bluuebunny/crossref_metadata_2025 huggingface dataset:
Embryonic stem cells: protein interaction networks
Authors: Miang-Lon Ng Patricia , Lufkin Thomas
Published: March 2011

Embryonic stem cells have the ability to differentiate into nearly all cell types. However, the molecular mechanism of its pluripotency is still unclear. Oct3/4, Sox2 and Nanog are important factors of pluripotency. Oct3/4 (hereafter referred to as Oct4), in particular, has been an irreplaceable factor in the induction of pluripotency in adult cells. Proteins interacting with Oct4 and Nanog have been identified via affinity purification and mass spectrometry. These data, together with iterative purifications of interacting proteins allowed a protein interaction network to be constructed. The network currently includes 77 transcription factors, all of which are interconnected in one network. In-depth studies of some of these transcription factors show that they all recruit the NuRD complex. Hence, transcription factor clustering and chromosomal remodeling are key mechanism used by embryonic stem cells. Studies using RNA interference suggest that more pluripotency genes are yet to be discovered via protein-protein interactions. More work is required to complete and curate the embryonic stem cell protein interaction network. Analysis of a saturated protein interaction network by system biology tools can greatly aid in the understanding of the embryonic stem cell pluripotency network.
The conformation of the estrogen receptor directs estrogen-induced apoptosis in breast cancer: a hypothesis
Authors: Maximov Philipp , Sengupta Surojeet , Lewis-Wambi Joan S. , Kim Helen R. , Curpan Ramona F. , Jordan V. Craig
Published: March 2011

Background: Estrogens are classified as type I (planar) and type II (angular) based on their structures. In this study, we used triphenylethylenes (TPEs) compounds related to 4-hydroxytamoxifen 4OHT to address the hypothesis that the conformation of the liganded estrogen receptor (ERα) can dictate the E2-induced apoptosis of the ER+ breast cancer cells.

Materials and methods: ERα positive MCF7:5C cells were used to study apoptosis induced by E2, 4OHT and TPEs. Growth and apoptosis assays were used to evaluate apoptosis and the ability to reverse E2-induced apoptosis. ERα protein was measured by Western blotting to investigate the destruction of ERα by TPEs in MCF7 cells. Chromatin immunoprecipitation (ChIP) assays were performed to study the in vivo recruitment of ERα and SRC3 at classical E2-responsive promoter TFF1 (PS2) by TPEs. Molecular modeling was used to predict the binding mode of the TPE to the ERα.

Results: TPEs were not only unable to induce efficient apoptosis in MCF7:5C cells but also reversed the E2-induced apoptosis similar to 4OHT. Furthermore, the TPEs and 4OHT did not reduce the ERα protein levels unlike E2. ChIP assay confirmed very weak recruitment of SRC3 despite modest recruitment of ERα in the presence of TPEs. Mole-ular modeling suggests that TPE would bind in antagonistic mode with ERα.

Conclusion: Our results advances the hypothesis that the TPE liganded ERα complex structurally resembles the 4OHT bound ERα and cannot efficiently recruit co-activator SRC3. As a result, the TPE complex cannot induce apoptosis of ER+ breast cancer cells, although it can cause growth of the breast cancer cells. The conformation of the estrogen-ER complex differentially controls growth and apoptosis.
Sex steroids in uterine endometrial cancers
Authors: Fujimoto Jiro , Sato Eriko
Published: March 2011

Some uterine endometrial cancers conserve estrogen dependency in advancement. However, the concept of advancement in tumor is complicated, because it involves simple growth in primary tumor and secondary spreading. The expression manner of estrogen receptor alpha exon 5 splicing variant, ER beta, progesterone receptor-A (N-terminus deletion mutant) is associated with metastatic potential in uterine endometrial cancers. Increased estrogen-related receptor alpha expression is related to tumor advancement with the loss of estrogen dependency. Steroid receptor coactivator-3 contributes to tumor progression and can be used as a treatment target for advanced uterine endometrial cancers. Estrogen responsive oncogenes, c-jun and c-Ha-ras, are not modi-fied by progestin in uterine endometrial cancer cells and are considered to be an instinct phenotype as such cancers. By contrast, metastatic potential of estrogen-dependent uterine endometrial cancers can be partially controlled by progestin via metastasis-related genes, E-cadherin/catenins, plasminogen activator inhibitor-1, vascular endothelial growth factor. Thus, sex steroids related phenomena are impress-ive in the advancement of uterine endometrial cancers.
Androgen receptor: acting in the three-dimensional chromatin landscape of prostate cancer cells
Authors: Makkonen Harri , Palvimo Jorma J.
Published: March 2011

