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Tratamentos para redução de metais alcalinos, enxofre e cloreto em celulignina destinada à obtenção de gás de síntese como substituto do gás natural para geração de energia termoelétrica em turbinas a gás; Treatments for reduction of alkali metals, sulfur and chloride in cellulignin designed to obtain synthesis gas as a substitute for natural gas for thermoelectric power generation with gas turbines

Romão, Erica Leonor
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Relevância na Pesquisa
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O presente trabalho se insere no Programa de Biomassa - Energia - Materiais - PROBEM?, cuja Refinaria de Biomassa desenvolve tecnologias para o aproveitamento integral de biomassas lignocelulósicas e oleosas, objetivando sua exploração autossustentada. Os principais produtos obtidos são combustíveis para geração de energia termoelétrica, produtos químicos, materiais inorgânicos e reciclagem de fertilizantes. Neste trabalho explorou-se a celulignina, que é um combustível obtido pela pré-hidrólise ácida da biomassa, visando à obtenção de gás de síntese (singás) da celulignina para geração de energia termoelétrica com turbinas a gás, como substituto do gás natural. Para essa aplicação, e também para aplicações em síntese de produtos químicos e combustíveis pelo processo Fischer Tropsch, teores de metais alcalinos, enxofre e cloretos são críticos. A biomassa considerada foi a madeira de Eucalyptus grandis. O trabalho propõe a lixiviação aquosa daqueles contaminantes por pré-hidrólise ácida da biomassa, seguida da moagem a úmido da celulignina para razões líquido/sólido (L/S) otimizadas em relação ao consumo de água e aos teores finais dos contaminantes na biomassa tratada. A eficiência da sequência de tratamentos foi verificada medindo os teores de potássio...

LATTICE-DYNAMICS OF ALKALI-METALS IN A 3-BODY INTERACTION

Coelho, A. A.; Shukla, M. M.
Tipo: Artigo de Revista Científica Formato: 599-609
ENG
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The original model of Das et al. is modified in extending the electron-ion interaction on a three-body forces and including the crystal equilibrium condition to reduce one independent parameter. We studied the phonon dispersion relations along the three principal symmetry directions i.e. [xi, 0, 0], [xi, xi, 0] and [xi, xi, xi] and theta-T curves of alkali metals, Na, K, Rb, Cs and Li. There is close agreement between the computed results and the experimental observations.

A study of the electronic properties of liquid alkali metals: a self-consistent approach

Geertsma,W.; Gonzalez,D.; Gonzalez,L. H.
Tipo: Artigo de Revista Científica Formato: text/html
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We study the electronic properties (density of states, conductivity and thermopower) of some nearly-freeelectron systems: the liquid alkali metals and two liquid alloys, Li-Na and Na-K. The study has been performed within the self-consistent second order Renormalized Propagator Perturbation Expansion (RPE) for the self-energy. The input ionic pseudopotentials and static correlation functions are derived from the neutral pseudoatom method and the modified hypernetted chain theory of liquids, respectively. Reasonable agreement with experiment is found for Na, K, Rb and Na-K, whereas for Li and Cs and Li-Na the agreement is less satisfactory.

Inclusion separation of alkali metals in emulsion liquid membranes by nanobaskets of calix[4]crown-3

Mokhtari,B.; Pourabdollah,K.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Relevância na Pesquisa
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Nano-assisted inclusion separation of alkali metals from basic solutions was reported by an inclusion-facilitated emulsion liquid membrane process. The novelty of this study is application of nanobaskets of calixcrown in the selective and efficient separation of alkali metals as both the carrier and the surfactant. For this purpose, two diacids, p-tert-butylcalix[4]arene-1,2-crown-3 in the cone and the 1,2alternate conformation, as well as another diacid, p-tert-butylcalix[4]arene-1,2-thiacrown-3 in the cone conformation, were synthesized. Their inclusion-extraction parameters were optimized, including the calixcrown scaffold (04, 4 wt%) as the carrier/demulsifier, commercial kerosene as the diluent in the membrane, sulphonic acid (0.2 M) and ammonium carbonate (0.4 M) as the strip and the feed phases; the phase and the treat ratios were 0.8 and 0.3, mixing speed (300 rpm), and initial solute concentration (100 mg/L). The selectivity of the membrane was examined for more than ten interfering cations was examined and the results reveled that, under the optimized operating condition, the degree of inclusion-extraction of alkali metals was as high as 98-99%.

