Change of existing circulating fluidized bed boilers to oxy-firing conditions for CO2 capture

This work investigates a circulating fluidized bed boiler, originally designed for air-firing, retrofitted to oxy-firing with the purpose of removing the CO2 emission from coal combustion. Previous studies have shown that the heat balance on the gas-particle side can be satisfied without changes in the boiler, but then the volume flow of gas is reduced. To retain the operation like that during air-firing, the volume flow, that is the fluidization velocity, in oxy-firing should be equal to that in air-firing. It is the main purpose of this work to determine the conditions for the transition from air to oxy-firing, while the heat transfer conditions are maintained at a constant fluidization velocity. Measures to achieve this, such as adjusting the supply of additional gas and the heat transfer surface, are analysed. The fulfilment of the furnace\u27s heat balance requires extra fuel or reduction of the heat-transfer surface in the furnace. These changes affect the performance of the back pass, which must be modified to accommodate the change in gas composition and the higher sensible heat content of the flue gas. Strategies to deal with these circumstances in CFB boilers are discussed

Amplification and cloning of cDNAS of cytochrome P4501A1 and metallothionein genes from Sparus aurata Linnaeus, 1758 and Liza aurata (Risso, 1810) by Race-PCR

The biotransformation of xenobiotics found in marine ecosystems is catalysed by inducible systems, a property that makes them useful as early-warning biomarkers of environmental pollution. We have focused our study on cytochrome P4501A1 (CYP 1A1) as a phase I response against organic aromatic xenobiotics, and metallothionein (MT), which reflects pollution by transition metals. The high homology existing between the sequences of both genes, already cloned in different fish species, enabled us to design degenerate oligos to amplify by RT-PCR specific sequences of CYP 1A1 and MT genes in two teleost fish species of the Spanish South Atlantic littoral, the gilthead seabream, Sparus aurata Linnaeus, 1758, and the grey mullet, Liza aurata (Risso 1810). To this end, the expression of both genes was previously induced by intraperitoneal injection with Aroclor 1254 (CYP 1A1) and CdCl2 (MT). The specific sequences for both genes amplified by RT-PCR with degenerate oligos were subsequently used to design new, specific oligos to obtain by Race-PCR (Rapid Amplification of cDNA Ends) the complete cDNAs coding for both genes in both fish species, which were subsequently cloned and sequenced. The coding sequences and the corresponding proteins were compared with those already obtained in other fish species. We are currently developing homologous probes for mRNA quantification using molecular biology techniques in both fish species, to be employed as molecular biomarkers of pollution in the Spanish South Atlantic littoral.La biotransformación de xenobióticos presentes en ecosistemas marinos está catalizada por varios sistemas inducibles, lo que permite su uso como biomarcadores de alerta temprana de contaminación ambiental. Este estudio se ha centrado en el citocromo P4501A1 (CYP 1A1), como respuesta de fase I contra xenobióticos orgánicos aromáticos, y la metalotioneína (MT), que refleja la contaminación por metales de transición. La alta homología existente entre las secuencias de ambos genes previamente clonados en diferentes especies de peces permitió diseñar oligos degenerados para amplificar por RT-PCR secuencias específicas de los genes CYP 1A1 y MT en dos especies de peces teleósteos del litoral suratlántico español, la dorada Sparus aurata Linnaeus, 1758 y la lisa Liza aurata (Risso, 1810). Para ello, la expresión de ambos genes se indujo por inyección intraperitoneal con Aroclor 1254 (CYP 1A1) y CdCl2 (MT). Las secuencias específicas de ambos genes, amplificadas por RT-PCR con tales oligos, se usaron posteriormente para diseñar nuevos oligos específicos; éstos se usaron para amplificar por Race-PCR (Rapid Amplification of cDNA Ends) los cDNAs completos que codifican tales genes en ambas especies de peces, que fueron posteriormente clonados y secuenciados. Las secuencias codificantes y las proteínas correspondientes se han comparado con las obtenidas en otras especies de peces. Actualmente se desarrollan sondas homólogas para cuantificar por métodos de biología molecular los mRNAs específicos en ambos peces, para su uso como biomarcadores moleculares de contaminación en el litoral suratlántico español.Instituto Español de Oceanografí

Amplification and cloning of cDNAS of cytochrome P4501A1 and metallothionein genes from Sparus aurata Linnaeus, 1758 and Liza aurata (Risso, 1810) by Race-PCR