Androgen receptor (AR) acts as a hormone-controlled transcription factor that conveys the messages of both natural and synthetic androgens to the level of genes and gene programs. Defective AR signaling leads to a wide array of androgen insensitivity disorders, and deregulated AR function, in particular overexpression of AR, is involved in the growth and progression of prostate cancer. Classic models of AR action view AR-binding sites as upstream regulatory elements in gene promoters or their proximity. However, recent wider genomic screens indicate that AR target genes are commonly activated through very distal chromatin-binding sites. This highlights the importance of long-range chromatin regulation of transcription by the AR, shifting the focus from the linear gene models to three-dimensional models of AR target genes and gene programs. The capability of AR to regulate promoters from long distances in the chromatin is particularly important when evaluating the role of AR in the regulation of genes in malignant prostate cells that frequently show striking genomic aberrations, especially gene fusions. Therefore, in addition to the mechanisms of DNA loop formation between the enhancer bound ARs and the transcription apparatus at the target core promoter, the mechanisms insulating distally bound ARs from promiscuously making contacts and activating other than their normal target gene promoters are critical for proper physiological regulation and thus currently under intense investigation. This review discusses the current knowledge about the AR action in the context of gene aberrations and the three-dimensional chromatin landscape of prostate cancer cells.
Exposure to the endocrine disruptor bisphenol A alters susceptibility for mammary cancer
Authors: Lamartiniere Coral A. , Jenkins Sarah , Betancourt Angela M. , Wang Jun , Russo Jose
Published: March 2011

Bisphenol A (BPA) is a synthetically made chemical used in the production of polycarbonate plastics and epoxy resins. Recent studies have shown that >90% of humans investigated have detectable BPA concentrations. Yet, the biggest concern for BPA is exposure during early development because BPA has been shown to bind to the estrogen receptors (ERs) and cause developmental and reproductive toxicity. We have investigated the potential of perinatal BPA to alter susceptibility for chemically induced mammary cancer in rats. We demonstrate that prepubertal exposure to low concentrations of orally administered BPA given to lactating dams resulted in a significantly decreased tumor latency and increased tumor multiplicity in the dimethylbenz[a]anthra-cene model of rodent mammary carcinogenesis. Our data suggested that the mechanism of action behind this carcinogenic response was mediated through increased cell proliferation, decreased apoptosis, and centered on an upregulation of steroid receptor coactivators (SRCs) 1–3, erbB3, and increased Akt signaling in the mammary gland. Also, we demonstrate that prenatal exposure to BPA shifts the time of susceptibility from 50 days to 100 days for chemically induced mammary carcinogenesis. Proteomic data suggest that prenatal BPA exposure alters the expression of several proteins involved in regulating protein metabolism, signal transduction, developmental processes, and cell cycle and proliferation. Increases in ER-α, SRCs 1–3, Bcl-2, epidermal growth factor-receptor, phospho-IGF-1R, phospho-c-Raf, phospho-ERKs 1/2, phospho-ErbB2, and phospho-Akt are accompanied by increases in cell proliferation. We conclude that exposure to low concentrations of BPA during the prenatal and early postnatal periods of life can predispose for chemically induced mammary cancer.
Assessment of steroidogenic pathways that do not require testosterone as intermediate
Authors: Luu-The Van
Published: March 2011

Traditional literature and textbooks generally describe that estradiol (E2) and dihydrotestosterone (DHT) are synthesized from the aromatization and 5α-reduction of testosterone (T), respectively, following a pathway in which T is an essential intermediate (Tpath). This pathway implies that the steps of aromatization and 5α-reduction follow the reaction of the androgenic 17β-hydroxysteroid dehydrogenase (17β-HSD) that catalyzes the conversion of 4-androstenedione (4-dione) into T, and that estrogenic 17β-HSDs are not required. Contrary to this belief, the cloning of many estrogen-specific 17β-HSDs and the observation of higher affinity of aromatase and 5α-reductase for 4-dione than T are strongly in favor of biosynthetic pathways in which the steps catalyzed by aromatase and 5α-reductase precede that catalyzed by 17β-HSDs. Such pathways do not require T as an intermediate, as demonstrated by experiments using [14C]-labeled DHEA and 4-dione as substrates and incubation with SZ95 sebaceous gland, DU-145 prostate cancer and JEG-3 choriocarcinoma cell lines cultured in the presence of inhibitors of 5α-reductase and aromatase. A review of early literature about patients with testicular 17β-HSD deficiency and of steroid metabolism appears to confirm the physiological functionality of the E2 and DHT biosynthetic pathway not requiring T as intermediate (noTpath).
Agent-noun polysemy in Slavic: some examples
Authors: Luschützky Hans Christian
Published: March 2011

Agentive formations in Slavic languages employ a vast amount of suffixes, some of which are common to all individual Slavic languages, while others are productive (or have evolved) only in particular regions of the Slavic-speaking area. This contribution presents examples of the most characteristic features of agentive formations across Slavic languages, including Old Church Slavonic as a representative of a diachronically earlier language state. In order to assess the specific setting of polysemy of agentive formations, attention focuses on enhancing factors such as multifunctionality, i.e., applicability of one and the same suffix to verbal and nominal (optionally including adjectival) bases.
The contribution of rapid KATP channel gene mutation analysis to the clinical management of children with congenital hyperinsulinism
Authors: Banerjee I , Skae M , Flanagan S E , Rigby L , Patel L , Didi M , Blair J , Ehtisham S , Ellard S , Cosgrove K E , Dunne M J , Clayton P E
Published: March 2011

Objective

In children with congenital hyperinsulinism (CHI), KATP channel genes (ABCC8 and KCNJ11) can be screened rapidly for potential pathogenic mutations. We aimed to assess the contribution of rapid genetic testing to the clinical management of CHI.

Design

Follow-up observational study at two CHI referral hospitals.

Methods

Clinical outcomes such as subtotal pancreatectomy, 18F-Dopa positron emission tomography–computed tomography (PET–CT) scanning, stability on medical treatment and remission were assessed in a cohort of 101 children with CHI.

