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A series of phase transformations of a novel fluoroaluminosilicate glass forming a range of fluorapatite glass-ceramics on sintering are reported. The sintering process induces formation of fluorapatite, mullite, and anorthite phases within the amorphous silicate matrices of the glass-ceramics. The fluoroaluminosilicate glass, SiO2–Al2O3–P2O5–CaO–CaF2, is prepared from waste materials, such as rice husk ash, pacific oyster shells, and disposable aluminium cans. The thermally induced crystallographic and microstructure evolution of the fluoroaluminosilicate glass towards the fluorapatite glass-ceramics, with applications in dental and bone restoration, are investigated by powder X-ray diffraction and small-angle neutron-scattering techniques.
We report here the first radiocarbon dating of blood residues on prehistoric stone tools. The residues found on two stone artifacts were subjected to various exploratory biochemical techniques to identify the species from which they were derived and to separate a suitable sample for dating by accelerator mass spectrometry. Although these techniques need much further development and detailed testing, the ages obtained in this first study were consistent with other data, indicating that the concept is viable. For the first time, the time of use of stone tools has been found directly, rather than by stratigraphic or other archaeologic inferential techniques.
Of the 13 US vancomycin-resistant Staphylococcus aureus (VRSA) cases, 8 were identified in southeastern Michigan, primarily in patients with chronic lower-extremity wounds. VRSA infections develop when the vanA gene from vancomycin-resistant enterococcus (VRE) transfers to S. aureus. Incl8-like plasmids in VRE and pSK41-like plasmids in S. aureus appear to be important precursors to this transfer.
Identify the prevalence of VRSA precursor organisms.
Prospective cohort with embedded case-control study.
Southeastern Michigan adults with chronic lower-extremity wounds.
Adults presenting to 3 southeastern Michigan medical centers during the period February 15 through March 4, 2011, with chronic lower-extremity wounds had wound, nares, and perirectal swab specimens cultured for S. aureus and VRE, which were tested for pSK41-like and Incl8-like plasmids by polymerase chain reaction. We interviewed participants and reviewed clinical records. Risk factors for pSK41-positive S. aureus were assessed among all study participants (cohort analysis) and among only S. aureus-colonized participants (case-control analysis).
Of 179 participants with wound cultures, 26% were colonized with methicillin-susceptible S. aureus, 27% were colonized with methicillin-resistant S. aureus, and 4% were colonized with VRE, although only 17% consented to perirectal culture. Six participants (3%) had pSK41-positive S. aureus, and none had Incl8-positive VRE. Having chronic wounds for over 2 years was associated with pSK41-positive S. aureus colonization in both analyses.
Colonization with VRSA precursor organisms was rare. Having long-standing chronic wounds was a risk factor for pSK41-positive S. aureus colonization. Additional investigation into the prevalence of VRSA precursors among a larger cohort of patients is warranted.
We investigated an increase in Trichosporon asahii isolates among inpatients. We identified 63 cases; 4 involved disseminated disease. Trichosporon species was recovered from equipment cleaning rooms, washbasins, and fomites, which suggests transmission through washbasins. Patient washbasins should be single-patient use only; adherence to appropriate hospital disinfection guidelines was recommended.
A survey of the Maine landscape and nursery industry was conducted to identify industry views on invasive plant issues, attitudes towards potential regulation, and to estimate the potential economic costs of banning the sale of specific invasive plant species in Maine. Analysis of the 190 surveys returned (19% of 980 mailed) revealed that 76% of industry member respondents were genuinely concerned about invasive plant issues, and the same percentage felt the horticulture industry is responsible for educating customers about invasive plants. Industry members (68%) did not feel compelled to sell invasive plants merely on the basis of customer attraction to the plant, or due to competition with a neighboring business that sells the invasive plant. Self-reporting of sales indicated that Norway maple ($96K), burningbush ($68K), and Japanese barberry ($44K) constituted the largest portion of annual industry revenue (maximum values reported for 2006 to 2008) derived from the sale of seven identified invasive plants. Industry self-regulation was the most favored form of regulation, although the industry likely would not be significantly affected by legislated state-wide bans of at least purple loosestrife and oriental bittersweet. Bans on other popular invasive plants, including burningbush, Japanese barberry, and Norway maple likely would have a relatively small, short-term impact on the horticulture industry until alternative plants with similar properties were identified. The results of this survey demonstrated a need for identifying which plants are truly invasive or potentially invasive in Maine, as well as a need for open discussion of invasive plant issues among all interested parties in Maine.
