USDOE/EPRI BIOMASS COFIRING COOPERATIVE AGREEMENT

The Eleventh Quarter of the USDOE-EPRI contract, April 1, 1999 through June 30, 1999, was characterized by extensive testing at the Seward cofiring demonstration of GPU Genco and the Bailly Unit No.7 demonstration of NIPSCO. Technical work that proceeded during the eleventh quarter of the contract included the following: Testing at up to {approx}15 percent cofiring on a mass basis ({approx}7 percent cofiring on a Btu basis) at the Seward Generating Station No.12 boiler, focusing upon the operability of the separate injection system and the combustion/emission formation characteristics of the cofiring process; and Testing at up to {approx}10 percent cofiring of waste wood on a mass basis ({approx}5 percent cofiring on a Btu basis) at the Bailly Generating Station No.7 boiler, focusing upon the impacts of urban wood waste blended with a mixture of eastern high sulfur coal and western low sulfur coal Both tests demonstrated the following general, and expected, results from cofiring at these locations: (1) Cofiring did not impact boiler capacity; (2) Cofiring did cause a modest reduction in boiler efficiency; (3) Cofiring did reduce NOx emissions; (4) Cofiring did reduce fossil CO2 emissions; and (5) Other impacts of cofiring were modest

Biomass Cofiring with Coal at Seward, Pennsylvania

The first test under the EPRI/FETC biomass cofiring process was at GPU Genco`s 32-MW{sub e} pulverized coal boiler at Seward, Pennsylvania. The unit used in the test (Boiler 12) is a wall-fired boiler built by Babcock & Wilcox, and has a nominal steaming capacity of 300,000 lb/hr of 675 psig/850 F stream. The furnace of Boiler 12 has a volume of 20,000 ft{sup 3} and has a volume in the primary combustion area of 12,700 ft{sup 3}. The boiler has two rows of burners, with three burners installed on each row. Typically it consumes coal at about 14 ton/hr when firing at 100 percent of capacity. This boiler, along with Boiler 14, supply steam to a 64 MW{sub e} Westinghouse turbine. The net station heat rate (NSHR) for Boilers 12 and 14, and the associated turbine, is 14,200 Btu/kWh. Boiler 14 has been used to test coal water slurry (CWS), and that experience contributed to the design and execution of this cofiring test, where sawdust was the biomass fuel

Momentum dependence of the superconducting gap in NdFeAsO1-xFx single crystals measured by angle resolved photoemission spectroscopy

We use angle resolved photoemission spectroscopy (ARPES) to study the momentum dependence of the superconducting gap in NdFeAsO1-xFx single crystals. We find that the Gamma hole pocket is fully gapped below the superconducting transition temperature. The value of the superconducting gap is 15 +- 1.5 meV and its anisotropy around the hole pocket is smaller than 20% of this value. This is consistent with an isotropic or anisotropic s-wave symmetry of the order parameter or exotic d-wave symmetry with nodes located off the Fermi surface sheets. This is a significant departure from the situation in the cuprates, pointing to possibility that the superconductivity in the iron arsenic based system arises from a different mechanism.Comment: 4 pages, 3 figure

Thermal expansion and magnetostriction of pure and doped RAgSb2 (R = Y, Sm, La) single crystals

Data on temperature-dependent, anisotropic thermal expansion in pure and doped RAgSb2 (R = Y, Sm, La) single crystals are presented. Using the Ehrenfest relation and heat capacity measurements, uniaxial pressure derivatives for long range magnetic ordering and charge density wave transition temperatures are evaluated and compared with the results of the direct measurements under hydrostatic pressure. In-plane and c-axis pressure have opposite effect on the phase transitions in these materials, with in-plane effects being significantly weaker. Quantum oscillations in magnetostriction were observed for the three pure compounds, with the possible detection of new frequencies in SmAgSb2 and LaAgSb2. The uniaxial (along the c-axis) pressure derivatives of the dominant extreme orbits (beta) were evaluated for YAgSb2 and LaAgSb2

Restrictions Limiting the Generation of DNA Double Strand Breaks during Chromosomal V(D)J Recombination

Antigen receptor loci are composed of numerous variable (V), diversity (D), and joining (J) gene segments, each flanked by recombination signal sequences (RSSs). The V(D)J recombination reaction proceeds through RSS recognition and DNA cleavage steps making it possible for multiple DNA double strand breaks (DSBs) to be introduced at a single locus. Here we use ligation-mediated PCR to analyze DNA cleavage intermediates in thymocytes from mice with targeted RSS mutations at the endogenous TCRβ locus. We show that DNA cleavage does not occur at individual RSSs but rather must be coordinated between RSS pairs flanking gene segments that ultimately form coding joins. Coordination of the DNA cleavage step occurs over great distances in the chromosome and favors intra- over interchromosomal recombination. Furthermore, through several restrictions imposed on the generation of both nonpaired and paired DNA DSBs, this requirement promotes antigen receptor gene integrity and genomic stability in developing lymphocytes undergoing V(D)J recombination