Results

In total, 32 (32%) children had pathogenic mutations in KATP channel genes (27 in ABCC8 and five in KCNJ11), of which 11 (34%) were novel. In those negative at initial screening, other mutations (GLUD1, GCK, and HNF4A) were identified in three children. Those with homozygous/compound heterozygous ABCC8/KCNJ11 mutations were more likely to require a subtotal pancreatectomy CHI (7/10, 70%). Those with paternal heterozygous mutations were investigated with 18F-Dopa PET–CT scanning and 7/13 (54%) had a focal lesionectomy, whereas four (31%) required subtotal pancreatectomy for diffuse CHI. Those with maternal heterozygous mutations were most likely to achieve remission (5/5, 100%). In 66 with no identified mutation, 43 (65%) achieved remission, 22 (33%) were stable on medical treatment and only one child required a subtotal pancreatectomy.

Conclusions

Rapid genetic analysis is important in the management pathway of CHI; it provides aetiological confirmation of the diagnosis, indicates the likely need for a subtotal pancreatectomy and identifies those who require 18F-Dopa PET–CT scanning. In the absence of a mutation, reassurance of a favourable outcome can be given early in the course of CHI.
Role of thyroglobulin on negative feedback autoregulation of thyroid follicular function and growth
Authors: Suzuki Koichi , Kawashima Akira , Yoshihara Aya , Akama Takeshi , Sue Mariko , Yoshida Akio , Kimura Hiroaki J
Published: March 2011

Thyroid function is tightly regulated by TSH. Although individual follicles are exposed to the same blood supply of TSH and express relatively homogenous levels of the TSH receptor, the function of individual follicles is variable. It was shown that thyroglobulin (Tg), stored in the follicular lumen, is a potent negative feedback regulator of follicular function. Thus, physiological concentrations of Tg significantly suppress thyroid-specific gene expression and antagonize the TSH-mediated stimulation that induces expression of thyroid-specific genes. Tg coordinately regulates both basal and apical iodide transporters in thyroid follicular cells. Recently, it was also reported that Tg could induce thyroid cell growth in the absence of TSH. These results indicate that Tg is an essential autocrine regulator of physiological thyroid follicular function that counteracts the effects of TSH.
Materials Interactions in the Firing of Copper Thick Film Multilayer Ceramics
Authors: Borland William , Siuta Vincent P.
Published: March 2011

In recent years, copper thick film materials have gained rapid acceptance in ceramic multilayer interconnect boards because of their ability to meet advanced packaging requirements at reasonable cost. With high volume production, however, problems such as opens, shorts, blisters and porosity have been experienced. Many of these failures may be attributed to undesirable materials interactions caused by reducing conditions which can be caused by incomplete burnout of thick film organics during firing.

This paper considers the interactions in current copper thick film material systems. Primary emphasis will be placed on chemical interactions that occur in both ideal and non-ideal conditions during firing. Failure modes will be related to chemistry and processing. New systems designed to overcome processing sensitivity will be discussed.
AEM Study of thin and Thick Film Metallization on AIN Substrates
Authors: Westwood Alistair D. , Notis Michael R.
Published: March 2011

Microstructural characterization of thin film (Au-Pt-Ti) and thick film (Mo-Mn) metallization on AIN substrates has been performed using Transmission Electron Microscopy (TEM), Analytical Electron Microscopy (AEM), Convergent Beam Electron Diffraction (CBED) and Auger Electron Spectroscopy (AES). The reaction mechanisms for both types of metallization methods are proposed. In particular, the microchemical and morphological nature of grain boundary penetration and precipitation within the AIN near the metallization interface has been examined.
Relationship Between Glass Leaching Mechanism and Geochemical Transport of Radionuclides
Authors: Avogadro A. , Lanza F.
Published: March 2011

When the leaching of glasses is taken into consideration in risk analysis models, it is necessary to make a distinction between accidental and normal conditions in the repository. In accidental conditions, it is assumed that the glass will be leached by ground-water which can also be renewed. The composition of this water will be related to the aquifer existing around the repository. Under normal repository conditions the leaching process has to be analyzed separately for each geological formation considered.
Sorption of Actinides in Well-Defined Oxidation States on Geologic Media
Authors: Allard B. , Olofsson U. , Torstenfelt B. , Kipatsi H. , Andersson K.
Published: March 2011

The long-lived actinides and their daughter products largely dominate the biological hazards from spent nuclear fuel already from some 300 years after the discharge from the reactor and onwards . Therefore it is essential to make reliable assessments of the geochemistry of these elements in any concept for long-term storage of spent fuel or reprocessing waste, etc.
Microwave Preparation of Mullite Powders
Authors: Komarneni Sridhar , Breval Else , Roy Rustum
Published: March 2011

Mullite, Al6Si2O13 composition gels were made by the single phase and diphasic routes. The wet mullite gels were heated in the insulated cavity of an ordinary kitchen microwave oven (2.45 GHz; 700 watts). Crystalline mullite powders were obtained from single phase gels while the diphasic gels yielded α-Al2O3 and mullite in a matter of 20–25 minutes of microwave heating. Trans- mission electron microscopy showed that the mullite particle size varied between 50 nm to 1 μm. The results of this study suggest that fine powders of mullite can be obtained from single phase mullite gels by optimizing the microwave processing parameters.
Microwave Heating of Fused Quartz to High Temperatures in the Fabrication Process of Optical Fibers
Authors: Hassler Y. , Johansen L.
Published: March 2011

Microwave heating in the fabrication process of high quality quartz fibers for telecommunication is described. In this process tubes and rods of ultrapure quartz are heated to temperatures above 2000 °C.

