The Effect of Waste Loading and Glass Structural Factors on Structure and Chemical Durability of SB2 and SB4 SRS Waste Glasses -11397

ABSTRACT Glassy materials simulating vitrified high-Na/Fe (Sludge Batch 2 -SB2) and high-Na/Fe/Al (Sludge Batch 4 -SB4) Savannah River Site high level wastes (HLW) were produced in a resistive furnace and 236 and 418 mm inner diameter cold crucibles. The effect of waste loading (WL) and glass structural factors (degree of connectedness of glass network, metal oxides to boron oxide ratios) on chemical durability of glassy materials was studied

Specific features of the substitution of Fe3+ impurity ions for Zr4+ in NaZr2(PO4)3 single crystals

The EPR spectra of Fe3+ impurity ions in NaZr 2(PO4)3 single crystals at 300 K are investigated, and the spin Hamiltonian of these ions is determined. A comparative analysis of the spin-Hamiltonian and crystal-field tensors is performed using the maximum invariant component method. It is demonstrated that Fe3+ impurity ions substitute for Zr4+ ions with local compensator ions located in cavities of the B type. It is revealed that the invariant of the spin-Hamiltonian tensor B4 and the crystal-field tensor V44 4 depend substantially on the mutual arrangement of ions in the first and second coordination spheres. The corresponding dependences are analyzed. © 2005 Pleiades Publishing, Inc

Epigenetic Engineering of Ribosomal RNA Genes Enhances Protein Production

Selection of mammalian high-producer cell lines remains a major challenge for the biopharmaceutical manufacturing industry. Ribosomal RNA (rRNA) genes encode the major component of the ribosome but many rRNA gene copies are not transcribed [1]–[5] due to epigenetic silencing by the nucleolar remodelling complex (NoRC) [6], which may limit the cell's full production capacity. Here we show that the knockdown of TIP5, a subunit of NoRC, decreases the number of silent rRNA genes, upregulates rRNA transcription, enhances ribosome synthesis and increases production of recombinant proteins. However, general enhancement of rRNA transcription rate did not stimulate protein synthesis. Our data demonstrates that the number of transcriptionally competent rRNA genes limits efficient ribosome synthesis. Epigenetic engineering of ribosomal RNA genes offers new possibilities for improving biopharmaceutical manufacturing and provides novel insights into the complex regulatory network which governs the translation machinery in normal cellular processes as well as in pathological conditions like cancer

Nucleosomes in gene regulation: theoretical approaches

This work reviews current theoretical approaches of biophysics and bioinformatics for the description of nucleosome arrangements in chromatin and transcription factor binding to nucleosomal organized DNA. The role of nucleosomes in gene regulation is discussed from molecular-mechanistic and biological point of view. In addition to classical problems of this field, actual questions of epigenetic regulation are discussed. The authors selected for discussion what seem to be the most interesting concepts and hypotheses. Mathematical approaches are described in a simplified language to attract attention to the most important directions of this field

The Chromatin Remodelling Complex B-WICH Changes the Chromatin Structure and Recruits Histone Acetyl-Transferases to Active rRNA Genes

The chromatin remodelling complex B-WICH, which comprises the William syndrome transcription factor (WSTF), SNF2h, and nuclear myosin 1 (NM1), is involved in regulating rDNA transcription, and SiRNA silencing of WSTF leads to a reduced level of 45S pre-rRNA. The mechanism behind the action of B-WICH is unclear. Here, we show that the B-WICH complex affects the chromatin structure and that silencing of the WSTF protein results in a compaction of the chromatin structure over a 200 basepair region at the rRNA promoter. WSTF knock down does not show an effect on the binding of the rRNA-specific enhancer and chromatin protein UBF, which contributes to the chromatin structure at active genes. Instead, WSTF knock down results in a reduced level of acetylated H3-Ac, in particular H3K9-Ac, at the promoter and along the gene. The association of the histone acetyl-transferases PCAF, p300 and GCN5 with the promoter is reduced in WSTF knock down cells, whereas the association of the histone acetyl-transferase MOF is retained. A low level of H3-Ac was also found in growing cells, but here histone acetyl-transferases were present at the rDNA promoter. We propose that the B-WICH complex remodels the chromatin structure at actively transcribed rRNA genes, and this allows for the association of specific histone acetyl-transferases

Comparison of Phases Formation Process in Initial and Mechanically Activated Ceramic Batches with Pyrochlore Formulations

Formation of two pyrochlore ceramics with formulations CaZr0.25U0.75Ti2O7 and CaUTi2O7 within the temperature range 1000-1500 C from batches prepared by grinding of oxide powders in a mortar and an activator with hydrostatic yokes AGO-2U as well as soaking of a Ca, Zr, and Ti oxide mixture with uranylnitrate solution was studied. The pyrochlore ceramics are produced through intermediate calcium uranate formation. Phase formation reactions in the batch pre-treated in the AGO-2U unit were completed within the temperature range 1000-1100 C that is lower than in the batches prepared by two other methods

The Effect of Waste Loading on Phase Composition, Structure and Chemical Durability of Glassy Materials for Immobilization of High-Sodium/Aluminum Waste -11475

ABSTRACT Mixtures of surrogates of high level waste with high sodium and aluminum contents and sodiumlithium borosilicate frit were placed in alumina crucible, heated to 1200-1300 °C depending on waste to frit ratio in a resistive furnace and kept at melting temperature for 1 hr. Portions of melts were poured onto a metal plate (quenched) and the residues were slowly cooled in turned-off furnace (annealed). The quenched materials contained up to 45 wt.% waste oxides were fully amorphous whereas in the materials with higher waste loadings minor spinel structure phases occurred. The annealed materials with waste loading of up to 45 wt.% contained minor spinel type phase and trace of nepheline (Na,K)AlSiO 4 . In the annealed materials contained waste oxides in amount of 50 wt.% and more nepheline and spinel were found to be major and minor phases, respectively. Two spinel varieties -first and second generation different in crystal size and geometry occurred. The materials at 55, 60 and 65 wt.% waste loadings are nearly fully crystalline and contain, except nepheline and spinel, extra Cs-bearing phases. These phases coexist with nepheline and their chemical compositions are recalculated to formulae with 4 oxygen ions. One of them contains up to 0.30 Cs + and 0.13 S 6+ ions per formula, chemical composition of the second one is close to CsAlSiO 4 . Chemical durability of the materials worsens with waste loading but even at waste loading of 55 wt.% normalized releases of B, Li, Na and Si from the material determined using PCT procedure remain lower than those from EA glass

Phase partitioning and uranium speciation in brannerite-based ceramics

Branneritecontaining ceramics were produced by cold pressing and sintering (CPS) and cold crucible inductive melting (CCIM) methods and examined by X-ray diffraction and absorption and by scanning electron microscopy. Brannerite content in the ceramics ranged between ∼20 and 90 vol.%. Uranium is mainly partitioned between brannerite and minor mixed U/RE oxide but since brannerite is a dominant phase, it takes up to 90% of total U. Uranium in the ceramics is present as U(IV) and U(V). In the low-brannerite ceramics U occurs as U(IV) whereas in the ceramics with brannerite as major phase U(V) dominates over U(IV). Ce in the brannerite ceramics is mainly trivalent. The first coordination shell of U in ceramics produced by CPS is split into two sub-shells with U-O distances of 1.7–1.9 Å and ∼2.1 Å while in the melted ceramics this interatomic distance is 2.1–2.2 Å. The next three atoms (Ti) are positioned at a distances of 3.1–3.2 Å