A low temperature amorphous zinc indium oxide (ZIO) thin film transistor (TFT) backplane technology for high information content flexible organic light emitting diode (OLED) displays has been developed. We have fabricated 4.1-in. diagonal OLED backplanes on the Flexible Display Center’s six-inch wafer-scale pilot line using ZIO as the active layer. The ZIO based TFTs exhibited an effective saturation mobility of 18.6 cm2/V-s and a threshold voltage shift of 2.2 Volts or less under positive and negative gate bias DC stress for 10000 seconds. We report on the critical steps in the evolution of the backplane process: the qualification of the low temperature (200°C) ZIO process, the stability of the devices under forward and reverse bias stress, the transfer of the process to flexible plastic substrates, and the fabrication of white organic light emitting diode (OLED) displays.
Zirconolite-glass and sphene -glass specimens, doped with REE as simulants for trivalent actinides, were leached under two conditions. The first was a solubility test using a powdered sample in deionized water at an SA/V ratio of 200 cm−1, to examine the long-term leaching behavior of the composite materials. The other test was carried out in the presence of moist clay, to assess the degree of surface alteration of the composites in the presence of potential geological repository materials. Both tests were carried out at 90°C.
The cw absorption, steady state photoluminescence (PL), photoinduced absorption (PA), PL-detected magnetic resonance (PLDMR), and the time resolved PL of a novel polyfluorene (PF) prepared with bulky polyphenylene dendrimer substituents are compared with those of (PF) with ethyl-hexyl substituents. We show that the dendronic sidechains suppress the contribution from unwanted low energetic emission, yielding a polymer with pure blue emission. The sidechains also strongly alter the dynamics of the excited entities. In particular, the time-resolved PL and temperature-dependence of the cw PL from 20-320 K reveal distinct singlet exciton (SE) dynamics in the polymer films, while the behavior in solution is essentially the same. However, the PA results show that the dynamics of polarons and triplet excitons (TEs) are similar, and the PLDMR shows that the interaction between the SEs and polarons are also similar.
Rb-doped Ba-hollandite and synroc-C samples were prepared for aqueous dissolution studies at 90°C in deionized water using MCC-1 protocols. Small amounts of possibly Rb-bearing BaTiO3, hibonite and alumina accompanied the major Rb-doped (0.1 formula units) hollandite phase. The Rb loadings in the synroc samples ranged from 0.89 to 2.67 wt%. Rb leached at <0.2 g/m2/d from hollandite samples and <0.1g/m2d from synroc, with the values decreasing with increasing dissolution time. The variance between the dissolution rates for the different Rb-doped hollandite and synroc samples is discussed, in terms of Rb-bearing minor phases.
The 13C NMR of FCC C60 under magic angle spinning (MAS) conditionsyields linewidths on the order of 1 Hz at fields of 4.7 T. The spectrum consists of a primary resonance at 143.7 ppm and a minor peak shifted 0.7 ppm downfield. The intensity of the minor resonance relative to the primary resonance was found to vary from 0.6 to 5.5 % depending on the sample history. The downfield shift obeys Curie's law and isattributed to the Fermi contact coupling interaction between paramagnetic oxygen molecules and all 60 carbon atoms of rapidly rotating adjacent C60 molecules. Exposure of the sample to 1 kbar oxygen for 1 3/4 hours resulted in a spectrum of 7 evenly spaced resonances corresponding to 0 to 6 of the adjacent octahedral interstitial sites being filled with oxygen molecules. At ambient pressure, the oxygen diffused out of the lattice on time scales ranging from hours to days.