High quality fibers, referring to both optical attenuation and geometrical properties, have been manufactured. The homogeneous nature of microwave heating results in a significantly decreased production time per fiberkilometer.

Measurements of the most important materials parameter, the dielecric loss factor of quartz as function of temperature and frequency, are presented.
Time-Resolved Study of Silicon During Pulsed-Laser Annealing
Authors: Larson B. C. , White C. W. , Noggle T. S. , Barhorst J. F. , Mills D. M.
Published: March 2011

Near surface temperatures and temperature gradients have been studied in silicon during pulsed laser annealing. The investigation was carried out using nanosecond resolution x-ray diffraction measurements made at the Cornell High Energy Synchrotron Source. Thermal-induced-strain analyses of these real-time, extended Bragg scattering measurements have shown that the lattice temperature reached the melting point during 15 ns, 1.1–1.5 J/cm2 ruby laser pulses and that the temperature of the liquid-solid interface remained at that temperature throughout the high reflectivity phase, after which time the surface temperature subsided rapidly. The temperature gradients below the liquid-solid interface were found to be in the range of 107°C/cm.
Electronic Structure of bcc Cr-Ru Alloys in the Region of Coexisting Antiferromagnetism and Superconductivity
Authors: Johnson D. D. , Pickett W. E.
Published: March 2011

The self-consistent Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) method is applied to determine the changes in the Cr electronic structure due to addition of up to 30% Ru. The results provide an interpretation of the coexisting antiferromagnetism and superconductivity in terms of specific pieces of Fermi surface. The strong nesting which occurs for the Cr Fermi surface survives the addition of at least 20% Ru, in agreement with the observed persistence of antiferromagnetism into this region.
Defect Studies in Silicon Dioxide by Local Density Approximation Total Energy Methods
Authors: Allan Douglas C. , Teter Michael P. , Joannopoulos John D. , Bar-Yam Yaneer , Pantelides Sokrates T.
Published: March 2011

The oxygen vacancy in silicon dioxide is currently believed to explain one of the most important defects observed in this material, the E1 ' center. To get a better understanding of the oxygen vacancy, we have investigated the equilibrium geometric structures, total energies, and charge densities of several charge states of the defect in alpha cristobalite. We also present some preliminary results for alpha quartz.
Variational Quantum Monte Carlo Calculation of Materials Properties
Authors: Louie Steven G.
Published: March 2011

A new method of calculating the total energy and other ground-state properties of solids which employs nonlocal pseudopotentials in conjunction with the variational quantum Monte Carlo approach is presented. Valence electron correlations are treated using the exact interaction with a correlated many-electron wavefunction of the Jastrow-Slater form. The use of pseudopotentials for the electron-ion interaction removes from the problem the large fluctuations of electron energies in the core region which occur in quantum Monte Carlo all-electron schemes. We discuss calculation of the cohesive energy and structural properties of diamond and graphite and the ionization energy and electron affinity of atoms using the present approach. The results are in excellent agreement with experiment.
In-Situ Hrem Observation of Low Temperature Fracture Near the Oxide Surface of Iron Doped Silicon
Authors: Rhee M.H. , Barry J.C. , Coghlan W.A.
Published: March 2011

Fracture of iron-doped silicon has been studied using HREM. Fractures were introduced into cross section specimens of oxidized silicon using microhardness indents. A crack is extended using thermal stresses generated by the electron beam. The tip of the advancing crack is made up of two or more parallel sub-cracks. As the crack grows, one of these sub-cracks appears to dominate while the multiple crack front still exists at the tip. Also shear strain has been seen across the crack interface. The process appears to be much more complicated that existing models suggest.
The Shear Strength Between Atomically Smooth Surfaces
Authors: Alsten John Van , Granick Steve
Published: March 2011

As surfaces slide over one another, work is done by the forces causing the motion and energy is lost. Origins of this friction behavior can be very complex and are still scarcely understood in molecular terms. Adhesion, plowing and asperity deformation, heat-induced chemical reactions, viscoelastic response of a sbustrate, and still other influences, can all dominate depending on the physical system in question. Conceptually it is convenient to group these many possible origins of energy dissipation into three categories: elastic and plastic deformation of the underlying substgrates, wear (i.e. degradation of the surfaces and substrates during the course of sliding, and surface mechanical properties of the interface itself. In favorable model systems a substantial degree of separation is possible. This paper is concerned with separating the surface chemical contributions to boundary layer friction from the mechanical ones.
A Non-Destructive Technique to Measure the Extent of Inter-Diffusion in Oxide Solid Solution Interfaces Between Metals and Ceramics
Authors: Narayan C. , Velosa A. , Purushothaman S. , Reddy S.N.S.
Published: March 2011

