle to measure or to control surface nucleation density by means of two-step nucleation and growth treatments and must therefore be claimed to be mainly responsible for the observed constancy of N

Sintering and crystallization of glasses with roedderite-type composition (Na, K)2Mg5Si12O30

Two glass powders of roedderite-type composition (Na2Mg5Si12O30 and NaKMg5Si12O30) have been prepared for sintering and crystallization experiments. Glass powder of sodium roedderite composition sinters to a dense body after 15 to 60 min at 800 to 850 °C before crystallization. The sintered body crystallizes easily to give roedderite as the main phase. Sodium-potassium-roedderite glass powder can be sintered to a dense body, too, though the sintering rate is lower. This is due to the higher viscosity of the sodium-potassium-roedderite glass. The amount of crystallized roedderite is smaller in the sodium-potassium composition whereas the amount of residual glass is higher. This influences the thermal expansion of the compact, which is higher than in the sodium roedderite glass-ceramic. The thermal expansion coefficient of the latter is close to that of pure crystaline sodium roedderite

Ionic conductivity in Li2O-Al2O3-SiO2 based glasses and glass ceramics

The complex conductivity of lithium aluminosilicate based glasses and glass-ceramics (Zerodur from Schott) has been investigated in a broad range of temperatures (200 K &lt; T &lt; 700 K) and frequencies (10 mHz&lt;v&lt;2.5 THz). The data are presented in terms of the conductivity and the electrical modulus formalisms. The width of the modulus loss peak as measured for the ceramic sample is broader than that determined for its precursor glass. This result is shown to be associated with the considerably smaller dc conductivity of this material.</jats:p

CP204L Is a Multifunctional Protein of African Swine Fever Virus That Interacts with the VPS39 Subunit of the Homotypic Fusion and Vacuole Protein Sorting Complex and Promotes Lysosome Clustering

Virus replication depends on a complex interplay between viral and host proteins. In the case of African swine fever virus (ASFV), a large DNA virus, only a few virus-host protein-protein interactions have been identified to date. In this study, we demonstrate that the ASFV protein CP204L interacts with the cellular homotypic fusion and protein sorting (HOPS) protein VPS39, blocking its association with the lysosomal HOPS complex, which modulates endolysosomal trafficking and promotes lysosome clustering. Instead, CP204L and VPS39 are targeted to virus factories and localized at the periphery of the virus DNA replication sites. Furthermore, we show that loss of VPS39 reduces the levels of virus proteins synthesized in the early phase of infection and delays ASFV replication but does not completely inhibit it. Collectively, these results identify a novel virus-host protein interaction that modulates host membrane rearrangement during infection and provide evidence that CP204L is a multifunctional protein engaged in distinct steps of the ASFV life cycle

The non-classical major histocompatibility complex II protein SLA-DM is crucial for African swine fever virus replication

African swine fever virus (ASFV) is a lethal animal pathogen that enters its host cells through endocytosis. So far, host factors specifically required for ASFV replication have been barely identified. In this study a genome-wide CRISPR/Cas9 knockout screen in porcine cells indicated that the genes RFXANK, RFXAP, SLA-DMA, SLA-DMB, and CIITA are important for productive ASFV infection. The proteins encoded by these genes belong to the major histocompatibility complex II (MHC II), or swine leucocyte antigen complex II (SLA II). RFXAP and CIITA are MHC II-specific transcription factors, whereas SLA-DMA/B are subunits of the non-classical MHC II molecule SLA-DM. Targeted knockout of either of these genes led to severe replication defects of different ASFV isolates, reflected by substantially reduced plating efficiency, cell-to-cell spread, progeny virus titers and viral DNA replication. Transgene-based reconstitution of SLA-DMA/B fully restored the replication capacity demonstrating that SLA-DM, which resides in late endosomes, plays a crucial role during early steps of ASFV infection