The biotransformation of xenobiotics found in marine ecosystems is catalysed by inducible systems, a property that makes them useful as early-warning biomarkers of environmental pollution. We have focused our study on cytochrome P4501A1 (CYP 1A1) as a phase I response against organic aromatic xenobiotics, and metallothionein (MT), which reflects pollution by transition metals. The high homology existing between the sequences of both genes, already cloned in different fish species, enabled us to design degenerate oligos to amplify by RT-PCR specific sequences of CYP 1A1 and MT genes in two teleost fish species of the Spanish South Atlantic littoral, the gilthead seabream, Sparus aurata Linnaeus, 1758, and the grey mullet, Liza aurata (Risso 1810). To this end, the expression of both genes was previously induced by intraperitoneal injection with Aroclor 1254 (CYP 1A1) and CdCl2 (MT). The specific sequences for both genes amplified by RT-PCR with degenerate oligos were subsequently used to design new, specific oligos to obtain by Race-PCR (Rapid Amplification of cDNA Ends) the complete cDNAs coding for both genes in both fish species, which were subsequently cloned and sequenced. The coding sequences and the corresponding proteins were compared with those already obtained in other fish species. We are currently developing homologous probes for mRNA quantification using molecular biology techniques in both fish species, to be employed as molecular biomarkers of pollution in the Spanish South Atlantic littoralLa biotransformación de xenobióticos presentes en ecosistemas marinos está catalizada por varios sistemas inducibles, lo que permite su uso como biomarcadores de alerta temprana de contaminación ambiental. Este estudio se ha centrado en el citocromo P4501A1 (CYP 1A1), como respuesta de fase I contra xenobióticos orgánicos aromáticos, y la metalotioneína (MT), que refleja la contaminación por metales de transición. La alta homología existente entre las secuencias de ambos genes previamente clonados en diferentes especies de peces permitió diseñar oligos degenerados para amplificar por RT-PCR secuencias específicas de los genes CYP 1A1 y MT en dos especies de peces teleósteos del litoral suratlántico español, la dorada Sparus aurata Linnaeus, 1758 y la lisa Liza aurata (Risso, 1810). Para ello, la expresión de ambos genes se indujo por inyección intraperitoneal con Aroclor 1254 (CYP 1A1) y CdCl2 (MT). Las secuencias específicas de ambos genes, amplificadas por RT-PCR con tales oligos, se usaron posteriormente para diseñar nuevos oligos específicos; éstos se usaron para amplificar por Race-PCR (Rapid Amplification of cDNA Ends) los cDNAs completos que codifican tales genes en ambas especies de peces, que fueron posteriormente clonados y secuenciados. Las secuencias codificantes y las proteínas correspondientes se han comparado con las obtenidas en otras especies de peces. Actualmente se desarrollan sondas homólogas para cuantificar por métodos de biología molecular los mRNAs específicos en ambos peces, para su uso como biomarcadores moleculares de contaminación en el litoral suratlántico españo

Single-particle transfer and nuclear supersymmetry

Transfer reactions constitute a stringent test for nuclear supersymmetry, a theory that simultaneously describes neighboring nuclei with bosonic and fermionic character. We construct and analytically evaluate one-nucleon transfer matrix elements between supersymmetric partners with the U( 6/4) case as an example, and stress the need for a careful treatment of bosonic and fermionic operators in the construction of mixed tensor operators.CONACyT 32416-E 32397-EPAGA-UNAM IN106400DGICYT PB98-111

Spectral Engineering with Coupled Microcavities: Active Control of Resonant Mode-Splitting

Optical mode-splitting is an efficient tool to shape and fine-tune the spectral response of resonant nanophotonic devices. The active control of mode-splitting, however, is either small or accompanied by undesired resonance shifts, often much larger than the resonance-splitting. We report a control mechanism that enables reconfigurable and widely tunable mode-splitting while efficiently mitigating undesired resonance shifts. This is achieved by actively controlling the excitation of counter-traveling modes in coupled resonators. The transition from a large splitting (80 GHz) to a single-notch resonance is demonstrated using low power microheaters (35 mW). We show that the spurious resonance-shift in our device is only limited by thermal crosstalk and resonance-shift-free splitting control may be achieved.Comment: 4 pages, 3 figure