Adhesion of metals to ceramics is an area of extreme importance for packaging of electronic devices. In one of the several adhesion schemes that can be employed to promote adhesion between metals and ceramics, the metal is preferentially oxidized at the interface and there is solid solution mixing between the substrate and the oxidized metal at the interface. An example is the Ni/MgO system. Estimation of the extent of mixing at the interface is often difficult and time consuming. This work describes a simple non-destructive method to estimate the extent of interdiffusion between the oxides using a standard x-ray diffraction measurement. This technique relies on the changes in the peak shapes and positions as a function of the nature and extent of interdiffusion. The technique is precise enough to allow one to estimate interdiffasion coefficients in some oxide/oxide systems. The diffusion and intermixing phenomena in the NiO/MgO system will be examined as an illustrative example.
Dislocation Related D-Band Luminescence; the Effects of Transition Metal Contamination
Authors: Higgs Victor , Lightowlers E.C. , Kightley P.
Published: March 2011

Photoluminescence measurements have been made on plastically formed silicon, free from metal contamination, with dislocation densities in the range 104-108cm-2. Only after deliberate contamination with Cu, Fe or Ni were the dislocation related D-bands the dominant spectral features observed. TEM analysis has revealed that there are no differences in the dislocation structures before and after contamination and that there is no evidence for precipitation on the dislocations or in their strain fields. The D-band features may, therefore, be due to impurities (metal atoms or point defect complexes) trapped in the strain fields of the dislocations.
Solvent Diffusion in Selected Polyimide Films
Authors: Pawlowski W. P. , Jacobson M. I. , Teixeira M. E. , Sakorafos K. G.
Published: March 2011

The absorption of several solvents including methylene chloride (MC), methyl chloroform (MCF), gamma-butyrolactone (BLO), dibromomethane (DBRO), 1,2-dichloroethane (DCE), and 1,2-dichloropropane (DCP) in Kapton H*, Upilex S**, and Upilex R** polyimide film was measured gravimetrically. A significant difference in the rate and amount of absorption of these chemicals by the various films was observed. Complimentary Rutherford Backscattering Spectrometry (RBS) measurements provided additional information regarding the amount of solvent absorbed and mode of transport.
Electromigration in Thin Films of Au on GaAs
Authors: Tang P. F. , Milnes A. G. , Bauer C. L. , Mahajan S.
Published: March 2011

Evolution of the fractional change of electrical resistance ΔR/R in thin films of Au on (001) substrates of semi-insulating GaAs has been investigated as a function of time t, temperature T, and current density j. Initially, ΔR/R increases linearly with increasing t for constant T and j, and exponentially with increasing T for constant t and j, characterized by an activation energy of 0.73 eV. An analytical model is developed to evaluate ΔR/R for the early stages of electromigration. This model is based on flux divergence at grain boundary triple junctions resulting from variations of grain boundary inclination and/or diffusivity. Using a Monte Carlo method, conducting lines containing a prescribed number of random triple junctions are simulated, wherein distribution of mass flux divergence determines initial values of ΔR/R. Moreover, by selection of an appropriate failure criterion, the sequence of cumulative failures is characterized by a log-normal-like distribution, which defines mean time to failure and corresponding standard deviation. In general, the model is in good agreement with experimental observations.
The Chemistry of Al-Tobermorite and its Coexisting Phases AT 175°C
Authors: Barnes Mary W. , Scheetz Barry E.
Published: March 2011

The substitution of Al into the structure of tobermorite was investigated, along with the resultant phase assemblages that compatibly coexist with the Al-tobermorite. All experiments were conducted under hydrothermal conditions at saturated steam pressure. The temperatures of the experiments varied from 90° to 190°C and times from 1 to 28 days. Ca/Si ratios varied from 0.7 to 1.7, Al/(Al+Si) from 0.12 to 0.30. NaOH varied from none to 5 moles/mole tobermorite constituents. X-ray diffraction was used not only to identify phases but to determine degree of substitution and the rate of approach to steady state.

Maximum Al substitution was found to be Al/(Al+Si) = 0.13, and the maximum interlayer spacing was 11.42 ± 0.015 Å. This is in agreement with previously published work which found a trace of hydrogarnet at Al(Al+Si) = 0.15 and a maximum interlayer spacing of 11.45 ± 0.02 A. When Al concentrations in the mix are greater than enough to make maximum Al-tobermorite, “low”-hydrogarnet (“low”-hydrogarnet has ∼0.1 SiO2 per mole). As Al concentration is raised, a variable composition hydrogamet is formed and then a “high”-garnet of constant composition (SiO2 = 0.7 moles/mole hydrogarnet) is formed.

NaOH was found to have a major effect on the kinetics and the phase assemblages at a given time. Al-tobermorite, although stable at 90°C, converts to xonotlite at 175°C in the absence of NaOH. In its presence, even at a level too low to make Na-containing phases, Al-tobermorite persists at 21 days at 175°C. In the absence of NaOH, at 175°C, Al-tobermorite forms at up to 7–10 days but is converted to xonotlite at 28 days. Coexisting phases are gyrolite and cowlesite at Ca/Si ≥ 1 and hillebrandite and “low”-garnet at Ca/Si > 1. When there is enough NaOH to form Na-containing phases, Al-tobermorite coexists with reyerite and analcime at Ca/Si > 1. At Ca/Si < 1 and Al less than the composition on the tie line between Al-tobermorite and “low”-garnet, Al-tobermorite coexists with “low”-garnet and portlandite. In the compatibility triangle between Al-tobermorite, “low”-garnet, and “high”-garnet, Al-tobermorite coexists with variable Si-gamet. When Al exceeds its limiting value on the tie line, Al-tobermorite-“high”-gamet, the assemblage is Al-tobermorite-“high”-gamet-cowlesite.
The Low Temperature Formation of Synthetic Bone
Authors: Brown Paul W. , Sample David , Hocker Nancy
Published: March 2011