Significant Structure Theory of Surface Tension of the Alkali Metals

Hsu, Chen C.; Eyring, Henry
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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The volume and temperature dependence of the solid-like structure in liquids has been properly taken into account in calculations of surface tension of the liquid alkali metals. The surface tension equation derived from the significant structure theory of liquids is used. The results are quite satisfactory when compared with observed values.

Significant Liquid-Structure Theory of Viscosity and Self-Diffusion of the Alkali Metals

Hsu, Chen C.; Eyring, Henry
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.53%
Significant liquid-structure theory has been used to calculate the transport properties of the alkali metals. Unlike previous calculations, the volume and temperature dependence of the solid-like structure has been taken into consideration. Equations for the potential energy as a function of volume of the alkali metals, which lead to agreement between calculated and experimental values of thermodynamic and transport properties, are given. The calculated results are in satisfactory agreement with the experimental data.

Alkali Metals in Addition to Acidic pH Activate the EvgS Histidine Kinase Sensor in Escherichia coli

Eguchi, Yoko; Utsumi, Ryutaro
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.53%
Two-component signal transduction systems (TCSs) in bacteria perceive environmental stress and transmit the information via phosphorelay to adjust multiple cellular functions for adaptation. The EvgS/EvgA system is a TCS that confers acid resistance to Escherichia coli cells. Activation of the EvgS sensor initiates a cascade of transcription factors, EvgA, YdeO, and GadE, which induce the expression of a large group of acid resistance genes. We searched for signals activating EvgS and found that a high concentration of alkali metals (Na+, K+) in addition to low pH was essential for the activation. EvgS is a histidine kinase, with a large periplasmic sensor region consisting of two tandem PBPb (bacterial periplasmic solute-binding protein) domains at its N terminus. The periplasmic sensor region of EvgS was necessary for EvgS activation, and Leu152, located within the first PBPb domain, was involved in the activation. Furthermore, chimeras of EvgS and PhoQ histidine kinases suggested that alkali metals were perceived at the periplasmic sensor region, whereas the cytoplasmic linker domain, connecting the transmembrane region and the histidine kinase domain, was required for low-pH perception.

Microscopic Surface Structure of Liquid Alkali Metals

Tostmann, E.; DiMasi, E.; Pershan, Peter S.; Ocko, B. M.; Shpyrko, O. G.; Deutsch, M.
Fonte: American Physical Society Publicador: American Physical Society
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
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We report an x-ray scattering study of the microscopic structure of the surface of a liquid alkali metal. The bulk liquid structure factor of the eutectic K67Na33 alloy is characteristic of an ideal mixture, and so shares the properties of an elemental liquid alkali metal. Analysis of off-specular diffuse scattering and specular x-ray reflectivity shows that the surface roughness of the K-Na alloy follows simple capillary wave behavior with a surface structure factor indicative of surface-induced layering. Comparison of the low-angle tail of the K67Na33 surface structure factor with the one measured for liquid Ga and In previously suggests that layering is less pronounced in alkali metals. Controlled exposure of the liquid to H2 and O2 gas does not affect the surface structure, indicating that oxide and hydride are not stable at the liquid surface under these experimental conditions.; Engineering and Applied Sciences

A fast atom bombardment mass spectrometry study of tris (3, 6-dioxaheptyl) amine-alkali metal halide complexes and hydrogen bonded complexes

Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
ENG
Relevância na Pesquisa
46.35%
The objective of this thesis was to demonstrate the potential of fast atom bombardment mass spectrometry (FABMS) as a probe of condensed phase systems and its possible uses for the study of hydrogen bonding. FABMS was used to study three different systems. The first study was aimed at investigating the selectivity of the ligand tris(3,6-dioxaheptyl) amine (tdoha) for the alkali metal cations. FABMS results correlated well with infrared and nmr data. Systems where a crown ether competed with tdoha for a given alkali metal cation were also investigated by fast atom bombardment. The results were found to correlate with the cation affinity of tdoha and the ability of the crown ether to bind the cation. In the second and third studies, H-bonded systems were investigated. The imidazole-electron donor complexes were investigated and FABMS results showed the expected H-bond strength of the respective complexes. The effects of concentration, liquid matrix, water content, deuterium exchange, and pre-ionization of the complex were also investigated. In the third system investigated, the abundance of the diphenyl sulfone-ammonium salt complexes (presumably H-bonded) in the FABMS spectrum were found to correlate with qualitative considerations such as steric hindrance and strength of ion pairs.