Flexible provisioning of Web service workflows

Web services promise to revolutionise the way computational resources and business processes are offered and invoked in open, distributed systems, such as the Internet. These services are described using machine-readable meta-data, which enables consumer applications to automatically discover and provision suitable services for their workflows at run-time. However, current approaches have typically assumed service descriptions are accurate and deterministic, and so have neglected to account for the fact that services in these open systems are inherently unreliable and uncertain. Specifically, network failures, software bugs and competition for services may regularly lead to execution delays or even service failures. To address this problem, the process of provisioning services needs to be performed in a more flexible manner than has so far been considered, in order to proactively deal with failures and to recover workflows that have partially failed. To this end, we devise and present a heuristic strategy that varies the provisioning of services according to their predicted performance. Using simulation, we then benchmark our algorithm and show that it leads to a 700% improvement in average utility, while successfully completing up to eight times as many workflows as approaches that do not consider service failures

Hydrostatic pressure study of pure and doped La1-xRxAgSb2 (R = Ce, Nd) charge-density-wave compounds

The intermetallic compound LaAgSb2 displays two charge-density-wave (CDW) transitions, which were detected with measurements of electrical resistivity (rho), magnetic susceptibility, and X-ray scattering; the upper transition takes place at T1 approx. 210 K, and it is accompanied by a large anomaly in rho(T), whereas the lower transition is marked by a much more subtle anomaly at T2 approx. 185 K. We studied the effect of hydrostatic pressure (P) on the formation of the upper CDW state in pure and doped La1-xRxAgSb2 (R = Ce, Nd) compounds, by means of measurements of rho(T) for P < 23 kbar. We found that the hydrostatic pressure, as well as the chemical pressure introduced by the partial substitution of the smaller Ce and Nd ions for La, result in the suppression of the CDW ground state, e.g. the reduction of the ordering temperature T1. The values of dT1/dP are approx. 2-4 times higher for the Ce-doped samples as compared to pure LaAgSb2, or even La0.75Nd0.25AgSb2 Nd-doped with a comparable T1 (P=0). This increased sensitivity to pressure may be due to increasing Ce- hybridization under pressure. The magnetic ordering temperature of the cerium-doped compounds is also reduced by pressure, and the high pressure behavior of the Ce-doped samples is dominated by Kondo impurity scattering.Comment: 22 pages, 11 figure

Single crystal of superconducting SmFeAsO1-xFy grown at high pressure

Single crystals of SmFeAsO1-xFy of a size up to 120 micrometers have been grown from NaCl/KCl flux at a pressure of 30 kbar and temperature of 1350-1450 C using the cubic anvil high-pressure technique. The superconducting transition temperature of the obtained single crystals varies between 45 and 53 K.Obtained crystals are characterized by a full diamagnetic response in low magnetic fields and by a high critical current density in high magnetic fields. Structural refinement has been performed on single crystal. Differential thermal analysis investigations at 1 bar Ar pressure show decomposition of SmFeAsO1-xFy at 1302 C.Comment: 12 pages, 3 tables, 6 figure

Intrinsic magnetic properties of NdFeAsO0.9_{0.9}F0.1_{0.1} superconductor from local and global measurements

Magneto-optical imaging was used to study the local magnetization in polycrystalline NdFeAsO$_{0.9}$F$_{0.1}$ (NFAOF). Individual crystallites up to $\sim200\times100\times30$ $\mu m^{3}$ in size could be mapped at various temperatures. The in-grain, persistent current density is about $j\sim10^{5}$ A/cm$^{2}$ and the magnetic relaxation rate in a remanent state peaks at about $T_{m}\sim38$ K. By comparison with with the total magnetization measured in a bar-shaped, dense, polycrystalline sample, we suggest that NdFeAsO$_{0.9}$F$_{0.1}$ is similar to a layered high-$T_{c}$, compound such as Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+x}$ and exhibits a $3D\to2D$ crossover in the vortex structure. The 2D Ginzburg parameter is about $Gi^{2D}$ implying electromagnetic anisotropy as large as $\epsilon \sim1/30$. Below $T_{m}$, the static and dynamic behaviors are consistent with collective pinning and creep