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Zhao, Linlin,Pence, Matthew G.,Christov, Plamen P.,Wawrzak, Zdzislaw,Choi, Jeong-Yun,Rizzo, Carmelo J.,Egli, Martin,Guengerich, F. Peter American Society for Biochemistry and Molecular Bi 2012 The Journal of biological chemistry Vol.287 No.42
<P><I>N</I><SUP>2</SUP>,3-Ethenoguanine (<I>N</I><SUP>2</SUP>,3-ϵG) is one of the exocyclic DNA adducts produced by endogenous processes (<I>e.g.</I> lipid peroxidation) and exposure to bioactivated vinyl monomers such as vinyl chloride, which is a known human carcinogen. Existing studies exploring the miscoding potential of this lesion are quite indirect because of the lability of the glycosidic bond. We utilized a 2′-fluoro isostere approach to stabilize this lesion and synthesized oligonucleotides containing 2′-fluoro-<I>N</I><SUP>2</SUP>,3-ϵ-2′-deoxyarabinoguanosine to investigate the miscoding potential of <I>N</I><SUP>2</SUP>,3-ϵG by Y-family human DNA polymerases (pols). In primer extension assays, pol η and pol κ replicated through <I>N</I><SUP>2</SUP>,3-ϵG, whereas pol ι and REV1 yielded only 1-base incorporation. Steady-state kinetics revealed that dCTP incorporation is preferred opposite <I>N</I><SUP>2</SUP>,3-ϵG with relative efficiencies in the order of pol κ > REV1 > pol η ≈ pol ι, and dTTP misincorporation is the major miscoding event by all four Y-family human DNA pols. Pol ι had the highest dTTP misincorporation frequency (0.71) followed by pol η (0.63). REV1 misincorporated dTTP and dGTP with much lower frequencies. Crystal structures of pol ι with <I>N</I><SUP>2</SUP>,3-ϵG paired to dCTP and dTTP revealed Hoogsteen-like base pairing mechanisms. Two hydrogen bonds were observed in the <I>N</I><SUP>2</SUP>,3-ϵG:dCTP base pair, whereas only one appears to be present in the case of the <I>N</I><SUP>2</SUP>,3-ϵG:dTTP pair. Base pairing mechanisms derived from the crystal structures explain the slightly favored dCTP insertion for pol ι in steady-state kinetic analysis. Taken together, these results provide a basis for the mutagenic potential of <I>N</I><SUP>2</SUP>,3-ϵG.</P>
Interface control of bulk ferroelectric polarization.
Yu, P,Luo, W,Yi, D,Zhang, J X,Rossell, M D,Yang, C-H,You, L,Singh-Bhalla, G,Yang, S Y,He, Q,Ramasse, Q M,Erni, R,Martin, L W,Chu, Y H,Pantelides, S T,Pennycook, S J,Ramesh, R National Academy of Sciences 2012 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.109 No.25
<P>The control of material interfaces at the atomic level has led to novel interfacial properties and functionalities. In particular, the study of polar discontinuities at interfaces between complex oxides lies at the frontier of modern condensed matter research. Here we employ a combination of experimental measurements and theoretical calculations to demonstrate the control of a bulk property, namely ferroelectric polarization, of a heteroepitaxial bilayer by precise atomic-scale interface engineering. More specifically, the control is achieved by exploiting the interfacial valence mismatch to influence the electrostatic potential step across the interface, which manifests itself as the biased-voltage in ferroelectric hysteresis loops and determines the ferroelectric state. A broad study of diverse systems comprising different ferroelectrics and conducting perovskite underlayers extends the generality of this phenomenon.</P>
Pearce, J V,Edler, F,Elliott, C J,Greenen, A,Harris, P M,Izquierdo, C Garcia,Kim, Y-G,Martin, M J,Smith, I M,Tucker, D,Veltcheva, R I BUREAU INTERNATIONAL DES POIDS ET MESURES 2018 METROLOGIA -BERLIN- Vol.55 No.4
<P>By using a simple model to relate the electromotive force drift rate of Pt–Rh thermoelements to d<I>S</I>/d<I>c</I>, i.e. the sensitivity of the Seebeck coefficient, <I>S</I>, to rhodium mass fraction, <I>c</I>, the composition of the optimal pair of Pt–Rh wires that minimizes thermoelectric drift can be determined. The model has been applied to four multi-wire thermocouples each comprising 5 or 7 Pt–Rh wires of different composition. Two thermocouples were exposed to a temperature of around 1324 °C, one thermocouple to around 1492 °C, i.e. the melting points of the Co–C and Pd–C high temperature fixed points, respectively, and one thermocouple to a series of temperatures between 1315 °C and 1450 °C. The duration of exposure at each temperature was several thousand hours. By performing repeated calibrations <I>in situ</I> with the appropriate fixed point during the high temperature exposure, the drift performance has been quantified with high accuracy, entirely free from errors associated with thermoelectric homogeneity. By combining these results it is concluded that the Pt-40%Rh versus Pt-6%Rh is the most stable at the temperatures investigated. A preliminary reference function was determined and is presented.</P>
Silva-Martin, N.,Bartual, Sergio G.,Ramirez-Aportela, E.,Chacon, P.,Park, C.,Hermoso, Juan A. Current Biology 2014 Structure Vol.22 No.11
SIGN-R1 is a principal receptor for microbial polysaccharides uptake and is responsible for C3 fixation via an unusual complement activation pathway on splenic marginal zone macrophages. In these macrophages, SIGN-R1 is also involved in anti-inflammatory activity of intravenous immunoglobulin by direct interaction with sialylated Fcs. The high-resolution crystal structures of SIGN-R1 carbohydrate recognition domain and its complexes with dextran sulfate or sialic acid, and of the sialylated Fc antibody provide insights into SIGN-R1's selective recognition of α-2,6-sialylated glycoproteins. Unexpectedly, an additional binding site has been found in the SIGN-R1 carbohydrate recognition domain, structurally separate from the calcium-dependent carbohydrate-binding site. This secondary binding site could bind repetitive molecular patterns, as observed in microbial polysaccharides, in a calcium-independent manner. These two binding sites may allow SIGN-R1 to simultaneously bind both immune glycoproteins and microbial polysaccharide components, accommodating SIGN-R1's ability to relate the recognition of microbes to the activation of the classical complement pathway.