Molecular dynamics calculation of mean square displacement in alkali metals and rare gas solids and comparison with lattice dynamics

Heiser, Gernot A.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
ENG
Relevância na Pesquisa
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Molec ul ar dynamics calculations of the mean sq ua re displacement have been carried out for the alkali metals Na, K and Cs and for an fcc nearest neighbour Lennard-Jones model applicable to rare gas solids. The computations for the alkalis were done for several temperatures for temperature vol ume a swell as for the the ze r 0 pressure ze ro zero pressure volume corresponding to each temperature. In the fcc case, results were obtained for a wide range of both the temperature and density. Lattice dynamics calculations of the harmonic and the lowe s t order anharmonic (cubic and quartic) contributions to the mean square displacement were performed for the same potential models as in the molecular dynamics calculations. The Brillouin zone sums arising in the harmonic and the quartic terms were computed for very large numbers of points in q-space, and were extrapolated to obtain results ful converged with respect to the number of points in the Brillouin zone.An excellent agreement between the lattice dynamics results was observed molecular dynamics and in the case of all the alkali metals, e~ept for the zero pressure case of CSt where the difference is about 15 % near the melting temperature. It was concluded that for the alkalis...

Surface properties of liquid alkali metals / John Edgar Lane.

Lane, John Edgar
Tipo: Tese de Doutorado Formato: 314158 bytes; application/pdf
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Thesis (Ph.D.)--University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1962; Typewritten; 1 v.; Title page, contents and abstract only. The complete thesis in print form is available from the University Library.

Anharmonicity in alkali metals : an x-ray approach with particular reference to potassium and lithium / by B. Bednarz

Bednarz, Bernard
Tipo: Tese de Doutorado Formato: 123331 bytes; application/pdf
Relevância na Pesquisa
46.34%
Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1978; 129 leaves : ill., tables ; 30 cm.; Title page, contents and abstract only. The complete thesis in print form is available from the University Library.

Alkalimetall-Dotierung von Perylentetracarbonsäuredianhydrid (PTCDA) : Charakterisierung mit oberflächenanalytischen, elektrischen und quantentheoretischen Methoden; Alkali metal-doping of perylenetetracarboxylicdianhydride (PTCDA) : characterization with surface analytical, electrical and theoretical methods

Ertl, Thomas
Tipo: Dissertação
DE_DE
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46.7%
Diese Arbeit beinhaltet im Wesentlichen die Untersuchung von dünnen halbleitenden PTCDA-Aufdampfschichten mit gezielt einstellbarer n-Leitfähigkeit. Die Einstellung der Leitfähigkeit durch kontrollierte n-Dotierung ist eine wichtige Voraussetzung für einen möglichen Einsatz dieses Materials als n-leitende Komponente in elektrischen Bauelementen. Neben der Charakterisierung von reinen PTCDA-Filmen lag der wesentliche Schwerpunkt auf der Untersuchung der Alkalimetall-Dotierung von PTCDA. Ziel war es zum einen, zu untersuchen, ob die Wechselwirkung mit Alkalimetallatomen zu einer erfolgreichen n-Dotierung des organischen Halbleiters führt, und zum anderen, diesen Dotierprozess detailliert zu charakterisieren. Zu diesem Zweck wurden verschiedene Untersuchungsmethoden angewandt. Die Analyse der geometrischen, chemischen und elektronischen Struktur der Schichten erfolgte mittels Rasterkraftmikroskopie (SFM), UV/VIS-Spektroskopie und Röntgen- bzw. Ultraviolett-Photoelektronenspektroskopie (XPS bzw. UPS). Die Charakterisierung der elektrischen Eigenschaften erfolgte durch temperaturabhängige Messungen der spezifischen Leitfähigkeit und des Seebeck-Koeffizienten. Dazu wurde eine vollständig neue UHV-Apparatur aufgebaut, die eine kombinierte und temperaturabhängige Bestimmung der o.g. elektrischen Messgrößen an in-situ präparierten PTCDA-Schichten erlaubt. Als wesentliches Ergebnis ist zu nennen...