Hard human tissues, teeth, and bone are composite materials. These composites are primarily composed of impure, calcium-deficient hydroxyapatite and collagen. The formula for stoichiometric hydroxyapatite is: Ca10(PO4)6(OH)2. However, this compound exists over a range of compositions that may be characterized in terms of a Ca/P ratio. The Ca/P ratio of stoichiometric material is 1.67. Stable compositions may have Ca/P ratios extending to 1.5:Ca9(PO4)6HOH. Structurally, hydroxyapatite contains two types of calcium sites. Four of the calcium sites per unit cell are each coordinated with 8 oxygens. Six of the calcium sites per unit cell are 7-coordinated. Six of these seven bonds are with oxygens, while the 7th is with a hydroxyl ion. Calcium deficiency results in the formation of up to one vacancy per unit cell on one of these seven coordinated calcium sites. Charge balance is maintained by the removal of one of the hydroxyl oxygens. The remaining proton becomes bound to an oxygen that is also coordinated with a phosphate. As a result, it is common to express the formula of calcium-deficient hydroxyapatite having a Ca/P ratio of 1.5 as Ca9(PO4)5(HPO4)OH.
Fracture-Exafs: A New Method for the Study of Interfaces in thin films and Polycrystalline Materials
Authors: Barrera E. V. , Maruyama Benji , Heald S. M.
Published: March 2011

Fracture-EXAFS is a technique, proposed here for the first time, which combines an appropriate mechanical test with EXAFS analysis to investigate the atomic processes involved in the fracture process. Fracture-EXAFS builds upon the fracture-Auger electron spectroscopy technique, which was used to study the elemental composition of fracture surfaces, and has yielded significant insight into phenomena such as grain boundary embrittlement and composite interface fracture. Extended X-ray Absorption Fine Structure (EXAFS) analysis yields structural, as well as chemical information. The identity, coordination number, position and degree of disorder of atoms in the vicinity of interfaces and surfaces can be determined. Thus, EXAFS comparison of the imminent (latent) fracture surface to the fracture surface can yield structural, as well as chemical information about the fracture process. In this preliminary report, emphasis will be given to the application of Fracture-EXAFS to the study of interfaces in thin films. Discussion will also include the use of Fracture-EXAFS to study grain boundaries in polycrystalline materials.
Metastable Phases in Rapidly Solidified Aluminum-Rich Al-Fe Alloys
Authors: Shechtman D. , Swartzendruber L.J.
Published: March 2011

Aluminum-rich Al-Fe binary alloys up to and including Al3Fe were prepared by melt spinning in order to study the metastable phase structure and its transformation following heat treatment. Transmission electron microscopy and nuclear gamma-ray resonance were utilized in the study. The rapidly solidified structure was found to contain up to three metastable phases. One of the phases, with a composition and a gamma-ray resonance spectrum appropriate for Al6Fe, has either a globular or a cellular morphology upon quenching.
Ta and Nb Reinforced MoSi2
Authors: Carter David H. , Martin Patrick L.
Published: March 2011

MoSi2matrix composites have been recognized lately as potential materials for structural applications at elevated temperatures. Specifically, MoSi2composites may exhibit useful properties at temperatures to 1400°C. Previous work improved the yield strength of MoSi2at 1400°C by a factor of five through SiC whisker reinforcement. Current research is directed towards increasing the fracture toughness of MoSi2through the addition of ductile phase reinforcements such as niobium and tantalum. The reaction between Nb and MoSi2to form (Mo,Nb)5Si3proceeds with faster kinetics at hot isostatic press temperatures as low as 1100°C when compared to the reaction between Ta and MoSi2to form (Mo,Ta)5Si3. This reaction product exhibits very poor properties, as evidenced by crack propagation through this layer during fracture. The feasibility of hot working these composites to produce tailored microstructures is examined.
Mechanical Behavior and Failure Mechanisms of SCS-6/Ti3Al Composites
Authors: Jeng S. M. , Yang C. J. , Yang J.-M. , Rosenthal D. G. , Goebel J.
Published: March 2011

The mechanical properties and failure mechanisms of the SCS-6/Ti3Al composite have been studied. Both tensile and notched bend tests were conducted at room temperature on the monolithic and fiber-reinforced Ti-25Al-10Nb-3V-1Mo. Optical and scanning electron microscopy were used to study the crack initiation and propagation mechanisms. The role of the fiber, matrix and interfacial properties on the composite behavior was also assessed.
Interfacial Shear Behavior of Sapphire-Reinforced NiAi Composites
Authors: Moose C. A. , Koss D. A. , Hellmann J. R.
Published: March 2011