Compaction of Aggregated Ceramic Powders, Discrete Element and Finite Element Simulations
Pizette P.,Martin C. L.,Delette G. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
In contrast with the Finite Element Method, the Discrete Element Method (DEM) takes explicitly into account the particulate nature of powders. DEM exhibits some drawbacks and many advantages. Simulations can be computationally expensive and they are only able to represent a volume element. However, these simulations have the great advantage of providing a wealth of information at the microstructural level. Here we demonstrate that the method is well suited for modelling, in coordination with FEM, the compaction of ceramic particles that have been aggregated. Aggregates of individual ceramic crystallites that are strongly bonded together are represented by porous spheres.
Status of the Astrid Core at the end of the Pre-Conceptual Design Phase 1
MS. CHENAUD,N. Devictor,G. Mignot,F. Varaine,C. Venard,L. Martin,M. Phelip,D. Lorenzo,F. Serre,F. Bertrand,N. Alpy,M. Le Flem,P. Gavoille,R. Lavastre,P. Richard,D. Verrier,D.Schmitt 한국원자력학회 2013 Nuclear Engineering and Technology Vol.45 No.6
Within the framework of the ASTRID project, core design studies are being conducted by the CEA with support from AREVA and EDF. The pre-conceptual design studies are being conducted in accordance with the GEN IV reactor objectives, particularly in terms of improving safety. This involves limiting the consequences of 1) a hypothetical control rod withdrawal accident (by minimizing the core reactivity loss during the irradiation cycle), and 2) an hypothetical loss-of-flow accident (by reducing the sodium void worth). Two types of cores are being studied for the ASTRID project. The first is based on a ‘large pin/small spacing wire’ concept derived from the SFR V2b, while the other is based on an innovative CFV design. A distinctive feature of the CFV core is its negative sodium void worth. In 2011, the evaluation of a preliminary version (v1) of this CFV core for ASTRID underlined its potential capacity to improve the prevention of severe accidents. An improved version of the ASTRID CFV core (v2) was proposed in 2012 to comply with all the control rod withdrawal criteria, while increasing safety margins for all unprotected-loss-of-flow (ULOF) transients and improving the general design. This paper describes the CFV v2 design options and reports on the progress of the studies at the end of pre-conceptual design phase 1 concerning: - Core performance, - Intrinsic behavior during unprotected transients, - Simulation of severe accident scenarios, - Qualification requirements. The paper also specifies the open options for the materials, sub-assemblies, absorbers, and core monitoring that will continue to be studied during the conceptual design phase. Within the framework of the ASTRID project, core design studies are being conducted by the CEA with support fromAREVA and EDF. The pre-conceptual design studies are being conducted in accordance with the GEN IV reactor objectives,particularly in terms of improving safety. This involves limiting the consequences of 1) a hypothetical control rod withdrawalaccident (by minimizing the core reactivity loss during the irradiation cycle), and 2) an hypothetical loss-of-flow accident (byreducing the sodium void worth). Two types of cores are being studied for the ASTRID project. The first is based on a ‘large pin/small spacing wire’concept derived from the SFR V2b, while the other is based on an innovative CFV design. A distinctive feature of the CFVcore is its negative sodium void worth. In 2011, the evaluation of a preliminary version (v1) of this CFV core for ASTRID underlined its potential capacity toimprove the prevention of severe accidents. An improved version of the ASTRID CFV core (v2) was proposed in 2012 to comply with all the control rod withdrawalcriteria, while increasing safety margins for all unprotected-loss-of-flow (ULOF) transients and improving the general design. This paper describes the CFV v2 design options and reports on the progress of the studies at the end of pre-conceptualdesign phase 1 concerning:- Core performance,- Intrinsic behavior during unprotected transients,- Simulation of severe accident scenarios,- Qualification requirements. The paper also specifies the open options for the materials, sub-assemblies, absorbers, and core monitoring that willcontinue to be studied during the conceptual design phase.