New Jellium Model for Alkali Metals and its Future Applications to Metal Clusters

Matranca, Guillermo
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Relevância na Pesquisa
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This research develops a new method for understanding the properties of materials. The new method was applied to alkali metals to examine how well it can predict the Wigner-Seitz radius, rs. Pseudo-potentials for the individual atoms were generated and utilized to obtain the interaction energy within these metals. The system involves 4 coulombic charges; two of them are the result of the neutral atom (one valence electron and one positive core charge for alkali atoms) and the other two are background charges of equal and opposite amount. This coulombic interaction will behave differently depending on the element that composes the system. There are four groups of energy for this system. One of them has the appearance of the Jellium model, which is solved with Density Functional Theory. From the other three groups, one of them will alter the minimum of the Jellium model for different elements in the system. This group is partially calculated with the help of Ewald summation. This calculation exemplifies that bcc is favored since it is lower in energy than fcc, which is in agreement with experiments for alkali metals. The correction to this energy will be due to the core electrons' interaction with a uniform negative charge background. This new method will also be beneficial to calculate the ground state energy of clusters by introducing surface boundaries in the system.

Pressure-induced s-band ferromagnetism in alkali metals

Pickard, Chris J; Needs, R J
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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First-principles density-functional-theory calculations show that compression of alkali metals stabilizes open structures with localized interstitial electrons which may exhibit a Stoner-type instability towards ferromagnetism. We find ferromagnetic phases of the lithium-IV-type, simple cubic, and simple hexagonal structures in the heavier alkali metals, which may be described as s-band ferromagnets. We predict that the most stable phases of potassium at low temperatures and pressures around 20 GPa are ferromagnets.; Comment: 5 pages, 3 figures

Relaxation time scales in collective dynamics of liquid alkali metals

Mokshin, Anatolii V.; Yulmetyev, Renat M.; Hänggi, Peter
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.53%
In this paper the investigation of the dynamical processes of liquid alkali metals is executed by analyzing the time scales of relaxation processes in liquids. The obtained theoretical dynamic structure factor $S(k,\omega)$ for the case of liquid lithium is found to be in excellent agreement with the recently received inelastic X-ray scattering data. The comparison and interrelation with other theories are given here. Finally, an important part of this paper is the confirmation of the scale uniformity of the dynamic processes in liquid alkali metals predicted by some previous molecular dynamic simulation studies.

Microscopic Surface Structure of Liquid Alkali Metals

Tostmann, Holger; DiMasi, Elaine; Shpyrko, Oleg G.; Pershan, Peter S.; Ocko, Benjamin M.; Deutsch, Moshe
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.51%
We report an x-ray scattering study of the microscopic structure of the surface of a liquid alkali metal. The bulk liquid structure factor of the eutectic K67Na33 alloy is characteristic of an ideal mixture, and so shares the properties of an elemental liquid alkali metal. Analysis of off-specular diffuse scattering and specular x-ray reflectivity shows that the surface roughness of the K-Na alloy follows simple capillary wave behavior with a surface structure factor indicative of surface induced layering. Comparison of thelow-angle tail of the K67Na33 surface structure factor with the one measured for liquid Ga and In previously suggests that layering is less pronounced in alkali metals. Controlled exposure of the liquid to H2 and O2 gas does not affect the surface structure, indicating that oxide and hydride are not stable at the liquid surface under these experimental conditions.; Comment: 12 pages, 3 figures, published in Phys. Rev. B

Towards first-principles understanding of the metal-insulator transition in fluid alkali metals

Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.45%
By treating the electron-ion interaction as perturbation in the first-principles Hamiltonian, we have calculated the density response functions of a fluid alkali metal to find an interesting charge instability due to anomalous electronic density fluctuations occurring at some finite wave vector ${\bi Q}$ in a dilute fluid phase above the liquid-gas critical point. Since $|{\bi Q}|$ is smaller than the diameter of the Fermi surface, this instability necessarily impedes the electric conduction, implying its close relevance to the metal-insulator transition in fluid alkali metals.; Comment: 11 pages, 5 figures

Hard-wall Potential Function for Transport Properties of Alkali Metals Vapor

Ghatee, M. H.; Niroomand-Hosseini, F.
Tipo: Artigo de Revista Científica