Response of Nd3+ and Sm3+ precipitating into rhabdophane and the leaching mechanism of associated monazite ceramics

Rhabdophane has been considered an important permeable reactive barrier to isolate groundwater radionuclides, and evaluating its precipitation response to different species of radionuclide in acid solutions is critical. In this work, the effects of pH values on the precipitation behavior of Nd³⁺ and Sm³⁺ into La-rhabdophane are systematically investigated. Some specific issues such as ions removal, precipitation reaction kinetics, and crystal growth affected ions incorporation are discussed in detail, along with uncovering the veil of the Ln (La, Nd, and Sm) leaching mechanism of associated La_0.666Nd_0.167Sm_0.167PO₄ monazite ceramic based on dissolution experiments and density functional theory. The results reveal that Nd³⁺ and Sm³⁺ can be removed more than 98% in pH = 1 solution within 12 h, whereas uneven precipitation process to form unexpected stoichiometric ratio of rhabdophane has been observed in 30–50 nm short crystal. Grain growth effects based on spark plasma sintering can contribute to homogenize the materials composition with obtaining La_0.666Nd_0.167Sm_0.167PO₄ monazite ceramics. Furthermore, the binding energy of Ln–O in (1 0 0) surface of monazite plays an important role in controlling the leaching stability of Ln³⁺, associated with the leaching activities are energetically favorable in the order of La > Nd > Sm for La_0.666Nd_0.167Sm_0.167PO₄ monazite.     

Synthesis of ethyl propionate catalyzed by poly(N‐AEAAm‐co‐AAc)‐cl‐MBAm hydrogel‐immobilized lipase of Bacillus coagulans MTCC‐6375

A purified alkaline thermotolerant bacterial lipase of Bacillus coagulans MTCC‐6375 was efficiently immobilized onto poly(N‐AEAAm‐co‐AAc‐cl‐MBAm)‐hydrogel at pH 8.5 and at temperature 55°C in 16 h. The hydrogel‐bound matrix possessed 1.04 U/g (matrix) lipase activity with a specific activity of 1.8 U/mg of protein. The immobilized lipase resulted in formation of 52.5 mM of ethyl propionate (52% conversion) at 55°C in 9 h in n‐nonane. Ethanol and propionic acid when used in a ratio of 300 : 100 mM, respectively, in n‐nonane along with 10 mg of hydrogel‐bound lipase resulted in optimal synthesis of ethyl propionate (82.5 mM). Addition of molecular sieves (3 Å, 0.7 g/reaction volume) further enhanced the conversion rate to 82.4% resulting in 83.5 mM of ethyl propionate. Incubation temperature below or above 55°C had a marked effect on the synthesis of ethyl propionate. However, esterification performed in n‐heptane at 65°C resulted in 87.5 mM of ethyl propionate with a conversation rate of 89.3%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Dimensional analysis for planetary mixer: Mixing time and Reynolds numbers

Mixing time number is a convenient parameter to characterize mixing performance of stirred tanks. This dimensionless number is now well established for agitated vessels equipped with vertically and centrally mounted impeller for Newtonian as well as for non-Newtonian fluids. To our knowledge, there is more ambiguity concerning its definition for planetary mixers especially when they have dual motion (around two perpendicular axes) to achieve homogenization. In this study, dimensional analysis of mixing time and reliability of the modified Reynolds and mixing time numbers are proposed for such a planetary mixer particularly named as TRIAXE^® system. These two numbers are based on the maximum tip speed of mixer as the characteristic velocity. Modified dimensionless numbers are consistent with the definition of conventional Reynolds and mixing numbers (when only one revolving motion around the vertical axis of the mixing device occurs in the vessel).Mixing time experiments with TRIAXE^® mixer for highly viscous Newtonian fluids showed that the proposed modified Reynolds and mixing time numbers succeeded to obtain a unique mixing curve irrespective of the different speed ratio chosens. This agreement proves that the proposed modified dimensionless numbers can be well adapted for engineering purposes and they can be used to compare the mixing performance of planetary mixers.     

Distributed Multi-Level Recovery in Main-Memory Databases

In this paper we present recovery techniques for distributed main-memory databases, specifically for client-server and shared-disk architectures. We present a recovery scheme for client-server architectures which is based on shipping log records to the server, and two recovery schemes for shared-disk architectures—one based on page shipping, and the other based on broadcasting of the log of updates. The schemes offer different tradeoffs, based on factors such as update rates.Our techniques are extensions to a distributed-memory setting of a centralized recovery scheme for main-memory databases, which has been implemented in the Dalì main-memory database system. Our centralized as well as distributed-memory recovery schemes have several attractive features—they support an explicit multi-level recovery abstraction for high concurrency, reduce disk I/O by writing only redo log records to disk during normal processing, and use per-transaction redo and undo logs to reduce contention on the system log. Further, the techniques use a fuzzy checkpointing scheme that writes only dirty pages to disk, yet minimally interferes with normal processing—all but one of our recovery schemes do not require updaters to even acquire a latch before updating a page. Our log shipping/broadcasting schemes also support concurrent updates to the same page at different sites.     