By definition, half of all interconnects fail before the measured mean time to failure (t50) is reached. To predict early failures the basic reactions occurring in the metallization and its environment must be understood. To this end, fatal interconnect failure sites were characterized by Auger electron spectroscopy, atomic force microscopy and backscattered scanning electron microscopy. CVD silicon dioxide passivation layer/fatal void interfaces of typical early failure voids were characterized and compared to a typical late failure void interface. The topographies of these fatal voids were also quantitatively compared to increase our understanding of early failure sites and electromigration.
We have used 13C magic-angle spinning (MAS) nuclear magnetic resonance (NMR) to characterize the structure and rotational dynamics of C60 containing oxygen molecules located in the interstitial sites of the fcc lattice. Under normal conditions, a narrow peak at 143.7 ppm is observed for C60. When exposed to oxygen at moderate pressures, several additional resonances appear in the 13C MAS NMR spectrum. These secondary resonances are shifted downfield from the main peak at 143.7 ppm and are due to the Fermi-contact interaction of the paramagnetic oxygen molecules with the 13C nuclear spins. The presence of oxygen depresses the orientational ordering transition by ca. 20 K as observed by DSC. The spin-lattice relaxation time (T1) of each secondary peak shows a minimum near the ordering transition, indicating that this transition is not dependent on the number of oxygen molecules surrounding an individual C60 molecule. The T1 due to paramagnetic relaxation, normalized by the number of surrounding oxygen molecules, is constant. This observation demonstrates that within a given sample, the dynamics of C60 molecules are independent of the number of surrounding oxygen molecules.
A titanate Synroc ceramic for the immobilization of Pu-bearing waste was designed to consist of 70 wt% zirconolite (CaZrTi2O7) + 15 wt% nepheline (NaAlSiO4) + 15 wt% rutile (TiO2). It contained 10 wt% of Pu plus 6 wt% of Gd as a neutron poison. The material was made by our standard sol-gel route, using a mixture of alkoxides and nitrates, followed by stirdrying and calcination. It was fabricated by hot-pressing at 1150–1250°C/20 MPa for 2 hours in a collapsible metal bellows. Though zirconolite was the majority phase, ∼20 wt% of perovskite also formed. Some of the Na, intended for nepheline, partitioned into the titanate phases. 84-day differential total leach rates of Pu were in the order of 10−5 g/m2/d at 90 and 200°C. Companion ceramics using molar substitution of Ce for Pu confirmed the idea that Ce is a good simulant of Pu from a solid state chemical view, but that there are limitations in terms of leach rate parallels.
Perovskite and zirconolite are two of the major phases of the Synroc titanate mineral assemblage. Their aqueous durability under a range of pH conditions at 90°C has been examined. Solution analysis, electron microscopy and X-ray diffraction have been used to investigate the dissolution behaviour of these phases, and a perovskite phase doped with Nd, Sr and Al, using buffered solutions at pH levels of 2.1, 3.7, 6.1, 7.9 and 12.9. After 43 days of leaching, Ca and Ti extractions from perovskite and zirconolite show only a weak pH-dependence.
SEM investigation of the samples leached at pH 2.1, 6.1 and 12.9 showed that a titanaceous surface layer formed on the perovskite specimens. XRD analysis of the perovskite samples showed that anatase formed on the leached surface at acidic and neutral pHs, but not under alkaline conditions, and that minor amounts of rutile also formed. In the leached perovskite specimens doped with Nd, Sr and Al, no rutile was found by XRD and anatase was only detected in the sample leached at pH 2.1. There were no detectable changes in the leached zirconolite samples examined by SEM and XRD.