The interfacial shear behavior in near-equiatomic NiA1 reinforced by sapphire filaments has been examined at room temperature using a fiber pushout test technique. The loaddisplacement data indicate a large variability in the initial interface failure stress, although reverse push behavior indicates a comparatively constant interfacial sliding friction stress. The observed behavior suggests that the presence of asperities on the fiber surfaces and nonuniformities in fiber diameter require constrained plastic flow within the NiAl matrix in order for interfacial shear to occur. The location, shape, severity, and distribution of fiber asperities as well as the uniformity of fiber diameter are critical to the interfacial shear process.
Ductile Phase Toughening of Brittle Intermetallics
Authors: Anton D. L. , Shah D. M.
Published: March 2011

One method of imparting damage tolerance into intermetallic compounds is to introduce ductile particles in a fine uniform distribution. Systematic criteria are given as to the necessary requirements for such ductile phase reinforced systems. Two composite systems, Cr2Nb/Nb and Nb3Al/Nb were selected for further evaluation. Both microstructural evaluations as well as thermal stability were demonstrated in both systems. Small cracks introduced via micro-hardness indentations were measured as a function of precipitate size. In Cr2Nb/Nb the crack lengths decreased with increasing particle size which was explained through increasing effectiveness of ductile particles with minimum effective particle radii calculated at 6-10 μm. Larger particles along with poor ductile phase distributions led to lower damage tolerance in aged Nb3Al/Nb. By maintaining uniform ductile particle distributions, intermetallic compounds possessing superior damage tolerance have been demonstrated.
High Strength, Porous, Brittle Materials
Authors: Haggerty J. S. , Lighfoot A. , Ritter J. E. , Nair S. V.
Published: March 2011

Contrary to existing models, strengths need not be a strong function of porosity for intermediate density, brittle materials. Flaw sizes can remain small (<50μm) if the void space is distributed uniformly in minimum dimension pores. For RBSN, fracture toughness decreases linearly with porosity for 0< porosity <40%. Strains to failure and specific strengths of these materials are higher than fully dense counterparts.
Micro-Reinforced Cementitious Materials
Authors: Banthia Nemkumar , Sheng Jiakang
Published: March 2011

Reinforcement of cements with very fine fibers of carbon and steel in mono- and hybrid-forms has been investigated. While both carbon and steel fibers led to considerable improvements in strength and toughness, on a comparative basis, carbon fibers bring about a better improvement in the toughness or energy absorption, and the steel fibers impart higher tensile strengths to the base cement matrices. In the hybrid-fiber systems, the improvements lie somewhere in between those of the equivalent mono-fiber systems.
Rapid Thermal Processing of Ferroelectric Thin Films
Authors: Wu Zheng , Pascual Roberto , Vasant Kumar C.V.R. , Amd David , Sayer Michael
Published: March 2011

The preparation of ferroelectric lead zirconate titanate (PZT) thin films by rapid thermal processing (RTP) is reported. The films were deposited by chemical sol gel and physical sputter techniques. The heating rate of RTP was found to have significant influence on the crystallization behavior. Faster heating rates lead to lowering of the crystallization temperature and reduction of grain size. PZT films were obtained with dielectric constants ~ 1000, remanent polarizations between 20 and 30μC/cm2, coercive fields 20 to 60kV/cm, and no significant fatigue for 109 to 1010 stressing cycles.
Diffusion Barriers with Sputtered TaN, Ta-Si-N, and TaSix for Thermal Stable Contact
Authors: Wang W.G. , Chang C.S. , Chen W.S. , Huang F.S.
Published: March 2011

Tantalum nitride, Ta-Si-N, and tantalum silicide films were investigated for use as a diffusion barrier in Al/Si metallization. The former two films were deposited by reactive sputtering of a Ta or TaSi2 target in Ar/N2 gas mixture. The TaSix films were fabricated by sputtering of TaSi2 target. Then, the Ta-Si-N and TaSix film were annealed at temperature 950°C for 15 seconds by RTA. The resistivities of Ta-Si-N, TaN, and TaSix films are about 180, 250, and 60 µohm-cm, respectively. The X-ray photoelectron spectroscopies were made to study the chemical structure of the films. For both nitrides, TaO comprises the native oxide formed at room temperature. A large amount of silicon nitride was formed on the surface of TaSix film during the RTA. Rutherford backscattering and Auger profile were performed to understand the degradation. It was found that these three films are effective diffusion barriers at temperature 620°C.
Advances in Ultrasonic Disk Cutting and Precision Dimpling
Authors: Fischione Paul E. , Kelly Thomas F. , Dalley Amber M. , Holzman Louis M. , Dawson-Elli David
Published: March 2011

Many of today's advanced materials are prepared using a combination of ultrasonic disk cutting, dimpling, and ion milling. In order to optimize the analytical results from a single specimen, several improvements have been made in instrumentation for ultrasonic disk cutting. Also, a system has been developed for detecting either at or near-electron transparency in TEM specimens. Both of these aspects are described. Examples are provided for silicon, metal/ceramic composites and blanket substrate layers for electronic devices.
Phase Stability and Diagrams from First Principles
Authors: Sanchez J.M. , Becker J.D.
Published: March 2011