Fluid dynamic analysis of dual fluidized bed gasifier for solar applications

A hydrodynamic model of a dual fluidized bed gasifier (DFBG) is developed and its predictions are compared with measurements of solids flux and pressure profiles from a cold flow model (CFM). Then, the performance of a DFBG gasifier is theoretically analyzed in terms of solids circulation and solids distribution under changes in riser and loop seal aeration, solids inventory and particle size, and a sensitivity analysis is made to delimit the model prediction capability. Furthermore, the model is applied to analyze the effects of key design aspects of DFBG, such as the relative size of riser and gasifier, the connection between both units, the circulation rate of solids and their distribution around the system. The model is further used to extend the DFBG operation with external solar energy carried by heated solid particles, i.e. to design solar DFBG (SDFBG). The analysis is focused on the performance with high solids inventory in the gasifier to increase the char conversion (operation with a large solar share) and the control of solids circulation to meet the heat demand of the gasifier with the availability of solar energy. The operation with large solids inventory in the gasifier requires the size of the gasifier to increase considerably compared to that of the conventional DFBG. The substitution of the connection pipe between the riser and the bubbling bed (current design in commercial DFBG) by a lower loop seal enables better control of the solids circulation, thus, benefiting the solar design

Collective states of the odd-mass nuclei within the framework of the Interacting Vector Boson Model

A supersymmetric extension of the dynamical symmetry group $Sp^{B}(12,R)$ of the Interacting Vector Boson Model (IVBM), to the orthosymplectic group $OSp(2\Omega/12,R)$ is developed in order to incorporate fermion degrees of freedom into the nuclear dynamics and to encompass the treatment of odd mass nuclei. The bosonic sector of the supergroup is used to describe the complex collective spectra of the neighboring even-even nuclei and is considered as a core structure of the odd nucleus. The fermionic sector is represented by the fermion spin group $SO^{F}(2\Omega)\supset SU^{F}(2)$. The so obtained, new exactly solvable limiting case is applied for the description of the nuclear collective spectra of odd mass nuclei. The theoretical predictions for different collective bands in three odd mass nuclei, namely $^{157}Gd$, $^{173}Yb$ and $^{163}Dy$ from rare earth region are compared with the experiment. The $B(E2)$ transition probabilities for the $^{157}Gd$ and $^{163}Dy$ between the states of the ground band are also studied. The important role of the symplectic structure of the model for the proper reproduction of the $B(E2)$ behavior is revealed. The obtained results reveal the applicability of the models extension.Comment: 18 pages, 8 figure

Ground state energy fluctuations in the Nuclear Shell Model

Statistical fluctuations of the nuclear ground state energies are estimated using shell model calculations in which particles in the valence shells interact through well defined forces, and are coupled to an upper shell governed by random 2-body interactions. Induced ground-state energy fluctuations are found to be one order of magnitude smaller than those previously associated with chaotic components, in close agreement with independent perturbative estimates based on the spreading widths of excited states.Comment: 4 pages, 4 figures, to be published in Physics Leters

New supersymmetric quartet of nuclei in the A=190 mass region

We present evidence for a new supersymmetric quartet in the A=190 region of the nuclear mass table. New experimental information on transfer and neutron capture reactions to the odd-odd nucleaus 194 Ir strongly suggests the existence of a new supersymmetric quartet, consisting of the 192,193 Os and 193,194 Ir nuclei. We make explicit predictions for the odd-neutron nucleus 193 Os, and suggest that its spectroscopic properties be measured in dedicated experiments.Comment: 5 pages, 4 figures, updated figures and revised text, Physical Review C, Rapid Communication, in pres

Garvey-Kelson Relations for Nuclear Charge Radii

The Garvey-Kelson relations (GKRs) are algebraic expressions originally developed to predict nuclear masses. In this letter we show that the GKRs provide a fruitful framework for the prediction of other physical observables that also display a slowly-varying dynamics. Based on this concept, we extend the GKRs to the study of nuclear charge radii. The GKRs are tested on 455 out of the approximately 800 nuclei whose charge radius is experimentally known. We find a rms deviation between the GK predictions and the experimental values of only 0.01 fm. This should be contrasted against some of the most successful microscopic models that yield rms deviations almost three times as large. Predictions - with reliable uncertainties - are provided for 116 nuclei whose charge radius is presently unknown.Comment: 4 pages and 3 figure