From elastic recoil detection analysis (ERDA) of 2 MeV He ions and secondary ion mass spectroscopy (SIMS), exposure of Synroc-C to D2O at 150°C for ∼ 30 days produced surface deuteration products of a few nm in thickness, with surface roughness after polishing down to 0.25 µm diamond finish not being of critical importance in the thickness determination. Reaction at 250°C produced more extensive deuteration and general surface alteration, over depths of about a micron. SIMS did not show any surface enhancement of rare earths or Zr on Synroc-C surfaces reacted at 90°C for up to 336 days. Pu-doped SynrocC exposed to deionised water at 70°C showed surface depletion of Pu by alpha-spectroscopy. Zirconolite-rich Synroc showed less surface deuteration than Synroc-C after reaction for 3 weeks at 150°C in D2O. Admixtures of 0.001 M of fluoride ions to dilute HCI (pH = 2) produced deposits of anatase, ∼ 20 µm thick, on perovskite after a few weeks at 90°C; these deposits were much thicker than those produced by the dilute HCI without the fluoride ions being present.
Aqueous durability has been assessed for fourteen pyrochlore- and zirconolite-rich titanate waste forms designed for the immobilisation of excess Pu. The ceramics used in this study contained about 12 wt% Pu and about 15 wt% of Hf and Gd oxides as neutron absorbers and were fabricated by cold-pressing and sintering or hot isostatic pressing.
Total release rates (i.e. unfiltered solution + vessel wall inventory) have been measured withthe MCC-1 test method at 90 °C in deionised water. For all samples, 7-day release rates of Pu are between 4 × 10−5 and about 10−3 g.m−2.d−1, reducing to between about 8 × 10−6 and 3 × 10−5 g.m−2.d−1after more than 300 days of leaching. Release rates of U from the baseline ceramic were found to decrease to values between 6 × 10−4 and 1 × 10−5 g.m−2.d−1after 200 days. Hf leach rates were generally < 5 × 10−6 g.m−2.d−l after more than 7 days. Further, the addition of several % of chemical impurities to the baseline sintered formulations was found to reduce U and Gd releases by about a factor of 10 after 200 days.
Hydrolysis and condensation of trialkoxysilanes, HSi(OMe)3 and HSi(OEt)3, has been used to prepare polyhydridosilsesquioxaes for dielectric applications. In this study we examined the ability of trimethoxysilane (TMS) and triethoxysilane (TES) to undergo sol-gel polymerization to afford gels. Sol-gel polymerization experiments were conducted under acidic (HCl), basic (NaOH), and neutral conditions in methanol or ethanol. Gels prepared with basic catalysts were exothermic with the evolution of hydrogen gas. Gel times are compared with silica gels prepared from tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS). Gels were worked up under aqueous conditions to afford xerogels. Surface area analyses by nitrogen sorption porosimetery revealed that the materials were mostly mesoporous materials with surface areas in the hundreds of square meters per gram. Solid state 29Si CP MAS NMR was used to determine the amount of hydrido group remaining in the xerogels. Gels prepared under acidic conditions were essentially polysilsesquioxanes with very little loss of hydride functionalities. In gels prepared under basic conditions the hydride groups were completely gone leaving silica gels. Gels prepared with neutral water lost approximately 66% of the hydride groups.
The dissolution of the thorium analogue of brannerite (ThTi2O6-I) and U(IV)/U(V) doped Th-brannerite (Th0.97U0.03Ti2O6-II and Th0.955U0.03Ca0.015Ti2O6-III) in aqueous media under atmospheric conditions has been studied to elucidate the effects of pH and uranium valence state on the dissolution rate.
The dissolution of I is nearly stoichiometric but slightly preferential release of U occurs for II and preferential release of Ca and U occur for III. The V-shape pH dependence previously observed for U-brannerite only occurs for U (not other matrix elements) for II, indicating that the pH dependence is related to the U oxidation state upon dissolution. The normalised U dissolution rates of III are nearly an order of magnitude higher than those of II for pH values over 3, suggesting brannerite is less durable with U(V) doping. TEM examination of specimens after leaching revealed few surface alteration products, which is consistent with the nearly stoichiometric dissolution of thorium brannerite.