First principles theories of alloy phase equilibrium have been successfully used in recent years to compute temperature-composition phase diagrams for solid state phases. One particular approach, originating with the successful phenomenological Ising models to describe the alloy Hamiltonian, uses a cluster expansion of the configurational energy in terms of short-ranged pair and many-body interactions. The approach is deeply rooted in our ability to compute accurate total energies of relatively complex compounds, using density functional theory in the local approximation, from which effective interactions may be obtained. Fundamental aspects of the method which include convergence of the cluster expansion, treatment of the configurational entropy and description of vibrational modes are reviewed. Applications of the theory are given for binary alloys in the Ru-Zr-Nb system using the Linear Muffin Tin Orbital method for the total energy calculations, the Cluster Variation method for the description of the configurational entropy, and the Debye-Gruneisen approximation for the vibrational modes. The results are used to compute the equilibrium phase diagram for the Zr-Nb system and to assess current experimental data on phase stability in the Ru-Nb system. In the latter case, the calculations indicate that the DO19 structure is a likely candidate structure for the experimentally observed hexagonal-based compound Ru3Nb. Investigation of the energies and interactions of tetragonal structures as a function of the c/a ratio suggest the L10 structure as a likely candidate for the observed tetragonal phase near 1:1 stoichiometry.
Effects of Radiation Exposure on Glass Alteration in a Steam Environment
Authors: Wronkiewicz D. J. , Wang L. M. , Bates J. K. , Tani B. S.
Published: March 2011

Several Savannah River Plant (SRL) glass compositions were reacted in steam at temperatures of 150 to 200°C. Half of the tests utilized actinide-doped monoliths and were exposed to an external ionizing gamma source, while the remainder were doped only with U and reacted without gamma exposure. All glass samples readily reacted to form secondary mineral phases within the first week of testing. An in situ layer of smectite initially developed on nonirradiated SRL 202 glass test samples. After 21 days, a thin layer of illite was precipitated from solution onto the smectite layer. A number of alteration products including zeolite, Casilicate, and alkali or alkaline earth uranyl silicate phases were also distributed over most sample surfaces. In the irradiated SRL 202 glass tests, up to three layers enveloped rounded, and sometimes fractured, glass cores. After 35 to 56 days these remnant cores were replaced by a mottled or banded Fe- and Si-rich material. The formation of some secondary mineral phases also has been accelerated in the irradiated tests, and in some instances, the irradiated environment may have led to the precipitation of a different suite of minerals. The alteration layer(s) developed at rates of 2.3 and 32 μm/day for the nonirradiated and irradiated SRL 202 glasses, respectively, indicating that layer development is accelerated by a factor of ∼10 to 15X due to radiation exposure under the test conditions.
Principles of the Selection of Effective and Economic Corrosion-Resistant Alloys in Contact with Biologically Active Environments
Authors: Dowling Nicholas J.E. , Lundin Carl , Sachs Dan , Bullen Jan A. , White David C.
Published: March 2011

Current field experience with microbiological influenced corrosion (MIC) has now extended into the medium-grade stainless steels containing 4% molybdenum and in excess of 20% chromium. These may indeed be special cases where a combination of synergistic effects, temperature, and wet-dry cycles have aggravated a situation that is already subject to a mild form of MIC. Data are presented from a fresh water field site, comparing the relative performance of several welded coupons, including AISI 304L, 316L, and higher alloyed grades, 622, C276, C-22, 25-6Mo exposed to principally iron-oxidizing bacteria. Specific data is also presented from a saltwater laboratory study of AISI 316/E308 welds where sulfate-reducing bacteria were included. Normally this weld configuration is considered “mismatched” however has nevertheless been employed at several inland power stations. Data is presented which suggests that under “freshwater” conditions (ie. < 150 ppm Cl−) excluding deposits originating from other sources, for example, calcareous scales, an increase in chromium content may significantly reduce the problem. The laboratory study showed that severe generalized rusting of 316/E308 welds may be expected in the presence of fermentative and sulfate-reducing bacteria in chloride environments. The relationship of these data, and of those available in the literature, to the problem of long-term radioactive waste disposal, is discussed with respect to materials selection.
Diffusion of Corrosion Products of Iron in Compacted Bentonite.
Authors: Idemitsu K. , Furuya H. , Inagaki Y.
Published: March 2011

Carbon steel is one of the candidate overpack materials for high-level waste disposal. The corrosion rate of carbon steel is reduced by the presence of buffer materials such as bentonite and seems to be affected by the diffusion of corrosive materials and corrosion products through the buffer material.

The apparent diffusivities of corrosion product of iron were measured in some bentonite specimens in contact with carbon steel. The apparent diffusivities of iron were also measured without carbon steel for comparison. The apparent diffusivities of corrosion product were on the order of 10−12 m2/s and showed a tendency to decrease with increasing density of the bentonite specimen. There was no significant effect of silica sand on the apparent diffusivities. The apparent diffusivities of iron in the system without carbon steel were in the range of 10−14 m2/s and showed a tendency to increase with increasing silica sand content. The difference of the diffusivities between corrosion product and iron without carbon steel seems to be due to the difference of diffusing species. The color of the corrosion product was dark-green during contact with bentonite specimens and became red on exposure to air in a few minutes. Gas bubbles were also observed in the corrosion product. This suggests hydrogen generation during corrosion of the carbon steel. Thus the diffusing species seems to be in a reduced state, probably ferrous ion. On the other hand, the diffusing species of iron without carbon steel was probably a ferric hydroxide complex that was negatively charged. This suggests that ferrous ion could diffuse in the surface water adsorbed on bentonite, while ferric complex was excluded.