Sequencing of N‐vinyl‐2‐pyrrolidone/glycidyl methacrylate copolymers by one‐dimensional and two‐dimensional nuclear magnetic resonance spectroscopy

Copolymers of N‐vinyl‐2‐pyrrolidone (V) and glycidyl methacrylate (G) monomers of different compositions were prepared by free‐radical solution polymerization. The copolymer composition of these copolymers was determined with ¹H‐NMR spectra. The reactivity ratios calculated from the Kelen–Tudos and nonlinear least‐square error‐in‐variable methods were r_V = 0.03 ± 0.01 and r_G = 5.05 ± 0.84 and r_V = 0.02 and r_G = 4.72, respectively. The triad sequence distribution in terms of V and G centered triads was determined from ¹³C{¹H}‐NMR spectroscopy. The complete spectral assignment of ¹³C{¹H}‐ and ¹H‐NMR spectra was performed with the help of distortionless enhancement by polarization transfer and two‐dimensional ¹³C–¹H heteronuclear single quantum coherence. The ¹H–¹H couplings were explained with total correlation spectroscopy and nuclear Overhauser enhancement spectroscopy spectra. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 50–60, 2002; DOI 10.1002/app.10186     

Structurally Diverse Histone Deacetylase Photoreactive Probes: Design,Synthesis, and Photolabeling Studies in Live Cells and Tissue

Histone deacetylase (HDAC) activity is modulated in vivo by post-translational modifications and formation of multiprotein complexes. Novel chemical tools to study how these factors affect engagement of HDAC isoforms by HDAC inhibitors (HDACi) in cells and tissues are needed. In this study, a synthetic strategy to access chemically diverse photoreactive probes (PRPs) was developed and used to prepare seven novel HDAC PRPs 9 – 15 . The class I HDAC isoform engagement by PRPs was determined in biochemical assays and photolabeling experiments in live SET-2, HepG2, HuH7, and HEK293T cell lines and in mouse liver tissue. Unlike the HDAC protein abundance and biochemical activity against recombinant HDACs, the chemotype of the PRPs and the type of cells were key in defining the engagement of HDAC isoforms in live cells. Our findings suggest that engagement of HDAC isoforms by HDACi in vivo may be substantially modulated in a cell- and tissue-type-dependent manner.     

In vitro biocompatibility and antimicrobial activity of wet chemically prepared Ca10−xAgx(PO4)6(OH)2 (0.0 ≤ x ≤ 0.5) hydroxyapatites

Herein, we report the effect of silver ions on the physical, antimicrobial and cytocompatibility properties of wet chemically synthesized silver doped Ca_10?xAg_x(PO₄)₆(OH)₂ (0.0 ≤ x ≤ 0.5) hydroxyapatites (HAp). Silver ions containing HAp exhibit the comparable density, hardness and enhanced antimicrobial properties, in comparison to parent HAp. The optical absorption measurements confirm the presence of silver ions in the doped compositions, which are responsible for as increased antimicrobial property of doped HAp materials for x > 0.3. The cytotoxicity behavior of the doped HAp was evaluated using mouse fibroblast (L929) cell line. The important result has been that doped HAp (x > 0.3) exhibit statistically (significant) lower cell viability in comparison to undoped HAp. However, no difference in cellular functionality on doped HAp surfaces, in terms of cell adhesion and proliferation could be qualitatively observed in reference to undoped HAp. In order to explain the observed antimicrobial and cell viability properties, the in vitro release of Ag⁺ ions has been quantified using Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) and solubility was measured by weight loss in acetate buffer solution.     

On adsorption of aluminium and methyl groups on silica for TMA/H<Subscript>2</Subscript>O process in atomic layer deposition of aluminium oxide nano layers

A detailed chemisorption mechanism is proposed for the atomic layer deposition (ALD) of aluminium oxide nano layers using trimethyl aluminum (TMA) and water as precursors. Six possible chemisorption mechanisms, complete ligand exchange, partial ligand exchange, simple dissociation, complete dissociation via ligand exchange, complete dissociation and association, are proposed and related parameters like ligand to metal ratio (L/M), concentrations of metal atoms and methyl groups adsorbed are calculated and compared against reported values. The maximum number of methyl groups that can get attached on the surface is calculated in a different way which yields a more realistic value of 6·25 per nm² substrate area. The dependence of the number of metal atoms adsorbed on OH concentration is explained clearly. It is proposed that a combination of complete ligand exchange and complete dissociation is the most probable chemisorption mechanism taking place at various OH concentrations.     

A study of dynamic meta-learning for failure prediction in large-scale systems

Despite years of study on failure prediction, it remains an open problem, especially in large-scale systems composed of vast amount of components. In this paper, we present a dynamic meta-learning framework for failure prediction. It intends to not only provide reasonable prediction accuracy, but also be of practical use in realistic environments. Two key techniques are developed to address technical challenges of failure prediction. One is meta-learning to boost prediction accuracy by combining the benefits of multiple predictive techniques. The other is a dynamic approach to dynamically obtain failure patterns from a changing training set and to dynamically extract effective rules by actively monitoring prediction accuracy at runtime. We demonstrate the effectiveness and practical use of this framework by means of real system logs collected from the production Blue Gene/L systems at Argonne National Laboratory and San Diego Supercomputer Center. Our case studies indicate that the proposed mechanism can provide reasonable prediction accuracy by forecasting up to 82% of the failures, with a runtime overhead less than 1.0 min.